JP5162483B2 - Pressure sensor - Google Patents

Description

  The present invention relates to a diaphragm type pressure sensor, and more particularly, to a device for measuring a water vapor pressure in a water vapor tank (hereinafter referred to as “tank”) for supplying water vapor to a vacuum chamber.

  In the film forming process of the transparent electrode film, water vapor may be supplied to the vacuum chamber as a reaction gas. In such a process, water vapor in the tank is supplied to the vacuum chamber via a supply path that communicates between the tank and the vacuum chamber. The flow rate of water vapor supplied to the vacuum chamber is controlled using a mass flow controller provided in the middle of the supply path. In order to determine whether or not this flow rate control is properly performed, the water vapor pressure in the tank is measured using a pressure sensor.

  Here, since the pressure in the vacuum chamber is lower than the water vapor pressure in the tank, when the tank and the vacuum chamber are connected to supply water vapor from the tank to the vacuum chamber, the water vapor pressure in the tank decreases, The heat of vaporization is taken away. As a result, condensation of water vapor occurs, and a part of the condensed water vapor freezes on the diaphragm surface of the pressure sensor. When water vapor freezes on the surface of the diaphragm, there is a problem that the measurement accuracy of the water vapor pressure is lowered.

  By the way, conventionally, a pressure sensor that measures a pressure in a vacuum chamber is known that includes a heater that heats a diaphragm (see, for example, Patent Document 1). It can be considered that such a configuration is applied to the above-mentioned use to prevent water vapor icing on the surface of the diaphragm.

  However, when the diaphragm is heated by the heater, there arises a problem that thermal deformation is caused and the measurement accuracy of the water vapor pressure is lowered. Furthermore, when the diaphragm is heated by a heater, there is a configuration for performing a calculation process for calibrating the measurement result according to the temperature of the diaphragm and a control for periodically turning the heater ON or OFF in order to keep the diaphragm temperature constant. There is a problem that the configuration of the pressure sensor becomes complicated because it is necessary to provide the pressure sensor separately.

JP-A-10-153510

  In view of the above points, the present invention has an object to provide a pressure sensor with a simple configuration capable of measuring the water vapor pressure in the tank with high accuracy while preventing freezing of water vapor on the surface of the diaphragm. To do.

  In order to solve the above problems, the present invention provides a first chamber maintained at a constant pressure, a second chamber communicating with a tank that supplies water vapor to the vacuum chamber, and a diaphragm that isolates the first chamber from the second chamber. And a pressure sensor for measuring the water vapor pressure in the tank based on the amount of displacement of the diaphragm in accordance with the pressure difference between the first chamber and the second chamber that occurs in response to the water vapor pressure fluctuation in the tank. The heating element is provided in the communication path from the second chamber to the tank, and the heating element is separated from the diaphragm so that the radiant heat from the heating element does not reach the diaphragm.

  In the present invention, the heating element may be a mesh electrode.

  According to the present invention, when the tank and the vacuum chamber are connected to supply the water vapor in the tank to the vacuum chamber, the pressure in the tank is reduced and the vaporization heat is removed, but the tank is transferred to the second chamber. By supplementing the heat of vaporization taken away by the heating element provided in the communication path communicating with the water vapor, icing of water vapor on the surface of the diaphragm can be prevented, and the water vapor pressure in the tank can be measured with high accuracy. Moreover, since the diaphragm is not heated by the radiant heat from the heating element, thermal deformation of the diaphragm can be prevented. Further, since the water vapor can be prevented from icing on the surface of the diaphragm simply by providing a heating element in the communication path, the configuration of the pressure sensor is simple.

It is the schematic which shows the supply system of water vapor | steam in embodiment of this invention. It is a figure which expands and shows the pressure sensor.

  Hereinafter, a pressure sensor according to an embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

  A diaphragm type pressure sensor 1 shown in FIG. 1 is provided in communication with a tank 2. The tank 2 stores water 20 and is filled with water vapor. The tank 2 communicates with the vacuum chamber 4 through the water vapor supply passage 3.

  The vacuum chamber 4 is a processing chamber in which, for example, a transparent electrode film forming process using water vapor as a reaction gas is performed. The water vapor supply passage 3 that communicates between the tank 2 and the vacuum chamber 4 is provided with a valve 5 and a mass flow controller 6 from the side closer to the tank 2. The mass flow controller 6 controls the flow rate of water vapor supplied into the vacuum chamber 4.

  Next, the details of the pressure sensor 1 will be described with reference to FIG. The pressure sensor 1 includes a housing 10. In the housing 10, the first chamber 11 maintained at a constant pressure, the second chamber 12 communicating with the tank 2 via the communication passage 17, and the first chamber 11 and the second chamber 12 are isolated. A diaphragm (diaphragm) 13 is provided.

  The diaphragm 13 is made of, for example, a nickel-based metal thin film, and is displaced according to the pressure difference between the first chamber 11 and the second chamber 12. As described above, since the pressure in the first chamber 11 is constant, the diaphragm 13 is displaced according to the pressure difference generated according to the water vapor pressure fluctuation in the tank 2.

  A fixed electrode 14 is arranged in the first chamber 11 so as to face the diaphragm 13. The fixed electrode 14 is connected to the measurement unit 16 via the signal line 15. An electrostatic capacity corresponding to the amount of displacement of the diaphragm 13 is generated between the fixed electrode 14 and the diaphragm 13, and the value of the electrostatic capacity is output from the fixed electrode 14. The measuring unit 16 measures the water vapor pressure in the second chamber 12, that is, the water vapor pressure in the tank 2 communicating with the second chamber 12 based on the capacitance value input from the fixed electrode 14.

  A heating element 18 is provided in the communication path 17 leading from the pressure measurement chamber 12 to the tank 2 so as to allow passage of water vapor. That is, the heating element 18 is configured so as not to cause a pressure difference between the second chamber 12 side and the tank 2 side of the heating element 18.

  A mesh electrode can be used as the heating element 18. The material of the metal wire 18a constituting the mesh electrode 18 can be selected from, for example, tungsten and nickel chrome. The diameter of the metal wire 18a is preferably set within a range of 0.5 mm to 1.5 mm, for example, and can be set to 1 mm. Considering the passage of water vapor, the interval between the metal wires 18a is preferably set within a range of 1 mm to 5 mm, for example, and can be set to 1 mm.

  The heating element 18 is not limited to the mesh electrode, and may be a coiled metal wire.

  When power is supplied to the heating element 18 from the power supply unit 19, the heating element 18 is heated to 40 ° C. to 50 ° C., for example. The heating element 18 is separated from the diaphragm 13 by a distance d so that the radiant heat from the heating element 18 does not reach the diaphragm 13, that is, the diaphragm 13 is not heated by the heating element 18. The distance d is set within a range of 3 to 7 times the pipe diameter when the pipe diameter is, for example, in the range of 3/8 inch (9.5 mm) to 1/2 inch (12.7 mm). It is preferable to do. This is because the amount of radiant heat transfer is inversely proportional (in inverse proportion) to the square of the distance. If the distance d is shorter than three times the pipe diameter, the radiant heat from the heating element 18 may reach the diaphragm 13. There is. On the other hand, if the distance d is longer than seven times the pipe diameter, the heat of vaporization in the tank 2 cannot be sufficiently compensated for, and water vapor condenses, and a part of the condensed water vapor is separated from the diaphragm 13. There is a possibility that the measurement accuracy of water vapor pressure may be reduced due to icing on the surface.

  Next, with reference to FIG.1 and FIG.2, the measurement of the water vapor pressure using the said pressure sensor 1 is demonstrated.

  In order to supply water vapor to the vacuum chamber 4, it is necessary to store the water 20 in advance in the tank 2 at atmospheric pressure. Then, after reducing the pressure in the tank 2 to about 10 kP, the water 20 is preferably supplied.

  When the water 20 is stored in the tank 2, the tank 2 is filled with water vapor. In this state, when the valve 5 is opened and the target flow rate is set to the mass flow controller 6 within a range of 0.1 sccm to 10 sccm, for example, the water vapor in the tank 2 passes through the water vapor supply passage 3 to the vacuum chamber. 4 is supplied.

  Here, in order to determine whether or not the flow rate of the water vapor supplied to the vacuum chamber 4 is properly controlled by the mass flow controller 6, the water vapor pressure in the tank 2 is measured using the pressure sensor 1. That is, it is monitored whether or not the water vapor pressure in the tank 2 is within a predetermined pressure range (for example, several kPa to 10 kPa) according to the set flow rate of the mass flow controller 6. When the water vapor pressure in the tank 2 fluctuates, the pressure in the second chamber 12 communicating with the tank 2 through the communication passage 17 fluctuates, and the pressure difference between the first chamber 11 and the second chamber 12 fluctuates. The diaphragm 13 is displaced. Based on the capacitance generated between the diaphragm 13 and the electrode 14 in accordance with the displacement of the diaphragm 13, the water vapor pressure in the tank 2 is measured by the measuring unit 16.

  By the way, the pressure in the vacuum chamber 4 is lower than the water vapor pressure in the tank 2 and is, for example, in the range of about 0.5 Pa to 1 Pa. For this reason, when the valve 5 and the mass flow controller 6 are operated as described above to cause the vacuum chamber 4 and the tank 2 to communicate with each other, the water vapor pressure in the tank 2 decreases, so that the heat of vaporization is deprived from the water vapor.

  By supplementing the deprived heat of vaporization with the heating element 18 provided in the communication passage 17 as described above, freezing of water vapor on the surface of the diaphragm 13 can be prevented.

  As described above, according to the present embodiment, when the tank 2 and the vacuum chamber 4 are communicated to supply the water vapor in the tank 2 to the vacuum chamber 4, the pressure in the tank 2 decreases, Although the heat of vaporization is deprived, the heat generated by the heating element 18 provided in the communication passage 17 leading from the tank 2 to the second chamber 12 is supplemented to prevent the vaporization of water vapor on the surface of the diaphragm 13. The water vapor pressure in the tank 2 can be measured with high accuracy. Moreover, since the diaphragm 13 is not heated by the radiant heat from the heat generating body 18, the thermal deformation of the diaphragm 13 can be prevented. Since the freezing of water vapor on the surface of the diaphragm 13 can be prevented only by providing the heating element 18, the configuration of the pressure sensor 1 can be simplified.

DESCRIPTION OF SYMBOLS 1 Pressure sensor 2 Tank 4 Vacuum chamber 11 1st chamber 12 2nd chamber 13 Diaphragm 17 Communication path 18 Heating body

Claims (2)

A first chamber maintained at a constant pressure;
A second chamber communicating with a tank for supplying water vapor to the vacuum chamber;
A diaphragm that separates the first chamber from the second chamber, and a displacement amount of the diaphragm according to a pressure difference between the first chamber and the second chamber that occurs in response to a change in water vapor pressure in the tank In the pressure sensor for measuring the water vapor pressure in the tank,
A pressure sensor characterized in that a heating element is provided in a communication path leading from the second chamber to the tank, and the heating element is separated from the diaphragm so that radiant heat from the heating element does not reach the diaphragm.   The pressure sensor according to claim 1, wherein the heating element is a mesh electrode.

Images