The transient supersaturation in a system undergoing Ostwald ripening is related to the cluster formation energy E fc as a function of cluster size n. We use this relation to study the energetics of self-interstitial clusters in Si. Measurements of transient enhanced diffusion of B in Si-implanted Si are used to determine S͑t͒, and inverse modeling is used to derive E fc ͑n͒. For clusters with n . 15, E fc ഠ 0.8 eV, close to the fault energy of ͕113͖ defects. For clusters with n , 10, E fc is typically 0.5 eV higher, but stabler clusters exist at n ഠ 4 (E fc ഠ 1.0 eV) and n ഠ 8 (E fc ഠ 0.6 eV). [S0031-9007(99)09311-4]
Motion of a substitutional impurity via a fast-diffusing intermediate species is discussed. An analytical solution is given for the case of low impurity concentration. For short times, few atoms migrate and the solution behaves exponentially. We observe this exponential signature in the diffusion of nanometer-scale B-doping profiles in Si. The migration frequency during oxidation-enhanced diffusion is consistent with diffusion-limited kickout of an interstitial-type B species. This is the first direct experimental evidence for dopant diffusion in Si via an intermediate species.
Impact of the end of range damage from low energy Ge preamorphizing implants on the thermal stability of shallow boron profiles Diffusion of B in Ge is studied in the temperature range 800-900°C using implantation doping and B doped epitaxial Ge layers. Concentration profiles before and after furnace annealing were obtained using high resolution secondary ion mass spectroscopy (SIMS). Diffusion coefficients were calculated by fitting the annealed profiles using TSUPREM. We obtained diffusivity values which are at least two orders of magnitude lower than the lowest values previously reported in the literature. Using our values an activation energy of 4.65͑±0.3͒ eV is calculated. Present experimental results suggest that interstitial mediated mechanism should be considered for B diffusion in Ge in accordance with recent theoretical calculations. Annealed SIMS profiles also suggest that B solid solubility in Ge is ϳ2 ϫ 10 18 cm −3 at 875°C which agrees with literature values.
A study of the relative thermal stability of perfect and faulted dislocation loops formed during annealing of preamorphized silicon wafers has been carried out. A series of transmission electron microscopy experiments has been designed to study the influence of the ion dose, the annealing ambient and 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 2×1015 cm−2 and annealed at 900 °C in N2, N2O, and O2. The calculations of formation energy of both types of dislocation loops show that, for defects of the same size, faulted dislocation loops (FDLs) are more energetically stable than perfect dislocation loops (PDLs) if their diameter is smaller than 80 nm and vice versa. The experimental results have been analyzed within the framework of the Ostwald ripening of two existing populations of interstitial defects. It is found that the defect ripening is nonconservative 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, respectively, during annealing, in agreement with the experimental results. During a conservative ripening process, a direct correspondence exists between the formation 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 implantation.
Articles you may be interested inInfluence of boron-interstitials clusters on hole mobility degradation in high dose boron-implanted ultrashallow junctions Impact of the end of range damage from low energy Ge preamorphizing implants on the thermal stability of shallow boron profiles
The diffusion of boron (B) in germanium (Ge) is studied. B was introduced in Ge wafers by ion implantation, and concentration profiles after furnace annealing were obtained using secondary ion mass spectroscopy. The diffusion coefficient and solid solubility of B in Ge has been calculated to be 1.5(±0.3)×10−16 cm2/s and 5.5(±1.0)×1018/cm3, respectively, at 850 °C by fitting experimentally obtained profiles. This value of diffusion coefficient is at least two orders of magnitude lower than the minimum value reported in the literature for B diffusion in Ge. The results are significant as they question the general agreement about vacancy diffusion as the mechanism responsible for diffusion of B in Ge.
Fluorine-enhanced boron diffusion in germanium-preamorphized silicon J. Appl. Phys. 98, 073521 (2005); 10.1063/1.2084336 Activation improvement of ion implanted boron in silicon through fluorine co-implantation J.
Interactions between self-interstitials (I) and {113} interstitial defects during annealing of Si implant damage have been studied. At low damage levels diffusion is ultrafast, driven by I released direct from the ion collision cascade. At higher damage levels, free I are quenched by nucleation of {113} defects. We show that the transient enhanced diffusion seen in most previous studies arises from the subsequent dissolution of the {113} defects.
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