Modeling of the surface roughness of thin TiSi2 films at the point of rupture

When a polycrystalline thin film on a substrate is annealed, grooving at gr ain boundaries will eventually lead to film rupture, followed by island for mation. Two models were developed to predict the surface roughness at the p oint of rupture (interface roughening effect included) of polycrystalline t hin films of TiSi2 on Si based on 2-D and 3-B film analysis. The modeling r esults predicted that the rms roughness at rupture (RMS*) is essentially Li near with film thickness (verified For thickness up to 150 nM), and that RM S* is not sensitive to grain size, 2R (for R = 1-10 mu m). Comparison is ma de with experimental data obtained with the atomic force microscope from th ermal stability testing of two TiSi2 thin film specimens on (111)-Si, for a nnealing treatments carried out at 950 degrees C in argon gas. The two spec imens had the same thickness of about 150 nm but were formed under differen t silicide formation schemes. The experimental rms roughness values at rupt ure were approximately two times higher than predictions of the 3-D film mo del. The positive deviation is attributed to one or more of the following p ossibilities: initial film roughness due to intrinsic roughness of the sili cide grains and presence of film defects like hillocks, faceting and relati ve subsidence of grains due to anisotropy and grain orientation effects, an d hole formation and impingement. (C) 1999 Elsevier Science S.A. All rights reserved.