Electrical properties of low-temperature epitaxial doped Si thin films fabricated by using a sputtering-type electron cyclotron resonance plasma

The electrical properties of Sb-doped n⁺ epitaxial Si films have been investigated. These films were fabricated at low temperatures of below 515°C and at a conventional base pressure of 5 × 10^-7 Torr using a sputtering-type electron cyclotron resonance plasma. It was found that the Sb dopants in the target were almost wholly incorporated into lattice sites of epilayers and the Hall mobility of the epilayers grown at 515°C was comparable to that of the bulk Si. A reverse current density as low as 1 × 10^-8 A cm^-2 was obtained by a direct deposition of an n⁺ epilayer on a p-type substrate, which suggests the formation of a high-quality interface between the epilayer and the substrate. The precise control of the deposition gas pressure, substrate potential and substrate temperature was found to be very important for the fabrication of high-quality epilayers. Heavily B-doped p⁺ epilayers were also fabricated at a substrate temperature of 515°C. The B dopant was wholly incorporated into the epitaxial layers, but annealing at temperatures of more than 700°C was required to electrically activate the B dopant. The electrical activation mechanism has been discussed and it has been inferred that the B dopant occupied interstitial sites in the as-grown epilayers.