CHANGE OF SURFACE-STRUCTURE OF THIN SILICON-NITRIDE LAYERS DURING ELECTRON-BEAM RAPID THERMAL ANNEALING

The surface of (100) Si specimens implanted at room temperature (RT) with N-15(2+) ions at 10 keV with fluences of 5 X 10(16) at./cm2 was subsequently annealed by electron beam rapid thermal annealing (EB-RTA) at temperatures between 900 and 1150-degrees-C forming SiN(x) layers 25-20 nm thick. The modification in surface structure of these layers by EB-RTA was investigated by atomic force microscopy (AFM) and nuclear reaction analysis (NRA). The N-15 depth profile measurement [N-15(p,alphagamma)C-12] at target tilt angles from 30-degrees to 7-degrees indicates a shift of the low energy edge which represents the SiN(x) sample surface. This shift is attributed to the shadowing effect of the SiN(x) sample surface. Detailed AFM analysis shows that the surfaces are covered with irregularly distributed vertical structures, being whiskers of approximately 16 nm height. These structures become more pronounced with increasing annealing temperatures.