Developments of blade dressing technique using SiC board for C90 low-k wafer sawing

Abstract

Blade preparation or conditioning is one of the critical factors (aside from dicing blades, process parameters, and dicing tapes) one needs to consider, in order to establish optimum sawing parameters for good dicing quality. Blade dressing is important, to dispose off the excess bonding material and to expose the diamond particles for cutting. The conventional medium use to condition/season the dicing blade is silicon wafers. However, the total completion time to prepare a blade for wafer cutting usually takes a few hours. The new method proposed in this project is the use of a dressing board, which is of a silicon carbide-based (SiC) material. The positive impacts of using SiC board for blade dressing are significant improvements in saw machine capacity time, increasing production throughputs, and cost reduction on the usages of dressing materials such as Si mirror wafer, and dicing tapes. The time needed to prepare a blade for wafer sawing become shorter with the new board dressing method, which takes less than an hour to complete. The savings observed are about 98% of total time needed from the current dressing method. This paper presents all the development works done from (1) feasibility study stage on blade dressing board selection, dressing parameters optimization and establishment. Also, (2) pre-evaluations and confirmation run activities were performed on low/small samples of low-k wafer dicing using the new board dressing method until (3) final stages for actual new dressing process which will cover product qualification, validation and (4) implementation phases for high volume production of low-k wafer sawing. The topside saw ILD peeling size, topside saw chipping size, and backside chipping size are the critical dicing responses collected for statistical data analysis and interpretation. Optical visual inspection was conducted on post-processed low-k test wafers and several scribe structures (which comprised of different levels of metal density), for a thorough quantification and categorization on the peeling mode. Worst case peeling measurements and characterizations were conducted by using optical microscope, scanning electron microscopy (SEM) and focused ion beam (FIB). Electrical test and device reliability assessments were conducted to reflect and confirm the quality of the die samples which were diced using blade dressed with SiC board compared to control/traditional blade dressing method. The optimum dicing parameters dressed with the SiC board, was finally established and implemented in high volume manufacturing for low-k products. Last but not least, a proposed fan-out activity to qualify and implement the new board dressing method on current legacy/non low-k products was also discussed, as part of the recommendation for future works.