JPH03113906A - Automatic matching device - Google Patents

Abstract

PURPOSE:To take the matching surely and automatically even when the capacitance of a matching element is any capacitance in the variable range by detecting a difference between a phase of a current flowing to a matching element in series with a load and a phase of a voltage at the entrance of the load so as to adjust the matching element of the matching circuit accordingly. CONSTITUTION:A current sensing element 4c is provided to a point N in a matching circuit 3 and a phase difference detector 5c detecting a difference between a phase of a current flowing to the point N and a phase of a voltage at the entrance of the matching circuit 3 is provided. The phase difference detector 5c detects a phase theta2 of the impedance at the point N in the matching circuit 3 based on a detection signal of the current sensor 4c and a detection signal of the voltage detection element 4b and gives the result to a control circuit 6. The control circuit 6 increases the capacitance of a variable capacitor 3b via a drive circuit 7b when, the phase theta2 is smaller than a reference value theta2. Thus, even when the capacitance of the matching elements 3a, 3b is not set near the matching point in advance, the matching is automatically taken.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic matching device, and particularly to an automatic matching device for reliably supplying power from a high-frequency power source to a high-frequency excitation type plasma CVD apparatus.

[Prior Art] A plasma CVD apparatus supplies high-frequency power to electrode pairs consisting of a high-frequency electrode and a substrate holder, each arranged in a chamber, and also introduces generated gas into the chamber to fill the gap between the electrode pairs. This is an apparatus that generates plasma discharge to form a thin film on a substrate placed on a substrate holder.

In order to reliably supply power output from a high frequency power source to this plasma CVD apparatus, an automatic matching device shown in FIG. 5 has been conventionally used.

In FIG. 5, the output power from the high frequency power source 2 is input to the plasma generator 1 via a matching circuit g3. on the other hand,
The current and voltage at the entrance of the matching circuit 3 are detected by a current detection element 4a and a voltage detection element 4b, and are input to a phase difference detector 5a and an impedance detector 5b. Then, the outputs of the phase difference detector 5a and the impedance detector 5b are inputted to the control circuit 6, which controls the drive circuit 7.
variable capacitors 3a, 3 of the matching circuit 3 via a, 7b
b is controlled.

The operation of this automatic matching device will be explained with reference to the flowchart in FIG. 6 and the diagram showing the discrimination area in FIG. The phase θ1 of the impedance is input to the phase difference detector 5a and the impedance detector 5b, when looking at the load side from the entrance of the matching circuit 3.
and the absolute value Z1 of impedance is detected. The detected phase θ and absolute value Z1 are input to the control circuit 6,
Automatic alignment is started. The control circuit 6 does not change the capacitance of the variable capacitor 3b when the absolute value 1θ11 of the phase 0□ is smaller than the reference value Δθ1.

The absolute value 1θ, 1 of the phase θ1 is greater than the reference value Δ01,
When the phase θ1 is negative, the control circuit 6 reduces the capacitance of the variable capacitor 3b via the drive circuit 7b. Further, when the absolute value 10E1 is larger than the reference value Δ0E and the phase 0□ is positive, the control circuit 6 increases the capacitance of the variable capacitor 3b via the drive circuit 7b.

On the other hand, when the absolute value IZI 501 of the difference between the absolute value 2□ of the impedance detected by the impedance detector 5b and the set impedance 50Ω is smaller than the reference value ΔZ, the control circuit 6 does not change the capacitance of the variable capacitor 3a. IZ Any01 is greater than the reference value Δ2□, and Z
When □-50 is negative, the TjIJ control circuit 6 reduces the capacitance of the variable capacitor 3a via the drive circuit 7a. Also,
IZl-501 is greater than the reference value ΔZ□, Z□-50
When is positive, the control circuit 6 increases the capacitance of the variable capacitor 3a via the drive circuit 7a. As a result, when the output impedance of the high frequency power supply 2 is 50Ω, θ,=0,
It is controlled so that Z=50Ω.

Here, the reason why the reference values Δθ0 and Δz1 are set to non-zero values is to provide a dead zone to prevent hunting during control.

[Problem i to be solved by the invention] In the conventional automatic matching device, due to the configuration of the matching circuit 3,
For example, the capacitance of the variable capacitor 3a is fixed to a value of
When the capacitance of the variable capacitor 3b is changed, the plasma C
In the case of a low impedance load (about several Ω) such as a VD device, the impedance phase θ□ is 0° as shown in Figure 8.
There are two points, A and B, where At this time, point A is a resonance point that is unrelated to the matching state, and point B is a resonance point that is related to the matching state. Therefore, if the capacitance of the variable capacitor 3b is near point A (resonance point), it is impossible to achieve matching based on the flowchart in FIG. Unless it was set near the matching point (near point B in FIG. 8), matching could not be achieved automatically.

The present invention was devised to eliminate the above-mentioned drawbacks of the prior art, and is capable of reliably and automatically matching the capacitance of the matching element at any value within the variable range. The purpose is to provide an automatic alignment device that can perform

[Means for Solving the Problems] In order to achieve the above object, an automatic matching device according to the present invention includes, in addition to a conventional automatic matching device, a current detection element that detects a current flowing through a matching element in series with a load. , and a phase difference detector that detects the phase difference between the detection signal of the current detection element and the voltage at the entrance of the matching circuit, and the output of this phase difference detector is input to the control circuit.

[Operation] The automatic matching device configured as described above detects the phase difference between the current flowing through the matching element in series with the load and the voltage at the input of the load, so that the phase of the impedance at the input of the load becomes near 00. When this happens, it is determined whether the resonance point is unrelated to the matching state or the resonance point is related to the matching state, and the matching elements of the matching circuit are adjusted accordingly.

[Example] An example will be described with reference to FIG. In this embodiment, the automatic matching device shown in FIG. 5 is further provided with a current detection element 4c at the N point in the matching circuit 3, and the phase difference between the current flowing at the N point and the voltage at the entrance of the matching circuit 3 is detected. A phase difference detector 5c is provided.

The operation of this automatic matching device will be explained with reference to the flowchart in FIG. 2 and the diagram showing the discrimination area in FIG. 3. As in FIG. The impedance phase θ□ and the impedance absolute value Z when looking at the side are detected and input to the control circuit 6. On the other hand, the phase difference detector 5c detects the phase θ2 of the impedance at the N point in the matching circuit 3 from the detection signal of the current detection element 4c and the detection signal of the voltage detection element 4b, and inputs it to the control circuit 6. The control circuit 6 increases the capacitance of the variable capacitor 3b via the drive circuit 7b when the phase θ2 is smaller than the reference value Δθ2. Phase θ2 is greater than 802, absolute value 1θ of phase 0□
When □ is smaller than the reference value 〇□, the control circuit 6 does not change the capacitance of the variable capacitor 3b. Also, the phase θ2 is Δ
Greater than θ2, absolute value of phase θ□] θ□ 1 is Δθ1
If the phase θ□ is negative, the control circuit 6 reduces the capacitance of the variable capacitor 3b via the drive circuit 7b, and if the phase θ□ is positive, the control circuit 6 increases the capacitance of the variable capacitor 3b.

On the other hand, when the absolute value 1z□-501 of the difference between the absolute value Z0 of the impedance detected by the impedance detector 5b and the set impedance 50Ω is smaller than the reference value Δ2□, the control circuit 6 does not change the capacitance of the variable capacitor 3a. . 1z□-501 is greater than the reference value ΔZ□, 2□
When -50 is negative, the control circuit 6 reduces the capacitance of the variable capacitor 3a via the drive circuit 7a. Also, IZ□5
When 01 is larger than the reference value ΔZ□ and 2□-50 is positive,
The control circuit 6 connects the variable capacitor 3a via the drive circuit 7a.
Increase the capacity of.

As a result, the phase 0□ of the impedance at the entrance of the matching circuit 3 is adjusted to the resonance point (point A) unrelated to the matching state and the resonance point (point A) related to the matching state, as shown in FIG.
oO at two points (point B), but N in the matching circuit 3
As shown in FIG. 4, the impedance phase θ2 at a point becomes OO only near the resonance point (point A), which is unrelated to the matching state, and furthermore, becomes an increasing function with respect to the capacitance of the variable capacitor 3b. Therefore, as shown in the flowchart of FIG. 2, the impedance phase θ at the entrance of the matching circuit 3
In addition to □ and the absolute value z1 of impedance, matching circuit 3
By using the phase θ2 of the impedance at point N within the range, matching can be automatically achieved even if the capacitances of matching elements 3a and 3b are not set in advance near the matching point.

[Effects of the Invention] As explained above, according to the present invention, when the phase of the impedance at the entrance of the matching circuit approaches 00, the resonance point unrelated to the matching state or the resonance point related to the matching state Therefore, even if the capacitance of the matching element is at a certain value within the variable range, matching can be reliably and automatically achieved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an automatic alignment device that implements the present invention, FIG. 2 is a flowchart for explaining the operation of the automatic alignment device of FIG. 1, and FIG. 3 is a discrimination method of the automatic alignment device of FIG. FIG. 4 is a diagram for explaining the phase fluctuation state of the automatic alignment device shown in FIG. 1, FIG. 5 is a block diagram showing a conventional automatic alignment device, and FIG. Flowchart for explaining the operation of the automatic alignment device, FIG. 7 is a diagram showing the discrimination area of the automatic alignment device of FIG. 5, and FIG. 8 is for explaining the phase fluctuation state of the automatic alignment device of FIG. 5. This is a diagram. 1. Plasma generator, 2. High frequency power supply, 3. Matching circuit, 3a, 3b.. Variable capacitor, 4a, 4c current detection element, 4b. Voltage detection element, 5a, 5c.. Phase difference detector 5b.・・Impedance detector, 6・・Control circuit, 7a, 7b・・Drive circuit (K) (b) δ diagram

Claims (1)

[Claims] (1) A matching circuit that has a matching element in series with the load and a matching element in parallel with the power supply, a current detection element that detects the current at the entrance of the matching circuit, and a voltage detection element that detects the voltage at the entrance of the matching circuit. , a current detection element that detects the current flowing through a matching element in series with the load, and a phase difference detector and an impedance detector that detect the phase and absolute value of impedance at the entrance of the matching circuit from the current and voltage at the entrance of the matching circuit. and a phase difference detector that detects the phase difference between the current flowing through the matching element in series with the load and the voltage at the entrance of the matching circuit, and the value of the matching element is determined by the outputs of the two phase difference detectors and impedance detector. An automatic matching device characterized in that it has a control circuit for controlling the device.