Investigation of 3-pass laser grooving process development for low-k devices

The low-k dielectric materials in wafer fabrication are widely used. The current advanced mechanical dicing is not able to meet the requirement of low-k technology, since the low-k materials are harder and brittle. Laser dicing is developed for low-k wafer dicing. There are various laser dicing techniques in the market. Depending on the wafer thickness, laser dicing can either be a though cut or a partial cut process, which is commonly known as laser grooving. In this paper, the study work mainly focus on laser grooving and mechanical dicing process for Low-k wafer. The laser grooving used in this study is a 3-pass laser beam, and the laser grooving process setup is discussed. High power optical microscope, SEM, FIB and IR were the inspection tools used in this study. After laser grooving, the characterize of laser grooving, including the die edge quality, grooving geometry, die strength, mechanical dicing and reliability results are all investigated. The die was packaged into a 19×19mm 529IO MAPBGA package. Post assembly, CSAM and electrical test were performed on the assembled parts at T0, post MSL3/260degree C, post 264h UHST (110°C/85%RH), and post TC500cycles (-55°C to 125°C). With optimized parameter, a good dicing quality was get, without metal burr, metal remaining, micro cracks on side wall etc. The packaged sample had passed all stress. No laser grooving and mechanical dicing defect related fail. It is concluded that the 3-pass laser grooving is a good solution for low-k wafer dicing.