Improving the performance of light-sensitive developer-soluble anti-reflective coatings by using adamantyl terpolymers

In a search for improved resolution and processing latitude for a family of light-sensitive developer-soluble bottom antireflective coatings (BARCs), the structure of the binder terpolymer was altered by incorporating acid-cleavable adamantyl methacrylates. Contrast curves and 193-nm microlithography were then used as tools in developing a novel developer-soluble adamantyl BARC which does not include a photoacid generator (PAG) or quencher, but instead depends on acid diffusing from the exposed resist for development. This formulation eliminates concern about PAG or quencher leaching out of the BARC during application of the photoresist. Resolution for a resist A and the new BARC was 150-nm L/S (1:1) for both 38-nm and 54- to 55-nm BARC thicknesses. Resolution and line shape were comparable to that of the non-adamantyl control BARC with same resist at 55-nm BARC thickness, with both BARCs giving some undercutting using an Amphibian TM XIS interferometer for the 193-nm exposures. Light-sensitive adamantyl BARCs that do require inclusion of a PAG for optimum lithography with resist A are also described in this paper. The series of developer-soluble adamantyl BARCs were solution and spin-bowl compatible. The 193-nm optical parameters (n and k) for all adamantyl BARCs were 1.7 and 0.5-0.6, respectively.