Reaction Kinetics, Stress and Microstructure in Titanium-Copper-Titanium Thin Films

Abstract

Interdiffusion, reactions and microstructure in Ti-Cu-Ti trilayer thin films deposited on silicon wafers have been investigated by Rutherford backscattering, and cross-sectional TEM techniques in the temperature range of 350 to 500 °C. The formation of intcrmetallic compounds was found to be symmetric at both interfaces in Ti-Cu-Ti film package. TiCu compound formed first at low temperature and was followed by TiCu₃ at higher temperatures. The stress in Ti-Cu film has also been measured in-situ as functions of both temperature and annealing time by thin fused quartz bending-cantilever beam technique. The stress in metallic Ti-Cu film couple on fused quartz was tensile. The stress increased as both annealing time and temperature increased and followed a parabolic relationship with time due to the growth of the intermetallic compound TiCu₃. It was possible to calculate stress in the TiCu₃ layer from the changes of stress in the bilayer thin film. The stress in TiCu₃ was computed to be at about 3 times larger than the stress in the unreacted Ti-Cu thin film couple.