WO2005107318A1 - 圧力波発生装置及びその製造方法 - Google Patents
圧力波発生装置及びその製造方法 Download PDFInfo
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- WO2005107318A1 WO2005107318A1 PCT/JP2005/008252 JP2005008252W WO2005107318A1 WO 2005107318 A1 WO2005107318 A1 WO 2005107318A1 JP 2005008252 W JP2005008252 W JP 2005008252W WO 2005107318 A1 WO2005107318 A1 WO 2005107318A1
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- heating element
- insulating layer
- heat insulating
- pressure wave
- wave generator
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Classifications
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R23/00—Transducers other than those covered by groups H04R9/00 - H04R21/00
- H04R23/002—Transducers other than those covered by groups H04R9/00 - H04R21/00 using electrothermic-effect transducer
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
- B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
- B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
- B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R31/00—Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor
- H04R31/003—Apparatus or processes specially adapted for the manufacture of transducers or diaphragms therefor for diaphragms or their outer suspension
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R2201/00—Details of transducers, loudspeakers or microphones covered by H04R1/00 but not provided for in any of its subgroups
- H04R2201/02—Details casings, cabinets or mounting therein for transducers covered by H04R1/02 but not provided for in any of its subgroups
- H04R2201/029—Manufacturing aspects of enclosures transducers
Definitions
- the present invention relates to a pressure wave generator for generating a pressure wave such as a sound wave, an ultrasonic wave, and a monopulse compression wave for a speaker, and a method for manufacturing the same.
- an ultrasonic generator that utilizes mechanical vibration caused by a piezoelectric effect.
- an ultrasonic generator using mechanical vibration for example, electrodes are provided on both sides of a crystal of a piezoelectric material such as barium titanate, and electric energy is applied between the two electrodes to generate mechanical vibration.
- Vibrating a medium such as air to generate ultrasonic waves Vibrating a medium such as air to generate ultrasonic waves.
- an ultrasonic generator using mechanical vibration has a unique resonance frequency, and therefore has a narrow frequency band and is susceptible to external vibrations and fluctuations in the atmospheric pressure.
- a pressure wave generator using thermal induction is composed of a semiconductor substrate 1 of a single-crystal silicon substrate and a semiconductor substrate 1 from one surface in the thickness direction of the semiconductor substrate 1.
- a heat insulating layer 2 is formed at a predetermined depth toward the inside of the device, and a heating element 3 of a metal thin film (for example, an A1 thin film) formed on the heat insulating layer 2 is provided.
- the heat insulating layer 2 is formed of a porous silicon layer, and is sufficiently smaller than the semiconductor substrate 1 to have a thermal conductivity and a volumetric heat capacity.
- the heating element 3 When an AC current is supplied from the AC power supply Vs to the heating element 3, the heating element 3 generates heat, and the temperature (or the heat generation amount) of the heating element 3 changes according to the frequency of the supplied AC current.
- a heat insulating layer 2 is formed immediately below the heating element 3, and the heating element 3 is thermally insulated from the semiconductor substrate 1, so that an efficient connection is established between the heating element 3 and the air in the vicinity thereof. Heat exchange occurs The Then, the air repeatedly expands and contracts in accordance with the temperature change (or the change in the amount of heat generated) of the heating element 3, and as a result, a pressure wave such as an ultrasonic wave is generated (the upward arrow in FIG. Indicate the direction of travel of the pressure wave.
- the pressure wave generator using such heat induction varies the frequency of the generated ultrasonic wave over a wide range by changing the frequency of the AC voltage (drive voltage) applied to the heating element 3. Can be changed. Therefore, for example, it can be used as an ultrasonic sound source or a sound source of a speaker.
- the thermal conductivity and the volumetric heat capacity of the thermal insulating layer 2 be smaller than the thermal conductivity and the volumetric heat capacity of the semiconductor substrate 1.
- the product of the thermal conductivity of the heat insulating layer 2 and the volumetric heat capacity is sufficiently smaller than the product of the thermal conductivity of the semiconductor substrate 1 and the volumetric heat capacity.
- the semiconductor substrate 1 is formed of a single-crystal silicon substrate and the heat insulating layer 2 is formed of a porous silicon layer
- the product of the thermal conductivity of the heat insulating layer 2 and the volumetric heat capacity is the semiconductor substrate.
- the product of the thermal conductivity of 1 and the volumetric heat capacity is about 1Z400.
- the heat insulating layer 2 of a porous silicon layer on one surface side of the semiconductor substrate 1 of a single crystal silicon substrate, for example, as shown in FIGS.
- a mask layer is formed in which a portion corresponding to a region where the heat insulating layer 2 is to be formed is opened.
- the current-carrying electrode 4 formed on the entire surface of the other surface of the semiconductor substrate 1 is used as an anode, and a current is passed between the electrode and a cathode disposed so as to face one surface of the semiconductor substrate 1 in an electrolytic solution. Anodizing treatment is performed.
- a chemical change occurs such as oxidation of the heat insulating layer 2 formed of a porous body by oxygen or moisture in the air.
- Table 1 shows that when porous silicon is used as the heat insulating layer 2, an example of a change in oxidation due to long-term use in air is a high-temperature, high-humidity atmosphere at a temperature of 85 ° C and a humidity of 85%. Shows the element ratio when evaluated after exposure to the atmosphere for 250 hours.
- the thickness of the heat insulating layer 2 which is a porous layer and its peripheral portion are substantially reduced in the section AA shown in FIG. 36B. It is uniform. For this reason, the thermal insulation layer 2 expands in volume due to an oxidation reaction due to long-term use in air and the like, and compressive stress is generated.
- the bottom part (point P2) of the heat insulating layer 2 is restrained by the semiconductor substrate 1 and becomes a fixed point.
- the thermal stress generated in the heat insulating layer 2 is concentrated on, for example, a portion (point PI) of the outer periphery 2e of the heat insulating layer 2 which is in contact with the surface of the semiconductor substrate 1. Therefore, cracks may be generated near the point P1 of the porous thermal insulating layer 2, and the thermal insulating layer 2 may be damaged. Such cracks in the heat insulating layer 2 also propagate inside. When the cracks in the heat insulating layer 2 reach the lower portion of the heating element 3, cracks also occur in the outer peripheral portion of the heating element 3.
- the size of the pressure wave generator was changed to 15 mm, which is the general size of an ultrasonic generator using mechanical vibration that has been widely used in the past.
- X about 15 mm, and generate the same sound pressure as the ultrasonic generator using mechanical vibration (for example, about 20 Pa at a distance of 30 cm at a frequency of OkHz at a distance of 30 cm).
- Temperature was examined. As a result, it became clear that the temperature of the heating element 3 instantaneously reached a very high temperature exceeding 1000 degrees.
- An object of the present invention is to provide a pressure wave that utilizes a compressive stress caused by a chemical change of a porous body due to long-term use, and a heat induction that hardly causes breakage of a heat insulating layer and a heating element due to thermal stress caused by driving.
- An object of the present invention is to provide a generator and a manufacturing method thereof.
- a pressure wave generator includes a substrate, a porous heat insulating layer formed on one surface in a thickness direction of the substrate, and a thin film formed on the heat insulating layer.
- a pressure wave generator comprising a heating element, wherein the temperature of the heating element changes according to a waveform of an electric input to the heating element, and a pressure wave is generated by heat exchange between the heating element and a medium, Assuming that the thickness of the central portion of the heat insulating layer in the width direction is a reference thickness, it is assumed that the thickness distribution of the heat insulating layer in the width direction is averaged by the reference thickness.
- the porosity at the outer peripheral portion is smaller than the porosity at the central portion.
- the substrate the porous heat insulating layer formed on one surface in the thickness direction of the substrate, and the thin-film heating element formed on the heat insulating layer
- a pressure wave generator that changes the temperature of the heating element according to the waveform of the electrical input to the heating element and generates a pressure wave by heat exchange between the heating element and the medium.
- the compressive stress can be dispersed by the portion of the outer peripheral portion of the thermal insulating layer having a small porosity. That is, by reducing the porosity of the outer peripheral portion of the heat insulating layer, for example, the number of fixed points on the outer peripheral portion of the heat insulating layer that are restrained by the substrate increases, as compared with the conventional pressure wave generator. Since the positions are dispersed, the compressive stress concentrated on the outer peripheral portion of the heat insulating layer can be dispersed.
- the thickness of the heat insulating layer at the outer peripheral portion is smaller than the thickness at the central portion.
- the conventional pressure In the wave generator even if the volume of the heat insulating layer expands due to a chemical reaction such as oxidation of the heat insulating layer in the outer peripheral portion of the heat insulating layer when used for a long time in the air, the conventional pressure In the wave generator, the compressive stress concentrated on the portion of the outer periphery of the heat insulating layer that is in contact with the surface of the substrate can be dispersed along the outer peripheral surface (for example, an inclined surface) of the heat insulating layer. As a result, the possibility of cracks occurring in the heat insulating layer can be reduced, and furthermore, damage to the heating element due to cracks in the heat insulating layer can be prevented. Furthermore, damage to the pressure wave generator is prevented, and stable ultrasonic waves can be generated for a long period of time.
- the amount of heat dissipated along the thickness direction of the substrate is larger than the amount of heat dissipated along the thickness direction of the substrate at the central portion.
- the mechanical strength of the heat insulating layer and the heating element near the boundary of the thermal insulation layer can be increased. As a result, damage to the heat insulating layer and the heating element due to stress can be prevented. Furthermore, it can be easily manufactured without having to change materials and compositions.
- the porosity per unit volume at the outer peripheral portion of the heat insulating layer may be smaller than the porosity per unit volume at the central portion.
- the fixed portion of the outer peripheral portion of the heat insulating layer which is bound to the substrate is fixed.
- the point positions are dispersed in regions where the porosity per unit volume is changing. Therefore, in the conventional pressure wave generator, the compressive stress concentrated on a portion of the outer periphery of the heat insulating layer that is in contact with the surface of the substrate is transferred along the outer peripheral surface (for example, a porosity inclined surface) of the heat insulating layer. Can be dispersed.
- the amount of heat dissipated along the thickness direction of the substrate is larger than the amount of heat dissipated along the thickness direction of the substrate at the central portion.
- the mechanical strength of the heat insulating layer and the heating element near the boundary can be increased.
- a combination with the feature of claim 2 in which the thickness at the outer peripheral portion of the heat insulating layer is smaller than the thickness at the central portion is also possible.
- one surface force in the thickness direction of the substrate is larger than the outer periphery of the heating element within the width direction defined by the reference thickness of the central portion in the width direction of the heat insulating layer toward the inside of the substrate.
- the average thermal conductivity in the thickness direction of the inner part is a in
- the average volumetric heat capacity is Cin
- the average thermal conductivity in the thickness direction of the outer side of the outer periphery of the heating element is a out
- the average volumetric heat capacity is Cout.
- the heat generation per unit time can be increased by increasing the product of the thermal conductivity of the heat insulating layer and the volumetric heat capacity. It is based on the technical idea of reducing the temperature gradient at the outer periphery of the heating element by increasing the amount of heat radiation so as to suppress the temperature rise at the periphery of the body.
- a is the thermal conductivity of the heat insulating layer
- C is the volumetric heat capacity of the heat insulating layer
- ⁇ is the angular frequency of an AC voltage input between both ends of the heating element
- q (co) is input to the heating element
- ⁇ ⁇ ( ⁇ ) is the temperature of the heating element.
- the average thermal conductivity in the thickness direction of the inner part of the heating element in the thickness direction is o; in, the average volumetric heat capacity is Cin, and the average in the thickness direction of the outer part of the heating element in the thickness direction is Cin.
- the thermal conductivity is a out and the average volumetric heat capacity is C out, o; in X Cin ⁇ a out X Cout, and the a in X Cin near the boundary between the inner part and the outer part is satisfied. Since the value becomes larger toward the outside, the amount of heat radiated along the thickness direction of the board at the outer periphery of the heating element is larger than the amount of heat radiated at the center of the heating element.
- the thermal stress applied to the heating element can be reduced as compared with the pressure wave generator. For this reason, the heating element may be damaged due to thermal stress as compared with the conventional pressure wave generator, and the life of the pressure wave generator can be extended. In other words, when driving the pressure wave generator, even if thermal stress is generated due to expansion and contraction of the heating element due to temperature rise and temperature drop of the heating element, the heating element is hardly damaged for a long period of time. Ultrasonic waves can be generated stably.
- FIG. 1A is a cross-sectional view showing one configuration example of a pressure wave generator according to a first embodiment of the present invention.
- FIG. 1B is a cross-sectional view showing another configuration example.
- FIG. 2A is a plan view showing a configuration of a pressure wave generator according to a second embodiment of the present invention.
- FIG. 2B is a sectional view taken along line AA in FIG. 2A.
- FIG. 2C is an explanatory diagram showing reference points when simulating the temperature distribution on the surface including the surface of the heat insulating layer and the first surface of the semiconductor substrate by the finite element method.
- FIG. 3 is a diagram conceptually showing a configuration of a pressure wave generator according to a second embodiment.
- FIG. 4A is a waveform diagram showing a waveform of an AC voltage applied to the pressure wave generator.
- FIG. 4B is a waveform diagram showing a temperature change of the heating element.
- FIG. 4C is a waveform diagram showing a waveform of a pressure wave (sound wave) generated by the pressure wave generator.
- 5A to 5C are process diagrams showing a method for manufacturing a pressure wave generator according to the second embodiment.
- FIG. 6 shows another step of the method for manufacturing a pressure wave generator according to the second embodiment.
- FIG. 7 is a view showing an anodizing apparatus used in a method for manufacturing a pressure wave generator according to a second embodiment.
- FIG. 8 is a graph showing temperature distribution characteristics of the pressure wave generator according to the second embodiment and a conventional pressure wave generator.
- FIG. 9 is a cross-sectional view showing another configuration example of the pressure wave generator according to the second embodiment.
- FIGS. 10A to 10C are process diagrams showing a method of manufacturing the pressure wave generator according to the third embodiment of the present invention.
- FIG. 11 is a view showing an anodizing apparatus used in a method of manufacturing a pressure wave generator according to a third embodiment.
- FIG. 12 is a sectional view showing a configuration of a pressure wave generator according to a fourth embodiment of the present invention.
- FIGS. 13A to 13E are process diagrams showing a method of manufacturing the pressure wave generator according to the fourth embodiment.
- FIG. 14 is a process chart showing another process of the method for manufacturing a pressure wave generator according to the fourth embodiment.
- FIG. 15A is a plan view showing a configuration of a pressure wave generator according to a fifth embodiment of the present invention.
- FIG. 15B is a sectional view taken along line AA in FIG. 15A.
- FIG. 15C is a sectional view taken along line BB in FIG. 15A.
- FIG. 16 is a sectional view showing a configuration of a pressure wave generator according to a sixth embodiment of the present invention.
- FIG. 17 is a cross-sectional view showing a configuration of a pressure wave generator according to a seventh embodiment of the present invention.
- FIG. 18 is a sectional view showing a configuration of a pressure wave generator according to an eighth embodiment of the present invention.
- FIG. 19 is a sectional view showing a configuration of a pressure wave generator according to a ninth embodiment of the present invention.
- FIG. 20 is a graph showing an example of a current density pattern at the time of anodizing treatment in the method of manufacturing a pressure wave generator according to the ninth embodiment.
- FIG. 21 is a sectional view showing a configuration of a pressure wave generator according to a tenth embodiment of the present invention.
- FIG. 22 is a graph showing an example of a current density pattern at the time of anodizing treatment in the method for manufacturing a pressure wave generator according to the tenth embodiment.
- FIG. 23A is a graph showing another example of the current density pattern at the time of the anodizing treatment in the method of manufacturing the pressure wave generator according to the tenth embodiment.
- FIG. 23B is a graph showing still another example of the current density pattern at the time of the anodic oxidation treatment in the method of manufacturing the pressure wave generator according to the tenth embodiment.
- FIG. 24 is a sectional view showing a configuration of a pressure wave generator according to an eleventh embodiment of the present invention.
- FIG. 25 is a graph showing an example of a current density pattern at the time of anodizing treatment in the method of manufacturing a pressure wave generator according to the eleventh embodiment.
- FIG. 26A is a graph showing another example of the current density pattern at the time of the anodizing treatment in the method for manufacturing the pressure wave generator according to the eleventh embodiment.
- FIG. 26B is a graph showing still another example of the current density pattern at the time of the anodic oxidation treatment in the method of manufacturing the pressure wave generator according to the eleventh embodiment.
- FIG. 27 is a sectional view showing a configuration of a pressure wave generator according to a twelfth embodiment of the present invention.
- FIG. 28 is a graph showing the output characteristics of the pressure wave generator according to the twelfth embodiment, which was prototyped using various materials.
- FIG. 29 is a graph showing the life characteristics of the pressure wave generator according to the twelfth embodiment, which was prototyped using various materials.
- FIG. 30A is a plan view showing a configuration of a pressure wave generator according to a twelfth embodiment.
- FIG. 30B is a sectional view taken along line AA in FIG. 30A.
- FIG. 30C is a sectional view taken along the line BB in FIG. 30A.
- FIG. 31A is a plan view showing a configuration of a pressure wave generator according to a thirteenth embodiment of the present invention.
- FIG. 31B is a sectional view showing the configuration of the pressure wave generator according to the thirteenth embodiment.
- FIG. 32 is a graph showing a relationship between an electric input supplied to a heating element of the pressure wave generator, a generated sound pressure, and a temperature of the heating element.
- FIG. 33A is a plan view showing a configuration of a pressure wave generator according to a fourteenth embodiment of the present invention.
- FIG. 33B is a sectional view showing the configuration of the pressure wave generator according to the fourteenth embodiment.
- FIG. 34A is a plan view showing another configuration of the pressure wave generator according to the fourteenth embodiment.
- FIG. 34B is a sectional view showing another configuration of the pressure wave generator according to the fourteenth embodiment.
- FIG. 35 is a cross-sectional view showing the configuration and operation of a conventional pressure wave generator.
- FIG. 36A is a plan view showing a configuration of a conventional pressure wave generator.
- FIG. 36B is a sectional view taken along line AA of FIG. 36A.
- FIG. 36C is an explanatory diagram showing reference points when simulating the temperature distribution on the surface including the surface of the heat insulating layer and the first surface of the semiconductor substrate by the finite element method.
- FIG. 37A is a plan view showing one step of a method for manufacturing a conventional pressure wave generator.
- FIG. 37B is a sectional view taken along line AA of FIG. 36A.
- FIG. 1A is a sectional view showing a basic configuration of the pressure wave generation device according to the first embodiment.
- a pressure wave generator includes, for example, a substrate 1 formed of a semiconductor substrate and a porous silicon layer formed on one surface (first surface) la of the substrate 1 in the thickness direction.
- a heat insulating layer 2 of a porous body and a heating element 3 of a thin film such as an aluminum thin film formed on the heat insulating layer 2 are provided.
- the pressure wave generator changes the temperature of the heating element 3 according to the waveform of the electric input to the heating element 3 and generates a pressure wave by heat exchange between the heating element 3 and a medium such as air. is there.
- the thickness distribution t of the heat insulating layer 2 in the width direction W is set as a reference, with the thickness t at the center in the width direction of the heat insulating layer 2 as the reference thickness. Averaging with thickness t As a result, the porosity D1 at the outer peripheral portion of the heat insulating layer 2 is smaller than the porosity D2 at the central portion.
- the magnitude relationship between the heat insulating layer 2 and the heating element 3 is not particularly limited. In the example shown in FIG. 1A, the heat generating element 3 is formed inside the outer periphery of the heat insulating layer 2. Further, by forming the inclined portion 2a on the outer peripheral portion of the heat insulating layer 2, the porosity of the outer peripheral portion of the heat insulating layer 2 in the width direction of the semiconductor substrate 1 is made smaller than the porosity of the central portion.
- the amount of heat dissipated along the thickness direction of the substrate is larger than the amount of heat dissipated along the thickness direction of the substrate at the central portion, and the heat dissipation of the semiconductor substrate 1 and the heat insulating layer 2 is increased.
- the mechanical strength of the heat insulating layer 2 and the heating element 3 in the vicinity of the boundary can be increased. As a result, damage to the heat insulating layer 2 and the heating element 3 due to stress can be prevented.
- the method of making the porosity D1 of the outer peripheral portion of the heat insulating layer 2 smaller than the porosity D2 of the central portion is to provide the inclined portion 2a on the outer peripheral portion of the heat insulating layer 2 as described above.
- the thickness of the heat insulating layer 2 is not limited to be smaller than the thickness of the central portion. As shown in FIG. 1B, the porosity per unit volume at the outer peripheral portion of the heat insulating layer 2 is equal to the porosity per unit volume at the central portion. It may be smaller than that.
- the physical properties of the outer peripheral portion of the heat insulating layer 2 are made non-uniform, so that the outer peripheral portion of the heat insulating layer 2 is constrained by the semiconductor substrate 1.
- the positions of the fixed points are dispersed in the area where the porosity per unit volume is changed.
- the compressive stress which is concentrated at a portion (point P1) of the outer periphery of the heat insulating layer 2 which is in contact with the surface la of the semiconductor substrate 1, is reduced by the outer peripheral surface of the heat insulating layer 2 (point P1).
- they can be dispersed along a porosity slope.
- the amount of heat dissipated along the thickness direction of the semiconductor substrate 1 becomes larger than the amount of heat dissipated along the thickness direction of the semiconductor substrate 1 at the center portion, and the semiconductor substrate 1
- the mechanical strength of the heat insulating layer 2 and the heating element 3 in the vicinity of the boundary between 1 and the heat insulating layer 2 can be increased. Further, a combination with the characteristic of FIG. 1A that the thickness at the outer peripheral portion of the heat insulating layer 2 is smaller than the thickness at the central portion is also possible.
- the volume of the heat insulating layer 2 expands due to chemical changes such as oxidation of the heat insulating layer 2 and compressive stress is generated.
- the compressive stress can be dispersed by the portion of the outer peripheral portion of the heat insulating layer 2 where the porosity is small. That is, by reducing the porosity of the outer peripheral portion of the heat insulating layer 2, for example, the fixed point of the outer peripheral portion of the heat insulating layer 2, which is fixed to the semiconductor substrate 1, is smaller than that of the conventional pressure wave generator.
- the positions are dispersed, so that the compressive stress concentrated on the outer peripheral portion of the heat insulating layer 2 can be dispersed.
- the possibility of cracks occurring in the heat insulating layer 2 can be reduced, and damage to the heating element due to cracks in the heat insulating layer can be prevented.
- damage to the pressure wave generator can be prevented, and stable ultrasonic waves can be generated for a long period of time.
- FIG. 2A is a plan view of a pressure wave generator according to a second embodiment
- FIG. 2B is a cross-sectional view taken along line AA in FIG. 2A.
- the pressure wave generator includes a semiconductor substrate (substrate) 1 of a single-crystal p-type silicon substrate and one surface of the semiconductor substrate 1 in the thickness direction (first surface).
- the planar shape of the semiconductor substrate 1 is rectangular (for example, rectangular), and the planar shapes of the heat insulating layer 2 and the heating element 3 are also rectangular (for example, rectangular). .
- the heating element 3 is set to have a long side of 12 mm and a short side of 10 mm.
- the thickness of the semiconductor substrate 1 is set to 525 m
- the thickness of the heat insulating layer 2 is set to 1 O ⁇ m
- the thickness of the heating element 3 is set to 50 nm. Note that these dimensions are not particularly limited.
- the heat insulating layer 2 generates heat in the width direction orthogonal to the thickness direction of the semiconductor substrate 1 (including both the long side direction and the short side direction of the rectangle). Except for a portion facing the outer peripheral portion of the body 3, it is formed to have a substantially uniform thickness so as to reach a predetermined depth.
- an inclined portion 2a is formed so that the thickness of the heat insulating layer 2 becomes gradually smaller toward the outside. That is, also in the second embodiment, it is assumed that the thickness distribution of the heat insulating layer 2 in the width direction is averaged by the reference thickness, with the thickness of the central portion in the width direction of the heat insulating layer 2 being the reference thickness.
- the porosity at the outer peripheral portion of the heat insulating layer 2 is smaller than the porosity at the central portion by the inclined portion 2a.
- an electric input for example, an alternating current
- a pressure wave for example, ultrasonic wave
- a medium for example, air
- the porous silicon layer constituting the heat insulating layer 2 is formed by subjecting a part of a p-type silicon substrate as the semiconductor substrate 1 to anodizing treatment in an electrolytic solution, as described in a manufacturing method described later. It is formed.
- the porosity of the heat insulating layer 2 can be changed by appropriately changing the conditions of the anodic oxidation treatment.
- the thermal conductivity and the heat capacity of the porous silicon layer decrease as the porosity increases. Therefore, by appropriately setting the porosity, the thermal conductivity of the porous silicon layer can be made sufficiently smaller than that of single crystal silicon.
- the thermal conductivity of the heat insulating layer 2 immediately below the heating element 3 is oc
- the volume heat capacity is C
- the angular frequency of the sinusoidal AC voltage applied to the heating element 3 is ⁇
- the temperature of the heating element 3 is ⁇ ( ⁇ ) (where ⁇ is a function of ⁇ )
- the surface force of the heat insulating layer 2 in the thickness direction of the semiconductor substrate 1 and the distance (depth) are lZe times the temperature of the surface of the heat insulating layer 2 (e Is the distance that is the base of natural logarithm) Is defined as the thermal diffusion length L, which is expressed by the following equation 2.
- the thickness of the thermal insulating layer 2 is preferably about 0.5 to 3 times the thermal diffusion length L.
- An inclined portion 2a is formed.
- the surface of the heat insulating layer 2 near the outer periphery of the heating element 3 (when electric energy is applied) when the heating element 3 is energized (when electric energy is applied) (between the heat insulating layer 2 and the heating element 3).
- the temperature distribution of the plane including the boundary) and the first surface la of the semiconductor substrate 1 was simulated by the finite element method. The result is shown as curve A in FIG.
- Curve B in FIG. 8 shows the result of a similar simulation performed on the conventional example shown in FIG.
- Curves A and B in Fig. 8 correspond to the heat insulating layer 2 and the outer periphery of the heating element 3 in a cross section in the short side direction (A-A section) of the heating element 3 as shown in Figs. 2C and 36C, respectively.
- the contact point of origin as the origin O
- the direction away from the thermal insulation layer 2 as the positive direction of the X-axis
- a simulation of the temperature distribution of the plane including the first surface la of the semiconductor substrate 1 was performed. This is the result.
- the pressure wave generator of the second embodiment and the conventional pressure wave generator In any of the arrangements, there is a temperature gradient (one dTZdx) along the X-axis direction, but the pressure wave generator of the second embodiment has a gentler temperature gradient than the conventional pressure wave generator. Has become. The reason is that the inclined surface 2a is formed so that the thickness of the heat insulating layer 2 becomes thinner toward the outside in the portion facing the outer periphery of the heating element 3 of the pressure wave generator of the second embodiment. This is because the amount of heat radiated along the thickness direction of the semiconductor substrate 1 is larger than that of the central portion of the heating element 3.
- the semiconductor substrate 1 extends from one surface (first surface) la in the thickness direction D to the inside of the semiconductor substrate 1.
- the average thermal conductivity in the thickness direction of the portion inside the outer periphery 3e of the heating element 3 is defined as a in
- the average volumetric heat capacity is Cin
- the average thermal conductivity in the thickness direction outside the outer periphery of the heating element is aout
- the average volumetric heat capacity is Cout
- the condition of ain X Cin ⁇ aout X Cout In the vicinity of the boundary between the inner part and the outer part, the value of a in X Cin becomes larger toward the outside.
- the amount of heat radiated along the thickness direction of the semiconductor substrate 1 at the outer peripheral portion of the heating element 3 is increased at the central portion of the heating element 3.
- the amount of heat generated is larger than the amount of heat generated, so that the heat stress applied to the heating element 3 can be reduced as compared with the conventional pressure wave generator, and the heating element 3 can be damaged due to the thermal stress.
- the life of the wave generator can be extended.
- the boundary of the region where the value of a in X Cin changes (that is, the outer peripheral end of the inclined portion 2a) is defined as the outer periphery of the heating element 3. Since the properties are almost the same, the properties of the porous silicon layer forming the heat insulation layer 2 are maintained while the properties of the outer circumference and the properties of the center of the heat insulation layer 2 are almost the same. While maintaining the uniformity, the vibration of the pressure wave, which does not increase the amount of heat radiated from the outer peripheral portion of the heating element 3 to the semiconductor substrate 1 too much. A decrease in width can be suppressed.
- a current-carrying electrode 4 having a rectangular planar shape used for anodizing is provided on the other surface (second surface) lb in the thickness direction of the semiconductor substrate 1 of the p-type silicon substrate.
- the center of the current-carrying electrode 4 is located in a region parallel to the first surface la of the semiconductor substrate 1 where the rectangular heating element 3 is to be formed (heating element formation area). ) It almost coincides with the center of 3a.
- the length of each side of the current-carrying electrode 4 is set to be shorter than the length of each corresponding side of the heating element forming region 3a by a predetermined reduced dimension.
- a conductive layer is formed on the second surface lb of the semiconductor substrate 1 by a sputtering method and a vapor deposition method, and the photolithography technique and the etching technique are used. Unnecessary portions other than the portion used for the current-carrying electrode 4 in the conductive layer may be removed.
- the long side of the heating element forming region 3a is 12 mm
- the short side is 10 mm
- the reduced dimension is set to 1 mm. That is, the length of the current-carrying electrode 4 smaller than the heating element formation region 3a is set to l lmm, and the short side is set to 9 mm.
- these numerical values are not particularly limited.
- one end of an energizing lead wire (not shown) is attached to the energizing electrode 4, and the mounting portion of the energizing electrode 4 and one end of the lead wire is anodized. It is covered with a hydrofluoric acid-resistant sealing material so as not to come in contact with the electrolytic solution used for the treatment.
- a heat insulating layer 2 made of a porous silicon layer as shown in FIG. 5B is formed on the semiconductor substrate 1.
- a heating element forming step on the heating element forming region 3a on the first surface la of the semiconductor substrate 1 a structure having the heating element 3 as shown in FIG. 5C is obtained.
- the heat insulating layer 2 is formed by anodizing.
- an object to be processed 24 having the semiconductor substrate 1 as a main component is immersed in an electrolytic solution 23 in a processing tank 22.
- the platinum electrode 21 is disposed in the electrolytic solution 23 so as to face the first surface la of the semiconductor substrate 1.
- the lead wire attached to the current-carrying electrode 4 is The gold electrode 21 is connected to the negative side of the current source 20 respectively.
- a current having a predetermined current density (for example, 20 mAZcm 2 ) is applied between the current supply electrode 4 and the platinum electrode 21 from the current source 20 by using the current supply electrode 4 as a positive electrode and the platinum electrode 21 as a cathode. Allow only time (eg, 8 minutes) to drain.
- a predetermined current density for example, 20 mAZcm 2
- the heat insulating layer 2 having a substantially constant thickness (for example, 10 m) except for the outer peripheral portion is formed on the first surface la side of the semiconductor substrate 1.
- the conditions at the time of the anodic oxidation treatment is not particularly limited, the current density, for example, may be appropriately set within a range of about l ⁇ 500m AZcm 2. Also, the predetermined energizing time may be appropriately set according to the thickness of the thermal insulation layer 2!
- the electrolytic solution used in the anodizing treatment for example, a mixed solution obtained by mixing a 55 wt% aqueous solution of hydrogen fluoride and ethanol in a ratio of 1: 1 is used.
- a sealing material made of fluorine resin such as Teflon (registered trademark) can be used.
- a metal thin film for example, an A1 thin film
- a photoresist is applied on the metal thin film, and a resist layer (not shown) patterned to form the heating element 3 is formed by a photolithography technique.
- unnecessary portions of the metal thin film are removed by a dry etching process, whereby the heating element 3 is formed.
- FIG. 5C is obtained by removing the resist layer.
- the size of the current-carrying electrode 4 is slightly smaller than the size of the heat insulating layer 2 to be formed as described above, and the size of the platinum electrode 21 is larger than the size of the heat insulating layer 2.
- the height is also increased, the direction of the electric field becomes oblique at the outer peripheral portion of the heat insulating layer 2 to be formed, and the electric field strength becomes weaker toward the outer side. Therefore, if the anodic oxidation treatment is performed under such conditions, the current flowing through the oxide film formed on the first surface la side of the semiconductor substrate 1, that is, the outer peripheral portion of the heat insulating layer 2 is reduced, and It is formed thin. Accordingly, as shown in FIG.
- an inclined portion 2a is formed on the outer peripheral portion of the heat insulating layer 2 formed on the first surface la side of the semiconductor substrate 1 so that the thickness becomes gradually smaller toward the outer side.
- the heating element is shaped according to the slope 2a. If it is formed, the thermal stress applied to the heating element 3 can be reduced as compared with the conventional pressure wave generator, and the heating element 3 may be damaged due to the thermal stress.
- the outer peripheral portion of the heat insulating layer 2 includes the first surface la including the first surface la of the semiconductor substrate 1.
- the boundary between the heat insulating layer 2 and the semiconductor substrate 1 is increased so that the distance d in the width direction of the second reference plane force including the end face (outer periphery) 3e of the heating element 3 increases. It turns out that it is inclined. Specifically, it was confirmed that at a position at a depth of 10 ⁇ m from the first reference plane, the distance of the heating element 3 from the second reference plane was approximately 0.5 mm.
- the outer circumference of the inclined portion 2a of the heat insulating layer 2 is made to substantially match the outer circumference of the heating element 3, or It can be located inside the outer circumference of body 3.
- the heat insulation when the length of each side of the current-carrying electrode 4 is shorter than each side of the heating element forming region 3a by lmm (when the reduced dimension is lmm), the heat insulation The outer periphery of the inclined portion 2a of the layer 2 substantially coincides with the outer periphery of the heating element 3.
- the heat insulating layer 2 It is formed inside the outer circumference.
- the projected area of the heat insulating layer 2 onto the heating element 3 is located inside the outer circumference of the heating element 3, so that the outer periphery of the heating element 3 is directly on the first surface la of the semiconductor substrate 1. Touch
- the thickness of the outer peripheral portion of the heat insulating layer 2 is changed to the thickness of the central portion (as described above). (Reference thickness).
- the thermal conductivity and the volumetric heat capacity of single-crystal silicon, which is the material of the semiconductor substrate 1 are aout and Cout, respectively
- the thermal conductivity of the porous silicon which is the material of the thermal insulating layer 2
- the rate and the volumetric heat capacity are ain and Cin, respectively, the magnitude relationship between the product of the thermal conductivity and the heat capacity satisfies the condition of ⁇ inXCin and ⁇ outXCout.
- the boundary of the region where the value of ⁇ in X Cin changes within the range of the reference thickness is located inside the outer periphery of the heating element 3, the temperature gradient at the outer periphery of the heating element 3 is further reduced. It can be moderated, and the thermal stress on the heating element 3 is further reduced compared to the conventional pressure wave generator. can do.
- the heat insulating layer 2 can be formed in the same manner as described above.
- a mask layer 5 may be provided on the first surface la of the semiconductor substrate 1 to define a region where the heat insulating layer 2 is formed.
- a single-crystal p-type silicon substrate is used as the semiconductor substrate 1.
- the semiconductor substrate 1 is not limited to a single-crystal p-type silicon substrate, but may be a polycrystalline or amorphous silicon substrate.
- a p-type silicon substrate may be used.
- the semiconductor substrate 1 is not limited to a p-type substrate, but may be an n-type substrate or a non-doped substrate. Then, the conditions of the anodizing process may be appropriately changed according to the type of the semiconductor substrate 1. Therefore, the porous body constituting the heat insulating layer 2 is not limited to the porous silicon layer. It may be a quality semiconductor layer.
- the material of the heating element 3 is not limited to A1.
- a metal material having higher heat resistance than A1 for example, W, Mo, Pt, Ir, etc.
- the basic configuration of the pressure wave generator of the third embodiment is the same as that of the above-described second embodiment, and differs only in that a single crystal n-type silicon substrate is used as the semiconductor substrate 1. Therefore, the illustration and description of the structure of the pressure wave generator are omitted, and only the manufacturing method will be described with reference to FIGS. 10A to 10C.
- a current-carrying electrode 4 used during anodic oxidation is formed on the entire second surface lb in the thickness direction of the semiconductor substrate 1 having the n-type silicon substrate strength.
- a conductive layer may be formed on the second surface lb of the semiconductor substrate 1 by, for example, a sputtering method or an evaporation method.
- an energizing lead wire (not shown) is attached to the energizing electrode 4, and an attachment portion between the energizing electrode 4 and one end of the lead wire is anodized. It is covered with a hydrofluoric acid-resistant sealing material so as not to come in contact with the electrolytic solution used for the treatment.
- anodizing treatment is performed using an anodizing apparatus as shown in FIG.
- a heat insulating layer 2 made of a porous silicon layer as shown is formed on a semiconductor substrate 1.
- a structure having the heating element 3 as shown in FIG. 10C is obtained.
- the heat insulating layer 2 is formed by the anodic oxidation treatment.
- an object 24 mainly composed of the semiconductor substrate 1 is immersed in an electrolytic solution 23 in a processing tank 22.
- a light shielding plate 30 made of a material having resistance to the electrolytic solution 23 is arranged so as to face the first surface la of the semiconductor substrate 1, and further, the light shielding plate 30 and The platinum electrode 21 is arranged so as to face the first surface la of the semiconductor substrate 1.
- the lead wire attached to the current-carrying electrode 4 is connected to the positive side of the current source 20, and the platinum electrode 21 is connected to the negative side of the current source 20, respectively.
- a current source 20 is used while the current-carrying electrode 4 is used as an anode and the platinum electrode 21 is used as a cathode.
- a current having a predetermined current density flows between the current-carrying electrode 4 and the platinum electrode 21 for a predetermined current-carrying time (for example, 8 minutes).
- the heat insulating layer 2 having a substantially constant thickness (for example, 10 m) except for the outer peripheral portion is formed on the first surface la side of the semiconductor substrate 1.
- the conditions at the time of the anodic oxidation treatment is not particularly limited, the current density, for example, may be appropriately set within a range of about 1 ⁇ 500 mAZcm 2.
- the predetermined energization time may be appropriately set according to the thickness of the heat insulating layer 2!
- the electrolytic solution used in the anodizing process for example, a mixed solution obtained by mixing a 55 wt% aqueous solution of hydrogen fluoride and ethanol in a ratio of 1: 1 is used.
- a sealing material for example, a sealing material made of fluorine resin such as Teflon (registered trademark) can be used.
- the light shielding plate 30 is formed in a planar shape as shown in FIG. 11B from a material (for example, silicon or the like) having resistance to the electrolytic solution 23. Specifically, in the semiconductor substrate 1 of the light shielding plate 30, the center of the region where the thermal insulating layer 2 is to be formed (the thermal insulating layer forming region) The opening ratio of the portion 32 corresponding to the outer portion of the heat insulating layer 2 is set to 0%, and the opening ratio of the portion 33 facing the outer peripheral portion of the heat insulating layer 2 is set to the inner side. From outside to outside.
- the step of forming the heating element 3 is the same as that of the second embodiment, and a metal thin film (for example, an A1 thin film) for the heating element 3 is sputtered on the first surface la of the semiconductor substrate 1. It is formed by a method. Thereafter, a photoresist is applied on the metal thin film, and a resist layer (not shown) patterned for forming the heating element 3 is formed by a photolithography technique. Then, using the resist layer as a mask, unnecessary portions of the metal thin film are removed by a dry etching process, whereby the heating element 3 is formed. Finally, the structure shown in FIG. 1OC is obtained by removing the resist layer.
- the light shielding plate 30 is used to form the heat insulating layer on the first surface la of the semiconductor substrate 1.
- the anodic oxidation treatment is performed while irradiating light such that the intensity of light applied to the outer peripheral portion of the layer forming region is smaller than the intensity of light applied to the central portion and becomes weaker toward the outer side. For this reason, the speed of the porous ridge at the outer peripheral portion of the heat insulating layer forming region on the first surface la of the semiconductor substrate 1 is lower than the speed of the porous ridge at the central portion.
- the inclined portion 2a is formed on the outer peripheral portion of the heat insulating layer 2 formed on the first surface la side of the semiconductor substrate 1 so that the thickness becomes gradually smaller toward the outer side.
- the thermal stress applied to the heat generating element 3 can be reduced as compared with the conventional pressure wave generator, and the heat generating element 3 is less likely to be damaged due to the thermal stress.
- the basic configuration of the pressure wave generator according to the fourth embodiment is almost the same as that of the second embodiment, but as shown in FIG.
- the difference is that the thermal insulation layer 2 is configured so that the porosity of the porous silicon layer gradually increases from the center toward the periphery. Note that the same components as those in the second embodiment are denoted by the same reference numerals, and description thereof is omitted.
- the outer periphery of the heat insulating layer 2 and the outer periphery of the heating element 3 are almost (I.e., the boundary of the area where the value of a in X Cin changes within the above reference thickness range coincides with the outer periphery of the heating element 3), and the thickness of the heat insulating layer 2 is set at the center and the outer periphery.
- the product of the average thermal conductivity and the average heat capacity at the outer peripheral portion of the heat insulating layer 2 is set to be larger than the product of the average thermal conductivity and the average volume heat capacity at the central portion, while setting the values substantially the same in the central portion. . That is, the physical properties of the heat insulating layer 2 are made non-uniform so that the porosity per unit volume at the outer peripheral portion of the heat insulating layer 2 is smaller than the porosity per unit volume at the central portion. .
- the amount of heat radiated from the outer peripheral portion of the heating element 3 along the thickness direction of the semiconductor substrate 1 can be increased.
- the force can be reduced.
- a predetermined thickness for example, 2 ⁇
- a thermal insulating layer 2 is to be formed (a thermal insulating layer forming region) on a first surface la of a semiconductor substrate 1 of a p-type silicon substrate.
- An impurity doping region 11 of ⁇ is formed by doping using an ion implantation method, a thermal diffusion method, etc.
- the specific resistance at the outer peripheral portion is smaller than the specific resistance at the central portion (the second region).
- the resistivity is reduced from the central portion toward the outer peripheral portion.
- the impurity concentration distribution is formed.
- the long side in the plane size of the heating element 3 is set to 12 mm and the short side is set to 10 mm, the specific resistance at the center of the impurity doping region 11 is approximately 30 ⁇ 'cm, and the specific resistance at the outer periphery is approximately 2 ⁇ ' cm is set. Further, doping is performed so that the specific resistance gradually changes between the central portion and the outer peripheral portion. Note that these numerical values are merely examples and are not particularly limited.
- a silicon nitride film for forming a mask at the time of anodic oxidation is formed on the entire first surface la of the semiconductor substrate 1 by a plasma CVD method or the like, and photolithography technology and etching technology are used. Then, a portion of the silicon nitride film that overlaps the heat insulating layer formation region is opened. As a result, as shown in FIG. 13B, the remaining silicon nitride film is formed on the first surface la of the semiconductor substrate 1. A mask layer 5 is formed.
- a current-carrying electrode 4 used during anodic oxidation is formed on the entire second surface lb of the semiconductor substrate 1 of a p-type silicon substrate.
- a conductive layer may be formed on the second surface lb of the semiconductor substrate 1 by, for example, a sputtering method or an evaporation method.
- one end of an energizing lead wire (not shown) is attached to the energizing electrode 4, and the mounting portion of the energizing electrode 4 and one end of the lead wire is anodized. It is covered with a hydrofluoric acid-resistant sealing material so as not to come in contact with the electrolytic solution used for the treatment.
- the heat insulating layer 2 of a porous silicon layer having different porosity in the central part and the outer peripheral part is formed.
- the structure shown in FIG. 13D is obtained by removing the mask layer 5.
- a heating element forming step on the heating element forming region 3a on the first surface la of the semiconductor substrate 1
- a structure having the heating element 3 as shown in FIG. 13E is obtained.
- the anodic oxidation treatment using the anodic oxidation treatment apparatus as shown in Fig. 7 is basically the same as in the case of the second embodiment.
- a current source 20 also applies a current of a predetermined current density (for example, 20 mA / cm 2 ) between the current-carrying electrode 4 and the platinum electrode 21 for a predetermined time (for example, By flowing for two minutes, the heat insulating layer 2 having a predetermined thickness (for example, 2.5 m) is formed on the first surface la side of the semiconductor substrate 1.
- the porosity at the center of the heat insulating layer 2 is approximately 60%, and the porosity at the outer periphery is approximately 0%.
- the conditions at the time of the anodic oxidation treatment is not particularly limited, the current density, for example, may be appropriately set within a range of about 1 ⁇ 500 mAZcm 2.
- the predetermined energization time may be appropriately set according to the thickness of the heat insulating layer 2!
- the electrolytic solution used for the anodizing treatment for example, a mixed solution obtained by mixing a 55 wt% aqueous solution of hydrogen fluoride and ethanol in a ratio of 1: 1 is used.
- a sealing material made of fluorine resin such as Teflon (registered trademark) can be used.
- the step of forming the heating element 3 is the same as that of the second embodiment, and a metal thin film (for example, an A1 thin film) for the heating element 3 is sputtered on the first surface la of the semiconductor substrate 1. It is formed by a method. After that, apply a photoresist on the metal thin film and use photolithography technology To form a resist layer (not shown) patterned for forming the heating element 3. Then, using the resist layer as a mask, unnecessary portions of the metal thin film are removed by a dry etching process, whereby the heating element 3 is formed. Finally, by removing the resist layer, the structure shown in FIG. 13E is obtained.
- a metal thin film for example, an A1 thin film
- the thickness of the heat insulating layer 2 formed on the semiconductor substrate 1 is made substantially uniform while the center of the heat insulating layer 2 in the width direction is formed.
- the porosity of the outer peripheral portion can be made lower than the porosity. That is, the product of the average thermal conductivity and the average volume heat capacity at the outer peripheral portion of the thermal insulating layer 2 is larger than the product of the average thermal conductivity and the average volume heat capacity at the central portion, and therefore, compared to the conventional pressure wave generator. As a result, the thermal stress applied to the heating element 3 can be reduced, and the heating element may be damaged due to the thermal stress.
- the thermal insulating layer 2 is arranged such that the thermal expansion coefficient at the boundary between the outer peripheral portion of the thermal insulating layer 2 and the portion of the semiconductor substrate 1 outside the thermal insulating layer 2 matches each other. If formed, discontinuous portions of the coefficient of thermal expansion will be eliminated.
- the planar shape of the current-carrying electrode 4 is formed in a shape that matches the heating element forming region 3a on the first surface la of the semiconductor substrate 1, the shape of the semiconductor substrate 1
- the heat insulating layer 2 made of a porous silicon layer can be formed.
- the pressure wave generator of the fifth embodiment includes a semiconductor substrate 1 of a single-crystal p-type silicon substrate and one surface (first surface) la of the semiconductor substrate 1 in the thickness direction.
- the heat insulating layer 2 is not limited to the porous silicon layer, but may be composed of, for example, a SiO film or a SiN film.
- the pressure wave generator according to the fifth embodiment has the heat insulating layer 2 formed on almost the entire surface of the semiconductor substrate 1.
- a temperature gradient reducing portion 15 is formed on the first surface la (the surface 2c of the heat insulating layer 2) of the semiconductor substrate 1 so as to be in contact with the end surfaces 3e of both outer peripheral portions on the long side of the heating element 3. The points are different.
- the temperature gradient relaxing section 15 is a high thermal conductive layer formed of a material having higher thermal conductivity than the thermal insulating layer 2.
- a material of the temperature gradient mitigation part 15 an inorganic material having a higher electric insulation property than the heating element 3 and a higher heat conductivity than the heat insulating layer 2 (for example, an A1N material or a SiC material, etc.) It is also desirable that A1N and SiC have a small difference in thermal expansion coefficient from Si.
- the temperature gradient relieving portion 15 made of these inorganic materials can be formed at a predetermined place by using a mask by a sputtering method.
- the temperature gradient reducing section 15 is formed on the heat insulating layer 2 and is in contact with both long side outer peripheral surfaces of the outer peripheral surface of the heating element 3, but the surface 3 c of the heating element 3 (see FIG. 15B) It is formed so as not to touch.
- the pressure wave generator of the fifth embodiment part of the heat generated at the outer periphery of the long side of the heating element 3 is transmitted to the temperature gradient relieving section 15, so that the long side of the heating element 3
- the temperature gradient in the outer peripheral portion that is, the temperature gradient near the surface of the heat insulating layer 2 is reduced.
- the thermal stress applied to the heating element 3 can be reduced as compared with the conventional pressure wave generator, and the heating element 3 is ruptured due to the thermal stress.
- the life of the pressure wave generating device can be extended, and when power is supplied to the heating element 3, the power can be increased as compared with the conventional device, and the amplitude of the generated pressure wave can be reduced. It is possible to increase.
- the temperature gradient relieving portion 15 is formed so as to be in contact with the end face 3e of the outer peripheral portion on the long side of the heating element 3 and not to be in contact with the surface 3c near the outer peripheral portion.
- the temperature gradient in the vicinity of the outer peripheral portion of the body 3 can be reduced while reducing the temperature drop.
- the heat resistance of the temperature gradient relieving section 15 can be increased as compared with the case where an organic material is used.
- the resistance of the temperature gradient reducing section 15 is sufficiently larger than the resistance of the heating element 3, and (the current flowing to the temperature gradient reducing section 15 is large enough to be ignored. ,) So warm It is possible to reduce power loss due to current flowing to the degree gradient mitigation unit 15.
- the heat insulating layer 2 is formed not in the entire surface of the semiconductor substrate 1 but in a predetermined region.
- the temperature gradient reducing portion 15 is in contact with not only the first surface la of the semiconductor substrate 1 but also the surface 2c of the heat insulating layer 2, the end surface 3e of the outer peripheral portion of the heating element 3 and the surface 3c near the outer peripheral portion. It is formed as!
- the temperature gradient relieving section 15 is in contact with not only the end face 3e but also the front face 3c on the outer peripheral portion of the heating element 3, so that the pressure wave generation section of the fifth embodiment described above.
- the structure is slightly more complicated than that of the generator, the temperature gradient around the heating element 3 can be further reduced.
- the temperature gradient mitigation unit 15 comes into contact with the semiconductor substrate 1! In comparison with the above, the heat generated in the peripheral portion of the heating element 3 can be efficiently released.
- the heat insulating layer 2 is formed only in a predetermined area on the first surface 1a side of the semiconductor substrate 1. Similarly, the heat insulating layer 2 may be formed on the entire first surface la side of the semiconductor substrate 1.
- a seventh embodiment of the present invention will be described.
- the thickness force of the temperature gradient relaxation portion 15 in the thickness direction of the semiconductor substrate 1 The difference is that the substrate 1 becomes thinner toward the inside of the heating element 3 from the outer periphery in the width direction.
- Such a temperature gradient mitigation portion 15 can be formed by, for example, providing a space between the semiconductor substrate 1 and the mask and performing film formation by a sputtering method.
- the shape of the temperature gradient mitigation unit 15 is more complicated than that of the pressure wave generator of the sixth embodiment, and there is a possibility that the production yield may decrease.
- the temperature gradient at the outer peripheral portion of the heating element 3 can be further reduced.
- a heat insulating layer 2 is formed on the entire surface of the semiconductor substrate 1 on the first surface la side. May be.
- the pressure wave generator according to the eighth embodiment in the width direction of the semiconductor substrate 1 in which the physical properties of the temperature gradient mitigation unit 15 are not uniform, the force from the inside of the heating element 3 toward the outer peripheral part increases. It is formed so as to have a distribution that increases the thermal conductivity.
- Other configurations are the same as those in the sixth embodiment.
- the temperature gradient reducing section 15 having such a distribution of thermal conductivity can be realized by, for example, inclining the composition ratio of A1N or SiC in a high thermal conductive layer made of A1N or SiC.
- the manufacturing process of the temperature gradient mitigation unit 15 is more complicated than that of the pressure wave generator of the sixth embodiment, The temperature gradient can be further reduced. Further, as in the case of the fifth embodiment, the heat insulating layer 2 may be formed on the entire surface of the semiconductor substrate 1 on the first surface la side.
- the pressure wave generator of the ninth embodiment is formed on a semiconductor substrate 1 of a single-crystal p-type silicon substrate and on one surface (first surface) la side of the semiconductor substrate 1 in the thickness direction.
- a pair of formed nodes 14 is used to energize the heating element 3.
- the heat insulating layer 2 is formed of two layers, the high porosity layer 26 and the low porosity layer 27.
- the high porosity layer 26 having a high porosity is formed of, for example, a porous silicon layer having a porosity of 70%, and is located on the heating element 3 side.
- the low porosity layer 27 having a low porosity is formed of, for example, a porous silicon layer having a porosity of 40%, and is located on the semiconductor substrate 1 side.
- porous layers can be formed by anodizing a part of a p-type silicon substrate as the semiconductor substrate 1 in an electrolytic solution. Since the thermal conductivity and volumetric heat capacity of the porous silicon layer decrease as the porosity increases, the porosity should be set appropriately. Thereby, the thermal conductivity can be made sufficiently smaller than that of single crystal silicon.
- the thickness of the semiconductor substrate 1 is 525 ⁇ m
- the thickness of the high porosity layer 26 of the heat insulating layer 2 is 5 ⁇ m
- the thickness of the heat insulating layer 2 is low.
- the thickness of the thermal layer 27 is 5 m
- the thickness of the heat generator 3 is 50 nm. Note that these thicknesses are merely examples, and are not particularly limited.
- the thickness of the high porosity layer 26 is desirably set to a value equal to or longer than the thermal diffusion length L.
- a current-carrying electrode (not shown) used for anodizing is formed on the second surface lb of the semiconductor substrate 1. After that, the area where the high porosity layer 26 is to be formed and the area where the low porosity layer 27 is to be formed on the first surface la side of the semiconductor substrate 1 are made porous by anodizing treatment, and the high porosity layer 26 and the low A heat insulating layer with the porosity layer 27 is formed.
- An object to be processed mainly composed of the semiconductor substrate 1 is immersed in an electrolytic solution in a processing tank, and the power supply electrode is used as an anode, and a platinum electrode arranged opposite to the first surface la of the semiconductor substrate 1 as a cathode is used as a power supply.
- a current having a predetermined current density flows between the anode and the cathode.
- an anodic oxidation treatment is performed at a first current, for example, 10 OmAZcm 2 ) for a first predetermined time T1 (for example, 2 minutes), and a low porosity layer is formed.
- an anodic oxidation treatment is performed for a second predetermined time T2 (for example, 15 minutes) with a second current 3 ⁇ 42 (for example, 10 mAZcm 2 ).
- a second current 3 ⁇ 42 for example, 10 mAZcm 2
- the object to be treated is taken out of the electrolytic solution, washed and dried sequentially, and then the heating element 3 is formed, and the pad 14 is further formed.
- the pressure wave generator shown in FIG. 19 is completed.
- various drying methods such as drying with nitrogen gas and drying with a centrifugal dryer may be appropriately adopted.
- the heating element forming step the heating element 3 may be formed by a vapor deposition method using a metal mask or the like. Even in the nod forming step, the pad 14 may be formed by a vapor deposition method using a metal mask or the like.
- stress generated in the vicinity of the boundary with the semiconductor substrate 1 in the heat insulating layer 2 can be reduced, and cracks in the heat insulating layer 2 and breakage of the heating element 3 during manufacturing and driving can be reduced. Can be prevented. Further, separation of the heat insulating layer 2 from the semiconductor substrate 1 can be prevented. As a result, it is possible to improve the yield and reliability during manufacturing.
- the heat insulating layer 2 includes the high porosity layer 26 located on the heating element 3 side and the low porosity layer 27 located on the semiconductor substrate 1 side. Therefore, the thermal insulation performance of the thermal insulation layer 2 can be determined by the porosity and thickness of the high porosity layer 26.
- the mechanical strength of the portion of the heat insulating layer 2 on the semiconductor substrate 1 side can be designed based on the porosity and thickness of the low porosity layer 27, so that the heat insulating layer 2 itself has two layers.
- the design of the thermal insulation performance of the thermal insulation layer 2 is facilitated, and the formation of the thermal insulation layer 2 is relatively easy.
- the manufacturing is performed without lowering the thermal insulation performance than when the porosity of the thermal insulation layer 2 is made uniform in the thickness direction of the semiconductor substrate 1. Also, the mechanical strength during driving can be increased. In addition, compared to conventional pressure wave generators, Since the heat property is improved, it is possible to increase the amplitude of the pressure wave by increasing the electric power applied to the heating element 3 during energization.
- the pressure wave generator of the tenth embodiment has the same configuration as that of the pressure wave generator of the ninth embodiment.
- the heat insulating layer 2 generates heat in the thickness direction of the semiconductor substrate 1. It is composed of a high porosity layer 26 formed on the body 3 side and a low porosity gradient layer 28 formed on the semiconductor substrate 1 side and having a porosity that continuously decreases as approaching the semiconductor substrate 1. Different.
- the porosity depth profile of the low porosity gradient layer 28 is set so that the porosity is continuous at the boundary with the high porosity layer 26 and becomes zero near the boundary with the semiconductor substrate 1. Te ru.
- the method for manufacturing the pressure wave generator according to the tenth embodiment is substantially the same as the method for manufacturing the pressure wave generator according to the ninth embodiment.
- an anodic oxidation treatment is performed at a first current density 1 (for example, 100 mAZcm 2 ) for a first predetermined time T1 (for example, 2 minutes).
- T1 for example, 100 mAZcm 2
- T3 for example, 10 minutes
- An oxidation treatment is performed.
- the current density is changed from the first current density 1 to the second current density 3 (for example, OmA / cm 2 ) during the second predetermined time ⁇ 3.
- a monotonous decreasing pattern is set to decrease continuously to the maximum. Note that the current density decreasing pattern is not limited to a monotonous decreasing pattern with a constant slope as shown in FIG. 22, but, for example, as shown in FIG. A pattern may be used, or a monotonically decreasing pattern in which the slope becomes smaller with time as shown in FIG. 23B may be used.
- the porosity is continuous at the boundary between the high porosity layer 26 and the low porosity gradient layer 28 of the heat insulating layer 2 in the thickness direction of the semiconductor substrate 1. Therefore, although the current density control when forming the low porosity layer is complicated, the porosity of the heat insulating layer 2 changes stepwise as in the pressure wave generator of the ninth embodiment. As compared with the case, the stress generated near the boundary between the high porosity layer 26 and the low porosity gradient layer 28 can be dispersed and reduced, and the mechanical strength of the heat insulating layer 2 can be increased.
- the low porosity gradient layer 28 is formed so that the porosity becomes zero near the boundary with the semiconductor substrate 1, the mechanical strength of the heat insulating layer 2 near the boundary with the semiconductor substrate 1 is reduced. In addition to increasing the stress, the stress generated near the boundary can be further reduced. Therefore, cracks in the heat insulating layer 2 during manufacturing and driving, breakage of the heating element 3 due to the cracks in the heat insulating layer 2 and peeling of the heat insulating layer 2 from the semiconductor substrate 1 are more reliably performed. Can be prevented.
- the pressure wave generating device of the eleventh embodiment has the same configuration as the pressure wave generating device of the ninth embodiment.
- the porosity is formed so as to decrease continuously as it approaches the semiconductor substrate 1 side from the heating element 3 side. That is, in the thickness direction of the semiconductor substrate 1, in the heat insulating layer 2, the porosity is higher in the region closer to the heating element 3, and the porosity is lower in the region closer to the semiconductor substrate 1.
- the porosity depth file is set so that the porosity of the heat insulating layer 2 becomes zero near the boundary with the semiconductor substrate 1.
- the method of manufacturing the pressure wave generator of the eleventh embodiment is the same as the method of manufacturing the pressure wave generator of the ninth embodiment.
- the anodizing process is performed for a predetermined time T4 (for example, 10 minutes) according to a predetermined current density decreasing pattern that is appropriately set.
- the current density A monotonic decreasing pattern is set to continuously reduce the current density from the first current density 4 (for example, 100 mAZcm 2 ) to the second current density 5 (for example, OmA / cm 2 ) during the predetermined time T4. ing.
- the current density decreasing pattern is not limited to a monotonous decreasing pattern with a constant slope as shown in FIG. 25, and may be a monotonous decreasing pattern with an increasing slope with time as shown in FIG. 26A, for example.
- a monotonically decreasing pattern in which the slope becomes smaller with time may be used.
- the porosity of the heat insulating layer 2 is continuously increased from the heating element 3 side to the semiconductor substrate 1 side in the thickness direction of the semiconductor substrate 1. Therefore, the mechanical strength of the heat insulating layer 2 can be further increased, and the stress generated near the boundary between the heat insulating layer 2 and the semiconductor substrate 1 can be reduced. Furthermore, since the porosity of the heat insulating layer 2 is formed to be zero near the boundary with the semiconductor substrate 1, the mechanical strength of the heat insulating layer 2 near the boundary with the semiconductor substrate 1 is improved. It is possible to increase the stress and to reduce the stress generated near the boundary. Therefore, cracks in the heat insulating layer 2 during manufacturing and driving, breakage of the heating element 3 due to cracks in the heat insulating layer 2, and peeling of the heat insulating layer 2 from the semiconductor substrate 1 are more reliably prevented. Can be prevented.
- the pressure wave generating device of the twelfth embodiment includes a heat insulating layer 2 of a porous layer formed on one surface (the first surface) la side of the semiconductor substrate 1 and a heat insulating layer 2.
- a heating element 3 of a thin film formed thereon for example, a metal thin film such as an aluminum thin film
- the protective film 16 includes a protective film 16 formed so as to cover a part of the surface of the heat insulating layer 25 and a pair of pads 14 formed on the protective film 16 and a part of the heating element 3.
- the heat insulating layer 2 is formed in a predetermined area on the first surface la side of the semiconductor substrate 1, and the heating element 3 is formed on the heat insulating layer 2 and It is formed inside the outer periphery of the heat insulating layer 2.
- the insulating film 25 is formed of a SiO film, and the semiconductor substrate 1
- the heating element 3 in the edge layer 2 is formed so as to cover the surface of the region and the insulating film 25 when it is laminated.
- the node 14 is formed so as to extend over the heating element 3 and the protective film 16.
- the protective film 16 is provided so as to surround the entire circumference of the heating element 3 in order to prevent oxidation of the heat insulating layer 2.
- a single-crystal silicon substrate is used as the semiconductor substrate 1, and the thermal insulation layer 2 is formed of a porous silicon layer having a porosity of approximately 70%.
- the predetermined region which is a part of the silicon substrate used as the semiconductor substrate 1
- anodizing treatment in an aqueous solution of hydrogen fluoride
- the conditions of the anodic oxidation treatment are appropriately set so that the porosity and thickness of the porous silicon layer serving as the heat insulating layer 2 are set to desired values. be able to.
- the porous silicon layer has a thermal conductivity as the porosity increases, and the volume heat capacity is small, for example, thermal conductivity 148WZ (m'K), volumetric heat capacity is 1. 63 X 10 6 JZ (m 3 ).
- the porous silicon layer having a porosity of 60% formed by anodizing a single crystal silicon substrate of 'K) has a thermal conductivity of lWZ (m'K) and a volumetric heat capacity of 0.7 X 10 It is known to be 6 jZ (m 3 .K).
- the heat insulating layer 2 is formed of a porous silicon layer having a porosity of about 70%, and the heat conductivity of the heat insulating layer 2 is 0.12 WZ (m ′). K), and the volumetric heat capacity is 0.5 X 10 6 jZ (m 3 'K).
- the protective film 16 As a material of the protective film 16, a material whose group strength of carbide, nitride, boride, and silicide is selected, and a material having a higher melting point than silicon may be used.
- the protective film 16 is formed of, for example, HfC having a higher melting point than silicon.
- TaC, HfC, NbC, ZrC, TiC, VC, WC, ThC, SiC, etc. can be used as the carbide having a higher melting point than silicon.
- the nitride having a higher melting point than silicon HfN, TiN, TaN, BN, SiN and the like can be adopted. Borides with a higher melting point than silicon include HfB, TaB, Zr
- the thickness of the heat insulating layer 2 is 2 ⁇ m
- the thickness of the heating element 3 is 50 nm
- the thickness of each pad 14 is 0.5 ⁇ m. These thicknesses are examples and are not particularly limited.
- a method of manufacturing the pressure wave generator according to the twelfth embodiment will be described. First, a conductive electrode (not shown) used at the time of anodizing is formed on the second surface lb side of the silicon substrate used as the semiconductor substrate 1.
- an insulating film 25 in which a portion corresponding to the predetermined region is opened is formed, and the predetermined region of the silicon substrate is made porous by anodizing. Thereby, the heat insulating layer 2 of the porous silicon layer is formed.
- anodizing process a mixture of a 55 wt% aqueous solution of hydrogen fluoride and ethanol in a ratio of 1: 1 was used as the electrolytic solution. Immerse in.
- a current-carrying electrode as the anode and a platinum electrode facing the first surface la side of the silicon substrate as the cathode, a current of a given current density is passed between the anode and cathode from the power supply for a given time, resulting in a porous structure.
- a heat insulating layer 2 of a silicon layer is formed.
- a protective film 16, a heating element 3, and a pad 14 are sequentially formed. Finally, a dicing process is performed to complete the pressure wave generator.
- the film may be formed by, for example, various sputtering methods, various evaporation methods, various CVD methods, or the like. For patterning, for example, a lithography technique and an etching technique may be appropriately used.
- the plane size (hereinafter simply referred to as the plane size) of the portion of the heating element 3 that generates a pressure wave is set to 20 mm X 20 mm.
- Pressure wave generators using Au, Pt, Mo, Ir, and W among the metallic materials shown in Table 3 were prototyped.
- the heating element 3 is composed of a 10 nm chromium film on the heat insulating layer 2 and a 40 nm gold film on the chromium film, and Pt, Mo, Ir, In the pressure wave generator using W respectively, the heating element 3 was made of a metal thin film of a single metal material with a thickness of 50 nm.
- the values in Table 2 are based on the “Metals Data Book” edited by the Japan Institute of Metals (Maruzen Co., Ltd., published on January 30, 1984, 2nd revised edition).
- the unit of melting point is [in]
- the unit of thermal conductivity is [W / (m-K)> the unit of specific heat is [J / (kgK)]
- the unit of specific 3 ⁇ 4 ⁇ is [ ⁇ ⁇ ⁇ cm]
- Unit of thermal expansion coefficient is [X10-K]
- Unit of tensile strength is (/ mm 2 L
- Unit of shochu force is (NZnim 2 :)
- Unit of # is [% ]
- the unit of Young's modulus is [GPa]
- the unit of rigidity is [GPa].
- FIG. 28 shows the results of measuring the output sound pressure when the input power to the heating element 3 was variously changed for each of the prototyped pressure wave generators.
- the horizontal axis represents the peak value (maximum input) of the input power when the peak value is variously changed with the input of a sine wave voltage having a frequency of 30 kHz
- the vertical axis represents the heating element 3.
- the maximum output sound pressures were 48 Pa, 150 Pa, 236 Pa, 226 Pa, and 264 Pa, respectively.
- Table 2 also shows the converted value of the maximum output sound pressure when the plane size is assumed to be 5 mm x 5 mm.
- Table 3 shows that by using any of Pt, Mo, Ir, and W as the material of the heating element 3, Compared to the case where gold is used as the material of the heating element 3, the breakdown power is higher and it is possible to increase the output.
- the Young's modulus of each of Pt, Mo, Ir, and W is higher than the Young's modulus of Au, and the Young's modulus of Au is 88 GPa, whereas the Young's modulus of Pt, Mo, Ir, and W is higher.
- the Young's moduli are 170 GPa, 327 GPa, 570 GPa and 403 GPa, respectively. Therefore, by using a metal material having a Young's modulus of 170 GPa or more, which is the Young's modulus of Pt, as the material of the heating element 3, compared to the case of using Au as the material of the heating element 3, the breakdown resistance is higher. And the output can be increased.
- the JIS standard (JIS C 2524) has previously standardized the "life test method for heating wires and bands". In this standard, the life test must be performed at 1.2 times the rated output. Is described. According to this life test method, if the pressure rating of the pressure wave generator is 8 Pa, the life test must be performed at a sound pressure of 9.6 Pa. Looking at the pressure wave generator with a plane size of 5 mm X 5 mm, the materials of the heating element 3 in the pressure wave generator with a maximum output sound pressure greater than 9.6 Pa are Mo, Ir, and W. From Table 1, it can be seen that for all of Mo, Ir, and W, hardness is the physical property for which the magnitude relationship with Pt is the same. Has been found to include Vickers hardness).
- the Vickers hardness of each of Mo, Ir and W is higher than the Vickers hardness of Pt, and the Vickers hardness of Pt is S39Hv, whereas the Vickers hardness of Mo, Ir and W is respectively , 160 Hv, 200 Hv, 360 ⁇ . Therefore, by using a metal material having a Young's modulus of 170 GPa or more and a Vickers hardness of 160 Hv or more as the material of the heating element 3, compared to the case where Au and Pt are used as the material of the heating element 3, The breakdown power can be increased, and higher output and higher reliability can be achieved.
- FIG. 29 shows the results.
- the horizontal axis indicates the number of times of driving, and the vertical axis indicates sound pressure (output sound pressure).
- curves al to a5 show the continuous driving life characteristics of the sample using Ir as the metal material of the heating element 3
- curves bl to b3 show the life of the sample using W as the metal material of the heating element 3. Show characteristics. Note that the downward arrow in FIG. 29 indicates the timing at which the pressure wave generating device is broken in the curves bl to b3.
- Various conditions can be considered as driving conditions of the pressure wave generator. For example, assuming that the life of a product that is driven once a second or continuously during the day or night is 10 years, about 300 million operations are performed. It is necessary to guarantee the number of drives.
- the pressure wave generator using W described above could only drive about 80 million times, the pressure wave generator using Ir generated 360 million times for all samples. It was confirmed that the wire did not break even if it was driven up to Regarding the continuous drive life characteristics, the reason why the pressure wave generator using Ir as the material of the heating element 3 is superior to the pressure wave generator using W is that W is a refractory metal. There are hundreds of things. Irradiation is likely to occur in C, whereas Ir is a noble metal, and oxidation of the heating element 3, which has higher oxidation resistance than W, can be prevented.
- the protective film 16 is provided on the first surface la side of the semiconductor substrate 1, it is possible to prevent the thermal insulation layer 2 from being oxidized. Can be. Therefore, it is possible to prevent a decrease in output due to oxidation of the heat insulating layer 2 and to improve reliability.
- the material of the protective film 16 is a group of carbides, nitrides, borides, and silicides. By using a material having a higher melting point than silicon among the selected materials, the protective film 16 can be formed by sputtering, vapor deposition, CVD, or the like. It can be formed by a general thin film forming method used in a semiconductor manufacturing process such as a method.
- the protective film 16 is formed on the first surface la side of the semiconductor substrate 1 so as to surround the entire periphery of the heating element 3, but as shown in FIGS. 30A to 30C, On the first surface la side of the substrate 1, a part of the pad 14 is interposed between the vicinity of both short sides of the heating element 3 and the insulating film 25, and the pad 14 is formed around the heating element 3.
- the protective film 16 may be formed only in a region where no protection film is provided. In this case, a part of each pad 14 and the protective film 16 can prevent the thermal insulation layer 2 from being oxidized.
- the pressure wave generating device of the thirteenth embodiment has a heat insulating layer 2 formed on one surface (first surface) la side of a semiconductor substrate 1 of a single crystal silicon substrate, Further, an oxidation preventing layer 35 is formed so as to cover heat insulating layer 2.
- the metal film heating element 3 is formed on the antioxidant layer 35.
- the pair of pads 14 are formed in contact with the first surface la of the semiconductor substrate 1, the antioxidant layer 35, and the vicinity of both sides of the heating element 3, respectively. Since the lengths of the long side and the short side of the oxidation preventing layer 35 in FIG. 31A are set to be longer than the long side and the short side of the heat insulating layer 2, respectively, the heating element 3 in the heat insulating layer 2 The surface of the region where is not laminated is covered with the oxidation preventing layer 35.
- Heating element 3 is formed of tungsten, which is a kind of high melting point metal.
- the thermal conductivity of the heating member 3 is 174WZ (m'K), volumetric heat capacity is 2. 5 X 10 6 jZ (m 3 'K).
- the material of the heating element 3 is not limited to tungsten, but may be any metal having a higher melting point than silicon. For example, tantalum, molybdenum, iridium, or the like can be used.
- the anti-oxidation layer 35 As a material of the anti-oxidation layer 35, a material whose group strength of carbide, nitride, boride, and silicide is also selected, and a material having a higher melting point than silicon may be used.
- the antioxidant layer 35 is formed of, for example, HfC having a higher melting point than silicon.
- TaC, HfC, NbC, ZrC, TiC, VC, WC, ThC, SiC, etc. can be used as carbides having a higher melting point than silicon.
- the nitride having a higher melting point than silicon HfN, TiN, TaN, BN, SiN and the like can be adopted.
- a boride with a higher melting point than silicon As a boride with a higher melting point than silicon, Hf
- the thickness of the silicon substrate before forming the heat insulating layer 2 was 525 ⁇ m
- the thickness of the heat insulating layer 2 was 2 ⁇ m
- the thickness is 50 nm
- the thickness of each pad 14 is 0.5 m
- the thickness of the antioxidant layer 35 is 50 nm.
- these thicknesses are examples and are not particularly limited.
- a current-carrying electrode (not shown) used for anodizing is formed on the second surface lb side of the silicon substrate used as the semiconductor substrate 1.
- an insulating film 25 in which a portion corresponding to the predetermined region is opened is formed, and the predetermined region of the silicon substrate is made porous by anodizing.
- the heat insulating layer 2 of the porous silicon layer is formed.
- a mixture of a 55 wt% aqueous solution of hydrogen fluoride and ethanol mixed in a ratio of 1: 1 was used as the electrolytic solution.
- the thermal insulating layer 2 is formed on the first surface la side of the semiconductor substrate 1, the antioxidant layer 35, the heating element 3, and the pad 14 are sequentially formed. Finally, a dicing process is performed to complete the pressure wave generator.
- the film may be formed by, for example, various sputtering methods, various evaporation methods, various CVD methods, or the like. For the turning, for example, a lithography technique and an etching technique may be appropriately used.
- FIG. 32 shows the results.
- the horizontal axis represents the peak value of the input power when the peak value is variously changed by inputting the voltage of a sine wave having a frequency of 30 kHz.
- the vertical axis on the left shows the sound pressure (output sound pressure) of an ultrasonic wave having a frequency of 60 kHz measured at a position 30 cm away from the surface of the heating element 3.
- the vertical axis on the right side shows the temperature of the surface of the heating element 3.
- a curve C indicates a change in sound pressure
- a curve D indicates a change in temperature of the heating element 3.
- the sound pressure and the temperature of the heating element 3 tend to increase as the input power to the heating element 3 increases.
- To obtain a sound pressure of about 15 Pa it is necessary to raise the temperature of the heating element 3 to about 400 ° C, and to obtain a sound pressure of about 30 Pa, raise the temperature of the heating element 3 to a high temperature of 1 000 ° C or more. Need to raise.
- the temperature of the heating element 3 reaches about 00 ° C, heat is applied in the air. Oxidation of the insulating layer 2 starts to occur, and the volumetric heat capacity of the heat insulating layer 2 increases.
- a porous silicon layer is very active because it has a large surface area compared to Balta silicon of the same thickness, and is susceptible to oxidation in air. Therefore, when heated by the heat of the heating element 3, the oxidation of the thermal insulating layer 2 is considered to be accelerated more.
- an antioxidant layer 35 is interposed between the heating element 3 and the heat insulating layer 2 in order to prevent the heat insulating layer 2 from being oxidized.
- the heating element 3 is laminated on the heat insulating layer 2 so that the surface of the heating element 3 is not exposed.
- the thickness (thickness) of the high melting point film constituting the antioxidant layer 35 is too large, the volumetric heat capacity of the antioxidant layer 35 becomes too large, and the function of the heat insulating layer 2 is not exhibited.
- the output of the pressure wave generator decreases.
- the thickness of the high-melting-point film allowed as the antioxidant layer 35 is set to be equal to or less than the thermal diffusion length L determined by the thermal conductivity, the volumetric heat capacity, and the waveform of the electric input to the heating element 3. You have set.
- the thermal diffusion length L is derived from Equation 2 described in the second embodiment. A numerical example in the case where an ultrasonic wave is generated from the pressure wave generator according to the thirteenth embodiment will be described.
- the thermal diffusion length L 11 m.
- the thickness of the prevention layer 35 may be set to 11 / zm or less.
- the frequency f is 100 kHz (that is, when an ultrasonic wave having a frequency of 100 kHz is generated)
- the thermal diffusion length L is 5.1 ⁇ m. It should be less than 1 ⁇ m.
- HfC is employed as the material of the oxidation preventing layer 35, and the thickness of the oxidation preventing layer 35 is set to 50 nm.
- the thermal diffusion length L is 5.9 ⁇ m, so that the thickness of the oxidation preventing layer 35 is reduced to 5. or less. Just fine.
- the thermal diffusion length L is 2.6 m, so that the thickness of the antioxidant layer 35 may be set to 2.6 m or less.
- the oxygen for preventing the thermal insulation layer 2 from being oxidized between the heating element 3 and the thermal insulation layer 2 of the porous silicon layer since the shading prevention layer 35 is interposed, even when the heating element 3 is heated to a high temperature, the shading of the heat insulating layer 2 of the porous silicon layer can be prevented, and the acid of the porous silicon layer can be prevented. Thus, it is possible to prevent the output from decreasing due to the dangling.
- the heating element 3 is formed of a metal having a higher melting point than silicon
- the oxidation preventing layer 35 is formed of a material having a higher melting point than silicon, the temperature of the heating element 3 is set to the maximum temperature of silicon.
- the temperature can be raised to a possible temperature (the melting point of silicon is 1140 ° C.). Therefore, the output can be increased as compared with the case where the heating element 3 is formed of a metal material having a relatively low melting point such as aluminum. Further, since the thickness of the oxidation preventing layer 35 is set to be equal to or less than the above-mentioned thermal diffusion length L, a decrease in output due to the provision of the oxidation preventing layer 35 can be suppressed.
- the anti-oxidation layer 35 can be formed by sputtering, vapor deposition, or CVD. It can be formed by a general thin film forming method used in a semiconductor manufacturing process such as a method.
- the pressure wave generating device has a heat insulating layer 2 formed on one surface (first surface) la side of a semiconductor substrate 1 of a single crystal silicon substrate. Further, a heating element 3 of a metal film is formed on the heat insulating layer 2. Further, an oxidation preventing layer 35 is formed so as to cover a region of the heating element 3 and the heat insulating layer 2 where the heating element 3 is not formed.
- the pair of pads 14 are formed so as to be in contact with the first surface la of the semiconductor substrate 1, the vicinity of both sides of the heating element 3, and the oxidation preventing layer 35, respectively. That is, as compared with the pressure wave generator of the thirteenth embodiment shown in FIGS. 31A and 31B, the difference is that the oxidation preventing layer 35 is formed on the heating element 3. Others are the same as the pressure wave generator of the thirteenth embodiment.
- the temperature of the heating element 3 needs to be raised to about 400 ° C. It is necessary to raise the temperature to a temperature higher than ° C.
- the oxidation preventing layer 35 of a high melting point film formed of a material having a higher melting point than silicon is provided on the surface of the heating element 3. Even if the temperature of the heating element 3 becomes 400 ° C or higher, the resistance and volumetric heat capacity of the heating element 3 can be maintained for a long period without oxidizing the heating element 3. .
- each of the heating element 3, the heat insulating layer 2, and the antioxidant layer 35 is rectangular. Since the length is set to be longer than the lengths of the long side and the short side of the thermal insulation layer 2, if the heating element 3 is not formed in the heat insulation layer 2, the surface of the region may have an oxidation prevention layer. Covered by 35. Therefore, the oxidation of the heat insulating layer 2 can also be prevented by the oxidation preventing layer 35, and a decrease in output due to an increase in the heat capacity of the thermal insulating layer 2 due to the oxidation of the heat insulating layer 2 can be prevented.
- Si was used as the material of the semiconductor substrate 1.
- the material is not limited to Si, and may be, for example, Ge, SiC, GaP, GaAs, InP, or another semiconductor material that can be porously formed by anodizing.
Abstract
Description
Claims
Priority Applications (3)
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US11/568,419 US7474590B2 (en) | 2004-04-28 | 2005-04-28 | Pressure wave generator and process for manufacturing the same |
CN2005800158353A CN1954640B (zh) | 2004-04-28 | 2005-04-28 | 压力波产生装置及其制造方法 |
EP05737154A EP1761105A4 (en) | 2004-04-28 | 2005-04-28 | PRESSURE GENERATOR AND MANUFACTURING METHOD THEREFOR |
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JP2004134313 | 2004-04-28 | ||
JP2004134312A JP4617710B2 (ja) | 2004-04-28 | 2004-04-28 | 圧力波発生素子 |
JP2004-134313 | 2004-04-28 | ||
JP2004-134312 | 2004-04-28 | ||
JP2004188785A JP4466231B2 (ja) | 2004-06-25 | 2004-06-25 | 圧力波発生素子およびその製造方法 |
JP2004-188790 | 2004-06-25 | ||
JP2004-188785 | 2004-06-25 | ||
JP2004188791A JP4649889B2 (ja) | 2004-06-25 | 2004-06-25 | 圧力波発生素子 |
JP2004188790A JP4534625B2 (ja) | 2004-06-25 | 2004-06-25 | 圧力波発生素子 |
JP2004-188791 | 2004-06-25 | ||
JP2004280417A JP4649929B2 (ja) | 2004-09-27 | 2004-09-27 | 圧力波発生素子 |
JP2004-280417 | 2004-09-27 |
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US (1) | US7474590B2 (ja) |
EP (1) | EP1761105A4 (ja) |
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WO2007049496A1 (ja) * | 2005-10-26 | 2007-05-03 | Matsushita Electric Works, Ltd. | 圧力波発生装置およびその製造方法 |
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US8249279B2 (en) * | 2008-04-28 | 2012-08-21 | Beijing Funate Innovation Technology Co., Ltd. | Thermoacoustic device |
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KR20100023642A (ko) * | 2008-08-22 | 2010-03-04 | 삼성전자주식회사 | 플로팅 바디 트랜지스터를 이용한 동적 메모리 셀을 가지는메모리 셀 어레이를 구비하는 반도체 메모리 장치 및 이 장치의 센스 앰프 |
CN101656907B (zh) * | 2008-08-22 | 2013-03-20 | 清华大学 | 音箱 |
CN101715160B (zh) * | 2008-10-08 | 2013-02-13 | 清华大学 | 柔性发声装置及发声旗帜 |
CN101715155B (zh) * | 2008-10-08 | 2013-07-03 | 清华大学 | 耳机 |
CN101771922B (zh) * | 2008-12-30 | 2013-04-24 | 清华大学 | 发声装置 |
US8300855B2 (en) * | 2008-12-30 | 2012-10-30 | Beijing Funate Innovation Technology Co., Ltd. | Thermoacoustic module, thermoacoustic device, and method for making the same |
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CN101922755A (zh) * | 2009-06-09 | 2010-12-22 | 清华大学 | 取暖墙 |
CN101943850B (zh) * | 2009-07-03 | 2013-04-24 | 清华大学 | 发声银幕及使用该发声银幕的放映系统 |
CN101990152B (zh) * | 2009-08-07 | 2013-08-28 | 清华大学 | 热致发声装置及其制备方法 |
TWI419575B (zh) * | 2009-08-19 | 2013-12-11 | Hon Hai Prec Ind Co Ltd | 熱致發聲裝置及其製備方法 |
CN102006542B (zh) | 2009-08-28 | 2014-03-26 | 清华大学 | 发声装置 |
CN102023297B (zh) * | 2009-09-11 | 2015-01-21 | 清华大学 | 声纳系统 |
CN102034467B (zh) * | 2009-09-25 | 2013-01-30 | 北京富纳特创新科技有限公司 | 发声装置 |
CN102056064B (zh) * | 2009-11-06 | 2013-11-06 | 清华大学 | 扬声器 |
CN102056065B (zh) * | 2009-11-10 | 2014-11-12 | 北京富纳特创新科技有限公司 | 发声装置 |
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2005
- 2005-04-28 KR KR1020067025008A patent/KR100855788B1/ko not_active IP Right Cessation
- 2005-04-28 WO PCT/JP2005/008252 patent/WO2005107318A1/ja active Application Filing
- 2005-04-28 US US11/568,419 patent/US7474590B2/en not_active Expired - Fee Related
- 2005-04-28 CN CN2005800158353A patent/CN1954640B/zh not_active Expired - Fee Related
- 2005-04-28 EP EP05737154A patent/EP1761105A4/en not_active Withdrawn
Patent Citations (3)
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JPH03140100A (ja) * | 1989-10-26 | 1991-06-14 | Fuji Xerox Co Ltd | 電気音響変換方法及びその為の装置 |
JPH11300274A (ja) * | 1998-04-23 | 1999-11-02 | Japan Science & Technology Corp | 圧力波発生装置 |
JP2002186097A (ja) * | 2000-12-15 | 2002-06-28 | Pioneer Electronic Corp | スピーカ |
Non-Patent Citations (1)
Title |
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See also references of EP1761105A4 * |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2007049496A1 (ja) * | 2005-10-26 | 2007-05-03 | Matsushita Electric Works, Ltd. | 圧力波発生装置およびその製造方法 |
US7881157B2 (en) | 2005-10-26 | 2011-02-01 | Panasonic Electric Works Co., Ltd, | Pressure wave generator and production method therefor |
Also Published As
Publication number | Publication date |
---|---|
US20070217289A1 (en) | 2007-09-20 |
CN1954640B (zh) | 2011-07-27 |
CN1954640A (zh) | 2007-04-25 |
US7474590B2 (en) | 2009-01-06 |
EP1761105A1 (en) | 2007-03-07 |
KR20070015214A (ko) | 2007-02-01 |
EP1761105A4 (en) | 2009-10-21 |
KR100855788B1 (ko) | 2008-09-01 |
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