Temporary Bonding and the Challenge of Cleaning Post-Debond

Temporary bonding is used for many applications in Advanced Packaging and Microelectromechanical Systems (MEMS). Device wafers are bonded to a carrier wafer with a temporary bonding material in order to perform subsequent backside processing without affecting the device side. After completing the fabrication steps, the wafer must be removed from the temporary carrier by a release mechanism appropriate to the type of temporary bonding material used. After debonding, the device wafer must be sufficiently clean in order to complete fabrication. If the device wafer was thinned it will be debonded onto a film frame with UV tape. The cleaning process and chemistry needs to be compatible with the tape and film frame structure.Optimized cleaning is a result of selecting the most effective chemistry, equipment and process. The chemistry should dissolve the temporary bonding material while leaving the device wafer undamaged. The equipment needs to maintain process parameters such as temperature and flow rates while recirculating the chemical for reduced chemical consumption. The process determines the optimized parameters and sequence for the most effective cleaning at the lowest cost of ownership.This paper describes the methodology and experimentation done to optimize the cleaning process for BrewerBOND® 305 bonding material. Parameters addressed included chemical purity, bath life and consumption, process temperature, dispense method, time and process sequence. A design of experiment (DOE) methodology was performed to determine the impact of tool and chemical parameters to yielding residue-free wafers. In addition, the effect of adhesive film thickness on process conditions was considered. Processes will be presented for both debonded wafers and wafers mounted onto film frames. The methodology provided an optimized cleaning process with lower cost using recirculated chemistry at ambient temperature.