Chemical vapour deposition of WSi2 thin films : Equilibrium W-Si-H-Cl-Ar system

• Published in: Journal of alloys and compounds Vol. 452; no. 1; pp. 116 - 121
• Main Author: RAO, Y. K
• Format: Conference Proceeding Journal Article
• Language: English
• Published: Lausanne Elsevier 06.03.2008
• Subjects: Chemical vapor deposition (including plasma-enhanced cvd, mocvd, etc.); Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Physics; Thin films; CVD; Phase diagrams; Chemical vapour deposition model; VLSI; Tungsten silicide; Phase diagram; Phase boundaries; Domain walls; Tungsten silicides; Polycrystals; Iterative methods
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2007.01.172

Tungsten disilicide (WSi2) can be used in lieu of polycrystalline silicon in very large scale integrated (VLSI) circuit manufacturing; WSi2(s) thin films have been deposited from a vapour-mix of WCl4, SiH2Cl2 (or SiH4), H2, and an argon diluent. The present work describes an equilibrium model for the W-Si-H-Cl-Ar system: the feed-gas mixture is characterized by the atom-ratios (Ar/H), (H/Cl), and (W/Si); during the chemical vapour deposition (CVD), only the latter ratio is expected to change as one or more of condensed phases Si(s), WSi2(s), W5Si3(s) and W(s) begin to form. In this work, the CVD-phase diagram was constructed by means of an iterative method that was coupled to the De Donder's extent of reaction formalism; the respective phase-domain boundaries Si(s)+WSi2(s)/WSi2(s)/WSi2(s)+W5Si3(s) were computed for the temperature range of 800-1000K at 1atm (101.325kPa); the SiH2Cl2-content of the feed-gas mixture, characterized by F=[SiO/(SiO+W0)], was gradually decreased ensuring a complete sweep from the Si(s)+WSi2(s) two-phase-domain to the phase-mixture WSi2(s)+W5Si3(s) for specific (H/Cl) and (Ar/H) ratios. The results are of value in determining the CVD-phase diagrams for the growth of crystalline materials.