Some Factors Affecting Hillock Formation Due to PECVD Processing of Sputtered Al--4Cu--1Si Films

• Published in: Journal of the Electrochemical Society 1992-01, Vol.139 (1), p.271-275
• Main Authors: Minkiewicz, V J, Moore, J O, Eldridge, J M
• Format: Article
• Language: English
• ISSN: 0013-4651

Deposition parameter effects and subsequent heating on certain properties of sputtered Al--4Cu--1Si films are discussed. Emphasis was placed on developing a process yielding metal films resistant to hillock growth during the deposition of passivating films in a plasma-enhanced chemical vapor deposition (PECVD) reactor at relatively high (400 deg C) temperatures. The films were made in a commercial sputtering system which did not provide a means to heat sink the Si substrates. In contrast to most earlier reports, film smoothness and morphological stability increased with decreasing substrate deposition temperatures. Films deposited onto substrates pre-heated to approx 200 deg C increased their average roughness from approx 25 to approx 320 A during the PECVD process, resulting in hillock heights up to 5000 A. By contrast, films deposited onto non pre-heated substrates underwent a roughness increase from approx 20 to approx 80 A with PECVD processing to yield maximum hillock heights of approx 500 A. This difference is attributed to substrate heating by the deposition process and the absence of heat sinking which leads to an estimated 150-200 deg C increase in effective deposition temperature above the nominal values; such films, when re-heated to 400 deg C, lack sufficient compressive stresses to produce large hillocks. Reductions in both grain size and preferred orientation were also found to enhance film stability.