Sputtering of tantalum-based diffusion barriers in SiCu metallization: effects of gas pressure and composition

A comparative study of DC sputter-deposited Ta and Ta(N) thin films (20 and 50 nm of thickness) as diffusion barriers for Cu has been performed using sheet resistance measurements, stress measurements, Auger electron spectroscopy, X-ray photoelectron spectroscopy, Rutherford backscattering, secondary ion mass spectrometry, scanning electron microscopy, atomic force microscopy and high temperature electron probe microanalysis. Film microstructure, chemical composition and surface roughness were found to depend on gas pressure and composition during deposition. 50 nm Ta thin films prevent CuSi interaction up to 450°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 the Si substrate for temperatures up to at least 560°C for 1 h, and 20 nm TaN films work as an effective barrier for 1 h at 450°C.