Effect of development process time on the surface of photoresist with various chemical compositions investigated by atomic force microscopy

Understanding the nature of photo-resist (PR) dissolution during the development process is the important factor to accomplish high-precision critical dimension (CD) control in photolithography. In this report, we investigate the effect of each process variable on the PR pattern CD size and surface roughness by scanning electron microscopy (SEM) and atomic force microscopy (AFM). From these experiments, we found out that the major factor to affect the CD and surface roughness control was the puddle time. On the basis of these result, we investigated the relationship between puddle time and chemical compositions of PR. According to the puddle time, top surface of PR became rougher, but finally converged to some value. As the molecular weight and protecting ratio of the PR increased, the degree of surface roughness of the PR increased. Soft bake temperature, which is one of the variables in PR coating process, also affected the surface roughness of the PR. These results must be useful data for the optimization of new developing recipe for the new PR systems which will achieve next generation photolithography.