RAPID THERMAL-OXIDATION OF SILICON IN N2O BETWEEN 800-DEGREES AND 1200-DEGREES-C - INCORPORATED NITROGEN AND INTERFACIAL ROUGHNESS

Oxynitrides can suppress the diffusion of boron from the polycrystalline silicon gate electrode to the channel region of an ultralarge scale integrated device, and are therefore important potential substrates for thin SiO2 gates. Direct oxynitridation of Si in N2O is a simple and manufacturable N incorporation scheme. We have used rapid thermal oxidation to grow O2- and N2O-oxides of technological importance (approximately 10 nm thick) in the temperature range 800-1200-degrees-C. Accurate measurements of the N content of the N2O-oxides were made using nuclear reaction analysis. N content increases linearly with oxidation temperature, but is in general small. A 1000-degrees-C N2O-oxide contains about 7 X 10(14) N/cm2, or the equivalent of about one monolayer of N on Si (100). Nonetheless, this small amount of N can retard boron penetration through the dielectric by two orders of magnitude as compared to 02-oxides. The N is contained in a Si-O-N phase within about 1.5 nm of the Si/SiO2 interface, and can be pushed away from the interface by O2-reoxidation. We have measured Si/SiO2 interfacial roughness by x-ray reflectometry, and found that it decreases with increasing oxidation temperature for both O2- and N2O-oxides, although the N2O-oxides are smoother. The enhanced smoothness of N2O-oxides is greater the greater the N content. N2O-oxides are promising candidates for thin ultralarge scale integrated circuit gate dielectrics.