INVESTIGATIONS OF ULTRATHIN SILICON-NITRIDE LAYERS PRODUCED BY LOW-ENERGY ION-IMPLANTATION AND EB-RTA

Ultrathin silicon nitride layers were produced by implanting 10 keV N-15(2)+ ions into [100] silicon at RT with fluences from 5.0 x 10(16) at/cm2 to 5.0 x 10(17) at/cm2. The N-15 depth distributions were analysed by the resonant nuclear reaction The NRA of the silicon nitride layers show understoichiometric, stoichiometric, and overstoichiometric N/Si ratios depending on the fluences. The implanted samples were processed by electron beam rapid thermal annealing (EB-RTA) between 900 and 1130-degrees-C under high vacuum conditions. The layer thicknesses and the 15N peak concentrations of EB-RTA samples varied with reference to non-annealed N-15 layers. The alteration of the chemical bonds of SiN, layers by EB-RTA was investigated by XPS. NRA analyses of the EB-RTA samples at tilt angles from 65 to 83-degrees indicated a shift of the low-energy edge which represents the sample surface. This shift is attributed to a shadowing effect of the SiN(x) surface. AFM analyses confirmed that the surfaces of EB-RTA samples were covered with irregularly distributed vertical very elastic, needlelike structures. Their average height was 16 nm (F = 5.0 X 10(16) at/cm2, EB-RTA at 900-degrees-C for 15 s).