Experimental verification of a new physically based low energy (<5 keV) ion implant model

Accurate modeling of ultra-low energy ion implantation is becoming increasingly more important as MOS devices shrink to deep submicron dimensions, and the required junction depths become shallower than 50 nm. To this end, an efficient Monte Carlo ion implantation model based on a substantially modified Binary Collision Approximation (BCA) has been developed and implemented in UT-MARLOWE. The model removes several of the limitations of the BCA at low energies, such as the asymptotic path approximation and the decoupling of nuclear and electronic stopping usually employed in BCA models. Additionally, multi-body interactions are important at very low energies, and are modeled explicitly for the 3-body case. The modified BCA gives very good agreement with experimental data and is a significant improvement over the classical BCA, particularly for heavy species and well-channeled implants. In this paper, we report on the experimental verification of the model, as well as refinements and corrections subsequently introduced. Surface effects are also discussed, and their impact on the dose-dependence of the profiles is examined. The model has been verified for arsenic and boron, for energies down to 2 keV and 1 keV, respectively. This new model is found to he in very good agreement with the experimental data