Dopant activation and surface morphology of ion implanted 4H and 6H silicon carbide

The activation of ion-implanted B into 4H-SiC, and B, and Al into 6H-SiC is investigated. Complete activation of B implants into 4H-SiC is achieved by annealing at 1750 degrees C for 40 min in an Ar environment. Significant activation (>10%) is not achieved unless the annealing temperature is 1600 degrees C or greater. Sheet resistances of Al-implanted 6H-SiC annealed at 1800 degrees C are 32.2 k Omega/square, indicating high activation of Al at this temperature. Annealing conditions which result in good acceptor activation are shown to be damaging to the surface of either 4H- or 6H-SiC. Atomic force microscopy and Nomarski differential interference contrast optical microscopy are applied to characterize the surfaces of these polytypes. Roughening of the surfaces is observed following annealing in Ar, with measured roughnesses as large as 10.1 nm for B-implanted 4H-SiC annealed at 1700 degrees C for 40 min. Based on data obtained from these techniques, a model is proposed to describe the roughening phenomenon. The premise of the model is that SiC sublimation and mobile molecules enable the surface to reconfigure itself into an equilibrium form.