Evaluation of alternative development process for high-aspect-ratio poly(methylmethacrylate) microstructures in deep x-ray lithography

The development of very thick commercial sheets of poly(methyl methacrylate ) (PMMA) resist patterned by deep x-ray lithography was investigated. The d evelopment characteristics were explored, with the alternative methyl-iso-b utyl-ketone (MIBK)-based developer systems, MIBK and MIBK/ iso-propyl-alcoh ol (IPA) 1:3, being compared with the "GG" developer system (2-butoxyethoxy -ethanol, morpholine, 2-aminoethanol, and water) more generally used. In pa rticular, the influence of various parameters were studied: PMMA characteri stics (resist thickness, pre-exposure thermal treatment), exposure conditio ns (x-ray incident energy, dose at the bottom of the resist, rate of dose d eposition, distribution of dose inside the resist), development conditions (temperature, megasonic-assistance, length of cycle into developer and rins e baths), postexposure treatments (storage, thermal treatment), etc. The st udy also focused on surface finish of the parts corresponding to different exposure and development conditions. Using MIBK/IPA megasonic assisted deve lopment and postexposure treatment at 40 degreesC resulted in the best cond itions, faster development rate, as well as smoother developed surfaces. (C ) 2000 American Vacuum Society. [S0734-211X(oo)14906-6].