Nitridation of niobium oxide films by rapid thermal processing |
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Authors: | V A Matylitskaya W Bock B O Kolbesen |
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Institution: | 1.Institut für Anorganische und Analytische Chemie,Johann Wolfgang Goethe-Universit?t,Frankfurt,Germany;2.Institut für Oberfl?chen- und Schichtanalytik (IFOS), Technische Universit?t Kaiserslautern,Kaiserslautern,Germany |
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Abstract: | The possibility of forming niobium oxynitride through the nitridation of niobium oxide films in molecular nitrogen by rapid
thermal processing (RTP) was investigated. Niobium films 200 and 500 nm thick were deposited via sputtering onto Si(100) wafers
covered with a thermally grown SiO2 layer 100 nm thick. These as-deposited films exhibited distinct texture effects. They were processed in two steps using an
RTP system. The as-deposited niobium films were first oxidized under an oxygen atmosphere at 450 °C for various periods of
time and subsequently nitridated under a nitrogen atmosphere at temperatures ranging from 600 to 1000 °C for 1 min. Investigations
of the oxidized films showed that samples where the start of niobium pentoxide formation was detected at the surface and the
film bulk still consisted of a substoichiometric NbOx phase exhibited distinctly lower surface roughness and microcrack densities than samples where complete oxidation of the
film to Nb2O5 had occurred. The niobium oxide phases formed at the Nb/substrate interface also showed distinct texture. Zones of niobium
oxide phases like NbO and NbO2, which did not exist in the initial oxidized films, were formed during the nitridation. This is attributed to a “snow-plough
effect” produced by the diffusion of nitrogen into the film, which pushes the oxygen deeper into the film bulk. These oxide
phases, in particular the NbO2 zone, act as barriers to the in-diffusion of nitrogen and also inhibit the outdiffusion of oxygen from the SiO2 substrate layer. Nitridation of the partially oxidized niobium films in molecular nitrogen leads to the formation of various
niobium oxide and nitride phases, but no indication of niobium oxynitride formation was found.
Figure Schematic representation of the phase distribution in 200 nm Nb film on SiO2/Si substrate after two steps annealing using an RTP system. The plot below represents the SIMS depth profiles of the nitridated
sample with the phase assignment |
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Keywords: | Niobium Thin films Rapid thermal processing (RTP) Niobium oxides Nitrides Oxynitrides Diffusion barrier X-ray diffraction (XRD) SIMS depth profile |
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