JP2002333512A - Curved reflection mirror and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a curved reflection mirror having an ideal reflection face form as the initial form and to provide a method for manufacturing the curved reflection mirror. SOLUTION: The curved reflection mirror 101 has a film 103 where the reflection face 104 is formed and a holding part 102 holding the peripheral edge of the film 103. An inner stress region 105 which generates stress in the direction along the film 103 with the distribution of the stress in the thickness direction is formed in the film 103. The film 103 has strain depending on the stress distribution of the inner stress region 105 and is distorted according to the strain to form the curved face on the reflection face 104.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a curved reflecting mirror and a method of manufacturing the same, and more particularly, to a curved reflecting mirror formed of a film and having a variable focal point, and a curved reflecting mirror using a semiconductor material or the like. A method for manufacturing a mirror.

[0002]

2. Description of the Related Art Various types of curved reflecting mirrors formed of a thin film and having a variable focal point have been studied for use in a mechanism for focusing a laser beam on a bar code and for an optical pickup. ing.

As one example, a curved reflecting mirror is known in which an electrode plate is provided behind a thin film, a voltage is applied between the two, and the thin film is bent by the electrostatic attraction, and the bent surface of the thin film is used as a reflecting surface. Have been. FIG. 11 shows a schematic configuration of a first conventional example of such a curved reflecting mirror. 11, a curved reflecting mirror 1100 has a configuration in which an upper substrate 1110 and a lower substrate 1120 are bonded to each other. The upper substrate 1110 includes a circular thin film 1111 of single crystal silicon and a framework 1112. An electrode 1121 is integrally formed on a surface of the lower substrate 1120 facing the circular thin film 1111. Wirings (not shown) are formed on the circular thin film 1111 and the electrodes 1121, respectively, and are electrically connected to each other. When a voltage is applied from the outside via this wiring, an electrostatic attraction is generated between the circular thin film 1111 and the electrode 1121. This electrostatic attraction deflects the circular thin film 1111 and makes its upper surface concave. This concave surface functions as a concave mirror.
The depth of the center of the concave surface increases as the applied voltage increases, and the focal length of the curved reflecting mirror changes accordingly.

Next, as a second conventional example, Japanese Patent Application Laid-Open No. 5-157
The variable focal length concave mirror disclosed in Japanese Patent Publication No. 903 will be described. The variable focal length concave mirror includes a single crystal silicon thin plate 1200. FIG. 12 schematically shows the configuration of the variable focal length concave mirror. The single-crystal silicon thin plate 1200 includes an outer peripheral frame portion 1210 and an inner peripheral portion 1220. The principle of the deformation of the reflecting surface in this conventional example is the same as that of the above-mentioned first conventional example.
The electrode is opposed to 220, and a voltage is applied between the two to bend the inner peripheral portion 1220. Upper surface 1220 of inner peripheral portion 1220
a is a plane and forms a reflection surface. The lower surface 1220b is a curved surface. The inner peripheral portion 1220 further includes a parabolic surface portion 1221 located at an inner peripheral position and a cubic curved surface portion 122 surrounding the outer peripheral portion.
2 is constituted. The plate thickness of the paraboloid 1221 gradually increases toward the center according to a predetermined formula. On the other hand, the thickness of the cubic curved surface portion 1222 gradually increases toward the outer periphery according to another formula. Inner circumference 1220
When a voltage is applied between the electrode and the electrode, the inner peripheral portion 1220 is deformed by electrostatic attraction, but the bending rigidity of the thin plate 1200 has a distribution due to the change in the plate thickness as described above. For this reason, the shape of the upper surface 1220a of the parabolic surface portion 1221 becomes a parabolic surface shape, and the aberration is small.

[0005]

The curved reflecting mirror 1100 according to the first conventional example has an initial state, that is, an applied voltage of 0V.
Is a flat plate, and its focal length is infinite. From this state, it is assumed that the applied voltage is increased and the focal length is reduced. Since the plate thickness of the circular thin film 1111 is uniform throughout, the bending stiffness of the circular thin film 1111 is also uniform throughout, so that an ideal reflecting surface shape such as a parabolic surface is not obtained. This aberration increases as the focal length is reduced. Considering a case where the focal length of the reflecting mirror is changed in a range of, for example, 20 cm to 30 cm, it is necessary to bend the circular thin film 1111 from a flat plate shape to a curved surface shape. Therefore, when the lens is bent so that the focal length becomes 30 cm, a considerable amount of aberration has already occurred. When the focal length is set to 20 cm, the aberration further increases.

In the second conventional example, there is no problem as in the first conventional example, but it is technically difficult to control the thickness of a silicon thin film having a film thickness distribution such as the inner peripheral portion 1220.

In order to solve the above-mentioned problems, it is effective to prepare a thin film whose initial shape is an ideal reflecting surface shape close to the focal length in actual use, and change the focal length from that state. Therefore, an object of the present invention is to provide a curved reflecting mirror whose initial shape is an ideal reflecting surface shape, and a method for manufacturing the curved reflecting mirror.

[0008]

In order to achieve the above object, a curved reflecting mirror according to claim 1 of the present invention comprises a film having a reflecting surface formed thereon, and a holding portion for holding a peripheral portion of the film. The film has an internal stress region that has a distribution in the thickness direction of the film and generates stress in a direction along the film, and the film has a strain corresponding to a stress distribution in the internal stress region. In addition, it is characterized in that it bends in response to this distortion and a curved surface is formed on the reflection surface.

[0009] Since the membrane is held around its periphery,
The film naturally becomes bent due to internal stress in the film. The internal stress region in the film is a region where the stress along the film is not uniform in the thickness direction. The film tends to bend in this internal stress region. The shape of the film can be arbitrarily controlled by setting the shape of the internal stress region and the strength of the internal stress in consideration of the rigidity of the film.

[0010] In the curved reflecting mirror according to claim 2 of the present invention, the film includes a first layer provided with the reflecting surface, and a surface of the first layer opposite to the reflecting surface in the first layer. A second layer provided on at least a part thereof, wherein the internal stress region extends over the second layer and a part of the first layer located around the second layer. It is characterized in that the stress in the direction along the film is different between the first layer and the second layer so as to be formed.

Since the first layer and the first layer have a difference in stress in the direction along the film, the second layer and the portion of the first layer located around the second layer Can be used as the internal stress region.

In the curved reflecting mirror according to a third aspect of the present invention, the film has a silicon film, and the silicon film has an impurity diffusion portion in which impurities are diffused. And a stress in a direction along the film is different between the silicon film and the impurity diffusion portion so that the internal stress region is formed over a portion of the silicon film located around the impurity diffusion portion. And

When an impurity is diffused into a silicon film, a tensile stress or a compressive stress can be generated in accordance with the atomic size or the diffusion concentration of the impurity. Therefore, in the above film, a stress difference is generated between the impurity diffusion portion and a portion of the silicon film located around the impurity diffusion portion, and a region including these is an internal stress region.

In the curved reflecting mirror according to a fourth aspect of the present invention, the internal stress region extends along the film, and has a plurality of concentrically arranged annular shapes.

When the internal stress region extends concentrically, the reflecting surface of the curved reflecting mirror naturally becomes a rotationally symmetric curved surface centered on the center of the concentric circle. Similarly, in the case of an ellipse, the reflecting surface of the reflecting mirror is an elliptical surface. For this reason, the design of the reflection surface becomes easy.

In a curved reflecting mirror according to a fifth aspect of the present invention, the substrate is opposed to the film at a predetermined interval, and a substrate provided with a first electrode and a second electrode provided on the film. Wherein the film is deformed when a voltage is applied between the first electrode and the second electrode, and the curvature of the reflection surface changes according to the voltage. Features.

If the curved reflecting mirror is formed such that a curved surface with less aberration is formed on the reflecting surface when no voltage is applied, a curved reflecting mirror with less aberration can be realized when the film is deformed by applying voltage. In addition, since a curved surface with less aberration is formed on the reflecting surface in advance, the amount of deformation of the reflecting surface can be relatively small, and the energy required for driving is reduced.

In the method of manufacturing a curved reflecting mirror according to claim 6 of the present invention, a first step of preparing a substrate and forming a first layer containing silicon on the substrate is provided. Forming a second layer containing silicon on the first layer under different conditions, wherein stress in a direction along the surface of the substrate is different between the first layer and the second layer. Step 2, a part of the second layer is removed, the second layer is processed into a predetermined shape, and the second layer and the first layer located around the second layer are removed. A third step of forming an internal stress region having a distribution in a thickness direction of the substrate and generating a stress in a direction along a surface of the substrate over a portion of the layer;
And a fourth step of removing the substrate while leaving the portion of the substrate in contact with the peripheral portion of the layer of the first layer. The film having the first layer and the second layer; A holding portion for holding the peripheral portion of the film is formed, the surface of the film functions as a reflection surface, and the film bends in response to the stress in the internal stress region. It is characterized in that a curved surface is formed on the surface.

When a part of the second layer is removed in the third step, the film formed in the fourth step includes the second layer and the second layer.
And a portion of the first layer located around the first layer. At the same time, a region of only the first layer is formed. The former is an internal stress region having a stress distribution in the thickness direction of the film. On the other hand, the latter is only the first layer and does not become an internal stress region because there is no stress distribution. As described above, the internal stress region and other regions can be formed in the film in any shape.

In the method for manufacturing a curved reflecting mirror according to claim 7 of the present invention, a first step of preparing a substrate and forming a layer containing silicon nitride or silicon oxide on the substrate, A step of implanting ions by ion implantation to form an ion-implanted portion in the layer, wherein the distribution in the thickness direction of the substrate is distributed over the ion-implanted portion and a portion of the layer located around the ion-implanted portion. A second step in which the stress in the direction along the surface of the substrate is different between the layer and the ion-implanted portion so that an internal stress region for generating stress in the direction along the surface of the substrate is formed; A third step of removing the substrate while leaving the portion of the substrate in contact with the peripheral edge of the substrate, wherein a film having a layer in which the ion-implanted portion is formed; A holding portion for holding a peripheral portion of the film is formed, the surface of the film functions as a reflection surface, and the film bends in response to the stress in the internal stress region, and the reflection surface A curved surface is formed.

When a layer containing silicon nitride or silicon oxide is formed on the substrate in the first step, a layer in a state of compressive stress, tensile stress or no stress can be formed depending on the conditions. However, the stress in the direction along the surface of the substrate in the layer is almost uniform in the thickness direction,
Since there is no distribution, the region does not become the above-mentioned internal stress region. When certain ions are implanted into this layer in the second step, the stress can be changed in accordance with the ion species and the amount of implantation. Further, it is possible to control the distance in the thickness direction that causes a stress distribution according to the ion implantation energy. In this manner, an internal stress region can be formed by generating a stress distribution at a predetermined position in the layer. In the above state, the shape of the film can be controlled by removing the substrate in the third step and bending the film.

In the method for manufacturing a curved reflecting mirror according to claim 8 of the present invention, a step of preparing a substrate, diffusing impurities into the substrate, and forming an impurity diffusion portion on the surface of the substrate is provided,
An internal stress region is formed over the impurity diffused portion and the portion of the substrate located around the impurity diffused portion, which has a distribution in the thickness direction of the substrate and generates stress in a direction along the surface of the substrate. As described above, the first step in which the stress in the direction along the surface of the substrate is different between the substrate and the impurity diffusion portion, the peripheral portion of the substrate, and the portion of the surface of the substrate including the impurity diffusion portion are left. A second step of removing a predetermined portion of the substrate, wherein the film having the portion on the surface of the substrate including the impurity diffusion portion and the peripheral portion of the substrate are provided. A holding portion for holding a peripheral portion of the film is formed, the surface of the film functions as a reflection surface, and the film bends according to the stress of the internal stress region, and a curved surface is formed on the reflection surface It is characterized by being done.

When impurity diffusion is performed on the substrate in the first step,
Tensile stress or compressive stress can be generated according to the atomic size or diffusion concentration of the impurity. In the above state, when a film is formed by removing a predetermined portion of the substrate in the second step, an internal stress region is formed in the film over an impurity diffusion portion and a portion of the substrate located around the impurity diffusion portion. Is done. Therefore, in consideration of the rigidity of the substrate, the shape of the impurity diffusion portion, the diffusion depth, and the impurity implantation amount are appropriately determined in advance, and the reflection surface has a desired shape by forming a film.

According to a method of manufacturing a curved reflecting mirror according to a ninth aspect of the present invention, a first silicon layer, an insulating layer laminated on the first silicon layer and containing an insulator, A step of preparing an SOI wafer having a second silicon layer laminated on the layer, diffusing impurities into the second silicon layer, and forming an impurity diffusion portion in the second silicon layer. Accordingly, stress is generated in the direction along the surface of the SOI wafer with distribution in the thickness direction of the SOI wafer over the impurity diffused portion and the portion of the second silicon layer located around the impurity diffused portion. A first step in which the stress in the direction along the surface of the SOI wafer is different between the second silicon layer and the impurity diffusion portion so as to form an internal stress region to be formed, and etching the first silicon layer. And above A second step of immersing the first silicon layer in an etchant that does not etch the edge layer, removing the first silicon layer while leaving a peripheral portion of the first silicon layer, and exposing a part of the insulating layer; A third step of immersing the insulating layer in an etchant that etches the insulating layer and does not etch the second silicon layer to remove the exposed portion of the insulating layer. Having a film including the second silicon layer including the above, and the above-described portion of the first silicon layer left in the second step, and holding the periphery of the film. Are formed, the surface of the film functions as a reflection surface, the film bends in response to the stress in the internal stress region, and a curved surface is formed on the reflection surface.

In the SOI wafer, a second silicon layer is formed on an insulator. In the third step, when an insulator is etched in the SOI wafer but is not etched in silicon, a film is formed and the film can be bent. The thickness accuracy of this film is the same as the thickness accuracy of the second silicon layer in the SOI wafer,
High accuracy. Therefore, the shape accuracy of the formed reflecting surface is increased.

In the method of manufacturing a curved reflecting mirror according to claim 10 of the present invention, a P-type or N-type silicon substrate is prepared,
A first step of diffusing impurities on the silicon substrate to form an impurity diffusion layer of a conductivity type different from the above conductivity type of the silicon substrate on the silicon substrate; Or diffuse the impurity of the same type as the impurity in the impurity diffused layer at a high concentration, thereby forming an impurity diffused portion in the impurity diffused layer. The internal stress region having a distribution in the thickness direction of the silicon substrate and generating a stress in a direction along the surface of the silicon substrate is formed over a portion of the impurity diffusion layer located around the diffusion portion. A second step in which the stress in the direction along the surface of the silicon substrate is different between the impurity diffusion layer and the impurity diffusion portion, and immersing the silicon substrate in an etching solution; A silicon substrate is etched while a voltage is applied between the solution and the impurity diffusion layer, and the silicon substrate is removed while leaving a peripheral portion of the silicon substrate by an electrochemical etching method that does not etch the impurity diffusion layer. A film having the impurity diffusion layer in which the impurity diffusion portion is formed;
The remaining portion of the silicon substrate is formed, a holding portion for holding a peripheral portion of the film is formed, a surface of the film functions as a reflection surface, and the film responds to the stress of the internal stress region. And a curved surface is formed on the reflection surface.

When an impurity is diffused into a silicon crystal, a tensile stress or a compressive stress can be generated according to the atomic size or the diffusion concentration of the impurity. Therefore, it is possible to cause a difference in stress in a direction along the surface of the silicon substrate between a portion where the impurity diffusion portion is formed and a portion where the impurity diffusion portion is not formed in the impurity diffusion layer. Therefore, an internal stress region is formed over the impurity diffusion portion and the portion of the impurity diffusion layer located around the impurity diffusion portion. The diffusion depth of the impurity diffusion portion can be controlled with high precision. When etching the silicon substrate in the third step, a so-called electrochemical etching method in which a voltage is applied to the impurity diffusion layer, that is, a so-called electrochemical etching method, is used to obtain a film having substantially the same thickness as the impurity diffusion layer. Can be. As a result, the thickness accuracy of the film is high. As described above, since a film having an internal stress region therein and having a controlled thickness can be obtained, a reflection surface with high shape accuracy can be obtained.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A curved reflecting mirror according to an embodiment of the present invention will be described with reference to FIGS. First, referring to FIGS. 1A, 1B and 1C, the first embodiment of the present invention will be described.
The curved reflecting mirror according to the embodiment will be described. 1A and 1B schematically show the configuration of a curved reflecting mirror, FIG. 1A is a plan view of the curved reflecting mirror, and FIG. 1B is a cross-sectional view taken along line 1B-1B of FIG. .

The curved reflecting mirror 101 includes a holding portion 102 and a film 103 having a peripheral portion fixed by the holding portion 102. On the upper surface of the film 103, a reflection surface 104 is formed. The film 103 is curved, and the reflection surface 104 has a concave surface. A stress is generated in the film 103 and the film 1
An internal stress region 105 that bends the internal stress region 03 is formed.
The internal stress region 105 extends along the film 103. FIG.
(A), the shape of the internal stress region 105 as viewed from above and below is a plurality of concentric circles.

FIG. 1C is an enlarged view of the portion P1 shown in FIG. 1B. The internal stress region 10
5 are included. The internal stress region 105 extends from the upper surface to the lower surface in the thickness direction of the film 103, and generates stress in the direction along the surface of the film 103. This stress is applied to the membrane 10
3 in the thickness direction. That is, the reflection surface 104
On the upper surface of the film 103 on which is formed, a tensile stress is generated in the internal stress region 105 so as to pull a portion of the film 103 located around the internal stress region 105 in a direction toward the internal stress region 105 (arrow 106). I do. On the other hand, the film 10
3, a portion of the film 103 located around the internal stress region 105 is formed in the internal stress region 105.
Compressive stress is generated in such a direction as to push away from the arrow (arrow 107). Accordingly, the internal stress region 105 is distorted in the direction of arrow 106 to shrink on the upper surface side of the film 103 and distorted in the direction of arrow 107 to extend on the upper surface side in accordance with such a stress distribution. As shown in FIG. 1B, the film 103 is bent to the lower surface side in response to the distortion, and as described above, the reflecting surface 1 is bent.
04 has a concave surface.

The shape of the bent film 103 is determined by the internal stress region 10.
5 is determined by the elastic modulus and thickness of the portion of the film 103 adjacent to 5, the arrangement and shape of the internal stress region 105, and the stress distribution in the thickness direction of the film 103. By determining the above parameters in consideration of these, the shape of the film 103 can be arbitrarily determined. By utilizing this, the film 103 can be bent into an ideal parabolic shape. In FIG. 1B, line 108 represents an ideal parabola.

As described above, the peripheral portion 103 of the film 103
a is held by the holding portion 102 having high rigidity. As shown in FIG. 1B, the peripheral portion 103a is
2 is fixed to the lower surface. The peripheral portion 103a is the holding portion 1
02 extends along this lower surface, and the extended portion curves and gradually approaches the parabola 108. Therefore, the peripheral portion 1
Since the cross section of 03a deviates from the parabola 108, an ideal concave surface is not formed on the upper surface of the peripheral portion 103a. Therefore, light reflected from the upper surface of the peripheral portion 103a causes aberration. To prevent this, the periphery 10
No reflection surface is formed on the upper surface of 3a.

In the curved reflecting mirror 101 according to the first embodiment of the present invention, which is configured as described above, the film 103 has an internal stress region 105 for generating stress and bending the film 103. By being formed, a concave surface can be formed on the reflection surface 104. By adjusting the shape of the internal stress region 105 and the strength of the internal stress in consideration of the rigidity of the film 103, the shape of the concave surface can be made an ideal paraboloid.

The shape of the internal stress region 105 as viewed from above and below is a plurality of concentric circles. This facilitates the design of the reflecting surface 104 when forming a paraboloid on the reflecting surface 104.

Various modifications and changes can be made to the present embodiment. In the present embodiment, the internal stress region 10
This stress is distributed such that the stress of No. 5 is a tensile stress on the upper surface side and a compressive stress on the lower surface side, but the present invention is not limited to this. It is sufficient if there is an imbalance between the upper surface side and the lower surface side in the stress distribution in the thickness direction. For example, the compression stress may be on the upper surface side and the tensile stress may be on the lower surface side.
Also, the tensile stress may be on the lower surface side and may be stronger on the upper surface side. At this time, the stress distribution may change stepwise or may change gently.

In this embodiment, no reflection surface is formed on the upper surface of the peripheral portion 103a of the film 103 in order to reduce aberration. When forming the film 103 with a material having a high reflectance instead of forming the reflection surface 104 on the film 103,
In order to reduce the aberration, the curved reflecting mirror 10 is set so that light incident on the curved reflecting mirror 101 is not irradiated to the peripheral portion 103a.
A stop may be arranged in front of the first stop. In order to minimize the portion of the peripheral portion 103a deviating from the ideal paraboloid, this portion is made thinner or the film 103 is bent by forming the film 103 with a material having a smaller elastic modulus. May be easier.

In this embodiment, an ideal paraboloid is formed on the reflection surface 104, but the shape of the reflection surface 104 is not limited to this.

In this embodiment, the internal stress region 10
The shape of 5 as viewed from above and below is a plurality of concentric circles,
The present invention is not limited to this. A plurality of concentrically arranged rings may be used. For example, a plurality of elliptical shapes arranged concentrically may be used.

Next, a curved reflecting mirror according to a second embodiment of the present invention will be described with reference to FIGS. 2A and 2B. Most of the configuration of the curved reflecting mirror of the present embodiment is basically the same as most of the configuration of the curved reflecting mirror of the first embodiment. Since the configuration of the curved reflecting mirror of the present embodiment viewed from the up and down direction is substantially the same as that of the curved reflecting mirror of the first embodiment, a plan view of the curved reflecting mirror of the first embodiment is shown. FIG. 1A is used as a plan view of the curved reflecting mirror of the present embodiment. Note that, in the present embodiment, components substantially the same as those described with reference to FIGS. 1A, 1B, and 1C of the first embodiment are the same as those of the first embodiment. The same reference numerals as those used in the first embodiment denote corresponding components, and a detailed description thereof will be omitted. 2A is a cross-sectional view taken along line 1B-1B of FIG. 1A, and FIG. 2B is an enlarged view of a portion P2 of FIG. 2A.

The configuration of this embodiment differs from the configuration of the first embodiment in the configuration of the internal stress region formed in the film. The film 203 has a first layer 211 and a second layer 212. The first layer 211 covers the whole of the film 203, and the reflection surface 104 is formed on the upper surface thereof. The second layer 212 is provided on at least a part of the surface of the first layer 211 opposite to the reflection surface 104. That is, the second layer 212 is stacked on the lower surface of the first layer 211, and is arranged concentrically along the first layer 211 as shown in FIG. The stress in the direction along the film 203 is different between the first layer 211 and the second layer 212.

That is, as shown in FIG. 2B, the second layer 2
12 includes a first layer 211 in contact with the second layer 212.
In the direction along the lower surface of the first layer 211 (arrow 20).
A compressive stress is generated as in (7). A stress that deforms the film 203 is not generated in a portion on the upper surface side of the first layer 211. As a result, in the thickness direction of the film 203, a stress imbalance occurs in the direction along the film 203,
The film 203 bends similarly to the film 103 of the first embodiment. The portion of the film 203 extending over the second layer 212 and the portion of the first layer 211 located around the second layer 212 functions as an internal stress region 205.

The imbalance in stress can be caused by a difference in the coefficient of thermal expansion between the first layer 211 and the second layer 212, a difference in conditions for forming the layers, and the like. Furthermore, the second
By appropriately selecting the arrangement and shape of the layer 212,
An ideal paraboloid can be formed on the film 203.

Of course, various modifications and changes can be made to the present embodiment. In the present embodiment, the second layer 21
2, a compressive stress is generated, and no stress is generated in a portion on the upper surface side of the first layer 211, but the present invention is not limited to such a stress distribution. For example, a tensile stress may be generated in the first layer 211 and the stress may be distributed so that no stress is generated in the second layer 212.

Next, a curved reflecting mirror according to a third embodiment of the present invention will be described with reference to FIGS. 3 (A) and 3 (B). Most of the configuration of the curved reflecting mirror of the present embodiment is basically the same as most of the configuration of the curved reflecting mirror of the first embodiment. Since the configuration of the curved reflecting mirror of the present embodiment viewed from above and below is substantially the same as that of the curved reflecting mirror of the first embodiment, FIG. 1A shows the curved reflecting mirror of the present embodiment. Used as a plan view of the mirror. In the present embodiment, components substantially the same as those described with reference to FIGS. 1A, 1B, and 1C of the first embodiment are the same as those in the first embodiment.
The same reference numerals as those in the first embodiment denote the corresponding components, and a detailed description thereof will be omitted.
3A is a cross-sectional view taken along the line 1B-1B of FIG. 1A, and FIG. 3B is an enlarged view of a portion P3 of FIG.

The structure of this embodiment differs from the structure of the first embodiment in the structure of the internal stress region formed in the film. The film 303 has a silicon film 311. The silicon film 311 extends over the entire film 303. The reflection surface 104 is formed on the upper surface of the silicon film 311.
On the lower surface of the silicon film 311, an impurity diffusion portion 312 in which an impurity is diffused is formed. The impurity diffusion portion 312 is formed from the lower surface of the silicon film 311 to a predetermined depth. This depth is selected so that an ideal paraboloid is formed on the reflecting surface 104 as described later. As shown in FIG. 1A, the impurity diffusion portion 312
1 are arranged concentrically.

The stress in the direction along the film 303 is different between the impurity diffusion portion 312 and the silicon film 311. That is,
In this embodiment mode, arsenic (As) is used as an impurity, and arsenic atoms are larger than silicon atoms. Therefore, a compressive stress is generated in the impurity diffusion portion 312 so as to push the portion of the silicon film 311 located therearound in a direction away from the impurity diffusion portion 312 (arrow 306). On the other hand, no stress is generated on the upper surface side portion of the silicon film 311. Thereby, in the thickness direction of the film 303, the film 3
An imbalance of stress occurs in the direction along 03, causing deflection. The portion of the film 303 including the impurity diffusion portion 312 and the portion of the silicon film 311 located therearound functions as an internal stress region 305. By appropriately selecting the arrangement, width, depth, diffusion concentration, and the like of the impurity diffusion portion 312, an ideal paraboloid can be formed on the film 203.

Various modifications and changes can be made to the present embodiment. In this embodiment, the impurity is arsenic. However, it is possible to use arsenic or various atoms that are soluble in silicon, such as boron (B) and phosphorus (P), depending on the atomic species, heat treatment conditions, diffusion concentration, and the like. Various stress states can be realized.

Furthermore, when an impurity diffusion portion using phosphorus atoms larger than silicon atoms is formed on the lower surface of the peripheral portion 303a of the film 303, a tensile stress opposite to that when arsenic is used on the lower surface of the peripheral portion 303a is reduced. Can be generated. As a result, the peripheral portion 303a bends convexly to the upper surface side, contrary to the portion of the film 303 in which arsenic is diffused. At this time, the peripheral portion 303a is formed in
Extending along this lower surface, and the extended portion approaches the parabola 108 relatively quickly. Therefore, the film 303 can be more ideally bent. As described above, since a compressive or tensile stress can be simultaneously generated at an arbitrary position of the film 303, the degree of freedom of the shape of the reflection surface 104 is large. still,
Since most of the film 303 and the holder 102 are made of the same material, silicon, there is no difference in their thermal expansion coefficients, so that the curved mirror is less deformed by heat.

The impurity diffusion portion 312 is formed of the silicon film 3
11 may be formed from the lower surface to the upper surface. Generally, when an impurity diffusion layer is formed in silicon, the impurity concentration is not constant in the thickness direction, but peaks at or near the diffusion surface, and becomes lower as the impurity becomes deeper.
Since the stress due to impurity diffusion also depends on the concentration, a stress distribution also occurs in the impurity diffusion portion 312. Therefore, as described above, the film 303 can be bent without using a combination of the impurity diffusion portion 312 and the silicon film 311 located around the impurity diffusion portion 312.

Next, a curved reflecting mirror according to a fourth embodiment of the present invention will be described with reference to FIGS. 4 (A) and 4 (B). Most of the configuration of the curved reflecting mirror of the present embodiment is basically the same as most of the configuration of the curved reflecting mirror of the first embodiment. Note that, in the present embodiment, components substantially the same as those described with reference to FIGS. 1A, 1B, and 1C of the first embodiment are the same as those of the first embodiment. The same reference numerals as those used in the first embodiment denote corresponding components, and a detailed description thereof will be omitted. FIG. 4A is a plan view of a curved reflecting mirror, and FIG. 4B is a plan view of FIG.
It is sectional drawing cut | disconnected by the 4B line.

The configuration of this embodiment differs from the configuration of the first embodiment in the arrangement of internal stress regions formed in the film as viewed from above and below. As shown in FIG. 4A, the internal stress regions 405 are symmetrically arranged along the film 403 with respect to the center of the film 403. That is, the internal stress region 4
05 is a central part 405 located substantially at the center of the film 403.
a and two spiral portions 405b spirally extending from the central portion 405a toward the peripheral portion of the film 403. These spirals 405b do not intersect. Spiral part 40
By appropriately selecting the width of 5b, the number of turns, the interval between adjacent spiral portions 405b, and the like, an ideal paraboloid can be formed on the reflection surface 104. Internal stress area 405
Extends from the upper surface to the lower surface in the thickness direction of the film 403.

As in the present embodiment, the internal stress region 405
Are symmetrically arranged with respect to the center of the film 403,
As in the first embodiment, an ideal paraboloid can be formed on the reflection surface 104.

Of course, various modifications and changes can be made to the present embodiment. In the present embodiment, the internal stress region 4
The two spiral portions 405b of 05 extend from the central portion 405a, but may extend three or more. Also, one may be extended.

The internal stress region 405 extends from the upper surface to the lower surface in the thickness direction of the film 403. The cross-sectional structure of the film 403 is the same as that of the film 103 of the first embodiment shown in FIG. Is substantially the same as the configuration of the cross section, but the present invention is not limited to this. For example, the configuration of the cross section of the film 403 may be the configuration of the second embodiment shown in FIG. 2B, or may be the configuration of the third embodiment shown in FIG. The configuration of the form may be used.

Next, a curved reflecting mirror according to a fifth embodiment of the present invention will be described with reference to FIGS. 5 (A) and 5 (B). FIG. 5A is a sectional view of a curved reflecting mirror. Curved reflector 5
01 includes an upper substrate 510 and a lower substrate 520. The upper substrate 510 is a curved reflecting mirror 1 according to the first embodiment.
01 has substantially the same holding part and film as the holding part 102 and the film 103. The cross section of FIG. 5A corresponds to the cross section of FIG. Note that, in the present embodiment, components substantially the same as those described with reference to FIGS. 1A, 1B, and 1C of the first embodiment are the same as those of the first embodiment. The same reference numerals as those used in the first embodiment denote corresponding components, and a detailed description thereof will be omitted. The lower substrate 520 is disposed to face the upper substrate 510. The first electrode 521 is provided on the lower substrate 520.
Is provided. On the lower surface of the film 103 of the upper substrate 510, a second electrode 511 is formed.
1 faces the first electrode 521. First electrode 52
The first and second electrodes 511 are in a state of being electrically insulated from each other, and a voltage can be applied between them from outside through a wiring (not shown).

When a voltage is applied between the first electrode 521 and the second electrode 511, an electrostatic attraction is generated between the first electrode 521 and the second electrode 511, and the film 103 is deformed. The curvature of the reflecting surface 104 changes according to this voltage. FIG. 5A corresponds to a state when no voltage is applied. FIG. 5B is a cross-sectional view illustrating a state of the curved reflecting mirror 501 when a voltage is applied.

Consider the operation of the curved reflecting mirror 501 whose focal length changes in the range of 20 cm to 30 cm. First, the curved reflecting mirror 501 is in the state of FIG. 5A where no voltage is applied. The film 103 of the curved reflecting mirror 501 is designed to have a focal length of 30 cm in this state. At this time, in the curved reflecting mirror 1100 in the first conventional example shown in FIG. 11, the circular thin film 1111 needs to be bent from a flat plate shape to a curved surface shape. Therefore, the focal length is 30 cm
When the lens is bent so as to satisfy the following condition, a considerable amount of aberration has already occurred. On the other hand, in the curved reflecting mirror 501, since an ideal paraboloid is formed on the reflecting surface 104 at this time, the aberration is relatively small. Also, unlike the first conventional example, no power is required at this time.

Next, when a predetermined voltage is applied, an electrostatic attraction corresponding to this voltage is generated between the first electrode 521 and the second electrode 511, and the curvature of the reflection surface 104 is increased (FIG. 9). 5 (B)). As a result, the focal length decreases according to this voltage, and reaches a predetermined distance. If you increase the voltage,
The focal length will be a minimum distance of 20 cm. Since the circular thin film 1111 of the first conventional example bends from a state where the aberration is not a little generated at a focal length of 30 cm to a state of a focal length of 20 cm, the aberration is accumulated and becomes larger. In contrast, the film 103 of the curved reflecting mirror 501 of the present embodiment
Is the focal length of 2 from the focal length of 30 cm without aberration.
Deflected to 0 cm. Accordingly, there is no accumulation of aberration, and even in this state, the aberration is relatively small. The curved reflecting mirror 1100 in the first conventional example requires a larger voltage when the focal length is 20 cm than when the focal length is 30 cm, whereas the curved reflecting mirror 501 according to the present embodiment requires a larger voltage than when the focal length is 30 cm.
Requires only a voltage corresponding to the difference between the amount of deflection of the film 103 at a focal length of 30 cm and the amount of deflection at a focal length of 20 cm. Therefore, it can be driven with relatively low power consumption.

Various modifications and changes can be made to the present embodiment. In the present embodiment, the electrostatic attraction is used to bend the film 103, but the present invention is not limited to this. For example, electromagnetic force, piezoelectricity, pressure, or the like may be used.

The upper substrate 510 of the curved reflecting mirror 501 of the present embodiment is the same as the curved reflecting mirror 101 of the first embodiment.
Has substantially the same holding portion and film as the holding portion 102 and the film 103, but the present invention is not limited to this. For example, it may have substantially the same film as the film 203 of the curved reflecting mirror 201 of the second embodiment,
May have substantially the same film as the film 303 of the curved reflecting mirror 301 of the embodiment. Further, the internal stress regions of the present embodiment are arranged concentrically along the film as shown in FIG. 1A, but with respect to the center of the film as shown in FIG. They may be arranged symmetrically.

In the present embodiment, the second electrode 511
Is formed on the lower surface of the film 103 of the upper substrate 510, but the present invention is not limited to this. Membrane 103
Can be formed in any part. Further, the reflective surface 104 formed of metal may be used as the second electrode 511.

Next, a method for manufacturing a curved reflecting mirror according to the first embodiment of the present invention will be described with reference to FIGS. 6A to 6E are side views of a silicon substrate 601 to be described later, and show a part of each step of the manufacturing method.

The first step will be described with reference to FIG. A silicon substrate 601 is prepared, and a CVD method (Chem
The nitride films 602a and 602b are formed on the upper surface and the lower surface of the silicon substrate 601 by using an "ical Vapor Deposition" (chemical vapor deposition method). The nitride film 602a is used as a first layer.

The second step will be described with reference to FIG. A nitride film 603 is formed on the nitride film 602a by using a CVD method under film formation conditions different from those in the first step. The nitride film 603 is used as a second layer. The stress in the direction along the surface of the silicon substrate 601 is
And the nitride film 602a are different from each other. Nitride film 602
While the stress in “a” is almost 0, the nitrided film 603 has a compressive stress.

The third step will be described with reference to FIG. A part of the nitride film 603 is removed by patterning, and the nitride film 603 is processed into a predetermined shape. As a result, the silicon substrate 601 has a distribution in the thickness direction of the silicon substrate 601 over the nitride film 603 and the portion of the nitride film 602a located around the nitride film 603.
An internal stress region that generates stress in a direction along the surface of is formed. When the silicon substrate 601 is viewed from the upper surface side, the shape of the nitrided film 603 is a concentric shape as shown in FIG. 1A or a symmetrical shape as shown in FIG.

The fourth step will be described with reference to FIGS. 6D and 6E. First, a nitride film 6 is formed by patterning.
A part of the nitride film 602b is removed so as to leave the peripheral portion of 02b. As a result, a part of the lower surface of the silicon substrate 601 is exposed (FIG. 6D). Next, the silicon substrate 601
Is immersed in an etchant, and etching is performed from an exposed portion of the lower surface. As a result, the silicon substrate 601 is removed while the peripheral portion of the silicon substrate 601 covered with the nitride film 602a remains.

As a result, a film 610 having a nitrided film 602a and a patterned nitrided film 603 is formed. The portion of the silicon substrate 601 remaining after the etching forms a holding portion 620 for holding the peripheral portion of the film 610.
The film 6 in contact with the removed silicon substrate 601
A reflecting surface 611 is formed on the lower surface of the substrate 10 by sputtering or depositing a metal film. The surface smoothness of the upper surface of the silicon substrate 601 is transferred to this portion of the film 610. Thereby, the lower surface of the film 610 becomes smooth, so that the reflectance of the reflection surface 611 is relatively high.

The membrane 610 is released from a member having high rigidity and is easily bent. In the film 610, the internal stress region described in the third step is formed. The stress in the direction along the surface of the film 610 in the internal stress region is a compressive stress on the upper surface side and 0 on the lower surface side as described above, and the film 610 has a concave surface on the reflecting surface 611 on the lower surface according to this stress distribution. Flex as formed. The shape of the reflection surface 611 can be arbitrarily formed by appropriately selecting the shape and arrangement of the patterned nitride film 603, the stress distribution in the internal stress region, and the like.
By utilizing this, the shape of the reflection surface 611 can be made an ideal paraboloid. In addition, since the nitrided film 602a and the nitrided film 603 are formed by the CVD method, it is easy to reduce the thickness, and the stress can be easily controlled by changing the deposition conditions. Can be created.

Of course, various modifications and changes can be made to the present embodiment. In the present embodiment, the nitrided film 602a and the nitrided film 6 are used as a first layer and a second layer, respectively.
Although 03 was used, any other conceivable film may be used. In particular, in the third step, it is more preferable that the second layer is selectively removed so as not to affect the first layer. From this viewpoint, the first layer and the second layer are made of different materials. It is good to consist of. In the present embodiment, the stress in the direction along the surface of the nitride film 602a corresponding to the first layer is 0, and the nitride film 603 corresponding to the second layer is zero.
The stress in the direction along the surface is a compressive stress.
The condition of the stress distribution for forming a desired curved surface on the surface 11 is not limited to this. Various conditions can be considered according to the desired shape of the reflection surface 611. For example, in the present embodiment, a concave mirror is assumed, but in the case of a convex mirror, the nitride film 6 is used.
03 stress needs to be tensile stress. Thus, it is sufficient if there is a stress difference between the first layer and the second layer.

Next, a method for manufacturing a curved reflecting mirror according to a second embodiment of the present invention will be described with reference to FIGS. FIGS. 7A to 7D are side views of a silicon substrate 701 described later, showing a part of each step of the manufacturing method.

The first step will be described with reference to FIG. A silicon substrate 701 is prepared.
Nitride films 702a and 702b are formed on the upper surface and the lower surface, respectively. The nitride film 702a is used as a layer containing silicon nitride. The stress in the direction along the surface of the silicon substrate 701 differs between the nitride film 702a and the silicon substrate 701. By adjusting the film forming conditions, the nitrided film 702a has a tensile stress with respect to the silicon substrate 701.

The second step will be described with reference to FIG. Ions are implanted into the nitrided film 702a by ion plantation. Here, argon ions are used as the ions. When argon ions are implanted from the upper surface of the nitride film 702a (the surface opposite to the surface in contact with the silicon substrate 701), the argon ions reach the inside of the nitride film 702a. At the portion of the nitrided film 702a into which the argon ions have been implanted, the tensile stress is relaxed, and the stress approaches zero. The depth at which the argon ions reach can be controlled in the range of several thousand angstroms by the ion implantation energy. Utilizing this, the nitride film 7
An ion implanted portion 703 having a stress in a direction along a plane different from 02a is formed on the nitrided film 702a. When the silicon substrate 701 is viewed from the upper surface side, the shape of the ion implantation portion 703 is a concentric shape as shown in FIG. 1A or a symmetrical shape as shown in FIG. Since the position where argon ions are implanted can be arbitrarily determined by a photolithography technique, the ion implanted portion 703 can be formed in an arbitrary shape. Ion implantation unit 70
3 and the portion of the nitrided film 702a located around the ion implanted portion 703.
An internal stress region having a distribution in the thickness direction and generating stress in a direction along the nitrided film 702a is formed.

The third step will be described with reference to FIGS. 7C and 7D. After removing a part of the nitrided film 702b (FIG. 7C) in the same manner as in the fourth step of the manufacturing method according to the first embodiment, the silicon substrate covered with the nitrided film 702a is removed. The substrate is removed while leaving the peripheral portion of 701 (FIG. 7D).

As a result, a film 710 having a nitrided film 702a having the ion-implanted portions 703 formed thereon is formed. The portion of the silicon substrate 701 remaining in the third step forms a holding portion 720 for holding the peripheral portion of the film 710.
The film 7 in contact with the removed silicon substrate 701
10, a film 61 of the manufacturing method of the first embodiment is provided.
A reflection surface 711 having a relatively high reflectance is formed as in the case of 0. When the reflecting surface is formed on the lower surface of the film 710 as described above, the curved reflecting mirror becomes a concave mirror, but when it is formed on the upper surface, it becomes a convex mirror.

The film 710 is released from a member having high rigidity and is easily bent. The internal stress region described in the second step is formed in the film 710. As described above, the stress in the direction along the film 710 in the internal stress region is 0 on the upper surface side and tensile stress on the lower surface side, and the film 610 has a concave surface formed on the reflection surface 711 on the lower surface in accordance with this stress distribution. To bend. The shape of the reflection surface 711 is
3 can be arbitrarily formed by appropriately selecting the shape, depth, arrangement, stress distribution in the internal stress region, and the like. By utilizing this, the shape of the reflection surface 711 can be made an ideal paraboloid.

Various modifications and changes can be made to the present embodiment. In the present embodiment, the silicon substrate 70
Although the nitride film 702a used as a layer containing silicon nitride is formed on the upper surface of the substrate 1, an oxide film used as a layer containing silicon oxide may be formed.

Next, a method for manufacturing a curved reflecting mirror according to a third embodiment of the present invention will be described with reference to FIGS. 8A to 8C are side views of a silicon substrate 801 to be described later, and show a part of each step of the manufacturing method.

The first step will be described with reference to FIG. A silicon substrate 801 is prepared, and an impurity is diffused on the upper surface of the silicon substrate 801 by using a semiconductor process technique to form an impurity diffusion portion 802 therein. Here, arsenic is used as an impurity. Since arsenic atoms are larger than silicon atoms, high-concentration diffusion generates compressive stress. The shape of the impurity diffusion portion 802 when the silicon substrate 801 is viewed from the upper surface side is a concentric shape as shown in FIG. 1A or a symmetrical shape as shown in FIG.

The second step will be described with reference to FIGS. 8B and 8C. Nitride films 803a and 803b are formed on the upper surface and the lower surface of the silicon substrate 801 respectively, and patterning is performed so as to leave a portion of the nitride film 803b in contact with the peripheral portion of the silicon substrate 801 (FIG. 8B). Thereby, a part of the lower surface of the silicon substrate 801 is exposed. Next, the silicon substrate 801 is immersed in an etchant, and is etched from the exposed portion on the lower surface of the silicon substrate 801.
When the silicon substrate 801 has a predetermined thickness, the etching is stopped. Thereafter, the nitride films 803a, 803b
Is removed (FIG. 8C).

As a result, the surface layer on the upper surface side of the substrate including the impurity diffusion portion 802 remains, and this portion becomes the film 810.
The portion of the silicon substrate 801 that has been protected from etching by the nitrided film 803b becomes a holding portion 820 that holds the peripheral portion of the film 810. The reflection surface 8 is provided on the lower surface of the film 810.
11 is formed.

The film 810 is released from a member having high rigidity and is easily bent. The film 810 includes an impurity diffusion portion 802.
Is formed from the upper surface of the film 810 to a predetermined depth.
As described above, compressive stress is generated in the impurity diffusion portion 802. On the other hand, no stress is generated in the portion of the silicon substrate 801 located around the impurity diffusion portion 802. In a region including this portion of the silicon substrate 801 and the impurity diffusion portion 802, the film 810 has a distribution in the thickness direction and has a film 810.
An internal stress region that generates stress in a direction along is formed. The stress in the direction along the film 810 in the internal stress region is a compressive stress on the upper surface side and 0 on the lower surface side.
Is bent so that a concave surface is formed on the reflection surface 811 on the lower surface according to the stress distribution. If a reflective surface is formed on the upper surface of the film 810, the reflective surface becomes a convex surface. The shape of the reflection surface 811 can be arbitrarily formed by appropriately selecting the shape, depth, arrangement, stress distribution, and the like of the impurity diffusion portion 802. By utilizing this, the shape of the reflection surface 811 can be made an ideal paraboloid.

Of course, various modifications and changes can be made to the present embodiment. In the present embodiment, arsenic atoms are used as impurities. For example, in the case of boron, tensile stress is generated instead of compression. In this case, contrary to the present embodiment, the film 810 bends convexly on the lower surface side, and a convex surface is formed on the reflection surface 811. In addition, any atom that generates a stress in the silicon substrate by diffusing it into silicon may be used.

Next, a method for manufacturing a curved reflecting mirror according to a fourth embodiment of the present invention will be described with reference to FIGS. 9A to 9E are side views of the SOI wafer 901 described later, and show a part of each step of the manufacturing method.

The first step will be described with reference to FIGS. 9A and 9B. First, an SOI wafer 901 is prepared (FIG. 9A). The SOI wafer 901 has a silicon substrate 902, and an oxide film layer 903 and a silicon thin film 904 formed thereon in this order. Silicon substrate 90
2. The oxide film layer 903 and the silicon thin film 904 are the first
As a silicon layer, an insulating layer, and a second silicon layer. Next, the upper surface of the silicon thin film 904 (the surface opposite to the surface in contact with the oxide film layer 903) in the same manner as in the first step of the method for manufacturing a curved mirror according to the third embodiment.
The impurity diffused portion 905 is formed by diffusing arsenic into the substrate (FIG. 9B). In the silicon thin film 904, an internal stress region having the same configuration and the same stress distribution as the internal stress region formed in the film 810 of the method for manufacturing a curved reflecting mirror according to the third embodiment is formed. The arrangement of the impurity diffusion portion 905 is substantially the same as that of the impurity diffusion portion 802 in the method for manufacturing a curved reflecting mirror according to the third embodiment.

The second step will be described with reference to FIGS. 9C and 9D. Nitride films 906a and 906b are formed on the upper surface and the lower surface of the SOI wafer 901, respectively, and patterning is performed so that a portion of the nitride film 906b covering the peripheral portion of the silicon substrate 902 is left (FIG. 9C). ). Thereby, a part of the lower surface of the silicon substrate 902 is exposed. Next, the silicon substrate 902 is immersed in an etching solution,
Etching is performed from the exposed portion on the lower surface of the silicon substrate 902. This etchant etches the silicon substrate 902 but does not etch the oxide film layer 903 and the nitride film 906b. The etching stops when it reaches the oxide film layer 903 (FIG. 9D). Thereby, the silicon substrate 902 is left while the peripheral portion of the silicon substrate 902 is left.
Can be removed. Part of the oxide film layer 903 is exposed.

The third step will be described with reference to FIG. An etching solution that etches the oxide film layer 903 and does not etch the silicon thin film 904 is used.
Then, the exposed portion of the oxide film layer 903 is removed. Thereafter, the nitride films 906a and 906b are removed.

As a result, the silicon thin film 904 becomes the film 910.
become. The portion of the silicon substrate 902 and the oxide film layer 903 left during the etching in the second and third steps is the film 9
It becomes the holding part 920 which holds the periphery of the ten. Membrane 910
A reflection surface 911 is formed on the lower surface of the.

The film 910 is released from a member having high rigidity and is easily bent. The internal stress region described in the first step is formed in the film 910. As described above, the stress distribution in the internal stress region is substantially the same as the stress distribution in the internal stress region formed in the film 810 in the method for manufacturing a curved reflector according to the third embodiment. The film 910 is a film 810
In the same manner as described above, the lower surface is bent such that a concave surface is formed on the reflection surface 911. If a reflection surface is formed on the upper surface of the film 910, the reflection surface becomes a convex surface. The shape of the reflection surface 911 can be arbitrarily formed by appropriately selecting the shape, depth, arrangement, stress distribution of the internal stress region, and the like of the impurity diffusion portion 905. By utilizing this, the shape of the reflection surface 911 can be made an ideal paraboloid.

In this embodiment, the thickness of the film 910 is substantially equal to the thickness of the silicon thin film 904. When preparing an SOI wafer, the silicon thin film 904 is formed by electrolytic polishing, and its thickness is realized to a minimum of several μm.
The thickness accuracy is also high. Therefore, the accuracy of the shape of the film 910 is improved by the manufacturing method of the present embodiment using the SOI wafer.

Next, a method for manufacturing a curved reflecting mirror according to a fifth embodiment of the present invention will be described with reference to FIGS. FIGS. 10A to 10E are side views of a P-type silicon substrate 1001 described later, showing a part of each step of the manufacturing method.

The first step will be described with reference to FIG. A P-type silicon substrate 1001 is prepared, arsenic is diffused on the upper surface of the P-type silicon substrate 1001, and an N-type diffusion layer 1 is formed.
002 is formed on the surface of the P-type silicon substrate 1001.
Here, an N-type diffusion layer 1002 is used as the impurity diffusion layer. The N-type diffusion layer 1002 is a P-type silicon substrate 10
01 from the center of the surface layer to the periphery.

The second step will be described with reference to FIG. Arsenic is diffused into the N-type diffusion layer 1002 at a high concentration,
An N-type diffusion portion 1003 having an arsenic concentration different from that of the N-type diffusion layer 1002 is formed. Since arsenic atoms are larger than silicon atoms, compressive stress is generated in the N-type diffusion layer 1002 and the N-type diffusion portion 1003. The compressive stress of the N-type diffusion portion 1003 is larger than the compressive stress of the N-type diffusion layer 1002. The N-type diffused portion 1003 and the portion of the N-type diffused layer 1002 located around the N-type diffused portion 1003 have an internal portion formed on the film 810 of the method for manufacturing a curved reflector according to the third embodiment. An internal stress region having the same stress distribution as the stress region is formed. The arrangement of the N-type diffusion portion 1003 is substantially the same as that of the impurity diffusion portion 802 in the method for manufacturing a curved reflector according to the third embodiment.

The third step will be described with reference to FIGS. Forming nitride films 1004a and 1004b on the upper and lower surfaces of a P-type silicon substrate 1001, respectively;
Patterning is performed so that a portion of the nitride film 1004b covering the peripheral portion of the P-type silicon substrate 1001 is left (FIG. 10C). Thereby, the P-type silicon substrate 1
Part of the lower surface of 001 is exposed. Next, the P-type silicon substrate 1001 is immersed in an etchant and etched. At this time, a voltage is externally applied to the N-type diffusion layer 1002,
By maintaining a positive potential with respect to the etching solution, P
The type silicon substrate 1001 is etched, but the N type diffusion layer 1002 is not etched. This is a technique called an electrochemical etching method, in which a film 1010 having substantially the same thickness as the diffusion depth of the N-type diffusion layer 1002 and including the N-type diffusion layer 1002 and the N-type diffusion portion 1003 is formed. ((D) of FIG. 10). At this time, the periphery of the P-type silicon substrate 1001 is left. Thereafter, the nitride film 100
4a and 1004b are removed (FIG. 10E). The remaining portion of the P-type silicon substrate 1001 becomes a holding portion 1020 for holding the peripheral portion of the film 1010. A reflection surface 1011 is formed on the lower surface of the film 1010.

The film 1010 is released from a member having high rigidity and is easily bent. In the film 1010, the internal stress region described in the second step is formed. As described above, the stress distribution in the internal stress region is substantially the same as the stress distribution in the internal stress region formed in the film 810 in the method for manufacturing a curved reflector according to the third embodiment. Like the film 810, the film 1010 bends so that a concave surface is formed on the lower reflective surface 1011. If a reflective surface is formed on the upper surface of the film 1010, the reflective surface becomes a convex surface. The shape of the reflection surface 1011 can be arbitrarily formed by appropriately selecting the shape, depth, arrangement, stress distribution of the internal stress region, and the like of the N-type diffusion portion 1003. By utilizing this, the shape of the reflection surface 1011 can be made an ideal paraboloid.

In this embodiment, the thickness of the film 1010 can be easily controlled by the diffusion depth of the N-type diffusion layer 1002 and the applied voltage in the third step shown in FIG. The shape accuracy of the reflecting surface 1011 formed by the manufacturing method of the present embodiment is improved.

Various changes and modifications can be made to the present embodiment. N instead of P-type silicon substrate 1001
A silicon substrate is prepared, a P-type diffusion layer having a conductivity type different from that of the N-type diffusion layer is formed in place of the N-type diffusion layer, and a positive voltage applied from the outside in the third step is applied to a forward current through a PN junction. May be lower than the voltage at which the current starts flowing. Even in such a case, the N-type silicon substrate is etched, and when the P-type diffusion layer is exposed to the etching solution, both are conductive,
Since the etching is stopped, the film 1010 can be formed.

In this embodiment, the N-type diffusion layer 100 is used.
The N-type diffused portion 1003 is formed by diffusing arsenic into the semiconductor substrate 2. The purpose of forming this is to form a portion in the N-type diffusion layer 1002 where stress is generated. For this reason, for example, an impurity diffusion portion made of boron may be formed, and various impurities may be diffused, such as generating a tensile stress instead of a compression.

The present invention is not limited to the above-described embodiment, and it is needless to say that various modifications and applications can be made without departing from the spirit of the invention.

[0099]

As is clear from the above description,
In the curved reflecting mirror according to the present invention, the initial shape becomes an ideal reflecting surface shape. Further, by using the manufacturing method according to the present invention, a curved reflecting mirror can be manufactured so as to realize such an ideal reflecting surface shape.

[Brief description of the drawings]

1A is a plan view of a curved reflecting mirror according to a first embodiment of the present invention, FIG. 1B is a cross-sectional view taken along line 1B-1B of FIG. 1A, and FIG. Part P indicated by B)
1 is an enlarged view of FIG.

FIG. 2A is a sectional view of a curved reflecting mirror according to a second embodiment of the present invention, and FIG. 2B is a section P2 shown in FIG.
An enlarged view of FIG.

FIG. 3A is a sectional view of a curved reflecting mirror according to a third embodiment of the present invention, and FIG. 3B is a section P3 shown in FIG.
An enlarged view of FIG.

FIG. 4A is a plan view of a curved reflecting mirror according to a fourth embodiment of the present invention, and FIG. 4B is a cross-sectional view taken along line 4B-4B of FIG.

5A and 5B are cross-sectional views of a curved reflecting mirror according to a fifth embodiment of the present invention, in which FIG. 5A shows a state when no voltage is applied, and FIG. 5B shows a state when voltage is applied. It is a figure showing the state of.

FIGS. 6A and 6B schematically show steps of a method for manufacturing a curved reflecting mirror according to the first embodiment of the present invention, wherein FIG. 6A is a first step, FIG. 6B is a second step, and FIG. ) Is the third step, (D)
And (E) show the fourth step, respectively.

FIGS. 7A and 7B schematically illustrate steps of a method for manufacturing a curved reflecting mirror according to a second embodiment of the present invention, wherein FIG. 7A is a first step, FIG. 7B is a second step, and FIG. ) And (D) show the third step, respectively.

8A and 8B are diagrams schematically showing steps of a method for manufacturing a curved reflecting mirror according to a third embodiment of the present invention, wherein FIG. 8A is a first step, and FIGS. Each step is shown.

FIG. 9 is a diagram schematically showing steps of a method for manufacturing a curved reflecting mirror according to a fourth embodiment of the present invention, wherein (A) and (B) are the first steps, (C) and (D). Indicates the second step, and (E) indicates the third step.

10A and 10B are diagrams schematically showing steps of a method for manufacturing a curved reflecting mirror according to a fifth embodiment of the present invention, wherein FIG. 10A is a first step, FIG. 10B is a second step, and FIG. ) To (E) show the third step, respectively.

FIG. 11 is a diagram showing a schematic configuration of a curved reflecting mirror of a first conventional example.

FIG. 12 is a diagram showing a schematic configuration of a curved reflecting mirror of a second conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Curved reflective mirror 102 Holding part 103 Film 103a Peripheral part 104 Reflective surface 105 Internal stress area 201 Curved reflective mirror 203 Film 205 Internal stress area 211 First layer 212 Second layer 301 Curved reflective mirror 303 Film 305 Internal stress area 311 Silicon film 312 Impurity diffusion portion 403 Film 405 Internal stress region 501 Curved reflector 510 Upper substrate 511 Second electrode 520 Lower substrate 521 First electrode 601 Silicon substrate (substrate) 602a Nitride film (first layer) 602b Chic Oxide film 603 Nitride film (second layer) 610 Film 611 Reflection surface 620 Holder 701 Silicon substrate (substrate) 702a Nitride film (layer) 702b Nitride film 703 Ion implanted portion 710 Film 711 Reflection surface 720 Holder 801 Silicon substrate (substrate) 802 Impurity expansion Part 803a Nitride film 803b Nitride film 810 Film 811 Reflection surface 820 Holder 901 SOI wafer 902 Silicon substrate (first silicon layer) 903 Oxide film layer (insulation layer) 904 Silicon thin film (second silicon layer) 905 Impurity Diffusion portion 906a Nitride film 906b Nitride film 910 Film 911 Reflection surface 920 Holding portion 1001 P-type silicon substrate (P-type silicon substrate) 1002 N-type diffusion layer (impurity diffusion layer) 1003 N-type diffusion portion (impurity diffusion portion) 1004a Nitride film 1004b Nitride film 1010 Film 1011 Reflective surface 1020 Holder

Claims (10)

[Claims] A film having a reflective surface formed thereon and a holding portion for holding a peripheral portion of the film, wherein the film has a distribution in a thickness direction of the film and has a stress in a direction along the film. A curved surface reflection is characterized in that an internal stress region to be generated is formed, and the film has a distortion according to a stress distribution in the internal stress region, bends in accordance with the distortion, and forms a curved surface on the reflection surface. mirror. 2. The method according to claim 1, wherein the film is a first film provided with the reflection surface.
And a second layer provided on at least a part of a surface of the first layer opposite to the reflection surface. The second layer and the second layer The stresses in the direction along the film are different between the first layer and the second layer so that the internal stress region is formed over the portion of the first layer located around the layer. Claim 1.
The curved reflecting mirror according to 1. 3. The semiconductor device according to claim 1, wherein the film has a silicon film, and the silicon film has an impurity diffused portion in which an impurity is diffused. The impurity diffused portion is located around the impurity diffused portion. 2. The curved mirror according to claim 1, wherein the stress in the direction along the film is different between the silicon film and the impurity diffusion portion so that the internal stress region is formed over the portion of the silicon film. . 4. The curved surface according to claim 1, wherein the internal stress region extends along the film, and has a plurality of concentrically arranged annular shapes. Reflector. 5. The semiconductor device according to claim 1, further comprising: a substrate provided with a first electrode and facing the film at a predetermined interval; and a second electrode provided on the film. 5. The method according to claim 1, wherein the film is deformed when a voltage is applied between the electrode and the second electrode, and the curvature of the reflection surface changes according to the voltage. A curved reflecting mirror according to the item. 6. A first step of preparing a substrate and forming a first layer containing silicon on the substrate, and a second step of forming a first layer containing silicon on the first layer under a condition different from that of the first step. Forming a second layer, wherein a stress in a direction along the surface of the substrate is different between the first layer and the second layer, and a part of the second layer is formed. Removing, processing the second layer into a predetermined shape, and distributing the distribution in the thickness direction of the substrate over the second layer and the portion of the first layer located around the second layer. A third step of forming an internal stress region for generating stress in a direction along the surface of the substrate, and a fourth step of removing the substrate while leaving a portion of the substrate in contact with a peripheral portion of the first layer. And a film including the first layer and the second layer, and the remaining portion of the substrate. A holding portion for holding a peripheral portion of the film is formed, the surface of the film functions as a reflection surface, the film bends in accordance with the stress in the internal stress region, and a curved surface is formed on the reflection surface. A method of manufacturing a curved reflecting mirror. 7. A first step of preparing a substrate and forming a layer containing silicon nitride or silicon oxide on the substrate, and implanting ions into the layer by ion plantation to form an ion implanted portion in the layer. An internal step of generating a stress in a direction along the surface of the substrate with a distribution in the thickness direction of the substrate over the ion-implanted portion and a portion of the layer located around the ion-implanted portion. A second step in which the stress in the direction along the surface of the substrate is different between the layer and the ion-implanted portion so that a stress region is formed, and while leaving a portion of the substrate in contact with a peripheral portion of the layer. A third step of removing the substrate, comprising a film having a layer with the ion-implanted portion formed thereon and a portion of the remaining substrate having a peripheral portion of the film. And a surface of the film functions as a reflection surface, the film bends in response to the stress in the internal stress region, and a curved surface is formed on the reflection surface. . 8. A step of preparing a substrate and diffusing an impurity into the substrate to form an impurity diffusion portion on the surface of the substrate, wherein the impurity diffusion portion and the substrate located around the impurity diffusion portion are formed. The stress in the direction along the surface of the substrate is formed so as to form an internal stress region that has a distribution in the thickness direction of the substrate and generates a stress in the direction along the surface of the substrate. And a second step of removing a predetermined portion of the substrate so as to leave a peripheral portion of the substrate and a portion of the surface of the substrate including the impurity diffusion portion. A film having the portion of the surface of the substrate including the impurity diffusion portion, and a holding portion having the peripheral portion of the substrate and holding the peripheral portion of the film are formed. And the surface of the film functions as a reflective surface. Deflection in response to the stress of the internal stress region, method of manufacturing a curved reflector, characterized in that the curved surface is formed on the reflecting surface. 9. A first silicon layer, an insulating layer laminated on the first silicon layer and containing an insulator, and a second silicon layer laminated on the insulating layer. Preparing an SOI wafer having the SOI wafer and diffusing impurities into the second silicon layer to form an impurity diffused portion in the second silicon layer. The SOI wafer has a distribution in the thickness direction of the SOI wafer over the portion of the second silicon layer located.
A first step in which the stress in the direction along the surface of the SOI wafer is different between the second silicon layer and the impurity diffusion portion so that an internal stress region for generating stress in the direction along the surface of the wafer is formed; Etching the first silicon layer and immersing the first silicon layer in an etchant that does not etch the insulating layer, thereby removing the first silicon layer while leaving a peripheral portion of the first silicon layer. A second step of exposing a part of the insulating layer; and immersing the insulating layer in an etchant that etches the insulating layer and does not etch the second silicon layer to remove the exposed part of the insulating layer. A film having the second silicon layer including the impurity diffusion portion, and a portion of the first silicon layer left in the second step. Have A holding portion for holding a peripheral portion of the film is formed, the surface of the film functions as a reflection surface, the film bends in accordance with the stress in the internal stress region, and a curved surface is formed on the reflection surface. A method of manufacturing a curved reflecting mirror. 10. A first method for preparing a P-type or N-type silicon substrate, diffusing impurities into the silicon substrate, and forming an impurity diffusion layer having a conductivity type different from the above-described conductivity type on the silicon substrate. And diffusing an impurity of a type different from the impurity into the impurity diffusion layer or diffusing an impurity of the same type as the impurity at a high concentration into the impurity diffusion layer. Forming a diffusion portion, the distribution being in the thickness direction of the silicon substrate along the impurity diffusion portion and a portion of the impurity diffusion layer located around the impurity diffusion portion, along the surface of the silicon substrate. The stress in the direction along the surface of the silicon substrate is different between the impurity diffusion layer and the impurity diffusion portion so as to form an internal stress region that generates stress in the second direction. And degree, the silicon substrate dipped in the etching solution, while applying a voltage between the etching solution and the impurity diffusion layer,
A third step of removing the silicon substrate by an electrochemical etching method that etches the silicon substrate and does not etch the impurity diffusion layer while leaving a peripheral portion of the silicon substrate, wherein the impurity diffusion portion is formed. A film having the impurity diffusion layer, and a holding portion for holding the peripheral portion of the silicon substrate having the portion of the silicon substrate left, and the surface of the film serving as a reflection surface The method of manufacturing a curved reflecting mirror, wherein the film functions, the film bends in response to the stress in the internal stress region, and a curved surface is formed on the reflecting surface.