Application of Self-aligned Quadruple Patterning to Fabrication of Nanoimprint Mold with Sub-12-nm Half-pitch

Nanoimprint lithography (NIL) is attracting attention as a next-generation lithography technology. However, because NIL molds are patterned by electron beam lithography, it is difficult to fabricate NIL molds with a half-pitch (HP) of ≤15 nm. In this study, we demonstrated the possibility of fabricating NIL molds by the multi-patterning method, which is a self-aligned quadruple patterning (SAQP) technique. In the first step of the spacer double patterning, a SiO2 layer is deposited on the mandrel HP 45-nm line and space (L/S) pattern of spin-on carbon by atomic layer deposition (ALD), followed by grating dry etching for the SiO2 spacer. Transfer etching of the amorphous silicon (a-Si) layer and removal etching of SiO2 using buffered hydrofluoric acid are subsequently performed. In the SAQP step, a SiO2 layer as the spacer is deposited on the mandrel HP 22.5 nm L/S pattern of a-Si by ALD, followed by grating dry etching for the SiO2 spacer. Using this method, we constructed the fabrication of HP 11.25 nm L/S patterns that can be applied to the NIL mold process.