JP2006250702A - Acceleration sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve high sensitivity and high accuracy of a capacitance-type acceleration sensor by reducing distortion of a sensor chip due to external stress such as package deformations etc. <P>SOLUTION: A movable electrode; a fixed electrode; and a beam making a movable electrode part movable are formed by machining a semiconductor substrate in a sensor chip 2. The sensor chip 2 is sealed between an upper glass 3 from above and a glass seating 4 from below, and the back surface of the glass seating 4 includes a counter bore 5 except at least part of an outer circumferential part. The chip 2 is joined to the bottom surface 11 of a recession-type package 10 at the remaining part of the outer circumferential part with an adhesive 7 to make the counter bore 5 to absorb stress to the censor chip 2 from the outside. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an acceleration sensor in a physical quantity sensor that senses a physical mechanical quantity, and more particularly to a capacitive sensor that detects acceleration from the electrostatic capacity between a fixed electrode and a movable electrode.

  2. Description of the Related Art Conventionally, there are acceleration sensors mounted on automobiles and the like as physical quantity sensors that are used for motion control of various vehicles. Generally, acceleration sensors include a weight portion and an electrode surface provided facing the weight portion. Capacitance type that detects the change of the configured capacitance, and piezoresistive type semiconductor sensor that detects mechanical distortion applied to the flexure as piezoresistance as a change in electrical resistance are known. Yes.

  Conventionally, as a capacitance type, a fixed electrode, a movable electrode facing the fixed electrode, a weight portion that supports the movable electrode and is displaced by a physical quantity, and a flexible shape formed in a frame shape surrounding each electrode and the weight portion, etc. 1 or a plurality of beam parts, one end of which is connected to the weight part, and a frame part to which the other end of the beam part is connected are formed on a semiconductor substrate. Various proposals have been made.

  A configuration of a conventional capacitive acceleration sensor will be described with reference to FIG. FIG. 7A shows the appearance of the capacitive acceleration sensor 100, FIG. 7B shows a cross section of the acceleration sensor mounted on the package, and FIG. 7C shows a cross section of the sensor chip of the acceleration sensor. .

  In these drawings, the acceleration sensor 100 includes an acceleration sensor chip 102 made of a semiconductor substrate, a support substrate 101 made of a glass material on which the acceleration sensor chip 102 is mounted, and an upper cover 103 made of a glass member covering the acceleration sensor chip 102. And the acceleration sensor 100 is formed by integrating them. The acceleration sensor 100 is fixed to the bottom portion 104 of a package such as ceramic with an adhesive 105 over the entire back surface of the support substrate 101.

  The acceleration sensor chip 102 supports a weight part 121 whose position is displaced in accordance with acceleration, a beam part 122 having a spring property that allows the weight part 121 to be displaced, and a support part that supports the weight part 121 via the beam part 122. And a comb-shaped fixed electrode portion 124 having a plurality of fixed electrodes, and a plurality of movable electrodes that are provided at both ends of the weight portion 121 and alternately enter in a comb shape between adjacent fixed electrodes. The fixed electrode and the movable electrode are parallel to each other and are disposed orthogonal to the direction in which acceleration is measured (see Patent Document 1).

  In this capacitance type sensor, the distance between the fixed electrode and the movable electrode changes due to the deformation of the beam due to the application of a physical quantity, and the change in the capacitance generated between the two electrodes due to this change is applied to the semiconductor integrated circuit (IC). ) To measure the magnitude of acceleration.

  However, in such a capacitive sensor, the beam has a thickness of several micrometers to several tens of micrometers. Therefore, even if a slight distortion is applied to the sensor chip from the outside, it is the same as when acceleration is applied. The movable electrode is displaced and the capacitance changes. For example, when a ceramic or plastic package with a sensor chip alone is mounted on a printed circuit board by soldering, the output of the sensor changes due to distortion caused by soldering heat. In addition, due to the change in ambient temperature, the temperature characteristics of the sensor deteriorate due to differences in thermal expansion coefficients among the solder, the printed board, and the package material. Therefore, in general, a method has been adopted in which a glass pedestal is bonded to the lower part of the sensor chip and external strain is absorbed by the glass pedestal.

  However, with the recent enhancement of performance such as automatic direction control technology, more sensitive acceleration sensors have been demanded. To achieve this, unnecessary stress from the outside can be eliminated as much as possible, and even smaller acceleration can be achieved. However, an acceleration sensor that can be detected has been demanded. For this reason, it is necessary to minimize the influence of external stress on the sensor, and it is necessary to prevent extremely weak external stress from being transmitted to the sensor.

  On the other hand, as another conventional example, in a piezoresistive acceleration sensor, as shown in FIG. 8, in order to reduce the influence of thermal strain of the mounting substrate 250 on the sensor chip 220, the sensor chip 220 is made of glass. The cap 240 and the lower cap 230 are covered from above and below, the lower cap 230 is formed in an inverted quadrangular pyramid shape, and a lower end surface 232 having a quadrangular pyramid as a joint surface with the mounting substrate 250 is formed, and the vicinity of the center of the sensor bottom surface There has been proposed one that joins to the mounting substrate 250 only in a part (see Patent Document 2).

  However, in the above conventional example, the back surface of the acceleration sensor 200 and the mounting substrate 250 are joined by the dotted or linear lower end surface 232, so that the area of the contact portion is small and it is difficult to attach at the time of joining. Since the bonding balance becomes unstable and the parallelism between the back surface of the acceleration sensor 200 and the mounting substrate 250 is difficult to maintain, the acceleration sensor 200 is mounted obliquely, the posture accuracy is lowered, and the sensor accuracy due to the mounting tilt is deteriorated. There was a fear.

JP 2004-28912 A JP 2001-337107 A

  The present invention has been made in order to solve the above-described problem, and suppresses the external strain that is transmitted to the sensor chip through the package and reduces the detection of unnecessary stress, thereby improving the sensitivity of the acceleration sensor. It is an object of the present invention to provide a capacitance type acceleration sensor capable of improving accuracy.

  In order to achieve the above object, the invention according to claim 1 is directed to a capacitance type acceleration sensor that detects a change in acceleration by a change in capacitance generated between the movable electrode and the fixed electrode. A sensor chip formed by processing a semiconductor substrate with a beam that moves an electrode and a movable electrode part, a glass substrate that seals the upper and lower sides of the sensor chip, and one glass substrate is fixed using an adhesive A concave package made of ceramic, and a spot facing is provided on the surface of the glass substrate to which the adhesive is applied, leaving at least a part of the outer periphery.

  According to a second aspect of the present invention, in the acceleration sensor according to the first aspect, the portions of the surface of the glass substrate to which the adhesive is applied are two opposite sides of the outer peripheral portion.

  According to a third aspect of the present invention, in the acceleration sensor according to the first aspect, the portions of the surface of the glass substrate to which the adhesive is applied are the four corners of the outer peripheral portion.

  According to a fourth aspect of the present invention, in the acceleration sensor according to any one of the first to third aspects, each of the glass substrates is bonded to the sensor chip by anodic bonding, and the sensor chip is sealed in an airtight state. It is what.

  According to the first aspect of the present invention, by providing the counterbore on the glass pedestal that is a contact surface with the package, the counterbore part of the glass pedestal is deformed from the external strain to be transmitted to the sensor through the package. Can be absorbed and difficult to be transmitted to the sensor chip. Thereby, detection of unnecessary external stress can be suppressed, the sensitivity of the sensor can be improved, parallel accuracy without oblique mounting can be maintained, and the accuracy of the sensor can be increased.

  According to the second aspect of the present invention, the external strain to be transmitted to the sensor through the package is absorbed by deformation of the spot facing portion of the glass substrate composed of two opposite sides of the outer peripheral portion, and is not easily transmitted to the sensor. Therefore, a sensor chip with high sensitivity and high accuracy can be mounted, and sensitivity and accuracy can be improved.

  According to the third aspect of the present invention, the external strain to be transmitted to the sensor through the package is absorbed by deformation of the spot facing portion of the glass substrate formed by the four corners of the outer peripheral portion, and further transmitted to the sensor chip. It becomes difficult.

  According to the invention of claim 4, since the bonding of the glass substrate and the semiconductor substrate is performed in a solid phase by anodic bonding, high-precision bonding is obtained, and the plastic molding material is obtained by hermetically sealing with glass from above and below. It is possible to realize a capacitance type acceleration sensor that can be molded at a low pressure.

  Hereinafter, a capacitive acceleration sensor according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an appearance of the acceleration sensor 1 according to the present embodiment, FIG. 2 shows a state in which the acceleration sensor 1 is mounted on a concave package 10 (hereinafter abbreviated as a package), and FIG. The sensor chip 2 is shown, FIG. 3B is an enlarged view of a portion A surrounded by a solid line in FIG. 4A, and FIG. 4 is a cross section of the acceleration sensor 1. In addition, the same code | symbol is attached | subjected to the member equivalent to the corresponding member of each figure (same below).

  1 and 2, an acceleration sensor 1 includes a sensor chip 2 formed by processing a semiconductor substrate 23, an upper glass 3 (glass substrate) and a glass pedestal 4 (glass) that seal the sensor chip 2 from above and below. Substrate). The back surface of the glass pedestal 4 is provided with spot facings 5 leaving at least a part of the outer periphery, and the remaining part of the outer periphery is formed on the bottom surface of the ceramic package 10 using the adhesive 7. 11 is joined.

  Thus, by providing the spot facing 5, the bonding area between the package 10 and the glass pedestal 4 is greatly reduced. Therefore, as compared with the conventional case where the entire bottom surface of the sensor chip 2 is in contact with the package 10, the distortion due to the temperature change of the package 10 is not directly transmitted to the sensor chip 2. In addition to this, distortion is further absorbed by the counterbore 5 of the glass pedestal 4 being deformed, so that the distortion is more difficult to be transmitted to the sensor chip 2. Thereby, since detection of unnecessary stress can be suppressed, the sensor chip 2 having high sensitivity and high accuracy can be mounted, and the sensitivity and accuracy of the acceleration sensor 1 can be increased. Furthermore, the capacitive acceleration sensor 1 capable of low-pressure molding using a plastic molding material can be realized by hermetically sealing the sensor chip 2 from above and below with the upper glass 3 and the glass pedestal 4.

  3 and 4, the sensor chip 2 includes a movable electrode portion 21 arranged on the upper side of the glass pedestal 4 and spaced apart from the glass pedestal 4, and a beam portion having a spring property that can displace the movable electrode portion 21. 22, a support portion 25 that supports the movable electrode portion 21 via the beam portion 22, a comb-shaped fixed electrode portion 24 having a plurality of fixed electrodes 24 b, and a comb shape provided at both ends of the movable electrode portion 21. And a plurality of movable electrodes 21a. The fixed electrode 24b and the movable electrode 21a are parallel to each other and are arranged orthogonal to the direction in which acceleration is detected.

  On both sides of the movable electrode portion 21, the fixed electrodes 24b and the movable electrodes 21a are alternately arranged along the direction in which the acceleration is detected, and one movable electrode 21a is placed in the comb groove 24c between the adjacent fixed electrodes 24b. One fixed electrode 24b enters between the comb grooves 21b between the adjacent movable electrodes 21a. Each fixed electrode 24b is connected by the connection part 24a which connects these, and forms the fixed electrode part 24. FIG.

  In the acceleration sensor 1 configured as described above, when acceleration is applied, the movable electrode portion 21 is displaced in the X direction, and the fixed electrode 24b and the movable electrode 21a of the fixed electrode portion 24 are displaced according to the amount of change in the X-axis direction. The gap d changes to change the capacitance between the two, and the magnitude of the change in capacitance is measured to detect the direction and magnitude of the applied acceleration. By converting this into a voltage change by a semiconductor integrated circuit (IC), a detection electric signal is taken out.

  And the counterbore 5 is provided in the bottom face of the glass base 4 substantially symmetrically in the bottom face, and the bottom face of the sensor chip 2 and the glass base 4 is arranged in parallel. As a result, there is no inclination between the planes of the sensor chip 2 and the glass pedestal 4, and in particular, detection of a change in capacitance is detected between the fixed electrode 24 b and the movable electrode 21 a configured in the plane of the semiconductor substrate 23. In the capacitance type acceleration sensor to be detected, the parallelism with respect to the mounting substrate can be ensured, and the occurrence of other-axis sensitivity due to the mounting tilt can be suppressed. Note that the movable electrode portion 21, the beam portion 22, the fixed electrode 24 b, the fixed electrode portion 24, and the movable electrode 21 a provided on the surface side of the glass pedestal 4 are formed by etching a single crystal silicon substrate that is the semiconductor substrate 23. Is formed by a part of the silicon substrate.

  Next, a capacitive acceleration sensor according to a second embodiment of the present invention will be described with reference to FIG. FIG. 5 shows the appearance of the acceleration sensor 1 according to the present embodiment. This acceleration sensor 1 has basically the same function as that of the first embodiment, and the portions of the surface of the glass pedestal 4 (glass substrate) to which the adhesive is applied are the two sides facing the outer peripheral portion. This is different from the embodiment described above.

  The glass pedestal 4 (glass substrate) of the acceleration sensor 1 is provided with a counterbore 5a that forms a rectangular groove on the bottom surface thereof to reduce the portion left on the bottom surface, and at the remaining two sides 8 around the parallel outer periphery. Since it is bonded to the package 10 in a well-balanced manner, a highly sensitive and accurate capacitive acceleration sensor can be obtained. Moreover, the air in a joint surface can be escaped from the spot facing 5a at the time of joining, and it can make adhesion easy.

  Next, a capacitive acceleration sensor according to a third embodiment of the present invention will be described with reference to FIG. FIG. 6A shows the appearance of the acceleration sensor 1 according to the present embodiment, and FIG. 6B shows the state where the sensor 1 is mounted on the bottom surface 11 of the package 10. This acceleration sensor 1 has basically the same function as that of the first embodiment, and the portions left on the surface of the glass pedestal 4 to which the adhesive 7 is applied are the four corners 9 of the outer peripheral portion. This is different from the embodiment described above.

  The glass pedestal 4 of the acceleration sensor 1 is provided with a cross-shaped counterbore 5b on the bottom surface to reduce the portion left on the bottom surface, and the package 10 and the package 10 in a well-balanced manner at the four symmetric corner portions 9 around the remaining outer periphery. Since they are joined, a capacitive acceleration sensor with high sensitivity and high accuracy can be obtained. Moreover, the air in a joint surface can be escaped from the spot facing 5b at the time of joining, and it can make it easy to adhere | attach.

  As described above, according to the acceleration sensor 1 according to the present embodiment, the counterbore 5 is provided on the bottom surface of the glass pedestal 4 to be bonded to the package 10, and the remaining outer peripheral portion 6 is provided symmetrically widely on the bottom surface of the glass pedestal 4. Thereby, it can reduce, keeping the junction area of the package 10 and the glass base 4 in parallel. As a result, external strain that is transmitted to the sensor chip 2 through the package 10 can be absorbed by the spot facing 5 portion, detection of unnecessary stress in the sensor chip 2 is suppressed, and high sensitivity without reducing the mounting posture accuracy. Thus, a highly accurate acceleration sensor can be obtained.

  Capacitive acceleration sensor that enables high-precision bonding between a glass substrate and a semiconductor substrate by anodic bonding, and enables low-pressure molding using plastic molding material by hermetically sealing the sensor chip with glass from above and below. Can be realized.

1 is an external view of a capacitive acceleration sensor according to a first embodiment of the present invention. The figure which shows the state which mounted the said acceleration sensor in the package. (A) is a top view of the sensor chip of the said acceleration sensor, (b) is an enlarged view of the A section in (a). Sectional drawing of the said acceleration sensor. The external view of the capacitive acceleration sensor which concerns on the 2nd Embodiment of this invention. (A) The external view of the capacitive acceleration sensor which concerns on the 3rd Embodiment of this invention, (b) is the figure which shows the state mounted in the package of the acceleration sensor. (A) The external view of the conventional capacitive acceleration sensor, (b) is a sectional view of the acceleration sensor, (c) is a sectional view of a sensor chip of the acceleration sensor. Sectional drawing of the other conventional electrostatic capacitance type acceleration sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Capacitance type acceleration sensor 2 Sensor chip 3 Upper glass (glass substrate)
4 Glass base (glass substrate)
5, 5a, 5b Spot facing 7 Adhesive 8 Two sides 9 Corner (corner)
DESCRIPTION OF SYMBOLS 10 Recessed package 21 Movable electrode part 21a Movable electrode 22 Beam 23 Semiconductor substrate 24, 24a, 24b Fixed electrode

Claims (4)

In a capacitance type acceleration sensor that detects a change in acceleration by a change in capacitance generated between a movable electrode and a fixed electrode,
A sensor chip formed by processing a movable substrate, a fixed electrode, and a beam that moves the movable electrode portion by processing a semiconductor substrate;
Glass substrates for sealing the upper and lower sides of the sensor chip,
A ceramic concave package to which one glass substrate is fixed using an adhesive,
An acceleration sensor, characterized in that a counterbore is provided on the surface of the glass substrate to which the adhesive is applied, leaving at least a part of the outer periphery.   The acceleration sensor according to claim 1, wherein the portions of the surface of the glass substrate to which the adhesive is applied are two opposite sides of the outer peripheral portion.   The acceleration sensor according to claim 1, wherein the portions of the glass substrate surface to which the adhesive is applied are four corners of the outer peripheral portion.   4. The acceleration sensor according to claim 1, wherein each of the glass substrates is bonded to a sensor chip by anodic bonding, and the sensor chip is sealed in an airtight state.

Images