JPH01244680A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To obtain an output corresponding with power supply voltage fluctuation, make the stress from a package be not sensible, and yet enable the sensitivity temperature compensation in a wide temperature region, by using a polysilicon thin film resistor as a one side gain resistor, and using a diffusion resistor almost equal to a sensor resistor as the other side gain resistor. CONSTITUTION:On one part of a P-type silicon semiconductor substrate 1, a diaphragm part 2 is arranged, and thereon piezo resistors R1-R4 are formed by using a P-type conducting layer 4 surrounded by an N-type isolation layer 3. Transistors, diodes, etc., are formed on the other part of the semiconductor substrate 1, by arranging a P-type conducting layer (p) or an N-type conducting layer (n), with an IC part for forming an output circuit such as an amplifier. A polysilicon resistor 8 and a diffusion resistor 9 are formed on the peripheral part of the substrate 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to sensitivity temperature compensation in a semiconductor pressure sensor incorporating an amplifier circuit.

Conventionally, sensitivity temperature compensation methods for silicon semiconductor pressure sensors include (a) a method in which the voltage applied to the sensor bridge resistance does not have temperature characteristics;

The disadvantage of this method is that if the sensor output is sent to the CPU, etc., it will be sent to the CP[J
The problem is that it is not possible to correct the fluctuations in the ill"C" power supply voltage.

(b) A method of driving the sensor bridge resistor with a constant current source to compensate for the negative sensitivity temperature characteristic by utilizing the positive resistance temperature characteristic of the sensor resistor itself.

In this method, the sensor resistor is P
A surface concentration near 2XIOI8 or 2XIO" is used, but both compensate based on the resistance-temperature characteristics of the sensor resistor itself inside the diaphragm, so the sensor's resistance-temperature characteristics change due to stress from the package etc. As a result, the yield is low, and furthermore, the matching including the second-order terms of the sensitivity temperature characteristics and resistance temperature characteristics of the sensor is poor.
The drawback was that compensation could not be performed over a wide temperature range.

(c) A method of giving temperature characteristics to the amplifier gain.

In this method, a reference resistor among the gain resistors has been used, but it still has the drawback of not being able to perform temperature compensation over a wide temperature range.

In view of the above-mentioned drawbacks of the conventional technology, the present invention makes it possible to obtain an output according to power supply fluctuations, to be insensitive to stress from the package, and to perform sensitivity temperature compensation over a wide temperature range. It is.

Furthermore, it makes it possible to supply a small and inexpensive pressure sensor with an integrated amplification section.

This will be explained below with reference to the drawings. FIG. 2 is an electrical equivalent circuit diagram of a semiconductor pressure sensor applied to the present invention, and FIG. 1(a)
(b) is a sectional view and a plane (pattern) view of the main part showing the construction of the third embodiment of the present invention.

First, in Fig. 2, R1-R4 are piezoresistors forming a bridge, R5-R18 are output adjustment resistors, and Al-A
4 is an amplifier, and the function of this circuit is to increase the resistance R1 due to pressure.
The change in ~R4 is input as an electrical output to the gain amplifiers A2 and A3 from terminals 11 and L, and is also input to the output amplifier A through the amplifier AI for offset adjustment and temperature adjustment.
4 to send out voltage and frequency outputs.

And this output 'A adjustment is resistor R5 to R8 and R17, R
Performed by 18 trimmings.

In FIG. 1, ■ is a P-type silicon semiconductor substrate, 2 is a diaphragm part provided in a part of the substrate, and on the top thereof, a P-type conductive layer 4 surrounded by an N-type separation layer 3 is used to form piezoresistors R1 to R1.
4 is formed. Reference numeral 5 denotes an IC section for forming an output circuit such as an amplifier formed on another part of the semiconductor substrate, and P-type or N-type conductive layers p and n are provided on the substrate to form a transistor,
Alternatively, the 0th order 7.10 in which a diode or the like is formed is an insulating film such as an oxide film, and 6 is a circuit wiring conductor such as aluminum. 8 and 9 constitute essential parts of the present invention. Next, in FIG. 2, R1 to R4 are piezoresistors forming a bridge, and AI and A2 are front-stage amplification circuits, which perform sensitivity temperature compensation. R5 and R8 are diffused resistors having substantially the same diffusion concentration as R1-R4, and R6 and R7 are polysilicon thin film resistors. A3 is a rear-stage intermediate circuit, which includes a gain adjustment resistor R9 and RIG.The main part of the present invention, which is normally placed outside the chip and is sampled using thick-film printed resistors, is the front-stage amplifier AI and A2. Resistor R5, Rh, 1N that determines the gain? , R8, is R1-R
If we write the sensitivity temperature characteristic of piezoresistor 4 as P(T), then the potential at the output point Q of the front stage amplifier is ■. becomes A B. The A part is a constant term, and for the purpose of widening the operating range of the amplifier, it is normally set to zero, ■b, 115
, R7, R8, and R6 are selected. A value around 1 is selected for the purpose of portion B being a portion corresponding to the original gain of the preceding stage amplifier. The resulting equation is expressed as: Here, R5 is a diffused resistor, R6 is a polysilicon thin film resistor, and P (
It has the same temperature characteristics as T). So RD R5
(T), l(6 is written as RC(T), then the formula 0 becomes.

According to experiments, one of the three sensors determined by Eq.
The error in pressure sensitivity between 0°C and 110°C is as shown in FIG. From this figure, in order to reduce the sensitivity output error to 2% or less, the sensor resistance and diffused resistance surface concentration must be set to 0.
, 5 to 4

The results obtained here are based on the skillful manipulation of the three characteristics: piezo temperature characteristic P (t), resistance temperature R8 (T) characteristic, and polysilicon 1 conductive film resistance temperature characteristic Rs ("I')". It is something that can only be obtained by doing things, and the properties of +t and ('r') play an especially important role.Part 3
In the case of the Cr thin film resistor shown as a comparative example in the figure, it can be seen that there is an output error of about 3% even at the mini-7 point.

As is clear from the following description, according to the present invention, in the method of compensating for the sensitivity temperature characteristic of a pressure sensor element by changing the gain of an amplifier circuit, a polysilicon thin film resistor is used as one of the gain resistors. - By using a diffused resistor that matches the sensor resistor as the gain resistor on the other hand, it is possible to perform temperature compensation with high accuracy over a wide temperature range, which has a great practical effect.

ll, l:;ll's simple explanation 1st F! ](a)(b) and FIG. 2 are cross-sectional views, plan views, and electrical equivalent circuit diagrams showing the structure of an embodiment of the present invention, and FIG. 3 is a characteristic diagram of the present invention in comparison with a conventional example. , l is the P-type silicon shrimp sublayer, 2 is the diaphragm part, and 3 is the diaphragm part.
is an epitaxymil layer, 4 is a pressure sensor piezoresistor, and 5 is a pressure sensor piezoresistor.
is the increased rt1 circuit area, 6 is the circuit connection conductor, 7 is the silicon oxide film, 8 is the sensitivity temperature characteristic river polysilicon thin film resistor, 9
is a diffused resistance for sensitivity temperature compensation.

1N1 to R4 are pressure sensor piezoresistors, R5 and R6 are diffused resistors for sensitivity temperature compensation, R7 and R8 are polysilicon thin film resistors for sensitivity and temperature compensation, R9 and RIO are rear stage gain adjustment resistors, A1. A2 indicates a front-stage amplifier, and A3 indicates a rear-stage amplifier.

Patent applicant: Shindengen Chogyo Co., Ltd. Kan-1
Area wharf map 2

Claims (2)

[Claims] (1) A diaphragm part is provided at the center of the base of a semiconductor pressure sensor using silicon, and an amplification circuit for amplifying the sensor output is provided at the periphery, and a sensor resistor is used as a gain resistor to determine the gain of the amplification circuit. A semiconductor pressure sensor characterized in that a diffused resistor and a polysilicon resistor having substantially the same diffusion concentration are provided around the base body. (2) Form the sensor resistance and diffusion resistance with a P-type conductive layer, and set the diffusion concentration to 0.5 to 4×10^1^8ato
Claim No. 1 (1) characterized in that m/cc is
) Semiconductor pressure sensor described in section 2.