Pulsed CVD of Tungsten Thin Film as a Nucleation Layer for Tungsten Plug-Fill

Abstract

Tungsten (W) thin film as a nucleation layer for a W plug-fill process was deposited using a modified chemical vapor deposition (CVD) called pulsed CVD, and properties of the films were investigated. Basically, the deposition stage was composed of four separate steps for one deposition cycle: (i) reaction of WF6 with SiH4; (ii) inert gas purge; (iii) SiH4 exposure without WF6; and (iv) inert gas purge. A higher deposition rate, similar to1.5 nm/cycle, was obtained as compared to that of atomic layer deposition (ALD) (similar to0.25 nm/cycle). The film deposited by pulsed CVD showed a much lower root mean square (rms) roughness (0.87 nm) and better conformality at the contact holes with an aspect ratio of 14 (contact height: 3.51 mum and top diameter: 240 nm) as compared to the layer deposited by conventional CVD using WF6 and SiH4. (C) 2004 The Electrochemical Society.