Improvement of Laser Groove Bottom Width in Complementary Metal-Oxide-Semiconductor (CMOS) Low-k Wafer Technology

This paper describes the development work of controlling the U-shape profiler during laser grooving in Complementary Metal-Oxide-Semiconductor (CMOS) low-k wafer technology. The effects of laser parameter, i.e. laser power frequency and feed speed were investigated. The sample dies were thoroughly examined and characterized, which included assessing the grooving quality, shape, and profile. The design of experiment (DOE) methodology was applied to understand parameter correlations and to statistically predict the optimum parameters. Subsequently, the parameters were fine-tuned to ensure that they fell within the acceptable limits for the production environment. In this study, various inspection tools and methods were utilized, including a 3D profiler high-power microscope, scanning electron microscope (SEM), and focused ion beam (FIB). Differential interference contrast (DIC) light was also employed to detect inter metal dielectric (IMD) layer cracks, which was crucial in distinguishing failures associated with the laser process or combination effects due to additional stress during mechanical sawing. This study provides significant benefits to the field of laser processing and CMOS low-k technology by improving product quality, establishing a robust process for the production line, enhancing knowledge and expertise in the field.