Fundamentals of Developer-Resist Interactions for Line–Edge Roughness and Critical Dimension control in Model 248 nm and 157 nm Photoresists * Vivek M. Prabhu § , Michael X. Wang, Erin L. Jablonski, Bryan D. Vogt, Eric K. Lin, Wen-li Wu, Polymers Division, National Institute of Standards and Technology, Gaithersburg, MD 20899-8541 Darío L. Goldfarb, Marie Angelopoulos, IBM T. J. Watson Research Center, Yorktown Heights, NY 10598 Hiroshi Ito, IBM Almaden Research Center, San Jose, CA 95120 1. 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-tert-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. Keywords: developer, dissolution, LER, CD, polyelectrolyte, reflectivity, AFM, roughness, swelling 2. INTRODUCTION To quantify the developer influence on photoresist critical dimension (CD) control and line-edge roughness (LER) minimization, a scheme is necessary to address material versus optical contributions. A model photoresist bilayer geometry was constructed to simplify this problem using standard processing conditions and a blanket ultra-violet (UV) light exposure. This method leads to a well defined deprotection gradient that can be tuned by post-exposure bake processing 2,3 , hence emphasizing the material contribution. This reaction front gradient is used to understand developer strength, additives, swelling and reaction front width effects on the final CD and model LER. Recently, polyelectrolyte effects were demonstrated to be the source of photoresist solubility, a direct result of the acid- base equilibrium. 4,5 These polyelectrolyte effects have also been correlated to wafer performance 6 . This result is extended to examine neutral versus polyelectrolyte dissolution effects on CD and LER with 1-butanol versus TMAH * Official contribution of the National Institute of Standards and Technology; not subject to copyright in the United States § Corresponding author, vprabhu@nist.gov, Tel.: (301) 975-3657; fax (301) 975-3928. Advances in Resist Technology and Processing XXI, edited by John L. Sturtevant, Proceedings of SPIE Vol. 5376 (SPIE, Bellingham, WA, 2004) 0277-786X/04/$15 · doi: 10.1117/12.535862 443