To understand polymer behavior in plasma etching, we must understand how polymers decompose in the high-energy reactive particle environment. Plasma etching is a very aggressive decomposition process that includes physical bombardment and chemical reaction. Physical bombardment is the force used to break the polymer bonds and cut the long chains to small pieces. Pieces that are small enough diffuse to the gas phase and are vacuumed out of the chamber;some pieces are redeposited back onto the surface. The scission can occur at backbone, side chain, and hydrogen.Chemical reaction between plasma and polymer, or between polymer segments, may increase the decomposition process or form a more stable structure to slow down the etch process.