JPH01145574A - Semiconductor acceleration sensor - Google Patents

Abstract

PURPOSE:To improve the precision in detection, by interposing correction resistances in series between reference resistances while providing a terminal at a node of the reference resistance and the correction resistance. CONSTITUTION:Correction resistances 9-12 are interposed in series between reference resistances 5 and 6, while terminals 7a-7h and 8a-8d are provided at the resistances 5 and 6, the resistances 9-12 and nodes. A constant-current source CR is connected between the terminal 7b or 7c and the terminals 7f or 7g, and the terminals 7d and 7h are connected with 8d and 8b respectively. Besides, the resistances 9-12 are selected appropriately so that a balance is secured when a bridge connection is made on the basis of the result of measurement of a resistance value of each resistance. On the occasion, the selection of the resistances 9-12 is made by connecting any one of the terminals 7a, 8a, 8b and 7h with an output terminal O1 and by connecting any one of the terminals 7e, 8c, 8d and 7d with an output terminal O2. By interposing the resistances 9-12 on the respective sides of a bridge circuit so that the balance can be secured and that the best one can be selected, in this way, a sensor output on the occasion when no acceleration acts can be made 0 substantially.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a semiconductor acceleration sensor that utilizes a piezoresistance effect, and particularly to a semiconductor acceleration sensor with improved detection accuracy.

[Prior Art] FIG. 3 is a perspective view showing the external configuration of a conventional semiconductor acceleration sensor, FIG. 4 is a sectional view taken along line AA in FIG. 3, and FIG. 5 is a sectional view taken along line BB in FIG. 3. In these figures, l is an n-type semiconductor substrate (hereinafter referred to as a support part) formed in a rectangular shape, and a void part 2 is formed along the peripheral edge of this support part l.

1a is a cantilever section in which a supporting section 1 is thinly formed by a cavity 2, and a rectangular weight section 1b is formed at the tip of this cantilever section 1a.

In FIG. 1, 3.4 is a diffused resistor (
5.6 (hereinafter referred to as a strain-sensitive resistor) and 5.6 are diffused resistors (hereinafter referred to as reference resistors) formed on the upper surface of the support portion l, respectively. The strain-sensitive resistor 3.4 and the reference resistor 5.6 are formed by diffusing a type element such as boron into the cantilever portion 1a and the support portion I. Reference numerals 78 to 7h indicate pounding pads each formed in a rectangular shape.
The pads 7e to 7h are arranged in a row along the longitudinal direction of the space l on the right side of the upper surface, and the pounding pads 7e to 7h are arranged in a row along the longitudinal direction of the space l on the left side of the top surface of the support part 1. .

A reference resistor 6 is connected between bonding pads 7a and 7b, and a strain-sensitive resistor 4 is connected between bonding pads 7c and 7d. Furthermore, bonding pads 7b and 7c are connected. On the other hand, a reference resistor 3 is connected between bonding pads 7e and 7f, and a strain-sensitive resistor 3 is connected between bonding pads 7g and 7h. Furthermore, the bonding pads 7'' and 7g are connected.

In order to operate the semiconductor acceleration sensor constructed in this manner as a sensor, wiring is performed between the strain-sensitive resistor 3.4 and the reference resistor 5.6.

FIG. 6 is its wiring diagram. As shown in this figure, a current source CR is connected between bonding pads 7f or 7g and bonding pads 7b or 7c, and bonding pads 7d and 7e and bonding pads 7a.
and 7h are connected to each other. These are the pounding pads 7 d and 7 e, and the pounding pad 7 a.
, 7 h, the sensor output VO is obtained.

Here, the resistance values of the strain-sensitive resistor 3.4 when no acceleration acts on the weight part tb are R3 and R4, and the reference resistor 5
．． If the resistance values of 6 are R5 and R6, these resistance values are R3-R4=R5=R6, and the sensor output Vo is from the following equation:

On the other hand, when acceleration acts on the weight part tb and the weight part tb deviates according to the magnitude of the acceleration, each resistance value of the strain-sensitive resistor 3.4 becomes R3' = R3 + ΔR3 R4' = r (4 + ΔR4, The sensor output Vo' corresponds to the amount of change in the strain-sensitive resistor 3.4.

[Problems to be Solved by the Invention] By the way, in a semiconductor acceleration sensor that utilizes the piezoresistance effect, the resistance value of the diffused resistor formed therein varies greatly depending on temperature changes, so There is a problem in that high accuracy cannot be obtained if the resistance change is detected only by forming the resistor. For this reason, if diffused resistance is formed in areas other than the beam part as in the conventional semiconductor acceleration sensor mentioned above, and if a bridge circuit is constructed by making all of these resistance values equal, the output changes with respect to temperature changes. This results in an acceleration sensor with a small amount of noise.

However, in the process of forming the diffused resistor, there is a problem in that it is not always possible to manufacture the diffused resistor with the same resistance value due to, for example, differences in the temperature distribution of the furnace, and as a result, there is a limit to the improvement in detection accuracy.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a semiconductor acceleration sensor that can improve detection accuracy.

[Means for Solving the Problems] In order to solve the above-mentioned problems, according to the present invention,
A support portion formed at a peripheral portion of a semiconductor substrate, a weight portion formed at a center portion of the substrate, a beam portion connecting the weight portion and the support portion, and two strain sensitive sensors provided on the beam portion. A semiconductor acceleration sensor comprising a resistor and two reference resistors provided on the support part, and configured in a bridge circuit such that the strain-sensitive resistors are opposite sides of each other, and the reference resistors are opposite sides of each other. The device is characterized in that it includes a correction resistor inserted in series with the reference resistor, and a terminal provided at a connection point between the correction resistor and the reference resistor.

[Function] According to configuration 1, a correction resistor is inserted in series with the reference resistor, and a terminal (for example, a bonding pad) is provided at a contact point between the reference resistor and the correction resistor. Thereby, it is possible to select whether or not to insert a low resistance correction resistor.

Therefore, if the bridge circuit constituted by the strain-sensitive resistor and the base resistor becomes unbalanced, it can be brought into a balanced state by inserting a correction resistor into the reference resistor.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective view showing the external configuration of an embodiment of the present invention. Note that in FIG. 1, the same reference numerals are given to the parts corresponding to those in FIG. , which are arranged at a predetermined interval above the above-mentioned pounding pad 7a.

A diffused resistor 9 is formed between bonding pads 7a and 8a, and a diffused resistor 10 is formed between bonding pads 8a and 8b. 8c and 8d are bonding pads formed on the upper surface of the support portion l, and are arranged at a predetermined interval above the above-described bonding pad 7e. A diffused resistor 11 is formed between the bonding pads 7e and 8C, and the bonding pad 8
A diffused resistor 12 is formed between c and 8d. The above-described diffused resistors 9 to 12 are hereinafter referred to as correction resistors. In addition, the resistance values of the correction resistors 9 to 12 are the same as those of the distortion-sensitive resistor 3 described above.
, 4 and the reference resistors 5, 6.

Also, the correction resistors 9 to 12 are made of a Group 1 element such as boron, similar to the strain-sensitive resistor 3.4 and the reference resistor 5.6 described above.

In the semiconductor acceleration sensor configured in this way, the strain-sensitive resistor 3 when no acceleration acts on the weight portion 1b
．． 4, the reference resistors 5 and 6, and the he positive resistors 9 to 12. After measuring the respective resistance values, wiring for operation as a sensor is performed.

FIG. 2 shows the electrical wiring of the above embodiment, and as shown in this figure, the bonding pads 7b or 7c
A constant current source CR is connected between the pad and the bonding pad 7f or 7g, and the bonding pads 7d and 8d and the bonding pads 7h and 8b are connected, respectively. Then, based on the measurement results of the resistance values of each resistor, correction resistors are appropriately selected so that balance can be maintained when bridge connection is performed. In this case, the correction resistance is selected from the bonding pad 7a.

8a, 8b or 7h and output terminal 0. and bonding pads 7e and 8c.
.

This is done by connecting either one of 8d or 7d to the output terminal 02.

As mentioned above, in order to balance the bridge circuit, correction resistors are inserted on each side of the bridge circuit, and the best one can be selected, so the sensor output when no acceleration is applied is approximately O. be able to. Further, since each resistor is formed of the same material (such as boron), the temperature coefficients are the same, and even if the ambient temperature changes, the amount of change in the resistance value of each resistor is the same. Therefore, the bridge will not become unbalanced even if the ambient temperature changes.

In the above embodiment, the case where four correction resistors are provided has been described, but the number is not limited and four or more may be provided.

Further, in the above embodiments, a case has been described in which the correction resistor is inserted in series with the reference resistor, but the correction resistor may be connected in parallel with the reference resistor.

Further, in the above embodiment, the case where the present invention is applied to a semiconductor acceleration sensor having a cantilever beam portion has been described, but it can of course be applied to a semiconductor acceleration sensor having a dual beam portion.

[Effects of the Invention] As explained above, according to the present invention, a support portion formed at the peripheral portion of a semiconductor substrate, a weight portion formed at the center portion of the substrate, and a combination of the weight portion and the support portion. It has a connecting beam portion, two strain-sensitive resistors provided on the beam portion, and two reference resistors provided on the support portion, each of the strain-sensitive resistors being opposite sides of each other, and In a semiconductor acceleration sensor configured in a bridge circuit such that reference resistors are on opposite sides of each other, a correction resistor inserted in series with the reference resistor, and a terminal provided at a connection point between the Moeki capture resistor and the Moeki reference resistor. Therefore, it is possible to arbitrarily select the best correction resistor for correcting the unbalanced state of the bridge circuit to a balanced state when no acceleration is applied. Therefore, it is not affected by the ambient temperature, the detection accuracy is improved, and acceleration sensors with uniform detection accuracy can be mass-produced.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the external configuration of an embodiment of the present invention;
Fig. 2 is a wiring diagram showing electrical connections for operating the same embodiment, Fig. 3 is a perspective view showing the external configuration of a conventional semiconductor acceleration sensor, Fig. 4 is a cross-sectional view taken along line AA in Fig. 3, FIG. 5 is a sectional view taken along line BB in FIG. 3, and FIG. 6 is a wiring diagram showing electrical connections for operating a conventional semiconductor acceleration sensor. l...Semiconductor substrate (support part), Ia...
・Cantilever beam part, tb... Weight part, 3.4... Diffusion resistance (strain sensitive resistance), 5.6...
...Diffused resistance (reference resistance), 9 to 12...
Diffusion resistance (correction resistance). 8a to 8d...Ponding pads (terminals).

Claims (1)

[Claims] (1) A support portion formed at the peripheral edge of the semiconductor substrate, a weight portion formed at the center of the substrate, a beam portion connecting the weight portion and the support portion, and two portions provided on the beam portion. a strain-sensitive resistor and two reference resistors provided on the support part, and a bridge circuit is configured such that the strain-sensitive resistors are opposite sides of each other and the reference resistors are opposite sides of each other. A semiconductor acceleration sensor comprising: a correction resistor inserted in series with the reference resistor; and a terminal provided at a connection point between the correction resistor and the reference resistor.