JP4665733B2 - Sensor element - Google Patents

Description

  The present invention relates to a sensor element such as an acceleration sensor element or a gyro sensor element.

  In recent years, as a sensor element having a chip size package (CSP), a sensor element formed by using a wafer level packaging technique has been researched and developed in various places (for example, see Patent Document 1).

  Here, in Patent Document 1, as shown in FIG. 11A, a plurality of MEMS (Micro Electro Mechanical System) elements 211 and a sensing unit (not shown) of the MEMS elements 211 are electrically connected. A recess 221 for forming a space for hermetically sealing the first semiconductor wafer 210 on which the metal wiring (lead electrode) 217 is formed, the through-hole wiring 224 and the MEMS element 211 that are electrically connected to the metal wiring 217. The wafer level package is obtained by attaching the first semiconductor wafer 210 and the second semiconductor wafer 220 to each other at the wafer level as shown in FIG. A technique for forming the structure 200 and dividing the wafer level package structure 200 into individual sensor elements is disclosed. In the sensor element manufactured in this way, a portion cut out from the first semiconductor wafer 210 constitutes a sensor substrate, and a portion cut out from the second semiconductor wafer 220 constitutes a through-hole wiring formation substrate. is doing.

  Here, on the surface of the first semiconductor wafer 210 facing the second semiconductor wafer 220, the MEMS element 211 and the metal wiring electrically connected to the MEMS element 211 are provided for each region corresponding to each sensor element. The first sealing bonding metal layer (sealing base metal film) 218 surrounding 217 is formed, and the surface of the second semiconductor wafer 220 facing the first semiconductor wafer 210 corresponds to each sensor element. For each region to be formed, a second sealing bonding metal layer (sealing base metal film) 228 surrounding the recess 221 and facing the first sealing bonding metal layer 218 is formed.

  Further, the first semiconductor wafer 210 is provided with a first connection bonding metal layer 219 electrically connected to the metal wiring 217 inside the first sealing bonding metal layer 218, In the semiconductor wafer 220, a second connection bonding metal layer 229 that is electrically connected to the through-hole wiring 224 is formed inside the second sealing bonding metal layer 228.

  In the wafer level package structure 200 described above, the first sealing bonding metal layer 218 of the first semiconductor wafer 210 and the second sealing bonding metal layer 228 of the second semiconductor wafer 220 are, for example, The first connecting joint metal layer 219 and the second connecting joining metal layer 229 are joined via the second solder part 239 while being joined via the first solder part 238 made of solder such as AuSn. It is joined.

  By the way, an acceleration sensor, a gyro sensor, and the like are widely known as MEMS, and as an acceleration sensor, a piezoelectric element that detects acceleration by a change in resistance value due to a strain of a gauge resistance composed of a piezoresistor when acceleration is applied. A resistance-type acceleration sensor, a capacitance-type acceleration sensor that detects acceleration based on a change in capacitance between a fixed electrode and a movable electrode when acceleration is applied, and the like are known.

  As a piezoresistive acceleration sensor, a cantilever type is supported in such a manner that a weight portion arranged inside a rectangular frame-like frame portion is swingably supported by the frame portion via a bending portion extended in one direction. Also proposed is a dual-support type that is swingably supported by the frame portion through a pair of flexure portions that are extended in two opposite directions with weight portions arranged inside the frame-shaped frame portion. In recent years, a weight portion arranged inside a frame-like frame portion is supported by the frame portion through four flexible portions extended in four directions so as to be swingable, and accelerations in three directions orthogonal to each other. Have been proposed (see, for example, Patent Documents 2 and 3).

In the piezoresistive acceleration sensor described above, the weight portion and the bending portion constitute a movable portion, and the piezoresistor constitutes a sensing portion. Further, in a capacitive acceleration sensor (for example, see Patent Document 4) and a gyro sensor (for example, see Patent Document 5), a weight part provided with a movable electrode or a weight part that also serves as a movable electrode constitutes the movable part. The sensing unit is configured by the fixed electrode and the movable electrode.
JP 2005-251898 A JP 2004-109114 A JP 2004-233072 A JP 2004-028912 A JP 2005-292117 A

  In the sensor element formed using the wafer level packaging technique described in Patent Document 1, the first connecting bonding metal layer 219 that is electrically connected to the metal wiring 217 has a thickness of the metal wiring 217. Since the first connection bonding metal layer 219 and the metal wiring 217 can be made relatively large in area, the contact area between the first connection bonding metal layer 219 and the metal wiring 217 can be made relatively large. The contact resistance between the connecting bonding metal layer 219 and the metal wiring 217 can be reduced.

  However, in the above-described sensor element, the second connecting bonding metal layer 229 and the second sealing bonding metal layer 228 formed on the second semiconductor wafer 220 side are approximately the same height on the same plane. On the other hand, on the first semiconductor wafer 210 side, the first connection bonding metal layer 219 and the first sealing layer with respect to the plane including the formation surface of the first connection bonding metal layer 219 are formed. The height of the bonding metal layer 228 is different, the distance between the second connection bonding metal layer 229 and the first connection bonding metal layer 219, the second sealing bonding metal layer 228, In order to absorb the difference in distance from the distance between the first sealing bonding metal layer 218 and bond the connecting bonding metal layers 229 and 219 to each other and the sealing bonding metal layers 228 and 218 to each other. At this time, the second joining metal layer 229 for connection is used. Then, a predetermined amount of solder is supplied to the joint location in each of the second sealing bonding metal layer 228 by the solder chute method, and then the first semiconductor wafer 210 and the second semiconductor wafer 220 are overlapped to perform reflow. Therefore, the manufacturing process is complicated, and it is difficult to increase the distance between the sensor substrate and the through hole wiring formation substrate. In the technique described in Patent Document 1, when AuSn is used as the solder, the process temperature in the reflow process becomes 280 ° C. or higher, and the residual stress in the vicinity of the joint interface increases, resulting in the residual stress. As a result, the sensor characteristics fluctuated.

  This invention is made | formed in view of the said reason, The objective is to provide the sensor element which can perform joining between a sensor board | substrate and a through-hole wiring formation board | substrate easily.

  According to the first aspect of the present invention, a sensor substrate formed using a first semiconductor substrate and having a metal wiring electrically connected to the sensing portion, and a metal wiring formed using the second semiconductor substrate. A through-hole wiring forming substrate having a through-hole wiring electrically connected and sealed to one surface side of the sensor substrate, the sensor substrate having a first circumference over the entire circumference of the peripheral portion on the one surface. The first bonding metal layer made of a metal material electrically connected to the metal wiring is formed inside the first sealing bonding metal layer. The through-hole wiring forming substrate has a second sealing bonding metal layer formed over the entire circumference of the peripheral portion of the surface on the sensor substrate side, and is further on the inner side than the second sealing bonding metal layer. Second made of a metal material electrically connected to the through-hole wiring A connection bonding metal layer is formed, and the sensor substrate and the through-hole wiring formation substrate are connected to the first sealing bonding metal layer and the second sealing bonding metal layer and to the first connection. The bonding metal layer for bonding and the second bonding metal layer for connection are bonded, and the sensor substrate has a connection portion with the metal wiring in the first connection bonding metal layer facing the sensor substrate in the through-hole wiring forming substrate. It is located in the recess formed in the surface.

  According to this invention, since the connection part with the metal wiring in the 1st joining metal layer for a connection of a sensor board | substrate is located in the recess formed in the opposing surface with the sensor board | substrate in a through-hole wiring formation board | substrate. The bonding portion to be bonded to the second connecting bonding metal layer in the first connecting bonding metal layer of the sensor substrate is formed on the same plane as the first sealing bonding metal layer of the sensor substrate. Thus, the sensor substrate and the through hole wiring forming substrate can be easily joined.

  According to a second aspect of the present invention, in the first aspect of the invention, each of the connecting bonding metal layers and each of the sealing bonding metal layers is formed of the same metal material.

  According to the present invention, the first sealing bonding metal layer and the second sealing bonding metal layer are simultaneously bonded to the first connecting bonding metal layer and the second connecting bonding metal layer. Can be directly bonded by, for example, a room temperature bonding method, and the conventional process of supplying solder and reflow for each bonding point can be eliminated, which simplifies the manufacturing process and penetrates the sensor substrate. It is possible to increase the accuracy of the distance to the hole wiring formation substrate, and to suppress fluctuations in sensor characteristics due to residual stress.

  According to a third aspect of the present invention, there is provided a cover substrate formed using the third semiconductor substrate according to the first or second aspect of the present invention, and sealed on the other surface side of the sensor substrate. The frame-shaped frame portion on which the first sealing bonding metal layer and the first connecting bonding metal layer are formed, and the frame-shaped frame portion disposed inside the frame portion and displaceable in a direction intersecting the one surface. A displacement space forming recess that secures a displacement space of the movable portion is formed on the surface of the through hole wiring formation substrate on the sensor substrate side, and the displacement The recess for forming a space also serves as the recess.

  According to the present invention, since the displacement space forming recess formed on the surface of the through hole wiring forming substrate on the sensor substrate side also serves as the recess, the recess is separately provided from the displacement space forming recess. There is no need to form it, and the design of the through-hole wiring forming substrate is facilitated.

  According to a fourth aspect of the present invention, in the third aspect of the invention, the first semiconductor substrate, the second semiconductor substrate, and the third semiconductor substrate are bonded to each other at a wafer level to obtain a desired chip size. It is characterized by being cut.

  According to this invention, the through-hole wiring forming substrate and the cover substrate have the same outer size as the sensor substrate, and a small chip size package can be realized.

  According to the first aspect of the present invention, the sensor substrate and the through hole wiring formation substrate can be easily joined, and the distance between the sensor substrate and the through hole wiring formation substrate can be increased. There is an effect.

  Hereinafter, the sensor element of this embodiment will be described with reference to FIGS.

  The sensor element of the present embodiment is an acceleration sensor element, and as shown in FIGS. 1 and 2, a sensor substrate 1 formed using a first semiconductor substrate and a sensor formed using a second semiconductor substrate. A through-hole wiring forming substrate 2 having a through-hole wiring 24 electrically connected to the metal wiring 17 of the substrate 1 and sealed on one surface side (the upper surface side of FIG. 1A) of the sensor substrate 1; And a cover substrate 3 formed using a third semiconductor substrate and sealed to the other surface side (the lower surface side of FIG. 1A) of the sensor substrate 1. Here, the outer peripheral shapes of the sensor substrate 1, the through-hole wiring formation substrate 2, and the cover substrate 3 are rectangular, and the through-hole wiring formation substrate 2 and the cover substrate 3 are formed to have the same outer dimensions as the sensor substrate 1. 1A is a schematic cross-sectional view taken along line AA ′ of FIG. 2, FIG. 1B is an enlarged view of a main part of FIG. 1A, and FIG. 1C is a schematic view of CC ′ of FIG. It is sectional drawing.

  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 through-hole wiring forming substrate 2 is formed by processing the first silicon wafer, and the cover substrate 3 is formed by processing the second silicon wafer. That is, in this embodiment, the SOI wafer constitutes the first semiconductor substrate, the first silicon wafer constitutes the second semiconductor substrate, and the second silicon wafer constitutes the third semiconductor substrate. . In this 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. 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. However, 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.

  As shown in FIGS. 3 to 5, the sensor substrate 1 includes a frame portion 11 having a frame shape (in this embodiment, a rectangular frame shape), and a weight portion 12 arranged inside the frame portion 11 is on one surface side. In FIG. 1 (a) and FIG. 3 (b), the frame portion 11 is swingably supported through 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. That is, each appendage portion 12b is disposed in a space 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 when viewed from the one surface side of the sensor substrate 1. In addition, a slit 14 is formed between each of the accompanying portions 12b and the frame portion 11, and the interval between the adjacent accompanying portions 12b with the bending portion 13 interposed therebetween is longer than the width dimension of the bending portion 13. Yes. 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. 1A 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 piezoresistors Rx2 and Rx4 in the vicinity of the core portion 12a. Is formed, and one piezoresistor 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) extending from the core portion 12a of the weight portion 12 in the negative direction of the x-axis is a pair of piezoresistors Rx1 in the vicinity of the core portion 12a. , Rx3 are formed, and one piezoresistor Rz3 is formed in the vicinity of the frame portion 11. Here, the four piezoresistors 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. The wiring is formed so that the longitudinal direction coincides with the longitudinal direction of the bending portion 13 and wiring (diffuse layer wiring, metal wiring 17 formed on the sensor substrate 1 is formed so as to constitute the left bridge circuit Bx in FIG. Etc.). Note that the piezoresistors Rx1 to Rx4 are formed in a stress concentration region where stress is concentrated in the bent 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 piezoresistors Ry1, in the vicinity of the core portion 12a. Ry3 is formed, and one piezoresistor Rz1 is formed in the vicinity of the frame portion 11. On the other hand, the bending portion 13 (lower bending portion 13 in FIG. 3A) extending from the core portion 12a of the weight portion 12 in the negative direction of the y-axis is a pair of piezoresistors Ry2 in the vicinity of the core portion 12a. , Ry4 are formed, and one piezoresistor Rz4 is formed at the end on the frame part 11 side. Here, the four piezoresistors 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. The wiring is formed so that the longitudinal direction coincides with the longitudinal direction of the bending portion 13 and wiring (diffuse layer wiring, metal wiring 17 formed on the sensor substrate 1 is formed so as to constitute the central bridge circuit By in FIG. Etc.). Note that the piezoresistors Ry1 to Ry4 are formed in a stress concentration region where stress is concentrated in the bent portion 13 when acceleration in the y-axis direction is applied.

  Further, the four piezoresistors Rz1, Rz2, Rz3, Rz4 formed in the vicinity of the frame portion 11 are formed for detecting acceleration in the z-axis direction, and constitute the right bridge circuit Bz in FIG. Thus, they are connected by wiring (a diffusion layer wiring formed on the sensor substrate 1, a metal wiring 17 or the like). However, the piezoresistors Rz1 and Rz4 formed in one set of the bent portions 13 and 13 of the two bent portions 13 and 13 are formed so that the longitudinal direction thereof coincides with the longitudinal direction of the bent portions 13 and 13. On the other hand, the piezoresistors Rz2 and Rz3 formed in 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.

  1 to 3, only the portion in the vicinity of the first connecting bonding metal layer 19 in the metal wiring 17 in the sensor substrate 1 is illustrated, and the diffusion layer wiring is not illustrated.

  Here, an example of the 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 piezoresistors Rx1 to Rx4 formed in the bending portions 13 and 13 are changed. Will do. In this case, the piezoresistors Rx1 and Rx3 are subjected to tensile stress, and the piezoresistors Rx2 and Rx4 are subjected to compressive stress. In general, a piezoresistor has a characteristic that a resistance value (resistivity) increases when subjected to a tensile stress, and a resistance value (resistivity) decreases when subjected to a compressive stress. Therefore, the piezoresistors Rx1 and Rx3 are resistant. The value increases, and the resistance values of the piezoresistors Rx2 and Rx4 decrease. Therefore, if a constant DC voltage is applied between the pair of input terminals VDD and GND shown in FIG. 6 from the external power supply, 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. 6 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. 6 changes according to the magnitude of the acceleration in the z-axis direction. Thus, the sensor body 1 described above detects the change in the output voltage of each of the bridge circuits Bx to Bz, thereby accelerating each acceleration acting on the sensor substrate 1 in the x-axis direction, the y-axis direction, and the z-axis direction. Can be detected. In this embodiment, the weight part 12 and each bending part 13 comprise a movable part, and each piezoresistor Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4 constitutes a sensing part in the sensor substrate 1. Yes.

  By the way, as shown in FIG. 6, the sensor substrate 1 includes two input terminals VDD and GND common to the three bridge circuits Bx, By, and Bz, two output terminals X1 and X2 of the bridge circuit Bx, Two output terminals Y1 and Y2 of the bridge circuit By and two output terminals Z1 and Z2 of the bridge circuit Bz are provided. These input terminals VDD and GND and output terminals X1, X2, Y1, Y2, and the like. Z1 and Z2 are provided as the first connection bonding metal layer 19 on the one surface side (that is, the through hole wiring forming substrate 2 side), and the through hole wiring 24 formed on the through hole wiring forming substrate 2 is provided. And are electrically connected. That is, eight connecting metal layers 19 for connection are formed on the sensor substrate 1, and eight through-hole wirings 24 are formed on the through-hole wiring forming substrate 2. Note that the eight first connecting bonding metal layers 19 have a rectangular outer peripheral shape (in this embodiment, a square shape) and are spaced apart in the circumferential direction of the frame portion 11 (rectangular frame shape). 2 are arranged on each of the four sides of the frame part 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 connection bonding metal layer 19 is disposed inside 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 17 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 set to 30 nm and an Au film thickness set to 500 nm. Although the thickness is set to 1 μm, these numerical values are merely examples and are not particularly limited.

  Each of the above-described piezoresistors Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4, and each of the diffusion layer wirings is formed by doping a p-type impurity with an appropriate concentration in each formation site in the silicon layer 10c. The metal wiring 17 described above is formed by patterning a metal film (for example, an Al film, an Al—Si film, etc.) formed on the insulating film 16 by sputtering or vapor deposition using lithography technology and etching technology. Thus, the metal wiring 17 is electrically connected to the diffusion layer wiring through a contact hole provided in the insulating film 16. The first connecting metal layer 19 for connection and the metal wiring 17 are connected to the metal wiring 17 in the first connecting metal layer 19 for connection 19b (see FIGS. 1B and 1C). The through-hole wiring forming substrate 2 is electrically connected so as to be positioned in a displacement space forming recess 21 which will be described later formed on the surface facing the sensor substrate 1. In this embodiment, the displacement space forming recess 21 in the through-hole wiring forming substrate 2 also serves as a recess in which the connection portion 19b with the metal wiring 17 in the first connecting bonding metal layer 19 of the sensor substrate 1 is disposed. ing.

  As shown in FIGS. 7 to 9, the through-hole wiring forming substrate 2 is formed on the surface of the sensor substrate 1 side (the lower surface side in FIG. 2A) with the weight portion 12 and each bending portion 13 of the sensor substrate 1. The above-mentioned displacement space forming recesses 21 that secure the displacement space of the movable portion that is configured are formed, and a plurality (eight in the present embodiment) penetrates in the thickness direction in the peripheral portion of the displacement space formation recesses 21. Through-holes 22 are 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-holes 22. A part of the insulating film 23 is interposed between the inner surface and the inner surface. Here, the eight through-hole wirings 24 of the through-hole wiring forming substrate 2 are formed apart from each other in the circumferential direction of the through-hole wiring forming 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, the through-hole wiring forming substrate 2 has a plurality (eight in this embodiment, eight) electrically connected to the respective through-hole wirings 24 on the periphery of the displacement space forming concave portion 21 on the surface on the sensor substrate 1 side. ) Second connecting bonding metal layer 29 is formed. The through-hole wiring forming 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 connecting bonding metal layers 29 have a rectangular shape whose outer peripheral shape is an elongated shape, and are disposed on the inner side of the second sealing bonding metal layer 28. 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 17 of the sensor substrate 1 and the sensor substrate 1. The first connecting bonding metal layer 19 is bonded and electrically connected.

  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 set to 30 nm and an Au film thickness set to 500 nm. It is an example and is not particularly limited.

  A plurality of external connection electrodes 25 electrically connected to the respective through-hole wirings 24 are formed on the surface of the through-hole wiring forming substrate 2 opposite to the sensor substrate 1 side. Here, each of the external connection electrodes 25 is constituted by, for example, a laminated film of a Cu film, a Ni film, and an Au film, and can be used as, for example, a reflow pad. The outer peripheral shape of each external connection electrode 25 is rectangular.

  As shown in FIG. 10, the cover substrate 3 is formed with a recess 31 having a predetermined depth (for example, about 5 μm to 10 μm) that forms a displacement space of the weight 12 on the surface facing the sensor substrate 1. Here, the recess 31 is formed using 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. Among these, the thickness of the portion formed using the support substrate 10a 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 portion 12 is made thinner by the allowable displacement amount, the weight 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 allows displacement of the portion 12 is formed between the weight portion 12 and the cover substrate 3.

  By the way, the sensor substrate 1 and the through-hole wiring formation substrate 2 in the acceleration sensor element described above are bonded to the first sealing bonding metal layer 18 and the second sealing bonding metal layer 28, The first connecting bonding metal layer 19 and the second connecting bonding metal layer 29 are bonded to each other, and the sensor substrate 1 and the cover substrate 3 are bonded to each other on the peripheral portions of the opposing surfaces. Further, the acceleration sensor element of the present embodiment includes an SOI wafer on which a large number of sensor substrates 1 are formed, a first silicon wafer on which a large number of through-hole wiring formation substrates 2 are formed, and a second silicon wafer on which a large number of cover substrates 3 are formed. Are bonded to each other at a wafer level and then cut into acceleration sensor elements having a desired chip size by a dicing process. Therefore, the through-hole wiring forming substrate 2 and the cover substrate 3 have the same outer size as the sensor substrate 1, and a small chip size package can be realized and manufacture is facilitated.

  Here, as a method for bonding the sensor substrate 1 to the through-hole wiring forming substrate 2 and the cover substrate 3, it is desirable to employ a bonding method that enables bonding at a lower temperature in order to reduce the residual stress of the sensor substrate 1. In this embodiment, a room temperature bonding method is employed. In the room temperature bonding method, before bonding, each bonding surface is irradiated with argon plasma, ion beam or atomic beam in vacuum to clean and activate each bonding surface, and then the bonding surfaces are brought into contact with each other. Join at room temperature. In the present embodiment, the first sealing bonding metal layer 18 and the second sealing bonding metal layer 28 are bonded by applying an appropriate load at normal 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 bonded, and the frame portion 11 and the cover substrate of the sensor substrate 1 are bonded at room temperature by the room temperature bonding method described above. 3 circumferences are joined. Thus, in the acceleration sensor element of the present embodiment, the bonding between the sensor substrate 1 and the through-hole wiring substrate 2 is an Au—Au bonding, and the bonding between the sensor substrate 1 and the cover substrate 3 is an Si—Si bonding. Compared to the case where the sensor substrate 1, the through-hole wiring forming substrate 2 and the cover substrate 3 are joined by a method that requires heating such as solder reflow or anodic bonding, the piezoresistors Rx1 to Rx4 constituting the sensing unit. , Ry1 to Ry4, Rz1 to Rz4 have the advantage that they are less susceptible to thermal stress. In the present embodiment, since the sensor substrate 1, the through-hole wiring formation substrate 2, and the cover substrate 3 are formed of Si, which is the same semiconductor material, the sensor substrate 1, the through-hole wiring formation substrate 2, and the cover substrate 3 are used. The stress (residual stress in the sensor substrate 1) caused by the difference in linear expansion coefficient with respect to the output signal of the bridge circuit can be reduced, and the through-hole wiring forming substrate 2 and the cover substrate 3 are made of a material different from that of the sensor substrate 1. Compared with the case where it is formed, variation in sensor characteristics can be reduced. The sensor substrate 1 is formed by processing an SOI wafer. However, the sensor substrate 1 is not limited to an SOI wafer, and may be formed by processing a silicon wafer, for example.

  In the acceleration sensor element of the present embodiment described above, the connection portion 19b of the first connecting bonding metal layer 19 of the sensor substrate 1 to the metal wiring 17 is the surface facing the sensor substrate 1 of the through-hole wiring forming substrate 2. Since it is located in the recess 21 for forming the displacement space, which is a recess formed in the joint, the joint for joining the second joint metal layer 29 for connection in the first joint metal layer 19 for connecting the sensor substrate 1. The part can be formed on the same plane as the first sealing bonding metal layer 19 of the sensor substrate 1, and the bonding between the sensor substrate 1 and the through-hole wiring forming substrate 2 can be easily performed. It becomes possible.

  Further, as described above, since each of the connecting bonding metal layers 19 and 29 and each of the sealing bonding metal layers 18 and 28 are formed of the same metal material, the first connecting bonding metal layer 19 and The first sealing bonding metal layer 18 and the second sealing bonding metal layer 28 may be directly bonded by, for example, a room temperature bonding method at the same time as the second connection bonding metal layer 29 is bonded. As a result, it is possible to eliminate the process of supplying solder and the reflow process for each joint portion as in the prior art, simplifying the manufacturing process, and reducing the distance between the sensor substrate 1 and the through-hole wiring forming substrate 2. High accuracy can be achieved, and fluctuations in sensor characteristics due to residual stress can be suppressed.

  Further, the displacement space forming recess 21 in the through-hole wiring forming substrate 2 also serves as a recess in which the connection portion 19b with the metal wiring 17 in the first connecting bonding metal layer 19 of the sensor substrate 1 is disposed. It is not necessary to form the recess separately from the displacement space forming recess 21, and the design of the through-hole wiring forming substrate 2 is facilitated.

  In the above-described embodiment, the piezoresistive acceleration sensor element is exemplified as the sensor element. However, the technical idea of the present invention is not limited to the piezoresistive acceleration sensor element, and for example, a capacitive acceleration sensor element or a gyro sensor. It can also be applied to other sensor elements such as elements. In capacitive acceleration sensor elements and gyro sensor elements, the weight part with a movable electrode or the weight part that also serves as the movable electrode constitutes the movable part, and the fixed electrode and the movable electrode Thus, a sensing unit is configured.

The acceleration sensor element of embodiment is shown, (a) is a schematic sectional drawing, (b) is the principal part enlarged view of (a), (c) is another principal part enlarged view. It is a schematic plan view of the acceleration sensor element same as the above. The sensor board | substrate in the same is shown, (a) is a schematic plan view, (b) is B-A 'schematic sectional drawing of (a). The sensor board | substrate in the same as the above is shown, (a) is A-A 'schematic sectional drawing of Fig.3 (a), (b) is C-C' schematic sectional drawing of Fig.3 (a). It is a schematic bottom view which shows the sensor board | substrate in the same as the above. It is a circuit diagram of the sensor board | substrate in the same as the above. The through-hole wiring formation board | substrate in the same as the above is shown, (a) is a schematic plan view, (b) is A-A 'schematic sectional drawing of (a). The through-hole wiring formation board | substrate in the same as the above is shown, and it is a principal part enlarged view of FIG.7 (b). It is a bottom view of the through-hole wiring formation board in the same as the above. The cover board | substrate in the same as the above is shown, (a) is a schematic plan view, (b) is A-A 'schematic sectional drawing of (a). It is explanatory drawing of the manufacturing method of the wafer level package structure of a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor substrate 2 Through-hole wiring formation board 3 Cover board 11 Frame part 12 Weight part 13 Deflection part 17 Metal wiring 18 1st joining metal layer for sealing 19 1st joining metal layer for connection 21 Recessed space formation recessed part 24 Through-hole wiring 25 External connection electrode 28 Second sealing bonding metal layer 29 Second connecting bonding metal layer

Claims (4)

  A sensor substrate formed using a first semiconductor substrate and having a metal wiring electrically connected to the sensing portion and a penetration formed using the second semiconductor substrate and electrically connected to the metal wiring A through-hole wiring forming substrate having a hole wiring and sealed on one surface side of the sensor substrate, wherein the sensor substrate has a first bonding metal layer for sealing over the entire circumference of the peripheral portion on the one surface. And a first connecting bonding metal layer electrically connected to the metal wiring is formed on the inner side of the first sealing bonding metal layer, and the through hole wiring forming substrate is formed on the sensor substrate side. The second sealing bonding metal layer is formed over the entire circumference of the peripheral portion of the surface of the first sealing layer, and the second sealing bonding metal layer is electrically connected to the through-hole wiring inside the second sealing bonding metal layer. 2 joint metal layers for connection are formed, and the sensor substrate and the through hole arrangement The formation substrate includes a first bonding metal layer for sealing and a second bonding metal layer for sealing, and a first bonding metal layer for connection and a second bonding metal layer for connection. The sensor substrate is bonded, and the connection portion with the metal wiring in the first connection bonding metal layer is located in a recess formed on the surface of the through-hole wiring forming substrate facing the sensor substrate. Sensor element.   2. The sensor element according to claim 1, wherein each of the connecting bonding metal layers and each of the sealing bonding metal layers is formed of the same metal material.   A cover substrate formed using a third semiconductor substrate and sealed on the other surface side of the sensor substrate, the sensor substrate comprising the first sealing bonding metal layer and the first connection bonding. A frame-shaped frame portion on which a metal layer is formed; and a movable portion disposed inside the frame portion and displaceable in a direction intersecting the one surface and having the sensing portion formed thereon, and the through hole A displacement space forming recess for securing a displacement space of the movable portion is formed on a surface of the wiring forming substrate on the sensor substrate side, and the displacement space forming recess also serves as the recess. Item 3. The sensor element according to item 1 or 2.   4. The sensor element according to claim 3, wherein the first semiconductor substrate, the second semiconductor substrate, and the third semiconductor substrate are bonded at a wafer level and then cut into a desired chip size. .

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