Substrate temperature influenced physical properties of silicon MOS devices with TiO ₂ gate dielectric

Abstract

DC reactive magnetron sputtering technique was employed for deposition of titanium dioxide (TiO 2 ) films. The films were formed on Corning glass and p‐Si (100) substrates by sputtering of titanium target in an oxygen partial pressure of 6×10 −2 Pa and at different substrate temperatures in the range 303 – 673 K. The films formed at 303 K were X‐ray amorphous whereas those deposited at substrate temperatures ≥ 473 K were transformed into polycrystalline nature with anatase phase of TiO 2 . Fourier transform infrared spectroscopic studies confirmed the presence of characteristic bonding configuration of TiO 2 . The surface morphology of the films was significantly influenced by the substrate temperature. MOS capacitor with Al/TiO 2 /p‐Si sandwich structure was fabricated and performed current–voltage and capacitance–voltage characteristics. At an applied gate voltage of 1.5 V, the leakage current density of the device decreased from 1.8 × 10 −6 to 5.4 × 10 −8 A/cm 2 with the increase of substrate temperature from 303 to 673 K. The electrical conduction in the MOS structure was more predominant with Schottky emission and Fowler‐Nordheim conduction. The dielectric constant (at 1 MHz) of the films increased from 6 to 20 with increase of substrate temperature. The optical band gap of the films increased from 3.50 to 3.56 eV and refractive index from 2.20 to 2.37 with the increase of substrate temperature from 303 to 673 K. Copyright © 2012 John Wiley & Sons, Ltd.