Integration of dry etching steps for double patterning and spacer patterning processes

Abstract

Double patterning (DP) is today the accepted solution to extend immersion lithography to the 32 nm node and beyond. Pitch splitting process and spacer process have been developed at CEA-LETI-Minatec. This paper will focus on the optimization of dry etching process to achieve these two patterning techniques. For each approach, we first discuss the choices of the starting integration flows based on the requirements to etch the final devices. Then, we develop how the etching steps were optimized to get a good step by step CD control for 45nm/45nm features.

Impact of CD and overlay errors on double-patterning processes

“…So the CD uniformity of a sidewall process is: ( 5 ) In the case where the final pattern is defined by the sidewalls themselves, the final CD uniformity only depends on the sidewall uniformity, and not on the lithography CD uniformity and overlay, i.e. :…”

“…This integration flow has been optimized in order to ensure a good pattern transfer through the spacer and to achieve the correct CD target. 5 The stack has been chosen in order to get the optimal optical properties to avoid any BARC layer and the lithography has been optimized directly on top of the SiOx/Carbon layer with a CD target of 65nm. Then resist trimming process has been applied to achieve a final CD of 45nm with vertical profiles.…”