Study on Cu-Cr-Zr Alloy Based High Performance Copper Interconnects Technology for Next Generation Flexible Display

摘要

In this study, 300-nm-thick Cu-0.3Cr-0.2Zr wt.% (Cu-Cr-Zr) films were deposited on 18-μm-thick polyimide (PI) substrates directly by direct current (DC) magnetron sputtering using Cu-Cr-Zr alloy target (high purity up to 99.99%). With the contrast of Al and pure copper films in the same condition, after 300°C annealing process (1h), there was an obvious resistivity reduction of the Cu-Cr-Zr film (under sputtering power of 150 W) from 4.79 μΩ cm to 3.01 μΩ cm, and the result is superior to Al that has the same thickness and process condition. The adhesion was evaluated, and it showed 4-5B adhesion classification after 300°C annealing process. A further high-resolution transmission electron microscopy was conducted, showing the mechanism of high bond strength and conductivity of the copper alloy film, that is, migration to the surface and oxidation of Cr and Zr elements. Furthermore, an extreme bending machine was used to test the flexible capacity of the alloy films, and the result showed that no detectable change of the resistivity was found by a four-point probe after 10k times bending under 1.82% strain (at 1mm radius of curvature), indicating that the Cu-Cr-Zr copper alloy has the potential in copper metallization of flexible display applications.