Characterization of Semiconductors by MeV He+ Backscattering Spectrometry, Channeling and Double Crystal Diffraction

Double Crystal Diffractometry (DCD) is used to characterize the strain produced by 2 MeV He+ at room temperature to simulate a Rutherford Backscattering Spectrometry (RBS) analysis of bulk Si, Ge and GaAs. The irradiation-induced strain is very small in both Si and Ge and persists after 15 min annealing at 400°C. The strain is significant in GaAs and largely reversible upon annealing. The capabilities of DCD are further demonstrated on an example involving characterization of a CoSi_2 epilayer grown on a Si(111) substrate whose surface is slightly offset from the (111) plane by an angle ø_s, in the [110] direction. There is a very small misorientation between the Si(111) and CoSi_2(111) planes. The misorientation angle, α, between these two planes is a fixed fraction 0.017 of the offset angle, ø_s up to ø_s = 4°. A simple geometrical model is proposed to explain the observation. The model agrees quantitatively with the experiment.