Development of titanium-silicon-nitrogen and tantalum-silicon-nitrogen as diffusion barriers.

摘要

Sputter deposited Ti-Si-N and Ta-Si-N films with different compositions were fabricated using Ti, Si, TiSi2, and Ta targets in Ar/N 2 plasmas with a variety of deposition parameters. A fractional factorial design (FFD) method was used to identify the significant deposition variables for the Ti-Si-N film deposition. The properties of the films as diffusion barriers between Cu and Si were studied using sheet resistance measurements, X-ray diffractometry (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), auger electron spectroscopy (AES) and annealing in a controlled ambient atmosphere.; The most important parameters during Ti-Si-N deposition were Si target sputtering power, N2 partial pressure and the interaction of the sputtering power of Ti and of Si targets. A Ti-Si-N film with 13.4 at. % Ti and 25.0 at. % Si could prevent copper from diffusing into the silicon substrate up to 650°C. Free silicon in the Ti-Si-N or Ta-Si-N films made the diffusion performance worse. Barriers with one TiN layer and one Ti-Si-N layer had better diffusion performance than the barriers with a Ti-Si-N layer only. A Ta-Si-N barrier with 6.0 % free Si was effective during annealing up to 650°C. With increasing N2 partial pressure in the sputtering gas, the diffusion performance of the Ta-Si-N barriers increased. Optimization of the N2 partial pressure resulted in an effective copper diffusion barrier up to 725°C with a relatively low resistivity of 524 mu O-cm.