Very low temperature epitaxy of Ge and Ge rich SiGe alloys with Ge2H6 in a Reduced Pressure – Chemical Vapour Deposition tool

Abstract We have studied the very low temperature epitaxy of pure Ge and of Ge-rich SiGe alloys in a 200 mm industrial reduced pressure chemical vapour deposition tool. We have, first of all, benchmarked germane (GeH 4 ) and digermane (Ge 2 H 6 ) for the growth of pure Ge. Used Ge 2 H 6 instead of GeH 4 enabled us to dramatically increase the Ge growth rate at temperatures 425 °C and lower (5.6 nm min −1 compared to 0.14 nm min −1 at 350 °C with a Ge 2 H 6 mass-flow one fourth that of GeH 4 ). We have also evaluated at 400 °C, 100 Torr, the impact of the GeH 4 or Ge 2 H 6 mass-flow on the Ge growth rate. For a given Ge atomic flow, the higher surface reactivity of digermane yielded roughly five times higher growth rates than with germane. We have then combined digermane with disilane (Si 2 H 6 ) or dichlorosilane (SiH 2 Cl 2 ) in order to study the GeSi growth kinetics at 475 °C, 100 Torr. While the SiH 2 Cl 2 mass-flow did not have any clear influence on the GeSi growth rate (with a 14 nm min −1 mean value, then), a Si 2 H 6 mass-flow increase resulted in a slight GeSi growth rate increase (from 11 nm min −1 up to 14 nm min −1 ). Significantly higher Ge concentrations were otherwise accessed with dichlorosilane than with disilane, in the 77–82% range compared to the 39–53% range, respectively.