Machine vision system for alignment in die-to-wafer bonder

In this paper, we suggested an alignment mark measurement system for die-to-wafer bonder. The system consisted of a vision system to measure the positions of alignment marks on die and wafer opposite to each other, and a height measurement system to detect the heights of the die and wafer to the vision system. Besides them, a tilt measurement system was also attached to check the parallelism between the die and wafer for exact measurement and bonding. For high precision measurement, the vision system used a special prism structure which minimized the distance between the die and wafer and measured alignment marks on both sides simultaneously. A focus tunable lens was also applied to control a focus position without changing the height of the system. We have designed and built the optical system in a compact size and presented some preliminary results here.