Tungsten interconnection layers formed by chemical vapor deposition

Thin and thick tungsten (W) layers deposited on silicon dioxide by chemical vapor deposition are studied, where Si-rich tungsten silicide (WSix) buffer layers were employed to avoid layer peeling. A sheet resistance of 0.14 Ω is achieved in 8000-Å-thick layer. When annealings are performed at temperatures above 500°C, excess silicon segregates from the Si-rich WSixbuffer layer at the W-WSixinterface. Therefore, the sheet resistance of thin W layers increases with the annealing. In thick W layers, however, this effect is not evident. Sheet resistance decreases slowly with increasing temperature and reaches 0.12 Ω at high temperatures of 700-800°C.