Exposure tool for 32-nm lithography: requirements and development progress

Double patterning is recognized as the best candidate for 32 nm half-pitch lithography. Currently pitch splitting processes are being considered for logic processes and spacer processes are being considered for memory. In pitch splitting, errors in overlay between the first and second exposure become CD errors on the final pattern. For this reason, overlay requirements are severe for pitch splitting double patterning. Revised CD and overlay budgets are presented, as well as technical requirements to satisfy these budgets. Spacer processes do not have similar restrictions on overlay, so they can be achieved using current immersion tools. Exposure tool requirements for double patterning are discussed and modifications to current platforms are described.