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 vapor deposition (CVD) process. The deposited film has shown reduced resistance compared with WSi2, and it also blocked the fluorine atoms from diffusing into the gate oxide. Furthermore, when the amorphous-like tungsten film was deposited prior to a typical CVD tungsten film with a columnar structure, it not only showed excellent barrier characteristics in impeding fluorine 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 containing typical CVD tungsten/amorphsus-like CVD tungsten is a better wordline structure due to its extraordinarily low resistivity and low fluorine contamination. (C) 1999 The Electrochemical Society. S0013-4651(98)11-071-6. All rights reserved.