Underlayer material design for extreme ultraviolet negative-tone development photolithography process by controlling photoresist-underlayer intermixing

BackgroundTo meet the challenging lithography targets for extreme ultraviolet (EUV) processes, the importance of EUV material development has been growing ever since. For a successful design of photolithography process exhibiting high sensitivity and high pattern uniformity without any pattern defect formation, the development of an underlayer (UL) material that is specifically designed for the photoresist (PR) is considered essential.AimTo this end, understanding of the interfacial interaction between the PR and UL is considered critical for the material design.ApproachWe investigated the intermixing between PR and UL designed for the EUV negative-tone development (NTD) process.ResultsBased on our investigation, we could design a pattern defect-free NTD UL material by controlling the intermixing between the two layers.ConclusionsTo maximize the effect of the UL, the diffusion of UL components into the PR layer was promoted while preventing the diffusion of PR components into the UL layer. To control the direction of interdiffusion between the layers, we present various ways to modify the physicochemical properties of UL, which was effective in reducing the pattern defect formation.