Development of 193-nm wet BARCs for implant applications

This paper describes the chemistry and performance of a new family of wet-developable (wet) bottom anti-reflective coatings (BARCs) that have been developed for 193-nm implant layer applications. These BARCs, which are light sensitive and positive working, are imaged and developed in the same steps as the covering 193-nm photoresist. The BARCs are spin coated from organic solvents and then insolubilized during a hot plate bake step. The resulting cured films exhibit minimal solubility in numerous organic solvents. Resolution of a photoresist A and light-sensitive BARC I at optimum exposure (Eop) on a silicon substrate was 150-nm L/S (1:1), with good sidewall angle and no scumming. These best-case results utilize a first reflectivity minimum BARC thickness and meet the desired resolution goals for noncritical implant layers. BARC optical parameters can easily be adjusted by altering the polymeric binder. PROLITH TM modeling shows that near zero reflectance can be achieved on a silicon substrate for both a first and a second reflectivity minimum BARC thickness. The light-sensitive, wet BARCs are both spin-bowl and solution compatible with most industry standard solvents. A selected BARC from this family of wet products was shown to be stable, providing reproducible film properties over several months of ambient storage conditions.