Cyst. zyxwvutsr Res. Technol. zyxwvut A. I. FEDORENKO, V. V. STARIKOV, Yu. L. POZDEEV, I. N. LYKOV Kharkov State Polytechnic University Kharkov, Ukraine zyxwv 32 zyxwv 1997 6 843-848 Layer Systems on the Base of Nitrogen-Doped Tantalum and Niobium with Enhanced Stability There are presented the results of the investigation of tantalum- and niobium-based metal-oxide bilayers degration in dependence on chemical composition of base metal. Nitrogen dissolved in me- tal increases stability of chemical composition and electrical properties of oxide films grown on the metal surface by anodic oxidation. This improves reliability and life time of electronic devices con- taining tantalum- or niobium-based layer systems. The best positive effect of doping tantalum and niobium by nitrogen was achieved after preliminary refining of these metals from oxygen. When nitrogen concentration in the base metal essentialy exceeds its solubility limit at room temperature and nitride phases are formed the dielectrical properties of oxide film get worsen. 1. Introduction Bilayers composed of a metal (Ta, Nb) and an amorphous dielectric film (TazO5, Nb2O5) are widely used in electronics as parts of various solid state devices [JACKSON, CAMPBELL]. It is well known [SMITH et al.] that the dielectric properties of the Taz05, (NbzO5) layer in the metal-oxide bilayers are deteriorated in the course of time, either spontaneously or under the influence of an external electrical field. This leads to failures of the components of electronic circuits containing tantalum- or niobium-based bilayers. The investigation of this phenomena showed [BOIKO et al. 19931 that the degradation nature is connected with thermodynamically non-equilibrium state of the Me-MezOs bilayers. The relaxation of bilayers into more thermodynamically stable state occurs through chemical redox reaction at the Me/MezOs interface, during which oxygen from Me205 dissolves in Me, and through ordering and crystallization of the amorphous Me205 film. Kinetics of these processe depend on type of the base metal [BOIKO et al. 19931. According to the corresponding Me-0 equilibrium diagrams [FROMM, GEBHARDT] zy , the dissolving oxygen in the tantalum and niobium before oxidation approaches the pair Me and Me205 to the more thermodynamically equilibrium state. However, this ap proach to more stable metal-oxide composition isn’t perspective because it leads to the essential activation of degradation processes connected with crystallization of amorphous oxides [PALATNIK, NABOKA et al. 1994; PALATNIK, et al. 19941. Changing the bilayer construction, for example, at the expense of contact of oxide with other metal [BOIKO et al. 19851 was another approach to more stable metal-oxide systems. If the oxide is grown by anodic oxidation of tantalum or niobium as in the case of electrolytic capacitors the thremodynamical equilibrium can not be reached in princi- ple. Therefore for such objects the decrease of degradation rate can be good alternative. Both the oxygen diffusivities rate can be good alternative. Both the oxygen diffusivities in the oxide and metallic layers and the rate of redox reaction at the interface boundary Me/MezO5 determine the degradation kinetics of metal-oxide bilayers.