JP2551625B2 - Semiconductor acceleration sensor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor acceleration sensor used in various fields such as aircraft and automobiles, and more particularly to a semiconductor acceleration sensor with improved detection sensitivity.

[Prior Art] FIG. 5 is a perspective view showing the structure of a conventional semiconductor acceleration sensor, and FIG. 6 is a sectional view taken along the line AA of FIG.

In these figures, 1 is a silicon single crystal substrate formed in a rectangular shape (hereinafter referred to as Si substrate), and a substantially C-shaped void portion 2 is formed along the peripheral portion of the Si substrate 1. . Reference numeral 1a denotes a cantilever portion, which is thin and thin (see FIG. 6) formed by the void portion 2.
A square-shaped weight portion 1b is formed at the tip of the. Reference numerals 3a and 3a denote gauge resistors formed on the cantilever portion 1a by thermal diffusion or ion implantation of a Group 3 element such as boron. 3b and 3b are gauge resistors formed by thermal diffusion or ion implantation of a Group 3 element such as boron similarly to the gauge resistors 3a and 3a, and as shown in FIG. 1, the cantilever portion 1a and the Si substrate. It is provided on the Si substrate 1 side of the connection portion 1. These gauge resistance
3a, 3a, 3b, 3b are gauge resistors 3a, 3a as shown in FIG.
Are bridge-connected so that they are opposite sides.

In the semiconductor acceleration sensor configured in this way,
As shown in FIG. 6, when acceleration is applied in the direction of arrow B, the weight portion 1b is displaced in the applied direction, and the cantilever portion 1a
Bends. As a result, the gauge resistors 3a, 3a provided on the cantilever portion 1a are respectively subjected to tensile strain, and the resistance value changes by an amount corresponding to this strain. Thus, the output Vo corresponding to the magnitude of the acceleration applied from the output end of the bridge circuit can be obtained.

[Problems to be Solved by the Invention] In the conventional semiconductor acceleration sensor described above, only the gauge resistors 3a and 3a provided on the cantilever portion 1a are changed by the acceleration applied from the outside. Since the remaining gauge resistors 3b and 3b are merely for forming a bridge, the detection sensitivity is determined by the values of these gauge resistors 3a and 3a. That is, the gauge resistance 3a, 3a
That is, it is not possible to obtain a detection sensitivity higher than the detection sensitivity determined by the change in the resistance value of. For example, cantilever 1a
In addition to the gauge resistors 3a and 3a provided in the
Only about half the detection sensitivity can be obtained compared with the case where 3b is also changed by the acceleration applied from the outside.

The present invention has been made in view of the above circumstances, and provides a semiconductor acceleration sensor capable of obtaining a detection sensitivity equal to or higher than the detection sensitivity determined by the change in the resistance value of the gauge resistance provided in the cantilever portion. Is intended.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a support portion formed on a peripheral portion of a sensor, a plurality of weight portions, between the weight portions, and the weight portion and the weight portion. It is characterized in that it is provided with a plurality of beam portions that connect with the support portion and a gauge resistance diffused and formed on at least one of these beam portions.

[Operation] According to the present invention, for example, when an acceleration is applied from the outside, the surface of the first beam portion of the plurality of beam portions to which the acceleration is applied is compressed. As a result, each of the two gauge resistors provided on the first beam portion is subjected to compression strain, and the resistance value increases by the amount of this strain. On the other hand, the acceleration-applied surfaces of the second and third beam portions of the plurality of beam portions are pulled.
As a result, each of the gauge resistors provided on the second and third beam portions receives tensile strain, and the resistance value decreases by the amount of this strain. Then, if the resistivity of each of the gauge resistors is equal, when these are connected to form a bridge circuit, the output of the bridge circuit is provided on the cantilever.
This is about twice as large as that of the conventional semiconductor acceleration sensor in which only one gauge resistance changes due to the acceleration applied from the outside.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing the construction of an embodiment of the present invention, and FIG. 2 is a sectional view taken along the line CC of FIG.

In these figures, 5 is a Si substrate formed in a rectangular shape. E-shaped voids 6a and 6b are formed in the Si substrate 5 so as to face each other in the width direction of the drawing. Reference numerals 7a and 7b are weight portions formed in a square shape by the void portions 6a and 6b, respectively. 8
a is a beam portion formed between the weight portion 7a and the weight portion 7b, 8
Reference numeral b denotes a beam portion formed between the weight portion 7a and a peripheral portion of the Si substrate 5 (hereinafter referred to as a support portion), and reference numeral 8c denotes a beam portion formed between the weight portion 7b and the support portion. Each of the beam portions 8a to 8c is formed thin and thin (see FIG. 2) by the void portions 6a and 6b. The weight portions 7a and 7b are supported from both sides by the above-mentioned beam portions 8b and 8c to form a so-called double-supported beam structure. 9a to 9d are gauge resistors,
Of these, the gauge resistances 9a and 9b are respectively in the beam portion 8a, the gauge resistance 9c is in the beam portion 8b, and the gauge resistance 9d is in the beam portion 8c.
Are provided respectively. These gauge resistors 9a to 9d are formed by thermal diffusion or ion implantation of a Group 3 element such as boron. Further, the gauge resistors 9a to 9d are bridge-connected so that the gauge resistors 9a and 9b are on opposite sides, as shown in FIG.

In the double-supported beam structure semiconductor acceleration sensor thus configured, as shown in FIG. 4, when acceleration is applied in the direction of arrow D, the surface of the beam portion 8a to which the acceleration is applied is compressed. As a result, the gauge resistors 9a and 9b provided on the beam 8a are
Each is subjected to compression strain, and the resistance value increases by the amount of this strain. On the other hand, the surfaces of the beam portions 8b and 8c to which the acceleration is applied are pulled. As a result, the gauge resistance 9 provided on the beams 8b and 8c
Each of c and 9d receives tensile strain, and the resistance value decreases by the amount of this strain. Then, the voltage corresponding to the variation of the resistance value of each of the gauge resistors 9a to 9d is output from the bridge circuit. In this case, by making the resistivity of the gauge resistors 9a to 9d equal, the output is approximately twice as large as that of the conventional semiconductor acceleration sensor (see FIG. 5) in which only two gauge resistors are changed. (2Vo). That is, the detection sensitivity is doubled.

By the way, in the above embodiment, the gauge resistance is bridge-wired on the sensor, and a very large detection output can be taken out. However, the gist of the present invention is to provide a plurality of weight portions, a plurality of beam portions that connect between the weight portions and between the weight portion and the support portion, and at least one of these beam portions. Since the gauge resistance is formed by diffusion, the number and the position of the gauge resistance are not limited, and the wiring structure is also changed in accordance with various modifications other than the basic wiring diagram of FIG. Is the one that exists. For example, the gauge resistance may be formed only in the central portion of FIG. 1 or may be formed on only one side. Further, when the reference resistance and the resistance for temperature correction are diffused and formed on the support portion, the wiring configuration includes them.

The weight portion and the beam portion may be made of any material. In this embodiment, when the beam portion is formed, the supporting portion is integrally etched from the same semiconductor single crystal substrate. Although the diffusion resistance is formed on the upper portion, the beam portion may be formed of a single layer or a plurality of layers of different materials such as polysilicon. In this case, the resistance change rate is smaller than that of the single crystal, but there is an advantage that the accuracy of the beam portion can be easily obtained.

[Effects of the Invention] As described above, according to the present invention, the support portion formed on the peripheral portion of the sensor, the plurality of weight portions, between the weight portions, and between the weight portion and the support portion. Since a plurality of beam portions that connect to each other and a gauge resistance that is diffused and formed on at least one of these beam portions are provided, the detection sensitivity is approximately double that of the conventional semiconductor acceleration sensor. . Also,
Since it has a double-supported beam structure, it also has the advantage of increased fracture strength.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showing the structure of an embodiment of the present invention, FIG. 2 is a sectional view taken along the line CC of FIG. 1, and FIG. 3 shows the electrical connection of the embodiment. Wiring diagram, FIG. 4 is a sectional view for explaining the operation of the embodiment, FIG. 5 is a perspective view showing the configuration of a conventional semiconductor acceleration sensor, FIG. 6 is a sectional view taken along the line AA of FIG. FIG. 7 is a wiring diagram showing the electrical connection of FIG. 5: Silicon single crystal substrate (support), 7a, 7b ... Weight, 8a-8c ... Beam, 9a-9d ... Gauge resistance.

Claims (1)

(57) [Claims] 1. A support portion formed on a peripheral portion of a sensor, a plurality of weight portions, a plurality of beam portions connecting between the weight portions and between the weight portion and the support portion, and these beams. A semiconductor acceleration sensor, comprising: a gauge resistance diffused and formed on at least one of the parts.