SADP for BEOL using chemical slimming with resist mandrel for beyond 22nm nodes

Abstract

The fundamental limits of optical lithography have driven semiconductor processing research to push the envelope. Double patterning (DP) techniques including litho-etch litho-etch (LELE), litho-litho etch (LLE), and self-aligned double patterning (SADP) have become standard vernacular for near term semiconductor processing as EUV is not yet ready for high volume production. The challenge, even with techniques like LLE and SADP, remains that printing small lines on tight pitches (for LLE) or even small lines on relaxed pitches for mandrel/spacer combinations is not trivial. We have demonstrated a track-based slimming technique that can produce sub-25 nm resist lines for either SADP or LLE DP processes. Our work includes results for varying shrink amounts at different target critical dimensions (CD) and for multiple pitches. We also investigated CD uniformity (CDU) and defectivity. In particular, optimization of the amount of slimming is critical as it allows for much greater process latitude at the lithography step. In addition to the lithography work, we have continued the processing for both integration schemes to include oxide deposition and etch for SADP and through etch performance for DP. We have demonstrated sub 45 nm pitch structures. The wide variety of process uses, as well as the ability to achieve a large range of shrink amounts shows that track based slimming is a viable solution to achieve target CD and pitch values for sub 22 nm technology node.