Post cleaned surface modification treatment to prevent near pellicle haze generation in sulfate free cleaned ArF EAPSM

Abstract

A lot of research has been carried on sulfate free cleaning process to minimize haze generating residual ions on mask surface. However sulfate free cleaned mask has been suffered from short life time of haze generation than we expected, because pellicle outgassing combines with ammonium residuals and formed haze near pellicle frame area and decrease yield. Therefore physical and PKL developed chemical surface modification treatment was studied and evaluated in term of near pellicle haze threshold energy, surface energy of mask substrate components (Qz/MoSi/Cr), AFM and AES depth profile. Dehydration bake treatment (physical surface modification treatment) and PKL developed chemical treatment increased near pellicle haze threshold energy by 2.5 and 4 times, respectively. Surface modification treatments didn't show negative effect on phase angle and transmittance losses of ArF EAPSM mask. The effect of illumination sources on surface modification treatment was also studied.

Haze generation model and prevention techniques for sulfate free cleaned mask

“…In our earlier published research paper [1], we studied haze threshold energy at near pellicle frame region. Figure 1 demonstrates that near pellicle frame region shows lower haze threshold energy than center region.…”