Chemically amplified negative resist optimized for high-resolution x-ray lithography

We have developed a three-component negative resist for x- ray lithography which is composed of monodispersed polyhydroxystyrene as a base polymer, hexamethoxymethylmelamine as a cross-linker, and alicyclic- bromides containing ketonic groups as an acid generator. To enlarge the contrast of the dissolution rate between the exposed and unexposed films, polyhydroxystyrene was partially protected by t-butoxycarbonyl groups and organic bases were added to the resist component. Among the bromic compounds we evaluated as acid generators, the alicyclic- bromides containing ketonic groups produced hydrobromic acids most efficiently. The resolution of the new resist remains nice down to 80-nm line-and-space patterns at a proximity gap of 20 micrometers , and 70-nm patterns at a gap of 10 micrometers with a resist sensitivity of 150 mJ/cm2.