Thin wafer processing - yield enhancement through integrated metrology

Thin wafer handling and processing is performed by temporary bonding to a rigid carrier wafer. The rigid carrier wafer gives mechanical support during wafer thinning and backside processing. Finally the thin wafer is debonded from the carrier wafer and attached to a dicing tape on film frame. While this technology has been demonstrated for a couple of years now in pilot line and small volume, it is an entirely different story to transfer such a technology to high volume manufacturing (HVM). Yield is the most important consideration for the transfer to HVM. At this point of the manufacturing flow the device wafers have seen complete front end processing and have a significant inherent value. Furthermore, wafer breakage does not only destroy the wafer, but it might be necessary to take the production tool down for chamber cleaning. However, wafer breakage itself is not the only concern. Defects at the wafer edge can nucleate micro cracks in the die, which can result in device failure at a later point of time. In this paper the potential defects during thin wafer processing are reviewed. A new integrated metrology module is presented, which allows 100% in-line inspection with full wafer scanning.