Fundamentals of developer-resist interactions for line-edge roughness and critical dimension control in model 248 nm and 157 nm photoresists

Abstract

Organic polar solvent (1-butanol) versus aqueous base (tetramethylammonium hydroxide, (TMAH)) development quality are distinguished by neutral versus charged polymer (polyelectrolyte) dissolution behavior of photoresist bilayers on silicon substrates comprising poly(4-hydroxystyrene) and poly(4-ferf- butoxycarbonyloxystyrene), PHOSt and PBOCSt, respectively. This model line-edge was broadened by photoacid catalyzed deprotection to a final interfacial width of 35.7 Å and subjected to different developers. 1-butanol develops with an increased penetration depth than aqueous base development consistent with an increased solubility of the protected containing component in the organic solvent. This enhanced dissolution with the polar solvent results in an increased surface roughness of 73 Å, whereas the development with TMAH at concentrations between (0.1 to 1.1) M 1 leads to surface roughness between (4.5 to 14.4) Å, as measured by atomic force microscopy. These measurements suggest that the elimination of resist swelling, in the presence of a protection gradient, is a viable strategy to reduce roughness and control critical dimensions. The influence of added salt to developer solutions was also examined by developing the model bilayer. A decrease in surface roughness from (10 to 6.5) Å was observed between (0 to 0.70) M KCl in 0.26 M TMAH.