A model bilayer geometry is used to examine fundamental contributions of in-situ reaction front profile width on resulting line edge roughness after development in standard 0.26 N tetramethyl ammonium hydroxide aqueous base developer. The bilayer geometry utilizes a bottom layer of protected photoresist polymer with a top layer of deprotected photoresist loaded with photoacid generator. Using neutron reflectivity, the results demonstrate that the reaction front profile broadens during the post-exposure bake (PEB) times between 15 s and 90 s to a width approaching than 150 . The subsequent development and atomic force microscopy experiments reveal an increase in nominal RMS roughness as well as increased lateral length scale features with PEB time. While the form and size of the deprotection profile have long been suspected as the controlling factor in LER formation, this study represents the first direct connection of sidewall morphology to a measured deprotection profile.
Citation: ACS Symposium Series
Publisher Info: American Chemical Society, Washington DC, DC
Pub Type: Books
acid diffusion, deprotection profile, neutron reflectivity, photolithography, photoresist imaging