JP6092590B2 - Manufacturing method of optical deflector - Google Patents

Description

  The present invention relates to a method of manufacturing a MEMS (Micro Electro Mechanical Systems) optical deflector equipped in an optical scanner or the like.

  2. Description of the Related Art In recent years, as one form of an image display device, a projection display has been proposed in which light from a light source is deflected and projected onto a screen using an optical deflector, and an image is projected on the screen. Examples of the optical deflector include a MEMS optical deflector in which mechanical parts such as a mirror and a piezoelectric actuator are integrally formed on a semiconductor substrate as a MEMS device using a semiconductor process or a micromachine technique (for example, patent document). 1).

  In this optical deflector, one end of the piezoelectric actuator is connected to and supported by a frame (support), and the torque generated by the piezoelectric actuator is transmitted to the torsion bar connected to the other end, and is provided at the end of the torsion bar. Oscillate (reciprocate) the mirror. Such an optical deflector has an advantage that a large driving force can be obtained with a small and simple structure. Each optical deflector element is processed into a pattern after batch processing of a silicon wafer, and then cut out as a single piece by a dicing process, and then mounted on a package such as a ceramic product.

  The element structure of the optical deflector is connected to an actuator by supporting a mirror having a diameter of about 1 mm with a thin torsion bar. As the torsion bar is twisted by the movement of the actuator, the mirror swings. By irradiating the oscillating mirror with a laser beam, a one-dimensional or two-dimensional scanning beam is obtained. A relatively wide space is provided around the mirror so as not to prevent the mirror from swinging. In particular, in a two-dimensional optical deflector that simultaneously swings one mirror around two orthogonal rotation axes, the ratio of the area of the movable portion to the entire element is large.

  In the process of dividing a processed wafer into chips by the most general blade dicing for such an element structure, the element structure of the MEMS optical deflector is broken when high-pressure pure water hits the processed wafer. The problem occurs.

  In order to avoid this problem, there is a method of attaching a protective tape to the surface of the processed wafer. However, when the tape is peeled later, the element structure of the MEMS optical deflector is broken. Even if a tape whose adhesive strength is weakened by ultraviolet irradiation or heat treatment is used, 100% element damage cannot be prevented for a complicated structure on the processed wafer surface. Even when a resist is applied without using a tape to form a protective layer, there is a problem that the element structure is damaged in the process of removing the resist later.

  As means for solving such a problem, a wafer level package has been recently developed in which dicing is performed after securing a mirror swing space by bonding to a glass wafer or the like at the wafer level.

  FIG. 15 shows a schematic diagram of a wafer level package. 15A is a perspective view of the packaged wafer 400 of the MEMS optical deflector, and FIG. 15B is a cross-sectional view of the optical deflector 405 cut out from the packaged wafer 400 as a chip. Each chip corresponds to one section of the packaged wafer 400.

  In FIG. 15A, the packaged wafer 400 has a sandwich structure in which the main body wafer 401 is sandwiched between the front side glass wafer 402 and the back side glass wafer 403 as transparent sealing material wafers from both the front and back sides. The packaged wafer 400 in FIG. 15A is diced vertically and horizontally along the dicing line 404, whereby a plurality of optical deflectors 405 are cut out.

  In FIG. 15B, the main body wafer 401 includes a BOX (Buried Oxide) layer 414, an SOI (Silicon on Insulator) layer 415 and a handle layer 416 that are stacked on the front side and the back side of the BOX layer 414. The internal space 410 is formed inside the optical deflector 405, and the mirror unit 411 and the actuator element 412 are formed by etching the SOI layer 415. The internal space 410 is formed on the lower surface and the back side of the front glass wafer 402. It is defined by the upper surface of the glass wafer 403 and the inner peripheral surface of the main body wafer 401, and has a volume that accommodates the mirror portion 411 and the like and allows the displacement of the mirror portion 411.

  In the case of the optical deflector 405 having the structure shown in FIG. 15, the structural damage of the mirror unit 411 and the actuator element 412 in the dicing process is eliminated. However, in the optical deflector 405, it is necessary to form a silicon through electrode (TSV) 409 or to form a through electrode 413 on the glass wafers 402 and 403, which complicates the process and increases the manufacturing cost. There is.

JP 2010-128116 A

  In order to solve this problem, Deep-RIE processing is first performed not on the packaged wafer 400 but on the back side of the optical deflector (the side opposite to the light incident side and the reflection side) as shown in FIG. The back side is bonded to the support substrate, and after the front side resist pattern is formed, blade dicing is performed first, and then front side deep-RIE processing is performed, while preventing element damage during dicing, There are also proposals to be able to use this package.

  On the other hand, prevention of mirror deformation during mirror scanning has recently been discussed as a required specification for MEMS optical deflectors. This is because the deformation of the mirror widens or distorts the spot diameter of the laser beam to be scanned, thereby causing the quality of the projected image on the screen to deteriorate. As a general countermeasure, it is known to form a reinforcing rib structure as shown in Patent Document 1 / FIG. By designing the rib thickness to be 3 to 4 times the mirror thickness, the rib structure increases the rigidity against the bending stress of the mirror and can suppress mirror deformation during scanning.

  However, the introduction of the rib structure may cause a new problem in the manufacturing process of the MEMS optical deflector. In other words, by forming a heavy object called a rib structure on the back side of the mirror, it is composed of a thin SOI layer of 50 μm or less when deep-side processing is performed on the back side following Deep-RIE processing on the front side of the MEMS optical deflector. The resulting element structure is damaged in the Deep-RIE apparatus due to the stress caused by the weight of the rib structure. Since this defect occurs in the wafer process step before the dicing step, none of the above-described element damage prevention measures in the dicing step is useful. Therefore, establishment of the manufacturing process of the MEMS optical deflector having the rib structure as described above is an issue.

  An object of the present invention is to provide a method of manufacturing an optical deflector that appropriately prevents damage to a mirror portion during wafer backside etching and dicing, and solves the problems caused by the tape used in the measures for preventing damage. That is.

The method of manufacturing an optical deflector according to the present invention includes a mirror part having a mirror surface on the front side, a support part that defines a front side space part that accommodates the mirror part and a back side space part that allows displacement of the mirror part. A wafer having an SOI layer, a BOX layer, and a handle layer in order from the front side to the back side, and etching the SOI layer from the front side to the front side of each section of the wafer. A first step of forming a front side space portion and a front side portion of the mirror portion, and a liquid coating agent that is soluble in a predetermined solution is applied to the front side of the wafer after the first step. A second step of forming a layer and applying a support substrate covering the front side of the coating layer; and fixing the support substrate to the wafer after the second step via the coating layer, The third step to solidify and the third work A fourth step of forming the back side space portion and the back side portion of the mirror portion on the back side of each section of the wafer by etching the handle layer and the BOX layer from the back side of the subsequent wafer, and after the fourth step For the wafer of No. 5, after attaching the front side tape to the front side of the support substrate, the fifth step of dicing along each partition line of the wafer from the back side of the wafer, and for the wafer after the fifth step, A stencil mask having an opening having a circumferential contour smaller than the circumferential contour of the back side space portion on the back side thereof, a sixth step of attaching a back side tape whose adhesive strength is reduced by ultraviolet irradiation, and a wafer after the sixth step. the, so that opening is inside the rear space portion, and a seventh step of applying the back side of the rear tape to the wafer after the seventh step, the stencil mask from the ultraviolet rays from the back An eighth step of separating, to the wafer after the eighth step, characterized in that it comprises a ninth step of removing the coating layer and the supporting substrate by immersing the wafer in the predetermined solution.

  According to the present invention, after the front side portion of the mirror portion from the front side is formed on the wafer, the liquid substrate is applied to the front side and the support substrate is fixed, and then etching from the back side and dicing from the back side are performed. Then, since it is immersed in the solution to separate the coating layer and the support substrate, it is possible to prevent damage to the mirror part during backside etching and dicing.

  According to the present invention, after a back side tape is attached to the back side of the wafer, a stencil mask with an opening is applied to the back side and the back side is irradiated with ultraviolet rays. As a result, the adhesive strength of the back tape is sufficiently reduced at the portion that contacts the back side portion of the mirror portion. As a result, when the immersion solution that separates the liquid coating is removed from the wafer, the mirror portion is taken toward the back side tape by the surface tension of the immersion solution, and the lower end of the back side portion of the mirror portion contacts the back side tape. However, it is avoided that the lower end sticks to the back tape. In this way, it is possible to prevent the mirror portion from being damaged without being returned to the original height in the depressed state due to the lower end of the back side portion of the mirror portion being stuck to the back side tape.

  In this invention, a rib can be provided in the back side part of the mirror part formed at a 4th process.

  In this case, ribs are added to the back side of the mirror part to reinforce the mirror part, which increases the weight of the mirror part and increases the possibility of breakage of the mirror part during dicing. After supporting the substrate with the supporting substrate, the rib is formed by etching from the back side of the wafer in the fourth step, and the dicing is performed in the fifth step, so that the mirror part is reliably damaged in the fourth and fifth steps. Can be prevented.

  Further, in the present invention, the optical deflector includes a movable structure portion that is interposed between the mirror portion and the support body and is displaced together with the mirror portion, and the movable structure portion includes the movable structure portion in the first step. It is preferable to have a front side part formed together with the front side part of the mirror part and a back side part formed together with the back side part of the mirror part in the fourth step.

  In this case, since the back side portion of the movable structure portion is prevented from sticking to the back side tape in the ninth step, the movable structure portion can be prevented from being damaged.

The block diagram of an optical deflector. The figure which shows the structure of a mirror part. The figure which shows the chip structure of a MEMS optical deflector. Process drawing of the 1st part of the preparation methods of a biaxial MEMS optical deflector. The figure which shows the process following the process of FIG. The figure which shows the process following the process of FIG. The figure which shows the process following the process of FIG. The figure which shows the process following the process of FIG. The figure which shows the process following the process of FIG. The figure which shows the process following the process of FIG. The figure which shows the process following the process of FIG. The figure which shows the process following the process of FIG. The figure which shows the process following the process of FIG. The perspective view of a stencil mask. The schematic diagram of the wafer level package as a prior art is shown.

  Hereinafter, an example of an optical deflector manufactured by the method of the present invention will be described. An optical deflector 1 shown in FIG. 1 includes a mirror part 2 disposed at the center, an inner rectangular frame part 3 surrounding the mirror part 2 from the outside, and an outer rectangular frame part 4 surrounding the inner rectangular frame part 3 from the outside. It has. The outer rectangular frame portion 24 (an example of the support of the present invention) of the optical deflector 1 is composed of a front outer rectangular frame portion 4 and a back outer rectangular frame portion 23 of FIG.

  For convenience of explanation, the vertical direction and the horizontal direction of the optical deflector 1 are defined as a direction parallel to the short side and a direction parallel to the long side of the outer rectangular frame part 4, respectively. In FIG. 1, the left diagonally lower-right diagonally upward is the vertical direction of the optical deflector 1, and the left diagonally upper-right diagonally downward is the lateral direction of the optical deflector 1. Further, the side on which the light deflector 1 enters and reflects light is defined as the front side of the light deflector 1, and the side opposite to the front side is defined as the back side of the light deflector 1. Furthermore, the front side and the back side of the optical deflector 1 are referred to as the front side and the back side of the optical deflector 1 as appropriate.

  The pair of torsion bars 5 are arranged on both sides in the vertical direction with respect to the mirror part 2 with their axes aligned in the vertical direction, and the tip side is coupled to the mirror part 2. The base end side of the torsion bar 5 is coupled to the central portion on the inner peripheral side of the lateral side of the inner rectangular frame portion 3. The base end side of the torsion bar 5 may be separated from the inner rectangular frame portion 3. In that case, the base end portion of the torsion bar 5 is supported by the inner rectangular frame portion 3 only by the inner actuator 6.

  The pair of inner actuators 6 are cantilever-type piezoelectric actuators, which are disposed on both lateral sides of each torsion bar 5, the distal end side is coupled to the proximal end portion of the torsion bar 5, and the proximal end side is an inner rectangular frame. It is coupled to the vertical side of the part 3. The inner actuator 6 reciprocates the base end portion of the torsion bar 5 around the axis of the torsion bar 5 at a predetermined frequency, and reciprocates the mirror unit 2 around the first rotation axis.

  Here, the first rotation axis is defined as a straight line that passes through the center of the mirror portion 2 and is parallel to the axis of the torsion bar 5. The second rotation axis described later is defined as a straight line that is substantially orthogonal to the first rotation axis at the center of the mirror unit 2. The first and second rotation axes are straight lines defined on a mirror surface 10 described later.

  The pair of piezoelectric outer actuators 7 is arranged on both sides in the lateral direction with respect to the inner rectangular frame portion 3 and has a structure in which four cantilevers are connected in series. 4 is coupled to the vertical side portion of the inner rectangular frame portion 3 on the front end side. Each outer actuator 7 bends the front end side of all the cantilevers constituting the same to either the front side or the back side alternately at a predetermined cycle with respect to the base end side, and causes the mirror unit 2 to move to the second rotation axis. Reciprocate around.

  The electrode pads 8 and 9 are respectively provided on the front side surfaces of one and the other vertical sides of the outer rectangular frame portion 4, and are electrode terminals of the inner actuator 6 and the outer actuator 7 via wiring in the optical deflector 1. It is connected to the.

  The structure of the mirror unit 2 will be described in detail with reference to FIG. 2A is a rear view of the mirror unit 2, and FIG. 2B is a side view of the mirror unit 2. The mirror surface 10 is formed as a surface on the front side of the mirror portion 2 and reflects incident light from a certain direction on the front side to the front side at a reflection angle corresponding to the direction of the normal. The annular rib 11 is erected on the back side of the mirror part 2 and is formed in a circumferential wall shape along the circular peripheral edge of the main body of the mirror part 2. The annular rib 11 reinforces the mirror part 2 and suppresses distortion of the mirror surface 10 during the reciprocating rotation of the mirror part 2.

  According to the optical deflector 1 configured as described above, the mirror unit 2 reciprocally rotates around the first and second rotation axes at predetermined intervals by the operation of the inner actuator 6 and the outer actuator 7. . When light in a fixed direction from a light source (not shown) (eg, laser light source) is incident on the mirror surface 10 from the front side, the mirror unit 2 rotates the light around the first and second rotation axes. The light is reflected at an angle corresponding to the angle and emitted to the front side. This emitted light becomes scanning light that reciprocates in a predetermined scanning angle range and a predetermined frequency in the horizontal and vertical directions.

  The optical deflector 1 and its light source are used, for example, in an optical scanner provided in a projector, a barcode reader, a laser printer, a laser head amplifier, or a head-up display.

  Here, the chip structure of the MEMS optical deflector 1 will be described with reference to FIG. The optical deflector 1 includes a laminate 15, an SOI layer 16, an oxide BOX layer 17, a handle layer 18, an oxide bonding layer 19, and a support substrate 20 in order from the front side to the back side. The support substrate 20 is, for example, a silicon wafer or glass.

The laminated body 15 is composed of a lower electrode adhesion layer 31 made of Ti (titanium, TiOx), a lower electrode layer 32 made of Pt (platinum), PZT (titanate) in order from the back side (lower side in FIG. 3) to the front side. A piezoelectric element layer 33 made of lead zirconate) and an upper electrode layer 34 made of Pt (platinum) are provided. The laminate 15 further includes a coating layer 37, which is made of SiO ₂ (silicon dioxide), and covers the surfaces of the lower electrode adhesion layer 31, the lower electrode layer 32, the piezoelectric element layer 33, and the upper electrode layer 34. It is covered.

The SOI layer 16 is made of Si (silicon). The BOX layer 17 is made of SiO ₂ (silicon dioxide) as an oxide film. The handle layer 18 is made of Si (silicon). The bonding layer 19 is made of SiO ₂ (silicon dioxide). The support substrate 20 is made of a Si (silicon) layer.

  From the laminate 15 and the SOI layer 16, the mirror part 2, the outer rectangular frame part 4, the inner actuator 6, the outer actuator 7, and the electrode pads 8 and 9 are produced as MEMS structures. The annular rib 40 is erected along the periphery of the back side of the inner rectangular frame portion 3 with the same height as the annular rib 11, and increases the rigidity of the inner rectangular frame portion 3.

  The annular ribs 11 and 40 and the back outer rectangular frame portion 23 are formed from the handle layer 18 as a MEMS structure. The back outer rectangular frame portion 23 has the same inner and outer contours as the outer rectangular frame portion 4. The front outer rectangular frame portion 4 and the back outer rectangular frame portion 23 are joined to each other to form an outer rectangular frame portion 24.

  The inner peripheral space 27 is defined on the inner peripheral side of the outer rectangular frame portion 24, and a front side space portion is formed by etching of the SOI layer 16 from the front side. Further, the BOX layer 17 and the handle layer 18 from the back side are formed. A back side space portion is formed by etching. The inner circumferential space 27 is a space that accommodates the movable structure portions of the mirror portion 2, the inner actuator 6, and the outer actuator 7 and allows displacement of these movable structure portions. The inner actuator 6 and the outer actuator 7 are an example of a movable structure portion interposed between the mirror portion 2 and the outer rectangular frame portion 24.

  Next, steps S1 to S20 (manufacturing method) for manufacturing a piezoelectric drive type biaxial MEMS optical deflector using a piezoelectric material lead zirconate titanate (PZT) thin film as an actuator will be described.

  4 to 12 show only the range of one biaxial MEMS optical deflector chip on the wafer. Steps S1 to S20 are performed on the wafer, and a plurality of two-axis MEMS optical deflector chips are manufactured from one wafer at a time. Although the structural diagram of the entire wafer in steps S1 to S20 is omitted, every section of the wafer (a section that eventually becomes a chip) has the same cross-sectional structure as the cross-sectional structure in steps S1 to S20 shown in the drawing.

  The waveform on the left and right of the cross section showing step S1 in FIG. 4 means that the illustrated structure continues in the horizontal direction. This waveform is omitted in the structural diagrams after step S2. Hereinafter, the MEMS processed wafers at the end stage of the steps S1 to S20 are denoted by reference numerals “101” to “120”.

  In step S1 of FIG. 4, a thermal insulating layer 30 of a thermal silicon oxide film having a thickness of 500 nm was formed on the surface of the SOI wafer 100 at the end stage of the step (not shown) before step S1 by a diffusion furnace.

  The SOI wafer 100 at the end stage of the process before the process S1 includes a bonding layer 19, a handle layer 18, a BOX layer 17, and an SOI layer 16 in order from the back side. For example, the SOI layer 16 has a thickness of 50 μm, the BOX layer 17 has a thickness of 2 μm, and the handle layer 18 has a thickness of 400 μm.

  In step S2, a Ti layer and a Pt layer were sequentially formed on the front side of the Si wafer 101 so as to have thicknesses of 50 nm and 150 nm, respectively, by sputtering. The Ti layer and the Pt layer constitute a lower electrode adhesion layer 31 and a lower electrode layer 32, respectively. 4 to 12, only the lower electrode layer 32 is shown, and the lower electrode adhesion layer 31 is not shown.

  Next, a film of lead zirconate titanate (hereinafter referred to as PZT), which is a piezoelectric material, is formed on the lower electrode layer 32 by a reactive arc discharge ion plating method, and the piezoelectric element layer 33 of the piezoelectric PZT film is formed. Formed. Thereafter, an upper electrode layer 34 of Pt layer was formed on the piezoelectric element layer 33 with a thickness of 150 nm by sputtering.

  In step S3, a pattern (movable) corresponding to the outer actuator 7 that drives the inner rectangular frame portion 3 by non-resonance driving and the inner actuator 6 for resonance driving of the mirror portion 2 on the substrate surface by photolithography and dry etching techniques. An example of the front side portion of the structure portion) is formed. Step S3 corresponds to the first step of the present invention.

  First, the upper electrode layer 34 and the piezoelectric element layer 33 were patterned to form patterns of the upper electrode and the piezoelectric PZT film corresponding to the outer actuator 7 and the upper electrode and the piezoelectric PZT film corresponding to the inner actuator 6. Similarly, the lower electrode layer 32 and the insulating layer 30 therebelow were also patterned, and the lower electrode and silicon oxide film for the outer actuator 7 and the lower electrode and silicon oxide film pattern for the inner actuator 6 were produced.

  In step S4, a silicon oxide film coating layer 37 having a thickness of 500 nm is formed on the entire surface of the wafer 103 in step S3 by plasma CVD.

  In step S5 of FIG. 5, a resist pattern is formed on the substrate surface by photolithography, a part of the silicon oxide film is removed by dry etching, and the contact hole 176 corresponding to the lower electrode and the upper electrode and single crystal silicon are processed The silicon oxide at the location 177 to be removed is removed by dry etching.

  In step S6, a resist pattern is formed by photolithography, an AlCu (1% Cu) film is formed by sputtering, and a wiring pattern is formed by lift-off. That is, the lower electrode and the upper electrode of the PZT actuator are electrically connected to the electrode pad on the outer periphery of the optical deflector via the AlCu film wiring 180.

  In step S7, after forming a resist pattern with photolithography, Ti and Ag are sequentially formed by sputtering, and a layer 187 of the mirror surface 10 of the mirror unit 2 is formed by lift-off.

  With the steps so far, the pre-process of silicon processing by deep-RIE is completed. Subsequent silicon processing steps will be described below.

  In step S8, the SOI layer 16 on the front side is etched by Deep-RIE, and the mirror part 2, the inner rectangular frame part 3 (FIG. 3), the outer rectangular frame part 4, the torsion bar 5, the inner actuator 6 and the outer actuator 7 are removed. Form. The inner rectangular frame (FIG. 3), the torsion bar 5, the inner actuator 6, and the outer actuator 7 correspond to the movable structure of the present invention.

  In step S9 of FIG. 6, a liquid wax is applied on the processed SOI layer 16 by using a spinner device or the like to fill the step of the structure formed by etching, and a flat wax layer (an example of a soluble coating layer) is obtained. ) 190 is formed.

  In step S10, the support substrate 192 is placed on the wax layer 190 of the wafer 109 heated to 100 ° C. to 150 ° C., and the wax layer 190 is solidified by cooling while applying an appropriate load (eg, 1 kN). The support substrate 192 is temporarily joined to the wafer 109. At this time, if bonded together in a vacuum, it is possible to form a good bonding state that does not include air voids.

  Of the steps S9 and S10, the portion of the process until the support substrate 192 is placed corresponds to the second step of the present invention. The process after placing the support substrate 192 in the process S10 corresponds to the third process of the present invention.

  In step S11, the bonding layer 19 and the handle layer 18 are etched by Deep-RIE to form a rib structure portion 197 on the back side of the mirror, a rocking space portion 198 of the mirror, and a rib structure portion 199 of the inner rectangular frame portion 3.

  In step S12, the buried oxide film (BOX layer 17) is also removed by BOE (Buffered Oxide Etch) processing. Thereby, the rib 11 (see also FIG. 3) on the back side of the mirror, the rib 40 (see also FIG. 3) of the inner rectangular frame portion 3, and the inner circumferential space 27 (see also FIG. 3) are completed. Step S12 corresponds to the fourth step of the present invention.

  In step S13 of FIG. 7, a UV (ultraviolet) type dicing tape (an example of a front side tape) 204 stretched around the rim is attached to the support substrate 192 side.

  In step S14, a full dice 208 is performed along a partition line as a predetermined dicing line together with the temporarily bonded support substrates by a blade dicing apparatus with the back side of the handle layer facing upward, and individual chips (of the wafer of the present invention). (Equivalent to each compartment). Steps S13 and S14 correspond to the fifth step of the present invention.

  In step S15 of FIG. 8, the back side of the handle layer 18 is attached to another UV type dicing tape 210 (an example of a back side tape) stretched on the rim, and the dicing tape 204 attached to the support substrate 192 side is attached. Then, UV light is irradiated (ultraviolet irradiation), and the dicing tape 204 is peeled off and removed. This means that the wafer is transferred from the dicing tape 204 to the dicing tape 210. Step S15 corresponds to the sixth step of the present invention.

  In step S16 in FIG. 9, a stencil mask 213 is applied to the dicing tape 210 from the back side of the wafer 115 in step S15. Details of the stencil mask 213 are shown in FIG. In FIG. 14, the stencil mask 213 is viewed from the dicing tape 210 side. The stencil mask 213 is made of, for example, a stainless steel plate having a thickness of 2 to 3 mm, has a width that completely covers the back surface of the wafer 115, and has a plurality of openings 214 in a grid-like arrangement. The number of openings 214 in one stencil mask 213 is equal to the number of optical deflector chips manufactured from the wafer 115.

  The stencil mask 213 also has mark patterns 215 at the four corners. The mark pattern 215 is formed as a cross-shaped convex portion, and when the stencil mask 213 is applied to the dicing tape 210, the mark pattern 215 is fitted to alignment marks (not shown) as cross-shaped concave portions at the four corners of the wafer 115, Positioned. The stencil mask 213 is not used every time but is used repeatedly.

  It returns to process S16 of FIG. The opening 214 will be described with the stencil mask 213 positioned on the wafer 115 and fixed to the wafer 115. The opening 214 is centered on the central axis of the inner circumferential space 27 of the wafer 115, and the circumferential contour line is inside the circumferential contour line of the inner circumferential space 27. The peripheral contour line of the opening 214 is outside the outer periphery of the annular rib 40 as viewed in the direction of the central axis of the inner peripheral space 27.

  In step S <b> 16, after the stencil mask 213 is fixed to the wafer 115, UV (ultraviolet) light 217 is irradiated from the back side of the wafer 115. The dicing tape 210 is divided into an exposed portion 219 exposed to the back side through the opening 214 and a non-exposed portion 220 that is prevented from being exposed by the stencil mask 213. The dicing tape 210 is irradiated with the UV light 217 through the stencil mask 213, whereby the exposed portion 219 is exposed and the sticking force is reduced. On the other hand, the non-exposed part 220 escapes exposure and maintains sticking force.

  In step S17 of FIG. 10, the stencil mask 213 is removed from the wafer 116 (step S16). The step of fixing the stencil mask 213 on the back side of the wafer 115 in step S16 corresponds to the seventh step of the present invention. The step of irradiating UV (ultraviolet) light 217 from the back side of the wafer 115 in step S16 and step S17 correspond to the eighth step of the present invention.

  In step S18 of FIG. 11, the wafer 117 of step S17 is immersed in the IPA solution together with the dicing tape 210. The liquid wax is dissolved in the IPA solution by immersion for several tens of minutes to several hours, and the support substrate 192 temporarily bonded to the wafer 117 is peeled off and removed.

  In step S19 of FIG. 12, the liquid level of the IPA solution decreases as the wafer 117 is dried, and the decrease in the liquid level of the IPA solution in the inner circumferential space 27 is caused by the mirror part 2, the inner rectangular frame part 3, and the inner actuator. 6 and the outer actuator 7 are entrained to the dicing tape 210 closer to the center of the inner circumferential space 27 due to the surface tension of the IPA solution. As a result, the tips of the annular ribs 11 and 40 come into contact with the dicing tape 210.

  If the adhering force remains at the portion of the dicing tape 210 that contacts the tips of the annular ribs 11 and 40, the annular ribs 11 and 40 are adhered to the dicing tape 210, and then the IPA solution is placed in the inner circumferential space. Even if it completely disappears from 27, the tips of the annular ribs 11 and 40 remain stuck to the dicing tape 210 and remain greatly depressed into the inner circumferential space 27, causing damage to these movable structures.

  However, since the tips of the annular ribs 11 and 40 come into contact with the exposed portion 219 whose adhesive strength has been sufficiently reduced in step S16 (FIG. 9), sticking to the dicing tape 210 is avoided, and the IPA solution is in the inner periphery. As soon as it disappears from the side space 27, the movable structure returns to its original height as shown in step S20 of FIG. In this way, a workpiece in which the MEMS optical deflector chips 120 are aligned on the dicing tape 210 is obtained. Steps S18 and S19 correspond to the ninth step of the present invention.

  After that, if the dicing tape 210 is expanded to increase the distance between the MEMS chips, and the adhesive power is reduced by irradiating the tape with UV light, each chip 120 can be picked up as a piece.

  Thereafter, the electrical characteristics of the PZT film and the wiring are evaluated by electrical inspection to mark a defective chip, and then only the non-defective chip 120 is mounted on the ceramic package to complete the MEMS optical deflector package.

  In this embodiment, the simplest open-air package form is adopted. The laser light from the light source is directly reflected and scanned by the movable mirror of the MEMS optical deflector and used for image projection.

  Assuming that the thickness of the mirror body is λ, as a result of introducing the reinforcing rib structure on the back side of the mirror, the static surface deformation of the mirror body changes from (1/4) λ or less before introduction to (1/8) λ The following was improved and the spread and distortion of the scanning laser beam were reduced. Moreover, since the processing structure of the SOI layer was protected with wax, the mirror surface reflectivity was 85% or more without being affected by high-pressure pure water during dicing.

  For this MEMS optical deflector package, an AC voltage of Vpp = 20V and a drive frequency (resonance frequency) of 17 kHz is applied to the resonance actuator for horizontal axis scanning, and Vpp = 20V is applied to the non-resonance actuator for vertical axis scanning. When an AC voltage with a driving frequency of 60 Hz was applied, a mechanical deflection angle of ± 12 ° on the horizontal axis and ± 8 ° on the vertical axis was observed. Since there was no damage at the periphery of the mirror in the dicing process, the yield rate within the wafer exceeded 90%, and the variation in deflection angle and resonance frequency was within ± 3%, indicating a very good yield.

  Although the present invention has been described with reference to the embodiment, the present invention is not limited to the embodiment, and can be implemented in various ways within the scope of the gist.

  For example, in the embodiment, the part processed from the back side of the mirror part is a rib, but the back side part of the mirror part formed by etching from the back side in the fourth step of the present invention is limited to the rib of the mirror part. Alternatively, it may be a back side portion other than the rib, for example, the back side itself.

  As a liquid coating, if the condition that the step generated by etching from the front side is smoothed and the support substrate is fixed to the wafer main body and can be dissolved by immersion in a predetermined solution is satisfied, Coating agents other than liquid wax in the form can be employed.

  In step S9 of FIG. 6, a liquid wax soluble in isopropyl alcohol is used, but a liquid coating material soluble in an alkaline solution can be used as the liquid coating material of the present invention.

  Although the opening 214 of FIG. 14 is rectangular according to the outer periphery contour of the annular rib 40, the opening of the stencil mask of the present invention has other peripheral contours according to the outer periphery contour of the back side portion of the movable structure portion. be able to. The stencil mask of the present invention can be made of a material other than stainless steel as long as it can block ultraviolet rays, easily form the opening 214, and has a predetermined strength.

DESCRIPTION OF SYMBOLS 1 ... Optical deflector, 2 ... Mirror part, 10 ... Mirror surface, 16 ... SOI layer, 17 ... BOX layer, 18 ... Handle layer, 14 ... Outside rectangular frame Part (support), 17 ... inner peripheral side space (front side space part and back side space part), 190 ... wax layer (coating material layer), 192 ... support substrate, 204 ... dicing tape ( Front side tape), 210 ... Dicing tape (back side tape), 213 ... Stencil mask, 214 ... Opening.

Claims (3)

A method of manufacturing an optical deflector comprising: a mirror part having a mirror surface on the front side; a support body that defines a front side space part that accommodates the mirror part and a back side space part that allows displacement of the mirror part; ,
By etching the SOI layer from the front side of the wafer having the SOI layer, the BOX layer, and the handle layer in order from the front side to the back side, the front side space part and the front side part of the mirror part are formed on the front side of each section of the wafer. A first step of forming;
A liquid coating agent that is soluble in a predetermined solution is applied to the front surface of the wafer after the first step to form a coating layer, and a support substrate that covers the front side of the coating layer is applied. Process,
A third step of fixing the support substrate to the wafer after the second step via the coating layer and solidifying the coating layer;
A fourth step of forming the back side space portion and the back side portion of the mirror portion on the back side of each section of the wafer by etching the handle layer and the BOX layer from the back side of the wafer after the third step;
A fifth step of attaching the front tape to the front side of the support substrate to the wafer after the fourth step, and then dicing along the partition lines of the wafer from the back side of the wafer;
For the wafer after the fifth step, on the back side, a sixth step of sticking a back side tape whose adhesive strength is reduced by ultraviolet irradiation; and
A stencil mask having an opening whose peripheral contour is smaller than the peripheral contour of the backside space portion is applied to the back side of the backside tape with respect to the wafer after the sixth step so that the opening is inside the backside space portion. A seventh step;
An eighth step of separating the stencil mask after irradiating ultraviolet rays from the back side to the wafer after the seventh step;
A method of manufacturing an optical deflector, comprising: a ninth step of removing the coating layer and the support substrate by immersing the wafer in the predetermined solution with respect to the wafer after the eighth step. In the manufacturing method of the optical deflector according to claim 1,
The method of manufacturing an optical deflector, wherein a back side portion of the mirror portion formed in the fourth step is a rib. In the manufacturing method of the optical deflector of Claim 1 or 2,
The optical deflector includes a movable structure part that is interposed between the mirror part and the support and is displaced together with the mirror part,
The movable structure portion has a front side portion formed together with the front side portion of the mirror portion in the first step, and a back side portion formed together with the back side portion of the mirror portion in the fourth step. A method of manufacturing an optical deflector.