High frequency power supply device

Abstract

To provide a high-frequency power source device that can generate, in a first power source, a waveform signal with the same period as that of a high-frequency voltage output from a second power source.SOLUTION: A high-frequency power source device according to the present disclosure includes a first power source 10 that supplies to a load a first high-frequency power with a first fundamental frequency, a second power source 20 that supplies to the load a second high-frequency power with a second fundamental frequency, and a matching unit 30. The matching unit 30 generates a clock signal CK with a higher frequency than the first fundamental frequency on the basis of detection information of the second high-frequency power. The first power source 10 generates a waveform signal with the same period as that of the high-frequency voltage output from the second power source 20 using the clock signal CK, and performs frequency modulation control of the first high-frequency voltage output from the first power source 10 using this waveform signal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a high frequency power supply device. [Background technology]

[0002] A high frequency power supply device used in a plasma processing apparatus has two high frequency power supplies (a first power supply and a second power supply), and each power supply outputs a high frequency voltage having a different fundamental frequency (the frequency of the fundamental wave) to a load. For example, the first power supply supplies a first high frequency power to the load by outputting a first high frequency voltage having a first fundamental frequency F1 suitable for generating plasma. The second power supply supplies a second high frequency power to the load by outputting a second high frequency voltage having a second fundamental frequency F2 (first fundamental frequency F1>second fundamental frequency F2) suitable for ion acceleration. (See Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2018-536295 [Patent Document 2] JP 2017-188434 A [Patent Document 3] U.S. Pat. No. 10,304,669 Summary of the Invention [Problem to be solved by the invention]

[0004] In such a case, intermodulation distortion (IMD) occurs, and a phenomenon occurs in which the reflected power fluctuates according to the period of the second fundamental frequency F2 on the first power supply side. In order to reduce the reflected power caused by this intermodulation distortion, a technique is known in which frequency modulation control is performed on the first power supply. In this case, it is considered to generate a waveform signal with the same frequency as the second fundamental frequency F2 based on information on the second fundamental frequency F2 of the second power supply that is known in advance (for example, information that is 400 kHz is known), and to perform frequency modulation control on the first power supply using the generated waveform signal. However, the period of the artificially generated waveform signal is different from the period of the high-frequency voltage output from the second power supply. When the periods of the two differ in this way, the effect of frequency modulation control in reducing the reflected wave power caused by intermodulation distortion decreases.

[0005] The present disclosure provides a high frequency power supply device capable of generating, in a first power supply, a waveform signal having the same period as the period of a high frequency voltage output from a second power supply. [Means for solving the problem]

[0006] A high frequency power supply device according to the present disclosure includes a first power supply that supplies a first high frequency power to a load by outputting a first high frequency voltage having a first fundamental frequency, a second power supply that supplies a second high frequency power to the load by outputting a second high frequency voltage having a second fundamental frequency lower than the first fundamental frequency, and a matching unit that is connected to each of the first power supply and the second power supply. the matching unit generates a clock signal having a frequency higher than the first fundamental frequency based on detection information of the second high frequency power, and supplies the clock signal to the first power supply; The first power supply uses the clock signal to generate a waveform signal having the same period as the period of the high-frequency voltage output from the second power supply, and uses the waveform signal to perform frequency modulation control of the first high-frequency voltage output from the first power supply. Effect of the Invention

[0007] According to the high frequency power supply device according to the present disclosure, a waveform signal having the same period as the period of the high frequency voltage output from the second power supply can be generated in the first power supply. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the configuration of a high-frequency power supply device according to an embodiment. [Diagram 2] 4 is a sequence chart showing the operation of the high frequency power supply device according to the embodiment. [Diagram 3] 5 is a waveform diagram showing the operation of the high frequency power supply device according to the embodiment. [Figure 4] 5 is a waveform diagram showing the operation of the high frequency power supply device according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, embodiments of a high frequency power supply device according to the present disclosure will be described with reference to the drawings.

[0010] (Embodiment) The high frequency power supply device according to the embodiment supplies high frequency power to a load (e.g., a plasma processing device) by outputting a high frequency voltage in the RF band (RF: Radio Frequency). Such a high frequency power supply device has two high frequency power supplies (a first power supply and a second power supply), and outputs high frequency voltages with different fundamental frequencies (frequencies of fundamental waves) (also called output frequencies) from the respective power supplies to the load. For example, the first power supply supplies the first high frequency power to the load by outputting a first high frequency voltage having a first fundamental frequency F1 suitable for generating plasma. The second power supply supplies the second high frequency power to the load by outputting a second high frequency voltage having a second fundamental frequency F2 (first fundamental frequency F1>second fundamental frequency F2) suitable for ion acceleration.

[0011] When multiple high-frequency powers with different levels are supplied to a load from multiple power sources in this way, a phenomenon occurs in which the reflected power on the first power source side fluctuates according to the fundamental period (the period of the fundamental wave) on the second power source side due to the influence of intermodulation distortion. Therefore, it is not possible to efficiently supply high-frequency power from the first power source to the load. Therefore, in this embodiment, frequency modulation control is performed as follows to reduce the reflected power caused by intermodulation distortion.

[0012] The high-frequency voltage output from the first power supply toward the load is called the first traveling wave voltage, and the high-frequency voltage reflected from the load side and returning to the first power supply is called the first reflected wave voltage. The high-frequency voltage output from the second power supply toward the load is called the second traveling wave voltage, and the high-frequency voltage reflected from the load side and returning to the second power supply is called the second reflected wave voltage.

[0013] FIG. 1 is a diagram showing the configuration of a high-frequency power supply device 1. The high-frequency power supply device 1 is applied to a plasma processing device PA. The plasma processing device PA is, for example, a parallel plate type, and a lower electrode EL1 and an upper electrode EL2 face each other in a chamber CH. A substrate SB to be processed can be placed on the lower electrode EL1. The high-frequency power supply device 1 is electrically connected to the lower electrode EL1. The upper electrode EL2 is electrically connected to a ground potential. The chamber CH is connected to a gas supply device (not shown) via an air supply pipe, and is connected to a vacuum device (not shown) via an exhaust pipe.

[0014] The high frequency power supply device 1 includes an HF power supply (first power supply) 10, an LF power supply (second power supply) 20, and a superposition matching box (matching section) 30. The HF power supply 10 supplies a first high frequency power (first traveling wave power) to a load by outputting a first high frequency voltage (first traveling wave voltage) having a first fundamental frequency F1. The first high frequency voltage mainly has a relatively high first fundamental frequency F1 suitable for generating plasma. The first fundamental frequency F1 is, for example, 40.68 MHz. The HF power supply 10 is also called a source power supply. Note that the fundamental frequency F1 is not limited to 40.68 MHz, and may be, for example, a frequency in the industrial RF (Radio Frequency) band, such as 13.56 MHz or 27.12 MHz.

[0015] The LF power supply 20 supplies a second high frequency power (second traveling wave power) to a load by outputting a second high frequency voltage (second traveling wave voltage) having a second fundamental frequency F2 lower than the first fundamental frequency F1. The second high frequency voltage has a relatively low second fundamental frequency F2 suitable for accelerating ions. The second fundamental frequency F2 is, for example, 400 kHz. The LF power supply 20 is also called a bias power supply. Note that the second fundamental frequency F2 is not limited to 400 kHz and may be another frequency.

[0016] The superposition matching box 30 is electrically connected to the HF power supply 10 and the LF power supply 20, respectively. The superposition matching box 30 is electrically connected between the HF power supply 10 and the LF power supply 20 and the lower electrode EL1. The superposition matching box 30 performs first impedance matching on the HF power supply 10 side and the lower electrode EL1 side, and performs second impedance matching on the LF power supply 20 side and the lower electrode EL1 side. With the first impedance matching and the second impedance matching performed, the superposition matching box 30 receives the first high frequency power from the HF power supply 10 and the second high frequency power from the LF power supply 20, and supplies the first high frequency power and the second high frequency power in a superimposed state to the lower electrode EL1.

[0017] The high frequency power supply device 1 and the plasma processing apparatus PA are not limited to the configuration shown in Fig. 1. For example, there are various configurations, such as a configuration in which a first high frequency power output from the HF power supply 10 is supplied to the upper electrode EL2 via the superposition matching device 30, and a second high frequency power output from the LF power supply 20 is supplied to the lower electrode EL1 via the superposition matching device 30. The high frequency power supply device 1 can also be used in such other configurations.

[0018] The superposition matching device 30 has a first matching section 31, a second matching section 32, and a clock generating section 33. The first matching section 31 has a sensor 311 and a matching circuit 312. The second matching section 32 has a sensor 321 (detection section 321) and a matching circuit 322. The clock generating section 33 has a sensor 321, a pulse conversion circuit 332, and a multiplication processing section 333. The second matching section 32 and the clock generating section 33 share the sensor 321. This allows the configuration of the superposition matching device 30 to be kept compact.

[0019] In first matching unit 31, sensor 311 detects waveform signal SG1f of the first forward wave voltage output from HF power supply 10, and detects waveform signal SG1r of the first reflected wave voltage reflected from matching circuit 312. Matching circuit 312 has a variable impedance circuit, and changes the impedance value of the variable impedance circuit by a control circuit (not shown) in response to waveform signal SG1f and waveform signal SG1r detected by sensor 311 (for example, so that the reflection coefficient calculated from waveform signal SG1f and waveform signal SG1r becomes smaller). Of course, the impedance value of the variable impedance circuit may be changed so that the reflected wave power becomes smaller, rather than the reflection coefficient. Note that the variable impedance circuit includes, for example, a variable capacitor and inductor (not shown), and the impedance value can be changed by changing the capacitance of the variable capacitor (similar to second matching unit 32). In the above example, the reflection coefficient is calculated using the first forward wave voltage waveform signal SG1f and the first reflected wave voltage waveform signal SG1r, but it is also possible to detect the voltage waveform signal and the current waveform signal and calculate the reflection coefficient based on them (the same applies to the second matching section 32).

[0020] In second matching section 32, sensor 321 detects waveform signal SG2f of a second forward wave voltage output from LF power supply 20, and also detects waveform signal SG2r of a second reflected wave voltage reflected from matching circuit 322. Matching circuit 322 has a variable impedance circuit, and changes the impedance value of the variable impedance circuit by a control circuit (not shown) in response to waveform signals SG2f and SG2r detected by sensor 321 (for example, so that the reflection coefficient calculated from waveform signals SG2f and SG2r becomes smaller). Of course, the impedance value of the variable impedance circuit may be changed so as to reduce the reflected wave power, rather than the reflection coefficient.

[0021] In the clock generating unit 33, the pulse conversion circuit 332 (conversion unit 332) converts the waveform signal SG2f of the second traveling wave voltage detected by the sensor 321 into a pulse signal. The pulse signal is converted into a rectangular signal having a second fundamental frequency F2. The pulse conversion circuit 332 has a comparator and uses the comparator to convert the sine wave signal into a rectangular signal. The multiplication processing unit 333 multiplies the pulse signal having the second fundamental frequency F2 by N to generate a clock signal CK of a frequency F3. N is an integer greater than 1. The frequency F3 is at least twice the fundamental frequency F1. This is to prevent aliasing.

[0022] When F2=400kHz and N=250, F3=F2×N=400kHz×250=100MHz. The clock signal CK is generated according to the second forward voltage, so it can be a signal synchronized with the second forward voltage. The multiplication processing unit 333 supplies the clock signal CK of the frequency F3 to the HF power supply 10.

[0023] The HF power supply 10 receives a clock signal CK generated by the clock generating unit 33. The HF power supply 10 generates a modulated fundamental signal corresponding to a second traveling wave voltage in response to the clock signal CK. The HF power supply 10 uses the modulated fundamental signal to generate a waveform signal having the same period as the period of the second traveling wave voltage (second high frequency voltage) output from the LF power supply 20. The HF power supply 10 uses this waveform signal to perform frequency modulation control of the first traveling wave voltage (first high frequency voltage) output from the HF power supply 10.

[0024] The HF power supply 10 has a direct digital synthesizer (DDS) 11, a phase setting section 12, a multiplier 13, a fundamental wave generating section 14, an adder 15, a direct digital synthesizer (DDS) 16, and an amplifier (AMP) 17.

[0025] The direct digital synthesis unit 11 receives the clock signal CK from the superposition matching unit 30 and receives the amplitude information from the HF power supply 10. The amplitude information is table information in which the amplitude for each clock timing is stored sequentially according to the frequency of the signal to be generated (for example, a sine wave signal), and is also called a frequency table. For example, when the frequency of the clock signal CK is F3 and the frequency of the signal to be generated is a second fundamental frequency F2, the amplitude information is table information in which (F3) / (F2)=N amplitudes are stored sequentially. The direct digital synthesis unit 11 uses the frequency information and the amplitude information to generate a modulated fundamental signal whose frequency is the same as the second fundamental frequency F2. This modulated fundamental signal is generated as, for example, a sine wave signal. The direct digital synthesis unit 11 supplies the modulated fundamental signal to the phase setting unit 12. The modulated fundamental signal is a signal equivalent to the second forward voltage generated by the LF power supply 20, and the period of the modulated fundamental signal is the same as the period of the second forward voltage.

[0026] The fundamental wave generating unit 14 generates a fundamental wave signal having a first fundamental frequency F1. The fundamental wave signal is generated, for example, as a sine wave signal. The fundamental wave generating unit 14 supplies the fundamental wave signal to the adder 15.

[0027] The phase setting unit 12 sets the phase at which modulation should start according to the modulated fundamental signal, and obtains a basic modulation amount normalized according to the set phase. For example, one period of the modulated fundamental signal is divided into multiple sections, and the basic modulation amount is calculated according to the occurrence rate of IMD in each section. The phase setting unit 12 supplies the basic modulation amount to the multiplier 13.

[0028] The multiplier 13 receives the basic modulation amount from the phase setting unit 12 and the modulation amount setting from the HF power supply 10. The modulation amount setting includes a gain for converting the basic modulation amount into a frequency change amount. The multiplier 13 multiplies the basic modulation amount by the modulation amount setting to obtain a frequency change amount ΔF. The multiplier 13 supplies the frequency change amount ΔF to the adder 15.

[0029] The adder 15 receives a fundamental signal having a first fundamental frequency F1, and also receives a frequency modulation amount ΔF. The adder 15 adds the frequency change amount to the fundamental signal to generate frequency information indicating the first fundamental frequency F1+ΔF. The adder 15 supplies the frequency information directly to the digital synthesis unit 16.

[0030] The direct digital synthesis unit 16 receives frequency information from the adder 15 and amplitude information from the HF power supply 10. Using the frequency information and the amplitude information, the direct digital synthesis unit 16 generates a high-frequency signal having a waveform in which a fundamental wave having a first fundamental frequency F1 is frequency-modulated by a frequency modulation amount ΔF. The direct digital synthesis unit 16 supplies the generated high-frequency signal to the amplification unit 17.

[0031] The amplifier 17 amplifies the high frequency signal output from the direct digital combiner 16. The amplifier 17 outputs the amplified high frequency signal (first traveling wave voltage) to the superposition matching device 30.

[0032] Next, the operation of the high frequency power supply device 1 will be described with reference to Fig. 2 to Fig. 4. Fig. 2 is a sequence chart showing the operation of the high frequency power supply device 1. Figs. 3 and 4 are waveform diagrams showing the operation of the high frequency power supply device 1.

[0033] The HF power supply 10 is previously set by inputting amplitude information (S0). The amplitude information is table information in which the amplitude for each clock timing is stored in sequence according to the frequency of the signal to be generated (e.g., a sine wave signal), and is also called a frequency table.

[0034] In response to a start-up command for the high frequency power supply device 1, the LF power supply 20 generates a second traveling wave voltage and outputs it to the superposition matching device 30 (S1).

[0035] Superimposing matching circuit 30 detects waveform signal SG2f of the second forward voltage output from LF power supply 20, and also detects waveform signal SG2r of the second reflected voltage reflected from matching circuit 322 (S2). Superimposing matching circuit 30 detects sinusoidal waveform signal SG2f having second fundamental frequency F2, as shown in Fig. 3(a), for example. For waveform signal SG2f, the periods from timing t1 to t17 and from timing t17 to t33 each correspond to one cycle corresponding to the fundamental cycle of LF power supply 20.

[0036] The superposition matching circuit 30 converts the waveform signal SG2f into a pulse signal (S3). The superposition matching circuit 30 may generate a pulse signal as shown in Fig. 3(b) by, for example, setting the signal to H level when the amplitude of the sine wave signal exceeds the amplitude center shown by the dotted line in Fig. 3(a) and setting the signal to L level when the amplitude falls below the amplitude center. The pulse signal has one cycle corresponding to the fundamental cycle of the LF power supply 20 in the periods t1 to t17 and t17 to t33.

[0037] The superposition matching device 30 multiplies the pulse signal having the second fundamental frequency F2 by N to generate a clock signal CK having a frequency F3 (S4). The relationship is F3=F2×N. The superposition matching device 30 multiplies the pulse signal shown in FIG. 3(b) by 8 to generate a clock signal CK shown in FIG. 3(c). In FIG. 3(c), for the sake of simplicity, N=8 is illustrated as an example, but in reality, the value satisfies the condition that the frequency F3 is at least twice the frequency of the first fundamental frequency F1 in the relationship F3=F2×N. The superposition matching device 30 outputs the clock signal CK to the HF power supply 10.

[0038] The HF power supply 10 generates a modulated fundamental signal in response to the clock signal CK (S5). The HF power supply 10 receives the clock signal CK shown in FIG. 4(a), for example. The HF power supply 10 refers to the amplitude information (frequency table) shown in FIG. 4(b) at each timing t1 to t36 synchronized with the clock signal CK, and generates a step-like signal as shown in FIG. 4(c). When the HF power supply 10 finishes referring to the amplitude for one period in the amplitude information (frequency table) at timing t1 to t16, it returns to the amplitude at the beginning of one period in the amplitude information (frequency table) at the next timing t17 and refers to it. This is repeated for each period of the sine wave. The HF power supply 10 smoothes the step-like signal shown in FIG. 4(c) to generate a sine-wave modulated fundamental signal as shown in FIG. 4(d).

[0039] The HF power supply 10 sets the phase at which modulation should start according to the modulated fundamental wave signal (S6), and obtains a fundamental modulation amount normalized according to the set phase. The HF power supply 10 multiplies the fundamental modulation amount by the modulation amount setting to obtain a frequency change amount ΔF (S7). The modulation amount setting includes a gain for converting the fundamental modulation amount into a frequency change amount. The HF power supply 10 adds the frequency change amount to the fundamental wave signal to generate frequency information indicating the first fundamental frequency F1+ΔF. As a result, the HF power supply 10 frequency-modulates the fundamental wave having the first fundamental frequency F1 with the frequency modulation amount ΔF (S8). The HF power supply 10 generates a first high-frequency voltage (first traveling wave voltage) using the frequency information and amplitude information, and outputs it to the superposition matching device 30 (S9).

[0040] Superposition matching device 30 detects waveform signal SG1f of a first forward voltage output from HF power supply 10, and detects waveform signal SG1r of a reflected voltage reflected from matching circuit 312 (S10). Superposition matching device 30 performs second impedance matching on the LF power supply 20 side and the lower electrode EL1 side in response to waveform signal SG2f and waveform signal SG2r detected in S2 (S11). In parallel with this, superposition matching device 30 performs first impedance matching on the HF power supply 10 side and the lower electrode EL1 side in response to waveform signal SG1f and waveform signal SG1r detected in S10 (S12). With the first impedance matching and the second impedance matching performed, the superposition matching device 30 receives the first traveling wave voltage from the HF power supply 10 and the second traveling wave voltage from the LF power supply 20, and superimposes the first traveling wave voltage (first high frequency power) and the second traveling wave voltage (second high frequency power) and supplies them to the lower electrode EL1 (S13).

[0041] As described above, in the present embodiment, in the high frequency power supply device 1, the superposition matching device 30 generates a clock signal CK in response to the second traveling wave voltage and supplies it to the HF power supply 10. The HF power supply 10 uses the modulated fundamental signal to generate a waveform signal having the same period as the period of the second traveling wave voltage (second high frequency voltage) output from the LF power supply 20. Using this waveform signal, the first traveling wave voltage (first high frequency voltage) output from the HF power supply 10 is frequency modulated and controlled.

[0042] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0043] 1 High frequency power supply 10 HF power supply (first power supply) 20 LF power supply (second power supply) 30 Superposition matcher (matching section) 311 Sensor (second detection unit) 312 Matching circuit (first matching circuit) 321 Sensor (first detection unit) 322 Matching circuit (second matching circuit) 332 Pulse conversion circuit (conversion section) 333 Multiplication Processing Unit (Multiplication Unit)

Claims

1. a first power supply that supplies a first high frequency power to a load by outputting a first high frequency voltage having a first fundamental frequency; a second power supply that supplies a second high frequency power to a load by outputting a second high frequency voltage having a second fundamental frequency lower than the first fundamental frequency; a matching unit connected to the first power supply and the second power supply, Equipped with the matching unit generates a clock signal having a frequency higher than the first fundamental frequency based on detection information of the second high frequency power, and supplies the clock signal to the first power supply; The first power supply uses the clock signal to generate a waveform signal having the same period as the period of the high frequency voltage output from the second power supply, and uses the waveform signal to perform frequency modulation control of the first high frequency voltage output from the first power supply.

2. 2. The high frequency power supply device according to claim 1, wherein the matching section extracts a pulse signal having the same period as the second fundamental frequency from the detection information of the second high frequency power, and generates the clock signal by multiplying the pulse signal.

3. The matching unit is a detection unit that detects the second high frequency voltage and outputs a detected waveform signal; A conversion unit that converts the detected waveform signal into the pulse signal; a multiplier unit that multiplies the pulse signal to generate the clock signal; 3. The high frequency power supply device according to claim 2, further comprising:

4. 4. The high frequency power supply device according to claim 1, wherein the clock frequency of the clock signal is at least twice as high as the first fundamental frequency.

Images