CROSS-REFERENCE TO RELATED APPLICATION

The present application is a national stage filing under 35 U.S.C § 371 of PCT application number PCT/KR2018/013310 filed on Nov. 5, 2018 which is based upon and claims the benefit of priorities to Korean Patent Application No. 10-2017-0147521, filed on Nov. 7, 2017, in the Korean Intellectual Property Office, which are incorporated herein in their entireties by reference.

FIELD

The present disclosure relates to a plasma generator having a matching apparatus for matching impedance by connecting a radio frequency (RF) power source and an antenna-plasma device, and an impedance matching method.

BACKGROUND

In a plasma generator, a matching apparatus is used to match impedances between an RF source and a load to efficiently deliver power of the RF source to the load (antenna-plasma device). Such a matching apparatus may include a pair of capacitors that are capable of adjusting reactance according to capacitance variation to match an impedance of the RF source with an impedance of the load.

In the matching apparatus of such typical plasma generator, when a measured impedance does not match a reference matching impedance, a preset gain index within a predetermined range is multiplied by a difference between the measured impedance and the reference matching impedance, to determine capacitance of each capacitor required for matching, and an impedance that has been changed according to the determined capacitance of the capacitor matches a matching impedance. These processes may be repeated until the changed impedance matches the reference matching impedance.

On the other hand, the matching method of re-measuring an impedance using a controlled gain index, and determining whether the re-measured impedance matches a reference matching impedance has a problem in that a long matching time is required or taken due to the repetition of the matching processes. In addition, it takes a much longer time to match impedances since more matching processes are repeatedly performed when a measured impedance and a reference matching impedance have a greater difference therebetween at the time of initial matching. In addition, when a plasma load having relatively high load variability is connected, there is a problem in that a proper gain index needs to be newly found or detected or it takes a long time to measure an average impedance.

DISCLOSURE

Technical Problem

The present disclosure aims to solve the above-mentioned and other problems. One aspect of the present disclosure is to provide a plasma generator having a matching apparatus, capable of shortening a time required for impedance matching between an antenna-plasma device and an RF source, and an impedance matching method.

Technical Solution

According to an aspect of the present disclosure to achieve the above or other advantages, there is provided a plasma generator that may include a Radio Frequency (RF) power supply unit configured to supply RF power for plasma generation, a load device part including a standard load having a predetermined impedance and an antenna-plasma device configured to generate plasma according to the RF power, and a matching unit configured to connect the RF power supply unit to any one of the antenna-plasma device or the standard load, and match impedances of the RF power supply unit and the antenna-plasma device when the RF power supply unit is connected to the antenna-plasma device. The matching unit may be configured to detect a parasitic impedance according to parasitic components inside a circuit by connecting the standard load and the RF power supply unit before connecting the antenna-plasma device and the RF power supply unit, connect the antenna-plasma device, instead of the standard load, when the parasitic impedance is detected, calculate reactance required for the impedance matching based on the detected parasitic impedance, and change capacitance of capacitors provided therein according to the calculated reactance.

In one implementation, the matching unit may be configured to perform the impedance matching according to whether a calibration process for detecting the parasitic impedance is necessary when the RF power supply unit is connected to the antenna-plasma device or detect the parasitic impedance through the calibration process by connecting the RF power supply unit to the standard load, instead of the antenna-plasma device. Whether the calibration process is necessary may be determined based on whether there is a previously-detected parasitic impedance, whether a system has been initialized, or whether there is a user selection for performing the calibration process.

In one implementation, the matching unit may perform re-matching by varying the capacitance of the capacitors thereof based on a difference in impedance when a difference between an impedance measured while the antenna-plasma device is in a connected state to the RF power supply unit and a preset reference matching impedance exceeds a preset range. The matching unit may determine that the calibration process is necessary when a number of times of performing the re-matching exceeds a preset number of times and perform the calibration process.

The matching unit may detect a reflection coefficient for RF power supplied to the standard load when the standard load is connected to the RF power supply unit, and detect the parasitic impedance based on the detected reflection coefficient and an impedance of the standard load.

The matching unit may vary capacitance of the capacitors thereof to detect different reflection coefficients at least two times for the respective variations, and calculate a reflection coefficient when the standard load is connected to the RF power supply unit based on an average of the detected reflection coefficients.

According to one aspect of the present disclosure to achieve the above and other advantages, there is provided a matching method that may include connecting an RF power supply unit to a standard load having a preset impedance, instead of an antenna-plasma device, to detect a parasitic impedance according to parasitic components inside a circuit, reconnecting the RF power supply unit to the antenna-plasma device when the parasitic impedance is detected, measuring a reflection coefficient according to RF power supplied to the antenna-plasma device when the antenna-plasma device is connected, calculating a reactance value required for impedance matching based on the measured reflection coefficient and the detected parasitic impedance, and performing the impedance matching by changing capacitance of variable capacitors provided in the matching unit, so as to generate reactance according to the calculated reactance value.

In one implementation, the method may further include, prior to detecting the parasitic impedance, determining whether it is necessary to detect the parasitic impedance. The detecting of the parasitic impedance and the reconnecting of the antenna-plasma device may be performed according to a result of the determination as to whether it is necessary to detect the parasitic impedance.

In one implementation, the determination as to whether it is necessary to detect the parasitic impedance may be made according to whether there is a previously-detected parasitic impedance, whether a system has been initialized, or whether there is a user selection for performing a calibration process.

In one implementation, the performing of the impedance matching may include detecting a difference between an impedance measured when the RF power supply unit is connected to the antenna-plasma device and a preset reference matching impedance, and performing re-matching by changing the capacitance of the variable capacitors based on the detected difference in impedance when the detected difference in impedance is out of a preset range.

In one implementation, the performing of the re-matching may include re-detecting a parasitic impedance by performing the detection of the parasitic impedance again when a number of times of performing the re-matching exceeds a preset number of times, re-performing the connection to the antenna-plasma device and the measurement of the reflection coefficient, recalculating a reactance value required for the impedance matching based on the re-detected parasitic impedance, and re-performing the impedance matching by changing the capacitance of the variable capacitors provided in the matching unit, so as to generate reactance according to the recalculated reactance value.

In one implementation, the detecting of the parasitic impedance may include detecting a reflection coefficient for the standard load corresponding to RF power supplied when the standard load is connected to the RF power supply unit, and detecting the parasitic impedance based on the detected reflection coefficient for the standard load and an impedance of the standard load.

In one embodiment, the detecting of the reflection coefficient for the standard load may include varying capacitance of the variable capacitors and detecting different reflection coefficients for the respective variations a plurality of times, and calculating the reflection coefficient for the standard load based on an average of the detected reflection coefficients.

Advantageous Effects

A plasma generator and an impedance matching method according to the present disclosure will obtain effects as follows.

According to at least one of embodiments of the present disclosure, when an antenna-plasma device is connected, a required impedance can be calculated based on a parasitic impedance inside a matching apparatus and an impedance of the connected antenna-plasma device, and reactance can be adjusted by varying capacitance of capacitors according to the calculated impedance. This may result in greatly reducing a number of matching operations for performing impedance matching, thereby remarkably shortening a time spent for the impedance matching.

