Ultrafast Laser Scribe: An Improved Metal and ILD Ablation Process

Traditional laser scribe which utilizes a nanosecond laser to ablate metal and interlayer dielectric layers (ILD) has been widely adopted by the microelectronics packaging industry as the gold standard for laser scribe processing in die prep singulation. Shrinking device size and thickness are driving increased demand for high die quality or die break strength. Next generation laser scribe tools are being developed to focus on minimizing thermal laser damage by using ultrafast lasers with short pulse widths in the picosecond to femtosecond range. This paper reports a robust ultrafast laser scribe process utilizing a femtosecond ultrafast laser platform developed through ESI and Intel collaboration. This first-of-a-kind equipment and process deliver significant improvement in die break strength and demonstrate a substantial reduction in bulk silicon cracking or voiding as seen in the nanosecond laser scribe heat affected zones (HAZ). Additionally, this ultrafast laser platform offers precise control over beam placement and scribe depth with onboard monitoring capability, key components to delivering a minimally needed scribe depth without sacrificing silicon integrity and processing time. This ultimately leads to a gentle coat-free ablation process that affords a low cost of ownership compare to its peers. Detailed scribe quality characteristics, process controls and overall system manufacturability will be discussed.