Study of a metal gate and silicon selective 'dry ash only' process for combined extension and halo implanted photo resist

摘要

A "dry only" two steps strip process with a controlled crust removal step for extension/halo implanted resist was studied. The optimized process results in clean device surfaces. Unfortunately, fluorine additives providing efficient crust removal and surface cleaning might consume Si and creating surface roughness. It was shown that Si roughness (haze) and residue formation only appears during the crust removal step. Keeping the crust removal step short reduces the haze formation and the related Si loss. Therefore more investigations to reduce the Si loss are needed.