EVOLUTION OF SURFACE-MORPHOLOGY IN THE INITIAL-STAGE OF NITRIDATION OF THE SI(111)-7X7 SURFACE BY NITROGEN-IONS

The evolution of surface morphology in the initial stage of nitridatio n of Si(111)-7 x 7 has been investigated by using a scanning tunneling microscope (STM) and low energy electron diffraction (LEED). The STM and LEED measurements were done on the Si(lll) surface nitrided under different experimental conditions including the variations in the nitr ogen ion energy, nitrogen ion dose, nitridation temperature, and the p ostannealing temperature. A growth mechanism of the silicon nitride la yer in the initial stage was proposed based upon a comparison of the s urface morphology obtained under different nitridation conditions. For the growth of uniform and large silicon nitride islands, it was neces sary to have proper heat treatment of the surface. In particular, the surface postannealed at 980 degrees C after nitridation at 950 degrees C produced dramatically enlarged flat silicon nitride islands compare d to that postannealed at the same temperature after nitridation at ro om temperature, and is probably due to improved mobilities of the reac ting species with elevation of the nitridation temperature. (C) 1997 A merican Vacuum Society.