Effect of a negative DC bias on a capacitively coupled Ar plasma operated at different radiofrequency voltages and gas pressures  

作　　者：相垚君 王晓坤 刘永新 王友年 Yaojun XIANG;Xiaokun WANG;Yongxin LIU;Younian WANG(Key Laboratory of Materials Modification by Laser,Ion,and Electron Beams(Ministry of Education),School of Physics,Dalian University of Technology,Dalian 116024,People’s Republic of China;Chair of Applied Electrodynamics and Plasma Technology,Ruhr University Bochum,Bochum 44801,Germany)

机构地区：[1]Key Laboratory of Materials Modification by Laser,Ion,and Electron Beams(Ministry of Education),School of Physics,Dalian University of Technology,Dalian 116024,People’s Republic of China [2]Chair of Applied Electrodynamics and Plasma Technology,Ruhr University Bochum,Bochum 44801,Germany

出　　处：《Plasma Science and Technology》2024年第5期62-71,共10页等离子体科学和技术（英文版）

基　　金：financially supported by National Natural Science Foundation of China(NSFC)(Nos.12275043 and 11935005);the Fundamental Research Funds for the Central Universities(No.DUT21TD104);China Scholarship Council(No.202106060085)。

摘　　要：The effect of a negative DC bias,|V_(dc)|,on the electrical parameters and discharge mode is investigated experimentally in a radiofrequency(RF)capacitively coupled Ar plasma operated at different RF voltage amplitudes and gas pressures.The electron density is measured using a hairpin probe and the spatio-temporal distribution of the electron-impact excitation rate is determined by phase-resolved optical emission spectroscopy.The electrical parameters are obtained based on the waveforms of the electrode voltage and plasma current measured by a voltage probe and a current probe.It was found that at a low|V_(dc)|,i.e.inα-mode,the electron density and RF current decline with increasing|V_(dc)|;meanwhile,the plasma impedance becomes more capacitive due to a widened sheath.Therefore,RF power deposition is suppressed.When|V_(dc)|exceeds a certain value,the plasma changes toα–γhybrid mode(or the discharge becomes dominated by theγ-mode),manifesting a drastically growing electron density and a moderately increasing RF current.Meanwhile,the plasma impedance becomes more resistive,so RF power deposition is enhanced with|V_(dc)|.We also found that the electrical parameters show similar dependence on|V_(dc)|at different RF voltages,andα–γmode transition occurs at a lower|V_(dc)|at a higher RF voltage.By increasing the pressure,plasma impedance becomes more resistive,so RF power deposition and electron density are enhanced.In particular,theα–γmode transition tends to occur at a lower|V_(dc)|with increase in pressure.

关 键 词：RF capacitively coupled plasma DC-overlapped RF discharge power deposition discharge mode transition 

分 类 号：O53[理学—等离子体物理]