JP2006250550A - Sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor which receives little effects from thermal stress, is excellent in detection accuracy, and has high productivity. <P>SOLUTION: In the rectangular sensor chip 111, since only one side of an inner frame 117A of a frame constituting the four sides of the sensor chip 111 is bonded and fixed to a substrate, and the remaining three sides of the sensor chip 111 freely move off the substrate, stress which occurs due to contraction of an adhesive 121 when set and to the difference between the coefficients of linear expansion of the substrate 112 and the sensor chip 111 is reduced. Since electric pads 122 for output provided for the sensor chip 111 are mounted onto the substrate 112 and the fixed frame 117A, the bonding strength of wires is not weakened at wire bonding. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sensor, and more particularly to a sensor having a structure that can reduce the influence of thermal stress.

  FIG. 24 is a schematic cross-sectional view of a conventional acceleration sensor 11. The acceleration sensor 11 includes a sensor chip 12, a substrate 13, and a cover 14. The cover 14 is fixed to the substrate 13 so as to cover the sensor chip 12, and isolates the sensor chip 12 from the outside. Yes. In the sensor chip 12, a frame 15 is installed around the weight 17, and a plurality of beams 16 are provided so as to connect the weight 17 and the frame 15. Further, the beam 16 is provided with a piezoresistor 18 made of a semiconductor resistance element. When the weight 17 is displaced by the acceleration and the beam 16 is bent, a stress acts on the piezoresistor 18 to change the resistance value. Therefore, the acceleration for each axis can be detected by converting the change in resistance value into the change in output voltage. The sensor chip 12 is fixed by bonding the entire frame 15 to the substrate 13 with an adhesive 19. The sensor chip 12 is provided with an electrode pad 20 electrically connected to the piezoresistor 18, and is electrically connected to an electrode pad 21 provided on the substrate 13 with a wire 22.

  However, in the conventional acceleration sensor 11, the entire frame 15 is bonded and restrained by the adhesive 19 to the substrate 13, so that it occurs due to a change in environmental temperature between the substrate 13 and the sensor chip 12 having different linear expansion coefficients. The stress also acts on the beam 16 due to factors other than the detection target (acceleration) such as the stress to be generated and the stress generated by the curing shrinkage of the adhesive, resulting in fluctuations in the zero point output value and reduction in detection accuracy. It was.

As a method for reducing the influence of stress generated by changes in environmental temperature and curing shrinkage of the adhesive, the invention described in Patent Document 1 proposes an adhesive area, an adhesive position, and an adhesive composition. Specifically, in the bonding of the sensor chip and the substrate, the bonding area is reduced so that the bonding strength can be obtained, and the bonding position is bonded so that the stress is applied evenly so that the substrate surface is symmetrical. Further, it is described that an adhesive having a low elastic modulus is used as the adhesive. However, when bonding is performed so that the bonding positions are symmetrical in this way, the relative displacement due to thermal deformation or the like between the sensor chip and the substrate remains the same, and output fluctuation due to stress still increases. In addition, when bonding with an adhesive having a low elastic modulus as described above, the beam is greatly shaken due to ultrasonic vibration when the wire is connected to the sensor chip by wire bonding, and the beam is bent or the wiring on the beam is deformed. There was a problem that damage such as the above was likely to occur and the yield decreased. As a workaround, if the energy of ultrasonic vibration at the time of wire bonding is reduced, there is a problem that the fixing strength of the wire is lowered.
JP 2004-212246 A

  The present invention has been made in view of the above technical problems, and an object of the present invention is to provide a sensor that is less affected by thermal stress and has good detection accuracy and high productivity. .

  The sensor according to the present invention is a sensor in which a sensor chip is mounted on the surface of a substrate, and when a plane parallel to the mounting surface of the sensor chip is divided into two areas by a straight line passing through the center of the sensor chip, A region where the sensor chip is fixed to the substrate belongs to only one of the areas divided by the straight line.

  In the sensor of the present invention, since at least one half is not bonded to the substrate, the side that is not bonded to the substrate is shifted, and this occurs due to the difference in linear expansion between the sensor chip and the substrate and the curing shrinkage of the adhesive as the environmental temperature changes. To relieve stress. Further, unnecessary stress is not transmitted to the detection unit of the sensor, and fluctuations in characteristics such as detection accuracy due to the stress can be suppressed. Further, the center of the sensor chip can be the center of gravity of the sensor chip as viewed from above, or the intersection when a perpendicular line is drawn from the center of weight of the sensor chip to the upper surface of the sensor chip.

  According to the embodiment of the sensor of the present invention, the sensor chip is a polygon having four or more sides when viewed from the vertical upper side, and only the whole or a part of one side of the outer peripheral area of the lower surface thereof. It is fixed to the substrate.

  In the embodiment of the present invention, only one side of the sensor chip is bonded and fixed to the substrate, and the remaining side can move freely away from the substrate. Therefore, the stress can be relieved by moving the remaining side.

  According to another embodiment of the sensor of the present invention, when the sensor chip is viewed from vertically above, the signal extraction electrode provided on the upper surface of the sensor chip has two areas separated by the straight line. Of these, the sensor chip belongs to the same area as the area to which the fixed area of the sensor chip belongs.

  According to still another embodiment of the sensor of the present invention, the signal extraction electrode provided on the upper surface of the sensor chip is located directly above the fixed region of the sensor chip. Yes.

  In the embodiment of the present invention, the portion immediately below or near the signal extraction electrode provided on the sensor chip is fixed to the substrate, so that the wire (wiring) is fixed when the wire (wiring) is connected to the signal extraction electrode by wire bonding. Insufficient strength is unlikely to occur.

  Another embodiment of the sensor according to the present invention is characterized in that a stopper component is provided to prevent an area other than the fixed area of the sensor chip from rising above a predetermined distance from the substrate.

  In the embodiment of the present invention, the distance by which the sensor chip can be moved in the direction perpendicular to the substrate surface of the substrate is limited by the stopper component, so even if a strong impact is applied due to dropping or the like, the sensor chip is more than necessary. The region that is not bonded to the substrate does not float above the substrate by a predetermined distance, and the sensor chip is not easily damaged.

  According to still another embodiment of the sensor of the present invention, a region other than the fixed region of the sensor chip and the substrate are connected by a dummy wire.

  In the embodiment of the present invention, since the dummy wire is provided in an area other than the sensor chip fixing area, even when a strong impact is applied due to dropping or the like, the dummy wire is not adhered to the sensor chip substrate due to elasticity. The region is less likely to lift from the substrate, and the sensor chip can be prevented from being damaged. Further, if the upper part of the dummy wire is in contact with the inner surface of the cover that covers the sensor chip, the dummy wire is applied to the sensor chip side by the cover, so that it is more difficult to lift.

According to another embodiment of the sensor of the present invention, a sensor having a sensor chip mounted on the surface of a substrate,
When a surface parallel to the mounting surface of the sensor chip is divided into two areas by a certain straight line passing through the center of the sensor chip, a part or the whole of one of the areas divided by the straight line is bonded with high hardness. It is characterized in that it is fixed to the substrate with an agent, and a part or the whole of the other area is fixed using a flexible adhesive.

  In the embodiment of the present invention, all or a part of the region other than the region bonded to the substrate with the adhesive having high hardness of the sensor chip is bonded to the substrate with a flexible adhesive, so that a strong impact is caused by dropping or the like. Even when the sensor chip is added, the sensor chip is not lifted from the substrate more than necessary, and the sensor chip is hardly damaged. In addition, the stress generated by changes in environmental temperature and curing shrinkage of the adhesive can be relaxed by the deformation of the flexible adhesive, so that the stress is not transmitted to the sensor's detector, and the detection accuracy caused by it Variations in characteristics such as can be suppressed.

  According to another embodiment of the sensor according to the present invention, the sensor chip is a polygon having four or more sides when viewed from vertically above, and the whole or a part of one side of the outer peripheral area of the lower surface thereof. Only the substrate is bonded to the substrate with a high-hardness adhesive, and a part or the whole of the other region is bonded to the substrate with a soft adhesive.

  In the embodiment of the present invention, the remaining side other than the one side bonded and fixed to the substrate with the adhesive having high hardness of the sensor chip is fixed with the flexible adhesive, so that the flexible adhesive is deformed. Stress can be relaxed.

  According to another embodiment of the sensor of the present invention, when the sensor chip is viewed from vertically above, the signal extraction electrode provided on the upper surface of the sensor chip has two areas separated by the straight line. Of these, the sensor chip belongs to the same area as the area to which the area bonded with the high-hardness adhesive belongs.

  According to another embodiment of the sensor of the present invention, the signal extraction electrode provided on the upper surface of the sensor chip is located directly above the region of the sensor chip bonded with the high-hardness adhesive. It is characterized by having.

  In the embodiment of the present invention, the signal extraction electrode provided on the sensor chip is fixed to the substrate with a high-hardness adhesive directly under or near the signal extraction electrode, so that the wire (wiring) is connected to the signal extraction electrode by wire bonding. When it is connected to the cable, it becomes difficult to cause a bad fixing strength.

  According to another embodiment of the sensor of the present invention, the sensor according to any one of claims 1 to 10 and a sensor for detecting acceleration, wherein the sensor is movable according to a change in external force. A sensor chip having a portion, a stationary member, an elastic support portion for supporting the movable portion on the stationary member, a measuring means for measuring a displacement amount of the elastic support member, and mounting the sensor chip It is characterized by comprising a fixed substrate.

  In the embodiment of the present invention, since the influence of the deformation of the substrate due to the change of the environmental temperature or the warpage of the substrate is difficult to be transmitted to the sensor chip, it is difficult to be influenced by the external stress other than the detection target, and the acceleration is detected with high accuracy. Can be measured.

  In addition, the component demonstrated above of this invention can be combined arbitrarily as much as possible.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, it goes without saying that the present invention is not limited to the examples described below.

  FIG. 1 shows a schematic cross section of an acceleration sensor 101 according to an embodiment of the present invention. The acceleration sensor 101 includes a substrate 112, a sensor chip 111 fixed on the substrate 112, and a cover 113. The sensor chip 111 is fixed to the substrate 112 and is housed in a space formed by the substrate 112 and the cover 113 to be isolated from the outside.

  FIG. 2 is a plan view of the sensor chip 111, and FIG. 3 is a schematic sectional view of the sensor chip. In the sensor chip 111, a movable member 119 is located at the center of frames 117A to 117H (stationary members), and the frames 117A, 117C, 117E, 117G and the movable member 119 have four beams 118A having flexibility. Connected by ~ 118D. That is, the movable member 119 is supported by the frames 117A, 117C, 117E, and 117G by the beams 118A to 118D, and the weight 120 is provided on the lower surface thereof. The sensor chip 111 has a two-layer structure of a glass substrate 115 and a silicon substrate 114. The frames 117A to 117H are constituted by two layers of a glass substrate 115 and a silicon substrate 114, the movable member 119 and the beams 118A to 118D are formed by the silicon substrate 114, and the weight 120 separates a part of the glass substrate 115 from the frame portion. And is fixed to the movable member 119. The frames 117A to 117H are separated from each other at the glass substrate 115 and are connected at the silicon substrate 114.

  The four beams 118A to 118D are arranged in a cross shape in a plane parallel to the upper surface of the movable member 119. The direction parallel to the pair of beams 118A and 118C is referred to as the X-axis direction, and the other pair of beams 118B. , 118D is referred to as a Y-axis direction, and a direction perpendicular to these beams 118A to 118D is referred to as a Z-axis direction. Piezoresistors Rx1, Rx2, Rz1, and Rz2 made of a semiconductor resistance element according to the present invention are formed on the upper surface of one beam 118A extending in the X-axis direction. Here, the piezo resistors Rx1 and Rz1 are arranged in parallel at the end portion of the beam 118A on the frame 117A side, and the piezo resistors Rx2 and Rz2 are arranged in parallel on the end portion of the beam 118A on the movable member 119 side. Similarly, piezoresistors Rx3, Rx4, Rz3, and Rz4 made of the semiconductor element according to the present invention are formed on the upper surface of the other beam 118C extending in the X-axis direction. Piezoresistors Rx3 and Rz3 are arranged in parallel at the end of the beam 118C on the movable member 119 side, and piezoresistors Rx4 and Rz4 are arranged in parallel at the end of the beam 118C on the frame 117E side. Piezoresistors Ry1 and Ry2 made of the semiconductor resistance element according to the present invention are formed on the upper surface of one beam 118B extending in the Y-axis direction. The piezoresistor Ry1 is an end of the beam 118B on the frame 117C side. The piezoresistor Ry2 is disposed at the end of the beam 118B on the movable member 119 side. Similarly, piezoresistors Ry3 and Ry4 made of semiconductor resistance elements according to the present invention are formed on the upper surface of the other beam 118D extending in the Y-axis direction, and the piezoresistor Ry4 is formed on the frame 117G side of the beam 118D. The piezoresistor Ry3 is disposed at the end, and is disposed at the end of the beam 118D on the movable member 119 side.

  Further, the upper surface of the silicon substrate 114 is etched shallowly leaving the periphery, and a recess 131 is provided, and a plurality of electrode pads 122 are provided on the frame 117A of the recess 131. The upper surfaces of the frames 117A to 117H, the movable member 119, and the beams 118A to 118D are covered with an insulating film 132. They are connected by the formed Al wiring 133 (not shown in FIG. 2).

  In addition, the sensor chip 111 is fixed to the substrate 112 with the adhesive 121 only at the frame 117 </ b> A (the portion where the matte finish is applied in FIG. 2). Therefore, the frames 117B to 117H are not bonded to the substrate 112 and can move independently of the substrate 112. Even if a difference in linear expansion between the substrate 112 and the sensor chip 111 occurs due to a change in environmental temperature, the substrate 112 It is not to be restrained by. Therefore, in the conventional acceleration sensor 11 shown in FIG. 4a, since the entire frame 15 is fixed by the adhesive 19, when a difference in linear expansion occurs between the substrate 13 and the sensor chip 12 due to a temperature change or the like, Since the sensor chip 12 is also deformed following the deformation of the substrate 13, the beam 16 is deformed into a convex shape or a concave shape, causing problems such as a change in zero point output due to environmental temperature and a decrease in detection accuracy. On the other hand, when only the frame 117A is bonded to the substrate 112 among the frames 117A to 117H as shown in FIG. 4B, since the frames 117B to 117H are not restrained by the substrate 112, the sensor chip 111 is not connected to the substrate 112. And the influence on the beams 118A to 118D is reduced. Note that it is desirable to use an epoxy adhesive having a strong adhesive force as the adhesive 121 used for fixing the sensor chip 111 and the substrate 112. In consideration of curing shrinkage of the adhesive 121, a room temperature curing type and a solventless type having a small curing shrinkage amount are preferable.

  Next, FIG. 5 shows a plan view of the substrate 112. The substrate 112 is a rectangular flat plate formed of alumina-based ceramics, a metal lid, or the like, and a cover mounting portion 136 and a sensor for soldering the cover 113 to the mounting surface of the sensor chip 111 and the cover 113 of the substrate 112. An electrode pad 124 for connecting a wiring drawn from the electrode pad 122 of the chip 111 is formed. The electrode pad 122 and the electrode pad 124 are connected by a wire 123 such as gold by wire bonding. Further, a position confirmation mark (indicated by a broken line in FIG. 4) is attached to the chip mounting part 137 indicating the position where the sensor chip 111 is mounted and the adhesive application part 138 indicating the place where the adhesive is applied. The adhesive application part 138 is marked at a position where the frame 117A is located when the sensor chip 111 is mounted on the chip mounting part 137. That is, when the sensor chip 111 is mounted, the sensor chip 111 and the substrate 112 are bonded and fixed only by the frame 117A. Further, since the electrode pad 122 is disposed on the frame 117A fixed to the substrate 112 by the adhesive 121, the connection of the wire 123 by wire bonding can be firmly connected. Further, although not particularly illustrated, the electrode pad 124 is formed by mounting electrodes and wiring for mounting on the parent substrate formed on the back surface of the substrate 112 (the surface opposite to the surface on which the sensor chip 111 is mounted). Electrically connected.

  As shown in FIG. 1, the cover 113 has a U-shaped cross section, and is formed of a material such as metal or ceramics. The cover 113 is installed on the substrate 112 so as to cover the sensor chip 111 bonded to the substrate 112 with a U-shaped portion, and the periphery thereof is joined to the cover mounting portion 136 provided on the substrate 112 with solder or the like. Thus, the sensor chip 111 is isolated from the outside. This prevents the sensor chip 111 from coming into contact with external moisture-containing air, corrosive gas, or the like, and makes it difficult for characteristics to deteriorate.

Next, a method for detecting the acceleration of each axis of XYZ will be described with reference to FIGS. FIG. 6 shows an X-axis direction acceleration detection circuit for detecting acceleration in the X-axis direction, and is shown in FIG. 6 using piezoresistors Rx1, Rx2, Rx3, and Rx4 formed on the beams 118A and 118C. Thus, the acceleration can be detected by configuring the full bridge circuit. That is, a branch where the piezo resistors Rx1 and Rx4 are connected in series and a branch where the piezo resistors Rx2 and Rx3 are connected in series are connected in parallel to form a full bridge circuit. A voltage is applied from the power supply 134. Therefore, the difference Vx between the midpoint potential of the piezoresistors Rx1 and Rx4 and the midpoint potential of the piezoresistors Rx2 and Rx3 measured by the potentiometer 135X is expressed by the following formula (1). However, Vo is the output voltage of the power supply 134, and the resistance values of the piezoresistors Rx1, Rx2, Rx3, and Rx4 are expressed using the same symbols (the same applies hereinafter).

Similarly, FIG. 7 shows a Y-axis direction acceleration detection circuit for detecting acceleration in the Y-axis direction. Piezoresistors Ry1, Ry2, Ry3, and Ry4 formed on the beams 118B and 118D are shown in FIG. The acceleration can be detected by configuring the full bridge circuit as shown in FIG. Therefore, also in this circuit, the difference Vy between the potential at the midpoint of the piezoresistors Ry1 and Ry4 measured by the potentiometer 135Y and the potential at the midpoint of the piezoresistors Ry2 and Ry3 is expressed by the following equation (2).

FIG. 8 shows a Z-axis direction acceleration detection circuit for detecting the acceleration in the Z-axis direction. Piezoresistors Rz1, Rz2, Rz3, Rz4 formed on the beams 118A and 118C are shown in FIG. Acceleration can be detected by configuring a full bridge circuit as shown. That is, a branch where the piezo resistors Rz1 and Rz3 are connected in series and a branch where the piezo resistors Rz2 and Rz4 are connected in series is connected in parallel to form a full bridge circuit. A voltage is applied from the power supply 134. Therefore, the difference Vz between the potential at the midpoint of the piezoresistors Rz1 and Rz3 measured by the potentiometer 135Z and the potential at the midpoint of the piezoresistors Rz2 and Rz4 is expressed by the following equation (3).

  Each of the full bridge circuits may be configured in the sensor chip 111 or may include the sensor chip 111 and the substrate 112 or the wiring of the parent substrate on which the acceleration sensor 101 is mounted. However, if the wiring other than the piezoresistor constituting the full bridge circuit becomes long, the wiring resistance becomes large, and the influence thereof becomes large. Therefore, it is desirable that the sensor chip 111 constitute the full bridge circuit.

  FIG. 9 shows a case where acceleration in the -X-axis direction is acting on the sensor chip 111, and FIG. 10 shows an enlarged portion of the beams 118A and 118C. Thus, if acceleration in the -X direction is applied to the sensor chip 111, the weight 120 is pulled in the X direction by inertial force. Therefore, both beams 118A and 118C are curved in an S shape as shown in FIG. At this time, as shown in FIG. 10, the piezoresistors Rx1 and Rx3 extend to receive a tensile stress, and the resistance value increases. Further, the piezo resistors Rx2 and Rx4 contract and receive compressive stress, and the resistance value decreases. Accordingly, in the X-axis direction acceleration detection circuit, the potential between the piezoresistors Rx1 and Rx4 decreases and the potential between the piezoresistors Rx2 and Rx3 increases according to the bending magnitude of the beams 118A and 118C. As can be seen from 1), a potential difference corresponding to the magnitude of acceleration is measured by the potentiometer 135X.

  When acceleration is acting in the -X direction, as shown in FIG. 10, the piezo resistances Rz1 and Rz3 are subjected to tensile stress and the resistance value is increased, and the piezo resistances Rz2 and Rz4 are subjected to compressive stress. In response, the resistance value decreases. Therefore, in the Z-axis direction acceleration detection circuit, even if the beams 118A and 118C are deformed, the resistance values of the piezoresistors Rz1 and Rz3 increase in the same way, so the potential between them does not change, and the piezoresistors Rz2 and Rz4 Similarly, since the resistance value decreases, the potential between them does not change. Therefore, as can be seen from FIG. 8 or Formula (3), no potential difference is detected by the potentiometer 135Z. Therefore, the acceleration in the X direction is not detected by the Z-axis direction acceleration detection circuit. Further, since the beams 118B and 118D in the Y-axis direction are only twisted, the resistance values of the piezoresistors Ry1 to Ry4 change in the same way, and as can be seen from FIG. The acceleration in the X direction is not detected by the axial acceleration detection circuit.

  Even when acceleration in the Y-axis direction is applied to the acceleration sensor 101, the acceleration in the Y-axis direction is detected by the Y-axis direction acceleration detection circuit in the same manner as described above. On the other hand, even if acceleration in the Y-axis direction is applied, the beams 118A and 118C are only twisted, so neither the X-axis direction acceleration detection circuit nor the Z-axis direction acceleration detection circuit detects the Y-axis direction acceleration.

  Next, as shown in FIG. 11, considering the case where acceleration in the −Z direction is acting on the acceleration sensor 101, the weight 120 is displaced in the + Z direction by the inertial force. At this time, since the beams 118A to 118D are deformed as shown in FIG. 11, the piezoresistors Rx1, Rx4, Ry1, Ry4, Rz1, and Rz4 are subjected to compressive stress and the resistance value is decreased, and the piezoresistors Rx2, Rx3, and Ry2 are reduced. , Ry3, Rz2, and Rz3 are subjected to tensile stress to increase the resistance value. Therefore, in the Z-axis direction acceleration detection circuit, the potential between the piezoresistors Rz1 and Rz3 rises and the potential between the piezoresistors Rz2 and Rz4 falls, and as can be seen from FIG. A potential difference corresponding to the magnitude of the direction acceleration is detected. Further, when acceleration in the Z-axis direction is working, the X-direction acceleration detection circuit does not change the potential between the piezoresistors Rx1 and Rx4 and does not change the potential between the piezoresistors Rx2 and Rx3. Is not detected by the X-axis direction acceleration detection circuit. Similarly, in the Y-axis direction acceleration detection circuit, the potential between the piezo resistors Ry1 and Ry4 does not change, and the potential between the piezo resistors Ry2 and Ry3 does not change. Not.

  As described above, according to the acceleration sensor 101, the acceleration in the X-axis direction, the acceleration in the Y-axis direction, and the acceleration in the Z-axis direction are respectively detected as the X-axis direction acceleration detection circuit, the Y-axis direction acceleration detection circuit, and the Z-axis direction. Measurements can be made independently by the acceleration detection circuit.

  12 to 16 are schematic views for explaining the manufacturing process of the acceleration sensor 101. FIG. Hereinafter, the manufacturing process of the acceleration sensor 101 will be described with reference to FIGS. First, the recess 131 is formed by shallowly etching the upper surface of the p-type silicon substrate (wafer) 114 (FIG. 12A). Next, n-type impurities such as P (phosphorus) are ion-implanted into the regions of the upper surface of the silicon substrate 114 where the frames 117A to 117H, the movable member 119, and the beams 118A to 118D are to be diffused and subjected to diffusion annealing. An n-type diffusion layer 141 is formed in the layer (FIG. 12B). The thickness of the beams 118 </ b> A to 118 </ b> D is controlled by the diffusion depth of the diffusion layer 141.

  A coating 142 such as an oxide film or a nitride film is formed on the back surface of the silicon substrate 114, and then a p-type impurity such as B (boron) is ion-implanted into the surface layer of the diffusion layer 141 to piezoresistors Rx1 to Rx4, Ry1. A p-type resistance element region 143 to be Ry4 and Rz1 to Rz4 is formed. Further, an insulating film 132 is formed on the diffusion layer 141, an opening is provided in the insulating film 132 at a position facing both ends of the resistance element region 143, and an Al wiring 133 is formed. The Al wiring 133 formed in this way is connected to both ends of each resistance element region 143 and to each electrode pad 122 (FIG. 13A).

  Next, after the silicon substrate 114 is polished on the back surface to reduce the thickness of the silicon substrate 114, a mask 144 made of a nitride film is formed on the back surface of the silicon substrate 114. The mask 144 is formed so as to cover the region that becomes the silicon substrate portion of the frames 117A to 117H and the region that becomes the lower surface of the movable member 119 (FIG. 13B). In regions other than the frames 117A to 117H, the movable member 119, and the beams 118A to 118D, the insulating film 132 on the upper surface is removed by etching to expose the silicon substrate 114.

  Thereafter, an etching solution is brought into contact with the lower surface of the silicon substrate 114 in a state where a voltage is applied between the diffusion layer 141 and the lower surface of the silicon substrate 114 so as to be a reverse bias, and the silicon substrate 114 is moved to the lower surface through the opening of the mask 144. Etch from the side. At this time, the diffusion layer 141 functions as an etching stop layer, and the etching is stopped at the pn junction surface between the silicon substrate 114 and the diffusion layer 141. Therefore, the etching depth and the thickness of the beams 118A to 118D can be accurately controlled. it can. This technique is known as ECE (Electro Chemical Etchstop). In this case, etching stops at the pn junction surface in the region where the beams 118A to 118D are formed, but in the region other than the beams 118A to 118D, the silicon substrate 114 is vertically opened and opened. Further, due to the etching anisotropy of the silicon substrate 114, the side surfaces of the movable member 119 and the inner peripheral surfaces of the frames 117A to 117H are inclined (FIG. 14A).

  After removing the mask 144 on the lower surface of the silicon substrate 114, the silicon substrate 114 is overlaid on the glass substrate 115, and is maintained at a temperature of 300 to 400 ° C. between the silicon substrate 114 and the glass substrate 115. A voltage of 1000 volts is applied, and the silicon substrate 114 and the glass substrate 115 are bonded together by anodic bonding (FIG. 14B). Next, in the area of each acceleration sensor 101, the glass substrate 115 is separated into the frame portion and the weight 120, and a plurality of sensor chips 111 formed on the silicon substrate (wafer) 114 are separated one by one by dicing (see FIG. 15 (a)).

  After the adhesive 121 is applied to the adhesive application part 138 of the substrate 112 shown in FIG. 5, the sensor chip 111 is mounted on the chip mounting part 137, and the adhesive 121 is cured (FIG. 15B). Next, the electrode pad 122 formed on the sensor chip 111 and the electrode pad 124 formed on the substrate 112 are electrically connected by a gold wire 123 by wire bonding (FIG. 16A). Finally, the cover 113 is mounted on the cover mounting portion 136 formed on the substrate 112, and is fixed by soldering (FIG. 16B).

  FIG. 17 shows a combination of a full bridge circuit as shown in FIGS. 6 to 8 using the acceleration sensor 101 of the first embodiment and the acceleration sensor having all of the frames 117A to 117H of the comparative example fixed, and the temperature characteristics of the zero point output of the bridge circuit. It is a figure which shows the result of having evaluated comparatively. In FIG. 17, the measurement result of the acceleration sensor 101 of the first embodiment is indicated by α, and the measurement result of the conventional acceleration sensor is indicated by β. In the acceleration sensor 101 of the comparative example 1, as shown in FIG. 17, it was found that the fluctuation of the zero point output when the temperature changed was about 10 to 20 times as compared with the conventional acceleration sensor. . As described above, if a full bridge circuit is assembled using the acceleration sensor 101 of the present invention, signal detection can be stably performed with respect to temperature change, and therefore, a highly accurate temperature characteristic is excellent without adding a complicated circuit. An acceleration sensor can be manufactured.

  As described above, by limiting the fixing location of the sensor chip 111 and the substrate 112 to only one side of the sensor chip 111, the location where the stress generated by the curing shrinkage of the adhesive or the temperature change is not fixed is shifted and relaxed. Therefore, the influence of the stress detection accuracy on the sensor is small, and the manufacturing process is the same as that of the conventional acceleration sensor. Therefore, it is possible to provide the acceleration sensor 101 with a high yield and high cost.

  In this embodiment, since the frame 117A is bonded to the substrate 112 only, the frame 117A is higher than the other frames 117B to 117H by the thickness of the adhesive. However, in this embodiment, the sensor chip 111 having a size of 2.5 mm square is used, and the thickness of the adhesive used for bonding the frame 117A and the substrate 112 is 20 μm or less (inclination is 0.45). Therefore, the influence of the inclination of the sensor chip 111 on the output due to the difference in the thickness of the adhesive is 0.01% or less, and the influence on the sensor output is not a problem.

  In this embodiment, the sensor chip 111 and the substrate 112 are bonded only by the frame 117A. However, as shown in FIGS. 18a and 18b, the sensor chip 111 is positioned in the center of gravity (center O of the sensor chip 111 in a plan view of the sensor chip 111. ) All or a part of the frame (area shown with a matte finish) existing on one side divided into two by an arbitrary straight line (PP ′) passing through () may be bonded. 18a and 18b are bottom views of the sensor chip 111. FIG.

  In the present embodiment, the frame is divided into eight (frames 117A to 117H). However, as shown in FIGS. 19a and 19b, the sensor chip 150 having the frame 151 that is integrated may be used. The present invention can be applied. Note that the bonding area between the sensor chip 150 and the substrate 112 is shown with a matte finish. Furthermore, the present invention can be applied even if the sensor chip is not limited to a rectangle, but may be other shapes such as a circle or a polygon.

  In the present embodiment, the substrate 112 and the cover 113 are fixed by soldering, but may be fixed by an adhesive or the like. In the case of fixing with an adhesive, it is not necessary that the cover mounting portion 136 be solderable, and it is sufficient that the position can be known at the time of alignment.

  In the acceleration sensor 101 shown in the first embodiment, since only one side of the sensor chip 111 is fixed to the substrate 112, when a strong impact is applied due to dropping or the like, the unfixed frames 117B to 117H are largely lifted from the substrate 112. As a result, the beams 118A to 118D may be damaged. The present embodiment is proposed to solve this problem.

  The acceleration sensor 102 of this embodiment is provided with a stopper for restricting upward movement on a frame (frames 117D to 117F in the first embodiment) that is not fixed to the substrate 113 with the adhesive 121. Specifically, as shown in FIGS. 20a and 20b, a structure 161 having an inverted L-shaped cross section is provided, and the overhanging portion 162 of the structure 161 is located above the frame 117E that is not fixed by the adhesive 121 of the sensor chip 111. It is installed in this way. The structure 161 is made of metal, resin, or the like, and is fixed to the substrate 112 with solder bonding or an adhesive. Therefore, even if a strong impact is applied to the acceleration sensor 102 due to dropping or the like, the sensor chip 111 does not float more than the distance between the upper surface of the sensor chip 111 and the bottom surface of the overhanging portion 162 from the substrate 112, and the beams 118A to 118D are damaged. Never do. The installation of the structure 161 is not limited to the frame 117E, and any one or more of the frames that are not fixed by the adhesive 121 so that the beams 118A to 118D are not damaged by a strong impact such as dropping. It can be installed to ensure performance (reliability).

  As a modification, as shown in FIGS. 21 a and 21 b, a cushion material 163 is installed instead of the structure 161 between the upper part of the frame on the side not bonded to the substrate 112 of the sensor chip 111 and the cover 113. The shock may be absorbed by the cushion material 163 and the sensor chip 111 and the substrate 112 may be supported so as not to leave. Therefore, even if an impact such as a drop is applied, the impact is absorbed by the cushion material 163, so that the sensor chip 111 does not float from the substrate 112, and the beams 118A to 118D are not damaged. The cushion material 163 can be made of elastic gel, sponge-like material, or the like.

  Furthermore, as another modification, as shown in FIGS. 22a and 22b, dummy electrodes 164 and 165 are provided on the upper surface of the sensor chip 111 and the substrate 112, and the dummy electrodes 164 and 165 are wire-bonded. For example, the dummy wire 166 may be connected to the cover 113 while being connected by the dummy wire 166. In this way, the elasticity of the dummy wire 166 and the dummy wire 166 are pushed to the substrate 112 side by the cover 113, so that even if an impact such as dropping is applied, the sensor chip 111 does not float from the substrate 112, and the beam 118A to 118D are not damaged.

  As described above, by installing a stopper to prevent the sensor chip 111 from floating on the substrate 112 (frames 117B to 117H in this embodiment) that is not fixed to the substrate 112, the stopper is not subject to impact such as dropping. Even if added, the sensor chip 111 does not float above the substrate 112 beyond the limit, and the beams 118A to 118D are not deformed beyond the limit and are not damaged. Thus, a highly reliable acceleration sensor can be provided.

  The present embodiment was made to increase the impact resistance of the acceleration sensor 101 described in the first embodiment in the same manner as the acceleration sensor 102 of the second embodiment, and the sensor of the acceleration sensor 101 described in the first embodiment. Only the bonding method between the chip 111 and the substrate 112 is different.

  FIG. 23a is a schematic cross-sectional view of the acceleration sensor 103 of this embodiment, and FIG. 23b is a plan view of the acceleration sensor 103 of this embodiment before the cover 113 is mounted. The acceleration sensor 103 is different from the acceleration sensor 101 described in the first embodiment in that the frames 117D and 117F are bonded to the substrate 112 with an adhesive 167. Further, as the adhesive 167, an adhesive having a weaker adhesive force than the adhesive 121 used for fixing the frame 117A and the substrate 112 and having elasticity (small elastic modulus) is used.

  In this way, all the frames other than the frame fixed with the adhesive 121 (frame 117A in the present embodiment, indicated by hatching in the drawing) or a part of the frames are less adhesive than the adhesive 121 and are elastic. Since it is fixed by the agent 167 (indicated by a matte surface in the drawing), the stress generated by the difference in linear expansion between the substrate 112 and the sensor chip 111 due to a change in environmental temperature can be relaxed by the deformation of the adhesive 167. Further, even if a strong impact such as dropping is applied, the sensor chip 111 does not float from the substrate 112 and the beams 118A to 118D are not damaged. Note that an elastic adhesive such as a silicone resin can be used for the adhesive 167.

  In the present application, an acceleration sensor using a piezoresistor has been described. However, the present invention is not limited to this, and any sensor that detects a physical quantity converted into stress or deformation can be applied. For example, the present invention can be applied to capacitance type and piezoelectric type acceleration sensors, pressure sensors, angular velocity sensors, and the like.

It is a schematic sectional drawing of the acceleration sensor of the Example of this invention. It is a top view of the sensor chip used for the acceleration sensor same as the above. It is a schematic sectional drawing of the sensor chip used for the acceleration sensor of FIG. (A) is a figure explaining the deformation | transformation by the change of the environmental temperature of the conventional acceleration sensor. (B) is a figure explaining the deformation | transformation by the change of the environmental temperature of the acceleration sensor of Example 1. FIG. It is a top view of the board | substrate used for the acceleration sensor of FIG. It is a circuit diagram which shows the X-axis direction acceleration detection circuit for detecting the acceleration of a X-axis direction. It is a circuit diagram which shows the Y-axis direction acceleration detection circuit for detecting the acceleration of a Y-axis direction. It is a circuit diagram which shows the Z-axis direction acceleration detection circuit for detecting the acceleration of a Z-axis direction. It is the schematic which shows the state which the acceleration of an X-axis direction has acted on the acceleration sensor. It is the schematic which expands and shows a part of FIG. It is the schematic which shows the state which the acceleration of a Z direction is acting on the acceleration sensor. (A) (b) is the schematic explaining the manufacturing process of the acceleration sensor concerning Example 1 of this invention. (A) (b) is the schematic explaining the process after the process shown in FIG. (A) and (b) are the schematic diagrams explaining the process after the process shown in FIG. (A) and (b) are the schematic diagrams explaining the process after the process shown in FIG. (A) and (b) are the schematic diagrams explaining the process after the process shown in FIG. It is a figure which shows the result of having evaluated the temperature characteristic of the zero point output in the full bridge circuit comprised using the acceleration sensor concerning this invention. (A) and (b) are the schematic diagrams explaining the adhesion position of a sensor chip and a board | substrate. (A) and (b) are figures which show the modification of Example 1. FIG. (A) is a schematic sectional drawing of the acceleration sensor concerning Example 2 of this invention. (B) is a schematic top view of the state which removed the cover of the acceleration sensor concerning Example 2 of this invention. (A) is a schematic sectional drawing of the acceleration sensor concerning Example 2 different from the acceleration sensor of FIG. FIG. 21B is a schematic plan view of the acceleration sensor according to the second embodiment different from the acceleration sensor of FIG. 20 with the cover removed. (A) is a schematic sectional drawing of the acceleration sensor different from the acceleration sensor of FIG. FIG. 21B is a schematic plan view of the acceleration sensor according to the second embodiment different from the acceleration sensor of FIG. 20 with the cover removed. (A) is a schematic sectional drawing of the acceleration sensor 103 concerning Example 3 of this invention. FIG. 7B is a schematic plan view of the acceleration sensor 103 according to the third embodiment with a cover removed. It is a schematic sectional drawing of the conventional acceleration sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Acceleration sensor 111 Sensor chip 112 Substrate 113 Cover 114 Silicon substrate 115 Glass substrate 117A-117H Frame 118A-118D Beam 119 Movable member 120 Weight 121 Adhesive 122, 124 Electrode pad 123 Wire 131 Recess 132 Insulating film 133 Al wiring 136 Cover mounting Part 137 Chip mounting part 138 Adhesive application part 150 Sensor chip 151 Frame 161 Structure 162 Overhang part 163 Cushion material 164 Dummy electrode 165 Dummy electrode 166 Dummy wire 167 Adhesive

Claims (11)

A sensor having a sensor chip mounted on the surface of a substrate,
When a plane parallel to the mounting surface of the sensor chip is divided into two areas by a certain straight line passing through the center of the sensor chip, one of the fixed areas of the sensor chip to the substrate is divided by the straight line A sensor characterized by belonging only to a certain area.   The sensor chip has a polygonal shape with four or more sides when viewed from vertically above, and the whole or a part of one side of the outer peripheral area of the lower surface thereof is fixed to the substrate. The sensor according to claim 1.   When the sensor chip is viewed from vertically above, the signal extraction electrode provided on the upper surface of the sensor chip is the same area as the area to which the sensor chip fixing area belongs, of the two areas divided by the straight line. The sensor according to claim 1, wherein the sensor belongs to.   2. The sensor according to claim 1, wherein the signal extraction electrode provided on the upper surface of the sensor chip is located immediately above a fixed region of the sensor chip.   5. The sensor according to claim 1, further comprising a stopper component for preventing an area other than the fixed area of the sensor chip from rising above a predetermined distance from the substrate.   The sensor according to claim 1, wherein an area other than a fixed area of the sensor chip and the substrate are connected by a dummy wire. A sensor having a sensor chip mounted on the surface of a substrate,
When a surface parallel to the mounting surface of the sensor chip is divided into two areas by a certain straight line passing through the center of the sensor chip, a part or the whole of one of the areas divided by the straight line is bonded with high hardness. A sensor which is fixed to the substrate with an agent, and a part or the whole of the other area is fixed using a flexible adhesive.   When the sensor chip is viewed from vertically above, the number of sides is a polygon of 4 or more, and only one part or all of one side of the outer peripheral area of the lower surface thereof is bonded to the substrate with a high-hardness adhesive, The sensor according to claim 7, wherein a part or the whole of the other area is bonded with a soft adhesive.   When the sensor chip is viewed from vertically above, the signal extraction electrode provided on the upper surface of the sensor chip is bonded with the high hardness adhesive of the sensor chip in the two areas divided by the straight line. Sensor according to claim 7, characterized in that it belongs to the same area as the area to which the defined region belongs.   The signal extraction electrode provided on the upper surface of the sensor chip is located immediately above the region of the sensor chip bonded with the high-hardness adhesive. Sensor. The sensor according to claim 1, and a sensor for detecting acceleration,
The sensor has a movable part that is displaced according to a change in external force;
A stationary member;
An elastic support part for supporting the movable part on the stationary member;
A sensor chip provided with a measuring means for measuring the amount of displacement of the elastic support member;
A sensor comprising a substrate on which the sensor chip is mounted and fixed.

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