JP2008008673A - Acceleration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acceleration sensor capable of easily recognizing operation in each of a plurality of directions where the acceleration can be detected. <P>SOLUTION: The acceleration sensor comprises a sensor substrate 1 that has gauge resistors Rx1-Rx4, Ry1-Ry4 and Rz1-Rz4 disposed in a movable section formed of a weight section 12 and four bending sections 13 and can detect accelerations in three directions, a first cover substrate 2 joined to one surface side of the sensor substrate 1, and a second cover substrate 3 joined to the other surface side of the sensor substrate 1. A package is constituted by the cover substrates 2 and 3 and a frame section 11 of the sensor substrate 1. The acceleration sensor has, as a driving means for operation recognition for forcibly moving the movable section with an electromagnetic force, a plurality of pairs of excitation sections 26 formed of coils and disposed on the first cover substrate 2 and magnetic coupling sections 15 that are disposed in the weight section 12 and can magnetically couple to the excitation sections 26, and can generate the electromagnetic force for operation recognition independently every pair of excitation section 26 and magnetic coupling section 15. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an acceleration sensor for detecting acceleration used in, for example, automobiles and mobile phones.

  2. Description of the Related Art Conventionally, as an acceleration sensor, a piezoresistive acceleration sensor that detects acceleration based on a change in resistance value due to strain of a gauge resistor formed by piezoresistance when acceleration is applied is known.

  Here, as a piezoresistive acceleration sensor, a weight portion disposed inside a rectangular frame-shaped frame portion formed using a semiconductor substrate swings to the frame portion via a bending portion extended in one direction. A sensor substrate that is freely supported and two glass covers that are joined to both sides in the thickness direction of the sensor substrate (see, for example, Patent Document 1), or the inside of a frame-shaped frame portion The weight portion disposed on the frame portion is swingably supported by the frame portion via four flexure portions extending in all directions, and is provided in a plurality of directions (for example, three directions orthogonal to each other in the x-axis direction, y-direction, respectively). A sensor board (refer to, for example, Patent Document 2) that includes a sensor board capable of separately detecting acceleration in the axial direction and the z-axis direction and a package that houses the sensor board has been proposed. Further, as a sensor substrate (acceleration sensor element) capable of separately detecting accelerations in a plurality of directions, the weight of the weight portion can be increased without increasing the size of the sensor substrate as compared with the one described in Patent Document 2. Some have been proposed that can increase sensitivity (see, for example, Patent Document 3). In the piezoresistive acceleration sensor described above, the weight portion and the bending portion constitute a movable portion. Moreover, in the sensor substrate in the acceleration sensor disclosed in Patent Documents 2 and 3, each of the three bridge circuits that detect acceleration in each axial direction has four gauge resistors arranged at appropriate positions of the movable portion by wiring. It is configured by connecting.

In addition, the acceleration sensor disclosed in Patent Document 1 is provided with a fixed electrode for forcibly moving the weight portion by electrostatic force on the cover, and a voltage is applied between the fixed electrode and the weight portion by electrostatic force. It is configured to perform self-diagnosis such as whether or not the sensor characteristics such as sensitivity are appropriate by moving the weight part.
JP-A-3-134552 JP 2006-133123 A JP 2002-296293 A

  By the way, in a multi-axis acceleration sensor that can detect accelerations in a plurality of directions, such as the acceleration sensor disclosed in Patent Document 2, the entire target device is used for checking the operation before shipment after being incorporated in the target device. The current situation is that the operation is confirmed by applying an acceleration to the operation, and it takes a lot of time to check the operation.

  Therefore, in order to add a self-diagnosis function similar to that of the acceleration sensor described in Patent Document 1 to the multi-axis acceleration sensor disclosed in Patent Document 2, a fixed electrode is provided at a portion facing the weight portion in the package. However, the operation can be confirmed only in the thickness direction (z-axis direction) of the sensor substrate, and the operation can be confirmed in other directions (x-axis direction, y-axis direction). Can not.

  The present invention has been made in view of the above-described reasons, and an object thereof is to provide an acceleration sensor capable of easily confirming an operation in each of a plurality of directions in which acceleration can be detected.

  According to a first aspect of the present invention, there is provided a sensor substrate formed of a semiconductor substrate and provided with a plurality of gauge resistors for detecting stress generated in the movable portion by the action of acceleration and capable of detecting accelerations in a plurality of directions, respectively, and a sensor An acceleration sensor comprising a package having a displacement space of a movable part in the thickness direction of the substrate, comprising an operation confirmation drive means for forcibly moving the movable part by electromagnetic force, the drive means comprising a sensor substrate A plurality of pairs of excitation parts consisting of coils provided on one of the opposing surfaces of the movable part and the package on one surface side and a magnetic coupling part provided on the other side that can be magnetically coupled to the excitation part. An electromagnetic force for confirming the operation can be generated for each pair of the magnetic part and the magnetic coupling part.

  According to the present invention, the driving means for confirming the operation for forcibly moving the movable part by the electromagnetic force in the sensor board capable of detecting accelerations in a plurality of directions provided with a plurality of gauge resistors on the movable part is provided on the sensor board. There are a plurality of pairs of an excitation part composed of a coil provided on one of the opposing surfaces of the movable part and the package on the surface side and a magnetic coupling part provided on the other side and magnetically coupled to the excitation part, Since it is possible to generate an electromagnetic force for operation confirmation for each pair with the magnetic coupling unit, the deformation of the movable unit can be performed by appropriately selecting the pair of the excitation unit and the magnetic coupling unit that generates the electromagnetic force for operation confirmation. It becomes possible to change the state, and it is possible to easily check the operation in each of a plurality of directions in which acceleration can be detected.

  According to a second aspect of the present invention, in the first aspect of the invention, the sensor substrate is swingable to the frame portion through four flexure portions having a frame portion surrounding the weight portion and the weight portions arranged in a cross shape. The movable part is composed of a weight part and each bending part, and the gauge resistance is arranged so that acceleration in each of three directions orthogonal to each other can be detected. A core portion to which one end portion of each bending portion is connected, and a space formed between each pair of bending portions formed integrally with the core portion and adjacent to each other in the circumferential direction of the core portion, the frame portion, and the frame portion in plan view. The four accompanying parts are provided, and each of the accompanying parts is provided with either one of the excitation part and the magnetic coupling part.

  According to the present invention, it is possible to easily check the operation in each of the three directions in which acceleration can be detected.

  According to a third aspect of the present invention, in the second aspect of the invention, the package includes a first cover substrate bonded to the one surface side of the sensor substrate and a first cover substrate bonded to the other surface side of the sensor substrate. And the frame portion of the sensor substrate, the first cover substrate is formed using a semiconductor substrate, and a through-hole for energizing the driving means is formed in the first cover substrate. A wiring is formed.

  According to the present invention, the distance between the excitation unit and the magnetic coupling unit can be accurately controlled by using micromachining technology, and the weight when the movable unit is forcibly moved by the driving unit. The variation in the amount of displacement of the part can be reduced.

  According to a fourth aspect of the present invention, in the first to third aspects of the present invention, at least one of the sensor substrate and the package is provided with a stopper for preventing contact between the exciting portion and the magnetic coupling portion. It is characterized by that.

  According to the present invention, it is possible to prevent the occurrence of a sticking phenomenon in which the excitation portion and the magnetic coupling portion adhere when the weight portion is forcibly moved.

  According to a fifth aspect of the present invention, in the first to fourth aspects of the invention, the magnetic coupling portion is made of a magnetic film.

  According to the present invention, it is possible to generate an attractive force or a repulsive force between the excitation unit and the magnetic coupling unit according to the direction of the current flowing to the excitation unit, so that a more accurate operation check can be performed. Is possible.

  According to a sixth aspect of the present invention, in the first to fourth aspects of the present invention, the magnetic coupling portion comprises a coil.

  According to this invention, since the same material can be adopted for the excitation part and the magnetic coupling part, as compared with the case where the magnetic coupling part is constituted by a magnetic film as in the invention of claim 5, Cost reduction can be achieved.

  According to a seventh aspect of the present invention, in the first to sixth aspects of the present invention, the sensor substrate is integrated with a control circuit that selects a pair of the excitation unit and the magnetic coupling unit that generates the electromagnetic force. It is characterized by becoming.

  According to the present invention, since the pair of the excitation unit and the magnetic coupling unit that generates the electromagnetic force is selected by the control circuit when performing the operation check, the operation check can be easily performed.

  According to the first aspect of the present invention, there is an effect that it is possible to easily confirm the operation in each of a plurality of directions in which acceleration can be detected.

(Embodiment 1)
Hereinafter, the acceleration sensor of the present embodiment will be described with reference to FIGS.

  The acceleration sensor of this embodiment includes a sensor substrate (acceleration sensor main body) 1 on which gauge resistors Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4 made of piezoresistors are formed, and one surface side of the sensor substrate 1 (FIG. 1 ( a first cover substrate 2 bonded to the upper surface side of b) and a second cover substrate 3 bonded to the other surface side of the sensor substrate 1 (lower surface side of FIG. 1B). . Here, the outer peripheral shape of the sensor substrate 1 and each cover substrate 2, 3 is rectangular, and each cover substrate 2, 3 is formed to have the same outer dimensions as the sensor substrate 1.

  The sensor substrate 1 described above processes an SOI wafer having an n-type silicon layer (active layer) 10c on an insulating layer (buried oxide film) 10b made of a silicon oxide film on a support substrate 10a made of a silicon substrate. The first cover substrate 2 is formed by processing the first silicon wafer, and the second cover substrate 3 is formed by processing the second silicon wafer. Here, in the present embodiment, the thickness of the support substrate 10a in the SOI wafer is about 300 μm to 500 μm, the thickness of the insulating layer 10b is about 0.3 μm to 1.5 μm, and the thickness of the silicon layer 10c is about 4 μm to 10 μm. In addition, although the thickness of the first silicon wafer is about 200 μm to 300 μm and the thickness of the second silicon wafer is about 100 to 300 μm, these numerical values are not particularly limited. The surface of the silicon layer 10c, which is the main surface of the SOI wafer, is a (100) plane. In the present embodiment, the above-described SOI wafer constitutes the semiconductor substrate serving as the basis of the sensor substrate 1, the first silicon wafer constitutes the semiconductor substrate serving as the basis of the first cover substrate 2, and the second The silicon wafer constitutes a semiconductor substrate that is the basis of the second cover substrate 3.

  As shown in FIG. 3, the sensor substrate 1 includes a frame portion 11 (a rectangular frame shape in the present embodiment), and a weight portion 12 arranged inside the frame portion 11 is on one surface side (FIG. 1). In (b) and the upper surface side of FIG. 3B), the frame portion 11 is supported so as to be swingable via four flexible strip-like bent portions 13 having flexibility. In other words, the sensor substrate 1 is swingably supported by the frame portion 11 via the four flexure portions 13 in which the weight portion 12 disposed inside the frame-shaped frame portion 11 extends from the weight portion 12 in four directions. Has been. Here, the frame portion 11 is formed using the above-described SOI wafer support substrate 10a, insulating layer 10b, and silicon layer 10c. On the other hand, the bending part 13 is formed using the silicon layer 10c in the above-described SOI wafer, and is sufficiently thinner than the frame part 11.

  The weight part 12 is continuously integrated with each of the rectangular parallelepiped core part 12a supported by the frame part 11 via the four flexure parts 13 and the four corners of the core part 12a when viewed from the one surface side of the sensor substrate 1. And four accompanying portions 12b having a rectangular parallelepiped shape connected to each other. In other words, the weight portion 12 is formed integrally with the core portion 12a and the core portion 12a in which the other end portion of each bending portion 13 whose one end portion is connected to the inner side surface of the frame portion 11 is connected to the outer surface. It has four accompanying parts 12b arranged in the space between the part 12a and the frame part 11. In other words, each associated portion 12b is surrounded by the frame portion 11 and the core portion 12a and the two bent portions 13 and 13 extending in a direction orthogonal to each other in a plan view as viewed from the one surface side of the sensor substrate 1. The slits 14 are formed between each of the accompanying portions 12 b and the frame portion 11, and the interval between the adjacent accompanying portions 12 b across the bending portion 13 is larger than the width dimension of the bending portion 13. It is getting longer. Here, the core portion 12a is formed using the above-described SOI wafer support substrate 10a, the insulating layer 10b, and the silicon layer 10c, and each accompanying portion 12b is formed using the SOI wafer support substrate 10a. It is. Thus, the surface of each associated portion 12b on the one surface side of the sensor substrate 1 is from the plane including the surface of the core portion 12a to the other surface side of the sensor substrate 1 (FIGS. 1B and 3B). (Lower surface side). Note that the above-described frame portion 11, weight portion 12, and each bending portion 13 of the sensor substrate 1 may be formed using a lithography technique and an etching technique.

  By the way, as shown in the lower right of each of FIGS. 3A and 3B, one direction along one side of the frame portion 11 in the plane parallel to the one surface of the sensor substrate 1 is the positive direction of the x axis. If one direction along the side orthogonal to the one side is defined as the positive direction of the y-axis and one direction of the thickness direction of the sensor substrate 1 is defined as the positive direction of the z-axis, the weight portion 12 is extended in the x-axis direction. The pair of flexible portions 13 and 13 sandwiching the core portion 12a and the pair of flexible portions 13 and 13 extending in the y-axis direction and sandwiching the core portion 12a are supported by the frame portion 11. Will be. In the orthogonal coordinates defined by the three axes of the above-described x axis, y axis, and z axis, the center position of the weight portion 12 on the surface of the portion of the sensor substrate 1 formed by the silicon layer 10c is the origin.

  The bending portion 13 (the bending portion 13 on the right side of FIG. 3A) extending from the core portion 12a of the weight portion 12 in the positive direction of the x axis is a pair of gauge resistances Rx2 and Rx4 in the vicinity of the core portion 12a. And one gauge resistor Rz2 is formed in the vicinity of the frame portion 11. On the other hand, the bending portion 13 (the bending portion 13 on the left side of FIG. 3A) extended from the core portion 12a of the weight portion 12 in the negative direction of the x-axis is a pair of gauge resistances Rx1 in the vicinity of the core portion 12a. , Rx3, and one gauge resistor Rz3 is formed in the vicinity of the frame portion 11. Here, the four gauge resistors Rx1, Rx2, Rx3, and Rx4 formed in the vicinity of the core portion 12a are formed to detect acceleration in the x-axis direction, and the planar shape is an elongated rectangular shape. 4 is formed so that the longitudinal direction thereof coincides with the longitudinal direction of the bending portion 13 and wiring (not shown) (diffuse layer wiring formed on the sensor substrate 1, metal) so as to constitute the left bridge circuit Bx in FIG. Connected by wiring). The gauge resistances Rx1 to Rx4 are formed in a stress concentration region where stress is concentrated in the bending portion 13 when acceleration in the x-axis direction is applied.

  Further, the bending portion 13 (the upper bending portion 13 in FIG. 3A) extended from the core portion 12a of the weight portion 12 in the positive direction of the y-axis is a pair of gauge resistors Ry1, in the vicinity of the core portion 12a. Ry3 is formed, and one gauge resistor Rz1 is formed in the vicinity of the frame portion 11. On the other hand, the bending portion 13 (the lower bending portion 13 in FIG. 3A) extended from the core portion 12a of the weight portion 12 in the negative direction of the y-axis is a pair of gauge resistances Ry2 in the vicinity of the core portion 12a. , Ry4 are formed, and one gauge resistor Rz4 is formed at the end on the frame part 11 side. Here, the four gauge resistors Ry1, Ry2, Ry3, and Ry4 formed in the vicinity of the core portion 12a are formed to detect acceleration in the y-axis direction, and the planar shape is an elongated rectangular shape. 4 is formed so that the longitudinal direction thereof coincides with the longitudinal direction of the bending portion 13 and wiring (not shown) (diffuse layer wiring formed on the sensor substrate 1, metal) so as to constitute the central bridge circuit By in FIG. Connected by wiring). Note that the gauge resistors Ry1 to Ry4 are formed in a stress concentration region where stress is concentrated in the flexure 13 when acceleration in the y-axis direction is applied.

  Further, the four gauge resistors Rz1, Rz2, Rz3, Rz4 formed in the vicinity of the frame portion 11 are formed to detect acceleration in the z-axis direction, and constitute the right bridge circuit Bz in FIG. Thus, they are connected by a wiring (not shown) (a diffusion layer wiring, a metal wiring, etc. formed on the sensor substrate 1). However, the gauge resistances Rz1 and Rz4 formed in one set of the bending portions 13 and 13 of the pair of bending portions 13 and 13 are formed so that the longitudinal direction thereof coincides with the longitudinal direction of the bending portions 13 and 13. On the other hand, the gauge resistances Rz2 and Rz3 formed on the other set of flexures 13 and 13 are formed such that the longitudinal direction coincides with the width direction (short direction) of the flexures 13 and 13. Yes.

  In the sensor substrate 1, a magnetic coupling portion 15 made of a magnetic film is formed on each surface side of each associated portion 12 b of the weight portion 12 on the one surface side of the sensor substrate 1. In short, on the sensor substrate 1, four magnetic coupling portions 15 are formed in a movable portion constituted by the weight portion 12 and each bending portion 13. As a material of the magnetic film constituting the magnetic coupling portion 15, for example, a soft magnetic material such as electromagnetic soft iron (pure iron), electromagnetic stainless steel (Fe—Cr alloy), permalloy (Ni—Fe alloy) may be employed. . Each magnetic coupling unit 15 will be described later.

  Here, an example of a basic operation of the sensor substrate 1 will be described.

  Now, assuming that acceleration is applied to the sensor substrate 1 in the positive x-axis direction while no acceleration is applied to the sensor substrate 1, the frame portion 11 is caused by the inertial force of the weight 12 acting in the negative x-axis direction. Accordingly, the weight 12 is displaced, and as a result, the bending portions 13 and 13 whose longitudinal direction is the x-axis direction are bent, and the resistance values of the gauge resistors Rx1 to Rx4 formed in the bending portions 13 and 13 change. Will do. In this case, the gauge resistances Rx1 and Rx3 are subjected to tensile stress, and the gauge resistances Rx2 and Rx4 are subjected to compressive stress. In general, gauge resistance has a characteristic that resistance value (resistivity) increases when subjected to tensile stress, and resistance value (resistivity) decreases when subjected to compressive stress. As the value increases, the resistance values of the gauge resistors Rx2 and Rx4 decrease. Therefore, if a constant DC voltage is applied from the external power source between the pair of input terminals VDD and GND shown in FIG. 4, the potential difference between the output terminals X1 and X2 of the left bridge circuit Bx shown in FIG. It changes according to the magnitude of the acceleration in the x-axis direction. Similarly, when acceleration in the y-axis direction is applied, the potential difference between the output terminals Y1 and Y2 of the central bridge circuit By shown in FIG. 4 changes according to the magnitude of the acceleration in the y-axis direction, and the z-axis When the acceleration in the direction is applied, the potential difference between the output terminals Z1 and Z2 of the right bridge circuit Bz shown in FIG. 4 changes according to the magnitude of the acceleration in the z-axis direction. Thus, the above-described sensor substrate 1 detects the change in the output voltage of each of the bridge circuits Bx to Bz, so that the acceleration in the x-axis direction, the y-axis direction, and the z-axis direction that acted on the sensor substrate 1 is detected. Can be detected. In this embodiment, the weight part 12 and each bending part 13 comprise the movable part.

  By the way, the sensor substrate 1 includes two input terminals VDD and GND common to the above-described three bridge circuits Bx, By, and Bz, two output terminals X1 and X2 of the bridge circuit Bx, and two of the bridge circuit By. Output terminals Y1 and Y2 (see FIG. 4) and two output terminals Z1 and Z2 (see FIG. 4) of the bridge circuit Bz. These input terminals VDD and GND and output terminals X1. , X2, Y1, Y2, Z1, and Z2 are provided as the first connection bonding metal layer 19 on the one surface side (that is, the first cover substrate 2 side). It is electrically connected to the formed through-hole wiring 24 for energization. That is, eight first connection bonding metal layers 19 are formed on the sensor substrate 1, and the first cover substrate 2 is electrically connected to the first connection bonding metal layer 19. Hole wiring 24 is formed at eight locations. The eight first connecting metal layers 19 for connection have an outer peripheral shape of a rectangle (in this embodiment, a square shape), and are spaced apart from each other in the circumferential direction of the frame portion 11.

  In addition, a frame-shaped (rectangular frame-shaped) first sealing bonding metal layer 18 having a larger opening area than the frame portion 11 is formed on the frame portion 11 of the sensor substrate 1. The first connecting bonding metal layer 19 is disposed inward of the first sealing bonding metal layer 18 in the frame portion 11. In short, the sensor substrate 1 is set so that the width dimension of the first sealing bonding metal layer 18 is smaller than the width dimension of the frame portion 11, and the first sealing bonding metal layer 18 and each connecting bonding metal. The layer 19 is formed on the same plane.

  Here, in the sensor substrate 1, an insulating film 16 made of a laminated film of a silicon oxide film and a silicon nitride film is formed on the silicon layer 10c on the one surface side, and a first connecting bonding metal layer 19 is formed. The first sealing bonding metal layer 18 and the metal wiring are formed on the insulating film 16.

  In addition, the first sealing bonding metal layer 18 and the first connecting bonding metal layer 19 have an adhesion improving Ti film interposed between the bonding Au film and the insulating film 16. In other words, the first sealing bonding metal layer 18 and the first connecting bonding metal layer 19 are a laminated film of a Ti film formed on the insulating film 16 and an Au film formed on the Ti film. It is comprised by. In short, since the first connecting bonding metal layer 19 and the first sealing bonding metal layer 18 are formed of the same metal material, the first connecting bonding metal layer 19 and the first sealing metal layer 19 are formed. The bonding metal layer 18 can be formed at the same time, and the first bonding metal layer 19 for connection and the first bonding metal layer 18 for sealing can be formed to have substantially the same thickness. The first sealing bonding metal layer 18 and the first connecting bonding metal layer 19 have a Ti film thickness of 15 to 50 nm and an Au film thickness of 500 nm. The film thickness is set to 1 μm, but these numerical values are merely examples and are not particularly limited. Here, the material of each Au film is not limited to pure gold, and may be added with impurities. In this embodiment, a Ti film is interposed as an adhesion layer for improving adhesion between each Au film and the insulating film 16. However, the material of the adhesion layer is not limited to Ti, and, for example, Cr, Nb Zr, TiN, TaN, etc. may be used.

  Each of the gauge resistors Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4, and the diffusion layer wirings described above are formed by doping p-type impurities with appropriate concentrations at respective formation sites in the silicon layer 10c. The metal wiring is formed by patterning a metal film (for example, an Al film, an Al alloy film, etc.) formed on the insulating film 16 by sputtering or vapor deposition using a lithography technique and an etching technique. The metal wiring is electrically connected to the diffusion layer wiring through a contact hole provided in the insulating film 16. Each magnetic coupling portion 15 described above is formed by patterning a magnetic film formed on each associated portion 12b of the weight portion 12 by a sputtering method or a CVD method using a lithography technique and an etching technique. ing. In addition, the first connecting metal layer 19 for connection and the metal wiring are such that the connection portion of the first connecting metal metal layer 19 for connection with the metal wiring is opposed to the sensor substrate 1 in the first cover substrate 2. It is electrically connected so as to be positioned in a later-described displacement space forming recess 21 formed on the surface. Here, in the present embodiment, the displacement space forming recess 21 in the first cover substrate 2 is a recess in which the connection portion with the metal wiring in the first connection bonding metal layer of the sensor substrate 1 is disposed. Also serves as.

  As shown in FIG. 1, the first cover substrate 2 is composed of a weight portion 12 and each bending portion 13 of the sensor substrate 1 on the surface of the sensor substrate 1 side (the lower surface side in FIG. 1B). A plurality of (eight in the present embodiment) through-holes that penetrate the circumferential portion of the displacement space forming recess 21 in the thickness direction are formed while the above-described displacement space forming recess 21 that secures the displacement space of the movable portion is formed. 22 is formed, and an insulating film 23 made of a thermal insulating film (silicon oxide film) is formed across both surfaces in the thickness direction and the inner surface of the through hole 22, and the through hole wiring 24 and the inner surface of the through hole 22 are formed. A part of the insulating film 23 is interposed therebetween. Here, the displacement space forming recess 21 is formed by utilizing a micromachining technique such as a lithography technique and an etching technique. Further, the eight through-hole wirings 24 of the first cover substrate 2 are formed apart from each other in the circumferential direction of the first cover substrate 2. Moreover, although Cu is adopted as the material of the through-hole wiring 24, it is not limited to Cu, and for example, Ni may be adopted.

  In addition, a plurality of first cover substrates 2 electrically connected to the respective through-hole wirings 24 on the peripheral portion of the displacement space forming concave portion 21 on the surface on the sensor substrate 1 side (in this embodiment, 8 ) Second connecting bonding metal layers 29 are formed. The first cover substrate 2 has a frame-shaped (rectangular frame-shaped) second sealing bonding metal layer 28 formed around the entire periphery of the surface on the sensor substrate 1 side. The eight second bonding metal layers 29 for connection have a rectangular shape whose outer peripheral shape is an elongated shape, and are disposed on the inner side of the second bonding metal layer 28 for sealing. Here, one end of the second connection bonding metal layer 29 is bonded to the through-hole wiring 24, and the other end side is outside the metal wiring of the sensor substrate 1 and the sensor substrate 1. The first connecting bonding metal layer 19 is bonded and electrically connected. In short, the positions of the through hole wiring 24 and the first connection bonding metal layer 19 corresponding to the through hole wiring 24 in the circumferential direction of the cover substrate 2 are shifted, and the second connection bonding metal layer 29 is The longitudinal direction coincides with the circumferential direction of the second sealing bonding metal layer 28 and is disposed so as to straddle the through-hole wiring 24 and the first connecting bonding metal layer 19.

  The second sealing bonding metal layer 28 and the second connecting bonding metal layer 29 have a Ti film for improving adhesion between the bonding Au film and the insulating film 23. In other words, the second sealing bonding metal layer 28 and the second connecting bonding metal layer 29 are a laminated film of a Ti film formed on the insulating film 23 and an Au film formed on the Ti film. It is comprised by. In short, since the second connecting bonding metal layer 29 and the second sealing bonding metal layer 28 are formed of the same metal material, the second connecting bonding metal layer 29 and the second sealing metal layer 29 are formed. The joint metal layer 28 can be formed at the same time, and the second joint metal layer 29 for connection and the second joint metal layer 28 for sealing can be formed to have substantially the same thickness. The second sealing bonding metal layer 28 and the second connecting bonding metal layer 29 have a Ti film thickness of 15 to 50 nm and an Au film thickness of 500 nm. The numerical value is an example and is not particularly limited. Here, the material of each Au film is not limited to pure gold, and may be added with impurities. In the present embodiment, a Ti film is interposed as an adhesion improving adhesive layer between each Au film and the insulating film 23. However, the material of the adhesion layer is not limited to Ti, and, for example, Cr, Nb Zr, TiN, TaN, etc. may be used.

  A plurality of external connection electrodes 25 electrically connected to the respective through-hole wirings 24 are formed on the surface of the first cover substrate 2 opposite to the sensor substrate 1 side. The outer peripheral shape of each external connection electrode 25 is rectangular.

  In contrast, as shown in FIGS. 1B and 5, the second cover substrate 3 has a predetermined depth (for example, forming a displacement space of the weight portion 12 on the surface facing the sensor substrate 1). A recess 31 of about 5 μm to 10 μm is formed. Here, the recess 31 is formed using a micromachining technique such as a lithography technique and an etching technique. In the present embodiment, the concave portion 31 that forms the displacement space of the weight portion 12 is formed on the surface of the cover substrate 3 that faces the sensor substrate 1, but the core portion 12a and each associated portion 12b of the weight portion 12 are formed. The thickness of the portion formed using the support substrate 10a of the sensor substrate 1 is compared with the thickness of the portion formed using the support substrate 10a in the frame portion 11 in the thickness direction of the sensor substrate 1. If the weight 12 is made thinner by the allowable displacement amount, the weight portion in the direction intersecting the other surface is formed on the other surface side of the sensor substrate 1 without forming the recess 31 in the cover substrate 3. A gap that enables the displacement of 12 is formed between the weight portion 12 and the cover substrate 3.

  By the way, the acceleration sensor of the present embodiment includes a first cover substrate 2 bonded to the one surface side of the sensor substrate 1, a second cover substrate 3 bonded to the other surface side of the sensor substrate 1, The frame portion 11 of the sensor substrate 1 constitutes a package having a displacement space of the movable portion in the thickness direction of the sensor substrate 1, and the movable portion composed of the weight portion 12 and each bending portion 13 is forced by electromagnetic force. As a driving means for confirming the movement, the magnetic coupling part 15 provided on the movable part on the one surface side of the sensor substrate 1 and a spiral shape provided on the first cover substrate 2 and facing the magnetic coupling part 15 are provided. There are a plurality of pairs with the excitation unit 26 made of a coil, and an electromagnetic force for operation confirmation can be generated independently for each pair of the magnetic coupling unit 15 and the excitation unit 26. That is, a plurality (eight in this embodiment) of through-holes 22 penetrating in the thickness direction are formed in the central portion of the first cover substrate 2, and the insulating film 23 is formed inside each through-hole 22. A through-hole wiring 24 for energization to the excitation part 26 is formed in a partly interposed manner. Each excitation portion 26 is formed on the inner bottom surface of the displacement space forming recess 21 in the first cover substrate 2. Here, each excitation unit 26 uses a lithography technique and an etching technique for a metal film (for example, an Au film, a Cu film, an Al film, etc.) formed on the inner bottom surface side of the displacement space forming recess 21 in the first cover substrate 2. It is formed by patterning in a spiral shape using the above. In addition, each excitation part 26 may employ | adopt the same material as the 2nd junction metal layer 29 for a connection, and the 2nd junction metal layer 28 for sealing, and you may make it form simultaneously.

  In addition, the sensor substrate 1 and the first cover substrate 2 in the acceleration sensor described above are bonded to the first sealing bonding metal layer 18 and the second sealing bonding metal layer 28 (first The cover substrate 2 is sealed around the entire periphery of the frame portion 11 of the sensor substrate 1), and the first connection bonding metal layer 19 and the second connection bonding metal layer 29 are bonded together. The sensor substrate 1 and the second cover substrate 3 are joined to each other at the peripheral portions of the opposing surfaces (the second cover substrate 3 is the entire frame portion 11 of the sensor substrate 1). The circumference is sealed over the circumference). The acceleration sensor of the present embodiment includes a sensor wafer in which a plurality of sensor substrates 1 are formed on the above-described SOI wafer, a first package wafer in which a plurality of first cover substrates 2 are formed on the above-described first silicon wafer, A wafer level package structure is formed by bonding at a wafer level a second package wafer in which a plurality of second cover substrates 3 are formed on the second silicon wafer described above, and then dicing to the size of the sensor substrate 1 It is divided according to the process. Therefore, the first cover substrate 2 and the second cover substrate 3 have the same outer size as the sensor substrate 1, and a small chip size package can be realized, and the manufacturing is facilitated.

  Here, in the present embodiment, as a bonding method of the sensor wafer, the first package wafer, and the second package wafer, a room temperature bonding method that enables direct bonding at a lower temperature to reduce the residual stress of the sensor substrate 1 is used. Adopted. In the room temperature bonding method, each bonding surface is irradiated with argon plasma or ion beam or atomic beam in vacuum before bonding to clean and activate each bonding surface, and then the bonding surfaces are brought into contact with each other. Join directly at room temperature. In the present embodiment, the first sealing bonding metal layer 18 and the second sealing bonding metal layer 28 are directly bonded by applying an appropriate load at room temperature by the above-described normal temperature bonding method. At the same time, the first connection bonding metal layer 19 and the second connection bonding metal layer 29 are directly bonded, and the frame portion 11 of the sensor substrate 1 is bonded to the sensor substrate 1 at room temperature by the above-described room temperature bonding method. The peripheral portion of the second cover substrate 3 is directly joined.

  Thus, in the wafer level package 100 according to the present embodiment, the sealing bonding metal layers 18 and 28 and the connecting bonding metal layers 19 and 29 of the sensor wafer and the first package wafer are directly bonded to each other. The two package wafers are directly bonded by a low-temperature process such as a room temperature bonding method, and the sensor wafer, the first package wafer, and the second package wafer are bonded by a method that requires heat treatment such as solder reflow. Compared to the case, there is an advantage that the gauge resistances Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4 are not easily affected by thermal stress, and the process temperature can be lowered and the manufacturing process can be simplified. There is an advantage. Further, since the sensor wafer is formed using an SOI wafer, and the first package wafer and the second package wafer are formed using a silicon wafer, the linear expansion of the sensor substrate 1 and the cover substrates 2 and 3 is performed. It is possible to reduce the stress generated in each bent portion 13 due to the difference in rate, and to reduce the influence of the stress due to the difference in linear expansion rate on the output signals of the bridge circuits Bx, By, Bz. It becomes possible to reduce the dependency. In the present embodiment, the sensor substrate 1 is formed by processing an SOI wafer. However, the sensor substrate 1 is not limited to the SOI wafer, and may be formed by processing a silicon wafer, for example.

  In the acceleration sensor of the present embodiment described above, a plurality of gauge resistances Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4 are provided on the movable part, and the movable part in the sensor substrate 1 capable of detecting accelerations in a plurality of directions is used as an electromagnetic force. The driving means for confirming the operation that is forcibly moved by the motor is provided on the one surface side of the sensor substrate 1 with the excitation part 26 formed of a coil provided on one of the opposing surfaces of the movable part and the package, and on the other side. Since there are a plurality of pairs of magnetic coupling portions 15 that can be magnetically coupled to the portion 26 and each pair of the excitation portion 26 and the magnetic coupling portion 15 can independently generate an electromagnetic force for operation confirmation. The deformation state of the movable portion is changed by appropriately selecting a pair of the excitation unit 26 and the magnetic coupling unit 15 that generate the electromagnetic force for use (the movable portion when the acceleration is applied only in the x-axis direction). Shape state, deformation state of the movable part when acceleration is applied only in the y-axis direction, and deformation state of the movable part when acceleration is applied only in the z-axis direction). , Bz output is confirmed through the corresponding pair of external connection electrodes 25, 25, so that appropriate sensor characteristics can be obtained in each of a plurality of directions in which acceleration can be detected even in a state before shipment after incorporation into the target device. It is possible to easily check the operation of whether or not

  Here, in order to simplify the description, for the four magnetic coupling portions 15, the upper left magnetic coupling portion 15 in FIG. 1A is denoted by 15 a, the upper right magnetic coupling portion 15 is denoted by 15 b, and the lower left The code of the magnetic coupling unit 15 is 15c, the code of the lower right magnetic coupling unit 15 is 15d, and the code of the excitation unit 26 facing each of the magnetic coupling units 15a, 15b, 15c, 15d is 26a, 26b, 26c, 26d. Will be described.

  In the acceleration sensor of the present embodiment, for example, a driving voltage is applied to the exciting unit 26b and the exciting unit 26d at the same time to cause an exciting current to flow, or a driving voltage is applied to the exciting unit 26a and the exciting unit 26c simultaneously. When an exciting current is passed, the output voltage of the bridge circuit Bx changes. In addition, when a driving voltage is applied to the exciting unit 26d and the exciting unit 26c at the same time to cause an exciting current to flow, the output voltage of the bridge circuit By changes. Moreover, if a drive voltage is simultaneously applied to all the excitation parts 26a-26d and excitation current is sent, the output voltage of the bridge circuit Bz will change. Therefore, it is possible to confirm the operations in the x-axis direction, the y-axis direction, and the z-axis direction. Further, the displacement amount of the accompanying portion 12b can be controlled by appropriately changing the voltage value of the driving voltage applied to the above-described exciting portions 26a to 26d. However, the displacement amount of the accompanying portion 12b is determined when acceleration is applied. Therefore, by changing the voltage value, the relationship between the displacement amount (that is, acceleration) of the associated portion 12b and the output voltage can be inspected, and whether the sensor characteristics are appropriate. It can be confirmed in more detail whether or not. In addition, since the magnetic coupling unit 15 is formed of a magnetic film, an attractive force or a repulsive force can be generated between the excitation unit 26 and the magnetic coupling unit 15 according to the direction of the current flowing to the excitation unit 26. Therefore, it is possible to check the operation with higher accuracy. Here, each of the sensor substrate 1 and the first cover substrate 2 is formed using a micromachining technique, and the distance between the magnetic coupling unit 15 and the excitation unit 26 can be accurately controlled and shortened. It is possible to reduce variation in the displacement amount of the weight portion 12 when the movable portion is forcibly moved by the driving means. Further, as described above, the sensor substrate 1 and the first cover substrate 2 are bonded by the room temperature bonding method, and the residual stress of the sensor substrate 1 can be reduced, so that the gap between the magnetic coupling portion 15 and the excitation portion 26 is reduced. The distance can be highly accurate, and variation in the amount of displacement of the weight portion 12 when the movable portion is forcibly moved by the driving means can be reduced.

(Embodiment 2)
Hereinafter, the acceleration sensor of the present embodiment will be described with reference to FIGS. 6 and 7.

  The basic configuration of the acceleration sensor of the present embodiment is substantially the same as that of the first embodiment, and an integrated circuit 4 that cooperates with the gauge resistors Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4 is formed on the sensor substrate 1. These are different from the first embodiment. Here, the integrated circuit 4 is an integrated circuit (CMOS IC) using CMOS, and the output signals of the bridge circuits Bx, By, Bz described in the first embodiment are amplified, offset adjusted, temperature compensated, etc. A signal processing circuit that performs signal processing and outputs it, an EEPROM that stores data used in the signal processing circuit, and the like are integrated. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted.

  The sensor substrate 1 in the present embodiment is formed with a part of the frame portion 11 described in the first embodiment, the weight portion 12, each bending portion 13, the gauge resistances Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4, and the like. The sensor region E1, the IC region E2 in which the integrated circuit 4 is formed, the first sealing bonding metal layer 18 described in the first embodiment, the first connecting bonding metal layer 19, and the like. Each of the region portions E1 to E3 so that the IC region portion E2 surrounds the sensor region portion E1 located at the center portion in plan view and the junction region portion E3 surrounds the IC region portion E2. The layout is designed. Here, in the present embodiment, the outer dimension of the frame portion 11 of the sensor substrate 1 in the first embodiment is increased (in other words, the width dimension of the frame portion 11 is increased), and the integrated circuit is included in the frame portion 11. 4 is formed. The sensor substrate 1 is formed using an SOI wafer in the same manner as in the first embodiment. In the IC region portion E2, the occupied area of the IC region portion E2 in the sensor substrate 1 is reduced using a multilayer wiring technique. We are trying to make it.

  In the present embodiment, similarly to the first embodiment, the first cover substrate 2 formed using the first silicon wafer and the second cover substrate 3 formed using the second silicon wafer are provided. The first cover substrate 2 in the present embodiment is formed in the same outer dimensions as the sensor substrate 1, and the sensor region portion E <b> 1 is within the projection region of the opening surface of the displacement space forming recess 21 described in the first embodiment. In addition, the opening area of the displacement space forming recess 21 is made larger than that of the first embodiment so that the IC region E2 can be accommodated, and the multilayer structure portion of the IC region E2 is arranged in the displacement space forming recess 21. It is like that.

  In the acceleration sensor of the present embodiment described above, an IC chip in which an integrated circuit that cooperates with the acceleration sensor of the first embodiment and the gauge resistors Rx1 to Rx4, Ry1 to Ry4, and Rz1 to Rz4 of the acceleration sensor of the first embodiment is formed. Can be reduced in size and cost compared to a sensor module housed in one package, and the wiring length between the gauge resistors Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4 and the integrated circuit 4 is shortened. Therefore, the sensor performance can be improved.

  By the way, a control circuit that selects a pair of the excitation unit 26 and the magnetic coupling unit 15 that generates electromagnetic force and applies an appropriate drive voltage to the excitation unit 26 may be integrated in the integrated circuit 4. By integrating the control circuit, when the operation is confirmed, a pair of the excitation unit 26 and the magnetic coupling unit 15 that generate electromagnetic force is selected by the control circuit, and a driving voltage is appropriately applied. It is possible to easily check the operation. Here, the output voltage of the bridge circuits Bx, By, Bz when the drive circuit is applied to the excitation unit 26 by selecting the pair of the excitation unit 26 and the magnetic coupling unit 15 by the control circuit is signaled by the signal processing circuit. It is possible to make a self-diagnosis as to whether or not the output value obtained by the processing is operating normally depending on whether or not the output value is within the range of the appropriate value stored in advance in the EEPROM.

(Embodiment 3)
The basic configuration of the acceleration sensor of this embodiment is substantially the same as that of the first embodiment. As shown in FIG. 8, each magnetic coupling portion 15 in the first cover substrate 2 is a spiral coil like each excitation portion 26. Each of the magnetic coupling portions 15 is different in that an insulating protective film 12c made of a silicon oxide film covering the magnetic coupling portion 15 is formed on the surface side of each associated portion 12b of the weight portion 12. Are electrically connected to a wiring (not shown) made of a metal material on the insulating protective film 12c through a contact hole (not shown) formed in the insulating protective film 12c. Here, the wiring connected to each magnetic coupling portion 15 is formed across the insulating protective film 12c on the surface of the associated portion 12b and the insulating film 16, and each of the wirings is formed on the insulating film 16. Eight first connecting bonding metal layers 19 to be connected are added. Here, although not shown, on the surface side of the first cover substrate 2 opposite to the sensor substrate 1 side, the wiring and the through-hole wiring 24 connected to both ends of each magnetic coupling portion 15 are provided. Eight external connection electrodes 25 that are electrically connected to each other are formed. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  Therefore, in the acceleration sensor of the present embodiment, the same material can be used for the excitation unit 26 and the magnetic coupling unit 15, and therefore when the magnetic coupling unit 15 is formed of a magnetic film as in the first embodiment. Compared with this, the cost can be reduced. In the present embodiment, the insulating protective film 12c constitutes a stopper that prevents contact between the excitation portion 26 and the magnetic coupling portion 15, and when the weight portion 12 is forcibly moved by electromagnetic force, the excitation portion It is possible to prevent the occurrence of a sticking phenomenon in which the magnetic layer 26 and the magnetic coupling portion 15 are attached. Note that, in the acceleration sensor of the second embodiment, the technical idea of the present embodiment may be applied, and each magnetic coupling unit 15 may be configured by a spiral coil as shown in FIG.

(Embodiment 4)
The basic configuration of the acceleration sensor of the present embodiment is substantially the same as that of the first embodiment. As shown in FIG. 10, the excitation unit 26 and the magnetic coupling are formed on the inner bottom surface of the displacement space forming recess 21 in the first cover substrate 2. The difference is that a stopper 5 that prevents contact with the portion 15 is provided. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  Therefore, in the acceleration sensor of the present embodiment, it is possible to prevent the occurrence of sticking phenomenon in which the excitation unit 26 and the magnetic coupling unit 15 adhere when the weight unit 12 is forcibly moved by electromagnetic force.

  In the present embodiment, the stopper 5 for preventing contact between the excitation portion 26 and the magnetic coupling portion 15 is provided in the package. However, the stopper 5 is not limited to the package and may be provided on the sensor substrate 1. If it is provided on at least one of the substrates 1, it is possible to prevent the occurrence of a sticking phenomenon in which the excitation portion 26 and the magnetic coupling portion 15 adhere when the weight portion 12 is forcibly moved by electromagnetic force. Further, the technical idea of the present embodiment may be applied to the acceleration sensors of the second to fourth embodiments.

  By the way, in each said embodiment, although each accompanying part 12b in the weight part 12 of the sensor board | substrate 1 is formed thinner than the core part 12a, the thickness of each accompanying part 12b and the core part 12a is arrange | equalized, and the sensor board 1 is provided. The surface of each associated portion 12b and the surface of the core portion 12a on the one surface side may be flush with each other. In each of the above embodiments, the magnetic coupling portion 15 is provided in the weight portion 12, but the magnetic coupling portion 15 is not limited to the weight portion 12 and may be provided in the bending portion 13. Further, the excitation unit 26 may be provided in the weight 12 and the magnetic coupling unit 15 may be provided in the package.

The acceleration sensor of Embodiment 1 is shown, (a) is a schematic plan view, (b) is A-A 'schematic sectional drawing of (a). The same as the above, (a) is a fragmentary sectional view, and (b) is another fragmentary sectional view. The sensor board | substrate in the same as the above is shown, (a) is a schematic plan view, (b) is A-A 'schematic schematic sectional drawing of (a). It is a circuit diagram of the sensor board | substrate in the same as the above. The 2nd cover board | substrate in the same as the above is shown, (a) is a schematic plan view, (b) is a schematic sectional drawing. The acceleration sensor of Embodiment 2 is shown, (a) is a schematic plan view, (b) is a schematic sectional drawing. The sensor board | substrate in the same as the above is shown, (a) is a schematic plan view, (b) is a schematic sectional view. FIG. 10 is a schematic plan view showing a sensor substrate in the acceleration sensor according to the third embodiment. It is a schematic plan view which shows the sensor board | substrate in the other structural example same as the above. It is a schematic sectional drawing which shows the acceleration sensor of Embodiment 4.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor substrate 2 1st cover substrate 3 2nd cover substrate 4 Integrated circuit 5 Stopper 11 Frame part 12 Weight part 12a Core part 12b Associated part 12c Insulation protective film (stopper)
DESCRIPTION OF SYMBOLS 13 Bending part 15 Magnetic coupling part 24 Through-hole wiring 25 External connection electrode 26 Excitation part Rx1-Rx4 Gauge resistance Ry1-Ry4 Gauge resistance Rz1-Rz4 Gauge resistance

Claims (7)

  A sensor substrate that is formed using a semiconductor substrate and that is provided with a plurality of gauge resistors that detect stress generated in the movable part due to the action of acceleration, and that can detect acceleration in a plurality of directions, respectively. An acceleration sensor comprising a package having a displacement space of a part, comprising an operation confirmation driving means for forcibly moving the movable part by electromagnetic force, and the driving means is movable on one surface side of the sensor substrate. There are a plurality of pairs of an excitation part made of a coil provided on one of the opposing surfaces of the package and a magnetic coupling part provided on the other and magnetically coupled to the excitation part. An acceleration sensor characterized in that an electromagnetic force for operation confirmation can be generated for each pair.   The sensor substrate has a frame portion surrounding a weight portion, and is supported by the frame portion so as to be swingable through four bending portions arranged in a cross shape. Each of the bending portions, and the gauge resistor is arranged so as to be able to detect accelerations in three directions orthogonal to each other, and the weight portion is a core portion to which one end portion of each bending portion is connected, and Each of the accompanying parts, which is formed integrally with the core part and arranged in a space between each of the pair of bending parts adjacent to each other in the circumferential direction of the core part, the frame part, and the frame part in a plan view. 2. The acceleration sensor according to claim 1, wherein either one of the excitation part and the magnetic coupling part is provided.   The package includes a first cover substrate bonded to the one surface side of the sensor substrate, a second cover substrate bonded to the other surface side of the sensor substrate, and the frame portion of the sensor substrate. The first cover substrate is formed using a semiconductor substrate, and a through-hole wiring for energizing the driving means is formed on the first cover substrate. The acceleration sensor described.   4. The stopper according to claim 1, wherein at least one of the sensor substrate and the package is provided with a stopper that prevents contact between the excitation unit and the magnetic coupling unit. 5. The acceleration sensor described.   The acceleration sensor according to claim 1, wherein the magnetic coupling portion is made of a magnetic film.   The acceleration sensor according to any one of claims 1 to 4, wherein the magnetic coupling portion includes a coil. 7. The sensor board according to claim 1, wherein a control circuit for selecting a pair of the excitation unit and the magnetic coupling unit that generates the electromagnetic force is integrated. The acceleration sensor described in 1.

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