JP2008233405A - Variable curvature mirror device and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized and accurate variable curvature mirror device which can be expected to perform accurate variable curvature control and, especially, is obtained by micromachining technology or microfabrication technology based on it, and a manufacturing method thereof. <P>SOLUTION: The variable curvature mirror device comprises: a thin base plate (1); a mirror metallic thin film (3) formed by depositing a material having a coefficient of thermal expansion different from that of the thin base plate, on a surface of the thin base plate; and a heating element (4) formed in or on the surface of the thin base plate. With respect to manufacturing of the variable curvature mirror device, a single crystal silicon wafer and an SOI wafer are available as a starting material of the thin base plate (1), and a manufacturing method comprising manufacturing processes using individual or combination of techniques such as semiconductor processing techniques and MEMS is applicable. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a variable curvature mirror device capable of converging, diffusing, reflecting, and changing a focus of radiation energy such as visible light, laser light, ultraviolet light, and infrared light by changing the curvature of a required portion in a mirror member, and It relates to the manufacturing method.

Variable curvature that can arbitrarily change the focus according to a predetermined control signal as a component of the variable focus mechanism in various cameras, optical recording / reproducing devices, automatic focusing devices, ranging devices, and other various optical devices A mirror device is convenient. In various conventional optical devices, lenses, reflecting mirrors, prisms, diaphragm mechanisms, etc., which are arranged in the appropriate order and position, depending on the purpose, the arrangement of required elements, the combination order, the combination of rotational displacement mechanisms, etc. Functions such as focusing (focusing), focusing, and diffusion have been achieved automatically or manually. Such optical devices are often small and lightweight and require automatic operation in applications such as cameras and video cameras directly used by the user, as well as applications incorporated into various devices. Such an automatic operation is required to have a quick and accurate response operation with as few parts as possible.

As a variable focus mirror that can change the focus according to the application and purpose, Patent Document 1 is provided with an electrode facing a thin film diaphragm made of a flexible material, and acts when a voltage is applied to the counter electrode. It discloses that the curvature of the thin film diaphragm surface is changed by utilizing electrostatic attraction force. Here, since the driving force for achieving the variable focus is a Coulomb force, its magnitude is inversely proportional to the square of the distance. Therefore, it is expected that the acting force changes nonlinearly from the initial state in accordance with the progress of the bending, and it becomes difficult to finely control the variable focus. In addition, since the distance between the electrode and the mirror varies depending on the location of the mirror, the force acting on each location is not uniform, and it is expected that deformation to a spherical surface is difficult. In Patent Document 2, a flexible member having a reflecting mirror surface provided on a surface thereof is disposed on a substrate having a required recess, and static electricity is applied to the surface of the required recess to electrostatically attract the flexible member. The shape of the reflecting mirror surface is changed by adsorbing with a force so as to conform to the required shape on the substrate, and the same problem as in Document 1 may occur.

In Patent Document 3, a flexible member having a reflecting surface formed thereon is attached to the surface of a cylindrical substrate provided with a recess having a required shape, and the pressure is reduced from a suction hole provided on the lower surface of the recess. It discloses that a flexible mirror surface can be obtained by sucking the flexible member into a shape along the concave portion. In such a structure, the mirror surface of the flexible member is stabilized only in a state where it is sucked into the shape of the concave portion of the required shape, so that it is difficult to achieve an arbitrary curvature. Further, a metal layer as a reflective film is deposited on the surface of the flexible material diaphragm in Patent Documents 2 and 3, but such a diaphragm film has a problem in terms of durability and the like.

Patent Document 4 discloses a variable focus mirror that includes a thin film that is supported by a substrate and that changes in curvature, and that has a reflecting surface that is attached to the thin film and changes in curvature as the curvature changes. The principle of changing the curvature is as follows: an electrostatic force by applying a potential difference, an electromagnetic force obtained by a combination of a magnetic body and a coil, an electromagnetic force by a permanent magnet and a coil, a combination of a piezoelectric body and a power source, and voltage application It is disclosed that a change in piezoelectric material at the time can be used. Furthermore, an annular thermal expansion body double layer is formed by laminating two kinds of thermal expansion means so as to surround the reflection surface, and the annular shape is changed by changing the amount of deflection based on the difference in thermal expansion coefficient of each layer forming material. The thermal expansion body is deformed. Here, due to the deformation of the annular thermal expansion body, it acts on the surrounding reflecting surface and causes a passive (indirect) curvature change. Further, when an electrostatic force or electromagnetic force is used, an external driving body is required, so that the structure is complicated and large. Further, Patent Document 5 discloses a variable focus mirror that uses an electromagnetic force obtained by one or more permanent magnets and coils in a mirror portion in which a reflecting surface is formed on a thin film. These variable focus mirrors based on the driving force that is inversely proportional to the square of the distance, such as electrostatic force and electromagnetic force, are difficult to achieve high precision control in applications that require extremely high accuracy. There are disadvantages.
JP 7-49460 A JP-A-9-152505 JP-A-10-31107 JP 2006-209136 A JP 2006-293367 A

It is an object of the present invention to provide a variable curvature mirror device that can be expected to perform accurate variable curvature control and a method for manufacturing the same, and in particular, micromachine technology (hereinafter, abbreviated as “MEMS”) or the like. It is an object of the present invention to provide a small and accurate variable curvature mirror device obtained by a microfabrication technique and a manufacturing method thereof.

The invention according to claim 1 is a substrate thin plate, a mirror metal thin film in which a material having a thermal expansion coefficient different from that of the substrate thin plate is deposited on the surface of the substrate thin plate, and the inside of the substrate thin plate or A variable curvature mirror device comprising a heating element formed on the surface, wherein an arbitrary curvature change is brought about on the surface of the mirror metal thin film in accordance with a temperature change caused by the heating element.

The invention according to claim 2 is a variable curvature mirror device in which an insulating thin film is interposed between the base thin plate and the mirror metal thin film so as to be in close contact with both. . According to a third aspect of the present invention, the heating element is a variable curvature mirror device formed on the substrate thin plate so as to be surrounded from the outside without directly contacting the mirror metal thin film portion. Features.

The invention according to claim 4 is a diaphragm structure in which the mirror metal thin film is any one of a circle, an ellipse, a square or a polygon, and the heating element is formed so as to surround the mirror metal thin film. It is a variable curvature mirror device that is shaped.

The invention according to claim 5 is a slit that surrounds the outside of the heating element, except for at least one beam portion that connects the device main part including the mirror metal thin film and the device outer frame part. And a variable curvature mirror device having a beam structure in which slits for promoting a change in curvature of the mirror metal thin film portion are provided.

The invention according to claim 6 improves the balance at the time of curvature change in the device main part by forming two or more of the beam portions connecting the device main part and the device outer frame part. It is a variable curvature mirror device. The invention according to claim 7 is a variable curvature mirror device in which the heating element is formed as a metal thin film resistor of the same quality as the mirror metal thin film.

The invention according to claim 8 is a variable curvature mirror device in which the heating element is a metal thin film resistor in which a metal different from the mirror metal thin film is deposited. The invention according to claim 9 is a variable curvature mirror device in which the substrate thin plate is made of silicon and the heating element is a diffusion layer resistor composed of an impurity diffusion layer formed in the silicon layer. It is characterized by that.

The invention according to claim 10 is a variable curvature mirror device in which the mirror metal thin film is selected as a convex surface, a concave surface or a flat surface in an unheated initial state. The invention according to claim 11 is a variable curvature mirror device in which at least one of a temperature sensor or a curvature detection sensor is attached to an appropriate part on the thin substrate sheet.

The invention according to claim 12 selects a silicon thin plate as a substrate thin plate, and a silicon dioxide (SiO ₂ ) film, a silicon nitride (Si ₃ N ₄ ) film as the insulating thin film formed on the silicon thin plate, A silicon oxynitride (SiON film) or a thin film having characteristics equivalent to these is formed, and the mirror metal thin film is made of either gold (Au), aluminum (Al), silver (Ag), or an alloy of these with another metal. It is a method for manufacturing a variable curvature mirror device in which a selected mirror metal thin film is formed and a heating element is formed so as to surround the mirror metal thin film region from the outside.

A thirteenth aspect of the present invention is a method of manufacturing a variable curvature mirror device, wherein the heating element is a diffusion layer heating body in which impurities are diffused in a desired portion of a base material thin plate.

The invention according to claim 14 is a method of manufacturing a variable curvature mirror device, wherein the heating element is a metal layer heating body in which a metal layer having a heat generation characteristic selected at a desired portion of a substrate thin plate is deposited. It is characterized by being.

The invention according to claim 15 is (1) using a single crystal silicon plate as a starting material, and forming an insulating thin film on the surface by an appropriate film forming method such as thermal oxidation treatment or CVD; (2) the insulating thin film Is processed into a desired pattern, and then an unnecessary portion of the single crystal silicon plate is etched to form a base material thin film; (3) vapor deposition film forming method on a desired region on the insulating thin film formed in the previous step Further, the present invention is characterized in that it is a method of manufacturing a variable curvature mirror device in which a mirror metal thin film and a heating element are formed by appropriately adopting film forming means such as a sputtering film forming method and a CVD film forming method.

The invention according to claim 16 is the variable curvature mirror device, wherein the etching treatment in the step (2) is wet etching by crystal anisotropic etching with an alkaline solution, isotropic etching with hydrofluoric acid and nitric acid based solution, or the like. It is the manufacturing method of this. The invention according to claim 17 is a method for manufacturing a variable curvature mirror device, wherein the etching process in the step (2) is dry etching by reactive ion etching (RIE) or the like.

The invention according to claim 18 is a variable curvature mirror device, which is formed as an impurity diffusion layer obtained by an impurity diffusion process on the substrate thin plate, instead of forming the heating element by the film forming method in the step (3). It is the manufacturing method of this.

The invention according to claim 19 is a method of manufacturing a variable curvature mirror device, wherein a single crystal silicon plate polished so that both surfaces thereof become mirror surfaces is selected as a starting material for forming the substrate thin plate. And The invention according to claim 20 is a variable curvature mirror device in which an SOI (Silicon on Insulator) material in which a silicon oxide film is formed at a certain depth from the surface is selected as a starting material for forming the substrate thin plate. It is a manufacturing method.

The invention according to claim 21 is characterized in that a sealed space is formed on the back surface of the substrate thin plate forming the mirror metal thin film, and the mirror metal is formed in a pressurized atmosphere or a reduced pressure atmosphere of the entire substrate thin plate. A method of manufacturing a variable curvature mirror device in which a film is formed to form either a convex surface or a concave surface in an unheated initial state, and the initial curvature is adjusted by adjusting the atmospheric pressure. It is characterized by.

The variable curvature mirror device obtained as a configuration specified by the present invention is a silicon plate (silicon wafer), SOI wafer by selectively adopting each method belonging to the manufacturing technology of various semiconductor circuit elements, MEMS technology, etc. On a base material sheet such as gold, aluminum, silver or a metal material such as an alloy of these and other metals having a different thermal expansion coefficient from that of the base material sheet, a circular shape having a diameter or span of several millimeters to several tens of millimeters, A mirror metal thin film having an appropriate shape such as an ellipse, a quadrangle, or a polygon is formed. And the curvature of the said mirror metal thin film changes arbitrarily by operating the heating element which gives a temperature change simultaneously to both this base-material thin plate and the mirror metal thin film from which a thermal expansion coefficient differs.

The curvature change at this time uses a so-called curvature change phenomenon based on the bimetal principle, which is caused by a difference in thermal expansion coefficients of a plurality of joined members. This curvature change phenomenon is caused by a thermal expansion phenomenon inherent to the constituent material itself, and is therefore a direct drive type variable curvature mirror device. The state of curvature change in this case can be accurately controlled by the heating state of the base material thin plate and the mirror metal thin film. When the whole is heated evenly, it becomes a substantially spherical shape, and is desired by partially forming temperature unevenness. It is also possible to have an aspherical shape.

Therefore, an indirect drive type that utilizes electrostatic force, electromagnetic force, piezoelectric power, mechanical force by an actuator, etc. generated by additional means arranged at the periphery of the mirror device itself, which has been widely adopted as the prior art. Unlike the element, a variable curvature mirror device can be obtained in which the change in curvature can be controlled with extremely high reproducibility. Although such a variable curvature mirror device is a small mirror device, it can be used as a variable focus mirror and other high-precision optical elements in various optical fields such as condensing, focusing, ranging, and reflection.

The variable curvature mirror device manufacturing method according to the present invention can use various semiconductor processing and manufacturing techniques established by integrated circuits (ICs), LSIs, VLSIs, etc., and further, by applying the above-described MEMS technology. More advantageous material processing and device manufacture are achieved. Since it is possible to use manufacturing technology established to a considerably high level in this way, high-precision element manufacturing is possible, and the accuracy of the optical apparatus using the obtained variable curvature mirror device is greatly improved. I can expect that.

Next, the configuration and characteristics of the variable curvature mirror device according to the present invention and a method for manufacturing such a variable curvature mirror device will be disclosed. As shown in FIG. 1 showing the first embodiment, the variable curvature mirror device according to the present invention is insulated directly on a silicon plate (silicon wafer) or a similar substrate thin plate 1 or a silicon oxide film. A mirror metal film made of a metal having a different thermal expansion coefficient from that of the base sheet through the coating 2 (see FIG. B), such as gold (Au), aluminum (Al), silver (Ag), or an alloy of these with an appropriate metal. 3 and a heating resistor 4 is disposed so as to surround the outside of the mirror metal thin film 3. In such a structure, the heating resistor 4 is energized through the terminal 10 from the power source 5 to generate heat, so that the bimetallic principle is based on the difference in the thermal expansion coefficient between the base thin plate 1 and the mirror metal thin film 3. Curvature changes occur. Instead of the heating resistor 4 or in addition to the heating resistor 4, a heating resistor may be added to the back surface of the substrate thin plate 1.

FIG. 2 shows a second embodiment of the variable curvature mirror device according to the present invention. Four supporting beam 7 portions (refer to the BB ′ cross section) along the outer periphery of the heating resistor 4. As shown by bold lines except for (), arc-shaped slits 6 (see B section) are provided by etching such as reactive ion etching and plasma etching. A device having the arc-shaped slit 6 as described above is hereinafter referred to as a “beam structure type”, and a device having no slit as shown in FIG. 1 is distinguished from a “diaphragm structure type”.

Such an arc-shaped slit 6 increases the response speed of heat generation by the heating resistor 4 by limiting to the mirror metal thin film 3 portion that truly requires temperature change, and is balanced with respect to the mirror metal thin film 3 portion. It has the effect of changing the curvature. In addition to the four-divided slits as shown in FIG. 2, the slits 6 are provided with support beams 7 at two upper and lower positions in consideration of the dimensions and application of the mirror device, the heat generation capacity of the heating resistor 4 and the like. A divided slit or a three-divided slit that divides the circumference into three equal parts may be used. Further, it may be a single beam shape in which the support beam 7 is formed only at one place where the power supply wiring is provided, and the other portion may be etched to form a substantially annular slit.

FIG. 3 shows a third embodiment in which the heating wiring 8 from the power source is connected to the mirror metal thin film 3 and this mirror metal thin film 3 is used as a heating element. By appropriately selecting the component, thickness, etc. of the mirror metal thin film 3 and adjusting the resistivity, a resistor having a desired resistivity can be obtained.

In these embodiments, the mirror metal thin film 3 can be formed on the substrate thin plate 1 by various metal film forming methods such as sputtering, vacuum deposition, and plating. When the mirror metal thin film 3 is formed, the heating resistor 4 can be formed of the same metal material at the same time. However, the heating resistor 4 is formed by a separate process before or after the mirror metal thin film 3 formation process. You can also. The mirror metal thin film 3 is required to have a thermal expansion coefficient different from that of the substrate thin plate 1, have excellent reflection characteristics, and have little secular change. The requirement is that it has an appropriate resistivity and does not cause characteristic changes or peeling due to heat generation. Therefore, although the number of steps increases, it is easy to obtain a configuration suitable for each step.

FIG. 4 shows a fourth embodiment in which a continuous diffusion resistor layer 9 is formed by subjecting a required portion of the substrate thin plate 1 as a heating resistor to impurity diffusion treatment. According to such a configuration, the selection of the resistivity and the shape can be changed according to the impurity diffusion state, and since heat is generated from the inside of the substrate thin plate 1, the heating efficiency is improved, and desirable thermal deformation can be caused. .

The variable curvature mirror device according to the present invention can deform the curvature of the spherical surface by uniformly heating the entire region including the mirror metal thin film of the device. There may be applications that require it. For such an application, for example, by connecting a power supply to the heating resistor 4 provided partially as shown in FIG. 5 showing the fifth embodiment, it is possible to bring about an uneven curvature change. . Since uneven heat generation occurs in the lower right section, the curvature change in this section can be made larger than that in the other sections as shown in FIG.

FIG. 6 shows a sixth embodiment in which the mirror metal thin film 13 is formed to be convex on the lower surface, and a concentric curvature controlling metal film 14 is deposited on the upper surface of the substrate thin plate 1. In this way, by arranging the curvature controlling metal film 14 on the back side of the mirror metal thin film 13 sticking surface, the shape of the mirror metal thin film 13 can be appropriately changed. As the pattern of the curvature controlling metal film, other patterns such as a radial shape and a mottled shape may be used depending on the target shape.

Thus, in the variable curvature mirror device according to the present invention, the curvature change is caused by heating at least the region of the substrate thin plate 1 including the mirror metal thin film 13. In this case, the change in curvature is caused by the difference in thermal expansion coefficient due to the change in temperature. Therefore, the change in curvature is controlled by measuring the temperature of the appropriate part and controlling the heating current according to the measurement result. can do. From such a point of view, FIG. 7 shows a seventh embodiment in which a thermistor 14 as a temperature measuring sensor is arranged on the support beam 7 in the upper part of the figure so as to be taken out from the terminals 10b and 10c. By detecting a temperature change based on the output of the thermistor 14 and feeding back the detection result to control the heating current, the curvature of the mirror metal thin film 13 can be automatically controlled within a desired range.

FIG. 8 shows an eighth embodiment. In place of the thermistor 15 in FIG. 7, a piezoresistive element 16 as a strain measuring sensor is arranged on the support beam 7 and can be taken out from the terminals 10b and 10c. It is a thing. Since such a piezoresistive element 16 captures the amount of strain at the location where the support beam 7 is disposed as a change in resistivity, a change in curvature at the attachment point can be detected more directly. By detecting and feeding back the curvature change thus obtained and controlling the heating current based on the result, the curvature of the mirror metal thin film 13 can be accurately controlled within a desired range.

In the variable curvature mirror device according to the present invention, the concave surface is used for applications such as condensing and variable focus, and the convex surface is used for examples such as variable wide-field observation and variable range virtual image formation in addition to variable focus. Whether the initial shape of the mirror metal thin film 3 is a concave surface or a convex surface can be appropriately determined depending on the material, film thickness, film forming method, and the like, and will be described later in the manufacturing process.

Hereinafter, the variable curvature mirror device according to the present invention can be manufactured by applying a manufacturing technology of various semiconductor elements such as an integrated circuit (IC), LSI, VLSI, or a technology such as MEMS. The following is disclosed in accordance with a typical manufacturing process, but it is added that a similar variable curvature mirror device can be obtained by incorporating many other peripheral techniques known in the art, either separately or in combination. Keep it.

In the variable curvature mirror device according to the present invention, a single crystal silicon wafer is advantageously used as a starting material, but an SOI (Silicon on Insulator) wafer can also be used. FIG. 9 illustrates a typical manufacturing process for manufacturing a variable curvature mirror device according to the present invention using a single crystal silicon wafer as a starting material.

In step 1, an oxide film (SiO ₂ ) is formed on the entire surface of the single crystal silicon wafer 20 and desired portions on the back surface. Next, in step 2, an unnecessary portion where no oxide film is formed is etched. Etching is performed by crystal anisotropic etching using an alkaline solution, wet etching using isotropic etching using a hydrofluoric acid and nitric acid-based solution, reactive ion etching using plasma, etching using high-density plasma, or the like. By the etching process, the process 2 is completed in a state where the substrate thin plate portion 1 has a desired thickness.

Next, in step 3, an annular heating resistor 4 is formed on the surface of the substrate thin plate portion 1 by appropriate means such as sputtering, vacuum deposition, CVD, plating, or the like. Since the process 4 is also a film forming process of the mirror metal thin film 3 using gold (Au), aluminum (Al), silver (Ag), or an alloy of these and other metals, a sputtering method similar to or similar to the previous process, Appropriate means such as vacuum deposition, CVD, plating, etc. are adopted. Note that the order of the steps 3 and 4 can be changed, or can be performed simultaneously.

In step 5, the support beam portion is excluded as described above, and the slit 6 is etched to thermally separate the mirror metal thin film 3 portion and the outer edge portion and to easily cause the curvature change of the mirror metal thin film 3. It is formed by a method or other appropriate means. Therefore, this step 5 is necessary only for the “beam structure type”, and is not necessary for the “diaphragm structure type” in which the slit 6 is not provided.

FIG. 10 shows a typical manufacturing process for manufacturing a variable curvature mirror device using an SOI (Silicon On Insulator) wafer as a starting material. In step 1, an oxide film (SiO ₂ ) is formed on the entire surface of the SOI wafer and desired portions on the back surface. Next, in step 2, an unnecessary silicon portion where the back oxide film is not formed is etched. Step 2 is completed with the silicon portion removed from the SOI by the etching step.

Next, in step 3, an annular heating resistor 4 is formed at a desired site on the surface of the base thin plate portion 1 by an appropriate means such as sputtering, vacuum deposition, CVD, or plating. Next, in step 4, an example in which the mirror metal thin film 3 is formed on the back surface of the substrate thin plate 31 is shown. This is possible as a result of using an SOI wafer as a starting material. Since the process 4 is also a film forming process of the mirror metal thin film 3 by using gold (Au), aluminum (Al), silver (Ag), an alloy of these and an appropriate metal, etc., the sputtering method or vacuum similar to or similar to the previous process. Appropriate means such as vapor deposition, CVD, plating, etc. are adopted.

In step 5, the support beam portion is excluded as described above, and the slit 6 is etched to thermally separate the mirror metal thin film 3 portion and the outer edge portion and to easily cause the curvature change of the mirror metal thin film 3. Etc. are formed. Therefore, this step 5 is necessary only for the “beam structure type”, and is not necessary for the “diaphragm structure type” in which the slit 6 is not provided.

The initial form of the mirror metal thin film 3 in the present invention may be both a concave surface and a convex surface as described above, and which of these is required depends on the application. The initial form of such a reflective surface differs depending on, for example, the material, film thickness, and film forming method. If a sputtering method as shown in FIG. 11 is employed when forming a metal film on the substrate thin plate 1, the metal thin film is subjected to compression or tensile stress depending on the film forming conditions, and becomes a convex surface or a concave surface. On the other hand, when a vacuum vapor deposition method as shown in FIG. 12 is adopted using a metal as a material, or when heat treatment is performed after film formation, tensile stress acts on the metal thin film to form a concave surface. Film thickness also affects the initial morphology.

By combining additional means with the already formed variable curvature mirror device, the initial form of the mirror metal thin film 3 can be adjusted. As shown in FIG. 13, the lower peripheral edge portion of the variable curvature mirror device MD created in advance is sealed and sealed to the surface of the glass substrate G under a reduced pressure atmosphere by a high temperature bonding method. The mirror surface of the glass substrate hermetically sealed variable curvature mirror device MD thus obtained is a concave surface when used under normal pressure because the hermetically sealed space AS is decompressed.

On the contrary, as shown in FIG. 14, the glass substrate G and the lower peripheral edge of the variable curvature mirror device MD are sealed and sealed to the surface of the glass substrate G by a high-temperature bonding method in a pressurized atmosphere. In this case, the inside of the sealed space AS is higher than the normal pressure, and the mirror surface becomes a convex surface when used under normal pressure. The unevenness and the curvature of the initial form of the mirror surface when sealing and sealing the lower peripheral edge of the variable curvature mirror device MD to the glass substrate G as shown in FIGS. 13 and 14 are the atmospheric pressure during the sealing and sealing operation. Can be finely adjusted. Furthermore, the initial form of the desired curvature can be realized by taking into consideration the atmospheric pressure and the like of the use environment in advance.

In the variable curvature mirror device according to the present invention, the state of curvature change can be controlled by selecting the combination of materials of the mirror metal thin film 1 and the oxide film (insulating film) 2 and the respective film thicknesses. For example, as shown in FIG. 15, the mirror metal thin film 1 having a thermal expansion coefficient larger than that of silicon of the substrate thin plate is sufficiently thick with respect to the insulating film 2, and the thermal stress of the mirror metal thin film 1 is higher than the thermal stress of the insulating film 2. When it is large, the curvature is increased in accordance with the temperature rise. On the other hand, as shown in FIG. 16, the insulating film 2 having a thermal expansion coefficient smaller than that of silicon of the substrate thin plate is sufficiently thicker than the mirror metal thin film, and the thermal stress of the insulating film 2 is larger than the thermal stress of the mirror metal thin film 1. When it is large, the curvature is reduced in accordance with the temperature rise. Furthermore, a finer change in curvature can be achieved by forming a film on the back surface.

FIG. 17 is an enlarged plan view of a diaphragm structure device including a triple heating resistor, showing an embodiment experimentally produced by embodying the variable curvature mirror device according to the present invention. FIG. 18 shows another embodiment of the variable curvature mirror device according to the present invention, in which four divided slits appearing in black except for four supporting beams in the upper, lower, left and right sides are provided outside the single heating resistor. It is an enlarged plane photograph of the beam structure device provided with the connection terminal along each of a support beam.

FIG. 19 shows a shape measurement result of an embodiment of the variable curvature mirror device embodying the present invention, and shows a circular concave mirror metal thin film in the center. FIG. 20 shows the shape of the concave mirror part, the horizontal axis (Distance) representing the diameter is 1 mm at the maximum, the vertical axis shows the depth of the concave part, and the unit is micron (μm).

Table 1 shows the temperature rise [K] and supply power [W] of the heating body when the applied voltage for heating is changed by 0 to 32 [V] in the embodiment of the variable curvature mirror device according to the present invention. The curvature radius R [m] of the mirror central portion, the change delta R [m] of the curvature radius, and the change of the change rate delta R / R are shown. FIG. 21 is a plot of changes in applied voltage when the horizontal axis is the X position (radial direction) and the vertical axis is the Z position (depth direction) in units [mm].

FIG. 22 is a graph with the horizontal axis representing the electric power [W] supplied to the heating resistor and the vertical axis representing the rate of change of the radius of curvature in the embodiment of the variable curvature mirror device according to the present invention. Indicates that it has occurred. FIG. 23 is a graph with the temperature change [K] on the horizontal axis and the change rate of the radius of curvature on the vertical axis, and shows that a substantially linear change has occurred as in FIG.

The variable curvature mirror device according to the present invention can arbitrarily set the curvature of the mirror surface on which the mirror metal thin film is applied to the base thin plate by changing the voltage and current applied to the heating resistor, that is, the supplied power. Can be changed. The mirror surface can be arbitrarily formed such as a circle, an ellipse, a square shape or a polygon more than that, and the initial shape of the concave or convex surface, and the initial curvature can be selected as appropriate. Such a variable curvature mirror device can be manufactured with high precision by completed manufacturing and processing technologies such as MEMS, as well as various semiconductor processing technologies. It can be used as a variable focus mirror and other high-precision optical elements in various optical fields such as distance and reflection, and can be expected to contribute to a reduction in size and weight by simplifying the structure of the optical devices used.

It is the top view (A) and elevation sectional view (B) which show the basic composition (diaphragm structure type) of the 1st example of the variable curvature mirror device concerning the present invention. It is the top view (A) and elevation sectional view (B, C) which show the basic composition (beam structure type) of the 2nd example of the variable curvature mirror device concerning the present invention. It is the top view (A) and elevation sectional view (B, C) which show the structure (beam structure form) of the 3rd Example of the variable curvature mirror device concerning this invention. It is the top view (A) and elevation sectional view (B, C) which show the structure (beam structure form) of the 4th Example of the variable curvature mirror device concerning this invention. It is the top view (A) and elevation sectional view (B, C) which show the structure (beam structure form) of the 5th Example of the variable curvature mirror device concerning this invention. It is a sectional elevation showing the configuration (beam structure) of the sixth embodiment of the variable curvature mirror device according to the present invention. It is a top view which shows the structure (beam structure form) of the 7th Example which added the temperature sensor to the variable curvature mirror device concerning this invention. It is a top view which shows the structure (beam structure form) of the 8th Example which added the distortion sensor to the variable curvature mirror device concerning this invention. It is process explanatory drawing in the variable curvature mirror device manufacturing process concerning this invention which used the single crystal silicon wafer as the initial raw material. It is process explanatory drawing in the variable curvature mirror device manufacturing process concerning this invention which used the SOI wafer as the initial stage raw material. It is explanatory drawing of the manufacturing process which makes the initial form of a mirror surface convex in the manufacturing process of the variable curvature mirror device concerning this invention. It is explanatory drawing of the manufacturing process which makes the initial form of a mirror surface convex in the manufacturing process of the variable curvature mirror device concerning this invention. It is explanatory drawing of the manufacturing process which makes the initial form of a mirror surface convex in the manufacturing process of the variable curvature mirror device concerning this invention. It is explanatory drawing of the manufacturing process which makes the initial form of a mirror surface convex in the manufacturing process of the variable curvature mirror device concerning this invention. It is a sectional elevation of the 1st example which shows that curvature change changes with combination of the component of the variable curvature mirror device concerning the present invention. It is an elevation sectional view of the 2nd example which shows that a curvature change changes with combination of the component of the variable curvature mirror device concerning the present invention. It is an enlarged photograph which shows the structural example (diaphragm structure) of the variable curvature mirror device concerning this invention. It is an enlarged photograph which shows the structural example (beam structure) of the variable curvature mirror device concerning this invention. It is the figure which displayed the shape measurement result of the Example of the variable curvature mirror device shown in FIG. It is the graph which displayed the shape of the concave mirror center cut surface of FIG. It is a graph which shows the example of a concave surface change by the change of the applied voltage of the variable curvature mirror device manufactured experimentally. It is a graph which shows a response | compatibility with the change of the power supply, and the change of the curvature radius of a mirror part concave surface. It is a graph which shows a response | compatibility with a temperature change and the change of the curvature radius of a mirror part concave surface.

Explanation of symbols

1 Substrate thin plate 2 Insulation coating (silicon oxide)
3 Mirror metal thin film 4 Heating resistor 5 Power source 6 Slit 7 Support beam 8 Heating wire 9 Heating diffusion resistor 10 Terminal 13 Mirror metal thin film 14 Curvature control metal film pattern 15 Temperature sensor (thermistor)
16 Strain sensor (piezoresistive element)
20 Silicon wafer 21 Insulation coating (silicon oxide)
30 SOI (Silicon On Insulator) wafer MD Variable curvature mirror device AS Air gap G Glass substrate

Claims (21)

A base metal sheet, a mirror metal thin film formed by depositing a material having a thermal expansion coefficient different from that of the base material sheet on the surface of the base material sheet, and a heating element formed on or inside the base material sheet, A variable curvature mirror device comprising: an arbitrary curvature change on the surface of the mirror metal thin film in accordance with a temperature change by the heating element. 2. The variable curvature mirror device according to claim 1, wherein an insulating thin film is interposed between the substrate thin plate and the mirror metal thin film so as to be in close contact with the two. 3. The variable according to claim 1, wherein the heating element is formed on the substrate thin plate so as to be surrounded from the outside without directly contacting the mirror metal thin film portion. 4. Curvature mirror device. The mirror metal thin film is any one of a circle, an ellipse, a square or a polygon, and has a diaphragm structure in which the heating element is formed so as to surround the mirror metal thin film. The variable curvature mirror device according to claim 1. A slit surrounding the outside of the heating element, wherein the mirror metal thin film portion is thermally separated except for at least one beam portion connecting the device main portion including the mirror metal thin film and the device outer frame portion. 4. The variable curvature mirror device according to claim 1, wherein the variable curvature mirror device has a beam structure in which a slit for facilitating a change in curvature is provided. The beam portion linking the device main portion and the device outer frame portion is formed at two or more locations, thereby improving the balance at the time of curvature change in the device main portion. Item 4. The variable curvature mirror device according to any one of Items 1 to 3. The variable curvature mirror device according to any one of claims 1 to 6, wherein the heating element is formed as a metal thin film resistor having the same quality as the mirror metal thin film. 7. The variable curvature mirror device according to claim 1, wherein the heating element is a metal thin film resistor in which a metal different from the mirror metal thin film is deposited. 9. The substrate according to claim 1, wherein the substrate thin plate is composed of a silicon wafer, and the heating element is a diffusion layer resistor composed of an impurity diffusion layer formed in the silicon layer. The variable curvature mirror device described. 10. The variable curvature mirror device according to claim 1, wherein the mirror metal thin film is selected as a convex surface, a concave surface, or a flat surface in an unheated initial state. The variable curvature mirror device according to any one of claims 1 to 10, wherein at least one of a temperature sensor or a curvature detection sensor is attached on the thin base plate. A silicon thin plate is selected as the substrate thin plate, and a silicon dioxide (SiO ₂ ) film, a silicon nitride (Si ₃ N ₄ ) film, a silicon oxynitride (SiON film) or these are used as the insulating thin film formed on the silicon thin plate A mirror metal thin film selected from gold (Au), aluminum (Al), silver (Ag) or an alloy of these and other metals is formed as a mirror metal thin film. A method of manufacturing a variable curvature mirror device, wherein a heating element is formed so as to surround the mirror metal thin film region from the outside. 13. The method of manufacturing a variable curvature mirror device according to claim 12, wherein the heating element is a diffusion layer heating body in which impurities are diffused in a desired portion of a thin substrate sheet. 13. The variable curvature mirror device according to claim 12, wherein the heating element is a metal layer heating body on which a metal layer having a heat generation characteristic selected at a desired portion of a base sheet is deposited. Method. (1) A single crystal silicon plate is used as a starting material, and an insulating thin film is formed on the surface by an appropriate film formation method such as thermal oxidation treatment or CVD;
(2) forming the base thin film by processing the insulating thin film into a desired pattern, and then etching unnecessary portions of the single crystal silicon plate;
(3) A mirror metal thin film and a heating element are formed in a desired region on the insulating thin film formed in the previous process by employing appropriate film forming means such as a vapor deposition film forming method, a sputter film forming method, and a CVD film forming method. A method of manufacturing a variable curvature mirror device, characterized in that: 16. The variable curvature according to claim 15, wherein the etching process in the step (2) is wet etching by crystal anisotropic etching with an alkaline solution, isotropic etching with hydrofluoric acid and nitric acid based solution, or the like. Mirror device manufacturing method. The method of manufacturing a variable curvature mirror device according to claim 15, wherein the etching process in the step (2) is dry etching by reactive ion etching (RIE) or the like. 16. The variable curvature according to claim 15, wherein the variable curvature is formed as an impurity diffusion layer obtained by an impurity diffusion process on the base thin plate instead of forming the heating element by the film forming method in the step (3). Mirror device manufacturing method. 16. The method of manufacturing a variable curvature mirror device according to claim 15, wherein a single crystal silicon plate polished so that both surfaces thereof are mirror surfaces is selected as a starting material for forming the substrate thin plate. 16. The method of manufacturing a variable curvature mirror device according to claim 15, wherein an SOI material in which a silicon oxide film is formed at a certain depth from the surface is selected as a starting material for forming the substrate thin plate. By forming a sealed space on the back surface of the substrate thin plate that forms the mirror metal thin film, and forming the mirror metal thin film in a regulated pressurized or reduced pressure atmosphere over the entire substrate thin plate, 21. The initial curvature is adjusted by forming an arbitrary state of either a convex surface or a concave surface in an initial state of heating, and adjusting an atmospheric pressure. A method of manufacturing a variable curvature mirror device.

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