Microscopic mechanism responsible for radiation-enhanced diffusion of impurity atoms

TL;DR

This paper models the microscopic mechanisms behind radiation-enhanced diffusion of boron and phosphorus in silicon, confirming impurity diffusion via impurity-defect pairs and exploring its potential for advanced semiconductor doping techniques.

Contribution

It provides a detailed model of impurity diffusion mechanisms under irradiation, highlighting the formation of specific impurity profiles and suggesting new doping methods.

Findings

Impurity diffusion occurs via impurity-defect pairs.

Local thermodynamic equilibrium conditions are valid during irradiation.

Radiation-enhanced diffusion can create retrograde impurity profiles.

Abstract

Modeling of radiation-enhanced diffusion of boron and phosphorus atoms during irradiation of silicon substrates respectively with high- and low-energy protons was carried out. The results obtained confirm the previously arrived conclusion that impurity diffusion occurs by means of the "impurity atom - intrinsic point defect" pairs and that the condition of the local thermodynamic equilibrium between substitutional impurity atoms, nonequilibrium point defects created by irradiation, and the pairs is valid. It is shown that using radiation-enhanced diffusion, one can form a special impurity distribution in the semiconductor substrate including retrograde profiles with increasing impurity concentration into the bulk of a semiconductor. The calculations performed give clear evidence in favor of further investigation of various doping processes based on radiation-enhanced diffusion, especially the processes of plasma doping, to develop a cheap method for formation of specific impurity distributions in the near surface region.