The removal of surface silica and its effect on the nitridation of high-purity silicon

Abstract

Compacts of high-purity silicon powder were pretreated in hydrogen or argon to remove the surface silica and then nitrided in gas at atmospheric pressure and at 1623 K. The kinetics of nitridation were monitored continuously, the fracture surfaces of the nitrided samples examined using scanning electron microscopy and the alpha/beta nitride contents determined by X-ray diffraction. The experiments confirm that high-purity silicon powder, usually regarded as unreactive, can be rapidly nitrided to nearly complete conversion following pretreatments designed to remove the silica layer. The results suggest that nitridation occurred by the reaction of silicon vapour with nitrogen gas resulting in the deposition of massive Si₃N₄.