Different shapes of impurity concentration profiles formed by long-range interstitial migration

TL;DR

This paper presents a model explaining how impurity profiles in silicon change during low-temperature annealing, accounting for different shapes of boron distribution tails based on impurity interstitial lifetime, and matches experimental data.

Contribution

A novel model of interstitial impurity migration that explains impurity profile shapes and matches experimental redistribution data in silicon annealing.

Findings

Impurity profile tails change shape depending on interstitial lifetime.

The model accurately fits experimental boron redistribution data.

Explains incomplete electrical activation in the tail region.

Abstract

A model of interstitial impurity migration is proposed which explains the redistribution of ion-implanted boron in low-temperature annealing of nonamorphized silicon layers. It is supposed that nonequilibrium boron interstitials are generated either in the course of ion implantation or at the initial stage of thermal treatment and that they migrate inward and to the surface of a semiconductor in the basic stage of annealing. It is shown that the form of the "tail" in the boron profile with the logarithmic concentration axis changes from a straight line if the average lifetime of impurity interstitials is substantially shorter than the annealing duration to that bending upwards for increasing lifetime. The calculated impurity concentration profiles are in excellent agreement with the experimental data describing the redistribution of implanted boron for low-temperature annealing at 750 Celsius degrees for 1 h and at 800 Celsius degrees for 35 min. Simultaneously, the experimental phenomenon of incomplete electrical activation of boron atoms in the "tail" region is naturally explained.