A Raman Study Of The Dopant Distribution In Submicron Pn Junctions In 11+ Or Bf2+ Ion Implanted Silicon

The wavelength dependence of Raman scattering from B + and BF 2 + implanted silicon is explored as a basis for a non-destructive method of evaluating dopant concentration profiles in submicron pn junctions. Depth resolution is obtained optically by making use of the change in the absorption coefficient with wavelength in the visible region. For comparison, chemical etching of the surface layers, in steps of ≈ 50 nm, to a depth of 550 nm enabled a direct measurement of the relative dopant concentration with depth by Raman spectroscopy. It is known that the increase in the intensity of the boron local mode at 618 cm -1 and the broadening of the silicon optical phonon at ≈520 cm -1 correlate with the increase in concentration of substitutional boron and its electrical activation. It was also observed that the intensity of the second order Raman band at ≈980 cm -1 is a useful indicator of the doping level. Results are compared with secondary ion mass spectrometry (SIMS) analyses. Suggestions are made for improvements in resolution, sensitivity and calibration in order to provide a rapid method of measuring simultaneously the depth profiles of electrically active and inactive dopant species after annealing or for studying implantation damage prior to annealing.