Spacer defined double patterning for sub-72 nm pitch logic technology

In order to extend the optical lithography into sub-72 nm pitch regime, spacer defined double patterning as a self-aligning process option was investigated. In the sidewall defined spacer process, spacer material was deposited directly on the resist to achieve process simplification and cost effectiveness. For the spacer defined double patterning, core mandrel CD uniformity is proven to be a main contributor to pitch-walking and defined a new lithographic process window. Here, the aerial image log-slope is shown to be a measurable predictor of CD uniformity and sidewall angle of the resist pattern. Through resist screening and illumination optimization, resist core-mandrel of 2.5 nm CD uniformity across a focus range more than 200 nm with +/- 3.5 % exposure latitude was developed having sidewall control close to the normal. Finally etch revealed that pitch-walking post pitch split can be suppressed below 2 nm within +/- 2.5 % exposure latitude.