Effects of polymer molecular weight and monomer concentration variations on resist stochastics and molecular segregation

The ability to control the polymer molecular weight and monomer concentrations within the polymers used in chemically amplified resists is important for reducing LER and defectivity in EUV lithography. In this paper, we study both the effect of energetic favorability of segregation due to the monomer concentration variations and the variation of molecular diffusion due to the resist polymer molecular weight. Changing the monomer concentration within the polymer film can change the energetically favorable segregation and defectivity. However, the segregated feature size is affected by the molecular motion during the spin-coating process after much of the solvent has evaporated. The molecular motion in this resist film can be partially controlled by varying the molecular weight of the polymers. Moving toward future nodes with smaller feature sizes will require improvements in roughness and defectivity. An open question is how carefully the polydispersity of the resist polymers will need to be controlled and how well the compositional uniformity between polymer molecules will need to be controlled. We propose and validate an approach to measure the relative risk of compositional and molecular weight variations on segregation and ultimately defectivity.