Magnet assisted alignment method for wafer bonding and wafer level chip scale packaging

Abstract

A high-precision alignment method with high throughput is proposed, which can be used for wafer-to-wafer, chip-to-wafer or chip-to-chip bonding. The scheme implements pairing patterned magnets predetermined designed and made using wafer level process on two components (wafer or chip). The magnetization in patterned magnet can be set at predetermined configuration before bonding starts. When, the two components are bought to close proximity after a coarse alignment, the magnetic force will bring the magnet pairs together and aligned the patterned magnet on one component with its mirrored or complimentary patterned magnets on the other component to minimize the overall the magnetic energy of the pairing magnet. A few patterned magnet structures and materials, with their unique merits are proposed as examples for magnet pair for the self-alignment purpose. This method enables solid contact at the bonding interface via patterned magnets under the magnetic force, which avoid the wafer drafting due to the formation of the liquid phases.