Self-aligned double patterning (SADP) process even-odd uniformity improvement

Abstract

Self-aligned spacer double patterning (SADP) scheme has been proposed as an alternative to litho-etch-litho-etch (LELE) scheme because if its superior control of the lines that are patterned by a uniform and conformal deposition of a spacer layer along sidewalls of the sacrificial patterning lines. However, it adds process complexity in the film stacks and extra challenges on both the linewidth and overlay variations induced by film thickness and etch uniformity, which was also called even-odd bias induced by the spacer. Effects of lithography and etch process deviations during sacrificial core formation are thought to be predominantly for the final space even-odd performance.In this paper, we will present an experimental study of process effect on the space even-odd uniformity, including the lithographic critical dimension uniformity (CDU), sacrificial core etch, spacer etch, hard mask etch and final Si etch. The contribution to the even-odd uniformity will be focused and analyzed step by step. DOMA application on 3X nm FLASH process was also carried out to improve the sacrificial core CDU, and its contribution and limitation to the final even-odd uniformity will be clarified as well.

A holistic study on metal pitch uniformity control in the scheme of self-aligned double patterning

“…To improve overall CD uniformity across the whole wafer, edge dose value can be adjusted if necessary in the lithography step to improve the overall wafer profile. Another method is to adopt dose mapper based compensation (DOMA) tuning at lithography step to improve overall uniformity [8]. Future study can work on the suppression of ARDE effect through Dry Etch steps.…”