JPS6091826A - Industrial high frequency power source with automatic resetting circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention is applicable to industrial applications, particularly high frequency sputtering and dry sputtering.
The purpose is to obtain a high-frequency power source suitable for low-pressure gas discharge work such as etching.

When high-frequency discharge is performed in the above-mentioned low-pressure gas, arc discharge or the like may suddenly occur within the processing tool due to an abnormality on the target surface. At this time, if the high-frequency power is not stopped, the power source and the sample will be damaged, so usually some method is used to detect that the reflected power from the load has become excessive, and then the high-frequency power supply is stopped. .

However, in many cases, such a phenomenon occurs at the beginning of the application of high-frequency power, but the degree of vacuum inside the heater is restored in a short time, and at worst, after a few discharges, the work can be continued without abnormalities. There are many things you can do.

For this reason, if a high-frequency power source is stopped due to circular arc discharge or the like and then restarted after a short period of time, work efficiency decreases, workers must be constantly nervous, and automated equipment I can't drive.

However, since the abnormal phenomenon recovers in a short time even in such cases, the present invention does not completely stop the high-frequency power source, but temporarily lowers the high-frequency output power and automatically adjusts the high-frequency power level after a certain period of time. I set it back to its original state. Furthermore, even if the same phenomenon occurs several times, it often recovers, but the degree differs depending on the type of load. The decision was made to completely stop the system, making automated operation possible.

FIG. 1 shows a system diagram of an embodiment of the present invention.

1 is a high-frequency power source, 2 is a power supply section thereof, 3 is a load, and 4 is a reflected wave detection section, which detects reflected wave components from the load based on mismatching. A normal directional coupler or the like may be used as this detection section. The detected output voltage of this detection section enters the comparator 6, but it is compared with the voltage of the set voltage generator 5, and only when the detected output voltage becomes higher than this set voltage, the comparator 6
The output voltage appears at . This output voltage is applied to the power supply section 2, gate voltage generation circuit 7. Enter gate circuit 8. When the output voltage #l of the comparator 6 is input, the power supply section 2 works to reduce the high frequency output. In other words, the level at which the high frequency output is reduced due to load abnormality is set by the output voltage of the set voltage generator 5. Can be set arbitrarily.

The output reduction circuit of the power supply unit 2 has a time constant for the recovery time using the method described below, so that after a certain period of time it returns to the normal operating state and normal high-frequency power is applied to the load. Become. If abnormal discharge occurs again, the high frequency output is reduced again, and the normal state is restored after a certain period of time has elapsed.

At this time, when the output voltage of the comparator 6 enters the gate voltage generation circuit 7, a gate voltage is generated, and the gate of the gate circuit 8 is opened with this gate voltage. Therefore, the number of times the comparator 6 operates while the gate is open is counted by a counting circuit 9, and if the number of times the comparator 6 operates exceeds a set number of times, the power supply 2 is completely stopped.

There are various methods to reduce the high frequency output of the output electron tube, but among these, reducing the anode voltage increases the control power, so an example of temporarily reducing the second grid voltage is shown in Figure 2. Ta. In Figure 2, 10 is the output electron tube, 11
is an anode power source, and an anode voltage is applied to the anode of the output electron tube 10 through the cold flow coil 12. The high frequency output is applied to the load from a matching circuit (not shown) through a capacitor 13. The excitation signal from the previous stage is applied to the first grid of the output electron tube IO via the coupling capacitor 20. At this time, the output voltage of the second grid power supply 14 is applied to the second grid of the output electron tube IO via a circuit including a resistor 15 and a capacitor 16. A switch 17 is attached to both ends of this capacitor 16, but this may be a normal relay or an electron tube relay such as SOR. When this switch is closed by the output voltage #l of the comparator 6, the output electron tube lO As the second grid voltage is reduced, the high frequency output level is reduced.

When the high frequency output power decreases, the reflected wave level also decreases, so the output voltage of the reflected wave detection circuit decreases and the output voltage of the comparator 6 disappears.

The switch 17 is then opened and the capacitor 16 is connected to the second
charged by the grid power supply 14, in this case resistor 1
The rate of rise is determined by a time constant based on the product of the resistance value of 5 and the capacitance value of capacitor 16. Therefore, if this time constant is selected appropriately, the normal state will be returned at the desired rate of rise.

In the circuit of FIG. 2, a bias voltage -Ec is applied to the first grid of the output electron tube lO through the blocking coil 18.

However, instead of changing the second grid voltage, the high frequency output can be lowered by deepening this bias voltage. Figure 3 shows this state,
The bias power supply 19 deepens the bias voltage based on the output voltage #1 of the comparator 6. This can be easily realized using a normal electron tube circuit. Also in this case, a circuit similar to that shown in FIG. 2 can provide an appropriate time constant for recovery.

Note that approximately 0.1 to 1 second was appropriate as this regression time constant.

Furthermore, similar effects can be obtained by applying these high frequency output reductions to the excitation circuit in the previous stage using a similar circuit.

As detailed above, according to the present invention, when an abnormal phenomenon occurs, the supply of high frequency power is first reduced, and when this abnormal phenomenon occurs more than a set number of times within a set time, the high frequency power is completely stopped. This makes it possible to reliably prevent damage to the power source and the test tube without reducing work efficiency. Furthermore, effects such as automated operation can be obtained without causing tension to the workers.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an embodiment of the present invention, FIG. 2 is a high frequency output reduction circuit diagram using a second grid voltage, and FIG. 3 is a similar high frequency output reduction circuit diagram using a first grid voltage. ■ is a high frequency power source, 2 is a power supply section, 3 is a load, 4 is a reflected wave detector, 5 is a set voltage generator, 6 is a comparator, 7 is a gate voltage generator, 8 is a gate circuit, 9 is a counting circuit , io is the output electron tube, 11 is the anode power supply, 12.18 is the blocking wire, 1
3.16.20 is a capacitor, 14 is a second grid power supply, 1
5 is a time constant resistor, 17 is a switch, and 19 is a first grid power source. Figure 2 Figure 3 Figure 1

Claims (1)

[Claims] (1) In a power source that supplies high frequency power for industrial use,
A reflected wave power detector is installed between the power supply and the load circuit, and an output reduction circuit with an appropriate time constant is placed in the power supply section or excitation stage, and high frequency power is detected when the reflected power from the load increases beyond a set value. In the event of a momentary abnormality, normal high-frequency power is supplied again after a certain period of time has elapsed, and the complete supply of high-frequency power is achieved only when the same phenomenon occurs a set number of times or more within a set time. An industrial high frequency power source with an automatic return circuit that performs a stop.