Investigation of single cut process in mechanical dicing for thick metal wafer

Abstract

Wafer with thicker metal is very challenge for mechanical dicing, especially the SGPC pattern in saw street. The chipping and peeling are easily happening on the SGPC pattern. In recent years, there are many effort spent on traditional sawing to process thick metal wafer. The current advanced mechanical dicing method for wafer with thick metal and narrower saw street is step cut. But the step cut UPH is lower than single cut, and it will be cost adder for two blade dicing. In this study, single cut is investigated. Topside chipping/Peeling is key challenge. The wafer tech used in this study is LFET with 3.6um metal thickness. Blade evaluation and dicing parameter optimization is discussed in this paper. High power optical microscope, SEM, FIB were the inspection tools used to evaluate the dicing performance. Die topside chipping and die edge quality were investigated. This die was packaged into a 54LD SOIC package. Post assembly, CSAM and electrical test were performed on the assembled parts at TO, post MSL3/260degree C, post 264h UHST (llOoC/85%RH), and post TC500cycles (-65°C to 150°C). With optimized parameter, a good dicing quality was get, without metal burr, metal peeling, micro cracks on side wall etc. The packaged sample had passed all stress. No mechanical dicing defect related fail. It is concluded that the single cut mechanical dicing is a good solution for thick metal wafer dicing.