双频容性耦合等离子体相分辨发射光谱诊断

Phase resolved optical emission spectroscopy of dual frequency capacitively coupled plasma

采用相分辨发射光谱法,对双频容性耦合纯Ar和不同含O2量的Ar-O2混合气体放电等离子体的鞘层激发模式进行了探究.放电腔室耦合电源电极的鞘层区域处观察到两种电子激发模式:鞘层扩张引起的电子碰撞激发模式和二次电子引起的电子碰撞激发模式;并发现这两种激发模式均受到低频射频电源周期的调制.在纯Ar放电等离子体中,两种激发模式的激发轮廓相似;而在Ar-O2混合气放电等离子体中,随着含O2量的增加,二次电子的激发轮廓变弱.此外,利用相分辨发射光谱法对不同含O2量的Ar-O2混合气放电下Ar的750.4 nm谱线在低频周期内的平均光强随轴向分布进行了研究,得到了距耦合电源电极约3.8 mm处为双频容性耦合射频等离子体的鞘层边界.

In this article we use phase resolved optical emission spectroscopy to study emission pattern in plasma sheath of dual frequency capacitively coupled plasma in Ar and Ar-O2 discharge. Two emission patterns are found in sheath region of radio-frequency coupled powered electrode. The first pattern is related to electron impact excitation because of the sheath expansion. The second pattern is caused by electron impact excitation of secondary electrons. Two emission patterns are also highly modulated with the low frequency cycle. Under the condition of argon discharge, the emission intensities of the two excitation processes are very similar. The emis-sion structure by secondary electrons becomes weak with the increase of O2 content in the gas mixture. In addition, we also use phase resolved optical emission spectroscopy to study low frequency cycle averaged axial emission profile of excited atomic argon at 751 nm in Ar-O2 mixture gas. Distance from the powered electrode （about 3.8 mm） is defined as the boundary sheath of dual frequency capacitively coupled plasma.