Channeling in Semiconductors and its Application to the Study of Ion Implantation

Citation

Picraux, Samuel Thomas (1969) Channeling in Semiconductors and its Application to the Study of Ion Implantation. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/EBXR-QS35. https://resolver.caltech.edu/CaltechTHESIS:05102017-142717261

Abstract

The channeling characteristics of protons and helium ions in various diamond-type lattices (diamond, Si, Ge, GaP, GaAs, GaSb) have been studied by means of elastic backscattering in the 0.5 to 2 MeV range. Critical angles (ψ_½) and minimum yields (ψ_½) have been measured and compared to theory. The values of ψ_½ for axial channeling have a functional dependence which agrees well with calculations based on the average potential along the row - both for uniform and for non-uniform spacing and (in the case of the compound semiconductors) for mixed atomic composition. Planar critical angles also show a functional dependence in agreement with average potential calculations. However, it is necessary to include in the calculation the effect of surface transmission which becomes increasingly important for higher order planar directions (e.g. lower atomic density of the planes). Measured full angular distributions are compared with calculated distributions for planar channeling. For both axial and planar channeling the measured critical angles are ≈ 25% lower in absolute magnitude than calculated.

Channeling and electrical measurements are combined to study ion implanted impurities in silicon. The lattice disorder and impurity atom lattice location are investigated by channeling effect measurements using a 1 MeV helium ion analyzing beam. The electrical type, number of carriers/cm² and mobility are determined by use of Hall effect and sheet resistivity measurements.

The anneal behavior of Cd and Te implantations (20-50 keV) into Si at substrate temperatures of 23°C and 350°C were investigated. The room temperature Te implants showed substitutional behavior and donor action after anneal at 600°C. In room temperature Cd implantations, outdiffusion of the Cd was observed when the disordered layer annealed. Implantations of Cd at 350°C indicated the presence of an interstitial component and n-type behavior was observed.

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