Inspection of Bonded Interfaces Using Scanning Infrared Interferometry

Nondestructive characterization of wafer bonded interfaces is essential for process monitoring and control. The dominant methods that are currently used to evaluate bonded interfaces and identify voids include infrared (IR) transmission imaging and scanning acoustic microscopy. IR transmission imaging is a non-contact technique that allows for rapid assessment of the bonded interface, but has limited resolution and as well as ability to detect small voids. Scanning acoustic microscopy provides considerably higher resolution that IR transmission imaging, but typically requires the use of a coupling fluid between the bonded wafer pair and transducer. In this paper, we present a new non-contact method for the inspection of wafer bonded interfaces based on IR Interferometry Scanning (IRISCN).