Suppression of fluorine penetration by use of in situ stacked chemical vapor deposited tungsten film

In this study, amorphous-like tungsten films were deposited by a chemical v apor deposition (CVD) process. The deposited film has shown reduced resista nce compared with WSi2, and it also blocked the fluorine atoms from diffusi ng into the gate oxide. Furthermore, when the amorphous-like tungsten film was deposited prior to a typical CVD tungsten film with a columnar structur e, it not only showed excellent barrier characteristics in impeding fluorin e impurities, but its resistance was also substantially lower than a single layer of a-W film. It is also found in our work that a bilayer film contai ning typical CVD tungsten/amorphsus-like CVD tungsten is a better wordline structure due to its extraordinarily low resistivity and low fluorine conta mination. (C) 1999 The Electrochemical Society. S0013-4651(98)11-071-6. All rights reserved.