AVS 49th International Symposium
    Plasma Science Tuesday Sessions
       Session PS2-TuA

Paper PS2-TuA10
Subsurface Diffusion and Reaction of Fluorine Atoms in Photoresist

Tuesday, November 5, 2002, 5:00 pm, Room C-105

Session: Plasma Surface Interactions I
Presenter: F. Greer, University of California, Berkeley
Authors: F. Greer, University of California, Berkeley
D. Fraser, University of California, Berkeley
J.W. Coburn, University of California, Berkeley
D.B. Graves, University of California, Berkeley
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Radicals created in plasmas are known to play important roles in thin film etching, deposition, cleaning, stripping and surface modification. The present study is aimed at developing a more quantitative model of radical-surface interactions. Room temperature measurements of F atoms abstracting D atoms from a deuterated photoresist surface to form DF were made in a vacuum beam apparatus, with simultaneous monitoring of film mass change with a quartz crystal microbalance. These measurements were interpreted as abstraction of D by F, followed by F saturation of dangling bonds previously occupied by D. However, the rate of DF formation and mass uptake due to F saturation showed a relatively long-lived tail, inconsistent with surface-only reactions. After the initial stage, subsequent DF formation and mass uptake appeared to be limited by F atom diffusion into the sub-surface since the measured rate of mass change and DF flux from the surface both varied inversely as t@super 1/2@. The surface abstraction probability of D by F was inferred to be 0.25, and the value of the F atom diffusivity was consistent with values reported for diffusion in polymers. These results will be discussed in terms of studies with other halogen radicals as well as nitrogen radicals. The application of these results to atomistic scale models of plasma etching will also be discussed.