Increased plasma etch resistance of thin polymeric and photoresist films
Plasma etch rate measurements of thin polymeric films are presented. Four commonly used polymers were etched (1) poly-methyl-methacrylate (PMMA), (2) poly-hydroxyethyl-methacrylate (PHEMA), (3) poly-hydroxystyrene (PHS), and (4) a commercial photoresist (GKRS). Their etch rates (ER) in a plasma reactor and their glass transition temperature (Tg), were both studied as functions of the initial film thickness. The results clearly show a strong relation between the ER and the initial polymer thickness. The etch rate is decreasing as the initial polymer thickness is decreasing for films thinner than ?200nm. By correlating the plasma ER rate with the Tg of the polymeric films, a clear inverse relation is revealed, namely that the ER decreases when the Tg increases.
plasma etching polymers glass transition temperature thin films