摘要
The novolak-based resist image is thoroughly hardened by baking with a conformable mold which is formed by spin coating polymethylmethacrylate (PMMA) over the novolak image. Therefore, instead of a deep-UV hardening exposure or a plasma hardening step followed with a high temperature bake, this hardening process consists of a PMMA coating followed with a high temperature bake. Experimental results show that hardening took place throughout the bulk of the resist. The resist profile remains intact after a 200 degree C bake and a second novolak resist image can be delineated on top of the hardened image without any mutual interaction, whereas conventional deep-UV or plasma hardening technique can only harden the resist surface layer. Large features hardened with these conventional techniques tend to deform. Recent results showed stability of resist profile for baking temperature up to at least 500 degree C in a nitrogen flushed furnace. The lateral dimension change of the resist image after resist hardening using a conformable mold (RHCM) and 500 degree C bake was shown to be less than 0. 05 mu m.