High rate deposition of insulating TiO2 and conducting ITO films for optical and display applications

Abstract

An innovative reactive pulse magnetron sputtering (PMS-) system allowing to change the pulse mode (unipolar, bipolar or pulse packet) and the pulse parameters (duty cycle, frequency) of the discharge has been used to deposit different materials at high deposition rates. The new pulse packet mode combines the two fundamental pulse modes of unipolar and bipolar by applying ‘packets’ of unidirectional pulses between the two targets and changing the polarity of the discharge after each packet. As a new pulse parameter, the number of pulses of each packet can be varied. The advantages of the PMS-system were demonstrated by the reactive deposition of insulating titanium oxide (TiO 2 ) and conducting indium tin oxide (ITO) films. The TiO 2 layers sputtered on unheated substrates at deposition rates of up to 50 nm*m/min exhibited amorphous, mixed anatase/rutile or rutile structure in dependence of the pulse mode and the pulse parameters that were applied. Hardness, Young's modulus, roughness and refractive index varied in dependence of the structure of the layers. Although the sputtering from ceramic target is the most common coating technique for ITO, another economical way is the use of metallic InSn-targets. The effect of various pulse modes on the optical and electrical properties of reactively sputtered ITO layers on float glass was investigated. The specific resistivity of ITO was minimized by process parameter optimisation.