Optimized Die Preparation and Handling for High Yield Hybrid Die to Wafer Bonding

Abstract

Hybrid Cu/dielectric bonding is a well-established technology for Wafer-To-Wafer (W2W) bonding, but it is challenging to apply this technology to Die-To-Wafer (D2W) bonding. Very small particles on the die or wafer can lead to voids/non-bonded regions. Processes to clean and activate wafers for hybrid W2W are quite mature, but it is very challenging to apply these to thinned and singulated dies for D2W bonding. To allow a (partial) re-use of the existing wafer level cleaning, metrology and activation processes and equipment, we propose a new concept where dies are being singulated, cleaned and activated on a glass carrier wafer. After the die preparation steps, the dies are directly picked from the carrier wafer. This approach does not involve additional pick & place steps and avoids the use of conventional dicing tapes. The first direct dielectric D2W bonding experiments using this new approach show a very promising bonding yield, with a high number of completely void-free bonded 50 μm thin dies. Additionally, by eliminating dicing tapes, thinned wafers and singulated dies are always supported by a rigid surface, enabling ultrathin die handling. In this study we also report the handling of dies down 10 μm thickness.