Enabling Thin Wafer Metal to Metal Bonding through Integration of High TemperaturePolyimide Adhesives and Effective Copper Surface Cleans

摘要

This paper will examine the use of high temperaturernPolyimide temporary adhesives and advanced copper cleaningrnsolutions for thin wafer handling during metal to metal (Cu-rnCu) bonding. In the case of Cu to Cu solid state diffusionrnbonding, temperature requirements can be up to 400C for asrnlong as 40 minutes. These extreme conditions pose arnsignificant challenge with existing materials used forrntemporary bonding.rnPolyimides are ideally suited for high temperaturernapplications and polyimide adhesives have been developedrnwhich can withstand 400°C processing without significantrnfailure in adhesion. As well, Cu to Cu bonding processes willrnrequire the need for contamination free surfaces, whichrnbecomes increasingly important if lower temperaturernprocesses (<400oC) are desired. Close-coupled copperrncleaning immediately prior to the bonding step offers anrnexcellent approach for providing process reproducibilityrnwhile achieving increased electrical yields. Utilizingrnadvanced wet cleaning solutions to obtain optimal Cu surfacernpreparation by removing undesirable copper oxide andrnBenzotriazole (BTA) layers, and potentially adding a copperrnoxidation barrier (COB) functionality will be discussed inrndetail.