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]

No abstract

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.

The formation and evolution of small cluster defects in 500 eV, 1×1015 cm−2 boron-implanted silicon is investigated. These clusters are identified by high-resolution transmission electron microscopy (TEM) as small dislocation loops lying on {100} planes with an interstitial character. Weak-beam dark-field TEM analysis shows that, during annealing at 650 °C, they evolve following an Ostwald ripening mechanism. Spike anneals at high temperatures make them dissolve but an immobile boron peak is still detected in the secondary ion mass spectroscopy profiles. Upon oxidation, the average size of the clusters increases, while boron electrical deactivation occurs. These results strongly indicate that the observed clusters contain both boron interstitials and silicon self-interstitials atoms.

No abstract

The formation of ultra-shallow junctions (USJs) for future integrated circuit technologies requires preamorphization and high dose boron doping to achieve high activation levels and abrupt profiles. To achieve the challenging targets set out in the semiconductor roadmap, it is crucial to reach a much better understanding of the basic physical processes taking place during USJ processing. In this paper we review current understanding of dopant-defect interactions during thermal processing of device structures – interactions which are at the heart of the dopant diffusion and activation anomalies seen in USJs. First, we recall the formation and thermal evolution of End of Range (EOR) defects upon annealing of preamorphized implants (PAI). It is shown that various types of extended defect can be formed: clusters, {113} defects and dislocation loops. During annealing, these defects exchange Si interstitial atoms and evolve following an Ostwald ripening mechanism. We review progress in developing models based on these concepts, which can accurately predict EOR defect evolution and interstitial transport between the defect layer and the surface. Based on this physically based defect modelling approach, combined with fully coupled multi-stream modelling of dopant diffusion, one can perform highly predictive simulations of boron diffusion and de/re-activation in Ge-PAI boron USJs. Agreement between simulations and experimental data is found over a wide range of experimental conditions, clearly indicating that the driving mechanism that degrades boron junction depth and activation is the dissolution of the interstitial defect band. Finally, we briefly outline some promising methods, such as co-implants and/or vacancy engineering, for further down-scaling of source-drain resistance and junction depth.

Silicon carbide n-type metal-oxide-semiconductor field effect transistors (MOSFETs) with different p-body acceptor concentrations were characterized by Hall effect. Normally OFF MOSFETs with good transfer characteristics and low threshold voltage were obtained with a peak mobility of ∼145 cm2 V−1 s−1 for the lowest acceptor concentration. The results are explained in terms of an increase of Coulomb scattering centers when increasing the background doping. These scattering centers are associated to fixed oxide and trapped interface charges. Additionally, the observed mobility improvement is not related to a decrease of the interface states density as a function of background doping

Damage evolution and dopant distribution during nanosecond laser thermal annealing of ion implanted silicon have been investigated by means of transmission electron microscopy, secondary ion mass spectrometry, and atom probe tomography. Different melting front positions were realized and studied: nonmelt, partial melt, and full melt with respect to the as-implanted dopant profile. In both boron and silicon implanted silicon samples, the most stable form among the observed defects is that of dislocation loops lying close to (001) and with Burgers vector parallel to the [001] direction, instead of conventional {111} dislocation loops or {311} rod-like defects, which are known to be more energetically favorable and are typically observed in ion implanted silicon. The observed results are explained in terms of a possible modification of the defect formation energy induced by the compressive stress developed in the nonmelted regions during laser annealing.