Paper PS1-ThM5
Modeling of Angular Dependence in Plasma Etching Used for Profile Simulation

Thursday, October 18, 2007, 9:20 am, Room 606

We have completely modeled the angular etching behavior for poly-silicon etching in chlorine chemistry as well as oxide in fluorocarbon chemistry at various operating conditions, including different neutral-to-ion flux ratios, ion energies and ion incidence angles. With this angular model incorporated into the 3-dimensional profile simulation, we can quantitatively predict the line-edge roughness on the sample sidewall. We developed the angular model within the framework of the translating mixed-layer kinetics model described previously. Unlike other kinetics models, we estimated the concentrations of chemical complexes based on the surface composition and assumptions of random atomic mixing and bonding within the top surface layer. Angular curves of various fundamental reactions including physical sputtering, ion-induced etching and dangling bond creation are analyzed using simulation tools such as TRIM. Based on those individual angular curves we predicted the apparent angular dependences at different neutral-to-ion flux ratios and ion energies for poly-silicon etching in chlorine plasmas as well as oxide etching in fluorocarbon chemistry. The simulated etching yields showed quantitative agreement with experimental data. At low neutral-to-ion flux ratio, the etching yield peaks around 60 degree off-normal angle then drops off, similar to physical sputtering. At high neutral-to-ion flux ratio, the etching yield monotonically decreases with ion incidence angle, which is indicative of ion-induced etching. Surface fractions remain stable as a function of ion incidence angle for both poly-silicon and oxide etching, consistent with experimental observation.