Dependence of linewidth and its edge roughness on electron beam exposure dose

Abstract

Electron beam lithography simulation is presented. A line pattern edge roughness of a resist after development process is discussed based on simulations of electron scattering in the resist film and the resist development process. Fixed threshold energy model is applied for the simulation and variations of linewidth and the line edge roughness are obtained as functions of the incident electron energy, resist thickness, and electron doses. The energy range calculated is from 1to5keV, the resist thickness ranges from 20to70nm, and the electron dose ranges from 1to100μC∕cm2. The resist assumed is poly(methylmethacrylate) and the film is on a Si substrate. In the present study, the threshold energy density is determined as 1.44×1021(eV∕cm3) to draw a given linewidth of 100nm, then the value of the line edge roughness is obtained. The minimum line edge roughness is obtained when the dose is more than that to produce the designed linewidth. As the dose is increased more than that to obtain the minimum edge roughness, the roughness increases with increasing the dose. For very large doses the roughness decreases with the dose, as it is explained by the statistical characteristics.