Smart Wire Bonding Processes for Smart Factories

More and more semiconductor manufacturers are adopting “smart” technology to improve throughput, yield and factory efficiency. In this paper, we examine how smart technology addresses two big challenges of wire bonding including fine pitch Cu first bond process and multi-tier looping. Fine pitch Cu first bond process has smaller process window and is harder to optimize than the traditional Au wire process. Through extensive research and development, a smart response based process was developed to provide wider process windows and easier adjustments. The main input to this process is desired ball diameter. Based on the desired ball diameter and other device information, optimal bonding parameters are calculated. This new smart 1st bond process is compared to traditional process to demonstrate fine pitch Cu wire bonding capability. In addition to the response based process with automatic parameter calculation, real time control is added for process monitoring and closed loop control. A new feature called Deformation Control is developed to control ball deformation using real time bonder signal feedback. Test results show that the ball size range and shear Cpk is significantly improved using this feature.The second area where major improvements have been made using smart wire bonding technology is multi-tier looping. For multi-tier devices, multiple tiers of loops with different loop heights and wire lengths need to be optimized to ensure high yield wire bonding production. A 1000 +I /O multi-tier package often requires more than 100 looping parameter groups. This results in months of looping development before a new device can be run in production. A new smart looping process was developed to address these challenges. The new looping process contains a 3D Loop Design software (3D AutoOLP) which is an offline loop design tool, and a wire loop model (ProCu Loop) that automatically calculates the looping motions to produce desired loop shapes. Four different real life applications were designed and tested with the new looping process and compared to traditional method. The average optimization time is reduced from 6 weeks to 1 week for these packages and there is a more than 50% reduction of the number of looping parameter groups. In addition, real time loop height monitor is developed to monitor loop height during production.