Electron-beam resist edge profile simulation

Abstract

Resist edge profiles of lines produced by electron-beam exposure are explored through the use of numerical simulation. The modeling approach uses Monte Carlo simulation of electron scattering and energy dissipation, a simple etch rate versus dose model for the resist, and a string development algorithm. The simulation was made on an IBM 370/158 and primarily considers a multiple-spot Gaussian beam exposure of PMMA resist. An absolute quantitative evaluation of the simulation accuracy is made based on resist exposure-development measurements and comparisons with SEM micrographs of experimental profiles. The comparisons show good quantitative agreement and indicate that modeling can be used as a quantitative processing aid. Simulation results illustrate the importance of resist, beam, and substrate parameters in the context of optical mask writing (0.5-µm resist on 0.08-µm Cr on SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> ) and direct wafer writing (1.0-µm resist on Si, Gd <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> Ga <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</inf> , and Au).