Formation of niobium nitride by rapid thermal processing

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2001-09, Vol.57 (10), p.2077-2089
• Main Authors: Angelkort, C, Lewalter, H, Warbichler, P, Hofer, F, Bock, W, Kolbesen, B.O
• Format: Article
• Language: English
• Subjects: Electrons; Hot Temperature; Mass Spectrometry; Microscopy, Electron; Niobium; Niobium - chemistry; Nitride; Nitrogen - chemistry; Oxygen - metabolism; Oxynitride; Rapid thermal processing (RTP); Temperature; Time Factors
• ISSN: 1386-1425
• DOI: 10.1016/S1386-1425(01)00490-5

The formation of group V transition metal nitride films by means of rapid thermal processing (RTP) has been investigated. Here we focus on the nitridation of niobium films of 200–500 nm thickness in the temperature range from 500 to 1100°C under laminar flow of molecular nitrogen or ammonia. The nitride phases formed were characterized by X-ray diffraction (XRD). Secondary neutral mass spectrometry (SNMS) and transmission electron microscopy (TEM) in combination with electron energy loss spectroscopy (EELS) were carried out on samples of selected experiments to provide more detailed information about the initial stages of nitride formation and the microstructure of the films. A classical formation sequence of nitride phases was observed with increasing nitrogen content in the order: α-Nb(N)→β-Nb 2N→γ-Nb 4N 3→δ′-NbN→Nb 5N 6. Furthermore, oxide enriched regions were discovered inside the metal films. These turned out to be formed mainly in the nitride sequence between the a-αNb(N) and β-Nb 2N-phases at the Nb/SiO 2 interface due to a reaction of the Nb with the SiO 2 layer of the silicon substrates on which the films had been deposited. The SiO 2 layer acts as diffusion barrier for nitrogen but also as source for oxygen, according to SNMS and TEM/EELS studies, resulting in the formation of Nb-oxides and/or oxynitrides at the Nb/SiO 2 interface.