Wafer-to-wafer bonding requires wafers with closely matching die-sort patterns, making it challenging to pair them successfully.

“So one-to-one die size is a challenge. So if they're not the exact same design device on top and bottom, that's a problem. So wafer to wafer, it's just challenging to make sure that you have wafers that match really well in terms of the sort, right?”

“So sort good array here versus sort good array here. If they match exactly, good die and bad die that they all match-”