title: Niobium nitride films formed by rapid thermal processing (RTP): a study of depth profiles and interface reactions by complementary analytical techniques.
abstract: The nitridation of niobium films approximately 250 and 650 nm thick by rapid thermal processing (RTP) at 800 degrees C in molecular nitrogen or ammonia was investigated. The niobium films were deposited by electron beam evaporation on silicon substrates covered by a 100 or 300 nm thick thermally grown SiO(2) layer. In these investigations the reactivity of ammonia and molecular nitrogen was compared with regard to nitride formation and reaction with the SiO(2) substrate layer. The phases formed were characterized by X-ray diffraction (XRD). Depth profiles of the elements in the films were recorded by use of secondary neutral mass spectrometry (SNMS). Microstructure and spatial distribution of the elements were imaged by transmission electron microscopy (TEM) and energy-filtered TEM (EFTEM). Electron energy loss spectra (EELS) were taken at selected positions to discriminate between different nitride, oxynitride, and oxide phases. The results provide clear evidence of the expected higher reactivity of ammonia in nitride formation and reaction with the SiO(2) substrate layer. Outdiffusion of oxygen into the niobium film and indiffusion of nitrogen from the surface of the film result in the formation of oxynitride in a zone adjacent to the Nb/SiO(2) interface. SNMS profiles of nitrogen reveal a distinct tail which is attributed to enhanced diffusion of nitrogen along grain boundaries.
authors.affiliation: Institut für Anorganische und Analytische Chemie, J.W. Goethe-Universität Frankfurt, Marie Curie Str. 11, 60439 Frankfurt, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Berendes
authors.forename: O
authors.initials: O
authors.lastname: Brunkahl
authors.forename: C
authors.initials: C
authors.lastname: Angelkort
authors.forename: W
authors.initials: W
authors.lastname: Bock
authors.forename: F
authors.initials: F
authors.lastname: Hofer
authors.forename: P
authors.initials: P
authors.lastname: Warbichler
authors.forename: B O
authors.initials: BO
authors.lastname: Kolbesen
mesh_terms: D000641:Ammonia / Q000737:chemistry; D003460:Crystallization; D013058:Mass Spectrometry / Q000379:methods; D008422:Materials Testing; D046032:Microscopy, Energy-Filtering Transmission Electron / Q000379:methods*; D009556:Niobium / Q000737:chemistry*; D009584:Nitrogen / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D018629:Spectrometry, Mass, Secondary Ion / Q000379:methods*; D013499:Surface Properties; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D009556:Niobium; D012822:Silicon Dioxide; D000641:Ammonia; D009584:Nitrogen