Prospects and initial exploratory results for double exposure/double pitch technique

We demonstrated a double patterning process with resolution limit of 47 nm features, or 94 nm pitch which corresponds to k₁ of 0.20. Process run on current 193 nm scanner with maximum NA of 0.85. Process consisted of two photo-etch steps and patterned trench features in nitride-type hardmask. Process analysis confirmed 2-nm control capability for CD and overlay, which are at the level required to achieve a final CD 10% tolerance. Line edge roughness was found to be the most critical process limitation. Reduced LER can be obtained by increased aerial image slope and by using high resolution resist formulated for higher chemical contrast.