Defects formed by pulsed laser annealing: Electrical properties and depth profiles in n-type silicon measured by deep level transient spectroscopy

The ongoing downscaling of microelectronic devices requires dopant activation with diffusion kept to a minimum. One method considered in device processing is microsecond annealing by pulsed lasers. This is a highly non-equilibrium process during which intrinsic point defects generated at the surface diffuse into the material and form a variety of defects during cooling-down. Since the defects lie close to the surface, they may well affect the effective concentration and the formation of leakage currents in pn-junctions of advanced technologies. These defects may be clusters of intrinsic point defects or contain residual impurities like oxygen or dopants. In this work, a bare n-type silicon substrate (phosphorus concentration 5E14 cm3) was annealed with a pulsed laser with maximum tempe ratures of about 800 K up to 1650 K. The defects remaining after annealing were characterized by deep level transient spectroscopy (DLTS) to obtain their activation energies and capture cross-sections for majority carriers in n-type silicon. Additionally, the depth profiles of these defects were measured via a variation of the pulse voltage. The dominating defects found have levels at EC 0.41 eV, EC 0.31 eV, EC 0.3 eV, EC 0.22 eV, and EC 0.17 eV.