Initiated Chemical Vapor Deposition of polysiloxane as adhesive nanolayer for silicon wafer bonding

Silicon wafer bonding is a fundamental process in the semi-conductor industry. In parallel, Initiated Chemical Vapor Deposition (iCVD) has gained interest for the deposition of polymer thin films. In the current study, we propose to use ultra-thin films of iCVD polysiloxane as adhesives for silicon wafer bonding. Various thin films of poly(1,3,5-trivinyltrimethylcyclotrisiloxane) with a thickness from 10 to 70 nm were deposited onto silicon wafer surfaces at a temperature ranging from 30°C to 100°C. Thermal compression was used to join such wafers with another silicon wafers. It led to bonded stacks with excellent bonding interfaces in terms of defects and adherence. Neither the polymer thickness nor the elaboration temperature had any significant impact on the bonding properties. Nevertheless, the bonding temperature increase led to a strong adherence increase: 4 J/m2 could be reached for temperatures higher than 200°C. Such a bonding stack is compatible with various manufacturing processes: grinding, dielectric deposition and annealing.