JP2551625C - - Google Patents

Description

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 a structure of a conventional semiconductor acceleration sensor, and FIG. 6 is a view A of FIG.
FIG. 3 is a sectional view taken along line A. In these figures, reference numeral 1 denotes a silicon single crystal substrate (hereinafter referred to as S
A substantially C-shaped gap 2 is formed along the periphery of the Si substrate 1. Reference numeral 1a denotes a cantilever portion, which is formed thin and thin (see FIG. 6) by the gap portion 2 and has a rectangular weight portion 1b formed at the tip of the cantilever portion 1a. Reference numerals 3a and 3a denote gauge resistors formed by thermally diffusing or ion-implanting a Group 3 element such as boron in the cantilever portion 1a. Reference numerals 3b and 3b denote gauge resistors formed by thermally diffusing or ion-implanting a Group 3 element such as boron in the same manner as the gauge resistors 3a and 3a. As shown in FIG. 1 is provided on the Si substrate 1 side of the connection portion. These gauge resistors 3a, 3a, 3b,
3b is bridge-connected such that the gauge resistors 3a, 3a are on opposite sides as shown in FIG. In the semiconductor acceleration sensor thus configured, as shown in FIG. 6, when acceleration is applied in the direction of arrow B, the weight 1b is displaced in the direction in which the acceleration is applied, and the cantilever 1a is bent. Thereby, the gauge resistors 3a, 3a provided on the cantilever 1a are provided.
Receive a tensile strain, and the resistance value changes by an amount corresponding to the strain. Then
An output Vo corresponding to the magnitude of the acceleration applied from the output terminal of the bridge circuit is obtained. [Problems to be Solved by the Invention] In the above-described conventional semiconductor acceleration sensor, only the gauge resistors 3a and 3a provided on the cantilever 1a are changed by an externally applied acceleration. (The remaining gauge resistances 3b and 3b are merely for forming a bridge), the detection sensitivity is determined by the values of the gauge resistances 3a and 3a.
That is, a detection sensitivity higher than the detection sensitivity determined by the change in the resistance value of the gauge resistors 3a, 3a cannot be obtained. For example, in addition to the gauge resistances 3a and 3a provided on the cantilever 1a, the remaining gauge resistances 3b and 3b can be detected only about half as sensitively as compared with the case where the remaining gauge resistances 3b and 3b are changed by an externally applied acceleration. . The present invention has been made in view of the above circumstances, and provides a semiconductor acceleration sensor capable of obtaining a detection sensitivity higher than a detection sensitivity determined by a change in a resistance value of a gauge resistor provided in a cantilever portion. It is intended to be. [Means for Solving the Problems] In order to achieve the above object, the present invention provides a support formed on a peripheral portion of a sensor, a plurality of weights, a space between the weights, and A plurality of beams that connect to the supporting portion and a surface that is compressed and a surface that is pulled when acceleration is applied are formed on at least two of the beams, respectively, by diffusion. And a gauge resistor. [Operation] According to the present invention, for example, when 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 receives a compressive strain, and the resistance value increases by the amount of the strain. On the other hand, the surface of the second and third beam portions of the plurality of beam portions to which the acceleration is applied is pulled. As a result, each of the gauge resistors provided on the second and third beams receives tensile strain, and the resistance value is reduced by the amount of the strain. If the resistivity of each of the gauge resistors is equal, if these are connected to form a bridge circuit, the output of the bridge circuit is only the two gauge resistors provided on the cantilever from outside. It is about twice as large as that of a conventional semiconductor acceleration sensor that changes according to the applied acceleration. Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing the structure of one embodiment of the present invention, and FIG. 2 is a sectional view taken along the line CC of FIG. In these figures, reference numeral 5 denotes a square-shaped Si substrate. E-shaped voids 6a and 6b are formed in the Si substrate 5 so as to face in the drawing width direction. 7
Reference numerals a and 7b denote weight portions formed in a square shape by the gap portions 6a and 6b, respectively. 8a is a beam formed between the weights 7a and 7b, and 8b is a weight 7
a formed between a and a peripheral portion (hereinafter referred to as a support portion) of Si substrate 5, 8 c
Is a beam formed between the weight 7b and the support. Each of these beam portions 8a to 8c is formed thin and thin (see FIG. 2) by the gap portions 6a and 6b. By supporting the weights 7a, 7b from both sides by the above-mentioned beams 8b, 8c, a so-called doubly supported beam structure is obtained. Reference numerals 9a to 9d denote gauge resistors. Of these, the gauge resistors 9a and 9b are respectively connected to the beam portions 8a and the gauge resistors 9c.
Is provided on the beam portion 8b, and a gauge resistor 9d is provided on the beam portion 8c.
Each of the gauge resistors 9a to 9d is formed by thermally diffusing or ion-implanting a Group 3 element such as boron. The gauge resistors 9a to 9d are bridge-connected such that the gauge resistors 9a and 9b are on opposite sides as shown in FIG. In the doubly-supported semiconductor acceleration sensor configured as described above, when acceleration is applied from the direction of arrow D as shown in FIG. 4, the surface of the beam portion 8a to which the acceleration is applied is compressed. As a result, each of the gauge resistors 9a and 9b provided on the beam portion 8a receives a compressive strain, and the resistance value increases by the amount of the strain. On the other hand, the surfaces of the beams 8b and 8c to which the acceleration is applied are pulled. As a result, the gauge resistors 9c and 9d provided in the beam portions 8b and 8c respectively receive the strain of the force bow I, and the resistance value decreases by the amount of the strain.
Thus, a voltage corresponding to the change in 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 each of the gauge resistors 9a to 9d equal, the output is approximately twice as large as that of a conventional semiconductor acceleration sensor (see FIG. 5) in which only two gauge resistors are changed. (2Vo). That is, the detection sensitivity is approximately doubled. In the above embodiment, the gauge resistance is bridge-wired on the sensor, and a very large detection output can be obtained. However, the gist of the present invention is that a plurality of weights, between the weights, and a plurality of beams connecting between the weights and the support, and a surface that is compressed when acceleration is applied. A gauge resistance diffused and formed on at least two of the beams having each of the surfaces to be pulled, so that the number and position of the gauge resistors are not limited. Accordingly, various modifications other than the basic wiring diagram of FIG. 4 exist. Further, when a reference resistance and a resistance for temperature correction are diffused and formed in the support portion, the wiring configuration includes them. The material of the weight portion and the beam portion is arbitrary. In this embodiment, when the beam portion is formed, the support portion is integrally etched from the same semiconductor single crystal substrate,
Although the diffusion resistance is formed on the beam portion, the beam portion may be formed by a single layer or a multi-layer of a different material such as polysilicon. In this case, although the resistance change rate is smaller than that of the single crystal, there is an advantage that the accuracy of the beam portion is easily obtained. [Effect 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, the space between the weight portions, and the space between the weight portion and the support portion are provided. A plurality of beams to be connected; and a gauge resistor diffusely formed on at least two of the beams having a surface that is compressed and a surface that is pulled when an acceleration is applied. Therefore, the detection sensitivity is increased as compared with the conventional semiconductor acceleration sensor. In addition, because of the double-supported beam structure, there is obtained an advantage that the breaking strength is increased.

[Brief description of the drawings]   FIG. 1 is a perspective view showing the structure of one embodiment of the present invention,   FIG. 2 is a sectional view taken along the line CC of FIG. 1,   FIG. 3 is a wiring diagram showing an electrical connection of the embodiment,   FIG. 4 is a sectional view for explaining the operation of the embodiment,   FIG. 5 is a perspective view showing a configuration of a conventional semiconductor acceleration sensor,   FIG. 6 is a sectional view taken along line AA of FIG. 5,   FIG. 7 is a wiring diagram showing the electrical connection of FIG. 5 ... silicon single crystal substrate (support) 7a, 7b ... weight part, 8a to 8c: beam part, 9a to 9d: gauge resistance.

Claims (1)

Claims: A support formed on a peripheral portion of a sensor, a plurality of weights, a plurality of beams connecting between the weights and between the weights and the support, A semiconductor acceleration sensor having a gauge resistance diffusely formed on at least two of these beams having a surface compressed and a surface pulled when applied. .