JPS58182529A - Semiconductor pressure transducer - Google Patents

Abstract

PURPOSE:To improve precision, by connecting the 2nd semiconductor gauge resistance which decreases in resistance and the 3rd semiconductor gauge resistance which increases in resistance to a bridge circuit consisting of the 1st semiconductor gauge resistances, and driving them with specific currents. CONSTITUTION:The full bridge circuit is constituted of 4 pieces of the 1st semiconductor gauge resistances which vary in resistance when applied with pressure constitute. Then, the 2nd semiconductor gauge resistance 4 which decreases in resistance by pressure application is connected to the bridge circuit 1 in series. Further, the 3rd semiconductor gauge resistance 5 which increases in resistance is connected to the bridge circuit 1 in parallel through the 2nd semiconductor gauge resistance 4. This device is driven with a specific current by a power source 6.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] This invention relates to a semiconductor pressure transducer comprising a pressure-sensitive gauge resistor [combination] bridge circuit. Q: The piezoresistance effect of semiconductor single crystals such as V Recon has a k14NLft pressure transducer, which is far more sensitive than the wire strain game i7! However, divine spirits have a high advantage. However, its disadvantages are that the strain-resistance change characteristics are highly nonlinear and the temperature coefficient is also large. Some modifications must be made to the pigeon house.

Normally, the characteristics of a semiconductor pressure transducer are that the pressure input is equal to the pressure input, that is, when a large pressure is applied, the output is
It shows a tendency for IK saturation. In order to correct such an output characteristic at, a negative path such as the first gt) is conventionally used. In the figure, [2 and l are gauge resistors that change the direction of resistance change in response to pressure input, and these and fixed resistors are combined to form a half-bridge circuit. is for zero point adjustment.The output of the bridge circuit 10 is taken out by the next output increase S*,t using the operational amplifier 0P, and 03 is the drive voltage adjustment circuit.
It consists of an operational amplifier OF, and balancing resistors Rb, , Rb, and at the same time a reference voltage VIQ is input to its inverting input terminal, the output t of the output amplifier 2 is linearized by a resistor R.
In this circuit, the dynamic voltage of the bridge 1 changes according to the drive voltage adjustment circuit JKJ and the bridge output. That is, as the pressure input increases, the bridge output is fed back to the drive voltage adjustment circuit S via the linearizing resistor Ill, and the drive voltage Vl increases. As is clear from the characteristics shown in the diagram, the linearity of the bridge output is determined by the linearization resistor RL.
It changes from Napu V Crystal A to Super Linear depending on the direction. l! , gauge resistance force ν, '11Nt) nonlinear I
If we set 9 = ARAI and < Fl m resistance according to the degree of k, the bridge output [Q that can be linearized with respect to the pressure input] Therefore, in the example shown in the JIIZ diagram, RL = 2
The optimum value is Ω at 00. In order to compensate for this nonlinearity of the element, it is necessary to compensate by increasing the applied voltage Vl f of the bridge circuit 1 for pressure measurement as the pressure input increases. The operation of the circuit is basically a bridge circuit "1 [driven by a constant voltage, and as a modification, the applied voltage VB li is applied by applying the positive ext to the pressure input. On the other hand, the temperature control which is usual for semiconductors Dependency (zero point, pressure sensitivity)
When compensating for , the method of compensation differs greatly depending on whether the bridge circuit 1 is operated with a constant voltage or with a constant current.

Therefore, the above pressure characteristic nonlinearity compensation circuit and 0.
In general, when a semiconductor pressure sensor is operated at a constant voltage, the pressure sensitivity to temperature changes varies greatly, for example, from -0.15 to -4L21.
/°C, 1 DIlk indicates 0. On the other hand, when operating at a constant current, it only causes a pressure sensitivity fluctuation of, for example, -0,0511 G/'C, and for general use, even without compensation. It can be used.

By the way, the present inventors previously filed Japanese Patent Application No. 1854-124989.
±0.00511i/l even in constant voltage operation due to the issue etc.
We proposed a high-precision temperature compensation method that could be used in different ways, and further developed this method and advocated a method for compensating for the nonlinearity of the pressure characteristics described above.After that, we also developed a method for nonlinearity of the pressure characteristics for constant current operation. A new means of compensation has been found.

As mentioned above, in order to compensate for the nonlinearity of pressure characteristics, the bridge applied voltage V
Temperature compensation in constant voltage operation (pressure sensitivity by changing bridge voltage vB in conjunction with temperature [voltage compensation to keep it constant) requires non-linear compensation. Both crystallized. On the other hand, when the bridge circuit 1 is operated with a constant current, there is a good point that there is little variation in the pressure sensitivity of the element, but when you try to do it, it becomes difficult. For the o-pattern, a constant current operation is used to compensate for a higher degree of 11111:01 [If this is done, an adjustment method is used in the manufacturing method of the semiconductor element, that is, in the impurity diffusion process. Figure 3 is an example of the temperature change rate of a strain resistance layer formed by diffusing p-type impurities into an n-type S1 substrate? Show me.

Standard resistance of strain resistance layer kRas Its temperature coefficient 1 (1 (1 (Resistance change due to pressure iJR, Its temperature coefficient ? β, ”/Ro
= a, S gauge factor, pressure output during constant current operation 4
v! becomes as follows.

]Vx =jli(1+/)Io” Go Re
(x+g)(1+β)I+1” Go Ro (1
+(α+β))l.

・・・・・・・・・(1) As can be seen from the characteristics shown in Figure 2 and the above equation (1),
If the impurity concentration of the strain resistance is around 10I8/- or 10"/son, we can obtain (α+β)-〇, that is, as soon as the temperature dependence becomes zero. In this method, when the temperature is changed, There is a condition where the sensitivity depends on once or no dependence, and if this condition is not exactly met, it is possible to improve the temperature characteristics of C as well.However, for this purpose, the applied voltage must be artificially changed, so It is generally considered that it is not suitable for non-linear compensation.

[Purpose of the invention]

The present invention has been made in consideration of these circumstances, and its purpose is to provide a simple and practical method that can effectively compensate for temperature changes in the pressure sensitivity of a bridge circuit driven by a constant current. The object of the present invention is to provide a high semiconductor pressure displacement device.

[Summary of the invention]

The present invention changes resistance in different directions in response to pressure.
A bridge circuit constructed using at least one set of semiconductor gauge resistors shown in FIG. A third semiconductor gauge resistor showing an increase is connected in parallel to the bridge circuit via the semiconductor gauge resistor of stripe 2, and these are driven at a constant current. According to the authors, the full-scale accuracy of the sensor's pressure sensitivity can be greatly improved by simplifying the method, and the effect is enormous. Also semiconductor gauge resistance O piezo effect [
, can be fully utilized regardless of sensitivity compensation.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

Figure 114 shows an example of the relationship between the bridge output and the pressure force p. The solid line A in FIG. 4 is the pressure output when the bridge circuit is operated with a constant current I, and is largely non-linear.

Therefore, assuming that the output when full pressure is applied [ΔVtr,''/2 and the full output ΔV change linearly, the output at the 172 pressure point in the good case (dotted line B) is Assuming that the O difference is 5 sv, the nonlinearity has the relationship shown below.The current flowing through the O nonlinearity t-bridge circuit is increased in accordance with the pressure input to linearize it.When the pressure input is zero, Bridge current [summer, current IIy when full pressure is applied]
If the nonlinearity is made zero by increasing , it is necessary to satisfy the following relationship.

Figure jI5 shows a diffusion resistance layer on the (100) plane of Sl. Electricity ILO increase (indicated by 9). In a diamond 72mm type sensor, the stress on the element is determined by the shape of the diamond 2mm, the thickness of the plate, and the applied pressure. ss 0
In the (100) plane diamond, the stress that causes the resistance change to reach 15- causes the diamond to break.
The vertical axis in the right example of Figure O is the current increase [expressed as a ratio] determined from the Jl (3) formula. FIG.

This device operates the strain gauge bridge circuit 1 with a constant current and further linearly compensates for pressure sensitivity. That is, this device is constructed of a full bridge circuit 1 by four first semiconductor gauge resistors that change (r±jr) in response to pressure.

Then, a JllI2 semiconductor gauge resistor 4 whose resistance changes to (R+-)R1) depending on the applied pressure is connected in series to the bridge circuit 1, and a JIS semiconductor gauge resistor 5t whose resistance changes to (R3+ΔRt) - the above #2 K is connected in parallel to the bridge circuit 1 through the semiconductor gauge resistor 4t.
These gauge resistors r1 for pressure detection, resistors RIs and R for linearity compensation, which are constructed by JI, are all provided on the same silicon substrate. Note that 6 in the figure is a power source for driving the above device with a constant current.

116! In the configuration of El, the reference resistance t-r when no pressure is applied is set as 4000B, and as pressure is applied, the current in the bridge circuit 1 increases. be. However, here R,=
4rΩ, and "*" is the parameter.The broken line is the required compensation current ratio shown in the jIs diagram above.Also, the constant current flowing through the entire circuit system shown in FIG. The current is 'ro% when no pressure is applied.
It is assumed that 1r is given when pressure is applied.

In addition, the JIB diagram is under the conditions shown in Figure 6 and Figure 7.
Compensation [Residual non-clamping property of the bridge circuit 10 after application. In general, compared to metal strain gauges, semiconductor single crystals such as 81 have greater strain sensitivity due to the piezoresistive effect, but Guyaftum type sensors cannot fully demonstrate their effectiveness due to nonlinear output. According to this device, as shown in the jIs diagram, piezo sensitivity [0 which can be fully demonstrated] Incidentally, the allowable error as a measuring instrument is said to be ±1% FB. For this reason, in the conventional Guyaftum type pressure sensor, this allowable lK difference is affected by the nonlinearity of the output, and as shown in Figure 8, the resistance sensitivity can only be achieved up to about t5% without compensation. On the other hand, according to the present device, the resistance sensitivity can be as high as kll to 12, so that the full-scale accuracy with respect to temperature drift of zero point, sensitivity, etc. can be more than doubled. Moreover, in terms of productivity of sensors, it is possible to improve the OTP trade and to achieve a great practical advantage of promoting a low cost ratio.The present invention is limited to the above embodiments. It is not something that will be done. For example, a half-bridge circuit can be realized by using one set of semiconductor gauge resistors constituting the bridge circuit 1. Further, the resistance value of each semiconductor gauge resistor is determined according to the specifications.However, the present invention can be implemented with various modifications without departing from the gist thereof.

[Brief explanation of drawings]

Figure JI1 is a configuration diagram showing an example of the conventional device, Figure 2 is a diagram showing the operating characteristics of the conventional device, and the third factor is a diagram showing the relationship between the temperature dependence of pressure sensitivity and the degree of diffusion S. Figure 4 5 and 5 are diagrams showing nonlinear compensation characteristics, FIG. 6 is a schematic configuration diagram of an embodiment of the device of the present invention, and Figures #I7 and WJ8 are diagrams showing the operating characteristics of the device, respectively. 1... Bridge circuit (first semiconductor gauge resistor), 4
. . . 1s2 semiconductor gauge resistance, 5 . . . third semiconductor gauge resistance, 6 . . . constant current power supply. Applicant's agent Patent attorney Suzue Takehiko Hikoga 3rd figure T wear #B Takama (%m1) 6th figure off figure 18 resistance due to pressure 9th grade.

Claims (1)

[Scope of Claims] A nine-bridge circuit configured using at least one set of first semiconductor gauge resistors exhibiting resistance changes in mutually different directions in response to pressure; A second semiconductor gauge resistor (indicated by 93M) whose resistance decreases in response to the pressure, and a second semiconductor gauge resistor (indicated by A pressure sensitive element formed on a semiconductor substrate, and a semiconductor pressure transducer characterized by a pressure sensitive element [equipped with an electric current driven by constant current]0