26 March 2008 Water-developable negative-tone single-molecule resists: high-sensitivity nonchemically amplified resists
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A water developable, non-chemically amplified, negative tone single molecule resist (tris(4-hydroxy-3,5-dimethylphenyl)sulfonium tosylate, otherwise referred to as TAS-tBoc-Ts) was synthesized, characterized, and imaged using high resolution electron beam lithography. The solubility switching in the negative tone imaging mode in this material, which occurs for no or low temperature post-exposure bakes, occurs through photolytic conversion of some fraction of the ionic PAG molecules into non-ionic photoproducts which act as strong dissolution inhibitors to the remaining unreacted molecules in the film. It was also shown that this resist system can dmonstrate positive tone chemically amplified imaging behavior under different processing conditions, i.e. when using higher temperature post-exposure bakes above 100 °C . Pure water was found to be the preferential developer as compared to conventional aqueous alkaline TMAH developers in this particular system for negative tone imaging. Under 100 keV e-beam imaging and water development, a sensitivity of 66 &mgr;C/cm2 and contrast of 7.9 was obtained. TAS-tBoc-Ts obtained 40 nm 1:2 line-space resolutions with a low LER of 5.3 nm using electron beam imaging with no apparent swelling or residue problems. This new material and its negative tone imaging process provide a possible path forward for designing non-chemically amplified resists that may obtain higher resolutions than current chemically amplified resists at competitive sensitivities.
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Richard A. Lawson, Richard A. Lawson, Cheng-Tsung Lee, Cheng-Tsung Lee, Wang Yueh, Wang Yueh, Laren Tolbert, Laren Tolbert, Clifford L. Henderson, Clifford L. Henderson, } "Water-developable negative-tone single-molecule resists: high-sensitivity nonchemically amplified resists", Proc. SPIE 6923, Advances in Resist Materials and Processing Technology XXV, 69231I (26 March 2008); doi: 10.1117/12.773188; https://doi.org/10.1117/12.773188

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