Epitaxial growth of heavily P-doped Si films at 450°C by alternately supplied PH₃ and SiH₄

Epitaxial growth of heavily P-doped Si films at 450°C by alternately supplied PH₃ and SiH₄ has been investigated using an ultraclean low-pressure chemical vapor deposition (CVD) system. By exposing the Si(100) surface to PH₃ at a partial pressure of 0.26Pa at 450-750°C, two or three atomic-layers of P are adsorbed. Thermal desorption of P occurs at 650°C and only slightly at 450°C. By alternately supplied PH₃ at 300-450°C and SiH₄ at 450°C, opitaxial growth of heavily P-doped Si films of average P concentrations of ∼10²¹cm^-3 are achieved. In the ease of 4 cycles of alternately supplied PH₃ and SiH₄ at 450°C, 26nm-thick P-doped epitaxial Si film, with the average P concentration of 6×102°cm^-3, is formed. It is found that about 60% of P is electrically active even in the heavily P-doped epitaxial Si film and the resistivity is as low as ∼3×10 ^-4Ωcm. By annealing the film at 550°C and above, it is found that the carder concentration decreases and the resistivity increases. It is suggested that very low-resistive epitaxial Si film is formed by alternately supplied PH₃ and SiH₄ only at a very low-temperature such as 450°C.