JP2007173637A - Sensor module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To further reduce a mounting area on a circuit board, and decrease stress transmitted from a mounting substrate or the circuit board to a sensor device. <P>SOLUTION: The sensor module is provided with a sensor device A composed of an acceleration sensor element, and a mounting substrate 5 on which the sensor element A is flip-chip bonded. The sensor device A has a plurality of external connection electrodes 25 on one surface side, and the mounting substrate 5 has a plurality of sensor connection electrodes 53 to which the external connection electrodes 25 are electrically connected. The sensor device A is bonded to the mounting substrate 5 via a plurality of bumps 9a, 9b superimposed in the thickness direction of the mounting substrate 5 for each combination of the external connection electrodes 25 and the sensor connection electrodes 53 for which a connection relation is defined. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sensor module including a sensor element and a mounting substrate on which the sensor element is mounted.

  Conventionally, as shown in FIG. 20, an acceleration sensor chip 101, which is a MEMS (Micro Electro Mechanical System) chip, and a mounting substrate 105, which has a box shape with one surface open and on which the acceleration sensor chip 101 is mounted on the inner bottom surface. In addition, a sensor module including a lid body 106 that closes the one surface of the mounting substrate 105 has been proposed (see, for example, Patent Documents 1 and 2).

  The sensor module having the configuration shown in FIG. 20 includes a stopper 102 that is separated from the acceleration sensor chip 101 on the main surface side of the acceleration sensor chip 101 and restricts excessive displacement of the weight portion 112 of the acceleration sensor chip 101. Each of a plurality of pads (not shown) on the main surface side of the chip 101 is electrically connected to a terminal pattern (not shown) on the mounting substrate via bonding wires (not shown). Here, in the acceleration sensor chip 101, a weight portion 112 disposed inside a frame portion 111 having a rectangular frame shape is supported by the frame portion 111 via four flexure portions 113. A pad is formed. Note that Patent Document 2 also describes that an IC chip on which a signal processing circuit for processing an output signal of the acceleration sensor chip 101 is formed is used as the stopper 102.

  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 3 and 4).

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 5) and a gyro sensor (for example, see Patent Document 6), a weight part provided with a movable electrode, a weight part also serving as a movable electrode, and the like constitute a movable part. The sensing unit is configured by the fixed electrode and the movable electrode.
JP 2004-212246 A JP 2005-169541 A JP 2004-109114 A JP 2004-233072 A JP 2004-028912 A JP 2005-292117 A

  However, in the sensor module having the configuration shown in FIG. 20, since the stopper 102 and the acceleration sensor chip 101 are bonded by an adhesive, the sensor characteristics are likely to change due to the influence of stress due to the shrinkage of the adhesive. There was a bug. Further, since the pads on the main surface side of the acceleration sensor chip 101 and the terminal patterns of the mounting substrate 105 are electrically connected via the bonding wires, the planar size of the mounting substrate 105 is relatively large. As a result, the mounting area on a circuit board such as a printed circuit board increases.

  Therefore, an external connection electrode on one surface side of the sensor element in which the package substrate is bonded to each of the main surface side and the back surface side of the acceleration sensor chip, and a sensor connection electrode provided in the projection surface of the sensor element on the mounting substrate Has been proposed, but the sensor module has been proposed to be electrically connected via bumps (that is, the sensor element is flip-chip mounted on the mounting board). In some cases, stress or the like due to a difference in linear expansion coefficient between the substrate and the circuit board is transmitted to the sensor element and the sensor characteristics of the sensor element fluctuate.

  The present invention has been made in view of the above-described reasons, and its object is to reduce the mounting area on the circuit board and to reduce the stress transmitted from the mounting board or the circuit board to the sensor element. It is to provide a sensor module capable of

  According to a first aspect of the present invention, there is provided a sensor element having a plurality of external connection electrodes on one surface side, and a plurality of sensor connection electrodes to which each external connection electrode is electrically connected. A mounting substrate to be mounted, and the sensor element and the mounting substrate are connected via a plurality of bumps that overlap each other in the thickness direction of the mounting substrate for each set of the external connection electrode and the sensor connection electrode for which the connection relationship is defined. It is characterized by being joined.

  According to the present invention, since the sensor element is flip-chip mounted on the mounting substrate, the planar size of the mounting substrate can be reduced, and the sensor element and the mounting substrate are external connection electrodes in which a connection relationship is defined. And the sensor connection electrodes are bonded via a plurality of bumps overlapping in the thickness direction of the mounting substrate, so that the stress transmitted from the mounting substrate or circuit board to the sensor element can be reduced.

  The invention of claim 2 is characterized in that, in the invention of claim 1, the sensor element and the mounting substrate are joined via bumps formed on the surfaces of the external connection electrode and the sensor connection electrode, respectively. To do.

  According to the present invention, it is possible to improve the bonding reliability between the external connection electrode and the sensor connection electrode and the bump.

  According to a third aspect of the present invention, in the first aspect of the invention, the sensor element and the mounting substrate are formed so as to overlap in the thickness direction of the mounting substrate on one surface side of the external connection electrode and the sensor connection electrode. It is characterized by being bonded through bumps.

  According to this invention, as compared with the invention of claim 2, it is easy to align the bumps to be overlapped.

  According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the sensor element and the mounting substrate are bonded at room temperature.

  According to this invention, the stress resulting from the linear expansion coefficient difference between the sensor element and the mounting substrate can be further reduced.

  According to the first aspect of the invention, there is an effect that the mounting area on the circuit board can be further reduced and the stress transmitted from the mounting board or the circuit board to the sensor element can be reduced.

(Embodiment 1)
The sensor module of this embodiment will be described with reference to FIGS.

  The sensor module of the present embodiment is an acceleration sensor module, and includes a sensor element A including an acceleration sensor element, an IC chip 4 on which a signal processing circuit for processing an output signal of the sensor element A is formed, a sensor element A, and A mounting substrate 5 made of a ceramic substrate on which the IC chip 4 is mounted, and an underfill 8 made of a thermosetting resin interposed between the mounting substrate 5 and the IC chip 4 are provided.

  The mounting substrate 5 described above is formed in a rectangular box shape with one open surface, and the IC chip 4 is flip-chip mounted on the outer bottom surface 5b side and the sensor element A is flip-chip mounted on the inner bottom surface 5a side. Yes. Accordingly, the above-described underfill 8 is interposed between the outer bottom surface 5 b of the mounting substrate 5 and the IC chip 4.

  By the way, in the acceleration sensor module of the present embodiment, the planar size of the IC chip 4 is larger than the planar size of the sensor element A, and the sensor element A fits within the projection surface of the IC chip 4 on the inner bottom surface 5a side of the mounting substrate 5. (In short, the mounting substrate 5 has the IC chip 4 flip-chip mounted on one surface side and the sensor element A flip-chip mounted on the projection surface of the IC chip 4 on the other surface side. ing).

  Hereinafter, the sensor element A will be described in detail, and then the acceleration sensor module will be described in detail.

  The sensor element A is formed using a first semiconductor substrate and has a sensor substrate 1 having a sensing unit described later, and a plurality of sensor elements A are formed using a second semiconductor substrate and electrically connected to the sensing unit of the sensor substrate 1. A through-hole wiring forming substrate 2 having a through-hole wiring 24 and sealed on one surface side (the upper surface side in FIGS. 1B and 8B) of the sensor substrate 1, and a third semiconductor substrate. And a cover substrate 3 formed and sealed on the other surface side of the sensor substrate 1 (the lower surface side in FIGS. 1B and 8B). 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. In the present embodiment, each of the through-hole wiring forming substrate 2 and the cover substrate 3 constitutes a package substrate. FIG. 9A is an enlarged view of a main part of FIG. 8B, and FIG. 9B is a schematic cross-sectional view taken along the line C-C ′ of FIG.

  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. 10 to 12, 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 disposed inside the frame portion 11 is on one surface side. In FIG. 8 (b) and FIG. 10 (b), the frame portion 11 is swingably supported via four flexible strip-like bent portions 13. 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 (see FIGS. 8B and 10B). (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. 10A and 10B, one direction along one side of the frame portion 11 in a 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. 10A) 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. 10A) extended 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 flexure 13 and the wiring (the diffusion layer wiring formed on the sensor substrate 1 and the metal wiring 17 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. 10A) 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. 10A) 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 flexure 13 and the wiring (diffuse layer wiring formed on the sensor substrate 1, the metal wiring 17 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 flexure 13 when acceleration in the y-axis direction is applied.

  The four piezoresistors Rz1, Rz2, Rz3, and 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 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.

  8-10, only the site | part of the metal wiring 17 in the sensor board | substrate 1 vicinity of the 1st joining metal layer 19 for connection is shown in figure, and illustration of a diffused layer wiring is abbreviate | omitted.

  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. 13 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 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. 13 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. 13 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 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. 13, the sensor substrate 1 includes two input terminals VDD and GND common to the three bridge circuits Bx, By, and Bz described above, 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 same level surface of the insulating film 16 with the same thickness.

  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 composed of a Ti film formed on the same level surface of the insulating film 16 and an Au film formed on the Ti film. And a laminated film. 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 first bonding metal layer 19 and the first sealing bonding metal layer 18 can be formed to have 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 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 alloy film, etc.) formed on the insulating film 16 by sputtering or vapor deposition using lithography technology and etching technology. The metal wiring 17 is electrically connected to the diffusion layer wiring through a contact hole provided in the insulating film 16. In addition, 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, as shown in FIG. 9B (see FIG. 9B). The substrate 2 is electrically connected so as to be positioned in a later-described displacement space forming recess 21 formed on the surface of the substrate 2 facing the sensor substrate 1.

  As shown in FIGS. 14 to 16, the through-hole wiring forming substrate 2 is formed on the surface on the sensor substrate 1 side (the lower surface side in FIG. 8B) 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. 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 through-hole wiring formation substrate 2 are shifted, and the second connection bonding metal layer 29 is arranged such that the longitudinal direction thereof coincides with the circumferential direction of the second sealing bonding metal layer 28 and straddles 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 include a Ti film formed on the same level surface of the insulating film 23 and an Au film formed on the Ti film. And a laminated film. 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 bonding metal layer 28 can be formed at the same time, and the second bonding metal layer 29 for connection and the second bonding metal layer 28 for sealing can be formed to 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 through-hole wiring forming substrate 2 opposite to the sensor substrate 1 side. Here, each external connection electrode 25 is constituted by a laminated film of a Ti film, a Cu film, a Ni film, and an Au film laminated in the thickness direction, and the uppermost layer is an Au film. The outer peripheral shape of each external connection electrode 25 is rectangular.

  As shown in FIG. 17, 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. 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 sensor substrate 1 and the through-hole wiring formation substrate 2 in the sensor element A 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. The sensor element A 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 forming substrates 2 are formed, and a second silicon wafer on which a large number of cover substrates 3 are formed on a wafer level. After joining, the sensor element A having a desired chip size is cut 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 sensor element A according to 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. ing. 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) due to 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.

  The IC chip 4 described above is integrated with an amplifier circuit that amplifies the output signal of the sensor element A, an offset adjustment circuit that adjusts an offset (offset voltage) of the output signal, a temperature compensation circuit that performs temperature compensation of the output signal, and the like. ASIC (Application Specific IC), which is formed using a silicon wafer.

  Further, the mounting substrate 5 is formed in a rectangular box shape with one surface opened as described above, the sensor element A is accommodated in the internal space 51, and the sensor element A is disposed on the inner bottom surface 5a side. The IC chip 4 is disposed on the outer bottom surface 5b side. Here, in the acceleration sensor module of the present embodiment, the external connection electrode 25 of the sensor element A and the sensor connection electrode 53 on the inner bottom surface 5a side of the mounting substrate 5 are formed on the external connection electrode 25. The bumps 9a made of bumps and the bumps 9b made of stud bumps formed on the sensor connection electrodes 53 are joined and electrically connected (see FIGS. 1B and 2), that is, with the sensor element A. The mounting substrate 5 is a plurality (two in this embodiment) of bumps 9 a that overlap in the thickness direction of the mounting substrate 5 for each set of the external connection electrode 25 and the sensor connection electrode 53 for which the connection relationship is defined. It is joined via 9b. Further, in the acceleration sensor module of the present embodiment, the bumps 7 made of stud bumps provided on the pads 41 of the IC chip 4 by the pads 41 of the IC chip 4 and the IC connection electrodes 54 on the outer bottom surface 5 b side of the mounting substrate 5 are provided. And are electrically connected. Here, each bump 9a, 9b, 7 employs Au as a material and is constituted by a stud bump formed by a stud bump method (also called a ball bump method). A formed bump (so-called plating bump) may be used. Further, the mounting substrate 5 has a wiring (not shown) for electrically connecting the sensor connection electrode 53 and the IC connection electrode 54 embedded in a portion between the inner bottom surface 5a and the outer bottom surface 5b. A wiring (not shown) for electrically connecting the IC connection electrode 54 and the lead electrode 55 formed on the one surface side of the mounting substrate 5 is embedded in the peripheral wall of the substrate 5.

  In the acceleration sensor module according to the present embodiment, the IC chip 4 has a planar size larger than the size of the inner bottom surface 5a of the mounting substrate 5 and the inner bottom surface 5a fits within the projection surface of the IC chip 4. 4 is flip-chip mounted on the outer bottom surface 5 b side of the mounting substrate 5.

  Hereinafter, the manufacturing method of the acceleration sensor module of this embodiment is demonstrated, referring FIGS.

  First, by performing a bump forming step of forming a plurality of bumps 9b by the stud bump method on the surface of each sensor connection electrode 53 provided on the inner bottom surface 5a of the mounting substrate 5, FIG. Get the structure shown.

  Thereafter, after applying a flattening step (leveling step) in which the tip of each bump 9b is pressed to flatten (leveling) the tip of each bump 9b, uncured heat is applied to the outer bottom surface 5b side of the mounting substrate 5. A structure shown in FIG. 5B is obtained by performing a resin material attaching step of attaching a sheet-like underfill resin material 81 made of a curable resin. In the resin material attaching step, an appropriate load is applied in a state where the underfill resin material 81 is appropriately heated to a temperature.

  Next, the plurality of bumps 7 (see FIG. 6) formed on the surface of each pad 41 of the IC chip 4 by the stud bump method and the plurality of IC connection electrodes 54 of the mounting substrate 5 are aligned. Then, the pad of the IC chip 4 is applied by heating and applying a load to the IC chip 4 with the underfill resin material 81 interposed between the IC chip 4 and the outer bottom surface 5b of the mounting substrate 5. The underfill resin material 81 is thermally cured at the same time that the IC chip 4 is flip-chip mounted on the mounting substrate 5 by thermocompression bonding of the bumps 7 on 41 to the IC connection electrodes 54 of the mounting substrate 5. By performing the first mounting process for forming 8, the structure shown in FIG. 5C is obtained.

  Thereafter, a plurality of bumps 9a (see FIG. 7) formed on the surface of each external connection electrode 25 of the sensor element A by the stud bump method and each surface of each sensor connection electrode 53 of the mounting substrate 5 are formed. Each of the plurality of formed bumps 9b is irradiated with an argon plasma, ion beam or atomic beam in vacuum to perform an activation process for cleaning and activating the surface, and then each outside of the sensor element A. The bumps 9a on the surfaces of the connection electrodes 25 and the bumps 9b on the surfaces of the sensor connection electrodes 53 of the mounting substrate 5 are aligned so that they overlap in the thickness direction of the mounting substrate 5, and the sensor element A is aligned. The sensor element A is flipped to the mounting substrate 5 by applying a load at normal temperature and bonding the bumps 9a and 9b overlapping in the thickness direction at normal temperature. By performing the second mounting step of-up implement, to obtain an acceleration sensor module having the structure shown in FIG. 5 (d).

  According to the method for manufacturing the acceleration sensor module described above, the bump 9b is formed on the sensor connection electrode 53 on the inner bottom surface 5a side of the mounting substrate 5 and the tip of each bump 9b is flattened, and then the first mounting step. After mounting the IC chip 4 having a large planar size on the outer bottom surface 5b side of the mounting substrate 5, the bump 9a and the sensor connecting electrode on the external connection electrode 25 of the sensor element A having a small planar size are mounted in the second mounting step. Since the bumps 9b on the 53 are bonded at room temperature, the residual stress caused by the difference in linear expansion coefficient between the sensor element A and the mounting substrate 5 can be reduced, and the fluctuation of the sensor characteristics of the sensor element A can be suppressed. can do. Further, in the second mounting step, the external connection electrode 25 and the sensor connection electrode 53 of the sensor element A are joined on the inner bottom surface 5a side of the mounting substrate 5 through bumps 9a and 9b that overlap in the thickness direction of the mounting substrate 5. In this case, since the underfill 8 is interposed between the IC chip 4 and the mounting substrate 5, the IC chip 4 is damaged when a load is applied to the sensor element A, or the IC chip 4 and the mounting substrate 5 The connection reliability between the sensor element A and the mounting substrate 5 can be improved.

  In the acceleration sensor module of the present embodiment described above, since the sensor element A is flip-chip mounted on the mounting board 5, the planar size of the mounting board 5 is reduced as compared with the mounting board 105 in the conventional configuration shown in FIG. In addition, the sensor element A and the mounting substrate 5 have a plurality of bumps 9a, which overlap in the thickness direction of the mounting substrate 5 for each set of the external connection electrode 25 and the sensor connection electrode 53 for which the connection relationship is defined. Since it is joined via 9b, the stress transmitted to the sensor element A from the mounting board 5 or the circuit board on which the mounting board 5 is mounted can be reduced. Further, in the acceleration sensor module of the present embodiment, the sensor element A and the mounting substrate 5 include the bump 9 a formed on the surface of the external connection electrode 25 and the bump 9 b formed on the surface of the sensor connection electrode 53. Therefore, it is possible to increase the bonding reliability between the external connection electrode 25 and the sensor connection electrode 53 and the bumps 9a and 9b. Moreover, in the acceleration sensor module of this embodiment, since the sensor element A and the mounting substrate 5 are joined at room temperature, the stress caused by the difference in linear expansion coefficient between the sensor element A and the mounting substrate 5 can be further reduced.

  By the way, in the above-described embodiment, the sensor element A and the mounting substrate 5 are connected via the bumps 9 a formed on the surface of the external connection electrode 25 and the bumps 9 b formed on the surface of the sensor connection electrode 53. Although they are joined, as shown in FIG. 18, through a plurality of (two in the illustrated example) bumps 9a and 9b formed so as to overlap in the thickness direction of the mounting substrate 5 on the surface side of the external connection electrode 25. Alternatively, it may be bonded, or may be bonded via a plurality of bumps formed so as to overlap the surface side of the sensor connection electrode 53 in the thickness direction of the mounting substrate 5. This makes it easy to align the bumps 9a and 9b to be overlapped. In the example shown in FIG. 18, the bump 9a is formed on the surface of the external connection electrode 25 by the stud bump method, and after the tip of the bump 9a is flattened, the bump 9b is formed on the bump 9a. Is formed.

(Embodiment 2)
The sensor module of the present embodiment is an acceleration sensor module having substantially the same configuration as that of the first embodiment. As shown in FIG. 19, the lead electrode 55 is formed on the outer bottom surface 5 b side of the rectangular box-shaped mounting substrate 5. In addition, an IC connection electrode 54 is formed on the one surface side of the mounting substrate 5, and the IC chip 4 is disposed so as to close the one surface of the mounting substrate 5. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted.

  In the acceleration sensor module of the present embodiment, the joint portion between the bump 7 on the pad 41 of the IC chip 4 and the IC connection electrode 54 of the mounting substrate 5 is reinforced, and the peripheral portion of the IC chip 4 is mounted over the entire circumference. A sealing portion 82 made of a thermosetting resin that is sealed to the substrate 5 is formed. Therefore, in the present embodiment, a package that houses the sensor element A can be configured by the mounting substrate 5 and the IC chip 4.

  In the acceleration sensor module of the present embodiment described above, since the sensor element A is flip-chip mounted on the mounting substrate 5 as in the first embodiment, the mounting area on the circuit substrate can be further reduced and the mounting substrate can be reduced. 5 and the stress transmitted from the circuit board to the sensor element A can be reduced.

  In each of the embodiments described above, the number of bumps stacked in the thickness direction of the mounting substrate 5 is two. However, the number of bumps stacked in the thickness direction is not limited to two and may be plural. In each of the above embodiments, 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. For example, a capacitive acceleration sensor element or It can also be applied to other sensor elements such as gyro sensor elements.In capacitive acceleration sensor elements and gyro sensor elements, the weight part provided with a movable electrode or the weight part that also serves as the movable electrode constitutes the movable part, and the fixed electrode and A sensing unit is constituted by the movable electrode.

The acceleration sensor module of Embodiment 1 is shown, (a) is a schematic plan view, (b) is a schematic front view partly broken. It is a principal part enlarged view in the acceleration sensor module same as the above. It is a schematic bottom view of an acceleration sensor module same as the above. It is the schematic perspective view which a part of acceleration sensor module same as the above fractured. It is principal process sectional drawing for demonstrating the manufacturing method of an acceleration sensor module same as the above. It is explanatory drawing of the manufacturing method of an acceleration sensor module same as the above. It is explanatory drawing of the manufacturing method of an acceleration sensor module same as the above. The sensor element in the same as above is shown, (a) is a schematic plan view, (b) is a D-D 'schematic sectional view of (a). The sensor element in the same as above is shown, (a) is an enlarged view of the main part of FIG. 8 (b), (b) is a schematic cross-sectional view of C-C 'of FIG. 8 (a). The sensor board | substrate in the same is shown, (a) is a schematic plan view, (b) is B-D 'schematic sectional drawing of (a). The sensor board | substrate in the same as the above is shown, (a) is D-D 'schematic sectional drawing of Fig.10 (a), (b) is C-C' schematic sectional drawing of Fig.10 (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 D-D 'schematic sectional drawing of (a). The through-hole wiring formation board | substrate in the same as the above is shown, and is a principal part enlarged view of FIG. 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 D-D 'schematic sectional drawing of (a). It is a principal part enlarged view of the other structural example same as the above. It is a schematic sectional drawing of the acceleration sensor module of Embodiment 2. It is a schematic sectional drawing which shows a prior art example.

Explanation of symbols

A sensor element 4 IC chip 5 mounting substrate 5a inner bottom surface 5b outer bottom surface 9a bump 9b bump 25 external connection electrode 53 sensor connection electrode 55 lead electrode

Claims (4)

  A sensor element having a plurality of external connection electrodes on one surface side, and a mounting substrate having a plurality of sensor connection electrodes to which each external connection electrode is electrically connected and on which the sensor element is flip-chip mounted The sensor element and the mounting board are joined via a plurality of bumps that overlap each other in the thickness direction of the mounting board for each set of the external connection electrode and the sensor connection electrode for which the connection relationship is defined. Sensor module.   2. The sensor module according to claim 1, wherein the sensor element and the mounting substrate are joined via bumps formed on the surfaces of the external connection electrode and the sensor connection electrode.   The sensor element and the mounting substrate are bonded via a plurality of bumps formed so as to overlap in the thickness direction of the mounting substrate on one surface side of the external connection electrode and the sensor connection electrode. The sensor module according to claim 1.   4. The sensor module according to claim 1, wherein the sensor element and the mounting substrate are bonded at room temperature.

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