JP2001337103A - 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 semiconductor acceleration sensor includes an acceleration sensor chip 1 having a beam-shaped deflecting part extended therefrom, with a weight part 13 supported against the end of the deflecting part by integral molding, the weight part 13 being displaced by acceleration; a first cap 2 having a joining face 23 joined to one face of the acceleration sensor chip 1 in such a manner as to face the weight part 13; and a second cap joined to the other face of the acceleration sensor chip 1, in such a manner as to face the weight part 13 from the side opposite to the first cap 1, with the second cap being supported on a base. The first cap 2 is formed with a recessed stress-relieving part 24 for releaving stresses is provided on the joining face 23 thereof.

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 Conventionally, there is a semiconductor acceleration sensor of this type shown in FIG. This device includes an acceleration sensor chip A, a first cap B, and a second cap C.

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.

The first cap B is made of glass and has a joint surface B1 whose base end is joined to one surface of the acceleration sensor chip A so as to face the weight portion A2. When the weight portion A2 is displaced due to excessive acceleration, the first cap B contacts the displaced weight portion A2 to restrict the weight portion A2 from being excessively displaced.
The weight 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 second cap is supported on, for example, an alumina substrate (base) provided at the bottom of a resin box-shaped package (not shown) that accommodates the acceleration sensor chip.

[0006]

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 first cap B has a coefficient of thermal expansion of about 3.31 × 10 ⁻⁶ / K (20 ° C.) and has a different coefficient of thermal expansion. When used in the above, there is a possibility that a thermal stress is generated from the joint.

As described above, 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.

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.

[0009]

According to a first aspect of the present invention, there is provided a semiconductor acceleration sensor, comprising a beam-like bent portion extending and a weight portion which is displaced by acceleration toward the tip end of the bent portion. A first cap having a joint surface joined to one surface of the acceleration sensor chip so as to face the weight portion;
A second cap that is joined to the other surface of the acceleration sensor chip so as to face the weight portion from the side opposite to the cap and that is supported by the base, wherein the first cap is And a structure in which a concave stress relaxing portion for relaxing stress is provided on the joint surface.

According to a second aspect of the present invention, in the semiconductor acceleration sensor according to the first aspect, the first cap has the joining surface along a direction in which the bending portion extends. The stress relief portion is provided along the extending direction.

According to a third aspect of the present invention, in the semiconductor acceleration sensor according to the second aspect, the first cap has a width substantially equal to a width of a portion where the joint surface is divided by the stress relaxation portion. It has a configuration.

According to a fourth aspect of the present invention, there is provided the semiconductor acceleration sensor according to the second aspect, wherein the first cap is formed of a plurality of surfaces formed by dividing the joining surface by the stress relaxation portion. The area of the surface near the bending portion is made smaller than the area of the surface remote from the bending portion.

According to a fifth aspect of the present invention, in the semiconductor acceleration sensor of the first aspect, the first cap has the joining surface along a direction in which the bending portion extends, and the joining surface is provided. The stress relaxation portion is provided along a direction orthogonal to the extending direction.

[0014]

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.

Reference numeral 1 denotes an acceleration sensor chip which is formed of a silicon substrate and is formed in a rectangular shape in plan view, as shown in FIG. 3, and has a rectangular hole 11 in plan view in the center thereof. In the acceleration sensor chip 1, a pair of beam-shaped flexures 12 having elasticity from one opening edge of the hole 11 are extended in a predetermined direction toward the opening of the hole 11, and the flexure A weight portion 13 that is displaced in the vertical direction in response to acceleration is supported at the tip of 12 by integral molding. 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.

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 an aluminum thin film 16 for joining a first cap 2 described later on both sides of one surface of the acceleration sensor chip 1 at a position corresponding to a joining surface 23 of the first cap 2 described later. On the other surface, an aluminum thin film (not shown) for joining a second cap 3 to be described later is provided in a rectangular shape in plan view.

Reference numeral 2 denotes a first cap, which is formed of heat-resistant glass 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 tip surfaces of both side portions 21 and 21 of the first cap 2 form a bonding surface 23 that is anodically bonded to the acceleration sensor chip 1 via the aluminum thin film 16 described above. This first cap 2
The concave portion 22 is opposed to the weight portion 13 because the joint surface 23 is anodically bonded to the acceleration sensor chip 1 via the aluminum thin film 16.

The first cap 2 is provided on a joint surface 23 with the acceleration sensor chip 1 along a predetermined direction which is a direction in which the bending portion 12 extends. Is provided over both ends in a predetermined direction,
The joining surface 23 is divided along both ends along a predetermined direction, and divided into two surfaces having substantially the same width. The stress relieving unit 24 relieves the thermal stress generated at the joint between different materials such as the acceleration sensor chip 1 and the first cap 2 via the aluminum thin film 16 by relieving it.

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. The surface 31 of the second cap 3 facing the weight portion 13 is formed in a concave shape. The second cap is supported on, for example, an alumina substrate (base) provided at the bottom of a resin box-shaped package (not shown) that accommodates the acceleration sensor chip.

When the weight portion 13 of the acceleration sensor chip 1 is displaced due to excessive acceleration, 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, based on the difference in thermal expansion coefficient between the first cap and the acceleration sensor chip, an orthogonal direction orthogonal to a predetermined direction in which the bending portion 12 extends is provided. Even if a stress is generated, the stress is absorbed and relieved by the stress relieving portion 24 provided so as to divide the joint surface 23 along the extending direction of the bending portion 12. And the temperature characteristics of acceleration detection are less likely to be reduced.

The first cap is provided with a stress relaxation portion 24.
Since the width of the portion where the joining surface 23 is divided is made substantially equal, the provision of the stress relaxation portion 24 eliminates the portion where the width is particularly narrowed and the mechanical strength is weakened, and it is hard to break. Become.

In this embodiment, the first cap 2
Are provided on the joint surface 23 with the acceleration sensor chip 1
2 along a predetermined direction which is the extension direction of the stress relaxation portion 24.
Are provided over both ends in a predetermined direction, so that the bonding surface 2
3 is divided along both ends along a predetermined direction and divided into two surfaces having substantially equal widths. Even if the widths are substantially equal, the effect of being hardly damaged can be obtained.

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.

In the semiconductor acceleration sensor according to the first embodiment,
The first cap 2 is provided with a stress relaxation portion 24 on a joint surface 23 with the acceleration sensor chip 1, and the two surfaces divided by the stress relaxation portion 24 have substantially the same width. In the embodiment, the first cap 2 is provided with the stress relaxation portion 24 near the bending portion 12 in the joining surface 23, so that the area of the surface near the bending portion 12 is reduced.
It is smaller than the area of the surface far from.

In this semiconductor acceleration sensor, similarly to the semiconductor acceleration sensor of the first embodiment, it is assumed that stress is generated between the first cap 2 and the acceleration sensor chip 1 based on the difference in the coefficient of thermal expansion. Also, since the stress is absorbed and relieved by the stress relieving portion 24, the stress is less likely to be transmitted to the bending portion 12 of the acceleration sensor chip 1 and the temperature characteristics of the acceleration detection are less likely to decrease.

In addition, considering that the smaller the area of the divided surface of the bonding surface 23 is, the smaller the stress based on the difference in the coefficient of thermal expansion between the first cap 2 and the acceleration sensor chip 1 is. By making the area of the surface closer to the bending portion 12 smaller, the stress generated near the bending portion 12 can be further reduced, so that the effect that the temperature characteristic of acceleration detection is less likely to decrease can be further exhibited. .

Next, a semiconductor acceleration sensor according to a third 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.

In the semiconductor acceleration sensor according to the first embodiment,
The first cap 2 has a stress relaxation portion 24 provided on a joint surface 23 with the acceleration sensor chip 1 along a predetermined direction which is a direction in which the bending portion 12 extends. The first cap 2 has a stress relaxing portion 24 provided on a joint surface 23 with the acceleration sensor chip 1 along a direction orthogonal to a predetermined direction which is a direction in which the bending portion 12 extends.

In such a semiconductor acceleration sensor, even if a stress in the extending direction of the bending portion 12 is generated between the first cap 2 and the acceleration sensor chip 1 based on the difference in the coefficient of thermal expansion. The stress is absorbed and relieved by the stress relieving portion 24 provided so as to divide the joint surface 23 along a direction orthogonal to the direction in which the bending portion 12 extends, so that the stress of the acceleration sensor chip 1 is reduced. It is difficult to be transmitted to the bending portion 12, and the temperature characteristic of acceleration detection is hard to decrease.

In each of the semiconductor acceleration sensors according to the first to third embodiments, the acceleration received by the weight portion 13 is detected by a change in the resistance value of the gauge resistor 13 provided in 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.

As in the first embodiment and the second embodiment, the stress relaxing portion 2 is provided on the joint surface 23 with the acceleration sensor chip 1 along a predetermined direction which is the direction in which the bending portion 12 extends.
4 and at the same time, by providing the stress relaxation portions 24 along an orthogonal direction perpendicular to the predetermined direction, the stress relaxation portions 24 may be formed in a lattice shape in a plan view, in which case, the extending direction of the bending portion 12 or Even if any stress in the direction perpendicular to the extending direction is generated, the stress is absorbed and relieved by the stress relieving portion 24, so that the stress is hardly transmitted to the bending portion 12 of the acceleration sensor chip 1, and the acceleration is detected. Temperature characteristics hardly deteriorate.

[0036]

According to the semiconductor acceleration sensor of the first aspect,
Even if a stress is generated between the first cap and the acceleration sensor chip based on the difference in the coefficient of thermal expansion, the stress is absorbed by the concave stress relief portion provided on the joint surface of the first cap and relaxed. Therefore, it is difficult for the stress to be transmitted to the bent portion of the acceleration sensor chip, and the temperature characteristics of acceleration detection are hardly reduced.

In the semiconductor acceleration sensor according to the second aspect, stress in the orthogonal direction perpendicular to the extending direction of the bending portion is generated based on the difference in the coefficient of thermal expansion between the first cap and the acceleration sensor chip. However, since the stress is absorbed and relieved by the stress relieving portion provided on the joint surface along the extending direction of the bending portion, the stress is hardly transmitted to the bending portion of the acceleration sensor chip, and the acceleration detection is performed. Temperature characteristics hardly deteriorate.

According to the semiconductor acceleration sensor of the third aspect, in addition to the effect of the semiconductor acceleration sensor of the second aspect, a first
In the cap, since the width of the portion where the joining surface is divided by the stress relaxation portion is made substantially equal, the location where the stress relaxation portion is provided particularly narrows the width and the mechanical strength is weakened. It is less likely to break.

In the semiconductor acceleration sensor according to the fourth aspect, the smaller the area of the plurality of divided surfaces of the bonding surface is,
Since the stress based on the difference in the coefficient of thermal expansion between the first cap and the acceleration sensor chip is reduced, the surface area near the bent portion is made smaller than the area away from the bent portion, so that the stress is generated near the bent portion. Therefore, the effect of the semiconductor acceleration sensor according to the second aspect, in which the temperature characteristic of acceleration detection does not easily decrease, can be further exhibited.

According to the semiconductor acceleration sensor of the present invention, even if a stress is generated in the extending direction of the bent portion based on the difference in the coefficient of thermal expansion between the first cap and the acceleration sensor chip, the stress is not changed. Is absorbed and relieved by the stress relieving portion provided on the joint surface along the orthogonal direction orthogonal to the extending direction of the bending portion, so that stress is less likely to be transmitted to the bending portion of the acceleration sensor chip, and acceleration is detected. Temperature characteristics hardly deteriorate.

[Brief description of the drawings]

FIG. 1 is a front sectional 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 side view of the same.

FIG. 5 is a front sectional view of a second embodiment of the present invention.

FIG. 6 is a top view of the acceleration sensor chip.

FIG. 7 is a front sectional view of a third embodiment of the present invention.

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

FIG. 9 is a side view of the same.

FIG. 10 is a sectional view of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Acceleration sensor chip 12 Flexure part 13 Weight part 2 First cap 23 Joining surface 24 Stress relaxation part 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, Kamon, Fumonma-shi Matsushita Electric Works F-term (reference) 4M112 AA02 BA01 CA24 CA26 CA36 DA18 EA02 EA13 FA09 GA01

Claims (5)

[Claims] An acceleration sensor chip in which a beam-shaped bending portion is extended and a weight portion displaced by acceleration is integrally formed and supported on a tip side of the bending portion, and one surface of the acceleration sensor chip is opposed to the weight portion. A first cap having a joining surface joined to the acceleration sensor chip, and a second cap supported on the base and 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. A semiconductor acceleration sensor comprising: a cap; wherein the first cap is provided with a concave stress relief portion for relaxing stress on the bonding surface. 2. The method according to claim 1, wherein the first cap has the joint surface along a direction in which the bending portion extends, and the stress relief portion is provided on the joint surface along the extension direction. The semiconductor acceleration sensor according to claim 1, wherein 3. The semiconductor acceleration sensor according to claim 2, wherein the first cap has substantially equal widths at portions where the joint surface is divided by the stress relieving portion. 4. The first cap includes a plurality of surfaces formed by dividing the joining surface by the stress relieving portion.
3. The semiconductor acceleration sensor according to claim 2, wherein an area of a surface near the bending portion is smaller than an area of a surface remote from the bending portion. 5. The first cap has the joint surface along a direction in which the bending portion extends, and the stress relief portion is formed on the joint surface along an orthogonal direction perpendicular to the extension direction. The semiconductor acceleration sensor according to claim 1, wherein the sensor is provided.