Impact of negative oxygen ions on the deposition processes of RF-magnetron sputtered SrTiO3 thin films

Abstract

This work reports on the deposition of strontium titanate (SrTiO3) thin films by on-axisradio-frequency magnetron sputtering. The on-axis sputter deposited SrTiO3 thin film showed drastic substrate etching due to the production of accelerated energetic negative oxygen ions, when applied power density on target is above a threshold value. The negative ion bombardment leads to the formation of surface micro-effects on the as-deposited SrTiO3 film or even complete removal of the substrate metallization. In order to understand the impact of negative ion bombardment and to limit these re-sputtering effects, the chemical composition and the thin film growth process were systematically studied as a function of deposition parameters. At high RF-power (~8 W/cm2), we observe surface etching at the center of the silicon wafer (~5.08 cm2). However, deposition of the thin film was possible in regions outside this etching zone. The key to achieve stoichiometric SrTiO3 thin film deposition at the axis-center was by controlling both deposition pressure and oxygen concentration, it minimized re-sputtering of the negative oxygen ions on the substrate surface. Polycrystalline growth of SrTiO3 thin films on platinized silicon substrates was optimized systematically and further extended to the deposition of polycrystalline SrTiO3 on MgO substrates.