Locking of dislocations by oxygen in Cz-silicon

The effect of dislocation locking by oxygen atoms in silicon has been studied for annealing temperatures between 400 degrees C and 850 degrees C and annealing times of 0-1300 h. Using an experimental technique based on four-point and three-point bending the unlocking stress of dislocations has been obtained. It has been shown that the unlocking stress increases with increasing annealing temperature, time and oxygen content. At high temperatures, however, after an initial increase the unlocking stress saturates. The saturation time and stress are dependent upon the annealing temperature and oxygen content and decrease with increasing temperature. From the temperature dependence of the saturation stress the binding energy of oxygen atoms to dislocations has been deduced to be about 1.05 eV. The increase of the unlocking stress during annealing has been used to interpret the oxygen transport to dislocations and to obtain the activation energy of oxygen diffusion in the temperature range 400 degrees C-600 degrees C

The segregation behaviour of oxygen at dislocations in silicon

The interaction between dislocations and oxygen atoms in silicon has been studied. The effect of immobilization of dislocations by the segregation of oxygen to the dislocation core (dislocation locking) has been investigated in the temperature range 400-800 °C and for different oxygen concentrations. It has been revealed that oxygen locking of dislocations shows three different regimes of behaviour. The experimental data have been used to determine the dislocation-oxygen interaction energy

Oxygen-dislocation interactions in silicon at temperatures below 700 degrees C: Dislocation locking and oxygen diffusion

The locking of dislocations by oxygen atoms in Czochralski-silicon at temperatures between 350 and 700°C has been studied. Both experimental and theoretical investigations were carried out for different oxygen concentrations, different annealing times (from 10 to 3 × 107 s), and different point defect concentrations. It was found that the unlocking stress of dislocations at low temperatures follows similar trends to those previously observed at higher temperatures and is determined by annealing temperature, time, and oxygen concentration. However, in the present temperature range, experimental results indicate an enhanced transport of oxygen to dislocations. Numerical simulations solving the diffusion equation for oxygen transport to the dislocations show that the effective diffusivity of oxygen at lower temperatures diverges from "normal" diffusivity of oxygen. We have shown that oxygen transport can be as much as three orders of magnitude higher than that which would be assumed by extrapolation of the "normal" data obtained at higher temperatures. In the low temperature regime the effective diffusivity is dependent on the oxygen concentration and has an activation energy of about 1.5 eV. © 2001 American Institute of Physics

Generation of dislocation glide loops in Czochralski silicon

Critical stresses necessary to generate dislocation glide loops in Czochralski silicon containing oxide precipitates have been investigated. Using three-point bending and etching techniques, it was possible to determine the minimum shear stress required to generate dislocation glide loops from controlled distribution of precipitates under constant-stress conditions. The generation of glide dislocations was investigated in samples with different oxide precipitate sizes and different numbers of dislocations initially attached to precipitates. It has been found that the value of the critical resolved shear stress for generating dislocation glide loops depends on the duration of the applied stress. A qualitative model involving punched-out presmatic loops was considered for the explanation of the experimental data. It was found that glide dislocations must be generated from pre-existing large loops probably associated with particular oxide precipitates or other complex defects

A study of oxygen dislocation interactions in CZ-Si

The interaction between dislocations and oxygen atoms in silicon has been studied. The effect of immobilization of dislocations by the segregation of oxygen to the dislocation core (dislocation locking) has been investigated for different oxygen concentrations and annealing conditions. It has been revealed that oxygen locking of dislocations shows three different regimes of behaviour. A numerical model for the dislocation locking process of oxygen atoms has been presented and used to interpret the experimental results. (C) 2000 Published by Elsevier Science S.A. All rights reserved

On the dislocation-oxygen interactions in Czochralski-grown Si: oxygen diffusion and binding at low temperatures

The interaction between oxygen atoms and dislocations in Czochralski-grown silicon has been studied experimentally. Measurements concerning the locking of dislocations by oxygen atoms have been carried out in the temperature range 450-850degreesC for different annealing times Using samples with low oxygen content (2.6 x 10(17) cm(-3)) it has been possible to investigate the nature of binding of oxygen atoms to dislocations for temperatures lower than 700 degreesC for which diffusion of oxygen in silicon has well known 'anomalous' behaviour. It has been found that although the binding enthalpy for temperatures larger than 700 degreesC agrees well with the previously published value, its value is different for lower temperatures. We measured the oxygen-dislocation binding enthalpy to be about 0.2 eV in the temperature range of 450-650degreesC

Dislocation locking by oxygen in silicon: New insights to oxygen diffusion at low temperatures

We investigated locking of dislocations by oxygen atoms in Czochralski silicon. Experiments were carried out in the temperature range 350-850degreesC for different annealing times (10 s to 10000 h) and three different oxygen concentrations. It has been observed that the locking of dislocations as a function of annealing time has five well-defined regimes. From the 14 temperature dependence of the unlocking stress of dislocations the binding energy of oxygen to dislocations has been deduced. Experimental results have indicated that at temperatures below 700degreesC an enhanced transport of oxygen to dislocations takes place. Numerical simulations of oxygen transport to dislocations showed that the effective diffusivity of oxygen at lower temperatures is different than "normal" diffusivity and can be several orders of magnitude larger. At lower temperatures the value of effective diffusivity becomes dependent on oxygen concentration and has an activation energy of about 1.5 eV. Possible mechanisms leading to "enhanced" oxygen transport are discussed

Dislocation locking in silicon by oxygen and oxygen transport at low temperatures

Dislocation-oxygen interactions in silicon have been studied experimentally and using numerical modelling. Experiments were performed to understand the locking of dislocations by oxygen and to measure the unlocking stress of dislocations in the temperature range 350-900degreesC for different annealing times and oxygen concentrations. Our observations revealed that the oxygen-dislocation interactions give rise to well defined regimes in locking of dislocations as a function of temperature. From the temperature dependence it was possible to deduce the oxygen-dislocation binding energy, and to estimate oxygen diffusivity in silicon. Modelling the transport of oxygen to dislocations, in connection with numerical simulations, showed that the effective diffusivity of oxygen at lower temperatures is different from normal diffusivity and can be several orders of magnitude larger, and is then dependent on oxygen concentration. Experimental measurements were made of the temperature dependence of the stress required to unlock dislocations from oxygen atoms bound to their core. These results were used, together with those concerning diffusivity and binding energy, in numerical simulations to predict the onset of plastic deformation of silicon wafers during device processing sequences

The role of prismatic dislocation loops in the generation of glide dislocations in Cz-silicon

The aim of this work is to understand the mechanisms that lead to warpage of Czochralski silicon wafers. We propose that under sufficiently large stresses, the prismatic loops which are punched-out from oxide precipitates during precipitation can initially grow as long dipoles until they cross-slip. Subsequently, dislocation multiplication can occur at the sites where cross-slip takes place, by creation of Frank-Read sources. A model describing the movement of dipoles has been developed to calculate the time needed for the source to be operative. Calculated curves are found to be in agreement with experimental results. During high temperature treatments oxygen atoms can diffuse to the core of prismatic dislocation loops and consequently hinder the dislocation motion, or completely lock them. A model has been developed to predict the amount of oxygen at the dislocation core (and then the "unlocking" stress for a loop) by taking into account the background oxygen concentration, thermal history and position of prismatic loops. It has been shown that the model is capable of simulating the experiments. (C) 2004 Elsevier B.V. All rights reserved

The segregation behaviour of oxygen at dislocations in silicon

The interaction between dislocations and oxygen atoms in silicon has been studied. The effect of immobilization of dislocations by the segregation of oxygen to the dislocation core (dislocation locking) has been investigated in the temperature range 400-800 °C and for different oxygen concentrations. It has been revealed that oxygen locking of dislocations shows three different regimes of behaviour. The experimental data have been used to determine the dislocation-oxygen interaction energy