The Selete R&D program evaluates the feasibility of the Extreme ultraviolet (EUV) lithography process for
manufacturing semiconductor devices. We therefore conducted a yield analysis of hp-2x-nm test chips by using the
EUV1 (Nikon) full-field exposure tool. However, the resist performance did not comply with the stringent requirements
of ultimate resolution, sensitivity, and line-width roughness.
We subsequently reported two new Selete standard resists (SSRs), i.e., SSR6 and SSR7. SSR6 is the polymer
resist used in hp-2x-nm test chip evaluation in which an ultimate resolution of 22 nm line-and-space (L/S) pattern was
achieved. SSR7 is the first molecular resist that was evaluated for feasibility at Selete. SSR7 is a fullerene based resist
with strong etching durability. By using this resist, an ultimate resolution of 24 nm L/S pattern was achieved.
We have also evaluated resist processing by using SSRs for hp-2x-nm test chip evaluation. An ultrathin
underlayer was evaluated for the improvement of pattern transferability. This optimized ultrathin underlayer was coated
on the test chip substrate that was devoid of nano-sized-pinholes, and a fine pattern was observed on this ultrathin
underlayer. In the evaluation of the development process, SSRs were evaluated with tetramethylammonium hydroxide
(TMAH) and tetrabutylammonium hydroxide (TBAH) developer solutions. In summary, it was clear that the lithographic
performance improvement varies depending on the type of polymer resist used with a particular developer solution.
Furthermore, a significant improvement in the prevention of pattern collapse was demonstrated using a combination of
the TBAH developer solution and alternative rinse solutions.