JPH06334456A - High frequency power supply - Google Patents

Abstract

PURPOSE:To obtain a high frequency power supply from which no excess high frequency power is outputted even when no discharge is caused in a load. CONSTITUTION:An incident high frequency power Pf and a reflected high frequency power Pr from a coupler 5 are fed to a divider 9, and its output is fed to an adder 10, in which the output is added to a level signal V2 from a level signal source 11. When discharge in the load is stopped, the relation of Pf=Pr is set and an output of the divider 9 reaches 1V. When a set value of the level signal source is set to be -5V, an output of an adder 10 is positive voltage and a transistor(TR) T is turned on. A signal of the reflected high frequency power Pr in this state is short-circuited and an output of a subtractor 8 becomes a signal of only the incident high frequency power Pf. Thus, the control to make the incident high frequency power Pf constant is executed. When discharge is caused in the load and an output voltage of the divider 9 reaches 5V or over, an output of the adder 10 becomes negative. As a result, the TR T is turned off and the control making the effective power constant is started.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency power source used in a high frequency sputtering apparatus, an etching apparatus or the like, which is designed to prevent generation of abnormal high frequency power.

[0002]

2. Description of the Related Art FIG. 1 shows a conventional high frequency power supply.
In the figure, 1 is a high-frequency oscillator such as a crystal oscillator,
The high frequency from the high frequency oscillator 1 is supplied to and amplified by the variable amplifier 2 whose amplification degree is automatically changed. The output of the variable amplifier 2 is supplied to the power amplifier 3 and further amplified, and the output of the power amplifier 3 is supplied to the terminal 4 and becomes a high frequency output.

The output of the power amplifier 3 is supplied to the coupler 5, and the signal Pf corresponding to the incident high frequency output from the coupler 5 is supplied to the differential amplifier 6. The reference signal from the reference signal source 7 is also supplied to the differential amplifier 6. The differential amplifier 6 compares the signal corresponding to the high frequency output with the reference signal from the reference signal source 7, and supplies the difference signal to the variable amplifier 2. The amplification degree of the variable amplifier 2 is changed according to the signal from the differential amplifier 5. The operation of such a configuration will be described below.

The high frequency wave from the high frequency oscillator 1 is first amplified by the variable amplifier 2 and further supplied to the terminal 4 via the power amplifier 3 as a high frequency output. The output of the power amplifier 3 is taken out by the coupler 5 and supplied to the differential amplifier 6. The differential amplifier 6 compares the high frequency output with the reference voltage signal from the reference signal source 7. The output signal of the differential amplifier 6 is supplied to the variable amplifier 2, and the amplification degree of the variable amplifier 2 is changed so that the output of the differential amplifier becomes zero. As a result, by setting the reference voltage signal from the reference signal source 7 to correspond to the desired high frequency output, the desired high frequency power can be stably obtained from the terminal 4.

The above-mentioned feedback circuit has been widely used in the past, but recently, there has been a demand for keeping the effective power constant by subtracting the reflected high frequency power from the incident high frequency power. FIG. 2 shows a power supply circuit which meets such requirements, and in this figure, the same parts as those in FIG. 1 are designated by the same reference numerals.

In FIG. 2, an incident high frequency power Pf supplied to the load and a reflected high frequency power Pr from the load are extracted from the coupler 5. These two types of signals Pf and Pr
Is supplied to the subtractor 8 and the difference (Pf-Pr) between its signals
Is required. This difference depends on the active power,
The signal is supplied to the differential amplifier 6 and compared with the signal from the reference signal source 7. In this way, the control for keeping the active power constant is performed.

[0007]

With the above configuration, the feedback loop is configured so that stable high frequency power can be obtained. By the way, in the control in which the active power is constant in FIG. 2, when the high frequency output is in the total reflection state, that is, when Pf = Pr, the output of the subtractor 8 becomes zero. When the high frequency power is in the total reflection state, it means that the load is not applied, that is, the discharge in the load is not occurring. In this case, since the feedback signal is 0, the feedback does not operate normally. Therefore, in the case of Pf = Pr, the high frequency output may become the maximum output in the circuit of FIG. 2, excessive high frequency power is supplied to the terminal 4, and each component of the circuit thereafter is damaged, This will adversely affect the load of high frequency power.

The present invention has been made in view of the above circumstances, and an object thereof is to realize a high-frequency power supply that does not output excessive high-frequency power even when discharge is not occurring in a load.

[0009]

A high frequency power supply according to the present invention comprises an oscillator, a variable amplifier for amplifying a high frequency from the oscillator, a power amplifier for amplifying a high frequency power from the variable amplifier, and an incident high frequency power to a load. And a circuit for obtaining the difference in the reflected high frequency power from the load, and a differential amplifier to which the difference signal is supplied. The differential amplifier compares the difference signal with a reference signal and responds to the comparison signal. In a high frequency power supply including a feedback loop configured to change the amplification degree of a variable amplifier, a circuit for determining a ratio of high frequency power incident to a load and high frequency power reflected from the load is provided, and a differential amplifier is provided according to the ratio. In addition, the difference signal and the signal according to the incident high frequency power to the load are switched and supplied.

[0010]

The high frequency power supply according to the present invention is provided with a circuit for determining the ratio of the incident high frequency power to the load and the reflected high frequency power from the load, and a differential amplifier forming a feedback loop according to the ratio is provided to the load. A difference signal between the incident high frequency power and the reflected high frequency power from the load and a signal corresponding to the incident high frequency power to the load are switched and supplied.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 3 shows an embodiment of the present invention, in which the same numbers as those in the conventional apparatus of FIG. 2 indicate the same components. In this embodiment, the signal corresponding to the incident high frequency power Pf and the signal corresponding to the reflected high frequency power Pr from the coupler 5 are divided by the divider 9
Is supplied to. The output signal of the divider 9 is supplied to the adder 10 and added to the signal from the level signal source 11. The output signal of the adder 10 is used to turn on / off the transistor T. Transistor T shorts the reflected high frequency power signal when in the on state. The operation of such a configuration will be described below.

In this embodiment, as in FIG. 2, the feedback loop is configured to keep the effective high frequency power constant, and in the normal operating state, the incident high frequency power Pf supplied from the coupler 5 to the load is set. , And the reflected high-frequency power Pr from the load is extracted. These two types of signals Pf, P
r is supplied to the subtracter 8 and the difference (Pf-P
r) is required. This difference depends on the active power and is supplied to the differential amplifier 6 and compared with the signal from the reference signal source 7. In this way, the control for keeping the active power constant is performed.

The incident high frequency power Pf from the coupler 5
And the reflected high frequency power Pr are supplied to the divider 9, and Pf / Pr is obtained in this divider. The output of the divider 9 is supplied to the adder 10 and added with the level signal V2 from the level signal source 11. As a result, the adder 10 outputs (Pf / Pr) + V2. Here, when the discharge in the load is stopped, Pf = Pr and the output of the divider 9 becomes 1V. Set the level signal source to -5V
Then, the output of the adder 10 becomes a positive voltage and the transistor T is turned on. When the transistor T is on, the signal of the reflected high frequency power Pr is short-circuited, and the output of the subtractor 8 becomes the signal of only the incident high frequency power Pf. Therefore, in this case, the same control as the conventional technique shown in FIG. 1 in which the incident high frequency power Pf is constant is performed.

Next, when the incident high frequency power Pf is controlled to be constant, discharge is generated in the load, the reflected high frequency power Pr is rapidly reduced, and the output voltage of the divider 9 becomes 5 V or more. The output will be negative. As a result, the transistor T is turned off, the output of the subtractor 8 becomes Pf-Pr, and the control for keeping the active power constant is started.

As described above, when the load is not discharged, the feedback loop is operated only by the incident high frequency power Pf, so that Pf =
Even in the case of Pr, the high frequency output is prevented from reaching the maximum output, excessive high frequency power is supplied to the terminal 4, and each component of the subsequent circuit is not damaged or the load of the high frequency power is not adversely affected. .

[0016]

As described above, the high frequency power source according to the present invention is provided with a circuit for obtaining the ratio of the incident high frequency power to the load and the reflected high frequency power from the load, and forms a feedback loop according to the ratio. In the differential amplifier, the difference signal between the incident high frequency power to the load and the reflected high frequency power from the load,
Since it is configured to switch and supply a signal according to the incident high frequency power to the load, control is performed to keep the active power constant in the normal operating state, and when no discharge occurs in the load, the feedback loop Is prevented from operating only by the incident high frequency power Pf, and the high frequency output is prevented from reaching the maximum output, excessive high frequency power is supplied to the terminals, each component of the circuit thereafter is damaged, and the load of the high frequency power is adversely affected. It has no effect.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a conventional high-frequency power source that keeps incident high-frequency power constant.

FIG. 2 is a diagram showing an outline of a conventional high-frequency power source that keeps active power constant.

FIG. 3 is a diagram showing a high frequency power supply according to the present invention.

[Explanation of symbols]

 1 High Frequency Oscillator 2 Variable Amplifier 3 Power Amplifier 4 Terminal 5 Coupler 6 Differential Amplifier 7 Reference Signal Source 8 Subtractor 9 Divider 10 Adder 11 Level Signal Source T Transistor

Claims (1)

[Claims] 1. An oscillator, a variable amplifier for amplifying a high frequency from the oscillator, a power amplifier for amplifying a high frequency power from the variable amplifier, and a circuit for obtaining a difference between an incident high frequency power to a load and a reflected high frequency power from the load. And a differential amplifier to which the difference signal is supplied. In the differential amplifier, the difference signal and the reference signal are compared, and the amplification degree of the variable amplifier is changed according to the comparison signal. In a high frequency power supply having a feedback loop, a circuit for determining the ratio of the incident high frequency power to the load and the reflected high frequency power from the load is provided, and the difference signal and the incident high frequency power to the load are provided to the differential amplifier according to the ratio. A high-frequency power supply characterized in that it is configured to switch and supply a corresponding signal.