AVS 47th International Symposium
    Plasma Science and Technology Tuesday Sessions
       Session PS2-TuA

Invited Paper PS2-TuA3
Planar Laser-Induced Fluorescence Investigation of Fluorocarbon Plasmas

Tuesday, October 3, 2000, 2:40 pm, Room 311

Session: Plasma Diagnostics I
Presenter: K.L. Steffens, National Institute of Standards and Technology
Authors: K.L. Steffens, National Institute of Standards and Technology
M.A. Sobolewski, National Institute of Standards and Technology
Correspondent: Click to Email
Fluorocarbon plasmas are extensively used in the semiconductor industry for etching and chamber-cleaning applications. The etching process involves a competition between substrate removal and deposition of a fluorocarbon polymer layer on the wafer surface. The CF@sub 2@ radical is thought to be a major participant in the formation of this polymer layer either directly or by forming gas phase precursors which deposit to form the layer. Thus, measurements of the CF@sub 2@ radical are crucial to the understanding of etching chemistries. In this work, the planar laser-induced fluorescence (PLIF) technique was used to measure two-dimensional images of CF@sub 2@ density in CF@sub 4@ and C@sub 2@F@sub 6@ plasmas in the capacitively-coupled Gaseous Electronics Conference rf Reference Cell. Measurements were made at 200 mTorr with power deposited in the plasma ranging from 30 to 150 W, both without a substrate and with a Si wafer present, in pure fluorocarbon and in oxygen/fluorocarbon mixtures. In addition to the PLIF images, we obtained broadband emission images, which indicate the regions where reactive species are formed in the gas phase, and measurements of the rf current and voltage at the electrodes. The spatial distribution of CF@sub 2@ is observed to go through a transition as power is increased, becoming more radially-uniform at higher powers. In addition, the presence of the wafer was found to have a strong effect on the CF@sub 2@ by both increasing the CF@sub 2@ density and affecting the spatial distribution. The addition of O@sub 2@ decreases the CF@sub 2@ density even in the presence of a wafer. Comparisons will also be made with previous studies in 100 - 1000 mTorr O@sub 2@/C@sub 2@F@sub 6@ and O@sub 2@/CF@sub 4@ chamber-cleaning plasmas. The results of this study will help to elucidate the role of CF@sub 2@ in fluorocarbon plasmas as well as provide data for development and validation of plasma simulations.