JP2007266320A - Sensor module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor module wherein despite of having its circuit portion cooperating with its sensing portion, its mounting area can be reduced. <P>SOLUTION: In the sensor module, a sensor substrate 1 has a sensing portion Ds, and the sensor substrate 1 is interposed in a laminar way between an electrode forming substrate 2 having formed pad-electrodes 25 connected with external circuits and a circuit forming substrate 3 having a formed circuit portion Dc which has an integrated circuit. The sensor substrate 1, the electrode forming substrate 2, and the circuit forming substrate 3 are stuck to each other in a sealing way by joining to each other sealing metal layers 18, 28, 38, 48 which are formed respectively on their peripheral portions. In the sensor substrate 1 and the electrode forming substrate 2, through-hole wirings 24, 44 are so formed as to connect electrically with each other via the through-hole wirings 24, 44 the sensing portion Ds of the sensor substrate 1, the circuit portion Dc of the circuit forming substrate 3, and the pad electrodes 25 of the electrode forming substrate 2. The circuit portion Dc, the sensing portion Ds, and the through-hole wirings 24, 44 are sealed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sensor module including a sensor substrate having a sensing unit provided on a semiconductor substrate, a circuit unit that cooperates with the sensing unit is formed by an integrated circuit, and the sensing unit is housed in a package.

  Conventionally, as this type of sensor module, for example, a sensor substrate (sensor portion) in which a sensing portion and a circuit portion (electric circuit device) are formed on a semiconductor substrate, and a cover substrate (lid portion) that protects the sensing portion and the circuit portion, The thing of the structure which laminated | stacked this is known (for example, refer patent document 1).

  The sensor module described in Patent Document 1 illustrates an angular velocity sensor having a movable part, and a sensing unit for detecting the angular velocity and a circuit unit that cooperates with the sensing unit are formed on the sensor substrate. ing. In addition, a cover substrate provided separately from the sensor substrate is stacked on the sensor substrate, and through-hole wiring formed in the sensor substrate and the cover substrate is used for electrical connection between the metal coating layer provided on the cover substrate and the circuit portion. (Bridge connection part, penetration connection part) is used. A circuit portion (evaluation electronic device) is also formed on the cover substrate, and this circuit portion is connected to the metal coating layer. The through-hole wiring (bridge connection portion) formed in the sensor substrate and the through-hole wiring (through connection portion) formed in the cover substrate are joined to each other.

Further, in the configuration described in Patent Document 1, a contact pad structure is formed at a portion where the through-hole wiring is joined, and a ring-shaped joining portion (aluminum) is formed to surround the sensing portion and the contact pad structure to seal the internal space. Ring) is formed.
JP-T-2004-53727

  By the way, in the structure described in patent document 1, since the sensing part and the circuit part are formed in the sensor board | substrate 1, and the sensing part is restricted in order to ensure a desired sensitivity, since the minimum dimension is controlled, As the circuit scale increases, it is necessary to increase the area of the sensor substrate 1. That is, when a circuit unit is formed on the sensor substrate 1 in addition to the sensing unit, there arises a problem that the sensor substrate 1 is enlarged.

  The present invention has been made in view of the above-mentioned reasons, and the object thereof is to provide a circuit unit together with a sensing unit on a sensor substrate in the case where a sensing unit of the same size is provided while the circuit unit cooperates with the sensing unit. It is an object of the present invention to provide a sensor module capable of reducing the mounting area as compared with the conventional configuration provided with the portion.

  According to a first aspect of the present invention, there is provided a sensor substrate comprising a semiconductor substrate and having a sensing portion, a circuit forming substrate comprising a semiconductor substrate and comprising an integrated circuit cooperating with the sensing portion, and an external circuit comprising the semiconductor substrate. An electrode forming substrate in which electrodes to be connected are arranged on the outer surface of the laminate, and the circuit forming substrate is laminated on one surface of the sensor substrate with the circuit portion facing the sensing portion, and the electrode forming substrate on the other surface Each of the semiconductor substrates is hermetically sealed by joining the sealing portions formed over the entire circumference to the peripheral portion of the opposing surface of each semiconductor substrate. As a result, the sensing unit formed on the sensor substrate and the circuit unit formed on the circuit formation substrate are hermetically sealed, and the sensor substrate and the electrode formation substrate penetrate in the stacking direction of the laminate. A through-hole wiring is formed, and a circuit unit formed on the circuit-forming substrate and a sensing unit formed on the sensor substrate are electrically connected to the electrode formed on the electrode-forming substrate via the through-hole wiring, and The connection part to which the through-hole wiring is electrically connected is surrounded by a sealing part.

  According to this configuration, since the circuit formation substrate is formed separately from the sensor substrate, the area of the sensor substrate is reduced compared to the case where the circuit portion is formed around the sensing portion in the sensor substrate. The mounting area can be reduced. In addition, the sensor substrate, the circuit formation substrate, and the electrode formation substrate are hermetically sealed by the sealing portion, and the sensing portion, the circuit portion, and the portion connecting the through-hole wiring are sealed by the semiconductor substrate. In addition to preventing exposure to corrosive gas and increasing durability, it is not necessary to provide a separate package for sealing, which contributes to miniaturization. In addition, since the sensor substrate, the circuit formation substrate, and the electrode formation substrate are provided separately, the degree of freedom of the combination of the sensing unit, the circuit unit, and the electrode is high, and the configuration is suitable for high-mix low-volume production.

  By the way, even in the case where the circuit part is formed on the sensor substrate, since the substrates are arranged on both sides of the sensing substrate in order to protect the sensing part, the dimensions in the stacking direction of the laminate of the present invention are The configuration of the present invention is not different from the case where the circuit portion is formed, and the entire volume can be reduced by the amount that the circuit area is separated from the sensor substrate and the mounting area is reduced.

  According to a second aspect of the present invention, in the first aspect of the invention, the laminate is formed by separating and cutting the sensor substrate, the circuit forming substrate, and the electrode forming substrate after forming and bonding them at a wafer level. It is characterized by.

  According to this configuration, since the sensor substrate, the circuit forming substrate, and the electrode forming substrate are formed using the semiconductor wafer and separated after the bonding, a well-known technique for handling the semiconductor wafer can be adopted, and the sensor substrate and the circuit formation are formed. It is easy to align the substrate and the electrode forming substrate. In addition, dicing technology for cutting and separating the semiconductor wafer can be used for the separation, and the manufacturing is easy. Since the size after separation and cutting is very small, a small sensor module can be provided.

  In invention of Claim 3, in invention of Claim 1 or Claim 2, the junction which electrically connects the circuit part and the penetration hole wiring, and the junction which electrically connects the penetration hole wiring, The bonding for sealing the sealing portions is a normal temperature bonding between a metal layer and a metal layer, and the position and dimensions of the bonding portion are such that the electrical connection of the through-hole wiring is performed simultaneously when the sealing portions are bonded. Is set.

  According to this configuration, since the mechanical coupling, sealing, and electrical connection of the sensor substrate, the circuit forming substrate, and the electrode forming substrate are performed at the same time, the number of manufacturing steps is reduced. Moreover, it is only necessary to perform alignment accurately in the joining process, and manufacturing is easy because there are few management items.

  According to the configuration of the present invention, the circuit unit cooperating with the sensing unit of the sensor substrate is formed on the circuit forming substrate provided separately from the sensor substrate, and the electric circuit between the electrode provided on the electrode forming substrate and the circuit unit and the sensing unit is formed. Connection is performed by through-hole wiring provided in the sensor substrate and the electrode forming substrate, and therefore, compared with the case where the circuit portion is formed around the sensing portion in the sensor substrate, the area of the sensor substrate is reduced, and the sensor module There is an advantage that the mounting area can be reduced. In other words, by reducing the mounting area of the sensor module, the mounting space for other components on the mounting board can be expanded.

  Since the sensor substrate, the circuit forming substrate, and the electrode forming substrate are hermetically sealed by the sealing portion, the sensing portion, the circuit portion, and the through-hole wiring are hermetically sealed without providing a separate sealing package. It has the advantage that it can be reduced in size compared with the case where a package is provided separately.

  In the embodiment described below, an example in which an acceleration sensor using a piezoresistor is used for a sensing unit is shown. In this acceleration sensor, the support portion surrounds the mass body, and the support portion and the mass body are connected via a flexible bending portion extending from the mass body in all directions. Each flexure is provided with a strain gauge made of a piezoresistor. The stress generated in the flexure as the mass body is displaced is detected by the strain gauge, and the acceleration is detected using the resistance change of the strain gauge. . In addition, by arranging strain gauges in the flexures that extend in four directions from each mass body, two axes in directions orthogonal to each other in a plane including the four flexures, and perpendicular to these two axes Thus, it is possible to individually detect the acceleration in a total of three axes including one axis in the direction to be performed. However, the technical idea of the present invention is not limited to the case where the sensing unit constitutes an acceleration sensor, but can be applied as long as the sensing unit is sealed in the package. As this type of sensing unit, there is a gyro sensor in addition to an acceleration sensor. Further, the detection of the displacement of the mass body is not limited to the piezoresistor, and a configuration for detecting the change of the capacitance may be adopted. Moreover, a bending part is not limited to the structure extended in all directions from a mass body.

  As shown in FIG. 1, the sensor device of this embodiment includes a sensor substrate 1 made of a semiconductor substrate on which a sensing portion Ds is formed and a pad electrode 25 for connecting an external circuit on one surface in the thickness direction (upper surface in FIG. 1). The electrode forming substrate 2 made of a semiconductor substrate sealed on one surface in the thickness direction of the sensor substrate 1 (upper surface in FIG. 1) and sealed on the other surface in the thickness direction of the sensor substrate 1 (lower surface in FIG. 1) And a circuit forming substrate 3 made of a semiconductor substrate. That is, the sensor device is composed of a laminate of three semiconductor substrates. The sensor substrate 1, the electrode forming substrate 2, and the circuit forming substrate 3 have a rectangular outer shape (square in the illustrated example), and the electrode forming substrate 2 and the circuit forming substrate 3 have the same outer dimensions as the sensor substrate 1.

  The sensor substrate 1 is formed by processing an SOI wafer. The SOI wafer used here has a support substrate 10a made of a silicon substrate, and an n-type silicon layer is formed on one surface in the thickness direction of the support substrate 10a via an insulating layer 10b as a buried oxide film made of a silicon oxide film. An active layer 10c made of is formed. Further, 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 surface of the active layer 10c. Therefore, the surface of the active layer 10 c is covered with the insulating film 16. In the sensor substrate 1, an insulating film 43 similar to the insulating film 16 is also formed on the surface of the support substrate 10a (the lower surface in FIG. 1). The electrode forming substrate 2 and the circuit forming substrate 3 are formed by processing different silicon wafers. That is, an SOI wafer is used as the semiconductor substrate of the sensor substrate 1, and a silicon wafer is used as the semiconductor substrate of the electrode forming substrate 2 and the circuit forming substrate 3.

  When the dimension example in this embodiment is illustrated, the thickness dimension of the support substrate 10a in an SOI wafer is 300-500 micrometers, the thickness dimension of the insulating layer 10b is 0.3-1.5 micrometers, and the thickness dimension of the silicon layer 10c is 4-10 micrometers. To do. Moreover, the thickness dimension of the silicon wafer which forms the electrode formation board | substrate 2 shall be 200-300 micrometers, and the thickness dimension of the silicon wafer which forms the circuit formation board | substrate 3 shall be 100-300 micrometers. However, these numerical values are not intended to limit, but are values indicating a guide. The surface of the silicon layer 10c, which is one surface of the SOI wafer, is a (100) plane.

  As shown in FIG. 2, the sensor substrate 1 has a mass body 12 at the center of a support 11 having a frame shape (in the present embodiment, a rectangular frame shape) in a plan view (when viewed from a direction orthogonal to the thickness direction). It is formed in the shape provided with. That is, the mass body 12 is surrounded by the support portion 11. In the present embodiment, the center of the support portion 11 and the center of the mass body 12 substantially coincide with each other in plan view. The support portion 11 and the mass body 12 are connected by four flexure portions 13 extending from the mass body 12 in all directions.

  Each bending part 13 has the flexibility formed in strip shape. Each bending portion 13 is arranged on two straight lines that pass through the center of the mass body 12 and are orthogonal to each other in plan view. In other words, each of the two bent portions 13 is arranged on each straight line orthogonal to each other. With this configuration, the mass body 12 can be displaced with respect to the support portion 11. As shown in FIG. 3, the support portion 11 uses the entire support substrate 10a, insulating layer 10b, and active layer 10c of the SOI wafer, and the bending portion 13 removes the support substrate 10a and insulating layer 10b of the SOI wafer. Only the active layer 10c is used. Therefore, the bending portion 13 is formed to be sufficiently thin as compared with the support portion 11 and the mass body 12.

  The mass body 12 includes a core portion 12a that is coupled to the support portion 11 via four flexure portions 13, and four leaf portions 12b that are continuously and integrally connected to the core portion 12a. In the plan view, the mass body 12 is arranged so that one of the five squares is centered on the other square so as to be rotationally symmetric about four times, and the other is located at each corner of the central square. Are formed in a shape in which one corner of each square is overlapped. In the present embodiment, the portion corresponding to the square arranged at the center corresponds to the core portion 12a, and the portion of the other squares excluding the portion overlapping with the core portion 12a corresponds to the leaf portion 12b. In other words, the core portion 12a has a square shape in plan view, and the leaf portion 12b has a shape in which one corner portion of the square is cut out. The bending portion 13 is integrally continuous with the central portion of each side of the core portion 12a, and leaf portions 12b are provided on both sides in the width direction of each bending portion 13 (a direction orthogonal to the extending direction of the bending portion 13 in plan view). Be placed.

  Each leaf portion 12b is disposed in a space surrounded by the two bending portions 13 and the support portion 11 that are orthogonal to each other in plan view, and the sensor substrate 1 is interposed between each leaf portion 12b and the support portion 11, respectively. A slit 14 penetrating in the thickness direction is formed. Moreover, the bending part 13 and each leaf part 12b are spaced apart, and the space | interval of each pair of leaf part 12b arrange | positioned on both sides of the bending part 13 is larger than the width dimension of each bending part 13. FIG. In the mass body 12, the core portion 12a uses the entire support substrate 10a, insulating layer 10b, and active layer 10c of the SOI wafer, and the leaf portion 12b uses only the support substrate 10a.

  In addition, the support part 11, the mass body 12, and the bending part 13 in the sensor board | substrate 1 can be formed using the lithography technique and etching technique known as a manufacturing technique of a semiconductor device.

  By the way, since the illustrated example is a triaxial acceleration sensor, a direction in which acceleration is detected is defined. A direction orthogonal to the thickness direction of the sensor substrate 1 is defined as a z-axis direction, and a direction from the support substrate 10a toward the active layer 10c is defined as a positive direction. The surface of the active layer 10c is the xy plane, and the center position of the mass body 12 is the origin in the xy plane. The x-axis direction and the y-axis direction are directions in which the bending portion 13 extends from the core portion 12a, respectively, and define a positive direction in the right-handed system. For example, the right direction in FIG. 3 is the positive direction in the x-axis direction, and the upward direction is the positive direction in the y-axis direction. Therefore, the mass body 12 is supported by the two bent portions 13 in the x-axis direction disposed with the core portion 12a interposed therebetween and the two bent portions 13 in the y-axis direction disposed with the core portion 12a interposed therebetween. It is connected to the part 11.

  A pair of piezoresistors Rx2 is provided at one end on the core 12a side of the bending portion 13 that extends in the positive direction in the x-axis direction from the core 12a of the mass body 12 (rightward from the core 12a in FIG. 2). , Rx4, and one piezoresistor Rz2 is formed at one end on the support 11 side. Similarly, a pair of piezoresistors Rx1 is provided at one end on the core 12a side in the bending portion 13 that extends from the core 12a in the negative direction in the x-axis direction (leftward from the core 12a in FIG. 2). , Rx3, and one piezoresistor Rz3 is formed at one end on the support 11 side.

  A pair of piezoresistors Ry1 at one end on the core 12a side is attached to the bending portion 13 that is extended from the core 12a of the mass body 12 in the positive direction in the y-axis direction (upward from the core 12a in FIG. 2). , Ry3, and one piezoresistor Rz1 is formed at one end on the support 11 side. Similarly, the bending portion 13 extended from the core portion 12a in the negative direction in the y-axis direction (downward from the core portion 12a in FIG. 2) has a pair of piezoresistors Ry2 at one end on the core portion 12a side. , Ry4 are formed, and one piezoresistor Rz4 is formed at one end on the support portion 11 side.

  In the two flexures 13 extended in the x-axis direction, the four piezoresistors Rx1, Rx2, Rx3, and Rx4 formed at one end on the core 12a side are for detecting acceleration in the x-axis direction. It is formed in a region where stress generated in the bending portion 13 is concentrated when acceleration in the x-axis direction acts on the mass body 12. The piezoresistors Rx1, Rx2, Rx3, and Rx4 are formed in a rectangular shape whose longitudinal direction is the x-axis direction in plan view. These piezo resistors Rx1, Rx2, Rx3, and Rx4 are connected so as to constitute the leftmost bridge circuit Bx in FIG.

  In the two flexures 13 extended in the y-axis direction, four piezoresistors Ry1, Ry2, Ry3, and Ry4 formed at one end on the core 12a side detect acceleration in the y-axis direction. For this reason, it is formed in a region where stress generated in the bending portion 13 is concentrated when acceleration in the y-axis direction acts on the mass body 12. The piezoresistors Ry1, Ry2, Ry3, Ry4 are formed in a rectangular shape whose longitudinal direction is the y-axis direction in plan view. These piezoresistors Ry1, Ry2, Ry3, and Ry4 are connected to form a central bridge circuit By in FIG.

  In the four flexures 13, four piezoresistors Rz1, Rz2, Rz3, and Rz4 formed at one end on the support 11 side are formed to detect acceleration in the z-axis direction. The piezoresistors Rz1, Rz2, Rz3, and Rz4 are all formed in a rectangular shape whose longitudinal direction is the y-axis direction. That is, the longitudinal directions of the piezoresistors Rz1 and Rz4 formed in the two flexures 13 extended in the y-axis direction coincide with the extension direction of the flexure 13 and the two flexures extended in the x-axis direction. The longitudinal direction of the piezoresistors Rz2 and Rz3 formed on 13 is orthogonal to the extending direction of the flexure 13. These piezoresistors Rz1, Rz2, Rz3, and Rz4 are connected so as to constitute the rightmost bridge circuit Bz in FIG.

  For the connection of each of the piezoresistors Rx1, Rx2, Rx3, Rx4, Ry1, Ry2, Ry3, Ry4, Rz1, Rz2, Rz3, Rz4, a diffusion layer wiring or a metal wiring formed on the sensor substrate 1 is used.

  In the circuit configuration shown in FIG. 6, input terminals T1 and T2 for applying a voltage to the three bridge circuits Bx, By and Bz are connected in common, and each bridge circuit Bx, By and Bz has an individual output terminal X1. , X2, Y1, Y2, Z1, Z2 are provided. In the present embodiment, the voltage applied to the input terminals T1 and T2 is a DC voltage, the voltage VDD is applied to the input terminal T1, and the input terminal T2 is connected to the circuit ground GND. Therefore, the stress generated in the bending portion 13 due to the displacement of the mass body 12 is caused by the piezoresistors Rx1, Rx2, Rx3, Rx4, Ry1, Ry2, Ry3, Ry4, Rz1, Rz2, Rz3, and Rz4. In addition, it is converted into an electric quantity (voltage) by the bridges Bx, By, Bz and output.

  Hereinafter, an operation example of the sensor substrate 1 will be described. Assuming that acceleration is applied in the positive direction in the x-axis direction to the sensor substrate 1 from a state in which no acceleration is applied to the sensor substrate 1, the inertial force of the mass body 12 acting in the negative direction in the x-axis direction is used. The mass body 12 is displaced with respect to the support portion 11, and the two bending portions 13 extended in the x-axis direction from the core portion 12a are bent to form the piezoresistors Rx1, Rx2, Rx3 formed in the bending portion 13. The resistance value of Rx4 changes. At this time, the piezoresistors Rx1 and Rx3 are subjected to tensile stress, and the piezoresistors Rx2 and Rx4 are subjected to compressive stress. In general, when a piezoresistor is subjected to a tensile stress, its resistance value (resistivity) increases, and when it receives a compressive stress, its resistance value (resistivity) decreases. Therefore, when acceleration acts in the positive direction in the x-axis direction, the resistance values of the piezo resistors Rx1 and Rx3 increase, and the resistance values of the piezo resistors Rx2 and Rx4 decrease. By this operation, the potential difference between the output terminals X1 and X2 of the leftmost bridge circuit Bx in FIG. 6 changes according to the magnitude of the acceleration in the x-axis direction.

  Similarly, if the acceleration in the y-axis direction acts, the potential difference between the output terminals Y1 and Y2 of the center bridge circuit By in FIG. 6 changes according to the magnitude of the acceleration in the y-axis direction, and the acceleration in the z-axis direction. As a result, the potential difference between the output terminals Z1 and Z2 of the rightmost bridge circuit Bz in FIG. 6 changes according to the magnitude of acceleration in the z-axis direction.

  Therefore, by detecting the change in the output voltage of each bridge circuit Bx, By, Bz, the acceleration in the x-axis direction, the y-axis direction, and the z-axis direction acting on the sensor substrate 1 can be detected. In the present embodiment, the sensing body Ds is configured by the mass body 12, the four bending portions 13, and the piezoresistors Rx1, Rx2, Rx3, Rx4, Ry1, Ry2, Ry3, Ry4, Rz1, Rz2, Rz3, Rz4. .

  A sealing metal layer 18 and a connection metal layer 19 are formed on one surface of the sensor substrate 1 (upper surface in FIG. 1). The connecting metal layer 19 is a part of the metal wiring, and functions as a connecting part for connecting the sensing part Ds to an external circuit. FIG. 5 shows the vicinity of the connecting metal layer 19 in the metal wiring. Note that the illustration of the diffusion layer wiring is omitted.

  The sealing metal layer 18 is formed along the entire circumference of the outer peripheral edge of the sensor substrate 1 and surrounds the sensing part Ds. The connecting metal layer 19 is also disposed inside the sealing metal layer 18 in the support portion 11. The metal wiring including the connecting metal layer 19 and the sealing metal layer 18 are formed on the insulating film 16 covering the surface of the active layer 10c. Further, the sealing metal layer 18 and the connecting metal layer 19 are formed of the same metal material, and the sealing metal layer 18 and the connecting metal layer 19 are formed simultaneously and substantially in the same thickness. Can do.

  In the sensor substrate 1, the piezoresistors Rx1, Rx2, Rx3, Rx4, Ry1, Ry2, Ry3, Ry4, Rz1, Rz2, Rz3, Rz4 and the diffusion layer wiring are p-types with appropriate concentrations at respective formation sites in the active layer 10c. It is formed by doping impurities. Further, the metal wiring excluding the connection metal layer 19 is obtained by applying a lithography technique and an etching technique to a metal film (for example, an Al film, an Al—Si film, etc.) formed on the insulating film 16 by a sputtering method or a vapor deposition method. The metal wiring is electrically connected to the diffusion layer wiring through a contact hole provided in the insulating film 16.

  The sealing metal layer 18 and the connection metal layer 19 have a bonding Au film on the surface, and a Ti film for improving adhesion is interposed between the Au film and the insulating film 16. That is, the sealing metal layer 18 and the connection metal layer 19 are formed of a laminated film of a Ti film formed on the insulating film 16 and an Au film formed on the Ti film.

  The sealing metal layer 18 and the connection metal layer 19 have a Ti film thickness of 15 to 50 nm and an Au film thickness of 500 nm. The metal wiring film excluding the connection metal layer 19 The thickness is set to 1 μm. However, these numerical values are merely examples and are not intended to be limiting.

  Since the present embodiment is a triaxial acceleration sensor, it is desirable to provide a circuit unit Dc that cooperates with the sensing unit Ds. As the circuit unit Dc, a power supply circuit that applies a voltage to the input terminals T1 and T2 of the bridge circuits Bx, By, and Bz, and an output terminal X1, X2, Y2, Y2, Z1, and Z2 of the bridge circuits Bx, By, and Bz are connected. An amplifier circuit that amplifies the output voltage of the bridge circuits Bx, By, Bz is required, and the circuit portion Dc is formed as an integrated circuit.

  The circuit portion Dc is formed on a surface facing the sensor substrate 1 in the circuit forming substrate 3 stacked on the sensor substrate 1. The circuit forming substrate 3 is sealed to the surface opposite to the electrode forming substrate 2 in the thickness direction of the sensor substrate 1. Since the circuit forming substrate 3 faces the sensor substrate 1, the thickness dimension of the mass body 12 is the thickness of the support portion 11 in the thickness direction of the sensor substrate 1 in order to secure a space allowing the displacement of the mass body 12. It is slightly smaller than the dimensions. In other words, the thickness dimension of the mass body 12 is adjusted so that a gap is formed between the mass body 12 and the circuit formation substrate 3 when the circuit formation substrate 3 is stacked on the sensor substrate 1. Here, the dimension of the gap between the mass body 12 and the circuit forming substrate 3 is set to 5 to 10 μm, for example.

  The circuit part Dc and the sensing part Ds are electrically connected using a through-hole wiring 44 provided in the sensor substrate 1. A through hole 42 penetrating the front and back in the thickness direction is formed in the support portion 11 of the sensor substrate 1, and a part of the insulating film 43 described above is continuously formed on the inner peripheral surface of the through hole 42. The region surrounded by the insulating film 43 is filled with a metal that forms the through-hole wiring 44. The insulating film 43 formed on the inner peripheral surface of the through hole 42 continues to the insulating film 16. Further, one end (the upper end in FIG. 1) of the through-hole wiring 44 is connected to the connecting metal layer 19. The other end of the through-hole wiring 44 is connected to a connection metal layer 49 formed on the sensor substrate 1 on the surface facing the circuit formation substrate 3. On the surface of the sensor substrate 1 facing the circuit forming substrate 3, a sealing metal layer 48 is formed over the entire circumference of the peripheral portion surrounding the connection metal layer 49 and the sensing portion Ds (see FIG. 4).

  A connection metal layer 39 that is a terminal of the circuit portion Dc made of an integrated circuit is formed on the surface of the circuit formation substrate 3 facing the sensor substrate 1 so as to surround the connection metal layer 39 and the circuit portion Dc. A sealing metal layer 38 is formed over the entire circumference of the circuit forming substrate 3. The connecting metal layer 39 is formed in a part of the sensor substrate 1 facing the connecting metal layer 49, and the sealing metal layer 38 is formed in a part of the sensor substrate 1 facing the sealing metal layer 48. Therefore, when the sensor substrate 1 and the circuit forming substrate 3 are aligned, the sealing metal layer 48 is bonded to the sealing metal layer 38, and the connection metal layer 49 is bonded to the connection metal layer 39, the sensor The substrate 1 and the circuit forming substrate 3 are integrally coupled, and the circuit portion Dc is electrically connected to the connection metal layer 19 through the through-hole wiring 44.

  A part of the connecting metal layer 19 is connected to the sensing part Ds, but many connecting metal layers 19 are not connected to the sensing part Ds. The connection metal layer 19 connected to the sensing part Ds is connected to the circuit part Dc through the through-hole wiring 44.

  By the way, as shown in FIG. 1, the electrode forming substrate 2 has a displacement space for the mass body 12 and the bending portion 13 in the thickness direction of the sensor substrate 1 at the center of the surface facing the sensor substrate 1 (lower surface in FIG. 1). A displacement recess 21 is formed for ensuring the above (regulating the amount of displacement of the mass body 12). In addition, a sealing metal layer 28 is formed along the entire circumference of the outer peripheral edge of the electrode forming substrate 2 on the peripheral portion of the electrode forming substrate 2 facing the sensor substrate 1. The sealing metal layer 28 of the electrode forming substrate 2 is formed in a portion that overlaps the sealing metal layer 18 of the sensor substrate 1 when the electrode forming substrate 2 is superimposed on the sensor substrate 1. The metal layer 18 and the sealing metal layer 28 are bonded to each other so that the space between the sensor substrate 1 and the electrode forming substrate 2 is sealed.

  A plurality of through holes 22 penetrating in the thickness direction of the electrode forming substrate 2 are formed at appropriate positions on the surface of the electrode forming substrate 2 facing the sensor substrate 1. An insulating film 23 which is a silicon oxide film formed by thermal oxidation is continuously formed on both surfaces in the thickness direction of the electrode forming substrate 2 and the inner peripheral surface of the through hole 22. Further, a through-hole wiring 24 penetrating the front and back in the thickness direction of the electrode forming substrate 2 is formed in the through-hole 22. Therefore, a part of the insulating film 23 is interposed between the through-hole wiring 24 and the inner peripheral surface of the through-hole 22. The plurality of through-hole wirings 24 provided on the electrode forming substrate 2 are arranged apart from each other. As the material of the through-hole wirings 24 and 44, it is desirable to adopt Cu, but not limited to Cu, for example, Ni may be employed.

  A plurality of connecting metal layers 29 electrically connected to the respective through-hole wirings 24 are formed on a portion of the electrode-forming substrate 2 facing the sensor substrate 1 and surrounding the displacement recess 21, and are connected to each other. The metal layer 29 is disposed inside the sealing metal layer 28. The connection metal layer 29 is electrically connected to one end portion of the through-hole wiring 24 and is disposed so as to be joined to the connection metal layer 19 of the sensor substrate 1. The connecting metal layer 29 and the sealing metal layer 28 are formed of the same metal material, and the connecting metal layer 29 and the sealing metal layer 28 can be formed simultaneously and substantially in the same thickness. .

  The sealing metal layers 28, 38, and 48 and the connection metal layers 29, 39, and 49 include a bonding Au film on the surface, and a Ti for improving adhesion between the Au film and the insulating film 23. A membrane is interposed. That is, the sealing metal layers 28, 38, and 48 and the connection metal layers 29, 39, and 49 are respectively composed of a Ti film formed on the insulating films 23, 33, and 43 and an Au film formed on the Ti film. It is formed of a laminated film with a film.

  The sealing metal layers 28, 38, and 48 and the connecting metal layers 29, 39, and 49 have a Ti film thickness of 15 to 50 nm and an Au film thickness of 500 nm. However, these numerical values are merely examples and are not intended to be limiting.

  A solder reflow pad electrode 25 serving as an electrode for connection to an external circuit is formed on the surface of the electrode forming substrate 2 in the thickness direction opposite to the surface facing the sensor substrate 1. Each pad electrode 25 is electrically connected to the other end of each through-hole wiring 24. Each pad electrode 25 has a rectangular outer shape (for example, a square shape), and is arranged on the surface of the electrode forming substrate 2 at substantially equal intervals. The size of each pad electrode 25 and the distance between adjacent pad electrodes 25 are designed so as not to fall below a size suitable for solder reflow.

  Each pad electrode 25 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, and the uppermost layer is an Au film. Each pad electrode 25 is composed of at least two layers of metal films laminated in the thickness direction, and if the uppermost metal film is formed of Au and the metal film immediately below the uppermost layer is formed of Ni, Since the uppermost metal film is made of Au, oxidation can be prevented, and the metal film immediately below the uppermost layer is made of Ni, so that it can be compared with the case of being made of Cu. It becomes difficult to be eroded by the solder, and the film thickness can be reduced. Further, since the lowermost metal film in the thickness direction of each pad electrode 25 is formed of Ti, the adhesion between each pad electrode 25 and the insulating film 23 can be enhanced.

  As described above, in the present embodiment, the circuit forming substrate 3 including the circuit unit Dc is provided separately from the sensor substrate 1 including the sensing unit Ds, and the electrode forming substrate 2 and the circuit forming substrate 3 are provided on the front and back of the sensor substrate 1. The sensor substrate 1 is packaged with the electrode formation substrate 2 and the circuit formation substrate 3 by sealing the sensor substrate 1, the electrode formation substrate 2 and the circuit formation substrate 3 with a laminated body having a three-layer structure. ing. Further, since the circuit portion Dc is formed on the surface of the circuit forming substrate 3 facing the sensor substrate 1, the circuit portion Dc is also sealed.

  In manufacturing the acceleration sensor described above, an SOI wafer on which a large number of sensor substrates 1 are formed, a silicon wafer on which a large number of electrode forming substrates 2 are formed, a silicon wafer on which a large number of circuit forming substrates 3 are formed, After being bonded to each other at the wafer level, they are individually cut and separated by a dicing process. At the time of bonding at the wafer level, the sealing metal layer 18 and the connection metal layer 19 formed on the sensor substrate 1, and the sealing metal layer 28 and the connection metal layer 29 formed on the electrode forming substrate 2 are formed. The electrode forming substrate 2 is bonded to the sensor substrate 1 by being bonded to each other. Further, the sealing metal layer 48 and the connection metal layer 49 formed on the sensor substrate 1 and the sealing metal layer 38 and the connection metal layer 39 formed on the circuit forming substrate 3 are bonded to each other. The circuit forming substrate 3 is bonded to the sensor substrate 1. By adopting such a manufacturing process, the electrode forming substrate 2 and the circuit forming substrate 3 have the same outer dimensions as the sensor substrate 1, and a small chip size package can be easily manufactured.

  By the way, as a joining method of the sensor substrate 1, the electrode forming substrate 2, and the circuit forming substrate 3, it is desirable to reduce the residual stress of the sensor substrate 1 after joining. Therefore, it is desirable to employ a bonding method that enables bonding at a low temperature. Therefore, in the present embodiment, a metal layer-to-metal layer room temperature bonding method is employed.

  In the room temperature bonding method, each bonding surface is cleaned and activated by irradiating the bonding surfaces with argon plasma, ion beam or atomic beam in vacuum before bonding, and then the bonding surfaces are brought into contact with each other. And apply an appropriate load at room temperature. At this time, the sealing metal layers 18, 28, 38, and 48 are joined together, and at the same time, the connecting metal layers 19, 29, 39, and 49 are joined together.

  In the sensor device of the present embodiment, the bonding between the sensor substrate 1 and the electrode forming substrate 2 and the circuit forming substrate 3 is an Au—Au bonding. In the present embodiment, since the sensor substrate 1, the electrode formation substrate 2, and the circuit formation substrate 3 are formed of Si, which is the same semiconductor material, the sensor substrate 1, the electrode formation substrate 2, and the circuit formation substrate 3 It is possible to reduce the influence of stress (residual stress in the sensor substrate 1) caused by the difference in linear expansion coefficient on the outputs of the bridge circuits Bx, By, Bz. That is, as compared with the case where the electrode forming substrate 2 and the circuit forming substrate 3 are formed of a material different from that of the sensor substrate 1, variations in sensor characteristics among products can be reduced.

  Here, since the same metal material is used for each of the connecting metal layers 19, 29, 39, and 49 and the sealing metal layers 18, 28, 38, and 49 that are joined to each other, the connecting metal layers 19, 29 are used. , 39, 49 and the sealing metal layers 18, 28, 38, 48 can be performed at the same time, compared with a manufacturing method involving a step of supplying solder and a reflow step at each joint location. The manufacturing process can be greatly simplified, and the positional accuracy of the electrode forming substrate 2 in the thickness direction of the sensor substrate 1 can be increased. In the configuration example described above, an SOI wafer is used to form the sensor substrate 1, but this configuration is not essential, and a silicon wafer, for example, may be employed instead of the SOI wafer.

  In the acceleration sensor described above, since the pad electrode 25 is formed on the surface of the electrode forming substrate 2 opposite to the surface facing the sensor substrate 1, it can be mounted on the mounting substrate by solder reflow without using an interposer. Is possible.

It is a longitudinal cross-sectional view which shows embodiment. It is a top view of the sensor board | substrate used for the same as the above. It is sectional drawing of the AA 'line cross section in FIG. It is a principal part longitudinal cross-sectional view same as the above. It is a principal part longitudinal cross-sectional view same as the above. It is a circuit diagram same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor substrate 2 Electrode formation board 3 Circuit formation board 18 Metal layer for sealing (sealing part)
19 Metal layer for connection (connection part)
24 Through-hole wiring 25 Pad electrode 28 Metal layer for sealing (sealing part)
29. Metal layer for connection (connection part)
38 Metal layer for sealing (sealing part)
39 Metal layer for connection (connection part)
44 Through-hole wiring 48 Metal layer for sealing (sealing part)
49 Metal layer for connection (connection part)
Dc circuit part Ds sensing part

Claims (3)

  A sensor substrate comprising a semiconductor substrate and having a sensing portion, a circuit forming substrate comprising a semiconductor substrate and comprising a circuit portion comprising an integrated circuit cooperating with the sensing portion, and an electrode comprising a semiconductor substrate and connected to an external circuit. An electrode forming substrate arranged on the outer surface of the sensor substrate, the circuit forming substrate is laminated on one surface of the sensor substrate with the circuit portion facing the sensing portion, and the electrode forming substrate is laminated on the other surface. Each of the semiconductor substrates is hermetically sealed by bonding sealing portions formed over the entire circumference to the peripheral portion of the opposing surface of each semiconductor substrate. The sensing part formed on the circuit board and the circuit part formed on the circuit forming substrate are hermetically sealed, and the sensor substrate and the electrode forming substrate have through-hole wiring penetrating in the stacking direction of the stacked body. The circuit portion formed on the circuit forming substrate and the sensing portion formed on the sensor substrate are electrically connected to the electrode formed on the electrode forming substrate via the through hole wiring, and the through hole wiring is electrically connected. The sensor module is characterized in that the connection portion to be connected is surrounded by the sealing portion.   2. The sensor module according to claim 1, wherein the laminated body is formed by separating and cutting the sensor substrate, the circuit forming substrate, and the electrode forming substrate after forming and bonding them at a wafer level. .   The bonding for electrically connecting the circuit portion and the through-hole wiring, the bonding for electrically connecting the through-hole wiring, and the bonding for sealing the sealing portions are a metal layer to a metal layer. 3. The position and size of the joint portion are set so that the through-hole wiring is electrically connected at the same time when the sealing portion is joined. Sensor module.

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