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

Abstract
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, epitaxial growth of heavily P-doped Si films of average P concentrations of ~10²¹cm^-3 are achieved. In the case 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 6xl0²⁰cm^-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 ˜30Ω.cm. By annealing the film at 550°C and above, it is found that the carrier 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.