JPS61139111A - Automatic load matching circuit of high frequency sputtering device - Google Patents

Abstract

PURPOSE:To facilitate the matching operation and to improve the work efficiency by placing a coupler, which detects the reflected wave voltage from a load, between a high frequency power source and a matching circuit and controlling individual variable reactance elements in accordance with a preliminarily set program and obtaining the point where the reflected power is minimum to perform the matching operation. CONSTITUTION:A matching circuit 3 and a reflected wave component detector 6 are placed between a high frequency power source 1 and a load 2. Only one of driving motors 8 and 9 is rotated to change one of parallel and series variable reactance elements in accordance with the program stored in a ROM10, and the value of the variable reactance element at the time when the output voltage of reflected wave components is minimum is stored in a RAM11. The other driving motor is rotated to change the other variable reactance element, and its value at the time when the reflected wave output voltage is minimum is stored in the RAM11. Both variable reactance elements are changed simultaneously in accordance with the program so that the reflected wave output voltage is always minimum, thus attaining an optimum matching state.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Object of the Invention [Field of Industrial Application] The present invention relates to an automatic load matching circuit in a high frequency sputtering device, an etching device, or the like.

[Conventional technology]

Conventionally, both the reflected wave component from the load and the traveling wave component from the high-frequency power supply are detected, the amplitude and phase of one reflected wave are determined, and the load matching reactance element is automatically adjusted so that the phase becomes almost zero at the minimum amplitude. I was being followed.

Figure 2 shows a conventional automatic load matching circuit
799 - Utility Model Application Publication No. 52-50032), the power of the high frequency power source l is transmitted through a matching circuit 3 consisting of a parallel variable reactance element 4 and a series variable reactance element 5.
is applied to load 2 through.

A reflected wave component detector 6 and a traveling wave component detector 12 are placed between the power source and the matching circuit, and their respective detection outputs are guided to a synthesis electronic circuit 13, which generates a 2 detector with information on the amplitude and phase of the reflected wave component. Calculate the signals and amplify this voltage to drive the electric motor j
Parallel variable reactance element 4 and series element 5 are changed by a8 and a9, respectively, and automatic matching is performed.

[Problem that the invention seeks to solve]

In high frequency sputtering and etching equipment,
Since the electrical constants of the load vary greatly during use, the range of variation of each variable reactance element of the automatic matching circuit is wide. Instead, if you look at the impedance Smith diagram of the reflected wave component at the reflection detection point, it will look like the one shown in Figure 3. The locus of the impedance point due to the change in variable reactance will be as shown by the solid line in the diagram, and the phase will be zero. There are two points, A and B, and in the conventional method, there are two stable points.

For this purpose, conventionally, at the beginning of operation, the automatic matching circuit was stopped, and both the parallel and series variable reactance elements were manually adjusted until they were close to the normal matching point B, and then automatic operation was started. I had to switch and track it. Therefore, there was a problem because it required time and effort.

1. Structure of the Invention [Means for Solving Problems] The present invention provides a high-frequency sputtering apparatus in which variable reactance elements for matching are placed in parallel and in series between a high-frequency power source and a load circuit. In between, a coupler is installed to detect the power of the reflected wave from the load, a control signal corresponding to the change in each reactance is detected, and each variable reactance element is controlled according to a preset program to find the point at which the reflected power is minimum. This is an automatic load matching circuit for a high frequency sputtering device, etc., which is characterized in that it calculates the value, stores the value in a storage circuit, and thereafter performs matching operations based on the stored value.

Furthermore, in the above circuit, a high-frequency sputtering device or the like is characterized in that a reactance value necessary to minimize reflected power is set and stored in a separate memory circuit at startup, and matching operations are thereafter performed based on the stored value. This is an automatic load matching circuit.

[For production]

In the present invention, an operation program is built in, and when starting up, one variable reactance element is first varied over a wide range and placed near the point where the reflected wave component is minimum, and then the other variable reactance element is varied. Therefore, we decided to similarly place it near the point where the reflected wave component is minimum, and then change both reactance elements simultaneously to find a normal matching state.

Further, in the invention of claim (2), the optimum reactance value at startup is set and stored in advance, and the automatic alignment tracking operation is performed at the start of the operation to shorten the alignment convergence time.

〔Example〕

FIG. 1 is a system diagram showing an embodiment of the present invention, in which a high frequency power source 1
A matching circuit 3 including a parallel variable reactance element 4 and a series variable reactance element 5 and a reflected wave component detector 6 are placed between the load 2 and the load 2, and the detected output voltage of the detector is detected by an electronic circuit 7.
digitized by an A/D converter, and ROMI
According to the program stored in O, first, only one of the drive electric motors Ia8 or 9 is rotated to change either the parallel or parallel variable reactance element,
The value at which the output voltage of the reflected wave component is the minimum is stored in RAM II, and then the other drive motor is rotated to change the other variable reactance element, and the reflected wave output voltage is also minimized. Store the value in IjAMll, firstly change both variable reactance elements at the same time, and according to the program, the reflected wave output voltage will always be the minimum,
Achieve optimal alignment. Thereafter, as the load changes, tracking of the optimal matching state will be automatically performed.

In the case of high frequency sputtering, etc., as described above. Since the load changes over a wide range, some time is required to initially set both variable reactance elements to their optimum initial values. However, in the invention of claim (2), both reactance elements are Either store the values of both reactances (corresponding to the circuit angle of the drive motor) at the time when the optimum initial state is reached in another RAM2 (14), or store the value that should be set in the vicinity from the outside into that RAM2. By setting this, you can shorten the matching convergence time when restarting.

A series circuit of a coil and a variable capacitor was used as the series variable reactance element, and a directional coupler was used as the reflected wave component detector.

C. Effects of the Invention As explained above, in the conventional method, first manually adjust both variable reactance elements alternately to achieve a nearly matching state, and then activate the automatic matching circuit to perform tracking. Even an experienced person would have to spend about a minute to adjust the alignment, but with the present invention, the alignment could be achieved in about 10 seconds. Furthermore, in the invention of claim (2), the convergence time was reduced to 2 to 3 seconds based on the amount of storage of the matching state.

[Brief explanation of drawings]

FIG. 1 is a system diagram of an embodiment of the present invention, FIG. 2 is a system diagram of a conventional automatic matching circuit, and FIG. 3 is an example of an impedance Smith diagram at a reflected wave component detection point.

Claims (2)

[Claims] (1) In a high-frequency sputtering device in which parallel and series matching variable reactance elements are placed between a high-frequency power source and a load circuit, a coupler is placed between the high-frequency power source and the matching circuit to detect the power of reflected waves from the load. , detects the control signal corresponding to the change in each reactance, controls each variable reactance element according to a preset program, finds the point of minimum reflected power, stores that value in the memory circuit, and uses that stored value from now on. An automatic load matching circuit for high-frequency sputtering equipment, etc., characterized by performing a matching operation based on the above. (2) In a high-frequency sputtering device in which parallel and series matching variable reactance elements are placed between the high-frequency power source and the load circuit, a coupler is placed between the high-frequency power source and the matching circuit to detect the power of reflected waves from the load. , detects the control signal corresponding to the change in each reactance, controls each variable reactance element according to a preset program, finds the point of minimum reflected power, stores that value in the memory circuit, and uses that stored value from now on. When performing a matching operation based on this, a reactance value necessary to minimize the reflected power is set and stored in a separate memory circuit at the time of startup, and thereafter a matching operation is performed based on the stored value. Automatic load matching circuit for sputtering equipment, etc.