Methods disclosed herein apply an electric field and/or a magnetic field during photolithography processes. The field application may control the diffusion of the charged species generated by the photoacid generator along the line and spacing direction, preventing the line edge/width roughness that results from random diffusion. The field application may additionally or alternatively control the diffusion of the charged species in a direction perpendicular to a plane formed by the photoresist layer. Such controlled perpendicular diffusion may increase the photoresist sensitivity. In other embodiments, the field may control the diffusion of the charged species within the plane of the photoresist layer but in a direction perpendicular or non-parallel to the line and spacing direction. Apparatuses for carrying out the aforementioned methods are also disclosed herein.