PREPARATION OF STRONTIUM-TITANATE FILMS BY MOCVD

Strontium titanate films have been prepared by MOCVD from Sr(thd)(2) and titanium isopropoxide. Ammonia was used as a carrier gas for the strontium precursor, and argon as the carrier for the titanium precursor. The films have been deposited on silicon and on Pt/Ti/SiO2/Si substrates at 700 degrees C using N2O as the oxidizing atmosphere. The films have been characterized by X-ray diffraction (XRD), Rutherford backseattering spectroscopy (RBS) and electrical measurements. X-ray diffraction showed that the crystallization of the films was strongly dependent on their composition. Films having a ratio Sr:Ti>0.8 crystallized in the perovskite phase, while films containing a lower Sr:Ti ratio did not crystallize at all. The diffractograms of strontium rich films showed that they contained also strontium oxide and strontium carbonate crystalline phases. However no crystalline phase could be identified in the titanium rich films. RBS measurements indicate a strong interaction between the strontium titanate and the platinum films and to a lesser extent with the silicon surface. A strontium titanate film, of random orientation and a thickness of 320 nm, had a dielectric constant of 131 and a dissipation factor of about 2% at 200 kHz and a leakage current of 10(-7)Amp.cm(-2).