Etching with an ECR Plasma

An Electron cyclotron resonance plasma is used to etch organic resist with oxygen and Si with SF6. Etch performance was studied as a function of operating conditions, resonance chamber geometry and composition of the microwave window results in the redeposition of a thin SiO2 layer on the Si substrate surface. This significantly impacts etch perfomance. Etch Rate studies performed on Si with a SF6 plasma revealed an unexpected saturation with atomic fluorine concentration. A model based on the Cabrera-Mott mechanis is developed to explain the saturation. The rate limiting step for conditions with both high free bombardment is due to electron tunnelling from the Si bulk, through the fluorosilyl layer, to the adsorbed fluorine.