JP2010156577A - Mems sensor and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a MEMS sensor having high impact resistance performance and thin. <P>SOLUTION: Provided is the method of manufacturing the MEMS sensor including: a frame-shaped support part; a beam-shaped flexible part coupled to the support part; a weight part coupled to the flexible part and moved relative to the support part to deform the flexible part; and a stopper part limiting a moving range of the weight part. The method also includes the steps of: forming a sacrifice layer made of an epitaxial crystal layer having a conductivity type different from that of a base layer on a surface of the base layer made of a single crystal silicon; exposing a part of the base layer from the sacrifice layer by etching the sacrifice layer; forming a non-planarization layer made of an epitaxial layer having a conductivity type in conformity with that of the base layer on the surfaces of the sacrifice layer and the base layer; forming a gap between the stopper part and the weight part; and making the non-planarization layer to function as the stopper part limiting the moving range of the weight part by forming the gap. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  2. Description of the Related Art Conventionally, MEMS (Micro Electro Mechanical Systems) sensors such as an acceleration sensor, a vibration gyroscope, and a vibration sensor that convert a displacement of a flexible portion connected to a weight portion into an electric signal are known (Patent Documents 1 to 11). reference). Patent Documents 1 to 4 describe MEMS sensors in which a beam portion and a weight portion face each other with a gap therebetween. When the structures described in Patent Documents 1 to 4 are adopted, the sensitivity is maintained without increasing the rigidity of the beam part as compared with the case where the beam part and the weight part are not opposed to each other with a gap in between. The MEMS sensor can be reduced in size. Patent Documents 5 to 11 describe MEMS sensors that have improved impact resistance performance by limiting the range of motion of the weight portion and limiting the deformation amount of the flexible portion.

JP-A-6-342006 JP-A-8-274349 JP-A-8-248061 Japanese Patent Laid-Open No. 9-15257 JP 2003-270262 A JP 2004-233072 A JP 2006-153519 A JP 2006-208272 A JP 2006-317180 A JP 2006-317181 A JP 2006-64532 A

  However, as described in Patent Documents 5 to 10, in the structure in which the movement range of the weight portion is limited by the plate-like component facing the die which is a laminated structure, the deformation amount of the flexible portion is limited. There is a problem that becomes thicker.

  An object of the present invention is to provide a thin MEMS sensor having high impact resistance.

(1) A MEMS sensor manufacturing method for achieving the above object includes a frame-shaped support portion, a beam-shaped flexible portion coupled to the support portion, and the support portion coupled to the flexible portion. A method for manufacturing a MEMS sensor, comprising: a weight part that deforms the flexible part by moving with respect to the surface; and a stopper part that limits a movement range of the weight part, the surface of the base layer made of single crystal silicon Forming a sacrificial layer made of an epitaxial crystal layer having a conductivity type different from that of the base layer, and etching the sacrificial layer to partially expose the base layer from the sacrificial layer. Forming a non-flat layer made of an epitaxial crystal layer having the same conductivity type as that of the base layer, and etching the non-flat layer at a portion continuous with the flexible portion and the support portion of the non-flat layer. A portion partially overlapping the sacrificial layer and a portion of the stopper portion of the non-flat layer and a portion partially overlapping the sacrificial layer, Then, an annular groove is formed by etching the base layer, and the base layer is divided into a portion that becomes the support portion outside the groove and a portion that becomes the weight portion inside from the groove. After forming the groove, the sacrificial layer is removed by isotropic etching, thereby forming a gap between the stopper portion and the weight portion, and forming the gap in the weight portion. A function of the stopper portion that limits a movement range of the weight portion in a direction from the weight portion toward the flexible portion in contact with the non-flat layer.
According to the present invention, a non-flat layer that is not flat is formed on the base layer using the patterned sacrificial layer, and then the base layer is etched to thereby form the support portion and the weight portion. An annular groove is formed in the base layer, and a sacrificial layer is removed to form a gap between the stopper portion including the non-flat layer and the weight portion. By forming the stopper portion in this manner, the movement range of the weight portion can be limited in the direction from the weight portion toward the flexible portion, so that the impact resistance performance is higher than when the movement range of the weight portion is not limited. Further, since the stopper portion can be constituted by the non-flat layer constituting the flexible portion, a thin MEMS sensor is manufactured as compared with the case where the movement range of the weight portion is limited by a plate-like component facing the die which is a laminated structure. be able to.

  (2) A MEMS sensor manufacturing method for achieving the above object includes a frame-shaped support portion, a beam-shaped flexible portion coupled to the support portion, and the support portion coupled to the flexible portion. A method of manufacturing a MEMS sensor comprising a weight part that deforms the flexible part by moving with respect to the stopper part and a stopper part that restricts the movement range of the weight part, and is made of a base layer and single crystal silicon. An annular groove is formed by etching the base layer of an SOI wafer including an SOI layer thinner than the base layer and an insulating layer between the base layer and the SOI layer, and the support outside the groove is formed. The base layer is divided into a portion to be a portion and a portion to be the weight portion on the inside from the groove, and penetrates the SOI layer at a position extending from the inner side to the outer side of the groove from the groove. By forming a rising stopper mold portion that is an annular recess that penetrates the insulating layer on the outside by etching, forming a stopper layer that is different from the insulating layer in the rising stopper mold portion, and etching the SOI layer A portion of the SOI layer that is continuous with the support portion and the flexible portion is formed, and the insulating layer is isotropically etched using the stopper layer as an etching stopper, and is formed in the rising stopper mold portion. By forming an air gap between the stopper layer and the weight portion, and forming the air gap, the movement range of the weight portion in the direction from the weight portion toward the flexible portion is brought into contact with the weight portion. The function as a rising stopper portion for limiting is manifested in the stopper layer formed in the rising stopper mold portion; Including.

  According to the present invention, the rising stopper mold portion which is a recess penetrating the SOI layer and the insulating layer is formed by etching, and after forming the stopper layer different from the insulating layer in the rising stopper mold portion, the stopper layer and the weight portion By forming a gap between them, a function as an ascending stopper portion that limits the movement range of the weight portion in the direction from the weight portion toward the flexible portion is manifested in the stopper layer. Therefore, the impact resistance performance is higher than when the movement range of the weight portion is not limited. In addition, since the movement range of the weight portion is limited by the stopper layer embedded in the single crystal silicon layer that becomes the flexible portion, the movement range of the weight portion is limited by a plate-like component facing the die that is a laminated structure. Compared to the above, a thin MEMS sensor can be manufactured. Furthermore, since the insulating layer is etched using the stopper layer itself serving as the rising stopper portion as an etching stopper, the gap between the weight portion and the rising stopper mold portion can be formed with an accurate dimension. Therefore, variation in characteristics of the MEMS sensor can be reduced.

(3) In the MEMS sensor manufacturing method for achieving the above object, the rising mold part and a connecting mold which is a recess located inside the rising stopper mold part and penetrating the SOI layer and the insulating layer. Are formed simultaneously by etching, the stopper layer is simultaneously formed in the connecting mold part and the rising stopper mold part, and when the gap is formed, a gap is formed between the weight part and the flexible part. And forming a function as a connecting portion for connecting the weight portion and the flexible portion to the stopper layer formed in the connecting mold portion.
According to the present invention, the gap between the flexible portion and the weight portion is formed by isotropic etching of the insulating layer of the SOI wafer. Therefore, it is possible to manufacture a highly sensitive MEMS sensor in which the flexible portion and the weight portion face each other with a gap therebetween. Also, according to the present invention, the insulating layer is etched using the stopper layer itself that becomes the rising stopper portion and the connecting portion as an etching stopper, so that the gap between the weight portion and the flexible portion, the weight portion, the rising stopper mold portion, Can be formed with accurate dimensions. Therefore, variation in characteristics of the MEMS sensor can be reduced.

(4) In the MEMS sensor manufacturing method for achieving the above object, the rising stopper mold part and the connection mold part are buried by laminating the stopper layer and a different core layer on the surface of the stopper layer. Also good.
According to the present invention, a balance of stress, manufacturing cost, strength, and the like can be optimized by forming the rising stopper portion and the connecting portion in a multilayer structure.

  (5) A MEMS sensor manufacturing method for achieving the above object includes a frame-shaped support part, a beam-shaped flexible part coupled to the support part, and the support part coupled to the flexible part. A method of manufacturing a MEMS sensor comprising a weight part that deforms the flexible part by moving with respect to the stopper part and a stopper part that restricts the movement range of the weight part, and is made of a base layer and single crystal silicon. An annular groove is formed by etching the base layer of an SOI wafer including an SOI layer thinner than the base layer and an insulating layer between the base layer and the SOI layer, and the support outside the groove is formed. The base layer is divided into a portion to be a portion and a portion to be the weight portion on the inside from the groove, and penetrates the SOI layer at a position extending from the inner side to the outer side of the groove from the groove. The supporting layer is formed by etching a descending stopper mold part that is a recess penetrating the insulating layer on the inside, forming a stopper layer different from the insulating layer in the descending stopper mold part, and etching the SOI layer. The stopper formed in the descending stopper mold part by forming a part of the SOI layer continuous with the flexible part and the isotropic etching of the insulating layer using the stopper layer as an etching stopper Forming a gap between the layer and the support, and forming the gap moves with the weight, contacts the support and contacts the weight in the direction from the flexible part to the weight The stopper formed in the descending stopper mold part has a function as a descending stopper part for limiting the movement range of Manifested in involves.

  According to the present invention, the lower stopper mold portion which is a recess penetrating the SOI layer and the insulating layer is formed by etching, and after forming the stopper layer different from the insulating layer in the lower stopper mold portion, the stopper layer and the support portion By forming a gap between them, a function as a lowering stopper part that limits the movement range of the weight part in the direction from the flexible part to the weight part becomes apparent in the stopper layer. Therefore, the impact resistance performance is higher than when the movement range of the weight portion is not limited. In addition, since the movement range of the weight portion is limited by the stopper layer embedded in the single crystal silicon layer that becomes the flexible portion, the movement range of the weight portion is limited by a plate-like component facing the die that is a laminated structure. Compared to the above, a thin MEMS sensor can be manufactured.

(6) In the MEMS sensor manufacturing method for achieving the above object, an annular shape that penetrates the SOI layer at a position extending from the inside to the outside of the groove and penetrates the insulating layer outside the groove. The rising stopper mold part, a connecting mold part which is a recess located inside the rising stopper mold part and penetrates the SOI layer and the insulating layer, and the lowering stopper mold part are simultaneously formed by etching. The stopper layer, which is different from the insulating layer, is simultaneously formed in the connecting mold part, the rising stopper mold part, and the falling stopper mold part, and when the insulating layer is isotropically etched, the weight part and the A machine as a connecting part that forms a gap between the flexible part and connects the weight part and the flexible part. The may be manifested in the stopper layer formed in the connecting mold section.
According to the present invention, an air gap is formed between the flexible portion and the weight portion by isotropic etching of the insulating layer of the SOI wafer. Therefore, it is possible to manufacture a MEMS sensor in which the flexible portion and the weight portion face each other with a gap therebetween. Further, according to the present invention, the stopper layer is formed differently from the insulating layer, and the insulating layer is etched using the stopper layer itself that becomes the connecting portion between the rising stopper portion and the falling stopper portion as an etching stopper. The gap between the flexure part, the gap between the weight part and the rising stopper part, and the gap between the weight part and the lowering stopper part can be formed with accurate dimensions. Therefore, variation in characteristics of the MEMS sensor can be reduced.

  (7) A MEMS sensor for achieving the above object includes a frame-type support part, a weight part located inside the support part, and spanned inside the support part and connected to the weight part. A flexible part that deforms as the part moves, and the weight part on the side of the flexible part from the weight part by contacting the weight part and contacting the weight part with a gap between the support part and the support part. A rising stopper portion that restricts the range of movement of the movable portion, wherein the flexible portion includes a single crystal silicon layer, and the rising stopper portion includes a stopper layer penetrating the single crystal silicon layer and facing the weight portion. Including.

  According to the present invention, since the movement range of the weight part is limited in the direction from the weight part to the flexible part by the rising stopper part, the impact resistance performance is higher than when the movement range of the weight part is not limited. In addition, since the movement range of the weight portion is limited by the stopper layer embedded in the single crystal silicon layer constituting the flexible portion, the movement range of the weight portion is limited by a plate-like component facing the die which is a laminated structure. Compared to the case, a thinner MEMS sensor can be realized.

(8) In the MEMS sensor for achieving the above object, a through hole may be formed in a region of the rising stopper portion facing the weight portion.
According to the present invention, even if the weight portion and the lift stopper portion are opposed to each other over a wide range, the through hole is formed in the region of the lift stopper portion facing the weight portion. In the manufacturing process in which voids are formed by isotropic etching, throughput is increased and generation of defective products due to residues can be prevented.

  (9) A MEMS sensor for achieving the above object includes a frame-shaped support part, a weight part located inside the support part, and spanned inside the support part and connected to the weight part. A beam-shaped flexible portion that deforms with the movement of the portion, and is connected to the weight portion and is opposed to the support portion with a gap interposed therebetween, and comes into contact with the support portion toward the weight portion. A downward stopper portion that limits a movement range of the weight portion in a direction, the flexible portion includes a single crystal silicon layer, and the downward stopper portion penetrates the single crystal silicon layer and faces the support portion. Including a stopper layer.

  According to the present invention, since the movement range of the weight part is limited in the direction from the flexible part to the weight part by the lowering stopper part, the impact resistance performance is higher than when the movement range of the weight part is not limited. In addition, since the movement range of the weight portion is limited by the stopper layer embedded in the single crystal silicon layer constituting the flexible portion, the movement range of the weight portion is limited by a plate-like component facing the die which is a laminated structure. Compared to the case, a thinner MEMS sensor can be realized.

(10) In the MEMS sensor for achieving the above object, the MEMS sensor includes a connecting portion coupled to the weight portion and the flexible portion and connecting the weight portion and the flexible portion, and a surface of the connecting portion. May be constituted by the stopper layer which is different from silicon oxide.
When this configuration is adopted, a gap can be formed between the weight part and the flexible part by etching silicon oxide while using the connecting part itself as an etching stopper, so that the gap between the weight part and the flexible part can be accurately determined. Can be formed to various dimensions. Therefore, variation in characteristics of the MEMS sensor can be reduced.

(11) In the MEMS sensor for achieving the above object, the ascending stopper portion or the descending stopper portion may have a multilayer structure including the stopper layer.
According to the present invention, the balance of stress, manufacturing cost, strength, and the like can be optimized by forming the ascending stopper portion or the descending stopper portion and the connecting portion into a multilayer structure.

  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)
The acceleration sensor which is 1st embodiment of the MEMS sensor of this invention is shown in FIG. 1 and FIG. 1B and 1C are sectional views showing a sensor die 1A of the acceleration sensor 1, and are sectional views taken along lines BB and CC shown in FIG. 1A, respectively. In FIG. 1B, FIG. 1C, 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 functional element which comprises the sensor die 1A is shown with the continuous line.

  The acceleration sensor 1 is a MEMS sensor for detecting three-axis acceleration components orthogonal to each other. The acceleration sensor 1 includes a package 1B shown in FIG. 2 and a sensor die 1A housed in the package 1B.

The sensor die 1A is a laminated structure including a base layer 11, a first insulating layer 12, an SOI layer 13, a second insulating layer 20, a stopper layer 30, a third insulating layer 40, and a surface conductive layer 50. It is. The base layer 11 and the SOI layer 13 are made of single crystal silicon. The thickness of the base layer 11 is 625 μm. The thickness of the SOI layer 13 is 10 μm. The first insulating layer 12, the second insulating layer 20, and the third insulating layer 40 are each made of silicon dioxide (SiO ₂ ). The thickness of the first insulating layer 12 is 1 μm. The thicknesses of the second insulating layer 20 and the third insulating layer 40 are each 0.5 μm. The stopper layer 30 penetrates the SOI layer 13 and the second insulating layer 20. In FIG. 1A, the pattern of the stopper layer 30 is indicated by a broken line. The stopper layer 30 is made of a material different from that of the first insulating layer 12. The surface conducting wire layer 50 is made of aluminum (Al). The thickness of the surface conducting wire layer 50 is 0.3 μm.

  The sensor die 1A of the acceleration sensor 1 includes a frame-shaped support portion S, a cross-shaped flexible portion F in which four ends are coupled to the inside of the support portion S, a weight portion M, and a flexible portion F. A connecting portion 30b connecting the weight portion M, a rising stopper portion 30a embedded in the support portion S, and a piezoresistive element 131 as a detecting means provided in the flexible portion F are provided.

  The support part S has a frame shape as shown in FIG. 1C. When viewed from the direction in which the layers constituting the sensor die 1A are stacked, the outer contour of the support portion S is rectangular, and the inner contour of the support portion S is octagonal. Since the support part S is fixed to the package 1B, it behaves substantially as a rigid body. The support part S includes a base layer 11, a first insulating layer 12, an SOI layer 13, a second insulating layer 20, and a third insulating layer 40.

  The cross-shaped flexible portion F has a form in which two beams fixed at both ends are coupled to each other at the center. The flexible part F is made of a multilayer film having flexibility and a constant thickness. The four ends of the flexible portion F are coupled to the four sides inside the support portion S. In other words, the flexible portion F has a beam shape hung inside the support portion S. Since the support portion S behaves as a rigid body, the end of the flexible portion F is a fixed end in the coordinate system fixed to the acceleration sensor 1. The flexible part F includes the SOI layer 13, the second insulating layer 20, and the third insulating layer 40.

The weight portion M is made of a base layer 11 and has a plate shape whose outer periphery is rectangular. The weight portion M is disposed inside the frame-shaped portion constituting the support portion S of the SOI layer 13 and overlaps the flexible portion F. An annular slit T is formed between the weight part M and the support part S. That is, the base layer 11 is divided into a portion constituting the weight portion M and a portion constituting the support portion S by the annular slit T. Since the weight portion M is made of the thick base layer 11, it behaves substantially as a rigid body. The gap G ₁ is formed between the weight portion M and the flexible portion F. The height of the gap G ₁ (the distance between the weight part M and the flexible part F) is equal to the thickness of the first insulating layer 12.

The connecting portion 30 b is made of the stopper layer 30. The connecting portion 30 b is embedded in the central portion of the flexible portion F until it penetrates the SOI layer 13 and the second insulating layer 20, and is coupled to the flexible portion F. The connecting portion 30 b protrudes from the flexible portion F by the thickness of the first insulating layer 12. The protruding end surface of the connecting portion 30b is coupled to the weight portion M. That is, the connecting portion 30b connects the weight portion M and the flexible portion F so as to face _{each other} with the gap G1 interposed therebetween. By connecting the weight part M and the flexible part F so as to face _{each other} with the gap G1 in between, the ratio of the size of the weight part M to the flexible part F can be increased. Thereby, the sensitivity of the acceleration sensor 1 increases.

The rising stopper portion 30a is embedded in the support portion S and goes around the support portion S once. As shown in FIGS. 1A and 1B, the rising stopper portion 30 a protrudes inward from the portion constituting the support portion S of the base layer 11 in the vicinity of the corner portion of the support portion S. The four corners of the weight part M overlap with the ascending stopper part 30a when viewed from the direction in which the layers constituting the sensor die 1A are stacked. More specifically, in the vicinity of the corner portion of the support portion S, the rising stopper portion 30a is coupled to the base layer 11 across the slit T between the weight portion M and the support portion S and the corner portion of the weight portion M. ing. A portion of the rising stopper portion 30a facing the base layer 11 is a portion that is not coupled to the base layer 11. Weight portion M are opposed across the gap G ₂ to the portion that is hollowed surface which is opposed to the base layer 11 of the raised stopper portion 30a. The height of the gap G ₂ is equal to the thickness of the first insulating layer 12. Direction increases the stopper portion 30a and the weight portion M are opposed across the gap G ₂ is a direction overlaps the weight portion M and the flexible portion F is. The rising stopper portion 30 a is made of the stopper layer 30. The rising stopper portion 30 a penetrates the SOI layer 13 and the second insulating layer 20 that constitute the flexible portion F.

  Since the weight part M is connected to the flexible part F by the connecting part 30b in a state of being separated from the bottom surface 90a and the support part S of the package 1B as shown in FIG. Exercise in the system. The flexible part F connected to the weight part M is deformed as the weight part M moves. When the flexible portion F is formed in a beam shape, the deformation amount of the flexible portion F accompanying the movement of the weight portion M can be increased as compared with the case where the flexible portion F is formed as a diaphragm whose entire outer periphery is coupled to the support portion S. That is, the sensitivity of the acceleration sensor 1 increases when the flexible portion F is formed in a beam shape.

  The range of motion of the weight portion M is limited by the support portion S, the bottom surface 90a of the package 1B, and the rising stopper portion 30a. This prevents the flexible portion F from being excessively deformed and damaged. Here, as shown in FIG. 1, xyz orthogonal coordinate axes are defined. The x axis and the y axis are parallel to the direction in which the two beams constituting the flexible portion F extend. The z axis is parallel to the direction in which the layers constituting the sensor die 1A are stacked. That is, the z axis is the direction of the thickness of each layer constituting the sensor die 1A, and is the direction in which the weight part M, the connecting part 30b, and the flexible part F overlap. A direction from the weight part M toward the flexible part F is defined as a positive direction of the z axis. The movement of the weight part M accompanying the movement of the surface of the weight part M in the direction parallel to the x-axis and the direction parallel to the y-axis is limited by the part constituting the support part S of the base layer 11. The movement of the weight part M accompanying the movement of the surface of the weight part M in the negative z-axis direction is limited by the bottom surface 90a of the package 1B. The movement of the weight part M accompanying the movement of the surface of the weight part M in the positive z-axis direction is limited by the ascending stopper part 30a.

When the corner portion of the weight portion M moves in the direction from the weight portion M toward the flexible portion F (z-axis positive direction), the initial state (the portion constituting the support portion S of the base layer 11 and the weight portion M are formed. a raised stopper portion 30a and the corner portion of the weight M is in contact when the to have parts moving amount from the state) that are aligned in the xy plane parallel to the direction is equal to the height of the air gap G ₂ . Then, in the direction from the weight part M toward the flexible part F, the range of motion of the weight part M is limited by the ascending stopper part 30a. Therefore, even if an impact that causes excessive acceleration in the negative z-axis direction is applied, the flexible portion F is not damaged. Similarly, even if an impact that causes excessive acceleration in the x and y axis directions is applied, the flexible portion F will not be damaged.

  In order to prevent the rising stopper portion 30a from being damaged by the collision with the weight portion M, the rising stopper portion 30a is preferably made of a material having high toughness. Further, in order to prevent the weight portion M from being damaged by the collision with the rising stopper portion 30a, the rising stopper portion 30a is preferably made of a material whose hardness is lower than that of the weight portion M.

When the stopper layer 30 constituting the rising stopper portion 30a is required to have higher toughness than single crystal silicon, the stopper layer 30 is made of a semiconductor such as silicon germanium (SiGe), aluminum nitride (Al _x N _y ), titanium nitride (Ti _{x Ny} ), nitrides such as silicon nitride (Si _x N _y ), oxides such as aluminum oxide (Al _x O _y ), tantalum oxide (TaO _x ), titanium oxide (TiO _x ), tungsten silicide (WSi _x ) , Molybdenum silicide (MoSi _x ), titanium silicide (TiSi _x ) and other silicide compounds, and copper (Cu), nickel (Ni), platinum (Pt), gold (Au) and other metals. If the stopper layer 30 does not require higher toughness than single crystal silicon, the stopper layer 30 may be made of single crystal silicon, polysilicon, amorphous silicon, or silicon oxide (SiO _x ).

The piezoresistive element 131 is a detecting means for detecting the deformation of the flexible portion F accompanying the movement of the weight portion M. The piezoresistive element 131 is composed of a high resistance portion 131a and a low resistance portion 131b formed in the SOI 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 conducting wire layer 50. The piezoresistive element 131 is connected to the surface conductor layer 50 through a contact hole formed in the second insulating layer 20 and the third insulating layer 40. The piezoresistive elements 131 are connected so as to form a total of three Wheatstone bridges, one set of four linearly arranged elements. A signal corresponding to each of the three-axis acceleration components orthogonal to each other can be obtained from each Wheatstone bridge.

  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 conductive layer 50 of the sensor die 1A, and the other end is bonded to the through electrode 91 of the package 1B. The lower surface of the support portion S constituted by the lower surface of the base layer 11 of the sensor die 1A is bonded to the inner bottom surface 90a of the base 90 by an adhesive layer 92. The height of the gap between the flexible portion F of the sensor die 1A and the bottom surface 90a inside the base 90 is set according to 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, a method of manufacturing the acceleration sensor 1 will be described with reference to FIGS. 5 to 9 and FIG. 13 to FIG. 15 are sectional views corresponding to the line BB shown in FIG. 1A. 3, FIG. 4, FIG. 10 to FIG. 12, FIG. 5 to FIG. 9 and FIG. 13 to FIG. 15 are sectional views corresponding to the CC line shown in FIG.

First, as shown in FIG. 3, a high resistance portion 131a is formed by introducing impurities into the SOI 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 base layer 11 made of single crystal silicon having a thickness of 625 μm, a first insulating layer 12 made of silicon dioxide (SiO ₂ ) having a thickness of 1 μm, and an SOI layer 13 made of single crystal silicon having a thickness of 10 μm. Are wafers stacked in this order.

  Next, as shown in FIG. 4, a second insulating layer 20 is formed on the surface of the SOI layer 13. As the second 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 FIGS. 5A and 5B, recesses H1 and H2 penetrating the second insulating layer 20 and the SOI layer 13 are formed by etching using a protective film R2 made of a photoresist. The pattern of the recess H2 corresponds to the pattern of the ascending stopper portion 30a. That is, the pattern of the recesses H2 is annular, and the corners extend from the inner side to the outer side of the region (the region indicated by the broken line) that becomes the annular slit T between the weight portion M and the support portion S. The recess H1 is formed inside the annular recess H2. The second insulating layer 20 and the SOI layer 13 are anisotropically etched by, for example, reactive ion etching. For example, the second insulating layer 20 is etched by reactive ion etching using CHF ₃ gas, and then the SOI layer 13 is etched by reactive ion etching using CF ₄ gas and O ₂ gas.

Next, after removing the protective film R2, as shown in FIG. 6, the portions exposed from the recesses H1 and H2 of the first insulating layer 12 are etched using the protective film R3 made of a photoresist, so that the first insulating layer 12 The base layer 11 is exposed from the recesses H1 and H2 penetrating the substrate. For example, the first insulating layer 12 is etched by reactive ion etching using CHF ₃ gas. At this time, for the portion exposed from the recess H2 of the first insulating layer 12, not all the exposed portion is removed by etching, but only the outside of the region that becomes the slit T is removed to become the slit T. The inside from the area remains. Such first insulating layer 12 remaining on the bottom of the recess H2 after etching serves as a sacrificial layer for forming a gap G ₂ between the rise stopper 30a and the weight portion M.

  In this way, by etching using the two protective films R2 and R3, the concave portion H1 as a connecting mold portion for forming the connecting portion 30b and the concave portion H2 as a rising stopper mold portion for forming the rising stopper portion 30a. And are formed.

  Next, a material different from the first insulating layer 12 is deposited on the surfaces of the base layer 11, the first insulating layer 12 and the second insulating layer 20 exposed from the concave portions H1 and H2, thereby forming the concave portions as shown in FIG. A stopper layer 30 that completely fills H1 and H2 is formed.

  Next, as shown in FIG. 8, a film R <b> 4 for etch back is formed on the surface of the stopper layer 30. As the material of the coating R4, a material that can make the etching selection ratio with the stopper layer 30 substantially 1 is selected. For example, a coating R4 having a flat surface is formed by applying a photoresist, SOG (Spin On Glass), polyimide or the like and baking.

  Next, as shown in FIG. 9, the upper surface of the second insulating layer 20 and the upper surface of the stopper layer 30 are made flat and continuous. Specifically, the surface layer of the stopper layer 30 is etched back together with the coating R4 until the second insulating layer 20 is exposed under the condition that the etching selectivity between the coating R4 and the stopper layer 30 is approximately 1: 1. As a result, the stopper layer 30 remains only in the recesses H1 and H2, the upper surface of the stopper layer 30 and the upper surface of the second insulating layer 20 are continuously flat, and the connecting portion 30b is formed in the recess H1. A rising stopper portion 30a is formed in the recess H2. Instead of etching using the film R4, the upper surface of the second insulating layer 20 and the upper surface of the stopper layer 30 may be made flat and continuous by grinding, polishing, or CMP (Chemical Mechanical Polishing).

Next, the third insulating layer 40 is formed on the upper surfaces of the second insulating layer 20 and the stopper layer 30. As the third insulating layer 40, a silicon dioxide (SiO ₂ ) film is formed by, for example, CVD. As the third insulating layer 40, a film such as PSG (Phospho Silicate Grass), BPSG (Boro-Phospho Silicate Grass), or silicon nitride (Si _x N _y ) may be formed. When the stopper layer 30 is made of an insulating film, the third insulating layer 40 is not necessary. Subsequently, as shown in FIG. 10, a contact hole H4 is formed in the second insulating layer 20 and the third insulating layer 40 using a protective film R5 made of a photoresist to expose the high resistance portion 131a. The contact hole H4 is formed by anisotropically etching the second insulating layer 20 and the third insulating layer 40 by reactive ion etching using, for example, CF ₄ gas. The contact hole H4 may be formed by wet etching using hydrofluoric acid (HF) or buffered hydrofluoric acid (BHF).

Next, as shown in FIG. 11, the low resistance portion 131b is formed by introducing impurities into the high resistance portion 131a exposed from the contact hole H4. 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. 12, a surface conductive layer 50 is formed on the surface of the third insulating layer 40, and the surface conductive layer 50 is etched using a protective film R6 made of a photoresist, thereby conducting a predetermined pattern of conductive lines and bonding pads. Is formed. As the surface conductive 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 conducting wire layer 50. The pattern of the surface conductive layer 50 is formed by reactive ion etching using, for example, chlorine (Cl ₂ ) gas. The pattern of the surface conductor layer 50 may be formed by wet etching.

Next, as shown in FIGS. 13A, 13B, and 13C, the flexible portion F and the third insulating layer 40 are etched by etching the SOI layer 13, the second insulating layer 20, and the third insulating layer 40 using the protective film R7 made of a photoresist. The pattern of the support portion S is formed on the SOI layer 13, the second insulating layer 20, and the third insulating layer 40. For example, the second insulating layer 20 and the third insulating layer 40 are etched by reactive ion etching using CHF ₃ gas, and then the SOI layer 13 is etched by reactive ion etching using CF ₄ gas and O ₂ gas. . The pattern of the flexible portion F and the support portion S may be formed by wet etching using hydrofluoric acid or buffered hydrofluoric acid.

Next, as shown in FIG. 14, the base layer 11 is etched to form a slit T that is an annular groove, and a portion of the base layer 11 that becomes the support portion S is left outside the slit T to leave the slit T. The portion of the base layer 11 that becomes the weight portion M is left inside. That is, by forming the slit T in the base layer 11, the base layer 11 is divided into a portion constituting the support portion S and a portion constituting the weight portion M. The slit T may be circular, and may be circular, rectangular, or polygonal. Further, the width of the slit T may be constant or may be different for each region. Specifically, the surface on which the third insulating layer 40 of the workpiece W, which is a laminated structure formed by the above-described steps, is bonded to the sacrificial substrate 99 as shown in FIG. As the adhesive layer 98, for example, a wax, a photoresist, a double-sided pressure-sensitive adhesive sheet or the like is used. Subsequently, a protective film R8 made of a photoresist is formed on the surface of the base layer 11, and a slit T is formed by anisotropic etching using the protective film R8. More specifically, the base layer 11 is anisotropic by Deep-RIE (so-called Bosch process) in which the steps of passivation using C ₄ F ₈ plasma and etching using SF ₆ plasma are alternately repeated at short time intervals. Is etched. Note that this step of forming the weight portion M may be performed as the first step of processing the SOI wafer 10 or may be performed immediately after the second insulating layer 20 is formed.

Next, as shown in FIG. 15, after the workpiece W is peeled from the sacrificial substrate 99, the first insulating layer 12 is isotropically etched. As a result, gaps G ₁ and G ₂ are formed between the rising stopper portion 30a and the weight portion M and between the flexible portion F and the weight portion M, and the function of the flexible portion F (the movement of the weight portion M) And the function of the ascending stopper portion 30a (the function of limiting the movement range of the weight portion M) and the function of the connecting portion 30b (the function of connecting the weight portion M and the flexible portion F). To do. At this time, since the rising stopper portion 30a and the connecting portion 30b that are in contact with the first insulating layer 12 are formed of the first insulating layer 12 and the different stopper layer 30, the interface between the first insulating layer 12 and the rising stopper portion 30a. The etching end point can be accurately determined at the interface between the first insulating layer 12 and the connecting portion 30b. That is, since the shapes of the gaps G ₁ and G ₂ can be accurately formed, the sensor die 1A with small variation in characteristics can be manufactured.

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

  According to the first embodiment described above, the movement range in the positive z-axis direction of the weight portion can be accurately limited by the thickness of the first insulating layer 12. Since the first insulating layer 12 can be formed extremely thin, the range of motion of the weight M in the positive z-axis direction can be extremely narrowed. Further, since the function of limiting the movement range of the weight part in the positive z-axis direction can be realized by the ascending stopper part 30a in the height range of the flexible part F with respect to the weight part M, the function can be added. Package 1B does not become thick. That is, a thin acceleration sensor with high impact resistance can be realized. Furthermore, since the region of the weight portion M facing the ascending stopper portion 30a is limited, it is possible to suppress a decrease in sensitivity due to air damping compared to the case where the movement range of the weight portion M is limited by a plate-like component.

In the first embodiment, the stopper layer 30 constituting the rising stopper portion 30a is directly bonded to the base layer 11. However, the stopper layer 30 and the base layer 11 may not be directly bonded. In this case, the first insulating layer 12 may be sandwiched between the raised stopper portion 30a and the base layer 11, between a raised stopper portion 30a and the base layer 11 may be all gaps G ₂ . When such a configuration is adopted, the stopper layer 30 is not used as a stopper when the first insulating layer 12 is etched, but the etching end point of the first insulating layer 12 is set only by the etching time. Become.

2. Second Embodiment FIG. 16 shows a sensor die 2A of an acceleration sensor which is a second embodiment of the MEMS sensor of the present invention. 16B and 16C are cross-sectional views corresponding to the BB line and CC line shown in FIG. 16A, respectively. In FIG. 16B and FIG. 16C, the interface of the layer which comprises the sensor die 2A is shown with the broken line, and the boundary of the functional element which comprises the sensor die 2A is shown with the continuous line.

As shown in FIG. 16, a through hole 30h may be formed in the rising stopper portion 30a. By forming the through hole 30h in the region facing the weight M, the first insulating layer 12 is etched to form the gaps G ₁ and G _{2, so} that it can be reliably inserted between the stopper layer 30 and the base layer 11. In addition, the first insulating layer 12 can be removed. Therefore, even if the rising stopper portion 30a widens the region facing the weight portion M, the defective product generation rate due to the residue of the first insulating layer 12 can be suppressed. Further, even if the region where the rising stopper portion 30a is opposed to the weight portion M is widened, it is possible to suppress a decrease in sensitivity due to air damping by the rising stopper portion 30a.

3. Third Embodiment (Configuration)
FIG. 17 shows a sensor die 3A of an acceleration sensor which is a third embodiment of the MEMS sensor of the present invention. 17B and 17C are cross-sectional views corresponding to the BB line and CC line shown in FIG. 17A, respectively. In FIG. 17B and FIG. 17C, the interface of the layer which comprises the sensor die 3A is shown with the broken line, and the boundary of the functional element which comprises the sensor die 3A is shown with the continuous line.

In the third embodiment, a lowering stopper portion 30c that limits the movement range of the weight portion M in the negative z-axis direction is added. Lowering the stopper portion 30c is coupled to the weight portion M, it is opposed to the support and the z-axis direction across the air gap G _3. The height of the gap G ₃ (the distance between the base layer 11 between the descending stopper portion 30c supporting portion S) is equal to the thickness of the first insulating layer 12. When the descending stopper portion 30c comes into contact with the base layer 11 of the support portion S, the range of motion of the weight portion M in the negative z-axis direction is limited. The descending stopper portion 30c is composed of the stopper layer 30 in the same manner as the ascending stopper portion 30a and the connecting portion 30b.

  By adding the descending stopper portion 30 c made of the stopper layer 30, the range of motion of the weight portion in the negative z-axis direction can be accurately limited by the thickness of the first insulating layer 12. Since the first insulating layer 12 can be formed extremely thin, the range of motion of the weight portion in the negative z-axis direction can be extremely narrowed. In addition, since the function of limiting the movement range of the weight part in the negative z-axis direction can be realized by the lowering stopper part 30c in the range of the height of the flexible part F with respect to the weight part M, the weight part in the negative z-axis direction. Even if a function for limiting the movement range of M is added, the package 1B does not become thick.

(Production method)
The sensor die 3A can be manufactured in the same manner as in the first embodiment only by changing the pattern of the protective films R2, R3, and R7 used in the first embodiment. 18A, 19A, and 20A are cross-sectional views corresponding to the line BB shown in FIG. 17A. 18B, 19B, and 20B are cross-sectional views corresponding to the CC line shown in FIG. 17A.

  When the recesses H1 and H2 are formed by etching using the protective film R2 made of a photoresist, as shown in FIG. 18, a recess H3 that is a lowering stopper mold part for forming the lowering stopper part 30c is formed at the same time. The recessed portion H3 extends from the inside to the outside from the region (the region shown by the broken line) that becomes the annular slit T between the weight portion M and the support portion S.

Next, after removing the protective film R2, as shown in FIG. 19, a portion exposed from the recesses H1, H2, and H3 of the first insulating layer 12 using the protective film R3 made of a photoresist as in the first embodiment. The base layer 11 is exposed from the recesses H1, H2, and H3 penetrating the first insulating layer 12. At this time, as for the portion exposed from the recess H3 of the first insulating layer 12, not all the exposed portion is removed by etching, but only the inner side from the region that becomes the slit T is removed to become the slit T. The outside from the area remains. The first insulating layer 12 remaining on the bottom of the recess H3 after etching so as to function as a sacrificial layer for forming a gap G ₃ between the descending stopper portion 30c and the weight portion M.

  When forming the portions to be the flexible portion F and the support portion S in the third insulating layer 40, the second insulating layer 20, and the SOI layer 13 using the protective film R7, the lowering stopper portion 30c is protected as shown in FIG. Thus, the protective film R7 may be formed. Then, the third insulating layer 40, the second insulating layer 20, and the SOI layer 13 are removed from the periphery of the descending stopper portion 30c by etching, and the descending stopper portion 30c remains.

  It is also possible to individually set the movement range in the z-axis positive direction and the negative movement range of the weight part. In this case, for example, after performing the process corresponding to FIG. 19, the protective film R3 is removed, and a film having the same quality as the first insulating layer 12 is formed only on the first insulating layer 12 exposed in the recess H3. Thereafter, the stopper layer 30 may be formed.

4). Fourth embodiment (Configuration)
FIG. 21 shows a sensor die 4A of an acceleration sensor which is a fourth embodiment of the MEMS sensor of the present invention. 21B and 21C are cross-sectional views corresponding to the BB line and the CC line shown in FIG. 21A, respectively. In FIG. 21B and FIG. 21C, the interface of the layer which comprises the sensor die 4A is shown with the broken line, and the boundary of the functional element which comprises the sensor die 4A is shown with the continuous line.

In the fourth embodiment, the ascending stopper portion 30 a, the descending stopper portion 30 c, and the connecting portion 30 b have a multilayer structure including the stopper layer 31 and the core layer 32. The stopper layer 31 serving as an etching stopper for the first insulating layer 12 constitutes the surface layer of the ascending stopper portion 30a, the descending stopper portion 30c, and the connecting portion 30b at the portions in contact with the gaps G ₁ , G ₂ , and G ₃ . By adopting a multilayer structure for the ascending stopper portion 30a, the descending stopper portion 30c, and the connecting portion 30b, the balance of stress, manufacturing cost, strength, etc. can be optimized.

(Production method)
Instead of filling the recesses H1, H2, and H3 with only the stopper layer 30 in the process corresponding to FIG. 7, the sensor die 4A forms the recess layer H1 by forming the core layer 32 after forming the stopper layer 31 thin as shown in FIG. , H2 and H3 may be filled. That is, after forming the recesses H1, H2, and H3, the stopper layer 31 is first formed thinly on the surfaces of the base layer 11, the first insulating layer 12, and the second insulating layer 20. For example, a silicon nitride (Si _x N _y ) film having a thickness of 0.2 μm is formed as the stopper layer 31 by using a CVD method. Instead of silicon nitride, nitrides such as aluminum nitride (Al _x N _y ), titanium nitride (Ti _x N _y ), aluminum oxide (Al _x O _y ), tantalum oxide (TaO _x ), titanium oxide (TiO _x ) The stopper layer 31 may be formed using an oxide such as. Next, by forming the core layer 32, the recesses H1, H2, and H3 are completely filled. For example, a silicon dioxide film having a thickness of 10 μm is formed as the core layer 32 by using the CVD method. Instead of silicon dioxide, polycrystalline silicon, aluminum nitride, aluminum oxide, tantalum oxide, titanium oxide, tungsten silicide (WSi _x ), molybdenum silicide (MoSi _x ), titanium silicide (TiSi _x ), copper (Cu), nickel ( The core layer 32 may be formed using a semiconductor such as Ni), platinum (Pt), or gold (Au), an oxide, a nitride, a silicide compound, or a metal. In selecting such a material, an optimum material is selected and combined in consideration of a balance of stress, manufacturing cost, strength, and the like.

5). Fifth Embodiment FIG. 23 shows a sensor die 5A of an angular velocity sensor which is a fifth embodiment of the MEMS sensor of the present invention. 23B, 23C, and 23D are cross-sectional views corresponding to the BB, CC, and DD lines shown in FIG. 23A, respectively. In FIG. 23B, FIG. 23C, and FIG. 24D, the interface of the layer which comprises the sensor die 5A is shown with the broken line, and the boundary of the functional element which comprises the sensor die 5A is shown with the continuous line.

  The sensor die 5A is a vibration gyroscope type. The flexible portion F coupled to the support portion S constitutes two beams that are stretched in parallel inside the support portion S. The deformation of the flexible portion F is detected by a detection piezoelectric element 80b provided in the flexible portion F. The driving piezoelectric element 80 a provided in the flexible portion F is a driving unit that vibrates the weight portion M by vibrating the flexible portion F. The detecting piezoelectric element 80 b and the driving piezoelectric element 80 a have a structure in which the piezoelectric layer 82 is sandwiched between two electrode layers 81 and 83. The cross-shaped weight part M is long in the x-axis direction where the two beams constituting the flexible part F are stretched over the support part S, and the center part protrudes in the y-axis positive direction and the y-axis negative direction. Yes. In the central portion of the weight portion M protruding in the positive y-axis direction and the negative y-axis direction, the weight portion M is connected to two beams constituting the flexible portion F via the first insulating layer 12. The weight part M and the flexible part F are connected by the first insulating layer 12. That is, in the present embodiment, the connecting portion that connects the weight portion M and the flexible portion F is not formed by the stopper layer 30 but is formed by the first insulating layer 12. Except for the point that the ascending stopper portion 30a is not embedded in the support portion S and is provided in a plurality of independent portions in the supporting portion S, the configuration and function of the ascending stopper portion 30a and the descending stopper portion 30c are as follows. The configuration and function described in the third embodiment are substantially the same.

  Thus, the present invention can be applied to MEMS sensors other than the acceleration sensor. Further, the present invention can be implemented as a motion sensor for detecting acceleration and angular velocity by forming a piezoresistive element 131 on the SOI layer 13 of the sensor die 5A and adding a surface conducting wire layer 50.

6). Sixth embodiment.
(Constitution)
FIG. 24 shows a sensor die 6A of an angular velocity sensor which is a sixth embodiment of the MEMS sensor of the present invention. The sensor die 6A is a vibration gyroscope type. 24B, 24C, and 24D are cross-sectional views corresponding to the BB, CC, and DD lines shown in FIG. 24A, respectively. In FIG. 24B, FIG. 24C, and FIG. 24D, the interface of the layer which comprises the sensor die 6A is shown with the broken line, and the boundary of the functional element which comprises the sensor die 6A is shown with the continuous line. For the sake of explanation, each figure shows an x-axis, a y-axis and a z-axis that are orthogonal to each other.

The sensor die 6 </ b> A is a laminated structure including the base layer 11, the non-flat layer 72, the insulating layer 73, the electrode layers 81 and 83, and the piezoelectric layer 82. The sensor die 6A is accommodated in the package 1B described in the first embodiment. The base layer 11 and the non-flat layer 72 are made of n-type single crystal silicon. The thickness of the base layer 11 is 625 μm. The thickness of the non-flat layer 72 is 10 μm. The insulating layer 73 is made of a silicon oxide film (SiO ₂ ). The thickness of the insulating layer 73 is 1 μm. The electrode layers 81 and 83 are made of platinum (Pt). The electrode layers 81 and 83 have a thickness of 0.1 μm. The piezoelectric layer 82 is made of PZT (lead zirconate titanate). The thickness of the piezoelectric layer 82 is 3 μm.

  The sensor die 6A includes a frame-shaped support portion S, a flexible portion F constituting two beams coupled to the support portion S, a weight portion M directly coupled to the flexible portion F, and a flexible portion. A driving piezoelectric element 80a and a detecting piezoelectric element 80b provided in F and a rising stopper portion 70a directly coupled to the support portion S are provided.

  The support portion S has a frame shape as shown in FIG. 24A. Since the support part S is fixed to the package 1B, it behaves substantially as a rigid body. The support part S includes a base layer 11, a non-flat layer 72, and an insulating layer 73. An annular gap T is formed between the support part S and the weight part M. In the region where the support part S and the weight part M are close to each other, the support part S is composed of only the base layer 11.

  The flexible part F constitutes two beams that are stretched in parallel inside the support part S. The flexible part F includes a non-flat layer 72 and an insulating layer 73. Each of the beams constituting the flexible portion F is bent so as to protrude in the negative z-axis direction at both end portions and the central portion. That is, the non-flat layer 72 and the insulating layer 73 constituting the flexible portion F are not flat, and are raised in the direction away from the base layer 11 between the support portion S and the weight portion M.

  The cross-shaped weight part M is long in the x-axis direction where the two beams constituting the flexible part F are stretched over the support part S, and the center part protrudes in the y-axis positive direction and the y-axis negative direction. Yes. In the central portion of the weight portion M protruding in the positive y-axis direction and the negative y-axis direction, the weight portion M is directly coupled to the two beams that constitute the flexible portion F. Since the weight part M is coupled only to the flexible part F and is separated from both the package 1B and the support part S, it moves relative to the support part S. The weight portion M deforms the flexible portion F by moving relative to the support portion S.

  The detecting piezoelectric element 80 b and the driving piezoelectric element 80 a have a structure in which the piezoelectric layer 82 is sandwiched between two electrode layers 81 and 83. The deformation of the flexible portion F is detected by a detection piezoelectric element 80b provided in the flexible portion F. The driving piezoelectric element 80 a provided in the flexible portion F is a driving unit that vibrates the weight portion M by vibrating the flexible portion F.

The rising stopper portion 70a is provided in a plurality of regions where the support portion S and the weight portion M are close to each other. Moreover, the raising stopper part 70a is provided in the area | region which opposes each of the four edge parts of the weight part M in az direction. The rising stopper portion 70 a includes a non-flat layer 72 and an insulating layer 73. That is, the rising stopper portion 70a has the same layer structure as the flexible portion F. One end of the rising stopper portion 70a is coupled to the base layer 11 in a region close to the weight portion M of the support portion S. The ascending stopper portion 70a extends from the support portion S toward the inside of the support portion S, beyond the gap T, to a region facing the weight portion M. The rising stopper portion 70 a also extends in the positive z-axis direction away from the base layer 11. More specifically, the rising stopper portion 70a is bent in the direction away from the base layer 11 (z-axis positive direction) at the end of the portion connected to the base layer 11. Therefore, faces the z direction across the air gap G ₂ is a front end portion and the weight portion M of the rise stopper 70a. The height of the gap G ₂ (distance between the tip portion and the weight portion M of the rise stopper portion 70a), the base layer in between the coupling regions between the coupling region and the weight portion M of the flexible portion F support portion S It is equal to the height rising in the direction away from 11.

When the end of the weight portion M moves in the direction from the weight portion M toward the flexible portion F (z-axis positive direction), the initial state (the portion constituting the support portion S of the base layer 11 and the weight portion M are formed. a raised stopper portion 70a and the end portion of the weight M is in contact when the to have parts moving amount from the state) that are aligned in the xy plane parallel to the direction is equal to the height of the air gap G ₂ . Thus, the range of motion of the weight part M in the direction from the weight part M toward the flexible part F is limited by the ascending stopper part 70a. Therefore, even if an impact that causes excessive acceleration in the negative z-axis direction is applied, the flexible portion F is not damaged.

(Production method)
Hereinafter, a method for manufacturing the sensor die 6A of the angular velocity sensor will be described with reference to FIGS. 25, 26A, 27A, 28, 29A, 30A, and 31A are cross-sectional views corresponding to the BB line shown in FIG. 24A. 26B, 27B, 29B, 30B, and 31B are cross-sectional views corresponding to the CC line shown in FIG. 24A.

  First, as shown in FIG. 25, a p-type single crystal silicon layer is epitaxially grown as a sacrificial layer 71 on the surface of the base layer 11. As the base layer 11, an n-type single crystal silicon wafer is used.

  Next, as shown in FIG. 26, the sacrificial layer 71 is patterned by crystal anisotropic etching using a protective film R10 made of a photoresist. The pattern of the sacrificial layer 71 is made to correspond to the region raised from the base layer 11 of the flexible portion F and the rising stopper portion 70a. As a result, the base layer 11 is exposed from under the sacrificial layer 71. The region of the base layer 11 exposed from under the sacrificial layer 71 is used as a region for coupling the flexible portion F and the weight portion M, and a region for coupling the rising stopper portion 70a and the support portion S. The sacrificial layer 71 made of single crystal silicon is subjected to crystal anisotropic etching, whereby the end surface of the sacrificial layer 71 can be inclined. Specifically, the base layer 11 is temporarily bonded to a support plate (not shown) using wax as an adhesive layer, and the sacrificial layer 71 is patterned by electrochemical etching in a state of being immersed in an etching solution. Then, the p-type sacrificial layer 71 can be selectively etched with respect to the n-type base layer 11. The base layer 11 and the non-flat layer 72 may be n-type, and the sacrificial layer 71 may be p-type.

  Next, as shown in FIG. 27, the non-flat layer 72 is formed by epitaxially growing n-type single crystal silicon on the surfaces of the base layer 11 and the sacrificial layer 71. As a result, a non-flat layer 72 partially rising from the base layer 11 is formed. Subsequently, an insulating layer 73 is formed on the surface of the non-flat layer 72. For example, an insulating layer 73 made of silicon dioxide having a thickness of 1 μm is formed by CVD or thermal oxidation.

  Next, as shown in FIG. 28, a driving piezoelectric element 80a and a detecting piezoelectric element 80b are formed on the surface of the insulating layer 73 by a known method.

Next, as shown in FIG. 29, the insulating layer 73 and the non-flat layer 72 are patterned by etching using a protective film R11 made of a photoresist. At this time, a portion of the insulating layer 70 and the non-flat layer 72 that are continuous from the support portion S to the flexible portion F and a portion of the rising stopper portion 70a are formed. Specifically, the insulating layer 73 is etched by reactive ion etching using CHF ₃ gas, and then the non-flat layer 72 is etched by reactive ion etching using CF ₄ gas and O ₂ gas.

Next, as shown in FIG. 30, the base layer 11 is etched using a protective film R12 made of a photoresist to form a gap T that is an annular groove, and the base that becomes the support portion S from the gap T to the outside. The portion of the layer 11 is left, and the portion of the base layer 11 that becomes the weight portion M is left inside the gap T. That is, by forming the gap T in the base layer 11, the base layer 11 is divided into a part constituting the support part S and a part constituting the weight part M. More specifically, the base layer 11 is anisotropic by Deep-RIE (so-called Bosch process) in which the steps of passivation using C ₄ F ₈ plasma and etching using SF ₆ plasma are alternately repeated at short time intervals. Is etched.

Next, as shown in FIG. 31, the sacrificial layer 71 is removed by isotropic etching. As a result, the gap G ₂ is formed between the raised stopper portion 70a and the weight portion M, the function of increasing the stopper portion 70a (function of limiting the range of motion of the weight M) is obvious. At this time, since the rising stopper portion 70a in contact with the sacrificial layer 71 and the non-flat layer 72 of the flexible portion F have different conductivity types from the sacrificial layer 71, the etching end point is formed at the interface between the sacrificial layer 71 and the non-flat layer 72. Can be determined accurately. That is, since the shape of the flexible portion F and the weight portion M and the gap G ₂ can be accurately formed, it is possible variations in characteristics to produce a small sensor die 6A.
Thereafter, when post-processes such as dicing and packaging are performed, an angular velocity sensor including the sensor die 6A shown in FIG. 24 is completed.
According to the sixth embodiment described above, the range of motion of the weight M in the positive z-axis direction can be accurately limited by the thickness of the sacrificial layer 71. Since the sacrificial layer 71 can be formed very thin, the range of motion of the weight M in the positive z-axis direction can be extremely narrowed. Further, the function of limiting the movement range of the weight portion M in the positive z-axis direction can be realized by the rising stopper portion 70a in the range of the height of the flexible portion F with respect to the weight portion M. However, the package 1B does not become thick. That is, a thin angular velocity sensor with high impact resistance can be realized. Furthermore, since the region of the weight portion M facing the ascending stopper portion 70a is limited, it is possible to suppress a decrease in sensitivity due to air damping as compared with the case where the movement range of the weight portion M is limited by a plate-like component.

7). Other Embodiments The technical scope of the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the scope of the present invention. For example, in the present invention, since the flexible portion F and the weight portion M are connected by the connecting portion made of the stopper layer, the shape of the flexible portion F can be freely designed. For this reason, the form of the flexible part F is not limited to the above-described embodiment, and can be changed to various forms, for example, the flexible part F is configured as one, three, four or more cantilever beams or both-end fixed beams. is there.

  Of course, various constituent elements illustrated in different embodiments can be combined. In addition, the materials, dimensions, film forming methods, pattern transfer methods, and process orders shown in the above embodiment are merely examples, and those skilled in the art will understand the addition and deletion of processes and the replacement of process orders. It is omitted.

FIG. 1A is a top view according to the first embodiment of the present invention. 1B and 1C are cross-sectional views 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. 5A and 5B are cross-sectional views according to the first embodiment of the present invention. 6A and 6B are cross-sectional views according to the first embodiment of the present invention. 7A and 7B are cross-sectional views according to the first embodiment of the present invention. 8A and 8B are cross-sectional views according to the first embodiment of the present invention. 9A and 9B are cross-sectional views 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. 13A and 13B are cross-sectional views according to the first embodiment of the present invention. FIG. 13C is a top view according to the first embodiment of the present invention. 14A and 14B are cross-sectional views according to the first embodiment of the present invention. 15A and 15B are cross-sectional views according to the first embodiment of the present invention. FIG. 16A is a top view according to the second embodiment of the present invention. FIG. 16B and FIG. 16C are sectional views according to the second embodiment of the present invention. FIG. 17A is a top view according to the third embodiment of the present invention. 17B and 17C are cross-sectional views according to a third embodiment of the present invention. 18A and 18B are cross-sectional views according to a third embodiment of the present invention. 19A and 19B are cross-sectional views according to a third embodiment of the present invention. 20A and 20B are cross-sectional views according to a third embodiment of the present invention. FIG. 20C is a top view according to the third embodiment of the present invention. FIG. 21A is a top view according to the fourth embodiment of the present invention. 21B and 21C are cross-sectional views according to a fourth embodiment of the present invention. 22A and 22B are sectional views according to a fourth embodiment of the present invention. FIG. 23A is a top view according to the fifth embodiment of the present invention. 23B and 23C are sectional views according to a fifth embodiment of the present invention. FIG. 24A is a top view according to the sixth embodiment of the present invention. 24B and 24C are cross-sectional views according to a sixth embodiment of the present invention. Sectional drawing concerning 6th embodiment of this invention. 26A and 26B are cross-sectional views according to a sixth embodiment of the present invention. 27A and 27B are sectional views according to a sixth embodiment of the present invention. Sectional drawing concerning 6th embodiment of this invention. Sectional drawing concerning 6th embodiment of this invention. 30A and 30B are sectional views according to a sixth embodiment of the present invention. 31A and 31B are sectional views according to a sixth embodiment of the present invention.

Explanation of symbols

1: acceleration sensor, 1A: sensor die, 1B: package, 2A: sensor die, 3A: sensor die, 4A: sensor die, 5A: sensor die, 6A: sensor die, 7A: sensor die, 10: SOI wafer, 11: base layer, 12: first 1 insulating layer, 13: SOI layer, 20: second insulating layer, 20h: hole, 30: stopper layer, 30a: ascending stopper part, 30b: connecting part, 30c: descending stopper part, 30h: through hole, 31: stopper Layer: 32: core layer, 40: third insulating layer, 50: surface conducting wire layer, 70a: rising stopper, 71: sacrificial layer, 72: non-flat layer, 73: insulating layer, 80a: piezoelectric element for driving, 80b : Piezoelectric element for detection, 81: Electrode layer, 82: Piezoelectric layer, 83: Electrode layer, 90: Base, 90a: Bottom surface, 91: Through electrode, 92: Adhesive layer, 93: Adhesive layer, 94: Cover , 95: wire, 98: adhesive layer, 99: a sacrificial substrate, 131: piezoresistive element, 131a: high resistance portion, 131b: low resistance part, F: flexible portion, G: gap, _{G 1:} gap, _{G 2} : void, _{G 3:} void, H1: recess, H2: recess, H4: contact hole, H3: recess, M: weight part, R1: protective film, R2: protective film, R3: protective film, R4: coating, R5 : Protective film, R6: protective film, R7: protective film, R8: protective film, R10: protective film, R11: protective film, R12: protective film, S: support, T: slit (gap), W: workpiece

Claims (11)

A frame-shaped support portion; a beam-shaped flexible portion coupled to the support portion; and a weight portion coupled to the flexible portion and deformed by moving with respect to the support portion. , A manufacturing method of a MEMS sensor comprising a stopper portion that limits a movement range of the weight portion,
Forming a sacrificial layer made of an epitaxial crystal layer having a conductivity type different from that of the base layer on the surface of the base layer made of single crystal silicon;
Partially exposing the base layer from the sacrificial layer by etching the sacrificial layer;
Forming a non-flat layer composed of an epitaxial crystal layer having a conductivity type matching that of the base layer on the surface of the sacrificial layer and the base layer;
Due to the etching of the non-flat layer, a portion of the non-flat layer that is continuous with the flexible portion and the support portion and partially overlaps the sacrificial layer and the stopper of the non-flat layer Forming a portion that partially overlaps the sacrificial layer,
After forming the sacrificial layer, an annular groove is formed by etching the base layer, and the base layer is formed in a portion that becomes the support portion outside the groove and a portion that becomes the weight portion inside the groove. Divide
After forming the groove, the sacrificial layer is removed by isotropic etching to form a gap between the stopper portion and the weight portion, and contact the weight portion by forming the gap. Then, in the direction from the weight portion toward the flexible portion, the function as the stopper portion that limits the movement range of the weight portion is manifested in the non-flat layer.
A method for manufacturing a MEMS sensor. A frame-shaped support portion; a beam-shaped flexible portion coupled to the support portion; and a weight portion coupled to the flexible portion and deformed by moving with respect to the support portion. , A manufacturing method of a MEMS sensor comprising a stopper portion that limits a movement range of the weight portion,
An annular groove is formed by etching the base layer of an SOI wafer comprising a base layer, an SOI layer made of single crystal silicon and thinner than the base layer, and an insulating layer between the base layer and the SOI layer. And dividing the base layer into a portion that becomes the support portion outside from the groove and a portion that becomes the weight portion inside from the groove,
Forming a rising stopper mold part that is an annular recess that penetrates the SOI layer at a position extending from the inside of the groove to the outside of the groove and penetrates the insulating layer outside the groove;
Forming a stopper layer that is different from the insulating layer in the rising stopper mold portion;
Etching the SOI layer to form a portion of the SOI layer that is continuous with the support portion and the flexible portion;
A gap is formed between the stopper layer formed in the rising stopper mold part and the weight part by isotropically etching the insulating layer using the stopper layer as an etching stopper, and the gap is formed. Thus, the stopper layer formed in the rising stopper mold portion has a function as a rising stopper portion that limits the movement range of the weight portion in a direction from the weight portion toward the flexible portion by contacting the weight portion. To manifest in the
A method for manufacturing a MEMS sensor. Forming the rising stopper mold part and a connecting mold part, which is a recess located inside the rising stopper mold part and penetrating the SOI layer and the insulating layer, by etching;
Forming the stopper layer simultaneously in the connection mold part and in the rising stopper mold part,
When the gap is formed, the gap is formed between the weight portion and the flexible portion, and a function as a connecting portion for connecting the weight portion and the flexible portion is formed in the connection mold portion. Manifested in the stopper layer,
The manufacturing method of the MEMS sensor of Claim 2 including this. Filling the rising stopper mold part and the connecting mold part by laminating the stopper layer and a heterogeneous core layer on the surface of the stopper layer;
A method for manufacturing the MEMS sensor according to claim 3. A frame-shaped support portion; a beam-shaped flexible portion coupled to the support portion; and a weight portion coupled to the flexible portion and deformed by moving with respect to the support portion. , A manufacturing method of a MEMS sensor comprising a stopper portion that limits a movement range of the weight portion,
An annular groove is formed by etching the base layer of an SOI wafer comprising a base layer, an SOI layer made of single crystal silicon and thinner than the base layer, and an insulating layer between the base layer and the SOI layer. And dividing the base layer into a portion that becomes the support portion outside from the groove and a portion that becomes the weight portion inside from the groove,
Etching a descending stopper mold part that is a recess penetrating the SOI layer at a position extending from the inside of the groove to the outside of the groove and penetrating the insulating layer inside the groove,
Forming a stopper layer that is different from the insulating layer in the descending stopper mold portion;
Etching the SOI layer to form a portion of the SOI layer that is continuous with the support portion and the flexible portion;
Using the stopper layer as an etching stopper, the insulating layer is isotropically etched to form a void between the stopper layer formed in the descending stopper mold portion and the support portion, thereby forming the void. Thus, the lower stopper mold part has a function as a lowering stopper part that moves together with the weight part, contacts the support part, and restricts the movement range of the weight part in the direction from the flexible part toward the weight part. Manifested in the stopper layer formed,
A method for manufacturing a MEMS sensor. An annular rising stopper mold portion that penetrates the SOI layer at a position extending from the inside of the groove to the outside of the groove and that penetrates the insulating layer outside the groove, and located inside the rising stopper mold portion. A connecting mold part that is a recess penetrating the SOI layer and the insulating layer and the lowering stopper mold part are simultaneously formed by etching,
Forming the stopper layer different from the insulating layer at the same time in the connecting mold part, in the rising stopper mold part and in the falling stopper mold part;
When the insulating layer is isotropically etched, a gap is formed between the weight portion and the flexible portion, and a function as a connection portion for connecting the weight portion and the flexible portion is provided in the connection mold portion. Manifested in the stopper layer formed in
A method for manufacturing the MEMS sensor according to claim 5. A frame-shaped support,
A weight portion located inside the support portion;
A flexible part that is spanned inside the support part, connected to the weight part, and deforms as the weight part moves;
An ascending stopper portion that limits the range of motion of the weight portion on the flexible portion side of the weight portion by contacting the weight portion and contacting the weight portion with the gap between the support portion and the weight portion;
With
The flexible portion includes a single crystal silicon layer,
The rising stopper portion includes a stopper layer penetrating the single crystal silicon layer and facing the weight portion.
MEMS sensor. A through hole is formed in a region of the rising stopper portion facing the weight portion,
The MEMS sensor according to claim 7. A frame-shaped support,
A weight portion located inside the support portion;
A beam-shaped flexible part that is spanned inside the support part, connected to the weight part, and deforms as the weight part moves;
A lowering stopper part that limits the range of motion of the weight part in the direction from the flexible part to the weight part by connecting to the weight part and facing the support part across the gap and contacting the support part;
With
The flexible portion includes a single crystal silicon layer,
The descending stopper portion includes a stopper layer penetrating the single crystal silicon layer and facing the support portion.
MEMS sensor. A coupling portion coupled to the weight portion and the flexible portion and coupling the weight portion and the flexible portion;
The surface of the connecting portion is constituted by the stopper layer which is different from silicon oxide.
The MEMS sensor according to any one of claims 7 to 9. The ascending stopper part or the descending stopper part has a multilayer structure including the stopper layer,
The MEMS sensor according to any one of claims 7 to 10.

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