Quartz crystal microbalance study of tungsten atomic layer deposition using WF6 and Si2H6

• Published in: Thin solid films 2005-09, Vol.488 (1-2), p.103-110
• Main Authors: FABREGUETTE, F. H, SECHRIST, Z. A, ELAM, J. W, GEORGE, S. M
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Exact sciences and technology; Physics; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2005.04.114

The atomic layer deposition (ALD) of tungsten can be accomplished using sequential exposures of WF6 and Si2H6 (disilane). In this paper, W ALD is explored using in situ quartz crystal microbalance (QCM) measurements as a function of the reactant exposure and deposition temperature. The QCM measurements revealed that the WF6 reaction is self-limiting. In contrast, W ALD growth rates exhibited a slow and continual increase for disilane exposures > 4x104L. The W ALD growth rate was also weakly temperature-dependent with an activation energy of 1DDT5+ /-0DDT1 kcal/mol at T < 250DDGC and a lower activation energy of 0DDT6+/-0DDT3 kcal/mol at T > 275 DDGC. The QCM results and previous Auger results for W ALD yield the relationship between the silicon coverage deposited during the Si2H6 exposure and the tungsten coverage deposited during the WF6 exposure. The W/Si atomic ratio of ~1:1 is consistent with earlier Auger investigations of the surface chemistry during W ALD at 200 DDGC. The QCM measurements are also consistent with silicon coverages of 1DDT7-2DDT1 monolayers after the Si2H6 exposures. These high silicon coverages are believed to result by silylene insertion from Si2H6 into surface Si-H bonds.