Water vapor barrier properties of Si-Zn-O/Al multilayer structures

Single-layer Si-Zn-O (SZO) and multilayer SZO/Al films are deposited as water vapor barriers on polyimide (PI) substrates, using magnetron sputtering with SiO2-ZnO composite and Al targets. The effect of negative substrate bias voltage (Vb) on the microstructure and water vapor barrier properties of the single layer SZO and multilayer SZO/Al films is investigated. The as-deposited SZO film is found by X-ray diffraction analysis to be amorphous. For deposition at Vb = 0 V, the SZO film has a columnar structure and rough surface morphology; the Al film exhibits pinholes on the surface. When moderate bias voltages (Vb = − 50 V for SZO and − 70 V for Al films) are applied during deposition, a dense SZO film with smooth surface morphology and a pinhole-free Al film are obtained. An SZO/Al multilayer film shows better water vapor barrier performance than a single-layer SZO, which could be further enhanced by application of Vb to the substrate during film growth.