JPH07302695A - Matching device - Google Patents

Abstract

PURPOSE:To provide a matching device with which matching adjustment on the load side can be performed easily in a wide frequency range solely by setting a continuous changeable range of a capacity component and an induction component in the matching device large, and setting its change ratio inconstant. CONSTITUTION:A variable capacity element comprising variable capacitors 2, 3, and an inductometer element comprising a coil 4 and a conductor 6 are provided to form a resonance circuit, and a capacity change per unit rotation quantity of the capacitors 2, 3 is set to be smaller as a frequency range is more on the high range side. Matching adjustment on the load side to a wide range of plasma excitation frequencies can thus be provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a matching device for a high frequency plasma generator, and more particularly to a matching device having a single structure which enables matching of high frequencies in a wide frequency range.

[0002]

2. Description of the Related Art In many cases, plasma is used in surface treatment and film formation processes. There are direct current, high frequency, microwave, etc. as a method of generating plasma, but especially in the case of high frequency plasma, a matching device is installed to maximize power consumption in the plasma part and protect the power supply or the oscillation circuit. . The matching unit performs frequency tuning and impedance adjustment in order to match the high frequency power supply side and the load side. In the plasma generator, for example, the output impedance on the high frequency power source side is a pure resistance of 50 [Ω]. On the other hand, the plasma load is composed of a device load including a capacitance component, a resistance component, and a stray capacitance component derived from the device shape such as an electrode. The matching unit is for coupling with the device load on the load side and adjusting the impedance on the load side to a pure resistance of 50 [Ω].

The matching unit is composed of a capacitive component such as a capacitor and an inductive component such as a coil.
There are various types such as type and T type, but an L type circuit is generally used. The L-type circuit selects the reactive component in series with the plasma so as to be capacitive as a whole,
It forms a parallel resonant circuit consisting of an inductive component and a resistive component. In the conventional matching device, a high frequency of 13.56 [MHz] is widely used industrially as a plasma generating power supply frequency and the frequency is constant. Also, in the case of a conventional matching device, it is difficult to continuously vary the inductive component, so after roughly adjusting the coiled inductive component by tap switching, fine adjustment with a variable capacitor is performed to tune to the power supply frequency. The structure was to adjust the impedance of the entire load.

As described above, the plasma generation power supply frequency has been constant in the past, but in recent years, the effect of the plasma excitation frequency on the plasma process has been noted, and the 13.56 [MHz] and 27 [MHz] described above are noted. , 40 [MH
Not only fixed frequency type plasma generators such as z] and 60 [MHz] but also a wide frequency variable type plasma generator of several [KHz] to several hundred [MHz] is adopted. Figure 2,
FIG. 3 shows a specific example of a matching device incorporated in a frequency variable plasma generator, FIG. 2 shows a matching device 1a when the power supply frequency is low, and FIG. 3 shows a matching device when the power supply frequency is high. It is 1b.

Matching device 1a shown within a dotted line in FIG.
Is a high frequency power source 9 (hereinafter referred to as power source 9) and a device load 10
(Hereinafter referred to as load 10). As the variable capacitance element, a variable capacitor 11 for power supply frequency tuning and a variable capacitor 1 for fine matching adjustment
2 (for example, an air-type variable capacitor) is used. The maximum capacitance of the former capacitor 11 is, for example, 1000 [pF], and the maximum capacitance of the latter capacitor 12 is, for example, 200 [pF]. On the other hand, the variable induction element has a maximum induction coefficient of 5 consisting of a hollow copper pipe.
A coil 13 with a [μH] tap 14 is used.

The matching unit 1b (shown within the dotted line) shown in FIG. 3 is interposed between the power source 9 and the load 10 as in FIG. 2, and the variable capacitance element has, for example, a maximum capacitance of 250 [pF].
The variable capacitor 15 for power supply frequency tuning and the variable capacitor 16 for fine matching adjustment with the maximum capacitance of 50 [pF] are used. Further, the variable inductive element does not have a coiled inductive component, and is a conductor 1 made of a copper plate.
7 is installed.

[0007]

When the traveling wave output is fixed to 100 [W] and the reflected wave output is adjusted to 1 [W] or less by using the matching device 1a shown in FIG. 2, the following result is obtained. Was obtained. Output frequency from power supply 9 is 10 [MH
From [z] to 58 [MHz], matching could be adjusted by the matching device 1a of FIG. 2, but from 58 [MHz] to 100 [MH]
In the case of z], the matching adjustment could not be performed unless the matching device 1b of FIG. 3 was replaced. Furthermore, in the matching device 1a,
10 [MHz] to 13 [MHz], 12 [MHz] to 18 [MHz], 17 [MHz] to 27 [MH]
z], 26 [MHz] to 40 [MHz], 39 [MH
After adjusting the tap 14 of the coil 13 corresponding to the five regions from z] to 58 [MHz], the power source frequency tuning variable capacitor 11 and the matching fine adjustment variable capacitor 12 must be adjusted to perform matching. There wasn't. However, in both capacitors 11 and 12, the rotation angle of the rotor corresponding to the frequency difference of 1 [MHz] is about 3 at minimum.
In some cases, the adjustment sensitivity is too high, and the adjustment sensitivity is too high.

Similarly, the matching device 1b shown in FIG. 3 was used to adjust the traveling wave output to a constant 100 [W] so that the reflected wave output was 1 [W] or less. That is, 54 [MHz]
To 80 [MHz], 70 [MHz] to 100 [MH]
After adjusting the length of the high-voltage lead-in wire of the copper plate that connects the matching unit 1b and the electrode of the load 9 in correspondence with the two regions of z], the variable capacitor 15 for power frequency tuning and the variable capacitor 16 for fine matching adjustment were adjusted. . In this case, since the change in the electrostatic capacitance with respect to the unit rotation angle on the rotor side is constant in both variable capacitors 15 and 16, the change may be relatively large in a high frequency region sensitive to the change in capacitance. In some cases, the rotation angle of the rotor corresponding to a frequency difference of 1 [MHz] may be at most about 3 degrees or less.
As in the case of FIG. 2, there was a problem of being too sensitive.

As described above, in the case of the conventional matching device, it is necessary to use a matching device corresponding to the frequency of the power supply, which is extremely complicated, and the adjustment is too sensitive. That is, the capacitive component and the inductive component in the matching box largely depend on the frequency. First, when the frequency of the inductive component changes, the above-mentioned fine adjustment by the variable capacitor cannot be made in time, and tap switching of the coil-shaped inductive component is required each time. Further, although depending on the shape of the device, the electrode, etc., the inductive component of the non-coiled conductor portion becomes large at a frequency of about 50 [MHz] or higher, and the coiled inductive component becomes unnecessary. In this case, for example, it is necessary to adjust the length of the high-voltage lead-in wire such as a copper plate connecting the matching unit and the electrode. Further, in the capacitance component, the higher the frequency is, the more sensitive the capacitance change is. Therefore, it is necessary to reduce the capacitance of the variable capacitor in order to reduce the resolution of capacitance adjustment. Therefore, for example, 1 [MHz] to 200
In a wide range of variable frequency power supplies such as [MHz], it is necessary to replace a plurality of matching devices with different capacitance components and inductive components according to the frequency used, and the above adjustment is necessary, so the matching operation is very complicated. It was

The present invention was devised in view of the above-mentioned circumstances, and by enlarging the continuously variable range of the capacitive component and the inductive component in the matching box and not keeping the rate of change thereof constant, a wide frequency range is obtained. It is an object of the present invention to provide a matching device that enables easy matching by using.

[0011]

In order to achieve the above object, the present invention comprises a high frequency power supply for supplying a high frequency which is continuously selectable within a predetermined frequency range to a load including electrodes. A matching device that is incorporated in a plasma generation device and intervenes between the load and a high frequency power source to perform matching between the loads and the high frequency power supply. Tuning and impedance adjustment to a high frequency by a variable capacitance element and a variable inductive element forming a resonance circuit. In addition, the capacitance value of the variable capacitance element and the induction coefficient of the variable inductive element are continuously settable, and have a capacitance range and an induction coefficient range that enable tuning and adjustment over the entire frequency range. It constitutes a matching unit. In addition, specifically, the variable capacitance element is formed of a rotary capacitor, and a capacitance change amount per unit rotation amount is set non-linearly according to a frequency in the high frequency range. More specifically, the rotary capacitor is characterized in that the amount of change in capacitance per unit amount of rotation becomes smaller on the higher side of the frequency range, and the variable inductive element is on the lower side of the frequency range. It is characterized in that it is connected to a conductor with a variable length and a coil with a variable number of turns that can be switched to the high frequency side.

[0012]

[Function] By performing tuning and impedance adjustment to a high frequency using a variable capacitance element and a variable induction element having an appropriate capacitance range and induction coefficient range,
The desired matching can be done with a single matcher.
Also, the capacitance of the variable capacitance element consisting of a rotary capacitor changes non-linearly with respect to frequency, and in particular, in order to reduce the capacitance change per unit amount of rotation on the high frequency side of the frequency range, the capacitance change on the high frequency side of the plasma excitation frequency. Since the resolution of is decreased, the rotation angle of the rotor corresponding to the frequency difference can be increased, and delicate adjustment can be realized with a large rotor rotation angle. In addition, a variable length conductor and a variable number of coils are used as the variable induction element,
In the high frequency region where the induction component of the coil is not needed, the conductor having a variable length may be made to function, and the matching adjustment can be easily performed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of the embodiment.

As shown in FIG. 1, the matching device 1 is composed of an L-type resonance circuit. In the figure, the part surrounded by the dotted line corresponds to the matching box 1. The matching device 1 is provided between a power source 9 and a load 10 having electrodes and the like. The present embodiment is premised on the use of a high frequency power source with a maximum output of 500 [W]. As the variable capacitance element, for example, a maximum capacitance of 100
A variable rotary capacitor 2 for power frequency tuning of 0 [pF] and a variable rotary capacitor 3 for fine matching adjustment with a maximum capacitance of 200 [pF] are installed. In the present embodiment, both capacitors 2 and 3 are air-type variable capacitors, but a vacuum variable capacitor having a high dielectric breakdown voltage (breakdown voltage) may be used when corresponding to a higher output power source 9. Further, as shown in the figure, fixed capacitors 2a and 3a may be connected in parallel with the variable capacitors 2 and 3 at the stage of performing matching adjustment by connecting to the actual load 10.

The variable rotary capacitors 2 and 3
Is designed so that the change in capacity per unit amount of rotation is reduced on the high frequency side of the frequency range. For example, among the plurality of rotor plates, the first plate has a semicircular shape, and the second and subsequent plates have a fan shape in which the central angles are sequentially reduced at equal intervals, and the linear end faces on one side are aligned. Further, a capacitor whose area and gap on the stator side may change may be used, contrary to the present embodiment.

On the other hand, as the variable induction element, for example, a coil 4 made of a hollow copper pipe and having a maximum induction coefficient of 5 [μH] is used.
Width 30 [mm], length 500 [mm], thickness 3 [m
m] and the conductor 6 made of a copper plate. The switch between the coil 4 and the conductor 6 is performed by the switch 8, and either one of them is connected to the load 10 side. The coil 4 is provided with a contactor 5 that moves along the outer circumference, so that the induction coefficient can be changed quasi-continuously. Further, the conductor 6 has a contactor 7, and the connection length can be continuously changed.

Next, the matching operation according to this embodiment will be described. As a device load, a parallel plate type electrode having a diameter of 120 [mm] and an inter-electrode distance of 60 [mm] was used in a vacuum chamber kept at an Ar pressure of 20 [mTorr]. As a power source for plasma excitation, the maximum output is 500 [W]
A high frequency power source with a variable frequency of 0 to 100 [MHz] was used. When the traveling wave output is kept constant at 100 [W] and the matching adjustment is performed until the reflected wave output falls below 1 [W], the changeover switch 8 is used to switch the coil 4 from the output frequency 10 [MHz] to 58 [MHz]. Connected to the load 10,
After adjusting the contactor 5 of the coil 4, the power source frequency tuning variable capacitor 2 and the matching fine adjustment variable capacitor 3 were adjusted so that matching adjustment could be easily performed. In the range of 54 [MHz] to 100 [MHz], the changeover switch 8 is used to load the conductor 6 into the load 1.
After adjusting the contactor 7 of the conductor 6 by connecting to 0, the power source frequency tuning variable capacitor 2 and the matching fine adjustment variable capacitor 3 were adjusted, so that the matching adjustment could be easily performed. Which variable capacitor 2,
3 also has a high resolution even in a high frequency region where a matching operation sensitive to the capacitance change is required because the amount of change in the capacitance per unit rotation amount of the rotor becomes small on the high frequency side of the frequency range. ] The rotation angle of the rotor corresponding to [] does not fall below about 10 degrees, and the adjustment was not too sensitive as in the prior art.

[0018]

According to the present invention, the following remarkable effects are obtained. 1) The variable capacitance element and the variable inductive element forming the resonance circuit can be freely varied according to the power supply frequency within an appropriate capacitance range and induction coefficient range, so tap switching is not required even if the plasma excitation frequency is changed. And matching adjustment can be performed by a single matching device without using another matching device. 2) The amount of change in capacity per unit amount of rotation is set non-linearly with respect to the frequency, and in particular, it is set smaller toward the high frequency side of the frequency range, so matching adjustment can be easily performed. 3) Further, since the variable inductive element has a structure that can be switched between the low band side and the high band side of the frequency range, a common matching box can easily perform matching adjustment for a wide range of frequencies.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

FIG. 2 is a configuration diagram of a conventional low-frequency side matching box.

FIG. 3 is a configuration diagram of a conventional high-frequency side matching box.

[Explanation of symbols]

1 Matching Device 2 Variable Rotary Capacitor for Power Frequency Tuning 2a Fixed Capacitor 3 Variable Rotary Capacitor for Fine Tuning Matching 3a Fixed Capacitor 4 Coil 5 Contactor 6 Conductor 7 Contactor 8 Changeover Switch 9 High Frequency Power Supply 10 Device Load (Load) )

Claims (4)

[Claims] 1. A plasma generator equipped with a high-frequency power supply that supplies a high-frequency power that can be continuously selected within a predetermined frequency range to a load including electrodes, and is interposed between the load and the high-frequency power supply. A matching device for performing matching between the two, the tuning of the high frequency and the adjustment of the impedance by the variable capacitance element and the variable inductive element forming the resonance circuit, and the capacitance value of the variable capacitance element and the variable inductive element. A matcher characterized in that the induction coefficient is continuously settable and has a capacitance range and an induction coefficient range that allow tuning and adjustment over the frequency range. 2. The matching device according to claim 1, wherein the variable capacitance element comprises a rotary capacitor, and a capacitance change amount per unit rotation amount is set non-linearly according to a frequency in the frequency range. 3. The matching device according to claim 2, wherein the rotary capacitor is such that the amount of change in capacitance per unit amount of rotation becomes smaller toward the higher frequency side of the frequency range. 4. The matching device according to claim 1, wherein the variable inductive element is composed of a conductor having a variable length and a coil having a variable number of turns, which are switchable between a low band side and a high band side of the frequency range. .