Improved resolution of thick film resist (verification by simulation)

Abstract

In the past there have been almost no analyses of mechanisms to achieve higher resolutions and higher aspect ratios in thick-film resist processes. In this work, the authors measures the effects of water in a thick-film resist on indenecarboxylic acid generation in thick-film resist image formation, and studies the mechanism of resolution enhancement through hydration processes. In addition, a development rate measurement system, a system for analysis of resist reactions during exposure, and lithography simulations are employed to simulate profiles in thick-film resists. Calculation results are then compared with actual resist profile. Specifically, a diazonaphthoquinone (DNQ)-novolac positive thick-film resist is used; after coating to a thickness of 22 µm and pre-baking, the sample is subjected to dehydration in a vacuum desiccator, samples are prepared both immersed in Water and without such immersion, and photochemical reaction rates are measured during exposure, while also measuring development rates. From the measured results for photochemical reaction rates of the resist during exposure, the state of indenecarboxylic acid generation can be determined. The development rate data is inputted to the SOLID-C lithography simulator, thick-film resist simulations are executed, and the results were compared with actual SEM observations of resist profiles. From the results of analyses of photochemical reactions during exposure, it is confirmed that differences in water quantity in the resist affect the generation of indenecarboxylic acid. Simulation results also confirms that by immersing the resist in water, the resolution is enhanced. The general trends of simulation results and actual patterning are in agreement, and it is concluded that in thick-film resist, resolution is improved when water is present in the resist in sufficient quantities for indenecarboxylic acid generation.