Influence of backbone chemistry on the post-exposure bake temperature sensitivity of 193-nm photoresists

It was found that the structure of a matrix polymer has strong influence on the PEB sensitivity of 193nm photoresists. As reported, photoresists containing CO polymers exhibited superior property in terms of PEB sensitivity to photoresists formulated with more popular 193 nm photoresist polymers such as VEMA, COMA and methacrylates. In addition, CO polymers exhibited little variation (< 1 nm/°C) in PEB sensitivity when formulated with different PAGs and/or bases. VEMA polymers exhibited PEB sensitivity in the range of 4 ~ 6 nm/°C. VEMA polymers with less leaving group (or lower blocking ratio) exhibited lower PEB sensitivity, but the nature of a leaving group (i.e., lower or higher temperature leaving groups) had little effect on PEB sensitivity. The most pronounced effect was found with functional monomers. For example, VEMA polymers prepared with novel functional monomers exhibited PEB sensitivity in the range of 3 ~ 4 nm/°C. Photoresists formulated with methacrylates exhibited significant variation in PEB sensitivity ranging from 4 ~ 15 nm/°C depending on the backbone chemistry and composition. For instance, with lower blocking ratio as well as lower temperature leaving group, PEB sensitivity of methacrylates were significantly improved by 40~45%. Again, the most pronounced effect was found with functional monomers with methacrylates and PEB sensitivity of methacrylates with novel monomers resulted in the range of 3 ~ 5 nm/°C.