Critical investigation of high performance spin-coated high-κ titania thin films based MOS capacitor

Abstract

We report the tunable dielectric constant of titania films with low leakage current density. Titanium dioxide (TiO2) films of three different thicknesses (36, 63 and 91 nm) were deposited by the consecutive steps of solution preparation, spin-coating, drying, and firing at different temperatures. The problem of poor adhesion between Si substrate and TiO2 insulating layer was resolved by using the plasma activation process. The surface roughness was found to increase with increasing thickness and annealing temperature. The electrical investigation was carried out using metal-oxide-semiconductor structure. The flat band voltage (VFB), oxide trapped charge (Qot), dielectric constant (κ) and equivalent oxide thicknesses are calculated from capacitance–voltage (C–V) curves. The C–V characteristics indicate a thickness dependent dielectric constant. The dielectric constant increases from 31 to 78 as thickness increases from 36 to 91 nm. In addition to that the dielectric constant was found to be annealing temperature and frequency dependent. The films having thickness 91 nm and annealed at 600 °C shows the low leakage current density. Our study provides a broad insight of the processing parameters towards the use of titania as high-κ insulating layer, which might be useful in Si and polymer based flexible devices.