JP2003257699A - High frequency power supply device for plasma generating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high frequency power supply device for a plasma generating device capable of enhancing the output accuracy of the high frequency output emitted intermittently. <P>SOLUTION: The high frequency power supply device includes a first control loop (22, 24, 29) furnished with a peak value sensing part to sense the peak value of the high frequency output emitted intermittently and an output control part 22 which compares the peak value sensed by the sensing part with the set value of the output peak predetermined and controls the output peak to the set value and a second control loop (24, 28, 35a) equipped with a monitor part to sense the mean of the high frequency output emitted intermittently, a calculating means to calculate the mean of the high frequency output on the basis of the set value of peak and the duty ratio set value, and a pulse generation part 35 to generate modulation reference signals for controlling a modulation part on the basis of the mean of the high frequency output sensed by the monitor part and the mean of the high frequency output calculated by the calculating means. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency power supply device for a plasma generator, and more particularly to a high frequency power supply device for a plasma generator capable of intermittently controlling a power output and controlling an average output thereof.

[0002]

2. Description of the Related Art First, a conventional technique will be described by taking a plasma processing apparatus called an ECR (electron cyclotron resonance) system as an example. In this ECR type plasma processing apparatus, plasma is generated by introducing microwaves into a vacuum container to which a magnetic field is applied from the outside. Electrons perform cyclotron motion by a magnetic field. Plasma can be efficiently generated by resonating the frequency of the cyclotron motion with the frequency of the microwave. Further, a high frequency voltage is applied to the sample in order to accelerate the ions incident on the sample. A halogen gas such as chlorine or fluorine is used as the plasma gas.

In such a plasma processing apparatus, the output of the high frequency power source applied to a sample (wafer) is controlled to be turned on and off to control the output for the purpose of improving the accuracy of processing. This makes it possible to increase the selection ratio between silicon (Si), which is the substance to be etched, and the underlying oxide film, and reduce the aspect ratio dependency.

Further, by controlling the output of the high frequency power source applied to the wafer on and off, it is possible to reduce the consumption of the sample table without lowering the processing speed of the wafer.
Therefore, the frequency of maintenance for exchanging the sample table can be reduced, and the throughput of the apparatus can be improved.

FIG. 6 is a diagram for explaining the relationship between the average output and the peak output value. In the figure, 141 is a waveform of the output of the high frequency power supply. 144 is the ON time of pulse output, 1
45 is the off time of the pulse output. 142 is a peak value of the output output from the high frequency power source, and 143 is an average output. For example, when etching Poly Si, 10 W to 100 W is supplied as an average output.

A typical duty ratio (ON time ratio) in the on / off control is about 20%, and when the peak output value of the high frequency power supply is 200 W, the average output of the high frequency power supply is about 40 W.

FIG. 7 is a diagram showing a conventional high frequency power supply device for a plasma generator. Reference numeral 1 is a control microcomputer for operating a high frequency power supply, 20 is a high frequency power supply device for a plasma generator (hereinafter simply referred to as a high frequency power supply), 21 is a peak value setting signal for setting a peak value of the high frequency power supply output, and 36 is on / off control repetition A repetition frequency setting signal for setting a frequency, 37 an on-time width setting signal for setting an on-time width when performing on / off control, and 22 for the peak value setting signal 2
1 and an output control unit for generating an operation signal 23 for operating an output peak based on the fed back peak value detection signal 30, and a high-frequency output 25 which is intermittent based on the operation signal 23 and a modulation reference signal 38 described later. Is a peak value detecting section for detecting the intermittent high frequency output at the timing of the pulse reference signal, and 35 is a repeat frequency setting signal 36 and an ON time width setting signal 37 supplied by the control microcomputer. It is a pulse generator that generates the modulation reference signal 31 and the pulse reference signal 38. The pulse generation unit 35 generates a rectangular wave having a predetermined duty ratio based on the signal indicating the repetition frequency and the ON time width,
The rectangular wave is used as a pulse reference signal 38, and a signal obtained by multiplying the pulse reference signal 38 and a high frequency reference signal (oscillator output) is output as a modulation reference signal 31.

First, the control microcomputer 1 sets the peak value setting signal 21. The output control unit 22 outputs an operation signal 23 for controlling the peak value output from the high frequency power supply 20 based on the peak value setting signal 21 and the peak value signal 30 detected by the peak value detection unit 29. The modulator 24 generates an intermittent high frequency output 25 based on the operation signal 23 and the modulation reference signal generated by the pulse generator 35. The peak value detector 29 detects a high frequency output which is intermittent at the timing when the pulse reference signal 38 is supplied. Accordingly, the detection unit can detect the peak value of the high frequency output (the peak output value during the ON period of the intermittent high frequency output). The pulse generator 35 generates a rectangular wave having a predetermined duty ratio based on the signal 36 representing the repetition frequency and the signal 37 representing the ON time width, and the rectangular wave is supplied to the peak value detector 29 as a pulse reference signal 38. Used as timing information to supply and detect peak value.
Further, a signal intermittently generated at the same timing as the pulse reference signal 38 is generated as the modulation reference signal 31, and the signal 31 is supplied to the modulator 24. The modulator 24 generates a high frequency output 25 having the peak value indicated by the peak value operation signal, the duty ratio indicated by the modulation reference signal, and the repetition frequency based on the peak value operation signal 23 and the modulation reference signal 31.

[0009]

The average value of the intermittent high frequency output as described above is calculated by multiplying the peak value detected by the peak value detecting section by the duty ratio (ON period / ON period + OFF period). can do. That is, a high frequency output having a desired average value can be supplied to the load by monitoring the peak value detected by the peak value detection unit and the repetition frequency setting signal and the ON period setting signal.

However, the actual output waveform (pulse waveform) of the intermittently controlled high-frequency output is distorted from the rectangular wave. FIG. 8 is a diagram showing a waveform of intermittent high-frequency output, FIG. 8A is an intermittent waveform of the high-frequency output, and FIG. 8B is an enlarged view of a part thereof. As shown in the figure, there is a difference in the waveform at the time of rising or falling of the output power due to the response characteristics of the modulator, individual differences in component level, and the like. Therefore, the actual output value (average value) cannot be accurately calculated by the above-mentioned method only by controlling the peak value only by monitoring.

The fluctuation of the average output supplied to the load has a great influence on the etching characteristics given to the wafer in the semiconductor processing process. Further, even when high-frequency power supplies having the same specifications are used at the same time, there arises a problem that, for example, the etching rate on the wafer surface is different, resulting in different process performance.

The present invention has been made in view of these problems, and provides a high-frequency power supply device for a plasma generator capable of improving the output accuracy of intermittent high-frequency output.

[0013]

The present invention adopts the following means in order to solve the above problems.

A high frequency power supply device for a plasma generator, comprising: a modulator for generating an intermittent high frequency output based on a modulation reference signal and a peak value setting signal, the high frequency power supply device comprising: A peak value detecting section for detecting a peak value, and comparing the peak value of the intermittent high-frequency output detected by the peak value detecting section and a preset peak value of the high-frequency output with the peak value of the high-frequency output. 1st equipped with the output control part which controls to a peak set value
Of the control loop, a monitor unit for detecting an average value of the intermittent high-frequency output, and a calculating means for calculating an average value of the intermittent high-frequency output based on the preset peak setting value and duty ratio setting value. And a pulse generator for generating a modulation reference signal for controlling the modulator based on the average value of the high frequency output detected by the monitor and the average value of the high frequency output calculated by the calculator. Control loop.

[0015]

DETAILED DESCRIPTION OF THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram showing a high frequency power supply device for a plasma generation device according to an embodiment of the present invention. In the figure, 28 is a monitor unit for detecting the average value of intermittent high frequency output, and 35a is a modulation based on the peak value setting signal 21, the repetition frequency setting signal 36 and the ON time width setting signal 37 supplied from the control microcomputer 1. It is a pulse generator that generates the reference signal 31 and the pulse reference signal 38. As will be described later, the pulse generator 35a uses the average value of the outputs calculated based on the peak value setting signal, the repetition frequency and the signal representing the ON time width and the average value of the outputs monitored by the monitor unit. A rectangular wave having a predetermined duty ratio is generated, and the rectangular wave is generated as the pulse reference signal 38. Further, the pulse reference signal 38 and the high frequency reference signal (oscillator output) are multiplied to generate the modulation reference signal 31. Reference numeral 39 is a display unit for displaying the state of the high frequency power supply device. In the figure, the same parts as those shown in FIG. 7 are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 2 is a diagram showing the details of the pulse generator 35a. In the figure, 351 is a peak value setting signal 2
1. The average output is calculated based on the ON time width setting signal 37 and the frequency setting signal 36, and the ON time width is reset based on the calculated average output and the average output 34 measured by the monitor unit 28. And an on-time width resetting unit for generating an on-time width reset signal 353, and a pulse reference signal generation unit for generating a pulse reference signal 38 based on the on-time width reset signal 353 and the repetition frequency setting signal 36. Part, 35
Reference numeral 4 denotes an oscillator that oscillates a high-frequency reference signal 355 (for example, 400 kHz) that serves as a reference for the frequency of the power supplied to the load, and 356 is a multiplier.
5 is multiplied by the pulse reference signal to generate the modulation reference signal 31.

Next, details of the on-time width resetting unit 351 will be described. First, the average output to be output is calculated from the peak value setting signal 21, the repetition frequency setting signal 36, and the ON time width signal 37. For example, peak value setting signal 2
When the set value of 1 is 200 W and the value of the duty ratio set based on the ON time width setting signal 37 and the repetition frequency setting signal 36 is 20% (ON time ratio), the average output value becomes 40 W. Calculate the output set value. In addition,
Instead of the ON time width setting signal 37, a signal representing the duty ratio can be input. In this case, the repetition frequency setting signal 36 becomes unnecessary.

Next, the calculated output set value is compared with the average output value measured by the monitor unit, and the ON time width is reset based on the comparison result, and the ON time width reset signal 353 is set. To generate. For example, the value of the average output 34 measured by the monitor unit serves as a reference value for the time average output signal 40.
When it is larger than W, it is determined that the average output output from the high frequency power supply is large, and the ON time width reset signal 353 in which the ON time width is set so as to narrow the ON time width and lower the average output value is output. To do. Further, when the value of the average output 34 measured by the monitor unit is smaller than the time average output 40W serving as the reference value, it is determined that the average output output from the high frequency power source is small, and the ON time width is widened to average. An on-time width reset signal 353 in which the on-time width is set so as to increase the output value is output.

The pulse reference signal generator 352 generates a pulse reference signal 38 based on the reset signal 353 and the frequency setting signal 36, and the pulse reference signal 38 is multiplied by a high frequency reference signal 355 by a multiplier 356. The modulated reference signal 31 is generated.

3A and 3B are diagrams showing waveforms of various parts of the pulse generator. FIG. 3A shows the waveform of the high frequency reference signal 355, FIG. 3B shows the waveform of the pulse reference signal 38, and FIG. 3C. Denote modulation reference signals, respectively. In the figure, 111
Is the ON period of the pulse reference signal and the modulation reference signal, 112
Is an off period of the pulse reference signal and the modulation reference signal, 113
Indicates the frequency (cycle) of the repetition frequency setting signal.

FIG. 4 is a diagram showing an example of the high frequency power supply device 20 provided with the display unit 39. In the figure, 41 is a case accommodating the high frequency power supply main body, 42 is a panel arranged on the front of the case, and 43, 44 and 45 are indicators,
The duty ratio, repetition frequency, peak value setting signal, average output measured by the monitor unit, etc. are displayed. Also,
Reference numerals 46, 47, and 48 denote setting buttons, through which the duty ratio, repetition frequency, peak value setting signal, etc. can be set and input. Further, it is also possible to display the command value of the output set from the duty ratio, the repetition frequency, the peak value setting signal, etc. and the deviation from the average output, and to give an alarm. By providing the setting button, various settings can be performed without going to the installation place of the control microcomputer 1.

Next, the operation of the high frequency power supply device shown in FIG. 1 will be described. As shown in the figure, the high frequency power supply device according to the present embodiment includes a first control loop that is a feedback loop (output control unit 22, modulation unit 24, peak value detection unit 29) that controls the peak value of the high frequency power supply output. A second feedback loop (modulation unit 24, monitor unit 28, pulse generation unit 35a) for controlling the average output of the high frequency power supply output
Control loop.

First, the first control loop will be described. The peak value setting signal 21 is set by the control microcomputer 1. The output control unit 22 outputs the peak value operation signal 23 based on the peak value setting signal 21 and the peak value signal 30 detected by the peak value detection unit 29. The modulation unit 24 uses the operation signal 23
And the modulation reference signal (including the output reference frequency component of the high-frequency power supply and the pulse reference signal component that repeats ON / OFF in a pulse shape at a predetermined duty ratio) shown in FIG. 3C generated by the pulse generation unit 35a. It is modulated and amplified, and the amplified output is supplied to a load (not shown). The peak value detection unit 29
The amplified output, that is, the intermittent high-frequency output is detected,
The detected peak value signal is fed back to the output control unit 22. At this time, it is preferable to supply the detected peak value signal to the control microcomputer 1 so that the control microcomputer side can collect data.

Next, the second control loop will be described. The monitor unit 28 monitors the time average value of the intermittent high frequency output 25. As a monitoring method, for example, a thermocouple method in which a high-frequency output is converted into a thermoelectromotive force and detected, such as a thermocouple, is known. Monitor output of the monitor unit 28 (time average value of intermittent high-frequency output 25) 32
Feeds back to the pulse generator 35a and the control microcomputer 1. At this time, the monitor output 32 can be displayed on the display unit 39.

FIG. 5 is a diagram showing another example of the high frequency power supply device 20. The monitor unit 28 can be externally attached.
That is, it is difficult to reduce the size of the monitor unit by using the high frequency power source 20.
By making it separate from, the high-frequency power supply device can be made compact and lightweight.

As described above, according to this embodiment, the feedback loop (modulation unit 24, monitor unit 28, pulse generation unit 3) for controlling the average output of the high frequency power supply output.
5a), which controls the duty ratio of the high-frequency power supply output while monitoring the average value of the intermittent high-frequency output, so that, for example, the response characteristic of the modulator, individual difference in component level, etc. As a result, a high-frequency output having a desired output value can be obtained even when there is a difference in the waveform of the output when the output rises or falls. Therefore, by using this power supply, the influence on the semiconductor process can be reduced. For example, it is possible to reduce variations in etching characteristics given to the wafer and perform uniform wafer processing. Also, the first
By providing the feedback loop (1), it is possible to obtain the average value of the high frequency output with less fluctuation.

The control microcomputer 1 uses the plurality of setting signals (eg, the first and second setting signals) in which the peak value setting signal 21 is set in advance.
Setting signal) can be selected and output. In this case, the modulator generates a high frequency output having the amplitude indicated by the first setting signal during the ON period of the modulation reference signal, for example.
A high frequency output having the amplitude indicated by the second setting signal may be generated during the off period of the modulation reference signal. In this case, instead of the intermittent high-frequency output, the high-frequency output whose amplitude fluctuates between the values indicated by the first and second setting signals is obtained. For example, when the first setting signal is set to a high potential and the second setting signal is set to a low potential, for example, when the output decreases, the ON period is increased, and when the output increases. The on period may be controlled to be reduced.

[0028]

As described above, it is possible to provide a high-frequency power supply device for a plasma generator, which can improve the output accuracy of intermittent high-frequency output.

[Brief description of drawings]

FIG. 1 is a diagram showing a power supply device for a plasma generation processing apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing details of a pulse generation unit.

FIG. 3 is a diagram showing a waveform of each part of a pulse generator.

FIG. 4 is a diagram showing a high frequency power supply device including a display unit.

FIG. 5 is a diagram showing another example of a high frequency power supply device.

FIG. 6 is a diagram showing a relationship between average output and peak output.

FIG. 7 is a diagram showing a conventional high-frequency power supply device for a plasma generation device.

FIG. 8 is a diagram showing an output waveform of intermittent high-frequency output.

[Explanation of symbols]

1 control microcomputer 20 high frequency power supply 22 Output control unit 24 Modulator 28 Monitor 29 Peak value detector 35, 35a pulse generator 39 Output display, 351 ON time width resetting section 352 pulse reference signal generator 354 oscillator 356 multiplier

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor ▲ Takahashi Yoji             Yamaguchi Prefecture Kudamatsu City Oita Toyoi 794 Stock Association             Hitachi High-Technologies Corporation Design / Manufacturing             Headquarters Kasado Office (72) Inventor Kim Kiyoshi Nemitsu             Yamaguchi Prefecture Kudamatsu City Oita Toyoi 794 Stock Association             Hitachi High-Technologies Corporation Design / Manufacturing             Headquarters Kasado Office (72) Inventor Tsuyoshi Umemoto             Yamaguchi Prefecture Kudamatsu City Oita Toyoi 794 Stock Association             Hitachi High-Technologies Corporation Design / Manufacturing             Headquarters Kasado Office

Claims (5)

[Claims] 1. A high frequency power supply device for a plasma generator, comprising: a modulator for generating an intermittent high frequency output based on a modulation reference signal and a peak value setting signal, wherein the high frequency power supply device is the intermittent high frequency power supply. A peak value detection unit for detecting a peak value of the output, and a peak value of the high frequency output by comparing a peak value of the intermittent high frequency output detected by the peak value detection unit with a preset peak value of the high frequency output A first control loop including an output control unit for controlling the peak set value, a monitor unit for detecting an average value of the intermittent high-frequency output, and a preset peak set value and duty ratio set value. And a calculation means for calculating an average value of the intermittent high-frequency output, and an average value of the high-frequency output detected by the monitor section and an average value of the high-frequency output calculated by the calculation means. Based on a plasma generating device for high-frequency power supply device, characterized in that it comprises a second control loop which includes a pulse generator for generating a modulation reference signal for controlling the modulation unit. 2. The high frequency power supply device for a plasma generator according to claim 1, wherein the high frequency power supply device includes a setting switching unit that switches and sets the peak value setting signal. 3. The high frequency power supply device for a plasma generator according to claim 1, wherein the output monitor unit is a thermocouple monitor. 4. The pulse generation unit according to claim 1, wherein the pulse generation unit has at least an average value of high-frequency outputs detected by the monitor unit and an average value of high-frequency outputs calculated by the calculation unit. A high-frequency power supply device for a plasma generation device, comprising: a display unit for displaying. 5. A high-frequency power supply device for a plasma generator, comprising: a modulator for generating an intermittent high-frequency output based on a modulation reference signal, wherein the high-frequency power supply device calculates an average value of the intermittent high-frequency output. An average value of the high frequency output detected by the monitor section, comprising a monitor section for detecting, and a calculating means for calculating the average value of the intermittent high frequency output based on the peak value setting signal and the duty ratio setting signal of the high frequency output. And a high-frequency power supply device for a plasma generator, which controls the modulator based on an average value of the high-frequency output calculated by the calculation means.