Plasma and Silane Surface Modification of SiC/Si: Adhesion and Durability for the Epoxy–SiC System

Gaseous plasma pretreatments and surface derivatization using silane coupling agents (SCA) have been used to enhance the adhesive bonding of an epoxy to SiC-coated Si wafers (SiC/Si). The surface modification approaches included 1) an SCA treatment using 3-aminopropyltriethoxysilane (APS) or 3-glycidoxypropyltrimethoxysilane (GPS) and 2) an oxygen plasma pretreatment followed by a silane treatment. Durability was evaluated by immersing epoxy-coated SiC/Si samples in aqueous solutions at various pHs at 60°C for selected times. Adhesion durability for the epoxy-coated SiC/Si systems was qualitatively evaluated by visual inspection to identify debonding and quantitatively evaluated with a probe test to determine the critical strain energy release rate, G c . Durability via either test approach varied as a function of surface treatment in this manner: oxygen plasma treatment plus silane modification > silane treated > no treatment. X-ray photoelectron spectroscopic characterization of surfaces was carried out following the surface treatments and after complete adhesion failure in the durability tests. The XPS results suggested that improved performance was due to plasma cleaning and modification of the substrate surface, promotion of silane surface interaction, and the formation of a thicker oxide layer.