Asymmetric Low Temperature Cu-Polymer Hybrid Bonding with Au Passivation Layer

Abstract

In this study, an asymmetric Cu-polymer hybrid bonding technology was successfully developed at 200 °C, which uses SU-8 for polymer bonding and Au passivation for Cu bonding. The polymer bonding performance was investigated by the analyses of sat, SEM and pulling test, indicating that bonding with the best quality was achieved at 200 °C. With the Au passivation layer capping on the Cu surface, a low temperature Cu-Cu bonding process can be realized at 200 °C. After demonstrating the bonding process with single material, a chip-level hybrid bonding structure was fabricated and bonded successfully. The hybrid bonding interface was observed by the SEM images, showing that both of the metal and polymer region were well bonded. Furthermore, the electrical properties and reliability performance were analyzed by electrical measurements with a modified Kelvin structure and after un-biased highly accelerated stress test for 168 hours. The bonded structure can still maintain excellent electrical property about 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> Ω·cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Based on the bonding results, this research provides a practical concept for low temperature hybrid bonding in 3D integration.