JP2002365318A - Waveform analyzer and plasma processing apparatus using the same - Google Patents

Abstract

(57) [Problem] To provide a waveform analyzer that accurately analyzes a waveform at a lower sampling clock frequency than in the past, and a plasma processing apparatus using the same. SOLUTION: The frequency of the RF wave is 13.56 MHz.
(Fundamental frequency f _osc ) is supplied from the RF power supply 1,
Since analysis is performed up to the fifth harmonic, order n is 5, l is 2 ⁴ ,
m is 3 ³ and the number of sampling data 1 × k is 4096 (k
Is 256), a waveform in which an RF wave and a plurality of harmonics reflected by the plasma load in the etching chamber 7 are superimposed is measured by the probe 3, and a discrete Fourier transform is performed by the measuring unit 4. To analyze the waveform. Since the sampling clock frequency used in the discrete Fourier transform is represented by f _osc × l / m under the above conditions, it is possible to accurately analyze the waveform at a lower sampling clock frequency than before.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waveform analyzer for analyzing a load state by analyzing a superimposed waveform superimposed on a sine wave and a plurality of harmonics obtained by reflection from a load, and using the same. The present invention relates to a plasma processing apparatus, and more particularly to a technique for performing analysis using a discrete Fourier transform.

[0002]

2. Description of the Related Art Conventionally, as an apparatus of this type, for example, a sine wave is injected into a chamber in which plasma is generated, a plurality of harmonics obtained by reflection by a plasma load, and a sine wave input into the plasma chamber. There is one that analyzes a superimposed waveform obtained by superimposing a wave.

The analysis of such a superimposed waveform is performed by digitally sampling the superimposed waveform data and performing a discrete Fourier transform (DFT) on the frequency domain.
m)) to measure the respective peak and phase differences of the signal amplitude (current amplitude or voltage amplitude). This analysis also reveals the amplitude and phase difference of each waveform signal,
It is possible to grasp the state of the plasma as the load (for example, the plasma density and the gas pressure).

[0004]

However, when the waveform is analyzed using the conventional discrete Fourier transform, there are the following problems. That is, in the conventional discrete Fourier transform, when digital sampling is performed at a sampling clock frequency less than twice the highest frequency among the waveforms that need to be analyzed, harmonics of different orders are obtained in the sampling data obtained by the discrete Fourier transform. Appear at the same data position (frequency band). As a result, it becomes difficult to measure the signal amplitude and the phase difference of the harmonic, and the amplitude / phase difference of the desired signal cannot be obtained accurately. Therefore, in order to prevent harmonics having different orders from appearing at the same data position (frequency band), digital sampling must be performed at a sampling clock frequency that is at least twice the highest frequency among the waveforms that need to be analyzed. No (sampling theorem).

For example, when the fundamental frequency of a sine wave used in a plasma etching apparatus or the like is 13.56 MHz, in order to perform analysis up to the fifth harmonic, the frequency of the fifth harmonic must be adjusted to the waveform of the waveform that needs to be analyzed. 13.56 MHz × 5th order (= 67.8)
MHz), which is twice or more that frequency, ie, 13.56 MHz × 5th order × 2 (= 135.6 MHz)
z) The above frequency is digitally sampled as a sampling clock frequency.

However, since the above-mentioned fundamental frequency is a high frequency of MHz level, the sampling clock frequency is higher than that. In the case of such a high frequency, it is difficult to obtain a high amplitude resolution in an A / D (Analog To Digital) conversion circuit that performs digital sampling by discrete Fourier transform. As a result, a high resolution cannot be obtained even in the amplitude of the signal obtained from the analysis result, and the waveform cannot be accurately analyzed.

The present invention has been made in view of such circumstances, and provides a waveform analysis apparatus for accurately analyzing a waveform at a lower sampling clock frequency than in the past, and a plasma processing apparatus using the same. The purpose is to:

[0008]

In order to achieve the above object, the present inventors conducted simulations by changing conditions such as the fundamental frequency of a sine wave, the number of sampling data, and the sampling clock frequency. The discrete Fourier transform was performed by superimposing waves and harmonics.

[0009] Among various above-mentioned conditions, under certain conditions, at a sampling clock frequency less than twice the highest frequency among the waveforms to be analyzed, harmonics of different orders fall into the same frequency band. A simulation result was obtained that did not appear and that the mutual intensity ratio of the amplitude value between the fundamental wave and the harmonic was equivalent to the actual data. Thus, the present inventors have reached the conclusion that the above object can be achieved based on the conditions.

The present invention based on the above knowledge has the following configuration. That is, claim 1
According to the invention described in the above, a sine wave power is supplied from an AC power supply to a load, and digital sampling is performed on at least a part of a superimposed waveform in which the sine wave and a plurality of harmonics obtained by reflection by the load are superimposed. Performing a discrete Fourier transform of the digitally sampled data, a waveform analyzer for analyzing the superimposed waveform and analyzing the state of the load. _osc , l, k,
m and n are natural numbers, n is the desired maximum order of the harmonic to be analyzed, l is greater than 2n + 1, l and m are relatively prime, and the number of sampling data is represented by l × k. Sometimes, digital sampling is performed at a sampling clock frequency of f _osc × l / m, and the digitally sampled data is subjected to discrete Fourier transform.

According to the first aspect of the present invention, when the fundamental frequency, which is the frequency of the sine wave output from the AC power supply, is f _osc and l, k, m, and n are natural numbers, n is the desired maximum order of the harmonics to be analyzed, l is 2n
When +1 is larger than +1 and l and m are relatively prime and the number of sampling data is represented by l × k,
Under the condition that digital sampling is performed at a sampling clock frequency of f _osc × l / m and the digitally sampled data is subjected to discrete Fourier transform, twice the highest frequency among the waveforms requiring analysis (f _osc × 2n)
At a sampling clock frequency less than, harmonics of different orders do not appear in the same frequency band, and the amplitude intensity ratio up to the desired harmonic matches the original data. That is, the sampling clock frequency in the present invention is f
_{Since osc} × l / m (> = _fosc × (2n + 1) / m), when 1 approaches 2n + 1, the sampling clock frequency _fosc × 2n becomes lower by about 1 / m.
Accordingly, the peak and the phase difference of the signal amplitude of each harmonic can be measured at a sampling clock frequency lower than the conventional one. As a result, at a lower sampling clock frequency than before, a high resolution can be obtained even in the amplitude and phase difference of the signal obtained from the analysis result, and the waveform can be accurately analyzed. Further, the load condition can be accurately analyzed by accurate analysis of the waveform.

As a load for supplying sine-wave power from an AC power supply (particularly, a high-frequency AC power supply), for example, plasma generated in a chamber can be cited. in this case,
When a sine wave enters the above-described chamber, the sine wave is reflected as a plurality of harmonics by the plasma load in the chamber. By analyzing a superimposed waveform obtained by superimposing the sine wave and a plurality of harmonics, it is possible to grasp the state of the plasma as the load, for example, the plasma density and the gas pressure.

As a plasma processing apparatus using plasma as a load, a substrate such as a semiconductor substrate, a glass substrate of a liquid crystal display, a glass substrate for a photomask, or a substrate for an optical disk is put into a chamber. A plasma etching apparatus for performing etching, a plasma CVD apparatus for performing CVD (chemical vapor deposition) of a thin film, a plasma ashing apparatus for performing ashing of dust and the like adhering to the surface of a substrate, and the like. In such a plasma device, the state of the plasma can be grasped by analyzing the superimposed waveform. Therefore, by controlling various parameters (input power of sine wave and gas pressure), the plasma is controlled.
In addition to accurately performing the processing of the substrate with the plasma, it is also possible to accurately detect an abnormal state and the end point of the etching.

Further, the invention described in claim 2 is the same as the invention described in claim 1.
A first fundamental frequency generating means for generating a fundamental frequency f _osc for deriving the sampling clock frequency, and a means for measuring the superimposed waveform and giving the result to a discrete Fourier transform Measuring means, and a reference clock signal of a basic frequency f _osc for deriving the sampling clock frequency, the basic frequency of the sine wave from the superimposed waveform measured by the measuring means, It is generated by taking out and rectifying by a fundamental frequency generating means.

According to the second aspect of the present invention, the fundamental frequency of the sine wave is extracted from the superimposed waveform measured by the measuring means and rectified by the first fundamental frequency generating means. Thus, the sampling frequency is generated as a basic frequency f _osc for deriving the sampling clock frequency. Digital sampling is performed at the sampling clock frequency, and the digitally sampled data is subjected to discrete Fourier transform. The fundamental frequency f _osc for deriving the sampling clock frequency is the fundamental frequency of the sine wave from the superimposed waveform. The fundamental frequency of the sine wave is used as it is such that it is extracted and rectified. Therefore, even if the fundamental frequency of the sine wave fluctuates and the result of the superimposed waveform measured by the measuring means fluctuates, the first
Fundamental frequency f generated by the fundamental frequency generating means
_{Since the osc} also fluctuates, the amplitude intensity ratio between each harmonic obtained by the discrete Fourier transform of the digitally sampled data matches the original data, so that the waveform can be accurately analyzed.

[0016] The invention according to claim 3 provides the invention according to claim 1.
Fundamental frequency f _osc of the waveform analysis apparatus, further comprising a second fundamental frequency generation means for generating the fundamental frequency f _osc for deriving the sampling clock frequency, for deriving the sampling clock frequency
Is generated by rectifying the sine wave itself output from the AC power supply by the second fundamental frequency generating means.

According to the third aspect of the present invention, the fundamental frequency of the sine wave output from the AC power supply is:
A fundamental frequency f which is rectified by the second fundamental frequency generating means and is used to derive a sampling clock frequency.
Generated as _osc . Digital sampling is performed at the sampling clock frequency, and discrete Fourier transform is performed. The fundamental frequency f _osc for deriving the sampling clock frequency is the same as the fundamental frequency of the sine wave output from the AC power supply. Therefore, even if the fundamental frequency of the sine wave output from the AC power supply varies, the fundamental frequency f _osc generated by the second fundamental frequency generating means also varies in synchronization with the fundamental frequency of the sine wave. Even if digital sampling is performed at a sampling clock frequency derived from the frequency f _osc and discrete Fourier transform is performed, it is possible to accurately analyze a waveform, particularly, an amplitude intensity ratio between each harmonic and a fundamental wave.

The invention described in claim 4 is the first invention.
4. The waveform analyzer according to claim 3, wherein the number of sampling data of 1 × k is a power of 2.

[Operation and Effect] According to the fourth aspect of the invention, the number of sampling data is a power of two. For example, a Cooley-Tukey type FFT (Fast
In a high-speed FFT typified by Fourier Transform, etc., arithmetic processing is faster than ordinary discrete Fourier transform. In such a high-speed FFT, since the number of sampling data is required to be a power of two, the high-speed FFT is particularly required when the power is a power of two as in the invention according to claim 4. Useful. Here, the symmetry of the waveform is, for example, sin θ = −s
in (−θ), cos θ = cos (−θ), sin (2
nπ + θ) = sin θ, cos (2nπ + θ) = cos
refers to θ.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a plasma processing apparatus provided with a waveform analyzer according to the present invention. The first
The embodiments to the third embodiment will be described using plasma etching as an example.

As shown in FIG. 1, a plasma processing apparatus equipped with a waveform analyzer according to the first embodiment has an RF (Radio Fr.
equency) Power supply 1, matching box 2, and probe 3
, Measurement unit 4, analysis unit 5, electrode 6, and etching chamber 7
It is composed of

The RF power source 1 supplies an RF wave (having a wavelength of 0.1 m to
10 ³ m) and corresponds to the AC power supply of the present invention. Although the RF power supply 1 is used as the AC power supply, a high-frequency power supply that outputs a higher frequency (for example, a microwave or a millimeter wave) than an RF wave or a low-frequency power supply that outputs a lower frequency than the RF wave may be used. It may be a power supply. Also, the RF output from the RF power supply 1
The wave and its frequency correspond to a sine wave and a fundamental frequency in the present invention, respectively.

The matching box 2 is for matching the frequency of the power (including voltage and current) and the amplitude of the signal (power, voltage and current) output from the RF power source 1 according to the set values. It also has a function of removing noise and mixing of harmonics reflected by a plasma load described later.

The probe 3 outputs a signal (frequency, amplitude, etc.) of a superimposed waveform in which an RF wave input from the RF power supply 1 via the matching box 2 and a plurality of harmonics reflected by the plasma load are superimposed. It is for measuring and corresponds to the measuring means in the present invention.

The measuring unit 4 converts the measured superimposed waveform into an A / D
The analysis unit 5 converts the information of the plasma state (for example, plasma density and gas pressure) based on the amplitude and phase information of the Fourier-transformed signal. It is for seeking.

The electrode 6 receives the RF wave input from the RF power source 1 via the matching box 2 and the probe 3 to generate plasma in the etching chamber 7, and generates a plurality of plasmas reflected by the plasma load. The harmonics are secondarily propagated to the probe 3. Further, the electrode 6 also has a function of performing etching of the substrate W by causing ions or the like in the plasma in the etching chamber 7 to be incident on the substrate W as a processing object.

The etching chamber 7 has an electrode 6 on the inner wall.
The substrate W, which is a processing object, is placed on the mounting table S inside.

Next, the plasma processing apparatus according to the first embodiment
For each process performed in step 2, refer to the flowchart in FIG.
It will be described in the light of the above. The frequency of the RF wave is 13.5.
6 MHz (fundamental frequency f_osc) From the RF power supply 1
Supply and perform analysis up to the fifth harmonic.
Let n, which is the desired maximum order of harmonics, be 5, and l be 2 ^Four
(= 16), m is 3^Three(= 27), sampling data
Let the number be 4096 (ie 256 where k is 4096 / l)
And l is 2^FourAnd m is 3^ThreeTherefore, l and m are
If the prime is 2^FourAnd because n is 5, l is
2n + 1 and the number of sampling data is 409
6 (= 2¹²), The number of sampling data is 2
Is a power of. In addition, the etching chamber 7
Gas for generating plasma is pre-filled.

(Step S1) Generation of Plasma The RF wave output from the RF power source 1 is incident on the electrode 6 of the etching chamber 7 via the matching box 2 and the probe 3. Then, a plasma is generated in the etching chamber 7 by the gas and the RF wave filled in the etching chamber 7.

(Step S2) Reflection of Harmonics When plasma is generated in the etching chamber 7, RF
The RF power source 1 is operated so that the RF wave is continuously supplied from the power source 1 into the etching chamber 7. Further, ions and the like in the plasma in the etching chamber 7 are incident on the substrate W from the electrode 6, and the substrate W is etched. Note that the timing of loading the substrate W into the etching chamber 7 may be such that the substrate W is already loaded at the time of step S2 as in the first embodiment, or the plasma processing apparatus according to the first embodiment may supply the plasma. After grasping the state, the substrate W may be loaded.

On the other hand, the incident RF wave due to the plasma load in the etching chamber 7 is reflected with a plurality of harmonics due to the accompanying distortion. The reflected harmonics are sent to the probe 3.

(Step S3) Measurement of Superimposed Waveform The plurality of transmitted harmonics (including the fundamental wave) and the RF wave input from the RF power source 1 are superimposed to form a superimposed waveform and the probe 3 Measured. The signal (frequency, amplitude, etc.) of the superimposed waveform measured by the probe 3 is sent to the measuring unit 4.

(Step S4) Discrete Fourier Transform The superimposed waveform sent to the measuring section 4 is 13.56 MHz to 13.56 by a band pass filter not shown.
Only a frequency band of × 5 MHz (that is, a harmonic from the RF wave to the fifth order) is extracted, and noise and the like in other frequency bands are removed. The superimposed waveform from which noise or the like has been removed is subjected to A / D conversion, and is subjected to frequency analysis by discrete Fourier transform.

At this time, a fundamental frequency f _osc (= 13.56 MHz) is taken out of the superimposed waveform by a transmitter (not shown) in the measuring section 4 and the fundamental frequency f _osc is obtained.
2 ^4/3 clock signal produced from the ^3-divided is not a signal _osc becomes a trigger, superimposed waveform is converted A / D.
This clock signal, the fundamental frequency ^{_{f osc × 2 4/3 3}} , i.e. f _osc × l / m, and the corresponds to the sampling clock frequency in the present invention.

Let the original waveform be x (T), the Fourier transformed data be X (ω), and the number of sample data be N
Then, the equation of the discrete Fourier transform is generally represented as the following equation (1).

[0036]

(Equation 1)

In the present invention, the number N of sampling data in the above equation (1) is 1 × k.

(Step S5) Analysis of Waveform and Plasma The data subjected to the discrete Fourier transform by the measuring unit 4 in this way is sent to the analyzing unit 5, and the amplitude and phase information of the Fourier-transformed signal is analyzed. ,
The state of the plasma is analyzed based on the data.

The following operations and effects are achieved by the processes in steps S1 to S5. That is, the conditions for performing this step are set as follows. Power of 13.56 MHz (basic frequency f _osc ) is supplied from the RF power source 1 as the frequency of the RF wave and analysis is performed up to the fifth harmonic. Therefore, n, which is the desired maximum order of the harmonic to be analyzed, is 5 Where l is 2 ⁴ (= 16) and m is 3 ³
(= 27), the number of sampling data is set to 4096 (that is, k is 256, which is 4096 / l). l is 2 ⁴
Since m is 3 ³ , l and m are relatively prime. Since l is 2 ⁴ and n is 5, l is larger than 2n + 1 and the number of sampling data is 4096 (= 2 ¹² ).
Therefore, the number of sampling data is a power of two.

Under these conditions, the conventional sampling clock frequency is twice as high as the highest frequency among the waveforms that need to be analyzed ( _fosc × 2n = 13.56 MHz).
× 2 × 5 = 135.6 MHz) or more, so that the sampling clock frequency f _osc × l used in the present invention.
/M(=13.56MHz×2 ^{4/3 3} = 8.036MH
z) is lower than the above-described conventional sampling clock frequency. Even when the sampling clock frequency is lower than the conventional sampling clock frequency, harmonics of different orders do not appear in the same frequency band under the above-mentioned conditions, and the mutual amplitude intensity ratio of the harmonics is not equal to the amplitude intensity ratio of the original waveform to be measured. I do. Therefore, the peak of the signal amplitude of each harmonic can be measured at a sampling clock frequency lower than before, and the analysis result such as the amplitude and phase information of the signal to be obtained can be obtained accurately. As a result, at a sampling clock frequency lower than before, a high resolution can be obtained even in the amplitude of the signal obtained from the analysis result, and the waveform can be accurately analyzed. Further, the state of the plasma, for example, the plasma density and the gas pressure can be accurately analyzed by the accurate analysis of the waveform.

In the apparatus of the first embodiment, since the state of the plasma can be grasped by analyzing the superimposed waveform, the plasma in the etching chamber 7 can be controlled by controlling the power and frequency of the RF wave. In addition, the processing of the substrate W by plasma etching can be appropriately performed, and the detection of an abnormal state and the detection of the end point of the etching can be accurately performed.

Further, satisfy and l and m are even relatively prime, since it is possible to increase the m (in the first embodiment 3 ^3), be reduced as possible sampling clock frequency, theoretically Can accurately obtain the amplitude, phase information, and the like of the signal to be obtained, and can also obtain high resolution in the amplitude of the signal obtained from the analysis result. However, if m is increased, the time required for sampling becomes enormous. Therefore, m is appropriately adjusted so that the time becomes a desired time.

Also, since the number of sampling data is a power of 2, a high-speed FFT, for example, a Cooley-Tukey type FFT (Fast Fourier Transf
If the CPU (central processing unit) of the measuring unit 4 is configured to perform the orm), the discrete Fourier transform in step 4 can be performed by a high-speed FFT, and the waveform can be analyzed at higher speed. .

[Second Embodiment] Next, a second embodiment of the present invention will be described. FIG. 3 is a block diagram showing a schematic configuration of the plasma processing apparatus according to the second embodiment. The first
The same reference numerals are given to the parts common to the embodiment device,
The illustration and description of that part are omitted.

As shown in FIG. 3, the plasma processing apparatus according to the second embodiment has an RF power source 1, a matching box 2, a probe 3, a measuring unit 4, and an analyzing unit 5, which are common to the first embodiment.
, An electrode 6, and an etching chamber 7, and a clock generation circuit 8.

The reference numerals 1 to 7 are the same as those in the first embodiment, but in the measuring section 4 according to the second embodiment, as described in the description of the clock generation circuit 8, as in the first embodiment. It is not always necessary to provide a suitable transmitter (not shown).

The clock generation circuit 8 calculates the fundamental frequency f of the RF wave from the superimposed waveform measured by the probe 3.
_osc (= 13.56 MHz) is extracted, and the extracted signal is rectified and generated. More specifically, a signal of a superimposed waveform measured by the probe 3 is sent to the measuring unit 4, while a part of the signal is branched and sent to the clock generation circuit 8. A band-pass filter (not shown) in the clock generation circuit 8
Only the fundamental frequency f _osc of the F wave is extracted, and the amplitude of the RF wave signal is made substantially constant by controlling the amplifier gain (not shown) in the clock generation circuit as necessary. For the rectified RF wave signal,
Like the first embodiment, the fundamental frequency f _osc 2 ^4/3 3
The clock signal generated from the divided signal is used as a trigger to be generated in the clock generation circuit 8. The generated clock signal is sent to the measuring unit 4 and used as a sampling clock frequency for A / D conversion of a superimposed waveform. This clock generation circuit 8 has a function similar to that of the transmitter in the measuring section 4 in the first embodiment, and corresponds to a first fundamental frequency generation means in the present invention.

Since the frequency of the RF wave is used as the fundamental frequency f _osc such that the frequency of the RF wave is extracted from the superimposed waveform and rectified by the clock generation circuit 8, even if the frequency of the RF wave fluctuates. , The fundamental frequency f _osc generated by the clock generation circuit 8 also fluctuates.
Therefore, as compared with the transmitter of the first embodiment, even if the discrete Fourier transform is performed by the measurement unit 4, the analysis unit 5 can more accurately analyze the waveform.

The flowchart of each process performed by the plasma processing apparatus according to the second embodiment is as follows. In the discrete Fourier transform in step S4 of the first embodiment, the superimposed waveform measured by the probe 3 is transmitted to the measuring unit 4. Except for the fact that the signal is branched at the time of sending out and one is sent out to the measuring unit 4 and the other is sent out to the clock generation circuit 8, the explanation is omitted because it is common to the first embodiment.

[Third Embodiment] Next, a third embodiment of the present invention will be described. FIG. 4 is a block diagram showing a schematic configuration of the plasma processing apparatus according to the third embodiment. In addition, the same reference numerals are given to portions common to the first and second embodiments, and illustration and description of those portions are omitted.

As shown in FIG. 4, the plasma processing apparatus according to the third embodiment has an RF power source 1, a matching box 2, a probe 3, a measuring unit 4, an analyzing unit 5, and an electrode 6 common to the second embodiment. , An etching chamber 7 and a clock generation circuit 8.

Reference numerals 1 to 8 are the same as in the second embodiment, but the clock generation circuit 8 according to the second embodiment generates a trigger based on a signal branched from the superimposed waveform measured by the probe 3. In contrast, the clock generation circuit 8 according to the third embodiment splits the frequency of the RF wave from the RF power supply 1 separately from the RF wave sent to the matching box 2, , And a trigger is generated and sent to the measuring unit 4. The clock generation circuit 8 according to the third embodiment corresponds to a second basic frequency generation unit according to the present invention.

Since the frequency of the RF wave output from the RF power supply 1 is used as it is, even if the frequency of the RF wave output from the RF power supply 1 fluctuates, the clock generation circuit synchronizes with the frequency of the RF wave. also varies the fundamental frequency f _osc generated by 8. Therefore, as compared with the transmitter of the first embodiment, even if the discrete Fourier transform is performed by the measurement unit 4, the analysis unit 5 can more accurately analyze the waveform. Furthermore, in comparison with the second embodiment, the second embodiment may have an amplifier gain for making the amplitude of the RF wave signal constant as needed, whereas In the embodiment, since the frequency of the RF wave output from the RF power supply 1 is used as it is, there is also an effect that it is not necessary to provide an amplifier gain.

The flowchart of each process performed by the plasma processing apparatus according to the third embodiment will be described with respect to the case where the signal is branched from the RF power supply 1 in the plasma generation in step S1 of the third embodiment. In the discrete Fourier transform of step S4 in the second embodiment, since the signal is branched when the superimposed waveform measured by the probe 3 is sent to the measuring unit 4, the description is omitted because it is common to the second embodiment. .

The present invention is not limited to the above embodiment, but can be modified as follows.

(1) In the above-described embodiment, the description has been made by taking plasma etching as an example. However, the present invention can be applied to plasma CVD, plasma ashing, and the like. Further, although the description has been given by taking the plasma as an example of the load, the load is constituted by a line circuit or the like in a case where power is propagated and reflected on the line in a normal line circuit (for example, a distributed constant circuit). As noted, the load is not limited to plasma only.

(2) In the above-described embodiment, the probe 4 is used as a means for measuring the waveform. However, as exemplified by a directional coupler, the incident waveform and the reflected waveform are superposed. There is no particular limitation as long as it is a means for measuring the waveform. Further, the measurement location of the probe 4 is not particularly limited.

[0058]

As is apparent from the above description, according to the present invention, even if the sampling clock frequency is lower than the conventional one, harmonics of different orders do not appear in the same frequency band, so that the harmonics obtained by the discrete Fourier transform can be obtained. The analysis results obtained can be obtained accurately. As a result, at a lower sampling clock frequency than before, a high resolution can be obtained even in the amplitude and phase difference of the signal obtained from the analysis result, and the waveform can be accurately analyzed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a first embodiment of a plasma processing apparatus according to the present invention.

FIG. 2 is a flowchart showing each process performed in the first embodiment apparatus.

FIG. 3 is a block diagram illustrating a schematic configuration of a plasma processing apparatus according to a second embodiment.

FIG. 4 is a block diagram illustrating a schematic configuration of a plasma processing apparatus according to a third embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... RF power supply 3 ... Probe 4 ... Measuring part 7 ... Etching chamber

Claims (5)

[Claims] 1. A sine wave power is supplied from an AC power supply to a load, and digital sampling is performed on at least a part of a superimposed waveform in which the sine wave and a plurality of harmonics obtained by reflection from the load are superimposed. A discrete Fourier transform of the digitally sampled data, thereby analyzing the superimposed waveform and analyzing the state of the load. In the waveform analyzer, a fundamental frequency which is a frequency of a sine wave output from the AC power supply is set to f _osc. , L, k,
m and n are natural numbers, n is the desired maximum order of the harmonic to be analyzed, l is greater than 2n + 1, l and m are relatively prime, and the number of sampling data is represented by l × k. A waveform analysis apparatus, wherein digital sampling is performed at a sampling clock frequency of f _osc × l / m, and the digitally sampled data is subjected to discrete Fourier transform. 2. The waveform analyzer according to claim 1, wherein a first fundamental frequency generating means for generating a fundamental frequency f _osc for deriving the sampling clock frequency, and the superimposed waveform is measured. And a measuring means for giving a discrete Fourier transform to the discrete Fourier transform, and a reference clock signal of a fundamental frequency f _osc for deriving the sampling clock frequency is a signal of the sine wave from the superimposed waveform measured by the measuring means. A waveform analyzer, wherein a fundamental frequency is generated by taking out and rectifying a fundamental frequency by the first fundamental frequency generating means. 3. The waveform analysis device according to claim 1, further comprising a second fundamental frequency generation unit that generates the basic frequency f _osc for deriving the sampling clock frequency, and derives the sampling clock frequency. A fundamental frequency f _osc for generating the sine wave output from the AC power supply by rectifying the sine wave itself by the second fundamental frequency generating means. 4. The waveform analyzer according to claim 1, wherein the number of sampling data of 1 × k is a power of two. 5. A plasma processing apparatus comprising the waveform analyzer according to claim 1. Description: