Post exposure bake temperature sensitivity (PEB sensitivity) becomes important as the pattern pitch size shrinks gradually. There are several factors affecting the PEB sensitivity including acidity and diffusion of photogenerated acid, activation energy for deprotection reaction, free volume of base polymer, and so on. Our works were conducted as a part of the basic study for searching influential parameter of PEB sensitivity. We found that PEB sensitivity relies largely on not only acid diffusion parameter, but also the hydrophilicity of base polymer and protection group ratio. Also, we observed that bulkiness of deprotection group has great influence on PEB sensitivity. Detailed results will be reported in this paper.
As the device design rule is continuously shrinking, line end shortening (LES) has grown to be one of the critical problems in 193 nm photolithography. Among several factors causing LES, diffusivity of photo-generated acid seems to have the most profound effect. Also, diffusivity of base quencher produces equivalent effects on LES, but in the reversed way. Besides, post-exposure bake (PEB) condition is another key factor by affecting diffusion length of photo-generated acid. Low LES can be achieved by lowering PEB temperature or shortening its time. In this paper, we will discuss our experimental results to assess the determining factors of LES and suggest controllability of LES in ArF lithographic process.
Sensitivity and resolution capability of photoresist depend on various parameters, such as efficiency of photoacid generation, base strength, types and concentration of protection groups on a polymer, as well as lithographic process condition. We have prepared polymers containing different protecting groups and investigated their effects on the sensitivity, and eventually, on ArF resist photolithographic behavior. Also, several different photoacid generators (PAGs) and bases were employed to study the influence of them on the resist sensitivity. We have changed process condition, especially, bake condition to discuss the role of bake temperature on the photochemical efficiency of the resist. It was found that the diffusion of the photogenerated acid and bases is the most significant factor to determine resist sensitivity than others. The detailed results will be discussed in this paper.
We have been interested in the effect of the residual solvent on lithographic performance. The concentration distribution of solvent molecules along the film depth and the amount of residual solvents depend on their physical properties: evaporation rate, boiling point, viscosity, and so on. Since fast-evaporating solvent can make a dense skin-like layer at the top of the resist film, faster evaporation rate of solvent makes thicker film, while slow rate results in thinner film. And the amount of residual solvent is dependent of the evaporation rate of the casting solvent. The amount of residual solvent was verified by TGA method. It was found that the amount of residual solvent is a major parameter to determine film thickness, stiffness of resist pattern, acid diffusion length, and pattern profile shape.