Line edge roughness in positive-tone chemically amplified resists: Effect of additives and processing conditions

Nanometer scale line edge roughness (LER) is an increasingly important factor in critical dimension control as the minimum feature sizes of devices continue to shrink. We previously studied the material origin of the resist LER in silicon containing positive-tone chemically amplified resists by emulating the resist compositions and analyzing morphology in the line edge region with atomic force microscopy (AFM). We concluded that the LER stems mainly from the phase incompatibility of the protected and de-protected polymers. In this paper, we expand our study to also include the non-silicon containing chemically amplified resists. We present results on the effects of casting solvent, photoacid generator, and base additive on the surface roughness of thin films of neat partially protected polymers and blends of the protected and the de-protected polymers. We also investigated the surface roughness of neat partially protected polymer films under various development conditions. The AFM results reinforce our previous conclusion on the material origin of LER in chemically amplified resists. Strategies to minimize LER will also be discussed.