JPH06201501A - Pressure measuring device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a pressure measuring device capable of detecting a drift amount from the equilibrium of a bridge circuit at a pressure lower than a resolution and measuring an accurate pressure. A capacitor 10, 11 is formed between a diaphragm that is displaced according to a change in pressure and an electrode that is disposed so as to face the diaphragm, so that equilibrium is achieved at a pressure below the displacement limit of the diaphragm. The pressure measuring device having the bridge circuit 3 configured as described above is provided with the drift detecting means 2 for detecting the drift amount from the equilibrium of the bridge circuit 3 when the pressure in the measurement chamber is equal to or less than the displacement limit of the diaphragm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure measuring device,
Particularly, it relates to a capacitance type pressure measuring device.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, low pressure CVD is used.
(Chemical Vapor Deposition) There is a step of treating a wafer by introducing a process gas while keeping a semiconductor device in a constant depressurized state. At this time, it is important to maintain the pressure in the semiconductor manufacturing apparatus at a predetermined pressure with high accuracy and process the wafers in order to improve the yield. Therefore, a pressure control device is usually provided in the semiconductor device.

FIG. 4 is a block diagram of a semiconductor manufacturing apparatus. As shown in FIG. 4, the semiconductor manufacturing apparatus includes a pressure measuring device 100 for measuring the pressure in the chamber 104, which is a reaction chamber, a vacuum pump 103 for exhausting the chamber 104, and an exhaust of the chamber 104. A conductance valve 102 for controlling and a pressure control device 101 for controlling opening / closing of the conductance valve 102 are arranged. The pressure in the chamber 104 measured by the pressure measuring device 100 is converted into a DC voltage of 0 to 10 V and output to the pressure control device 101. Pressure control device 10
In No. 1, the open / close amount of the conductance valve 102 is controlled according to the input voltage, and the pressure inside the chamber 104 is maintained at a desired pressure by maintaining the voltage at a predetermined value. Then, the wafer is processed while introducing the process gas into the chamber 104.

FIG. 5 is a block diagram of a pressure sensor of the pressure measuring device 100. As shown in FIG. 5, the pressure sensor is composed of two chambers partitioned by a diaphragm 30 made of a metal that is sufficiently tensioned. Since the process gas is introduced into the measuring side 35, it is made of only a metal having excellent corrosion resistance. The other reference side 36 is provided with electrodes 31 and 32 for sensing the displacement of the diaphragm 30, and a high vacuum (10 ⁻⁶ To
It is evacuated and sealed with rr) to maintain a high vacuum state. A high frequency AC voltage is applied to the introduction terminal 33.

In the pressure sensor, when the diaphragm 30 moves due to a change in absolute pressure, the diaphragm 30, the electrodes 31 and 3
The capacitance between the two changes, the signal is taken out as a change in the voltage, signal processing is performed, and the signal is converted to a voltage of 0 to 10 V.
Output to the pressure control device 101.

FIG. 6 is a circuit diagram of a conventional pressure measuring device. Capacitors 10 and 11 shown in FIG. 6 are capacitors formed between the diaphragm 30 and electrodes 31 and 32 shown in FIG. Capacitors 10, 11 and resistors 12,
A bridge circuit is configured between the bridge circuit 13 and the circuit 13. The bridge circuit includes an AC reference voltage generator 15 of the controller 14.
Is supplied with a high frequency AC voltage, and the detection / amplification circuit 16 detects the AC voltage output from the bridge circuit from 0 to 10
It is converted into a DC voltage of V and output to the pressure control device 101.

Next, the operation of the bridge circuit will be described. The bridge circuit enters an equilibrium state (C2 × R2 = C1 × R1) when the pressure on the measurement side 35 shown in FIG. 5 becomes equal to or lower than the displacement limit (hereinafter referred to as resolution) of the diaphragm 30, and the bridge circuit A , B is designed to be 0 (hereinafter referred to as reference voltage). When the pressure on the measurement side 35 exceeds the resolution of the pressure sensor, the bridge circuit shifts from the equilibrium state, and an AC voltage is generated between A and B. This AC voltage is used as the difference from the reference voltage, and the detection / amplification circuit 1
The pressure on the measurement side 35 is obtained by inputting to 6 and performing signal processing.

[0008]

As described above, as shown in FIG.
The pressure in the chamber 104 shown in FIG. 2 is obtained by performing signal processing on the AC voltage output from the bridge circuit by the detection / amplification circuit 16, but the diaphragm 30 changes due to temperature change or humidity change in the chamber 104 due to process gas. A so-called zero point drift phenomenon occurs in which the reference voltage becomes non-zero at a pressure below the resolution of the measurement side 35 due to deformation. If the zero point drifts, an error will occur in the pressure measurement in the chamber 104 due to the drift, and it will become a problem that an accurate pressure cannot be monitored. A method of temperature correction is generally used for the zero point drift due to the temperature change of the diaphragm 30, but delay control by feedback is used, and further, the distortion of the diaphragm 30 due to other environmental factors such as humidity and running. Since the zero point is not corrected by, it is difficult to monitor the accurate pressure.

Therefore, an object of the present invention is to provide a pressure measuring device capable of detecting a drift amount from the equilibrium of a bridge circuit at a pressure lower than the resolution and measuring the pressure accurately.

[0010]

According to the present invention, a capacitor is formed between a diaphragm that is displaced in response to a change in pressure and an electrode that is disposed so as to face the diaphragm, and the diaphragm is used. In a pressure measuring device provided with a bridge circuit configured to be in equilibrium at a pressure equal to or lower than the displacement limit, the amount of drift from equilibrium of the bridge circuit when the pressure in the measurement chamber is equal to or lower than the displacement limit of the diaphragm. It is solved by a pressure measuring device comprising a drift detecting means for detecting

Further, according to the present invention, the above-mentioned problem is that the drift detecting means determines whether the drift amount from the equilibrium of the bridge circuit is within a predetermined range, and the drift amount is When the specified range is exceeded,
The present invention is preferably solved by a pressure measuring device including an abnormality notifying unit that cuts an output from the bridge circuit or indicates an abnormality.

[0012]

According to the present invention, as shown in FIG. 1, the pressure measuring device is provided with a drift detecting circuit 2 for detecting a drift amount at a pressure below the displacement limit (resolution) of the diaphragm 30 shown in FIG. There is.

An AC voltage is input from the bridge circuit 3 to the drift detection circuit 2, and the comparator 5 shown in FIG.
2, 53, it is determined whether the voltage value is within a predetermined allowable range. If the AC voltage value is within the allowable range,
As shown in (4), the switch 57 is turned on and the output from the bridge circuit 3 is output. If it is outside the allowable range, the switch 57 is turned off and the output from the bridge circuit 3 is cut, pressure control becomes impossible, and a drift abnormality occurs. Can be notified. Similarly, if the voltage value of the AC voltage is outside the allowable range, the drift abnormality can be notified by turning on the indicator lamp 59 as shown in FIG.

[0014]

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

FIG. 1 is a circuit diagram of an embodiment of the pressure measuring device according to the present invention. As shown in FIG. 1, the pressure measuring device includes a capacitor 10, 1 formed between a diaphragm 30 and electrodes 31, 32 of the pressure sensor shown in FIG.
1 and resistors 12 and 13 and a bridge circuit 3 and a controller 1.

A high frequency voltage is supplied to the bridge circuit 3 by an AC reference voltage generator 15 in the controller 1. The AC voltage between A and B of the bridge circuit 3 is input to the drift detection circuit 2 in the controller 1. The drift detection circuit 2 detects the drift amount x (mV) at the zero point when the pressure inside the measurement side 35 shown in FIG. 5 is below the resolution, and this drift amount is within the allowable range (−y (mV) to y).
(MV)), and if it is outside the allowable range, the output from the bridge circuit 3 to the detection / amplification circuit 16 is cut or an abnormality is displayed. The detection / amplification circuit 16 in the controller 1 detects and amplifies the AC voltage output from the bridge circuit 3 and
It is converted into a DC voltage of 10 V and output to the pressure control device 101 shown in FIG.

As shown in the conventional example, in the pressure control device 101 shown in FIG. 4, the opening / closing amount of the conductance valve 102 is controlled according to the input voltage value, and the vacuum pump 103 exhausts the inside of the chamber 104 to obtain a desired value. Hold at pressure.

FIG. 2 is a block diagram of the drift detection circuit 2 according to the first embodiment. As shown in FIG. 2, the bridge circuit 3
Are input to the differential device 51 from A and B (FIG. 1). In the differential device 51, an AC voltage between the bridge circuits A and B is obtained.
The differential device 51 is input to the comparators 52 and 53. Comparator 5
2, the maximum value of the AC voltage is -y (mV) or more and y (m
V) When it is less than or equal to, the Low voltage '0' is output, and at other times, the High voltage '1' is output. In the comparator 53, when the minimum value of the AC voltage is −y (mV) or more and y (mV) or less,
It outputs Low voltage "0", and outputs High voltage "1" at other times. The comparators 52 and 53 are input to the NOR 54 and output the values shown in Table 1 below.

[0019]

[Table 1]

Therefore, the maximum voltage value and the minimum voltage value of the voltage between A and B of the bridge circuit 3 are -y (mV) or more and y, respectively.
NOR 54 outputs High “1” when the voltage is (mV) or less, and Low “0” is output at other times.

That is, when the NOR 54 outputs "1", it means that the drift amount at the zero point is normal within the allowable range, and when "0" is output, it means that it is abnormal. . The NOR 54 is connected to the latch circuit 55 and holds the output from the NOR 54. The latch circuit 55 is connected to the switch circuit 56, and the latch circuit 55
The switch 57 is turned off when the output of is 0, the differential device 51 and the detection / amplification circuit 16 are separated, and when the output of the latch circuit 55 is 1, the switch 57 is turned on and the differential device 51 and the detection / amplification circuit 16 are connected. The switch circuit 56 is connected to a mode input terminal 58 for identifying before and after the detection of the zero point drift amount, and the switch 57 is turned on before the detection of the zero point drift amount to detect the zero point drift amount. If it is later, the switch 57 is turned off.

Next, the operation of the above drift detection circuit will be described.

First, the mode input terminal 58 inputs the zero point drift amount pre-detection mode. Switch 57
Is turned on, the output from the bridge circuit 3 is input to the detection / amplification circuit 16, a voltage of 0 to 10 V is output to the pressure control device 101, the conductance valve 102 is fully opened, and the pressure in the chamber 104 is below the resolution. Is evacuated by the vacuum pump 103. As shown in FIG. 2, the differential device 51 outputs the data to the comparators 52 and 53,
The OR 54 outputs "1" if there is no zero point drift abnormality, and outputs "0" if there is. The output of the NOR 54 is held by the latch circuit 55 connected to the NOR 54. When the pressure in the chamber 104 becomes equal to or lower than the resolution, the mode after the drift amount detection at the zero point is input by the mode input terminal 58, and the switch 57 is turned on or off according to the output of the latch circuit 55.

Next, the process gas is introduced into the chamber 104 to increase the pressure. At this time, when the switch 57 is off, the output to the detection / amplification circuit 16 is cut and nothing is output to the pressure control device 101, so that the zero point drift abnormality is determined.

FIG. 3 is a block diagram of the drift detection circuit according to the second embodiment. In the second embodiment, the presence or absence of a zero point drift abnormality is determined by turning on the indicator lamp 59. As shown in FIG. 3, as in the first embodiment, the differential 5
1, comparators 52 and 53, and a latch circuit 55 are provided. The OR 63 outputs "1" if there is a zero point drift abnormality and "0" if not. OR6
3 is connected to the latch circuit 55. Latch circuit 55
Is input to the switch circuit 60. Switch circuit 6
A mode input terminal 62 for identifying before and after the zero-point drift amount detection is connected to 0. The switch 61 is turned off before the zero-point drift amount detection, and the switch 61 is turned on after the drift amount detection. However, when the latch circuit 55 and the indicator lamp 59 are connected and "1" is output from the latch circuit 55, that is, when the zero-point drift abnormality is output, the indicator lamp 59 is turned on for the first time, and otherwise. Since the indicator light 59 does not light, the indicator light 59
A zero point drift abnormality is determined by lighting.

[0026]

As described above, according to the present invention, since the zero point drift abnormality can be detected, accurate measurement can be performed, and the timing of pressure sensor replacement can be predicted to prevent Preventive Maintenane. It will be possible.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a pressure measuring device according to an embodiment.

FIG. 2 is a configuration diagram of a drift detection circuit according to the first embodiment.

FIG. 3 is a configuration diagram of a drift detection circuit according to a second embodiment.

FIG. 4 is a configuration diagram of a semiconductor manufacturing apparatus.

FIG. 5 is a block diagram of a pressure sensor.

FIG. 6 is a circuit configuration diagram of a conventional pressure measuring device.

[Explanation of symbols]

 1 Controller 2 Drift Detection Circuit 3 Bridge Circuit 10, 11 Capacitor 12, 13 Resistance 14 Controller 15 AC Reference Voltage Generator 16, 17 Detection / Amplification Circuit 30 Diaphragm 31, 32 Electrode 33 Introduction Terminal 34 Getter Pump 35 Measurement Side 36 Reference Side 51 Differential device 52,53 Comparator 54 NOR 55 Latch circuit 56,60 Switch circuit 57,61 Switch 58,62 Mode input terminal 59 Indicator light 63 OR 100 Pressure measuring device 101 Pressure control device 102 Conductance valve 103 Vacuum pump 104 Chamber

Claims (2)

[Claims] 1. A capacitor is formed between a diaphragm that displaces in response to a change in pressure and an electrode that is disposed so as to face the diaphragm, and is balanced at a pressure below a displacement limit of the diaphragm. A pressure measuring device having a bridge circuit configured, wherein the pressure measuring device comprises drift detecting means for detecting a drift amount from the equilibrium of the bridge circuit when the pressure in the measurement chamber is equal to or less than a displacement limit of the diaphragm. And pressure measuring device. 2. A drift amount determining means for determining whether or not a drift amount from equilibrium of the bridge circuit is within a predetermined range, and the drift detecting means, when the drift amount exceeds a predetermined range, The pressure measuring device according to claim 1, further comprising an abnormality notifying unit that cuts an output from the bridge circuit or indicates an abnormality.