Deposition of Niobium Nitride Thin Films from Tert-Butylamido-Tris-(Diethylamido)-Niobium by a Modified Industrial MOCVD Reactor

Niobium nitride thin films are deposited on 200 silicon (100) wafers using a modified industrial metal-organic (MO)CVD reactor of the type AIX-200RF, starting from tert-butylamido-tris-(diethylamido)-niobium (TBTDEN) and ammonia. Films of thicknesses 50-200nm are deposited at temperatures ranging from 400°C to 800°C under reactor pressures of 1 and 5 mbar using various ammonia flow rates, and are characterized by the use of complementary techniques, namely X-ray diffraction (XRD), scanning electron microscopy (SEM), secondary neutral mass spectrometry (SNMS), Rutherford backscattering spectrometry (RBS), X-ray photoelectron spectroscopy (XPS), and electrical measurements. Films deposited above 450°C consist of the cubic d-NbN phase, apart from the presence of Nb-O and Nb-O-N species predominantly in the outermost film regions. The lowest specific resistivities, determined by four point probe measurements, are in the range 500-–600mV cm. A NbN/SiO2/p-Si gate stack is fabricated using the grown niobium nitride films. From the capacitance-voltage (C-V)-curves, flatband voltages are extracted which, when plotted against SiO2-insulator thickness, yield a work function of 4.72 eV for as-deposited films.