JP2015195158A - High-frequency power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-frequency power source that can improve reduction of detection precision of different frequency components whose frequencies are different from those of the fundamental waves of traveling waves and reflection waves based on the characteristic of a directional coupler.SOLUTION: With respect to preset different frequencies, an S parameter representing the transmission characteristic between the traveling and reflection waves transmitted through two input and output ports of an RF detector 24 and the traveling and reflection waves output from two detection ports is actually measured every different frequency in advance, and stored in a corrected data storage unit 274d. A different frequency detector 274 passes the traveling and reflection waves output from the RF detector 24 through BPFs 274a, 274b to extract different frequency components, and converts to the different frequency components of the traveling and reflection waves at the two input and output ports of the RF detector 24 through predetermined calculation processing using the extraction values and the S parameter of the different frequencies, thereby correcting the detection values of the different frequencies.

Description

  The present invention relates to a high-frequency power source used in a plasma processing system.

  A plasma processing system, for example, encloses a fluorine-based gas and a workpiece such as a semiconductor wafer or a liquid crystal substrate in a chamber of a plasma processing apparatus, and supplies high-frequency power from a high-frequency power source to a pair of electrodes in the chamber. This is a system in which discharge is performed and gas plasma is generated by the discharge to perform thin film formation processing or etching processing on a workpiece.

Conventionally, a plasma processing system of a type in which two high frequencies having different frequencies are superimposed and supplied to a plasma processing apparatus is known. The first frequency f ₁ and the second frequency f ₂ used in this plasma processing system are a combination of 40 MHz and 2 MHz, for example. The high frequency of the first frequency f ₁ is mainly used for generating plasma in the plasma processing apparatus, and the high frequency of the second frequency f ₂ is used as a bias for efficiently performing plasma processing.

In a plasma processing system that superimposes two types of high frequencies and supplies them to the plasma processing apparatus, when the high frequency power supply and the plasma processing apparatus are in an impedance mismatch state, high frequency reflection occurs in the plasma processing apparatus. The reflected wave enters the high frequency power source and adversely affects the amplifying element in the high frequency power source. The frequency component of the reflected wave includes a high-frequency fundamental wave and a harmonic wave output from the high-frequency power source and frequencies different from these frequencies. For example, when the first frequency f ₁ is 40 MHz and the second frequency f ₂ is 2 MHz, frequency components such as 40 ± 2 MHz and 40 ± 4 MHz are included.

In general, a high-frequency power supply is provided with a low-pass filter at an output stage in order to suppress output of a frequency component higher than a fundamental wave. When the first frequency f ₁ is 40 MHz and the second frequency f ₂ is 2 MHz, a high-frequency power source that outputs a high frequency of 2 MHz uses a low-pass filter to reflect a reflected wave or a fundamental frequency of 2 MHz higher than the fundamental frequency. Since a reflected wave having a frequency such as 40 ± 2 MHz or 40 ± 4 MHz close to can be blocked, the adverse effect of the reflected wave on the amplifying element is small. However, in a high frequency power source that outputs a high frequency of 40 MHz, a reflected wave having a harmonic of 2 MHz or a reflected wave having a frequency such as 40 ± 2 MHz or 40 ± 4 MHz cannot be blocked by a low-pass filter. There is a risk of entering the high frequency power source and destroying the amplifying element.

  Conventionally, as a method of reducing the adverse effect of the reflected wave on the amplification element, the total value of the traveling wave and the reflected wave is the maximum of the amplification element by detecting the level of the reflected wave and suppressing the output power according to the level. There is known output control (hereinafter referred to as “reflection protection control”) that does not exceed the rating (see Patent Document 1).

Specifically, as shown in FIG. 11, a directional coupler 105 is provided after the low-pass filter 104 of the high-frequency power supply 100, and (1) the traveling wave voltage v _f and the reflected wave voltage v are generated by the directional coupler 105. separating the _t input to the control unit 106 obtains the (2) and the forward power detector 106b in the control unit 106 and the respective forward power P _f in the reflected wave power detection unit 106c reflected power P _r, ( 3) The high-frequency output control unit 106d compares the total value P _m (= P _f + P _r ) of both powers with a preset reference value P _th and (4) the total value P _m exceeds the reference value P _th In this case, the control shifts to reflection protection control, and an output control command signal S _C for reducing the output power amount by an amount corresponding to the excess ΔP (= P _th −P _m ) is output to the DC-DC conversion unit 102. The process is performed. When the total value P _m does not exceed the reference value P _th , the traveling wave power P _fF of the fundamental wave detected by the traveling wave power detection unit 106 b matches the target output power P _set set by the output power setting unit 107. The normal output control for outputting the output control command signal S _C to the DC-DC converter 102 is performed.

  The AC-DC converter 101 is a block that generates a DC voltage from a commercial power supply and supplies the DC voltage to the DC-DC converter 102 as a drive voltage. The AC-DC converter 101 and the DC-DC converter 102 serve to supply DC power to the DC-RF converter 103. The DC-RF conversion unit 103 is configured by a switching amplifier, and converts DC power into high-frequency power by switching DC power with a high-frequency signal v input from the high-frequency control unit 106a in the control unit 106.

The traveling wave power detection unit 106b extracts the traveling wave voltage v _fF of the fundamental wave through the traveling wave voltage v _f output from the directional coupler 105 to a bandpass filter (BPF) having the fundamental frequency as the center frequency, The converter 110 detects the traveling wave power P _fF of the fundamental wave by a predetermined calculation process, and performs the same calculation process on the traveling wave voltage v _f output from the directional coupler 105. It fulfills the function of detecting the traveling wave power P _f including the fundamental wave and frequency components other than the fundamental wave. The reflected wave power detection unit 106c has the same configuration as that of the traveling wave power detection unit 106b, and uses the reflected wave voltage v _r output from the directional coupler 105, the reflected wave power P _rF of the fundamental wave, the fundamental wave, and the fundamental wave. It serves to detect the reflected power P _r that includes a frequency component other than.

Patent No. 5090986

In the configuration of FIG. 11, the directional coupler 105 is generally designed such that sufficient isolation characteristics are guaranteed for a narrow-band frequency range including a fundamental wave of high-frequency power output from the high-frequency power supply 100. Therefore, frequency components outside the above frequency range included in the traveling wave voltage v _f output from the directional coupler 105 do not have sufficient detection accuracy. The same applies to the frequency components other than the above frequency range included in the reflected wave voltage v _r outputted from the directional coupler 105.

Therefore, the detection accuracy of the levels of the traveling wave power P _f and the reflected wave power P _r detected by the traveling wave power detection unit 106b and the reflected wave power detection unit 106c, respectively, is the fundamental wave traveling wave power P _fF and the reflected wave power P Since it is lower than the detection accuracy of _rF , there is a problem that the protection accuracy by the reflection protection control using the traveling wave power P _f and the reflected wave power P _r is also lowered.

In particular, in a high frequency power source that supplies a high frequency of the first frequency f ₁ higher than the second frequency f ₂ to the plasma processing system using two types of high frequencies, the second frequency f is changed to the first frequency f ₁ in the case of impedance mismatch. returning to the high frequency power source ₂ from the frequency components (f ₁ + f ₂₎ and the first frequency f ₁ obtained by adding at a second frequency f ₂ obtained by subtracting the frequency components (f ₁ -f ₂₎ relatively high levels of reflected waves, etc. Therefore, if the detection accuracy of the reflected wave power _Pr of these frequency components is insufficient, the reflection protection control does not function sufficiently, and the semiconductor switch element in the DC-RF conversion unit 103 is damaged or destroyed. There is a risk of inviting.

In order to avoid this problem, a frequency component having a dominant level other than the fundamental wave (the primary harmonic, the second harmonic, the third harmonic, and the second frequency f ₂ are added to the first frequency f ₁ . A directional coupler 105 is provided for each frequency component (frequency component (f ₁ + f ₂ ) or frequency component (f ₁ -f ₂ ) obtained by subtracting the second frequency f ₂ from the first frequency f ₁ ). However, in this method, it is necessary to arrange a large number of directional couplers 105 in the subsequent stage of the low-pass filter 104, which is not practical in view of downsizing and cost reduction of the high-frequency power supply. It ’s difficult.

  The present invention has been made in view of the above problems, and by correcting the traveling wave and reflected wave of the frequency component other than the fundamental wave output from the directional coupler, the frequency component other than the fundamental wave is corrected. An object of the present invention is to provide a high frequency power source capable of suppressing a decrease in accuracy of the used output control.

  The high-frequency power source according to the present invention detects a high-frequency generation unit that generates a high frequency, a traveling wave from the high-frequency generation unit to the load, and a reflected wave from the load to the high-frequency generation unit at the subsequent stage of the high-frequency generation unit. For the predetermined different frequency different from the high-frequency detection means and the high-frequency fundamental wave, the traveling wave of the different frequency is extracted from the traveling wave detected by the high-frequency detection means, and the detected by the high-frequency detection means A different frequency extraction means for extracting the reflected wave of the different frequency from the reflected wave, and each of the different frequencies from the two input / output ports of the high frequency detection means acquired in advance. Matrix data indicating transmission characteristics between the two input waves input to the power detection means and the traveling wave and the reflected wave output from the high frequency detection means Matrix data storage means for storing, and performing predetermined arithmetic processing using the matrix data stored in the matrix data storage means for the traveling wave and reflected wave of the different frequency extracted by the different frequency extraction means, Correction means for correcting the traveling wave and the reflected wave of different frequencies to the traveling wave and the reflected wave respectively input from the two input / output ports of the high-frequency detection means is provided.

In the high-frequency power source, the high-frequency detection means includes a first port to which the high-frequency generated by the high-frequency generation means is input, a second port from which the high-frequency is output, and a third port that outputs the traveling wave. consists of a port and a directional coupler having a fourth port for outputting said reflected wave, said matrix data, different frequency f _n to be input the first, the second port to the directional coupler Are the input waves of a ₁ (f _n ) and a ₂ (f _n ), respectively, and the traveling wave and the reflected wave of different frequencies f _n output from the third and fourth ports are b ₃ (f _n ), b ₄ (f _n ), S ₃₁ (f _n ) = b ₃ (f _n ) / a ₁ (f _n ), S ₃₂ (f _n ) = b ₃ (f _n ) / a ₂ ( f _n ), S ₄₁ (f _n ) = b ₄ (f _n ) / a ₁ (f _n ), S ₄₂ (f _n ) = b ₄ (f _n ) / a ₂ (f _n ) Parameter, and the correction means is the different frequency. Different frequency f _n, respectively b ₃ traveling wave and a reflected wave of which is extracted by means output (f _n), when the b ₄ (f _n),
a ₁ (f _n ) = S ₁₃ (f _n ) · b ₃ (f _n ) + S ₁₄ (f _n ) · b ₄ (f _n ) (A1)
a ₂ (f _n ) = S ₂₃ (f _n ) · b ₃ (f _n ) + S ₂₄ (f _n ) · b ₄ (f _n ) (A2)
However, S ₁₃ (f _n ) = S ₄₂ (f _n ) / Δ (f _n ) (B1)
S ₂₃ (f _n ) = − S ₄₁ (f _n ) / Δ (f _n ) (B2)
S ₁₄ (f _n ) = − S ₃₂ (f _n ) / Δ (f _n ) (B3)
S ₂₄ (f _n ) = S ₃₁ (f _n ) / Δ (f _n ) (B4)
Δ (f _n ) = S ₃₁ (f _n ) · S ₄₂ (f _n ) + S ₃₂ (f _n ) · S ₄₁ (f _n ) (B5)
By calculating the different frequency f _n to be input to the second port of the first traveling wave a ₁ of different frequency f _n to be input to the port (f _n) and said high-frequency detecting means of the high-frequency detecting means The reflected wave a ₂ (f _n ) is preferably calculated (claim 2).

  In the high-frequency power source, the matrix data storage means may store measurement data obtained by actually measuring the S parameter of the high-frequency detection means.

In the above-described high frequency power source, the matrix data storage means has measured data S ₃₁ (f _n ), S ₃₂ (f _n ), S ₄₁ (f _n ), S ₄₂ ( f _n ) are converted into the components S ₁₃ (f _n ), S ₂₃ (f _n ), S ₁₄ (f _n ), and S ₂₄ (f _n ) obtained by converting the equations (B1) to (B5). The correction means uses the traveling wave b ₃ (f _n ) and the reflected wave b ₄ (f _n ) of the different frequency f _n extracted by the different frequency extraction means (A1). The traveling wave a ₁ (f _n ) and the reflected wave a ₂ (f _n ) of the different frequency f _n may be calculated by calculating the expression (A) and the expression (A2).

  In the high frequency power source described above, fundamental wave extracting means for extracting a component of the high frequency fundamental wave from the traveling wave and the reflected wave detected by the high frequency detecting means, and the correcting means among the predetermined different frequencies Different frequency determination means for determining the different frequency to be corrected in step (a), and the different frequencies determined by the traveling wave and reflected wave of the fundamental wave extracted by the fundamental wave extraction means and the different frequency determined by the different frequency determination means. Output control means for controlling the high frequency output from the high frequency generating means based on the corrected traveling wave and reflected wave calculated by the detecting means and the correcting means, and further comprising the different frequency determination The means is a traveling wave and a reflected wave input from two input / output ports of the high-frequency detection means by the different-frequency detection means and the correction means with respect to the predetermined different frequency at a predetermined cycle. A different frequency setting means for setting a different frequency to be corrected by the correction means, out of the predetermined different frequencies, based on a calculation means for calculating, and a calculation result of the calculation means and a threshold value of a preset different frequency level. (Claim 5).

  In the high frequency power source described above, the predetermined wave extracting means for extracting the component of the high frequency fundamental wave from the traveling wave and the reflected wave detected by the high frequency detecting means, respectively, and the predetermined frequency according to an instruction from an operator Of the different frequencies, the different frequency determining means for determining the different frequency to be corrected by the correcting means, and the traveling wave and reflected wave of the fundamental wave extracted by the fundamental wave extracting means and the different frequency determining means are determined. Output control means for controlling the high frequency output from the high frequency generation means, based on the corrected traveling wave and reflected wave calculated by the different frequency detection means and the correction means for different frequencies; The different frequency determination means is configured to detect the different frequency by the different frequency detection means and the correction means when the operator instructs the different frequency determination processing. The calculation means for calculating the traveling wave and the reflected wave input from the two input / output ports of the high frequency detection means, and the level of each different frequency is displayed so that the operator can monitor based on the calculation result of the calculation means. Different frequency display means, and different frequency setting means for setting different frequency information input from the operator based on the display of the different frequency display means to a different frequency to be corrected by the correction means. Claim 6).

  In the above high frequency power supply, the matrix data storage means stores the matrix data for a part of the predetermined different frequencies, and stores the different frequency matrix data not stored in the matrix data storage means. Matrix data interpolating means for interpolating by a predetermined interpolation operation using matrix data stored in the matrix data storing means, and the correcting means is a traveling wave of a different frequency that is not stored in the matrix data storing means. When the reflected wave and the reflected wave are corrected, the matrix data interpolating means interpolates the matrix data of the different frequency and corrects the traveling wave and reflected wave of the different frequency using the interpolated value.

  According to the present invention, the different frequency traveling wave detected by the high frequency detecting means and the different frequency extracting means includes a reflected wave having a different frequency due to the frequency characteristic separating the traveling wave and the reflected wave of the high frequency detecting means. However, the detection value of the traveling wave of the different frequency is corrected by using the matrix data of the different frequency acquired in advance to convert it to the traveling wave of the different frequency that does not include the reflected wave of the different frequency. The same applies to the reflected wave of the different frequency detected by the high frequency detection means and the different frequency extraction means. For the detected value of the reflected wave, the traveling wave of the different frequency is obtained using the matrix data of the different frequency acquired in advance. Correction for conversion to a reflected wave of a different frequency not included is performed.

For example, the detected values of the traveling wave and the reflected wave of the different frequency f _n are b ₃ (f _n ) and b ₄ (f _n ), respectively, and the matrix data of the different frequency f _n are S ₃₁ (f _n ) and S ₃₂ ( f _n ), S ₄₁ (f _n ), S ₄₂ (f _n )
a ₁ (f _n ) = S ₁₃ (f _n ) · b ₃ (f _n ) + S ₁₄ (f _n ) · b ₄ (f _n ) (A1)
a ₂ (f _n ) = S ₂₃ (f _n ) · b ₃ (f _n ) + S ₂₄ (f _n ) · b ₄ (f _n ) (A2)
However, S ₁₃ (f _n ) = S ₄₂ (f _n ) / Δ (f _n ) (B1)
S ₂₃ (f _n ) = − S ₄₁ (f _n ) / Δ (f _n ) (B2)
S ₁₄ (f _n ) = − S ₃₂ (f _n ) / Δ (f _n ) (B3)
S ₂₄ (f _n ) = S ₃₁ (f _n ) / Δ (f _n ) (B4)
Δ (f _n ) = (S ₃₁ · S ₄₂ + S ₃₂ · S ₄₁ ) (B5)
, The detected values b ₃ (f _n ) and b ₄ (f _n ) are obtained from the traveling wave a ₁ (f _n ) of the different frequency f _n input from the first port to the high frequency detecting means and the second value. To the reflected wave a ₂ (f _n ) of the different frequency f _n inputted to the high frequency detecting means from the other port.

Traveling wave a ₁ of different frequency f _n (f _n) is the high-frequency generating means reflected waves a ₂ input to the high-frequency detecting means from the wave that does not contain components (f _n) (estimated value), different frequency f _n since the reflected wave a ₂ (f _n) is a progressive wave a ₁ inputted from the load side to the high-frequency detecting means waves do not contain components (f _n) (estimated value), the traveling wave of a different frequency f _n The detection accuracy of the reflected wave can be increased. As a result, when high-frequency output control is performed using detection values of high-frequency fundamental waves and different frequencies, the accuracy of high-frequency output control can be improved without complicating or increasing the size of the configuration of the high-frequency power supply. .

  Also, instead of correcting the traveling wave and reflected wave for all of the predetermined different frequencies, the different frequencies to be corrected are set automatically or by the operator's operation, and only the set different frequencies are advanced. Since the correction process of the wave and the reflected wave is performed, the burden of the correction process can be reduced.

  Further, matrix data is stored in the matrix data storage means for a part of the predetermined different frequencies, and the remaining matrix data is calculated by a predetermined interpolation operation using the matrix data stored in the matrix data storage means. With the configuration, the storage capacity of the matrix data storage means can be reduced.

It is a figure which shows the structure of the plasma processing system to which the high frequency power supply which concerns on this invention is applied. It is a block diagram which shows the internal structure of the high frequency power supply which concerns on invention. It is a figure which shows the circuit example of a DC-RF conversion part. It is a figure for demonstrating the transmission characteristic of the bidirectional | two-way coupler used for RF detection part. It is a figure which shows the memory content of the correction data in a correction data storage part. It is a flowchart which shows the control procedure of the output power in RF power control part. It is a flowchart which shows the modification of the control procedure of the output power in RF power control part. It is a flowchart which shows the process sequence of the "setting of the different frequency to extract" of FIG. It is a figure which shows the correction point of the modification of the flowchart of FIG. It is a block diagram which shows the internal structure of the high frequency power supply corresponding to the modification of the flowchart of FIG. It is a figure which shows an example of the circuit block of the conventional high frequency power supply.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In particular, a high frequency power supply applied to a plasma processing system will be described as an example.

  FIG. 1 is a diagram illustrating a configuration of a plasma processing system. FIG. 2 is a block diagram showing the internal configuration of the high-frequency power supply according to the present invention.

The basic configuration of the plasma processing system 1 includes a high-frequency power source 2, an impedance matching device 3, a plasma processing device 4, and a system control unit 5. In the present embodiment, the high frequency power supply 2 is designed to output high frequency power with optimum power transmission efficiency when a load of 50 [Ω] is connected. The coaxial cable 6 having an impedance Z _o of 50 [Ω] is connected to the input port of the impedance matching device 3. On the other hand, the plasma processing apparatus 4 is connected so as to be directly connected to the output port of the impedance matching apparatus 3.

  For example, the plasma processing apparatus 4 encloses a fluorine-based gas and a workpiece such as a semiconductor wafer or a liquid crystal substrate in a chamber, supplies high-frequency power to the chamber, generates plasma, and uses the plasma. An apparatus for performing a thin film forming process or an etching process on a workpiece. Although not shown, the plasma processing apparatus 4 includes a hermetically sealed chamber that encloses a gas and a workpiece, a decompression pump that adjusts the gas pressure in the chamber, and high-frequency power supplied from the high-frequency power source 2. A pair of electrodes to be discharged is provided.

When high-frequency power is supplied from the high-frequency power source 2, the plasma processing apparatus 4 discharges the high-frequency power between the pair of electrodes to bring the gas sealed in the chamber into a plasma state, and uses the plasma to perform etching or the like. Process. The plasma processing apparatus 4 has an impedance Z _L = R _L + j · X _L (hereinafter referred to as “load”) when the plasma processing apparatus 4 side is viewed from the input end of the plasma processing apparatus 4 between the start and end of the plasma processing. The impedance Z _L ") fluctuates greatly. Predetermined plasma treatment to provide a plasma processing apparatus 4 at optimum power transfer efficiency high-frequency power outputted from the high frequency power source 2, for 50 [Omega] the load impedance Z _L according to the fluctuation of the load impedance Z _L An impedance matching device 3 is provided for converting to the impedance matching range.

  Although not shown, the impedance matching device 3 includes, for example, a configuration disclosed in Japanese Patent Application Laid-Open No. 2007-295447. That is, the impedance matching device 3 includes an impedance matching circuit in which a series circuit of a first variable capacitor and an inductor and a second variable capacitor are connected in an inverted L shape, and a high frequency voltage (RF voltage) at an input port of the impedance matching device 3. , An RF detector for detecting a phase difference between the high-frequency current (RF current), the FR voltage and the RF current, and a control unit for controlling the capacitance values of the first and second variable capacitors to perform an impedance conversion operation. It is a configuration.

The impedance matching device 3 calculates the impedance Z ₁ when the load side is viewed from the input port based on the detection value of the RF detector in the control unit, and the calculated value is a predetermined impedance matching range (reflection coefficient) with respect to 50 [Ω]. Each capacitance value (or each adjustment position) of the first and second variable capacitors is controlled so as to be within a predetermined reference value. The impedance matching device 3 performs impedance matching between the high-frequency power source 2 and the plasma processing device 4 by the control unit changing the capacitance value of each variable capacitor to the capacitance value in the impedance matching range.

The system control unit 5 is a control unit that comprehensively controls the operation of the entire plasma processing system 1. The system control unit 5 acquires transmission characteristic data (data such as load impedance Z _L ) at the input port of the plasma processing apparatus 4 with the control unit in the impedance matching apparatus 3, and uses the data to obtain plasma The operation state of the processing system 1 is monitored, the occurrence of abnormality is detected, the result of plasma processing is predicted, and the like. For example, when detecting the occurrence of an abnormality, the system control unit 5 notifies the abnormality by a not-illustrated notifying means such as a message display or an alarm sound, or outputs a stop signal to the high frequency power source 2 to stop the output of the high frequency power. Or

  The high-frequency power supply 2 is configured by a switching power supply that generates a high-frequency signal and amplifies and outputs the high-frequency signal with a switching amplifier composed of, for example, a class D amplifier. As shown in FIG. 2, the high-frequency power source 2 includes an AC-DC converter 21, a DC-DC converter 22, a DC-RF converter 23, an RF detector 24, a drive signal generator 25, a high-frequency generator 26, and The RF power control unit 27 is included.

AC-DC converter 21 generates an input voltage (DC voltage) V _cc from the commercial power supply to the DC-DC converter 22. For example, the AC-DC converter 21 performs full-wave rectification on a commercial voltage (for example, AC 200 [V]) input from a commercial power source by a rectifier circuit in which four semiconductor rectifier elements are bridge-connected, and the level after rectification is obtained. It is constituted by a known power supply circuit that generates a DC voltage _Vcc by smoothing with a smoothing circuit.

The DC-DC converter 22 converts the DC voltage Vcc input from the AC-DC converter 21 into a DC voltage _Vdc having an arbitrary voltage value and inputs the DC voltage _Vcc to the DC-RF converter 23. A DC voltage detection unit 28 </ b> A and a DC current detection unit 28 </ b> B are provided at the subsequent stage of the DC-DC conversion unit 22. Both detected values V _dc and I _dc of the DC voltage detector 28A and the DC current detector 28B are input to the RF power controller 27 in order to calculate the DC power P _dc output from the DC-DC converter 22. .

Since the impedance when the load side is viewed from the high-frequency power source 2 can be practically regarded as the impedance when the load side is viewed from the DC-RF conversion unit 23, the impedance of the load connected to the DC-RF conversion unit 23 is “ Z ”, and the coefficient determined by the operating state of the DC-RF converter 23 is“ K ”, the output voltage V _{dc of the} DC-DC converter 22 and the output power P _out of the DC-RF converter 23 Is
P _out = K × (V _dc ² / | Z |) (1)
There is a relationship. In a state where the impedance Z is controlled within a predetermined impedance matching range with respect to 50 [Ω] by the impedance matching device 3, the output power P _out of the DC-RF conversion unit 23 is expressed by the equation (1) as the DC-DC conversion unit 22. _Is proportional to the square of the output voltage _Vdc .

Since the output power P _out of the DC-RF converter 23 is determined by the output voltage V _dc of the DC-DC converter 22 from the equation (1), the RF power controller 27 outputs the output voltage V of the DC-DC converter 22. _The output power _Pout output from the DC-RF converter 23 is controlled by changing _dc . In the present embodiment, the RF power control unit 27 controls the output power _Pout of the DC-RF conversion unit 23 by the traveling wave power constant control method and the loss reduction control method.

The control by the traveling wave constant power control method is a control for matching the output power P _out output from the DC-RF converter 23 with a preset target value P _set . The target value P _set is _set in the RF power control unit 27 by an input operation by an operator or a preset program. At the output port of the high frequency power source 2, there are traveling wave power P _f that travels from the high frequency power source 2 to the plasma processing apparatus 4 and reflected wave power _{Pr that} is reflected by the plasma processing apparatus 4 and returns to the high frequency power source 2. Since the output power P _out of the DC-RF conversion unit 23 corresponds to the traveling wave power P _f at the output port of the high-frequency power supply 2, hereinafter, the sign of the output power of the DC-RF conversion unit 23 is used to avoid confusion. Indicated as “P _f ”.

The traveling wave power P _f and the reflected wave power _Pr include components of frequencies other than the fundamental wave (hereinafter, this frequency is referred to as “different frequency”), but according to the traveling wave power constant control method of the present embodiment. In the control, as described later, there is a control for making the traveling wave power P _fF of the fundamental wave (subscript “F” indicates that of the fundamental wave; the same _applies hereinafter) to the target value P _set . Done.

The traveling wave power P _fF is obtained by extracting the traveling wave voltage v _fF of the fundamental wave from the traveling wave voltage v _f detected by the RF detection unit 24 when the impedance of the RF detection unit 24 is 50 [Ω]. It is calculated by the calculation of P _fF = v _fF ^2/50 using the voltage v _fF.

The control by the loss reduction control method is control for suppressing the power loss P _loss in the DC-RF conversion unit 23 to be equal to or less than a preset reference value P _k . The reference value P _{k is} also set in the RF power control unit 27 by an input operation by an operator or a preset program. The power loss P _loss is
P _loss = P _dc − (P _f −P _r ) (2)
Or
P _loss = P _dc -P _f (3)
It is calculated by calculating.

DC power P _dc is calculated by multiplication of the detected value I _dc between the detection value V _dc of the DC voltage detection unit 28A DC current detector 28B. It reflected power P _r and forward power P _f, using a reflected wave voltage v _r and the traveling wave voltage v _f detected by the RF detector ^{_{24, P f = v f 2}} /50, P r = v r It is calculated by calculating the ^2/50. Specific output control by the traveling wave power constant control method and the loss reduction control method of the RF power control unit 27 will be described later.

For example, the DC-DC converter 22 includes a known DC-DC converter in which a rectification / smoothing circuit is combined with an inverter composed of a full bridge circuit in which four semiconductor switch elements are bridge-connected. Output voltage V _dc of the DC-DC converter 22, the on-off operation of the four semiconductor switching elements in the drive signal S _d supplied from the driving signal generator 25 is controlled by being controlled.

The DC-RF converter 23 converts the DC power P _dc input from the DC-DC converter 3 into a high-frequency power P _fF having a preset frequency f _F and outputs it. The frequency f _F of the high frequency power P _{fF is} a frequency defined for plasma processing such as 2.0 MHz, 13.56 MHz, 27.12 MHz, 40.0 MHz, and the like.

The DC-RF conversion unit 23 is constituted by, for example, a half-bridge type switching amplifier shown in FIG. Drive switching amplifier shown in the figure, the input switching circuit with a series circuit of two identical types of semiconductor switching elements Q _B between the pair of power terminals b, b ', a drive signal to the switching circuit The circuit includes an output circuit that outputs a high-frequency signal output from the switching circuit to the outside.

  The drive circuit is composed of a transformer T in which two secondary windings wound in opposite directions to the primary winding are coupled. A high frequency signal v applied from the high frequency generator 26 is input to the primary winding of the transformer T, and a high frequency in phase with the high frequency signal v from one secondary winding (upper winding in FIG. 3) of the transformer T. A signal v ′ is output, and a high-frequency signal −v ′ having a phase opposite to that of the high-frequency signal v is output from the other secondary winding (lower winding in FIG. 3) of the transformer T.

The output circuit includes a filter circuit 231 in which a resonance circuit in which a capacitor C ₁ and an inductor are connected in series, and an impedance conversion circuit in which the inductor and the capacitor C ₂ are connected in an L shape are connected. The inductor L in FIG. 3 is a combination of an inductor of a resonance circuit and an inductor of an impedance conversion circuit. The filter circuit 231 removes a DC component and an unnecessary high frequency component (noise component) from the high frequency signal output from the switching circuit. The high frequency signal v _out output from the filter circuit 231 is output to the load.

N-channel MOSFETs are used for the pair of semiconductor switching elements Q _B , but other types of transistors such as bipolar transistors can be used. Further, the pair of semiconductor switch elements Q _B may be a complementary type in which an N channel type and a P channel type are combined. In this case, the transformer T may have only one secondary winding, and the high-frequency voltage v ′ may be input to the gates of the N-channel MOSFET and P-channel MOSFET, respectively.

  In the present embodiment, the DC-RF conversion unit 23 is configured with a half-bridge type switching amplifier, but may be configured with a full-bridge type or push-pull type switching amplifier.

A high-frequency signal v (voltage signal; hereinafter referred to as “high-frequency voltage” if necessary) input to the primary winding of the transformer T is represented by v = A · sin (2πf _F · t) (f _F : fundamental frequency) ), The DC-RF converter 23 outputs an in-phase high-frequency voltage v ′ = A ′ · sin (2πf _F · t) from one secondary winding of the transformer T, and the other secondary of the transformer T A high-frequency voltage -v '=-A' · sin (2πf _F · t) having an opposite phase is output from the winding. Phase high frequency voltage v 'is input to one of the semiconductor switching element Q _B (semiconductor switching elements of the upper in FIG. 3 Q _B), the other high-frequency voltage -v reverse phase' of the other semiconductor switching element Q _B (In FIG. 3, the lower semiconductor switch element Q _B ). Since the two semiconductor switch elements Q _B are N-channel MOSFETs, one semiconductor switch element Q _B is turned on during the high level period of the high frequency voltage v ′, and the other semiconductor switch element Q _B is a high frequency The on-operation is performed during a high level period of the voltage −v ′. That is, the two semiconductor switch elements Q _B repeat the on / off operation alternately every half cycle of the high-frequency voltage v ′.

A ≦ 0 period to the ground level '"V_dc" and, v the duration of>0' voltage v _a is v connection point a by the two semiconductor switching elements Q _B is repeatedly turned on and off alternately operate In this way, the rectangular wave is removed by the filter circuit 231 from the DC component and the switching noise, and a high frequency voltage v _out = V · sin (2πf _F · t + φ) is output from the output terminals c and c ′. . The high-frequency voltage _vout is a voltage obtained by amplifying the sine wave high-frequency voltage v.

For example, the RF detection unit 24 includes a bidirectional coupler having a characteristic impedance of 50 [Ω] and including a frequency f _F in a usable frequency band. For example, when the frequency f _F is 13.56 [MHz], the frequency band of the RF detection unit 24 is designed to be a predetermined frequency band f _o ± Δf [MHz] with 13.56 [MHz] as the center frequency f _o. Has been. In the RF detection unit 24, the high-frequency voltage at the output port of the high-frequency power source 2 is separated into the traveling wave voltage v _f and the reflected wave voltage v _r and is output and input to the RF power control unit 27. The traveling wave voltage v _f and the reflected wave voltage v _r detected by the RF detection unit 24 are used by the RF power control unit 27 to calculate the traveling wave power P _f and the reflected wave power P _r at the output port of the high frequency power supply 2. .

Drive signal generator 25, as the drive signal S _d, for example, generates a pulse width modulation (PWM) signal by the triangular wave comparison method. The drive signal generation unit 25 includes, for example, a carrier signal generation circuit configured by a direct digital synthesizer and a PWM signal generation circuit configured by a level comparator such as a comparator. Drive signal generating unit 25, for example, by comparing the level of the control command value C _o inputted from the carrier signal C _c and the RF power control unit 27 of the sawtooth wave generated by the carrier signal generating circuit by the level comparator C _c A first pulse width modulation signal having a pulse width in the period of ≦ C _o is generated, and the first pulse width modulation signal is output to the DC-DC converter 22. Further, the drive signal generation unit 25 inverts the level of the first pulse width modulation signal, generates a second pulse width modulation signal in which the pulse width of each pulse is adjusted with a predetermined dead time, and the second pulse width modulation signal is generated. The pulse width modulation signal is output to the DC-DC converter 22.

The two semiconductor switch elements located on the high side and the low side of the first arm of the full bridge circuit in the DC-DC converter 22 are defined as a first semiconductor switch element and a second semiconductor switch element, and the second arm Assuming that the two semiconductor switch elements located on the high side and the low side are the third semiconductor switch element and the fourth semiconductor switch element, the first pulse width modulation signal is the first semiconductor switch element and the fourth semiconductor switch element. a drive signal S _d to the switch element, a second pulse width modulation signal is a drive signal S _d for the second semiconductor switching element and the third semiconductor switching element.

In the DC-DC converter 22, the on / off operation of the first and fourth semiconductor switch elements and the on / off operation of the second and third semiconductor switch elements are alternately repeated, and a rectangular wave is generated from the full bridge circuit. AC voltage is output. Then, the AC voltage is full-wave rectified by a rectifying / smoothing circuit, leveling is performed, and a DC voltage V _dc is output from the DC-DC converter 22.

The high frequency generation unit 26 is configured by, for example, a direct digital synthesizer. The high-frequency generation unit 26 is based on high-frequency information (information such as frequency f _F , amplitude A, initial phase φ, etc.) input from the RF power control unit 27, and the semiconductor switch element Q _{B in} the DC-RF conversion unit 23. A high-frequency voltage v = A · sin (2πf _F · t + φ) for controlling driving is generated and output to the DC-RF converter 23.

RF power control unit 27 controls the output power P _fF of the high frequency power source 2, the semiconductor switching element in the DC-RF converter 23 according to the reflected power P _r is reverse input from the output port of the high frequency power source 2 Q _B Control to prevent damage (hereinafter referred to as “reflection protection control”). The RF power control unit 27 includes a microcomputer including a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The RF power control unit 27 may be configured by an arithmetic device such as an FPGA (field-programmable gate array).

The RF power control unit 27 includes a direct current control unit 271 that controls the output voltage V _dc of the DC-DC conversion unit 22 as a processing function, and a high frequency control unit that controls the high frequency voltage v _out output from the DC-RF conversion unit 23. 272, a fundamental wave detection unit 273 that detects components v _fF and v _rF of the fundamental wave f _F of the traveling wave voltage v _f and the reflected wave voltage v _r detected by the RF detection unit 24, and a detection by the RF detection unit 24 Components v _fn and v _rn (subscript n) of the frequency f _n (hereinafter referred to as “different frequency f _n ”) other than the fundamental wave f _{F of} the traveling wave voltage v _f and the reflected wave voltage v _r . Indicates that when N different frequencies f _n are extracted, they correspond to numbers n (= 1, 2,..., N) assigned to identify the different frequencies f _n . The same applies to other codes.

It should be noted that the high frequency voltage v _out is equivalent to the traveling wave voltage v _fF. Further, the components v _fn and v _rn of the different frequency f _n of the traveling wave voltage v _f and the reflected wave voltage v _r are frequency components other than the fundamental wave f _F. The different frequency components include harmonic components such as a first harmonic and a second harmonic. When two high frequency powers having different frequencies are input to the plasma processing system 1, the two frequencies f ₁ and f _{2 are used.} Frequency components such as the difference frequency (f ₁ −f ₂ ) and the sum frequency (f ₁ + f ₂ ) are also included.

The DC controller 271 is a functional block that controls the DC voltage V _dc output from the DC-DC converter 22 by controlling the control command value _Co input to the drive signal generator 25 by feedback control. In this control, the control command value _Co is controlled by the above-described traveling wave constant power control method, loss reduction control method, and reflection protection control. The DC controller 271 includes a DC power calculator 271 a that calculates the DC power P _dc output from the DC-DC converter 22 and a traveling wave power P _fF of the fundamental wave f _F output from the DC-RF converter 23. forward power P _fn and reflected power of different frequency f _n of different frequency f _n to be output from the fundamental wave power calculating unit 271b, DC-RF converter 23 which calculates the reflected power P _rF of the fundamental wave f _F A different frequency power calculation unit 271c that calculates P _rn and a control command value generation unit 271d are included.

The DC power calculation unit 271a calculates the DC power P _dc (= V _dc × I _dc ) by multiplying the detection values V _dc and I _dc input from the DC voltage detection unit 28A and the DC current detection unit 28B. The fundamental wave power calculator 271b outputs the traveling wave voltage v _fF of the fundamental wave f _{F and} the reflected wave voltage v _{rF of the} fundamental wave f _F output from the fundamental wave detector 273 and the characteristic impedance Z _o (50 [Omega]) and computes the forward power P _fF of the fundamental wave ^{_{f F (= v fF 2/}} 50) and the reflected wave power of the fundamental wave _{f F P rF (= v rF} 2/50) from.

The different frequency power calculation unit 271c outputs the traveling wave voltage v _fn and the reflected wave voltage v _{rn of} each different frequency f _n output from the different frequency detection unit 274 and the characteristic impedance Z _o (50 [Ω]) of the RF detection unit 24. calculating a forward power ^{_{P fn (= v fn 2/}} 50) and the reflected wave power ^{_{P rn (= v rn 2/}} 50) for each different frequency f _n of the different frequency f _n and a.

The control command value generation unit 271d calculates the difference ΔP _fF (= P _set −P _fF ) of the traveling wave power P _fF of the fundamental wave f _F calculated by the fundamental wave power calculation unit 271b with respect to the preset target value P _set . The control command value _Co is generated by calculating and performing a predetermined PI compensation process on the difference _PfF . This control command value C _o is a control command value for generating a drive signal S _d that makes the difference ΔP _fF zero. That is, the control command value C _o is the RF power control unit 27 in order to maintain the forward power P _fF of the fundamental wave f _F outputted from the DC-RF converter 23 by the feedback control to the target value P _{The set} DC- This is a control command value input to the RF conversion unit 23 (RF output control by the traveling wave power constant control method).

The control command value generator 271d includes the DC power P _dc calculated by the DC power calculator 271a, the traveling wave power P _fF of the fundamental wave f _F and the reflected wave power P _rF calculated by the fundamental wave calculator 271b. Using the traveling wave power P _fn of each different frequency f _n calculated by the different frequency power calculation unit 271c and the fundamental wave components P _fF and P _{rF of the} reflected wave power P _rn , the power in the DC-RF conversion unit 23 The loss P _loss is calculated. The control command value generation unit 271d adds the traveling wave power P _fF of the fundamental wave f _F and the traveling wave power P _fn of each different frequency f _n to add the traveling wave power P _f (= P _fF + ΣP _fn (n = 1, 2,..., N)), and the reflected wave power P _rF of the fundamental wave f _F and the reflected wave power P _rn of each different frequency f _n are added to determine the reflected wave power P _r (= P _rF + ΣP _rn ( n = 1, 2,..., N)), and the power loss P _loss is calculated by calculating the formula (2) or (3) using both the powers P _f and P _r .

The control command value generation unit 271d compares the calculated power loss P _loss with a preset reference value P _k, and if P _loss ≦ P _k , the control command value C _o generated by the control command value generation unit 271d. Is output to the drive signal generator 25. On the other hand, if P _k <P _loss , the control command value generation unit 271d calculates a difference ΔP _loss (= P _k −P _loss ) of the power loss P _loss with respect to the threshold P _{th and} uses the difference ΔP _loss as a fundamental wave. After the traveling wave power P _fF of f _F is corrected, a predetermined PI compensation process is performed to generate a control command value C _o ′, and the control command value C _o ′ is output to the drive signal generator 25. This control command value C _o ′ is a control command value for generating the drive signal S _d that makes the power loss P _loss equal to or less than the threshold value P _k (RF output control by the loss reduction control method).

Further, the control command value generation unit 271d adds the calculated traveling wave power P _f and the reflected wave power P _r and presets the power value P (= P _f + P _r = P _fF + P _rF + ΣP _fn + ΣP _rn ). It has been compared with the reference value P _h, if P ≦ P _h, and outputs the control command value C _o generated by the control command value generating unit 271d to the drive signal generator 25. On the other hand, if P _h <P, the control command value generation unit 271d calculates a difference ΔP (= P _h −P) of the power value P with respect to the reference value P _h , and the progression of the fundamental wave f _{F with} the difference ΔP. After correcting the wave power P _fF , a predetermined PI compensation process is performed to generate a control command value C _o ″, and the control command value C _o ″ is output to the drive signal generator 25. This control command value C _o ″ is a control command value for generating a drive signal S _d that makes the power value P equal to or less than the reference value P _h (RF output control by reflection protection control).

The high frequency control unit 272 is a functional block that controls high frequency information input to the high frequency generation unit 26 to control the waveform of the traveling wave voltage v _fF output from the DC-RF conversion unit 23. The high frequency controller 272 inputs the parameter information of the amplitude A, the frequency f _F , and the initial phase φ of the high frequency voltage v generated by the high frequency generator 26 to the high frequency generator 26.

The fundamental wave detection unit 273 is a functional block that extracts the traveling wave voltage v _fF and the reflected wave voltage v _rF of the fundamental wave f _F from the traveling wave voltage v _f and the reflected wave voltage v _r detected by the RF detection unit 24. . The fundamental wave detection unit 273 includes two digital bandpass filters 273a and 273b (hereinafter referred to as “BPF273a” and “BPF273b”) having the fundamental wave f _F as a center frequency. The BPF 273a and the BPF 273b are configured by, for example, an IIR (Infinite Impulse Response) filter or an active filter (adaptive filter). The fundamental wave detection unit 273 extracts the traveling wave voltage v _fF of the fundamental wave f _F by performing filtering calculation processing with the BPF 273a on the traveling wave voltage v _f detected by the RF detection unit 24, and the RF detection unit 24. The reflected wave voltage v _rF of the fundamental wave f _F is extracted by performing filtering operation processing with the BPF 273b on the reflected wave voltage v _r detected in step (b).

Different frequency detecting unit 274 is a functional block for extracting a reflected wave voltage v _rn traveling wave voltage v _fn of different frequency f _n from the traveling wave voltage v _f and the reflected wave voltage v _r detected by the RF detector 24 . Different frequency detecting unit 274, for each different frequency f _n, for different frequency _{f n (n = 1,2, ...} N) and BPF274a for traveling wave having a center frequency of a center frequency different frequency f _n reflection BPF 274b for waves, different frequency correction unit 274c for correcting traveling wave voltage v _fn and reflected wave voltage v _rn detected by BPF 274a and BPF 274b, and correction data storage for storing correction data used by different frequency correction unit 274c Part 274d.

Each _of BPF 274a _and BPF 274b includes N digital bandpass filters corresponding to N different frequencies f _n , but is not shown in FIG. The different frequency correction unit 274c and the correction data storage unit 274d are characteristic configurations of the high frequency power supply 2 according to the present embodiment.

The bidirectional coupler used in the RF detection unit 24 is designed to guarantee a predetermined detection accuracy for a certain frequency range including the fundamental wave f _F , but the frequency range is narrow band (fundamental wave f since _F is a several percent), different frequency f _n traveling wave voltage v _fn and reflected wave voltage v _rn for the fundamental wave f _F traveling wave voltage v _fF and reflected wave voltage v _rF and similar detection of Accuracy is not guaranteed. When you try to guarantee a similar detection accuracy and the fundamental wave f _F the reflected wave voltage v _rn traveling wave voltage v _fn of different frequency f _n, it is necessary to provide a bi-directional coupler for each different frequency f _n, When the number N of different frequencies _fn to be detected increases, bidirectional couplers are applied to all traveling wave voltages v _fn and reflected wave voltages v _rn (n = 1, 2,..., N) of all different frequencies. Providing it is impossible in terms of structure and cost.

Therefore, in the present embodiment, transmission characteristics (S parameters) for each different frequency f _n between the two input / output ports and the two detection ports of the bidirectional coupler used in the RF detection unit 24 are measured in advance. Place, and a progressive wave voltage v _f output from the two detection ports reflected wave voltage v _r and the traveling wave voltage v _fn different frequency f _n to detect the reflected wave voltage v _rn, as described below, the By using the detection values v _fn and v _rn and the transmission characteristics (S parameter), the traveling wave voltage v _fn and the reflected wave voltage v _rn of the different frequency f _{n at} the input / output port are obtained to ensure the detection accuracy. .

In the bidirectional coupler used in the RF detector 24, as shown in FIG. 4, the high frequency from the input port P ₁ to the output port P ₂ is referred to as “traveling wave”, and the output port P ₂ to the input port P ₁ . The high frequency that travels is referred to as a “reflected wave”, the high frequency that is transmitted through the transmission line on the input port P ₁ side is referred to as traveling wave a ₁ and the reflected wave b _1, and the high frequency that is transmitted through the transmission line at the output port P _{2 is 2} and reflected wave a ₂ . Further, a high frequency output from the first detection port P ₃ is a traveling wave b ₃ , and a high frequency output from the second detection port P ₄ is a reflected wave b ₄ .

Assuming that S parameter components indicating transmission characteristics between the input port P1 and the first and second detection ports P3 and P4 are S ₃₁ , S ₃₂ , S ₄₁ and S ₄₂ , the traveling wave a ₁ and the reflected wave b ₂ between the traveling wave b ₃ and the reflected wave b ₄
b ₃ = S ₃₁ · a ₁ + S ₃₂ · a ₂ (4)
b ₄ = S ₄₁ · a ₁ + S ₄₂ · a ₂ (5)
There is a relationship.

When the equations (4) and (5) are transformed into equations for obtaining the traveling wave a ₁ and the reflected wave a ₂ from the traveling wave b ₃ and the reflected wave b ₄ ,
a ₁ = S ₁₃ · b ₃ + S ₁₄ · b ₄ (6)
a ₂ = S ₂₃ · b ₃ + S ₂₄ · b ₄ (7)
However, S ₁₃ = S ₄₂ / Δ (8a)
S ₂₃ = −S ₄₁ / Δ (8b)
S ₁₄ = −S ₃₂ / Δ (8c)
S ₂₄ = S ₃₁ / Δ (8d)
Δ = S ₃₁ · S ₄₂ + S ₃₂ · S ₄₁ (8e)
It becomes.

In the equations (6) and (7), the S parameter (S ₃₁ , S ₃₂ , S ₄₁ , S ₄₂ ) or (S ₁₃ , S ₂₃ , S ₁₄ , S ₂₄ ) for each different frequency f _n is known. if component b ₃ different frequency f _n from the traveling wave b ₃ (f _n) ((f _n) is shown. below that is a component of a different frequency f _n, the same.) and different from the reflected wave b ₄ detecting the frequency f _n component b ₄ of (f _n), both detection values _{b 3 (f n), b} 4 (f n) and S parameters of different frequency _{f n (S 31 (f n} ), S 32 ( f _n ), S ₄₁ (f _n ), S ₄₂ (f _n )) or (S ₁₃ (f _n ), S ₂₃ (f _n ), S ₁₄ (f _n ), S ₂₄ (f _n )) (6) and (7) are calculated, the traveling wave a ₁ (f _n ) (estimated value) of the different frequency f _n transmitted through the transmission line on the input port P ₁ side and the output port P ₂ side are calculated. It shows that the reflected wave a ₂ (f _n ) (estimated value) of the different frequency f _n transmitted through the transmission line can be obtained.

In the frequency domain the different frequency f _n, because isolation characteristics of the bidirectional coupler is insufficient, to the traveling wave a ₁ (f _n) is the traveling wave b ₃ different frequency f _n (f _n) The reflected wave a ₂ (f _n ) is included at a rate that cannot be ignored, and the reflected wave b ₄ (f _n ) of the different frequency f _n is a traveling wave a at a rate that cannot be ignored relative to the reflected wave a ₂ (f _n ). ₁ (f _n ) is included. For this reason, the detection accuracy of the traveling wave b ₃ (f _n ) and the reflected wave b ₄ (f _n ) of the different frequency f _n is insufficient.

On the other hand, a traveling wave a ₁ of different frequency f _n (f _n) is an estimate of the traveling wave of a different frequency f _n to transmit the transmission line of the input port P ₁ side of the bidirectional coupler, different frequency f _n The reflected wave a ₂ (f _n ) is an estimated value of the reflected wave of the different frequency f _n transmitted through the transmission line on the output port P ₂ side of the bidirectional coupler. And has higher accuracy than the traveling wave b ₃ (f _n ) and the reflected wave b ₄ (f _n ). In the present embodiment, the detection value of the traveling wave b ₃ (f _n ) output from the first detection port P ₃ and the detection value of the reflected wave b ₄ (f _n ) output from the second detection port P ₄ the frequency S-parameters of _{f n (S 31 (f n} ), S 32 (f n), S 41 (f n), S 42 (f n)) or _{(S 13 (f n),} S 23 (f _n ), S ₁₄ (f _n ), S ₂₄ (f _n )) to correct the traveling wave a ₁ (f _n ) of the input port P ₁ and the reflected wave a ₂ (f _n ) of the output port P ₂ By doing so, the detection accuracy of the traveling wave voltage v _fn and the reflected wave voltage v _rn of the different frequency f _n is set to a reliable level.

As described above, in this embodiment, the S parameter (S ₃₁ (f _n ), S ₃₂ (f _n ), S ₄₁ (f _n ) for each different frequency f _n of the bidirectional coupler used in the RF detector 24 is used. ), S ₄₂ (f _n )) or (S ₁₃ (f _n ), S ₂₃ (f _n ), S ₁₄ (f _n ), S ₂₄ (f _n )), a network analyzer is used. For all the different frequencies f _n to be extracted, the S-parameters (S ₃₁ (f _n ), S ₃₂ (f _n ), S ₄₁ (f _n ), S ₄₂ (f _n ) of the bidirectional coupler are extracted. ) Or (S ₁₃ (f _n ), S ₂₃ (f _n ), S ₁₄ (f _n ), S ₂₄ (f _n )), and stores the correction data in association with each measured value corresponding to the different frequency f _n Stored in the unit 274d.

The S parameter component S ₃₁ connects the first port P _A and the second port P _B of the network analyzer to the input port P ₁ and the first detection port P ₃ of the bidirectional coupler, respectively. a reference frequency signal of a different frequency f _n which is output from the first port P _a inputted from the input port P ₁ to the bidirectional coupler, a high-frequency signal outputted from the first detection port P ₃ second port Measured with configuration input to P _B. Assuming that the reference high frequency signal of the different frequency f _n is “a ₁ (f _n )” and the high frequency signal output from the first detection port P ₃ is “b ₃ (f _n )”, the network analyzer uses b ₃ ( The component S ₃₁ (f _n ) is measured by calculating f _n ) / a ₁ (f _n ).

The S parameter component S ₄₁ connects the first port P _A and the second port P _B of the network analyzer to the input port P ₁ and the second detection port P ₄ of the bidirectional coupler, respectively. a reference frequency signal of a different frequency f _n which is output from the first port P _a inputted from the input port P ₁ to the bidirectional coupler, a high-frequency signal outputted from the second detection port P ₄ second port Measured with configuration input to P _B. Assuming that the reference high-frequency signal of the different frequency f _n is “a ₁ (f _n )” and the high-frequency signal output from the second detection port P ₄ is “b ₄ (f _n )”, the network analyzer uses b ₄ ( The component S ₄₁ (f _n ) is measured by calculating f _n ) / a ₁ (f _n ).

The S parameter component S ₃₂ connects the first port P _A and the second port P _B of the network analyzer to the output port P ₂ and the first detection port P ₃ of the bidirectional coupler, respectively. a reference frequency signal of a different frequency f _n output from first port P _a input from the output port P ₂ to the bidirectional coupler, a high-frequency signal outputted from the first detection port P ₃ second port Measured with configuration input to P _B. A reference frequency signal of different frequency f _n "a ₂ (f _n)", when the high frequency signal outputted from the second detection port P ₃ and "b ₃ (f _n)", b ₃ a network analyzer ( The component S ₃₂ (f _n ) is measured by calculating f _n ) / a ₂ (f _n ).

The S parameter component S ₄₂ connects the first port P _A and the second port P _B of the network analyzer to the output port P ₂ and the second detection port P ₄ of the bidirectional coupler, respectively. a reference frequency signal of a different frequency f _n which is output from the first port P _a input from the output port P ₂ to the bidirectional coupler, a high-frequency signal outputted from the second detection port P ₄ second port Measured with configuration input to P _B. Assuming that the reference high-frequency signal of the different frequency f _n is “a ₂ (f _n )” and the high-frequency signal output from the second detection port P ₄ is “b ₄ (f _n )”, the network analyzer uses b ₄ ( The component S ₄₂ (f _n ) is measured by calculating f _n ) / a ₂ (f _n ).

The S parameter (S ₃₁ (f _n ), S ₃₂ (f _n ), S ₄₁ (f _n ), S ₄₂ (f _n )) for each different frequency f _n measured by the network analyzer is an RF power control unit. 27 and stored in the correction data storage unit 274d in association with the different frequency f _n . Note that the RF power control unit 27 performs calculations of equations (8a) to (8e) to obtain S parameters (S ₃₁ (f _n ), S ₃₂ (f _n ), S ₄₁ (f _n ), S ₄₂ (f _n )) are converted into S parameters (S ₁₃ (f _n ), S ₂₃ (f _n ), S ₁₄ (f _n ), S ₂₄ (f _n )) and then associated with different frequencies f _n Then, it may be stored in the correction data storage unit 274d.

  FIG. 5 is an image diagram showing the contents of correction data (S parameter data) stored in the correction data storage unit 274d.

The correction data storage unit 274d is divided into N storage areas. Each storage area has a different frequency f _n and S parameters (S ₃₁ (f _n ), S ₃₂ (f _n ), S ₄₁ (f _n ), S ₄₂ (f _n )) is stored. The measured values of the different frequency f _n and the S parameter (S ₃₁ (f _n ), S ₃₂ (f _n ), S ₄₁ (f _n ), S ₄₂ (f _n )) are arranged in the order of the identification number and addressed to each storage area. They are stored in order. In FIG. 5, the measured values of the S parameter (S ₃₁ (f _n ), S ₃₂ (f _n ), S ₄₁ (f _n ), S ₄₂ (f _n )) are stored, but the S parameter (S ₃₁ (f _n ), S ₃₂ (f _n ), S ₄₁ (f _n ), S ₄₂ (f _n )) are changed to S parameters (S ₁₃ (f _n ), S ₂₃ (f _n ), S ₁₄ (f _n )) , S ₂₄ (f _n )) may be stored.

If the measured values of the S parameter (S ₃₁ (f _n ), S ₃₂ (f _n ), S ₄₁ (f _n ), S ₄₂ (f _n )) are directly stored in the correction data storage unit 274d, the correction data storage unit 274d First, the frequency correction unit 274c first sets S parameters (S ₃₁ (f _n ), S ₃₂ (f _n ), S ₄₁ (f _n )) corresponding to the different frequencies f _n of the traveling wave voltage v _fn and the reflected wave voltage v _rn. , S ₄₂ (f _n )) is read out from the correction data storage unit 274d, the equations (8a) to (8e) are calculated, and the S parameters (S ₃₁ (f _n ), S ₃₂ (f _n ), S ₄₁ ) are calculated. (f _n ), S ₄₂ (f _n )) are converted into S parameters (S ₁₃ (f _n ), S ₂₃ (f _n ), S ₁₄ (f _n ), S ₂₄ (f _n )). Thereafter, the different frequency correction unit 274c outputs the traveling wave voltage v _fn output from the BPF 274a, the reflected wave voltage v _rn output from the BPF 274b, and the S parameters (S ₁₃ (f _n ), S ₂₃ (f _n ), S ₁₄ (f _n ), S ₂₄ (f _n )) are used to calculate the equations (6) and (7), and the traveling wave of the different frequency f _n transmitted through the transmission line on the input port P ₁ side. Voltage v _fn ′ (estimated value) (corresponding to the above a ₁ (f _n )) and reflected wave voltage v _rn ′ (estimated value) of different frequency f _n transmitted through the transmission line on the output port P ₂ side (above a ₂ (f _n )).

On the other hand, when the converted S parameters (S ₁₃ (f _n ), S ₂₃ (f _n ), S ₁₄ (f _n ), S ₂₄ (f _n )) are stored in the correction data storage unit 274d, The different frequency correction unit 274c includes S parameters (S ₁₃ (f _n ), S ₂₃ (f _n ), S ₁₄ (f _n ), S ₁₄ corresponding to the different frequencies f _n of the traveling wave voltage v _fn and the reflected wave voltage v _rn . S ₂₄ (f _n )) is read from the correction data storage unit 274d, and its S parameters (S ₁₃ (f _n ), S ₂₃ (f _n ), S ₁₄ (f _n ), S ₂₄ (f _n )) are The transmission wave on the input port P ₁ side is transmitted by calculating the expressions (6) and (7) using the traveling wave voltage v _fn output from the BPF 274a and the reflected wave voltage v _rn output from the BPF 274b. to calculate the traveling wave voltage v _fn of different frequency f _n 'reflected wave voltage v _rn different frequency f _n to transmit transmission lines (estimated value) and the output port P ₂ side' (estimated value).

  Next, the control procedure of the output power in the RF power control unit 27 will be described using the flowchart of FIG.

  When the high frequency power supply 2 starts outputting high frequency power, the RF power control unit 27 repeats the control procedure of FIG. 6 at a predetermined cycle until the output is stopped.

When starting the control process, the RF power control unit 27 first _sets the output target value P _set of the high frequency power (S1). Subsequently, the RF power control unit 27 reads the DC voltage V _dc output from the DC voltage detection unit 28A and the DC current I _dc output from the DC current detection unit 28B, and the progress output from the RF detection unit 24. The wave voltage v _f and the reflected wave voltage v _r are read (S2). The RF power control unit 27 calculates the DC power P _dc supplied from the DC-DC conversion unit 22 to the DC-RF conversion unit 23 by multiplying the read DC voltage V _dc and the DC current I _dc (S3). .

Subsequently, the RF power control unit 27 performs a filtering process of a band-pass filter having the fundamental wave f _F as a center frequency on the read traveling wave voltage v _f and the reflected wave voltage v _r , thereby obtaining the fundamental wave f _F. The traveling wave voltage v _fF and the reflected wave voltage v _rF are extracted (S4), and the traveling wave power P _fF of the fundamental wave f _F is obtained by a predetermined calculation process using the traveling wave voltage v _fF and the reflected wave voltage v _rF. The reflected wave power P _rF is calculated (S5). Further, the RF power control unit 27 calculates the traveling wave power P _fn and the reflected wave power P _rn for each different frequency f _{n in} parallel with the calculation processing of the traveling wave power P _fF and the reflected wave power P _rF of the fundamental wave f _F. Calculation processing is performed (S6 to S10).

That is, the RF power control unit 27 performs a bandpass filter filtering process with the different frequency f _n as the center frequency on the read traveling wave voltage v _f and reflected wave voltage v _r , and outputs each different frequency f _n. The traveling wave voltage v _fn and the reflected wave voltage v _rn are extracted (S6). Subsequently, the RF power control unit 27 stores the S parameters S ₃₁ (f _n ), S ₃₂ (f _n ), S ₄₁ (f _n ), S ₄₂ (f _n ) of each different frequency f _n from the correction data storage unit 274d. ) reads (S7), and the equation (8a) ~ (S parameter S ₁₃ performs an operation of 8e) formula _{(f n), S 23 (} f n), S 14 (f n), S 24 (f _n ) (S8). Subsequently, the RF power control unit 27 extracts the traveling wave voltage v _fn and reflected wave voltage v _{rn of} each extracted different frequency f _n and S parameters S ₁₃ (f _n ), S ₂₃ (f _n ), S ₁₄ (f _n ) and S ₂₄ (f _n ) are used to calculate the above-described equations (6) and (7), and the traveling wave voltages v _fn ′ of the different frequencies f _n at the input port P ₁ of the RF detector 24. And the reflected wave voltage v _rn ′ of the different frequency f _n at the output port P ₂ of the RF detector 24 is calculated (S9). Then, the RF power control unit 27 uses the calculated traveling wave voltage v _fn ′ of each different frequency f _n and the reflected wave voltage v _rn ′ to calculate the traveling wave power P _fn of each different frequency f _n by a predetermined calculation process. The reflected wave power P _rn is calculated (S10).

When the traveling wave power P _fF and the reflected wave power P _{rF of the} fundamental wave f _F and the traveling wave power P _fn and the reflected wave power P _rn of each different frequency f _n are calculated, the RF power control unit 27 calculates the fundamental wave f _F. by adding the forward power P _fF and forward power P _fn of all the different frequency f _n to calculate the forward power P _f, the reflected power P _rF and all of the fundamental wave f _F of different frequencies f _n by adding the reflected power P _rn calculates the reflected power P _r (S11). Further, the RF power control unit 27 adds the calculated traveling wave power P _f and the reflected wave power P _r to calculate the high frequency power P = P _f + P _r transmitted through the input port P ₁ of the RF detection unit 24 ( S11).

Subsequently, the RF power control unit 27 uses the calculated DC power P _dc , traveling wave power P _f, and reflected wave power P _r to calculate the above equation (2), and thereby the DC-RF conversion unit 23 The power loss P _loss is calculated (S12). In step S12, it may be calculated (2) of the place of the power loss P _loss (3) expression of the power loss P _loss.

Then, RF power control unit 27, the calculated power loss P _loss the preset well as compared with the reference value P _k (S13), compares the calculated high-frequency power P a preset reference value P _h (S14). If P _k <P _loss (S13: NO), the RF power control unit 27 controls the power value of the high-frequency power output from the DC-RF conversion unit 23 by the loss reduction control described above (S15). Returning to step S1, if P _loss ≦ P _k and P ≦ P _h (S13: YES, S14: YES), the power of the high-frequency power output from the DC-RF converter 23 by the traveling wave power constant control described above. The value is controlled (S16), and the process returns to step S1. If P _loss ≦ P _k and P _h <P (S13: YES, S14: NO), the DC-RF converter 23 performs the above-described reflection protection control. The power value of the output high frequency power is controlled (S17), and the process returns to step S1.

In the control procedure of FIG. 6, S parameters S ₃₁ (f _n ), S ₃₂ (f _n ), S ₄₁ (f _n ), S ₄₂ (f) are applied to all N different frequencies f _n to be detected. _{Although n} ) was measured in advance and stored in the correction data storage unit 274d, an approximate curve may be obtained for the frequency characteristics of each component of the S parameter acquired for N different frequencies f _n. if, to set the approximate curve for each component, S parameter S ₃₁ (f _n) for some of the n different frequency _{f n, S 32 (f n} ), S 41 (f n), S 42 (f n ) Is stored in the correction data storage unit 274d, and the remaining components of the S parameter of the different frequency f _n are calculated by interpolation using an approximate curve using the measured S parameter. Good. In this case, there is an advantage that the storage capacity of the correction data storage unit 274d can be reduced.

For example, in unmeasured S parameters for different frequency f _m, different frequency f _m-1 adjacent to the different frequency f _m, f _{m + 1} if already measured for, at step S7, for each component of the S-parameter The measurement values of the different frequencies f _m−1 and f _{m + 1} may be read out and the S parameter component of the different frequency f _m may be calculated by interpolation using the approximate curve for each component and both measurement values.

As described above, according to the high frequency power supply 2 according to the present embodiment, the band-pass filter having a different frequency f _n set in advance from the traveling wave voltage v _f and the reflected wave voltage v _r detected by the RF detection unit 24. the filtering process and the traveling wave voltage v _fn of different frequency f _n after extracting the reflected wave voltage v _rn, S parameter S ₃₁ of the RF detector 24 in advance acquired for each different frequency f _n (f _n), S ₃₂ Using (f _n ), S ₄₁ (f _n ), and S ₄₂ (f _n ), the traveling wave voltage v _fn ′ at the input port P ₁ of the RF detector 24 and the reflected wave voltage v _rn ′ at the output port P ₂ are obtained. Since the conversion is performed, the detection accuracy of the traveling wave voltage v _fn ′ and the reflected wave voltage v _rn ′ of the different frequency f _n can be improved without complicating or increasing the size of the configuration of the RF detection unit 24. it can.

Further, since the output control is performed by the loss reduction control and the reflection protection control using the traveling wave voltage v _fn ′ and the reflected wave voltage v _rn ′ of the different frequency f _n , the output control can be performed with high accuracy.

In the above embodiment, the traveling wave power P _fn and the reflected wave power P _rn are calculated for all the different frequencies f _n (n = 1, 2,... N) for which the S parameter is measured. (see the process in step S10, S11 in FIG. 6), depending on the contents of the plasma treatment, among the n different frequency f _n, some of the different frequency f _n is forward power P _f of the step S11 (= P _fF + ΣP _fn ) and reflected wave power P _r (= P _rF + ΣP _rn ) may not be affected.

Further, in the plasma processing apparatus 4, the load impedance Z _L during plasma processing are changed every moment, the load impedance Z _L according to the change of the traveling-wave power of each different frequency f _n P _fn and the reflected wave power P _rn also varies, and among the N different frequencies f _n , some of the different frequencies f _n are the traveling wave power P _f (= P _fF + ΣP _fn ) and the reflected wave power P _r (= P _rF + ΣP _rn ) in step S11. ) May not affect the calculated value.

In such a case, the processing of steps S6 to S10 is performed on the RF power control unit 27 for different frequencies f _n that do not affect the calculated values of the traveling wave power P _f and the reflected wave power P _r in step S11. it means to increase the processing load and processing time than necessary, the process of only step S6~S10 for different frequency f _n that affect the calculated value of the reflected power P _r and forward power P _f of the step S11 It is preferable to

FIG. 7 is a process in which the processes of steps S6 to S10 are performed only for different frequencies f _n that affect the calculated values of the traveling wave power P _f and the reflected wave power P _r in step S11. It is an example of the flowchart which deform | transformed the procedure.

The flowchart of FIG. 7 is obtained by adding the process of step S20 shown in FIG. 8 before step S1 (that is, before starting control of output power) in the flowchart of FIG. Processing in step S20 is a process of setting a different frequency f _n that affect the calculated value of the reflected power P _r and forward power P _f of the step S11 as the different frequency f _n to be extracted in different frequency detecting unit 274 is there.

  The flowchart of FIG. 7 differs from the above-described processing procedure of FIG. 6 only in the processing contents of step S20 and step S6 ', and only the differences will be described below.

In the processing procedure of FIG. 7, when the control of the output power is started, first, the process proceeds to step S20, and the different frequency f _n to be extracted by the different frequency detection unit 274 is set according to the processing procedure shown in FIG.

When the process proceeds to step S20, the RF power control unit 27 sets the power threshold P _th for different frequency extraction input by the operator's input operation or a preset program (S20-1). Subsequently, the RF power control unit 27 sets “1” to a counter n that counts the number N of different frequencies f _n for which the S parameter is measured (S20-2), and sets the n-th different frequency f _n . The traveling wave voltage v _fn and the reflected wave voltage v _rn are extracted (S20-3).

RF power control unit 27 reads the traveling wave voltage v _f and the reflected wave voltage v _r outputted from the RF detector 24, mainly in different frequency f _n with respect to its traveling wave voltage v _f reflected wave voltage v _r A band-pass filter filtering process is performed to extract a traveling wave voltage v _fn and a reflected wave voltage v _rn having different frequencies f _n .

Then, RF power control unit 27, the traveling of the traveling wave voltage v _fn and the reflected wave voltage v performs processing similar to the processing in step S6~S10 respect _rn different frequency f _n of the extracted inter-frequency f _n The wave power P _fn and the reflected wave power P _rn are calculated. That, RF power control unit 27, S parameters S ₃₁ (f _n) of the traveling wave voltage v _fn and the reflected wave voltage v corresponding to _rn different frequency f _n of the extracted inter-frequency _{f n, S 32 (f n} ), Using S ₄₁ (f _n ) and S ₄₂ (f _n ), the traveling wave voltage v _fn ′ of the different frequency f _n at the input port P ₁ of the RF detector 24 and the different frequency at the output port P ₂ of the RF detector 24 are used. 'after conversion into, the traveling wave voltage v _fn' reflected wave voltage v _rn of f _n reflected power and forward power P _fn of different frequency f _n by a predetermined calculation processing by using the reflected wave voltage v _rn 'and P _rn is calculated.

Then, the RF power control unit 27 adds the traveling wave power P _fn and the reflected wave power P _rn to calculate the power P _n of the different frequency f _n (S20-4).

Subsequently, the RF power control unit 27 compares the calculated power P _n with the threshold value P _th (S20-5), and if P _th <P _n (S20-5: YES), the nth different frequency f. _n is stored in the RAM (S20-6), and the process proceeds to step S20-7. On the other hand, if P _n ≦ P _th (S20-5: NO), the RF power control unit 27 skips step S20-6 and proceeds to step S20-7.

In step S20-7, the RF power control unit 27 determines whether or not the value of the counter n has reached “N” (S20-7), and if n <N (S20-7: NO). ), the counter n increases by "1" (S20-8), the process returns to step S20-3, if turned n = n (S20-7: YES) , ends the setting processing of the different frequency f _n Then, the process proceeds to step S1 in FIG. That is, the process proceeds to the output power control process described with reference to FIG.

In the flowchart of FIG. 7, of the N different frequency f _n in step S20, since different frequency f _n to be extracted in different frequency detecting unit 274 is set, in step S6 ', set in step S20 different A traveling wave voltage v _fn and a reflected wave voltage v _rn are extracted only for the frequency f _n . Accordingly, also in steps S7 to S10, the traveling wave power P _fn and the reflected wave power P _rn are calculated only for the different frequency f _n set in step S20.

Therefore, according to the processing procedure of FIG. 7, the calculation processing of the traveling wave power P _fn and the reflected wave power P _rn is not performed for all of the N different frequencies f _n for which the S parameter is measured. The processing load and processing time of the RF power control unit 27 can be reduced as compared with the procedure.

In the flowchart of FIG. 7, the output power control method is determined in steps S15 to S17, and then the process returns to step S1. However, the process may return to step S20 as indicated by the dotted line in FIG. . When returning to step S1, the different frequency f _n to be extracted by the different frequency detection unit 274 is set at the start of the output power control, and the set value is held until the control of the output power is completed. When the process returns to step S20, the power P _n of the different frequency f _n is periodically monitored, and the different frequency f _n to be extracted each time is set.

As described above, since the power P _n of the different frequency f _n varies according to the load impedance Z _L during the plasma processing, the different frequency f _n to be extracted according to the variation of the power P _n of the different frequency f _n is determined. It is preferable to set appropriately. If the process returns to step S20 indicated by the dotted line in FIG. 7, the optimum different frequency f _n to be extracted is always set, so that the different frequency f to be extracted in accordance with the fluctuation of the power P _n of the different frequency f _{n. It} is possible to sufficiently cope with the case where _n changes.

In FIG. 7, it is possible to return from step S15 to S17 to step S1 as indicated by a solid line, and to return from step S15 to S17 to step S20 as indicated by a dotted line when a predetermined time has elapsed. . Such was the case of the, it is possible to lengthen the period of changes of different frequency f _n, can be treated different frequency f _n is frequently changed can be inhibited from complication.

In the processing procedures of FIGS. 6 and 7, the timing for setting the different frequency f _n to be extracted is determined in advance by the program, but the operator monitors the fluctuation state of the power P _{n at} the different frequency f _n. Thus, the different frequency f _n to be extracted may be set.

9, with respect to the flowchart of FIG. 7, the operator has changed the processing procedure including a process for setting the different frequency f _n to be extracted by monitoring the variation state of the power P _n of different frequency f _n Furocha It is. Specifically, those workers processing contents of step S20 in FIG. 7 is changed to the processing procedure for setting different frequency f _n to be extracted by monitoring the variation state of the power P _n of different frequency f _n is there.

The high-frequency power supply 2 corresponding to the processing procedure of FIG. 9, as shown in FIG. 10, different frequency f _n of the power P and a display unit 29 for level display of _n, worker different frequency f _n to the display unit The operation unit 30 is provided for displaying the level of the power P _n and setting the different frequency f _n to be extracted based on the display.

In the configuration of FIG. 10, the power P _n of the different frequency f _n calculated by the different frequency power calculation unit 271 c is displayed on the display unit 29, and the operator can use the power of each different frequency f _n displayed on the display unit 29. The different frequency f _n to be extracted is determined by looking at P _n , and the determination result is input to the RF power control unit 27 by operating the operation unit 30. The different frequency correction unit 274c, based on the information of the different frequency f _n entered by the operator, different frequency f _n to be the correction processing is set.

In the processing procedure of FIG. 9, when the RF power control unit 27 starts controlling the output power, first, the operator performs an operation of shifting to a different frequency setting mode for the worker to set the different frequency f _n. If it is determined whether or not an operation has been performed (S20-1 ′: NO), the process immediately proceeds to step S1 in FIG. In this case, since different frequency f _n to be extracted is set to all N different frequency f _n, the process proceeds from step S1 to the step S6 ', to all of the N different frequency f _n The traveling wave voltage v _fn and the reflected wave voltage v _rn are extracted.

On the other hand, if the operation has been performed (S20-1 ′: YES), the RF power control unit 27 sets “1” to the counter n (S20-2 ′), and the nth different frequency f _n progresses. The wave voltage v _fn and the reflected wave voltage v _rn are extracted (S20-3 ′). RF power control unit 27 reads the traveling wave voltage v _f and the reflected wave voltage v _r outputted from the RF detector 24, mainly in different frequency f _n with respect to its traveling wave voltage v _f reflected wave voltage v _r A band-pass filter filtering process is performed to extract a traveling wave voltage v _fn and a reflected wave voltage v _rn having different frequencies f _n .

Then, RF power control unit 27, the traveling of the traveling wave voltage v _fn and the reflected wave voltage v performs processing similar to the processing in step S6~S10 respect _rn different frequency f _n of the extracted inter-frequency f _n The wave power P _fn and the reflected wave power P _rn are calculated. That, RF power control unit 27, S parameters S ₃₁ (f _n) of the traveling wave voltage v _fn and the reflected wave voltage v corresponding to _rn different frequency f _n of the extracted inter-frequency _{f n, S 32 (f n} ), Using S ₄₁ (f _n ) and S ₄₂ (f _n ), the traveling wave voltage v _fn ′ of the different frequency f _n at the input port P ₁ of the RF detector 24 and the different frequency at the output port P ₂ of the RF detector 24 are used. 'after conversion into, the traveling wave voltage v _fn' reflected wave voltage v _rn of f _n reflected power and forward power P _fn of different frequency f _n by a predetermined calculation processing by using the reflected wave voltage v _rn 'and P _rn is calculated.

Then, the RF power control unit 27 adds the traveling wave power P _fn and the reflected wave power P _rn to calculate the power P _n of the different frequency f _n (S20-4 ′).

Subsequently, the RF power control unit 27 determines whether or not the value of the counter n has reached “N” (S20-5 ′), and if n <N (S20-5 ′: NO), the counter n is incremented by “1” (S20-6 ′), the process returns to step S20-3 ′, and if n = N (S20-5 ′: YES), the N different values calculated on the display unit The power P _n of the frequency f _n is displayed (S20-7 ′). Thereby, the worker can monitor the distribution of the level of the power P _n of N different frequencies f _n .

Subsequently, the RF power control unit 27 determines whether or not the operator has performed an operation for setting the different frequency f _n to be extracted (S20-8 ′), and an operation for not setting the different frequency f _n is performed. (S20-8 ′: NO), the process proceeds to step S1 without changing the current setting value of the different frequency f _n . On the other hand, when the different frequency f _n setting operation is performed (S20-8 ′: YES), the current set value of the different frequency f _n written in the RAM is changed to the different frequency f _n set by the operator. (S20-9 ′), the process proceeds to step S1.

If different frequency f _n is changed in step S20-9 ', since different frequency f _n to be extracted is set to a portion of the N different frequency f _n by the operator, steps S1 When the process proceeds to step S6 ′, the traveling wave voltage v _fn and the reflected wave voltage v _rn are extracted only for a part of the set different frequencies f _n .

In the processing procedure of FIG. 9, when the operator performs an operation to shift to the different frequency setting mode, the power P _n of the different frequency f _n is displayed on the display unit in steps S20-1 ′ to S20-9 ′. it is possible to workers on the basis of the display is set to a different frequency f _n to be extracted a desired different frequency f _n, in this case it is possible to reduce the processing load and processing time of the RF power control unit 27 also.

Further, when the RF power control unit 27 determines the output power control method in steps S15 to S17, the RF power control unit 27 returns to step S20-1 ′ and monitors whether or not the operator performs an operation for shifting to the different frequency setting mode. Therefore, the operator can change the content of the different frequency f _n to be extracted at a desired timing during the plasma processing. Then, in the process procedures shown in FIG. 9, the operator so to set a different frequency f _n to be extracted by monitoring the levels of different frequency f _n, it is possible to improve the reliability of setting the different frequency f _n .

DESCRIPTION OF SYMBOLS 1 Plasma processing system 2 High frequency power supply 21 AC-DC conversion part 22 DC-DC conversion part 23 DC-RF conversion part (high frequency production | generation means)
231 Filter circuit 24 RF detection section (high frequency detection means)
25 Drive signal generator 26 High frequency generator 27 RF power controller 271 DC controller (different frequency determining means)
271a DC power calculator 271b Fundamental power calculator (fundamental wave extraction means)
271c Different frequency power calculation unit (different frequency extraction means, calculation means)
271d Control command value generator (output control means)
272 High-frequency control unit 273 Fundamental wave detection unit 273a, 273b Band pass filter 274 Different frequency detection unit 274a, 274b Band pass filter 274c Different frequency correction unit (matrix data interpolation means)
274d Correction data storage unit (matrix data storage means)
28A DC voltage detection unit 28B DC current detection unit 29 Display unit (different frequency display means)
30 Operation part (different frequency setting means)
3 Impedance matching device 4 Plasma processing device (load)
5 System controller 6 Coaxial cable

Claims (7)

High frequency generating means for generating high frequency;
High-frequency detection means for detecting a traveling wave from the high-frequency generation means to the load and a reflected wave from the load to the high-frequency generation means at a subsequent stage of the high-frequency generation means,
For a predetermined different frequency different from the high frequency fundamental wave, the different frequency traveling wave is extracted from the traveling wave detected by the high frequency detecting means, and the different wave is extracted from the reflected wave detected by the high frequency detecting means. Different frequency extraction means for extracting the reflected wave of the frequency,
A high frequency power source with
Two input waves input to the power detection means from two input / output ports of the high-frequency detection means, and the traveling wave and the reflected wave output from the high-frequency detection means, acquired in advance for each different frequency. Matrix data storage means for storing matrix data indicating transmission characteristics between
The different frequency traveling wave and the reflected wave are subjected to predetermined arithmetic processing using the matrix data stored in the matrix data storage means for the different frequency traveling wave and the reflected wave extracted by the different frequency extracting means. Correcting means for correcting the traveling wave and the reflected wave respectively input from two input / output ports of the high-frequency detection means,
A high frequency power source characterized by comprising: The high frequency detection means includes a first port to which the high frequency generated by the high frequency generation means is input, a second port from which the high frequency is output, a third port to output the traveling wave, and the reflected wave. A directional coupler having a fourth port for outputting
The matrix data includes two input waves of different frequencies f _n input from the first and second ports to the directional coupler, a ₁ (f _n ), a ₂ (f _n ), and 3 , S ₃₁ (f _n ) = b ₃ (f) _where b ₃ (f _n ) and b ₄ (f _n ) are the traveling wave and the reflected wave of different frequency f _n output from the fourth port, respectively. _n ) / a ₁ (f _n ), S ₃₂ (f _n ) = b ₃ (f _n ) / a ₂ (f _n ), S ₄₁ (f _n ) = b ₄ (f _n ) / a ₁ (f _n ), S ₄₂ (f _n ) = b ₄ (f _n ) / a ₂ (f _n ) as S components,
The correction means has b ₃ (f _n ) and b ₄ (f _n ) as traveling and reflected waves of different frequencies f _n extracted by the different frequency extraction means, respectively.
a ₁ (f _n ) = S ₁₃ (f _n ) · b ₃ (f _n ) + S ₁₄ (f _n ) · b ₄ (f _n ) (A1)
a ₂ (f _n ) = S ₂₃ (f _n ) · b ₃ (f _n ) + S ₂₄ (f _n ) · b ₄ (f _n ) (A2)
However, S ₁₃ (f _n ) = S ₄₂ (f _n ) / Δ (f _n ) (B1)
S ₂₃ (f _n ) = − S ₄₁ (f _n ) / Δ (f _n ) (B2)
S ₁₄ (f _n ) = − S ₃₂ (f _n ) / Δ (f _n ) (B3)
S ₂₄ (f _n ) = S ₃₁ (f _n ) / Δ (f _n ) (B4)
Δ (f _n ) = S ₃₁ (f _n ) · S ₄₂ (f _n ) + S ₃₂ (f _n ) · S ₄₁ (f _n ) (B5)
By calculating the different frequency f _n to be input to the second port of the first traveling wave a ₁ of different frequency f _n to be input to the port (f _n) and said high-frequency detecting means of the high-frequency detecting means The high frequency power supply according to claim 1, wherein the reflected wave a ₂ (f _n ) is calculated.   The high frequency power supply according to claim 2, wherein the matrix data storage means stores measurement data obtained by actually measuring the S parameter of the high frequency detection means. The matrix data storage means stores measurement data S ₃₁ (f _n ), S ₃₂ (f _n ), S ₄₁ (f _n ), S ₄₂ (f _n ) obtained by actually measuring the S parameter of the high-frequency detection means ( S parameters with the components S ₁₃ (f _n ), S ₂₃ (f _n ), S ₁₄ (f _n ), and S ₂₄ (f _n ) converted by the arithmetic expressions of B1) to (B5) are stored. And
The correcting means uses the traveling wave b ₃ (f _n ) and the reflected wave b ₄ (f _n ) of the different frequency f _n extracted by the different frequency extracting means, and the equations (A1) and (A2) The high frequency power supply according to claim 2, wherein a traveling wave a ₁ (f _n ) and a reflected wave a ₂ (f _n ) of the different frequency f _n are calculated by calculating Fundamental wave extraction means for extracting the component of the high frequency fundamental wave from the traveling wave and the reflected wave detected by the high frequency detection means;
Of the predetermined different frequencies, different frequency determining means for determining different frequencies to be corrected by the correcting means,
The corrected wave calculated by the different frequency detecting means and the correcting means for the traveling wave and reflected wave of the fundamental wave extracted by the fundamental wave extracting means and the different frequency determined by the different frequency determining means. An output control means for controlling the high frequency output from the high frequency generation means based on a traveling wave and a reflected wave;
Further comprising
The different frequency determination means is configured to reflect a traveling wave and a reflection input from two input / output ports of the high frequency detection means by the different frequency detection means and the correction means with respect to the predetermined different frequency at a predetermined cycle. A calculating means for calculating a wave;
Different frequency setting means for setting a different frequency to be corrected by the correction means among the predetermined different frequencies based on a calculation result of the calculation means and a threshold value of a preset different frequency level;
The high frequency power supply according to any one of claims 1 to 4, comprising: Fundamental wave extraction means for extracting the component of the high frequency fundamental wave from the traveling wave and the reflected wave detected by the high frequency detection means;
Different frequency determination means for determining a different frequency to be corrected by the correction means among the predetermined different frequencies according to an instruction from an operator;
The corrected wave calculated by the different frequency detecting means and the correcting means for the traveling wave and reflected wave of the fundamental wave extracted by the fundamental wave extracting means and the different frequency determined by the different frequency determining means. An output control means for controlling the high frequency output from the high frequency generation means based on a traveling wave and a reflected wave;
Further comprising
The different frequency determination means includes
When a different frequency determination process is instructed by the operator, a process of inputting the predetermined different frequency from the two input / output ports of the high frequency detecting means by the different frequency detecting means and the correcting means. Calculating means for calculating the wave and the reflected wave;
Different frequency display means for displaying the level of each different frequency so that the operator can monitor based on the calculation result of the calculation means,
Different frequency setting means for setting different frequency information input from the operator based on the display of the different frequency display means to a different frequency to be corrected by the correction means,
The high frequency power supply according to any one of claims 1 to 4, comprising: The matrix data storage means stores the matrix data for a part of the predetermined different frequency,
Matrix data interpolating means for interpolating different frequency matrix data not stored in the matrix data storage means by a predetermined interpolation operation using matrix data stored in the matrix data storage means;
The correction means interpolates the matrix data of the different frequency by the matrix data interpolation means when correcting the traveling wave and the reflected wave of the different frequency which are not stored in the matrix data storage means, and uses the interpolated value. The high-frequency power source according to claim 1, which corrects a traveling wave and a reflected wave of different frequencies.

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