Characterization of Tungsten Nucleation Layers Deposited Using Various Sih4 and Wf6 Flows

ABSTRACTChemical vapor deposition (CVD) of tungsten nucleation films is typically done using silane (SiH4) reduction of tungsten hexafluoride (WF6). For SiH4/WF6 flow ratios of ≤ 1, pure tungsten of bulk density and resistivity is deposited. Upon increasing the ratio to 2, nearly 40 at.% Si is incorporated in tungsten films. At a ratio of 3, hexagonal WSi2 is deposited, and at ratios of > 6 WSi2 along with silicon is deposited. A maximum in deposition rate is obtained for WSi2 at the ratio of 3, and the deposition rate drops as more silicon is being deposited. The step coverage of films drops dramatically as one moves away from pure W films. The deposition of these films takes place without any incubation time.