JPH01211986A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To obtain an output excellent in linearity, by arranging diffusion resistors for gauge in the <110> axis direction wherein a piezo resistance coefficient becomes maximum, and arranging diffusion connection signal wires in the direction at 45 deg. to the <110> axis, which direction has no piezo resistance coefficient. CONSTITUTION:In the central part of a substrate 1 using the 100 surface of silicon single crystal, a diaphragm 1a is formed. In the vicinity of its four sides, diffusion resistors 2a-2d for gauge are arranged. At four corners of the substrate 1, electromagnetic pads 3a-3d are arranged. The diffusion resistors 2a-2d and the electromagnetic pads 3a-3d are connected with diffusion connection signal wires 5a, 5b and 6a, 5c, 5d, 5e and 6b, and 5f arranged in the direction at 45 deg. to the <110> axis. Thereby, when pressure is applied to the diaphragm 1a, resistance change due to expansion and contraction of the diffusion connection signal wires 5a-5f, 6a, 6b is avoided, so that the output voltage of a bridge circuit depends only on the diffusion resistors 2a-2d for gauge, and the linearity of applied pressure output is enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a semiconductor pressure sensor that converts pressure into an electrical signal, and particularly relates to a semiconductor pressure sensor that converts pressure into an electrical signal, and particularly relates to a semiconductor pressure sensor that converts pressure into an electrical signal.
Or it relates to a semiconductor pressure sensor used to detect exhaust pressure or the like.

(Prior Art) In recent years, as exhaust gas regulations have been tightened, it is necessary to control automobile engines so that they always have the best combustion state no matter the operating state. To do this, there are methods to maintain optimal combustion conditions by controlling the fuel supply amount and ignition timing using electrical signals detected by the engine's intake pressure using a pressure-electric signal converter, and methods to detect changes in atmospheric pressure and make altitude corrections. Methods of doing this have begun to be adopted. When such a pressure electric signal converter is used for automobiles, heat resistance and vibration resistance are required, and semiconductor pressure sensors using semiconductors as strain gauges are widely used to meet these requirements.

This type of conventional semiconductor pressure sensor will be explained with reference to FIGS. 3 and 4.

FIG. 3 is a plan view of a conventional semiconductor pressure sensor, in which a rectangular diaphragm 1a drawn by a broken line is formed at the center of a substrate 1 made of silicon single crystal (100). (110) Four gauge diffused resistors 2a, 2b, 2c and 2d are arranged in the axial direction to form a Wheatstone bridge, and electrode pads 3ap 3b+ 3c and 3d are formed around them, and these and the above diffusion resistors are formed. Between the resistors 2a, 2b, 2c and 2d, (110) axial diffusion connection signal lines 4a, 4b, 4
c and 4d. Diaphragm 1a
When pressure is applied to the diaphragm 1a, the diaphragm 1a is distorted, and the difference in the amount of distortion generated between the gauge diffused resistors 2a and 20, or 2a and 2d causes the resistance value of the Wheatstone bridge circuit to become unbalanced, and an output is obtained.

FIG. 4 is an equivalent circuit of the Wheatstone bridge circuit formed in the diaphragm 1a. In the figure, the rectangular shapes are the gauge diffused resistors 2a, 2b, 2c, and 2d, the sawtooth shapes are the diffused connection signal lines 4a, 4b, 4c, and 4d, and the circles are the electrode pads 3a, 3b.

3c and 3d, and the reference numerals are assigned according to FIG. 3, respectively.

As is clear from FIG. 4, a diffusion connection signal line 4b is formed in series with the bias voltage VB application circuit applied to the bridge.

In addition, ■ in the figure. ,. l+Va(-1 indicates the output voltages (+) and (-) of the electrodes 3a and 3c, respectively.

(Problem to be Solved by the Invention) However, in such a configuration, the spread connection signal line 4
a, 4b, 4c and 4d are formed in the (110) axial direction on the diaphragm 1a which expands and contracts with pressure, so that the gauge diffusion resistors 2a, 2b, 2c and 2d having piezoresistance coefficients are formed in the (110) axial direction. As the connection signal lines 4a, 4b, 4c and 4d also expand and contract, their resistance values also change. Therefore, in Figure 4,
Even if a constant bias voltage (■8) is applied between the electrode 3b and the electrode 3d, the actual bias voltage applied to the bridge varies, so the output voltage (■). There was a problem in that the linearity of the output was deteriorated.

The present invention solves the above problems and provides a semiconductor pressure sensor having output characteristics with good linearity.

(Means for Solving the Problems) In order to achieve the above problems, the present invention arranges a gauge diffused resistor in the 010> axial direction where the piezoresistance coefficient is maximum, and also connects the above diffused resistor and electrode pad. Connect the diffused connection signal line with a piezoresistance coefficient of <110
By arranging the resistor in a direction having an angle of 45'' with the axis, the sensitivity of the diffused resistor is maximized and the influence of the diffused connection signal line is eliminated.

Furthermore, the diffusion connection signal line on the bias side is built into the bridge circuit to eliminate fluctuations in the bias voltage value applied to the bridge circuit when pressure is applied.

(Function) With the above configuration, the diffusion connection signal line is connected to the <110> axis and the 4
It has an angle of 5° and is formed in the piezoresistance-insensitive direction, so when pressure is applied to the diaphragm, there is no change in resistance due to expansion and contraction of the diffusion connection signal line, and the output voltage of the bridge circuit is determined by the diffusion resistance for the gauge. The linearity of the applied pressure car output is greatly improved.

(Example) An example of the present invention will be described with reference to FIGS. 1 and 2. Note that the same components as in the conventional example shown in FIG. 3 are given the same reference numerals.

FIG. 1 is a plan view of a semiconductor pressure sensor according to the present invention.
, and gauge diffused resistors 2a, 2b, 2c, and 2d are formed near its four sides in the (110) axis direction, and the substrate 1
Electrode pads 3a at the four corners.

3b, 3c and 3d are arranged respectively, and the above diffusion resistors 2a, 2b, 2c and 2d and the above electrode pad 3a are arranged.
, 3b, 3c and 3d, (110> axis and 45
Diffuse connection signals, s5 a , arranged in the direction of .degree.

5b and 6a, 5c, 5d, and 5e are connected by 6b and 5f.

Note that the electrode pad 3a connected to ground and the bias voltage VB
Diffused resistors 2 are connected to the electrode pad 3C through diffusion connection signal lines 5b and 5e, respectively.
a and 2b, and 2C and 2d are connected in parallel to the electrode pads 3a and 3c, and the diffused resistor 2a at both ends is connected to the electrode pads 3a and 3c in parallel.
and 2d, and 2b and 20, respectively, are connected to the diffusion connection signal lines 5.
A and 5f and 5C and 5d are connected in series. Further, the diffusion connection signal lines 5b and 5e inserted in the middle and the electrode pads 3b and 3d for outputting signals are connected by diffusion connection signal lines 6a and 6b, respectively.

FIG. 2 shows an equivalent circuit of the Wheatstone bridge circuit formed on the substrate 1 described above. The rectangular shape is diffused resistance 2
a, 2b, 2c and 2d, the sawtooth shape is the diffusion connection signal line 5
a, 5b, 5c, 5d, 5e, 5f.

6a and 6b, circle marks are electrode pads 3a, 3b, 3
c and 3d, which correspond to FIG. 3, respectively.

The operation of the embodiment configured in this way will be explained.

When pressure is applied to the diaphragm 1a, the diaphragm 1a
is distorted, the resistance values of the gauge diffused resistors 2a, 2b, 2c and 2d formed in the (110) axis direction change, and an output is obtained. Diffused connection signal lines 5a, 5b, 5c, 5d,
5e, 5f, 6a, and 6b are all arranged in a direction forming an angle of 45° with respect to the (110) axis, so that no change in resistance value occurs, so there is no effect on the output of the semiconductor pressure sensor.

Furthermore, since there is no serially connected diffusion connection signal line in the bias voltage VB application section, a factor that deteriorates the linearity of the applied pressure Kerr output voltage value is eliminated.

(Effects of the Invention) As described above, according to the present invention, the diffused connection signal line connecting between the gauge diffused resistor and the electrode pad is arranged in a direction that is not affected by strain, and is connected to the bias applying section. Since there is no spread connection signal line inserted in series, the linearity of the output characteristics can be greatly improved.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a semiconductor pressure sensor according to the present invention, FIG. 2 is an equivalent circuit diagram thereof, FIG. 3 is a plan view of a conventional semiconductor pressure sensor, and FIG. 4 is an equivalent circuit diagram thereof. 1...Substrate, 1a...Diaphragm, 2a. 2b, 2c, 2d-gauge diffused resistor,
3a. 3b, 3c, 3d-electrode pad, 4
a, 4b. 4ct 4d, 5a, 5b, 5c, 5d, 5
e, 5f. 6a, 6b... Diffusion connection signal lines. Fig. 1 C 1-9 board]]a me diaphragm 2a, 2b, 22d-Lee-"j#41i dispersion%t7
L 3a, 3b, 3c, 3d-Electric M bar, 7 Do 5a,
5b, 5c, 5d, 5e, 5f, 6a, 6b JE dispersion duration '=n Fig. 2 b Fig. 3 - <410> 1 - Substrate 1a - Diaphragm 2a, 2b, 2C, 2d - For goo i [Defeated MFA
3a, 3b, 3c, 3d-, electric cypress pa., de 4a, 4b,
4c, 4d-J:fi! Nii (546 people in one person)
Figure 4h

Claims (1)

[Claims] A diffused resistor for a gauge is arranged in the <110> axis direction on a diaphragm formed on a silicon single crystal plate having a (100) plane, and a diffused connection signal line connects between the diffused resistors and the electrode pad. A semiconductor pressure sensor characterized in that the pressure sensor is formed in a direction making an angle of 45 degrees with the <110> axis.