Thermal Nitridation of SiO2 Films in Ammonia: The Role of Hydrogen

Abstract

We investigated the transport of hydrogenous species during thermal nitridation of silicon dioxide films in ammonia by means of isotopic tracing of hydrogen. The dependence of the amount of hydrogen incorporated in the oxynitride films on the nitriding temperature and time, ammonia pressure, and on the initial oxide thickness was determined using methods that allow discrimination between the incorporation of hydrogen in the oxynitride films during nitridation and the effect of hydrogen adsorption during exposure of the oxynitride films to air. The depth profiles of hydrogen and the numher of hydrogen atoms that are exchanged between the oxynitride films and the ammonia gas are also established. The results indicate that the nitridation is driven by a mechanism whereby ammonia diffuses toward the oxide/Si interface reacting with the silica network. The nitridation of the surface and of the interface creates diffusion barriers whose effect on the nitridation process, as well as on the incorporation of hydrogen in the oxynitride films, is discussed.) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 138.251.14.35 Downloaded on 2015-03-14 to IP

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

“…24 shows the energy locations of several defect centers in oxynitride, oxide, and nitride using numerical calculation [124]. Due to the fabrication methods, most of the defects in oxynitride are tied to the hydrogen and hydroxyl groups and are the major sources for hot-carrier induced related trap generation in nitrided oxide films [125][126][127][128]. Even in silicon oxide, it was shown that the neutral traps for electrons (r % 10 À17 cm 2 ) could be created due to the water diffusion into thermal oxide.…”

Nitridation of Silicon With Ammonia and Nitrogen

“…22 Ammonia begins to dissociate at 760 • C onto the silicon surface from where the reactive NH 2− , NH 2− , N 3− and H + species are able to interact and diffuse through the surface layer to create the silicon nitride film. 23,24 On the other hand, nitrogen does not begin to dissociate until substantial higher temperatures (> 1200 • C) and therefore is unable to interact with silicon substrate at lower temperatures. Ellipsometry reflectance measurement is a common and strong tool.…”

Isotopic tracing during rapid thermal growth of silicon oxynitride films on Si in O2, NH3, and N2O

“…7-11, namely ͑i͒ growth of a SiO 2 film in O 2 , followed by nitridation in NH 3 , and then followed by reoxynitridation in N 2 O͑O 2 →NH 3 →N 2 O, samples 1-5 in Table I͒, [7][8][9] and ͑ii͒ growth of oxynitride films in N 2 O, followed by renitridation in NH 3 ͑N 2 O→NH 3 , samples 6-8͒. 10,11 Isotopically enriched gases were used for the RTP growth, namely, 99% 18 Table I, together with the total amounts of all isotopes present in the resulting oxynitride films as measured by nuclear reaction analyses ͑NRA͒. 12 Since the overall N concentrations in most of the films are rather moderate, their density can be taken as being approximately that of vitreous silica, giving the equivalent thickness relationship 10 15 ͑OϩN͒ atoms/cm 2 ϭ0.226 nm.…”

“…12 Since the overall N concentrations in most of the films are rather moderate, their density can be taken as being approximately that of vitreous silica, giving the equivalent thickness relationship 10 15 ͑OϩN͒ atoms/cm 2 ϭ0.226 nm. The 15 N and 18 O depth profiles were obtained by nuclear resonance profiling ͑NRP͒, using the strong, narrow, isolated resonances in the cross sections of the nuclear reactions 18 O͑p,␣) 15 N at 151 keV, and 15 N͑p,␣␥) 12 C at 429 keV, and a tilted sample geometry ͑⌿ϭ65°͒. 12-15 The measured excitation curves ͑i.e., ␣ or ␥ yields versus incident proton energy͒ around the resonance energy E R can be converted into concentration versus depth profiles by means of the SPACES simulation program.…”

“…The excitation curves of the 18 O(p,␣) 15 N nuclear reaction in samples 1-3 and the corresponding 18 Fig. 2͑b͒.…”