JP2022049135A - Dc pulse power supply device and plasma processing device - Google Patents

Abstract

To provide a DC pulse power supply device and a plasma processing device capable of measuring a voltage value of a DC pulse at high accuracy.SOLUTION: A DC pulse power supply device 200 comprises a pulse conversion unit 205 that includes a first switching element Q1 and a second switching element Q2 and converts a DC voltage into a DC pulse by switching a conduction state of the first switching element and the second switching element, and a voltage detection unit 209 (a voltage divider circuit). The voltage detection unit detects a voltage value of a DC pulse voltage. A calibration data generation unit 214 generates as calibration data an inverse function of a transfer function of the voltage detection unit acquired on the basis of an output signal of the voltage detection unit in response to an input signal to the voltage detection unit. A voltage calibration unit 215 calibrates an output of the voltage detection unit on the basis of the calibration data.SELECTED DRAWING: Figure 2

Description

The present invention relates to a DC pulse power supply device and a plasma processing device.

The plasma processing apparatus used in processing such as etching, deposition, oxidation, and sputtering in the manufacture of semiconductor devices and flat panel displays includes a high frequency power supply device for generating plasma (see, for example, Patent Document 1). ). Further, in addition to the high frequency power supply device, a plasma processing device provided with a DC pulse power supply device for generating a DC pulse has also been proposed.

The DC pulse power supply device is a circuit that generates a pulse voltage whose amplitude changes in only one direction by controlling ON / OFF of the DC voltage at a predetermined timing. Such a DC pulse power supply device is provided to correct the so-called non-uniformity of the self-bias voltage generated between the electrodes of the plasma processing device by applying high frequency power. For example, a phenomenon may occur in which the self-bias voltage generated between the electrodes of the plasma processing apparatus is high near the center of the electrodes and low near the periphery. Such a phenomenon is particularly likely to occur when the device deteriorates over time.

By applying a DC pulse from the DC pulse power supply device, the non-uniformity of the self-bias voltage can be corrected and the self-bias voltage can be uniformly generated between the electrodes. As a result, in the plasma processing apparatus, high ion acceleration energy is uniformly generated between the electrodes, and it becomes possible to uniformly irradiate the object to be processed with ions at high speed.

The DC pulse power supply device is provided with a voltage detection circuit for detecting the voltage value of the generated DC pulse. This voltage detection circuit is provided with a voltage divider circuit that divides the input voltage. The voltage divider circuit is composed of a plurality of resistance elements and / or capacitors connected in series, and outputs a voltage corresponding to the voltage divider ratio. The voltage value of the generated DC pulse is calculated based on the value of the output voltage. When detecting a high voltage, a resistance element or a capacitor having a high impedance is used in the voltage dividing circuit in order to reduce the influence on the main circuit.

The voltage detection circuit in the DC pulse power supply device is required to have a stable frequency characteristic up to several times the frequency (fundamental frequency) of the pulse. In general, the higher the resistance of a resistance element, the lower the impedance tends to be even in the low frequency region. Further, the lower the capacitance of the capacitor, the higher the impedance and the better the frequency characteristic, but the capacitor is affected by the parasitic capacitance generated between the wiring, the substrate, or the housing. For this reason, it is difficult to obtain stable frequency characteristics when detecting the voltage of a DC pulse in the voltage detection circuit of a DC pulse power supply device. Therefore, the voltage value of the DC pulse is measured with high accuracy. It is difficult to do.

Japanese Unexamined Patent Publication No. 2015-9077

An object of the present invention is to provide a DC pulse power supply device and a plasma processing device capable of measuring the voltage value of a DC pulse with high accuracy.

In order to solve the above problems, the DC pulse power supply device according to the present invention includes a first switching element and a second switching element, and by switching the conduction state between the first switching element and the second switching element. , A pulse conversion unit that converts a DC voltage into a DC pulse, a voltage detection unit that includes a voltage dividing circuit and detects the voltage value of the DC pulse voltage, and an output of the voltage detection unit for an input signal to the voltage detection unit. A calibration data generation unit that generates the inverse function of the transmission function of the voltage detection unit acquired based on the signal as calibration data, and a voltage calibration unit that calibrates the output of the voltage detection unit based on the calibration data. Be prepared.

Further, the plasma processing apparatus according to the present invention is arranged so as to face the first electrode arranged in the processing container and the first electrode in the processing container, and the workpiece can be placed on the surface thereof. It includes a second electrode, a high-frequency power supply device that outputs high-frequency power to the first electrode, and a DC pulse power supply device that outputs a DC pulse to the first electrode. The DC pulse power supply device includes a first switching element and a second switching element, and a pulse conversion that converts a DC voltage into a DC pulse by switching the conduction state between the first switching element and the second switching element. A voltage detection unit that includes a voltage dividing circuit and detects the voltage value of the DC pulse voltage, and the voltage detection unit acquired based on the output signal of the voltage detection unit with respect to the input signal to the voltage detection unit. It is provided with a calibration data generation unit that generates an inverse function of the transmission function of the above as calibration data, and a voltage calibration unit that outputs the voltage detection unit based on the calibration data.

According to the present invention, it is possible to provide a DC pulse power supply device and a plasma processing device capable of measuring the voltage value of a DC pulse with high accuracy.

It is a block diagram explaining the structure of the plasma processing apparatus 100 which used the DC pulse power supply apparatus 200 which concerns on embodiment. It is a circuit diagram explaining the structure of the DC pulse power supply device 200 in more detail. It is a circuit diagram explaining the structure of the voltage detection unit 209. It is an operation diagram explaining the operation of the calibration signal generation unit 213, the calibration data generation unit 214, and the voltage calibration unit 215. An example of setting the circuit constant of the voltage detection unit 209, an example of the transfer function G (s), and an example of the inverse function G ^-1 (s) are shown. It is a graph which shows an example of the input signal to the voltage detection unit 209, the output signal, and the output signal after calibration. An example of setting the circuit constant of the voltage detection unit 209, an example of the transfer function G (s), and another example of the inverse function G ^-1 (s) are shown. It is a graph which shows an example of the input signal to the voltage detection unit 209, the output signal, and the output signal after calibration.

Hereinafter, the present embodiment will be described with reference to the accompanying drawings. In the attached drawings, functionally the same elements may be displayed with the same number. The accompanying drawings show embodiments and implementation examples in accordance with the principles of the present disclosure, but these are for the purpose of understanding the present disclosure and are never used for the limited interpretation of the present disclosure. is not it. The description of the present specification is merely a typical example, and does not limit the scope of claims or application examples of the present disclosure in any sense.

In this embodiment, the description is given in sufficient detail for those skilled in the art to implement the present disclosure, but other implementations and embodiments are also possible and do not deviate from the scope and spirit of the technical idea of the present disclosure. It is necessary to understand that it is possible to change the structure and structure and replace various elements. Therefore, the following description should not be construed as limited to this.

FIG. 1 is a block diagram illustrating a configuration of a plasma processing device 100 using the DC pulse power supply device 200 according to the embodiment. The plasma processing apparatus 100 is arranged in a processing container, and is arranged so as to face a cathode electrode 101 (first electrode) to which a high-frequency power and a DC pulse, which will be described later, are applied, and the cathode electrode 101, and is processed on the surface thereof. It is provided with a counter electrode 102 (second electrode) on which an object (for example, a semiconductor wafer) can be placed. The object to be machined can be fixed to the counter electrode 102 by an electrostatic chuck (not shown) installed on the counter electrode 102.

The counter electrode 102 is electrically grounded together with the processing container. In the processing container, for example, the object to be processed is installed on the surface of the counter electrode 102. The processing container is connected to a processing gas supply device (not shown) and an exhaust device (not shown).

High-frequency power is applied to the cathode electrode 101 from the high-frequency power supply device 400, and a (negative-negative) DC pulse whose amplitude changes only in the negative direction is applied from the DC pulse power supply device 200 to the cathode electrode 101. The high frequency power supply device 400 may be a high frequency power supply device that outputs a single frequency, or may be a high frequency power supply device that outputs a plurality of, for example, two types of frequencies superimposed. As an example, a high frequency power supply device may be used in which a high frequency (for example, about 13.56 MHz to 60 MHz) and a low frequency (for example, about 400 kHz to 2 MHz) are superimposed and generated.

As is well known, the DC pulse applied from the DC pulse power supply device 200 corrects the non-uniformity of the self-bias voltage when the high-frequency power supply device 400 excites the discharge plasma in the processing container, and the self-bias between the electrodes. It is applied to generate a uniform voltage. The voltage value of the DC pulse supplied from the DC pulse power supply device 200 is set to, for example, about -1500V when the self-bias voltage is about −1000V. That is, the voltage value of the DC pulse is set to a voltage having an absolute value larger than the self-bias voltage. A low-pass filter 300 for blocking high frequency from the high frequency power supply device 400 is connected between the DC pulse power supply device 200 and the plasma processing device 100. Further, a matching device 500 for matching the load impedance of the plasma processing device 100 with the impedance of the high frequency power supply device 400 is connected between the high frequency power supply device 400 and the plasma processing device 100. An upper control device 600 is provided as a control unit for controlling the high frequency power supply device 400 and the DC pulse power supply device 200.

The configuration of the DC pulse power supply device 200 will be described in more detail with reference to FIG. The DC pulse power supply device 200 includes a DC power supply 201, a DC / DC conversion unit 202, a DC / DC control unit 203, a voltage detection unit 204, a pulse conversion unit 205, a damping resistance 206, and a voltage detection unit 209. A current detection unit 210, a pulse control unit 211, a loss calculation unit 212, a calibration signal generation unit 213, a calibration data generation unit 214, a voltage calibration unit 215, and an abnormality detection unit 216 are provided. ..

The DC power supply 201 is a power supply circuit that generates a DC voltage for generating a DC pulse. The DC / DC converter 202 is a circuit that converts a DC voltage into a DC voltage having a different voltage value. The DC / DC conversion unit 202 operates according to the control from the DC / DC control unit 203. The DC / DC control unit 203 controls the DC / DC conversion unit 202 according to the voltage set value Vset set from the outside. The voltage detection unit 204 detects the voltage value of the DC voltage output by the DC / DC conversion unit 202, and outputs the detection result to the DC / DC control unit 203. The DC / DC control unit 203 controls the output voltage of the DC / DC conversion unit 202 according to this detection result.

The pulse conversion unit 205 includes a transistor Q1 as a first switching element (high-side switching element) and a transistor Q2 as a second switching element (low-side switching element). The transistors Q1 and Q2 are connected in series between the input terminal of the pulse conversion unit 205 and the reference terminal (ground terminal) via the damping resistor 206. Gate signals SW1 and SW2 are supplied from the pulse control unit 211 to the gate terminals of the transistors Q1 and Q2, and the transistors Q1 and Q2 are alternately switched to the conduction state. As a result, a DC pulse is supplied via the damping resistor 206. The pulse control unit 211 can operate in synchronization with the high frequency power supply device 400 according to the synchronization signal Ssy received from the high frequency power supply device 400. The pulse conversion unit 205 is, for example, a high-side grounded pulse conversion unit in which the drain of the transistor Q1 is electrically grounded. Instead of this, it is also possible to use a low-side installation type pulse conversion unit in which the drain of the transistor Q2 is electrically grounded.

The damping resistor 206 is configured by connecting the first resistance element 207 and the second resistance element 208 in series. The voltage detection unit 209 is configured to detect the voltage of the connection node between the first resistance element 207 and the second resistance element 208. Details of the configuration of the voltage detection unit 209 will be described later. The current detection unit 210 is provided after the voltage detection unit 209 to detect the current flowing through the damping resistor 206 (first resistance element 207 or second resistance element 208). The installation positions of the voltage detection unit 209 and the current detection unit 210 may be reversed.

The calibration signal generation unit 213 generates a calibration signal for calibrating the voltage detection unit 209 according to the signal from the voltage detection unit 209. The calibration signal is, for example, the transfer function G (s) of the voltage detection unit 209. As an example, the calibration signal generation unit 213 generates an input signal x (t), inputs it to the voltage detection unit 209, and acquires the output signal y (t), whereby the transmission function G of the voltage detection unit 209 is obtained. (S) = y (t) / x (t) can be obtained. The input signal x (t) is, for example, an AC signal of about 100 Hz to 1 MHz. The calibration data generation unit 214 generates calibration data for calibration of the voltage detection unit 209 according to the calibration signal. When the calibration signal is the transfer function G (s) of the voltage detection unit 209, the calibration data may be the inverse function 1 / G (s) of the transfer function. The voltage calibration unit 215 calibrates the detection voltage of the voltage detection unit 209 according to the calibration data obtained by the calibration data generation unit 214. The output signal (detection signal after calibration) of the voltage calibration unit 215 is output to the loss calculation unit 212 and the abnormality detection unit 216.

The loss calculation unit 212 calculates the loss of the DC pulse power supply device 200 according to the output signals of the gate signals SW1, SW2, the voltage calibration unit 215, and the current detection unit 210, and the loss exceeds the threshold value THloss. If so, the abnormality signal Sab1 is output to the DC / DC control unit 203 and the host control device 600. When the DC / DC control unit 203 receives the abnormal signal Sab1, the DC / DC control unit 203 controls the DC / DC conversion unit 202 to stop the supply of the DC voltage. Further, when the host control device 600 receives the abnormal signal Sab1, it controls the high frequency power supply device 400 to stop the output of the high frequency signal.

When the output of the voltage calibration unit 215 exceeds the voltage upper limit value THv, the abnormality detection unit 216 outputs the abnormality signal Sab2 toward the DC / DC control unit 203 and the host control device 600. When the DC / DC control unit 203 receives the abnormal signal Sab2, the DC / DC control unit 203 controls the DC / DC conversion unit 202 to stop the supply of the DC voltage. Further, when the host control device 600 receives the abnormal signal Sab2, it controls the high frequency power supply device 400 to stop the output of the high frequency signal.

The configuration of the voltage detection unit 209 will be described in more detail with reference to FIG. In the voltage detection unit 209, the first resistance element 2091 (resistance value R3) and the second resistance element 2092 (resistance value R4) are connected in series between the node O1 and the node O4 via the node O2. The node O1 is an input terminal of the voltage detection unit 209. Further, the first capacitor 2093 (capacity value C3) and the second capacitor 2094 (capacity value C4) are similarly connected in series between the node O1 and the node O4 via the node O3. The nodes O2 and O3 are output terminals of the voltage detection unit 209.

Next, with reference to FIG. 4, the operations of the calibration signal generation unit 213, the calibration data generation unit 214, and the voltage calibration unit 215 will be described. When performing the calibration operation, the output terminal of the current detection unit 210 and the output terminal of the calibration signal generation unit 213 are connected by a coaxial cable. Then, the calibration signal generation unit 213 causes the voltage detection unit 209 to input the input signal x (t) via the current detection unit 210, and receives the output signal y (t). The calibration signal generation unit 213 acquires the transfer function G (s) = y (t) / x (t) of the voltage detection unit 209 based on the input signals x (t) and y (t).

The calibration data generation unit 214 acquires the inverse function G ^-1 (s) = 1 / G (s) of the transfer function G (s) from the obtained transfer function G (s). The voltage calibration unit 215 calibrates the output signal of the voltage detection unit 209 by multiplying the output signal of the voltage detection unit 209 by this inverse function G ^-1 (s).

In the voltage detection unit 209 (voltage dividing circuit) of FIG. 3, when R3 × C3 = R4 × C4 is established, the transfer function G (s) of the voltage detection unit 209 is theoretically a constant (= R4 / (= R4 /). It becomes R3 + R4))) and has no frequency dependence. However, it is difficult to avoid the influence of parasitic capacitance generated on surrounding wiring, elements, boards, housings, and the like. Further, even if the device does not have frequency dependence at the time of design and shipment, frequency dependence may gradually occur due to aged deterioration of the device. Therefore, it is difficult to remove the frequency dependence from the voltage detection unit 209.

On the other hand, according to the method of this embodiment, it is possible to obtain the output of the voltage detection unit 209 from which the frequency dependence is removed by the calculation on the software. Since it is not affected by aging deterioration, it is possible to detect the voltage value of the DC pulse with high accuracy and reliability. Further, since the transfer function of the voltage detection unit 209 is acquired, it is possible to guarantee the transfer function in the form of including the parasitic capacitance component due to the structure such as the wiring around the voltage detection unit 209.

FIG. 5 shows R3 = 10MΩ, R4 = 10kΩ, C3 = 0.5pF in the first resistance element 2091, the second resistance element 2092, the first capacitor 2093, and the second capacitor 2094 of the voltage detection unit 209. , An example ((b)) of the transfer function G (s) in the case where C4 = 1000 pF is set ((a)), and an example ((c)) of its inverse function G ^-1 (s) are shown. Further, FIG. 6 shows the waveform ((a)) of the input signal to the voltage detection unit 209 of FIG. 5 (a), the waveform of the output signal from the voltage detection unit 209 ((b)), and the output signal after calibration. An example of the waveform ((c)) of is shown. When the circuit constant as shown in FIG. 5A is set, the voltage dividing ratio of the voltage dividing circuit of the first resistance element 2091 and the second resistance element 2092 is 10 kΩ / 10 MΩ = 1/1000, and the attenuation factor is -60 dB. Is. On the other hand, the voltage dividing ratio of the voltage dividing circuit of the first capacitor 2093 and the second capacitor 2094 is 0.5 pF / 1000 pF = 1/2000, the attenuation factor is -66 dB, and there is a difference of -6 dB. The inflection point (cutoff frequency) is 1 / (2πR1 · C1) = 16 kHz, 1 / (2πR2 · C2) = 32 kHz.

When the voltage detection unit 209 has the transfer function G (s) as shown in FIG. 5 (b), even if the rectangular wave as shown in FIG. 6 (a) is input to the voltage detection unit 209, The output signal is a dull signal as shown in FIG. 6 (b). However, by calculating the inverse function G-1 (s) of the transfer function G (s) and multiplying this by the output signal of the voltage detection unit 209 to calibrate, the calibrated signal is obtained in FIG. 6 (c). It can be a square wave with the bluntness removed. That is, it becomes possible to detect a voltage without frequency dependence.

FIG. 7 shows R3 = 10MΩ, R4 = 10kΩ, C3 = 2pF, C4 in the first resistance element 2091, the second resistance element 2092, the first capacitor 2093, and the second capacitor 2094 of the voltage detection unit 209. An example ((b)) of the transfer function G (s) in the case where = 1000 pF is set ((a)) and an example ((c)) of the inverse function G ^-1 (s) thereof are shown. Further, FIG. 8 shows the waveform ((a)) of the input signal to the voltage detection unit 209 of FIG. 7 (a), the waveform of the output signal from the voltage detection unit 209 ((b)), and the output signal after calibration. An example of the waveform ((c)) of is shown. When the circuit constant as shown in FIG. 7A is set, the voltage dividing ratio of the voltage dividing circuit of the first resistance element 2091 and the second resistance element 2092 is 10 kΩ / 10 MΩ = 1/1000, and the attenuation factor is -60 dB. Is. On the other hand, the voltage dividing ratio of the voltage dividing circuit of the first capacitor 2093 and the second capacitor 2094 is 2pF / 1000pF = 1/500, the attenuation factor is −54 dB, and there is a difference of 6 dB. The inflection point (cutoff frequency) is 1 / (2πR1 · C1) = 16 kHz, 1 / (2πR2 · C2) = 8 kHz.

When the voltage detection unit 209 has the transfer function G (s) as shown in FIG. 7 (b), even if the rectangular wave as shown in FIG. 8 (a) is input to the voltage detection unit 209, The output signal is a dull signal as shown in FIG. 8 (b). However, by calculating the inverse function G-1 (s) of the transfer function G (s) and multiplying this by the output signal of the voltage detection unit 209 to calibrate, the calibrated signal is obtained in FIG. 8 (c). It can be a square wave with the bluntness removed. That is, it becomes possible to detect a voltage without frequency dependence.

The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to the one including all the described configurations. Further, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. Further, it is possible to add / delete / replace a part of the configuration of each embodiment with another configuration.

100 ... Plasma processing device, 101 ... Cathode electrode, 102 ... Opposite electrode, 200 ... DC pulse power supply device, 201 ... DC power supply, 202 ... DC / DC conversion unit, 203 ... DC / DC control unit, 204 ... Voltage detection unit, 205 ... Pulse conversion unit, 206 ... Damping resistance, 207 ... First resistance element, 208 ... Second resistance element, 209 ... Voltage detection unit, 210 ... Current detection unit, 211 ... Pulse control unit, 212 ... Loss calculation unit , 213 ... Calibration signal generator, 214 ... Calibration data generation unit, 215 ... Voltage calibration unit, 216 ... Abnormality detection unit, 300 ... Low pass filter, 400 ... High frequency power supply device, 500 ... Matcher, 600 ... Upper control device, 2091 ... 1st resistance element, 2092 ... 2nd resistance element, 2093 ... 1st capacitor, 2094 ... 2nd capacitor, Q1 ... transistor, Q2 ... transistor.

Claims (4)

A pulse conversion unit that includes a first switching element and a second switching element, and converts a DC voltage into a DC pulse by switching the conduction state between the first switching element and the second switching element.
A voltage detector that includes a voltage divider circuit and detects the voltage value of the DC pulse,
A calibration data generation unit that generates as calibration data the inverse function of the transmission function of the voltage detection unit acquired based on the output signal of the voltage detection unit with respect to the input signal to the voltage detection unit.
A DC pulse power supply device including a voltage calibration unit that calibrates the output of the voltage detection unit based on the calibration data. The voltage divider circuit
Multiple resistance elements connected in series between the input terminal and the reference terminal,
A plurality of capacitive elements connected in series between the input terminal and the reference terminal, and
The DC pulse power supply device according to claim 1, wherein the connection nodes of the plurality of resistance elements and the plurality of capacitance elements are output terminals. Further, a damping resistor including a first resistance element and a second resistance element connected in series between the first switching element and the second switching element is provided.
The DC pulse power supply device according to claim 1 or 2, wherein the voltage dividing circuit is configured to measure the voltage of the connection node between the first resistance element and the second resistance element. The first electrode placed in the processing container and
A second electrode, which is arranged in the processing container so as to face the first electrode and on which a workpiece can be placed,
A high-frequency power supply device that outputs high-frequency power to the first electrode,
It is equipped with a DC pulse power supply device that outputs a DC pulse to the first electrode.
The DC pulse power supply device
A pulse conversion unit that includes a first switching element and a second switching element, and converts a DC voltage into a DC pulse by switching the conduction state between the first switching element and the second switching element.
A voltage detector that includes a voltage divider circuit and detects the voltage value of the DC pulse,
A calibration data generation unit that generates as calibration data the inverse function of the transmission function of the voltage detection unit acquired based on the output signal of the voltage detection unit with respect to the input signal to the voltage detection unit.
A plasma processing apparatus including a voltage calibration unit that outputs a voltage detection unit based on the calibration data.

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