Simulation of Boron Diffusion during Annealing of Silicon Substrates Undergone a High Fluence Ion Implantation

TL;DR

This paper presents a theoretical model explaining boron diffusion during rapid thermal annealing of silicon substrates implanted with high fluence ions, highlighting temperature-dependent mechanisms involving interstitials and pairs.

Contribution

It introduces a model distinguishing the roles of boron interstitials and pairs in transient enhanced diffusion at different annealing temperatures.

Findings

At 850°C and below, boron interstitials dominate diffusion.

Above 850°C, boron-silicon interstitial pairs are the main contributors.

Model aligns well with experimental concentration profiles.

Abstract

A theoretical investigation of the microscopic mechanisms provided the transient enhanced diffusion of boron atoms during rapid thermal annealing of silicon substrates doped by high fluence ion implantation was carried out. To compare the mechanisms a model of the transient enhanced diffusion due to migration of the pairs "boron atom - silicon interstitial" was developed. It is supposed that during annealing dissolution of the clusters incorporated boron atoms occurs. During cluster dissolution, a fraction of boron atoms occupies a substitutional position, whereas other atoms become interstitial. It was shown from the comparison of the shape of calculated boron concentration profile after annealing with the experimental data that at a temperature of 850 Celcius degrees and below the nonequilibrium boron interstitials are responsible for the transient enhanced diffusion. On the other hand, at a temperature of 850 Celcius degrees and above a major contribution to the transient enhanced diffusion is provided by the pairs "boron atom - silicon interstitial".