JP2001337106A - Semiconductor acceleration sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a temperature characteristic relating to the detection of acceleration hard to deteriorate. SOLUTION: This sensor includes an acceleration sensor chip 1 having a beam-shaped deflecting part extended therefrom in a predetermined direction, with a weight part supported against the end of the deflecting part by integral molding, the weight part being displaced by acceleration; a first cap 2 joined to one face of the acceleration sensor chip 1 to face the weight part; and a second cap 3 joined to the other face of the acceleration sensor chip 1 to face the weight part from the side opposite to the first cap 1. The acceleration sensor chip 1 has a joining face 17, to which the first cap 1 is joined, the joining face being located closer to the end along a prescribed direction than to the vicinity of the root of the deflecting part from which the deflecting part is extended.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor acceleration sensor for detecting an acceleration by an electric signal proportional to the acceleration.

[0002]

2. Description of the Related Art The applicant of the present invention has proposed a semiconductor acceleration sensor of this type in Japanese Patent Application No. 11-240449. As shown in FIGS. 7 to 9, the acceleration sensor chip A, the first cap B and the second cap C
It has.

The acceleration sensor chip A is made of a silicon substrate, has a beam-shaped bent portion A1 extending therefrom, and supports a weight portion A2, which is displaced by receiving an acceleration, integrally formed on the tip side of the bent portion A1. I have. The flexure portion A1 of the acceleration sensor chip A is provided with a gauge resistor A3 whose resistance value changes according to the flexure state of the flexure portion A1. The acceleration sensor chip A detects the acceleration based on the output from the gauge resistor A3. Further, the acceleration sensor chip A has a bonding surface A4 to be bonded to a first cap B described later only along a predetermined direction from near both sides of the bending portion A1.

[0004] The first cap B is made of heat-resistant glass, and the acceleration sensor chip A is joined to one surface of the first cap B so as to face the weight portion A2. The first cap B restricts the weight portion A2 from being excessively displaced by contacting the displaced weight portion A2 when the weight portion A2 is displaced due to excessive acceleration. The portion A2 is prevented from being damaged.

[0005] The second cap C is joined to the other surface of the acceleration sensor chip A so as to face the weight portion A2 from the side opposite to the first cap B. When the weight portion A2 is excessively accelerated and displaced, the second cap C contacts the displaced weight portion A2, thereby restricting the weight portion A2 from being excessively displaced. The portion A2 is prevented from being damaged.

The acceleration sensor chip A has a first
Has a joint surface A4 joined to the cap B only along a predetermined direction from the vicinity of both sides of the bent portion A1, and when the size of the acceleration sensor chip A is the same, the weight portion A2 is seen in a plan view. As compared with the case where the joint surface A4 is also provided in a direction orthogonal to the predetermined direction so as to surround the joint surface A4, the joint surface A4 can be made smaller, and the weight A2 can be made larger by that amount. The sensitivity can be improved without increasing the size of the sensor chip A.

[0007]

In the above-described conventional semiconductor acceleration sensor, the silicon constituting the acceleration sensor chip A has a coefficient of thermal expansion of about 2.81 × 10 ⁻⁶ / K (20
° C), and the glass forming the second cap C has a coefficient of thermal expansion of about 3.31 × 10 ⁻⁶ / K (20 ° C.). When used in the above, there is a possibility that a thermal stress is generated from the joint.

Thus, the acceleration sensor chip A and the first
When the thermal stress is transmitted to the bent portion A1 when the thermal stress is generated from the joint portion with the cap B, the resistance value of the gauge resistor A3 changes, and the temperature characteristic of acceleration detection may be deteriorated.

On the other hand, the thermal stress is reduced by reducing the area of the joint surface A4 in the acceleration sensor chip A. However, considering the joint strength between the acceleration sensor chip A and the first cap B, the thermal stress is reduced. There is a limit to reducing the area.

The present invention has been made in view of the above points, and an object of the present invention is to provide a semiconductor acceleration sensor in which the temperature characteristic of acceleration detection is hardly reduced.

[0011]

In order to solve the above-mentioned problems, in the semiconductor acceleration sensor according to the present invention, a beam-like bent portion is extended in a predetermined direction and displaced by acceleration toward the tip end of the bent portion. An acceleration sensor chip integrally supporting a weight portion, a first cap joined to one surface of the acceleration sensor chip to face the weight portion, and an acceleration so as to face the weight portion from a side opposite to the first cap. A second cap joined to the other surface of the sensor chip, wherein the acceleration sensor chip is joined to the first cap closer to the tip in the predetermined direction than near the extension base of the bending portion. It has a configuration having a joint surface.

According to a second aspect of the present invention, in the semiconductor acceleration sensor according to the first aspect, the joining surface has a configuration in which a front end portion in the predetermined direction is locally widened.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor acceleration sensor according to a first embodiment of the present invention will be described below with reference to FIGS.

An acceleration sensor chip 1 is formed of a silicon substrate and is formed in a rectangular shape in plan view, as shown in FIG. 3, and a rectangular hole 11 in plan view is formed in the center thereof. The acceleration sensor chip 1 has a pair of beam-like bending portions 12 having elasticity from one opening edge of the hole 11.
A weight portion 13 extending along a predetermined direction toward the opening 1 and supporting a weight portion 13 which is displaced in the vertical direction by receiving acceleration at an end portion of the bending portion 12 is integrally formed.
When the weight portion 13 is displaced in the vertical direction under acceleration, the flexure portion 12 bends in accordance with the displacement.

The bending portion 12 of the acceleration sensor chip 1 is formed with two gauge resistors 14 whose resistance values change in accordance with the bending of the bending portion 12. Therefore, it is possible to take out a voltage proportional to the acceleration received by the weight portion 13 as an output by the gauge resistor 14.

Further, at one end of the acceleration sensor chip 1, five wire bonding pads 15 are arranged in a line at equal intervals from each other for inputting and outputting signals. An output signal output from the gauge resistor 14 in proportion to the acceleration is taken out from the wire bonding pad 15.

The acceleration sensor chip 1 has a first cap 2, which will be described later, provided on both sides of the hole 11 on one side thereof, closer to the tip in a predetermined direction than near the base of the extension of the bending portion 12.
Is provided along a predetermined direction. In other words, the portion of the acceleration sensor chip where the aluminum thin film 16 is provided serves as a bonding surface 17 to which the first cap 2 is bonded. In addition, the acceleration sensor chip 1 is provided with an aluminum thin film (not shown) for joining a second cap 3 described later in a rectangular shape in plan view on the other side.

Reference numeral 2 denotes a first cap, which is made of heat-resistant glass and formed in a bridge shape, that is, a plate shape as shown in FIG. It has a recess 22 having a depth of several μm formed by both side portions 21 and 21. The first cap 2 has the front end surfaces of both side portions 21 and 21 anodically bonded to the acceleration sensor chip 1 via the above-described aluminum thin film 16, and has a notch 23 at one end in a predetermined direction. Thus, only the front end surface from the center to the other end is anodically bonded to the acceleration sensor chip 1. As described above, the first cap 2 is anodically bonded to the acceleration sensor chip 1 so that the concave portion 22 faces the weight portion 13.

When the weight portion 13 of the acceleration sensor chip 1 is displaced due to excessive acceleration, the first cap 2 comes into contact with the displaced weight portion 13,
The weight portion 13 is prevented from being excessively displaced,
To prevent damage.

Reference numeral 3 denotes a second cap, and the first cap 2
In the same manner as described above, the acceleration sensor chip 1 is made of heat-resistant glass and is anodically bonded via the above-described rectangular aluminum thin film in plan view. A concave portion 31 is provided at a position of the second cap 3 facing the weight portion 13. The second cap 3 is supported on, for example, an alumina substrate (base) provided at the bottom of a resin box-shaped package (not shown) that accommodates the semiconductor acceleration sensor.

When the weight portion 13 of the acceleration sensor chip 1 is excessively accelerated and displaced, the second cap 3 comes into contact with the displaced weight portion 13,
The weight portion 13 is prevented from being excessively displaced,
To prevent damage.

In such a semiconductor acceleration sensor, even if a stress is generated between the acceleration sensor chip 1 and the first cap 2 due to a difference in thermal expansion coefficient, the acceleration sensor is a portion where the stress is generated. Bonding surface 1 of chip 1
Numeral 7 is closer to the front end in a predetermined direction than near the base of the extension of the flexure 12 and is far from the flexure 12, so that the flexure 12 is less affected by stress. Characteristics are unlikely to deteriorate.

Next, a semiconductor acceleration sensor according to a second embodiment of the present invention will be described below with reference to FIGS. The portions having substantially the same functions as those of the semiconductor acceleration sensor according to the first embodiment are denoted by the same reference numerals, and only the differences from the semiconductor acceleration sensor according to the first embodiment will be described.

The semiconductor acceleration sensor of this embodiment is basically the same as the semiconductor acceleration sensor of the first embodiment, except that an aluminum thin film 1
6 are provided in an L-shape in plan view, and the front end of the joint surface 17 in a predetermined direction is locally widened.

In such a semiconductor acceleration sensor, in addition to the effect of the semiconductor acceleration sensor of the first embodiment, even if the front end of the bonding surface 17 in a predetermined direction is locally widened to increase the bonding area, Since the distal end in the predetermined direction is a part farthest from the bending portion 12 along the predetermined direction, even if thermal stress occurs, the bending portion 12 is hardly affected by the stress and increases the bonding strength. be able to.

The semiconductor acceleration sensors of the first embodiment and the second embodiment both detect the acceleration received by the weight portion 13 based on a change in the resistance value of a gauge resistor 14 provided on the bending portion 12. However, for example, the first cap 2
Alternatively, a capacitor may be provided on the mutually opposing surfaces of the second cap 3 and the weight portion 13, and based on a change in the capacitance corresponding to a change in the facing distance based on the displacement of the weight portion 13, the weight portion 1 may be provided.
3 may detect the acceleration received.

[0027]

According to the semiconductor acceleration sensor of the first aspect,
Even if a stress is generated between the acceleration sensor chip and the first cap based on the difference in the coefficient of thermal expansion, the joint surface of the acceleration sensor chip where the stress is generated is located closer to the base of the extension of the bending portion. Is also closer to the tip in the predetermined direction,
Since it is far from the bent portion, the bent portion is hardly affected by the stress, so that the temperature characteristic of acceleration detection is hardly reduced.

According to the semiconductor acceleration sensor of the second aspect, in addition to the effect of the semiconductor acceleration sensor of the first aspect, even if the front end of the bonding surface in a predetermined direction is locally widened to increase the bonding area, Since the distal end in the predetermined direction is a part farthest from the bent portion along the predetermined direction, even if thermal stress occurs, the bent portion is hardly affected by the stress, and the bonding strength can be increased. it can.

[Brief description of the drawings]

FIG. 1 is a side view of a first embodiment of the present invention.

FIG. 2 is a perspective view of a first cap of the above.

FIG. 3 is a top view of the acceleration sensor chip.

FIG. 4 is a sectional view taken along line XX of FIG. 3;

FIG. 5 is a top view of an acceleration sensor chip according to a second embodiment of the present invention.

FIG. 6 is a rear view of the same.

FIG. 7 is a sectional view of a conventional example.

FIG. 8 is a top view of the acceleration sensor chip.

FIG. 9 is a perspective view of the first cap of the above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Acceleration sensor chip 12 Flexure part 13 Weight part 17 Joining surface 2 First cap 3 Second cap

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Saito 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. 72) Inventor Masashi Kataoka 1048 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Works Co., Ltd. 1048 Kadoma, Kadoma, Fumonma-shi F-term in Matsushita Electric Works, Ltd. (reference) 4M112 AA02 BA01 CA24 EA02 EA13 FA09 GA01

Claims (2)

[Claims] An acceleration sensor chip in which a beam-shaped bending portion is extended in a predetermined direction and a weight portion which is displaced by acceleration at an end side of the bending portion is integrally formed and supported, and is joined to one surface of the acceleration sensor chip. A first cap facing the weight portion; and a second cap joined to the other surface of the acceleration sensor chip so as to face the weight portion from the side opposite to the first cap, wherein the acceleration sensor chip has A semiconductor acceleration sensor having a joint surface to which the first cap is joined closer to the front end in the predetermined direction than near the extension base of the bending portion. 2. The semiconductor acceleration sensor according to claim 1, wherein the joining surface has a locally widened front end portion in the predetermined direction.