JPH0615997B2 - Temperature pressure detector - Google Patents

Description

The present invention relates to a temperature / pressure detection device suitable for application to, for example, a device for automatically controlling the temperature and atmospheric pressure in a semiconductor manufacturing room.

In the past, each sensor was required to detect temperature and pressure. Therefore, in reality, the temperature and the pressure are separately displayed and detected by the outputs from the respective sensors.

Therefore, in order to detect the temperature and the pressure, it is necessary to attach a dedicated sensor to each of the installation locations, which poses a problem in selecting a location and man-hours. Further, the respective sensors are influenced by each other to generate an error. That is, the temperature sensor is detrimental to changes in pressure and the pressure sensor is detrimental to temperature. Therefore, since the respective change values are not mutually compensated, it is impossible to continuously and automatically detect the temperature and pressure with good accuracy.

In view of the above points, the present invention integrates a piezoelectric vibrator that mainly detects temperature and a silicon pressure sensor that mainly detects pressure to cancel out adverse effects of each other and to insert a temperature compensation circuit. The main purpose of the present invention is to propose a detection device of this kind that improves the accuracy of the detected value of pressure.

Hereinafter, one practical example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a circuit configuration diagram showing an example of the present invention. Reference numeral 9 denotes an oscillator, the output from which is applied to the composite sensor 2.

As shown in FIG. 2, the composite sensor 2 has a structure in which a piezoelectric vibrator 3 and a silicon element 4 are bonded together. That is, paste-like silver was applied to the soldering surface of the piezoelectric vibrator 3, a metal such as nickel was attached to the silicon element 4 by vapor deposition or sputtering, and both were used as electrodes and soldering surfaces to be heat-treated for close integration. It is a thing. A synthetic resin adhesive may be used depending on the environment in which the composite sensor is used. Then, as shown in FIG. 3, the composite sensor 2 is mounted on the case 5 having the pressure introducing portion 5a at the center. A, B in the figure
Is a lead wire of the piezoelectric vibrator 3, is a silicon element 4
Shows the lead wire of.

As shown in FIG. 4, the piezoelectric vibrator 3 exhibits impedance characteristics that show maximum and minimum values by changing the frequency. Assuming that the minimum impedance point is fr and the maximum impedance point is fa, an inductance L resonating at a frequency fo intermediate between the capacitance CD of the piezoelectric vibrator 3 and substantially fr and fa is connected in parallel as shown in FIG. As a result, as shown in FIG. 6, it is possible to obtain a configuration that exhibits the maximum impedance characteristic at the intermediate frequency fo. This impedance characteristic changes with temperature and pressure. That is, as shown in FIG. 7, it shows the characteristic that fo decreases as the temperature T rises, and as shown in FIG. 8, the value of the impedance Z decreases as the pressure P increases. As the piezoelectric vibrator, a PZT type ceramic plate having a thickness of about 0.5 to 1 mm can be used. The characteristics of the piezoelectric vibrator are the same as the resonance frequency characteristics of the bimorph vibration element. Using the above materials, the relationship between temperature and frequency is −
It has the characteristic of changing in a substantially linear manner in the range of 20 ° C to + 60 ° C.

The temperature can be detected by using the temperature characteristics of the piezoelectric vibrator 3 as described above. When the piezoelectric vibrator 3 has a slight temperature change, the intermediate frequency value fo increases or decreases as shown in FIG. Therefore, as shown in FIG. 5, it is possible to obtain and detect the change amount of the piezoelectric constant value from the output end of the piezoelectric vibrator 3.

On the other hand, the silicon element 4 is configured by connecting electrical low antibodies R _{1 to} R ₄ provided on a silicon wafer by a diffusion method in a bridge shape. FIG. 9 shows a silicon element 4
FIG. 4 is a circuit diagram showing the configuration of the above. In this case, the terminals are input terminals and the terminals are output terminals. When a predetermined voltage is applied to the input terminal, no output is produced when all the resistors R _{1 to} R ₄ are in equilibrium, but when pressure strain is applied to the silicon element 4, R _{1 to} R ₄ The resistance balance is lost and an output is produced. This output appears in proportion to the pressure and shows a characteristic curve as shown in FIG.

However, as shown in FIG. 2 and FIG.
Since the silicon element 4 and the silicon element 4 are bonded together, the silicon element 4 vibrates together with the piezoelectric vibrator 3 when the piezoelectric vibrator 3 is subjected to a certain pressure strain. An alternating current having the same frequency as the frequency at which 3 vibrates is detected, and this frequency matches the intermediate frequency fo. The output voltage level generated at the output terminal at this time corresponds to the impedance value Z ₀ at the intermediate frequency fo. Therefore, by adopting the maximum value of the intermediate frequency fo of the piezoelectric vibrator 3, the vibration amplitude becomes large, and further, the silicon element 4
The inter-output voltage of is also increased. Then, in FIG. 3, if there is a slight change in pressure from the pressure introduction point 5a,
Composite sensor 2 including piezoelectric vibrator 3 and silicon element 4
The new vibration width (Zo value in FIG. 6) changes, and the voltage across the output terminals also changes. However, even if the pressure strain is constant, this voltage changes when the temperature changes (see FIG. 7).

Therefore, in FIG. 1, the output end of the composite sensor 2 is supplied to the temperature compensating circuit 6 via the wave detector 5, while the temperature detection output from the piezoelectric vibrator 3 is used as a comparison reference voltage for the temperature compensating circuit 6. It is configured to supply a compensation signal. The temperature compensation circuit 6 is composed of an operational amplifier. The output of the silicon element 4 is a combination of the intermediate frequency fo component of the piezoelectric vibrator 3 and the vibration amplitude Zo component. Therefore, by inputting the temperature detection output from the piezoelectric vibrator 3 to the differential amplifier as the comparison reference voltage, the intermediate frequency component of the output of the silicon element 4 that contributes to the temperature change is canceled by the comparison reference voltage. , Only the vibration amplitude component is extracted, and the output of the temperature compensation circuit 6 is amplified by the amplifier 7 and output to the pressure display unit 8. Therefore, in the output stage of the composite sensor 2, as shown in FIG. 11, even if the output voltage changes due to temperature change when the pressure is constant, the output voltage at the pressure display unit 8 is
As shown in FIG. 12, even if the temperature changes, the output voltage does not change and temperature compensation is performed.

In addition, with the above-described configuration of the composite sensor 2, by increasing the output level of the oscillator,
Since the peak value Zo of the intermediate frequency value fo shown in the figure can be increased, the bias pressure can be appropriately applied by the piezoelectric vibrator 3 so that the point P _{1 in} FIG. 10 is centered. Therefore, the characteristic curve shown in FIG. 10 can be sharply improved, and thus the sensitivity of pressure detection can be increased.

In FIG. 1, the composite sensor 2 is driven by an oscillator 9, the output of which is passed through a discriminative detector 10 to be a DC component and an output, which is amplified by an amplifier 11 and output to a temperature display unit 12. The oscillator 9 has a structure in which the output is constant by controlling the voltage of the frequency fo and the frequency is controlled so that the output becomes maximum. To drive the silicon element 4, the output from the oscillator 9 is processed by the rectifying circuit 13 and the stabilizing circuit 14 and applied.
FIG. 13 is a diagram showing the relationship between the output end voltage of the composite sensor 2 and the pressure.

FIG. 14 is a circuit diagram showing another example of the present invention. In this example, as apparent from FIGS. 7 and 11, the output voltage of the composite sensor 2 is a function of temperature,
The resonance frequency component is directly extracted from this output and added to the temperature display unit 12. The first
The same elements as those in the illustrated example will be described with the same reference numerals. Therefore, also in this example, the same operation as that of the example of FIG. 1 can be performed.

As described above, according to the present invention, the inductance that resonates at a frequency substantially intermediate between the capacitance of the piezoelectric element and the maximum and minimum impedance is connected in parallel, and a bias pressure is applied to obtain the maximum impedance value at the intermediate frequency. A piezoelectric sensor and a silicon pressure element that produces an output when pressure strain is applied are integrated into a composite sensor, and the temperature is detected using the resonance frequency component that is a function of the temperature of the output of the composite sensor. Since the pressure is detected by using the temperature-compensated output through the operational amplifier that receives the vibration amplitude component and the resonance frequency component that are functions of pressure, it is possible to improve the sensitivity of the pressure detection value. The temperature-compensated detection value can be obtained.

Therefore, there is a practical advantage when it is used, for example, when detecting the temperature and pressure of a semiconductor manufacturing room.

[Brief description of drawings]

1 is a circuit diagram showing an example of the present invention, FIG. 2 is a diagram showing an example of a composite sensor, FIG. 3 is a diagram showing a mounting state of the composite sensor, FIG. 4 is a characteristic diagram of a piezoelectric vibrator, FIG. FIG. 5 is a circuit diagram showing an example of a piezoelectric vibrator incorporating a coil, FIG. 6 is a characteristic diagram of the example of FIG. 5, and FIG. 7 is a characteristic of the piezoelectric vibrator showing the relationship between frequency and temperature near room temperature. FIG. 8 is a diagram showing the relationship between pressure and impedance, FIG. 9 is a diagram showing the configuration of a silicon element, FIG. 10 is a characteristic diagram of the example of FIG. 9, and FIG.
FIG. 1 is a characteristic diagram of the composite sensor, FIG. 12 is a curve diagram for explaining the output voltage of the device of the present invention, FIG. 13 is a curve diagram showing the relationship between the output voltage and pressure, and FIG. 14 is the present invention. It is a circuit diagram which shows the other example. 2 ... Composite sensor, 3 ... Piezoelectric vibrator, 4 ... Silicon element, 6 ... Temperature compensation circuit.

Claims (3)

[Claims] 1. A piezoelectric vibrator in which an electrostatic capacitance of a piezoelectric element and an inductance which resonates at a frequency substantially intermediate between maximum and minimum impedance are connected in parallel, and a bias pressure is applied to obtain a maximum impedance value at the intermediate frequency. ,
A composite sensor is provided that is in close contact with a silicon pressure element that outputs when pressure strain is applied, and the temperature is detected using the resonant frequency component that is a function of the temperature of the output of the composite sensor, and it is a function of pressure. A temperature and pressure detecting device characterized in that a pressure is detected by utilizing a temperature-compensated output via an operational amplifier which receives a vibration amplitude component and a resonance frequency component. 2. The temperature / pressure detection device according to claim 1, wherein the temperature of the resonance frequency component, which is a function of the temperature of the output of the composite sensor, is detected by the output taken out from the piezoelectric vibrator. 3. A temperature / pressure detection device according to claim 1, wherein the temperature of the resonance frequency component, which is a function of the temperature of the output of the composite sensor, is detected by the output taken out from the pressure sensor.