WO2009089946A2

WO2009089946A2 - Micromechanical component and method for producing a micromechanical component

Info

Publication number: WO2009089946A2
Application number: PCT/EP2008/065572
Authority: WO
Inventors: Hubert Benzel; Christoph Schelling
Original assignee: Robert Bosch Gmbh
Priority date: 2008-01-16
Filing date: 2008-11-14
Publication date: 2009-07-23
Also published as: WO2009089946A3; DE102008004639A1

Abstract

The invention relates to a micromechanical component (10) comprising a support (12) having a recess (14) on a surface of the support (12); a membrane (16) which covers the recess (14) to at least some degree; at least one active element (24) with voltage connections arranged on the membrane (16); the active element (24) being designed to vary its spatial extension when a voltage is applied to the active element (24) and to deform the membrane (16); and a microelement (22), arranged on the membrane (16), which can be adjusted by way of a deformation of the membrane (16) due to the application of voltage to the active element (24). The invention further relates to a method for producing a micromechanical component (10) and to a method for operating a micromechanical component (10).

Description

description

title

Micromechanical component and production method for a micromechanical component

The invention relates to a micromechanical component and to a production method for a micromechanical component. Furthermore, the invention relates to a method for operating a corresponding micromechanical component.

State of the art

Micromechanical components, such as Micromirrors are commonly used nowadays. For example, micromirrors are used in light projectors or in optical communication technology. A corresponding micromirror may be a Digital Mirror Device (DMD) as described in US 5,272,262, US 5,600,383 and US 6,819,470. For adjusting a micromirror electrostatic drive mechanisms can be used, as described in US 6,914,710 and US 2005/0013533. An electromagnetic drive mechanism for a micromechanical component is also known from WO 03098918.

Due to the frequent use of micromechanical components, in particular in relatively small devices, it is desirable to have a possibility to reduce the size of a micromechanical component and / or the manufacturing costs for a micromechanical component.

Disclosure of the invention

The invention provides a micromechanical component having the features of claim 1, a manufacturing method for a micromechanical component having the features of claim 9 and a method for operating a micromechanical component having the features of the claim A micromechanical component according to the invention has a membrane with at least one active element which serves as a fastening element for the microelement and as an adjusting element for adjusting the microelement. Since the membrane with the at least one active element can be produced relatively inexpensively and has a comparatively small size, the micromechanical component according to the invention is suitable for many devices. especially the

Multifunctionality of the membrane with the at least one active element is a great advantage.

Preferably, an anchor point at which the microelement contacts the membrane is definable, which is arranged on a natural deformation node line of the membrane. The

In this case, the microelement is rotatable about a certain angular range about an axis of rotation passing through the anchor point, without the microelement being simultaneously lifted.

By way of example, the microelement is a micromirror, a micropincette and / or a micromechanical clamping element. In this case, the micromirror, the micro tweezers or the micromechanical clamping element can easily be adjusted over a relatively large angular range and / or over a comparatively large adjustment difference, whereby a small grid size is ensured due to the high sensitivity of the active elements.

In a preferred embodiment, the at least one active element comprises at least two electrodes, which are each fixedly arranged on the membrane with one end, and whose voltage terminals are designed to apply the voltage between the at least two electrodes, so that the ends facing away from the membrane are at least two electrodes experience attraction or repulsion upon application of the voltage. Due to the fixed arrangement of the at least two electrodes on the membrane, this causes an indentation or bulge of the membrane. In this way, the microelement can easily be adjusted by deforming the membrane.

As an alternative or in addition thereto, the at least one active element may comprise a piezoelectric actuator. When a voltage is applied to the piezoelectric actuator, it is deformed. The deformation of the piezoelectric actuator also affects the membrane, which is in this way on or bulged. Piezoelectric actuators can be formed in a cost effective manner on a membrane by known methods. Thus, a piezoelectric actuator is a cost effective way to realize an active element for the micromechanical component. Furthermore, the active elements may also comprise electromagnetic or thermal transducers. In this case, an active element has the property that, when a voltage is applied, it performs a mechanical work in the form of a volume change and / or a change in position of individual components of the active element.

In a preferred refinement of the micromechanical component, an air opening for pressure equalization in the interior of the recess is formed on the recess. For example, the membrane covers the recess only partially. This prevents a negative or positive pressure in the interior of the recess in a deformation of the membrane and ensures a high flexibility of the membrane.

By way of example, the holder comprises a semiconductor substrate with a cavity. An SOI substrate is not necessary. It is advantageous if a puncture channel is formed in the semiconductor substrate, which runs as an air opening for the pressure equalization between the cavern and a surface of the semiconductor substrate. Such a branch channel can be formed in a simple manner in the semiconductor substrate.

Preferably, at least one sensor element is arranged on the membrane, which is deformed by the deformation of the membrane and which is designed so that upon deformation of the sensor element, a voltage or a change in resistance is induced. On the basis of the induced voltage or the change in resistance, a deformation of the membrane can be detected. Such a sensor element may for example be a piezoelectric element. The data on the behavior of the membrane obtained in this way can be used for a more advantageous activation of the at least one active element.

The advantages described in the upper paragraphs are also ensured by a corresponding method for operating a micromechanical component. Preferably, during the deformation of the membrane, the first deformation fundamental mode or the first deformation upper mode of the membrane is used.

Brief description of the drawings

Further features and advantages of the present invention will be explained below with reference to the figures. Show it:

Fig. 1 shows a cross section through a first embodiment of the micromechanical

component; Fig. 2 shows a cross section through a second embodiment of the micromechanical

component;

3 shows a plan view of a membrane of a third embodiment of the micromechanical component;

Fig. 4 shows an enlarged partial section of Fig. 3;

5 shows a plan view of a membrane of a fourth embodiment of the micromechanical component; and

6 shows an enlarged detail of FIG. 5.

Embodiments of the invention

1 shows a cross section through a first embodiment of the micromechanical component.

The illustrated micromechanical component 10 comprises a semiconductor substrate 12, preferably a silicon substrate. In the semiconductor substrate 12, a cavity 14 is etched. The cavern 14 is completely covered by a membrane 16. The membrane 16 may be made by conventional methods

Silicon are formed. Preferably, the membrane 16 is monocrystalline and wavy.

A monocrystalline membrane has a higher reliability than a polycrystalline membrane, since the latter breaks faster in a multiple deformation. On the membrane 16, an insulating layer 18 is formed. For example, the insulating layer 18 is made of silicon oxide. If the membrane 16 is made of silicon, the insulating layer 18 can be formed by thermal oxidation.

In the middle of the membrane 16, a base 20 is disposed on the insulating layer 18. The base 20 carries a microelement, for example a micromirror 22. The base 20 and the micromirror 22 may be made in one piece from polysilicon. Optionally, a (not shown) reflective layer is applied to the micromirror 22. Instead of the micromirror 22, a micropincet or a micromechanical clamping element can also be arranged on the base 20.

On the insulating layer 18 active elements 24 are arranged. The active elements 24 are electrically insulated from the membrane 16 by means of the insulating layer 18. The active elements 24 may, as shown in Fig. 1, be piezoelectric actuators. As an alternative or as a supplement to the Piezoelectric actuators may be mounted on the insulating layer 18 and electrostatic, thermal and / or electromagnetic actuators as active elements 24. A variety of transducers that perform mechanical work to vary their spatial extent upon application of a voltage are suitable for use as an active element 24.

Each of the active elements 24 has its own voltage connections, so that a voltage can be selectively applied to each of the active elements 24. The voltage applied to the voltage terminals causes a deformation of the associated active element 24. Due to the fixed connection of the active elements 24 formed as piezoelectric actuators with the insulating layer 18, a deformation of an active element 24 is transferred to the insulating layer 18 and the membrane 16. Thus, deformation of an active element 24 may also cause deformation of the membrane 16. Since the voltage terminals of the active elements 24 are formed so that each of the active elements 24 can be controlled individually, the active elements 24 can be deformed so that the membrane 16 is deformed into a desired corrugated final shape.

If the membrane 16 is not deformed, the pedestal 20 is parallel to a vertical axis 26 which intersects the surface of the semiconductor substrate 12 at a right angle. In a deformation of the membrane 16, the base 20 and the micromirror 22 are moved from their (not shown) starting position by an angle α in a desired end position.

In the example shown in FIG. 1, the cavern 14 is completely covered by the membrane 16. Alternatively, the membrane 16 may only partially cover the cavity 14. The incomplete coverage of the cavern 14 prevents in this case that a deformation of the membrane 16, a negative or positive pressure in the cavern 14 occurs.

Likewise, the cavern 14 may be formed open to one side. In the example of FIG. 1, a branch channel 28 is etched into the semiconductor substrate 12, which connects the interior of the cavity 14 with the surface of the insulating layer 18. Through the branch channel 28, air can be sucked into the cavern 14 or flow out of the cavern 14. Thus, the puncture channel 28 prevents the occurrence of an underpressure or overpressure in the cavern 14 in the event of a deformation of the membrane 16. The pressure compensation made possible by means of the puncture channel 28 increases the flexibility of the membrane 16.

2 shows a cross section through a second embodiment of the micromechanical component.

The illustrated micromechanical component 50 comprises a semiconductor substrate 52, preferably made of

Silicon and p-doped, with a cavern 54. The cavity 54 may for example have a height of about 1 to 10 microns. As an alternative to the shown closed formation of the cavern 54 For example, the semiconductor substrate 52 may also have an open cavity, the possible edges of which are represented by the dashed lines 56.

Cavern 54 is completely covered by a membrane 58. The membrane 58 may extend over the entire surface of the semiconductor substrate 52. Alternatively, the membrane 58 may be limited to portions of the surface and edges of the cavity 54. Preferably, the membrane 58 is made of monocrystalline silicon and is corrugated.

On the surface of the membrane 58, an insulating layer 60 is formed. The insulating layer 60 may include, for example, silicon oxide. If the membrane 58 is made of silicon, the insulating layer 60 can be formed by thermal oxidation of the membrane 58.

The micromechanical component 50 has, as a microelement, a micromirror 62, which is arranged above the insulating layer 60 by means of a base 64. In this case, the base 64 is preferably attached to the insulating layer 60 in such a way that a center axis of the cavity 54 running vertically to the semiconductor substrate 52 extends through the base 64. Instead of the micromirror 62, the base 64 may also carry a micropincet or a micromechanical clamping element. Above the insulating layer 60, a plurality of pedestals 64 may be fixed with the same or different microelements.

In a deformation of the diaphragm 58, the micromirror 62 can be tilted with the base 64 from its starting position shown in Fig. 2 by a certain angular range. For deforming the membrane 58 60 active elements 66 are formed on the insulating layer. The two active elements 66 are arranged on different sides of the base 64.

Each of the two active elements 66 comprises a plurality of electrodes 68. The electrodes 68 are preferably designed as interdigital electrodes. Each of the electrodes 68 of an active element 66 is fixedly connected to the micromechanical component 50 by one end 70. In addition, the electrodes 68 are electrically connected at their ends 70 to leads 72. However, only one supply line 72 is shown by way of example in FIG. In this case, the electrical contacting of the electrodes 68 via the leads 72 is formed so that each of the electrodes 68, which is arranged between two adjacent electrodes 68, is electrically connected to a different feed line 72, as the adjacent electrodes 68 to her. This is feasible in that the leads 72 formed on the insulating layer 60 are covered with a passivation layer 74. The passivation layer 74 may be made of silicon nitride (SiN), for example. The electrodes 68 are on a surface of the

Passivation layer 74 arranged. In order to allow an electrical contact between a feed line 72 and its associated electrodes 68 are within the passivation layer 74th Line contacts 76 are formed, which each electrically connect a supply line 72 with one of the supply line 72 associated electrodes 68.

The active elements 66 described in the above paragraph can be made by applying polysilicon on the insulating layer 60 to form the leads 72. Subsequently, the leads 72 are covered with the passivation layer 74. Recesses can now be etched into the passivation layer 74, by means of which the positions of the later formed line contacts 76 are determined. Subsequently, the material for the electrodes 68 and the line contacts 76 is applied to the passivation layer 74. For example, a polysilicon layer may be formed on the passivation layer 74 for this purpose. This also fill the recesses in the

Passivation layer 74 with polysilicon for forming the line contacts 76. Subsequently, in an etching step, the electrodes 68 are etched from the layer applied to the passivation layer 74.

Preferably, the electrodes 68 are formed as thin plates, which are arranged perpendicular to the surface of the semiconductor substrate 52. Via the leads 72, a voltage between adjacent electrodes 68 can be applied. In this case, the ends 78 of the electrodes 68 which project from the micromechanical component 50 are attracted or repelled, depending on the voltage applied between the electrodes 68. In this case, the electrodes 68 pass from their initial position shown in FIG. 2 into an end position in which the ends 78 are either approached to one another or are spread apart from one another. The distance between two adjacent ends 78 is thus dependent on the voltage applied between the electrodes 68.

Since the electrodes 68 are connected at their ends 70 fixed to the micromechanical device 50, causes a change in the distance between two adjacent ends 78 a on or

Bumping of the membrane 58. In this way, the micromirror 62 and the base 64 can be adjusted from its initial position to a desired end position.

In order to apply a voltage between two adjacent electrodes 68, the micromechanical component 50 has circuit devices 80. Such circuit devices 80 can be manufactured by known manufacturing methods. The production of the circuit device 80 will therefore not be discussed in more detail here.

Preferably, at least one diffusion 82, for example of the p-type, is formed between the circuit device 80 and the cavity 54 within the membrane 58 formed as an epitaxial layer. Likewise, the circuit device 80 may be covered by a dielectric layer 84. Furthermore, the cavern 54 may have an outwardly communicating connection. Piezo resistors 86 are in the membrane 58. Each of the piezoresistors 86 includes a highly doped diffusion and a piezoelectric layer 90 as a contact region 88. Upon deformation of the membrane 58, a change in resistance is induced in the piezoresistors 86, based on which the deformation of the membrane 58 for a ( not shown) evaluation is detected. The activation of the active elements 66 can take place in this case taking into account the deformation of the membrane 58 detected by the evaluation device.

In the example of FIG. 2, the insulating layer 60 extends over the entire extent of the membrane 58. Alternatively, the insulating layer 60 may be formed only between the membrane 58 and the leads 72.

The micromechanical component 50 has a good integration of micromechanics and microelectronics on a semiconductor substrate 52 (chip). The semiconductor substrate 52 may be a simple substrate. An SOI substrate is not necessary. This reduces the manufacturing costs for the micromechanical component 50.

Further cost advantages lie in the small and thin dimensions of the membrane 58. An evaluation circuit can easily be integrated into the micromechanical component 50, in particular into the membrane 58. The multifunction of the membrane 58 as a fastening element for the microelement, as an adjusting element and as a sensor component contributes to the reduction of the size of the micromechanical component 50. In addition, the structure and the connection technique of the micromechanical component 50 are simplified in this way.

In particular, in the case of a monocrystalline membrane 58 made of silicon, a desired spring constant can be easily adjusted by the mechanical layer stress. This guarantees a defined behavior of the diaphragm 58, if necessary with high flexibility.

3 shows a plan view of a membrane of a third embodiment of the micromechanical component. 4 shows an enlarged partial section of FIG. 3. The micromechanical component shown is particularly well suited for a linear scanning mirror.

The membrane 100 shown in FIG. 3 is made of monocrystalline silicon. Instead of the shown square shape, the membrane 100 may also be circular or oval in shape. Accordingly, the shape of the (not outlined) cavern can adapt to the shape of the membrane 100. In the example shown in Fig. 3, the cavern has a nearly square base, which is represented by the line 102. The dashed line AA 'marks the cross section of FIGS. 1 and 2.

In the middle of the membrane 100, or on a nodal line 104 of a deformation mode of the membrane 100, there is an anchor point 106 of a (not shown) base, on which a

Microelement, such as a micromirror, is arranged. The microelement may be adjusted by deforming the membrane 100 for a particular angular range about the nodal line 104. For deforming the membrane 100 are within the areas 108 and 110 of the membrane 100 active elements, which are not shown in Fig. 3, however. The regions 108 and 110 have the largest membrane curvature when the membrane 100 is deformed. In addition, they include the regions 108 of the deformation bellies and the regions 110 at the edges of the membrane 100. The regions 110 at the edges of the membrane 100, especially at the edges parallel to the nodal line 104, are also particularly well suited for mounting sensor elements for detection a current deformation of the membrane 100, such as piezoresistors.

Fig. 4 shows two groups of electrodes 112 and 114 which are mounted parallel to each other within the region 108 of a deformation belly on the membrane (not shown). In this case, the first group of electrodes 112 and the second group of electrodes 114 are arranged relative to one another such that exactly one electrode 114 of the second group is arranged between two electrodes 112 of the first group. Between each electrode 112 of the first group and an adjacent electrode 114 of the second group 114, a voltage can be applied, through which the projecting from the membrane ends of the electrodes 112 and 114 attract or repel. This causes a bulge or bulge of the membrane 100.

The membrane 100 can be set in vibration by the active elements, so that sets a certain deflection mode. The deflections are preferably parallel to the edges of the membrane 100.

In Fig. 3, the membrane 100 on a first side 116 of the node line 104 has a (light marked) bulge. On the opposite second side 118 of the node line 104 is a

(darker marked) vaulting. The concavity and the bulge cause a tilt of the attached to the anchor point 106 microelement to the second side 118th

5 shows a plan view of a membrane of a fourth embodiment of the micromechanical component. FIG. 6 shows an enlarged detail of FIG. 5. The micromechanical component shown is well suited for a surface grid scanner. The illustrated membrane 150 is formed above a cavern (not shown) having a circular bottom surface 152. Above a center of the bottom surface 152, the diaphragm 150 has an anchor point 154 for securing a pedestal and a microelement. The membrane 150 lying around the anchor point 154 is subdivided into sectors 156.

FIG. 6 shows a sector 156 having first and second sets of electrodes 158 and 160 disposed thereon. Electrodes 158 and 160 have an arcuate shape that conforms to the boundaries of sector 156. Each electrode 160 of the second group is disposed between two electrodes 158 of the first group. Between each of the first group electrode 158 and an adjacent second group electrode 160, a voltage may be applied through which the ends of the electrodes 158 and 160 protruding from the membrane (not shown) attract or repel. This causes convexities or bulges on the membrane 150. FIG. 5 shows membrane height lines 162 of an exemplary deformation of the membrane 150.

For deforming the membrane 150, other active elements can also be arranged in each of the sectors 156. For example, piezoelectric, thermal and / or electromagnetic transducers may be used to deform the diaphragm 150.

By dividing the membrane 150 into at least three sectors 156 surrounding the anchor point 154, a deflection of the microelement attached to the anchor point 154 is in all

Spatial directions possible. The micromechanical component explained with reference to FIGS. 5 and 6 therefore has a high number of degrees of freedom for adjusting the microelement.

For the application, the first excited oscillation or deformation modes and less the fundamental mode of the membrane 150 are primarily interesting. The anchor point of the to be actuated

Elements is preferably located on a natural deformation node line of the membrane, i. one of those lines that undergoes no amplitude deflection at a vibration. In this way, it is easy to achieve a tilting of the membrane center point, or of the anchor point 154, and of the microelement anchored thereon, without an elevation of the entire microelement being connected to it. It is both a static and a dynamic operation for adjusting the microelement conceivable.

The micromechanical component described with reference to the above paragraphs can be used both for image projectors, for example head-up displays or video projectors, and for laser printers.

Claims

Claims:

1. micromechanical component (10.50) with

a holder (12, 52) having a recess (14, 54) formed on a surface of the holder (12, 52);

a membrane (16, 58, 100, 150) which at least partially covers the recess (14, 54);

at least one on the membrane (16,58,100,150) arranged active element (24,66) with

Voltage terminals (72); wherein the active element (24,66) is adapted to vary its spatial extent upon application of a voltage to the active element (24,66) and to deform the membrane (16,58,100,150); and

a on the membrane (16,58,100,150) arranged microelement (22,62), which via a

Deformation of the membrane (16,58,100,150) by applying the voltage to the active element (24,66) is adjustable.

2. The micromechanical component (10, 50) according to claim 1, wherein an anchor point (106, 154) on which the microelement (22, 62) contacts the membrane (16, 58, 100, 150) is definable, which is located on a natural deformation node line (104) Membrane (16,58,100,150) is arranged.

3. The micromechanical component (10, 50) according to claim 1, wherein the microelement (22, 62) is a micromirror (22, 62), a micropincette and / or a micromechanical clamping element.

4. micromechanical component (10,50) according to any one of the preceding claims, wherein the at least one active element (24,66) comprises at least two electrodes (68,112,114,158,160), which with one end (70) fixed to the membrane (16,58,100,150) are arranged, and whose voltage terminals (72) for applying the voltage between the at least two electrodes (68,112,114,158,160) are formed, so that the of the membrane (16,58,100,150) facing away from the ends (78) of the at least two electrodes (68,112,114,158,160) upon application of Stress experience an attraction or a repulsion.

5. micromechanical component (10,50) according to any one of the preceding claims, wherein the at least one active element (24,66) comprises a piezoelectric actuator (24).

6. micromechanical component (10,50) according to any one of the preceding claims, wherein at the recess (14,54) an air opening (28) for a pressure equalization in the interior of the recess

(14,54) is formed.

7. Micromechanical component (10, 50) according to one of the preceding claims, wherein the holder (12, 52) comprises a semiconductor substrate (12, 52) with a cavity (14, 54), and wherein in the semiconductor substrate (12, 52) a puncture channel (28) is formed, which as an air opening (28) for the pressure equalization between the cavern (14,54) and a surface of the semiconductor substrate (12,52) extends.

8. micromechanical component (10.50) according to any one of the preceding claims, wherein on the membrane (16,58,100,150) at least one sensor element (86) is arranged, which by the

Deformation of the membrane (16,58,100,150) is deformed and which is designed so that upon deformation of the sensor element (86), a voltage or a change in resistance is induced.

9. Manufacturing Method for a Micromechanical Component (10,50) with the Steps:

Forming a support (12, 52) with a recess (14, 54) formed on a surface of the support (12, 52);

Attaching a membrane (16, 58, 100, 150) to the support (12, 52) and at least partially covering the recess (14, 54) with the membrane (16, 58, 100, 150);

Arranging at least one active element (24, 66) with voltage terminals (72) on the membrane (16, 58, 100, 150), the active element (24, 66) being designed to expand its spatial extent when a voltage is applied to the active element (24, 66) to vary and deform the membrane (16,58,100,150); and

Arranging a microelement (22, 62) on the membrane (16, 58, 100, 150) such that the microelement (22, 62) is adjustable by deforming the membrane (16, 58, 100, 150) by applying the voltage to the active element (24, 66) ,

10. A method for operating a micromechanical component (10,50), comprising a holder (12,52) with a on a surface of the holder (12,52) formed recess (14,54), a Membrane (16, 58, 100, 150) which at least partially covers the recess (14, 54), at least one active element (24, 66) with voltage connections (72) arranged on the membrane (16, 58, 100, 150), the active element (24, 66) being is designed to vary its spatial extent upon application of a voltage to the active element (24, 66) and to a microelement (22, 62) arranged on the membrane (16, 58, 100, 150), comprising the steps:

Deforming the membrane (16,58,100,150) by applying the voltage to the active element (24,66) for adjusting the micro-element (22,62).