JP4925272B2 - Semiconductor device - Google Patents

Description

  The present invention relates to a semiconductor device in which a thin flexible element portion formed of a part of a semiconductor substrate is formed using a micromachining technique.

  Conventionally, as a semiconductor device in which a thin flexible element portion formed of a part of a semiconductor substrate is formed using micromachining technology, for example, an acceleration sensor, a gyro sensor, a pressure sensor, a micro actuator, a micro relay, a micro valve Etc. are known.

  As this type of semiconductor device, for example, a functional substrate formed using a semiconductor substrate and having a movable element portion, the functional substrate is bonded to one surface side, and a plurality of external connection electrodes are formed on the other surface side. A first cover substrate and a second cover substrate joined to the one surface side of the first cover substrate so as to surround the functional substrate between the first cover substrate and a material of the cover substrate As the semiconductor substrate, the same material as that of the above-described semiconductor substrate is used to suppress the characteristic variation due to the difference in linear expansion coefficient between the functional substrate and each cover substrate (for example, see Patent Document 1). . In a piezoresistive acceleration sensor or pressure sensor, a piezoresistor is formed at an appropriate position of the flexible element portion.

  By the way, when this type of semiconductor device is used by being mounted on a mounting substrate (for example, a glass epoxy resin substrate), a plurality of external connection electrodes of the semiconductor device and the mounting substrate are provided within the projection surface of the semiconductor device. Although it is necessary to electrically connect a plurality of conductor patterns via joints such as solder and bumps, the stress caused by the difference in linear expansion coefficient between the semiconductor device and the mounting board causes the flexibility of the functional board from the mounting board. As a result, the characteristics of the semiconductor device are deteriorated.

Therefore, it is possible to apply a technique (for example, refer to Patent Documents 2, 3, and 4) in which a groove portion is provided as a stress relaxation portion that relieves stress associated with bonding with another member on a bonding surface with another member in the semiconductor device. Conceivable.
JP 2006-186358 A JP 2000-187040 A JP 2001-168139 A JP-A-2-240942

  However, it is difficult to eliminate the stress generated in the flexible element portion due to the difference in linear expansion coefficient from the mounting substrate even if the technique of providing the groove portion as the stress relaxation portion as in Patent Documents 2 to 4 is applied. .

  The present invention has been made in view of the above-described reasons, and an object of the present invention is to provide a semiconductor device capable of further relaxing stress generated in a flexible element portion due to a difference in linear expansion coefficient from a mounting substrate. It is to provide.

  According to a first aspect of the present invention, there is provided a functional substrate having a thin flexible element formed using a semiconductor substrate, and a plurality of first electrical connection metal layers of the functional substrate bonded to one surface side. First having a second electrical connection metal layer and a plurality of external connection electrodes electrically connected to each of the plurality of second electrical connection metal layers on the other surface side through through-hole wirings And a second cover substrate joined to the one surface side of the first cover substrate so as to surround the functional substrate between the cover substrate and the first cover substrate. The first cover substrate includes: The second electrical connection metal layer and the external connection electrode electrically connected to the second electrical connection metal layer are shifted so as not to overlap each other in the thickness direction of the functional board. Externally connected to the metal layer and the second metal layer for electrical connection Groove portions that relieve stress generated in the flexible element portion due to the joining of the external connection electrode and the conductor pattern of the mounting substrate on the one surface side and the other surface side in the region between the connection electrodes. The one surface side so that a bellows-like structure portion is formed between the second electrical connection metal layer and the external connection electrode electrically connected to the second electrical connection metal layer. The groove forming position is shifted from the groove forming position on the other surface side.

  According to this invention, the first cover substrate has the first cover substrate in a region between the second electrical connection metal layer and the external connection electrode electrically connected to the second electrical connection metal layer. Grooves are formed on the surface side and the other surface side to alleviate the stress generated in the flexible element part due to the bonding between the external connection electrode and the conductor pattern of the mounting substrate, and the second metal layer for electrical connection The groove portion on the one surface side and the other surface side so that an accordion-like structure portion is formed between the external connection electrode electrically connected to the second electrical connection metal layer. Since the groove formation position is shifted, a bellows-like structure portion exists between the external connection electrode and the flexible element portion, and the stress transmission distance from the mounting substrate to the flexible element portion is long. Therefore, due to the difference in coefficient of linear expansion from the mounting substrate, Stress it is possible to further alleviate that.

Another invention is the invention of claim 1, wherein the first cover substrate is shifted in position so that the external connection electrode is positioned inside the second electrical connection metal layer. It is characterized by being.

  According to this invention, compared with the case where both the formation positions are shifted so that the external connection electrode is positioned outside the second electrical connection metal layer in the first cover substrate. The stress generated in the flexible element portion can be reduced, and the planar size of the semiconductor device can be reduced.

According to a second aspect of the present invention, in the first cover substrate of the first aspect, the external connection electrode is a solder reflow pad, and the solder reflow pad is formed around the solder reflow pad. A solder spread prevention portion made of a material having lower solder wettability is formed.

  According to this invention, when mounting on the mounting substrate by solder reflow, it is possible to prevent the solder from flowing out to the periphery of the external connection electrode, and to suppress an increase in stress due to an increase in the bonding area. it can.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the wiring for electrically connecting the external connection electrode and the through-hole wiring on the other surface side of the first cover substrate is the It is formed by avoiding the groove.

  According to this invention, the formation of the wiring on the other surface side of the first cover substrate is facilitated.

  According to the first aspect of the invention, there is an effect that the stress generated in the flexible element portion due to the difference in linear expansion coefficient from the mounting substrate can be further relaxed.

(Embodiment 1)
The semiconductor device of this embodiment will be described with reference to FIGS. 1 to 4. In this embodiment, the semiconductor device is mounted on a mounting substrate (for example, a glass epoxy resin substrate) 40 as shown in FIG. The acceleration sensor A to be used is exemplified.

  The acceleration sensor A is formed by using a first semiconductor substrate and has a sensor substrate 1 having a sensing unit described later, and a plurality of acceleration sensors A are formed by using a second semiconductor substrate and are electrically connected to the sensing unit of the sensor substrate 1. The first cover substrate 2 is formed using a first cover substrate 2 having a through-hole wiring 24 and bonded to one surface side (the lower surface side in FIG. 1) of the sensor substrate 1 and a third semiconductor substrate. And a second cover substrate 3 joined to one surface side (upper surface side in FIG. 1) of the first cover substrate 2 so as to surround the sensor substrate 1. Here, the outer peripheral shape of the sensor substrate 1 and each of the cover substrates 2 and 3 is a rectangular shape, and each of the cover substrates 2 and 3 is formed to have a larger outer dimension than the sensor substrate 1.

  Further, the sensor substrate 1 processes an SOI wafer having an n-type silicon layer (active layer) 10c on an insulating layer (buried oxide film) 10b made of a silicon oxide film on a support substrate 10a made of a silicon substrate. The first cover substrate 2 is formed by processing the first silicon wafer, and the second cover substrate 3 is formed by processing the second silicon wafer. 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. Yes. In the present embodiment, the surface of the silicon layer 10c that is the main surface of the SOI wafer is the (100) plane.

  As shown in FIGS. 1 and 3, the sensor substrate 1 includes a frame portion 11 (a rectangular frame shape in the present embodiment), and a weight portion 12 arranged inside the frame portion 11 is on one surface side. (On the upper surface side in FIG. 3B), the frame portion 11 is swingably supported via four flexible strip-shaped bending 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. In other words, each associated portion 12b is surrounded by the frame portion 11 and the core portion 12a and the two bent portions 13 and 13 extending in a direction orthogonal to each other in a plan view as viewed from the one surface side of the sensor substrate 1. The slits 14 are formed between each of the accompanying portions 12 b and the frame portion 11, and the interval between the adjacent accompanying portions 12 b across the bending portion 13 is larger than the width dimension of the bending portion 13. It is getting longer. Here, the core portion 12a is formed using the above-described SOI wafer support substrate 10a, the insulating layer 10b, and the silicon layer 10c, and each accompanying portion 12b is formed using the SOI wafer support substrate 10a. It is. Thus, the surface of each associated portion 12b on the one surface side of the sensor substrate 1 is separated from the plane including the surface of the core portion 12a to the other surface side (the lower surface side in FIG. 3B) of the sensor substrate 1. Is located. In addition, what is necessary is just to form the above-mentioned frame part 11, the weight part 12, and each bending part 13 of the sensor board | substrate 1 using a micromachining technique.

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

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

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

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

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

  Now, assuming that acceleration is applied to the sensor substrate 1 in the positive x-axis direction while no acceleration is applied to the sensor substrate 1, the frame portion 11 is caused by the inertial force of the weight 12 acting in the negative x-axis direction. Accordingly, the weight 12 is displaced, and as a result, the bending portions 13 and 13 whose longitudinal direction is the x-axis direction are bent, and the resistance values of the gauge resistors Rx1 to Rx4 formed in the bending portions 13 and 13 change. Will do. In this case, the gauge resistances Rx1 and Rx3 are subjected to tensile stress, and the gauge resistances Rx2 and Rx4 are subjected to compressive stress. In general, gauge resistance has a characteristic that resistance value (resistivity) increases when subjected to tensile stress, and resistance value (resistivity) decreases when subjected to compressive stress. As the value increases, the resistance values of the gauge resistors Rx2 and Rx4 decrease. Therefore, if a constant DC voltage is applied from the external power source between the pair of input terminals VDD and GND shown in FIG. 4, the potential difference between the output terminals X1 and X2 of the left bridge circuit Bx shown in FIG. It changes according to the magnitude of the acceleration in the x-axis direction. Similarly, when acceleration in the y-axis direction is applied, the potential difference between the output terminals Y1 and Y2 of the central bridge circuit By shown in FIG. 4 changes according to the magnitude of the acceleration in the y-axis direction, and the z-axis When the acceleration in the direction is applied, the potential difference between the output terminals Z1 and Z2 of the right bridge circuit Bz shown in FIG. 4 changes according to the magnitude of the acceleration in the z-axis direction. Thus, the above-described sensor substrate 1 detects the change in the output voltage of each of the bridge circuits Bx to Bz, so that the acceleration in the x-axis direction, the y-axis direction, and the z-axis direction that acted on the sensor substrate 1 is detected. Can be detected. In the present embodiment, each bending portion 13 constitutes a flexible element portion, and the sensor substrate 1 constitutes a functional substrate. Moreover, the weight part 12 and each bending part 13 comprise a movable part, and each gauge resistance (piezoresistor) Rx1-Rx4, Ry1-Ry4, Rz1-Rz4 each comprises the sensing part in the sensor board | substrate 1. FIG. .

  By the way, the sensor substrate 1 has two input terminals VDD and GND common to the above-described three bridge circuits Bx, By, and Bz, two output terminals X1 and X2 of the bridge circuit Bx, and two outputs of the bridge circuit By. Terminals Y1 and Y2 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, Z1 and Z2 The first metal layer 19 for electrical connection is provided on the front surface side (that is, the first cover substrate 2 side), and is electrically connected to the through-hole wiring 24 formed in the first cover substrate 2. Yes. That is, eight metal layers 19 for electrical connection are formed on the sensor substrate 1, and eight through-hole wirings 24 are formed on the first cover substrate 2. The eight first electrical connection metal layers 19 have a rectangular outer periphery shape (in this embodiment, a square shape), and are arranged apart from each other 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).

  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 the first metal layer 19 for electrical connection. The metal wiring is formed on the insulating film 16.

  The first electrical connection metal layer 19 has an adhesion improving Ti film interposed between the bonding Au film and the insulating film 16. In other words, the first metal layer 19 for electrical connection is composed of a laminated film of a Ti film formed on the insulating film 16 and an Au film formed on the Ti film. The first electrical connection metal layer 19 has a Ti film thickness set to 15 to 50 nm and an Au film thickness set to 500 nm. However, these values are only examples and are not particularly limited. Absent. Here, the material of the 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 adhesion layer between the Au film and the insulating film 16, but the material of the adhesion layer is not limited to Ti. For example, Cr, Nb, Zr, TiN, TaN, etc. may be used.

  The gauge resistances Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4 and the diffusion layer wirings described above are formed by doping p-type impurities with appropriate concentrations at the respective formation sites in the silicon layer 10c. The wiring is formed by patterning a metal film (for example, an Al film, an Al alloy film, etc.) formed on the insulating film 16 by sputtering or vapor deposition using lithography technology and etching technology. The metal wiring is electrically connected to the diffusion layer wiring through a contact hole provided in the insulating film 16.

  The first cover substrate 2 has a plurality of (in this embodiment, eight) through holes 22 penetrating in the thickness direction, and is thermally insulated across both surfaces in the thickness direction and the inner surface of each through hole 22. An insulating film 23 made of a film (silicon oxide film) is formed, and a part of the insulating film 23 is interposed between the through hole wiring 24 and the inner surface of the through hole 22. Here, the eight through-hole wirings 24 of the first cover substrate 2 are formed apart from each other in the circumferential direction of the first cover substrate 2. In addition, although Cu is employ | adopted as a material of the through-hole wiring 24, not only Cu but Ni etc. may be employ | adopted, for example.

  The first cover substrate 2 has a plurality (eight in this embodiment) of second electrodes electrically connected to each through-hole wiring 24 on one surface side (surface side on the sensor substrate 1 side). The metal layer 29 for electrical connection is formed. Here, in the first cover substrate 2, the outer peripheral shape of the second electrical connection metal layer 29 is rectangular (in this embodiment, a square shape), and the first electrical connection metal layer of the sensor substrate 1. 19 is arranged so as to be joined to and electrically connected.

  Here, in the second metal layer 29 for electrical connection, an adhesion improving Ti film is interposed between the bonding Au film and the insulating film 23. In other words, the second electrical connection metal layer 29 is composed of a laminated film of a Ti film formed on the insulating film 23 and an Au film formed on the Ti film. In the second electrical connection metal layer 29, the thickness of the Ti film is set to 15 to 50 nm and the thickness of the Au film is set to 500 nm. However, these numerical values are only examples and are not particularly limited. Absent. Further, the material of the Au film is not limited to pure gold and may be added with impurities. In this embodiment, a Ti film is interposed between the Au film and the insulating film 23 as an adhesive layer for improving adhesiveness. However, the material of the adhesive layer is not limited to Ti. For example, Cr, Nb, Zr, TiN, TaN, etc. may be used.

  The first cover substrate 2 has a plurality of external connection electrodes 25 electrically connected to the respective through-hole wirings 24 on the other surface side (surface side opposite to the sensor substrate 1 side). Has been. 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. In the present embodiment, the outer peripheral shape of each external connection electrode 25 is rectangular, and each external connection electrode 25 and each through-hole wiring 24 are electrically connected to the other surface side of the first cover substrate 2. A plurality of (eight in the present embodiment) wirings 26 are connected. Each wiring 26 is composed of a laminated film of a Ti film, a Cu film, a Ni film, and an Au film laminated in the thickness direction in the same manner as each external connection electrode 25. It is formed continuously. In the present embodiment, each external connection electrode 25 constitutes a solder reflow pad, and the size of each external connection electrode 25 does not fall below the size suitable for solder reflow (200 μm □ or more). The distance between adjacent external connection electrodes 25 is designed so as not to fall below a distance suitable for solder reflow.

  By the way, the sensor substrate 1 and the first cover substrate 2 in the acceleration sensor A of the present embodiment are the first electrical connection metal layer 19 of the sensor substrate 1 and the second electrical connection of the first cover substrate 2. The metal layer 29 is joined and electrically connected via a joint 9 made of Au bumps. In the present embodiment, the joint portion 9 between the sensor substrate 1 and the first cover substrate 2 is formed by Au bumps as described above, and the sensor substrate 1 and the first cover substrate 2 are in the temperature range of 30 ° C. to 400 ° C. However, the joining portion 9 may be formed by soldering and may be joined by solder reflow at a temperature of about 270 ° C.

  In the present embodiment, the distance between the movable portion of the sensor substrate 1 and the first cover substrate 2 can be controlled by the protruding height of the joint portion 9, and the movable portion toward the first cover substrate 2 can be controlled. A displacement space can be secured. In the acceleration sensor A of the present embodiment, the planar size of each of the cover substrates 2 and 3 is larger than the planar size of the sensor substrate 1, and the external connection electrode 25 of the first cover substrate 2 is connected to the sensor substrate 1. It is formed in a region that does not overlap the sensor substrate 1 in the peripheral portion of the surface opposite to the side. In short, in the acceleration sensor A of the present embodiment, the external connection electrode 25 of the first cover substrate 2 is formed outside the bonding region of the first cover substrate 2 with the sensor substrate 1.

The second cover substrate 3 is formed with an accommodation recess 32 for accommodating the sensor substrate 1 on the surface facing the first cover substrate 2, and the first cover substrate 2, the second cover substrate 3, The peripheral portions are joined over the entire circumference. Here, in the present embodiment, the first cover substrate 2 and the second cover substrate 3 are directly bonded at room temperature (for example, 30 ° C.) by a room temperature bonding method of a combination of Si—SiO ₂ . Alternatively, a sealing metal layer having an Au film may be formed on the surface sides of the peripheral portions of the two, and may be directly bonded by room temperature bonding using a combination of Au—Au. 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. Note that when the acceleration sensor A of the present embodiment is manufactured, the first cover substrate 2 and the second cover substrate 3 are bonded at the wafer level. In short, at the time of manufacturing the acceleration sensor A of the present embodiment, a large number of first cover substrates 2 are formed, and a large number of first silicon wafers and a large number of second cover substrates 3 formed by bonding a large number of chip-shaped sensor substrates 1 are formed. After the second silicon wafer is bonded to the wafer level, a dicing process of cutting into individual acceleration sensors A is performed.

  In the present embodiment, since the room temperature bonding method is employed as the bonding method between the first cover substrate 2 and the second cover substrate 3, the residual stress of the sensor substrate 1 can be reduced. Here, in the present embodiment, the sensor substrate 1 and the cover substrates 2 and 3 are made of Si, which is the same semiconductor material, so that the sensor substrate 1 and the cover substrates 2 and 3 are caused by a difference in linear expansion coefficient. Since the effect of the applied stress (residual stress in the sensor substrate 1) on the resistance values of the gauge resistors Rx1 to Rx4, Ry1 to Ry4, Rz1 to Rz4 can be reduced, When the cover substrates 2 and 3 are made of a material different from that of the sensor substrate 1, the variation in sensor characteristics can be reduced as compared with the case where the cover substrates 2 and 3 are made of different materials. 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 storage recess 32 of the second cover substrate 3 is formed by using a lithography technique and an etching technique. Here, in the present embodiment, the depth of the storage recess 32 is formed so that the displacement space of the weight portion 12 is formed between the inner bottom surface of the storage recess 32 in the second cover substrate 3 and the sensor substrate 1. The dimensions are set. In short, in the acceleration sensor A of the present embodiment, the sensor substrate 1 is flip-chip mounted on the first cover substrate 2 via the joint portion 9 made of Au bumps, and the first cover substrate 2 and the first cover substrate 2 A package is constituted by the second cover substrate 3 joined to the first cover substrate 2 so as to surround the sensor substrate 1 on the one surface side of the cover substrate 2.

  By the way, the above-mentioned first cover substrate 2 is a functional substrate including the second electrical connection metal layer 29 and the external connection electrode 25 electrically connected to the second electrical connection metal layer 29. Between the second electrical connection metal layer 29 and the external connection electrode 25 electrically connected to the second electrical connection metal layer 29, the sensor substrate 1 is shifted so as not to overlap in the thickness direction of the sensor substrate 1. In this region, the flexure which is a flexible element portion is produced by joining the external connection electrode 25 and the conductor pattern 43 of the mounting substrate 40 to the one surface side and the other surface side by the joint portion 50 made of solder. A groove portion 20b is formed to relieve stress generated in the portion 13. Here, the first cover substrate 2 includes a second electrical connection metal layer 29 and an external connection electrode 25 that are electrically connected to each other in the in-plane direction (left-right direction in FIG. 1). The formation positions of both are shifted so that the external connection electrode 25 is positioned outside the connection metal layer 29. The first cover substrate 2 includes a bellows-like structure portion between the second electrical connection metal layer 29 and the external connection electrode 25 electrically connected to the second electrical connection metal layer 29. The formation position of the groove portion 20b on the one surface side and the formation position of the groove portion 20b on the other surface side are shifted in the in-plane direction so that 28 is formed.

  The depth dimension of each of the groove portions 20b described above is set to be slightly larger than half the thickness dimension of the first cover substrate 2, but the groove portion 20b formed on the one surface side of the first cover substrate 2 is used. The depth dimension of the first cover substrate 2 does not necessarily have to be set to the same value as the depth dimension of the groove 20b formed on the other surface side, and the thickness dimension of the first cover substrate 2 is T1. If the depth dimension of the groove 20b formed on one surface is D1, and the depth dimension of the groove 20b formed on the other surface of the second cover substrate 2 is D2, the condition of T1 ≦ (D1 + D2) is satisfied. What is necessary is just to set suitably. Here, the groove 20b of the first cover substrate 2 may be formed using an anisotropic etching technique using, for example, an inductively coupled plasma (ICP) type dry etching apparatus. In the present embodiment, since the insulating film 23 is formed after the groove 20b is formed, a part of the insulating film 23 is also formed on the inner surface of the groove 20b.

  In the acceleration sensor A of the present embodiment, a part of the wiring 26 that electrically connects the external connection electrode 25 and the through-hole wiring 24 on the other surface side of the first cover substrate 2 is formed on the inner surface of the groove 20b. In the case where a part of the wiring 26 is formed along the inner surface of the groove portion 20b, it is desirable to adopt Cu as the material of the wiring 26 in the same manner as the through-hole wiring 24.

  In the acceleration sensor A of the present embodiment described above, the second electrical connection metal layer 29 of the first cover substrate 2 and the external connection electrode electrically connected to the second electrical connection metal layer 29. In the region between the first and second surfaces, the bending portion 13 which is a flexible element portion is generated on the one surface side and the other surface side as the external connection electrode 25 and the conductor pattern 43 of the mounting substrate 40 are joined. The bellows-like structure portion is formed between the second electrical connection metal layer 29 and the external connection electrode 25 electrically connected to the second electrical connection metal layer 29 in which a groove portion 20b for relaxing stress is formed. Since the formation position of the groove portion 20b on the one surface side and the formation position of the groove portion 20b on the other surface side are shifted so that 28 is formed, an accordion-like shape is formed between the external connection electrode 25 and the bending portion 13. The structure part 28 exists, Since the stress transmission distance from the mounting substrate 20 to the bent portion 13 becomes longer, the stress generated in the bent portion 13 due to the difference in linear expansion coefficient with the mounting substrate 40 can be further relaxed, and the characteristic deterioration (this embodiment) In the embodiment, deterioration of sensor characteristics) can be suppressed.

Further, the acceleration sensor A of the present embodiment is formed around the external connection electrode 25 by a material having lower solder wettability than the material of the external connection electrode 25 (for example, an insulating material such as SiO ₂ or resist). Since the solder spread prevention portion 27 made of an insulating film is formed, it is possible to prevent the solder from flowing out to the periphery of the external connection electrode 25 when mounting on the mounting substrate 40 by solder reflow. It is possible to suppress an increase in stress due to an increase in.

  In this embodiment, the joint portion 50 between the acceleration sensor A and the mounting substrate 40 is formed by solder. However, the joint portion 50 is not limited to solder, and may be formed by bumps such as Au bumps. When the portion 50 is formed of Au bumps, the size of each external connection electrode 25 can be reduced as compared with the case where the bonding portion 50 is formed of solder (for example, when formed by solder). Is preferably set to a size of 200 μm □ or more, but when formed by Au bumps, it can be set to a size of 100 μm □ or less). Here, the bonding temperature when the bonding portion 50 is formed of solder may be set to about 270 ° C., and the bonding temperature when the bonding portion 50 is formed of Au bumps may be set to about 100 to 400 ° C.

  In the present embodiment, the first cover substrate 2 is formed by processing the first silicon wafer, and the second cover substrate 3 is formed by processing the second silicon wafer. The cover substrates 2 and 3 are not limited to silicon wafers, and may be any substrate that has a small difference in linear expansion coefficient from the SOI wafer that is the basis of the sensor substrate 1. For example, a glass substrate such as Pyrex (registered trademark) or a ceramic substrate. (For example, an alumina ceramic substrate) may be employed.

(Embodiment 2)
The basic configuration of the acceleration sensor A of the present embodiment is substantially the same as that of the first embodiment. As shown in FIG. 5, the opening area gradually increases as the grooves 20b of the first cover substrate 2 move away from the inner bottom surface. The difference is that it is formed in a tapered shape, and the other configuration is the same as that of the first embodiment, so that the description thereof is omitted.

  Therefore, in the acceleration sensor A of the present embodiment, it is easy to form the wiring 26 that is partially formed along the groove 20b on the other surface side (the lower surface side in FIG. 5) of the first cover substrate 2. The disconnection of the wiring 26 is less likely to occur.

(Embodiment 3)
The basic configuration of the acceleration sensor A of the present embodiment is substantially the same as that of the first embodiment. As shown in FIG. 6, the second electrical connection metal layer 29 and the external connection electrode 25 are electrically connected to each other. The positions of the first cover substrate 2 are shifted so that the external connection electrode 25 is positioned on the inner side of the second electrical connection metal layer 29 in the in-plane direction of the first cover substrate 2 (left and right direction in FIG. 6). is there. The first cover substrate 2 includes a bellows-like structure portion between the second electrical connection metal layer 29 and the external connection electrode 25 electrically connected to the second electrical connection metal layer 29. The formation position of the groove portion 20b on the one surface side and the formation position of the groove portion 20b on the other surface side are shifted in the in-plane direction so that 28 is formed. Since other configurations are the same as those of the first embodiment, the description thereof is omitted.

  Thus, in the acceleration sensor A of the present embodiment, when the formation positions of both are shifted so that the external connection electrode 25 is positioned outside the second electrical connection metal layer 29 as in the first embodiment. Compared to the above, it is possible to reduce the stress generated in the flexible portion 13 (see FIG. 1), which is a flexible element portion, and to reduce the planar size of the acceleration sensor A (that is, to reduce the package size). ). In the acceleration sensor A of the present embodiment, each groove portion 20b may be formed in a tapered shape in which the opening area gradually increases as the distance from the inner bottom surface increases, as in the second embodiment.

(Embodiment 4)
The basic configuration of the acceleration sensor A of the present embodiment is substantially the same as that of the third embodiment, and as shown in FIG. 7, the wiring 26 electrically connected to the external connection electrode 25 is formed avoiding the groove 20b. The other configuration is the same as that of the third embodiment, and the description thereof is omitted.

  Therefore, in the acceleration sensor A of the present embodiment, the wiring 26 that is electrically connected to the external connection electrode 25 is formed so as to avoid the groove 20b, so that the formation of the wiring 26 is facilitated. The disconnection of the wiring 26 due to the difference in level can be prevented.

  In the acceleration sensor A of each of the above embodiments, each groove 20b is enriched with a low elastic material having a lower elastic modulus (Young's modulus) than Si, which is the material of the first cover substrate 2, thereby increasing the mechanical strength. While increasing, you may make it prevent the penetration | invasion of the foreign material to the groove part 20b.

As the above-mentioned low-elasticity material, a resin (for example, polyethylene) or a metal (for example, Au, Ag, Al, Zn, etc.) may be employed. When the resin is employed, a potting technique, a spin coating technique, etc. The groove portion 20b may be enriched by using a metal, and when a metal is used, the groove portion 20b may be enriched by using a plating method or a sputtering method. Here, if a resin is used as the low-elasticity material, the groove 20b can be easily enriched as compared with the case where a metal is used. Further, when the groove 20b is formed in a tapered shape as in the second embodiment, the groove 20b can be easily enriched. The Young's modulus of Si that is the material of the first cover substrate 2 is 130 GPa, whereas the Young's modulus of polyethylene, Au, Ag, Al, and Zn that can be used as the low-elasticity material is as follows. 7.6 × 10 ⁻¹ GPa, 78 GPa, 82.7 GPa, 70.3 GPa, and 108 GPa. Further, when alumina ceramic is employed as the material of the first cover substrate 2, a material having a lower elastic modulus than alumina ceramic may be employed as the above-described low elastic material, and the Young's modulus of alumina ceramic is 355 GPa. Since it is larger than the Young's modulus of Si, for example, it is possible to adopt metals such as Cu, Ni, Pt, and steel, and the choice of low-elasticity materials increases. The Young's modulus of Cu, Ni, Pt, and steel is 130 GPa, 199 GPa to 220 GPa, and 206 GPa, respectively.

  In each of the above-described embodiments, the piezoresistive acceleration sensor is exemplified as the semiconductor device. However, the technical idea of the present invention is not limited to the piezoresistive acceleration sensor, for example, a capacitive acceleration sensor or a gyro sensor, It can also be applied to pressure sensors, microactuators, microrelays, microvalves, etc.

It is a schematic sectional drawing which shows the state which mounted the acceleration sensor of Embodiment 1 on the mounting board | substrate. It is a principal part schematic sectional drawing which shows the state which mounted the acceleration sensor same as the above on the mounting substrate. The sensor board | substrate in an acceleration sensor same as the above is shown, (a) is a schematic plan view, (b) is a schematic sectional drawing. It is a circuit diagram of the sensor board | substrate in the acceleration sensor same as the above. It is a principal part schematic sectional drawing which shows the state which mounted the acceleration sensor of Embodiment 2 on the mounting board | substrate. It is a principal part schematic sectional drawing which shows the state which mounted the acceleration sensor of Embodiment 3 on the mounting board | substrate. It is a principal part schematic sectional drawing which shows the state which mounted the acceleration sensor of Embodiment 4 on the mounting board | substrate.

Explanation of symbols

A Acceleration sensor (semiconductor device)
1 Sensor board (functional board)
2 First cover substrate 3 Second cover substrate 9 Joining portion 13 Deflection portion (flexible element portion)
19 First metal layer for electrical connection 20b Groove 23 Insulating film 25 External connection electrode (pad for solder reflow)
26 Wiring 27 Solder spreading preventing portion 28 Bellows-like structure portion 29 Second metal layer for electrical connection 40 Mounting substrate 43 Conductor pattern 50 Joint portion

Claims (3)

  A functional substrate formed using a semiconductor substrate and having a thin flexible element portion, and a plurality of second electrical connection metals bonded to a plurality of first electrical connection metal layers of the functional substrate on one surface side A first cover substrate having a plurality of external connection electrodes electrically connected to each of the plurality of second electrical connection metal layers on the other surface side through through-hole wirings, A second cover substrate joined to the one surface side of the first cover substrate so as to surround the functional substrate with the cover substrate, and the first cover substrate is a second metal layer for electrical connection And the external connection electrode electrically connected to the second electrical connection metal layer are shifted so as not to overlap in the thickness direction of the functional board, and the second electrical connection metal layer and the second electrical connection metal layer Between the external connection electrode electrically connected to the metal layer for electrical connection In the region, a groove portion is formed on each of the one surface side and the other surface side to relieve stress generated in the flexible element portion due to the joining of the external connection electrode and the conductor pattern of the mounting substrate, and the second electric The position of the groove on the one surface side so as to form a bellows-like structure portion between the connection metal layer and the external connection electrode electrically connected to the second electrical connection metal layer, and A semiconductor device, wherein the position of the groove on the other surface side is shifted. The first cover substrate, prior Kigaibu a connection electrode pads for solder reflow, consists material of low solder wettability than the material of the solder reflow pad around the pad for solder reflow soldering spread prevention The semiconductor device according to claim 1, wherein a portion is formed . Claim 1, wherein the first of said cover board is connected to other surface side to the external connection electrode and said through-hole interconnection electrically wiring becomes been made form to avoid the groove Alternatively, the semiconductor device according to claim 2 .

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