JP2016031327A - High-frequency measuring device and high-frequency measuring device calibration method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of facilitating calibrating a high-frequency measuring device.SOLUTION: A high-frequency measuring device including a sensor head 31 and an arithmetic device 32 is configured so that a network analyzer 8 is connected to the sensor head 31, an incident signal is input to an input end P1' of the sensor head 31, a reference load is reproduced at an output end P2', a transmission signal output from a current signal output port P3' of the sensor head 31 and a transmission signal output from a voltage signal output port P4' thereof are detected, and an S parameter is calculated. Furthermore, a signal generator 9 is connected to the arithmetic device 32 and two reproduction signals are generated by the signal generator 9 on the basis of the S parameter and are input to the arithmetic device 32 to cause the arithmetic device 32 to calculate an impedance. A calibration parameter is calculated on the basis of a true value of an impedance of the reference load and the impedance calculated by the arithmetic device 32.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a high-frequency measurement apparatus that measures high-frequency parameters such as impedance by detecting a high-frequency voltage and a high-frequency current, and a calibration method for the high-frequency measurement apparatus.

  A high-frequency measuring device used for monitoring the state of a plasma processing apparatus during plasma processing has been developed. The high-frequency measuring device is a so-called RF sensor, detects a high-frequency voltage and a high-frequency current, obtains a phase difference θ between the voltage and the current from the detected value, and also calculates a voltage effective value V, current effective value I, impedance Z = R + jX High frequency parameters such as reflection coefficient Γ, traveling wave power Pf, and reflected wave power Pr are calculated.

  In general, since the sensitivity of a sensor varies, a measurement value calculated from a detection value detected by the sensor is different from a correct value. Therefore, the measurement device or the measurement device measures the measurement object serving as a reference in advance, obtains a calibration parameter for converting the measurement value calculated from the detection value into a correct value, and in actual measurement, obtains the measurement value. The calibration parameter is converted into a correct value and output. The calibration parameters are calculated based on the three reference loads and stored in the memory of the high frequency measurement device. With respect to the three reference loads, the impedance is measured by the high-frequency measuring device, and the calibration parameters are calculated from these measured impedance values and the true values of the impedances of the three reference loads.

  For example, Patent Document 1 describes a system for generating calibration parameters for a high-frequency measuring device. The system first measures the impedance of the reference load by the high frequency measurement device in a state where power is supplied from the high frequency power supply device to the reference load. Next, the true value of the impedance of the reference load is measured by an impedance analyzer. Calibration parameters are calculated from the impedances of the three reference loads measured with the high-frequency measuring device and those measured with the impedance analyzer.

JP 2013-190324 A

  When measuring a high-frequency parameter of a high frequency having a different frequency with a high-frequency measuring device, it is necessary to prepare a calibration parameter for each frequency. For example, when measuring a high-frequency parameter of a harmonic, it is necessary to calculate calibration parameters for a plurality of frequencies other than the fundamental frequency in advance and store them in a memory. Since the reference load includes a capacitor and an inductor, impedance varies with frequency. Therefore, in order to calculate a calibration parameter for each frequency, it is necessary to prepare a reference load for each frequency. Even when the reference load is reproduced with a dummy load, it is necessary to adjust the dummy load for each frequency. The same applies to the high-frequency power supply device connected to the input side of the high-frequency measurement device and the impedance matching device arranged between the high-frequency power supply device and the high-frequency measurement device, and must be changed for each frequency. Therefore, there is a problem that it takes time, cost and cost to calculate the calibration parameters of the high-frequency measuring device that can handle a plurality of frequencies.

  The present invention has been conceived under the circumstances described above, and an object thereof is to provide a method for easily calibrating a high-frequency measuring device.

  In order to solve the above problems, the present invention takes the following technical means.

  The calibration method provided by the first aspect of the present invention includes a sensor head that detects a high-frequency current and a high-frequency voltage and outputs the detected current signal and voltage signal, and a current signal and a voltage signal input from the sensor head. A calibration method for a high-frequency measurement device comprising an arithmetic device that calculates an impedance based on a first step of inputting an incident signal to an input end of the sensor head and reproducing a reference load at an output end; A second step of detecting a transmission signal output from the output port of the current signal of the sensor head and a transmission signal output from the output port of the voltage signal, and generating two reproduction signals based on the two transmission signals Then, a third step for inputting to the arithmetic device, a fourth step for causing the arithmetic device to calculate impedance, and a reference negative reproduced in the first step The true value of the impedance based on said fourth impedance calculated in step, to calculate the calibration parameters, characterized in that it comprises a fifth step of setting the high-frequency measuring device.

  The “calibration parameter” is a parameter for converting the measured value of the high-frequency measuring device into a correct value. The action of calculating the calibration parameter and setting it in the high-frequency measuring device is referred to as “calibration” in the present application. That is, the method of calculating and setting the calibration parameter is the “calibration method”. The high-frequency measuring device is connected to the plasma processing apparatus and measures a high-frequency parameter to monitor the plasma processing apparatus, or is provided inside the impedance matching apparatus to measure the high-frequency parameter to control the matching operation. There are things to do.

  In a preferred embodiment of the present invention, the first to fourth steps are performed for three reference loads, and the fifth step includes a true value of impedances of the three reference loads and an arithmetic unit. A calibration parameter is calculated based on the calculated impedance.

  In a preferred embodiment of the present invention, the first and second steps are performed in a state where the sensor head is connected to a high-frequency circuit measuring device having four ports, and after the second step. A first parameter which is a ratio of the transmission signal output from the output port of the current signal to the incident signal, and a second parameter which is a ratio of the transmission signal output from the output port of the voltage signal to the incident signal. A sixth step of calculating a parameter, wherein the third and fourth steps are performed with the arithmetic unit connected to a signal generator, wherein the signal generator includes the first parameter and The two reproduction signals are generated based on the second parameter.

In a preferred embodiment of the present invention, the first parameter is S ₃₁ , the second parameter is S ₄₁ , the frequency of the incident signal is f, A is a predetermined constant, and arg () represents the declination angle. In this case, the reproduction signals are a signal i ′ and a signal v ′ of the following equations.

  In a preferred embodiment of the present invention, one of the reference loads is a load having the same impedance as a characteristic impedance of a system in which the high-frequency measuring device performs measurement.

  The high-frequency measuring device provided by the second aspect of the present invention is characterized in that calibration is performed by the calibration method provided by the first aspect of the present invention.

  According to the present invention, when the incident signal is input to the input end of the sensor head and the reference load is reproduced at the output end, the transmission signal output from the output port of the current signal and the voltage signal is detected. Two reproduction signals based on one transmission signal are input to the arithmetic unit to calculate the impedance. If information of two detected transmission signals is recorded, two reproduction signals can be generated later. Thus, the first and second steps are performed while changing the frequency, and the information of the two detected transmission signals is recorded for each frequency, and then the third and fourth steps are performed later. Impedance can be calculated for each frequency. For example, if the information of two transmission signals is recorded for each frequency while reproducing the reference load by changing the frequency of the incident signal using a high-frequency circuit measurement device or the like, the dummy load can be adjusted or the high frequency for each frequency. There is no need to change the power supply. Further, if a signal generation device or the like is used, two reproduction signals can be generated for each frequency from the recorded information. Therefore, labor, time and cost can be reduced as compared with the conventional method, and the high-frequency measuring apparatus can be easily calibrated.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a block diagram for demonstrating the structure of the plasma processing system using the high frequency measurement apparatus which concerns on 1st Embodiment. It is a figure for demonstrating the internal structure of the high frequency measurement apparatus which concerns on 1st Embodiment. It is a figure for demonstrating a calibration parameter. It is a figure for demonstrating the conventional calibration method. It is a figure for demonstrating the calibration method which concerns on 1st Embodiment. It is a flowchart for demonstrating the procedure of the calibration method which concerns on 1st Embodiment. It is a figure for demonstrating the other Example of the calibration method which concerns on 1st Embodiment.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings, taking as an example a case of a high-frequency measuring device used for monitoring a plasma processing apparatus.

  FIG. 1 is a block diagram for explaining a configuration of a plasma processing system using the high-frequency measuring device according to the first embodiment.

  The plasma processing system A supplies high-frequency power to a workpiece such as a semiconductor wafer or a liquid crystal substrate, and performs processing such as plasma etching. As shown in the figure, the plasma processing system A includes a high frequency power supply device 1, an impedance matching device 2, a high frequency measuring device 3, and a plasma processing device 4. An impedance matching device 2 is connected to the high frequency power supply device 1 via a transmission line made of, for example, a coaxial cable, and a plasma processing device 4 is connected to the impedance matching device 2 via a transmission line 5 made of, for example, a rod-like copper. It is connected. The high frequency measuring device 3 is installed on the transmission line 5. The plasma processing system A is configured with a characteristic impedance of 50Ω.

  The high frequency power supply device 1 supplies high frequency power, and is a power supply device that can output high frequency power having a frequency of, for example, several hundred kHz or more.

  The impedance matching device 2 matches the impedance of the high frequency power supply device 1 and the plasma processing device 4. The impedance matching device 2 includes a variable reactance element (not shown) (for example, a variable capacitor, a variable inductor, etc.), and changes the impedance by changing the reactance of the variable reactance element. The impedance matching device 2 converts the impedance seen from the output end of the impedance matching device 2 so that the impedance seen from the input end of the impedance matching device 2 becomes the characteristic impedance.

  A high-frequency measuring device (not shown) is provided on the power supply side inside the impedance matching device 2. The high-frequency measuring device measures the impedance when the load side is viewed from the input end of the impedance matching device 2, and the impedance matching device 2 changes the reactance of the variable reactance element so that the measured impedance becomes the characteristic impedance. Let

  The plasma processing apparatus 4 is an apparatus for processing a workpiece such as a semiconductor wafer or a liquid crystal substrate using a method such as etching or CVD. Although not shown, the plasma processing apparatus 4 includes a container (chamber) for enclosing a predetermined gas such as nitrogen gas or argon gas for generating plasma, and high-frequency power from the high-frequency power supply device 1 in the container. A pair of electrodes for supplying the gas.

  In order to monitor the state of the plasma processing apparatus 4 during the plasma processing, the high-frequency measuring apparatus 3 monitors the impedance and reflection coefficient of the plasma processing apparatus 4, the high-frequency voltage, the high-frequency current, and the traveling wave power at the input terminal of the plasma processing apparatus 4. , And so-called RF sensors that measure high-frequency parameters such as reflected wave power. The impedance to be measured is the impedance when the load side is viewed from the point (measurement point) for detecting the high-frequency voltage and high-frequency current, but since the measurement point is near the input end of the plasma processing apparatus 4, the impedance of the plasma processing apparatus 4 It corresponds to.

  FIG. 2 is a block diagram for explaining the internal configuration of the high-frequency measuring device 3.

  As shown in the figure, the high-frequency measuring device 3 includes a sensor head 31 and an arithmetic device 32.

  The sensor head 31 is disposed on the transmission line 5, detects the current signal i and the voltage signal v, and outputs the current signal i and the voltage signal v to the arithmetic device 32, and includes a current transformer unit 311 and a capacitor unit 312.

  The current transformer unit 311 includes a coil magnetically coupled to the transmission line 5, detects a current corresponding to the high-frequency current flowing through the transmission line 5, and outputs the detected current signal i to the arithmetic device 32. The capacitor unit 312 includes a capacitor that is capacitively coupled to the transmission line 5, detects a voltage corresponding to the high-frequency voltage generated in the transmission line 5, and outputs the detected voltage signal v to the arithmetic device 32.

  The computing device 32 computes each high-frequency parameter based on the current signal i and the voltage signal v input from the sensor head 31, and includes A / D conversion units 321, 322, effective value calculation units 323, 324, A phase difference detection unit 325, a vector conversion unit 326, a calibration unit 327, a vector inverse conversion unit 328, and an impedance calculation unit 329 are provided.

  The A / D conversion unit 321 converts the current signal i input from the current transformer unit 311 into a digital signal and outputs the digital signal to the effective value calculation unit 323 and the phase difference detection unit 325. The A / D conversion unit 322 converts the voltage signal v input from the capacitor unit 312 into a digital signal and outputs the digital signal to the effective value calculation unit 324 and the phase difference detection unit 325.

  The effective value calculation unit 323 calculates the current effective value. The effective value calculation unit 323 calculates the current effective value I from the current signal i input from the A / D conversion unit 321 and outputs the current effective value I to the vector conversion unit 326. The effective value calculation unit 324 calculates a voltage effective value. The effective value calculation unit 324 calculates the voltage effective value V from the voltage signal v input from the A / D conversion unit 322 and outputs the voltage effective value V to the vector conversion unit 326. The phase difference detection unit 325 detects a phase difference between current and voltage. The phase difference detection unit 325 calculates the phase difference θ from the current signal i input from the A / D conversion unit 321 and the voltage signal v input from the A / D conversion unit 322, and outputs the phase difference θ to the vector conversion unit 326. To do.

The vector conversion unit 326 is based on the current effective value I input from the effective value calculation unit 323, the voltage effective value V input from the effective value calculation unit 324, and the phase difference θ input from the phase difference detection unit 325. A current signal I ₀ and a voltage signal V ₀ which are vectors (complex numbers) are calculated and output to the calibration unit 327. The current signal I ₀ and the voltage signal V ₀ are calculated as I ₀ = I + j0, V ₀ = V cos θ + j V sin θ, with the phase of the current signal I ₀ as a reference (real number axis, imaginary part 0).

The calibration unit 327 performs calibration on the current signal I ₀ and the voltage signal V ₀ input from the vector conversion unit 326. The calibration unit 327 calibrates the current signal I ₀ and the voltage signal V ₀ using a calibration parameter X recorded in a memory (not shown), and converts the current signal I ₁ and the voltage signal V ₁ after calibration into a vector inverse conversion unit. To 328. In the present application, conversion of a measured value to a correct value using a calibration parameter is also referred to as “calibration”.

The calibration parameter X is calculated based on the three reference loads and recorded in the memory. When the relationship between the current signal I ₀ and the voltage signal V ₀ output from the vector conversion unit 326 and the high-frequency current flowing in the transmission line 5 and the high-frequency voltage generated in the transmission line 5 is replaced with a two-terminal pair circuit, the current signal I _0. The calibration parameter X for calibrating the voltage signal V ₀ to the current signal I ₁ and the voltage signal V ₁ can be considered as a two-dimensional vector matrix shown in FIG.

Each element X ₁₁ , X ₁₂ , X ₂₁ , X ₂₂ of the calibration parameter X can be calculated from the impedances of the three reference loads measured by the high-frequency measuring device 3 and the true values of the impedances of the three reference loads. . In order to perform the calculation, a reference voltage value and an absolute value of the current value are required. In order to use the absolute value of the voltage value and the current value as a reference value, a highly accurate power measurement value is required. In order to measure a power measurement value with high accuracy, it is best to connect and measure a load where the reflected power is zero. Therefore, in this embodiment, in order to realize the reflected power of 0, a load having the same impedance as the characteristic impedance (that is, 50Ω) is selected as one of the reference loads. As described above, one of the reference loads is a load having characteristic impedance in order to measure a highly accurate power measurement value. Therefore, if the power measurement value can be measured with high accuracy, A load other than impedance may be used.

Note that two of the reference loads are preferably loads having impedances close to the impedance in the open state and the impedance in the short-circuit state in order to include the widest possible impedance range. On the other hand, when a load having an impedance that is too close to an open state or a short-circuit state is used as the reference load, one of the voltage value or the current value detected by the high-frequency measuring device 3 is extremely smaller than the other. In this case, each element X ₁₁ , X ₁₂ , X ₂₁ , X ₂₂ of the first calibration parameter X cannot be calculated appropriately. Therefore, in the present embodiment, a load whose reflection coefficient is 0.9 or less is used as the reference load. In addition, when the measurement range of the impedance of the high-frequency measuring device 3 is limited, the impedances of the three reference loads are in a narrow impedance range so that the impedance of the measurement range can be calibrated with high accuracy. You may set as follows.

  In the conventional calibration method, the reference load is connected to the high frequency measurement device 3, the power of the high frequency power supply device 1 is supplied to the reference load, the impedance of the reference load is measured by the high frequency measurement device 3, and the reference is measured by the impedance analyzer. The true value of the load impedance was measured.

  FIG. 4 is a diagram for explaining a method of measuring the impedance of a reference load in a conventional general calibration method.

  First, as shown in FIG. 4A, the impedance analyzer 7 is connected to the dummy load 6, and the dummy load 6 is set to the reference load impedance (for example, 50Ω). The dummy load 6 is a load device for reproducing a predetermined reference load, and changes the impedance by changing the reactance of a variable reactance element (for example, a variable capacitor, a variable inductor, etc.) not shown. The impedance analyzer 7 measures impedance. The dummy load 6 is set to the impedance of the reference load by adjusting the reactance of the variable reactance element of the dummy load 6 while measuring the impedance of the dummy load 6 with the impedance analyzer 7.

  Next, as shown in FIG. 4B, the dummy load 6 on which the reference load is reproduced is connected to the output end of the sensor head 31 of the high-frequency measuring device 3, and the impedance matching device 2 is connected to the input end of the sensor head 31. The high frequency power supply device 1 is connected via Then, power is supplied from the high frequency power supply device 1, and the impedance of the dummy load 6 is measured by the high frequency measurement device 3.

  The above is performed for three reference loads, and the true value of each impedance and the impedance measured by the high-frequency measuring device 3 are acquired. Using these values, the calibration parameter X is calculated and recorded in the memory of the arithmetic unit 32 of the high-frequency measuring device 3.

  Since the high-frequency measuring device 3 supports high-frequency measurement of a plurality of frequencies so as to measure high-frequency parameters of harmonics, it is necessary to prepare the calibration parameter X for each frequency. Since the impedance of the dummy load 6 varies depending on the frequency, it needs to be adjusted again when the frequency changes. In some cases, the impedance of the reference load cannot be reproduced depending on the frequency. In this case, it is necessary to prepare another dummy load 6. The same applies to the high-frequency power supply device 1 and the impedance matching device 2, and it is necessary to change the frequency for each frequency. Thus, in the conventional method, there is a problem that calibration of the high-frequency measuring device 3 that can handle a plurality of frequencies takes time, cost, and cost.

  Next, the calibration method according to the first embodiment will be described with reference to FIGS.

  FIG. 5 is a diagram for explaining a method of measuring the impedance of the reference load in the calibration method according to the first embodiment. FIG. 6 is a flowchart for explaining the processing procedure of the calibration method according to the first embodiment. The flowchart shows a processing procedure for calculating the calibration parameter X of the high-frequency measuring device 3.

First, as shown in FIG. 5A, the network analyzer 8 is connected to the sensor head 31 (S1). The network analyzer 8 is a high-frequency circuit measurement device that inputs a high-frequency signal (incident signal) to a high-frequency circuit network, measures a reflected signal and a transmission signal, and measures high-frequency characteristics of the high-frequency circuit network. The network analyzer 8 has four ports, can measure a reflected signal and a transmission signal with respect to an incident signal from each port, and calculates an S parameter of 4 rows and 4 columns shown in the following equation (1). be able to. For example, when the input from the port P1 to the measured incident signal, the ratio of the reflected signal to the incident signal is S _11, respective proportions of the transmission signal of each port P2~P4 for incident signal S _21, S _31, is the S _41. Since the network analyzer 8 is a vector network analyzer, each element of the S parameter is a vector, is represented by a complex number, and includes information on the signal magnitude ratio and phase difference.

  The port P 1 of the network analyzer 8 is connected to the port P 1 ′ that is the input end of the sensor head 31, and the port P 2 of the network analyzer 8 is connected to the port P 2 ′ that is the output end of the sensor head 31. The port P3 of the network analyzer 8 is connected to a port P3 ′ from which the sensor head 31 outputs a current signal i. The port P4 of the network analyzer 8 is a port P4 ′ from which the sensor head 31 outputs a voltage signal v. It is connected to the.

The network analyzer 8 outputs a high-frequency signal having a frequency f1 from an internal signal source (not shown) to the port P1 (S4), and reproduces a reference load (for example, 50Ω) to the port P2 (S5). The high frequency signal output from the port P1 is input to the sensor head 31 from the port P1 ′ as an incident signal. The network analyzer 8 detects a reflected signal that is reflected at the port P1 ′ and input to the port P1. The network analyzer 8 detects transmission signals output from the ports P2 ′, P3 ′, and P4 ′ and input to the ports P2, P3, and P4, respectively. The network analyzer 8 calculates S parameters S ₁₁ , S ₂₁ , S ₃₁ , and S ₄₁ from the incident signal, the reflected signal, and the transmission signal (S 6). That is, the network analyzer 8 is used in place of the high frequency power supply device 1, the impedance matching device 2 and the dummy load 6 shown in FIG. Then, instead of outputting the current signal i and the voltage signal v from the sensor head 31, the S parameter is calculated. Since S ₃₁ and S ₄₁ are necessary, other S parameters need not be calculated.

Next, the network analyzer 8 outputs a high-frequency signal having the frequency f2 from the internal signal source to the port P1 (S4), reproduces the reference load at the port P2 (S5), an incident signal, a reflected signal, and a transmission signal. S parameters S ₃₁ and S ₄₁ are calculated from the above. Similarly, the reference load is reproduced while changing the frequency of the high-frequency signal of the internal signal source, and the S parameters S ₃₁ and S ₄₁ for the necessary frequencies (f3, f4,...) Are calculated (S3-S3 ′). ).

The above is performed for each of the three reference loads (S2-S2 ′), and the S parameters S ₃₁ and S ₄₁ for each frequency are recorded for each reference load. Since the change of the frequency and the change of the reference load can be performed by changing the setting of the network analyzer 8, it is not necessary to change the connection between the sensor head 31 and the network analyzer 8.

Next, using the calculated S parameters S ₃₁ and S ₄₁ , the current signal i and the voltage signal v output from the sensor head 31 are reproduced and input to the arithmetic device 32, so that the measurement is performed by the high-frequency measuring device 3. The calculation device 32 is made to calculate the impedance to be performed. Specifically, as shown in FIG. 5B, the signal generator 9 is connected to the arithmetic device 32 of the high-frequency measuring device 3 (S7). The signal generator 9 is a so-called signal generator that generates a signal, and can change the frequency and level of the signal to be generated. The signal generator 9 includes two output ports, and can generate two types of signals and output them from the respective output ports. The two output ports of the signal generator 9 are respectively connected to the input ports to which the current signal i and the voltage signal v of the arithmetic device 32 are input.

  Next, the signal generator 9 generates reproduction signals i 'and v' shown in the following equations (2) and (3) and outputs them to the arithmetic unit 32 (S10). A is a predetermined constant, and f is a frequency. Further, arg () represents a declination and represents a phase difference of the transmission signal with respect to the incident signal. The reproduction signals i 'and v' are reproductions of the current signal i and the voltage signal v, respectively. The reproduction signal i ′ is input to the current signal i input port of the arithmetic device 32, and the reproduction signal v ′ is input to the voltage signal v input port of the arithmetic device 32.

S ₃₁ is the ratio of the transmission signal of the port P3 ′ to the incident signal, and S ₄₁ is the ratio of the transmission signal of the port P4 ′ to the incident signal. Therefore, the amplitude of the signal output from the port P4 ′ is (| S ₄₁ | / | S ₃₁ |) times the amplitude of the signal output from the port P3 ′. Further, the phase of the transmission signal at the port P3 ′ is delayed by arg (S ₃₁ ) from the phase of the incident signal, and the phase of the transmission signal at the port P4 ′ is delayed by arg (S ₄₁ ) from the phase of the incident signal. Therefore, the phase of the signal output from the port P4 ′ is delayed by the phase difference θ from the phase of the signal output from the port P3 ′. The reproduction signal v ′ is obtained by multiplying the amplitude of the reproduction signal i ′ by (| S ₄₁ | / | S ₃₁ |) times and delaying the phase by θ. In the calculation of the impedance, the ratio of the amplitude of the current signal i and the voltage signal v is related, but the amplitude itself is irrelevant. And can be used instead of the voltage signal v.

  The arithmetic unit 32 receives the reproduction signals i 'and v' shown in the above equations (2) and (3) instead of the current signal i and the voltage signal v, and calculates the impedance (S11). That is, the signal generating device 9 is substituted for the high frequency power supply device 1, the impedance matching device 2, the sensor head 31, and the dummy load 6 shown in FIG.

This is performed using the corresponding S parameters S ₃₁ and S ₄₁ for each reference load and each frequency. That is, the reproduced signal i ′ obtained by substituting the S parameters S ₃₁ and S ₄₁ and f = f1 calculated in the case of the first reference load (for example, 50Ω) at the frequency f1 into the above equations (2) and (3). , V ′ are generated by the signal generator 9 and output to the arithmetic unit 32 (S10), and the arithmetic unit 32 calculates the impedance at the frequency f1 of the first reference load (S11). Then, the signal generator 9 changes the frequency f and outputs the reproduction signals i ′ and v ′, and the arithmetic unit 32 calculates the impedance of the first reference load for each frequency (S9−). S9 ').

  The above is performed for each of the three reference loads (S8-S8 '), and the impedance for each frequency is recorded for each reference load. Since the change of the frequency and the change of the reference load can be performed by changing the setting of the signal generator 9, it is not necessary to change the connection between the signal generator 9 and the arithmetic unit 32.

  Next, the calibration parameter X is calculated from the true values of the impedances of the three reference loads and the impedance measured by the high-frequency measuring device 3 (S12). The calibration parameter X is calculated for each frequency and recorded in the memory of the arithmetic unit 32 of the high frequency measuring device 3.

Processing for calculating the S parameters S ₃₁ and S ₄₁ using the network analyzer 8 (see FIG. 5A and steps S 2 to S 2 ′ in FIG. 6), the reproduced signals i ′ and v ′ in the signal generator 9. Generation and processing for impedance calculation in the arithmetic unit 32 (see FIG. 5B and steps S8 to S8 ′ in FIG. 6), and processing for calculation of the calibration parameter X (see step S12 in FIG. 6). ) May be performed manually by an operator or may be performed by a control device. In the case where the control is performed by the control device, the calculated S parameters S ₃₁ and S ₄₁ are stored in the memory while the control device 10 changes the reference load and frequency of the network analyzer 8 as shown in FIG. To do. Then, the control device 10 sets the signal generator 9 so as to generate the reproduction signals i ′ and v ′ corresponding to the stored S parameters S ₃₁ and S ₄₁ , and the impedance calculated by the arithmetic device 32 is stored in the memory. To remember. And the control apparatus 10 should just calculate the calibration parameter X for every frequency, and should just record it in the memory of the arithmetic unit 32.

Returning to FIG. 2, the calibration unit 327 calibrates the current signal I ₀ and the voltage signal V ₀ using the recorded calibration parameter X. At this time, the calibration parameter X corresponding to the frequency of the high frequency signal detected by the high frequency measuring device 3 is read from the memory and used. The frequency is detected from, for example, a current signal i input from the A / D converter 321 (or a voltage signal v input from the A / D converter 322). Using the calibration parameter X, the current signal I ₀ and the voltage signal V ₀ can be converted into the current signal I ₁ and the voltage signal V ₁ after calibration from FIG. That is, the calibrated current signal I ₁ and voltage signal V ₁ can be calculated from the following equations (4) and (5) derived from FIG.

The vector inverse conversion unit 328 calculates the current effective value I ′, the voltage effective value V ′, and the phase difference θ ′ after the correction from the current signal I ₁ and the voltage signal V ₁ that are input from the calibration unit 327. And output.

  The impedance calculation unit 329 calculates impedance. The impedance calculation unit 329 calculates the impedance Z from the corrected current effective value I ′, voltage effective value V ′, and phase difference θ ′ input from the vector inverse conversion unit 328 according to the following equations (6) to (8). Is calculated and output. The high-frequency measuring device 3 also calculates and outputs high-frequency parameters such as traveling wave power Pf and reflected wave power Pr. However, in FIG.

  Next, the effect of the calibration method according to the first embodiment will be described.

In the first embodiment, the network analyzer 8 inputs the incident signal to the input end of the sensor head 31 and calculates the S parameters S ₃₁ and S ₄₁ when the reference load is reproduced at the output end. This is performed for each load and each frequency, and the calculated parameters S ₃₁ and S ₄₁ are recorded. Since the change of the frequency and the change of the reference load can be performed by changing the setting of the network analyzer 8, it is not necessary to change the connection between the sensor head 31 and the network analyzer 8. Further, the signal generator 9 outputs the reproduction signals i ′ and v ′ based on the parameters S ₃₁ and S ₄₁ corresponding to each reference load and each frequency to the arithmetic device 32, and the arithmetic device 32 calculates the impedance. Since the change of the frequency and the change of the reference load can be performed by changing the setting of the signal generator 9, it is not necessary to change the connection between the signal generator 9 and the arithmetic unit 32. Moreover, if there is the network analyzer 8 and the signal generator 9, it can calibrate and it is not necessary to prepare the dummy load 6, the high frequency power supply device 1, etc. for every frequency. Therefore, compared with the conventional calibration method, labor, time, and cost can be reduced, and the high-frequency measuring device 3 can be easily calibrated.

In the present embodiment, the case has been described in which the arithmetic device 32 calibrates the current signal I ₀ and the voltage signal V ₀ that are vectors, but is not limited thereto. For example, the current effective value I, the voltage effective value V, and the phase difference θ may be calibrated.

  In the present embodiment, the case where calibration is performed based on three reference loads has been described. However, calibration may be performed based on four or more reference loads.

Although the case where the network analyzer 8 is used has been described in the present embodiment, the present invention is not limited to this. Any high-frequency circuit measuring device capable of calculating the S parameters S ₃₁ and S ₄₁ may be used. For example, a high frequency power supply device that can change the frequency and a dummy load that automatically adjusts the impedance according to the frequency may be used.

In the present embodiment, the case where the S parameters S ₃₁ and S ₄₁ are calculated and the reproduction signals i ′ and v ′ are generated based on them is described, but the present invention is not limited to this. The reproduction signals i ′ and v ′ are generated based on the transmission signals detected at the ports P3 and P4 when the incident signal is output from the port P1 without calculating the S parameters S ₃₁ and S _41. May be. When the transmission signal b ₃ detected at the port P3 and the transmission signal b ₄ detected at the port P4 are respectively expressed by the following equations (9) and (10), the reproduction signals i ′ and v ′ are respectively expressed by the following (11) and ( 12).

  In the present embodiment, the case where the signal generation device 9 generates the reproduction signals i ′ and v ′ in an analog manner has been described. However, the present invention is not limited to this. For example, the reproduction signals i ′ and v ′ may be generated as digital signals using a direct digital synthesizer (DDS).

  The high-frequency measurement device and the high-frequency measurement device calibration method according to the present invention are not limited to the above-described embodiments. The specific configuration of each part of the high-frequency measuring device and the calibration method for the high-frequency measuring device according to the present invention can be varied in design in various ways.

A Plasma processing system 1 High frequency power supply device 2 Impedance matching device 3 High frequency measurement device 31 Sensor head 311 Current transformer unit 312 Capacitor unit 32 Arithmetic device 321, 322 A / D conversion unit 323, 324 Effective value calculation unit 325 Phase difference detection unit 326 Vector conversion unit 327 Calibration unit 328 Vector inverse conversion unit 329 Impedance calculation unit 4 Plasma processing device 5 Transmission line 6 Dummy load 7 Impedance analyzer 8 Network analyzer (high frequency circuit measurement device)
9 Signal generator 10 Control device

Claims (6)

A high-frequency measuring device comprising: a sensor head that detects a high-frequency current and a high-frequency voltage and outputs the current signal and a voltage signal; and an arithmetic unit that calculates an impedance based on a current signal and a voltage signal input from the sensor head. A calibration method,
A first step of inputting an incident signal to the input end of the sensor head and reproducing a reference load at the output end;
A second step of detecting a transmission signal output from the output port of the current signal of the sensor head and a transmission signal output from the output port of the voltage signal;
A third step of generating two reproduction signals based on the two transmission signals and inputting them to the arithmetic unit;
A fourth step of causing the arithmetic device to calculate impedance;
A fifth step of calculating a calibration parameter based on the true value of the impedance of the reference load reproduced in the first step and the impedance calculated in the fourth step, and setting the calibration parameter in the high-frequency measurement device;
A calibration method characterized by comprising: The first to fourth steps are performed for three reference loads,
The fifth step calculates calibration parameters based on the true values of the impedances of the three reference loads and the impedances calculated by the arithmetic unit.
The calibration method according to claim 1. The first and second steps are performed in a state where the sensor head is connected to a high-frequency circuit measuring device having four ports.
Following the second step, a first parameter that is a ratio of a transmission signal output from an output port of a current signal to the incident signal, and a transmission output from an output port of a voltage signal with respect to the incident signal A sixth step of calculating a second parameter that is a ratio of the signal;
The third and fourth steps are performed with the arithmetic unit connected to a signal generator,
The signal generator generates the two reproduction signals based on the first parameter and the second parameter;
The calibration method according to claim 1 or 2. When the first parameter is S ₃₁ , the second parameter is S ₄₁ , the frequency of the incident signal is f, A is a predetermined constant, and arg () represents a declination, the reproduction signal is a signal of the following formula: i ′ and signal v ′,
The calibration method according to claim 3.

One of the reference loads is a load having the same impedance as a characteristic impedance of a system in which the high-frequency measuring device performs measurement.
The calibration method according to claim 1. Calibration is performed by the calibration method according to claim 1,
A high-frequency measuring device characterized by that.

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