Gas-phase transport of WF6 through annular nanopipes in TiN during chemical vapor deposition of W on TiN/Ti/SiO2 structures for integrated circuit fabrication
- 18 November 1996
- journal article
- Published by AIP Publishing in Applied Physics Letters
- Vol. 69 (21) , 3179-3181
- https://doi.org/10.1063/1.117953
Abstract
Delamination of TiN/Ti bilayers on SiO2 is a serious problem during W chemical vapor deposition (CVD) using WF6 to form vertical interconnects in integrated circuits. In order to obtain insight into the delamination mechanism, we have determined depth-distributions of W and F in sputter-deposited TiN/Ti bilayers on SiO2 as a function of WF6 exposure time tWF6 at 445 °C. Even for tWF6<6 s, significant concentrations of both W (≊3.5 at. %) and F (≊2 at. %) penetrate through the 106-nm-thick TiN film. W piles up at the TiN/Ti interface, while F rapidly saturates the TiN layer and accumulates in the Ti underlayer at concentrations up to ≊10 at. % for tWF6=60 s. Cross-sectional and scanning transmission electron microscopy analyses demonstrate that WF6 penetrates into the TiN layer through nanometer-scale intercolumnar voids spanning the entire film thickness and reacts with the Ti underlayer. We propose that the high F concentrations in the Ti layer weakens the Ti/SiO2 interface leading to adhesion failure of the TiN/Ti bilayer.Keywords
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