CN100567923C - Quartz pressure sensor and manufacture method thereof - Google Patents
Quartz pressure sensor and manufacture method thereof Download PDFInfo
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- CN100567923C CN100567923C CNB2004800181798A CN200480018179A CN100567923C CN 100567923 C CN100567923 C CN 100567923C CN B2004800181798 A CNB2004800181798 A CN B2004800181798A CN 200480018179 A CN200480018179 A CN 200480018179A CN 100567923 C CN100567923 C CN 100567923C
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Abstract
A kind of quartz type pressure transducer, thereby it can solve the shortcoming of the pressure transducer that uses the silicon detection lug by using quartzy detection lug as pressure transducer, for example cause being difficult to control diaphragm thickness owing to etching precision is low and the accuracy of detection that causes thus low poor with the elastic deformation repeatability.This pressure transducer comprises: the base plate that is made of insulating material; Sequential cascade is at the lip-deep lower electrode film and the dielectric film of described base plate; Detection lug is provided with thinner wall section in the position relative with described dielectric film and is fixed to the surface of described base plate; Upper electrode film is formed at least a portion of described thinner wall section and to close be relative with described lower electrode film in the position; And at the lower surface of described detection lug and the minim gap airtight space between the described dielectric film, this pressure transducer is characterised in that described detection lug is made of quartz material.
Description
Technical field
The present invention relates to the improvement to pressure transducer, relate to a kind ofly by constitute quartz pressure sensor and the manufacture method thereof that detection lug improves reliability with piezoid, detection lug is fabricated from a silicon routinely.
Background technology
Known routinely a kind of tire pressure monitoring system, its working pressure sensor detects the air pressure that is assemblied in such as each tire in the vehicle of automobile, and gives the alarm when appearance is unusual.
As in the rubber tyre that is arranged on automobile etc. and measure the baroceptor of air pressure, following technology is disclosed in Japanese Patent Application Laid-Open No.2001-174357: wherein, diaphragm of being made by pottery (diaphragm) and the substrate (base) of being made by pottery are engaged with each other, and the variation of the electrostatic capacitance in the gap that will form between these two parts is converted to pressure.Yet, in the baroceptor that uses pottery as detection lug, have the problem of wishing to improve accuracy of detection.
As the baroceptor that does not have this shortcoming, paying close attention to the contact mode capacitor type pressure transducer of the detection lug that use as shown in Figure 7 made by silicon (Si) recently.This pressure transducer is equipped with electrode film 101, dielectric film 102, electrode film 103 and is made by silicon on glass sheet 100 detection lug 104.This pressure transducer utilization since according to pressure cause being out of shape make detection lug 104 film section (diaphragm) thus 104a and dielectric film 102 directly contact the electrostatic capacitance change of appearance carries out pressure detection.For example, at IEEJ Trans.SM, Vol.123, No.1,2003 (Transaction of The Institute of Electrical Engineers of Japan, SM, Vol.123, No.1,2003) this baroceptor is disclosed in " Touch Mode Capacitive Pressure Sensor for Passive TireMonitoring System ".
[patent documentation 1] Japanese Patent Application Laid-Open No.2001-174357
[non-patent literature 1] IEEJ Trans.SM, Vol.123, No.1,2003 (Transaction ofThe Institute of Electrical Engineers of Japan, SM, Vol.123, No.1,2003), " Touch Mode Capacitive Pressure Sensor for PassiveTire MonitoringSystem "
Summary of the invention
The problem to be solved in the present invention
In the baroceptor that uses the detection lug of making by silicon, not only must utilize etching that the diaphragm 104a of silicon wafer is treated to the degree that its thickness becomes about 3 μ m that is as thin as, and the minimum gap of about 3 μ m must be set between diaphragm 104a and dielectric film 102.
As described in the above-mentioned communique, the process that forms diaphragm 104a may further comprise the steps: a surface that boron is doped to silicon chip; Carry out etching by carrying out etching from another surface of wafer; And time stop etching at the layer that arrival is doped with boron.That is, the thickness of the reformation layer that forms by doped with boron becomes the thickness of diaphragm.Yet, must be for example doping time by management boron come controlled doping that the thickness of the layer of boron is arranged, that is, and the thickness of diaphragm 104a.Therefore, even owing to the fluctuation of creating conditions etc. causes the doping speed of boron to change, owing to can not carry out control, so widely different between the individuality based on this variation.As a result, the fluctuation of making in the baroceptor is very big.In addition, because the Q value of silicon materials is not high, therefore also there is the problem of elastically-deformable reproducibility.As be described in further detail, in the diaphragm-type pressure transducer, because electrostatic capacitance is owing to the deflection of diaphragm changes, so, when machined diaphragm, will carry out high-precision THICKNESS CONTROL so that the flexural property of diaphragm is even inevitably in order to make the variable quantity of the electrostatic capacitance between the individuality even.
In addition, in contact mode capacitor type pressure transducer, because stress concentrates on the moving part that becomes the diaphragm that contacts with base plate, therefore unavoidably will carry out THICKNESS CONTROL with high precision more when machined diaphragm, this is not only in order to realize sensor accuracy and to be for physical strength is remained on level of hope.
In this, particularly, in the contact mode capacitor type pressure transducer that uses silicon, owing to can not during processing, measure and control accurate thickness, so the thickness difference between each diaphragm is very big.As a result, the problem of the decline of appearance such as output or the miniaturization limit.That is, when the miniaturization of propelling pressure sensor because therefore the sensory characteristic that must keep-up pressure in the area of the moving part that reduces diaphragm requires the moving part attenuation of diaphragm, this cause need be higher the diaphragm machining precision.
Consider that the problems referred to above obtain the present invention, the purpose of this invention is to provide a kind of quartz pressure sensor, this quartz pressure sensor is by utilizing quartz (particularly, be the AT cutting) (even conventionally not used as the material that constitutes detection lug and material that those skilled in the art do not recognize its purposes yet) as the detection lug of the pressure transducer in the contact mode capacitor type pressure transducer, can solve respectively because the difficulty of the diaphragm thickness control that low etching precision causes (this is the shortcoming in the pressure transducer of the detection lug that use is made by silicon), and accuracy of detection deterioration that causes owing to this difficulty and bad elastic deformation reproducibility.
The means of dealing with problems
In order to address the above problem, the invention provides a kind of contact mode type quartz pressure sensor, comprising: base plate; Be arranged on the lower electrode film on this plate upper surface; Be provided with the detection lug of thin portion; And at least one side's the lip-deep upper electrode film that is formed on the described thin portion of this detection lug, by described detection lug being fixed on the upper surface of described base plate, make described upper electrode film be positioned at the top of described lower electrode film, described detection lug is the contact mode type, can make the quartz material of the cutting angle measured based on the natural frequency of the thickness of this thin portion by having when described thin portion is switched on, in the pressure survey environment, be always following structure: the thin portion of described detection lug or upper electrode film contact with the upper surface of described base plate, and described upper electrode film and described lower electrode film keep state of insulation.
The invention provides a kind of contact mode type quartz pressure sensor, comprising: base plate; Be arranged on the lower electrode film on this plate upper surface; Be provided with the detection lug of thin portion; And at least one side's the lip-deep upper electrode film that is formed on the described thin portion of this detection lug, by described detection lug being fixed on the upper surface of described base plate, make described upper electrode film be positioned at the top of described lower electrode film, described detection lug is the contact mode type, can make the thickness slip mode of oscillation measured based on the natural frequency of the thickness of this thin portion or the quartz material of thickness vertical mode by having when described thin portion is switched on, in the pressure survey environment, be always following structure: the thin portion of described detection lug or upper electrode film contact with the upper surface of described base plate, and described upper electrode film and described lower electrode film keep state of insulation.
The invention provides a kind of contact mode type quartz pressure sensor, comprising: base plate; Be arranged on the lower electrode film on this plate upper surface; Be provided with the detection lug of thin portion; And at least one side's the lip-deep upper electrode film that is formed on the described thin portion of this detection lug, by described detection lug being fixed on the upper surface of described base plate, make described upper electrode film be positioned at the top of described lower electrode film, described detection lug is the contact mode type, can the AT cutting piezoid of measuring based on the natural frequency of the thickness of this thin portion be constituted by having when described thin portion is switched on, in the pressure survey environment, be always following structure: the thin portion of described detection lug or upper electrode film contact with the upper surface of described base plate, and described upper electrode film and described lower electrode film keep state of insulation.
The invention provides a kind of pressure transducer, this pressure transducer comprises: the base plate of being made by insulating material; Sequential cascade is at the lip-deep lower electrode film and the dielectric film of base plate; Be provided with thin portion in its position relative and be fixed on the lip-deep detection lug of base plate with dielectric film; And be formed at least a portion of thin portion and upper electrode film with position relation relative with lower electrode film, wherein, be provided with the airtight space of minim gap between upper electrode film and dielectric film, described pressure transducer is characterised in that detection lug made by quartz material.
According to the present invention,, therefore provide following superiority owing to use the material of the quartzy rather than conventional silicon that uses as detection lug.That is, compare with silicon, quartz is the material of physically stable, and through annual variation little and because the repeatability height (sluggishness reduces) of mechanically deform.Utilize quartz, strictly manage thickness easily, thereby can obtain diaphragm with even sheet thickness for thickness difference between the thin portion of each individuality as the thin 10a of portion of diaphragm.
The invention provides a kind of pressure transducer, this pressure transducer comprises: the base plate of being made by insulating material; Be layered in the lip-deep lower electrode film of base plate; Be provided with thin portion in its position relative and be fixed on the lip-deep detection lug of base plate with lower electrode film; And be formed at least a portion of thin portion and upper electrode film with position relation relative with lower electrode film, wherein, be provided with the airtight space of minim gap between upper electrode film and lower electrode film, described pressure transducer is characterised in that detection lug made by quartz material.
Do not use dielectric film just can constitute according to pressure transducer of the present invention.In this case, the thin portion of the quartz of formation detection lug can also be used as dielectric film and diaphragm.
In pressure transducer provided by the invention, described airtight space is by the recess on the part of the lower surface that is formed on detection lug or is formed on the lip-deep of insulcrete and is recessed to form.
Airtight space is formed in the minim gap between thin portion and the base plate, but airtight space can or be formed on being recessed to form on the base plate by the recess on the lower surface that is formed on detection lug.
The invention provides a kind of pressure transducer, this pressure transducer comprises: sequential cascade is at the lip-deep lower electrode film and the dielectric film of the base plate of being made by insulating material; Thick detection lug that constitutes by thin portion and this thin portion of encirclement; And be formed on upper electrode film at least a portion of lower surface of thin portion of detection lug, wherein be formed with the airtight space of minim gap between thin portion and base plate by the lower surface of the thick portion of detection lug is fixed in the surface of base plate via upper electrode film in the mode of tight contact, described pressure transducer is characterised in that detection lug made by quartz material.
In pressure transducer provided by the invention, base plate is made by quartz material.
The invention provides a kind of pressure transducer, this pressure transducer comprises: dielectric film, also as lower electrode film and being layered on the surface of the base plate of making by conductive material; Detection lug is made of with thick of this thin portion of encirclement thin portion; And upper electrode film, be formed at least a portion of the lower surface of thin portion of detection lug or upper surface, wherein by the lower surface of the thick portion of the detection lug mode with tight contact is fixed in the surface of base plate and is formed with the airtight space that is limited by minim gap between thin portion and base plate, described pressure transducer is characterised in that detection lug made by quartz material.
By making base plate, can save lower electrode film with conductor.
In a kind of pressure transducer provided by the invention, described detection lug is provided so that thin portion surperficial relative at the interarea of its tabular surface side and base plate.
When an interarea of detection lug is tabular surface and its another interarea when being uneven surface, relative by the tabular surface that makes detection lug with the upper surface of base plate, can easily obtain airtight space.
In pressure transducer provided by the invention, make detection lug be formed with thin portion by piezoid being carried out attenuation processing with etching.
In attenuation processing, can control thickness subtly by etching to quartz material.
At pressure transducer provided by the invention, detection lug and base plate are by making with a kind of quartz material, and detection lug is by making the consistent each other mode of crystallographic axis of detection lug and base plate join base plate to.
By not only making the material that must use consistent each other but also make that the crystallographic axis of detection lug and base plate is consistent each other, can so that detection lug and base plate to the characteristic of temperature variation strict conformance each other.
In the pressure transducer that invention provides, described quartz pressure sensor is a contact mode capacitor type pressure transducer.
Compare with the semiconductor material such as silicon, quartz has very high thickness processing accuracy and feasible can the manufacturing has the detection lug of wishing thickness.Therefore, in the high contact mode capacitor type pressure transducer of the precision that requires thin portion thickness, quartz material provides excellent convenience.
In the pressure transducer that invention provides, thin portion in the detection lug or upper electrode film contact with the surface of dielectric film or base plate during non-measurement.
In contact mode capacitor type pressure transducer, when thin portion during non-measurement with base plate when spaced apart, under initial measured state, fluctuate, if but make thin portion from measuring beginning and just contacting then begin just can measure with stabilized accuracy from measuring with base plate.
In the pressure transducer that invention provides, described airtight space is in vacuum state.
The vacuum state that does not have air in the airtight space has been cleared up the adverse effect that the gas that causes owing to heat etc. expands and brings.
In pressure transducer provided by the invention, described detection lug can be made by the quartz material that sheet thickness is adjusted the cutting angle (cut angle) of controlling resonance frequency by having.
Owing to can accurately measure thickness based on the natural mode shape of thin portion, so can improve machining precision and improve output.
In the invention provides a kind of pressure transducer, described quartz material is to be made by the quartz material with thickness slip mode of oscillation (thickness sliding oscillation mode) or thickness vertical mode (thickness vertical mode).
Described quartz material can be illustrated as the quartz material with thickness slip mode of oscillation or thickness vertical mode.
In pressure transducer provided by the invention, detection lug is made of AT cutting piezoid.
When AT cutting piezoid being handled by wet etching etc., thickness difference appears at moving part, still, owing to can convert and control the thickness of thin portion by carrying out frequency, so this is very easily.
The invention provides a kind of manufacture method of quartz pressure sensor, comprise that the thickness to thin portion carries out the step of frequency conversion so that it is confirmed.
Pressure transducer provided by the invention, described pressure transducer are wherein to have the contact mode type pressure transducer of the piezoid of the roughly consistent cutting angle of piezoid normal to a surface and quartz crystal Z-direction as the piezoid that constitutes detection lug.
The invention effect
According to the present invention, by utilizing quartz (particularly, AT cutting) as the detection lug of the pressure transducer in the capacitor type pressure transducer, a kind of quartz pressure sensor can be provided, and this quartz pressure sensor can solve the difficulty (this is to use the shortcoming of the pressure transducer of the detection lug of being made by silicon) of diaphragm thickness control and accuracy of detection deterioration that causes owing to this difficulty and bad elastic deformation reproducibility respectively.
Conventionally do not adopt quartzy material as the detection lug that constitutes the capacitor type pressure transducer, even and quartz be the material that those skilled in the art do not recognize its purposes yet.
In the present invention, owing to use the material of the quartzy rather than conventional silicon that uses as detection lug, so following superiority is provided.That is, compare with silicon, quartz is the material of physically stable, and little through annual variation, because the repeatability height (sluggishness reduces) of mechanically deform.Utilize quartz, strictly manage thickness easily, thereby can obtain diaphragm with even sheet thickness for thickness difference between the thin portion of each individuality as the thin 10a of portion of diaphragm.
In the present invention, need not to use dielectric film just can constitute pressure transducer.In this case, the thin portion of the quartz of formation detection lug can also be used as dielectric film and diaphragm.
In the present invention, airtight space is formed in the minim gap between thin portion and the base plate, but described airtight space can or be formed on being recessed to form on the base plate by the recess on the lower surface that is formed on detection lug.
In the present invention, by making base plate, can save lower electrode film with conductor.
In the present invention, when an interarea of detection lug is tabular surface and its another interarea when being uneven surface,, can easily form airtight space by the tabular surface of detection lug is relative with the upper surface of base plate.
In the present invention, can control thickness subtly by in to the processing of quartz material, carrying out etching.
In the present invention, consistent each other but also make crystallographic axis consistent each other by not only making the material that must use, can make detection lug and base plate to the characteristic of temperature variation strict conformance each other.
In the present invention, quartz pressure sensor is a contact mode capacitor type pressure transducer.Compare with the semiconductor material such as silicon, quartz has very high thickness processing accuracy and feasible can the manufacturing has the detection lug of wishing thickness.Therefore, in the high contact mode capacitor type pressure transducer of the precision that requires thin portion thickness, quartz material provides excellent convenience.
In the present invention, in contact mode capacitor type pressure transducer, when thin portion, fluctuates under initial measured state when spaced apart with base plate during non-measurement, if but make thin portion from measuring beginning and just contacting then begin just can measure with stabilized accuracy from measuring with base plate.
In the present invention, the vacuum state that does not have air in the airtight space has been cleared up the adverse effect that the gas that causes owing to heat etc. expands and brings.
In the present invention, owing to can accurately measure thickness based on the natural mode shape of thin portion, so can improve processing accuracy and improve output.
In the present invention, the quartz material that has thickness slip mode of oscillation or thickness vertical mode.
In the present invention, when by wet etching etc. AT cutting piezoid being handled, at moving part thickness difference appears, still, owing to can convert and control the thickness of thin portion by carrying out frequency, so this is very easily.
In the present invention, owing to provide thickness to carry out the step of frequency conversion so that it is confirmed to thin portion, so can be with the thickness of the thin portion of High Accuracy Control.
In the present invention, owing to will have the piezoid that the piezoid of the roughly consistent cutting angle of piezoid surface normal and quartz crystal Z-direction is used as detection lug described in the present invention, become easy so process.
Description of drawings
Fig. 1 (a) and 1 (b) are to illustrate according to the integrally-built vertical cross section of the contact mode capacitor type pressure transducer of the embodiment of the invention and are the cut-open views of the contact mode capacitor type pressure transducer of A-A intercepting along the line.
Fig. 2 (a) is the key diagram of the operation of pressure transducer shown in Figure 1 to 2 (d).
Fig. 3 illustrates the sectional view of the structure of pressure transducer according to another embodiment of the present invention.
Fig. 4 is the curve map that the characteristic of pressure transducer shown in Figure 3 is shown.
Fig. 5 illustrates the sectional view of the structure of pressure transducer according to another embodiment of the present invention.
Fig. 6 (a) is that Fig. 6 (b) is the sectional view according to the detection lug of the embodiment of the invention by the sectional view with detection lug that anisotropic quartz material makes.
Fig. 7 is the key diagram of conventional example.
Embodiment
To describe the embodiments of the invention shown in the accompanying drawing in detail below.
Fig. 1 (a) and 1 (b) illustrate according to the integrally-built vertical cross section of the contact mode capacitor type pressure transducer of the embodiment of the invention and the cut-open view of getting along the line A-A shown in Fig. 1 (a).
Contact mode capacitor type pressure transducer (hereinafter referred to as " pressure transducer " or " contact mode type pressure transducer ") 1 is contained in by in the container of making such as the insulating material of pottery 20.Four sidewalls 22 that ceramic vessel 20 generally comprises base plate 21, erect from the periphery of base plate 21 and be fixed in upper shed that sidewall 22 forms and the loam cake 23 that is provided with air hole 23a.
Because sidewall 22 and loam cake 23 are optional, even therefore the structure that is assemblied on the base plate 21 in practical application detection lug 10 grades is just enough.
Be contained in pressure transducer 1 in the ceramic vessel 20 by this way and be arranged on the suitable part of the tire of vehicle (for example automobile) with its state that is assembled to the transponder beacon that will use regularly.Transponder beacon is provided with aerial coil.By the current start pressure transducer of aerial coil, inducting from the electromagnetic wave of the antenna of automobile side output.Then, the pressure information of measuring outputs to automobile side as electromagnetic wave.Because the air pressure in the tire is via being formed on the thin 10a of portion that opening 23a in the loam cake 23 is applied to the pressure transducer 1 in the container 20, so when the air pressure in the tire is that deflection and distortion take place the thin 10a of portion when surpassing the pressure that for example is set to as the pressure in the atmospheric airtight space S of datum pressure.
Substrate is made of base plate 21, lower electrode film 2 and dielectric film 3.
The characteristic structure of pressure transducer 1 of the present invention is the piezoelectric such as quartz is used for detection lug 10, is that more specifically detection lug 10 is this point of being made by the patch of piezoelectric material with thickness slip mode of oscillation or thickness vertical mode (for example AT cutting piezoid).
In an embodiment, although the lower surface corresponding to the thin 10a of portion of detection lug 10 forms recess 10A to form airtight space S, as described later, this structure only is as example.That is,, then can adopt arbitrary structures if form airtight space by between the upper electrode film 11 on the lower surface of dielectric film 3 and the thin 10a of portion, forming minim gap (about 3 μ m).
In an embodiment, form the leading electrode 2a that extends to external container such as the lower electrode film 2 on the upper surface of the insulcrete 21 of pottery from being arranged on.Formation extends to the leading electrode 11a of external container from the top electrode 11 on the lower surface that is formed on detection lug 10.Use two leading electrode 2a and 11a, can detect the variation that is set to via the capacitance between airtight space and dielectric film 3 upper electrode films 11 respect to one another and the lower electrode film 2, and calculate external pressure based on testing result.
That is, express the capacitance C of capacitor by following formula:
(ε represents dielectric specific inductive capacity to C=ε (S/d); S represents electrode area; D represents distance between electrodes)
That is, when being set to when very little apart from d between electrode film 2 and 11, it is big that capacitance C becomes, but when being set to when very big apart from d between electrode 2 and 11, capacitor C diminishes.On the other hand, when making the relative area of two electrode films respect to one another very big, it is big that capacitance C becomes.On the contrary, when the relative area of two electrode films respect to one another was very little, capacitance C diminished.
The contact mode type pressure transducer 1 of structure is arranged in the atmosphere with the state that is configured in the container 20 in the above described manner.The inside of airtight space S is set to approximate atmospheric pressure.When external pressure when air pressure in the airtight space S equates, shown in Fig. 2 (a), because the air pressure in the airtight space keeps balance with external pressure, the thin 10a of portion that therefore is used as diaphragm is indeformable.On the other hand, during air pressure in external pressure is higher than airtight space, shown in Fig. 2 (b), the thin 10a of portion is deformed near dielectric film 3.Fig. 2 (c) and 2 (d) show the state that the contact area S1 of thin 10a of portion and dielectric film 3 and S2 change according to the size of external pressure.Under to the situation of contact area S1 shown in Fig. 2 (c) and under the situation of contact area S2 shown in Fig. 2 (d) (when the capacitance C1 of S1＜S2) and C2 carry out mutually relatively, obtain C1=ε (S1/d) during for S1 in contact area, obtain C2=ε (S2/d) during for S2 in contact area.
When external pressure during greater than the pressure in the airtight space S (atmospheric pressure), the thin 10a of portion (diaphragm) deforms and upper electrode film 11 becomes with dielectric film 3 and contacts.Therefore, detect as capacitance by the variation of the contact area of upper electrode film 11 and dielectric film 3 at this moment, can sensed pressure.
Conductive material such as metal can be replaced insulating material be used for base plate 21.In this case, base plate 21 as conductive material own can be used as bottom electrode, and need not on base plate, to form lower electrode film 2.
Fig. 3 is the sectional view that illustrates according to the modification embodiment of pressure transducer of the present invention.In this embodiment, the piezoid with the about 0.25mm of thickness is used as base plate 21.By using the bonding agent 6 such as epoxy adhesive (epoxy adhesive) to seal, the mode that is arranged on the depression 5 on the upper surface of quartzy base plate 21 with covering will closely be fixed on the upper surface of base plate by the detection lug 10 that quartz is made.Therefore, the inside of depression 5 constitutes the airtight space S of the about 3 μ m of the degree of depth.On the surface of the base plate 21 that comprises depression 5 inwall, be formed with the lower electrode film of making by Cu-Al etc. 2.Form electric terminal by coating electroconductive binder 7 on an end of lower electrode film 2.Form another electric terminal by coating electroconductive binder 12 near the part being positioned at one end thereof at upper electrode film 11.
In the present embodiment, by only on the upper surface of detection lug 10 (it is a piezoid), forming recess 10A and its lower surface being formed tabular surface, form the thin 10a of portion of about 5 μ m.The periphery of thick the thin 10a of portion of 10b supporting.The upper electrode film of being made by Cu-Al etc. 11 is formed on the upper surface of detection lug 10.This embodiment is characterised in that: dielectric film is not set individually, will be used as diaphragm by the thin portion that quartz is made and be used as dielectric film.That is, during air pressure in external pressure surpasses airtight space S,, the thin downward deflection of the 10a of portion contacts with lower electrode film 2 thereby making smooth lower surface become.Detect as capacitance by the variation that will approach the contact area of subordinate surface and lower electrode film 2 this moment, can the perception external pressure.
In this embodiment, depression 5 is formed on the surface of base plate 21, and the lower surface of detection lug 10 is formed smooth.On the contrary, the surface of base plate 21 can be formed smoothly, recess can be formed on the lower surface of detection lug 10 on the other side.
In this embodiment, the piezoid that constitutes thin portion is used as dielectric, and need not to be provided with independent dielectric film.In addition, pressure transducer can be constituted and the independent dielectric film of being made by the dielectric material except that quartz is set on a part that is positioned at depression 5 lower electrode film 2 and makes the lower surface and the dielectric film of the portion of approaching be in contactless state usually.
Fig. 4 is the curve map that illustrates according to the characteristic of contact mode capacitor type pressure transducer embodiment illustrated in fig. 3.In Fig. 4, the longitudinal axis is represented the capacitance (pF) that records, and transverse axis is represented the external pressure corresponding with each capacitance.Obvious as institute among this figure, according to present embodiment, can measure external pressure with high sensitivity.
Then, Fig. 5 is the sectional view of contact mode capacitor type pressure transducer according to another embodiment of the present invention.Pressure transducer 1 is provided with: base plate 21, and thickness is about 0.25mm, by making such as pottery, glass or quartzy insulating material; And detection lug 10, to make by quartz, its upper surface has depressed part and its lower surface is smooth.This pressure sensing appliance has following structure: detection lug 10 is set near the depression on the upper surface that is formed on base plate 21 5 (the about 3 μ m of the degree of depth), and depression 5 is hermetic closed by bonding agent 6.Detection lug 10 has recess on the surface thereon, and the bottom of recess constitutes the thin 10a of portion.On the bottom surface of the thin 10a of portion, be formed with upper electrode film 11, and upper electrode film 11 is electrically connected to another electrode film 8 (itself and lower electrode film 2 electrical isolations) that is arranged on the base plate 21.Lower electrode film 2 is formed inwall and the inner bottom surface that extends to depression 5 from the upper surface of base plate 21, and is provided with such as SiO in the mode that does not contact with the lower surface of detection lug on the lower electrode film on the depression inner bottom surface
2Dielectric film 3 (thickness be 2000 to
).Therefore, the dielectric film 3 in top electrode on the lower surface of detection lug 10 11 and the airtight space S via predetermined gap toward each other.In addition, lower electrode film 2 is positioned at below the dielectric film 3.
Utilize said structure, during air pressure in external pressure surpasses airtight space S, the variation that the lower surface when thin downward deflection of the 10a of portion and top electrode 11 can be become the top electrode 11 that takes place when contacting with dielectric film 3 and the contact area of dielectric film 3 detects as capacitance, and the perception external pressure.
Common structure in each embodiment of foregoing invention is characterised in that and replaces silicon to be used as the material of detection lug 10 in quartz, and superiority of the present invention is following point.
At first, compare with silicon, quartz is the material of physically stable, and little through annual variation, because the repeatability height (sluggishness reduces) of mechanically deform.
Secondly, utilize quartz, management strictly promptly, for the portion of approaching is processed as target thickness, at first forms the thin 10a of portion by piezoid being carried out etching as the thickness of the thin 10a of portion of diaphragm easily.Then, measure natural frequency by making electric current flow through the thin 10a of portion, and frequency and the target frequency (target thickness) that records compared based on thin portion thickness.When the frequency that records and target frequency are inconsistent, carry out meticulous etching and reach target frequency up to recording frequency.So, can obtain in the diaphragm individuality diaphragm with even sheet thickness of thin portion thickness difference.
In brief, as the material of the detection lug of the contact mode capacitor type pressure transducer that is used for the suitable high dimensional accuracy of requirement,, we can say that quartz is only to the easiness of the THICKNESS CONTROL of thin portion and the angle of processibility.To in handling by the processing of the thin portion in the detection lug of making such as the semiconductor material of silicon, use and carried out boron doped silicon chip from the one surface layer.Then, carry out by staying the step of boron-dopped layer only to remove silicon portion as thin portion from silicon chip being carried out etching with its boron doping surfaces facing surfaces.Yet,, therefore appear at the film thickness fluctuation in the boron-dopped layer that stays after the etching owing to can not when boron mixes, accurately control the layer thickness of boron-dopped layer.On the other hand, when using piezoid, can therefore not we can say that piezoid is best suited in the material of contact mode type pressure transducer with the thickness of the thin portion of High Accuracy Control owing to do not carry out doping process by only carrying out etching.
The natural frequency that is used for measuring the thin 10a of portion that makes such as the piezoelectric of quartz for example is known as in the disclosed process technology to the ultrathin section piezoelectric oscillator that is obtained by the applicant of the flat No.06-021740 of Japanese Patent Application Laid-Open with the technology of meticulous its thickness of adjustment, and this technology can be applied to former state measuring technique.
Then, when detection lug 10 by having when making the quartz material of the cutting angle that can control resonance frequency according to sheet thickness constitute, during processing, can accurately measure the thickness of thin portion based on the resonance frequency of thin portion.That is, owing to conventionally by measuring method or investigation method thin portion thickness is measured, so error is very big, this causes the fluctuation of characteristic between product.On the other hand,, can in the affirmation thickness that converts according to frequency, control, therefore can obtain precision thickness by utilizing the characteristic that to control resonance frequency according to sheet thickness.
For example, when when detection lug 10 is made by the patch of piezoelectric material with thickness slip mode of oscillation and by patch of piezoelectric material, making, can accurately measure thin portion thickness based on the resonance frequency of thin portion with thickness vertical mode.That is,, can carry out frequency to thickness and convert, thereby can obtain precision by utilizing thickness sliding properties or thickness vertical mode characteristic.
Particularly, when thin portion being added man-hour, has the thin portion that wishes minimal thickness by utilizing the measuring method of the thickness of thin portion being carried out the frequency conversion, can forming by etching technics such as wet etching or dry etching.That is, when the piezoelectric that has the thickness sliding properties by use is made detection lug, preferably carry out the thickness of the thin 10a of portion is carried out the step of frequency conversion so that it is confirmed, thereby realize the raising of output owing to the raising of machining precision.
When thin portion makes can constitute according to the quartz material (patch of piezoelectric material that for example has thickness slip mode of oscillation or thickness vertical mode) that sheet thickness be controlled the cutting angle of resonance frequency the time by having, any piezoelectric can be used for thin portion, but AT cutting piezoid can be illustrated as typical case.
In addition, by constituting detection lug 10 with piezoelectric crystal material of the same race with base plate 21 and so that the consistent each other mode of crystallographic axis of detection lug and base plate joins detection lug to base plate, compare when only adopting same material, can be so that both thermal expansion characters strict conformance each other, and can be so that the stable performance of pressure transducer.
Pressure transducer of the present invention not only can be used for coming based on the contact area of the thin portion of dielectric film on the base plate and detection lug the contact mode type pressure transducer of gaging pressure, and can be used for the clearance type pressure transducer (electrostatic capacitance being controlled based on the distance between diaphragm and the base plate) except that contact mode type pressure transducer.That is, when detection lug is made by the piezoelectric with thickness sliding-modes, the thickness of the thin 10a of portion can be set with high precision.Therefore, by being applied to contact mode type pressure transducer, can suppress the electrical characteristics between individuality and the fluctuation of mechanical property.In addition, even when the detection lug of clearance type pressure transducer is made by the piezoelectric with thickness sliding-modes, also can suppress the electrical characteristics between individuality and the fluctuation of mechanical property.
In the above-described embodiments, thus show and be set to atmospheric pressure by airtight space S and make the thin 10a of portion of during non-measurement detection lug and dielectric film etc. be in the example of contactless state.On the other hand, initial setting up can be carried out so that the thin 10a of portion (upper electrode film 11) of detection lug contacts with the surface of dielectric film 3, upper electrode film 2 or base plate 21 during non-measurement.Promptly, in this case, be set to pressure below atmospheric pressure (for example, vacuum state) by the air pressure among the airtight space S, can be so that the thin 10a of portion be in and dielectric film 3, upper electrode film 2 or base plate 21 contacted states during pressure transducer places non-measurement under the atmospheric pressure.
That is, when airtight space S was remained on atmospheric pressure, gas expansion in this space and the variation of shrinking with environment temperature occurred.Therefore, fluctuate owing to approach the initial position of the 10a of portion, so be difficult to accurately measure.When airtight space S is set to vacuum state when (comprising the subatmospheric pressure state that reduces), expanding and shrinking can not appear owing to the variation of environment temperature in airtight space S.Therefore, diaphragm only moves according to the air pressure change of measuring.Therefore, particularly, in the contact mode sensor, because external pressure, the thin 10a of portion is in the state to bottom deformation all the time, thereby the contact condition of the upper surface of its maintenance and dielectric film 3 or base plate 21 is as original state.Be set to vacuum by airtight space by this way, because the datum pressure value is an absolute zero pressure, thus eliminated the leeway that allows the thin 10a of portion to be offset owing to exterior temperature change, thus sensitivity and stable accuracy made.Because pressure survey starts from the contact condition of thin 10a of portion and base plate side, so can measure with the excellent sensitivity of linearity excellence.That is, when separating with base plate in the thin portion of original state, accuracy of detection deterioration before thin portion contacts the base plate side according to the variation of external pressure, but when when the contact condition that approaches portion and base plate begins to detect, can eliminate this shortcoming.
More particularly, as mentioned above, the capacitance C of capacitor can be expressed from the next.
(ε represents the specific inductive capacity of dielectric to C=ε (S/d); S represents the area of electrode; D represents interelectrode distance)
For example, in contact mode type pressure transducer, when measurement is equal to or greater than atmospheric pressure, be set to vacuum state as the airtight space S of reference pressure chamber.Therefore, can be so that the thin portion of detection lug near to or in contact with the upper surface of base plate, can obtain the transducer sensitivity characteristic from low-pressure state to high pressure conditions linearity excellence.That is, when interelectrode when relatively large apart from d, pressure transducer detects under low-pressure state the capacitance C at the variation of interelectrode distance d.Afterwards, when owing to proceeding to high pressure conditions and make that thin portion begins to contact backplate surface, pressure transducer is operated to detect the capacitance C at the variable quantity of the area S (contact area) of electrode.
In this case, since capacitance C at the variable quantity of the variation of interelectrode distance d less than capacitance C at the variable quantity of the variation of electrode area S (capacitance variation that changes at unit pressure), so the capacitance variations characteristic (transducer sensitivity characteristic) that changes at pressure becomes non-linear sometimes.Therefore, in order to realize transducer sensitivity characteristic from low-pressure state to high pressure conditions linearity excellence, must be set to vacuum state by airtight space S and make thin portion, contact with each other or approximating state thereby make upper electrode film and lower electrode film be in it all the time to the deflection of base plate side.
As the material that constitutes detection lug 10, it is effective using the quartz material of the hexagonal quartz construction with relative higher toughness.That is, because the piezoid with hexagonal quartz construction has excellent toughness, so it also can be used as oscillator, and it is to be applicable to that stress concentrates on the material of the contact mode type pressure transducer on the specific part of detection lug (approaching portion).
When detection lug is made of the quartz as the transparent body, can measure the thickness of thin portion with high-precision optical ground.
On the other hand, for example, when by processing when making the detection lug 10 with thin 10a of portion having anisotropic AT cutting piezoid with wet etching, shown in Fig. 6 (a), in the thickness of the thin 10a of portion thickness difference appears.Owing to will approach the average that thickness difference among the 10a of portion is scaled thin portion thickness, thickness difference is greater than the thinnest part 10a ' of thin portion.Therefore, handle thinly as far as possible, also processing can not be proceeded to the ultimate value of etching technics even must will approach portion 10.
On the other hand, when when carrying out wet etching, the etching speed fluctuation that causes owing to the anisotropic etching at etching surface taking place hardly to Z axle piezoid (normal of piezoid interarea is consistent with the direction of quartzy crystallographic axis Z).Therefore, shown in Fig. 6 (b), owing to can make thickness attenuation that approaches the 10a of portion and the ultimate value that can in the physical strength that keeps thin portion, reach etching technics equably, so Z axle piezoid is applicable to contact mode type pressure transducer especially effectively.
It can be the oscillating characteristic of frequency with thickness conversion that Z axle piezoid does not have.Therefore, as the method for confirming thickness, can utilize piezoid is that transparent feature adopts optical measurement.
Used the diaphragm of depression that the present invention has been described, but the diaphragm that the present invention is not limited to cave in also can use the diaphragm with writing board shape.
Except measuring the pressure variation such as the gas in the confined space of tire, pressure transducer of the present invention can also be applied to the pressure survey of convection cell.
Label declaration
1 contact mode capacitor type pressure sensor (pressure sensor)
2 lower electrode film
3 dielectric films
5 depressions
6 adhesives
10 detection lugs
The thin section of 10a
The thick portion of 10b
The 10A recess
11 upper electrode films
20 containers
21 base plates
22 sidewalls
23 loam cakes
Claims (13)
1, a kind of contact mode type quartz pressure sensor comprises:
Base plate;
Be arranged on the lower electrode film on this plate upper surface;
Be provided with the detection lug of thin portion; And
Be formed on the upper electrode film on the upper surface of described thin portion of this detection lug,
By described detection lug is fixed on the upper surface of described base plate, make described upper electrode film be positioned at the top of described lower electrode film,
Described detection lug is the contact mode type that makes when electric current is made the quartz material of the cutting angle measured based on the natural frequency of the thickness of described thin portion when mobile in described thin portion by having,
In the pressure survey environment, be always following structure:
The thin portion of described detection lug contacts with described lower electrode film.
2, a kind of contact mode type quartz pressure sensor comprises:
Base plate;
Be arranged on the lower electrode film on this plate upper surface;
Be provided with the detection lug of thin portion; And
Be formed on the upper electrode film on the upper surface of described thin portion of this detection lug,
By described detection lug is fixed on the upper surface of described base plate, make described upper electrode film be positioned at the top of described lower electrode film,
Described detection lug is the contact mode type that makes when electric current is made the quartz material of the thickness slip mode of oscillation measured based on the natural frequency of the thickness of described thin portion or thickness vertical mode when mobile in described thin portion by having,
In the pressure survey environment, be always following structure:
The thin portion of described detection lug contacts with described lower electrode film.
3, a kind of contact mode type quartz pressure sensor comprises:
Base plate;
Be arranged on the lower electrode film on this plate upper surface;
Be provided with the detection lug of thin portion; And
Be formed on the upper electrode film on the upper surface of described thin portion of this detection lug,
By described detection lug is fixed on the upper surface of described base plate, make described upper electrode film be positioned at the top of described lower electrode film,
Described detection lug is by making when electric current is flowed in described thin portion the AT to measuring based on the natural frequency of the thickness of described thin portion cut the contact mode type that piezoid constitutes,
In the pressure survey environment, be always following structure:
The thin portion of described detection lug contacts with described lower electrode film.
4,, it is characterized in that described detection lug comprises the thick portion of described thin portion and the described thin portion of encirclement, and described at least thick portion is fixed on the surface of described base plate according to the described contact mode type of one of claim 1 to 3 quartz pressure sensor.
5, according to the described contact mode type of one of claim 1 to 3 quartz pressure sensor, it is characterized in that described detection lug comprises the thick portion of described thin portion and the described thin portion of encirclement, described base plate is made by quartz material, obtained recess by a part of quartz material being formed thin portion, and on the bottom surface of described recess the stacked lower electrode film of stating to some extent, and, make the thick portion of described detection lug be fixed on the upper surface of thick portion of described base plate by making the thin portion of described detection lug be positioned at mode on the upper surface of recess of described base plate.
6, according to the described contact mode type of one of claim 1 to 3 quartz pressure sensor, it is characterized in that described detection lug and described base plate by making with a kind of quartz material, and by making the consistent each other mode of crystallographic axis of described detection lug and described base plate make described detection lug be fixed on the described base plate.
7,, it is characterized in that described thin portion obtains by with etching technics piezoid being formed thin portion according to the described contact mode type of one of claim 1 to 3 quartz pressure sensor.
8,, it is characterized in that described detection lug comprises the thick portion of described thin portion and the described thin portion of encirclement, and described thin portion obtains by with etching technics piezoid being formed thin portion according to the described quartz pressure sensor of one of claim 1 to 3.
9,, wherein, between the upper surface of the lower surface of the described thin portion of described detection lug and described base plate, be provided with the vacuum space according to the described contact mode type of one of claim 1 to 3 quartz pressure sensor.
10, a kind of manufacture method according to the described contact mode type of one of claim 1 to 3 quartz pressure sensor is characterized in that the thickness of piezoid processed with the step that forms described thin portion and comprises that thickness to described thin portion carries out convert step so that it is confirmed of frequency.
11. the quartz pressure sensor of a contact mode type comprises: base plate; Lower electrode film and the dielectric film of sequential cascade on the upper surface of described base plate; The position relative with described dielectric film is provided with the detection lug on the upper surface that has thin portion and be fixed to described base plate; And be formed at least a portion of described thin portion and be in the upper electrode film of relative position relation with described lower electrode film, described detection lug is the contact mode type that makes when electric current is made the quartz material of the cutting angle measured based on the natural frequency of the thickness of described thin portion when mobile in described thin portion by having, in the pressure survey environment, be always following structure: the upper electrode film of described detection lug contacts with the surface of described dielectric film.
12. the quartz pressure sensor of a contact mode type comprises: base plate; Lower electrode film and the dielectric film of sequential cascade on the upper surface of described base plate; The position relative with described dielectric film is provided with the detection lug on the upper surface that has thin portion and be fixed to described base plate; And be formed at least a portion of described thin portion and be in the upper electrode film of relative position relation with described lower electrode film, described detection lug is the contact mode type that makes when electric current is made the quartz material of the thickness slip mode of oscillation measured based on the natural frequency of the thickness of described thin portion or thickness vertical mode when mobile in described thin portion by having, in the pressure survey environment, be always following structure: the upper electrode film of described detection lug contacts with the surface of described dielectric film.
13. the quartz pressure sensor of a contact mode type comprises: base plate; Lower electrode film and the dielectric film of sequential cascade on the upper surface of described base plate; The position relative with described dielectric film is provided with the detection lug on the upper surface that has thin portion and be fixed to described base plate; And be formed at least a portion of described thin portion and be in the upper electrode film of relative position relation with described lower electrode film, described detection lug is by making when electric current is flowed in described thin portion the AT to measuring based on the natural frequency of the thickness of described thin portion cut the contact mode type that piezoid constitutes, in the pressure survey environment, be always following structure: the upper electrode film of described detection lug contacts with the surface of described dielectric film.
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| JP2003191066 | 2003-07-03 | ||
| JP191066/2003 | 2003-07-03 | ||
| JP152063/2004 | 2004-05-21 |
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| CN100567923C true CN100567923C (en) | 2009-12-09 |
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Families Citing this family (11)
| Publication number | Priority date | Publication date | Assignee | Title |
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| DE102009001924A1 (en) * | 2009-03-27 | 2010-09-30 | Robert Bosch Gmbh | pressure sensor |
| GB2470398B (en) * | 2009-05-21 | 2014-03-19 | Ge Infrastructure Sensing Inc | A resonant sensor for measuring the pressure of a fluid |
| TWI461669B (en) * | 2012-07-18 | 2014-11-21 | Kye Systems Corp | Variable frequency generator and press-sensing cursor controlling device and air shoes using the same |
| CN105897217B (en) * | 2015-08-18 | 2019-04-02 | 应达利电子股份有限公司 | A kind of quartz-crystal resonator, intelligent pressure sensor and its sensing measuring method |
| CN107843384A (en) * | 2016-09-19 | 2018-03-27 | 中国科学院微电子研究所 | A kind of quartz thin film piece vacuum gauge |
| CN107152985A (en) * | 2017-05-04 | 2017-09-12 | 明达实业(厦门)有限公司 | The pressure measxurement control device and its pressure measxurement control method of a kind of air bag |
| CN112867913A (en) * | 2018-10-10 | 2021-05-28 | 约阿内研究有限责任公司 | Piezoelectric sensor |
| CN109520404A (en) * | 2018-12-11 | 2019-03-26 | 王永强 | A kind of device that pressure inductive detection foot is long |
| JP7127534B2 (en) * | 2018-12-26 | 2022-08-30 | セイコーエプソン株式会社 | Force sensing device and robot |
| CN111086755B (en) * | 2019-12-23 | 2022-04-15 | 业成科技（成都）有限公司 | Package assembly |
| CN114334452A (en) * | 2021-12-03 | 2022-04-12 | 北京晨晶精仪电子有限公司 | Capacitor structure and pressure sensor |
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2004
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| 电容式石英膜盒压力传感器的研制. 杨乐民，孙光裕，李耀文，袁峰，彭月璇.哈尔滨工业大学学报，第3期. 1991 |
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