WO2009086976A2

WO2009086976A2 - Micromechanical component and production method for a micromechanical component

Info

Publication number: WO2009086976A2
Application number: PCT/EP2008/065524
Authority: WO
Inventors: Tjalf Pirk; Stefan Pinter; Joachim Fritz; Christoph Friese
Original assignee: Robert Bosch Gmbh
Priority date: 2008-01-07
Filing date: 2008-11-14
Publication date: 2009-07-16
Also published as: DE102008003344A1; WO2009086976A3

Abstract

The invention relates to a micromechanical component, comprising at least one stator electrode (21) with at least one lateral surface, divided into at least two electrically conducting sections (26, 27, 29, 30) which are electrically insulated from each other and which are subjected to differing voltages. The micromechanical component further comprises at least one moving actuator electrode (22), which has a lateral surface divided into at least two electrically conducting sections (32, 34; 80, 82) which are electrically insulated from each other and which are subjected to differing voltages. The lateral surface of the actuator electrode (22) is arranged to face the lateral surface of the stator electrode (21; 71a, 71b; 103, 104).

Description

description

title

Micromechanical component and production method for a micromechanical component

STATE OF THE ART

The present invention relates to a micromechanical component and to a production method for a micromechanical component.

Techniques that have been developed for the progressive miniaturization of electrical systems, in particular on the basis of semiconductor materials, are now also applied to electro-mechanical components. Among other things, miniaturized electro-mechanical systems, so-called MEMS (micro electro-mechanical systems), which can represent, for example, control elements for miniaturized mirrors made of semiconductor materials, are produced.

An actuator or an actuator is known from US 2007/0215961 A1. Two comb-shaped electrodes interlock. When applying an electrical voltage across the two electrodes, the two electrodes are attracted by electrostatic forces. A restoring force results from bending or twisting solid-state joints, over which one of the electrodes is suspended.

DISCLOSURE OF THE INVENTION

The micromechanical component according to the invention comprises at least one stator electrode which has a side surface which is subdivided into at least two electrically insulated sections which are insulated from one another and which can be acted on with different potentials; and at least one movable actuator electrode having a side surface which is subdivided into at least two electrically insulated sections which are electrically insulated from one another and which can be subjected to different electrical potentials. The side surface of the actuator electrode is arranged facing the side surface of the stator electrode. Electrostatic forces act only between the electrodes of the actuator and a portion of an electrode of the stator when they are at a different electrical potential. The respective subdivision of the actuator and the stator or their electrodes into at least two sections makes it possible by appropriate application of electrical potentials that the actuator is attracted only by individual ones of the sections. The actuator electrode will rotate in the direction that allows the greatest possible overlap with the portion or portions of the stator electrode that are at a different electrical potential. The actuator can thus be actively rotated in both directions.

A further aspect of the present invention relates to a production method for a micromechanical component with the following method steps. A substrate of a first semiconductor substrate, a second semiconductor substrate and an intermediate insulating layer is provided. From one side of the substrate, a trench structure is etched into the first semiconductor substrate, the insulating layer, and the second semiconductor substrate for patterning area electrodes of the first and second semiconductor substrates for a stator and an actuator of the actuator.

The geometrical arrangement of the stator to the actuator is determined by an etching process. A deviation of the relative positioning can be essentially limited to the manufacturing tolerances of lithographic patterning methods. Complex assembly of the actuator from a separately produced actuator and a stator can be avoided.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be explained below with reference to preferred embodiments and attached figures. In the figures show:

1 shows a gimbal-mounted mirror with micromechanical device,

2 shows a first embodiment of a micromechanical component,

3 shows an illustration of the actuation of the micromechanical component,

4 shows a second embodiment of a micromechanical component,

Fig. 5 to 9 cross-sections for illustrating process steps for the production of a micromechanical device 10 is a plan view of a third embodiment of a micromechanical device,

11 is a side view of the third embodiment of a micromechanical device,

12 is a side view of the fourth embodiment of a micromechanical device and

13 is a plan view of a fourth embodiment of a micromechanical device.

EMBODIMENTS OF THE INVENTION

In the following figures, like reference characters designate the same or functionally identical elements. The individual elements are reproduced in their essential spatial arrangement corresponding to each other by embodiments in the figures, but not to scale.

An adjustable mirror 2 is shown by way of example as an application for a micromechanical component 1 in a plan view in FIG. The micromechanical component 1 is produced from a monolithic substrate 3 by patterning methods which include lithographic mask techniques, etching methods and deposition methods, in particular of metallic surfaces. An exemplary manufacturing method will be explained in detail after the structural description of embodiments of the micromechanical components and their operating principles.

The adjustable mirror 2 may have a metallized surface. The metallic layer may be made, for example, of aluminum or silver having a thickness in the range of 50 nm to 500 nm. The supporting body of the mirror 2 consists of the substrate 3.

The mirror 2 is attached via two twistable inner solid joints 4 to an inner frame 5a, 5b, 5c, 5d, 5e, 5f. The inner solid joints 4 and the inner frame 5a, 5b, 5c, 5d consist of the substrate 3. The inner frame 5a, 5b, 5c, 5d, 5e, 5f is a mechanically coherent structure, which preferably has a rigid and torsionally rigid shape.

The mirror 2 is separated from the inner frame 5a, 5b, 5c, 5d, 5e, 5f by two trenches 6 or cavities. The trenches 6 span the entire mirror 2 and are interrupted only by the two inner solid-state joints 4. The depth of the trenches 6 corresponds at least to the thickness of the mirror 2, so that it is suspended only at the two inner solid-body joints 4. The mirror 2 can thus be turned or tilted relative to the inner frame 5a, 5b, 5c, 5d, 5e, 5f. The trenches 6 are made by removing the substrate 3. The inner frame 5a, 5b, 5c, 5d, 5e, 5f is also separated from the substrate 3 by two trenches 7. The only mechanical suspension of the inner frame 5a, 5b, 5c, 5d, 5e, 5f on the substrate 3 via outer solid joints 8. The outer solid joints 8 are equal to the inner solid joints torsionally, so that the inner frame 5a, 5b, 5c, 5d, 5e, 5f can be tilted or rotated relative to the substrate 3. The torsion axes of the inner and outer solid joints 4, 8 are preferably perpendicular to each other or at least not parallel to each other, to allow a tilt of the mirror in any direction.

Tilting of the mirror 2 is effected by micromechanical components or electrostatic actuators 10, 12. The structure of the actuators 12 for tilting the inner frame 5a, 5b, 5c, 5d, 5e, 5f and the actuators 10 for the mirror 2 can be made according to the same schematic structure. Because of the different torques to be provided, the actuators 10, 12 can be dimensioned differently.

The actuator 10 has a stator 14 and a rotor 15. The stator 14 is mechanically fixed to the inner frame 5a, 5b, 5c, 5d, 5e, 5f. The rotor 15 is mechanically fastened to the mirror 2. The shaft of the rotor 15 is formed by the mirror 2 and the solid-state joints 4. Both the stator 14 and the rotor 15 have a plurality of flat or lamellar electrodes arranged in parallel. This results in a comb-like structure. The electrodes of the stator 14 (stator electrodes) and the electrodes of the rotor 15 (rotor electrodes) interlock, so that the electrodes overlap in a lateral projection (see FIG. 2).

An electrical supply to the stator 14 via a part 5b of the inner frame. The rotor 15 is contacted via the mirror 2, one of the solid-state joints 4 and another part 5a of the inner frame. The electrical lines can be electrically insulated from one another by isolation trenches 16, which can be filled with a dielectric. The lines are preferably formed by the substrate 3. For improved conductivity, metallic interconnects may be disposed on the inner frame 5a, 5b, 5c, 5d, 5e, 5f, or the substrate 3 may be heavily doped.

When applying different electrical potentials to the stator 14 and to the rotor 15, an electrostatic force acts, pulling the rotor electrodes between the stator electrodes. Since a lateral movement of the mirror 2 in the direction of the stator 14 is prevented by the solid-state joints 4, the mirror 2 twists until the greatest possible overlap between the rotor electrodes and the stator electrodes is established. There is no possibility to generate repulsive forces by electrostatic actuators. The stator electrodes 14 can not push out the rotor electrodes 15 to support their electrodes mirrored to the shaft.

A schematic cross section through an embodiment of a micromechanical component or actuator 20 is shown in FIG. The actuator 20 has a stator 21 and a rotor 22, of which in each case a planar electrode is shown.

The rotor 22 includes a shaft 23 which is rotatably suspended. For this purpose, the shaft 23 can be fastened to a frame 5 a, 5 b, 5 c, 5 d, 5 e, 5 f or a substrate 3 by means of a twistable solid-body joint 4. The planar rotor electrode can be subdivided into two conductive sections 32, 34 by means of an electrically insulating insulation layer 33. In this embodiment, different potentials can be applied to the two sections 32, 34.

The planar electrode of the stator 21 is separated into at least two separate opposite regions 24, 25. The two regions 24, 25 are preferably arranged mirror-symmetrically to the shaft 23. In the illustrated embodiment, each of the regions 24, 25 has two conductive portions 26, 27 and 29, 30, respectively. The conductive portions 26, 27 and 29, 30 are separated by an electrically insulating insulating layer 28 and 31, respectively. Via electrical lines of the micromechanical component can thus be applied to the four mutually electrically insulated regions 26, 27, 28, 29 of the planar stator electrode 21 different potentials.

An exemplary control scheme for the actuator 20 serves to explain its operating principle. FIG. 2 shows a rotation of the rotor or rotor electrode 22 in the counterclockwise direction 35. A first torque is generated by applying different electrical potentials to the upper right portion 26 of the stator electrode 21 and the lower portion 34 of the rotor electrode 32. A second torque is generated by applying different potentials to the left lower portion 30 of the stator electrode 21 and the upper portion 32 of the rotor electrode 22.

To the left upper portion 29 of the stator electrode 21 and the right lower portion 27 of the stator electrode 21 is preferably applied a potential which exerts only a small force on the rotor electrode 22. In this case, an averaged potential from the two potentials on the upper and lower sections 32, 34 of the rotor electrodes 22 can prove to be advantageous.

As an example, two different potentials are indicated symbolically in FIG. 2 as "+" or "-" and their mean value as "0". The total torque is approximately composed of the first and second torque and acts on the shaft 23. The rotation 35 is in the counterclockwise direction. The mirror 2 or the inner frame 5a, 5b, 5c, 5d, 5e, 5f, which is connected to the shaft 23, is accordingly tilted from its rest position.

The rotor can, for example, together with the mirror 2 or the inner frame 5a, 5b, 5c, 5d, 5e, 5f, be actively moved by electrostatic forces back to its rest position. To the sections 26, 27, 28, 29 of the stator electrode 21 to other potentials are applied, as indicated in Figure 3. The two upper sections 26, 29 of the stator 22 have a different potential to the upper section 32 of the rotor electrode 22. The two lower sections 27, 28 of the stator electrode 22 have a different potential to the lower section 34 of the rotor electrode 22.

A tilting of the rotor electrode 22 from its rest position in a clockwise direction (not shown) is possible by a further change in the potentials, for example, with a permutation of the stator potentials of Fig. 2.

The electrostatic forces also cause lateral forces on the shaft 23. The stator electrode 21 and the rotor electrode 22 may be symmetrical, e.g. mirror-symmetrical to the shaft 23 as indicated in Figure 2, be constructed. The lateral forces then act symmetrically and compensate each other.

The structure of the stator 21 and the rotor 22 is not limited to the illustrated embodiments.

The planar electrodes of the stator 40 and rotor 41 may be divided into a larger number of mutually electrically isolated sections. FIG. 4 shows a structure of a stator 40 with six sections 41, 43, 45. By further insulation layers 44 arranged in parallel to a first insulation layer 42, the planar electrode of the stator 40 can be subdivided into any number of sections 41, 43, 45.

Similarly, the rotor may additionally or alternatively have more than two sections.

An embodiment of an actuator 10, 12, 20 has a rotor and a stator, each having more than one planar electrode (see Fig. 1). The planar electrodes of the stator or rotor are arranged parallel to one another and connected to one another electrically and mechanically. The electrical connection essentially takes place through the substrate 3, from which they are formed as a coherent piece. The electrical insulation of the individual sections of the electrodes is achieved by the insulation layer 33 or insulating trenches 6, 62 running parallel to the surface of the substrate 3. The sections of the electrodes with the same spatial orientation with respect to the shaft of the rotor remain electrically connected by the substrate 3.

An embodiment of a manufacturing method for actuators will be explained in conjunction with FIGS. 5 to 9.

The starting point is a substrate 50, preferably a semiconductor substrate, e.g. Silicon (see Fig. 5). In the substrate 50, an insulating layer 52 is buried, which divides the substrate 50 into an upper and a lower electrically insulated section 51, 53. The substrate 50 may be, for example, a silicon on insulator (SOI) substrate in which the insulating layer 52 is formed by silicon oxide or silicon nitride. Alternatively, the insulating layer 52 may be formed by a barrier doping.

The upper substrate portion 51 must have a sufficient thickness for the elements to be subsequently structured. Typically, a thickness of 40 to 100 microns is sufficient. The upper and lower substrate portions 51, 53 may be doped to increase their electrical conductivity.

In the upper substrate portion 51, an opening 54 for via is etched up to the insulating layer 52 (FIG. 6). A cavity 55 or a wide depression is etched into the lower substrate portion 53. Cavern 55 lies below the areas in which subsequently movable elements of the actuator or of the micromechanical component are located. The cavern 55 and the opening 54 can be etched together wet-chemically, for example with a potassium hydroxide solution.

The lower substrate portion 53 is preferably further patterned by an anisotropic etching process, for example, a plasma assisted etching process, reactive ion etching. Below the areas for solid joints 56, a mirror 57 or other movable elements, the lower substrate portion 53 is removed up to the insulating layer 52. Excluded are the areas 58, in which subsequently the actuators are formed.

As processing aid, trenches 59 circulating in the lower substrate section 53 can be structured in the edge region outside the cavern 55. A metallization can be applied to the insulating layer 52 in the area 57, which later forms the back of a mirror 2.

Cavern 55 is filled with a varnish 58 or other easily removable sacrificial material (FIG. 8). On the one hand, this increases the mechanical stability for the subsequent structuring step and, on the other hand, prevents the subsequent trenches produced from forming through-flow channels between a front and the back of the fabricated structure during the manufacturing process.

A metallization can be applied on the front side in order, on the one hand, to generate printed conductors, through-contacts 69 and, on the other hand, a reflective surface 60. The via holes 69 may have waveguides insulated from the upper substrate portion 51 to individually contact the lower substrate portion 53. Accordingly, additional insulation layers can be deposited (not shown).

The reflective surface 60 may be fabricated together or separately with the conductive traces 69 depending on whether a different thickness of metal layer is required.

The actuators 61 are manufactured by an etching process. Trenches 62 are etched in the upper substrate section 51, laterally delimiting and insulating the electrodes 63, 64 of the stator and the rotor. Thereafter, the structure of the trenches 62 is transferred into the insulating layer 52 by a second etching step, and the trenches 62 are extended into the lower substrate section 53 by means of a third etching step. The trenches 62 extend as far as the sacrificial layer 58 filled into the cavern 55.

The relative location and spacing of the electrodes 63, 64 of the stator and the rotor are defined by the trenches 62. The reproducibility of an actuator is thus essentially limited only by the etching methods and lithographic imaging methods used.

The reproducibility can be increased by using a single mask. For this purpose, a hard mask is applied to the surface before the trenches 62 are etched into the upper substrate section 51. The hard mask is preferably made of the same material as the buried insulating layer 52. The hard mask is structured lithographically by a resist mask. The resist mask remains in the etching of the trenches 62 in the upper substrate portion 51 and in the insulating layer 52 on the hard mask. Thereafter, it is preferably removed. The trenches 62 are extended into the lower substrate portion 53 using the hard mask. Alternatively, a mask can be made other material which is not etched by etching processes that attack the buried insulating layer.

Finally, the sacrificial layer 58 is removed. The structure produced can still be suitably capped to protect it from environmental influences.

A third embodiment of a micromechanical device 70 is shown in plan view and side view in Figures 10 and 11. The micromechanical component 70 has two stators which are electrically insulated from one another and each having at least one electrode 71a, 71b. Between the stators electrodes 72 of an actuator are arranged. The actuator is suspended by a solid-body joint 74 on a substrate 73. The solid-state joint 74 may be twistable and / or bendable. This can allow both a translational movement between the two stator electrodes 71a, 71b or perpendicular to the stator electrodes 71a, 71b. Further, rotational movement about the solid-state hinge 74 may be enabled, as in the previously described embodiments.

The stator electrodes 71a, 71b and the actuator electrode 72 are in mutually insulated portions 72a, 73a as in the previously described embodiments; 72b, 73b and 80, 81, respectively, through insulating layers 76a, 76b; 81 isolated. The opposite side surfaces of the electrodes are thus in the separate sections 72a, 73a; 72b, 73b; 80, 81 divided. Preferably, the sections extend over the entire longitudinal extent of the electrodes. The sections are arranged successively in the transverse direction of the side surface.

A method for displacing the actuator 72 between the stators 71a, 71b in the direction 75 applies the opposite potentials to the opposite portions of the one of the stators 71a and the actuator 72 and the same potentials to the portions of the other of the stators 71a Sections of the actuator 72 at.

A method of shifting the actuator 72 in the direction 76 perpendicular to the stators 71a, 71b applies a first potential (+) to the upper portions 72a, 72b of the stators 71a, 71b, and a middle potential to the lower portions 73a, 73b 0, to the lower portion 82 of the actuator 72, a second potential (-) and to the upper portion 80 of the actuator 72, a middle 0 or first potential (+). The first potential (+) and the second potential (-) are different. The mean potential 0 is between the first (+) and second potential (-). For displacement opposite to direction 76, the potentials are to be reversed symmetrically to the illustrated horizontal plane.

A method for rotating the actuator 72 relative to the stators 71a, 71b specifies potentials analogous to the embodiment described in connection with FIG. A fourth embodiment 90 has only one stator 91. The stator 91 is insulated in at least two mutually insulated portions 93, 94 by an insulating layer 94. An actuator 92 of the fourth embodiment 90 is also divided into at least two mutually insulated portions 96, 97 by an insulating layer 97. The actuator 92 can be shifted and rotated by applying corresponding potentials, as described in connection with the third embodiment.

A fifth embodiment of a micromechanical device uses three actuators 102 arranged in a triangle or along a circle 106. Each of the actuators 102 has stators 103, 104 and an actuator 105. The structure of the actuators 102 may correspond to one of the preceding embodiments. The arrangement of the actuators 102 allows a base plate 101 to rotate, translate and pivot in any direction.

Claims

claims

A micromechanical component (10, 12, 20) having at least one stator electrode (21; 71a, 71b; 103, 104) which has a side surface which is divided into at least two electrically conductive sections (26, 27, 29 , 30, 41, 43, 45, 72a, 72b, 73a, 73b), which can be subjected to different potentials; and at least one movable actuator electrode (22; 72; 105) which has a side surface which is subdivided into at least two electrically-insulated sections (32, 34; 80, 82) which are electrically insulated from one another and which can be subjected to different electrical potentials. and the side surface of the actuator electrode (22; 72; 105) is disposed facing the side surface of the stator electrode (21; 71a, 71b; 103,104).

2. The micromechanical device according to claim 1, wherein the side surface of the actuator electrode overlaps with at least one of the electrically insulated portions (26, 27, 29, 30, 41, 43, 45, 72a, 72b, 73a, 73b) of the stator electrode is arranged.

3. A micromechanical device according to claim 1 or 2, wherein the at least two mutually electrically insulated, electrically conductive portions (32, 34, 80, 82) are arranged in succession in the transverse direction of the side surface.

4. A micromechanical device according to one of the preceding claims, which has in each case one of the stator electrodes (21; 71a, 71b; 103, 104) arranged on mutually opposite end regions of at least one of the movable actuator electrodes (22; 72; 105).

5. A micromechanical device according to one of the preceding claims, comprising a first comb formed from a plurality of the stator electrodes (13, 14, 41, 103, 104), which are arranged with their side surfaces parallel to each other, and a second comb formed from a A plurality of the actuator electrodes (22; 72; 105) arranged with their side surfaces parallel to each other, and wherein the first comb is arranged engaging in the second comb.

6. A micromechanical device according to one of the preceding claims, wherein at least three of the actuator electrodes are arranged along a circle and a movable support is connected to the three actuator electrodes for tilting about each spatial direction.

7. A manufacturing method for a micromechanical device comprising the following method steps: providing a substrate (50) comprising a first semiconductor substrate (51), a second semiconductor substrate (53) and an intermediate insulating layer (52); Etching a trench structure (62) from a side of the substrate (50) into the first semiconductor substrate (51), the insulating layer (52) and the second semiconductor substrate (53) for patterning planar electrodes from the first and second semiconductor substrates (51, 53 ) for a stator (13, 14, 21) and a rotor (11, 15, 22) of the micromechanical device (10, 12, 20).

The fabrication method of claim 7, wherein before the trench structure (62) is etched, another trench structure (55) is etched into the side of the substrate (53) opposite the trench structure (62) and a sacrificial material (58) in the trench structure (62 ), and after the further trench structure (62) is etched, the sacrificial material (58) is removed.

The manufacturing method according to claim 8, wherein before the trench structure (62) is etched and the sacrificial material is deposited, additional regions (56, 57) are removed from the second semiconductor substrate (53) into the trench structure (55).

10. The manufacturing method according to claim 8, wherein, before the sacrificial material (58) is applied, a further region of the second semiconductor substrate (53) is etched around a trench structure (55), which trench encloses all movable parts of the micromechanical device ,

11. Manufacturing method according to one of claims 7 to 10, wherein conductor tracks (69) on the first semiconductor substrate (51) for contacting the flat electrodes are patterned before the

Trench structure (62) is etched.