Reducing Damage to Si Substrates during Gate Etching Processes

The mechanism of formation of a "Si recess" that appears during gate poly-Si etching was studied. Hydrogen in HBr plasma penetrates through a thin gate oxide film and generates dislocated sites in the Si substrate. We developed a molecular dynamics (MD) simulation to clarify both the penetration depth of H and O and the dislocation of Si. The damage was successfully minimized by controlling the high energy peak in the ion energy distribution function (IEDF) to be lower than the threshold energy of ion penetration.