1,956 research outputs found
Different shapes of impurity concentration profiles formed by long-range interstitial migration
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.Comment: 13 pages, 3 figure
Modeling of the transient interstitial diffusion of implanted atoms during low-temperature annealing of silicon substrates
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.Comment: 10 pages, 6 figures, RevTe
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