Flash Annealing Technology for USJ: Modeling and Metrology
Millisecond annealing either by flash lamp or laser appears to be the leading approach to meet the needs of ultra-shallow junction annealing and polysilicon activation for advanced technology nodes. There are many advantages to this technology including high electrical activation, excellent lateral abruptness, controlled and limited dopant diffusion and the ability to engineer the extended defects remaining from the ion implantation. There are also many challenges such as potential pattern effects, local and global wafer stress and difficulty in process integration. Additional challenges include the need to extend the capabilities of process TCAD to allow accurate simulation and prediction of the ms processes. Modeling of diffusion, activation and defect evolution for a variety of technologically interesting doping conditions must be dependable to allow the device designer and process engineer to predict the device behavior after ms annealing. Existing models fall short or still need to be validated. Metrology for ultra-shallow junctions is also a challenge. The ability to accurately and repeatably measure sheet resistance and junction leakage on junctions of the order of 10nm deep is very difficult. This paper provides an overview of flash lamp annealing and deal with some promising extensions of process simulation to enable the predictive modeling of junction behavior under flash lamp annealing conditions. We also examine some of the new metrology techniques for characterization of these very shallow junctions and look at some of the trends exhibited for different junction formation details
Clusters formation in ultralow-energy high-dose boron-implanted silicon
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.
On the application of the weak-beam technique to the determination of the sizes of small point-defect clusters in ion-irradiated copper
We have made an analysis of the conditions necessary for the successful use of the weak-beam technique for identifying and characterizing small point-defect clusters in ion-irradiated copper. The visibility of small defects was found to depend only weakly on the magnitude of the beam-convergence. In general, the image sizes of small clusters were found to be most sensitive to the magnitude of Sa with the image sizes of some individual defects changing by large amounts with changes as small as 0.025 nm{sup {minus}1}. The most reliable information on the true defect size is likely to be obtained by taking a series of 5-9 micrographs with a systematic variation of deviation parameter from 0.2-0.3 nm{sup {minus}1}. This procedure allows size information to be obtained down to a resolution limit of about 0.5 nm for defects situated throughout a foil thickness of 60 nm. The technique has been applied to the determination of changes in the sizes of small defects produced by a low-temperature in-situ irradiation and annealing experiment.