Work function of in situ heavily P- or B-doped poly-Si 1-x-y Ge x C y films were investigated. The poly-Si 1-x-y Ge x C y films were deposited on thermally oxidized Si(100) at 550°C using an ultraclean hot-wall low-pressure chemical vapor deposition system in a SiH 4 -GeH 4 -SiH 3 CH 3 -dopnat (PH 3 or B 2 H 6 ) gas mixture, and the gate-to-substrate work function difference was estimated from flat-band voltage determined by high-frequency capacitance-voltage measurement. With increasing Ge and C fractions, the work function of B-doped poly-Si 1-x-y Ge x C y film decreases, although that of P-doped poly-Si 1-x-y Ge x C y scarcely changes. X-ray diffraction results show that the lattice constant increases with the C fraction, in other words, C is incorporated at interstitial site in the film at least at 550°C. It is suggested that the change in the work function of doped poly-Si 1-x-y Ge x C y is universally explained by the change in the lattice constant as function of the Ge and C fractions.
- Chemical vapor deposition
- Metal-oxide-semiconductor (MOS) device
- Polycrystalline Si Ge C gate
- Work function