JPH05284046A - Impedance matching control circuit for rf generator - Google Patents

Abstract

PURPOSE:To select the matching control method of an RF generator used for a high-efficiency and stable-quality semiconductor manufacture device or the like by turning reflective power to zero in a short time and maximizing power supplied to a load by most effectively performing the control of impedance matching for the RF generator used for sputtering or the like. CONSTITUTION:The estimation based on results and experiences to the matching point of the load in the past is inputted to a CPU 7, and the movable range of variable condenser C1 and C2 is set to the load to be executed. Thus, the impedance matching control circuit for the RF generator detects the matching point in a short time as a result by performing trial based on a CPU command while dividing the entire movable range of the variable condenser C1 and C2 even concerning any unknown load.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control circuit for controlling a variable capacitor in a matching box connected in series with an RF power source at a matching point.

[0002]

2. Description of the Related Art In order to reduce the reflected power of the output of an RF power source to zero, a matching box 2A is inserted between the RF power source 1A and a load 3A as shown in FIG. 1 so that the output impedance Z seen from the power source 1A is constant. , So that the phase angle φ is zero, the variable condenser C in the matching box shown in FIG.
1. Adjust C2. As shown in FIG. 3, a conventional digital control circuit for controlling C1 and C2 detects reflected power Pr or traveling wave power Pi and reflected power Pr from a power detector (PD) 4A built in the power supply of FIG. Then, the reflected power coefficient Kr = ΔPr / ΔPi indicating the rate of change in reflected power
Signal is discriminated by the A / D converter 8 and the I / O port 9
Output signals M1CW, M1CCW, M2CW, M2CC
By alternately turning W on or off, Kr is controlled to be minimum. FIG. 5 shows an example of the control, which shows the Kr characteristic due to the movement of C2 while varying C1 as a parameter, and the horizontal axis indicates the clockwise (CW) or counterclockwise (CCW) rotation of C2. The dotted line is the parameter C1
(C11 to C14) shows the load characteristics, the solid line is C2
From the origin position of 0%, set value of parameter C1 (C11
C14) shows the locus of controlling C2 so that Kr at that time becomes the minimum value.

When the origin positions of C1 and C2 are extremely deviated from the matching point M, C1 to be controlled is C1.
The switching frequency of C2 becomes large, the total moving distance of C1 and C2 becomes large, and as a result, the time until the matching point is detected becomes long. Although FIG. 5 shows an example in which C2 is moved as the C1 parameter, the same applies to a control example in which C1 is moved using the C2 as a parameter.

[0004]

DISCLOSURE OF THE INVENTION The present invention sets the movable range of the variable condenser for the load to be executed by estimating the past load matching points with experience and estimation based on experience, Even if it is, the matching point is not detected by moving the entire range (0 to 100%) of the variable condenser, but the moving range is divided and the trial is performed, resulting in the control to detect the matching point in a short time. It proposes a circuit.

[0005]

Means of the Invention for Solving the Problems

FIG. 4 shows an embodiment of the present invention in which a motor M
1, the output signal VC1 of the position detector 2 directly connected to M2,
The VC2 is input to the A / D converter 9. On the other hand, the output signals M1CW and M1 of the I / O port 11 are controlled by the CPU 7.
Compatible with CCW, M2CW, M2CCW, Varicon C
D / A signals L1 to L4 that limit the movement range of C1 and C2
Output from the converter 10 and input to the position detector 2.
As a result, the limit signal LM1 for the motor M1 in the clockwise direction (CW direction), the limit signal LM2 for the counterclockwise direction (CCW direction), and similarly the limit signal LM3 for the motor M2 in the CW direction, the limit signal for the CCW direction. The signal LM4 becomes the output of the D / A converter 10 and is connected to the control terminal of the motor drive circuit.

For the M1CW signal, the LM1
LM2 for CW, LM3 for M2CW as well
However, in M2CCW, LM4 becomes an inhibition signal for the I / O port output signal. At the same time, those prohibition signals are I /
I / O connected to O port 11 and controlled
The CPU 7 is notified that the port output has become the prohibition condition, and the ON state is controlled to the OFF state. The aforementioned limit signal L1
~ L4 can be set by the operation switch of the operation circuit 12,
The value is displayed on the panel of the operation circuit 12. Further C
When the setting operation for limiting C1 and C2 is completed, the actual position of the variable capacitor is switched so as to be displayed. By doing so, the operation circuit 12 can be used for displaying the status and setting the limit range.

Next, FIG. 6 shows operation characteristics when the movement limit of the variable capacitor C2 is provided based on the control characteristics shown in FIG. 5 according to FIG. Assuming that the origin of C2 is at the limit value L4 on the CCW side in FIG. 6, the movement from L4 to the CCW direction is the prohibited area indicated by the diagonal line of LM4, so that C2 can move only between L3 and L4, and the solid line With the characteristics shown in
Reach the point.

It can be seen that the characteristic of FIG. 6 is clearly improved over the characteristic shown in FIG. 5 and reaches the point M in a short time. C
As in the case of 2, the limit ranges L1 and L2 are provided in C1 as well.
FIG. 7 shows an example in which the movable range of two variable capacitors is set. It is obvious that the matching point M can be further shortened as compared with FIG. 6 by providing the limited range as shown in FIG. If it is the load of Suchi, the matching point is L in FIG.
Even if it is unknown where the variable capacitors C1 and C2 are not located within the range surrounded by 1 to L4, the work of dividing the variable range of the variable capacitors C1 and C2 and repeating until the matching point is found is shown in FIG.
Is more effective than the method of scanning the entire range of C1 and C2 with the circuit according to. In particular, it is effective for a load having sharp characteristics in which the range of the matching points C1 and C2 is extremely narrow.

[0009]

By limiting the moving range of the variable capacitors C1 and C2 according to the present invention, the matching point can be easily detected in a short time as described above. Especially for unknown loads, the work in the operation circuit is manually changed to C1, C
Search for the effective range of 2 and set that value as the limit range,
It is considered to be extremely effective to make the operation circuit automatic again and let the operation of the circuit reduce the time.

[Brief description of drawings]

FIG. 1 is a main circuit configuration diagram of an RF generator.

[Fig.2] Circuit diagram inside the matching box

FIG. 3 is a conventional matching control circuit diagram

FIG. 4 is a matching control circuit diagram of the present invention.

FIG. 5: Conventional matching control characteristic diagram

FIG. 6 is a matching control characteristic diagram of the present invention.

FIG. 7 is a matching control range diagram of the present invention.

[Explanation of symbols]

 1A RF power supply 2A Matching box 3A Load 4A Power detector (PD) L Matching box inductance C1 Matching box variable capacitor C2 Matching box variable capacitor 1 Kr Arithmetic circuit 2 Position detector 3 Conventional driver circuit 4 Drive of the present invention Circuit 5 Motor M1 6 Motor M2 7 CPU 8 Memory 9 A / D converter 10 D / A converter 11 I / O port 12 Operation circuit

Claims (1)

[Claims] 1. A CPU-controlled I for varying two variable capacitors in the power supply built in a matching box in an AC power supply circuit in which an RF power source, a matching box and a load are connected in series via a motor. / O port In the digital control circuit including its drive circuit, D / A conversion circuit, operation circuit, etc., output the output signal of the position detector directly connected to the motor and the value set by the operation circuit to the D / A converter. A digital control circuit for impedance matching of the RF generator, characterized in that a comparison circuit with the above-mentioned value is provided, the output signal thereof is connected to the control terminal of the drive circuit, and an effective variable range of the two variable capacitors is provided. ..