WO2007061050A1 - Sensor device and method for manufacturing same - Google Patents

Abstract

Provided is a thin sensor device having a small sensor characteristic fluctuation. The sensor device includes a sensor unit having a supporting section, a movable section movably held to the supporting section and a detecting section for outputting an electric signal based on the positional displacement of the movable section. The sensor device also includes a base substrate bonded on the surface of the sensor unit. A conductor section is provided on the supporting section, and an electrode having a bump is arranged on the base substrate. The height of the bump is determined so that a distance between the movable section and the base substrate is equal to a distance specified by a dislocation quantity permitted by the movable section. Since the activating surface of the conductor section is directly bonded on the activating surface of the bump at a room temperature, the sensor characteristics are prevented from being fluctuated by residual stress on the bonding section.

Description

 Specification

 Sensor device and manufacturing method thereof

 Technical field

 The present invention relates to a small sensor device that outputs an electric signal based on a displacement of a movable part and a method for manufacturing the same.

 Background art

 [0002] Acceleration sensors and gyro sensors are widely known as sensor devices having a movable part. For example, JP 2005-169541 A discloses an acceleration sensor as shown in FIG. This acceleration sensor is formed on a semiconductor substrate and has a support part 111 having a connection part with an external circuit, a weight part 112 movable relative to the support part 111, a support part 111, and a weight part 112. And a greasing part 113 for connecting the two. The technology to convert acceleration (external force) acting on the weight 112 into an electric quantity is to change the acceleration by providing a strain gauge that also has a piezoresistive force that detects the stress generated in the stagnation portion 113 as the weight 112 is displaced. Is detected as a change in electric resistance, and the movable electrode provided on the weight part 112 and the fixed electrode fixed relative to the support part 111 are arranged so as to face each other. A configuration that detects a change in capacity is known.

 A circuit unit that cooperates with the sensor unit 101 that constitutes the acceleration sensor described above is formed as an integrated circuit on a circuit chip 104 that is different from the sensor unit 101. The sensor unit 101 and the circuit chip 104 are stacked in the thickness direction, and are electrically connected via a bonding wire 108. The sensor unit 101 and the circuit chip 104 are housed in a knocker made up of a substrate 105 and a case 106. An electrode (not shown) for connecting to an external circuit is formed on the substrate 105, and is electrically connected to the circuit chip 104 by a bonding wire.

[0004] By the way, in this type of sensor device, since the weight portion 112 functions as a movable portion when the stagnation portion 113 is displaced with respect to the support portion 111, the stagnation portion is not damaged by an impact force or the like. As described above, it is necessary to regulate the amount of displacement of the weight portion 112. For example, the downward displacement amount of the weight portion 112 is regulated by the substrate 105, and the upward displacement amount of the weight portion 112 is It is regulated by a circuit chip 104 that is stacked above the unit 101. However, when the strobe of the movable part is formed with such a configuration, there arises a problem that the sensor device becomes bulky. In particular, when a bonding wire is used for electrical connection between the circuit chip 104 and the sensor unit 101, or between the electrode provided on the substrate 105 and the circuit chip 104, the bonding wire 108 is disposed above the circuit chip 104. It is necessary to secure a space for the sensor device, and the thickness of the sensor device is further increased.

[0005] When a bonding method using heat treatment such as solder reflow is used to bond the sensor unit 101 and the substrate 105, the characteristics of the sensor mute vary depending on the residual stress in the bonded portion. May occur. Therefore, it is conceivable to reduce the influence of the residual stress by separating the sensing portion including the weight portion 112 and the stagnation portion 113, but as a result, the sensor device is increased in size. Therefore, in the field where further downsizing of the sensor device is required, another solution for reducing the effect of residual stress more effectively is desired.

 Disclosure of the invention

 [0006] Therefore, the present invention has been made in view of the above-described reasons, and an object of the present invention is to prevent variations in sensor characteristics by performing flip-chip mounting without causing residual stress in the joint. Another object of the present invention is to provide a thin sensor device which has a stagger function of a movable part and suppresses an increase in thickness dimension.

 That is, the sensor device of the present invention includes a support unit, a movable unit that is movably held with respect to the support unit, and a detection unit that outputs an electrical signal based on a positional displacement of the movable unit! A sensor unit including a base unit bonded to the sensor unit,

 The region bonded to the base substrate of the support portion includes a first conductor portion having an activated surface, and the region bonded to the support portion of the base substrate has a second conductor having an activated surface. Part

 The bonding between the sensor unit and the base substrate includes a solid-phase direct bonding that does not involve diffusion between the surfaces of the active conductors of the first conductor portion and the second conductor portion.

[0008] According to this configuration, the thickness of the first conductor portion and the second conductor portion is appropriately set. Thus, the base substrate to which the sensor unit is joined can function as a stagger that restricts the movement of the movable part. In other words, compared to the case where a separate stagger is provided, the height can be reduced by the amount that the stover is unnecessary. In addition, since the first conductor portion and the second conductor portion are directly bonded to the solid phase, it is possible to prevent variations in characteristics of the sensor device due to the residual stress of the bonded portion formed by heat treatment such as solder reflow. it can.

 As a particularly preferred embodiment of the present invention, the activation surface of the first conductor portion is an active surface of an electrode provided on the support portion or an activity of a bump having a desired height provided on the electrode. The activation surface of the second conductor portion is an activation surface of the electrode provided on the base substrate or an activation surface of a bump having a desired height provided on the electrode. In any case, the bonding between the sensor unit and the base substrate includes solid phase direct bonding without diffusion between the surfaces of the active layers in the presence of at least one of the bumps. In this case, it is possible to obtain a stagger function that regulates the amount of displacement of the movable part by appropriately determining the protruding dimension of the bump. Further, since the electrical connection between the sensor unit and the base substrate is formed by flip chip mounting using bumps instead of wire bonding, the sensor device can be further reduced in height.

 [0010] Further, in order to obtain good adhesion strength of the above-described solid-phase direct bonding, the activated surface is preferably any of a plasma-treated surface, an ion beam irradiation surface, and an atomic beam irradiation surface. In addition, when the solid phase direct bonding described above is a solid phase direct bonding between the active surfaces of the electrode and the bump, the electrode and the bump are formed of the same metal material, and the metal material includes gold, copper, and copper. It is desirable that the aluminum force is also selected. The activation surface of the first conductor portion is the surface of the bump provided on the electrode, and the activation surface of the second conductor portion is the surface of the bump provided on the electrode. In this case, it is preferable that both of the bumps are formed of the same metal material selected from gold, copper and aluminum force.

[0011] Further, a cover substrate having a recess for accommodating the sensor unit is further included, and the recess of the cover substrate is closed by the base substrate in a state where the sensor unit is accommodated therein, and the cover substrate and the base substrate The solid-state direct bonding without diffusion between the surface activation region provided on the cover substrate and the surface activation region provided on the base substrate. It is preferable. In particular, the surface activation region of the cover substrate is formed so as to surround the entire circumference of the recess, and the inside of the recess is predetermined by solid-phase direct bonding between the surface activation region of the cover substrate and the base substrate. It is preferable to be hermetically sealed so as to maintain the atmosphere.

 [0012] In order to obtain good airtightness by the above-described solid-phase direct bonding, the direct bonding between the surface activation region of the cover substrate and the surface activation region of the base substrate is performed by solid-phase direct bonding between Si and Si. Bonding, solid phase direct bonding between Si and SiO, or solid phase direct bonding between SiO and SiO

 2 2 2

 It is preferable that. Alternatively, direct bonding between the surface activation region of the cover substrate and the surface activation region of the base substrate can be achieved by solid phase direct bonding between Au and Au, solid phase direct bonding between Cu and Cu, or A1-A1. It is also preferable to use any of solid phase direct bonding between the two.

[0013] Further, in the above-described sensor device, it is preferable that an integrated circuit that cooperates with the detection unit is provided in the support unit of the sensor unit. In this case, the wiring between the sensing part including the movable part of the sensor unit and the integrated circuit is shortened compared to the case of using another semiconductor substrate for forming the circuit part, which is affected by noise. become. It is also effective in reducing the mounting area and reducing the height of the sensor device.

[0014] A further object of the present invention is to provide a method for manufacturing the sensor device described above.

 That is, this method includes a sensor unit including a support unit, a movable unit that is movably held with respect to the support unit, and a detection unit that outputs an electric signal based on a positional displacement of the movable unit, and a base Providing a substrate; and

 Forming a first conductor on the support of the sensor unit;

 Forming a second conductor on the base substrate;

 Performing a surface activation treatment in a reduced-pressure atmosphere to form activated surfaces on the first conductor portion and the second conductor portion; and

 After the surface activation treatment, the method includes a step of directly joining the activation conductor surfaces of the first conductor portion of the sensor unit and the second conductor portion of the base substrate at room temperature.

[0015] The active conductor surface of the first conductor portion may be either an active conductor surface of an electrode provided on the support portion or an active conductor surface of a bump having a desired height provided on the electrode. The active conductor surface of the second conductor portion is either an activation surface of an electrode provided on the base substrate or an active conductor surface of a bump having a desired height provided on the electrode. And In the bonding step between the sensor unit and the base substrate, it is preferable that the surfaces of the active electrodes are directly bonded at room temperature in the presence of at least one of the bumps. As described above, the electrical connection between the sensor unit and the base substrate can be formed by flip-chip mounting, and the amount of displacement of the movable part is regulated by appropriately determining the bump protrusion dimensions. A stagger function can be obtained.

 [0016] In addition, the manufacturing method includes a step of providing a cover substrate having a recess for accommodating the sensor unit, and a direct connection between the first conductor portion and the second conductor portion, and then the periphery of the recess of the cover substrate. It is preferable to further include a step of directly bonding the provided surface active region and the surface active region provided on the base substrate at room temperature to hermetically seal the sensor unit in the recess of the cover substrate. . In addition, the process of airtightly bonding the cover substrate and the base substrate is performed in the chamber. After adjusting the interior of the chamber to a desired atmosphere, the surface active region of the cover substrate and the base substrate is brought to room temperature. It is particularly preferred to join directly below.

 Brief Description of Drawings

FIG. 1 is a longitudinal sectional view of a sensor device according to a first embodiment of the present invention.

 FIG. 2 is a plan view of the sensor unit.

 FIG. 3 is an enlarged plan view of the main part of the sensor unit.

 4 is a cross-sectional view taken along line AA ′ in FIG.

 FIG. 5 is a cross-sectional view taken along the line B-A 'in FIG.

 FIG. 6 is a circuit diagram of the sensor unit.

 FIG. 7A is a plan view showing a bonding film provided on a cover substrate, and FIG. 7B is a plan view showing an insulating film provided on a base substrate.

 FIG. 8 is a longitudinal sectional view of a sensor device according to Embodiment 2 of the present invention.

 FIG. 9 is a schematic sectional view showing a conventional sensor device.

 BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a sensor device and a manufacturing method thereof according to the present invention will be described in detail based on preferred embodiments with reference to the accompanying drawings. In the following embodiments, the sensor unit is connected to the support unit by a knurled part extending from the weight part in four directions, and the weight part is changed. The case where an acceleration sensor that detects the stress of the stagnation part according to the position based on the change in resistance of a strain gauge, which is a piezoresistive body force provided in the stagnation part, will be described. It is not limited to sensors. For example, a structure may be employed in which the weight portion is connected to the support portion in the form of a cantilever or a double-supported beam by using a rubbing portion. Further, the detection of the displacement of the weight portion is not limited to the piezoresistor, and a configuration may be adopted in which detection is performed as a change in capacitance. Further, the sensor unit is not limited to the acceleration sensor, and other sensors such as a gyro sensor may be employed.

 (Embodiment 1)

 As shown in FIG. 1, the sensor device of the present embodiment includes a sensor unit 1 having a semiconductor substrate force on which a sensing unit Ds is formed, and a package in which the sensor unit 1 is housed. The package includes a nod electrode 25 for connecting an external circuit on the lower surface, and the base unit 2 on which the sensor unit 1 is mounted by flip chip mounting and the sensor unit 1 are accommodated between the base substrate 2 on the upper surface. And a cover substrate 3 sealed on the upper surface of the base substrate 2. Base substrate 2 and cover substrate 3 are formed of semiconductor substrates. The outer peripheral shape of the sensor unit 1 is a rectangular shape (square in the illustrated example).

 2 to 5 show the sensor unit 1 of the present embodiment. In FIG. 1, the sensor units shown in FIGS. 4 and 5 are drawn upside down. The sensor unit 1 is formed by caloring the SOI wafer. As shown in FIGS. 4 and 5, the SOI wafer used here has a support substrate 10a having a silicon substrate force, and is formed as a buried oxide film made of a silicon oxide film on the surface of the support substrate 10a. An active layer 10c made of an n-type silicon layer is formed through the insulating layer 10b. Further, in the sensor unit 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 10c is covered with the insulating film 16. The base substrate 2 and the cover substrate 3 are formed by covering different silicon wafers. That is, an SOI wafer is used as the semiconductor substrate of the sensor unit 1, and a silicon wafer is used as the semiconductor substrate of the base substrate 2 and the cover substrate 3.

In the present embodiment, the support substrate 10a has a thickness dimension of 300 to 500 / zm, the insulating layer 10b has a thickness dimension of 0.3 to 1.5 / zm, and the silicon layer 10c has a thickness dimension of 4 to 10 / zm. Also The thickness dimension of the silicon wafer forming the base substrate 2 is 200 to 300 μm, and the thickness dimension of the silicon wafer forming the cover substrate 3 is 100 to 300 μm. These numerical values are examples and do not limit the present invention. The surface of the silicon layer 10c is a (100) plane.

 As shown in the plan view of FIG. 2, the sensor unit 1 is formed in a shape having a weight portion 12 in an opening in the center of a frame-like (rectangular frame shape in this embodiment) support portion 11. The That is, the weight portion 12 is surrounded by the support portion 11. Further, the center of the support portion 11 and the center of the weight portion 12 are substantially coincident with each other. The support portion 11 and the weight portion 12 are connected to each other by four scooping portions 13 extending from the weight portion 12 in all directions.

 [0022] Each stagnation portion 13 is formed in a strip shape and has flexibility. Each stagnation portion 13 is arranged on two straight lines that pass through the center of the weight portion 12 and are orthogonal to each other in plan view. That is, each of the two stagnation portions 13 is arranged on each straight line orthogonal to each other. With this configuration, the weight portion 12 can be displaced with respect to the support portion 11. As shown in FIGS. 4 and 5, the support part 11 uses the entire support substrate 10a, insulating layer 10b, and active layer 10c of the SOI wafer, and the holding part 13 is the support substrate 10a and insulating layer 10b in the SOI wafer. And only the active layer 10c is used. Therefore, the stagnation part 13 is formed to be sufficiently thin compared to the support part 11 and the weight part 12.

[0023] The weight portion 12 includes a core portion 12a coupled to the support portion 11 via four stagnation portions 13, and four leaf portions 12b continuously and integrally connected to the core portion 12a. Prepare. In plan view, the weight part 12 is arranged so that one of the five squares is centered on the other square so that it is rotationally symmetrical four times around the square, and the other part is placed at each corner of the central square. It is formed in a shape where one corner of each square is overlapped. In the present embodiment, the portion corresponding to the square disposed 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 stagnation portion 13 is integrally continuous with the central portion of each side of the core portion 12a, and the width direction of each stagnation portion 13 (a direction orthogonal to the extending direction of the stagnation portion 13 in plan view). The leaf portions 12b are arranged on both sides of the frame. [0024] Each leaf portion 12b is disposed in a space surrounded by two stagnation portions 13 and a support portion 11 that are orthogonal to each other in plan view, and between each leaf portion 12b and the support portion 11, Each of the slits 14 is formed through the sensor unit 1 in the thickness direction. Further, the stagnation portion 13 and each leaf portion 12b are separated from each other, and the interval between each pair of leaf portions 12b arranged with the stagnation portion 13 interposed therebetween is larger than the width dimension of each stagnation portion 13. ing. In the weight portion 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. Note that the support portion 11, the weight portion 12, and the stagnation portion 13 in the sensor unit 1 can be formed using a lithography technique and an etching technique known as a semiconductor device manufacturing technique.

 Incidentally, since the illustrated example is a triaxial acceleration sensor, a direction in which acceleration is detected is defined. The direction orthogonal to the thickness direction of the sensor unit 1 is defined as the z-axis direction, and the direction of the support substrate 10a force on 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 weight portion 12 is the origin in the xy plane. The X-axis direction and the y-axis direction are directions in which the stagnation portion 13 extends from the core portion 12a. For example, the right direction in Fig. 2 is the positive direction in the X axis direction, and the upward direction is the positive direction in the y axis direction. Therefore, the weight part 12 includes two stagnation parts 13 in the X-axis direction arranged with the core part 12a interposed therebetween, and two stagnation parts 13 in the y-axis direction arranged with the core part 12a interposed therebetween. Thus, it is connected to the support part 11.

 [0026] The stagnation part 13 extending from the core part 12a of the weight part 12 in the positive direction in the X-axis direction (rightward from the core part 12a in FIG. 2) has two sets at one end on the core part 12a side. Piezoresistors Rx2 and Rx4 are formed, and one piezoresistor Rz2 is formed at one end on the support 11 side. Similarly, the stagnation portion 13 extending from the core portion 12a in the negative direction in the X-axis direction (leftward from the core portion 12a in FIG. 2) has two piezos at one end on the core portion 12a side. Resistors Rxl and Rx3 are formed, and one piezoresistor Rz3 is formed at one end on the support portion 11 side.

[0027] The squeeze portion 13 extended from the core portion 12a of the weight portion 12 in the positive direction in the y-axis direction (upward from the core portion 12a in FIG. 2) has two sets at one end on the core portion 12a side. Piezoresistors Ryl and Ry3 are formed, and one piezoresistor Rzl is formed at one end on the support 11 side. Similarly, it extends from the core portion 12a in the negative direction in the y-axis direction (downward from the core portion 12a in FIG. 2). A pair of piezoresistors Ry2 and Ry4 is formed at one end on the core 12a side, and one piezoresistor Rz4 is formed on one end on the support 11 side. .

[0028] In the two stagnation portions 13 extended in the X-axis direction, four piezoresistors Rxl, Rx2, Rx3, and Rx4 formed at one end portion on the core portion 12a side are accelerations in the x-axis direction. It is formed in a region where stress generated in the stagnation portion 13 is concentrated when acceleration in the X-axis direction acts on the weight portion 12. The piezoresistors Rxl, Rx2, Rx3, and Rx4 are formed in a rectangular shape whose longitudinal direction is the X-axis direction in plan view. These piezoresistors Rxl, Rx2, Rx3, and Rx4 are connected to form the leftmost bridge circuit Bx in FIG.

 [0029] In the two stagnation portions 13 extended in the y-axis direction, four piezoresistors Ryl, Ry2, Ry3, and Ry4 formed at one end portion on the core portion 12a side are in the y-axis direction. It is formed in a region where stress generated in the stagnation portion 13 is concentrated when acceleration in the y-axis direction acts on the weight portion 12. Piezoresistors Ryl, Ry2, Ry3, and Ry4 are formed in a rectangular shape whose longitudinal direction is the y-axis direction in plan view. These piezo resistances Ryl, Ry2, Ry3, and Ry4 are connected to form the central bridge circuit By in FIG.

 [0030] In the four stagnation sections 13, four piezoresistors Rzl, Rz2, Rz3, and Rz4 formed at one end on the support section 11 side are formed to detect acceleration in the z-axis direction. It has been done. Piezoresistors Rzl, Rz2, Rz3, and Rz4 are all formed in a rectangular shape whose longitudinal direction is the y-axis direction. In other words, the longitudinal direction of the piezoresistors Rzl and Rz4 formed in the two stagnation parts 13 extended in the y-axis direction coincides with the extension direction of the stagnation part 13, and two piezoresistors Rzl and Rz4 are extended in the X-axis direction. The longitudinal directions of the piezoresistors Rz2 and Rz3 formed in the stagnation portion 13 are orthogonal to the extending direction of the stagnation portion 13. These piezoresistors Rzl, Rz2, Rz3, and Rz4 are connected to form the rightmost bridge circuit Bz in FIG.

 [0031] For the connection of each of the piezoresistors Rxl to Rx4, Ryl to Ry4, and Rzl to Rz4, the diffusion layer wiring or metal wiring formed in the sensor unit 1 is used.

[0032] In the circuit configuration shown in FIG. 6, the input terminals Tl and Τ2 that apply voltage to the three bridge circuits Bx, By, and Bz are connected in common, and each bridge circuit Bx, By, and Bz is individually connected. Output terminal XI, X2, Yl, Y2, Zl, Z2 are provided. In this embodiment, the voltage applied to the input terminals Tl and Τ2 is a DC voltage, the voltage VDD is applied to the input terminal T1, and the input terminal Τ2 is connected to the circuit ground GND. Therefore, the stress generated in the stagnation part 13 due to the displacement of the weight part 12 is converted into an electric quantity (resistance value) by the piezo resistances Rxl to Rx4, Ryl to Ry4, Rzl to Rz4, and further, the bridge Bx, By , Converted into electricity (voltage) by Bz and output.

 Hereinafter, an operation example of the sensor unit 1 will be described. Now, assuming that acceleration is acting on sensor unit 1 in the positive direction in the X-axis direction even if the state force is not acting on sensor unit 1, the inertial force of weight 12 acting in the negative direction in X-axis direction Accordingly, the weight portion 12 is displaced with respect to the support portion 11, and the two stagnation portions 13 extending in the X-axis direction from the core portion 12a are squeezed and formed in the stagnation portion 13. The resistance value of Rx4 changes. At this time, the piezoresistors Rxl and Rx3 receive tensile stress, and the piezoresistors Rx2 and Rx4 receive compressive stress. In general, a piezoresistor increases in resistance (resistivity) when subjected to tensile stress and decreases in resistance (resistivity) when subjected to compressive stress. Therefore, when the acceleration acts in the positive direction along the X axis, the resistance values of the piezo resistors Rxl and Rx3 increase, and the resistance values of the piezo resistors Rx2 and Rx4 decrease. This action changes the potential difference between the output terminals XI and X2 of the leftmost bridge circuit Bx in Fig. 6 according to the magnitude of acceleration in the X-axis direction.

 [0034] Similarly, if acceleration in the y-axis direction is applied, the potential difference between the output terminals Yl and ブ リ ッ ジ 2 of the bridge circuit By in the center of Fig. 6 changes according to the magnitude of the acceleration in the z-axis direction. If this acceleration acts, 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 the acceleration in the z-axis direction.

 [0035] Therefore, by detecting the change in the output voltage of each bridge circuit Bx, By, Bz, respectively, it is possible to detect the acceleration in the X axis direction, the y axis direction, and the z axis direction that acted on the sensor unit 1. it can. In this embodiment, the weight part 12, the four stagnation parts 13, and the piezoresistors Rxl to Rx4, Ryl to Ry4, and Rzl to Rz4 constitute a sensing part Ds.

An electrode 19 is formed on the lower surface of the sensor unit 1 shown in FIG. The electrode 19 is a part of the metal wiring formed on the sensor unit 1 and functions as a connection part for connecting the sensor unit 1 to an external circuit. Note that the illustration of the diffusion layer wiring is omitted. Electrode 19 The included metal wiring is formed on the insulating film 16 covering the surface of the active layer 10c.

[0037] In the sensor unit 1, the piezoresistors Rxl to Rx4, Ryl to Ry4, Rzl to Rz4, and the diffusion layer wiring are formed by doping p-type impurities with appropriate concentrations at respective formation sites in the active layer 10c. . In addition, the metal wiring excluding the electrode 19 is obtained by applying a metal film (for example, A1 film, Al-Si 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.

 Since this embodiment is a triaxial acceleration sensor, a circuit unit Dc that cooperates with the sensing unit Ds is provided. The circuit part Dc includes the power supply circuit that applies voltage to the input terminals Tl and Τ2 of the bridge circuit Bx, By, and Bz, and the output terminals XI, X2, Yl, Υ2, Zl, and Ζ2 of the bridge circuit Bx, By, and Bz. An amplifier circuit that amplifies the output voltage of the bridge circuits Βχ, By, and Bz is required, and the circuit part Dc is formed as an integrated circuit. In the present embodiment, the circuit unit Dc is formed in the sensor unit 1 so as to surround the sensing unit Ds. That is, the circuit portion Dc is formed as an integrated circuit on the surface of the support portion 11 (the lower surface in FIG. 1). Therefore, the electrodes 19 described above are arranged around the circuit portion Dc as shown in FIG.

 The electrode 19 includes an 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 electrode 19 is formed of a laminated film of a Ti film formed on the insulating film 16 and an Au film formed on the Ti film. In this embodiment, the thickness of the Ti film is set to 15 to 50 nm, the thickness of the Au film is set to 500 nm, and the thickness of the metal wiring excluding the electrode 19 is set to: m. However, these numerical values are examples and do not limit the present invention.

As shown in FIG. 1, the base substrate 2 has a plurality of bumps 21 protruding from the upper surface, which is the surface facing the sensor unit 1, to be bonded to the electrodes 19 provided on the sensor unit 1. The A plurality of through holes 22 penetrating the front and back in the thickness direction are formed at portions corresponding to the bumps 21 of the base substrate 2. 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 base substrate 2 and the inner peripheral surface of the through hole 22. Further, the through hole 22 penetrates through the front and back of the base substrate 2 in the thickness direction. 4 is formed. 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 in the base substrate 2 are arranged apart from each other. Au is used for the material of the bump 21. Further, although it is desirable to use Cu as the material of the through-hole wiring 24, it is not limited to Cu, and for example, Ni may be used.

[0041] The sensor unit 1 described above is flip-chip mounted on the base substrate 2 using the bumps 21. The protruding dimension of the bump 21 ensures a displacement space of the weight portion 12 and the stagnation portion 13 in the thickness direction of the sensor unit 1 in a state in which the sensor unit 1 is bonded to the base substrate 2 (of the weight portion 12). The amount of displacement is regulated). As a result, a space allowing the displacement of the movable part composed of the weight part 12 and the stagnation part 13 can be secured between the sensor unit 1 and the base substrate 2, and the weight part 12 when an impact force or the like is applied. The base substrate 2 can function as a stagger that regulates the amount of displacement.

 A further feature of the present embodiment is that the sensor unit 1 and the base substrate 2 are joined by solid phase direct joining without diffusion through the bumps 21. As a result, the residual stress in the sensor unit 1 after joining can be reduced, and as a result, the variation in sensor characteristics can be reduced. As described later, this solid-phase direct bonding is obtained by directly bonding the active surface of the electrode 19 and the active surface of the bump 21 at room temperature.

On the lower surface of the base substrate 2 opposite to the surface facing the sensor unit 1, a solder reflow pad electrode 25 serving as an electrode for connection with an external circuit is formed. Each pad electrode 25 is electrically connected to the other end of each through-hole wiring 24. Each pad electrode 25 has a rectangular shape (for example, a square shape) and is disposed on the surface of the base substrate 2 so as to be spaced 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.

[0044] 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 the uppermost metal film is formed of Au and the metal film immediately below the uppermost layer is formed of Ni. The top gold Oxidation can be prevented by forming the metal film with Au. In addition, since the metal film immediately below the uppermost layer is made of Ni, it becomes less eroded by the solder than when it is made of Cu, and the film thickness can be reduced. Furthermore, 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.

 The cover substrate 3 is sealed to the surface on which the sensor unit 1 of the base substrate 2 is mounted.

 In the cover substrate 3, a storage recess 31 is formed on the surface facing the base substrate 2 in order to form a storage space for storing the sensor unit 1 between the cover substrate 3 and the base substrate 2. The base substrate 2 and the cover substrate 3 are hermetically bonded to the base substrate 2 over the entire circumference of the recess 31 with the same outer dimensions in plan view. Here, a bonding film 32, which is a silicon oxide film, is formed at a portion of the cover substrate 3 to be bonded to the base substrate 2.

 It should be noted that the depth of the storage recess 31 of the cover substrate 3 is between the inner bottom surface of the storage recess 31 and the weight portion 12 provided in the sensor unit 1 in a state where the cover substrate 3 is joined to the base substrate 2. In addition, a gap that allows the displacement of the weight portion 12 is designed. As a result, when an acceleration that causes a displacement exceeding the dimension of the gap acts on the weight portion 12, the weight portion 12 contacts the cover substrate 3, so that the cover substrate 3 has an upper weight portion in FIG. It functions as a stagger that regulates the amount of displacement of 12. As an example, the dimension of the gap between the weight portion 12 and the cover substrate 3 is set to 5 to: LO m, for example. The thickness dimension of the weight portion 12 may be adjusted in order to secure a gap between the inner bottom surface of the storage recess 31 and the weight portion 12.

 [0047] Another feature of the present embodiment is that the base substrate 2 and the cover substrate 3 are bonded by solid-phase direct bonding without diffusion. Thereby, the residual stress at the joint can be reduced, and the inside of the recess 31 in which the sensor unit 1 is housed can be hermetically sealed in a desired atmosphere. In this solid phase direct bonding, as described later, the active surface of the bonding film 32 provided on the cover substrate 3 and the active surface of the insulating film 23 provided on the base substrate 2 are directly bonded at room temperature. Is obtained.

[0048] Next, a method for manufacturing the above-described acceleration sensor device will be described in detail. First, an SOI wafer on which a large number of sensor units 1 are formed is cut and separated to form individual sensor units 1, and through-hole wiring 24 and bumps 21 are formed on the silicon wafer on which the base substrate 2 is formed. Then, each sensor unit 1 is flip-chip mounted on a portion of the silicon wafer corresponding to each base substrate 2.

 Here, since the electrode 19 and the bump 21 of the sensor unit 1 are each formed of Au, Au—Au direct solid phase bonding can be obtained by room temperature bump bonding. The materials that make up the electrodes 19 and bumps 21 are Au, Cu, Cu-Cu solid phase direct bonding, or A1, Al—A1 solid phase direct bonding. May be formed. The electrode 19 and the bump 21 are irradiated with argon plasma, ion beam, or atomic beam in vacuum before bonding, so that each bonded surface is cleaned and activated. The force between the active electrode surfaces of the electrode 19 and the bump 21 obtained as described above is solid-phase bonded at room temperature while applying an appropriate load.

 [0050] Instead of directly bonding between the electrode 19 and the bump 21, a bump may be provided on the electrode 19 of the sensor unit 1 and the active surfaces of the bump and the bump 21 may be directly bonded to each other. . In this case, both bumps are made of the same metal material selected from gold, copper and aluminum forces. Further, a desired distance can be obtained between the sensor cut 1 and the base substrate 2 by appropriately setting the projecting dimensions of both bumps.

 [0051] Next, a silicon wafer on which a large number of sensor units 1 are flip-chip mounted and a silicon wafer on which a large number of cover substrates 3 are formed are bonded to each other at the wafer level to produce a wafer level package structure. If the obtained wafer level package structure is cut and separated individually by dicing, a plurality of sensor devices can be efficiently manufactured. During bonding at the wafer level, it is preferable to solid-phase bond the activated surfaces of the insulating film 23 formed on the base substrate 2 and the bonding film 32 formed on the cover substrate 3 at room temperature.

 In the present embodiment, the insulating film 2 made of SiO is the same as the active surface of the bonding film 32 made of SiO.

 twenty two

 Solid-state direct bonding between SiO and SiO is obtained by bonding at room temperature to the active surface of 3

 twenty two

 However, solid-state direct bonding between Si and Si and direct solid-phase bonding between Si and SiO

2 The first substrate 2 may be bonded to the cover substrate 3. Similarly to the bonding between the electrodes 19 and the bumps 21 described above, the base substrate 2 can be bonded to the cover substrate 3 by metal-metal room temperature bonding. That is, joining each of the cover substrate and the base substrate If a metal layer composed of any of Au, Cu, and Al is provided at the site, and after performing the surface activation treatment described above, bonding at room temperature can be achieved by direct solid-state bonding between Au and Au, and between Cu and Cu. The base substrate 2 can be bonded to the cover substrate 3 by either solid phase direct bonding or solid phase direct bonding between A1 and A1. If the space in which the sensor unit 1 is stored is kept in a reduced-pressure atmosphere, solid-phase direct bonding between SiO and SiO, which has a high sealing effect with the outside, is also possible.

 twenty two

 In particular, it is particularly preferable to employ solid-phase direct bonding between Si and Si.

[0053] When adjusting the space in which the sensor unit 1 is accommodated to a desired atmosphere, the cover substrate 3 and the base substrate 2 are arranged in the chamber 1 and a predetermined surface activation process is performed. The inside of the chamber may be adjusted to a predetermined atmosphere, and then the room temperature bonding process may be performed. Note that after the surface activation treatment is performed, the cover substrate 3 and the base substrate 2 are bonded at room temperature without being exposed to the outside air. The viewpoint power for preventing the decrease in the thickness is also particularly preferable. If the sensor unit is an acceleration sensor, it is preferable to place the inside of the chamber in an inert gas atmosphere and then hermetically seal it by room temperature bonding. If the sensor unit 1 is a gyro sensor, the inside of the chamber is surface activated. It is preferable to adjust the atmosphere so that the degree of vacuum is higher than that during the air treatment, and then perform hermetic sealing by ordinary temperature bonding.

Further, as shown in FIG. 7A, the bonding film 32 of the cover substrate 3 includes an annular external bonding film 32a formed so as to surround the recess 31 of the cover substrate 3 over the entire circumference, and external bonding. The inner side of the film 32a may be constituted by an annular inner bonding film 32b formed so as to surround the recess 31 over the entire circumference. In this case, also in the base substrate 2, as shown in FIG. 7B, at the position facing the bonding film 32, the annular outer insulating film 23a and the inner insulating film 23b formed inside the outer insulating film 23a However, as shown in FIG. 1, it may be bonded to an insulating film 23 formed uniformly on the upper surface of the base substrate 2. Thus, in the case where a double bonded portion is provided between the bonding film 32 and the insulating film 23, the reliability of the hermetic sealing of the sensor unit can be further enhanced.

In FIG. 7A, reference numeral 35 denotes an auxiliary sealing layer provided so as to connect the outer bonding film 32a and the inner bonding film 32b. The auxiliary sealing layer 35 is a cover substrate. In the circumferential direction of the three concave portions 31, a plurality of them are arranged at a predetermined distance. As shown in Fig. 7 (B), the base An auxiliary sealing layer 28 is also provided on the substrate 2 at a position corresponding to the auxiliary sealing layer 35 of the cover substrate 3. When the base substrate 2 and the cover substrate 3 are joined, these auxiliary sealing layers (35 28) The active surfaces of 28) are also directly bonded to the solid phase.

[0056] When such an auxiliary sealing layer (35, 28) is provided, the following effects can be expected. In other words, due to the foreign matter existing on the outer bonding film 32a, the airtightness is reduced in the bonding of the outer bonding film 32a and the outer insulating film 23a, and the foreign matter existing on the inner bonding film 32b. When the airtightness is lowered in the bonding between the bonding film 32b and the internal insulating film 23b, it becomes difficult to hermetically seal the inside of the recess 31 of the cover substrate. However, by providing bonding between the auxiliary sealing layers (35, 28), a plurality of airtight spaces are formed between the outer bonding film 32a and the inner bonding film 32b, and the presence of foreign matter is reduced. If they are separated, the airtightness of the bonding between the external bonding film 32a and the external insulating film 23a is reduced, and the airtightness of the bonding between the internal bonding film 32b and the internal insulating film 23b is reduced. The area can be spatially blocked. In short, the airtightness obtained by joining between the cover substrate 3 and the base substrate 2 can be made more reliable by joining the auxiliary sealing layers (35, 28).

 [0057] By adopting such a manufacturing process, the base substrate 2 and the sensor unit 1 are connected without using a bonding wire, and the force also restricts the amount of displacement of the movable part provided in the sensor unit 1. Since there is no need to provide a separate stopper, the height dimension of the package composed of the base substrate 2 and the cover substrate 3 (dimension in the thickness direction of the sensor device) ) Can be reduced.

 In the present embodiment, since the sensor unit 1, the base substrate 2, and the cover substrate 3 are formed of Si, which is the same semiconductor material, the sensor unit 1, the base substrate 2, the cover substrate 3, and the like. Can reduce the effect of stress (residual stress in sensor unit 1) on the output of the bridge circuit Bx, By, Bz due to the difference in linear expansion coefficient. That is, as compared with the case where the base substrate 2 and the cover substrate 3 are formed of a material different from that of the sensor unit 1, variations in sensor characteristics for each product can be reduced.

[0059] In the configuration example described above, the force of using an SOI wafer to form the sensor unit 1 is described. For example, a silicon wafer may be used instead of the SOI wafer, which is not essential. Further, by using the pad electrode 25 provided on the surface of the base substrate 2, it is possible to mount it on the mounting substrate by solder reflow without using an interposer.

 (Embodiment 2)

 In the first embodiment, an example in which the circuit unit Dc is formed together with the sensing unit Ds in the sensor unit 1 is shown, but in this embodiment, only the sensing unit Ds is formed in the sensor unit 1 as shown in FIG. An example in which the circuit part Dc is formed on the circuit chip 4 provided separately from the sensor unit 1 is shown. The circuit chip 4 is housed in a package formed by the base substrate 2 and the cover substrate 3 together with the sensor unit 1.

 The circuit chip 4 includes an electrode 41 having the same configuration as the electrode 19 formed on the sensor unit 1 in the first embodiment. A connection pattern made of a metal layer 26 is formed on the surface on which the sensor cut 1 is mounted on the base substrate 2, and the sensor unit 1 and the circuit chip 4 are electrically connected via the connection pattern.

 On the other hand, the through-hole wiring 24 is formed at a site where the circuit chip 4 is mounted. In the present embodiment, in the portion where the circuit chip 4 is mounted on the base substrate 2, the metal layer 26 is formed in the portion corresponding to each electrode 41, and the metal layer 26 and the electrode 41 are connected to the first embodiment. Similarly, bonding is performed by metal-metal bonding at room temperature. In other words, before the bonding, the metal layer 26 and the electrode 41 are irradiated with argon plasma, ion beam or atomic beam in vacuum to perform cleaning and activation of each bonding surface, and then the metal layer 26 and the electrode 41. The layer 26 and the electrode 41 are brought into contact with each other and bonded directly at room temperature while applying an appropriate load. As a result, solid phase direct bonding without diffusion between the metal layer 26 and the electrode 41 can be obtained. In this way, the electrode of the circuit chip 4 is electrically connected to the pad electrode 25 via the metal layer 26 and the through-hole wiring 24.

 [0062] If necessary, bumps may be formed between the metal layer 26 and the electrode 41, and flip chip mounting may be performed in the same manner as in the first embodiment. In this case, a desired distance can be obtained between the circuit chip 4 and the base substrate 2 by appropriately setting the protruding dimension of the bump provided between the metal layer 26 and the electrode 41.

[0063] In this embodiment, the mounting area is larger than that in the first embodiment. 4 is separated from the sensor unit 1, it is possible to form sensor devices having different specifications by combining the sensor unit 1 and the circuit chip 4. Other configurations and operations are the same as those in the first embodiment.

 Industrial applicability

As is clear from the above embodiment force, the active surface of the conductor provided on the sensor unit and the active surface of the bump provided on the base substrate are bonded by solid phase direct bonding without diffusion. By joining, it is possible to prevent variations in sensor characteristics caused by residual stress in the joint. This effect is particularly important in a sensor unit having a movable part such as an acceleration sensor or a gyro sensor. In addition, by appropriately determining the height of the bump, the area of the substrate that faces the movable part functions as a strobe of the movable part. The advantage is that it becomes possible.

 As described above, the present invention capable of providing a thin sensor device with small variations in sensor characteristics is expected to be widely used in fields where further downsizing of the sensor device is required.

Claims

The scope of the claims  [1] A sensor unit including a support unit, a movable unit that is movably held with respect to the support unit, and a detection unit that outputs an electric signal based on a positional displacement of the movable unit, and the sensor unit. A sensor device including a base substrate,  The region bonded to the base substrate of the support portion includes a first conductor portion having an activated surface, and the region bonded to the support portion of the base substrate has a second conductor having an activated surface. Part  The sensor device is characterized in that the bonding between the sensor unit and the base substrate includes a solid-phase direct bonding that does not involve diffusion between the surfaces of the active conductors of the first conductor portion and the second conductor portion. .  [2] The active conductor surface of the first conductor portion is either an active conductor surface of an electrode provided on the support portion or an activated surface of a bump having a desired height provided on the electrode. The active conductor surface of the second conductor portion is either an active conductor surface of an electrode provided on the base substrate or an activated surface of a bump having a desired height provided on the electrode. The bonding between the sensor unit and the base substrate includes solid phase direct bonding without diffusion between the surfaces of the active layers in the presence of at least one of the bumps. The sensor device according to 1.  [3] The height of the at least one bump is determined such that a distance between the movable part and the base substrate is a distance defined by a displacement amount allowed for the movable part. The sensor device according to claim 2.  [4] The base substrate has through-hole wiring, and the activation surface of the second conductor portion is an active surface of a bump formed on one end of the through-hole wiring. Item 1. The sensor device according to Item 1.  [5] The sensor device according to [1], wherein the activated surface is any one of a plasma processing surface, an ion beam irradiation surface, and an atomic beam irradiation surface.  6. The sensor device according to claim 2, wherein the electrode and the bump are made of the same metal material, and the metal material is selected from gold, copper and aluminum force. [7] The active surface of the first conductor portion is an active surface of a bump provided on the electrode, The active conductor surface of the second conductor portion is the active conductor surface of a bump provided on the electrode, and both of the bumps are formed of the same metal material selected from gold, copper and aluminum force. The sensor device according to claim 2.  [8] Further comprising a cover substrate having a recess for accommodating the sensor unit, the recess of the force bar substrate is closed by the base substrate in a state where the sensor unit is accommodated therein, and the cover substrate and The bonding between the base substrate and the base substrate is a solid phase direct bonding without diffusion between the surface active region provided on the cover substrate and the surface active region provided on the base substrate. The sensor device according to claim 1.  [9] The bonding between the surface active region of the cover substrate and the surface active region of the base substrate includes solid phase direct bonding between Si and Si, solid phase direct bonding between Si and SiO, Or SiO- SiO  9. The sensor device according to claim 8, wherein the sensor device is one of solid-phase direct bonding between 2 2. 2 [10] Bonding between the surface active region of the cover substrate and the surface active region of the base substrate includes solid phase direct bonding between Au and Au, solid phase direct bonding between Cu and Cu, 9. The sensor device according to claim 8, wherein the sensor device is any one of solid-phase direct bonding between Al—A1.  [11] The surface activation region of the cover substrate is formed so as to surround the entire periphery of the concave portion, and is formed in the concave portion by solid-phase direct bonding between the cover substrate and the surface active region of the base substrate. 9. The sensor device according to claim 8, wherein the sensor device is hermetically sealed so as to be maintained in a predetermined atmosphere.  12. The sensor device according to claim 1, wherein the support unit of the sensor unit is provided with an integrated circuit that cooperates with the detection unit.  [13] Provided is a sensor unit including a support unit, a movable unit held movably with respect to the support unit, and a detection unit that outputs an electric signal based on a positional displacement of the movable unit, and a base substrate Process,  Forming a first conductor portion on a support portion of the sensor unit;  Forming a second conductor portion on the base substrate; Performing a surface activation treatment in a reduced-pressure atmosphere to form activated surfaces on the first conductor portion and the second conductor portion; and A sensor device comprising: a step of directly joining the active conductor surfaces of the first conductor portion of the sensor unit and the second conductor portion of the base substrate to each other at room temperature after the surface active solder treatment. Production method.  [14] The active conductor surface of the first conductor portion is either an active conductor surface of an electrode provided on the support portion or an activated surface of a bump having a desired height provided on the electrode. The active conductor surface of the second conductor portion is either an active conductor surface of an electrode provided on the base substrate or an activated surface of a bump having a desired height provided on the electrode. The bonding step between the sensor unit and the base substrate is performed by directly bonding the active surfaces to each other at room temperature in the presence of at least one of the bumps. Manufacturing method.  15. The method according to claim 13, wherein the surface active treatment is performed using an inert gas plasma, an ion beam, or an atomic beam.  [16] A step of providing a cover substrate having a recess for accommodating the sensor unit, and a surface provided around the recess of the cover substrate after directly joining the first conductor portion and the second conductor portion. And a step of directly joining the active active regions and the surface active regions provided on the base substrate at room temperature to hermetically seal the sensor unit in the recess. Item 14. The manufacturing method according to Item 13.  [17] The bonding process of the cover substrate and the base substrate is performed in a chamber. After adjusting the chamber to a desired atmosphere, the surface activation regions of the cover substrate and the base substrate are directly connected to each other at room temperature. The manufacturing method according to claim 16, wherein bonding is performed.