Innovative self-aligned triple patterning for 1x half pitch using single spacer deposition-spacer etch step

We successfully demonstrate a new approach to achieve 15nm half pitch with a spacer based self-aligned triple patterning (SATP). This new concept has a single spacer deposition and etch step to achieve 15nm half pitch using immersion lithography. Current spacer based triple or quadruple patterning approaches use two iterations of "spacer deposition / spacer etch" for pitch splitting, thus generating multi-modal trench CD, line CD and, trench depth population leading to challenging process control. The new concept overcomes CD population issues and reduces additional steps over implemented double patterning, thus could relax process window. The key innovative aspect is an undercut dry trim achieved by a selective dry etch process, followed by a flowable CVD (Eterna (TM) FCVD (TM)) based gap-fill that can fill the undercut structures.