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A physical model is presented for calculating infrared reflection interference spectra from ion implanted and annealed crystalline materials. The utility of the method is illustrated by presenting best fit spectra for a <111> silicon sample implanted with 2.7 MeV phosphorous to a fluence of 1.74 × 1016 ions/cm2 and isothermally annealed at 500°C. Non-linear least-squares fitting of reflection data yields structural and electrical information about the implanted region with reasonable precision. The physical quantities determined are (i) the depth of the amorphous layer produced by implantation both before and during isothermal annealing, the thickness of the recrystallized material, and the widths of any transition regions, (ii) the dielectric properties of the amorphous and recrystallized material, and (iii) the characteristics of the free carrier plasma which yield the carrier density profile, the mobility near the carrier density maximum, and the carrier activation efficiency. Up to nine fitting parameters are necessary to describe these physical quantities. A critical discussion of the sensitivity of data fit to variation in the parameters is given to establish the uniqueness of fitted parameters. The infrared method is non-destructive, is applicable to other dopants and semiconductors, and provides information complementary to both ion channeling and resistivity profiling techniques.

Single crystal silicon has been implanted with nitrogen and phosphorus ions at MeV energies to fluences between 1016 and 1.6 × 1018 ions/cm2. Infrared transmission and reflection spectra in the range of 1.25 to 40 μm were measured for as-implanted samples and after various annealing treatments. Interference fringes were observed in the IR spectra which are produced by the interference of light which has been multiply reflected between the front surface and the buried layers. By detailed theoretical analyses of the interference fringe structure, we obtained refractive index profiles, which, under suitable interpretation, provide accurate measurements and several quantities of interest. These quantities are the range and straggling of the implanted ions, the depth of disordered layers, and the width of the order-disorder transition. Mechanisms for the refractive index changes which have been identified include amorphization of the implanted silicon, bulk compositional change in the buried layer, localized vibrational mode dispersion, and free electron dispersion. Experimental results and theoretical predictions are presented, demonstrating each of these mechanisms.