JP2013040914A - Cold-cathode type ionization vacuum gauge with calibration function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for calibrating a measurement error caused by change of situation of a sensor, particularly a method for easy calibration of a cold-cathode type ionization vacuum gauge at a production field.SOLUTION: Displays of a measuring instrument 12 with correct display and a measuring instrument 1 with error are displayed in an E2 PROM data reference system, and calibration is performed in a state where both sensors are in the same atmosphere. Also, calibration of a cold-cathode type ionization vacuum gauge 1 is performed in a spot system.

Description

The present invention belongs to the field of cold cathode ionization gauges.

In the fields of semiconductor products, thin film manufacturing, metallurgy, and the like, a vacuum apparatus is used that places a vacuum or gas atmosphere inside a container that is shut off from the atmosphere. In such a case, it is necessary to know the pressure in the container, that is, the degree of vacuum, and a vacuum gauge exists as a measuring instrument.

There are various types of high vacuum range vacuum gauges that are generally used, and the cold cathode ionization vacuum gauge is one type. For this, a Penning type, a magnetron type, a reverse magnetron type, and a number of highly sophisticated ones each having a complicated auxiliary electrode are used. None of them are structurally robust because they do not have delicate heat filaments. However, since electric discharge is used, internal contamination occurs with time, and even if reassembly is performed with the contamination removed, there is a slight difference in measured values from the standard vacuum gauge.

The structure of the cold cathode ionization vacuum gauge, except for some large-scale production lines, is mechanically fixed to the main body with a display function, inside or outside the vacuum chamber, and kept at the same atmospheric pressure as the vacuum chamber. And three parts of a cable for electronically coupling the main body and the measuring element.

Problems to be solved by the present invention

The difference in measurement value, that is, the error that occurs in the cold cathode ionization gauge is caused by the probe.
However, there was no simple method for removing such errors in conventional equipment. From such an actual situation, a simple method for correcting an error caused by the probe with the vacuum gauge main body is an object to be solved by the present invention.

Means for solving the problem

In the following description, a vacuum gauge causing an error is called a machine to be calibrated, and a vacuum gauge showing the correct degree of vacuum is called a standard machine. Both probes are attached to the same vacuum chamber and placed under the same pressure.

The following technical description covers all of the cold cathode ionization vacuum gauges, but the explanation will be made with the reverse magnetron type cold cathode ionization vacuum gauge shown in FIG. The upper right part of the figure is a cross-sectional view of the probe and is connected to the vacuum chamber by an exhaust pipe 2. A magnetic field is applied by the ring-shaped magnet 3, and the ion collector 4 is grounded with a donut-shaped disk at both ends of the cylinder. The anode 5 is at a high potential of 2000 to 3000 V by the high voltage power source 6, and the negative current generated at the anode flows into the main body 8 including the amplifier circuit 7 and the central operator in the main body of the vacuum gauge.

The display 9 displays the degree of vacuum in response to a signal from the main body, and if necessary, sends data and signals relating to the degree of vacuum from the interface terminal 10.

Calibration of the machine to be calibrated is performed by overwriting a memory table under the control of the central processing element necessary for indicating the degree of vacuum. At that time, the machine to be calibrated is not in a normal measurement state, and it is necessary to place the memory in a state where it can be rewritten. Such a state is called a calibration mode, which is a mode different from normal measurement.
To enter the calibration mode, a mode change switch may be provided, but the following description is a method using an operation switch on the panel surface. Since calibration is performed while changing the degree of vacuum, it is necessary to select whether the vacuum apparatus is changed from the high vacuum side to the low vacuum side or vice versa.

Because of these factors, Mode 1 and Mode 2 were provided and programmed so that either selection was possible. The mode was changed using the panel button on the front of the main body shown in FIG. FIG. 2 shows an outline of the panel surface.
The uppermost window is a mantissa part and a multiplier part of the display vacuum degree. For the operation at the start of measurement, after the power is turned on by the POWER switch, the measurement is started by the START button, and the measurement is ended by the STOP button. The P / T button is used when it is desired to know the TORR value.

In SET1 to SET4, a desired numerical value is selected by a triangle button of SET POINT, and when a desired vacuum degree is reached, a signal is transmitted to the rear panel.

Modes 1 and 2 can be selected by turning on the POWER switch while pressing the STOP button or turning on the POWER switch while pressing the P / T button.

All three examples of calibration described below describe only the method of shifting from high vacuum to low vacuum. At this time, overwriting of E2PROM is programmed to start from the lower address and is called mode 1.
Mode 2 may be selected when it is easy to shift from a low vacuum to a high vacuum depending on the structure of the vacuum apparatus.

Means for solving the problem, part 1

The probe of the machine to be calibrated and the standard machine are placed under the same pressure, and both are connected and calibrated by an interface function, for example, RS-232C.

That is, the interface terminal 13 of the standard vacuum gauge consisting of the probe 11 on the left side of FIG. 1 and the main body 12 and the interface terminal 10 of the machine to be calibrated are connected as shown by a dotted line in the figure. Calibration is sent from the standard machine by the shake hand method. The transmission data is transmitted by the ASCII data method, but the content is only vacuum degree data and does not include other elements.

Others are only three elements: a signal line indicating whether or not transmission is possible and a transmission request line sent from the device to be calibrated.

A transmission request sent from the device to be calibrated to the standard device starts when the device to be calibrated is put into the calibration mode, a signal corresponding to OK appears in the display window of SET1, and the STAT button is pressed.

In the above state, the current vacuum degree data is always transmitted from the RS-232C by the ASCII data method from the standard machine. On the other hand, the machine to be calibrated always receives the true vacuum degree data, records it in the memory according to a predetermined procedure, and develops the calibrated true vacuum degree data on the memory table. In the measurement of the calibrator, the new table is referred to as the measurement result.

When the calibration range is in the range of 1.0E-5 PASCAL to 1.0E0 PASCAL, current does not begin to flow through the probe of the machine to be calibrated when the standard machine display is the -5th power PASCAL stage. That is, the discharge may not start. In such a case, the machine to be calibrated prepares a program such as sending data corresponding to the letter L to the E2PROM and developing data equal to that of the standard machine on the memory table after the current begins to flow to the measuring element.

The method of automatic calibration using the data continuously sent from the standard machine using the interface is used even when, for example, a plurality of fixed points are set within the measurement range, and the calculation method using mathematical formulas between the points is used. it can.

Means for solving the problem, part 2

In the method of using the interface function of the standard machine for the calibration of the machine to be calibrated, the following manual calibration is programmed when entering the calibration mode. Specifically, the machine to be calibrated is calibrated while observing the vacuum level display of the standard machine. Five fixed points are set for each first power of the degree of vacuum index, and a calculation method using a mathematical formula is adopted between the points. The calibration range is from 1.0E-5 PASCAL to 1.0E0 PASCAL.

Install the sensor to be calibrated and the standard sensor in the same vacuum chamber.

The method is the same as that of the means 1 such as entering the calibration mode. When entering the calibration mode, adjust the vacuum chamber so that the standard display shows a high vacuum of 1.0E-5PASCAL or higher.

Set the machine under calibration to calibration mode. At this time, 1 appears on SET1 and 1.0-5 appears on SET2 on the front panel surface.

Adjust the vacuum chamber valve and press the START button on the panel when the standard machine indicates 1.0E-5PASCAL.

Next, numbers 2 and 2.0-5 appear on SE1 and SET2 on the panel surface.

Adjust the vacuum chamber valve and press the START button on the panel when the standard machine indicates 2.0E-5PASCAL.

The above method is sequentially performed until 1.0E0 PASCAL, and the calibration is completed. As a result, the degree of vacuum corresponding to the value flowing in from the measurement is developed on the E2PROM table of the machine to be calibrated.

When the START button is pressed in the high vacuum range, the numbers appearing on SET1 and SET2 may blink. In this case, the discharge current does not flow through the probe.
Pressing the button again advances to the next number, so the pressure in the vacuum chamber is further increased and the START button is pressed.
By repeating this, the pressure is increased until the SET1 and SET2 numbers no longer flash with the START button. If the operation is advanced, the calibration operation up to 1.0E0 PASCAL is completed.

Means for solving the problem, part 3

The method for entering the calibration mode is the same as the means for solving the problem, a method close to the second method.

The difference from the means 2 is that the START button is not pressed when the vacuum level of the standard machine matches the vacuum level displayed on the SET 2 of the machine to be calibrated. For example, when the standard machine is 1.0E-5 PASCAL, 1 is displayed in SET1 of the machine to be calibrated, 1.0-5 is displayed in SET2, and the same current is held in the probe of the machine to be calibrated for several seconds. Automatically recognizes 1.0-5 and changes to 2.0-5 in the next SET2.

Further, if the valve is adjusted and the inside of the tank is kept at 2.0E-5 PASCAL for several seconds according to the instruction of the standard meter, the data corresponding to 2.0E-5 PASCAL is automatically written. If this is carried out sequentially, it is developed on the ROM table without pressing the START button each time as in means 2.

By the means 2 and 3 for solving the above, it is possible to set five fixed points per power and display the correct degree of vacuum between the points by a mathematical calculation method.

In any of the above-mentioned cases 1, 2, and 3, after the calibration work is completed, if the power is turned off and the power is turned on again after exiting the calibration mode, the normal vacuum degree measurement can be resumed.

Application of calibration method for cold cathode ionization gauge

1. Thermal conductivity gauge

There are various types of heat conduction vacuum gauges such as thermocouple vacuum gauges and constant temperature type Pirani vacuum gauges. In either case, the gauge is heated inside by passing a filament inside the probe, and the phenomenon that occurs in the temperature change is read to make a vacuum gauge.

A major drawback of the heat conduction vacuum gauge is a change in wire diameter caused by aging and a change in sensitivity due to a change in the surface state of the filament. Since this change causes an error in the degree of vacuum indication, calibration is required. Further, depending on the situation of the vacuum apparatus, it may be necessary to extend the connecting line connecting the vacuum gauge main body and the measuring element more than usual. In such a case, since the extension of the connecting line lowers the temperature of the filament, it is predicted that an error will occur in the degree of vacuum from the beginning, so that calibration is necessary. If these vacuum gauges that require calibration are called vacuum gauge gauges for calibration, it is easy to mount the gauge gauges for calibration and standard gauge gauges that display accurate standard values in the same vacuum atmosphere. .

Therefore, if the machine to be calibrated is set in the calibration mode in advance and the standard vacuum gauge and the vacuum gauge for calibration are connected through the interface and the degree of vacuum is changed sequentially, the vacuum for calibration is determined by the ASCII vacuum degree data sent from the standard vacuum gauge. The E2ROM necessary for displaying the vacuum level of the meter is overwritten, and the same vacuum level is displayed for the vacuum gauge for calibration and the standard vacuum gauge, and the calibration is completed.

2. Thermocouple thermometer

In general thermocouple type thermometers, an error is caused by evaporation of the thermocouple due to secular change or chemical change of the temperature sensitive portion at the tip of the thermocouple. Further, depending on the temperature measurement location, the thermocouple and the temperature compensating lead may be further extended. In such a case, an error may occur depending on the display temperature due to induction or the like, and calibration is required.

If the area and volume occupied by the thermocouple tip is very small compared to the heating element temperature measurement unit, display the thermocouple tip of the thermometer that is accurate and standard, and the thermocouple tip of the thermometer for calibration first. Even if installed, both thermocouple tips are at the same temperature.

In the above-mentioned state, if the thermometer for calibration and the standard thermometer that were previously set in the calibration mode are connected to each other through the interface and the heat generation temperature is gradually increased, the calibration is performed using the ASCII temperature data sent from the standard thermometer. The E2PROM necessary for the temperature display of the thermometer is overwritten, the thermometer for calibration becomes the same temperature display as the standard thermometer, and the calibration is completed.

In the above, two examples of applying the calibration method of the cold cathode ionization vacuum gauge to other measuring devices are given, but there are various other examples.

Effect of the invention

There is a measuring instrument with an accurate display, and the display of the measuring instrument with an error is displayed by the E2PROM data reference method, and it is possible to calibrate relatively easily in the measuring instrument that can put the sensor in the same atmosphere. I was able to show that.

It is a schematic diagram of a cold cathode ionization vacuum gauge and a standard vacuum gauge that require calibration. It is a front panel figure of the cold cathode type ionization vacuum gauge which requires calibration.

1 A cross section of a reverse magnetron cold cathode ionization gauge gauge probe.
2 Connection tube of reverse magnetron cold cathode ionization vacuum gauge probe.
3 Donut-shaped magnet 4 Cathode 5 Anode 6 High-voltage power supply 7 Amplifier 8 Electronic circuit including central processing element 9 Display 10 Test machine interface terminal 11 Standard vacuum gauge probe 12 Standard vacuum gauge body 13 Standard vacuum gauge interface terminal

Claims (3)

In the calibration method of overwriting the correct instrument data transmitted in ASCII format through the interface on the E2PROM developed on the table necessary for the display of the machine to be calibrated, and referring to this data as a new display, E2PROM Calibration method and measuring instrument that can select either overwriting from the smaller address or overwriting from the larger EP2ROM. In the calibration method in which the correct vacuum degree data transmitted in ASCII format through the interface is overwritten on the EP2ROM developed on the table necessary for the vacuum degree display of the machine to be calibrated, and this is used as a new display by referring to the data. A calibration method capable of selecting either a calibration method from a high vacuum to a low vacuum or a calibration method from a low vacuum to a high vacuum, and a cold cathode ionization vacuum gauge. In E2PROM under the control of the central processing element, each multiplier of the measurement range is divided into multiple points, and when each point matches the visual display of the standard vacuum gauge, new data is written to each point. In the calibration method in which the interval is calculated by the calculation format and the result is displayed as the new vacuum level, either the method of calibrating from high vacuum to low vacuum or the method of calibrating from low vacuum to high vacuum can be selected Calibration method and cold cathode ionization gauge.

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