Change of surface structure of thin silicon nitride layers during electron beam rapid thermal annealing

Abstract

The surface of 〈100〉 Si specimens implanted at room temperature (RT) with 15N+2 ions at 10 keV with fluences of 5×1016 at./cm2 was subsequently annealed by electron beam rapid thermal annealing (EB-RTA) at temperatures between 900 and 1150 °C forming SiNx 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 15N depth profile measurement [15N(p,αγ)12C] at target tilt angles from 30° to 7° indicates a shift of the low energy edge which represents the SiNx sample surface. This shift is attributed to the shadowing effect of the SiNx sample surface. Detailed AFM analysis shows that the surfaces are covered with irregularly distributed vertical structures, being whiskers of ∼16 nm height. These structures become more pronounced with increasing annealing temperatures.