Polymer structure modifications for immersion leaching control

摘要

ArF Immersion lithography is the most promising technology for 45nm node and possibly beyond. However, serious issues in ArF immersion lithography for semiconductor mass production still exist. One of the issues is immersion specific defects, which are caused by photoresist component leaching and residual water droplets. In order to minimize immersion specific defects, preventing water penetration into the resist film is regarded as an important factor. Several research groups have reported that higher receding contact angle reduced defectivity. High receding contact angle of film surface prevent water penetration into the resist film due to the hydrophobic nature. Resist component leaching phenomenon also can be caused by the water penetration into the film, so hydrophobic resist can reduce leaching quantity. In this paper, to investigate chemical leaching from resist surface, we evaluated the leaching value of PAG anion and contact angles of various polymers according to their hydrophobicity. Hydrophilicity of a polymer was changed by the degree of hydrophobic group substitution to polymer chain. We measured receding contact angle with four different resists composed of water-repellent functiona group. Receding contact angle of resist surface increased as the portion of water-repellent functional group increased. Also, the leaching amount of PAG anion decreased as the receding contact angle of film surface increased. We expect that higher receding contact angle prevents chemical leaching from resist film by repelling water at the surface. We will report detailed results in this paper.