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A p–n junction location technique for determining ion-implanted profiles of dopant ions in semiconducting substrates is described. This method allows detection of the implanted concentration up to eight orders of magnitude below the peak. Distributions of boron, nitrogen, phosphorus, and arsenic ions implanted in [Formula: see text] oriented silicon crystals as well as boron in [Formula: see text] silicon crystals are given. The samples were implanted at energies from 10 to 70 keV and were annealed during implant at 625 °C. The results are compared to theoretical estimates. In the cases of boron and arsenic in [Formula: see text] silicon, and boron in [Formula: see text] silicon, a definite maximum range Rmax is apparent. In these cases Rmax increases as the square root of the incident energy, indicating a channeling phenomenon. The phosphorus profiles do not show a maximum range, but rather decrease exponentially with depth for five orders of magnitude in concentration.

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The use of ion accelerators to implant impurities in crystals has become the subject of widespread research. Such studies have been limited mainly to low energies with acceleration voltages of 50 to 500 kilovolts. In this energy range, impurities are implanted into the upper micron or less of the surface.The present work describes certain characteristics of high energy ion implantation. The ions used were boron and phosphorus. They were implanted into silicon with energies of 2 to 4 megavolts. In this energy range, the impurities have a useful positive impurit,r concentration gradient from the surface. The surface concentration is about 4 X 10 16 em-3, and the peak concentration exceeds 10 1 ern-3 depending on dosage. The peak concentration occurs about 2.5 /Lm deep. After annealing the radiation damage introduced into the semiconductor, it was determined that the surface silicon recovered over 90% of its expected maximum conductivity and mobility.A discussion is given of the concentration gradients required to fabricate a collector pedestal for a high-speed switching transistor, and it is shown that such gradients can be obtained by using high energy ion-implantation. The pedestal may be implanted after the base and emitter diffusions, and annealed at a low temperature, thus keeping a sharp impurity gradient. Also, since it is put into the final epitaxial layer, its vertical position relative to the emitter-base junction will be independent of epitaxial undulations. Figure 1 Cross section of a pedestal-collector transistor. The first epitaxial layer contains the pedestal diffusion and a reachthrough diffusion to the buried collector. After the second epitaxial layer is grown, the base and emitter are diffused into the top surface.