Modeling of the transient interstitial diffusion of implanted atoms during low-temperature annealing of silicon substrates

TL;DR

This paper models the transient interstitial diffusion of implanted atoms during low-temperature annealing of silicon, demonstrating how impurity migration lengths are affected by different implantation and annealing conditions, with validation against experimental data.

Contribution

It introduces a simulation approach for boron redistribution during low-temperature annealing, revealing how impurity interstitial migration lengths vary with processing conditions.

Findings

Migration length of boron interstitials is reduced by nitrogen implantation.

Lower annealing temperatures further shorten impurity interstitial migration.

Simulation results align well with experimental data.

Abstract

It has been shown that many of the phenomena related to the formation of "tails" in the low-concentration region of ion-implanted impurity distribution are due to the anomalous diffusion of nonequilibrium impurity interstitials. These phenomena include boron implantation in preamorphized silicon, a "hot" implantation of indium ions, annealing of ion-implanted layers et cetera. In particular, to verify this microscopic mechanism, a simulation of boron redistribution during low-temperature annealing of ion-implanted layers has been carried out under different conditions of transient enhanced diffusion suppression. Due to the good agreement with the experimental data, the values of the average migration length of nonequilibrium impurity interstitials have been obtained. It has been shown that for boron implanted into a silicon layer preamorphized by germanium ions the average migration length of impurity interstitials at the annealing temperature of 800 Celsius degrees be reduced from 11 nm to approximately 6 nm due to additional implantation of nitrogen. The further shortening of the average migration length is observed if the processing temperature is reduced to 750 Celsius degrees. It is also found that for implantation of BF2 ions into silicon crystal, the value of the average migration length of boron interstitials is equal to 7.2 nm for thermal treatment at a temperature of 800 Celsius degrees.