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1 June 1990 Investigation of the exposure and bake of a positive acting resist with chemical amplification
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The exposure and post-exposure bake of a chemical amplification resist that relies on the acid catalyzed removal of a tert-butyloxycarbonyl (t-BOC) group have been investigated. The effects of the acid generator on the production of acid during exposure and the extent of deprotection during the bake were examined by using different weight percent mixtures of both a 2,6 dinitrobenzyl tosylate and a triarylsulfonium salt. The generation of acid was monitored by measuring the resist transmission during exposure. The decrease during exposure of the nitro group absorbance at 1540 cm' In the FFIR spectrum of the tosylate was correlated with the transmission measurements. The experimental results were used to determine absorption coefficients and acid generation rate constants for both acid generators. The extent of deprotection that occurred during the bake was determined by monitoring the characteristic FTIR absorbance band at 1760 cm1 over a range of exposure doses, bake temperatures, and bake times. The extent of deprotection was related to the local acid concentration generated during exposure through chemical reaction kinetics. The model for the resist with the tosylate consisted of a primary deprotection reaction where the rate of deprotection was proportional to the acid concentration to the mth power (m > 1). For the resist with the onium salt, an additional acid loss reaction was required to account for saturation of the deprotection reaction with increasing bake time. The resist with the onium salt was less sensitive to the bake conditions in comparison to the resist with the tosylate. Improved resist performance during the bake was obtained when using higher loadings of both the tosylate and the onium salt acid generators.
© (1990) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Richard A. Ferguson, Chris A. Spence, Elsa Reichmanis, Larry F. Thompson, and Andrew R. Neureuther "Investigation of the exposure and bake of a positive acting resist with chemical amplification", Proc. SPIE 1262, Advances in Resist Technology and Processing VII, (1 June 1990);

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