Diaphragm vacuum gauge

Abstract

To measure the temperature of a sensor chip without providing a temperature sensor.SOLUTION: A diaphragm gauge comprises: a sensor chip in which the interval between first and second electrodes changes according to displacement of a diaphragm; a signal generator 120 that applies a drive signal to the second electrode; a signal generator 121 that outputs a signal with a phase shifted from that of the drive signal; an amplifier 122 that converts current output from the first electrode into voltage; a synchronization detection unit 128 that demodulates a signal synchronized with the drive signal from an output signal from the amplifier 122; a synchronization detection unit 129 that demodulates a signal synchronized with an output signal from the signal generator 121 from an output signal from the amplifier 122; and a temperature calculation unit 127 that calculates a value proportional to the series resistance of the first and second electrodes from outputs from the synchronization detection units 128, 129, and determines a value proportional to the temperature of the sensor chip from the value proportional to the series resistance as the temperature of the sensor chip.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a diaphragm vacuum gauge. [Background technology]

[0002] Diaphragm vacuum gauges measure pressure by detecting the displacement of a diaphragm as a change in capacitance. Diaphragm vacuum gauges are used to measure the pressure in semiconductor process chambers. In recent years, semiconductor processes have become more sophisticated, and accurate pressure measurement is required. However, with a diaphragm vacuum gauge, the capacitance not only changes with pressure, but also with temperature, so accurate pressure is measured by detecting the temperature and correcting the capacitance.

[0003] A temperature sensor needs to be installed to detect temperature, but installing a temperature sensor inside the sensor chip poses the problem that the electrodes for pressure detection must be made smaller. In addition, the sensor chip becomes larger because it is necessary to attach the temperature sensor to the sensor chip and to provide wiring to extract the temperature sensor signal. For this reason, in conventional diaphragm vacuum gauges, the temperature sensor is attached to the outside of the sensor chip (see Patent Document 1).

[0004] However, when a temperature sensor is attached to the outside of the sensor chip as in conventional diaphragm vacuum gauges, the temperature of the sensor chip cannot be measured accurately, and there is a problem that errors occur in capacitance correction and pressure measurement errors due to delays in temperature detection response when temperature changes occur. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-7906 A Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in order to solve the above-mentioned problems, and has an object to provide a diaphragm vacuum gauge that can accurately measure the temperature of a sensor chip without providing a temperature sensor on the outside of the sensor chip. [Means for solving the problem]

[0007] A diaphragm vacuum gauge (first embodiment) of the present invention includes a sensor chip including a first electrode formed on a base and a second electrode formed on a diaphragm disposed across a gap from the base so as to face the first electrode, the distance between the first and second electrodes being changed in response to displacement of the diaphragm due to pressure of a medium to be measured, a first signal generator configured to apply a sensor drive signal to the second electrode, a second signal generator configured to output a signal out of phase with the sensor drive signal, an amplifier configured to convert a current output from the first electrode into a voltage and amplify it, and a voltage measuring circuit configured to measure the pressure of the sensor from the output signal of the amplifier. a first synchronous detection unit configured to demodulate a signal synchronized with the output signal of the second signal generator from the output signal of the amplifier; a capacitance calculation unit configured to calculate a value proportional to the capacitance between the first and second electrodes as a capacitance value from the output signals of the first and second synchronous detection units; and a temperature calculation unit configured to calculate a value proportional to the series resistance of the first and second electrodes from the output signals of the first and second synchronous detection units, and to obtain a value proportional to the temperature of the sensor chip as the sensor chip temperature from the value proportional to the series resistance. Moreover, one configuration example (first embodiment) of the diaphragm vacuum gauge of the present invention is characterized in that it further comprises a pressure measuring unit configured to correct the calculated capacitance value based on the temperature of the sensor chip and convert it into a measured pressure value.

[0008] A diaphragm vacuum gauge (second embodiment) of the present invention includes a first electrode formed on a base, a second electrode formed on a diaphragm disposed across a gap from the base so as to face the first electrode, a third electrode formed on the base outside the first electrode, and a fourth electrode formed on the diaphragm outside the second electrode so as to face the third electrode, and includes a sensor chip configured so that the distance between the first and second electrodes changes in response to the displacement of the diaphragm due to the pressure of a medium to be measured, a first signal generator configured to apply a sensor drive signal to the second and fourth electrodes, a second signal generator configured to output a signal out of phase with the sensor drive signal, and a second signal generator configured to output a signal from the first electrode. a first amplifier configured to convert a current output from the third electrode into a voltage and amplify the voltage; a subtractor configured to subtract an output signal of the second amplifier from an output signal of the first amplifier; a first synchronous detection unit configured to demodulate a signal synchronized with the sensor drive signal from the output signal of the first amplifier; a second synchronous detection unit configured to demodulate a signal synchronized with the sensor drive signal from the output signal of the subtractor; a third synchronous detection unit configured to demodulate a signal synchronized with the output signal of the second signal generator from the output signal of the first amplifier; The value of the first capacitance Cx is a first capacitance calculation unit configured to calculate a capacitance from an output signal of the second synchronous detection unit; , a value Cx-Cr obtained by subtracting the second capacitance Cr between the third and fourth electrodes from the first capacitance Cx a second capacitance calculation unit configured to calculate a capacitance proportional to the series resistance of the first and second electrodes from the output signals of the first and third synchronous detection units, and a temperature calculation unit configured to obtain a value proportional to the temperature of the sensor chip from the value proportional to the series resistance as the sensor chip temperature; From the calculation results of the first and second capacitance calculation units, The second capacitance Cr The first capacitance Cx Correction Calculate the value (Cx-Cr) / Cx and a capacitance correction unit configured to correct the capacitance.

[0009] A diaphragm vacuum gauge (third embodiment) of the present invention includes a first electrode formed on a base, a second electrode formed on a diaphragm disposed across a gap from the base so as to face the first electrode, a third electrode formed on the base outside the first electrode, and a fourth electrode formed on the diaphragm outside the second electrode so as to face the third electrode, and includes a sensor chip configured so that a distance between the first and second electrodes changes in response to a displacement of the diaphragm due to a pressure of a medium to be measured, a first signal generator configured to apply a sensor drive signal to the second and fourth electrodes, a second signal generator configured to output a signal out of phase with the sensor drive signal, and a voltage generator configured to output a voltage from the first electrode. a first amplifier configured to convert a current output from the third electrode into a voltage and amplify the voltage; a second amplifier configured to convert a current output from the third electrode into a voltage and amplify the voltage; a subtractor configured to subtract an output signal of the second amplifier from an output signal of the first amplifier; a first synchronous detection unit configured to demodulate a signal synchronized with the sensor drive signal from the output signal of the first amplifier; a second synchronous detection unit configured to demodulate a signal synchronized with the sensor drive signal from the output signal of the subtractor; a third synchronous detection unit configured to demodulate a signal synchronized with the output signal of the second signal generator from the output signal of the subtractor; The value of the first capacitance Cx is a first capacitance calculation unit configured to calculate a capacitance from output signals of the second and third synchronous detection units; A value Cx-Cr obtained by subtracting the second capacitance Cr between the third and fourth electrodes from the first capacitance Cx is a second capacitance calculation unit configured to calculate a capacitance of the third and fourth electrodes from the output signals of the second and third synchronous detection units, and a temperature calculation unit configured to calculate a value proportional to the series resistance of the third and fourth electrodes from the output signals of the second and third synchronous detection units, and to obtain a value proportional to the temperature of the sensor chip from the value proportional to the series resistance as the sensor chip temperature; From the calculation results of the first and second capacitance calculation units, The second capacitance Cr The first capacitance Cx Correction Calculate the value (Cx-Cr) / Cx and a capacitance correction unit configured to correct the capacitance. In addition, in one configuration example (second and third embodiments) of the diaphragm vacuum gauge of the present invention, the second electrode and the fourth electrode are electrically connected to each other and formed as a single electrode. In addition, in one configuration example (second and third embodiments) of the diaphragm vacuum gauge of the present invention, the corrected first capacitance value (Cx-Cr) / Cx The pressure measuring device further comprises a pressure measuring unit configured to convert the pressure value into a measured pressure value by correcting the pressure value based on the sensor chip temperature.

[0010] In addition, in one configuration example (first to third embodiments) of the diaphragm vacuum gauge of the present invention, the second signal generator outputs a signal that is shifted in phase by 90 degrees with respect to the sensor drive signal. Moreover, one configuration example (first to third embodiments) of the diaphragm vacuum gauge of the present invention is characterized in that it further comprises a temperature notification section configured to notify a user of the sensor chip temperature. Effect of the Invention

[0011] According to the present invention, by providing the first and second signal generators, the amplifier, the first and second synchronous detection units, the capacitance calculation unit, and the temperature calculation unit, the temperature of the sensor chip can be measured by utilizing the fact that the series resistance of the first electrode and the second electrode changes with temperature, and pressure measurement and temperature measurement can be realized with one sensor chip. Since the present invention can accurately measure the temperature of the sensor chip, it is possible to suppress correction errors and pressure measurement errors compared to a conventional configuration in which a temperature sensor is provided outside the sensor chip. Furthermore, since the present invention does not require the attachment of a temperature sensor to the sensor chip and wiring for extracting a signal from the temperature sensor, it is possible to make the sensor chip smaller than when a temperature sensor is attached to the sensor chip.

[0012] In addition, in the present invention, a first and a second signal generator, a first and a second amplifier, a subtractor, first to third synchronous detection units, a first and a second capacitance calculation unit, a temperature calculation unit, and a capacitance correction unit are provided, and a sensor drive signal is applied to the second and fourth electrodes of the sensor chip, so that capacitance measurement and temperature measurement for pressure measurement can be performed using the first and second electrodes of the sensor chip, and capacitance measurement for capacitance correction can be performed using the third and fourth electrodes of the sensor chip, and pressure measurement, temperature measurement, and capacitance correction can be realized with a single sensor chip.

[0013] In addition, in the present invention, a first and a second signal generator, a first and a second amplifier, a subtractor, first to third synchronous detection units, a first and a second capacitance calculation unit, a temperature calculation unit, and a capacitance correction unit are provided, and a sensor drive signal is applied to the second and fourth electrodes of the sensor chip, so that capacitance measurement for pressure measurement can be performed using the first and second electrodes of the sensor chip, and capacitance measurement and temperature measurement for capacitance correction can be performed using the third and fourth electrodes of the sensor chip, and pressure measurement, temperature measurement, and capacitance correction can be realized with a single sensor chip.

[0014] Furthermore, in the present invention, by providing a temperature notification section, it is possible to notify the user of the temperature of the sensor chip. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a block diagram showing the configuration of a diaphragm vacuum gauge according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing the configuration of a main part of a sensor chip of a diaphragm vacuum gauge according to a first embodiment of the present invention. [Diagram 3] FIG. 3 is a flowchart illustrating the pressure and temperature measurement operation of the diaphragm vacuum gauge according to the first embodiment of the present invention. [Figure 4] FIG. 4 is a block diagram showing the configuration of a capacitance / temperature detection section of a diaphragm vacuum gauge according to a first embodiment of the present invention. [Diagram 5]FIG. 5 is a diagram showing a waveform of an amplifier output when the diaphragm vacuum gauge according to the first embodiment of the present invention measures pressure and temperature. [Figure 6] FIG. 6 is a diagram showing waveforms of the output of the synchronous detection unit when the diaphragm vacuum gauge according to the first embodiment of the present invention measures pressure and temperature. [Figure 7] FIG. 7 is a diagram showing waveforms of the output of the synchronous detection unit when the diaphragm vacuum gauge according to the first embodiment of the present invention measures pressure and temperature. [Figure 8] FIG. 8 is a block diagram showing the configuration of a diaphragm vacuum gauge according to a second embodiment of the present invention. [Figure 9] FIG. 9 is a cross-sectional view showing the configuration of a main part of a sensor chip of a diaphragm vacuum gauge according to a second embodiment of the present invention. [Figure 10] FIG. 10 is a flowchart illustrating the pressure and temperature measurement operation of the diaphragm vacuum gauge according to the second embodiment of the present invention. [Figure 11] FIG. 11 is a block diagram showing the configuration of a capacitance / temperature detection section of a diaphragm vacuum gauge according to a second embodiment of the present invention. [Figure 12] FIG. 12 is a block diagram showing the configuration of a diaphragm vacuum gauge according to a third embodiment of the present invention. [Figure 13] FIG. 13 is a block diagram showing the configuration of a capacitance / temperature detection section of a diaphragm vacuum gauge according to a third embodiment of the present invention. [Figure 14] FIG. 14 is a block diagram showing an example of the configuration of a computer that realizes the circuitry of the diaphragm vacuum gauge according to the first to third embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] [First Example] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a block diagram showing the configuration of a diaphragm vacuum gauge according to a first embodiment of the present invention, and Fig. 2 is a cross-sectional view showing the configuration of a main part of a sensor chip used in the diaphragm vacuum gauge.

[0017] The diaphragm vacuum gauge comprises a pressure receiving section 10 whose capacitance changes in response to the displacement of a diaphragm (membrane) due to the pressure of the medium to be measured (e.g., a process gas), and a circuit section 11 that converts the change in capacitance of the pressure receiving section 10 into a measured pressure value.

[0018] A recess is formed in the center of the base 101 of the sensor chip 1 of the pressure receiving portion 10. A diaphragm 102 configured to be deformable in response to the pressure P of a medium to be measured (e.g., a process gas) is bonded to the surface of the base 101 on which the recess is formed. The recess of the base 101 forms a reference vacuum chamber 104 together with the diaphragm 102.

[0019] In the sensor chip 1, a fixed electrode 105 is formed on the surface of the base 101 facing the reference vacuum chamber 104, and a movable electrode 106 is formed on the surface of the diaphragm 102 facing the reference vacuum chamber 104 so as to face the fixed electrode 105. In this way, the fixed electrode 105 and the movable electrode 106 are arranged to face each other across a gap. When the diaphragm 102 is deflected by receiving a pressure P of the medium to be measured, the distance between the movable electrode 106 and the fixed electrode 105 changes, and the electrostatic capacitance between the movable electrode 106 and the fixed electrode 105 changes. The pressure P of the medium to be measured received by the diaphragm 102 can be detected from this change in electrostatic capacitance. The diaphragm component 100 and the base 101 are made of an insulator such as sapphire.

[0020] The diaphragm vacuum gauge shown in FIG. 1 comprises the sensor chip 1 configured as described above, a housing 2 that accommodates the sensor chip 1, a pressure introduction tube 3 that introduces the pressure P of the medium to be measured to the diaphragm 102 of the sensor chip 1, and a sensor case 4 that covers the housing 2.

[0021] A partition wall 7 is provided inside the housing 2. The partition wall 7 is composed of a base plate 7a and a support plate 7b, and divides the internal space of the housing 2 into a first space 2a and a second space 2b. The outer periphery of the support plate 7b is fixed to the housing 2, and supports the base plate 7a in a state where it is raised in the internal space of the housing 2. The sensor chip 1 is fixed to the second space 2b side of the base plate 7a. The base plate 7a is also formed with a pressure introduction hole 7c that introduces the pressure in the first space 2a to the diaphragm 102 of the sensor chip 1. The second space 2b is in communication with a reference vacuum chamber 104 of the sensor chip 1, and is in a vacuum state.

[0022] The pressure introduction pipe 3 is connected to the first space 2a side of the housing 2. A baffle 8 is provided between the pressure introduction pipe 3 and the housing 2. The medium to be measured introduced through the pressure introduction pipe 3 hits the plate surface of the baffle 8 and flows into the first space 2a of the housing 2 through the gap around the baffle 8.

[0023] The circuit section 11 of the diaphragm vacuum gauge is composed of a capacitance / temperature detection section 12 that calculates a value proportional to the capacitance between the movable electrode 106 and the fixed electrode 105 as a capacitance value and also calculates a value proportional to the temperature of the sensor chip 1, a pressure measurement section 13 that converts the calculated capacitance value into a measured pressure value, and a temperature notification section 14 that notifies the user of the calculated temperature of the sensor chip 1.

[0024] FIG. 3 is a flow chart for explaining the pressure / temperature measurement operation of the diaphragm vacuum gauge of this embodiment, and FIG. The capacitance / temperature detection unit 12 is composed of a signal generator 120 that outputs a sensor drive signal, a signal generator 121 that outputs a signal out of phase with the sensor drive signal, an amplifier 122 consisting of a capacitance Cf and an operational amplifier A1, differential input type low-pass filters 123-1, 123-2, a switch 124 provided between the amplifier 122 and the low-pass filter 123-1, a switch 125 provided between the amplifier 122 and the low-pass filter 123-2, a capacitance calculation unit 126 that calculates the electrostatic capacitance value between the movable electrode 106 and the fixed electrode 105, and a temperature calculation unit 127 that calculates the temperature of the sensor chip 1.

[0025] 4, the electrostatic capacitance between the movable electrode 106 and the fixed electrode 105 of the sensor chip 1 is represented by Cx. Also, the component of the series resistance between the movable electrode 106 and the fixed electrode 105 is represented by Rx.

[0026] During pressure and temperature measurement, the signal generator 120 applies a sine wave sensor drive signal Esin(2πft) to the second electrode (e.g., the movable electrode 106) of the sensor chip 1 and the switch 124 (step S100 in FIG. 3), where E is the amplitude, f is the frequency, and t is the time. During pressure and temperature measurement, the signal generator 121 applies a signal Esin(2πft+π / 2) that is out of phase with the sensor drive signal Esin(2πft) by 90 degrees to the switch 125 (step S101 in FIG. 3).

[0027] The amplifier 122 converts the current output from the first electrode (for example, the fixed electrode 105) of the sensor chip 1 into a voltage, amplifies it, and outputs a signal with an amplitude proportional to the capacitance Cx.

[0028] The switch 124 and the low-pass filter 123-1 constitute a synchronous detection unit 128. The cutoff frequency of the low-pass filter 123-1 is set so as to pass the sensor drive signal Esin(2πft). The synchronous detection unit 128 demodulates the output of the amplifier 122 into a signal synchronized with the sensor drive signal Esin(2πft).

[0029] Specifically, when the sensor drive signal Esin(2πft) output from the signal generator 120 during pressure and temperature measurement is positive, the switch 124 connects the output terminal of the amplifier 122 to the non-inverting input terminal of the low-pass filter 123-1. In addition, when the sensor drive signal Esin(2πft) is negative, the switch 124 connects the output terminal of the amplifier 122 to the inverting input terminal of the low-pass filter 123-1. This makes it possible to demodulate a signal synchronized with the sensor drive signal Esin(2πft) from the output of the amplifier 122.

[0030] Meanwhile, switch 125 and low-pass filter 123-2 constitute a synchronous detection unit 129. The cutoff frequency of low-pass filter 123-2 is set to pass sensor drive signal Esin(2πft). Synchronous detection unit 129 demodulates the output of amplifier 122 into a signal synchronized with signal Esin(2πft+π / 2) that is out of phase with sensor drive signal Esin(2πft) by 90 degrees.

[0031] Specifically, when signal Esin(2πft+π / 2) output from signal generator 121 during pressure and temperature measurement is positive, switch 125 connects the output terminal of amplifier 122 to the non-inverting input terminal of low-pass filter 123-2. In addition, when signal Esin(2πft+π / 2) is negative, switch 125 connects the output terminal of amplifier 122 to the inverting input terminal of low-pass filter 123-2. This makes it possible to demodulate, from the output of amplifier 122, a signal synchronized with signal Esin(2πft+π / 2) that is 90 degrees out of phase with sensor drive signal Esin(2πft).

[0032] 5 is a diagram showing the waveform of the output A of the amplifier 122 during pressure and temperature measurement. The output A of the amplifier 122 can be expressed by the following equation.

[0033]

number

[0034] 6 is a diagram showing the waveform of the output vc of the synchronous detection unit 128 during pressure and temperature measurement. The output vc of the synchronous detection unit 128 can be expressed by the following equation. This vc mainly depends on the capacitance Cx, but is also affected by the value of the series resistance Rx.

[0035]

number

[0036] 7 is a diagram showing the waveform of the output vt of the synchronous detection unit 129 when measuring pressure and temperature. The output vt of the synchronous detection unit 129 can be expressed by the following equation. This vt depends on the value of the series resistance Rx, but is also affected by the value of the electrostatic capacitance Cx.

[0037]

number

[0038] When the following equation is calculated from the output vc of the synchronous detection section 128 and the output vt of the synchronous detection section 129, a value proportional to only the capacitance Cx is obtained.

[0039]

number

[0040] Furthermore, when the following equation is calculated from the output vc of the synchronous detection section 128 and the output vt of the synchronous detection section 129, a value proportional to only the series resistance Rx is obtained.

[0041]

number

[0042] In equations (4) and (5), α and β are constants depending on the circuit constants Cf, f, and E, which are independent of the capacitance Cx and the series resistance Rx.

[0043] The capacitance calculation section 126 calculates the value of the capacitance Cx from the output vc of the synchronous detection section 128 and the output vt of the synchronous detection section 129 by using the formula (4) (Step S102 in FIG. 3).

[0044] The temperature calculation unit 127 calculates the value of the series resistance Rx by equation (5) from the output vc of the synchronous detection unit 128 and the output vt of the synchronous detection unit 129 (step S103 in FIG. 3). Then, the temperature calculation unit 127 derives the temperature of the sensor chip 1 from the value of the series resistance Rx (step S104 in FIG. 3). The relationship between the series resistance Rx and the temperature is stored in advance in the temperature calculation unit 127. The temperature calculation unit 127 may calculate the temperature from the value of the series resistance Rx by a preset equation, or may obtain the value of the temperature corresponding to the value of the series resistance Rx from a preset table.

[0045] The pressure measurement unit 13 corrects the capacitance Cx calculated by the capacitance-temperature detection unit 12 based on the temperature of the sensor chip 1 calculated by the capacitance-temperature detection unit 12, converts it into a measured pressure value MP, and outputs it (step S105 in FIG. 3). The method of correcting the capacitance Cx based on the temperature of the sensor chip 1 is performed using, for example, the following formula (6).

[0046]

number

[0047] In equation (6), Vo is the capacitance Cx calculated by the capacitance-temperature detection unit 12, Vt is the temperature of the sensor chip 1 calculated by the capacitance-temperature detection unit 12, a ij is the correction coefficient, and i,j are the orders of the polynomial.

[0048] The temperature notification unit 14 notifies the user of the temperature of the sensor chip 1 calculated by the capacitance / temperature detection unit 12 (step S106 in FIG. 3). Examples of notification methods include displaying the temperature calculation result, transmitting the temperature calculation result to the outside, etc.

[0049] The capacitance / temperature detection unit 12, pressure measurement unit 13, and temperature notification unit 14 perform the processes of steps S100 to S106 every measurement period until the pressure / temperature measurement operation is ended, for example, by a user instruction (YES in step S107 in FIG. 3).

[0050] In this embodiment, the temperature of the sensor chip 1 can be measured by utilizing the fact that the series resistance Rx of the movable electrode 106 and the fixed electrode 105 changes with temperature, and pressure measurement and temperature measurement can be realized with one sensor chip 1. In this embodiment, the accurate temperature of the sensor chip 1 can be measured, so that correction errors can be suppressed compared to a conventional configuration in which a temperature sensor is provided on the outside of the sensor chip, and pressure measurement errors can be suppressed. Furthermore, in this embodiment, it is not necessary to attach a temperature sensor to the sensor chip 1 and to wire to extract a signal from the temperature sensor, so that the sensor chip 1 can be made smaller than when a temperature sensor is attached to the sensor chip.

[0051] [Second Example] Next, a second embodiment of the present invention will be described. Figure 8 is a block diagram showing the configuration of a diaphragm vacuum gauge according to the second embodiment of the present invention, and the same components as those in Figure 1 are given the same reference numerals. The diaphragm vacuum gauge of this embodiment comprises a pressure receiving portion 10a and a circuit portion 11a.

[0052] 9 is a cross-sectional view showing the configuration of the main part of sensor chip 1a of this embodiment. In sensor chip 1a, fixed electrode 107 is formed on the surface of base 101 facing reference vacuum chamber 104, outside fixed electrode 105. Movable electrode 108 is formed on the surface of diaphragm 102 facing reference vacuum chamber 104, outside movable electrode 106, so as to face fixed electrode 107. The other configuration of sensor chip 1a is the same as that of sensor chip 1.

[0053] The fixed electrode 107 and the movable electrode 108 are formed on the edge of the diaphragm 102. Even if the diaphragm 102 is bent by pressure P of the medium to be measured, the edge of the diaphragm 102 is hardly deformed, so the capacitance between the movable electrode 108 and the fixed electrode 107 is unlikely to change. This capacitance is provided to eliminate measurement errors due to temperature changes inside and outside the sensor, humidity changes inside the reference vacuum chamber 104, etc.

[0054] The circuit section 11 a is made up of a capacitance / temperature detection section 12 a, a pressure measurement section 13 a, and a temperature notification section 14.

[0055] FIG. 10 is a flow chart for explaining the pressure / temperature measurement operation of the diaphragm vacuum gauge of this embodiment, and FIG. 11 is a block diagram showing the configuration of the capacitance / temperature detection section 12a. The capacitance / temperature detection unit 12a is composed of a signal generator 130 that outputs a sensor drive signal, a signal generator 131 that outputs a signal out of phase with the sensor drive signal, amplifiers 132, 133, a subtractor 134, differential input type low-pass filters 135-137, a switch 138 provided between the amplifier 132 and the low-pass filter 135, a switch 139 provided between the subtractor 134 and the low-pass filter 136, a switch 140 provided between the amplifier 132 and the low-pass filter 137, a capacitance calculation unit 141, a reference capacitance calculation unit 142, a temperature calculation unit 143, and a capacitance correction unit 144.

[0056] 11, the capacitance between the movable electrode 108 and the fixed electrode 107 of the sensor chip 1a is represented by Cr. Also, the component of the series resistance between the movable electrode 108 and the fixed electrode 107 is represented by Rr.

[0057] During pressure and temperature measurement, the signal generator 130 applies a sensor drive signal Esin(2πft) to the second electrode (eg, the movable electrode 106) and the fourth electrode (eg, the movable electrode 108) of the sensor chip 1a and to the switches 138 and 139 (FIG. 10, step S200).

[0058] During pressure and temperature measurement, the signal generator 131 applies a signal Esin(2πft+π / 2) that is out of phase with the sensor drive signal Esin(2πft) by 90 degrees to the switch 140 (step S201 in FIG. 10).

[0059] The amplifier 132 converts the current output from the first electrode (e.g., the fixed electrode 105) of the sensor chip 1a into a voltage, amplifies the voltage, and outputs a signal with an amplitude proportional to the capacitance Cx. The amplifier 133 converts the current output from the third electrode (e.g., the fixed electrode 107) of the sensor chip 1a into a voltage, amplifies the voltage, and outputs a signal with an amplitude proportional to the capacitance Cr. The subtractor 134 subtracts the output signal B of the amplifier 133 from the output signal A of the amplifier 132 .

[0060] The switch 138 and the low-pass filter 135 constitute a synchronous detection unit 145. The cutoff frequency of the low-pass filter 135 is set so as to pass the sensor drive signal Esin(2πft). The synchronous detection unit 145 demodulates the output of the amplifier 132 into a signal synchronized with the sensor drive signal Esin(2πft).

[0061] Specifically, when the sensor drive signal Esin(2πft) output from the signal generator 130 during pressure and temperature measurement is positive, the switch 138 connects the output terminal of the amplifier 132 to the non-inverting input terminal of the low-pass filter 135. In addition, when the sensor drive signal Esin(2πft) is negative, the switch 138 connects the output terminal of the amplifier 132 to the inverting input terminal of the low-pass filter 135. This makes it possible to demodulate a signal synchronized with the sensor drive signal Esin(2πft) from the output of the amplifier 132.

[0062] Meanwhile, switch 139 and low-pass filter 136 constitute a synchronous detection unit 146. The cutoff frequency of low-pass filter 136 is set to pass sensor drive signal Esin(2πft). Synchronous detection unit 146 demodulates the output of subtractor 134 into a signal synchronized with sensor drive signal Esin(2πft).

[0063] Specifically, when the sensor drive signal Esin(2πft) output from the signal generator 130 during pressure and temperature measurement is positive, the switch 139 connects the output terminal of the subtractor 134 to the non-inverting input terminal of the low-pass filter 136. In addition, when the sensor drive signal Esin(2πft) is negative, the switch 139 connects the output terminal of the subtractor 134 to the inverting input terminal of the low-pass filter 136. This makes it possible to demodulate a signal synchronized with the sensor drive signal Esin(2πft) from the output of the subtractor 134.

[0064] The switch 140 and the low-pass filter 137 constitute a synchronous detection unit 147. The low-pass filter 137 has a cutoff frequency set to pass the sensor drive signal Esin(2πft). The synchronous detection unit 147 demodulates the output of the amplifier 132 into a signal synchronized with a signal Esin(2πft+π / 2) that is out of phase with the sensor drive signal Esin(2πft) by 90 degrees.

[0065] Specifically, when signal Esin(2πft+π / 2) output from signal generator 131 during pressure and temperature measurement is positive, switch 140 connects the output terminal of amplifier 132 to the non-inverting input terminal of low-pass filter 137. In addition, when signal Esin(2πft+π / 2) is negative, switch 140 connects the output terminal of amplifier 132 to the inverting input terminal of low-pass filter 137. This makes it possible to demodulate, from the output of amplifier 132, a signal synchronized with signal Esin(2πft+π / 2) that is 90 degrees out of phase with sensor drive signal Esin(2πft).

[0066] The capacitance calculation unit 141 calculates the value of the capacitance Cx from the output vc of the synchronous detection unit 145 and the output vt of the synchronous detection unit 147 by using the formula (4) (Step S202 in FIG. 10). The reference capacitance calculation section 142 calculates the value of the capacitance (reference capacitance) Cr from the amplitude of the output vr of the synchronous detection section 146 (Step S203 in FIG. 10).

[0067] The capacitance corrector 144 calculates a value (Cx-Cr) / Cx obtained by correcting the capacitance Cx using the reference capacitance Cr (Step S204 in FIG. 10). As in the first embodiment, the temperature calculation unit 143 calculates the value of the series resistance Rx using equation (5) from the output vc of the synchronous detection unit 145 and the output vt of the synchronous detection unit 147 (step S205 in FIG. 10), and derives the temperature of the sensor chip 1a from the value of the series resistance Rx (step S206 in FIG. 10).

[0068] The pressure measuring unit 13a corrects the capacitance (Cx-Cr) / Cx calculated by the capacitance-temperature detecting unit 12a based on the temperature of the sensor chip 1a calculated by the capacitance-temperature detecting unit 12a, converts it into a measured pressure value MP, and outputs it (FIG. 10, step S207). The method of correcting the capacitance (Cx-Cr) / Cx based on the temperature of the sensor chip 1a is performed using the following formula (7).

[0069]

number

[0070] In formula (7), Vx is the capacitance Cx calculated by the capacitance calculation unit 141, Vt is the temperature of the sensor chip 1a calculated by the temperature calculation unit 143, Vr is the capacitance Cr calculated by the reference capacitance calculation unit 142, a ijk is a correction coefficient, and i, j, and k are the orders of the polynomial. In the example of equation (7), the capacitance Cx is corrected by the reference capacitance Cr by using the calculation results of the capacitance calculation units 141 and 143, without using the calculation result of the capacitance correction unit 144.

[0071] As in the first embodiment, the temperature notification unit 14 notifies the user of the temperature of the sensor chip 1a calculated by the capacitance / temperature detection unit 12a (step S208 in FIG. 10).

[0072] The capacitance / temperature detection unit 12a, the pressure measurement unit 13a, and the temperature notification unit 14 perform the processes of steps S200 to S208 every measurement period until the pressure measurement operation is ended, for example, by a user instruction (YES in step S209 in FIG. 10).

[0073] Thus, in this embodiment, capacitance measurement for pressure measurement and temperature measurement can be performed using the fixed electrode 105 and movable electrode 106 of the sensor chip 1a, and reference capacitance measurement for capacitance correction can be performed using the fixed electrode 107 and movable electrode 108 of the sensor chip 1a, making it possible to realize pressure measurement, temperature measurement, and capacitance correction with a single sensor chip 1a.

[0074] [Third Example] Next, a third embodiment of the present invention will be described. Fig. 12 is a block diagram showing the configuration of a diaphragm vacuum gauge according to the third embodiment of the present invention, where the same components as those in Figs. 1 and 8 are given the same reference numerals. The diaphragm vacuum gauge of this embodiment comprises a pressure receiving portion 10a and a circuit portion 11b. The configuration of the pressure receiving portion 10a is as described in the second embodiment. The circuit section 11b is made up of a capacitance / temperature detection section 12b, a pressure measurement section 13b, and a temperature notification section .

[0075] 13 is a block diagram showing the configuration of the capacitance / temperature detection unit 12b of this embodiment. The capacitance / temperature detection unit 12b is composed of signal generators 130 and 131b, amplifiers 132 and 133, a subtractor 134, low-pass filters 135 and 136, switches 138 and 139, a capacitance calculation unit 141b, a reference capacitance calculation unit 142b, a temperature calculation unit 143b, a capacitance correction unit 144, a differential input type low-pass filter 148, and a switch 149 provided between the subtractor 134 and the low-pass filter 148.

[0076] The process flow of the pressure / temperature measurement operation of the diaphragm vacuum gauge of this embodiment is similar to that of the second embodiment, and will therefore be described using the reference numerals in FIG. During pressure and temperature measurement, the signal generator 130 applies a sensor drive signal Esin(2πft) to the second electrode (eg, the movable electrode 106) and the fourth electrode (eg, the movable electrode 108) of the sensor chip 1a and to the switches 138 and 139 (FIG. 10, step S200).

[0077] During pressure and temperature measurement, the signal generator 131b applies a signal Esin(2πft+π / 2) that is out of phase with the sensor drive signal Esin(2πft) by 90 degrees to the switch 149 (step S201 in FIG. 10).

[0078] As in the second embodiment, synchronous detection section 145 demodulates a signal synchronized with sensor drive signal Esin(2πft) from the output of amplifier 132. Synchronous detection section 146 demodulates a signal synchronized with sensor drive signal Esin(2πft) from the output of subtractor 134.

[0079] The switch 149 and the low-pass filter 148 constitute a synchronous detection unit 150. The low-pass filter 148 has a cutoff frequency set to pass the sensor drive signal Esin(2πft). The synchronous detection unit 150 demodulates the output of the subtractor 134 into a signal synchronized with a signal Esin(2πft+π / 2) that is out of phase with the sensor drive signal Esin(2πft) by 90 degrees.

[0080] Specifically, when the signal Esin(2πft+π / 2) output from the signal generator 131b during pressure and temperature measurement is positive, the switch 149 connects the output terminal of the subtractor 134 to the non-inverting input terminal of the low-pass filter 148. In addition, when the signal Esin(2πft+π / 2) is negative, the switch 149 connects the output terminal of the subtractor 134 to the inverting input terminal of the low-pass filter 148. This makes it possible to demodulate, from the output of the subtractor 134, a signal synchronized with the signal Esin(2πft+π / 2) that is 90 degrees out of phase with the sensor drive signal Esin(2πft).

[0081] The capacitance calculation unit 141b calculates the value of the capacitance Cx from the amplitude of the output vc of the synchronous detection unit 145 (Step S202 in FIG. 10). The reference capacitance calculation unit 142b calculates the value of the capacitance (reference capacitance) Cr from the output vr of the synchronous detection unit 146 and the output vt of the synchronous detection unit 150 (step S203 in FIG. 10). This reference capacitance Cr can be calculated by replacing Cx with Cr and vc with vr in equation (4).

[0082] The capacitance corrector 144 calculates a value (Cx-Cr) / Cx obtained by correcting the capacitance Cx using the reference capacitance Cr (Step S204 in FIG. 10). The temperature calculation unit 143b calculates the value of the series resistance Rr from the output vr of the synchronous detection unit 146 and the output vt of the synchronous detection unit 150 (step S205 in FIG. 10), and derives the temperature of the sensor chip 1a from the value of the series resistance Rr (step S206 in FIG. 10).

[0083] The series resistance Rr can be calculated by replacing Rx with Rr and vc with vr in equation (5). The relationship between the series resistance Rr and the temperature is stored in advance in the temperature calculation unit 143b. The temperature calculation unit 143b may calculate the temperature from the value of the series resistance Rr using a preset equation, or may obtain the temperature value corresponding to the value of the series resistance Rr from a preset table.

[0084] As in the second embodiment, the pressure measuring unit 13b corrects the capacitance (Cx-Cr) / Cx calculated by the capacitance-temperature detecting unit 12b based on the temperature of the sensor chip 1a calculated by the capacitance-temperature detecting unit 12b, converts it into a measured pressure value MP, and outputs it (step S207 in FIG. 10).

[0085] As in the second embodiment, the temperature notification unit 14 notifies the user of the temperature of the sensor chip 1a calculated by the capacitance / temperature detection unit 12b (step S208 in FIG. 10).

[0086] The capacitance / temperature detection unit 12b, the pressure measurement unit 13b, and the temperature notification unit 14 perform the processes of steps S200 to S208 every measurement period until the pressure / temperature measurement operation is ended, for example, by a user instruction (YES in step S209 in FIG. 10).

[0087] Thus, in this embodiment, capacitance measurement for pressure measurement can be performed using the fixed electrode 105 and the movable electrode 106 of the sensor chip 1a, and reference capacitance measurement for capacitance correction and temperature measurement can be performed using the fixed electrode 107 and the movable electrode 108 of the sensor chip 1a, making it possible to realize pressure measurement, temperature measurement, and capacitance correction with a single sensor chip 1a.

[0088] In the description of this embodiment, in the process of pressure measurement and temperature measurement, the first capacitance value calculated by the first capacitance calculation unit may be a value proportional to the capacitance between the first and second electrodes, and similarly, the second capacitance value calculated by the second capacitance calculation unit may be a value proportional to the capacitance between the third and fourth electrodes. Also, the sensor chip temperature calculated by the temperature calculation unit may be a value proportional to the temperature of the sensor chip. Furthermore, in the second and third embodiments, the second electrode and the fourth electrode do not have to be separate electrodes, but may be electrically connected to each other and formed as a single electrode.

[0089] The circuit units 11, 11a, and 11b described in the first to third embodiments can be realized by a computer equipped with a CPU (Central Processing Unit), a storage device, and an interface, and a program that controls these hardware resources. An example of the configuration of this computer is shown in FIG.

[0090] The computer includes a CPU 200, a storage device 201, and an interface device (I / F) 202. The I / F 202 is connected to the hardware of the capacitance / temperature detection units 12, 12a, 12b, etc. In such a computer, a program for implementing the method of the present invention is stored in the storage device 201. The CPU 200 executes the processes described in the first to third embodiments in accordance with the program stored in the storage device 201. [Industrial Applicability]

[0091] The present invention is applicable to diaphragm vacuum gauges. [Explanation of symbols]

[0092] 1, 1a... sensor chip, 10, 10a... pressure receiving section, 11, 11a, 11b... circuit section, 12, 12a, 12b... capacitance / temperature detection section, 13, 13a, 13b... pressure measurement section, 14... temperature notification section, 102... diaphragm, 105, 107... fixed electrode, 106, 108... movable electrode, 120, 121, 130, 131, 131b... signal generator, 122, 132, 133... Amplifiers, 123-1, 123-2, 135 to 137, 148... low-pass filters, 124, 125, 138 to 140, 149... switches, 126, 141, 141b... capacitance calculation unit, 127, 143, 143b... temperature calculation unit, 128, 129, 145 to 147, 150... synchronous detection unit, 134... subtractor, 142, 142b... reference capacitance calculation unit, 144... capacitance correction unit.

Claims

1. a sensor chip including a first electrode formed on a base and a second electrode formed on a diaphragm disposed across a gap from the base so as to face the first electrode, the distance between the first and second electrodes changing in response to displacement of the diaphragm due to pressure of a medium to be measured; a first signal generator configured to apply a sensor drive signal to the second electrode; a second signal generator configured to output a signal out of phase with the sensor drive signal; an amplifier configured to convert the current output from the first electrode into a voltage and amplify the voltage; a first synchronous detection unit configured to demodulate a signal synchronized with the sensor drive signal from the output signal of the amplifier; a second synchronous detection unit configured to demodulate, from the output signal of the amplifier, a signal synchronized with the output signal of the second signal generator; a capacitance calculation unit configured to calculate a value proportional to the capacitance between the first and second electrodes as a capacitance value from output signals of the first and second synchronous detection units; a temperature calculation unit configured to calculate a value proportional to a series resistance of the first and second electrodes from output signals of the first and second synchronous detection units, and to determine a value proportional to a temperature of the sensor chip as the sensor chip temperature from the value proportional to the series resistance.

2. 2. The diaphragm vacuum gauge according to claim 1, 4. A diaphragm vacuum gauge, further comprising: a pressure measuring unit configured to convert the calculated capacitance value into a measured pressure value by correcting the calculated capacitance value based on a temperature of the sensor chip.

3. a sensor chip including a first electrode formed on a base, a second electrode formed on a diaphragm disposed across a gap from the base so as to face the first electrode, a third electrode formed on the base outside the first electrode, and a fourth electrode formed on the diaphragm outside the second electrode so as to face the third electrode, wherein the distance between the first and second electrodes changes in response to displacement of the diaphragm due to pressure of a medium to be measured; a first signal generator configured to apply a sensor drive signal to the second and fourth electrodes; a second signal generator configured to output a signal out of phase with the sensor drive signal; a first amplifier configured to convert a current output from the first electrode into a voltage and amplify the voltage; a second amplifier configured to convert the current output from the third electrode into a voltage and amplify the voltage; a subtractor configured to subtract the output signal of the second amplifier from the output signal of the first amplifier; a first synchronous detection unit configured to demodulate a signal synchronized with the sensor drive signal from the output signal of the first amplifier; a second synchronous detection unit configured to demodulate a signal synchronized with the sensor drive signal from the output signal of the subtractor; a third synchronous detection unit configured to demodulate a signal synchronized with the output signal of the second signal generator from the output signal of the first amplifier; a first capacitance calculation unit configured to calculate a value of a first capacitance Cx between the first and second electrodes from output signals of the first and third synchronous detection units; a second capacitance calculation unit configured to calculate a value Cx-Cr obtained by subtracting a second capacitance Cr between the third and fourth electrodes from the first capacitance Cx, based on an output signal of the second synchronous detection unit; a temperature calculation unit configured to calculate a value proportional to a series resistance of the first and second electrodes from the output signals of the first and third synchronous detection units, and to obtain a value proportional to a temperature of the sensor chip from the value proportional to the series resistance as the sensor chip temperature; and a capacitance correction unit configured to calculate a value (Cx-Cr) / Cx obtained by correcting the first capacitance Cx by the second capacitance Cr from calculation results of the first and second capacitance calculation units.

4. a sensor chip including a first electrode formed on a base, a second electrode formed on a diaphragm disposed across a gap from the base so as to face the first electrode, a third electrode formed on the base outside the first electrode, and a fourth electrode formed on the diaphragm outside the second electrode so as to face the third electrode, wherein the distance between the first and second electrodes changes in response to displacement of the diaphragm due to pressure of a medium to be measured; a first signal generator configured to apply a sensor drive signal to the second and fourth electrodes; a second signal generator configured to output a signal out of phase with the sensor drive signal; a first amplifier configured to convert a current output from the first electrode into a voltage and amplify the voltage; a second amplifier configured to convert the current output from the third electrode into a voltage and amplify the voltage; a subtractor configured to subtract the output signal of the second amplifier from the output signal of the first amplifier; a first synchronous detection unit configured to demodulate a signal synchronized with the sensor drive signal from the output signal of the first amplifier; a second synchronous detection unit configured to demodulate a signal synchronized with the sensor drive signal from the output signal of the subtractor; a third synchronous detection unit configured to demodulate a signal synchronized with the output signal of the second signal generator from the output signal of the subtractor; a first capacitance calculation unit configured to calculate a value of a first capacitance Cx between the first and second electrodes from an output signal of the first synchronous detection unit; a second capacitance calculation unit configured to calculate a value Cx-Cr obtained by subtracting a second capacitance Cr between the third and fourth electrodes from the first capacitance Cx, based on output signals from the second and third synchronous detection units; a temperature calculation unit configured to calculate a value proportional to a series resistance of the third and fourth electrodes from the output signals of the second and third synchronous detection units, and to obtain a value proportional to a temperature of the sensor chip from the value proportional to the series resistance as the sensor chip temperature; and a capacitance correction unit configured to calculate a value (Cx-Cr) / Cx obtained by correcting the first capacitance Cx by the second capacitance Cr from calculation results of the first and second capacitance calculation units.

5. 5. The diaphragm vacuum gauge according to claim 3, 2. A diaphragm vacuum gauge comprising: a first electrode and a second electrode; a second electrode and a fourth electrode electrically connected to each other to form a single electrode;

6. 6. The diaphragm vacuum gauge according to claim 3, a pressure measuring unit configured to convert the corrected first capacitance value (Cx-Cr) / Cx into a measured pressure value by correcting the first capacitance value (Cx-Cr) / Cx based on the sensor chip temperature.

7. 7. The diaphragm vacuum gauge according to claim 1, The second signal generator outputs a signal which is out of phase with the sensor drive signal by 90 degrees.

8. 8. The diaphragm vacuum gauge according to claim 1, The diaphragm vacuum gauge further comprising a temperature notification unit configured to notify a user of the sensor tip temperature.

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