Characterization of In Situ Phosphorus‐Doped Polycrystalline Silicon Films Grown by Disilane‐Based Low‐Pressure Chemical Vapor Deposition

Abstract

Low‐pressure chemical vapor deposition of in situ phosphorus‐doped silicon films using disilane and phosphine has been investigated in the growth temperature range of 415 to 560°C and for doping levels between 1019 and . Regarding the film deposition, no significant difference in apparent activation energy was observed between the undoped and heavily doped deposition process. The electrical and structural properties of the films grown at 480°C have been studied as a function of doping level and post‐heat‐treatment including furnace and rapid thermal annealings. The observed changes in film resistivity after isochronal annealings for doping levels above are interpreted in terms of dopant segregation and supersaturation of carriers. The impact on resulting film properties when replacing disilane with silane in the deposition process has been investigated. The films were grown under identical conditions except for the deposition temperature which was 80°C higher for the silane than for the disilane case. There is no indication of different phosphorus incorporation when comparing electrical properties of crystallized silane‐ and disilane‐based films. However, the disilane layers exhibit larger crystallite grains and lower specific resistivities than the silane layers. In addition, the disilane films demonstrate a strongly preferred 〈111〉 texture after crystallization which is absent for the silane films. The observations are attributed to the higher degree of disorder of the as‐deposited disilane films compared to the silane films resulting from the difference in deposition temperature.