AVS 56th International Symposium & Exhibition
    Plasma Science and Technology Wednesday Sessions
       Session PS1-WeA

Paper PS1-WeA11
Investigation of Standing Wave Formation in the Large Area Capacitively Coupled RF Driven Processing Plasma Source

Wednesday, November 11, 2009, 5:20 pm, Room A1

Session: Plasma Modeling
Presenter: S.H. Lee, Seoul National University, Republic of Korea
Authors: S.H. Lee, Seoul National University, Republic of Korea
M.S. Choi, Seoul National University, Republic of Korea
G.H. Kim, Seoul National University, Republic of Korea
Correspondent: Click to Email
Large area capacitively coupled plasma (CCP) sources are widely used in etch and deposition processes for the fabrication of flat panel display and solar cells. In general, the plasma density may increase with increasing frequency and it may improve the process rate. However the wavelength reduces with increasing frequency and the field variation on the substrate becomes serious due to the formation of standing wave pattern on the electrode. It causes the difficulty to control the process uniformity for the large process area. Many experimental investigations have been carried out for intermediate size plasma source as 1m x 1m and the wave patterns are observed. However, in practice, the reactor size becomes more than 2m x 2m with 13.56 MHz or higher RF frequency. Thus the standing wave effects are issued on the development of large area plasma process. The mechanism of standing wave formation and measurement are the theme of this study. Transmission line and wave models were developed to investigate the standing wave effect, skin effect, and telegraph effect, which have been reported separately. Here the new 1 D analytic model is introduced to describe the formation of standing wave on the reactor of 1.4m x 1.6m with applying 60 MHz, which consists of the transmission line model adapted to analysis of wave pattern from the matcher to the electrode and the wave propagation model for the formation of standing wave between sheath boundary and conducting electrode. Strategically, the wave conditions obtained from the transmission line model are adapted to the boundary values for the wave model. From this model, it reveals that the standing wave formation is related to the structure between the electrode and matching units as well as plasma property. Experimentally, the amplitude of plasma potential fluctuation was monitored from Langmuir probe measurement, being compared to the prediction of wave pattern from the model. It shows fairly good agreement between the model and the measurement. As expected, with increasing the plasma density, the wavelength becomes decreased due to shortening of the sheath thickness. Further results will be presented.