Journal of Vacuum Science & Technology B, Vol.12, No.5, 2980-2984, 1994
Compositional Variation in Sputtered Ti-W Films Due to Reemission
To test for re-emission of titanium and/or tungsten during sputter deposition (PVD) of Ti and Ti-W, films were deposited on wafers with test structures which have large interior areas which are not in line of sight to the source volume. Auger electron spectroscopy (AES), scanning electron microscopy, and transmission electron microscopy results show that very little Ti is re-emitted during Ti PVD, but a significant fraction of incoming Ti is re-emitted during Ti-W PVD. AES spectra along the perimeter of a cross section show that Ti-W films become Ti rich in areas of the test structures without line of sight to the source volume. We also considered Ti-W deposited into trench structures. Physically based, three dimensional deposition process simulations, assuming either diffuse or specular re-emission of Ti, qualitatively explain the experimental results for these trenches. The available information is not sufficient to decide whether the Ti sticking factor is lower on Ti-W films or if Ti is resputtered by incoming W.