JP3963428B2 - High frequency power supply - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-frequency power source, and more particularly to a high-frequency power source for a plasma processing apparatus that performs plasma processing on a semiconductor wafer.
[0002]
[Prior art]
Conventionally, in a semiconductor device manufacturing process, a plasma processing apparatus that generates high-density plasma and performs etching on a semiconductor wafer is used. The plasma processing apparatus applies a high frequency for plasma generation and a high frequency for bias for drawing ions in the plasma superimposed on electrodes arranged in the plasma chamber by a high frequency power source.
[0003]
In the plasma processing apparatus, the reflected wave (reflected power: Pr) returns from the plasma chamber due to the fluctuation of the load impedance at the time of plasma generation with respect to the incident wave (incident power: Pf) output from the high-frequency power source to the plasma chamber. Therefore, in order to protect the high-frequency power supply from the reflected wave, for example, there is a method of detecting the reflected wave to reduce the incident wave, a method of inserting a circulator for removing the reflected wave between the high-frequency power supply and the plasma chamber, etc. It is taken. In particular, a method of inserting a circulator between the high frequency power source and the plasma chamber is effective for a high frequency power source for plasma generation in order to ensure an ignition margin during plasma generation.
[0004]
FIG. 3 is a block diagram showing a schematic configuration of a conventional plasma processing apparatus.
[0005]
In FIG. 3, a plasma processing apparatus 20 is a matching circuit for matching the input impedance on the plasma chamber 21 side with the output impedance on the high frequency power supply 26 side so as to minimize the reflected wave, and the plasma chamber 21 which is a main body device. A matching box 22, a power monitor 23 that detects incident waves and reflected waves and controls high-frequency power supplied to the plasma chamber 21, a circulator 24 made of a magnetic material, a dummy load 25 that is a terminal resistor, and plasma generation And a high frequency power supply 26 for use.
[0006]
The high frequency power supply 26 includes a power monitor 27 having the same function as the power monitor 23 and a plurality of power combiners 28 to 34 that combine and output electric power, for example, for generating plasma of 100 MHz and 3 kW as incident waves. The high frequency of is output.
[0007]
The circulator 24 outputs the incident wave Pf output from the high frequency power supply 26 side to the plasma chamber 21 side (Pf ′), and outputs the reflected wave Pr returning from the plasma chamber 21 side to the dummy load 25. The dummy load 25 consumes the reflected wave output from the circulator 24.
[0008]
In the plasma processing apparatus 20, the circulator 24 prevents the reflected wave generated from the plasma chamber 21 from returning directly to the high-frequency power source 26 due to fluctuations in load impedance during plasma generation, thereby protecting the high-frequency power source 26 from the reflected wave. Yes.
[0009]
[Problems to be solved by the invention]
However, in the conventional plasma processing apparatus 20, the high-power circulator 24 and the dummy load 25 are disposed outside the high-frequency power supply 26, so that it is necessary to take a wide apparatus space corresponding to them.
[0010]
In addition, since the circulator 24 is made of a magnetic material, when the incident wave (Pf) from the high frequency power supply 26 passes through the circulator 24, it is slightly attenuated (ΔPf = Pf−Pf ′) due to magnetic loss or the like, and as a result, the plasma chamber 21 In order to accurately control the incident wave input to the side, it is necessary to install the power monitor 23 in front of the matching box 22.
[0011]
The present invention has been made in view of the above problems, and provides a high-frequency power supply capable of reducing the space for the apparatus in the plasma processing apparatus, simplifying the overall structure of the apparatus, and preventing the loss of incident waves. For the purpose.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a high-frequency power supply according to claim 1 comprises power combining means for combining at least two high-frequency powers, and control means for controlling the high-frequency power combined by the power combining means, In the high frequency power supply for supplying the plasma processing apparatus with the high frequency power controlled by the control means as the incident power, the power combining means includes a branching means for branching the reflected power with respect to the incident power supplied to the plasma processing apparatus, and the branch Consumption means for consuming the reflected power branched by the means.
[0013]
The high-frequency power supply according to claim 2 is characterized in that, according to the high-frequency power supply according to claim 1, the branching means comprises at least two circulators made of ferrite connected in parallel to the control means. .
[0014]
The high frequency power supply according to claim 3 is the high frequency power supply according to claim 1 or 2, characterized in that the consuming means is composed of a resistor connected to each of the circulators.
[0015]
A high-frequency power source according to claim 4 is the high-frequency power source according to any one of claims 1 to 3, comprising a plurality of other power combining means for combining at least two high-frequency powers and supplying the power combining means. It is characterized by that.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 is a block diagram showing a schematic configuration of a plasma processing apparatus including a high frequency power source according to an embodiment of the present invention.
[0018]
In FIG. 1, a plasma processing apparatus 1 includes a plasma chamber 2 as a main body apparatus, a matching box 3 connected to the plasma chamber 2, and a high-frequency power source 4 for generating plasma.
[0019]
The plasma processing apparatus 1 arranges a pair of parallel plate electrodes (not shown) (upper electrode and lower electrode) in the plasma chamber 2 to introduce a processing gas, and applies a high frequency to one of the electrodes by a high frequency power source 4. Then, a high-frequency electric field is formed between the electrodes, plasma is generated by the high-frequency electric field, and plasma processing is performed on a semiconductor wafer (hereinafter referred to as “wafer”).
[0020]
The matching box 3 includes a circuit (not shown) including a variable capacitor and a coil, and is a matching circuit for matching the input impedance on the plasma chamber 2 side with the output impedance on the high frequency power source 4 side. In particular, the impedance viewed from the input side of the matching box 3 and the impedance viewed from the output side of the high frequency power supply 4 are set to be the same (50Ω).
[0021]
The high-frequency power source 4 detects the incident wave (incident power: Pf) traveling to the plasma chamber 2 and the reflected wave (reflected power: Pr) returning from the plasma chamber 2 due to fluctuations in load impedance during plasma generation. And a plurality of power combiners 6 to 12 for combining electric power, and outputs a high frequency for generating plasma of 100 MHz and 3 kW as incident waves.
[0022]
In general, in order to obtain a large amount of power with a high-frequency power source, since the output of one amplifying element is limited to about 200 to 300 W, power synthesis is required. In particular, when outputting a high frequency of 100 MHz and 3 kW, the number is not limited to the illustrated number, and a plurality of power combiners 6 to 12 are connected in a plurality of stages to perform power combining.
[0023]
The power combiners 7 to 12 are composed of Wilkinson combiners. Unlike the other power combiners 7 to 12, the power combiner 6 includes circulators 13 and 14 made of ferrite (magnetic material) and dummy loads 15 and 16 that are termination resistors. The power combiner 6 functions as a power combiner by connecting the circulators 13 and 14 in parallel to the power monitor 5 as shown in the figure, and outputs from the power combiner 7 and output from the power combiner 8. Are combined and output.
[0024]
FIG. 2 is an explanatory diagram for explaining a power combining method of the power combiners 7 to 12 in FIG. This synthesis method is generally called a Wilkinson synthesis / distribution method that applies impedance conversion using a coaxial cable having a quarter wavelength (1 / 4λ).
[0025]
In FIG. 2, 30 and 31 are coaxial cables having a quarter λ and an impedance of 70Ω. Rx is a resistance component arranged to maintain isolation between P1 and P2. As shown in the figure, power can be synthesized by connecting the power combiners 7 to 12.
[0026]
Returning to FIG. 1, the circulators 13 and 14 synthesize the high frequency powers input from the power combiners 7 and 8 and output them as incident waves to the power monitor 5, while from the plasma chamber 2 via the power monitor 5. Returned reflected waves are output to the dummy loads 15 and 16 using the magnetic resonance phenomenon of ferrite. The reflected waves output to the dummy loads 15 and 16 are consumed by the resistances in the dummy loads 15 and 16.
[0027]
As described above, the reflected wave generated from the plasma chamber 2 due to the load impedance fluctuation at the time of plasma generation is consumed by the dummy loads 15 and 16 via the circulators 13 and 14, thereby protecting the high-frequency power source 4 as the final stage from the reflected wave. In addition, stable energy can be supplied to the plasma chamber 2.
[0028]
When the circulators 13 and 14 are outside the high frequency power source 4, the output of the high frequency power source 4 is a constant output regardless of the state of the plasma chamber 2 as a load. The power monitor 5 must be provided to provide power feedback with the main body of the high frequency power source 4. In the present embodiment, incident waves can be processed inside the high-frequency power supply 4 by power synthesis by the circulators 13 and 14, and the overall configuration of the apparatus is simplified.
[0029]
According to the above-described embodiment, the reflected waves from the plasma chamber 2 side are branched by the circulators 13 and 14 made of ferrite provided in the power combiner 6 in the high frequency power supply 4 and output to the dummy loads 15 and 16. Since the reflected waves are consumed by the loads 15 and 16, the space for the apparatus in the plasma processing apparatus can be reduced, the entire structure of the apparatus can be simplified, and the loss of incident waves can be prevented.
[0030]
Further, since the two circulators 13 and 14 are connected in parallel to the power monitor 5 in the power combiner 6, two high frequency powers can be combined and extracted without using the power combiner. . Furthermore, since the dummy loads 15 and 16 connected to the circulators 13 and 14 can be mounted in the cooling device of the power amplification unit (not shown) of the high-frequency power supply 4, the space for the device can be reduced.
[0031]
In the above embodiment, the circulators 13 and 14 are provided separately, but may be integrated.
[0032]
【The invention's effect】
As described in detail above, according to the high frequency power supply of claim 1, in the power combining means for combining at least two high frequency powers, the branching means branches the reflected power with respect to the incident power supplied to the plasma processing apparatus. Since the reflected power is consumed by the consuming means, the space for the apparatus in the plasma processing apparatus can be reduced, the structure of the apparatus can be simplified, and the loss of the incident wave can be prevented.
[0033]
According to the high frequency power supply of claim 2, since the branching means is composed of at least two circulators made of ferrite connected in parallel to the control means, it synthesizes two high frequency powers without using a power combiner. Can be taken out.
[0034]
According to the high frequency power supply of claim 3, since the consuming means is composed of resistors connected to the circulator, the consumption means can be used by being mounted in the cooling device of the power amplifying unit in the high frequency power supply. Can be reduced.
[0035]
According to the high frequency power supply of the fourth aspect, since a plurality of other power combining means for combining at least two high frequency powers and supplying them to the power combining means are provided, desired high frequency power can be output.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a schematic configuration of a plasma processing apparatus including a high-frequency power source according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram for explaining a power combining method of power combiners 7 to 12 in FIG. 1;
FIG. 3 is a block diagram showing a schematic configuration of a conventional plasma processing apparatus.
[Explanation of symbols]
1 Plasma processing equipment 2 Plasma chamber 3 Matching box (matching circuit)
4 High-frequency power supply 5 Power monitor 6, 7, 8, 9, 10, 11, 12 Power combiner 13, 14 Circulator 15, 16 Dummy load

Claims (4)

A power combining unit configured to combine at least two high-frequency powers; and a control unit configured to control the high-frequency power combined by the power combining unit, and supply the high-frequency power controlled by the control unit to the plasma processing apparatus as incident power. In the high frequency power supply
The power synthesizing means includes a branching means for branching the reflected power with respect to the incident power supplied to the plasma processing apparatus,
A high frequency power supply comprising: consumption means for consuming the reflected power branched by the branching means. 2. The high-frequency power supply according to claim 1, wherein the branching means comprises at least two circulators made of ferrite connected in parallel to the control means. The high-frequency power source according to claim 1 or 2, wherein the consuming means comprises a resistor connected to each of the circulators. The high frequency power supply according to any one of claims 1 to 3, further comprising a plurality of other power combining units that combine at least two high frequency powers and supply the combined power to the power combining unit.

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