Influence of optical nonlinearities of photoresists on the photolithographic process

Using a new simulation method, the influence of refractive index changes during the bleaching of the photoresist on process parameters is investigated. For standard applications using thin resists, refractive index changes above 0.1 result in considerably modified dose latitudes, swing curves and iso-dense bias. In special applications with thick resists, the same effect occurs for much smaller refractive index changes. Optimized refractive index changes can be used for the fabrication of structures with high aspect ratios.