Dependence of polymer main-chain structure on roughness formation of ArF photoresists in the plasma etching processes

In 193nm lithography processes that use ArF photoresists, roughness formation caused by plasma etching is a serious problem. We previously found that a decisive factor affecting roughness formation in an ArF photoresist is chemical reactions caused by irradiated species from plasma. In this paper, we investigated the structural dependence of a polymer main chain to find the degradation mechanism of ArF photoresists in plasma etching processes. The glass transition temperature of photoresist polymer depends on the structure of the main chain, and a low glass transition temperature causes increases in the flow property at the molecular level, which leads to a reduction in roughness formation in plasma etching. Therefore, the glass transition temperature is a key factor in designing a novel ArF photoresist polymer.