JP4317231B2 - Micromirror device and manufacturing method thereof - Google Patents

Description

  The present invention is an element incorporated in an optical switching device that switches an optical path between a plurality of optical fibers, an optical disc device that performs data recording / reproduction processing on an optical disc, and the like, and a light traveling direction by light reflection The present invention relates to a micromirror element for changing the above and a manufacturing method thereof.

  In recent years, optical communication technology has been widely used in various fields. In optical communication, an optical signal is transmitted using an optical fiber as a medium, and a so-called optical switching device is generally used to switch the transmission path of the optical signal from one fiber to another. Characteristics required for an optical switching device to achieve good optical communication include large capacity, high speed, and high reliability in the switching operation. From these viewpoints, as a switching element incorporated in an optical switching device, a micromirror element manufactured by a micromachining technique has attracted attention. According to the micromirror element, it is possible to perform a switching process between an optical transmission path on the input side and an optical transmission path on the output side in the optical switching device without converting the optical signal into an electrical signal. This is because it is suitable for obtaining the above-mentioned characteristics.

  The micromirror element is disclosed in, for example, the following Patent Documents 1 and 2 and Non-Patent Document 1. An optical switching device using a micromirror element manufactured by a micromachining technique is disclosed in a paper, for example.

JP-A-4-343318 Japanese Patent Laid-Open No. 11-52278 “MEMS Components for WDM Transmission Systems” (Optical Fiber Communication [OFC] 2002, pp.89-90)

  FIG. 21 shows a schematic configuration of a general optical switching device 500. The optical switching device 500 includes a pair of micromirror arrays 501 and 502, an input fiber array 503, an output fiber array 504, and a plurality of microlenses 505 and 506. The input fiber array 503 includes a predetermined number of input fibers 503a, and the micromirror array 501 is provided with a plurality of micromirror elements 501a corresponding to the input fibers 503a. Similarly, the output fiber array 504 includes a predetermined number of output fibers 504a, and the micromirror array 502 is provided with a plurality of micromirror elements 502a corresponding to the respective output fibers 504a. Each of the micromirror elements 501a and 502a has a mirror surface for reflecting light, and is configured so that the direction of the mirror surface can be controlled. The plurality of microlenses 505 are disposed so as to face the end of the input fiber 503a. Similarly, each of the plurality of microlenses 506 is disposed so as to face the end of the output fiber 504a.

  At the time of optical transmission, the light L1 emitted from the input fiber 503a passes through the corresponding microlens 505 to be converted into parallel light and travels toward the micromirror array 501. The light L1 is reflected by the corresponding micromirror element 501a and deflected to the micromirror array 502. At this time, the mirror surface of the micromirror element 501a is directed in a predetermined direction so that the light L1 is incident on the desired micromirror element 502a. Next, the light L 1 is reflected by the micromirror element 502 a and deflected to the output fiber array 504. At this time, the mirror surface of the micromirror element 502a is directed in a predetermined direction so that the light L1 is incident on the desired output fiber 504a.

  Thus, according to the optical switching device 500, the light L1 emitted from each input fiber 503a reaches the desired output fiber 504a by the deflection in the micromirror arrays 501 and 502. That is, the input fiber 503a and the output fiber 504a are connected on a one-to-one basis. Then, by appropriately changing the deflection angle in the micromirror elements 501a and 502a, the output fiber 504a to which the light L1 reaches is switched.

  FIG. 22 shows a schematic configuration of another general optical switching device 600. The optical switching device 600 includes a micro mirror array 601, a fixed mirror 602, an input / output fiber array 603, and a plurality of micro lenses 604. The input / output fiber array 603 includes a predetermined number of input fibers 603a and a predetermined number of output fibers 603b. The micromirror array 601 includes a plurality of micromirror elements 601a corresponding to the fibers 603a and 603b. Each of the micromirror elements 601a has a mirror surface for reflecting light, and is configured so that the direction of the mirror surface can be controlled. The plurality of microlenses 604 are disposed so as to face the ends of the fibers 603a and 603b, respectively.

  At the time of optical transmission, the light L2 emitted from the input fiber 603a is emitted toward the micromirror array 601 through the microlens 604. The light L2 is reflected by the corresponding first micromirror element 601a to be deflected to the fixed mirror 602, reflected by the fixed mirror 602, and then incident on the second micromirror element 601a. At this time, the mirror surface of the first micromirror element 601a faces in a predetermined direction in advance so that the light L2 is incident on the desired second micromirror element 601a. Next, the light L2 is reflected to the input / output fiber array 603 by being reflected by the second micromirror element 601a. At this time, the mirror surface of the second micromirror element 601a faces in a predetermined direction in advance so that the light L2 enters the desired output fiber 603b.

  Thus, according to the optical switching device 600, the light L2 emitted from each input fiber 603a reaches the desired output fiber 603b by the deflection in the micromirror array 601 and the fixed mirror 602. That is, the input fiber 603a and the output fiber 603b are connected on a one-to-one basis. Then, by appropriately changing the deflection angle in the first and second micromirror elements 601a, the output fiber 603b to which the light L2 reaches is switched.

  FIG. 23 is a partially omitted perspective view of a micromirror element 700 that has been proposed as a micromirror element to be incorporated in the optical switching devices 500 and 600. The micromirror element 700 includes a mirror forming portion 710 having an upper surface provided with a mirror surface (not shown), an inner frame 720, and an outer frame 730 (partially omitted), and comb electrodes are integrated with each other. Is formed. Specifically, the mirror forming portion 710 has a pair of comb electrodes 710a and 710b formed at opposite ends thereof. The inner frame 720 has a pair of comb electrodes 720a and 720b extending inwardly corresponding to the comb electrodes 710a and 710b, and a pair of comb electrodes 720c and 720d extending outward. Is formed. A pair of comb electrodes 730a and 730b are formed on the outer frame 730 so as to extend inward corresponding to the comb electrodes 720c and 720d. The mirror forming portion 710 and the inner frame 720 are connected by a pair of torsion bars 740, and the inner frame 720 and the outer frame 730 are connected by a pair of torsion bars 750. The pair of torsion bars 740 define the rotation axis of the rotation operation of the mirror forming portion 710 relative to the inner frame 720, and the pair of torsion bars 750 rotate the inner frame 720 relative to the outer frame 730 and the accompanying mirror forming portion 710. Specifies the rotational axis of operation.

  In the micromirror element 700 having such a configuration, a pair of comb electrodes, for example, the comb electrode 710a and the comb electrode 720a, which are provided in close proximity to generate an electrostatic force, As shown in FIG. 24 (a), the upper and lower stages are separated. When a voltage is applied, as shown in FIG. 24B, the comb electrode 710a is drawn into the comb electrode 720a, and thereby the mirror forming portion 710 swings. More specifically, in FIG. 23, for example, when the comb electrode 710a is positively charged and the comb electrode 720a is negatively charged, the mirror forming unit 710 twists the pair of torsion bars 740 in the direction of M1. Rotate to. On the other hand, when the comb electrode 720c is positively charged and the comb electrode 730a is negatively charged, the inner frame 720 rotates in the direction of M2 while twisting the pair of torsion bars 750.

  As a conventional method for manufacturing the micromirror element 700, for example, a method of forming an SOI (Silicon on Insulator) wafer in which an insulating layer is sandwiched between silicon layers is known. Specifically, first, as shown in FIG. 25A, a wafer 800 having a laminated structure including a first silicon layer 801, a second silicon layer 802, and an insulating layer 803 sandwiched therebetween is prepared. To do. Next, as shown in FIG. 25B, anisotropic etching is performed on the first silicon layer 801 through a predetermined mask so that the mirror forming portion 710, the torsion bar 140, the comb electrode 710a, etc. Then, a structure to be formed in the first silicon layer 801 is formed. Next, as shown in FIG. 25C, anisotropic etching is performed on the second silicon layer 802 through a predetermined mask to form the second silicon layer 802 such as the comb electrode 720a. The structure to be formed is formed. However, FIG. 25A to FIG. 25C show cross sections at a plurality of locations on the wafer 800 in a single cross-sectional view from the viewpoint of simplifying the drawings.

  However, in the conventional manufacturing method as described above, the thickness of the wafer 800 is directly reflected in the thickness of the micromirror element 700. That is, the thickness of the micromirror element 700 is the same as the thickness of the wafer 800 used to form the micromirror element 700. Therefore, in the conventional manufacturing method, it is necessary to use a wafer 800 having the same thickness as that of the micromirror element 700 to be manufactured. When the thickness of the micromirror element 700 is thin, the thin wafer 800 is used. There must be. For example, when the micromirror element 700 having a mirror surface size of about 100 to 1000 μm is formed, the mass of the entire movable portion including the mirror forming portion 710 and the inner frame 720, the amount of movement of the movable portion, and the amount of movement are achieved. In consideration of the size of the comb electrode necessary for the operation, the thickness of the movable part and thus the micromirror element 700 is preferably about 100 to 200 μm. Therefore, in order to form such a micromirror element 700 In this case, a wafer 800 having a thickness of about 100 to 200 μm is used.

  In the conventional manufacturing method, since it is necessary to use such a thin wafer 800 according to the thickness of the thin micromirror element 700, the handling becomes difficult as the wafer 800 has a larger diameter. For example, when the micromirror element 700 is manufactured from the SOI wafer 800 having a thickness of 200 μm and a diameter of 6 inches as described above, the wafer 800 often breaks during a series of steps. As shown in FIG. 25 (b), after a predetermined structure is formed in the first silicon layer 801, the strength of the wafer 800 decreases, and handling when processing the second silicon layer 802 is particularly difficult. Become. If the wafer 800 is thin, the planar size of the wafer is thus limited from the viewpoint of handling. In addition, when the planar size of the wafer is limited, the array size is limited when a micromirror array chip is manufactured by forming a plurality of micromirror elements in an array on a single substrate. Become.

  FIG. 26 shows a micromirror element 700 mounted on a wiring board. The micromirror element 700 has a cross section taken along line XXVI-XXVI in FIG. In the conventional micromirror element 700 of FIG. 23, the movable part including the mirror forming part 710 and the inner frame 720 has the same thickness as the outer frame 730. Therefore, in order to appropriately operate the movable portion in a state where the micromirror element 700 is mounted on the wiring board 810, a spacer 811 is interposed between the wiring board 810 and the outer frame 730 as shown in FIG. It is necessary to let By interposing a spacer 811 having a sufficient thickness between the micromirror element 700 and the wiring substrate 810, it is possible to prevent the movable portion from coming into contact with the wiring substrate 810 and hindering its operation. When the micromirror element 700 is mounted on the wiring board 810, it is not efficient to separately provide such a spacer 811 in the process of mounting the micromirror element 700 on the wiring board 810.

  The present invention has been conceived under such circumstances, and an object of the present invention is to provide a micromirror element capable of reducing the restriction on the planar size of a wafer used for manufacturing, and a manufacturing method thereof. And

  According to a first aspect of the present invention, a micromirror element is provided. The micromirror element includes a movable part having a mirror part, which is integrally formed from a material substrate, a frame part, and a torsion bar that connects the frame part and the movable part. It is characterized by having a thick part.

  In the micromirror element having such a configuration, the restriction on the size of the material substrate or wafer to be used is reduced during the manufacturing process. The micromirror element according to the first aspect includes a frame portion having a portion thicker than the movable portion. Therefore, the thickness of the movable part is set to 100 to 200 μm, for example, considering the mass of the entire movable part, the operation amount of the movable part, and the size of, for example, a comb electrode necessary for achieving the operation amount. Even in the case of setting the first thickness as thin as possible, a wafer having a second thickness larger than the first thickness can be used in manufacturing the micromirror element. When such a wafer is used, the strength of the wafer can be maintained by maintaining the second thickness in a predetermined region or more in the frame portion in the process of forming each structure of the element. As a result, it is possible to appropriately prevent the material substrate or wafer from being cracked in the process of manufacturing the micromirror element.

  The micromirror element according to the first side surface includes a frame portion having a portion thicker than the movable portion. That is, the frame part protrudes from the movable part in at least one of the element thickness directions. Therefore, for example, when the frame part protrudes sufficiently on the side opposite to the mirror surface of the movable part, the micromirror element can be directly mounted on the wiring board via the frame part. It becomes. This is because the sufficiently protruding frame portion ensures an appropriate separation state between the movable portion and the wiring substrate, and as a result, the operation of the movable portion is not hindered by the wiring substrate. On the other hand, when the frame part protrudes sufficiently on the same side as the mirror surface of the movable part, the micromirror element has a transparent cover such as a glass substrate through the frame part so as to protect the mirror surface. Can be directly joined. This is because the sufficiently protruding frame portion ensures an appropriate separation state between the movable portion and the transparent cover, and as a result, the operation of the movable portion is not hindered by the transparent cover.

  As described above, according to the micromirror element according to the first aspect of the present invention, it is possible to reduce the limitation on the planar size of the wafer used for manufacturing, and further, the members such as the wiring board and the transparent cover to be disposed adjacent to each other Therefore, it is possible to appropriately join without using a spacer separately.

  According to the second aspect of the present invention, another micromirror device is provided. The micromirror element includes a movable portion, a frame portion, and a torsion bar that connects the movable portion and the frame portion, which are integrally formed from a material substrate having a laminated structure including an intermediate layer and a silicon layer sandwiching the intermediate layer. The movable portion includes a first intermediate portion derived from the intermediate layer, a first structure in contact with the first intermediate portion, and a second structure in contact with the first intermediate portion on the opposite side of the first structure. The mirror part is formed on the first structure, and the frame part is in contact with the second intermediate part derived from the intermediate layer and the second intermediate part on the same side as the first structure. Including a third structure and a fourth structure in contact with the second intermediate portion on the same side as the second structure, and the fourth structure projects beyond the second structure in the stacking direction of the stacked structure. It is characterized by.

  Even with the micromirror element having such a configuration, the limitation on the planar size of the wafer used for manufacturing can be reduced in the same manner as described above with respect to the first side surface. Further, as described above with respect to the first side surface, it is possible to appropriately join the adjacently arranged member such as the wiring board to the element without using a spacer separately. In a preferred embodiment of the micromirror element according to the second aspect, a wiring board bonded to the fourth structure is further provided.

  Preferably, the third structure projects beyond the first structure in the stacking direction. According to such a configuration, as described above with respect to the first side surface, it is possible to appropriately join the adjacent arrangement member such as a transparent cover to the element without using a spacer separately.

  According to the third aspect of the present invention, another micromirror device is provided. The micromirror element includes a movable portion, a frame portion, and a torsion bar that connects the movable portion and the frame portion, which are integrally formed from a material substrate having a laminated structure including an intermediate layer and a silicon layer sandwiching the intermediate layer. The movable portion includes a first intermediate portion derived from the intermediate layer, a first structure in contact with the first intermediate portion, and a second structure in contact with the first intermediate portion on the opposite side of the first structure. The mirror part is formed on the first structure, and the frame part is in contact with the second intermediate part derived from the intermediate layer and the second intermediate part on the same side as the first structure. Including a third structure and a fourth structure in contact with the second intermediate portion on the same side as the second structure, and the third structure projects beyond the first structure in the stacking direction of the stacked structure. It is characterized by.

  Also with the micromirror element having such a configuration, the limitation on the planar size of the wafer used for manufacturing can be reduced in the same manner as described above with respect to the first side surface. In addition, as described above with respect to the first side surface, it is possible to appropriately join adjacent elements such as a transparent cover to the element without using a spacer.

  In a preferred embodiment of the micromirror element according to the third aspect, a transparent cover joined to the third structure is further provided.

  In the first to third embodiments of the present invention, preferably, the movable part has a first comb electrode part, and the frame part generates an electrostatic force between the first comb electrode part and the frame part. It has the 2nd comb-tooth electrode part for displacing a movable part. Thus, the micromirror element of the present invention preferably includes a comb electrode as a drive electrode. In this case, it is preferable that the first comb electrode portion is formed in the first structure, and the second comb electrode portion is formed in a portion in contact with the second intermediate portion in the fourth structure.

  In a preferred embodiment, the movable part includes a relay frame connected to the frame part via a torsion bar, a mirror forming part separated from the relay frame, and a relay torsion bar connecting the relay frame and the mirror forming part. The relay torsion bar extends in a direction intersecting with the extending direction of the torsion bar. Thus, the micromirror element of the present invention is preferably configured as a biaxial type. In this case, the mirror forming part has a third comb electrode part, and the relay frame generates a fourth comb tooth for displacing the mirror forming part by generating an electrostatic force with the third comb electrode part. It is preferable to have an electrode part. The third comb electrode part is preferably formed on the first structure, and the fourth comb electrode part is preferably formed on the second structure.

  According to a fourth aspect of the present invention, there is provided a method for manufacturing a micromirror device comprising a movable part, a frame part, and a torsion bar connecting the movable part and the frame part. This method has a first mask pattern for masking a portion to be processed into at least a part of the frame portion with respect to the material substrate, and a portion for masking a portion to be processed into the movable portion. A step of performing a first etching process in the thickness direction of the material substrate through the second mask pattern, a step of removing the second mask pattern, and a second etching process of the material substrate through the first mask pattern And a step of performing.

  Preferably, the first etching process is performed halfway in the thickness direction, and the second etching process is performed until the material substrate is penetrated so as to form at least the movable part. Alternatively, the first etching process is performed until the material substrate is penetrated, and the second etching process is performed halfway in the thickness direction of the material substrate so as to form at least the movable portion.

  According to the fifth aspect of the present invention, another method for manufacturing a micromirror element is provided. This method is a method for manufacturing a micromirror device including a movable portion, a frame portion, and a torsion bar, and includes a first silicon layer, a second silicon layer, and an intermediate layer therebetween. A first mask pattern for masking a portion to be processed into at least a part of the frame portion and a portion to be processed into a movable portion with respect to the first silicon layer in the material substrate having a structure A step of performing a first etching process through a second mask pattern having a portion, a step of removing the second mask pattern, and a second etching process through the first mask pattern on the first silicon layer. And a step of performing.

  Preferably, the first etching process is performed halfway in the thickness direction of the first silicon layer, and the second etching process is performed until the intermediate layer is reached. Alternatively, the first etching process is performed up to the intermediate layer, and the second etching process is performed halfway in the thickness direction of the first silicon layer. Preferably, the second mask pattern further has a portion for masking a portion to be processed into a comb electrode portion formed in the frame portion.

  According to a sixth aspect of the present invention, there is provided another method for manufacturing a micromirror device comprising a movable part, a frame part, and a torsion bar. This method masks a portion to be processed into a movable portion with respect to a first silicon layer in a first material substrate having a stacked structure of a first silicon layer, a second silicon layer, and an intermediate layer therebetween. Forming a first mask pattern having a portion for forming a first mask pattern by bonding a third silicon layer to a surface of the first silicon layer on which the first mask pattern is formed First etching until the first silicon layer is reached through the step of manufacturing the second material substrate and the second mask pattern having a portion for masking at least a part of the frame portion with respect to the third silicon layer. And a second etching process on the first silicon layer exposed by the first etching process up to the intermediate layer through the first mask pattern. Characterized in that it comprises a, and performing.

  Preferably, the first mask pattern further has a portion for masking a portion to be processed into a comb-tooth electrode portion formed in the frame portion.

  According to a seventh aspect of the present invention, there is provided another method for manufacturing a micromirror device comprising a movable part, a frame part, and a torsion bar. With this method, a first material substrate made of a first silicon layer is passed through a first mask pattern having a portion for masking a portion to be processed into a comb electrode portion formed in a frame portion. A step of performing a first etching treatment to a depth corresponding to the thickness of the comb electrode portion, a first material substrate, an intermediate layer in contact with the etched surface of the first material substrate, and a second silicon layer in contact with the intermediate layer A second material substrate having a layered structure according to the above, a second mask pattern having a portion for masking a portion to be processed into at least a part of the frame portion with respect to the first silicon layer, and Performing a second etching process halfway through the first silicon layer through a third mask pattern having a portion for masking a portion to be processed into the movable portion and the comb electrode portion; Removing the mask pattern, the first silicon layer, through the second mask pattern, characterized by comprising a step of performing a third etching treatment until the comb-tooth electrode portion.

  According to an eighth aspect of the present invention, there is provided another method for manufacturing a micromirror device comprising a movable part, a frame part, and a torsion bar. The method includes a first silicon layer, a second silicon layer, an intermediate layer between them, and a first material substrate having a torsion bar built in the first silicon layer in contact with the intermediate layer. Forming a first mask pattern having a portion for masking a portion to be processed into a movable portion with respect to the silicon layer; and a surface of the first silicon layer on which the first mask pattern is formed. Bonding the three silicon layers to manufacture a second material substrate having the first mask pattern embedded therein, and masking a portion to be processed into at least a part of the frame portion with respect to the third silicon layer; A step of performing a first etching process until the first mask pattern is exposed through the second mask pattern, and a first silicon layer through the first mask pattern. Characterized in that it comprises a step of performing a second etching treatment until the layer, the.

  According to the method according to the fourth to eighth aspects of the present invention, the micromirror element according to the first to third aspects of the present invention can be manufactured. Therefore, according to the method according to the fourth to eighth aspects, it is possible to reduce the restriction on the planar size of the wafer used for manufacturing. In addition, it is possible to appropriately bond adjacently arranged members to the manufactured element without using a separate spacer.

  FIG. 1 is a perspective view of a micromirror element X1 according to the first embodiment of the present invention. FIG. 2 is a sectional view taken along line II-II in FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1, and FIG. 4 is a cross-sectional view taken along line IV-IV in FIG.

  As shown in FIG. 1, the micromirror element X1 includes a mirror forming part 110, an inner frame 120 surrounding the mirror forming part 110, an outer frame 130 surrounding the inner frame 120, and a pair of torsion bars that connect the mirror forming part 110 and the inner frame 120. 140, a pair of torsion bars 150 that connect the inner frame 120 and the outer frame 130 are provided. The pair of torsion bars 140 defines a rotation axis A1 of the rotation operation of the mirror forming unit 110 with respect to the inner frame 120. The pair of torsion bars 150 define a rotation axis A2 of the rotation operation of the inner frame 120 and the accompanying mirror forming portion 110 with respect to the outer frame 130. In the present embodiment, the rotation axis A1 and the rotation axis A2 are substantially orthogonal. The micromirror element X1 is integrally formed of a conductive material except for a mirror surface 111 and an insulating layer 160 described later. As the conductive material, a material obtained by doping silicon or polysilicon with an n-type impurity such as P or As or a p-type impurity such as B is used.

  A mirror surface 111 is formed as a thin film on the upper surface of the mirror forming portion 110. Further, comb electrodes 110 a and 110 b are extended and formed on two opposite side surfaces of the mirror forming portion 110.

  The inner frame 120 has a laminated structure including an inner frame main part 121, a pair of electrode bases 122, and an insulating layer 160 therebetween, as can be understood with reference to FIGS. 1 to 4 together. . The inner frame main part 121 and the electrode base 122 are electrically separated by an insulating layer 160. Comb electrodes 122a and 122b extending inward are integrally formed on the pair of electrode bases 122. Comb electrodes 121a and 121b extending outward are formed on the inner frame main part 121. Are integrally molded. The comb-tooth electrodes 122a and 122b are located below the comb-tooth electrodes 110a and 110b of the mirror forming portion 110, as clearly shown in FIG. The comb-tooth electrodes 110a and 110b and the comb-tooth electrodes 122a and 122b do not contact each other during the rotation operation of the mirror forming unit 110, for example, in the form shown in FIG. The teeth are arranged so as to be displaced.

  The pair of torsion bars 140 are each thinner than the mirror forming part 110 and are connected to the mirror forming part 110 and the inner frame main part 121 as shown in FIG.

  As shown in FIG. 2, the outer frame 130 has a laminated structure including a first outer frame portion 131, a second outer frame portion 132, and an insulating layer 160 therebetween. The first outer frame part 131 and the second outer frame part 132 are electrically separated by an insulating layer 160. As clearly shown in FIG. 3, comb electrodes 132 a and 132 b extending inward are integrally formed on the second outer frame portion 132. The comb electrodes 132a and 132b are located below the comb electrodes 121a and 121b of the inner frame main portion 121, respectively. The comb-tooth electrodes 121a and 121b and the comb-tooth electrodes 132a and 132b are arranged such that their teeth are displaced so that they do not come into contact with each other when the inner frame 120 rotates. 2 to 4, the second outer frame portion 132 is formed on the electrode base 122 and the comb electrodes 122 a and 122 b of the inner frame 120 that is a movable portion, and the outer frame 130. It protrudes downward by a predetermined length from the comb electrodes 132a and 132b.

  As shown in FIG. 2, each of the pair of torsion bars 150 has a laminated structure including an upper layer 151, a lower layer 152, and an insulating layer 160 therebetween. The upper layer 151 and the lower layer 152 are electrically separated by an insulating layer. The upper layer 151 is connected to the inner frame main part 121 and the first outer frame part 131, and the lower layer 152 is connected to the electrode base 122 and the second outer frame part 132.

  In the micromirror element X1 having such a configuration, when the first outer frame portion 131 is grounded, the upper layer 151 of the torsion bar 150 integrally formed of the same silicon-based material as the first outer frame portion 131, the inner The comb electrodes 110a and 110b and the comb electrodes 121a and 121b are connected to the ground via the frame main portion 121, the torsion bar 140, and the mirror forming portion 110. In this state, a desired potential is applied to the comb electrode 122a or the comb electrode 122b, and static electricity is applied between the comb electrode 110a and the comb electrode 122a, or between the comb electrode 110b and the comb electrode 122b. By generating electric power, the mirror forming unit 110 can be swung around the rotation axis A1. Further, a desired potential is applied to the comb electrode 132a or the comb electrode 132b, and an electrostatic force is generated between the comb electrode 121a and the comb electrode 132a or between the comb electrode 121b and the comb electrode 132b. By generating, the inner frame 120 and the mirror forming part 110 can be swung around the rotation axis A2. The second outer frame portion 132 is appropriately electrically separated by a gap or the like so as to function as a field where a conductive path for selectively applying a potential to the comb electrodes 122a, 122b, 132a, 132b is formed. A plurality of divided sections.

  FIG. 5 shows a state in which the micromirror element X1 is mounted on the wiring board 400. FIG. About the micromirror element X1, the cross section along line VV of FIG. 1 is represented. In the micromirror element X1, the outer frame 130 is thicker than the movable part including the mirror forming part 110 and the inner frame 120. Specifically, the second outer frame portion 132 of the outer frame 130 includes an electrode base 122 and comb electrodes 122 a and 122 b of the inner frame 120, and comb electrodes 132 a and 132 b formed on the outer frame 130. Also protrudes downward by a predetermined length. The second outer frame part 132 protrudes downward from the lowest position of the movable part during driving, for example, the lowest position of the electrode base 122 of the inner frame 120. Therefore, in a state where the wiring substrate 400 is bonded to the lower surface of the second outer frame portion 132, a space for operating the movable portion is secured, and the movable portion is prevented from coming into contact with the wiring substrate 400. Therefore, when the micromirror element X1 is mounted on the wiring board 400, it is not necessary to interpose a spacer between the micromirror element X1 and the wiring board 400.

  6 to 8 show a first manufacturing method of the micromirror element X1. This method is one method for manufacturing the above-described micromirror element X1 by micromachining technology. 6 to 8, from the viewpoint of simplification, the forming process of the mirror forming portion M, the torsion bar T, the inner frame F1, the pair of comb electrodes E1 and E2, and the outer frame F2 is represented by one cross section. . The one cross section is obtained by modeling a plurality of predetermined cross sections in a material substrate on which micromachining is performed. Specifically, the mirror forming part M represents a partial cross section of the mirror forming part 110, the torsion bar T represents a cross section of the torsion bar 140 or a partial cross section of the torsion bar 150, and the inner frame F1 represents the main part of the inner frame. 121 represents a partial cross section of the inner frame 120 including the electrode base 122, the comb electrode E1 represents a part of the cross section of the comb electrodes 110a and 110b or the comb electrodes 121a and 121b, and the comb electrode E2 represents a comb. A part of the cross section of the tooth electrodes 122a and 122b or the comb electrodes 132a and 132b is shown, and a partial cross section of the outer frame 130 including the first outer frame part 131 and the second outer frame part 132 is shown by the outer frame F2.

  In the manufacture of the micromirror element X1, first, as shown in FIG. 6A, an SOI (Silicon on Insulator) wafer 1 is prepared as a substrate. The SOI wafer 1 has a laminated structure including a relatively thin first silicon layer 11, a thick second silicon layer 12, and an insulating layer 160 as an intermediate layer sandwiched therebetween. The first silicon layer 11 is made of silicon imparted with conductivity by doping an n-type impurity such as P or As. The second silicon layer 12 is made of silicon or polysilicon imparted with conductivity by doping an n-type impurity such as P or As. However, p-type impurities such as B may be used for imparting conductivity. The insulating layer 160 is made of silicon oxide grown on the surface of the first silicon layer 11 or the second silicon layer 12 by a thermal oxidation method. As a film forming means for the insulating layer 160, a CVD method may be employed instead of the thermal oxidation method. After the formation and growth of the insulating layer 160, the SOI wafer 1 is manufactured by bonding the first silicon layer 11 and the second silicon layer 12 via the insulating layer 160. In the present embodiment, the thickness of the first silicon layer 11 is 100 μm, the thickness of the second silicon layer 12 is 200 μm, and the thickness of the insulating layer 160 is 1 μm.

  Next, as shown in FIG. 6B, an oxide film pattern 51 is formed on the first silicon layer 11 and an oxide film pattern 52 is formed on the second silicon layer 12. Specifically, first, an oxide film made of silicon oxide is grown on the first silicon layer 11 and the second silicon layer 12 by a CVD method. Then, the oxide film is patterned by etching through a predetermined mask. As an etching chemical solution in this patterning, for example, buffered hydrofluoric acid composed of hydrofluoric acid and ammonium fluoride can be used. Subsequent oxide film patterns can also be formed by such oxide film growth and subsequent etching treatment. The oxide film pattern 51 is for masking a portion of the first silicon layer 11 that is processed into the mirror forming portion M, the inner frame F1, the comb electrode E1, and the outer frame F2. More specifically, the oxide film pattern 51 includes the mirror forming portion 110, the inner frame main portion 121, the comb electrodes 110a and 110b, the comb electrodes 121a and 121b, and the first outer frame portion 131 shown in FIG. It is formed corresponding to a planar view form. The oxide film pattern 52 is for masking a portion of the second silicon layer 12 that is processed into the outer frame F2. More specifically, the oxide film pattern 52 is formed corresponding to the plan view form of the second outer frame portion 132 shown in FIG.

  Next, as shown in FIG. 6C, a resist pattern 53 is formed on the first silicon layer 11. Specifically, a liquid photoresist is formed on the first silicon layer 11 by spin coating, and a resist pattern 53 is formed through exposure and development. For example, AZP4210 (manufactured by Clariant Japan) or AZ1500 (manufactured by Clariant Japan) can be used as the photoresist. Subsequent resist patterns are also formed through such photoresist film formation and subsequent exposure / phenomenon. The resist pattern 53 is for masking the mirror forming portion M, the torsion bar T, the inner frame F1, the formation region of the comb-tooth electrode E1, and the outer frame F2 in the first silicon layer 11. More specifically, the resist pattern 53 includes the mirror forming portion 110, the torsion bars 140 and 150, the inner frame main portion 121, the comb electrode electrodes 110a and 110b, and the comb electrode electrodes 121a and 121b shown in FIG. The formation region of the first outer frame portion 131 is formed corresponding to the planar view form.

Next, as shown in FIG. 6D, the first silicon layer 11 is etched to a depth corresponding to the thickness of the torsion bar T by DRIE (Deep Reactive Ion Etching) using the resist pattern 53 as a mask. I do. In this embodiment, the depth is 5 μm. In DRIE, in the Bosch process in which etching and sidewall protection are alternately performed, etching with SF ₆ gas is performed for 8 seconds, sidewall protection with C ₄ F ₈ gas is performed for 6.5 seconds, and the bias applied to the wafer is 23 W. Therefore, a good etching process can be performed. This condition can also be adopted for subsequent DRIE on the silicon layer.

  Next, as shown in FIG. 7A, the resist pattern 53 is peeled off. As the remover, AZ remover 700 (manufactured by Clariant Japan) can be used. This can also be used for subsequent peeling of the resist pattern.

  Next, as shown in FIG. 7B, the first silicon layer 11 is etched by DRIE to the insulating layer 160 using the oxide film pattern 51 as a mask. Thereby, the mirror forming portion M, the torsion bar T, a part of the inner frame F1, the comb-tooth electrode E1, and a part of the outer frame F2 are formed.

  Next, as shown in FIG. 7C, a resist pattern 54 is formed on the second silicon layer 12. The resist pattern 54 is for masking the inner frame F1 and the comb-tooth electrode E2 in the second silicon layer 12. More specifically, the resist pattern 54 is formed corresponding to the planar view form of the electrode base 122, the comb electrodes 122a and 122b, and the comb electrodes 132a and 132b shown in FIG.

  Next, as shown in FIG. 7D, using the oxide film pattern 52 and the resist pattern 54 as a mask, the second silicon layer 12 is etched by DRIE to a depth corresponding to the thickness of the comb electrode E2. I do.

  Next, after removing the resist pattern 54 as shown in FIG. 8A, the insulating layer 160 is formed on the second silicon layer 12 through the oxide film pattern 52 as shown in FIG. 8B. Etching is performed until the process is completed. Thereby, a part of the inner frame F1, the comb electrode E2, and a part of the outer frame F2 are formed.

  Next, as shown in FIG. 8C, the exposed insulating layer 160 is removed by being immersed in an etching solution. At this time, the oxide film patterns 51 and 52 exposed on the element surface are also removed at the same time. Thus, the mirror forming portion M, the torsion bar T, the inner frame F1, the comb-tooth electrodes E1 and E2 are formed within 100 μm from the insulating layer 160, and the outer frame F2 having the second outer frame portion 132 having a thickness of 200 μm. Is formed. In this way, the micromirror element X1 is manufactured.

  According to such a method, a movable part thinner than the material substrate to be used, that is, the wafer, and a two-stage comb-tooth structure are formed. Therefore, it is possible to use a wafer having a thickness capable of maintaining sufficient strength in a series of steps in manufacturing a micromirror element regardless of the thickness required for the movable part and the two-stage comb-tooth structure. It becomes. Regardless of the thickness required for the movable part and the two-stage comb-tooth structure, it is possible to use a wafer having a thickness that can maintain sufficient strength, so that the restriction on the planar size of the wafer is reduced.

  9 and 10 show a second manufacturing method of the micromirror element X1. This method is also a method for manufacturing the above-described micromirror element X1 by micromachining technology. 9 and 10, as in FIGS. 6 to 8, the mirror forming portion M, the torsion bar T, the inner frame F 1, the pair of comb-shaped electrodes E 1 and E 2, and the outer frame according to one modeled cross section. It represents the formation process of F2.

  In the second manufacturing method, first, the same steps as those described with reference to FIGS. 6A to 6D and FIGS. 7A to 7C for the first manufacturing method are performed. Then, the SOI wafer 1 is processed to the state shown in FIG. Specifically, in the SOI wafer 1 shown in FIG. 9A, the first silicon layer 11 is processed by DRIE using the oxide film pattern 51 as a mask, and the second silicon layer 12 is oxidized. A film pattern 52 and a resist pattern 54 are formed.

  Next, as shown in FIG. 9B, the first silicon layer 11 is etched by DRIE to the insulating layer 160 using the resist pattern 54 and the oxide film pattern 52 as a mask. Thereafter, as shown in FIG. 9C, the resist pattern 54 is removed.

  Next, as shown in FIG. 9D, a photoresist 55 'is formed by spraying from below in the drawing. As the photoresist solution to be used for spraying, for example, AZP4210 (manufactured by Clariant Japan) diluted 4 times with AZ5200 thinner (manufactured by Clariant Japan) can be used.

  Next, a resist pattern 55 is formed through exposure and development on the photoresist 55 'as shown in FIG. The resist pattern 55 is mainly for protecting the insulating layer 160.

  Next, as shown in FIG. 10B, the second silicon layer 12 is etched to a predetermined depth by DRIE using the oxide film pattern 52 as a mask. Thus, a part of the inner frame F1 and the comb electrode E2 are formed.

  Next, after removing the resist pattern 55 as shown in FIG. 10C, the exposed insulating layer 160 is etched away by being immersed in an etchant as shown in FIG. 10D. At this time, the oxide film patterns 51 and 52 exposed on the element surface are also removed at the same time. Thus, the mirror forming portion M, the torsion bar T, the inner frame F1, the comb-tooth electrodes E1 and E2 are formed within 100 μm from the insulating layer 160, and the outer frame F1 having the second outer frame portion 132 having a thickness of 200 μm. Is formed. In this way, the micromirror element X1 is manufactured.

  According to such a method, it is possible to form a movable part and a two-stage comb-tooth structure that are thinner than the material substrate to be used, that is, the wafer. Therefore, the same effects as described above with respect to the first manufacturing method can be obtained by the second manufacturing method.

  11 and 12 show a third manufacturing method of the micromirror element X1. This method is also a method for manufacturing the above-described micromirror element X1 by micromachining technology. 11 and 12, similarly to FIGS. 6 to 8, the mirror forming portion M, the torsion bar T, the inner frame F 1, the pair of comb-shaped electrodes E 1 and E 2, and the outer frame according to one modeled cross section. It represents the formation process of F2.

  In the third manufacturing method, first, as shown in FIG. 11A, an SOI wafer 2 is prepared as a substrate. The SOI wafer 2 has a laminated structure including a first silicon layer 13, a second silicon layer 14, and an insulating layer 160 as an intermediate layer sandwiched therebetween. In the present embodiment, the thickness of the first silicon layer 13 is 100 μm, the thickness of the second silicon layer 14 is 100 μm, and the thickness of the insulating layer 160 is 1 μm. In the formation of the SOI wafer 2, the method for imparting conductivity to the silicon layer and the method for forming the insulating layer 160 are the same as those described above with respect to the first manufacturing method.

  Next, as shown in FIG. 11B, an oxide film pattern 56 is formed on the first silicon layer 13 and an oxide film pattern 57 is formed on the second silicon layer 14. The oxide film pattern 56 is for masking a portion of the first silicon layer 13 that is processed into the mirror forming portion M, the inner frame F1, the comb electrode E1, and the outer frame F2. More specifically, the oxide film pattern 56 includes the mirror forming portion 110, the inner frame main portion 121, the comb electrodes 110a and 110b, the comb electrodes 121a and 121b, and the first outer frame portion 131 shown in FIG. It is formed corresponding to a planar view form. The oxide film pattern 57 is for masking a portion of the second silicon layer 14 that is processed into the inner frame F1 and the comb electrode E2. More specifically, the oxide film pattern 57 is formed corresponding to the planar view form of the electrode base 122, the comb electrodes 122a and 122b, and the comb electrodes 132a and 132b shown in FIG.

Next, as shown in FIG. 11C, the third silicon layer 15 is directly bonded to the second silicon layer 14 of the SOI wafer 2. The third silicon layer 15 is made of silicon imparted with conductivity by doping impurities and has a thickness of 100 μm. Further, in the third silicon layer 15, a retracting portion is formed in advance at a location corresponding to the oxide film pattern 57 by DRIE. In the present embodiment, the depth of the retracting portion is 5 μm. The bonding in this step is performed, for example, at a degree of vacuum of 10 ⁻⁴ Torr and a heating temperature of 1100 ° C. By this bonding, the third silicon layer 15 is integrated with the second silicon layer 14.

  Next, as shown in FIG. 11D, the first silicon layer 13 is etched by DRIE until the insulating layer 160 is reached using the oxide film pattern 56 as a mask. Thereby, the mirror forming portion M, the torsion bar T, a part of the inner frame F1, the comb electrode E1, and a part of the outer frame F2 are formed.

  Next, as shown in FIG. 12A, an oxide film pattern 58 is formed on the third silicon layer 15. The oxide film pattern 58 is for masking a portion to be processed into the outer frame F2. More specifically, the oxide film pattern 58 is formed corresponding to the planar view form of the second outer frame portion 132 shown in FIG.

  Next, as shown in FIG. 12B, the third silicon layer 15 is etched by DRIE using the oxide film pattern 58 as a mask until the oxide film pattern 57 is exposed.

  Next, as shown in FIG. 12C, the second silicon layer 14 is etched by DRIE to the insulating layer 160 using the oxide film patterns 57 and 58 as a mask. Thereby, a part of the inner frame F1, a comb electrode E2, and a part of the outer frame F2 are formed.

  Next, as shown in FIG. 12D, the exposed insulating layer 160 is etched away by being immersed in an etching solution. At this time, the oxide film patterns 56, 57, and 58 exposed on the element surface are also removed at the same time. Thus, the mirror forming portion M, the torsion bar T, the inner frame F1, the comb-tooth electrodes E1 and E2 are formed within 100 μm from the insulating layer 160, and the outer frame 130 having the second outer frame portion 132 having a thickness of 200 μm. Is formed. In this way, the micromirror element X1 is manufactured.

  According to such a method, the movable portion and the two-stage comb-tooth structure can be formed on a material substrate or wafer having a thickness greater than these. Therefore, the third manufacturing method also provides the same effects as described above with respect to the first manufacturing method. Prior to the step shown in FIG. 11D, the structure forming step for the silicon layer, which is a factor for reducing the strength of the wafer, is not performed. Therefore, before the step shown in FIG. 11D, the planar size of the wafer is not excessively suppressed.

  13 and 14 show a fourth manufacturing method of the micromirror element X1. This method is also a method for manufacturing the above-described micromirror element X1 by micromachining technology. In FIGS. 13 and 14, similarly to FIGS. 6 to 8, the mirror forming portion M, the torsion bar T, the inner frame F 1, the pair of comb-shaped electrodes E 1 and E 2, and the outer frame are formed by one modeled cross section. It represents the formation process of F2.

  In the fourth manufacturing method, first, as shown in FIG. 13A, an SOI wafer 3 is prepared as a substrate. The SOI wafer 3 has a laminated structure including a first silicon layer 16, a second silicon layer 17, and an insulating layer 160 as an intermediate layer sandwiched between them. The second silicon layer 17 has a shape corresponding to the comb-shaped electrode E2 formed in advance by DRIE. The second silicon layer 17 has the insulating layer 160 so that the comb-shaped electrode E2 is joined to the insulating layer 160. Bonded to the formed first silicon layer 16. In the present embodiment, the thickness of the first silicon layer 16 is 100 μm, the thickness of the second silicon layer 17 is 200 μm, and the thickness of the insulating layer 160 is 1 μm. In the formation of the SOI wafer 3, the method for imparting conductivity to the silicon layer and the method for forming the insulating layer 160 are the same as those described above with respect to the first manufacturing method.

  Next, as shown in FIG. 13B, an oxide film pattern 59 is formed on the first silicon layer 16 and an oxide film pattern 60 is formed on the second silicon layer 17. The oxide film pattern 59 is for masking a portion of the first silicon layer 16 that is processed into the mirror forming portion M, the inner frame F1, the comb electrode E1, and the outer frame F2. More specifically, the oxide film pattern 59 includes the mirror forming portion 110, the inner frame main portion 121, the comb electrodes 110a and 110b, the comb electrodes 121a and 121b, and the first outer frame portion 131 shown in FIG. It is formed corresponding to a planar view form. The oxide film pattern 60 is for masking a portion of the second silicon layer 17 that is processed into the outer frame F2. More specifically, the oxide film pattern 60 is formed corresponding to the plan view form of the second outer frame portion 132 shown in FIG.

  Next, a process similar to that described above with respect to the first manufacturing method is performed with reference to FIGS. 6C to 6D and FIGS. Process to the state shown in (c).

  Next, as shown in FIG. 13D, a resist pattern 61 is formed on the second silicon layer 17. The resist pattern 61 is for masking a portion of the second silicon layer 17 where the inner frame F1, the formation area of the comb electrode E2, and the outer frame F2 are processed.

  Next, as shown in FIG. 14A, the second silicon layer 17 is etched to a predetermined depth that leaves the height of the comb-tooth electrode E2 by DRIE using the resist pattern 61 as a mask. Thereafter, as shown in FIG. 14B, the resist pattern 61 is removed.

  Next, as shown in FIG. 14C, the second silicon layer 17 is etched by DRIE until the insulating layer 160 is reached using the oxide film pattern 60 as a mask. Thereby, a part of the inner frame F1, a comb electrode E2, and a part of the outer frame F2 are formed.

  Next, as shown in FIG. 14D, the exposed insulating layer 160 is removed by being immersed in an etching solution. At this time, the oxide film patterns 59 and 60 exposed on the element surface are also removed at the same time. Thus, the mirror forming portion M, the torsion bar T, the inner frame F1, the comb-tooth electrodes E1 and E2 are formed within 100 μm from the insulating layer 160, and the outer frame F2 having the second outer frame portion 132 having a thickness of 200 μm. Is formed. In this way, the micromirror element X1 is manufactured.

  According to such a method, it is possible to form a movable part and a two-stage comb-tooth structure that are thinner than the material substrate to be used, that is, the wafer. Therefore, the same effects as described above with respect to the first manufacturing method can be achieved by the fourth manufacturing method.

  FIG. 15 is a perspective view of a micromirror element X2 according to the second embodiment of the present invention. 16 is a cross-sectional view taken along line XVI-XVI in FIG. The micromirror element X2 includes a mirror forming part 110, an inner frame 120 surrounding the mirror forming part 110, an outer frame 130 ′ surrounding the inner frame 120, a pair of torsion bars 140 connecting the mirror forming part 110 and the inner frame 120, and an inner frame 120 A pair of torsion bars 150 connecting the outer frame 130 'is provided. The micromirror element X2 is different from the micromirror element X1 in the configuration of the outer frame. The configurations of the mirror forming portion 110, the inner frame 120, and the torsion bars 140, 150 of the micromirror element X2 are the same as those described above with respect to the micromirror element X1.

  As shown in FIG. 16, the outer frame 130 ′ has a laminated structure including a first outer frame portion 131 ′, a second outer frame portion 132, and an insulating layer 160 therebetween. The first outer frame portion 131 ′ and the second outer frame portion 132 are electrically separated by the insulating layer 160. The first outer frame portion 131 ′ protrudes upward from the mirror forming portion 110, which is a movable portion, and the inner frame main portion 121 of the inner frame 120, as shown well in FIG. 16. The configuration of the second outer frame portion 132 is the same as that described above with respect to the first embodiment.

  FIG. 17 shows a mode in which the micromirror element X2 is mounted on the wiring board 400 and covered with the transparent cover 401. The micromirror element X2 represents a cross section taken along line XVII-XVII in FIG. In the micromirror element X2, the outer frame 130 ′ is thicker than the movable part including the mirror forming part 110 and the inner frame 120. Specifically, the second outer frame portion 132 protrudes below the electrode base 122 and the comb electrodes 122 a and 122 b of the inner frame 120 and the comb electrodes 132 a and 132 b formed on the outer frame 130. ing. The second outer frame part 132 protrudes downward from the lowest position of the movable part during driving, for example, the lowest position of the electrode base 122 of the inner frame 120. Therefore, in a state where the wiring substrate 400 is bonded to the lower surface of the second outer frame portion 132, a space for operating the movable portion is secured, and the movable portion is prevented from coming into contact with the wiring substrate 400. The first outer frame portion 131 ′ protrudes upward from the mirror forming portion 110 and the comb-tooth electrodes 110 a and 110 b, the inner frame main portion 121 of the inner frame 120 and the comb-tooth electrodes 121 a and 121 b. The first outer frame portion 131 ′ protrudes upward from the highest reach position of the movable portion during driving, for example, the highest reach position of the comb-tooth electrodes 121 a and 121 b of the inner frame 120. Therefore, in a state where the transparent cover 401 is joined to the upper surface of the first outer frame portion 131 ′, a space for operating the movable portion is secured, and the movable portion is prevented from coming into contact with the transparent cover 401. As described above, in the micromirror element X2, the first outer frame portion 131 ′ and the second outer frame portion 132 protrude beyond the movable portion, and therefore the micromirror element X2 is mounted on the wiring board 400 or the transparent cover 401. Therefore, it is not necessary to interpose a spacer between the micromirror element X2 and the wiring board 400 or the transparent cover 401.

  18 to 20 show a method for manufacturing the micromirror element X2. This method is one method for manufacturing the above-described micromirror element X2 by micromachining technology. 18 to 20, as in FIGS. 6 to 8, the mirror forming portion M, the torsion bar T, the inner frame F <b> 1, the pair of comb-shaped electrodes E <b> 1 and E <b> 2, and the outer frame are formed by one modeled section. It represents the formation process of F2.

  In manufacturing the micromirror element X2, first, as shown in FIG. 18A, an SOI wafer 4 is prepared as a substrate. The SOI wafer 4 has a laminated structure including a first silicon layer 18, a second silicon layer 19, and an insulating layer 160 as an intermediate layer sandwiched between them. A torsion bar T is embedded in the first silicon layer 18 in advance. Specifically, a predetermined groove is formed in the first silicon layer 18, an oxide film is formed on the surface of the groove, and then the groove is filled with polysilicon, thereby torsion the first silicon layer 18. The bar T can be embedded and formed. The first silicon layer 18 is bonded to the second silicon layer 19 on which the insulating layer 160 is formed so that the torsion bar T is in contact with the insulating layer 160. In the present embodiment, the thickness of the first silicon layer 18 is 100 μm, the thickness of the second silicon layer 19 is 100 μm, and the thickness of the insulating layer 160 is 1 μm. The thickness of the torsion bar T is 5 μm. In the formation of the SOI wafer 4, the method for imparting conductivity to the silicon layer and the method for forming the insulating layer 160 are the same as those described above with respect to the first manufacturing method of the micromirror element X1.

  Next, as shown in FIG. 18B, an oxide film pattern 62 is formed on the first silicon layer 18 and an oxide film pattern 63 is formed on the second silicon layer 19. The oxide film pattern 62 is for masking a portion of the first silicon layer 18 that is processed into the mirror forming portion M, the inner frame F1, and the comb-tooth electrode E1. More specifically, the oxide film pattern 62 corresponds to the planar view form of the mirror forming portion 110, the inner frame main portion 121, the comb electrodes 110a and 110b, and the comb electrodes 121a and 121b shown in FIG. It is formed. The oxide film pattern 63 is for masking a portion of the second silicon layer 19 that is processed into the inner frame F1 and the comb electrode E2. More specifically, the oxide film pattern 63 is formed corresponding to the planar view form of the electrode base 122, the comb electrodes 122a and 122b, and the comb electrodes 132a and 132b shown in FIG.

Next, as shown in FIG. 18C, the third silicon layer 20 is directly bonded to the first silicon layer 18 of the SOI wafer 4, and the fourth silicon layer 21 is bonded to the second silicon layer 19. Join directly. Each of the third silicon layer 20 and the fourth silicon layer 21 is made of silicon imparted with conductivity by doping impurities and has a thickness of 100 μm. In addition, in the third silicon layer 20 and the fourth silicon layer 21, retreat portions are formed in advance by DRIE at locations corresponding to the oxide film patterns 62 and 63, respectively. In the present embodiment, the depth of the retracting portion is 5 μm. The bonding in this step is performed, for example, at a degree of vacuum of 10 ⁻⁴ Torr and a heating temperature of 1100 ° C. By this bonding, the third silicon layer 20 is integrated with the first silicon layer 18, and the fourth silicon layer 21 is integrated with the second silicon layer 19.

  Next, as shown in FIG. 19A, an oxide film pattern 64 is formed on the third silicon layer 20, and an oxide film pattern 65 is formed on the fourth silicon layer 21. The oxide film pattern 64 is for masking a portion to be processed into the outer frame F2 in the third silicon layer 20 and the first silicon layer 18. More specifically, the oxide film pattern 64 is formed corresponding to the planar view form of the first outer frame portion 131 ′ shown in FIG. 15. The oxide film pattern 65 is for masking a portion of the fourth silicon layer 21 that is processed into the outer frame F2. More specifically, the oxide film pattern 65 is formed corresponding to the planar view form of the second outer frame portion 132 shown in FIG.

  Next, as shown in FIG. 19B, the third silicon layer 20 is etched by DRIE using the oxide film pattern 64 as a mask until the oxide film pattern 62 is exposed. Subsequently, as shown in FIG. 19C, the first silicon layer 18 is etched by DRIE to the insulating layer 160 using the oxide film patterns 62 and 64 as a mask.

  Next, as shown in FIG. 20A, the fourth silicon layer 21 is etched by DRIE using the oxide film pattern 65 as a mask until the oxide film pattern 63 is exposed. Subsequently, as shown in FIG. 20B, the second silicon layer 19 is etched by DRIE until the insulating layer 160 is reached using the oxide film patterns 63 and 65 as a mask.

  Next, as shown in FIG. 20C, the exposed insulating layer 160 is removed by being immersed in an etching solution. At this time, the oxide film patterns 62 to 65 exposed on the element surface are also removed at the same time. As a result, the mirror forming portion M, the torsion bar T, the inner frame F1, the comb-tooth electrodes E1 and E2 are formed within 100 μm from the insulating layer 160, and the first outer frame portion 131 ′ and the second outer frame having a thickness of 200 μm are formed. An outer frame F2 having a frame portion 132 is formed. In this way, the micromirror element X2 is manufactured.

  According to such a method, the movable portion and the two-stage comb-tooth structure can be formed on a material substrate or wafer having a thickness greater than these. Therefore, the manufacturing method has the same effect as described above with respect to the first manufacturing method of the micromirror element X1. Prior to the step shown in FIG. 19B, the structure forming step for the silicon layer, which is a factor for reducing the strength of the wafer, is not performed. Therefore, before the step shown in FIG. 19B, the planar size of the wafer is not excessively suppressed.

  In any of the micromirror element manufacturing methods described above, the mirror surface 111 is formed on the mirror forming unit 110 before the portion to be processed into the mirror forming unit 110 is covered with the oxide film pattern by the CVD method. For example, the mirror surface 111 can be formed by sputtering Au or Cr on the silicon layer processed into the mirror forming portion 110.

  In addition, regarding the processing of the lower layer for the insulating layer 160 of the micromirror element X2, any of the lower layer processing methods described above with respect to the first to fourth manufacturing methods of the micromirror element X1 can be used instead of the above processing method. It may be adopted. Even with such a combination method, it is possible to manufacture the micromirror element X2 having the outer frame 130 'protruding upward and downward.

  As a summary of the above, the configurations of the present invention and variations thereof are listed below as supplementary notes.

(Supplementary Note 1) A movable part having a mirror part, which is integrally formed from a material substrate, a frame part, and a torsion bar connecting the frame part and the movable part,
The micromirror element, wherein the frame part has a thicker part than the movable part.
(Supplementary Note 2) A movable part, a frame part, and a torsion bar connecting the movable part and the frame part, which are integrally formed from a material substrate having a laminated structure including an intermediate layer and a silicon layer sandwiching the intermediate layer. Prepared,
The movable portion includes a first intermediate portion derived from the intermediate layer, a first structure in contact with the first intermediate portion, and a second structure in contact with the first intermediate portion on a side opposite to the first structure. A mirror portion is formed on the first structure,
The frame portion includes a second intermediate portion derived from the intermediate layer, a third structure in contact with the second intermediate portion on the same side as the first structure, and the third structure on the same side as the second structure. A fourth structure in contact with the intermediate portion,
The fourth structure body projects beyond the second structure body in the stacking direction of the stacked structure.
(Supplementary note 3) The micromirror element according to supplementary note 2, further comprising a wiring board joined to the fourth structure.
(Additional remark 4) The said 3rd structure is a micromirror element of Additional remark 2 which protrudes rather than the said 1st structure in the said lamination direction.
(Supplementary Note 5) A movable part, a frame part, and a torsion bar connecting the movable part and the frame part, which are integrally formed from a material substrate having a laminated structure including an intermediate layer and a silicon layer sandwiching the intermediate layer. Prepared,
The movable portion includes a first intermediate portion derived from the intermediate layer, a first structure in contact with the first intermediate portion, and a second structure in contact with the first intermediate portion on a side opposite to the first structure. A mirror portion is formed on the first structure,
The frame portion includes a second intermediate portion derived from the intermediate layer, a third structure in contact with the second intermediate portion on the same side as the first structure, and the third structure on the same side as the second structure. A fourth structure in contact with the intermediate portion,
The micromirror element, wherein the third structure protrudes beyond the first structure in the stacking direction of the stacked structure.
(Appendix 6) The micromirror element according to appendix 4 or 5, further comprising a transparent cover joined to the third structure.
(Supplementary Note 7) The movable portion includes a first comb electrode portion, and the frame portion is configured to displace the movable portion by generating an electrostatic force between the frame portion and the first comb electrode portion. The micromirror element according to any one of supplementary notes 1 to 6, having two comb electrode portions.
(Additional remark 8) The said 1st comb-tooth electrode part is formed in the said 1st structure, and the said 2nd comb-tooth electrode part is formed in the site | part which contact | connects the said 2nd intermediate part in the said 4th structure. The micromirror element according to appendix 7.
(Supplementary Note 9) The movable portion includes a relay frame connected to the frame portion via the torsion bar, a mirror forming portion separated from the relay frame, and a relay torsion bar connecting the relay frame and the mirror forming portion. And the relay torsion bar extends in a direction crossing the extending direction of the torsion bar. 9. The micromirror element according to any one of appendices 1 to 8.
(Additional remark 10) The said mirror formation part has a 3rd comb-tooth electrode part, and the said relay frame displaces the said mirror formation part by producing an electrostatic force between the said 3rd comb-tooth electrode part. The micromirror element according to appendix 9, having the fourth comb electrode portion.
(Additional remark 11) The said 3rd comb-tooth electrode part is formed in the said 1st structure, The said 4th comb-tooth electrode part is formed in the said 2nd structure, The micromirror element of Additional remark 10 .
(Additional remark 12) It is a method for manufacturing a micromirror element provided with a movable part, a frame part, and a torsion bar,
A second mask having a first mask pattern for masking a portion processed into at least a part of the frame portion and a portion for masking a portion processed into the movable portion with respect to the material substrate. Performing a first etching process in the thickness direction of the material substrate through a mask pattern;
Removing the second mask pattern;
Performing a second etching process on the material substrate through the first mask pattern. A method for manufacturing a micromirror element, comprising:
(Additional remark 13) The said 1st etching process is performed to the middle of the said thickness direction, and the said 2nd etching process is performed until it penetrates the said material board | substrate so that the said movable part may be formed at least. A manufacturing method of a mirror element.
(Additional remark 14) The said 1st etching process is performed until it penetrates the said material substrate, The said 2nd etching process is performed to the middle of the thickness direction of the said material substrate so that the said movable part may be formed at least. The manufacturing method of the micromirror element of description.
(Supplementary note 15) A method for manufacturing a micromirror device including a movable part, a frame part, and a torsion bar,
A portion to be processed into at least a part of the frame portion is masked with respect to the first silicon layer in the material substrate having a laminated structure including the first silicon layer, the second silicon layer, and an intermediate layer therebetween. Performing a first etching process through a first mask pattern for performing a second mask pattern having a portion for masking a portion to be processed into the movable portion;
Removing the second mask pattern;
Performing a second etching process on the first silicon layer through the first mask pattern. A method of manufacturing a micromirror element, comprising:
(Supplementary note 16) The method for manufacturing a micromirror element according to supplementary note 15, wherein the first etching process is performed halfway in a thickness direction of the first silicon layer, and the second etching process is performed until the intermediate layer is reached. .
(Supplementary note 17) The method of manufacturing a micromirror element according to supplementary note 15, wherein the first etching process is performed up to the intermediate layer, and the second etching process is performed halfway in a thickness direction of the first silicon layer. .
(Additional remark 18) The said 2nd mask pattern has a site | part for masking the location further processed into the comb-tooth electrode part formed in the said frame part, It is any one of Additional remarks 15 to 17 Of manufacturing a micromirror element.
(Supplementary note 19) A method for manufacturing a micromirror device including a movable part, a frame part, and a torsion bar,
For masking a portion to be processed into the movable portion with respect to the first silicon layer in the first material substrate having a stacked structure of a first silicon layer, a second silicon layer, and an intermediate layer therebetween. Forming a first mask pattern having a portion;
Bonding a third silicon layer to a surface of the first silicon layer on which the first mask pattern is formed, thereby producing a second material substrate in which the first mask pattern is built;
Performing a first etching process on the third silicon layer through the second mask pattern having a portion for masking at least a part of the frame portion up to the first silicon layer;
Performing a second etching process on the first silicon layer exposed by the first etching process up to the intermediate layer through the first mask pattern. A manufacturing method of a mirror element.
(Additional remark 20) The said 1st mask pattern has a site | part for masking the location further processed into the comb-tooth electrode part formed in the said frame part, The manufacturing method of the micromirror element of Additional remark 19 .
(Supplementary note 21) A method for manufacturing a micromirror device including a movable part, a frame part, and a torsion bar,
For the first material substrate made of the first silicon layer, the comb teeth are provided via a first mask pattern having a portion for masking a portion to be processed into the comb electrode portion formed in the frame portion. Performing a first etching process to a depth corresponding to the thickness of the electrode part;
Producing a second material substrate having a laminated structure of the first material substrate, an intermediate layer in contact with the etched surface of the first material substrate, and a second silicon layer in contact with the intermediate layer;
The first silicon layer is processed into a second mask pattern having a portion for masking a portion to be processed into at least a part of the frame portion, and the movable portion and the comb electrode portion. Performing a second etching process halfway through the first silicon layer through a third mask pattern having a portion for masking a portion to be masked;
Removing the third mask pattern;
Performing a third etching process on the first silicon layer through the second mask pattern to reach the comb electrode part. A method for manufacturing a micromirror element, comprising:
(Supplementary note 22) A method for manufacturing a micromirror device including a movable part, a frame part, and a torsion bar,
A first silicon layer in a first material substrate having a first silicon layer, a second silicon layer, an intermediate layer between them, and a torsion bar built into the first silicon layer in contact with the intermediate layer In contrast, a step of forming a first mask pattern having a portion for masking a portion to be processed into the movable portion;
Bonding a third silicon layer to a surface of the first silicon layer on which the first mask pattern is formed, thereby producing a second material substrate in which the first mask pattern is built;
A first etching process is performed on the third silicon layer through a second mask pattern for masking a portion to be processed into at least a part of the frame portion until the first mask pattern is exposed. Process,
Performing a second etching process on the first silicon layer through the first mask pattern to reach the intermediate layer. A method of manufacturing a micromirror element, comprising:

1 is a perspective view of a micromirror element according to a first embodiment of the present invention. It is sectional drawing along line II-II of the micromirror element shown in FIG. It is sectional drawing along line III-III of the micromirror element shown in FIG. It is sectional drawing along line IV-IV of the micromirror element shown in FIG. The mode at the time of the drive of the micromirror element shown in FIG. 1 is represented. It is sectional drawing showing the one part process in the manufacturing method of the micromirror element shown in FIG. The process following FIG. 6 is represented. The process following FIG. 7 is represented. It is sectional drawing showing the one part process in the other manufacturing method of the micromirror element shown in FIG. The process following FIG. 9 is represented. It is sectional drawing showing the one part process in the other manufacturing method of the micromirror element shown in FIG. The process following FIG. 11 is represented. It is sectional drawing showing the one part process in the other manufacturing method of the micromirror element shown in FIG. The process following FIG. 13 is represented. It is a perspective view of the micromirror element which concerns on the 2nd Embodiment of this invention. FIG. 16 is a cross-sectional view taken along line XVI-XVI in FIG. 15. 15 shows a mode in which the micromirror element shown in FIG. 15 is mounted on a wiring board and a transparent cover is joined. FIG. 16 is a cross-sectional view illustrating a part of the process in the method for manufacturing the micromirror element illustrated in FIG. 15. The process following FIG. 18 is represented. The process following FIG. 19 is represented. It is a schematic block diagram of an example of an optical switching apparatus. It is a schematic block diagram of the other example of an optical switching apparatus. It is a partial omission perspective view of the conventional comb electrode type micromirror element. It is a fragmentary perspective view showing orientation of a set of comb-tooth electrodes. The manufacturing method of the micromirror element shown in FIG. 23 is represented. The mode at the time of the drive of the micromirror element shown in FIG. 23 is represented.

Explanation of symbols

X1, X2 Micromirror element 110 Mirror forming part 110a, 110b First comb electrode 120 Inner frame 121 Inner frame main part 121a, 121b Third comb electrode 122 Electrode base 122a, 122b Second comb electrode 130, 130 ' Outer frame 131, 131 ′ First outer frame part 132 Second outer frame part 132a, 132b Fourth comb electrode 140, 150 Torsion bar 160 Insulating layer M Mirror forming part T Torsion bar E1, E2 Comb electrode F1 Inner frame F2 Outside frame

Claims (1)

A method for manufacturing a micromirror device comprising a movable part, a frame part, and a torsion bar,
For the first layer in the first material substrate having the first layer, the second layer, the intermediate layer between them, and the torsion bar built in on the first layer side in contact with the intermediate layer, Forming a first mask pattern having a portion for masking a portion to be processed into the movable portion;
Forming a second material substrate having the first mask pattern built therein by bonding a third layer to the surface of the first layer on which the first mask pattern is formed;
Performing a first etching process on the third layer through a second mask pattern for masking a portion to be processed into at least a part of the frame portion until the first mask pattern is exposed. When,
Performing a second etching process on the first layer up to the intermediate layer through the first mask pattern.

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