JPH01302119A - Semiconductor acceleration sensor - Google Patents

Abstract

PURPOSE:To reduce the temp. offset drift of sensor output, by bonding a wt. having an engaging projection to the cut groove, which is provided to the surface of the movable end part of a support beam, in an engaged state. CONSTITUTION:A groove part 11a is provided to a semiconductor cantilevered beam 11 composed of Si in the vicinity of the fixed end thereof and a thin wall part 11b is locally formed. A piezoelectric resistor 12 constituted into a bridge circuit is formed to the surface of the thin wall part 11b and cut grooves 11c, 11d for the concentration of stress are formed to the upper and lower parts of the movable end part of the cantilevered beam in the lateral direction. A grasping groove 13a is formed to a wt. 13 composed of Si or solder and the projection 13b engaged with the cut groove 11c is formed to the grasping groove 13a and the wt. 13 is adhered to the movable end part of the cantilevered beam 11 by an adhesive. By this method, the wt. is easily adhered at an accurate position and the drift caused by the heat stress due to adhesion can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention relates to a piezoresistive semiconductor acceleration sensor using a semiconductor support beam, and particularly to a means for attaching a weight to a movable end.

[Conventional technology]

4 and 5 are, for example, Japanese Patent Application Laid-Open No. 62-221184.
FIG. 1 is a plan view and a front view of main parts of a semiconductor acceleration sensor disclosed in the publication. In the figure, reference numeral 1 denotes a cantilever beam made of silicon, and a groove 1 is provided on the back surface near the fixed end, and the upper portion is locally made into a thin wall 1b to enhance sensor sensitivity. A plurality of (
In the figure, four piezoresistors 2) are formed, and are configured into a bridge circuit. A weight 3 is glued to the movable end of the cantilever 1. The fixed end of the support beam 1 is joined and fixed to a pedestal 4, which is a fixed part.

Add the weight 3 to the movable end of the cantilever beam 1 as described above,
Sensitivity is increased by increasing deflection due to acceleration.

[Problem to be solved by the invention]

In the conventional semiconductor acceleration sensor as described above, the cantilever 9
The weight bonded to 1 may shift from its normal position when bonding is completed, resulting in a decrease in detection accuracy.Also, as a result of bonding, thermal stress is generated due to temperature changes, and the diffused piezoresistance is affected by this. As a result, there were problems such as a temperature offset drift in the sensor output.

This invention was made to solve these problems, and allows the weight to be easily adhered to the support beam at an accurate position, thereby reducing temperature offset drift in the sensor output caused by thermal stress caused by adhesion. The purpose is to

[Means to solve the problem]

In the semiconductor acceleration sensor according to the present invention, cut grooves in the width direction are provided on at least the front and back surfaces of the movable end portion of the semiconductor support beam, and a protrusion that engages with the cut groove is provided on the joint surface of the weight 9. The protrusion of the weight is engaged with the notched groove, and the weight is bonded to the movable end of the support rod using an adhesive.

[Effect]

In this invention, the protrusion of the weight is engaged with the cut groove at the movable end of the support beam, so that the support beam can be accurately aligned without being displaced. In addition, residual stress generated in the support beam due to weight adhesion is concentrated in this notch groove, and does not affect the thin wall portion near the fixed end. Therefore, the amount of drift in the offset output of the sensor caused by residual stress that varies due to environmental temperature changes is reduced.

〔Example〕

FIGS. 1 and 2 show a cantilever portion and a weight of an embodiment of a semiconductor acceleration sensor according to the present invention.

In FIG. 1, a semiconductor cantilever beam If made of silicon
A groove portion 11m is provided by etching near the fixed end portion, and thin portions 11h are locally formed to enhance sensor sensitivity. At the upper and lower portions of the movable ends of the cantilever beams 11, cut grooves 11e and lids for stress concentration are formed in the width direction. These grooves 11c, lld
is formed by etching or cutting. On the surface of the thin portion 11b of the cantilever 11, a plurality of piezoresistors 12 are formed by diffusion as in FIG. 4, forming a bridge circuit. The fixed end of the cantilever 11 is joined and fixed to the pedestal 4.

In FIG. 2, a clamping groove 13m is formed in the weight 13 made of silicon, solder, brass, Kovar alloy, etc., and in this clamping groove 13m, a joint surface in contact with the upper surface of the movable end of the support beam 11 has a clamping groove 13m. Projection 1 that engages with the cut groove lie
3b is formed.

This weight 13 is bonded to the movable end of the cantilever beam 11 with an adhesive, as shown in FIG. It fits across the support beam 11 in the pinch groove 13g, and the protrusion 13b fits into the cut groove 11.
c, and are accurately positioned and joined without shifting.

In the acceleration sensor of the above embodiment, the thermal stress generated due to temperature change as a result of adhering the weight 13 to the cantilever beam 11, that is, the thermal stress due to the difference in the coefficient of linear expansion between the two, is
The cut grooves 11c and lld are provided to reduce the influence on the thin portion 11b, thereby eliminating detection errors.

In the above embodiment, the semiconductor cantilever beam 11 was used as the semiconductor support beam, but the present invention can also be applied to a semiconductor double-sided beam in which both ends are fixed, the middle part is a movable part, and a weight is attached.

Further, in the above embodiment, the cut groove lid was provided on the back surface of the movable end of the cantilever 11, but it may be omitted depending on the case.

〔Effect of the invention〕

As described above, according to the present invention, a cut groove in the width direction is provided on at least the front surface and the back surface of the movable end portion of the semiconductor support beam, and a protrusion that engages with the cut groove is provided on the joint surface of the weight. , the protrusion is engaged with the cut groove, and the weight is bonded to the movable end of the support beam with adhesive, so the weight can be joined to the support beam in an accurate position without shifting.
In addition, the thermal stress caused by the difference in thermal expansion between the weight and the beam material caused by adhesion is concentrated in the cut groove, and is prevented from affecting the thin wall part near the fixed end of the support beam. , fluctuations in the sensor offset output caused by this thermal stress are reduced.

[Brief explanation of the drawing]

1 to 3 show an embodiment of a semiconductor acceleration sensor according to the present invention, in which FIG. 1 is a perspective view of a cantilever beam, and FIG. 2 is a perspective view of a cantilever beam;
Figures (a) and (b) are a partially sectional front view and side view of the weight 9, Figure 3 is a perspective view of an acceleration sensor with the weight shown in Figure 2 added to the cantilever beam of Figure 1, and Figure 4. 5 are a plan view and a front view of a conventional semiconductor acceleration sensor. In the figure, 11 is a semiconductor support beam (cantilever beam), l1m is a groove part, llb is a thin wall part, lie and lid are cut grooves, 12
13 is a piezoresistor, 13 is a weight, 13a is a clamping groove, and 13b is a protrusion. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] A semiconductor supporting burr having a groove portion formed on the back surface near the fixed end and a thin-walled upper portion, and a semiconductor support burr having a cut groove for stress concentration formed in the width direction on at least the front surface and the back surface of the movable end portion; A plurality of piezoresistors are formed on the surface of the thin wall part and configured into a bridge circuit, and an engagement protrusion that fits into the cut groove is formed on the joint surface that contacts the surface of the movable end of the support beam. A semiconductor acceleration sensor having a protrusion engaged in a notch and a weight adhesively attached onto a movable end of a support beam.