JP2002258176A - Method of manufacturing optical modulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical modulator of which yield can be made high. SOLUTION: A first substrate 100A formed with driving electrodes 130 and a second substrate 200A are prepared. The second substrate 200A is formed by using an SOI substrate consisting of a silicon substrate 250, a silicon oxidized layer 225 and a silicon single crystal layer 260. The first substrate 100A and the second substrate 200A are joined to each other. The silicon substrate 250 is removed by wet etching with the silicon oxidized layer 225 as an etching stopper. After a reflection layer 227 is formed, the silicon single crystal layer 260 is patterned, by which micromirrors 220 are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a method for manufacturing a light modulation device.

[0002]

2. Description of the Related Art A light modulation device tilts and drives a micro mirror by electrostatic force generated by a potential difference between the micro mirror and a driving electrode, thereby modulating light from a light source. As an optical modulation device, for example, a DMD (Digital Micromirror) having a structure in which many micromirrors are arranged in a matrix is used.
r Device) is known. According to the DMD, a large screen with high resolution and high luminance can be provided. Therefore, DMD
Are used in projection-type image devices such as projectors.

[0003]

The light modulation device has a structure in which a substrate on which a micro mirror is formed is joined to a substrate on which a drive electrode is formed. The thickness of the micromirror is, for example, several μm, and is very thin. Therefore, a layer serving as a base is required to form the micromirror. The base layer is eventually removed, which can result in the formation of defective micromirrors.

An object of the present invention is to provide a method for manufacturing an optical modulation device capable of increasing the yield.

[0005]

(1) The present invention relates to a method for manufacturing an optical modulator for tilting and driving the micro mirror by an electrostatic force generated by a potential difference between a driving electrode and the micro mirror. A first substrate including an electrode;
A first layer on which the micromirror is formed, a second layer serving as a base of the first layer, and a stopper located between the first layer and the second layer for removing the second layer Fixing a second substrate to the first substrate such that the drive electrodes and the first layer face each other in a second substrate including a third layer to be formed; and (B) the step (A) a step of removing the second layer using the third layer as a stopper, and (C) a step of forming the micromirror by patterning the first layer after the step (B). ,
Is provided.

According to the present invention, the second layer serving as a base is removed using the third layer as a stopper. Therefore, the second
During layer removal, the first layer on which the micromirrors are formed is not damaged. Therefore, the production yield of the light modulation device can be increased. The thickness of the third layer is 0.1
μm to 0.5 μm. If the thickness is smaller than this, the function as a stopper is not achieved.

Further, according to the present invention, since the second layer is removed using the third layer as a stopper, it is possible to prevent the surface roughness of the micro mirror from increasing. Therefore, it is possible to manufacture a light modulation device including a micromirror having a high reflectance.

The fixing in the present invention includes, for example, anodic bonding and bonding with an adhesive.

(2) In the present invention, the second substrate comprises:
At least one of an SOI substrate and an SOS substrate may be included.

In the case of an SOI substrate, the first layer may be a silicon single crystal layer, the second layer may be a silicon substrate, and the third layer may be a silicon oxide layer. In the case of an SOS substrate, the first layer may be a silicon single crystal layer, the second layer may be a sapphire substrate, and the third layer may be a silicon oxide layer.

(3) In the present invention, a step of forming a reflection layer of the micromirror on the third layer may be included between the step (B) and the step (C).

The material of the reflection layer includes, for example, aluminum, gold and silver. In the case where light is reflected by the micromirrors formed on the first layer, such a reflective layer is unnecessary.

(4) In the present invention, wet etching may be used for removing the second layer in the step (B).

According to this, since batch processing is possible,
The productivity of the light modulation device can be improved.

(5) In the present invention, dry etching may be used for removing the second layer in the step (B).

In the case of wet etching, if there is a defect such as a pinhole in the first substrate or the second substrate, the etchant may enter the region where the drive electrode is formed, thereby damaging the drive electrode. In the case of dry etching, such a situation can be prevented because an etching solution is not used.

(6) In the present invention, polishing may be used for removing the second layer in the step (B).

Generally, the speed of polishing the second layer is higher in polishing than in etching. Therefore, according to this, the second
The time required for removing the layer can be reduced. As polishing, for example, mechanical polishing, chemical polishing, chemical mechanical polishing (CM
P), electropolishing, or a combination thereof.

(7) In the present invention, the step (B)
May include a step of removing a part of the second layer by polishing, and a step of removing a remaining part of the second layer by etching.

[0020] Polishing has a higher rate of shaving the second layer than etching. In addition, the etching can remove the second layer with higher precision than the polishing. Therefore, according to this, the first layer can be removed while reducing the time required for removing the second layer.
The layer can be prevented from being damaged. The etching includes dry etching and wet etching.

(8) In the present invention, before the step (A), a step of forming a support portion serving as a fulcrum when the micromirror is tilted by patterning the first layer is included. Alternatively, the step (C) may include a step of patterning the first layer to form a shaft fixed to the support portion, the shaft serving as an axis when the micromirror is tilted and driven.

According to this, since the shaft and the support are formed by patterning the first layer, the shaft and the support can be firmly connected. For this reason,
According to the light modulation device manufactured by this method, even when stress concentrates on the joint between the shaft and the support during the tilt driving of the micromirror, the joint is not easily broken.

(9) In the present invention, before the step (A), a step of forming a support portion serving as a fulcrum when the micromirror is tilted by patterning the first substrate is included. The step (C) may include a step of forming a shaft part which becomes an axis when the micro mirror is tilted and driven and is fixed to the support part by patterning the first layer of the second substrate. May be included.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the drawings.

[Structure of Light Modulator] FIG. 1 is an exploded perspective view of the light modulator according to the present embodiment. Light modulation device 1
Includes an electrode substrate 100, a mirror substrate 200, and a cover glass substrate 300.

The material of the mirror substrate 200 is, for example, single crystal silicon. The mirror substrate 200 includes a plurality of micro mirrors 220 arranged in a matrix in a frame portion 210. Note that the arrangement of the micromirrors 220 is not limited to a matrix, and for example, depending on the application of the light modulation device 1,
They can be arranged arbitrarily, such as in one line.

The plane shape of the micro mirror 220 is, for example,
It has a square shape with a side length of 15 μm. Light modulation device 1
Is used for a projection-type imaging device such as a projector,
One micro mirror 220 functions as one pixel. The micro mirrors 220 arranged in one direction are connected by a shaft 230. The shaft portion 230 is
This is the axis for tilt driving. That is, the micromirror 220 is twisted in the directions of the arrows A and B around the shaft 230. Thus, the micromirror 220 can be tilted, for example, by about 10 degrees in each of the arrow A direction and the arrow B direction. FIG. 2 shows a part of the plurality of micro mirrors 220 arranged in a matrix shown in FIG.
The micro mirror 220 has slits 240 formed on both sides of a portion connected to the shaft 230. Slit 240
This facilitates the tilt driving of the micro mirror 220.

Next, the electrode substrate 100 shown in FIG. 1 will be described. The material of the electrode substrate 100 is, for example, glass containing sodium. This is the mirror substrate 200
Is fixed to the electrode substrate 100 using anodic bonding as described later.

The electrode substrate 100 has a concave region 110 and side walls 120 located on four sides thereof. In the concave area 110, a plurality of drive electrodes 130 arranged in a matrix are formed. The driving electrode 130 is
And is an electrode for tilting and driving the micro mirror 220. The two drive electrodes 130 serve as electrodes for driving one micro mirror 220. For example, in the case of the micromirror 220-1, the driving electrode 130-1,
130-2 is an electrode for driving the micro mirror 220-1.

Of the plurality of drive electrodes 130, the shaft 230
The drive electrodes 130 arranged in a direction substantially perpendicular to the direction in which the electrodes extend are electrically connected in common by a wiring 140.
The wiring 140 is formed by patterning the conductive layer.
It is formed simultaneously with the drive electrode 130.

A plurality of columnar support portions 150 are formed in the concave region 110. The height of the support 150 is the same as the height of the side wall 120. The support 150 serves as a fulcrum when the micro mirror 220 is tilted. Note that the support 150 may be formed on the shaft 230 of the mirror substrate 200.

The support 150 is fixed to the shaft 230. Some of the shafts 230 are fixed to the frame 210. For example, in the case of the micromirrors 220 (220-1 to 220-3) connected by the shafts 230 (230-1 to 230-4), the shaft 230-1 is composed of the support 150-1 and the shaft 23.
0-2 is the support 150-2, and the shaft 230-3 is the support 15
0-3 and the shaft portion 230-4 are fixed to the frame portion 210, respectively.

The mirror substrate 200 is anodically bonded to the electrode substrate 100 at the frame 210 and the side wall 120. At this time, each support 150 is anodically bonded to each corresponding shaft 230. The frame portion 210 includes the cover glass substrate 30
0 is joined. When the space of the light modulation device 1 in which the micromirror 220 is arranged is hermetically sealed by inert gas filling by various methods, resistance is low when the micromirror 220 is driven, high-speed response operation, and power consumption. Is reduced.

[Principle of Tilt Drive of Micro Mirror] Next, the principle of tilt drive of the micro mirror 220 will be described. FIG.
FIG. 3 is a cross-sectional view of a portion where a micro mirror 220-1 is arranged in the light modulation device 1. On the surface of the micromirror 220-1, a reflective layer 227 is provided via a silicon oxide layer 225.
Is formed, and an insulating layer 221 is formed on the back surface of the micro mirror 220-1.

The micro mirror 220 is manufactured using an SOI substrate, as described later. The silicon single crystal layer of the SOI substrate becomes the micromirror 220, and the silicon oxide layer of the SOI substrate becomes the silicon oxide layer 225. The reflective layer 227 may have a property of reflecting light, and examples of the material include aluminum, gold, and silver. The insulating layer 221 has a function of preventing the micro mirror 220 from short-circuiting with the drive electrode 130. Instead of forming the insulating layer 221 on the micro mirror 220, an insulating layer may be formed on the surface of the drive electrode. Examples of the insulating layer 221 include a silicon oxide layer and a silicon nitride layer such as a TEOS and a thermal oxide film. The minute mirror 220 is the driving electrode 13
If the problem of short circuit with 0 does not occur, the insulating layer 221 is unnecessary.

Since the micromirror 220 is a silicon single crystal layer, it can function as a reflection layer. Therefore, when light is reflected by the micro mirror 220 itself, the reflection layer 227 is unnecessary. Since the silicon oxide layer 225 is transparent, it need not be removed, but may be removed according to the characteristics required for the micromirror 220.

FIG. 4 shows the micro mirror 220-1 shown in FIG.
It is sectional drawing which shows the state which inclined. Micro mirror 2
With the bias voltage Va applied to 20-1, for example, a plus voltage is applied to the drive electrode 130-1 and a minus voltage is applied to the drive electrode 130-2. This allows
Since a repulsive electrostatic force acts between the micromirror 220-1 and the drive electrode 130-1, and an attraction electrostatic force acts between the micromirror 220-1 and the drive electrode 130-2, The mirror 220-1 is tilted and driven as shown in FIG. This is an ON state in which light is reflected toward a predetermined position. On the other hand, the drive electrodes 130-1, 13
By inverting the polarity of the voltage applied to 0-2, the micromirror 220-1 is tilted and driven as shown in FIG. 4B. This is an OFF state in which light is reflected in a direction different from the predetermined position. In this embodiment, the ON state and the O
By changing the switching time of the FF state, for example, 25
Six gradation display is possible.

[Method of Manufacturing Light Modulator] The light modulator 1 according to the present embodiment includes a first substrate serving as an electrode substrate 100;
The second substrate serving as the mirror substrate 200 is manufactured, and these are joined to each other. For this production, for example, a silicon micromachine technology is used. The manufacturing method of the light modulation device 1 includes a first manufacturing method, a second manufacturing method, and modifications thereof.

<< First Manufacturing Method >> (Manufacture of First Substrate) First, the manufacture of the first substrate to be the electrode substrate 100 will be described. FIG. 5 is a process chart for explaining this.

As shown in FIG. 5A, the electrode substrate 100
A glass substrate 160 serving as a base is prepared. The glass substrate 160 is, for example, to perform anodic bonding described below,
It is made of glass containing an alkali metal such as sodium (Na). As such a glass substrate 160, sodium borosilicate glass can be used, and for example, Pyrex glass (trade name) manufactured by Corning Incorporated can be used. Especially, considering that the glass substrate 160 is heated during anodic bonding and that the thermal expansion coefficient is substantially equal to that of silicon, Corning # 7740 (trade name) is most suitable.

A resist R1 is applied on the glass substrate 160, and a predetermined pattern is formed on the resist R1 by photolithography. The concave region 110 is formed by wet-etching the glass substrate 160 with, for example, a hydrofluoric acid aqueous solution using the resist R1 as a mask.
The portion of the glass substrate 160 masked with the resist R1 becomes the side wall 120. The height of the side wall portion 120, in other words, the depth of the concave region 110 is, for example, 2 μm.

As shown in FIG. 5B, the glass substrate 16
A conductive layer 170 to be a drive electrode is formed on the entire surface of the substrate.
The thickness of the conductive layer 170 is, for example, 0.1 μm to 0.2 μm.
m. The conductive layer 170 may be, for example, a transparent conductive material such as ITO, or gold or chromium. The conductive layer 170 can be formed by an evaporation method, a sputtering method, an ion plating method, or the like.

As shown in FIG. 5C, a resist R2 is applied on the conductive layer 170, and the resist R2 is patterned by photolithography. Resist R2
The conductive layer 170 is patterned by, for example, dry-etching using the mask as a mask. Thereby, the drive electrode 130 is formed. The conductive layer 170 can be patterned by wet etching.

As shown in FIG. 5D, the drive electrode 130
By removing the upper resist R2, the first substrate 100A to be the electrode substrate 100 is completed.

(Manufacture of Second Substrate) The manufacture of the second substrate to be the mirror substrate 200 will be described. FIG. 6 is a process chart for explaining this. The cross section of the process diagram in FIG. 6 is a surface cut in the same direction as the direction along the line XX and the line YY in FIG.

As shown in FIG. 6A, the silicon substrate 2
50, silicon oxide layer 225, silicon single crystal layer 260
Are prepared in order. The silicon single crystal layer 260 is an example of a first layer, and includes a micro mirror,
A support and a shaft are formed. The silicon substrate 250 is an example of the second layer and serves as a base of the silicon single crystal layer 260. Since the silicon single crystal layer 260 is very thin, a base layer is required. The silicon oxide layer 225 is the third
This is an example of a layer and serves as a stopper when the silicon substrate 250 is removed.

The thickness of the silicon single crystal layer 260 is determined in consideration of the thickness of the micromirror and the shaft, and the height of the support, and is, for example, 2 μm to 4 μm. Silicon substrate 25
The thickness of 0 is, for example, 525 μm to 600 μm.
The thickness of the silicon oxide layer 225 is, for example, 0.1 μm to
0.5 μm. Instead of the SOI substrate, an SOS substrate can be used.

As shown in FIG. 6B, a resist R3 is applied on the silicon single crystal layer 260, and a predetermined pattern is formed on the resist R3 by photolithography. Using the resist R3 as a mask, the upper part of the silicon single crystal layer 260 is patterned using, for example, anisotropic dry etching to form the support portion 280.
The support portion 280 has the same function as the support portion 150 shown in FIG. 1 and serves as a fulcrum when the micro mirror 220 is driven to tilt. In FIG. 1, the support 150 is formed on the electrode substrate 100. However, as in the first manufacturing method, the mirror substrate 20 is formed.
The support portion 280 may be formed at zero.

As shown in FIG. 6C, for example, dry thermal oxidation is performed on the SOI substrate. An insulating layer 221 made of a thermal silicon oxide layer is formed on the surfaces of the silicon single crystal layer 260 and the support 280. The thickness of the insulating layer 221 is, for example, 0.1 μm to 0.12 μm. Note that the insulating layer 221 may be formed by a CVD method instead of dry thermal oxidation. Examples of the insulating layer formed by this method include a silicon oxide layer and a silicon nitride layer such as TEOS. As described above, the mirror substrate 2
00 is completed.

(From Fixing of the Second Substrate to the First Substrate to Completion of the Optical Modulation Device) FIGS. 7 and 8 are process diagrams for explaining this. The cross section of the process diagram of FIG. 7 is a surface cut in the same direction as the direction along the line XX of FIG. 8 is a plane cut in the same direction as the direction along the line YY in FIG.

As shown in FIGS. 7A and 8A,
The silicon single crystal layer 260 as the first layer and the driving electrode 130
And the second substrate 200A so as to face the first substrate 10
Place on 0A. Silicon single crystal layer 26 as first layer
At 0, a support portion 280 is formed. Then, the second substrate 200A is connected to the first substrate 10 by, for example, anodic bonding.
Fix to 0A. The anodic bonding is performed, for example, as follows. First, the first substrate 100A is connected to the minus terminal of the DC power supply, and the second substrate 200A is connected to the plus terminal of the DC power supply. Then, a voltage is applied to the first substrate 100A and the second substrate 200A while heating the first substrate 100A. By this heating, the Na ^{+ in} the first substrate 100A
Becomes easier to move. Due to the movement of Na ⁺ , the bonding surface of the first substrate 100A is negatively charged, and the second substrate 20A is charged.
The bonding surface of 0A is positively charged. As a result, the first substrate 100A and the second substrate 200A are firmly joined. In addition to anodic bonding, for example, with an adhesive and low melting glass,
The second substrate 200A may be fixed to the first substrate 100A.

As shown in FIGS. 7B and 8B,
The silicon substrate 250 which is an example of the second layer is removed. For this removal, for example, wet etching, dry etching, and polishing are used. In any case, when the silicon substrate 250 is removed, the silicon oxide layer 225 serves as a stopper. Therefore, it is possible to prevent the silicon single crystal layer 260 on which the micro mirror is formed from being damaged. Therefore, according to the present embodiment, it is possible to increase the yield of the light modulation device.

First, the case of wet etching will be described. The first substrate 100A and the second
The substrate 200A is, for example, KO having a concentration of 1 to 40 wt%.
Put into H aqueous solution. The concentration of the KOH aqueous solution is 10% by weight
Before and after is optimal. The reaction formula of this etching is as follows.

Since the etching rate of the silicon substrate 250 by the aqueous solution of Si + 2KOH + H ₂ O → K ₂ SiO ₃ + 2H ₂ KOH is considerably higher than the etching rate of the silicon oxide layer 225, the silicon oxide layer 225 functions as an etching stopper. In addition, as an etching solution used in this step, in addition to the KOH aqueous solution, TMA
H (tetramethylammonium hydroxide) aqueous solution, EPD (ethylenediamine-pyrocatechol-diazine) aqueous solution, hydrazine aqueous solution and the like. According to wet etching, batch processing is possible,
The productivity of the light modulation device can be improved.

Next, the case of dry etching will be described. The joined first substrate 100A and second substrate 200A are put into a chamber. In the chamber,
For example, XeF ₂ at a pressure of 390 Pa is introduced for 60 seconds. The reaction formula of this etching is as follows.

According to the dry etching of 2XeF ₂ + Si → 2Xe + SiF ₄ XeF ₂ , the etching rate of the silicon substrate 250 is
, The silicon oxide layer 225 functions as an etching stopper. Since this etching is not performed by plasma, the first substrate 100A and the second substrate 200A are hardly damaged. Instead of XeF ₂ , for example, CF ₄ or SF ₆
Can be used.

In the case of wet etching, the first substrate 10
If there is a defect such as a pinhole in the second substrate 200A or the second substrate 200A, the etchant enters the region where the drive electrode 130 and the support portion 280 are formed, and thereby the drive electrode 13
0 and the support 280 may be damaged. In the case of dry etching, such a situation can be prevented because an etching solution is not used.

The polishing is a normal polishing used in the field of semiconductors, and the description is omitted.

As described above, according to the present embodiment, the silicon substrate 25 is used with the silicon oxide layer 225 as a stopper.
Since 0 is removed, it is possible to prevent the surface roughness of the micro mirror 220 from increasing. For example, a comparison is made with a case where a micromirror is formed using a silicon substrate whose surface layer is a boron-doped layer. In this substrate, a micro mirror is formed on the boron-doped layer. Of the silicon substrate,
The portion other than the boron doped layer becomes the base. When the base portion is removed, the boron-doped layer has a surface roughness reflecting the non-uniformity due to non-uniform boron diffusion. When this surface roughness is represented by Ra (Roughness Average), it is, for example, 2.8 to 5.1 nm. Ra is the arithmetic average roughness and is one of the definitions of the surface roughness (JISB06)
01-1994). According to the present embodiment, the micro mirror 2
The surface roughness of 20 is the surface roughness of a normal silicon wafer, and is, for example, 0.1 to 0.4 nm in terms of Ra. As described above, according to the present embodiment, it is possible to manufacture an optical modulation device including a micromirror having a high reflectance.

As shown in FIGS. 7 (C) and 8 (C),
A reflection layer 227 made of aluminum is formed on the silicon oxide layer 225 by, for example, sputtering.
The thickness of the reflective layer 227 is, for example, 0.1 μm to
0.2 μm.

Next, a resist R6 is applied on the reflective layer 227, and a predetermined pattern is formed on the resist R6 by photolithography. Using the resist R6 as a mask, for example, anisotropic dry etching is performed on the reflection layer 227, the silicon oxide layer 225, and the silicon single crystal layer 260. Thus, the micro mirror 220 and the shaft 230 are formed. The micromirror 220 has a reflective layer 227 on the surface via a silicon oxide layer 225. And
The resist R6 is removed. The first substrate 100A becomes the electrode substrate 100. The mirror substrate 200 is configured by the micro mirror 220, the shaft 230, the support 280, and the frame 210.

As shown in FIGS. 7D and 8D,
The cover glass substrate 300 is attached to the frame 210 of the second substrate 200.
The light modulation device 1 is completed.
This attachment may be anodic bonding. However, the second substrate 2
Since the bonding between the cover glass substrate 300 and the cover glass substrate 300 does not require precision, another bonding method, for example, a bonding method using an adhesive can be adopted.

When the surface of the micromirror 220 is used as a reflective layer, the step of forming the reflective layer 227 is unnecessary. Since the silicon oxide layer 225 is transparent, it need not be removed, but may be removed according to the characteristics required for the micromirror 220. In this case, dry etching is preferably used for removing the silicon oxide layer 225 in order to prevent the drive electrode 130 and the like from being damaged by the etchant.

According to the first manufacturing method, an optical modulator having excellent durability can be manufactured. That is, as shown in FIG. 1 and FIG.
It is driven to tilt in the direction. At this time, stress concentrates on the joint between the shaft 230 and the support 150. According to the first manufacturing method, as shown in FIG. 8C, since the shaft 230 and the support 280 are formed by patterning the silicon single crystal layer 260, the shaft 230 and the support 28 are formed.
0 can be firmly bonded. Therefore, when the micromirror 220 is tilted, the shaft 230 and the support 2
Even when stress concentrates on the joint 290 (FIG. 8D) with the joint 80, the joint 290 is not easily broken. Therefore, an optical modulator having excellent durability can be obtained.

{Second Manufacturing Method} The second manufacturing method differs from the first manufacturing method in that a supporting portion is formed on the first substrate.

(Manufacture of First Substrate) First, the electrode substrate 100
Of the first substrate will be described. FIG. 9 is a process chart for explaining this. Differences from the first substrate manufacturing method according to the first manufacturing method shown in FIG. 5 will be mainly described. The same components as those shown by the reference numerals in FIG. 5 are denoted by the same reference numerals.

As shown in FIG. 9A, the glass substrate 16
A resist R7 is applied on the resist pattern 0, and a predetermined pattern is formed on the resist R7 by photolithography. Using the resist R7 as a mask, the glass substrate 160 is selectively shaved by, for example, etching with CHF ₃ to form the support 150 and the recessed region 110.

As shown in FIG. 9B, the glass substrate 16
A conductive layer 170 to be a drive electrode is formed on the entire surface of the substrate.

As shown in FIG. 9C, the drive electrode 130 is formed by patterning the conductive layer 170.

As shown in FIG. 9D, the driving electrode 130
By removing the upper resist R2, the first substrate 100B to be the electrode substrate 100 is completed. The support 150 has a free end 151, which is fixed to the shaft 230, as described below.

(Manufacture of Second Substrate) The manufacture of the second substrate to be the mirror substrate 200 will be described. FIG. 10 is a process chart for explaining this. The cross section of the process diagram of FIG. 10 is a surface cut in the same direction as the direction along the line XX and the line YY of FIG. Differences from the manufacture of the second substrate according to the first manufacturing method shown in FIG. 6 will be mainly described. 6 that are the same as those shown in FIG. 6 are given the same reference numerals.

As shown in FIG. 10A, a silicon substrate 250, a silicon oxide layer 225, a silicon single crystal layer 26
An SOI substrate having a structure in which 0s are sequentially stacked is prepared. Second
In the manufacturing method, no support is formed on the silicon single crystal layer 260. Therefore, the thickness of the silicon single crystal layer 260 is
For example, it is 2 μm, which is the same as the thickness of the micro mirror 220.

As shown in FIG. 10B, dry thermal oxidation is performed on the SOI substrate. Thus, an insulating layer 221 made of a thermal silicon oxide layer is formed on the surface of silicon single crystal layer 260. Note that the insulating layer 221 may be formed by a CVD method instead of dry thermal oxidation.
As described above, the second substrate 200B serving as the mirror substrate 200
Is completed.

(From Fixing of the Second Substrate to the First Substrate to Completion of the Optical Modulation Device) FIGS. 11 and 12 are process diagrams for explaining this. The cross section of the process diagram of FIG.
-A surface cut in the same direction as the direction along the X-ray. The cross section of the process diagram of FIG. 12 is a surface cut in the same direction as the direction along the line YY of FIG. The first shown in FIGS. 7 and 8
The points different from the manufacturing of the second substrate according to the manufacturing method will be mainly described. The same reference numerals as those shown in FIGS. 7 and 8 denote the same parts.

As shown in FIGS. 11A and 12A, the silicon single crystal layer 260 as the first layer and the driving electrode 1
The second substrate 200B is arranged on the first substrate 100B so that the second substrate 30 faces the second substrate 200B. Then, for example, the second substrate 200B is fixed to the first substrate 100B by anodic bonding.
By this anodic bonding, the free end 151 of the support part 150 is fixed to a part to be a shaft part.

As shown in FIGS. 11B and 12B, the silicon substrate 250 as an example of the second layer is removed. For this removal, for example, wet etching, dry etching, and polishing are used. In any case, when the silicon substrate 250 is removed, the silicon oxide layer 225 is removed.
Becomes a stopper.

As shown in FIGS. 11C and 12C, a reflection layer 227 is formed on the silicon oxide layer 225. Then, using the resist R6 as a mask, the reflection layer 22 is used.
7, silicon oxide layer 225 and silicon single crystal layer 260
Then, for example, anisotropic dry etching is performed. Thus, the micro mirror 220 and the shaft 230 are formed.
The first substrate 100B includes the electrode substrate 10 including the support 150.
It becomes 0. Micro mirror 220, shaft 230 and frame 21
0 forms the mirror substrate 200.

As shown in FIGS. 11D and 12D, the cover glass substrate 300 is
10, the light modulation device 1 is completed.

[Modification] In the first and second manufacturing methods, the silicon substrate 250 is removed by one of wet etching, dry etching, and polishing. However, these may be combined. This will be described in a first manufacturing method. After the step shown in FIG. 7A, a part of the silicon substrate 250 is removed by polishing as shown in FIG. Here, when the thickness of the silicon substrate 250 is, for example, 525 μm to 600 μm, the thickness is 515 μm to 59 μm.
0 μm. Then, the remaining portion of the silicon substrate 250 is removed by wet etching or dry etching, and the state shown in FIG. 7B is obtained.

The speed of polishing the silicon substrate 250 is higher in polishing than in etching. In addition, etching can remove the silicon substrate 250 with higher precision than polishing. Therefore, according to the modification, the silicon substrate 250
While reducing the time required to remove the
It is possible to prevent the silicon single crystal layer 260 on which the like is formed from being damaged.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a light modulation device according to an embodiment.

FIG. 2 is a plan view showing a part of a plurality of micro mirrors arranged in a matrix shown in FIG.

FIG. 3 is a sectional view of a portion where a certain micromirror is arranged in the light modulation device shown in FIG. 1;

FIG. 4 is a cross-sectional view showing a state where the micro mirror shown in FIG. 3 is inclined.

FIG. 5 is a process chart for explaining the manufacture of the first substrate in the first manufacturing method of the present embodiment.

FIG. 6 is a process chart for explaining the manufacture of the second substrate in the first manufacturing method of the embodiment.

FIG. 7 is a process diagram for describing from the fixing of the second substrate to the first substrate to the completion of the light modulation device in the first manufacturing method of the embodiment.

FIG. 8 is a process diagram for describing from the fixing of the second substrate to the first substrate to the completion of the light modulation device in the first manufacturing method of the present embodiment.

FIG. 9 is a process chart for explaining the manufacture of the first substrate in the second manufacturing method of the embodiment.

FIG. 10 is a process chart for explaining the manufacture of the second substrate in the second manufacturing method of the embodiment.

FIG. 11 is a process diagram for describing from the fixing of the second substrate to the first substrate to the completion of the light modulation device in the second manufacturing method of the present embodiment.

FIG. 12 is a process diagram for describing from the fixing of the second substrate to the first substrate to the completion of the light modulation device in the second manufacturing method of the present embodiment.

FIG. 13 is a cross-sectional view for explaining a modification of the manufacturing method according to the embodiment.

[Explanation of symbols]

 Reference Signs List 1 light modulation device 100 electrode substrate 100A, 100B first substrate 110 concave region 120 side wall portion 130 drive electrode 140 wiring 150 support portion 151 free end 160 glass substrate 170 conductive layer 200 mirror substrate 200A, 200B second substrate 210 frame portion 220 minute Mirror 221 Insulating layer 225 Silicon oxide layer 227 Reflective layer 230 Shaft part 240 Slit 250 Silicon substrate 260 Silicon single crystal layer 280 Support part 290 Coupling part 300 Cover glass substrate R1 to R8 Resist

Claims (9)

[The claims] 1. A method of manufacturing an optical modulator in which a micro mirror is tilted and driven by an electrostatic force generated by a potential difference between a driving electrode and a micro mirror, wherein: (A) a first substrate including the driving electrode; Is formed, a second layer serving as a base of the first layer, and a second layer located between the first layer and the second layer and serving as a stopper when the second layer is removed. Fixing a second substrate to the first substrate so that the drive electrode and the first layer face each other; and (B) the step (A). And (C) forming the micromirror by patterning the first layer after the step (B), using the third layer as a stopper. , A method of manufacturing a light modulation device. 2. The method according to claim 1, wherein the second substrate includes at least one of an SOI substrate and an SOS substrate. 3. The optical modulation device according to claim 1, further comprising, between the step (B) and the step (C), forming a reflection layer of the micromirror on the third layer. Manufacturing method. 4. The method for manufacturing a light modulation device according to claim 1, wherein wet etching is used for removing the second layer in the step (B). 5. The method for manufacturing a light modulation device according to claim 1, wherein dry etching is used for removing the second layer in the step (B). 6. The method for manufacturing an optical modulation device according to claim 1, wherein polishing is used for removing the second layer in the step (B). 7. The method according to claim 1, wherein in the step (B), a part of the second layer is removed by polishing, and a remaining part of the second layer is removed by etching. A method for manufacturing a light modulation device, comprising: 8. The support according to claim 1, wherein before the step (A), the first layer is patterned to form a support portion serving as a fulcrum when the micro mirror is tilted and driven. The step (C) includes a step of patterning the first layer to form a shaft fixed to the support portion as an axis when the micro mirror is tilted and driven.
A method for manufacturing a light modulation device. 9. The support according to claim 1, wherein before the step (A), the first substrate is patterned to form a support portion serving as a fulcrum when the micro mirror is tilted and driven. The step (C) is a step of forming a shaft fixed to the support portion, which is used as an axis when the micromirror is tilted by patterning the first layer of the second substrate. A method for manufacturing a light modulation device, comprising: