Paper PS1-ThA2
Measurement of Absolute Density of Argon Metastables by using Laser Adsorption Spectroscopy

Thursday, October 18, 2007, 2:20 pm, Room 606

Absolute density of Ar metastables(1s_3,5) was measured in a two-frequency capacitively coupled plasma (2f-CCP) in pure Ar by using Laser Adsorption Spectroscopy (LAS) in order to investigate the spatial profile. The axial density distribution of metastables is experimentally characterized as a function of pressure (25 mTorr - 100 mTorr) and bias amplitude (100 V - 400 V). Axial density profile of Ar metastables shows a broad peak in front of the electrode driven at 100 MHz, and gradually decreases toward the opposite electrode biased at 500 kHz. With decreasing pressure, the density approaches to more defusive profile as expected. The typical density of Ar(1s₅) is 10¹¹ cm^-3, and the density ratio between Ar(1s₅) and Ar(1s₃) changes from 10 to 9.3, when we increase the pressure. Under the present external plasma condition, the bias amplitude has less influence on the axial magnitude and distribution of the metastables. It implies the complete functional separation between the driving and bias power in the 2f-CCP in the present system. The spatiotemporal transport of low energy electrons will be discussed through the fundamental collision process of Ar(1s₅) by using optical emission and absorption spectroscopy.