Detrimental effects of residual silicon oxides on LPCVD tungsten depositions in shallow junction devices

Integrity of shallow junction devices is dependent on maintaining smooth films of constant thickness where metal contacts doped silicon. Localized silicon oxide residue can enhance the WF/sub 6//Si reaction used in LPCVD tungsten depositions resulting in unacceptably large amounts of silicon consumption. The authors investigated phenomena which cause excess WF/sub 6//Si interaction that can lead to incursions of tungsten into silicon structures. In layers between 1.0 nm and 2.0 nm thick, silicon oxide appears to catalyze the WF/sub 6//Si reaction and prevent or delay the self-limiting condition of LPCVD W film formation. Consequences for shallow junction devices are discussed, and methods to avoid this problem are presented