The Synthesis of Metal Oxide Films from Compound Powder Targets
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THE SYNTHESIS OF METAL OXIDE FILMS FROM COMPOUND POWDER TARGETS A.I.STOGNIJ, V.V.TOKAREV AND Yu.N.MITIN Institute of Solid State and Semiconductor Physics, ka 17, Minsk 220072, USSR
P.Brov-
ABSTRACT The paper presents the results of AES, SIMS, RBS and electron microscopy investigation of compound metal oxide films. The films were deposited by sputtering compound targets with oxygen ion beam, extracted from hollow cold cathode ion source. INTRODUCTION The progress achieved nowadays in the processes of thin film deposition and in the development of the equipment makes it possible to obtain metal oxide film structures of complex nature. Synthesis of such structures is a high-priority task because of the unique properties, exhibited by the films. Among them superconductivity, ferroelectricity, piezoelectricity, anisotropic conductivity, etc. EXPERIMENT Oxygen ion beam (up to 150 mm in diameter, 0.3-1.5 keV, ) was extracted from the ion source with a hollow cold cathode [i3 . Operating pressure in the target-sample region was not less than 10- Torr. The target was a compound structure composed of powders of metals, oxides and carbonates. CuO,Y 2 0 3 , TiO, Ta, Ta205 , SrO, BaCO3 etc. were used as target constituents. The constituent ratio was varied over a wide range and was estimated by weight accurate within 0.001g. The arrangement of ion source, target and substrate was determined from mathematical calculations. A number of silicon substrates with the deposited films were nnealed at 200-9000C in a diffusion furnace. Metal oxide film structure was inves-
1 mA/cm2
tigated using electron microscopy, Auger electron spectroscopy,, secondary-ion mass spectroscopy and Rutherford backscattering. Dielectric constant and leakage currents in dielectric layers were also determined for some samples.
Mat. Res. Soc. Symp. Proc. Vol. 236. 91992 Materials Research Society
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SPUTTERING MODEL The review of ion-beam sputtering of multicomponent targets is given in j2,3] . It was shown, that ion bobardment forms at the surface a layer with a modified composition. The thickness of this layer is greater than the depth of the region from which atoms are sputtered. Equilibrium sputtering conditions are achieved after this layer has been formed (when the diffusion from the depth of the target is negligible). In equilibrium conditions the sputtering of the components is occuring proportional to the concentration of components in the modified layer and is a stationary process. Time t during which sputtering is stationary, is an important parameter for the process of deposition of a film with a constant composition. For single phase targets t can be assumed as equal to t where t s • 2R p N /jY
(1)
where R is the average statistical ion range in the target (* 0 p A), N is the surface concentration of the implanted ions, j - ion beam density, Y - sputtering constant. For our arrangement of ion source, target and substrate q.rv 103 s. Multiphase targets include grains of different composition. At each grain there forms a layer with a mo
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