Paradoxical boron profile broadening caused by implantation through a screen oxide layer

The effects of an overlaying silicon dioxide layer on boron ion channeling and implant profile depths have been examined through analysis of experimentally measured profiles and the results of Monte Carlo simulations using the UT-MARLOWE code. Details of the randomizing effects of the oxide layer are presented, and a surprising anomaly is revealed: implantations through screen oxide layers can actually result in broader (deeper) profiles than similar implantations into bare silicon. The effectiveness of the screen oxide in randomizing the directions of implanted ions was found to be strongly dependent on the correlation between the ion energy and the oxide thickness. It has also been shown that even the total randomization of the directions of the ions does not completely eliminate ion channeling.< >