JPS61246619A - Resistance-type conversion device - Google Patents

Abstract

PURPOSE:To enable the highly accurate detection of a physical quantity to be measured, by providing a pair of gage resistances whose resistance values change differentially according to the physical quantity to be measured, a gage resistance whose resistance value does not change differentially, and a compensation signal generating means. CONSTITUTION:Resistance value detecting circuits 22 and 23 detect resistance values of paired gage resistances 15 and 16 and deliver outputs Ea and Eb respectively. A difference detecting circuit 24 receiving said outputs Ea and Eb operates a difference voltage Ec of the outputs Ea and Eb and delivers same. Meanwhile, a compensation signal generating circuit 25, receiving an output of an output circuit 26, forms and delivers a compensation signal Ed based on a current flowing through a gage resistance 17. Then, the output signal 26 adds up the compensation signal Ed and the output Ec of the difference detecting circuit and delivers the sum. An effect produced by fluctuations of ambient temperature is thereby compensated effectively, and thus a physical quantity to be measured can be detected with high accuracy.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a resistance converter using a gauge resistor whose resistance value changes depending on a physical object to be measured such as pressure or differential pressure.

<Conventional technology> Generally, in a resistance type converter, a high concentration impurity (boron) is diffused onto a pressure receiving diaphragm made of a single crystal semiconductor such as silicon to form a gauge resistance, and the pressure applied to both sides of the pressure receiving diaphragm is reduced. A stress based on the difference is applied to the gauge resistor, and the change in the resistance value of the gauge resistor due to the piezoresistance effect is made to correspond to the pressure difference, that is, the physical quantity to be measured.

Then, two or four gauge resistors are provided on the pressure-receiving diaphragm to form a half bridge or full bridge, and a signal representing the physical quantity to be measured is obtained.

<Problems to be Solved by the Invention> By the way, in this type of resistance converter, the gauge resistance has a large temperature dependence, so there is a drawback that the output fluctuates due to the influence of changes in ambient temperature.

Therefore, in general, a temperature sensing element such as a thermistor, a posistor, or a transistor is used to control the power supply voltage of the bridge according to the concentration change to compensate for the output fluctuation. In order to perform accurate compensation using this method, it is necessary to match the S* characteristics of the gauge resistance and the temperature characteristics of the compensation temperature sensing element. However, it is not easy to match these, and highly accurate compensation is required. was difficult.

The present invention effectively compensates for the effects of changes in ambient temperature,
The object of the present invention is to realize a resistive conversion device that can detect physical quantities to be measured with high precision.

Means for Solving the Problems> The present invention provides a first semiconductor device formed on a semiconductor single crystal substrate and having a resistance value of at least one of which changes depending on a physical quantity to be measured.
a second gauge resistor; a third gauge resistor formed on the single crystal substrate and whose resistance value is unrelated to the physical quantity to be measured;
Said 1st. a circuit that supplies current to a second gauge resistor;
an output circuit that obtains an output signal by adding a compensation signal to a difference signal based on the difference in resistance value of these first and second gauge resistors;
The present invention is characterized in that a compensation signal generating circuit is provided for supplying a current of 1131 to this output signal to a third gauge resistor to obtain the compensation signal.

Effect> The present invention provides a compensating signal by supplying m currents related to the output signal to the third gauge resistor, and transmits this compensating signal to the first gage resistor. By simply selecting the value of the compensation signal, the ambient I! This makes it possible to effectively eliminate the effects of

<Example> FIG. 1 is a connection diagram showing an example of the present invention, and FIG. 2 is a configuration explanatory diagram showing an example of a detector used in the device of the present invention.
A) is a cross-sectional view, and (b) is a perspective view. In both figures,
10 is a detector, and 20 is a signal processing circuit.

In the detector 10, a single crystal semiconductor substrate 1 such as silicon
A pressure receiving diaphragm 12 is formed in the center of the pressure receiving diaphragm 1 by etching, which is sensitive to the difference between a reference pressure Po (for example, atmospheric pressure) and a measured pressure PM.

A fixed portion 13 around the substrate 11 is joined to a base 14 . Through diffusion technology, ion implantation, etc., the pressure receiving diaphragm 12 has a first. A second gauge resistor 15 , 16 is provided, and a third gauge resistor 17 is provided on the fixed part 13 . 1st. Stresses σ and σ2 according to the pressure to be measured PM act on the second gauge resistor 15 and 16, and the gauge resistor 15.
The resistance value RMI of the gauge resistor 16 and the resistance value RM2 of the gauge resistor 16 are respectively given by the following equations.

RMI-Rot(1+α+1) × (1+π1 σI (1+β item 1>)...
(1) RM2 −RO2(1+αzi) X(1+π2 σ2 (1+β2 t) )... (
2) However, Ro I, Ro 2: l! q! Resistance value α1 at temperature 1o. α2: Temperature coefficient π1 of resistance value Ro+*Roa. π2: Piezoresistance coefficient β7 at M quasi-temperature to. β2: Temperature coefficient of piezoresistance coefficient π1゜π2 t: Concentration change from Jl quasi-temperature to Also, stress due to the measured pressure PM does not act on the third gauge resistor 17, and its resistance value RM3 is given by the following formula. It will be done.

Rr+5-Ro*(1+α3t)-self...
(3) However, RO3: Resistance value at reference temperature 1o α3: Temperature coefficient of resistance value Ro3 Note that the gauge resistors 15, 16, and 17 are formed on the same substrate 11, and the temperature coefficients are α1-α2-αcoα, respectively. β
The kneading properties that can be considered as 1-R2-β can be made uniform. Also π1σ1. Regarding π2σ, for example, on the (100) plane of silicon, if the gauge resistance is 1 in the [1101 direction]
If 5.16 are placed at right angles to each other, π1σ1−−π2
It can be set to σ2−πσ. In this way,
The resistance value of one of the gauge resistors 15 and 16 increases and the resistance value of the other decreases depending on the measured pressure PM acting on the pressure receiving diaphragm.

In the signal processing circuit 20, 21 is a reference voltage source, 22.
23 is a resistance value detection circuit, 24 is a difference detection circuit, 25 is a compensation signal generation circuit, and 26 is an output circuit. 1! The resistance value detection circuit 22 has an operational amplifier OPt, a gauge resistor 15 is connected to the feedback circuit of OPs, and a constant voltage is supplied from the reference voltage source 21 to the input terminal (-) of OP+ via a resistor R1. Er is added. The resistance value detection circuit 23 has an operational amplifier OPa, a gauge resistor 16 is connected to the feedback circuit of OF2, and a resistor R is connected to the input terminal (-) of OPx.
A constant voltage E" from the reference voltage 11i21 is applied to the gauge resistor 15 through Er/R+
A current 11 flows through the gauge 16, and a current I2 flows through the gauge 16, which becomes Er/R2. The difference detection circuit 24 is an operational amplifier OPs
The resistor R4 is connected to the feedback circuit of OP3,
A resistance value detection circuit N2 is connected to the input terminal (-) via a resistor R3.
3, and the output voltage Ea of the resistance value detection circuit 22 is applied to the input terminal (+) after being divided by the resistors Rs and Re. And the difference detection circuit 24 is R3
-R4-R5-R6, resistance value detection circuit 22.2
The difference (Ea - Eb) between the output voltages Ea+E'b of No. 3 is calculated and output. The compensation signal generation circuit 25 is an operational amplifier OP.
4, a gauge resistor 17 is connected to the feedback circuit, and the output voltage Eo of the output circuit 26 is applied to the input terminal (-) via the resistor R7. The output circuit 26 consists of an operational amplifier of 10 Ps, and a resistor RI is connected to the feedback circuit of the OPs.
G is connected to the input terminal (-), and the output EC of the difference detection circuit 24 is applied to the input terminal (-) via the resistor Rs.
The output voltage Ed of the compensation signal generation circuit 25 is applied via e. And the output times WI26 is 88m R, m
R. Then, (Ec + Ed) is calculated and output.

In the device of the present invention configured in this manner, the output voltages Ea and Eb of the resistance value detection circuits 22.23 are EO−−Er.
・RM+/R+ ・・・・・・(4) Eb−−Er
-RM2/R2 (5), and the output voltage Ec of the difference detection circuit 24 is expressed as R+-mR2 as shown in the following equation.

Ec = (Ea-Eb) =-Er (RMl-RM2)/R+...
...(6) On the other hand, the gauge resistor 17 has E o related to the output signal Eo.
/Ry current I3 flows, and the compensation signal generation circuit 25
The output voltage Ed is given by the following equation.

Ea --RM 3 (EO/R?) ”” (
7) Therefore, the output voltage Eo of the output circuit 26 is EO
-(R? (RMI RM2)/R1(RM 3-
R? >)Er...(8) Substituting equations (1), (2), and (3) into equation (8) to obtain Ro I-RO2-Ro s -Ro, Eo-2 Peng πσR? (1+((Z+β)t)Er/R+
(1+Mato αt) ・・・・・・(9) However, αβt2
(1 1=Ro /Ro -R? Therefore, if α+β--α ... (1o) is satisfied, the output voltage Eo becomes Eo-2 πσE r ... (11) However, k- IRy/R+, and the α and β terms of the temperature coefficient can be effectively removed, and the pressure to be measured P can be measured with high accuracy without being affected by temperature fluctuations.
A signal representing M can be obtained.

and the impurity concentration and temperature coefficient α of the gauge resistance.

The relationship of β is that when the impurity concentration is in the range of 1018 to 1020, α>0, β<Q, α+β×O, and α+
Since β is a small value, the relationship in equation (10) can be satisfied by selecting the resistance value of the resistor R7 of the compensation signal generating circuit 25.

Note that the initial resistance value R of the gauge resistance is 15.16.

If 11RO2 are not equal, adjust the resistance value of either resistor R1 or resistor R2 to obtain R+Ro2.
l −R2Ro 2 =O”” (12) may be satisfied. In other words, zero adjustment can be performed using resistors R+ and R2.

Furthermore, in the above description, the output voltage E of the resistance value detection circuit 22.23 is
Although the case where the difference between a and Eb is calculated by the difference detection circuit 24 has been illustrated, as shown in FIG.
In addition to the non-inverting input terminal (+) of s, the resistance value detection circuit 2
The output voltage Ea of 2 is connected to the operational amplifier OP via the resistor R8.
In addition to the inverting input terminal (-) of a, the output circuit 26 may be used for calculation. In this case Re =R* =R+
.

By setting -R+ + -2R12, the relationship of equation (8) can be obtained.

Furthermore, in the above description, the case where the gauge resistors 15 and 16 are formed on the pressure receiving diaphragm 12 and both have their resistance values changed according to the measured pressure PM has been illustrated, but one of the gauge resistors 15 and 16 (for example, the gauge resistor 16) is provided on the fixed part 13. Therefore, only the resistance value of the other one (for example, the gauge resistor 15) may be changed in accordance with the measured pressure P-. In this case, the output signal voltage Eo is E
C−k yrσE r −・・・−・(13
).

Furthermore, in the above example, the compensation signal voltage Ed is adjusted by the resistance wire of the resistor R7, but after dividing the output signal voltage Eo by the voltage dividing resistor, the operational amplification @OP is performed via the resistor R7.
It may be applied to the input terminal (-) of No. 4 to adjust the Ecseil voltage using the voltage dividing ratio of the voltage dividing resistor.

FIG. 4 is a connection diagram showing another embodiment of the present invention.

The embodiment shown in FIG. 4 differs from the embodiment shown in FIG. 1 in that an operational amplifier IQ P g and an operational resistor R+3. R+4
．． An adder circuit 27 consisting of R+s and an error amplifier 28 are provided, and the outputs Ea and Eb of the resistance value detection circuits 22 and 23 are added together in the adder circuit 27, and one input terminal of the error amplifier 28 (
-), the resistance value detection circuit 22 is set so that (Ea +Eb) is equal to the constant voltage Er from the reference voltage source 21 applied to the other input terminal (+) in the error amplifier 28.
．． It controls the input voltage Ee of 23, that is, the currents I+ and I2 flowing through the gauge resistor 15°16. As a result, r+, Iz
is R1-R2, then I+ -12-t=r/(R
M t +RM, 2 ) (14), which changes in relation to the sum of the resistance values of the gauge resistors 15.16. Therefore, the output voltage Ec of the difference detection circuit 24 is Ec = -Er (RM I - RM 2 >/ (
RM + +RM 2 ) (15), and the output voltage Eo of the output circuit 26 is Eo-21πσ
R7Er x (1+βt)/<1 + error αt)・・・・・・
(16) However, since the theory becomes -Ro/Ro-Ry, if the resistance value of the resistor R7 of the compensation signal generation circuit 25 is adjusted so as to satisfy β--α, the influence of the temperature coefficients α and β can be suppressed. Can be effectively removed.

In the above description, the output voltage E of the resistance value detection circuit 22.23
The input voltage of the resistance value detection circuit 22.23 is set as l1tillL, , so that the sum of a and Eb becomes equal to the reference voltage E
Then, the current Iz, I2 flowing through the gauge resistor 15.16 is R.
Although we have illustrated the case where the relationship is related to the sum of M++*Rr+2, as shown in FIG. The current flowing through .16 is Er /
(RM 1+R52) may be used. Fifth
In the figure, an operational amplifier OPs is used as the difference detection circuit 24.
and a resistor Rco+R4 are shown, and OF2
The voltage across the series circuit of gauge resistor 15.16 (Ea + Eb) is applied to the inverting input terminal (-) of OF2, and the voltage across the gauge resistor 16 Eb is applied to the non-inverting input terminal of OF2 (<+).
has been added. Therefore, the difference detection circuit 24 has R3-Rn
Then, (Eb Ea) is calculated and output. Note that when using the circuit shown in FIG. 1 as the difference detection circuit 24, a series circuit of resistors RIIIRI7 is connected in parallel with a series circuit of gauge resistors 15 and 16, as shown in FIG.
The voltage Er(-Er/2>) at the midpoint is the resistance Rs, Re
In addition, the voltage Ea across the gauge resistor 15 is applied to the non-inverting input terminal (+) of OF2 through the resistor R3 to OP3.
It should be added to the inverting input terminal (-) of the . In this case, the resistance RIIIRI? A gauge resistance may be used as the

Furthermore, in FIG. 5, the output of the reference voltage source 21 is
5.16, but as shown in Figure 7, the output Er of the reference voltage 1121 is applied to the operational amplifier OP.
? In addition to the non-inverting input terminal (+) of the gauge resistor 15.1
The voltage across the series circuit of 6 (Ea + Eb) is OP 7
In addition to the inverting input terminal (−) of .

FIG. 8 is a connection diagram showing another embodiment of the device of the present invention.

In the embodiment shown in FIG. 8, the difference from the embodiment shown in FIG.
) is added to the input terminal (-) of the input terminal (-). In this case, the voltage dividing ratio of the voltage dividing resistor 29 is n, and R1-R
2-818''RI I, the output EC of the difference detection circuit 24 is given by the following equation.

Ec =-(Er+nEo) X (RM + RM2)/R...
(17) Therefore, the output voltage EO is Eo-2k ytaE r/ (1+2nkπσ)...
(18) Since k is negative, the larger the stress σ, the higher the rate of increase in the output voltage Eo, making the input-output relationship non-linear. On the other hand, the nonlinearity between the measured pressure PM and stress σ is PM
As σ increases, the rate of increase in σ tends to decrease. Therefore, by adjusting the voltage division ratio n of the voltage division resistor 29, it is possible to compensate for the influence of nonlinearity between the measured pressure PM and the stress σ. This adjustment is performed by adjusting the output voltages Eo + e Eo 2 e Eo corresponding to the measured pressures PM1, PM21, and PM3, which have a relationship of PH2-(PH+ +Pr+z >/2).
This can be easily done by determining the voltage dividing ratio n of the voltage dividing resistor 29 so that E02- (Eo + +Eo3)/2. Note that as shown in FIG. 4, the outputs Ea and Eb of the resistance value detection circuits 22.23 are added by the adder circuit 27 and added to the error amplifier 28, and the outputs Ea and Eb of the resistance value detection circuits 22.23 are added to the gauge resistance 15.16.
When controlling the current flowing through the resistor Rzo, after dividing the output voltage Eo by a voltage dividing resistor 29 as shown in FIG.
It may be applied to the inverting input terminal (-) of OP e via the OP e.

<Effects of the Invention> As explained above, in the present invention, since the temperature coefficient term can be effectively removed, a resistive converter can be obtained that can measure the physical quantity to be measured with high precision without being affected by temperature fluctuations. It will be done.

[Brief explanation of the drawing]

FIG. 1 is an electrical connection diagram showing one embodiment of the present invention, FIG. 2 is a configuration explanatory diagram showing an example of a detector used in the present invention,
3 to 9 are electrical connection diagrams showing other embodiments of the present invention. 10...Detector 11...Single crystal semiconductor substrate 12...Pressure diaphragm section 13...Fixing section 15.16.17... Gauge resistance 20...
...Signal processing circuit 21...Reference voltage source 22.23...Resistance value detection circuit 24...
- Difference detection circuit 25... Compensation signal generation circuit 26... Output circuit 27... Addition circuit 28... Error amplifier 29... Piezoresistor Figure 3 (b) 4th! ! 1 Figure 5 Figure 6 Figure 7

Claims (2)

[Claims] (1) The first and second resistors are formed on a semiconductor single crystal substrate and the resistance value of at least one of them changes depending on the physical quantity to be measured.
a third gauge resistor formed on the semiconductor substrate and whose resistance value is unrelated to the physical quantity to be measured; a circuit for supplying current to the first and second gauge resistors; an output circuit that obtains an output signal by adding a compensation signal to a difference signal based on a difference in resistance value of the second gauge resistor; and supplying a current related to the output signal of the output circuit to the third gauge resistor. and a compensation signal generation circuit for obtaining the compensation signal. (2) The first and second electrodes are formed on a semiconductor single crystal substrate and the resistance value of at least one of them changes depending on the physical quantity to be measured.
a third gauge resistor formed on the semiconductor substrate and whose resistance value is unrelated to the physical quantity to be measured; a circuit for supplying current to the first and second gauge resistors; an output circuit that obtains an output signal by adding a compensation signal to a difference signal based on a difference in resistance value of the second gauge resistor; and supplying a current related to the output signal of the output circuit to the third gauge resistor. a compensation signal generation circuit that obtains the compensation signal by
and means for controlling currents flowing through the first and second gauge resistors according to the output signal.