Rapid thermal oxidation of silicon in N2O between 800 and 1200 °C: Incorporated nitrogen and interfacial roughness

Abstract

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 (∼10 nm thick) in the temperature range 800–1200 °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 °C N2O-oxide contains about 7×1014 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 O2-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.

On the scaling issues and high-κ replacement of ultrathin gate dielectrics for nanoscale MOS transistors

“…It was further found with X-ray photoelectron spectroscopy (XPS) that the total nitrogen surface concentration of the prepared ''oxynitride'' is about (3 ± 1) · 10 14 cm À2 . This amount is close to the surface density of a half monolayer of solid and is close to the values of other reports [108][109][110][111][112]. The distribution of nitrogen atoms are mainly found at the Si/dielectric interface and it was believed that the nitrogen incorporation is made mainly via the chemical reaction with the interface Si-Si bonds [105,111], i.e.…”

High resolution ion scattering study of silicon oxynitridation

“…Two approaches have been used, secondary ion mass spectroscopy ͑SIMS͒ 2,5,9,12 and HF etch-back methods 3,13,14 In addition to the limited depth resolution of these methods, SIMS analysis is complicated by matrix effects, while HF etching may introduce nonuniform oxide removal ͑especially in the presence of nitrogen-rich regions͒.…”

Electronic structure of ultrathin Si oxynitrides

“…In addition, N atom incorporation at the SiO 2 /Si interface can stabilize the SiO 2 /Si interface. 3 Electrical performance measurements on MOS capacitor and field effect transistor (FET) also confirmed that the N atoms enhanced both defect densities at the interface as well as reliability. 4 It was also demonstrated that the oxynitride gate dielectrics had a number of properties superior to conventional oxides, such as lower leakage current and improved electrical stress properties.…”