Photoacid structure effects on environmental stability of 193-nm chemically amplified positive resists

The effects of photoacid structure on environmental stability at post exposure bake (PEB) and during post exposure delay (PED) for 193-nm chemically amplified positive resists were investigated. It was found that the influence of airborne contamination at PEB was less than that during PED. The acidity and size of generated photoacids have a great impact on environmental stability, as well as on lithographic performance; weak acid with moderate size (/spl sim/ 100 /spl Aring//sup 3/) exhibited both high environmental stability and high resist contrast.