JP2005195837A - Shape variable mirror element and method for manufacturing it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a shape variable mirror element that can convert generating force of a piezoelectric film to displacement efficiently. <P>SOLUTION: Using an area where the sum of the inner tensile force of a film constituting a piezoelectric operating part 5 and the generating tensile force of a piezoelectric film results in a compressive tensile force relative to a substrate, large deformation becomes possible without being controlled by the tensile force. Further, as the manufacturing method of the element, the inner tensile force of the film constituting the piezoelectric operating part 5 is controlled by a heat treatment; therefore, the shape variable mirror element 1 can be stably manufactured that is large in the shape variable amount with low voltage. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a deformable mirror element that changes its shape by applying a predetermined voltage to a piezoelectric film, and a method for manufacturing the deformable mirror element.

  As a conventional deformable mirror element, an element that can change the mirror surface shape by pulling the mirror surface with a cable and changing the amount of tension (for example, refer to Patent Document 1), or holding an elastic mirror surface from the back surface, concave surface, convex surface An element that can be deformed into a plane (see, for example, Patent Document 2) is disclosed. However, any of these variable shape mirror elements has a complicated structure because it deforms the shape of the mirror body by a mechanical deformation mechanism, and is an extremely large optical component.

  Further, as a small-size variable shape mirror element, an element (for example, refer to Patent Document 3) in which lead wires are soldered to the upper surface of a ceramic piezoelectric material and the reflecting mirror surface and electrodes is disclosed. However, since the deformable mirror element uses a bulk material as the piezoelectric material, the thickness of the piezoelectric material is very large. As a result, a very high applied voltage is required to greatly change the shape.

  As a further minute size variable mirror element, an element (for example, see Patent Document 4) in which a piezoelectric film is attached to a reflection mirror plate is disclosed. As the reflecting mirror plate, for example, a glass reflecting mirror, a reflecting film, a silicon wafer or the like is used. In the case of this element as well, it is easily guessed that a very high applied voltage is required. That is, very thin glass reflectors, silicon wafers, and the like are manufactured by grinding or high-precision polishing. However, since a high-level manufacturing technique is required, the manufacturing cost is high and the realization is difficult. Further, an element having a structure in which the piezoelectric film and the reflection mirror plate are simply bonded has a low bonding strength, and cannot be self-supported by itself, and is not suitable for practical use. That is, when a reflecting mirror, a reflecting film, a silicon wafer or the like is practically used as a reflecting mirror, a certain thickness is required.

As a variable shape mirror element using a thin film, an element (for example, Japanese Patent Application No. 2003-143027) in which the variable shape portion has a diaphragm in the opening of the hollow portion of the substrate is disclosed. In the case of a deformable mirror element using a thin film diaphragm, since the film thickness of the element can be 10 μm or less, it is possible to change the shape at a low voltage. However, when a thin film diaphragm is used, an internal tension peculiar to the thin film is generated, and a large internal tension may exist as a residual tension even in the case of a diaphragm configuration. As a result, the displacement of the shape variable portion may be limited by the residual tension. That is, when the tensile tension is present as the residual tension, the piezoelectric constant indicating the displacement performance of the piezoelectric film is reduced (for example, see Non-Patent Document 1), and the shape variable performance of the piezoelectric film itself may be lowered. Furthermore, when a tensile tension greater than the force generated by the piezoelectric film is present, the shape variable amount may become extremely small. In addition, when the internal tension is very large, it is easily guessed that the diaphragm itself is broken.
Japanese Patent Laid-Open No. 5-127067 JP-A-7-1305 Japanese Patent Laid-Open No. 10-10459 JP 2001-34993 A Kenji Uchino, “Piezoelectric / Electrostrictive Actuator”, Morikita Publishing, July 1, 1986, p. 62-64

  The present invention solves the above-mentioned conventional problems, and a first object of the present invention is to efficiently maintain the internal tension of the film constituting the piezoelectric operating portion, thereby efficiently generating the piezoelectric film. An object of the present invention is to provide a deformable mirror element that can be converted into a displacement and, as a result, has a low voltage and a large shape variable amount. A second object of the present invention is to provide a manufacturing method capable of stably forming a deformable mirror element having a large shape variable amount at a low voltage.

  In order to solve the above problems, the deformable mirror element of the present invention includes a piezoelectric operation unit that can change its shape by applying a voltage, and a reflection unit that is directly or indirectly attached to the piezoelectric operation unit. A variable shape mirror element that displaces a reflecting portion by a piezoelectric operating portion, wherein the piezoelectric operating portion is in compressive tension in a state where a voltage is not applied or applied to the piezoelectric operating portion.

  In addition, the method for manufacturing a deformable mirror element according to the present invention is characterized in that the tension is adjusted by controlling the internal tension of the film constituting the piezoelectric operating unit by an internal tension adjusting process such as a heat treatment.

  According to the deformable mirror element of the present invention, since the piezoelectric film can be displaced without being restricted by the internal tension of the film, it is possible to provide a deformable mirror element having a large shape variable amount at a low voltage. Is obtained.

  In addition, according to the method of manufacturing a deformable mirror element of the present invention, the internal tension of the film constituting the piezoelectric operation unit can be controlled to an appropriate value by heat treatment, so that a deformable mirror element having a large shape variable amount at a low voltage can be obtained. An excellent effect that it can be stably produced is obtained.

  The invention according to claim 1 includes a piezoelectric operation unit capable of changing its shape by applying a voltage, and a reflection unit attached directly or indirectly to the piezoelectric operation unit, and the reflection unit is arranged by the piezoelectric operation unit. The deformable mirror element is characterized in that the piezoelectric operating part is in compression tension with no voltage applied or applied to the piezoelectric operating part. Since the piezoelectric film can be displaced without being restricted by the internal tension of the film, an excellent effect of providing a deformable mirror element having a large shape variable amount at a low voltage can be obtained.

  The invention according to claim 2 is the deformable mirror element according to claim 1, wherein the piezoelectric operating part already has a compressive tension when no voltage is applied to the piezoelectric operating part. Since the internal tension can be already set to the compression tension without applying an electric current, a large displacement can be obtained at a lower voltage.

  The invention according to claim 3 is the deformable mirror according to claim 1, wherein the piezoelectric action part is in compression tension only after a predetermined voltage is applied to the piezoelectric action part. It is possible to maintain a certain level of flatness in the absence, and this is effective depending on the specifications.

  According to a fourth aspect of the present invention, the piezoelectric operating portion is provided on a substrate, and at least a part of the piezoelectric operating portion faces a diaphragm portion provided on the substrate. In this shape variable mirror element, the piezoelectric operation part can be held on a substrate having a relatively high mechanical strength, so that the attachment to other members can be improved and the handling becomes easy.

  The invention according to claim 5 is the deformable mirror element according to claim 1, wherein the piezoelectric operation unit includes at least a piezoelectric film and an electrode for applying a voltage to the piezoelectric film. The piezoelectric film can be driven and the thickness can be reduced.

  The invention according to claim 6 is the deformable mirror according to claim 5, wherein at least one of the pair of electrodes and at least one member of the piezoelectric film have an elastic plate function. Even if it is not provided, a predetermined elasticity can be obtained, so that a reduction in thickness can be realized.

  The invention according to claim 7 is characterized in that a tension adjusting section is provided at any one position in the piezoelectric operating section in contact with the piezoelectric operating section or between the piezoelectric operating section and the reflecting section. It is effective when the internal tension cannot be adjusted due to the relationship of the constituent material of the piezoelectric operation part itself, etc., and the internal tension is the compression tension when no voltage is applied to the piezoelectric operation part. Alternatively, the internal tension can be set as the compression tension by applying a slight voltage to the piezoelectric operating portion.

  According to an eighth aspect of the present invention, a first electrode, a piezoelectric film, and a second electrode film are sequentially laminated on a substrate having a diaphragm portion to form a piezoelectric operation portion, and a reflection film is formed on the piezoelectric operation portion. A method for manufacturing a deformable mirror, characterized in that a process for adjusting the internal tension of the piezoelectric operating unit is performed, wherein the internal tension of the piezoelectric operating unit is reduced to a compression tension or a slight amount. The tension can be adjusted.

  The invention according to claim 9 is characterized in that at least one of the first electrode film and the second electrode film is subjected to a heat treatment as an adjustment process of the internal tension. This is a method in which each electrode film is made of a material whose internal tension can be changed by heat treatment, so that the internal tension can be easily adjusted, and the heat treatment time and heat treatment temperature can be increased to increase the compression tension. It is preferable to configure.

  The invention described in claim 10 is the method of manufacturing a variable shape mirror according to claim 8, wherein the laminated film is provided with an internal tension adjusting film as the internal tension adjusting process, and the structure of the piezoelectric operation part itself Even if the internal tension cannot be adjusted or can be adjusted with a material or the like, it is preferably used when a desired magnitude of tension cannot be obtained.

  Next, the internal tension state of the membrane and the shape of the diaphragm 23 will be described with reference to the drawings. FIG. 20 is a perspective view of the film 22 formed on the substrate 21. FIG. 21 is a perspective view of the diaphragm 23 formed on the substrate 21. FIG. 22 is a cross-sectional view of the main part of the diaphragm 23. For the purpose of facilitating understanding, the film thickness in the drawing, the thickness of the substrate, the amount of deformation, and the like are different from the actual dimensions.

  When a hollow portion is formed by processing a part of the substrate 21 by etching or the like, the film 22 as shown in FIGS. 21 and 22 remains, and a diaphragm 23 composed only of the film 22 is formed.

  When the film 22 on the substrate is in tensile tension with respect to the substrate 21, a contraction force acts on the film 22, and the substrate 21 is deformed into a concave shape as shown in FIG. When the diaphragm 23 is formed, the film 22 of the diaphragm 23 is not restrained from the substrate 21 and further contracts. However, since the end portion of the diaphragm 23 is fixedly supported by the substrate 21, there is a limit to the shrinkage, and the diaphragm 23 exists without being distorted as shown in FIG. Further, since the amount of contraction is restricted, the tension of the film 22 remains as a residual tension even when the diaphragm 23 is formed.

  On the other hand, when the film 22 on the substrate 21 has a compressive tension with respect to the substrate 21, an extension force acts on the film 22 and the substrate 21 is deformed into a convex shape as shown in FIG. When the diaphragm 23 is formed, the film 22 of the diaphragm 23 is not restrained from the substrate 21 and further expands. As a result, the diaphragm 23 is greatly deformed and bent as shown in FIG. Further, since the amount of deformation is very large as compared with the case of the tensile tension, the tension of the film 22 hardly remains when the diaphragm 23 is in the state.

  The generated force in the in-plane direction of the piezoelectric film acts on the deformation of the substrate or the deformation of the diaphragm 23 in the same manner as the above-described internal tension of the film. In the deformable mirror element of the present invention, at least a part of the deformable portion and the piezoelectric operating portion is made of the diaphragm 23. Therefore, regarding the deformation of the diaphragm 23, the generated force of the piezoelectric film is the same as the internal tension of the film 22 of the diaphragm 23 described above. Act on.

  That is, when the internal tension of the film 22 constituting the piezoelectric operating unit is a tensile tension and a tensile tension is generated by applying a voltage to the piezoelectric film, the tensile tension of the piezoelectric operating unit further increases. As a result, the diaphragm 23 exists in a stretched state.

  When the internal tension of the film 22 constituting the piezoelectric operating unit is a tensile tension and a compressive tension is generated by applying a voltage to the piezoelectric film, the tensile tension of the piezoelectric operating unit is reduced. As a result, when the total tension of the piezoelectric operating portion becomes a tensile tension, the diaphragm 23 exists in a tensioned state, and the diaphragm 23 is not deformed. Even if it is deformed, it is very small. When the total tension of the piezoelectric operating part becomes a compressive tension, the diaphragm 23 bends and changes its shape.

  When the internal tension of the film constituting the piezoelectric operating unit is a compressive tension and a tensile tension is generated by applying a voltage to the piezoelectric film, the compressive tension of the piezoelectric operating unit decreases. As a result, the diaphragm 23 changes to a stretched shape. When a compressive tension is generated by applying a voltage to the piezoelectric film, the compressive tension of the piezoelectric operating unit further increases. As a result, the diaphragm 23 changes to a further bent shape.

  As described above, if the region where the sum of the internal tension of the film constituting the piezoelectric operating part and the generated tension of the piezoelectric film is composed of compressive tension is used, the shape variable part is efficiently deformed, so that the shape can be changed at a low voltage. A large amount of deformable mirror element can be realized.

  Further, the present invention is a method for manufacturing a deformable mirror element, characterized in that the internal tension of a film constituting the piezoelectric operating part is adjusted by heat treatment. According to this manufacturing method, the surface tension, crystal state, or interface state between constituent films is changed by heat treatment, so that the internal tension of the film constituting the piezoelectric operating unit can be controlled to a desired value. It becomes possible to stably produce a deformable mirror element having excellent performance.

  Embodiments of the deformable mirror element of the present invention will be described below with reference to the drawings. For the purpose of facilitating understanding, the film thickness, the substrate thickness, the shape variable amount, etc. in the drawings are different from the actual dimensions. Hereinafter, the same applies to all drawings.

  FIG. 1 is a perspective view seen from the surface of the deformable mirror element of the present invention. FIG. 2 is a perspective view of the deformable mirror element of the present invention viewed from the back side. FIG. 3 is a cross-sectional view of an essential part of the deformable mirror element of the present invention.

The deformable mirror element 1 includes a substrate 2, a shape variable portion 3 provided on a diaphragm 13 formed on the substrate 2, and an electrode pad 4 for applying a voltage to the shape variable portion 3. Yes. The variable shape portion 3 is formed by laminating thin films as described below, and the laminated thin film is formed on the substrate 2 and on the diaphragm 13 portion, and the variable shape portion 3 is formed on the diaphragm 13 portion of the laminated thin film. The part formed above is defined in this embodiment. That is, the shape variable portion 3 is a portion facing the diaphragm 13 portion of the laminated thin film provided on the substrate 2 and fixed to the substrate. The shape variable unit 3 includes a piezoelectric operation unit 5 and a reflection mirror unit 6. The piezoelectric operation unit 5 includes a first electrode film 7 for applying a voltage to the piezoelectric film 8 from below, a piezoelectric film 8 for deforming the shape variable unit 3 by expansion and contraction, and a second electrode for applying a voltage to the piezoelectric film 8. A two-electrode film 9 is used. The reflection mirror unit 6 is made of a material that reflects light and, in the present embodiment, also functions as an elastic plate film that determines a deformation direction and a deformation shape. Accordingly, as another embodiment, it is conceivable that the reflection mirror section 6 has a two-layer structure of an elastic plate film and a reflection film. As a matter of course, a configuration in which an elastic plate film is separately provided in the piezoelectric operation unit 5 and only the reflection film is provided as the reflection mirror unit 6 may be employed. In this embodiment, by configuring the reflection mirror 6 with a structure or material having reflection characteristics and elastic characteristics, it is possible to omit the provision of an elastic plate film, thereby simplifying the structure and associated processes. it can. In other words, the reflection mirror unit 6 may be formed of an elastic plate film, and the elastic plate film may have reflection characteristics.

  As the material of the substrate 2, a single crystal material such as Si or MgO is suitably used because the piezoelectric characteristics of the piezoelectric film 8 are likely to be good, but is not particularly limited. However, when a process for high-temperature treatment is required in the process of manufacturing the deformable mirror element 1, a substrate material having good heat resistance may be selected. Further, since the substrate 2 is etched to form the diaphragm 13, a relatively thin substrate is preferably used.

  As the material of the piezoelectric film 8, a material having a high piezoelectric constant and a large displacement such as PZT or a perovskite oxide containing Pb similar to PZT is preferably used. There are many methods for forming the piezoelectric film 8 such as a sputtering method, a CVD method, or a sol-gel method, but there is no particular limitation as long as it is a technology capable of forming a film.

  Furthermore, in this embodiment, when the reflecting mirror portion does not have the function of an elastic plate film, it is necessary to provide a separate elastic plate film. As the material of the elastic plate film at that time, resin, metal, ceramic, etc. Can be used. In this embodiment, a dielectric multilayer film is used as the material for the elastic plate film. Also, the elastic plate film forming method is similar to the piezoelectric film 8 forming method, for example, sputtering, CVD, or vapor deposition, but is not particularly limited as long as it is a technique capable of forming a film.

As the material of the reflection film constituting the reflection mirror section 6, a material or material configuration having a high reflectance such as Au or Ag having a high reflectivity or a dielectric multilayer film is preferably used. The material and configuration of the dielectric multilayer film vary depending on the purpose of use of the mirror. For example, a λ / 4 multilayer film of low refractive index dielectric / high refractive index dielectric such as SiO ₂ / Ta ₂ O ₅ is preferably used. Is done. As with the method for forming the piezoelectric film 8, there are many methods for forming the reflective mirror film 11, for example, a sputtering method or a vapor deposition method. Further, when the reflection mirror portion 6 has a function of an elastic plate film, the reflection mirror portion 6 is formed of a material having a predetermined elasticity.

  As a material for the first electrode film 7 and the second electrode film 9, a highly conductive metal is preferably used. In the case of using a high temperature processing step in the process of manufacturing the deformable mirror element 1, a material resistant to high temperatures such as Ti, Ti alloy, Pt, Pt alloy, Ir, Ir alloy is desirable. The method for forming the first and second electrode films 7 and 9 is not particularly limited as long as the technique can form the film. In the process of forming the diaphragm 13, the substrate 11 is etched. There are many processing methods such as a wet etching method, a dry etching method, and mechanical processing. However, any technique that can form the diaphragm 13 is particularly limited. There is no.

A method for manufacturing the variable shape mirror element of this embodiment will be described with reference to FIGS.
4 to 9 are cross-sectional views of the main part of the deformable mirror element showing the manufacturing process of the deformable mirror element.

  First, as shown in FIGS. 4 to 8, a reflection mirror having the functions of a first electrode film 7, a piezoelectric film 8, a second electrode film 9 and an elastic plate film on a thin Si substrate 12 having a thickness of 100 μm to 500 μm. Portions 6 are formed sequentially.

  An Ir—Ti alloy was used as the material for the first electrode film 7, and the film thickness was 0.5 μm to 1.5 μm. PZT was used as the material of the piezoelectric film 8, and the film thickness was 1 μm to 3 μm. Ir—Ti alloy and PZT were both formed by sputtering, and the substrate temperature during Ir—Ti formation was 350 ° C. to 500 ° C., and the substrate temperature during PZT formation was 550 ° C. to 700 ° C. The piezoelectric constant indicating the displacement performance of the piezoelectric film 8 in this example was 100 pm / V to 150 pm / V, and the generated tension of the piezoelectric film 8 was 7 to 9 Pa · m per 1V.

  Ti was used as the material of the second electrode film 9, and the Ti film thickness was 0.3 to 0.7 μm. Ti was formed by sputtering, and the substrate temperature during Ti formation was normal temperature.

A dielectric multilayer film in which SiO ₂ and Ta ₂ O ₅ which are excellent in adhesion and corrosion resistance are alternately laminated is used as the material of the reflection mirror section 6 having an elastic plate film function. As described above, the reflection mirror unit 6 has an elastic plate function and a reflection function, and thus the film thickness is set to 0.3 to 0.7 μm. The reflective mirror part 6 was formed by vapor deposition.

  Next, the internal tension value of the film is adjusted as necessary. The main material that changes the tension is Ti of the second electrode film 9, and the amount of change in tension depends on the method of forming the second electrode film 9 (Ti film). FIG. 10 shows a change in internal tension of the second electrode film 9 (Ti film) when the heat treatment is performed. For example, the internal tension changes by about 12 Pa · m in the tension direction by heat treatment at 200 ° C. As the heat treatment temperature was further increased, the tensile tension increased and changed by about 29 Pa · m at 250 ° C. and by about 43 Pa · m at 300 ° C.

  In the internal tension adjusting method of the present invention, when the desired film tension is the tensile tension, the film is formed with a weaker tensile tension, and when the desired film tension is the compressive tension, the film is formed, and then the heat treatment is performed. Thus, it is possible to obtain a desired tension. This is because when adjusting the internal tension of the film by heat treatment, the tension adjustment direction only works in the tension tension direction, and by performing film formation in a state of compression tension direction rather than desired tension at the time of film formation, Adjustment is possible. The tension of the piezoelectric operating unit 5 is adjusted by this heat treatment. Finally, in order to form the diaphragm 13, the shape variable portion 3 becomes the diaphragm 13 by etching from the back surface of the Si substrate 12 to a desired thickness using a reactive ion etching technique. In addition, the diameter of the diaphragm 13 of the variable shape mirror element 1 of the present embodiment was 1 to 2 mm.

  With respect to the variable shape mirror element manufactured as described above, variable shape mirror elements having different tension directions and tension values as shown in Table 1 were prepared.

  The operation of the deformable mirror element formed as shown in Table 1 will be described with reference to the drawings. The tension values of the films of the respective structures are as follows. For all elements, the laminated film of the piezoelectric film 8 (PZT) and the first electrode film 7 (Ir-Ti) has a tensile tension of 100 Pa · m, and has a function of an elastic plate film. Since the mirror portion 6 has a compression tension of 50 Pa · m, the total tension of the reflection mirror portion 6 and the laminated film of the piezoelectric film 8 (PZT) and the first electrode film 7 (Ir-Ti) becomes a tensile tension, and the magnitude thereof is 50 Pa · m. The tension | tensile_strength of the 2nd electrode film 9 (Ti) was adjusted by changing with the formation method and heat processing temperature at the time of film-forming.

  First, element no. The operation of 1 will be described with reference to the drawings. 11 to 13 are cross-sectional views of the main part of the deformable mirror element 1 when the tensile tension is large. Since the internal tension of the film composed of the shape variable portion 3 of the present embodiment was adjusted so that the tension value of Ti of the second electrode film 9 becomes a tensile tension of 150 Pa · m, the reflection mirror portion 6 and the piezoelectric film 8 ( The total tension of the laminated film of PZT) and the first electrode film 7 (Ir-Ti) is a tensile tension, and the magnitude is 50 Pa · m. Therefore, the total tension value in the diaphragm 13 portion is a tensile tension of 200 Pa · m. .

  When no voltage is applied to the variable shape mirror element 1, the variable shape portion 3 is uniformly stretched as shown in FIG. Here, when a voltage of 5 V is applied to the piezoelectric film 8, a compressive tension of about 40 Pa · m is generated in the piezoelectric film 8, but even if the tension of the piezoelectric film 8 is applied, the total tension is the tensile tension (about 160 Pa). -M). Accordingly, as shown in FIG. 12, the shape variable portion 3 has a uniformly stretched shape without distortion, and the shape variable portion 3 is not deformed. Or, even if it is deformed, it is extremely small. Furthermore, when a voltage of 10 V is applied, a force of about 80 Pa · m is generated in the piezoelectric film 8, but the total tension is also a tensile tension, so that the shape variable portion 3 is not deformed as shown in FIG. 13. Or, even if it is deformed, it is extremely small.

  When the total tension of the piezoelectric operation unit 5 including the first electrode film 7, the piezoelectric film 8, and the second electrode film 9 becomes a tensile tension with respect to the substrate 2, and the magnitude is 200 Pa · m or more, the piezoelectric film Even when a large voltage section was added to 8, the amount of deformation was extremely small.

Next, element No. The operation of 2 will be described with reference to the drawings. 14-16 is principal part sectional drawing of the shape variable mirror element 1 in case a tension | tensile_strength is small. Since the total tension of the film composed of the shape variable portion 3 of the present embodiment was adjusted so that the tension value of Ti of the second electrode film 9 becomes no tension of 0 Pa · m, the reflection mirror portion 6 and the piezoelectric film 8 ( The total tension of the laminated film of PZT) and the first electrode film 7 (Ir-Ti) is a tensile tension, and the magnitude is 50 Pa · m. Therefore, the total tension value in the diaphragm 13 is 50 Pa · m. . When no voltage is applied to the deformable mirror element 1, the variable shape portion 3 made of the diaphragm 13 is uniformly stretched as shown in FIG. Here, when a voltage of 5 V is applied to the piezoelectric film 8, about 40 Pa ·
Although a compressive tension of about m is generated, the total tension is in the tension direction, so that the shape variable portion 3 has a uniformly stretched shape, and has a stretched cross-sectional shape as shown in FIG. That is, the shape variable unit 3 is not deformed. Or even if it is deformed, it is extremely small. Further, when a voltage of 10 V is applied, a compressive tension of about 80 Pa · m is generated in the piezoelectric film 8, the total tension becomes the compressive tension, and the shape variable portion 3 is deformed as shown in FIG. Therefore, when the total tension of the piezoelectric operation unit 5 including the first electrode film 7, the piezoelectric film 8, and the second electrode film 9 becomes a tensile tension with respect to the substrate 2, and the magnitude is 50 Pa · m or more, piezoelectric When the voltage applied to the film 8 was small, the amount of deformation was extremely small. However, when a large voltage was applied to the piezoelectric film 8, the tension of the piezoelectric operating unit 5 itself became a compression tension, and a relatively large displacement could be obtained.

  Furthermore, element No. The operation of 3 will be described with reference to the drawings. 17 to 19 are cross-sectional views of the main part of the deformable mirror element 1 when the compression tension is small. Since the total tension of the film composed of the shape variable portion 3 of this embodiment is adjusted so that the Ti tension value of the second electrode film 9 becomes a compressive tension of 150 Pa · m, the reflection mirror portion 6 and the piezoelectric film 8 ( The total tension of the laminated film of the PZT) and the first electrode film 7 (Ir-Ti) is a tensile tension, and the magnitude is 50 Pa · m. Therefore, the total tension value in the diaphragm 13 portion is a compressive tension of 100 Pa · m. . When no voltage is applied to the deformable mirror element 1, the shape variable portion 3 made of the diaphragm 13 has a slightly bent shape as shown in FIG. When a voltage of 5 V is applied to the piezoelectric film 8 so that, for example, a force is generated in the compression direction, a compressive tension of about 40 Pa · m is generated in the piezoelectric film 8 and is further bent as shown in FIG. It becomes a state. Further, when a voltage of 10 V is applied, the compression tension increases, and the shape variable portion 3 is further deformed as shown in FIG. Accordingly, when the total tension of the piezoelectric operation unit 5 including the first electrode film 7, the piezoelectric film 8, and the second electrode film 9 becomes a compressive tension with respect to the substrate 2, and the magnitude is 100 Pa · m or more, piezoelectric Even when the voltage applied to the film 8 was small, an extremely large deformation amount could be obtained. Further, when a large voltage was applied to the piezoelectric film 8, a larger displacement could be obtained.

  In addition, element No. The operation of element No. The operation was the same as that of No. 3. The difference is that the amount of deformation when no voltage is applied to the deformable mirror element 1 is the element number. The operation is omitted because it is larger than 3.

  As described above, according to the deformable mirror element 1 of the present embodiment, the internal tension of the film constituting the piezoelectric operation unit 5 and the piezoelectric film 8 when a predetermined voltage is applied to the piezoelectric film 8 in the piezoelectric operation unit 5 are described. By using a region in which the sum of the generated tension and the substrate 2 is composed of compressive tension, the shape variable portion 3 can efficiently realize large deformation. Furthermore, according to the manufacturing method of this example, it has been clarified that a deformable mirror element capable of realizing a large deformation can be stably manufactured by controlling the internal tension of the film.

  In the variable shape mirror element of the present embodiment, the variable shape portion 3 and the piezoelectric operating portion 5 have the same configuration and the same member, but are not limited to the same configuration. For example, as shown in FIG. 27, the reflection mirror unit 6 is arranged at the center of the diaphragm 13 and the piezoelectric operation unit 5 is arranged around the diaphragm 13 so that the piezoelectric operation unit 5 becomes a part of the shape variable unit. It is good.

  Similarly, in the variable shape mirror element of this embodiment, the reflective mirror film 11 has the function of an elastic plate film, but is not limited to the same member. Furthermore, although the reflection mirror part 6 was formed with a film structure such as a reflection mirror film, for example, a reflection sheet or the like may be attached, and the reflection mirror part 6 is not limited to a film formed by sputtering or vapor deposition.

Furthermore, when the piezoelectric operating unit 5 itself is configured to have a tensile tension, the piezoelectric operating unit 5 becomes a compression tension when a predetermined voltage is applied to the piezoelectric film 8 in the piezoelectric operating unit 5. By adjusting as described above, the flatness can be relatively maintained in the piezoelectric operation unit 5, which may be preferable depending on the specifications. That is, when no voltage is applied to the piezoelectric film 8, the reflection mirror unit 6 has a flat shape, so that light incident on the reflection mirror unit 6 can be reflected without correcting aberrations or the like. Only when necessary, by applying a voltage to the piezoelectric film 8 and applying a voltage so as to achieve a compression tension as the piezoelectric operation unit 5, it is possible to correct the aberration of incident light.

  Further, in this embodiment, attention has been paid to the fact that the material composed of the second electrode film 9 can easily adjust the tension depending on the degree of heat treatment, but heat treatment is also applied to members other than the second electrode film 9. Therefore, the internal tension can be adjusted. That is, for example, in the case where the first electrode film 7 is made of a material that can adjust the tension by heat treatment in a relatively easy manner, the internal tension can be adjusted by paying attention to the first electrode film 7. From another point of view, in consideration of the characteristics of the thin film formed on the substrate 2, if the tension of each thin film can be adjusted by heat treatment, the total internal tension is within a predetermined range. Can be controlled. That is, for example, when a thin film to be laminated contains a film that increases tensile tension and a film that increases compressive tension by heat treatment, the constituent material and film of each thin film are adjusted so that a desired internal tension is obtained by heat treatment. It is necessary to adjust the thickness. With respect to the constituent material of the thin film and the film thickness, it is possible to measure in advance what kind of tension is generated by experiments or the like in advance.

  Further, in this embodiment, the internal tension of the deformable mirror element 1 is adjusted by providing each member on the substrate 2 and then performing a heat treatment at a predetermined temperature or for a predetermined time, but the first electrode film 7 is formed. After that, the tension of the first electrode film may be adjusted, the tension of at least one of the first electrode film 7 and the piezoelectric film 8 may be adjusted after forming the piezoelectric film 8, or the second electrode film 9 may be adjusted. After forming, the tension of at least one of the first electrode film 7, the piezoelectric film 8, and the second electrode film 9 may be adjusted.

  In this embodiment, the method of adjusting the internal tension by heat treatment is adopted, but a film capable of adjusting the internal tension can be separately provided. That is, for example, a thin film capable of adjusting the tension is provided between the piezoelectric operation unit 5 and the reflection mirror unit 6. The tension-adjustable thin film has, for example, a predetermined compressive tension at the time of formation, and as a result, the deformable mirror element 1 can be adjusted so that the internal tension becomes the compressive tension. As a film capable of adjusting the tension, a film whose tension can be adjusted by naturally performing a heat treatment can be used, and a film whose tension is hardly changed even in the heat treatment may be used. As a specific example, a configuration in which a silicon oxide film is provided between the piezoelectric operation unit 5 and the reflection mirror unit 6 can be given.

  Here, a method for measuring the tension value will be described. The tension value is obtained from the following (Equation 1) by measuring the amount of warping of the substrate after the thin film is formed. However, (Equation 1) is an approximate expression based on the assumption that the thin film that constitutes the piezoelectric action part or the like is sufficiently thin with respect to the substrate (for example, “Thin Film Mechanical Characteristic Evaluation Technology”, Realize Co., Ltd., 1992). March 19, p. 228).

S is the tension value of the thin film, E is the Young's modulus of the substrate, D is the thickness of the substrate, l is the length of the substrate, ν is the substrate Poisson's ratio, and δ is the amount of warpage of the substrate after forming the thin film. Therefore, the tension S of the thin film in (Equation 1) can be easily obtained by obtaining each characteristic of the substrate. As a matter of course, the tension of the thin film may be obtained by other methods.

  According to the deformable mirror element of the present invention, it is possible to provide a deformable mirror element having a large shape variable amount at a low voltage. Therefore, for example, a video projector, a digital camera, or an optical disc apparatus provided with an optical system including the variable optical element. It can also be applied to applications such as pickup parts.

The perspective view seen from the surface of the deformable mirror element of the present invention The perspective view seen from the back surface of the deformable mirror element of the present invention Sectional drawing of the principal part of the deformable mirror element of the present invention Sectional view of deformable mirror element showing manufacturing process of deformable mirror element Sectional view of deformable mirror element showing manufacturing process of deformable mirror element Sectional view of deformable mirror element showing manufacturing process of deformable mirror element Sectional view of deformable mirror element showing manufacturing process of deformable mirror element Sectional view of deformable mirror element showing manufacturing process of deformable mirror element Sectional view of deformable mirror element showing manufacturing process of deformable mirror element Relationship between heat treatment temperature and tension change Cross section of the main part of the deformable mirror element when the tensile tension is large Cross section of the main part of the deformable mirror element when the tensile tension is large Cross section of the main part of the deformable mirror element when the tensile tension is large Cross section of the main part of the deformable mirror element when the tensile tension is small Cross section of the main part of the deformable mirror element when the tensile tension is small Cross section of the main part of the deformable mirror element when the tensile tension is small Cross section of the main part of the deformable mirror element when the compression tension is low Cross section of the main part of the deformable mirror element when the compression tension is low Cross section of the main part of the deformable mirror element when the compression tension is low Perspective view of a film formed on a substrate The figure which shows the diaphragm 13 formed on the board | substrate Sectional drawing of the principal part of the diaphragm 13 formed on the board | substrate Diagram showing deformation of the substrate when the film is in tensile tension with respect to the substrate The figure which shows the deformation | transformation of the diaphragm 13 when a film | membrane is tension | tensile_strength with respect to a board | substrate. Diagram showing deformation of the substrate when the membrane is in compressive tension with respect to the substrate The figure which shows the deformation | transformation of the diaphragm 13 when a film | membrane is a compression tension with respect to a board | substrate. Sectional drawing of the principal part of the variable shape mirror of another structure of a present Example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shape variable mirror element 2 Board | substrate 3 Shape variable part 4 Electrode pad 5 Piezoelectric action | operation part 6 Reflection mirror part 7 1st electrode film 8 Piezoelectric film 9 2nd electrode film 10 Elastic board film 11 Reflection mirror film 12 Si substrate 13 Diaphragm 21 board | substrate 22 Membrane 23 Diaphragm

Claims (10)

A variable shape mirror element that includes a piezoelectric operation unit that can change its shape by applying a voltage, and a reflection unit that is directly or indirectly attached to the piezoelectric operation unit, and that displaces the reflection unit by the piezoelectric operation unit. A variable shape mirror element characterized in that the piezoelectric operating part is in compression tension in a state where a voltage is not applied or applied to the piezoelectric operating part. 2. The deformable mirror element according to claim 1, wherein the piezoelectric operating part already has a compressive tension when no voltage is applied to the piezoelectric operating part. 2. The deformable mirror element according to claim 1, wherein the piezoelectric operating part is in compression tension only after a predetermined voltage is applied to the piezoelectric operating part. 2. The variable shape mirror element according to claim 1, wherein the piezoelectric operating portion is provided on a substrate, and at least a part of the piezoelectric operating portion is opposed to a diaphragm portion provided on the substrate. The variable shape mirror element according to claim 1, wherein the piezoelectric operation unit includes at least a piezoelectric film and an electrode for applying a voltage to the piezoelectric film. 6. The variable shape mirror element according to claim 5, wherein at least one of the pair of electrodes and at least one member of the piezoelectric film have an elastic plate function. 2. The variable shape mirror element according to claim 1, wherein a tension adjusting unit is provided at any one position of the piezoelectric operating unit in contact with the piezoelectric operating unit or between the piezoelectric operating unit and the reflecting unit. Method for manufacturing variable shape mirror element, wherein first electrode, piezoelectric film and second electrode film are sequentially laminated on a substrate having a diaphragm portion to form a piezoelectric operating portion, and a reflective film is formed on the piezoelectric operating portion A method of manufacturing a deformable mirror element, characterized in that a process for adjusting the internal tension of the piezoelectric operating portion is performed. 9. The method of manufacturing a deformable mirror element according to claim 8, wherein at least one of the first electrode film, the piezoelectric film, and the second electrode film is subjected to heat treatment as the internal tension adjustment process. 9. The method of manufacturing a deformable mirror element according to claim 8, wherein an internal tension adjusting film is provided on the laminated film as the internal tension adjusting process.

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