JP2010145260A - Method for manufacturing mems sensor, and mems - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a MEMS sensor wherein a wafer used as a weight part is hardly damaged. <P>SOLUTION: This method is described as follows: a laminated structure is formed, which includes a support part, a flexible part having flexibility with one end bonded to the support part, a connection part bonded to the other end of the flexible part, and a detection part for detecting deformation of the flexible part; a heterogeneous domain which is heterogeneous from a residual part is formed in an object domain of the wafer circumscribed with a domain used as the weight part to be bonded to a bottom surface of the connection part; a domain of the residual part used as the weight part inside the heterogeneous domain is bonded to the bottom surface of the connection part; and the heterogeneous domain is removed from the wafer bonded to the connection part. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a MEMS (Micro Electro Mechanical Systems) sensor and a MEMS sensor.

2. Description of the Related Art Conventionally, MEMS sensors such as an acceleration sensor and a vibration gyroscope that convert deformation of a flexible portion coupled to a weight portion into an electrical signal are known (see, for example, Patent Documents 1 and 2). In such a MEMS sensor, the side surface of the weight portion is formed by dicing a silicon wafer or a glass wafer that becomes the weight portion.
JP-A-8-54413 Japanese Patent No. 2892788 JP-A-6-324076

  However, in the process of dicing the wafer to be the weight part, the wafer is easily damaged by the frictional force between the wafer and the rotary blade of the dicer, or the thin flexible part previously formed is easily damaged.

  The present invention was created to solve this problem, and an object of the present invention is to provide a method for manufacturing a MEMS sensor in which a wafer serving as a weight portion is less likely to be damaged.

  (1) A manufacturing method of a MEMS sensor for achieving the above object includes: a supporting part; a flexible part having one end coupled to the supporting part and having flexibility; and the other end of the flexible part. Forming a laminated structure including a connecting portion and a detecting portion for detecting deformation of the flexible portion, and a remaining portion in a target region of the wafer circumscribing a region to be a weight portion coupled to a bottom surface of the connecting portion. A heterogeneous heterogeneous region is formed, the remaining region that is inside the heterogeneous region and becomes the weight portion is bonded to the bottom surface of the connecting portion, and the extraneous region is removed from the wafer bonded to the connecting portion. Including.

  According to the present invention, since the weight portion can be released in the wafer by removing the heterogeneous region from the wafer by etching, the wafer serving as the weight portion is not easily damaged. In the present specification, the terms “upper” and “bottom” are used with the positional relationship of the flexible part with respect to the weight part as the upper part.

(2) In the MEMS sensor manufacturing method for achieving the above object, the wafer may be made of photosensitive glass, and the heterogeneous region may be formed by crystallizing the target region by exposure.
According to the present invention, since it is not necessary to form a sacrificial film that becomes a heterogeneous region, the manufacturing process can be simplified.

(3) In the MEMS sensor manufacturing method for achieving the above object, the surface layer of the heterogeneous region is removed from the upper surface side of the wafer before bonding the wafer to the connecting portion, and the wafer is used as the connecting portion. After the bonding, the remaining part of the heterogeneous region may be removed from the bottom surface side of the wafer.
According to the present invention, it is possible to reduce the etching time performed to remove the heterogeneous region after the wafer is bonded to the connecting portion, so that it is possible to reduce the damage given to the laminated structure by the etching.

(4) In the method of manufacturing a MEMS sensor for achieving the above object, the target region may be crystallized by irradiating a laser beam condensed by a lens.
According to the present invention, since the target area to be exposed can be freely controlled, the shape of the weight portion can be freely designed.

(5) In the MEMS sensor manufacturing method for achieving the above object, the wafer is bonded to the bottom surface of the connecting portion and the bottom surface of the support portion via a resin layer, and the pattern of the support portion and the weight portion A part of the pattern may overlap, and the resin layer bonded to the bottom surface of the support portion may serve as a buffer layer between the weight portion and the support portion.
According to the present invention, since the resin layer used for adhesion between the connecting portion and the weight portion is formed as a buffer layer between the weight portion and the support portion, a MEMS sensor with high impact resistance can be realized with a simple structure. In the present specification, the “pattern” refers to a shape viewed from a direction perpendicular to the bottom surface of the connecting portion.

(6) In the MEMS sensor manufacturing method for achieving the above object, the wafer may be directly bonded to the bottom surface of the connection portion and the bottom surface of the support portion.
According to the present invention, the connecting portion and the weight portion can be firmly joined.

(7) A MEMS sensor for achieving the above object includes a support part, a flexible part having one end coupled to the support part and having flexibility, and a connecting part coupled to the other end of the flexible part. And a weight part made of crystallized glass and joined to the bottom surface of the connecting part, and a detection part for detecting deformation of the flexible part accompanying the movement of the weight part.
According to the present invention, since the weight portion joined to the connecting portion is made of crystallized glass, the wafer serving as the weight portion is not easily damaged in the manufacturing process.

  The order of the operations described in the claims is not limited to the order of description as long as there is no technical obstruction factor, and may be executed at the same time, may be executed in the reverse order of the description order, or may be continuous. It does not have to be executed in order. Further, the order of the operations described in the claims is not limited to the order of description as long as there is no technical obstruction factor, and may be executed at the same time, may be executed in the reverse order of the description order, or may be continuous. It does not have to be executed in order.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the same code | symbol is attached | subjected to the corresponding component in each figure, and the overlapping description is abbreviate | omitted.
1. First embodiment (Configuration)
A motion sensor which is a first embodiment of the MEMS sensor of the present invention is shown in FIG. 1A, FIG. 1B and FIG. 1A is a cross-sectional view showing a sensor die 1A of the motion sensor 1, and is a cross-sectional view taken along line AA shown in FIG. 1B. FIG. 1B is a top view of the sensor die 1A. FIG. 2 is a sectional view showing the motion sensor 1. In FIG. 1A and FIG. 2, the interface of the layer which comprises the sensor die 1A is shown with the broken line, and the boundary of the mechanical component which comprises the sensor die 1A is shown with the continuous line.

  The motion sensor 1 is a MEMS sensor for detecting a three-axis acceleration component and an angular velocity component orthogonal to each other. The motion sensor 1 includes a package 1B shown in FIG. 2 and a sensor die 1A accommodated in the package 1B.

As shown in FIG. 1A, the sensor die 1A includes a base layer 80, a thick silicon layer 11 as a thick layer, an etching stopper layer 12, a thin silicon layer 13 as a thin layer, a first insulating layer 20, and an electrode. This is a laminated structure including layers 31 and 33, a piezoelectric layer 32, a second insulating layer 40, and a surface wiring layer 50. The base layer 80 is made of glass such as Pyrex (registered trademark) or crystallized glass in which SiO ₂ and B ₂ O ₃ are mixed. The thickness of the base layer 80 is 300 μm. Both the thick silicon layer 11 and the thin silicon layer 13 are made of single crystal silicon (Si). The thickness of the thick silicon layer 11 is 625 μm. The thickness of the thin silicon layer 13 is 10 μm. The etching stopper layer 12 and the first insulating layer 20 are made of a silicon oxide film (SiO ₂ ). The thickness of the etching stopper layer 12 is 1 μm. The thickness of the first insulating layer 20 is 0.5 μm. The electrode layers 31 and 33 are made of platinum (Pt). The electrode layers 31 and 33 have a thickness of 0.1 μm. The piezoelectric layer 32 is made of PZT (lead zirconate titanate). The thickness of the piezoelectric layer 32 is 3 μm. The second insulating layer 40 is made of photosensitive polyimide. The thickness of the second insulating layer 40 is 10 μm. The surface wiring layer 50 is made of aluminum (Al). The thickness of the surface wiring layer 50 is 0.5 μm.

  A sensor die 1A of the motion sensor 1 includes a frame-shaped support portion S, four beams F arranged in a cross shape inside the support portion S, and a column-shaped connecting portion coupled to each of the four beams F. C, a weight portion M coupled to the connecting portion C, a piezoresistive element 131 as a detecting means provided on each of the four beams F, a detecting piezoelectric element 30b, and each of the four beams F And a driving piezoelectric element 30a for driving the weight M by bending the four beams F.

  The support portion S has a rectangular frame shape as shown in FIG. 1B. The support S includes a thick silicon layer 11, an etching stopper layer 12, a thin silicon layer 13, a first insulating layer 20, and a second insulating layer 40. Since the support portion S includes the thick silicon layer 11 and is fixed to the package 1B via the base layer 80, the support portion S behaves as a substantially rigid body that does not move in the coordinate system fixed to the motion sensor 1. A rectangular frame-shaped portion of the base layer 80 is coupled to the bottom surface of the support portion S. The bottom surface of the portion of the base layer 80 that is bonded to the support portion S is joined to the bottom surface of the package 1B via the adhesive layer 92.

  Each of the four beams F as the flexible portion has a cantilever shape. The beam F includes a thin silicon layer 13, a first insulating layer 20, and a second insulating layer 40. Since the beam F does not include the thick silicon layer 11, the beam F behaves as a flexible film. One end of each of the four beams F is coupled to four sides inside the support portion S. Since the support portion S behaves as an immovable rigid body, one end of the beam F is a fixed end in the coordinate system fixed to the motion sensor 1. The four beams F protrude from the four sides inside the support part S toward the center of the space inside the support part S. The protruding ends of the four beams F are coupled to the connecting portion C. Since the weight portion M is coupled only to the connecting portion C and is lifted from the bottom surface 90a of the package 1B as shown in FIG. 2, the protruding end of the beam F coupled to the connecting portion C is a coordinate fixed to the motion sensor 1. Act as a free end in the system. The four beams F are deformed as the weight M moves.

  The weight part M has the form of a plate whose outer periphery is rectangular when viewed from the thickness direction of the beam F. The weight portion M includes a base layer 80. Since the weight part M includes the base layer 80, it behaves substantially as a rigid body. The pattern of the weight portion M (the shape seen from the direction perpendicular to the bottom surface of the connecting portion C and the shape seen from the thickness direction of the beam F) and the pattern of the thick silicon layer 11 of the support portion S are one. The parts overlap. Specifically, the rectangular inner periphery of the thick silicon layer 11 of the support part S is located inside the outer periphery of the rectangular part of the weight part M, and the vicinity of the outer periphery of the weight part M is the bottom surface of the thick silicon layer 11 of the support part S. And the beam F in the thickness direction. A gap G is formed between the upper surface of the weight portion M and the bottom surface of the thick silicon layer 11 of the support portion S. Depending on the height of the gap G, the range of motion of the weight M is regulated. That is, since the thick silicon layer 11 of the support portion S functions as a stopper for the weight portion M, the deformation range of the beam F is restricted according to the height of the gap G. The gap G is formed by an annular recess 80a formed on the outer peripheral portion of the upper surface of the weight portion M.

  The connecting portion C is formed by four prisms F of the thick silicon layer 11, the quadrangular column of the etching stopper layer 12, the thin silicon layer 13, the first insulating layer 20, and the second insulating layer 40. It is composed of an enclosed quadrangular prism. Since the connecting portion C includes the thick silicon layer 13, it behaves substantially as a rigid body. The bottom surface of the connecting portion C connected to the four beams F is connected to the upper surface of the weight portion M. That is, the connecting part C connects the weight part M and the four beams F. The shape and dimensions of the connecting portion C may be set so that the connecting portion C connects the weight portion M and the beam F and behaves as a substantially rigid body that moves integrally with the weight portion M. When there is a difference in thermal expansion coefficient between the part M and the thick silicon layer constituting the connecting part C so that the stress generated by the difference in thermal expansion coefficient between the beam F and the weight part M is not transmitted to the thin beam F The thickness of 11 is preferably thicker. For this reason, in this embodiment, the thick silicon layer 11 is comprised from the single crystal silicon wafer which is a bulk material.

The piezoresistive element 131 is a detecting means for detecting the deformation of the beam F accompanying the movement of the weight portion M. The piezoresistive element 131 is formed in the vicinity of the boundary between the beam F and the support portion S. The piezoresistive element 131 includes a high resistance portion 131a and a low resistance portion 131b formed in the thin silicon layer 13. Boron (B) ions are diffused in the high resistance portion 131a at a concentration of 2 × 10 ¹⁸ / cm ³ . Boron ions are diffused in the low resistance portion 131b at a concentration of 2 × 10 ²⁰ / cm ³ . The low resistance portion 131b having a smaller specific resistance than the high resistance portion 131a reduces the connection resistance between the high resistance portion 131a and the surface wiring layer 50. The piezoresistive element 131 is connected to the electrode layer 31 through a contact hole formed in the first insulating layer 20. The electrode layer 31 is connected to the surface wiring layer 50 through a contact hole formed in the second insulating layer 40. The piezoresistive elements 131 are connected so as to form a total of three Wheatstone bridges, one set of four formed on the two beams F arranged linearly in the longitudinal direction. A signal corresponding to each of the three-axis acceleration components orthogonal to each other can be obtained from each Wheatstone bridge.

  Each of the driving piezoelectric element 30 a and the detecting piezoelectric element 30 b includes electrode layers 31 and 33 and a piezoelectric layer 32. The electrode layer 31 constituting the lower electrode of the driving piezoelectric element 30a and the detecting piezoelectric element 30b is connected to the surface wiring layer 50 through a contact hole formed in the periphery of the sensor die 1A. The electrode layer 33 constituting the upper electrode of the driving piezoelectric element 30a and the detecting piezoelectric element 30b is connected to the surface wiring layer 50 through a contact hole formed immediately above the driving piezoelectric element 30a and the detecting piezoelectric element 30b. is doing.

  The driving piezoelectric element 30 a is formed in the vicinity of the boundary between the beam F and the support portion S. The driving piezoelectric element 30a is a driving means for vibrating the weight portion M. A sinusoidal signal for rotating the weight M is applied to the driving piezoelectric element 30a.

  The detecting piezoelectric element 30b is formed in the vicinity of the boundary between the beam F and the connecting portion C. The detecting piezoelectric element 30b is a detecting means for detecting the deformation of the beam F accompanying the movement of the weight portion M. Stress and strain associated with the deformation of the beam F are concentrated at the boundary between the weight portion M that behaves substantially as a rigid body and the beam F having flexibility. For this reason, by providing the detecting piezoelectric element 30b on the boundary between the weight part M and the beam F, it is possible to efficiently detect the strain accompanying the deformation of the flexible part F. From the detection piezoelectric element 30b, a signal corresponding to the three-axis angular velocity components can be obtained by synchronous detection or the like.

  The driving piezoelectric element 30a may be provided on each boundary between the connecting portion C and the four beams F. Moreover, you may provide the piezoelectric element 30b for a detection on each boundary of the support part S and the four beams F. FIG. In any case, it is desirable to provide the driving piezoelectric element 30a and the detecting piezoelectric element 30b in the vicinity of the boundary (vibration end) between the beam F and a substantially rigid body coupled thereto.

  A package 1 </ b> B shown in FIG. 2 includes a lidless box-type base 90 and a cover 94 that closes the internal space of the base 90. The base 90 and the cover 94 are joined via an adhesive layer 93. The base 90 is provided with a plurality of through electrodes 91. One end of the wire 95 is bonded to the surface wiring layer 50 of the sensor die 1A, and the other end is bonded to the through electrode 91 of the package 1B. The portion of the rectangular frame that is bonded to the support portion S of the base layer 80 of the sensor die 1A is bonded to the bottom surface 90a on the inner side of the base 90 by the adhesive layer 92. The height of the gap between the weight portion M of the sensor die 1A and the bottom surface 90a inside the base 90 is set by the depth of the recess formed in the bottom surface 90a and the thickness of the adhesive layer 92. Note that an LSI die connected to the sensor die 1A may be accommodated in the package 1B.

(Production method)
Hereinafter, an example of a method for manufacturing the motion sensor 1 will be described with reference to FIGS. 3 to 19 are all cross-sectional views corresponding to the line AA shown in FIG. 1B except for FIGS. 9B and 11. 9B and 11 are cross-sectional views corresponding to the line BB shown in FIG. 9C.

First, as shown in FIG. 3, a high resistance portion 131a is formed by introducing impurities into the thinner thin silicon layer 13 of the SOI wafer 10 using a protective film R1 made of a photoresist. As impurities, boron (B) ions are implanted at a concentration of 2 × 10 ¹⁸ / cm ³ , for example. After ion implantation, activation by annealing is performed. The SOI wafer 10 includes a thick silicon layer 11, an etching stopper layer 12, and a thin silicon layer 13. The thick silicon layer 11 of the SOI wafer 10 is made of single crystal silicon having a thickness of 625 μm. The etching stopper layer 12 is made of silicon dioxide having a thickness of 1 μm. The thin silicon layer is made of single crystal silicon having a thickness of 10 μm.

  Next, a first insulating layer 20 is formed on the surface of the thin silicon layer 13 as shown in FIG. As the first insulating layer 20, a silicon dioxide film having a thickness of 0.5 μm is formed by, for example, thermal oxidation or CVD.

Next, as shown in FIG. 5, a contact hole 20h is formed in the first insulating layer 20 using a protective film R2 made of a photoresist to expose the high resistance portion 131a. The contact hole 20h is formed by anisotropically etching the first insulating layer 20 by reactive ion etching using, for example, CF ₄ + H ₂ or CHF ₃ gas. The contact hole 20h may be formed by wet etching using hydrofluoric acid (HF) or buffered hydrofluoric acid (BHF).

Subsequently, the low resistance portion 131b is formed by introducing impurities into the high resistance portion 131a exposed from the contact hole 20h. As impurities, boron ions are implanted at a concentration of 2 × 10 ²⁰ / cm ³ , for example. After ion implantation, activation by annealing is performed.

Next, as shown in FIG. 6, the electrode layer 31, the piezoelectric layer 32, and the electrode layer 33 are laminated in this order on the surface of the first insulating layer 20. As the electrode layers 31 and 33, films made of platinum are formed by sputtering or the like. Titanium (Ti) having a thickness of 30 nm may be formed as an adhesion layer between the first insulating layer 20 and the electrode layer 31. The material of the electrode layer 31 may be iridium (Ir) or iridium oxide (IrO ₂ ). As a material of the electrode layer 33, iridium, iridium oxide, gold (Au), or the like may be used. As the piezoelectric layer 32, a film made of PZT is formed by sputtering, sol-gel method or the like. Titanium having a thickness of 30 nm may be formed as an adhesion layer between the electrode layer 33 and the piezoelectric layer 32.

Next, as shown in FIG. 7, the electrode layer 33 and the piezoelectric layer 32 are etched into a predetermined shape by etching the electrode layer 33 and the piezoelectric layer 32 using a protective film R3 made of a photoresist. Specifically, the electrode layer 33 made of platinum is patterned by ion milling using argon (Ar) ions. The piezoelectric layer 32 made of PZT is patterned by reactive ion etching using chlorine (Cl ₂ ) as an etching gas.

  Next, as shown in FIG. 8, the electrode layer 31 is etched into a predetermined shape by etching using the protective film R4 made of a photoresist. As a result, the driving piezoelectric element 30a and the detecting piezoelectric element 30b are formed. At the same time, the wiring of the piezoresistive element 131 and the wiring of the lower electrode of the driving piezoelectric element 30a and the detecting piezoelectric element 30b are formed. Specifically, the electrode layer 31 made of platinum is patterned by ion milling using argon (Ar) ions. The electrode layer 31 may be patterned by reactive ion etching.

  Next, as shown in FIGS. 9A, 9B, and 9C, the second insulating layer 40 is formed on the surfaces of the insulating layer 20, the electrode layer 31, and the electrode layer 33. Specifically, photosensitive polyimide is applied, and the contact hole 40h and the opening 40e are formed by exposure and development, thereby forming the second insulating layer 40 having a predetermined pattern. Note that an inorganic material such as a silicon oxide film, a silicon nitride film, or alumina may be used as the material of the second insulating layer 40.

Next, as shown in FIG. 10, a surface wiring layer 50 is formed on the surface of the second insulating layer 40, and the surface wiring layer 50 is etched to form a surface wiring layer 50 constituting a predetermined pattern of wiring. As a result, the wiring of the upper electrode of the piezoelectric element and the bonding pad are constituted by the surface wiring layer 50. As the surface wiring layer 50, an aluminum (Al) film having a thickness of 0.3 μm is formed by sputtering, for example. A copper or aluminum silicon (AlSi) film may be formed as the surface wiring layer 50. The pattern of the surface wiring layer 50 is formed by reactive ion etching using, for example, chlorine (Cl ₂ ) gas.

Next, as shown in FIG. 11, the first insulating layer 20 and the thin silicon layer 13 are patterned into a predetermined shape using the second insulating layer 40 as a protective film. As a result, a pattern of four beams F is formed. The first insulating layer 20 is patterned by reactive ion etching using CHF ₃ or CF ₄ + H ₂ as an etching gas. The thin silicon layer 13 is patterned by reactive ion etching using CF ₄ + O ₂ as an etching gas. The pattern of the beam F may be formed by wet etching using tetramethylammonium hydroxide (TMAH) or potassium hydroxide (KOH).

  Next, the surface on which the surface wiring layer 50 of the laminated structure W formed by the above-described process is formed is bonded to the sacrificial substrate 71 as shown in FIG. As the adhesive layer B, for example, a wax, a photoresist, a double-sided pressure-sensitive adhesive sheet, or the like is used.

Next, as shown in FIG. 13, the thick silicon layer 11 is etched using the protective film R5 made of a photoresist to form an annular through hole 11h in the thick silicon layer 11, thereby forming the thick silicon layer 11 in the connecting portion C. The part which consists of is formed. Specifically, for example, the thick silicon layer 11 is patterned by deep-RIE (so-called Bosch process) in which the steps of passivation using SF ₆ plasma gas and etching using C ₄ F ₈ plasma gas are alternately repeated at short time intervals. To do. The patterning of the thick silicon layer 11 may be performed first, or may be performed during the process of processing the surface side of the thin silicon layer 11.

  Next, the etching stopper layer 12 exposed from the annular through hole 11h is isotropically etched as shown in FIG. By performing the above steps, the support portion S, the beam F as a flexible portion having one end coupled to the support portion S, the connecting portion C coupled to the other end of the beam F, and the deformation of the beam F The laminated structure W including the piezoresistive element 131 and the detecting piezoelectric element 30b as a detection unit for detecting the above is completed.

Next, processing of the wafer that becomes the base layer 80 constituting the weight portion M will be described.
First, as shown in FIG. 14, an annular recess 80a is formed on the upper surface (one of the main surfaces) of the wafer 80 to be the base layer 80 using a protective film R6 made of photoresist. The annular recess 80 a secures a gap G between the weight part M and the support part S. The wafer 80 is preferably made of a transparent bulk material such as a glass wafer. Specifically, for example, Pyrex (registered trademark) glass having a thickness of 500 μm is used as the wafer 80. Then, an annular recess 80a having a depth of 10 μm is formed by reactive ion etching using CHF ₃ + O ₂ as an etching gas. Note that crystallized glass may be used for the wafer 80. By using crystallized glass for the wafer 80, the wafer 80 is less likely to be damaged in a bonding process or a dicing process between the laminated structure W and the wafer 80 described later. Further, instead of forming the annular recess 80a by a combination of formation of the protective film R6 by photolithography and etching, the annular recess 80a may be formed by mechanical processing such as nanoimprinting, laser processing, or sandblasting.

Next, an annular groove 80b is formed on the upper surface of the wafer 80 using a protective film R7 made of photoresist. The depth of the annular groove 80b is set to be equal to the thickness of the weight portion M or set slightly deeper than the thickness of the weight portion M with reference to the thickness of the weight portion M. Here, the depth of the annular groove 80b is 300 μm, which is equal to the thickness of the weight portion M. The side surface of the weight portion M is determined by forming the annular groove 80b. That is, by making the annular groove 80 b circumscribe the region that becomes the weight portion M, the inner side surface of the annular groove 80 b becomes the side surface of the weight portion M. At this time, the annular groove 80b is formed in a region continuous with the annular recess 80a or inside the annular recess 80a so that the annular recess 80a reaches the outer periphery of the upper surface of the weight portion M. The annular groove 80b is formed by reactive ion etching using CHF ₃ as an etching gas.

  Instead of forming the annular recess 80a and the annular groove 80b using the two protective films R6 and R7, the wafer 80 is different from the wafer 80 together with a protective film having a one-dimensional pattern formed using a halftone mask or a laser. The annular recess 80a and the annular groove 80b may be formed in one step by etching in the isotropic direction.

Next, as shown in FIG. 16, by forming a sacrificial film 60 on the upper surface of the wafer 80, the annular recess 80a and the annular groove 80b are filled. As a result, a heterogeneous region made of a sacrificial film 60 that is different from the rest is formed on the wafer 80. As the sacrificial film 60, a titanium nitride (TiNx) film having a thickness of 0.3 μm as an adhesion layer is formed on the upper surface of the wafer 80 by a CVD method, and then a copper (Cu) film having a thickness of 10 μm is formed by an electroplating method. . The interface between the sacrificial film 60 and the wafer 80 serves as a stopper for end point control when the bottom surface of the wafer 80 is retracted by CMP or etching. Therefore, when the sacrificial film 60 has a multi-layer structure, a material that functions as a stopper for polishing or etching of the wafer 80 is used for a layer in contact with the wafer 80, and the same material as that of the wafer 80 is used for a layer that does not contact the wafer 80. You can also. Thus, by making the sacrificial film 60 into a multilayer structure, the material of the sacrificial film 60 can be optimized from the viewpoint of stress and throughput. As the single-layer sacrificial film 60, an inorganic film such as polycrystalline silicon or silicon nitride may be formed by a CVD method, or an organic film such as polyimide / photoresist may be formed by spin coating or the like. Alternatively, the lower layer of the sacrificial film 60 in contact with the wafer 80 may be formed of a silicon nitride (Si _x N _y ) film, and the upper layer of the sacrificial film 60 in contact with the wafer 80 may be formed of a polyimide film.

Next, as shown in FIG. 17, the surface layer of the sacrificial film 60 is removed until the upper surface of the wafer 80 is exposed. When the sacrificial film 60 has a two-layer structure of a lower layer of titanium nitride and an upper layer of copper, the end point of CMP of the copper film is controlled using the titanium nitride film as a polishing stopper, and the titanium nitride film is removed for a predetermined time. The upper surface of the wafer 80 is exposed. When the sacrificial film 60 has a two-layer structure of a lower layer of silicon nitride and an upper layer of polycrystalline silicon, the surface layer of the polycrystalline silicon film is removed by reactive ion etching using CF ₄ as an etching gas to expose the silicon nitride film Let The end point of the etching of the polycrystalline silicon film is preferably controlled by observing the plasma emission spectrum. Alternatively, the surface layer of the polycrystalline silicon film may be removed by CMP, and the silicon nitride film may be used as a polishing stopper. The silicon nitride film in contact with the wafer 80 is removed by reactive ion etching using CF ₄ + H ₂ or CHF ₃ as an etching gas to expose the upper surface of the wafer 80. The etching end point of the silicon nitride film is also preferably controlled by observing the emission spectrum of the plasma.

  Next, the laminated structure W formed by performing the steps corresponding to FIGS. 3 to 13 is bonded to the upper surface of the wafer 80 as shown in FIG. At this time, the laminated structure W and the wafer 80 are aligned so that the inner region of the annular groove 80 b filled with the sacrificial film 60 is bonded to the bottom surface of the connecting portion C. Although the annular groove 80b having a depth equal to the thickness of the weight portion M is deeply formed in the wafer 80, the annular groove 80b and the annular recess 80a are filled with the sacrificial film 60. Even if a load necessary to join the wafer 80 is applied to the wafer 80, the wafer 80 is hardly damaged. The thick silicon layer 11 constituting the bottom surface of the connecting portion C and the wafer 80 are directly bonded by anodic bonding. The conditions for anodic bonding are, for example, a temperature of 250 ° C. and a voltage applied to the thick silicon layer 11 and the wafer 80 of 800V.

Next, as shown in FIG. 19, the thickness of the weight portion M is adjusted by retracting the bottom surface of the wafer 80 until at least the sacrificial film 60 is exposed. When the lower layer of the sacrificial film 60 in contact with the wafer 80 is made of a titanium nitride film, the bottom surface of the wafer 80 is moved back by reactive ion etching using CHF ₃ + O ₂ as an etching gas, and the lower layer of the sacrificial film 60 made of the titanium nitride film is formed. The end point is controlled as an etching stopper. As a result, the thickness of the wafer 80 is adjusted to the design thickness of the weight portion M. The bottom surface of the wafer 80 may be retreated by CMP instead of reactive ion etching. In this step, the end point of CMP may be set when a predetermined time has elapsed after the lower layer of the sacrificial film 60 is exposed, and the upper layer of the sacrificial film 60 may be exposed on the bottom surface of the wafer 80. In this step, the end point for retreating the bottom surface of the wafer 80 can be controlled when the sacrificial film 60 is exposed. The sacrificial film 60 is embedded in the wafer 80 up to the depth of the annular groove 80b formed by anisotropic etching. In anisotropic etching of the wafer 80, the depth of the annular groove 80b can be accurately controlled. Therefore, the end point for retreating the bottom surface of the wafer 80 set in this step is controlled to an accurate depth from the top surface of the wafer 80. As a result, the thickness of the weight portion M made of the wafer 80 is accurately adjusted to the design value. In this step, the bottom surface of the wafer 80 is processed in a state where the annular recess 80a and the annular groove 80b are filled with the sacrificial film 60, so that the wafer 80 is hardly damaged.

Next, the weight M is released in the wafer 80 by removing the sacrificial film 60 that is a heterogeneous region exposed on the bottom surface of the wafer 80. For example, the titanium nitride film constituting the lower layer of the sacrificial film 60 is removed by reactive ion etching using CF ₄ + O ₂ + H ₂ + NH ₃ as an etching gas, and the upper layer made of the copper film of the sacrificial film 60 is exposed. Subsequently, the upper layer of the sacrificial film 60 made of a copper film is removed by isotropic etching. Further, the lower layer made of the titanium nitride film of the sacrificial film 60 remaining on the surface of the annular recess 80a of the wafer 80 is removed using an SC1 solution (DI: H ₂ O ₂ : NH ₄ OH) as an etchant. Note that the lower layer of the sacrificial film 60 remaining on the surface of the annular recess 80a of the wafer 80 may be left without being removed. In this process, since it is not necessary to apply physical force by dicing or the like to the wafer 80 when releasing the weight M in the wafer 80, the wafer 80 and the laminated structure W are not easily damaged.

  Thereafter, when post-processes such as dicing and packaging are performed, the motion sensor 1 shown in FIGS. 1 and 2 is completed.

  According to the manufacturing method of the motion sensor 1 described above, since the thickness of the weight portion M can be accurately adjusted, the motion sensor 1 with small variation in characteristics can be manufactured. Further, since the side surface of the weight portion M can be determined only by processing from the upper surface side of the wafer 80, the dimensional accuracy of the weight portion M can be increased.

2. Second embodiment (Configuration)
FIG. 20 is a sectional view showing a sensor die 2A of the motion sensor according to the second embodiment of the present invention. In FIG. 20, the interface of the layers constituting the sensor die 2A is indicated by a broken line, and the boundary of the mechanical components constituting the sensor die 2A is indicated by a solid line.

  The bottom surface of the connecting portion C and the top surface of the weight portion M may be joined by bonding with a resin layer 75 as shown in FIG. In this case, the resin layer 75 inserted between the bottom surface of the support portion S and the top surface of the base layer 80 is a buffer layer between the weight portion M and the support portion S in a region where the support portion S and the weight portion M face each other. It is also preferable to use as. As a result, the impact resistance performance of the motion sensor can be improved without complicating the structure.

(Production method)
FIG. 21 is a cross-sectional view showing a method for manufacturing the sensor die 2A, and corresponds to a cross section taken along line AA shown in FIG. 1B.
After the process corresponding to FIG. 17 described in the first embodiment is performed, in the process of bonding the laminated structure W and the wafer 80 that becomes the weight M, the resin layer 75 is laminated as shown in FIG. The wafer W may be bonded to the bottom surface of the thick silicon layer 11 and then the upper surface of the wafer 80 may be bonded to the resin layer 75. The pattern of the resin layer 75 bonded to the thick silicon layer 11 is matched with the pattern on the bottom surface of the thick silicon layer 11. Then, since the pattern on the bottom surface of the thick silicon layer 11 and the pattern on the top surface of the weight portion M overlap, the resin layer 75 becomes a buffer layer. As the resin layer 75, a thermoplastic resin adhesive such as polyimide is used. At this time, the protective film made of the photoresist used for patterning the thick silicon layer 11 may be used as the resin layer 75 without being removed. When the wafer 80 is bonded to the resin layer 75, for example, the wafer 80 is heated to 200 ° C., and is subjected to thermocompression bonding by applying a load of 2 t per 6 inch wafer. Thereafter, when the sacrificial film 60 is removed as in the first embodiment, the sensor die 2A is completed. As shown in FIG. 21, the thickness of the weight portion M may be adjusted by retracting the bottom surface of the wafer 80 before bonding to the laminated structure W.

  According to the present embodiment, since voltage application necessary for anodic bonding is unnecessary, it is possible to prevent dielectric breakdown due to voltage application in the process of bonding the laminated structure W and the wafer 80 serving as the weight part M. . In addition, since the laminated structure W and the wafer 80 serving as the weight portion M can be bonded under a low temperature condition as compared with anodic bonding, stress due to thermal expansion during bonding can be reduced. Also, bonding defects due to unevenness of the bonding surface and adhesion of dust are less likely to occur than with anodic bonding.

3. Third Embodiment FIGS. 22 to 25 are sectional views showing a third embodiment for manufacturing a sensor die 1A of the motion sensor 1. FIG. 22 to 25 correspond to the AA line cross section shown in FIG. 1B.
In this embodiment, the wafer 80 to be the weight portion M is assumed to be photosensitive glass. A wafer 80 having a thickness equal to the thickness of the weight portion M is used. The photosensitive glass is a glass that contains a certain kind of metal and crystallizes when heated by exposure to light such as ultraviolet rays. For example, a 300 μm-thick lithium silicate glass plate containing 0.01 to 0.5% of a core forming agent such as gold, silver or palladium and a small amount of cesium oxide (CeO ₂ ) as a photosensitizer is used as a wafer. Used as 80.

First, as shown in FIG. 22, an annular recess 80a is formed on the upper surface of the wafer 80 by etching using a protective film R6 made of a photoresist. For example, an annular recess 80a having a depth of 10 μm is formed by reactive ion etching using CHF ₃ + O ₂ as an etching gas. Before depositing the protective film R6 on the wafer 80, a chromium (Cr) film having a thickness of 100 nm is formed as a sacrificial film (light-shielding film), and the sacrificial film (light-shielding film) is etched using the protective film R6 as a mask. The annular recess 80a may be formed using at least one of the film R6 and the sacrificial film (light-shielding film). In this case, the sacrificial film (light-shielding film) is removed together with the protective film R6.

  Next, as shown in FIG. 23, the wafer 80 is irradiated with ultraviolet rays through a photomask 81 having a light transmitting region and a light shielding region, and the target region having a shape corresponding to the annular groove 80b described in the first embodiment is formed. An exposure region 80d that is a latent image is formed. That is, the exposure region 80d is formed in a target region that circumscribes the region that becomes the weight portion M.

  Next, the wafer 80 is heat-treated at a temperature higher than the glass transition temperature to crystallize the exposed region 80d, thereby forming a microcrystalline region 80e which is a heterogeneous region different from the remaining portion as shown in FIG. For example, when the wafer 80 is heated at 850 ° C. for 2 hours, the exposure region 80d, which is a latent image, becomes apparent as the microcrystalline region 80e.

Next, the wafer 80 on which the microcrystalline region 80e is formed is bonded to the laminated structure W as in the first embodiment. At this time, since the deep groove is not formed in the wafer 80 as in the first embodiment, the wafer 80 is hardly damaged. Since the region where the stress is concentrated by the annular recess 80a is made of crystallized glass, the wafer 80 is more difficult to break.
Next, when the microcrystalline region 80e is selectively removed from the wafer 80 bonded to the laminated structure W and the weight M is released in the wafer 80, the sensor die 1A is completed. Specifically, for example, after covering the surface where the surface wiring layer 50 of the laminated structure W is formed with a protective film (not shown), the microcrystalline region 80e is removed using buffered hydrofluoric acid. As the protective film covering the surface of the laminated structure W, a photoresist or an adhesive tape that is foamed by heating can be used.

  According to the present embodiment, it is not necessary to form a sacrificial film that becomes a heterogeneous region necessary for releasing the weight portion M in the wafer 80, so that the manufacturing process can be simplified. Further, since the side surface of the weight portion M can be determined only by processing from the upper surface side of the wafer 80, the dimensional accuracy of the weight portion M can be increased. Further, in the step of releasing the weight portion W in the wafer 80, the frictional force with the dicer is not applied to the wafer 80, so that the wafer 80 and the laminated structure W are not damaged.

4). Fourth Embodiment FIGS. 26 and 27 are cross-sectional views showing a fourth embodiment for manufacturing the sensor die 1A of the motion sensor 1, and correspond to the cross section taken along the line AA shown in FIG. 1B.
After performing the process corresponding to FIG. 24 described in the third embodiment, a reinforcing plate 76 made of a photoresist is formed on the bottom surface of the wafer 80 as shown in FIG.

  Next, before bonding the wafer 80 to the laminated structure W, the surface layer of the microcrystalline region 80e (a layer close to the upper surface of the wafer) is selectively removed by etching. As a result, as shown in FIG. 27, the time required to remove the microcrystalline region 80e after bonding the wafer 80 to the laminated structure W can be shortened. As a result, damage to the laminated structure W by the etchant used for selectively removing the microcrystalline region 80e can be reduced. Although the strength of the wafer 80 is reduced by removing the surface layer of the microcrystalline region 80e as compared with the third embodiment, the thin portion of the wafer 80 is constituted by the microcrystalline region 80e made of crystallized glass. It has sufficient strength. Even if the etching time after the bonding of the wafer 80 and the laminated structure W is shortened by reducing the remaining thickness of the microcrystalline region 80e so that the strength of the wafer 80 cannot be secured, the wafer with the reinforcing plate 76 bonded. If the bonding between the laminated structure W and the wafer 80 is performed, the wafer 80 is hardly damaged.

5). Fifth Embodiment FIGS. 28 and 29 are cross-sectional views showing a fifth embodiment for manufacturing the sensor die 1A of the motion sensor 1, and correspond to the cross section taken along the line AA shown in FIG. 1B.
The exposure region 80d of the wafer 80 may be formed by condensing the laser beam with the lens L as shown in FIG. For example, the femtosecond laser is condensed by the lens L, and the condensing point is moved to form the exposure region 80d corresponding to the annular recess 80a and the annular groove 80b. Since exposure is performed by the laser beam condensed at one point, an exposure region 80d having a free shape can be formed.

Next, the wafer 80 is heat-treated in the same manner as in the fourth embodiment, thereby exposing the exposed region 80d as a microcrystalline region 80e as shown in FIG.
According to the present embodiment, since the wafer 80 and the laminated structure W can be bonded with no recesses or grooves formed on the wafer 80, the wafer 80 is further less likely to be damaged.

5). Sixth Embodiment FIG. 30A shows a cross section taken along line AA shown in FIG. 30B. When an exposure region is formed on a wafer made of photosensitive glass by condensing laser light, the design of the weight portion M is high. For example, as shown in FIG. 30, it is also possible to form a weight portion M shaped to fill most of the inner space of the support portion S. The weight part M shown in FIG. 30 is a form which has four convex parts which protrude in the space of the beam F side rather than the bottom face of the connection part C. FIG. Thus, by increasing the proportion of the weight portion M in the inner space of the support portion S, the sensitivity of the motion sensor can be increased.

31 to 34 are cross-sectional views showing a method of manufacturing the sensor die 5A shown in FIG. 30, and correspond to the cross section along the line AA shown in FIG. 30B.
As shown in FIG. 31, the laser light is condensed by the lens L to form an exposure area 80 d having a three-dimensional shape on the wafer 80. The pattern of the exposure region 80d is configured such that the pattern of the thick silicon layer 11 of the sensor die 5A is accommodated inside.

Next, as shown in FIG. 32, a heat treatment is performed on the wafer 80, thereby exposing the exposed region 80d to the microcrystalline region 80e.
Next, the surface layer of the microcrystalline region 80e is selectively removed using buffered hydrofluoric acid with the reinforcing plate 76 formed on the bottom surface of the wafer 80 as shown in FIG. In this embodiment, since the microcrystalline region 80e is thick, it is very effective to remove most of the microcrystalline region 80e before the wafer 80 is bonded to the laminated structure W.

Next, as shown in FIG. 34, the wafer 80 may be bonded to the laminated structure W, and then the reinforcing plate 76 may be removed and the remaining portion of the microcrystalline region 80e may be selectively removed.
Instead of directly bonding the wafer 80 to the laminated structure W, the laminated structure W and the wafer 80 may be bonded via a resin layer 75 as shown in FIG. In this case, as in the second embodiment, as shown in FIG. 36, the resin layer 75 can function as a buffer layer between the support portion S that functions as a stopper of the weight portion M and the weight portion M.

6). Other Embodiments The technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. For example, the thick silicon layer 11 and the etching stopper layer 12 may be omitted, the bottom surface of the connecting portion C may be configured by the bottom surface of the thin silicon layer 13, and the thin silicon layer 13 and the wafer 80 may be bonded. In this case, it is preferable to bond the thin silicon layer 13 and the wafer 80 via the resin layer 75 in order to relieve stress. The present invention can also be applied to other MEMS sensors such as an acceleration sensor, a vibration gyroscope, and a posture sensor in addition to a motion sensor.

  Further, for example, the materials, dimensions, film formation methods, and pattern transfer methods shown in the above embodiment are merely examples, and descriptions of addition and deletion of processes and replacement of process orders that are obvious to those skilled in the art are omitted. Has been. Also, for example, in the above-described manufacturing process, the film composition, film forming method, film contour forming method, process sequence, etc. are appropriately selected according to the combination of film materials, film thickness, required contour shape accuracy, etc. There is no particular limitation.

FIG. 1A is a cross-sectional view according to the first embodiment of the present invention. FIG. 1B is a top view according to the first embodiment of the present invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. 9A and 9B are cross-sectional views according to the first embodiment of the present invention. FIG. 9C is a top view according to the first embodiment of the present invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 1st embodiment of this invention. Sectional drawing concerning 2nd embodiment of this invention. Sectional drawing concerning 2nd embodiment of this invention. Sectional drawing concerning 3rd embodiment of this invention. Sectional drawing concerning 3rd embodiment of this invention. Sectional drawing concerning 3rd embodiment of this invention. Sectional drawing concerning 3rd embodiment of this invention. Sectional drawing concerning 4th embodiment of this invention. Sectional drawing concerning 4th embodiment of this invention. Sectional drawing concerning 5th embodiment of this invention. Sectional drawing concerning 5th embodiment of this invention. FIG. 30A is a cross-sectional view according to a sixth embodiment of the present invention. FIG. 30B is a top view according to the sixth embodiment of the present invention. Sectional drawing concerning 6th embodiment of this invention. Sectional drawing concerning 6th embodiment of this invention. Sectional drawing concerning 6th embodiment of this invention. Sectional drawing concerning 6th embodiment of this invention. Sectional drawing concerning 6th embodiment of this invention. Sectional drawing concerning 6th embodiment of this invention.

Explanation of symbols

1: motion sensor, 1A: sensor die, 1B: package, 2A: sensor die, 5A: sensor die, 10: SOI wafer, 11: silicon layer, 11h: through-hole, 12: etching stopper layer, 13: silicon layer, 20: first One insulating layer, 30a: driving piezoelectric element, 30b: detecting piezoelectric element, 31: electrode layer, 32: piezoelectric layer, 33: electrode layer, 40: second insulating layer, 40e: opening, 40h: contact hole, 50: surface wiring layer, 60: sacrificial film, 71: sacrificial substrate, 75: resin layer, 76: reinforcing plate, 80: base layer, 80: wafer, 80a: annular recess, 80b: annular groove, 80d: exposure region, 80e: microcrystalline region, 81: photomask, 90: base, 90a: bottom surface, 91: through electrode, 92: adhesive layer, 93: adhesive layer, 94: cover, 95: wire, 131: Ezoresistive element, 131a: high resistance part, 131b: low resistance part, B: adhesive layer, C: coupling part, F: flexible part, F: beam, G: gap, L: lens, M: weight part, R1 : Protective film, R2: protective film, R3: protective film, R4: protective film, R5: protective film, R7: protective film, R7: protective film, S: support part, W: laminated structure

Claims (7)

A support part; a flexible part having one end coupled to the support part and having flexibility; a connecting part coupled to the other end of the flexible part; and a detection part for detecting deformation of the flexible part. Forming a laminated structure comprising
Forming a heterogeneous region that is different from the rest in the target region of the wafer that circumscribes the region that becomes the weight portion coupled to the bottom surface of the connecting portion;
Bonding the remaining region that is the weight portion inside the heterogeneous region to the bottom surface of the connecting portion,
Removing the heterogeneous region by etching from the wafer bonded to the connecting portion;
A method for manufacturing a MEMS sensor. The wafer is made of photosensitive glass,
Forming the heterogeneous region by crystallizing the target region by exposure;
A method for manufacturing the MEMS sensor according to claim 1. Removing the surface layer of the heterogeneous region from the upper surface side of the wafer before bonding the wafer to the connecting portion;
Removing the remainder of the heterogeneous region from the bottom side of the wafer after bonding the wafer to the connecting portion;
A method for manufacturing the MEMS sensor according to claim 2. Crystallizing the target region by irradiating a laser beam condensed by a lens;
The manufacturing method of the MEMS sensor of Claim 2 or 3. Adhering the wafer via a resin layer to the bottom surface of the connecting portion and the bottom surface of the support portion,
The pattern of the support part and the pattern of the weight part partially overlap, and the resin layer bonded to the bottom surface of the support part serves as a buffer layer between the weight part and the support part.
The manufacturing method of the MEMS sensor as described in any one of Claim 2 to 4. Directly bonding the wafer to the bottom surface of the connecting portion and the bottom surface of the support portion;
The manufacturing method of the MEMS sensor as described in any one of Claim 2 to 4. A support part;
A flexible portion having one end coupled to the support portion and having flexibility;
A connecting portion coupled to the other end of the flexible portion;
A weight portion made of crystallized glass and bonded to the bottom surface of the connecting portion;
A detection unit for detecting deformation of the flexible part accompanying the movement of the weight part;
A MEMS sensor comprising:

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