JP2011112806A - Mems optical scanner and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a micro electromechanical system (MEMS) optical scanner which is inexpensive, has high reliability and suppresses unnecessary reflection of light; and to provide a method of manufacturing the MEMS optical scanner. <P>SOLUTION: The MEMS optical scanner includes: a mirror forming substrate 1 which is formed by using a silicon-on-insulator (SOI) substrate (semiconductor substrate) 100 and has an outside frame part 10, a movable part 20 provided with a mirror face 21 and a pair of torsion spring parts 30, 30; a first cover substrate 2 which is formed by using a first glass substrate 200 and connected to one surface side of the mirror forming substrate 1; and a second cover substrate 3 connected to the other surface side of the mirror forming substrate 1. The first cover substrate 2 and the second cover substrate 3 are formed in the same overall dimensions as the overall dimensions of the mirror forming substrate 1, and the first cover substrate 2 has, on the outer surface side opposite to the mirror forming substrate 1, a fine cyclic structure 6 which is formed of a translucent resin or a low melting point glass and suppresses light reflection. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a MEMS optical scanner and a manufacturing method thereof.

  In recent years, as a kind of MEMS (micro electro mechanical systems) device formed using micromachining technology or the like, a movable portion formed using micromachining technology or the like and provided with a mirror surface for reflecting light; A MEMS optical scanner that includes a driving unit that drives a movable portion and scans light incident on a mirror surface has been researched and developed in various places (for example, see Patent Document 1). Note that this type of MEMS optical scanner is considered to be applied to various optical devices such as a laser projector, a laser beam printer, a barcode reader, an endoscope, and a distance image sensor.

Here, in the above-mentioned Patent Document 1, as shown in FIG. 8, a first silicon substrate 101a ′ and a second silicon substrate 101b ′ are bonded as semiconductor substrates via an insulating layer (SiO ₂ layer) 101c ′. A mirror-formed substrate 1 ′ formed using a SOI (Silicon on Insulator) substrate 100 ′ and having a mirror surface (not shown) on one surface side, and a mirror formed using a first glass substrate 200 ′. A first cover substrate 2 ′ bonded to the one surface side of the formation substrate 1 ′ and a second glass substrate 300 ′ formed using the second glass substrate 300 ′ and bonded to the other surface side of the mirror formation substrate 1 ′. A MEMS optical scanner including a cover substrate 3 ′ has been proposed.

  The mirror forming substrate 1 ′ includes a rectangular frame-shaped outer frame portion 10 ′, a rectangular plate-shaped movable portion 20 ′ provided inside the outer frame portion 10 ′ and provided with the mirror surface, and an outer frame portion. A pair of torsion springs 30 'and 30' are arranged so as to sandwich the movable part 20 'inside 10' and connect the outer frame part 10 'and the movable part 20' to allow torsional deformation. Further, the mirror forming substrate 1 ′ includes comb-shaped movable electrodes 22 ′ and 22 ′ formed on both sides in a direction orthogonal to a direction connecting the pair of torsion spring portions 30 ′ and 30 ′ in the movable portion 20 ′, and an outer side. Comb-shaped fixed electrodes 12 ′, 12 ′ having a plurality of fixed comb teeth 12b ′, 12b ′ opposed to the plurality of movable comb teeth 22b ′, 22b ′ of the movable electrode 22 ′ formed on the frame portion 10 ′; And an electrostatic drive means for driving the movable portion 20 ′ by electrostatic force. In the above-described SOI substrate 100 ′, the thickness of the second silicon substrate 101 b ′ is about 500 μm, and the thickness of the first silicon substrate 101 a ′ is 100 μm or less.

  Further, in the MEMS optical scanner having the configuration shown in FIG. 8, the second cover substrate 3 ′ secures a displacement space of the movable portion 20 ′ on the surface of the second glass substrate 300 ′ on the mirror forming substrate 1 ′ side. The displacement space forming recess 301 ′ is formed, and the airtight space surrounded by the first cover substrate 2 ′, the outer frame portion 10 ′, and the second cover substrate 3 ′ is evacuated. It is possible to secure a necessary deflection angle while reducing the voltage.

  Incidentally, in the MEMS optical scanner having the configuration shown in FIG. 8, the light is emitted from a separate light source (for example, a laser light source) and is incident on the outer surface of the first cover substrate 2 ′ opposite to the mirror forming substrate 1 ′ side. Of the received light, the first light transmitted through the first cover substrate 2 ′, reflected by the mirror surface of the mirror forming substrate 1 ′, and emitted from the outer surface of the first cover substrate 2 ′; The traveling direction with the unnecessary light reflected by the outer surface of the cover substrate 2 'may be aligned. For example, when applied to a laser projector, an unnecessary bright spot is generated on the screen.

  Further, conventionally, in the field of optical elements and the like, there has been known a technique for suppressing light reflection (Fresnel reflection) and increasing transmittance by providing a fine periodic structure having a period smaller than the wavelength of incident light. (For example, see Patent Documents 2 and 3).

JP 2004-109651 A JP 2004-219626 A JP 2002-182003 A

  Therefore, in the MEMS optical scanner having the configuration shown in FIG. 8, a fine concavo-convex structure is formed on the surface side of the first glass substrate 200 ′ opposite to the mirror forming substrate 1 ′ as the first cover substrate 2 ′. Although it is conceivable to use a substrate, the fine periodic structure is damaged due to the load when the mirror forming substrate 1 ′ and the first cover substrate 2 ′ are bonded by anodic bonding or the like, and the optical characteristics (antireflection performance) ) Is reduced, resulting in an increase in cost due to a decrease in yield. Further, when dicing is performed after joining the mirror forming substrate 1 ′ and the first cover substrate 2 ′, fine powder (silicon or glass powder) adheres to the fine periodic structure and the fine periodic structure It is considered that the optical characteristics are affected.

  In addition, after joining the mirror forming substrate 1 ′ and the first cover substrate 2 ′, the torsion spring portions 30 ′, 30 ′, the fixed comb teeth 12b ′, and the movable comb by visual inspection or visual inspection using an optical microscope or the like. Although it is conceivable to inspect whether the tooth piece 22b ′ or the like is not bent, adhesion of foreign matter, sticking, etc., in the appearance inspection by optical microscope or visual inspection, sufficient inspection cannot be performed due to the fine periodic structure, Even when a defective product is generated in the joining process, the occurrence of a defect is not known until it is incorporated into a system and operated, resulting in an increase in cost. The material of the first cover substrate 2 ′ includes bonding properties with the mirror forming substrate 1 ′ for hermetic sealing, a difference in linear expansion coefficient with silicon that is the main material of the SOI substrate 100 ′, and a mirror forming substrate. A glass substrate is employed in consideration of the translucency of the first cover substrate 2 ′ of 1 ′.

  The present invention has been made in view of the above-described reasons, and an object of the present invention is to provide a MEMS optical scanner that is low in cost, highly reliable, and capable of suppressing unnecessary reflection of light, and a method for manufacturing the same. It is in.

  The invention of claim 1 is formed by using a semiconductor substrate, and is arranged in such a manner that the outer frame part, the movable part arranged inside the outer frame part and provided with a mirror surface, and the movable part sandwiched inside the outer frame part. A mirror forming substrate having a pair of torsion springs that can be deformed by connecting the outer frame portion and the movable portion, and a glass substrate bonded to one surface side of the mirror forming substrate on which the mirror surface is provided. A MEMS optical scanner comprising a first cover substrate, a second cover substrate joined to the other surface side of the mirror forming substrate, and a driving means for driving the movable portion, wherein the first cover substrate and the second cover substrate The cover substrate is formed with the same outer dimensions as the mirror formation substrate, and is formed on the outer surface side of the first cover substrate opposite to the mirror formation substrate with a light-transmitting resin or low-melting glass. And having a suppressing fine periodic structure reflection.

  According to the present invention, the first cover substrate and the second cover substrate are formed to have the same outer dimensions as the mirror formation substrate, and the first cover substrate has a translucent property on the outer surface side opposite to the mirror formation substrate. Since it has a fine periodic structure that is made of resin or low-melting-point glass and suppresses reflection of light, a mirror is formed on the first cover substrate after visual inspection is performed after the mirror-formed substrate and each cover substrate are joined. It is possible to adopt a manufacturing process in which a fine periodic structure is formed by applying a translucent resin or low melting point glass on the outer surface side opposite to the substrate and then forming, and then dicing. A manufacturing process is adopted in which the first glass substrate that forms the basis of the cover substrate is processed to form a fine periodic structure, and then the first cover substrate is bonded to the mirror forming substrate. As compared to the case so that a, it is possible to reliable low-cost high, to suppress unwanted reflection of light.

  According to a second aspect of the present invention, in the first aspect of the invention, the mirror forming substrate includes a plurality of pads formed on the outer frame portion on the one surface side and connected to the driving unit, and the first cover. The substrate is characterized in that a plurality of through holes are formed to expose each pad over the entire circumference.

  According to the present invention, the first cover substrate does not overlap with each pad, and a part of each pad does not intervene between the first cover substrate and the outer frame portion. Since it is possible to prevent the bonding between the first cover substrate and the outer frame portion of the mirror forming substrate from being disturbed by each pad, the bonding property and the airtightness are impaired due to the influence of the thickness of each pad. It is possible to reduce the cost by improving the yield without increasing the width of the outer frame, which causes the outer dimensions of the mirror-forming substrate to be increased. Deterioration can be suppressed.

  A third aspect of the present invention is the method of manufacturing the MEMS optical scanner according to the first or second aspect, wherein a first wafer on which a plurality of mirror-formed substrates are formed and a plurality of first cover substrates are formed. After forming a wafer level package structure in which a second wafer and a third wafer on which a plurality of second cover substrates are formed are joined, forming each mirror on each first cover substrate of the wafer level package structure A fine periodic structure is formed by applying a light-transmitting resin or low-melting glass on the outer surface opposite to the substrate and then forming it, and then dividing the wafer-level package structure into the outer size of the mirror forming substrate. A method for manufacturing a MEMS optical scanner.

  According to the present invention, since the wafer level package structure is formed and each fine periodic structure is formed and then divided, it is possible to reduce the size, and after the wafer level package structure is formed, an optical microscope or visual inspection is performed. Can be performed, and after the appearance inspection, a plurality of fine periodic structures can be simultaneously formed on the wafer-level package structure, so that it is low-cost, highly reliable, and can suppress unnecessary reflection of light. A simple MEMS optical scanner can be provided.

  The invention of claim 1 is advantageous in that it is low in cost and high in reliability and can suppress unnecessary reflection of light.

  According to the invention of claim 3, there is an effect that it is possible to provide a MEMS optical scanner that is low in cost, high in reliability, and capable of suppressing unnecessary reflection of light.

1 shows a MEMS optical scanner according to Embodiment 1, wherein (a) is a schematic plan view, (b) is a schematic cross-sectional view taken along line A-A ′ of (a), and (c) is an enlarged plan view of a main part. It is a schematic exploded perspective view of a MEMS optical scanner same as the above. It is main process sectional drawing for demonstrating the manufacturing method of a MEMS optical scanner same as the above. FIG. 5 is a schematic exploded perspective view of a MEMS optical scanner according to a second embodiment. It is a schematic perspective view of a MEMS optical scanner same as the above. It is main process sectional drawing for demonstrating the manufacturing method of a MEMS optical scanner same as the above. It is a schematic sectional drawing of the other structural example of a MEMS optical scanner same as the above. The MEMS optical scanner of a prior art example is shown, (a) is a schematic exploded perspective view, (b) is a schematic sectional drawing.

(Embodiment 1)
Hereinafter, the MEMS optical scanner of the present embodiment will be described with reference to FIGS. 1 and 2.

  The MEMS optical scanner according to the present embodiment is formed using an SOI substrate 100 which is a semiconductor substrate, and has an outer frame portion (fixed frame portion) 10 having an outer peripheral shape of a rectangular shape (here, a rectangular frame shape) and an outer side. The movable portion 20 having a rectangular shape in plan view and provided with a mirror surface 21 having a rectangular shape in plan view disposed inside the frame portion 10 and the outer frame portion 10 disposed so as to sandwich the movable portion 20 inside the outer frame portion 10. The mirror forming substrate 1 having a pair of torsion spring portions 30, 30 that can be connected to the movable portion 20 and capable of torsional deformation, and a mirror surface 21 is provided on the mirror forming substrate 1 formed using the first glass substrate 200. The first cover substrate 2 bonded to the one surface side and the second cover substrate 3 formed using the second glass substrate 300 and bonded to the other surface side of the mirror forming substrate 1 are provided. There.

  Here, the outer peripheral shape of the mirror forming substrate 1 and each of the cover substrates 2 and 3 is a rectangular shape, and each of the cover substrates 2 and 3 is formed to have the same outer dimensions as the mirror forming substrate 1.

In the mirror forming substrate 1 described above, the insulating layer (SiO ₂ layer) 100c is interposed between the conductive first silicon layer (active layer) 100a and the second silicon layer (silicon substrate) 100b. The SOI substrate 100 is formed by processing using a bulk micromachining technique or the like. The first cover substrate 2 is formed by using a first glass substrate 200 formed by stacking and joining two glass plates each made of Pyrex (registered trademark) glass or the like in the thickness direction. The second cover substrate 3 is formed by processing a second glass substrate 300 made of Pyrex (registered trademark) glass or the like. Note that in the SOI substrate 100, the thickness of the first silicon layer 100a is set to 30 μm, the thickness of the second silicon layer 100b is set to 400 μm, and the thicknesses of the first glass substrate 200 and the second glass substrate 300 are set. Is set in the range of about 0.5 mm to 1.5 mm, but these numerical values are examples and are not particularly limited. The surface of the first silicon layer 10c, which is one surface of the SOI substrate 100 as a semiconductor substrate, is a (100) plane.

  The outer frame portion 10 of the mirror forming substrate 1 is formed using each of the first silicon layer 100 a, the insulating layer 100 c, and the second silicon layer 100 b of the SOI substrate 100. The portion formed by the silicon layer 100a is joined to the entire periphery of the first cover substrate 2, and the portion formed by the second silicon layer 100c in the outer frame portion 10 is the second cover. Two pads 13, 13 that are joined to the outer peripheral portion of the substrate 3 over the entire periphery and are electrically connected to the outer frame portion 10 on the one surface side to a driving means that drives the movable portion 20 described later. Is formed. Each of the pads 13 and 13 has a circular shape in plan view, and is composed of a first metal film (for example, an Al—Si film). In the present embodiment, the thickness of each of the pads 13 and 13 is set to 500 nm, but this numerical value is an example and is not particularly limited.

  Further, the movable portion 20 and the torsion spring portions 30, 30 of the mirror forming substrate 1 are formed using the first silicon layer 100 a of the SOI substrate 100 and are sufficiently thinner than the outer frame portion 10. Yes. The mirror surface 21 provided on the movable portion 20 reflects light from a light source (for example, a laser light source) and is formed on a portion of the movable portion 20 formed by the first silicon layer 100a. The surface of the reflective film 21a made of the second metal film (for example, an Al—Si film) is formed. In the present embodiment, the thickness of the reflective film 21a is set to 500 nm, but this numerical value is an example and is not particularly limited.

  In the following, as shown in the lower left of each of FIGS. 1A, 1B, and 1C, the direction perpendicular to the parallel arrangement direction of the pair of torsion spring portions 30, 30 in plan view is the x-axis direction, and the pair of The parallel arrangement direction of the torsion springs 30 and 30 will be described as the y-axis direction, and the direction orthogonal to the x-axis direction and the y-axis direction will be described as the z-axis direction.

  In the above-described mirror forming substrate 1, a pair of torsion spring portions 30, 30 are arranged in parallel in the y-axis direction, and the movable portion 20 is around the pair of torsion spring portions 30, 30 with respect to the outer frame portion 10. It can be displaced (it can be rotated around the axis in the y-axis direction). That is, the pair of torsion spring portions 30, 30 connects the outer frame portion 10 and the movable portion 20 so that the movable portion 20 can swing with respect to the outer frame portion 10. In other words, the movable part 20 arranged inside the outer frame part 10 swings to the outer frame part 10 via two torsion spring parts 30 and 30 that are continuously and integrally extended in two opposite directions from the movable part 20. It is supported freely. Here, the pair of torsion spring portions 30 and 30 are formed such that a straight line connecting the center lines along the y-axis direction passes through the center of gravity of the movable portion 20 in plan view. Each of the torsion spring portions 30 and 30 has a thickness dimension (dimension in the z-axis direction) set to 30 μm and a width dimension (dimension in the x-axis direction) set to 5 μm, but these numerical values are examples. There is no particular limitation. Moreover, the planar view shape of the movable part 20 and the mirror surface 21 is not limited to a rectangular shape, and may be a circular shape, for example. Further, the inner peripheral shape of the outer frame portion 10 is not limited to a rectangular shape, and may be a circular shape, for example.

  The mirror forming substrate 1 described above has both sides in a direction (that is, the x-axis direction) orthogonal to the direction connecting the pair of torsion spring portions 30 and 30 (the direction in which the pair of torsion spring portions 30 and 30 are juxtaposed) in the movable portion 20. A comb-shaped movable electrode 22 formed on the outer frame portion 10 and a comb-shaped fixed electrode 12 having a plurality of fixed comb-tooth pieces 12 b that are formed on the outer frame portion 10 and face the plurality of movable comb-tooth pieces 22 b of the movable electrode 22. An electrostatic drive type driving means configured to drive the movable portion 20 by electrostatic force is provided. In the present embodiment, the driving means drives the movable portion 20 by electrostatic force, but is not limited to the electrostatic drive type that drives the movable portion 20 by electrostatic force, and drives the movable portion 20 by electromagnetic force. It may be an electromagnetic driving type, or a piezoelectric driving type in which the movable portion 20 is driven by a piezoelectric element.

  The above-described fixed electrodes 12 and 12 have a comb shape in plan view, and a portion where the comb bone portion 12a is formed by the first silicon layer 100a in the frame piece portion along the y-axis direction in the outer frame portion 10. The surface of the comb bone portion 12a facing the movable portion 20 (the inner side surface along the y-axis direction in the outer frame portion 10) is made of a portion of the first silicon layer 100a. A large number of fixed comb teeth 12b are arranged along the direction in which the pair of torsion spring portions 30 and 30 are arranged side by side. On the other hand, the movable electrodes 22, 22 are the first silicon on the side surfaces (side surfaces along the y-axis direction in the movable portion 20) of the comb portions 22 a, 22 a on the comb bone portion 12 a side of the fixed electrode 12 in the movable portion 20. A large number of movable comb teeth 22b that are constituted by a part of the layer 100a and that face the fixed comb teeth 12b, respectively, are arranged in the above-mentioned parallel direction. Here, in the comb-shaped fixed electrode 12 and the comb-shaped movable electrode 22, the comb bone portions 12 a and 22 a face each other, and the fixed comb teeth 12 b of the fixed electrode 12 enter the comb groove of the movable electrode 22. The fixed comb tooth piece 12b and the movable comb tooth piece 22b are separated from each other in the y-axis direction, and a voltage is applied between the fixed electrode 12 and the movable electrode 22, whereby the fixed electrode 12 and the movable electrode tooth 22b are movable. An electrostatic force acting in a direction attracting each other is generated between the electrodes 22. In addition, what is necessary is just to set the clearance gap between the fixed comb-tooth piece 12b and the movable comb-tooth piece 22b in a y-axis direction suitably in the range of about 2 micrometers-5 micrometers, for example.

  One pad 13 (the right pad 13b in FIG. 2) is electrically connected to the fixed electrodes 12 and 12 at a portion formed by the first silicon layer 100a in the outer frame portion 10 of the mirror forming substrate 1. In addition, the other pad 13 (the left pad 13a in FIG. 2) is electrically connected to the movable electrodes 22 and 22, and the fixed electrodes 12 and 12 and the movable electrodes 22 and 22 are electrically insulated. The plurality of slits 10a, 10a, 10a are formed to a depth reaching the insulating layer 100c. Here, in this embodiment, each slit 10a, 10a, 10a is made into a trench, and the plan view shape of each slit 10a, 10a, 10a is made into the shape which is not open | released by the outer surface side of the outer side frame part 10, By this While adopting the structure in which the slits 10a, 10a, 10a are formed in the portion 10, it is possible to prevent the bonding property between the outer frame portion 10 and the first cover substrate 2 from being lowered, and the outer frame portion 10 and each cover substrate. The airtightness of the space surrounded by 2 and 3 is secured.

  Here, the portion formed by the first silicon layer 100a in the outer frame portion 10 is connected to the outer surface of the movable portion 20 in an integrated manner by forming the slits 10a, 10a, 10a described above. In addition, the torsion springs 30 and 30 have a rectangular island formed with two anchor portions 11a and 11b in which the other end portions of the torsion spring portions 30 and 30 are continuously and integrally connected to the inner surface, and one anchor portion 11aa and one pad 13a. The first conductive structure 11a composed of the part 11c and the L-shaped conductive part 11ad in plan view connecting the one anchor part 11ab and the island part 11ac is the movable electrodes 22, 22 of the movable part 20. And the second conductive structure 11b formed of the remaining portion and having the other pad 13b formed is at the same potential as the fixed electrodes 12 and 12.

  As described above, the first cover substrate 2 uses the first glass substrate 200 and penetrates in the thickness direction of the first glass substrate 200 to expose the pads 13 and 13 over the entire circumference. Two through holes 202, 202 are formed. Here, each through-hole 202, 202 of the first glass substrate 200 is formed in a tapered shape in which the opening area gradually increases as the distance from the mirror forming substrate 1 increases. Here, each of the through holes 202 and 202 of the first cover substrate 2 is formed by the sand blasting method. However, the present invention is not limited to the sand blasting method, and depending on the shape of the through holes 202 and 202, a drilling method or etching is performed. You may employ | adopt a law etc. suitably.

  In the MEMS optical scanner of the present embodiment, the planar view shape of each pad 13, 13 is a circular shape having a diameter of 0.5 mm, and the opening diameter of each through-hole 202, 202 on the first mirror forming substrate 1 side is the same. Although it is made larger than 0.5 mm, the diameter of each pad 13 and 13 is not specifically limited, Moreover, it does not necessarily need to be circular shape, For example, although it may be square shape, a through-hole In order to reduce the opening diameters of 202 and 202, a circular shape is preferable to a square shape.

  Here, when a part of each of the pads 13 and 13 overlaps the first cover substrate 2 in the thickness direction, the bondability and the airtightness are impaired due to the thickness of the pads 13 and 13, and the yield during manufacturing is reduced. In addition, there is a concern that the stability of the operation and the stability over time may be deteriorated, and the width dimension of the outer frame portion 10 (the distance between the outer surface and the inner surface of the outer frame portion 10) needs to be increased. It is conceivable that downsizing of the MEMS optical scanner is limited.

  On the other hand, in the MEMS optical scanner of the present embodiment, the first cover substrate 2 does not overlap the pads 13 and 13, and the pads 13 and 13 are disposed between the first cover substrate 2 and the outer frame portion 10. Since a part of 13 does not intervene, it is possible to prevent the bonding between the first cover substrate 2 and the outer frame portion 10 of the mirror forming substrate 1 from being obstructed by the pads 13, 13. It is possible to prevent the bondability and airtightness from being impaired due to the influence of the thicknesses 13 and 13, and it is possible to reduce the cost by improving the yield without increasing the width dimension of the outer frame portion 10, and the operational stability. And deterioration of stability over time can be suppressed.

  Further, in the MEMS optical scanner of the present embodiment, the movable portion 20 is achieved while reducing power consumption by making the airtight space surrounded by the outer frame portion 10 of the mirror forming substrate 1 and the cover substrates 2 and 3 vacuum. Therefore, the airtight space is evacuated and the surface of the second cover substrate 3 facing the mirror forming substrate 1 is more than the portion bonded to the outer frame portion 10. A non-evaporable getter (not shown) is provided at an appropriate site inside. The non-evaporable getter may be formed of, for example, an alloy containing Zr as a main component or an alloy containing Ti as a main component. Further, in the MEMS optical scanner of the present embodiment, an airtight space surrounded by the outer frame portion 10, the first cover substrate 2 and the second cover substrate 3 is an inert gas atmosphere (for example, a dry nitrogen gas atmosphere). In both the vacuum (vacuum atmosphere) and the inert gas atmosphere, the mirror surface 21 can be prevented from being oxidized. It is possible to suppress changes in reflection characteristics with time.

  Incidentally, the first glass substrate 200 has a displacement space forming recess (hereinafter referred to as a first displacement space forming recess) 201 that secures a displacement space of the movable portion 20 on the surface facing the mirror forming substrate 1. However, it is formed by joining two glass plates as described above, and the first glass plate (hereinafter referred to as the first glass plate) disposed on the side close to the mirror forming substrate 1 is used. A glass plate (hereinafter referred to as a second glass plate) that is formed on the side far from the mirror forming substrate 1 while forming an opening portion penetrating in the thickness direction in a portion corresponding to the displacement space forming recess 201 is formed into a flat plate shape. Therefore, compared to the case where the first displacement space forming recess 201 is formed on the glass substrate by sandblasting or the like using a single glass substrate, the inner bottom surface of the first displacement space forming recess 201 is smoother. It can be a surface, it can be reduced diffuse reflection at the inner bottom surface of the first displacement space forming recess 201, light diffusion, and the like scattering loss.

  The second cover substrate 3 is formed by using the second glass substrate 300, and both surfaces in the thickness direction are planar, but the thickness of the movable portion 20 and the first of the SOI substrate 100 that constitutes the semiconductor substrate. Depending on the thickness of the second silicon layer 100b and the like, a recess for securing a displacement space of the movable portion 20 on one surface of the second glass substrate 300 on the mirror forming substrate 1 side (hereinafter referred to as a second displacement space formation). May be formed). Here, when the second displacement space forming recess is formed on the one surface of the second glass substrate 300, for example, it may be formed by a sandblast method or the like. Since the second cover substrate 3 does not need to transmit light, the second cover substrate 3 is not limited to the second glass substrate 300 and may be formed using, for example, a silicon substrate. In this case, the second displacement space is used. The formation recess may be formed using a photolithography technique and an etching technique.

  In addition, as a glass material of each of the glass substrates 200 and 300 described above, Pyrex (registered trademark) which is a borosilicate glass is adopted, but not limited to a borosilicate glass, for example, soda lime glass, non-alkali glass, Quartz glass or the like may be employed. In this embodiment, the thickness of each cover substrate 2 and 3 is set in the range of about 0.5 mm to 1.5 mm, and the depth of the first displacement space forming recess 201 is set to about 0.3 mm. However, these numerical values are examples and are not particularly limited.

  Next, the operation of the MEMS optical scanner of this embodiment will be briefly described.

  In the MEMS optical scanner of the present embodiment, the movable electrode 22 is fixed by applying a pulse voltage for driving the movable portion 20 between the movable electrode 22 and the fixed electrode 12 facing each other through the pair of pads 13 and 13. An electrostatic force is generated between the electrodes 12, and the movable part 20 rotates about the axis in the y-axis direction. Thus, in the MEMS optical scanner of this embodiment, by applying a pulse voltage having a predetermined drive frequency between the movable electrode 22 and the fixed electrode 12, an electrostatic force can be periodically generated, and the movable unit 20 is It can be swung.

  Here, the above-mentioned movable part 20 is not in a horizontal posture (attitude parallel to the xy plane) and is tilted slightly though it is stationary due to internal stress. For example, the movable electrode 22 is fixed. When a pulse voltage is applied between the electrodes 12, a driving force in a direction substantially perpendicular to the movable portion 20 (z-axis direction) is applied even from a stationary state, so that the movable portion 20 has a pair of torsion spring portions 30, The pair of torsion springs 30 and 30 are rotated while twisting about 30 as a rotation axis. Then, when the driving force between the movable electrode 22 and the fixed electrode 12 is released when the movable comb tooth piece 22b and the fixed comb tooth piece 12b are in a posture that completely overlaps, the movable portion 20 has an inertial force. Thus, the pair of torsion springs 30 and 30 continue to rotate while twisting. Then, when the inertial force in the rotational direction of the movable portion 20 and the restoring force of the pair of torsion spring portions 30 and 30 become equal, the rotation of the movable portion 20 in the rotational direction stops. At this time, when an electrostatic force is generated again by applying a pulse voltage between the movable electrode 22 and the fixed electrode 12, the movable portion 20 is caused by the restoring force of the pair of torsion spring portions 30, 30 and the movable electrode 22 and the fixed electrode 12. By the driving force of the configured driving means, the rotation in the opposite direction is started. The movable portion 20 repeats the rotation by the driving force of the driving means and the restoring force of the pair of torsion spring portions 30 and 30, and swings about the pair of torsion spring portions 30 and 30 as the rotation shaft.

  In the MEMS optical scanner of this embodiment, the movable part 20 is applied by applying a pulse voltage having a frequency approximately twice the resonance frequency of the vibration system constituted by the movable part 20 and the pair of torsion spring parts 30 and 30. Driven with a resonance phenomenon, the mechanical deflection angle (tilt with respect to a horizontal plane parallel to the xy plane) increases. The application form and frequency of the voltage (drive voltage) between the movable electrode 22 and the fixed electrode 12 are not particularly limited. For example, the voltage applied between the movable electrode 22 and the fixed electrode 12 may be a sine wave voltage. Good.

  By the way, the MEMS optical scanner of the present embodiment has a translucent resin (for example, silicone resin, epoxy resin, acrylic resin, polycarbonate resin, etc.) on the outer surface side of the first cover substrate 2 opposite to the mirror forming substrate 1. Or it has the fine periodic structure 6 which is formed with low melting glass and suppresses reflection of light. In addition, although the thermosetting resin is used as the translucent resin, it is not limited to the thermosetting resin, and an ultraviolet curable resin or a UV / heat combined curable resin may be used. Further, as the low melting point glass, it is preferable to use lead-free low melting point glass from the viewpoint of reducing the environmental load.

  In the fine periodic structure 6 described above, as shown in FIGS. 1B and 1C, square pyramidal peaks 61 are arranged in a two-dimensional array. For example, a conical shape or a quadrangular prism shape may be used. Here, the fine periodic structure 6 has a period of the fine periodic structure (pitch of the peak portion 61) approximately equal to the wavelength of the light to be scanned (scanned object) on the mirror surface 21 (preferably, 1 / wavelength of the light. It is preferable to set the aspect ratio of the peak portion 61 to about 1-2. In the present embodiment, the effective refractive index of the refractive index periodic structure composed of the peak portion 61 of the fine periodic structure 6 and a medium (here, air) between the adjacent peak portions 61 of the fine periodic structure 6 is Since the medium of the peak portion 61 of the fine periodic structure 6 (translucent resin or low-melting glass) and the medium (air) between the adjacent peak portions 61 can be set, the medium of the peak portion 61 is If the refractive index is approximately the same as that of the medium of the first glass substrate 200, the effective refractive index of the refractive index periodic structure can be set to an intermediate value between the refractive index of the first glass substrate 200 and the refractive index of air.

  Hereinafter, the manufacturing method of the MEMS optical scanner according to the present embodiment will be described with reference to FIG. 3, and (a) to (d) are schematic cross sections of portions corresponding to the cross section AB ′ of FIG. Show.

  First, a metal film forming step of forming a metal film (for example, an Al—Si film) having a predetermined film thickness (for example, 500 nm) on the one surface side of the SOI substrate 100 as a semiconductor substrate by a sputtering method, a vapor deposition method, or the like. 3A is obtained by performing a metal film patterning process for forming the pads 13, 13 and the reflective film 21a by patterning the metal film using photolithography technology and etching technology. . In this embodiment, since the materials and film thicknesses of the pads 13 and 13 and the reflective film 21a are set to be the same, the pads 13 and 13 and the reflective film 21a are formed simultaneously. When the materials and film thicknesses of the pads 13 and 13 and the reflective film 21a are different, the pad forming process for forming the pads 13 and 13 and the reflective film forming process for forming the reflective film may be provided separately. The order of the pad forming step and the reflective film forming step may be either.

  After forming the pads 13 and 13 and the reflective film 21a, the movable portion 20, the pair of torsion spring portions 30 and 30, and the outer frame portion of the first silicon layer 100a are formed on the one surface side of the SOI substrate 100. 10. Depth reaching the first silicon layer 100a to the insulating layer 100c using the first resist layer 130 patterned so as to cover the portions corresponding to the fixed electrodes 12 and 12 and the movable electrodes 22 and 22 (a first thickness). The structure shown in FIG. 3B is obtained by performing a first silicon layer patterning step (surface side patterning step) for patterning the first silicon layer 100a by etching to a predetermined depth of 1). In short, the first silicon layer patterning step constitutes a surface side patterning step of etching the SOI substrate 100, which is a semiconductor substrate, from the one surface to a first predetermined depth. Etching of the first silicon layer 100a in the first silicon layer patterning step may be performed by a dry etching apparatus capable of highly anisotropic etching such as an inductively coupled plasma (ICP) type etching apparatus. In the first silicon layer patterning step, the insulating layer 100c is used as an etching stopper layer.

  After the first silicon layer patterning step, the first resist layer 130 on the one surface side of the SOI substrate 100 is removed, and then the second resist layer 131 is formed on the entire surface on the one surface side of the SOI substrate 100. Then, on the other surface side of the SOI substrate 100, the third resist layer 132 patterned so as to expose the second silicon layer 100b other than the portion corresponding to the outer frame portion 10 is used as a mask. By performing a second silicon layer patterning step of patterning the second silicon layer 100b by etching the second silicon layer 100b to a depth (second predetermined depth) reaching the insulating layer 100c, FIG. The structure shown in 3 (c) is obtained. In short, the second silicon layer patterning step constitutes a back side patterning step of etching the SOI substrate 100, which is a semiconductor substrate, from the other surface to a second predetermined depth. Etching of the second silicon layer 100b in the second silicon layer patterning step may be performed by a dry etching apparatus that has high anisotropy and enables vertical deepening, such as an inductively coupled plasma (ICP) etching apparatus. In the second silicon layer patterning step, the insulating layer 100c is used as an etching stopper layer.

  After the above-described second silicon layer patterning step, a portion between the outer frame portion 10 and the movable portion 20 and a portion between the movable electrodes 22, 22 and the fixed electrodes 12, 12 in the insulating layer 100c of the SOI substrate 100. After forming the mirror forming substrate 1 by performing an insulating layer patterning step of etching from the other surface side of the SOI substrate 100, the second resist layer 131 and the third resist layer 132 are removed, and then A joining step of joining the mirror forming substrate 1 to the first cover substrate 2 and the second cover substrate 3 by anodic bonding or the like is performed, followed by mirror formation from the first cover substrate 2 side by an optical microscope. Appearance inspection of the mirror surface 21 of the substrate 1, the torsion spring portions 30 and 30, the fixed comb teeth 12b, and the movable comb teeth 22b is performed. By performing a fine periodic structure forming step of forming the fine periodic structure 6 by applying a translucent resin or low-melting glass on the outer surface side opposite to the ring forming substrate 1 to form the fine periodic structure 6 in FIG. The MEMS optical scanner having the structure shown in FIG.

  Here, in the bonding step, from the viewpoint of protecting the mirror surface 21 of the mirror forming substrate 1, after performing a first bonding process for bonding the first cover substrate 2 and the mirror forming substrate 1, the mirror forming substrate 1. It is preferable to perform a second joining process for joining the first cover substrate 3 and the second cover substrate 3. Here, in the first bonding process, first, the first cover substrate 2 and the mirror forming substrate 1 in which the first displacement space forming recesses 201 and the through holes 202 and 202 are formed in the first glass substrate 200, In a state where the stacked body is heated to a predetermined bonding temperature (for example, about 300 ° C. to 400 ° C.) in a vacuum with a predetermined degree of vacuum (for example, 10 Pa or less), the first silicon layer 100a and the first layer are stacked. A predetermined voltage (for example, about 400V to 800V) is applied between the cover substrate 2 and the first cover substrate 2 side as a low potential side, and this state is maintained for a predetermined bonding time (for example, about 20 minutes to 60 minutes). Just hold it. In the second bonding process, anodic bonding between the second silicon layer 100b and the second cover substrate 3 is performed in accordance with the first bonding process described above. Note that the bonding method for bonding the mirror forming substrate 1 and the cover substrates 2 and 3 is not limited to anodic bonding, and may be, for example, a room temperature bonding method. In addition, after the first silicon layer patterning step, the SOI substrate 100 and the first cover substrate 2 are bonded together, and then the second silicon layer patterning step and the insulating layer patterning step are performed, so that the mirror forming substrate 1 is formed. Then, the mirror forming substrate 1 and the second cover substrate 3 may be bonded.

  In the fine periodic structure forming step, a thermosetting translucent resin or low-melting glass is applied to the outer surface of the first cover substrate 2 opposite to the mirror forming substrate 1, and then the fine periodic structure 6 is applied. By pressing a mold corresponding to the shape of the mold and heating the translucent resin or low-melting glass through the mold, the translucent resin or low-melting glass is cured, and the mold is released. Yes. In the case of using an ultraviolet curable resin as the translucent resin, the translucent resin may be cured by pressing the mold and irradiating the ultraviolet ray. In the case of using a thing, it is sufficient to irradiate ultraviolet rays and perform heating. Further, in the fine periodic structure forming step for forming the fine periodic structure 6, a frame member or a mask is appropriately used so that the translucent resin or the low melting point glass does not enter the through holes 202, 202 of the first cover substrate 2. May be provided.

  By the way, in the manufacturing method of the MEMS optical scanner of the present embodiment, the MEMS optical scanner is manufactured by performing all the processes up to the end of the fine periodic structure forming process on the mirror forming substrate 1 and each of the cover substrates 2 and 3 at the wafer level. A plurality of wafer level package structures are formed, and a dividing step of dividing the wafer level package structures into individual MEMS optical scanners is performed. In short, in the manufacturing method of the MEMS optical scanner of this embodiment, the first wafer on which a plurality of mirror forming substrates 1 are formed, the second wafer on which a plurality of first cover substrates 2 are formed, and the second cover substrate 3 are provided. After a plurality of formed third wafers are bonded together to form a wafer level package structure, on the outer surface side of each first cover substrate 2 of the wafer level package structure opposite to each mirror forming substrate 1 Since each fine periodic structure 6 is formed by applying a light-transmitting resin or low-melting glass and then forming, and then dividing the wafer-level package structure into the outer size of the mirror forming substrate 1, Since the planar size of each of the cover substrates 2 and 3 can be adjusted to the outer size of the mirror forming substrate 1, a small MEMS optical fiber having the fine periodic structure 6 can be used. Yanasensa can be produced by a simple process, also, it is possible to improve the mass productivity.

  In the MEMS optical scanner of the present embodiment described above, the first cover substrate 2 and the second cover substrate 3 are formed to have the same outer dimensions as the mirror formation substrate 1, and the mirror formation substrate 1 in the first cover substrate 2 Has a fine periodic structure 6 that is formed of a translucent resin or low-melting glass on the opposite outer surface side and suppresses reflection of light, so that after the mirror forming substrate 1 and the cover substrates 2 and 3 are joined, After performing the appearance inspection, the fine periodic structure 6 is formed by applying a light-transmitting resin or low-melting glass on the outer surface of the first cover substrate 2 opposite to the mirror-forming substrate 1 and then forming it. Thereafter, it becomes possible to adopt a manufacturing process in which dicing is performed. After the first glass substrate 200 serving as the basis of the first cover substrate 2 is processed to form a fine periodic structure, the first process is performed. Compared to a case where a manufacturing process for joining the cover substrate 2 to the mirror forming substrate 1 is adopted, the cost is low and the reliability is high, and the light incident on the MEMS optical scanner and the light reflected on the mirror surface are unnecessary. Reflection can be suppressed. Accordingly, it is possible to prevent the direction of the light incident on the MEMS optical scanner and reflected unnecessarily from being aligned with the direction of the light reflected by the mirror surface 21 and emitted from the MEMS optical scanner.

  Further, in the MEMS optical scanner of this embodiment, since the peaks 61 of the fine periodic structure 6 are arranged in a two-dimensional array, the incident direction of light to the MEMS optical scanner and the reflection direction of light on the mirror surface 21. Regardless of this, it is possible to prevent the direction of light reflected unnecessarily from aligning with the direction of light reflected by the mirror surface 21.

  In the MEMS optical scanner of this embodiment, the torsion springs 30 and 30 are formed by the first silicon layer 100a of the SOI substrate 100. Therefore, each torsion spring is compared with a case where a silicon substrate is used as the semiconductor substrate. The precision of the thickness dimension of the parts 30 and 30 can be raised, and the precision of the resonant frequency of the vibration system comprised by the movable part 20 and a pair of torsion spring parts 30 and 30 can be raised.

  In the method for manufacturing the MEMS optical scanner according to the present embodiment, the first wafer on which a plurality of mirror forming substrates 1 are formed, the second wafer on which a plurality of first cover substrates 2 are formed, and the second cover substrate. After forming a wafer level package structure in which a plurality of third wafers 3 are joined, an outer surface opposite to each mirror forming substrate 1 in each first cover substrate 2 of the wafer level package structure Each fine periodic structure 6 is formed by applying a translucent resin or low-melting-point glass on the side and then forming, and then dividing the wafer-level package structure into the outer size of the mirror-forming substrate 1, thereby reducing the size In addition, after the formation of the wafer level package structure, an optical microscope or visual inspection can be performed, and the wafer level can be checked after the visual inspection. Can be simultaneously molded multiple fine periodic structure 6 in a package structure, reliable, low cost, it is possible to provide a MEMS scanner capable of suppressing unwanted reflection of light.

(Embodiment 2)
The basic configuration of the MEMS optical scanner of the present embodiment is substantially the same as that of the first embodiment, and as shown in FIGS. 4, 5, and 6 (f), the structure of the movable portion 20, the second cover substrate 3 and the like. Is different. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted suitably.

  In the present embodiment, the movable portion 20 is a frame-like shape that is swingably supported by the outer frame portion 10 via a pair of torsion spring portions 30 and 30 (hereinafter referred to as first torsion spring portions 30 and 30). A movable frame portion 23 (here, a rectangular frame shape), a mirror portion 24 having a rectangular shape in plan view provided on the inner side of the movable frame portion 23 and provided with a mirror surface 21, and a mirror portion inside the movable frame portion 23 And a pair of torsion spring portions 25 and 25 (hereinafter referred to as second torsion spring portions 25 and 25) that are arranged so as to sandwich 24 and connect the movable frame portion 23 and the mirror portion 24 and can be torsionally deformed. is doing.

  The second torsion spring portions 25, 25 are arranged in parallel in a direction (x-axis direction) orthogonal to the parallel arrangement direction (y-axis direction) of the first torsion spring portions 30, 30. In short, the movable portion 20 has a pair of second torsion spring portions 25, 25 arranged in parallel in the x-axis direction, and the mirror portion 24 is a pair of second torsion spring portions 25 with respect to the movable frame portion 23. , 25 (displaceable around the axis in the x-axis direction). That is, the pair of second torsion spring portions 25, 25 connect the movable frame portion 23 and the mirror portion 24 so that the mirror portion 24 can swing with respect to the movable frame portion 23. In other words, the mirror part 24 disposed inside the movable frame part 23 is movable frame part via two second torsion spring parts 25, 25 extended continuously and integrally from the mirror part 24 in two opposite directions. 23 is swingably supported. Here, the pair of second torsion spring portions 25 and 25 are formed such that a straight line connecting the center lines along the x-axis direction passes through the center of gravity of the mirror portion 24 in plan view. Each of the second torsion springs 25 and 25 has a thickness dimension (z-axis direction dimension) set to 30 μm and a width dimension (y-axis direction dimension) set to 30 μm. There is no particular limitation. Moreover, the planar view shape of the mirror part 24 and the mirror surface 21 is not restricted to a rectangular shape, For example, a circular shape may be sufficient. Further, the inner peripheral shape of the movable frame portion 23 is not limited to a rectangular shape, and may be a circular shape, for example.

  As can be seen from the above description, the mirror portion 24 is configured to rotate around the axis of the pair of first torsion spring portions 30 and 30 and rotate around the axis of the pair of second torsion spring portions 25 and 25. Is possible. In short, the mirror surface 21 of the mirror unit 24 is configured to be two-dimensionally rotatable. Here, the movable portion 20 includes a frame-like support body 29 that is integrally provided on the opposite side of the movable frame portion 23 to the first cover substrate 2 side, and supports the movable frame portion 23. 29 is rotatable integrally with the movable frame portion 23.

  Therefore, the second cover substrate 3 has a second displacement space forming recess 301 for securing a displacement space of the movable portion 20 on the one surface of the second glass substrate 300 on the mirror forming substrate 1 side. It is.

  Further, in the present embodiment, three pads 13, 13, 13 are arranged in parallel at substantially equal intervals so as to be aligned in a plan view on the outer frame portion 10. Three tapered through-holes 202, 202, 202 are provided through which the pads 13, 13, 13 are respectively exposed.

  Further, the mirror forming substrate 1 in the MEMS optical scanner of the present embodiment is similar to the first embodiment in the direction in which the pair of first torsion spring portions 30 and 30 are connected in the movable portion 20 (the pair of first torsion spring portions 30. , 30 in parallel with each other in the direction (that is, the x-axis direction) orthogonal to the comb-shaped movable electrodes 22, 22 (hereinafter referred to as the first movable electrodes 22, 22) and the outer frame Comb-shaped fixed electrodes 12, 12 (hereinafter referred to as first fixed electrode 12) having a plurality of fixed comb-teeth pieces 12 b formed in the portion 10 and facing the plurality of movable comb-teeth pieces 22 b of the first movable electrodes 22, 22. , 12), and a direction in which the pair of second torsion springs 25, 25 are connected in the mirror part 24 (a direction in which the pair of second torsion springs 25, 25 are arranged side by side) ) (Ie y-axis) A plurality of fixed comb-shaped movable electrodes 27, 27 formed on both sides of the second movable electrode 27, 27, and a plurality of fixed comb electrodes 27 b formed on the movable frame portion 23. Comb-shaped second fixed electrodes 26 and 26 each having a comb-tooth piece 26 b are provided. A set of the first movable electrodes 22 and 22 and the first fixed electrodes 12 and 12, and a second movable electrode 27. , 27 and the second fixed electrodes 26, 26 constitute electrostatic drive means for driving the movable part 20 by electrostatic force.

  The above-mentioned second fixed electrodes 26, 26 have a comb shape in plan view, and the comb bone portion 26a is constituted by a part of the movable frame portion 23, and the comb bone portion 26a faces the mirror portion 24. A large number of fixed comb teeth 26b are arranged in a line along the direction in which the pair of second torsion spring portions 25, 25 are arranged on the surface (the inner surface along the x-axis direction in the movable frame portion 23). On the other hand, the second movable electrodes 27 and 27 are constituted by a part of the mirror portion 24, and the side surfaces of the second fixed electrodes 26 and 26 on the side of the comb portions 26 a and 26 a (in the x-axis direction of the mirror portion 24). A large number of movable comb teeth 27b respectively facing the fixed comb teeth 26b are arranged in the side-by-side direction. Here, in the comb-shaped second fixed electrode 26 and the comb-shaped second movable electrode 27, the comb bone portions 26a and 27a are opposed to each other, and each fixed comb tooth piece 26b of the second fixed electrode 26 is The fixed comb teeth piece 26b and the movable comb teeth piece 27b are spaced apart from each other in the x-axis direction, and the second fixed electrode 26 and the second movable electrode are arranged in the comb groove of the second movable electrode 27. When a voltage is applied between the second fixed electrode 26 and the second movable electrode 27, an electrostatic force acting in a mutually attracting direction is generated. In addition, what is necessary is just to set the clearance gap between the fixed comb-tooth piece 26b in the x-axis direction and the movable comb-tooth piece 27b suitably in the range of about 2 micrometers-5 micrometers, for example.

  The mirror forming substrate 1 forms a plurality of slits 10 a, 10 a, 10 a in a portion formed by the first silicon layer 100 a in the outer frame portion 10, and the first silicon layer in the movable frame portion 23 of the movable portion 20. A plurality of slits 20a, 20a, 20a, and 20a are formed in the portion formed by 100a, so that the middle pad 13 (13b) in FIG. 4 among the three pads 13, 13, and 13 is the first fixed electrode 12. 12 are electrically connected to the same potential, and the right pad 13 (13a) is electrically connected to the first movable electrodes 22 and 22 and the second movable electrodes 26 and 26 to have the same potential, and the left side. The pad 13 (13c) is electrically connected to the second movable electrodes 27, 27 of the mirror portion 24 and has the same potential.

  Here, the plurality of slits 10a, 10a, 10a of the outer frame portion 10 are formed to a depth reaching the insulating layer 100c. Also in the present embodiment, as in the first embodiment, each slit 10a, 10a, 10a is a trench, and the shape of each slit 10a, 10a, 10a in plan view is a shape that is not opened to the outer surface side of the outer frame portion 10. Thus, while adopting the structure in which the slits 10 a, 10 a, 10 a are formed in the outer frame portion 10, it is possible to prevent the bonding property between the outer frame portion 10 and the first cover substrate 2 from being deteriorated. The airtightness of the space surrounded by the cover substrates 2 and 3 is ensured.

  Further, each slit 20a, 20a, 20a, 20a of the movable frame portion 23 in the movable portion 20 is a trench, and is constituted by a part of the insulating layer 100c of the SOI substrate 100 and a part of the second silicon layer 100b. The above-described support 29 is formed to a depth reaching the insulating layer 100c. In short, in the present embodiment, the movable frame portion 23 is supported by the support 29 while adopting a configuration in which a plurality of slits 20a, 20a, 20a, 20a are formed in the movable frame portion 23. And the support 29 can be integrally rotated around the axis of the pair of first torsion spring portions 30 and 30. Here, the support 29 is formed in a frame shape (rectangular frame shape) that covers a portion of the movable frame portion 23 excluding each fixed comb tooth piece 26b and each movable comb tooth piece 22b (see FIG. 5). In addition, the plurality of trenches 20a, 20a, 20a, 20a of the movable frame portion 23 has the center of gravity of the movable portion 20 including the support 29 in the y-axis direction of the pair of first torsion spring portions 30, 30 in plan view. The shape is designed so as to be positioned approximately in the middle of the straight line connecting the center lines along the line. Accordingly, the movable portion 20 smoothly swings around the axis of the pair of first torsion spring portions 30 and 30, and the reflected light is properly scanned. In the present embodiment, the thickness of the portion constituted by the second silicon layer 100b in the support 29 is set to the same thickness as the portion constituted by the second silicon layer 100b in the outer frame portion 10. Although it is not limited to the same, it may be thicker or thinner.

  In the MEMS optical scanner of the present embodiment, for example, the first fixed electrode 12 and the second fixed electrode 12 and the second fixed electrode 26 are set using the potential of the pad 13a to which the first movable electrode 22 and the second fixed electrode 26 are electrically connected as a reference potential. By periodically changing the potential of each of the movable electrodes 27, the movable portion 20 can be rotated about the axis of the pair of first torsion spring portions 30 and 30, and the mirror portion 24 is paired with the second pair of second torsion spring portions 30 and 30. The torsion springs 25, 25 can be rotated around the axis. In short, by applying a pulse voltage for driving the movable portion 20 between the first fixed electrode 12 and the movable electrode 22 facing each other through the pair of pads 13b and 13a, the first fixed electrode 12 and the first fixed electrode 12. An electrostatic force is generated between the movable electrodes 22, the movable portion 20 rotates about the axis in the y-axis direction, and the second fixed electrode 26 and the second movable electrode that face each other through the pair of pads 13 a and 13 c. By applying a pulse voltage for driving the mirror section 24 between the electrode 27 and the second fixed electrode 26 and the second movable electrode 27, an electrostatic force is generated, and the mirror section 24 is moved in the x-axis direction. It rotates around the axis. Therefore, in the MEMS optical scanner of this embodiment, an electrostatic force is generated periodically by applying a pulse voltage of a predetermined first driving frequency between the first fixed electrode 12 and the first movable electrode 22. The entire movable part 20 can be swung, and furthermore, by applying a pulse voltage of a predetermined second driving frequency between the second fixed electrode 26 and the second movable electrode 27, An electrostatic force can be periodically generated, and the mirror part 24 of the movable part 20 can be swung. The mirror forming substrate 1 in the present embodiment is a surface of a portion where the reflective film 21a of the first silicon layer 100a is not formed on the space side surrounded by the outer frame portion 10 and the first cover substrate 2. In addition, a silicon oxide film 111a (see FIG. 6F) is formed.

  In the MEMS optical scanner of this embodiment, the resonance frequency of the vibration system configured by the movable portion 20 and the pair of first torsion spring portions 30 and 30 between the first fixed electrode 12 and the first movable electrode 22. By applying a pulse voltage having a frequency approximately twice that of the movable portion 20, the movable portion 20 is driven with a resonance phenomenon, and the mechanical deflection angle (inclination with respect to a horizontal plane parallel to the xy plane) is increased. Further, in the MEMS optical scanner of the present embodiment, the vibration system configured by the mirror portion 24 and the pair of second torsion spring portions 25 and 25 between the second fixed electrode 26 and the second movable electrode 27. By applying a pulse voltage having a frequency approximately twice the resonance frequency, the mirror unit 24 is driven with a resonance phenomenon, and the mechanical deflection angle (parallel to the surface of the movable frame unit 23 on the first cover substrate 2 side) is driven. The inclination with respect to the surface becomes larger.

  Hereinafter, the manufacturing method of the MEMS optical scanner of the present embodiment will be described with reference to FIG. 6, wherein (a) to (d) show schematic cross sections of portions corresponding to the cross section AB in FIG. 4.

  First, by performing an oxide film forming step of forming silicon oxide films 111a and 111b on the one surface side and the other surface side of the SOI substrate 100, which is a semiconductor substrate, by thermal oxidation or the like, FIG. Get the structure shown.

  Thereafter, a portion of the silicon oxide film 111a on the one surface side of the SOI substrate 100 other than the region where the reflective film 21a is to be formed in the movable portion 20, a portion corresponding to the first torsion spring portions 30, 30, and the like remain. A structure shown in FIG. 6B is obtained by performing a first silicon layer patterning process for patterning the first silicon layer 100a using a photolithography technique and an etching technique.

  Thereafter, a metal film forming step is performed in which a metal film (for example, an Al—Si film) having a predetermined film thickness (for example, 500 nm) is formed on the one surface side of the SOI substrate 100 by a sputtering method, a vapor deposition method, or the like. By performing a metal film patterning process for forming the pads 13, 13 and the reflective film 21a by patterning the metal film using the technique and the etching technique, the structure shown in FIG. 6C is obtained. In this embodiment, since the materials and film thicknesses of the pads 13 and 13 and the reflective film 21a are set to be the same, the pads 13 and 13 and the reflective film 21a are formed simultaneously. When the materials and film thicknesses of the pads 13 and 13 and the reflective film 21a are different, the pad forming process for forming the pads 13 and 13 and the reflective film forming process for forming the reflective film may be provided separately. .

  After forming each of the pads 13 and 13 and the reflective film 21a, the movable frame portion 23, the mirror portion 24, and the pair of first torsion springs in the first silicon layer 100a are formed on the one surface side of the SOI substrate 100. Portions 30, 30, a pair of second torsion spring portions 25, 25, outer frame portion 10, first fixed electrodes 12, 12, second movable electrodes 22, 22, second fixed electrodes 26, 26, second A depth (first predetermined depth) at which the first silicon layer 100a reaches the insulating layer 100c using the first resist layer 130 patterned so as to cover the portions corresponding to the two movable electrodes 27, 27 as a mask. The structure shown in FIG. 6D is obtained by performing a first silicon layer patterning step (surface-side patterning step) for patterning the first silicon layer 100a by etching up to That. Etching of the first silicon layer 100a in the first silicon layer patterning step may be performed by a dry etching apparatus capable of highly anisotropic etching such as an inductively coupled plasma (ICP) type etching apparatus. In the first silicon layer patterning step, the insulating layer 100c is used as an etching stopper layer.

  After the first silicon layer patterning step, the first resist layer 130 on the one surface side of the SOI substrate 100 is removed, and then the second resist layer 131 is formed on the entire surface on the one surface side of the SOI substrate 100. Subsequently, on the other surface side of the SOI substrate 100, a third resist layer patterned so as to expose portions of the second silicon layer 100 b other than those corresponding to the outer frame portion 10 and the support 29. A second silicon layer patterning process is performed in which the second silicon layer 100b is patterned by etching the second silicon layer 100b to a depth (second predetermined depth) reaching the insulating layer 100c using the mask 132 as a mask. As a result, the structure shown in FIG. Etching of the second silicon layer 100b in the second silicon layer patterning step may be performed by a dry etching apparatus that has high anisotropy and enables vertical deepening, such as an inductively coupled plasma (ICP) etching apparatus. In the second silicon layer patterning step, the insulating layer 100c is used as an etching stopper layer.

  After the second silicon layer patterning step, the mirror forming substrate 1 is formed by performing an insulating layer patterning step of etching unnecessary portions of the insulating layer 100c of the SOI substrate 100 from the other surface side of the SOI substrate 100, Subsequently, the second resist layer 131 and the third resist layer 132 are removed, and then the junction for joining the mirror forming substrate 1 to the first cover substrate 2 and the second cover substrate 3 by anodic bonding or the like. The process is performed, and subsequently, using an optical microscope, from the first cover substrate 2 side, the mirror surface 21 of the mirror forming substrate 1, the torsion spring portions 25, 25, 30, 30, the fixed comb teeth 12 b, 26 b, Each movable comb tooth piece 22b, 27b is inspected, and then a translucent resin or a low melting point is formed on the outer surface of the first cover substrate 2 opposite to the mirror forming substrate 1. By performing the fine periodic structure forming step of forming a fine periodic structure 6 by molding are coated with the lath to obtain a MEMS scanner having the structure shown in FIG. 6 (f). Here, in the bonding step, from the viewpoint of protecting the mirror surface 21 of the mirror forming substrate 1, after performing a first bonding process for bonding the first cover substrate 2 and the mirror forming substrate 1, the mirror forming substrate 1. It is preferable to perform a second joining process for joining the first cover substrate 3 and the second cover substrate 3. Note that, after the first silicon layer patterning step, the SOI substrate 100 and the first cover substrate 2 are bonded together, and then the second silicon layer patterning step and the insulating layer patterning step are performed, whereby the mirror forming substrate 1 is formed. Then, the mirror forming substrate 1 and the second cover substrate 3 may be bonded.

  By the way, in the manufacturing method of the MEMS optical scanner of the present embodiment, the MEMS optical scanner is manufactured by performing all the processes up to the end of the fine periodic structure forming process on the mirror forming substrate 1 and each of the cover substrates 2 and 3 at the wafer level. A plurality of wafer level package structures are formed, and a dividing step of dividing the wafer level package structures into individual MEMS optical scanners is performed. In short, in the manufacturing method of the MEMS optical scanner of this embodiment, the first wafer on which a plurality of mirror forming substrates 1 are formed, the second wafer on which a plurality of first cover substrates 2 are formed, and the second cover substrate 3 are provided. After the wafer level package structure is formed by bonding a plurality of formed third wafers, light is transmitted to the outer surface side of each first cover substrate of the wafer level package structure opposite to each mirror forming substrate. Each fine periodic structure 6 is formed by molding after applying a functional resin or low-melting glass, and then the wafer level package structure is divided into the outer size of the mirror forming substrate 1. Since the planar size of the substrates 2 and 3 can be adjusted to the external size of the mirror forming substrate 1, a small MEMS optical scanner having the fine periodic structure 6 can be used. Can be produced by a simple process, also, it is possible to improve the mass productivity.

  In the MEMS optical scanner of the present embodiment described above, as in the first embodiment, the first cover substrate 2 and the second cover substrate 3 are formed to have the same outer dimensions as the mirror forming substrate 1, and the first cover substrate 2. The mirror-forming substrate 1 has a fine periodic structure 6 that is formed by applying a translucent resin or low-melting-point glass on the outer surface opposite to the mirror-forming substrate 1 and suppressing the reflection of light. After each of the cover substrates 2 and 3 is joined, a visual inspection is performed, and then a translucent resin or low-melting glass is applied to the outer surface of the first cover substrate 2 opposite to the mirror forming substrate 1. Then, the fine periodic structure 6 can be formed by molding, and then a manufacturing process in which dicing is performed can be adopted, and the first glass substrate 2 serving as the basis of the first cover substrate 2 can be adopted. Compared to a case where a manufacturing process is employed in which the first cover substrate 2 is bonded to the mirror forming substrate 1 after forming a fine periodic structure by processing 0, the MEMS is low in cost and high in reliability. Unnecessary reflection of light incident on the optical scanner and light reflected by the mirror surface can be suppressed. Accordingly, it is possible to prevent the direction of the light incident on the MEMS optical scanner and reflected unnecessarily from being aligned with the direction of the light reflected by the mirror surface 21 and emitted from the MEMS optical scanner.

  Further, in the MEMS optical scanner of the present embodiment, instead of each pad 13, for example, as shown in FIG. 7, the outer surface of the first cover substrate 2 and the surface of the outer frame portion 10 in the mirror forming substrate 1 A through wiring 213 formed across the inner surface of the through hole 202 may be formed as an external connection electrode, and the same external connection electrode may be employed in the first embodiment.

DESCRIPTION OF SYMBOLS 1 Mirror formation board | substrate 2 1st cover board | substrate 3 2nd cover board | substrate 6 Fine periodic structure 13 Pad 20 Movable part 21 Mirror surface 30 Torsion spring part 61 Mountain part 100 SOI substrate (semiconductor substrate)
200 First glass substrate 202 Through-hole 300 Second glass substrate

Claims (3)

  An outer frame portion formed by using a semiconductor substrate, a movable portion disposed inside the outer frame portion and provided with a mirror surface, and an outer frame portion and a movable portion disposed so as to sandwich the movable portion inside the outer frame portion. A mirror forming substrate having a pair of torsion springs that can be torsionally deformed, a first cover substrate made of a glass substrate bonded to one surface side provided with a mirror surface in the mirror forming substrate, and a mirror A MEMS optical scanner comprising a second cover substrate bonded to the other surface side of the formation substrate and a driving means for driving the movable portion, wherein the first cover substrate and the second cover substrate are mirror formation substrates. The first cover substrate is formed of a light-transmitting resin or low-melting glass on the outer surface opposite to the mirror-forming substrate, so that the reflection of light is suppressed. MEMS optical scanner, characterized by having a periodic structure.   The mirror forming substrate includes a plurality of pads formed on the outer frame portion on the one surface side and connected to the driving means, and the first cover substrate exposes each pad over the entire circumference. The MEMS optical scanner according to claim 1, wherein a plurality of through holes are formed.   3. The method of manufacturing a MEMS optical scanner according to claim 1, wherein the first wafer has a plurality of mirror-formed substrates, the second wafer has a plurality of first cover substrates, and the second wafer. After forming a wafer level package structure bonded to a third wafer on which a plurality of cover substrates are formed, an outer surface opposite to each mirror forming substrate in each first cover substrate of the wafer level package structure A fine periodic structure is formed by applying a light-transmitting resin or low-melting glass on the side and then forming, and then dividing the wafer-level package structure into the outer size of the mirror forming substrate. Manufacturing method of the scanner.

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