Formation energies and relative stability of perfect and faulted dislocation loops in silicon

A study of the relative thermal stability of perfect and faulted dislocatio n loops formed during annealing of preamorphized silicon wafers has been ca rried out. A series of transmission electron microscopy experiments has bee n designed to study the influence of the ion dose, the annealing ambient an d the proximity of a free surface on the evolution of both types of loops. Samples were implanted with either 150 keV Ge+ or 50 keV Si+ ions to a dose of 2x10(15) cm(-2) and annealed at 900 degrees C in N-2, N2O, and O-2. The calculations of formation energy of both types of dislocation loops show t hat, for defects of the same size, faulted dislocation loops (FDLs) are mor e energetically stable than perfect dislocation loops (PDLs) if their diame ter is smaller than 80 nm and vice versa. The experimental results have bee n analyzed within the framework of the Ostwald ripening of two existing pop ulations of interstitial defects. It is found that the defect ripening is n onconservative if the surface is close to the end of range defect layer or if the sample is oxidized during annealing. In both cases, the knowledge of the formation energy of both types of dislocation loops allows a realistic estimate of the interstitial flux towards and from the surface, respective ly, during annealing, in agreement with the experimental results. During a conservative ripening process, a direct correspondence exists between the f ormation energy of the two defect families and the number of atoms bound to them. In this case, the relative stability of FDLs and PDLs depends on the initial supersaturation of Si interstitial atoms created during implantati on. (C) 2000 American Institute of Physics. [S0021-8979(00)03812-3].