JP2007173638A - Sensor module and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a sensor module capable of suppressing variations in the sensor characteristics of a sensor element, and enhancing the connection reliability between a packaging substrate and the sensor element, and between the substrate and an IC chip, and to provide the sensor module. <P>SOLUTION: The manufacturing method of a sensor module has a step of forming first Au bumps 9 on an electrode 53 for connecting sensors in the packaging substrate 5, has a step of forming a resin material 81 for undefills to the side of an external bottom surface 5b applying in the packaging substrate 5, aligning the IC chip 4, heating the IC chip 4 and applying a load to it for thermocompression bonding of a second Au bump 7 on a pad 41 in the IC chip 4 to an electrode 54 for connecting ICs, forming and an underfill 8 by thermosetting the resin material 81 for underfills. Then, the electrode 25 for external connections of an acceleration sensor element A of a sensor element, and an electrode 53 for connecting sensors at the side of the inner bottom surface of the packaging substrate 5, are jointed at normal temperature via the first Au bump 9. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a sensor module manufacturing method and a sensor module in which a sensor element and an IC chip on which a signal processing circuit for processing an output signal of the sensor element is formed are mounted on one mounting substrate.

  In recent years, as a sensor element having a chip size package (CSP), sensor elements (for example, MEMS such as an acceleration sensor and a gyro sensor) formed by using wafer level packaging technology have been researched and developed in various places. A sensor module has been proposed in which a sensor element and an IC chip on which a signal processing circuit for processing an output signal of the sensor element is formed are mounted on a single mounting board.

  Conventionally, as a semiconductor mounting module in which a semiconductor bare chip is flip-chip mounted on one surface side of one circuit board and a semiconductor component is solder-mounted on the other surface side, the semiconductor component is larger than the planar size of the semiconductor bare chip. The reliability of the connection between the semiconductor bare chip and the circuit board is improved by setting the relative positional relationship between the semiconductor bare chip and the semiconductor component so that the semiconductor bare chip is within the projection plane of the semiconductor component when the planar size of the semiconductor component is large. A semiconductor mounting module has been proposed (see, for example, Patent Document 1).

  Here, in Patent Document 1, as a method for manufacturing the semiconductor mounting module described above, an uncured thermosetting resin layer covering the chip connection electrode is formed on the one surface side of the circuit board, and then the semiconductor bare chip is formed. After aligning the Au bump provided on the pad with the chip connection electrode of the circuit board, the Au bump is thermocompression bonded to the chip connection electrode by applying an appropriate load to the semiconductor bare chip while the semiconductor bare chip is heated. At the same time, the thermosetting resin layer is thermally cured, and then a solder part is formed on the component connecting electrode on the other surface side of the circuit board, and then the terminal of the semiconductor component is aligned and brought into contact with the solder part. After that, a method is described in which the component connection electrode of the circuit board and the terminal of the semiconductor component are joined by performing reflow.

  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 (see, for example, Patent Document 4) and a gyro sensor (see, for example, Patent Document 5), 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.
Japanese Patent Laid-Open No. 2003-282811 JP 2004-109114 A JP 2004-233072 A JP 2004-028912 A JP 2005-292117 A

  By the way, in the sensor module in which the sensor element and the IC chip described above are mounted on one mounting substrate, when the planar size of the IC chip is larger than the planar size of the sensor element, as a manufacturing method of the sensor module, It is conceivable to employ a manufacturing method according to the manufacturing method of the semiconductor mounting module described in 1.

  That is, as a method for manufacturing the sensor module described above, the sensor element is mounted by thermocompression bonding of the Au bump provided on the external connection electrode of the sensor element having a small planar size to the sensor connection electrode on one surface of the mounting substrate. After flip-chip mounting on the one surface side of the substrate, an uncured thermosetting resin layer (underfill resin) is formed so as to cover the IC connection electrode on the other surface of the mounting substrate, By thermally bonding the Au bumps provided on the pads of the IC chip having a large planar size to the IC connection electrodes on the other surface of the mounting substrate, the thermosetting resin layer is thermally cured to form an underfill. A manufacturing method in which an IC chip is flip-chip mounted on the other surface side of the mounting substrate is conceivable.

  However, when such a manufacturing method is adopted, there is a problem in that the sensor element has a residual stress due to a difference in linear expansion coefficient between the sensor element and the mounting substrate, and the sensor characteristics of the sensor element fluctuate. It was.

  The present invention has been made in view of the above-described reasons, and an object of the present invention is to suppress fluctuations in sensor characteristics of the sensor element, and to improve the connection reliability between the mounting substrate, the sensor element, and the IC chip. Another object is to provide a method for manufacturing a sensor module and a sensor module.

  The invention of claim 1 is an IC chip on which a sensor element and a signal processing circuit for signal processing of an output signal of the sensor element are formed, an IC chip having a plane size larger than the plane size of the sensor element, and an IC on one surface side. The sensor element includes a mounting substrate on which the chip is flip-chip mounted and the sensor element is flip-chip mounted in the projection surface of the IC chip on the other surface side, and an underfill interposed between the mounting substrate and the IC chip. The external connection electrode and the sensor connection electrode on the other surface side of the mounting substrate are bonded via the first bump, and the IC chip pad and the IC connection electrode on the one surface side of the mounting substrate are connected to each other. A method for manufacturing a sensor module bonded through two bumps, comprising an uncured thermosetting resin between the IC chip and the one surface of the mounting substrate. For underfill, at the same time as the second bump formed in advance on the IC chip pad is thermocompression-bonded to the IC connection electrode by heating and applying a load with the resin resin material interposed A first mounting step for thermosetting the resin material, and a first bump interposed between the external connection electrode of the sensor element and the sensor connection electrode of the mounting substrate after the first mounting step. And a second mounting step in which the external connection electrode and the sensor connection electrode are bonded at normal temperature via the first bump by applying a load at normal temperature to the sensor element. To do.

  According to the present invention, after mounting an IC chip having a large planar size on one surface side of the mounting substrate in the first mounting process, the external connection electrode and mounting substrate of the sensor element having a small planar size are mounted in the second mounting process. Since the sensor connection electrode is bonded at room temperature via the first bump, the residual stress due to the difference in linear expansion coefficient between the sensor element and the mounting substrate can be reduced, and the sensor characteristics of the sensor element can be reduced. Fluctuations can be suppressed. Further, when the external connection electrode and the sensor connection electrode of the sensor element are bonded via the first bump on the other surface side of the mounting substrate in the second mounting step, the gap between the IC chip and the mounting substrate is determined. Since underfill is present in the IC, it is possible to prevent the IC chip from being damaged or the connection reliability between the IC chip and the mounting substrate from being reduced when a load is applied to the sensor element. Connection reliability with the substrate can be improved.

  The invention of claim 2 is an IC chip on which a sensor element and a signal processing circuit for signal processing of the output signal of the sensor element are formed, an IC chip having a plane size larger than the plane size of the sensor element, and a box-shaped opening on one side A mounting module on which an IC chip is flip-chip mounted on the outer bottom surface side and a mounting substrate on which a sensor element is flip-chip mounted in the projection surface of the IC chip on the inner bottom surface side, An underfill made of a thermosetting resin is provided between the outer bottom surface of the mounting substrate and the IC chip, and the external connection electrode of the sensor element and the sensor connection electrode on the inner bottom surface side of the mounting substrate are the first. The second Au bump is formed by bonding the IC chip pad and the IC connection electrode on the outer bottom surface side of the mounting substrate to the IC chip pad. And characterized by comprising been joined.

  According to the present invention, after mounting an IC chip having a large planar size on the outer bottom surface side of the mounting substrate, the external connection electrode of the sensor element having a small planar size and the sensor connecting electrode on the inner bottom surface side of the mounting substrate are It is possible to adopt a manufacturing method in which room-temperature bonding is performed through one Au bump, and it is possible to reduce residual stress due to a difference in linear expansion coefficient between the sensor element and the mounting substrate, and to change the sensor characteristics of the sensor element. Can be suppressed. Further, when the above manufacturing method is adopted, when the external connection electrode of the sensor element and the sensor connection electrode are joined via the first Au bump on the inner bottom surface side of the mounting substrate, the IC chip and the mounting substrate are used. Since there is an underfill between the IC chip and the sensor element, an underfill is interposed between the IC chip and the outer bottom surface of the mounting board. When a load is applied to the sensor element, It is possible to prevent the IC chip from being damaged or the connection reliability between the IC chip and the mounting substrate from being lowered, and the connection reliability between the sensor element and the mounting substrate can be increased.

  According to a third aspect of the present invention, in the third aspect of the invention, the planar size of the IC chip is larger than the size of the inner bottom surface of the mounting substrate, and the inner bottom surface fits within the projection surface of the IC chip. The IC chip is flip-chip mounted on the outer bottom surface side of the mounting substrate.

  According to the present invention, it is possible to prevent the mounting substrate from warping when the IC chip is mounted or when the sensor element is mounted, and the connection reliability between the IC chip and the sensor element and the mounting substrate can be prevented. Can be increased.

  According to the first aspect of the present invention, it is possible to suppress fluctuations in the sensor characteristics of the sensor element and to improve the connection reliability between the mounting substrate, the sensor element, and the IC chip.

  According to the invention of claim 2, it is possible to suppress fluctuations in sensor characteristics of the sensor element, and to improve the connection reliability between the mounting substrate, the sensor element, and the IC chip.

  The sensor module of this embodiment will be described with reference to FIGS.

  The sensor module of this embodiment is an acceleration sensor module, and as shown in FIGS. 3 to 5, an acceleration sensor element A that is a sensor element and a signal processing circuit that processes an output signal of the acceleration sensor element A are formed. The mounted IC chip 4, the mounting substrate 5 made of a ceramic substrate on which the acceleration sensor element A and the IC chip 4 are mounted, and the underfill 8 made of a thermosetting resin interposed between the mounting substrate 5 and the IC chip 4. And.

  The above-described mounting substrate 5 is formed in a box shape having an opening on one surface, and the IC chip 4 is flip-chip mounted on the outer bottom surface 5b side and the acceleration sensor element A is flip-chip mounted on the inner bottom surface 5a side. 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 acceleration sensor element A, and the acceleration sensor element A is within the projection plane 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 acceleration sensor element A flips on the projection surface of the IC chip 4 on the other surface side. Chip mounted).

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

  As shown in FIG. 6, the acceleration sensor element A is formed using a first semiconductor substrate and includes a sensor substrate 1 having a sensing unit, which will be described later, and a sensing unit of the sensor substrate 1 formed using a second semiconductor substrate. A through-hole wiring forming substrate 2 having a plurality of through-hole wirings 24 electrically connected to each other and sealed on one surface side (the upper surface side in FIG. 6B) of the sensor substrate 1, and a third semiconductor And a cover substrate 3 formed using the substrate and sealed on the other surface side of the sensor substrate 1 (the lower surface side in FIG. 6B). 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. 7A is an enlarged view of a main part of FIG. 6B, and FIG. 7B 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. 8 to 10, 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. 6 (b) and FIG. 8 (b), the frame portion 11 is supported so as to be swingable through four flexible strip-shaped bending 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 (see FIGS. 6B and 8B). (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. 8A and 8B, 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. 8A) extended 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. 8A) 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 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. 8A) 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 (the lower bending portion 13 in FIG. 8A) extended 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 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 the wiring (the diffusion 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. 11. 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.

  Further, 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.

  6-8, 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. 11 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. 11 changes according to the magnitude of 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. 11 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. 11, the sensor substrate 1 includes two input terminals VDD and GND common to the above-described three bridge circuits Bx, By, and Bz, two output terminals X1 and X2 of the bridge circuit Bx, 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. Further, 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. 7B (see FIG. 7B). 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. 12 to 14, the through-hole wiring forming substrate 2 is formed on the surface on the sensor substrate 1 side (the lower surface side in FIG. 6B) 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. 15, 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 portion 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 acceleration 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 connection bonding metal layer 19 and the second connection 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 A 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 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. Therefore, in the acceleration sensor element A 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. It has become. 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.

  Further, the above-described IC chip 4 includes an amplifier circuit that amplifies the output signal of the acceleration 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 box shape opened on one surface as described above, the acceleration sensor element A is accommodated in the internal space 51, the acceleration sensor element A is disposed on the inner bottom surface 5a side, and the outer The IC chip 4 is disposed on the bottom surface 5b side. Here, in the acceleration sensor module of the present embodiment, the external connection electrode 25 of the acceleration sensor element A and the sensor connection electrode 53 on the inner bottom surface 5 a side of the mounting substrate 5 are provided on the sensor connection electrode 53. The second IC chip 4 is provided with 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 provided on the pads 41 of the IC chip 4. They are joined and electrically connected via Au bumps 7. 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 present embodiment, the first Au bump 9 constitutes the first bump, and the second Au bump 7 constitutes the second bump.

  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, a method for manufacturing the acceleration sensor module of the present embodiment will be described with reference to FIGS.

  First, by performing a bump forming step of forming first Au bumps 9 made of stud bumps on the surface of each sensor connection electrode 53 provided on the inner bottom surface 5a of the mounting substrate 5, FIG. ) Is obtained.

  Thereafter, by performing a resin material adhering step of adhering a sheet-like underfill resin material 81 made of an uncured thermosetting resin to the outer bottom surface 5b side of the mounting substrate 5, as shown in FIG. Get the structure. 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 second Au bump 7 (see FIG. 2) made of a stud bump formed in advance on the pad 41 of the IC chip 4 and the IC connection electrode 54 of the mounting substrate 5 are aligned, and then the IC For example, by applying heat and applying a load to the IC chip 4 with the underfill resin material 81 interposed between the chip 4 and the outer bottom surface 5 b of the mounting substrate 5, the IC chip 4 is placed on the pad 41. By performing the first mounting step of forming the underfill 8 by thermosetting the second Au bump 7 to the IC connection electrode 54 of the mounting substrate 5 and simultaneously thermosetting the underfill resin material 81. The structure shown in FIG. 1C is obtained. The second Au bump 7 is not limited to a stud bump but may be a plating bump.

  Thereafter, the external connection electrode 25 of the acceleration sensor element A and the first Au bump 9 formed on the mounting substrate 5 are each irradiated with argon plasma, ion beam or atomic beam in vacuum to clean and activate the surface. After the activation step is performed, the external connection electrode 25 of the acceleration sensor element A and the sensor connection electrode 53 of the mounting substrate 5 are aligned with each other with the first Au bump 9 interposed therebetween (here Then, the external connection electrode 25 of the acceleration sensor element A and the first Au bump 9 are aligned), and a load is applied to the acceleration sensor element A at room temperature, whereby the external connection electrode 25 and the sensor connection electrode are applied. 53 is bonded at room temperature via the first Au bump 9 (the external connection electrode 25 and the first Au bump 9 are bonded at room temperature). By performing obtain an acceleration sensor module having the structure shown in FIG. 1 (d).

  According to the acceleration sensor module manufacturing method described above, the first Au bump 9 is formed on the sensor connection electrode 53 on the inner bottom surface 5a side of the mounting substrate 5, and then the planar size is reduced in the first mounting step. After the large IC chip 4 is mounted on the outer bottom surface 5b side of the mounting substrate 5, the external connection electrode 25 of the acceleration sensor element A having a small planar size and the sensor connection electrode 53 of the mounting substrate 5 are mounted in the second mounting step. Since bonding at room temperature is performed via the first Au bump 9, it is not necessary to form the first Au bump 9 on the external connection electrode 25 of the acceleration sensor element A, and the acceleration sensor element A is mounted. Residual stress due to the difference in linear expansion coefficient with the substrate 5 can be reduced, and fluctuations in sensor characteristics of the acceleration sensor element A can be suppressed. Further, when the external connection electrode 25 and the sensor connection electrode 53 of the acceleration sensor element A are joined via the first Au bump 9 on the inner bottom surface 5a side of the mounting substrate 5 in the second mounting step, 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 acceleration sensor element A, or the connection reliability between the IC chip 4 and the mounting substrate 5. Can be prevented, and the connection reliability between the acceleration sensor element A and the mounting substrate 5 can be improved.

  In other words, in the acceleration sensor module of the present embodiment, the first Au bump 9 is formed on the sensor connection electrode 53 on the inner bottom surface 5a side of the mounting substrate 5 by adopting the above configuration. Then, after mounting the IC chip 4 having a large planar size on the outer bottom surface 5b side of the mounting substrate 5, the external connection electrode 25 of the acceleration sensor element A having a small planar size and the sensor connecting electrode on the inner bottom surface side of the mounting substrate 5 are mounted. 53 can be bonded at room temperature via the first Au bump 9 (in the above example, the external connection electrode 25 and the first Au bump 9 are bonded at room temperature). It is not necessary to form the first Au bump 9 on the external connection electrode 25 of the acceleration sensor element A at the time of manufacture, and it is caused by the difference in linear expansion coefficient between the acceleration sensor element A and the mounting substrate 5. Reduction of the residual stress becomes possible, it becomes possible to suppress variations in sensor characteristics of the acceleration sensor element A. The planar size of the IC chip 4 is larger than the size of the inner bottom surface 5 a of the mounting substrate 5, and the IC chip 4 is placed on the outer bottom surface 5 b side of the mounting substrate 5 such that the inner bottom surface 5 a is within the projection surface of the IC chip 4. Since the flip chip mounting is performed, it is possible to prevent the mounting substrate 5 from warping when the IC chip 4 is mounted or when the acceleration sensor element A is mounted, and the IC chip 4 and the acceleration sensor element A and the mounting substrate 5 It becomes possible to improve the connection reliability.

  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.

It is principal process sectional drawing for demonstrating the manufacturing method of the acceleration sensor module of embodiment. It is explanatory drawing of the manufacturing method of an acceleration sensor module same as the above. The acceleration sensor module same as the above is shown, (a) is a schematic plan view, and (b) is a schematic front view partly broken. 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. The acceleration sensor element in the same as above is shown, (a) is a schematic plan view, (b) is a schematic cross-sectional view along D-D 'of (a). The acceleration sensor element in the same as above is shown, (a) is an enlarged view of a main part of FIG. 6 (b), (b) is a schematic cross-sectional view of C-C ′ of FIG. 6 (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.8 (a), (b) is C-C' schematic sectional drawing of Fig.8 (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 it is a principal part enlarged view of FIG.12 (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 D-D 'schematic sectional drawing of (a).

Explanation of symbols

A Acceleration sensor element 4 IC chip 5 Mounting substrate 5a Inner bottom surface 5b Outer bottom surface 7 Second Au bump 8 Underfill 9 First Au bump 25 External connection electrode 41 Pad 53 Sensor connection electrode 54 IC connection electrode 81 Under Filling resin material

Claims (3)

  An IC chip on which a sensor element and a signal processing circuit for processing an output signal of the sensor element are formed, an IC chip having a planar size larger than the planar size of the sensor element, and an IC chip flip-chip mounted on one surface side And a mounting substrate on which the sensor element is flip-chip mounted within the projection surface of the IC chip on the other surface side, and an underfill interposed between the mounting substrate and the IC chip, and mounting with the external connection electrode of the sensor element The sensor connection electrode on the other surface side of the substrate is bonded via the first bump, and the pad of the IC chip and the IC connection electrode on the one surface side of the mounting substrate are bonded via the second bump. An underfill resin material made of uncured thermosetting resin is interposed between the IC chip and the one surface of the mounting substrate. In this state, by applying heat and applying a load, the second bump formed in advance on the pad of the IC chip is thermocompression bonded to the IC connection electrode, and at the same time, the resin material for underfill is thermally cured. 1 and after the first mounting step, the external connection electrode of the sensor element and the sensor connection electrode of the mounting substrate are aligned so that the first bump is interposed therebetween to form the sensor element. A sensor module manufacturing method comprising: a second mounting step of applying a load at room temperature to the external connection electrode and the sensor connection electrode via the first bump at room temperature.   An IC chip on which a sensor element and a signal processing circuit for processing an output signal of the sensor element are formed. The IC chip has a planar size equal to or larger than the planar size of the sensor element, and a box-shaped mounting substrate that is open on one side. A sensor module including a mounting substrate on which an IC chip is flip-chip mounted on a bottom surface side and a sensor element is flip-chip mounted on a projection surface of the IC chip on an inner bottom surface side, and the outer bottom surface of the mounting substrate and the IC An underfill made of a thermosetting resin interposed between the chip and the external connection electrode of the sensor element and the sensor connection electrode on the inner bottom surface side of the mounting substrate are bonded via the first Au bump The IC chip pad and the IC connection electrode on the outer bottom surface side of the mounting substrate are joined via the second Au bump provided on the IC chip pad. Sensor module, characterized in that.   The planar size of the IC chip is larger than the size of the inner bottom surface of the mounting substrate, and the IC chip is flipped to the outer bottom surface side of the mounting substrate so that the inner bottom surface fits within the projection surface of the IC chip. The sensor module according to claim 2, wherein the sensor module is mounted on a chip.

Images