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Analytical description of high energy implantation profiles of bordon and phosphorus into crystalline silicon

: Gong, L.; Bogen, S.; Frey, L.; Jung, W.; Ryssel, H.


Radiation effects and defects in solids 127 (1994), S.385-395
ISSN: 1042-0150
Fraunhofer IIS B ( IISB) ()
analytical description; boron; concentration profile; high energy implantation; ion implantation; phosphorus; silicon; simulation

In this paper, we have compared experimental range data and profiles of high energy implants with theoretical values and profiles predicted by LSS, TRIM and RAMM calculations. In order to simulate the dopant profiles of high energy implants, an analytical description of boron and phosphorus profile for high energy implantation has been developed. The sum of two weighted Pearson IV distributions was used in this description. In the case of boron implants, the first Pearson IV function describes the core part of the profiles while the second Pearson IV function describes the low concentration regions due to backscattered and channeled ions. In the case of phosphorus implants, the first Pearson IV function represents the core part of profiles while the second one describes only the channeling region. Values of projected range and standard deviation are reflected in both cases by the first Pearson IV distribution (Figure 1 and Figure 2) which match the experimental values. The asymmetry of the profiles was described by the second Pearson distribution which also give a small contribution to the projected range and the standard deviation. Using this approach implantation profiles can be simulated for implantation energies ranging from 1 MeV to 7.1 MeV for boron implantations and from 1 MeV to 5 MeV for phosphorus implantations. The parameters were extracted from experimental SIMS profiles. The initial nine parameters of the combined Pearson functions were reduced to constant values or simple functions of the implantation energy. For phosphorus implantation, an additional parameter, the dose partition, accounting for dose effects that modify the implantation profiles was applied. Using this description, concentration range of about 5 orders of magnitude is covered. Good agreement to experimental data in this energy and dose range makes this approach suitable for the use in process simulation. The description has been implemented in the process simulation program ICECREM ve rsion 4.3. For further improvement of the description of high energy profiles, e.g. taking into account concentration ranges of more than five orders of magnitude or increased contribution of channeled ions, special attention has to be paid to the function describing the low concentration part of the profile. The steepness of the channeling tail may not be representable by Pearson IV functions any more and may require a different sign of curvature.