Improvement in linewidth roughness by postprocessing

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In order to meet the linewidth roughness (LWR) requirements for the 16nm node, postprocessing methods need to be investigated to reduce the LWR after the lithography step. We present the results of five different techniques applied to a single extreme ultraviolet photoresist. The results show that rinse has the most promise in achieving the nearly two time LWR improvement needed. However, other techniques such as etch/trim, hardbake, vapor smoothing, and ozonation give at least 10%–20% LWR reduction and could be further optimized. Some of the physical based techniques which melt the photoresist reduce the midspatial frequency (50–10nm period) roughness, whereas chemical based techniques reduce the low order spatial frequencies (∼500–50nm period). Hence, a combination of techniques may be the ultimate solution.