SPUTTERING OF TANTALUM-BASED DIFFUSION-BARRIERS IN SI CU METALLIZATION - EFFECTS OF GAS-PRESSURE AND COMPOSITION/

A comparative study of DC sputter-deposited Ta and Ta(N) thin films (2 0 and 50 nm of thickness) as diffusion barriers for Cu has been perfor med using sheet resistance measurements, stress measurements, Auger el ectron spectroscopy, X-ray photoelectron spectroscopy, Rutherford back scattering, secondary ion mass spectrometry, scanning electron microsc opy, atomic force microscopy and high temperature electron probe micro analysis. Film microstructure, chemical composition and surface roughn ess were found to depend on gas pressure and composition during deposi tion. 50 nm Ta thin films prevent Cu-Si interaction up to 450 degrees C for 5 h in vacuum, It was found that TaN is a more effective barrier to copper penetration; 50 nm TaN films prevent the Cu reaction with t he Si substrate for temperatures up to at least 560 degrees C for 1 h, and 20 nm TaN films work as an effective barrier for 1 h at 450 degre es C.