JPH0261220B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The object of the present invention is to obtain a high frequency power source suitable for industrial use, in particular for low pressure gas discharge operations such as high frequency sputtering and dry 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 is stopped. There is.

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

For this reason, if the high-frequency power source is stopped due to a single arc discharge, etc., and then restarted after a short period of time, work efficiency will decrease, and 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. Also, even if a similar phenomenon occurs several times, it often recovers;
Since the degree differs depending on the type of load, in the present invention, the high frequency power source is completely stopped only when abnormal phenomena occur more than a set number of times within a set time, 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 its power supply part, 3 is a load,
Reference numeral 4 denotes a reflected wave detection unit that detects a reflected wave component from a 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 is input to a comparator 6, where it is compared with the voltage of the set voltage generator 5, and the output voltage appears at the comparator 6 only when the detected output voltage becomes higher than this set voltage. This output voltage enters the power supply section 2, gate voltage generation circuit 7, and gate circuit 8. Power supply section 2
works to reduce the high frequency output when the output voltage #1 of the comparator 6 is input. In other words, the level at which the high frequency output is reduced due to load abnormality can be set arbitrarily by the output voltage of the set voltage generator 5. Can be set to

The output reduction circuit of the power supply section 2 has a time constant for the recovery time using the method described below, so that after a certain period of time, the normal operating state is returned and normal high-frequency power is applied to the load. It turns out. If abnormal discharge occurs again, the high frequency output is reduced again, and the normal state returns 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 during the time 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, 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 FIG. 2, 10 is an output electron tube, 11 is an anode power supply, and an anode voltage is applied to the anode of the output electron tube 10 through a blocking wire 12. High frequency output is capacitor 1
3 to the load from a matching circuit (not shown). The excitation signal from the previous stage is connected to coupling capacitor 2.
0 and is added to the first grid of the output electron tube 10. At this time, the output voltage of the second grid power supply 14 is applied to the second grid of the output electron tube 10 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 an SCR. When this switch is closed at output voltage #1 of comparator 6, the second grid voltage of output electron tube 10 is reduced, so that the high frequency output level is reduced.

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

Then switch 17 is opened and capacitor 1
6 is charged by the second grid power supply 14, and in this case, the rising speed is determined by a time constant based on the product of the resistance value of the resistor 15 and the capacitance value of the 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 shown in FIG. 2, a bias voltage -Ec ₁ is applied to the first grid of the output electron tube 10 through the blocking wire 18, but instead of changing the second grid voltage, this bias voltage is deeply changed. By doing so, it is also possible to reduce the high frequency output. FIG. 3 shows this state, in which the bias power supply 19 is connected to the comparator 6.
The bias voltage is deepened by the output voltage #1. 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 sample without reducing work efficiency. Furthermore, effects such as automated operation can be obtained without causing tension to the workers.

[Brief explanation of drawings]

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. 1 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
1 is a counting circuit, 10 is an output electron tube, 11 is an anode power supply, 12, 18 are blockage wires, 13, 16, 20 are capacitors, 14 is a second grid power supply, 15 is a time constant resistor, 17 is a switch, 19 is the first grid power supply.

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 source and the load circuit, and an output reduction circuit with an appropriate time constant is placed in the power supply section or excitation stage to reduce the power from the load. When the reflected power increases beyond the set value, the supply of high frequency power is reduced, and in the event of a momentary abnormality, normal high frequency power is supplied again after a certain period of time has passed, and the same phenomenon occurs more than the set number of times within the set time. An industrial high-frequency power source having an automatic return circuit that completely stops the supply of high-frequency power by generating .