Methods and apparatuses for minimizing line edge/width roughness in lines formed by photolithography are provided. In one example, a method of processing a substrate includes applying a photoresist layer comprising a photoacid generator to on a multi-layer disposed on a substrate, wherein the multi-layer comprises an underlayer formed from an organic material, inorganic material, or a mixture of organic and inorganic materials, exposing a first portion of the photoresist layer unprotected by a photomask to a radiation light in a lithographic exposure process, and applying an electric field or a magnetic field to alter movement of photoacid generated from the photoacid generator substantially in a vertical direction.