GROWTH AND MICROSTRUCTURAL STUDY OF RADIO-FREQUENCY MAGNETRON SPUTTERED MGO FILMS ON SILICON

Abstract

Microstructure of magnesium oxide films radio frequency (rf) sputtered on <100> silicon substrates at various argon: oxygen (9:1) gas pressures in the range 1-6.7 Pa and at various substrate temperatures up to 700-degrees-C have been studied using x-ray diffraction and scanning electron microscopy. The films have shown a tendency for oriented structure with growth orientation perpendicular to the <200> planes. The tendency for columnar growth has been found to be strong at high argon pressures and has been found to persist to higher substrate temperatures. This observation is consistent with the structure zone model proposed by Movchan and Demchishin [Phys. Met. Mettallogr. 28, 83 (1969)] and later studied by Thornton [J. Vac. Sci. Technol. 11, 666 (1974)]. Annealing of films at 900-degrees-C in oxygen which is needed to reduce oxygen deficiencies and strain generated during growth, and to improve crystallinity by increasing grain size, has been found to cause microcracks in the films depending upon the microstructure and thickness. Films with columnar structure have shown microcracks and the threshold thickness at which microcracks develop has been found to be strongly dependent on the nature of the columnar structure. Dense MgO films deposited at 600-degrees-C at a low pressure of 1 Pa have not shown microcracks upto a thickness of 600 nm. Such films should be potentially applicable as buffer layers for the growth of high quality Y1Ba2Cu3O7-delta films on silicon.