JP2014085409A - Method for manufacturing micromirror device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a micromirror device capable of being simply and inexpensively manufactured.SOLUTION: A silicon oxide film 21 is formed at least on the surface of a silicon substrate 20, and a flattened epitaxial polysilicon film 23 is formed on the silicon oxide film 21. This epitaxial polysilicon film 23 is made to undergo through etching until reaching the silicon oxide film 21, thereby forming a micromirror device structure on the silicon oxide film 21 (f). After that, the silicon substrate 20 is etched from the rear surface while leaving a temporary reinforcement silicon part 20a for temporarily reinforcing an internal through part h which strides over at least the internal through part h of the micromirror device structure (g). After that, the silicon oxide film 21 is etched so as to remove the temporary reinforcement silicon part 20a and release the micromirror device structure (h).

Description

  The present invention relates to a method of manufacturing a micromirror device used in a laser display, a small projector, a laser range finder, an optical switch for communication, and the like.

  Conventionally, micromirror devices such as optical scanners, acceleration sensors, gyrosensors, and the like are widely known as MEMS (Micro Electro Mechanical Systems) devices.

  These MEMS devices include an SOI (Silicon On Insulator) wafer in which a silicon layer (referred to as a device layer) is formed on a support substrate (referred to as a handle layer) via an insulator layer (referred to as a buried oxide film layer). It is formed by processing. In particular, the micromirror device is generally formed using an SOI wafer (see Patent Document 1).

JP 2012-24897 A

  By the way, a micromirror device has a structure in which a mirror is supported via a torsion spring. When this is formed using an SOI wafer, first, the torsion spring and the mirror are formed on a device layer that becomes the surface of the SOI wafer. Thereafter, all or part of the underlying handle layer is etched away from the back side of the SOI wafer, and the buried oxide layer is etched to release the mirror and the torsion spring. . When the handle layer is etched from the back side of the SOI wafer, only a thin buried oxide film remains in a part of the wafer, but this oxide film receiving high compressive stress is broken and the wafer is cooled from the back side. In order to prevent problems such as leakage of helium flowing into the etching chamber, it is necessary to attach and support this SOI wafer with another substrate. For this reason, there existed a problem that a manufacturing process became complicated and the number of processes increased. The process of attaching and supporting this SOI wafer on another substrate and the process of removing the support substrate after etching are not standard in a general semiconductor manufacturing line.

  On the other hand, SOI wafers themselves are expensive.

  This invention is made | formed in view of the above, Comprising: It aims at providing the manufacturing method of the micromirror device which can be manufactured simply and cheaply.

  In order to solve the above-described problems and achieve the object, a method of manufacturing a micromirror device according to the present invention includes a silicon oxide film forming step of forming a silicon oxide film on at least a surface of a silicon substrate, A silicon film forming step of forming a flattened silicon film, a device forming step of forming a micromirror device structure on the silicon oxide film by penetrating etching the silicon film until reaching the silicon oxide film, Etching the silicon oxide film, a back surface etching step for etching the silicon substrate from the back surface, leaving a temporarily reinforcing silicon portion that temporarily reinforces the internal through portion across the internal through portion of the micromirror device structure, Remove the temporarily reinforcing silicon part to create a micromirror device structure Characterized in that it comprises a removal step to lease, the.

  The method of manufacturing a micromirror device according to the present invention further includes an oxide film etching step of etching the silicon oxide film by patterning the silicon oxide film after the silicon oxide film forming step in the above invention. The oxide film etching step forms an anchor formation through portion that penetrates the silicon oxide film in a portion corresponding to a lower plate portion of the micromirror device structure, and the silicon film formation step includes forming the anchor formation through portion. The silicon film is formed while forming the embedded anchor portion, and the back surface etching step is performed by etching while leaving a portion of the silicon substrate corresponding to the back surface of the anchor portion, and reinforcing ribs of the plate coupled to the anchor portion It is characterized by forming.

  Further, in the method of manufacturing a micromirror device according to the present invention, in the above invention, the temporary reinforcing silicon portion has a periphery of the temporary reinforcing silicon portion overlapping the micromirror device structure, and the width of the overlapping portion is The width of the comb teeth and / or the torsion spring of the micromirror device structure is about the same or less.

  In the method of manufacturing a micromirror device according to the present invention, in the above invention, the silicon film is a columnar polycrystalline silicon film (epi-poly silicon film) grown under epitaxial conditions. The manufacturing method of the micromirror device as described in any one of Claims 1-3.

  According to the present invention, when the silicon substrate is etched from the back surface side, the penetration part (inner penetration part) of the silicon layer forming the micromirror device structure is tightly blocked by the temporary reinforcing silicon part, and mechanically Since the weak torsion spring and the comb teeth are fixed, it is not necessary to support the attachment on another substrate, and the manufacturing process is simplified, so that the micromirror device can be manufactured easily and inexpensively.

  The temporary reinforcing silicon portion is unnecessary for the completed micromirror device and must be removed, but can be easily removed by etching the silicon oxide film. At this time, since the reinforcing rib is bonded to the micromirror device structure without the silicon oxide via the anchor portion, the reinforcing rib is removed together with the temporary reinforcing silicon portion in the removing step of etching the silicon oxide film. It will never be. The anchor portion cannot be formed using an SOI wafer.

  In addition, the epipolysilicon film is suitable for forming a micromirror device structure because it is not warped by stress even if it is formed to a thickness of several tens of μm. If this is used, since a flat mirror can be formed without using an expensive SOI wafer, the manufacturing cost can be reduced.

FIG. 1 is a plan view showing a configuration of a micromirror device according to an embodiment of the present invention. FIG. 2A is a diagram schematically showing a manufacturing process of the micromirror device shown in FIG. 1 (No. 1). FIG. 2B is a diagram schematically showing a manufacturing process of the micromirror device shown in FIG. 1 (part 2). FIG. 3 is a diagram illustrating an example of an arrangement position of the temporary reinforcing silicon portion. FIG. 4 is a diagram showing a detailed formation process of the insulating trench in the process of FIG. 2A (c) in a portion corresponding to the cross section taken along the line AA of FIG. FIG. 5 is a plan view of the insulating trench. FIG. 6 is an SEM image showing a cross section of the insulating trench. FIG. 7 is a diagram showing a manufacturing process of a conventional insulating trench. FIG. 8 is an SEM image showing a cross section of a conventional insulating trench. FIG. 9 is a plan view of a crank-shaped insulating trench. FIG. 10 is an SEM image showing the plane of the etched crank-shaped trench. FIG. 11 is an SEM image showing a state in which LPCVD polysilicon is filled in the etched crank-shaped trench.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

(Overall structure of micromirror device)
FIG. 1 is a plan view showing a configuration of a micromirror device according to an embodiment of the present invention. This micromirror device is an electrostatic two-axis MEMS optical scanner device, which is a micro light reflecting mirror that can rotate independently on two axes by electrostatic force of an electrostatic vertical comb electrode using MEMS technology. The micromirror device is an example of a semiconductor device and an example of a MEMS.

  As shown in FIG. 1, the micromirror device includes a frame-shaped fixed plate 1 and a frame-shaped movable plate 2 that is pivotally supported inside the fixed plate 1 by a pair of torsion springs 2a, 2b extending in the Y direction. And a rectangular movable plate 3 pivotally supported inside the movable plate 2 by a pair of torsion springs 3a, 3b extending in the X direction. These are basically formed from an epipolysilicon film. Epipoly is a polycrystal grown in a columnar shape under epitaxial conditions. The epipolysilicon film is characterized by low stress even when it is formed to a thickness of several tens of μm.

  Here, a rectangular mirror 4 made of aluminum is formed on the surface of the movable plate 3 in the Z direction. Therefore, the mirror 4 can be rotated around an axis CY with the pair of torsion springs 2a and 2b as an axis, and can be rotated about an axis CX with the pair of torsion springs 3a and 3b as an axis. For this reason, the mirror 4 can scan the input light two-dimensionally.

  The fixed comb-tooth electrodes 1c and 1d provided on the inner side of the fixed plate 1 and the movable comb-tooth electrodes 12c and 12d provided on the outer side of the movable plate 2 are interleaved between the comb teeth, and the arrangement direction of the comb teeth A plurality of capacitors are formed in a state separated from each other. Here, when an AC voltage matched to the mechanical resonance frequency around the axis CY is applied between the fixed comb electrode 1c and the movable comb electrode 12c and between the fixed comb electrode 1d and the movable comb electrode 12d, The movable plate 2 is rotated about the axis CY by the electrostatic force, and the mirror 4 on the movable plate 3 is also rotated about the axis CY.

  Further, the fixed comb electrodes 2c and 2d provided on the inner side of the movable plate 2 and the movable comb electrodes 13c and 13d provided on the outer side of the movable plate 3 are interdigitated with each other so that the comb teeth are arranged. A plurality of capacitors are formed in a state separated in the direction. Here, when an AC voltage that matches the mechanical resonance frequency around the axis CX is applied between the fixed comb electrode 2c and the movable comb electrode 13c and between the fixed comb electrode 2d and the movable comb electrode 13d, The movable plate 3 rotates around the axis CX by electrostatic force.

  For this reason, by applying an AC voltage between the fixed comb electrodes 1c and 1d and the movable comb electrodes 12c and 12d and between the fixed comb electrodes 2c and 2d and the movable comb electrodes 13c and 13d, respectively. The mirror 4 can be scanned two-dimensionally.

  A total of four internal through-holes h are formed between the fixed plate 1 and the movable plate 2 in a portion other than the torsion springs 2a and 2b, and between the movable plates 2 and 3 in a portion other than the torsion springs 3a and 3b. The

  As described above, voltage is applied between the fixed comb electrodes 1c and 1d and the movable comb electrodes 12c and 12d, and between the fixed comb electrodes 2c and 2d and the movable comb electrodes 13c and 13d. Therefore, it is necessary to provide an insulating structure on the fixed plate 1 and the movable plate 2. This insulating structure is achieved by providing an insulating trench 10 on the fixed plate 1 and the movable plate 2.

  In FIG. 1, a voltage is applied from the terminal T1 to the fixed comb electrodes 1c and 1d, and a voltage is applied from the terminal T2 to the movable comb electrodes 12c and 12d and the fixed comb electrodes 2c and 2d. A voltage is applied to the electrodes 13c and 13d from the terminal T3. Specifically, the voltage applied from the terminal T3 is applied to a region indicated by hatching in the drawing. That is, between the insulating trenches 11 and 12 on the fixed plate 1, between the torsion spring 2 b, between the insulating trenches 13 and 14 on the movable plate 2, torsion springs 3 a and 3 b, inside the insulating trench 15 on the movable plate 2, movable The plate and the movable comb electrodes 13c and 13d are in a conductive state, and a voltage is applied. Further, the voltage applied from the terminal T2 is generated between the insulating trenches 16 and 17 on the movable plate 2, the torsion spring 2a, the region on the movable plate 2 connected to the torsion spring 2a, the movable comb electrodes 12c and 12d, The fixed comb electrodes 2c and 2d are in a conductive state, and a voltage is applied.

  This insulating trench 10 forms an enlarged portion 10a in which the width dimension of the trench formed by etching is partially enlarged, and the enlarged portion 10a of the trench becomes an opening portion embedded in the trench from the lateral direction. The CVD material gas is continuously supplied to the void in the deep part of the trench whose size is not enlarged, and the trench is embedded so that the void is eliminated. The enlarged portion 10a may be a bent portion 10b. The enlarged portion 10a and the bent portion 10b are provided at regular intervals along the longitudinal direction. Details of the structure and formation of the insulating trench 10 will be described later.

(Manufacturing method of micromirror device)
Next, with reference to FIG. 2A and FIG. 2B, the manufacturing method of a micromirror device is demonstrated typically.

  First, as shown in FIG. 2A (a), the silicon substrate 20 is thermally oxidized at 1100 ° C. to form silicon oxide films 21 and 22 having a thickness of 1 μm. Thereafter, a photoresist is patterned on the surface of the portion where the anchor is to be formed (anchor forming through-hole 21a), and the silicon oxide 21 on the surface side of the patterned portion is mixed and diluted with ammonia and hydrogen fluoride (BHF). ) To etch. When an SOI substrate is used, it is difficult to form the anchor formation through-hole 21a that penetrates the silicon oxide 21.

  Thereafter, as shown in FIG. 2A (b), a seed polysilicon having a thickness of 100 nm is first formed on the surface of the silicon oxide film 21 at 800 ° C. by atmospheric pressure CVD, and 20 μm containing phosphorus is formed on the seed polysilicon. A thick epipolysilicon film is formed at 1000 ° C. Thereafter, the surface of the epipolysilicon is subjected to mirror finishing by CMP (Chemical Mechanical Polish). Thereby, an epipolysilicon film 23 is formed. The anchor portion 23a is formed by embedding epipolysilicon in the anchor formation through portion 21a.

  Thereafter, as shown in FIG. 2A (c), on the surface of the epipolysilicon film 23, a portion corresponding to the insulating trench 10 is patterned with a photoresist. Then, the patterned epipolysilicon film 23 is etched and the etching is stopped by the silicon oxide film 21 which has become a buried silicon oxide film, thereby forming a trench 23b. Thereafter, thermal oxidation is performed at 1100 ° C. to form silicon oxide films 24 and 25 having a thickness of 100 nm on the sidewalls of the trench 23b and the surface of the epipolysilicon film 23, respectively. Thereafter, polysilicon (LPCVD polysilicon) 26a is filled in the trench 23b at 600 ° C. by low pressure CVD (LPCVD). At this time, the LPCVD polysilicon film 26 is also formed on the silicon oxide film 25. As described above, the enlarged portion 10a and the bent portion 10b are formed when the portion corresponding to the insulating trench 10 is patterned.

  Thereafter, as shown in FIG. 2A (d), the LPCVD polysilicon film 26 on the surface of the epipolysilicon film 23 is etched off without patterning, and the silicon oxide film 25 on the surface of the already formed epipolysilicon film 23 is then removed. The insulating trench 10 is formed by stopping the etching.

  Thereafter, as shown in FIG. 2B (e), all of the silicon oxide film 25 on the surface of the epipolysilicon film 23 is removed by BHF. Further, aluminum is sputtered onto the region where the mirror 4 is disposed on the surface of the epipolysilicon film 23 to form an aluminum film 27 having a thickness of 200 nm. Thereafter, the surface of the aluminum film 27 is patterned with a photoresist, and the patterned portion of aluminum is etched using a diluted mixed solution of phosphoric acid, nitric acid, and acetic acid to form the mirror 4.

  Thereafter, as shown in FIG. 2B (f), the surface of the epipolysilicon film 23 is patterned with a photoresist, the patterned epipolysilicon film 23 is etched by a silicon deep etching technique, and etching stop is performed with the silicon oxide film 21. Thus, the fixed plate 1 and the movable plates 2 and 3 including the torsion springs 2a, 2b, 3a and 3b, the fixed comb electrodes 1c, 1d, 2c and 2d, the movable comb electrodes 12c, 12d, 13c and 13d, etc. Form. Thereby, an internal through-hole h is formed between the fixed plate 1 and the movable plate and between the movable plates 2 and 3.

  Thereafter, as shown in FIG. 2B (g), the back side silicon oxide film 22 is patterned with a photoresist, and the patterned back side silicon oxide film 22 is etched with BHF. Thereafter, the silicon substrate 20 is etched by a silicon deep etching technique using the photoresist and the silicon oxide film 22 as a mask material, and this etching is stopped by the silicon oxide film 21.

  In this patterning, a part of the silicon substrate 20 corresponding to the anchor portion 23a is left, and the reinforcing rib 24a directly coupled to the anchor portion 23a is formed. The reinforcing rib 24a is coupled to the anchor portion 23a, and is erected in a cylindrical shape, for example, in the vicinity of the outer edges of the movable plates 2 and 3 together with the anchor portion 23a. Thereby, when the movable plates 2 and 3 are rotated, distortion of the plates can be reduced. In particular, in the case of the movable plate 3 on which the mirror 4 is disposed, the distortion of the mirror 4 can be reduced.

  Further, this patterning is performed so as to straddle the internal through-hole h and leave an overlapping portion with respect to the fixed plate 1 and the movable plates 2 and 3 via the silicon oxide film 21 on the back surface side. As a result, by temporarily etching the silicon substrate 20, a temporary reinforcing silicon portion 20a is formed that bridges and closes the internal through-hole portion h via the silicon oxide film 21. Specifically, as shown in FIG. 3, from the outer edges of the fixed plate 1 and the movable plates 2 and 3, there is an overlapping portion having a width equal to or smaller than the width of the comb teeth and the width of the torsion spring. Part 20a is formed. In this state, the movable plates 2 and 3 and the movable plate 2 and the fixed plate 1 are not completely separated via the silicon oxide film 21. In addition, there is no portion that penetrates anywhere in the entire surface and a portion that is only a silicon oxide film.

  As a result, when the silicon substrate 20 is etched by the silicon deep etching technique, the thin silicon oxide film 21 is broken, and the wafer cooling gas does not leak into the etching chamber and the etching gas does not pass through to the top. Here, if there is no temporary reinforcing silicon portion 20a, only the silicon oxide film 21 remains in the lower part of the internal through-hole h. However, the silicon oxide film 21 is thin and is subjected to high compressive stress, and is very easily broken. If this breaks, the wafer is penetrated. On the other hand, in this embodiment, the vicinity of the internal through-hole h is reinforced by the temporary reinforcing silicon portion 20a described above. As a result, it is not necessary to attach and support the wafer on which the micromirror device structure is formed on another substrate during etching by this patterning. Thereafter, the remaining silicon oxide film 22 on the back surface is removed using BHF.

  Thereafter, as shown in FIG. 2B (h), the remaining back-side silicon oxide film 21 is etched by 10 μm in the horizontal direction using HF vapor, and when the overlapping portion is removed, the movable plate 2 excluding the torsion spring is removed. , 3 and between the movable plate 2 and the fixed plate 1 are penetrating, and at the same time, unnecessary temporary reinforcing silicon portions 20a are removed. As a result, the movable plates 2 and 3 move.

  Further, when the silicon oxide film 21 is etched to remove the temporary reinforcing silicon portion 20a, the anchor portion 23a penetrates the silicon oxide film 21 and is formed of the epipolysilicon film 23. It will not be removed. Since the reinforcing ribs 24a are directly bonded to the epipolysilicon film 23 having the micromirror device structure, high bonding strength can be obtained.

  The above-described epipolysilicon film 23 is formed of epipolysilicon. However, the present invention is not limited to this, and the warpage of the silicon film formed by another deposition method is within an allowable range in the operation of the micromirror device. It only has to be within.

(Insulation trench formation)
Here, the detailed formation and structure of the insulating trench 10 described above will be described. FIG. 4 shows a detailed formation process of the insulating trench 10 in the process of FIG. 2A (c) in a portion corresponding to the cross section taken along the line AA of FIG. As shown in FIG. 4, the epitaxial polysilicon film 23 on the silicon oxide film 21 formed on the surface of the silicon substrate 20 is etched to form a trench 23b having an insulating part formed at the bottom (FIG. 4A). .

  Thereafter, as shown in FIG. 4B, silicon oxide films 24 and 25 are formed on the sidewalls of the trench 23b and the surface of the epipolysilicon film 23, respectively. As a result, a trench whose inner wall is covered with an insulating film is formed.

  After that, as shown in FIG. 4C, LPCVD polysilicon 26a is filled in the trench 23b to form the insulating trench 10. At this time, as shown in FIG. 5, enlarged portions 10 a in which the width of the trench 23 b is partially enlarged are formed at regular intervals L along the longitudinal direction of the trench 23 b. The width W2 of the trench 23b in the enlarged portion 10a is larger than the width W1 of the trench 23b in the portion that is not enlarged. In this state, the CVD material gas is supplied to fill the trench 23b with the LPCVD polysilicon 26a. If the CVD material gas is continuously supplied, the enlarged portion 10a becomes an opening, and the trench is not enlarged. A CVD material gas is supplied to the deep voids of 23b from the longitudinal direction of the trench 23b. As a result, the LPCVD polysilicon 26a is filled in the trench 23b without forming a void. When the insulating trench 10 in which no void is formed is formed, the electrical insulation and mechanical strength of the insulating trench 10 can be improved. FIG. 6 is an SEM image of the insulating trench 10, and it can be seen that no void is formed even in the insulating trench 10 having an aspect ratio as high as 7.

  Conventionally, as shown in FIGS. 7 and 8, if LPCVD polysilicon is filled in the trench without forming the enlarged portion 10a, a void is formed.

  Further, a bent portion 10b may be formed in the longitudinal direction of the trench, and the bent portion 10b may have a function as the enlarged portion 10a. As shown in FIG. 1, the enlarged portion 10a and the bent portion 10b may be used in combination. In FIG. 9, the trench is formed in a crank shape, and the insulating trench 10 is formed using only the bent portion 10b. The width W12 of the bent portion 10b shown in FIG. 9 is wider than the width W11 of the straight portion, and here, it is √ (2) times.

  FIG. 10 is an SEM image of the crank-shaped trench shown in FIG. 9, where the width W11 is 4.2 μm and the width W12 is 5.2 μm. FIG. 11 is an SEM image showing a state in the middle of filling the crank-shaped trench shown in FIG. 10 with LPCVD polysilicon 26a. As shown in FIG. 11, the straight portion of the trench first forms a closed portion, and a void is formed in the deep portion, but since the width of the bent portion 10b of the trench is wide, an opening is formed in the bent portion 10b. Through this opening, the LPCVD polysilicon 26a can be filled into the void in the deep portion of the straight portion, and the void can be eliminated.

  The relationship between the widths W2 and W12 and the widths W1 and W11 and the distance between the constant interval L or the bent portion 10b described above are the openings until the LPCVD polysilicon 26a is filled in the void formed in the central deep portion of the straight portion. Should just be formed. Further, the cross-sectional shape in plan view of the enlarged portion 10a may not be a rectangle, but may be a shape in which a curved portion such as a circle or an ellipse is formed. Similarly, the plan view shape of the bent portion 10b may not be bent at a right angle, and may be a shape having a predetermined radius of curvature.

  The above-described micromirror device is applied to a laser display, a small projector, a laser range finder, a communication optical switch, and the like.

  Furthermore, the above-described manufacturing method and structure of the insulating trench 10 are not limited to the micromirror device, and can be applied to, for example, a trench for a capacitor of a semiconductor device described in Patent Documents 1 and 2, for example. The insulating trench 10 can also be formed using an SOI substrate.

  In the above-described embodiment, the electrostatic drive micromirror device using the comb-teeth actuator has been described. Of course, the manufacturing method and structural features of the present invention are not limited to the electrostatic drive type. It can also be applied to electromagnetic drive as it is.

DESCRIPTION OF SYMBOLS 1 Fixed plate 1c, 1d, 2c, 2d Fixed comb electrode 2,3 Movable plate 2a, 2b, 3a, 3b Torsion spring 4 Mirror 12c, 12d, 13c, 13d Movable comb electrode 10-17 Insulation trench 10a Enlarged part 10b Bending portion 20 Silicon substrate 20a Temporary reinforcing silicon portion 21, 22, 24, 25 Silicon oxide film 21a Anchor forming penetration portion 23 Epipolysilicon film 23a Anchor portion 23b Trench 24a Reinforcement rib 26 LPCVD polysilicon film 26a LPCVD polysilicon 27 Aluminum Film h Internal penetration CX, CY axis T1-T3 Terminal W1, W2, W11, W12 Width

Claims (4)

A silicon oxide film forming step of forming a silicon oxide film on at least the surface of the silicon substrate;
A silicon film forming step of forming a planarized silicon film on the silicon oxide film;
Through-etching the silicon film until reaching the silicon oxide film, and forming a micromirror device structure on the silicon oxide film; and
A back surface etching step of etching the silicon substrate from the back surface, leaving a temporarily reinforcing silicon portion that temporarily reinforces the internal through portion across at least the internal through portion of the micromirror device structure;
Etching the silicon oxide film to remove the temporary reinforcing silicon part and releasing the micromirror device structure;
A method of manufacturing a micromirror device, comprising: After the silicon oxide film forming step, further comprising an oxide film etching step of patterning the silicon oxide film and etching the silicon oxide film,
The oxide film etching step forms an anchor-forming through-hole that penetrates the silicon oxide film in a portion corresponding to the lower plate of the micromirror device structure,
In the silicon film forming step, the silicon film is formed while forming an anchor portion in which the anchor formation penetration portion is embedded,
2. The micro of claim 1, wherein in the back surface etching step, the portion of the silicon substrate corresponding to the back surface of the anchor portion is etched to form a reinforcing rib of the plate coupled to the anchor portion. Mirror device manufacturing method.   In the temporary reinforcing silicon portion, the periphery of the temporary reinforcing silicon portion overlaps with the micromirror device structure, and the width of the overlapping portion is about the same as the width of the comb teeth and / or the torsion spring of the micromirror device structure. The method for producing a micromirror device according to claim 1 or 2, wherein:   The method of manufacturing a micromirror device according to claim 1, wherein the silicon film is a columnar polycrystalline silicon film grown under epitaxial conditions.