Detection of photo resist residue on advanced gate layers using optical scattering and advanced analysis techniques

Detection of resist residue and organic contamination after photo resist strip and wafer clean early in the high K/metal gate (HK/MG) manufacturing process flow is critical as it has been known to significantly impact yield. This residue, when exposed to subsequent thermal process steps, transforms into solid hard spot(s), and can then be detected by a wafer inspection tool, but unfortunately it is too late to take corrective action. A unique process control solution to detect the presence of residues was developed using advanced analysis of an optical scattering inspection of a litho checkerboard pattern. The presence of residue was then validated with film thickness measurements.