Influence of Glass Surface Modification on Thin Film Copper Electrodes

Abstract

Large-area and ultra-high resolution displays continue to progress driven by new performance requirements and applications. As display sizes become larger, the industry demands metal electrodes with low resistance to reduce the gate delay time and signal distortion. Cu is an attractive candidate due to its relative low resistivity and its superior resistance to electromigration as opposed to materials such as Al or Mo. For bottom gate TFT technologies, the metal electrode is deposited directly on the glass substrate. Cu is known to have poor adhesion with oxide materials such as the substrate glass. Typically, an adhesion layer such as Ti, Mo, or other metal/alloy is required to improve the adhesion of Cu to the substrate. In this work, we modify Corning® Eagle XG® glass surfaces by various treatments to study the impact of the glass surface on the structural and electrical properties of Cu. Ti was used the adhesion layer in this study. Atomic force microscopy is used to examine the surface topography and the surface roughness of Cu. In-plane X-ray diffraction results characterize the crystallization and crystalline in-plane orientation of Cu. Transmission electron microscopy is used to further investigate the structure of the Ti and Cu films. The films properties are correlated with 4-point probe measurement of the sheet resistance. The film adhesion performance is determined using the tape test. The role of the glass surface state is demonstrated through its impact on the structural and electrical properties of Ti/Cu electrodes emanating from glass surface treatments.