Scanning electron beam annealing techniques have been applied to the study of diffusion of implanted arsenic and boron difluoride. Electron beam anneals over the time range 0-180s (at Tmax), with peak temperatures in the range 1100-1200°C have been performed on uniformly implanted samples. Controlled slow cooling has been performed for some samples. Direct sample temperature measurements were made using a dual-colour pyrometer under control of a microcomputer, which provided data-logging and feedback control of temperature. The accurate temperature control achieved using this system is important for realistic diffusion modelling.
Measurement of the resulting chemical and electrical dopant profiles, using SIMS, RBS and spreading resistance methodshas shown the presence of non-equilibrium diffusion at short times . Channelling RBS studies used to investigate the activation and clustering behaviour of arsenic during the first stages of these very rapid anneals is reported.
Modelling of the arsenic diffusion occuring for a range of implant doses subjected to these anneals has been performed,applying avariety of models, including a dynamic clustering model. This dynamic clustering model, based upon an equilibrium cluster model and a measured de-clustering rate, has been shown previously to give good agreementwith experiment. Forthese experiments, a modified de-clustering coefficient was needed to model the diffusion occuring for a wider range of arsenic implants. A solution of the Poisson equation for the internal electric field has also been incorporated.
DLTS techniques have been used to study the defects remaining in diodes fabricated using these implagts andanneals. Trap densities of <5×1010cm−3 and leakages of <2×10−9 A.cm2 at −5V have been measured for the best devices, similar tothose observed for control furnace anneals.