Application of digital scanner for die to wafer bonding with sub-micron bonding pad pitch

Digital Scanner (DS), a DUV optical maskless exposure tool, is being developed which has a fine resolution of 130 nm or smaller of L/S half-pitch and patterning flexibility that each chip design can be customized on wafer. In this paper, application of DS for Die to Wafer (D2W) bonding is studied to achieve fine pitch of bonding pads. DS exposure on carrier wafer before bonding can move the pads’ position to the ideal position by changing exposure pattern adjusted for each die placement error. We estimate the minimum bonding pad pitch at die placement accuracy of 200 nm is about 2 μm without DS while it can be down to 0.85 μm with DS248, increasing interconnect density by 5.8 times. Conceptual exposure experiment of placement compensation was performed assuming 5 × 5 dies that each die includes 8333 × 8333 pads with 1.2 μm pitch. The exposure experiment shows DS capability of improvement of pad placement accuracy of 50 nm.