Electrical variable capacitor using symmetrical switch configuration for reducing switch voltage in RF plasma systems
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ORIGINAL ARTICLE
Electrical variable capacitor using symmetrical switch configuration for reducing switch voltage in RF plasma systems Juhwa Min1 · Beomseok Chae1 · Yongsug Suh1 · Jinho Kim2 · Hyunbae Kim2 Received: 24 March 2020 / Revised: 16 July 2020 / Accepted: 28 July 2020 © The Korean Institute of Power Electronics 2020
Abstract This paper introduces a novel method to reduce the voltage stress experienced by 320 V/1 kW/13.56 MHz electrical variable capacitor (EVC) circuits with an asymmetrical switch configuration applied in the impedance matching circuits of RF plasma systems. The proposed method employs a symmetrical switch configuration in place of the asymmetrical switch configuration in each of the capacitor legs in an EVC circuit. The symmetrical switch configuration reduces the voltage stress in the EVC circuit due to symmetrical charging and discharging modes. As a result, the proposed circuit can be used in etching systems. The major idea is verified by simulation and experimental results, which successfully demonstrate that the voltage stress on the switch of an EVC circuit is reduced by more than 35%. Keywords Electrical variable capacitor (EVC) · RF plasma system · Voltage stress · Impedance matching
1 Introduction RF plasma is used in various industrial applications [1–4]. One RF plasma system is the semiconductor device manufacturing process. The semiconductor device manufacturing process uses plasma processing at different stages of the process. Plasma processing involves the energizing of a gas mixture by imparting energy to the gas molecules by introducing RF (radio frequency) energy into the gas mixture. This gas mixture is typically contained in a vacuum chamber, referred to as a plasma chamber, and the RF energy is typically introduced into the plasma chamber through electrodes. In a typical RF plasma process, the RF generator generates power at the RF (which is broadly understood to be within the range of 3 kHz–300 GHz), and this power is transmitted through RF cables and networks to the plasma chamber, in order to provide an efficient transfer of power from the RF generator to the plasma load, where an intermediary circuit is used to match the fixed impedance of the * Yongsug Suh [email protected] 1
Department of Electrical Engineering, Jeonbuk National University, Chonju, Korea
Manufacturing Technology Center, Samsung Electronics, Hwaseong, Korea
2
RF generator with the variable impedance of the plasma load [5–9]. Impedance matchers are required to achieve efficient power transmission in RF plasma systems. Impedance matchers essentially require variable components. The most common types are variable inductors and variable capacitors. However, variable inductors have a disadvantage since they are large and difficult to control. Therefore, impedance matchers use a vacuum variable capacitors (VVCs) that mechanically changes the capacitance. However, VVC takes a long time to achieve a match. In order to reduce the matching time, EVCs using power electronic technology have been r
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