Investigation Of Multi Beam Laser Grooving Process And Die Strength for 55nm Code Low-k Wafer

With the drive of lower feature size on today's IC, low-k dielectric was implemented in interconnection of advanced chips due to its providing more function capacity and better performance. The low-k material is fragile and has a significantly risk of peeling, delamination and crack by traditional mechanical dicing process. Compared with mechanical dicing, laser grooving is more efficient and provide excellent cut quality for the wafer with low-k. But the thermal effect and ablation during the laser grooving process could cause the reduce of die strength. This paper demonstrate the development work on multi beam laser grooving for 55nm code low-k semiconductor device to achieve the balance of both dicing quality and improvement of die strength. A serious parameter has been studied, like the power, feed speed, and laser frequency. The laser kerf geometry, laser groove depth and the die strength has been inspected and evaluated during the experiment. This paper also analyzes the reason of the decline of die strength after laser groove. The optical microscopy, scanning electron microscopy (SEM) and focused ion beam (FIB) were inspection tools used in this study. The die was packaged into a 27×27mm MAPBGA package. Post assembly, e-test and reliability test were applied and the package sample has pass all stress. No dicing related failures were observed. It's conclude that compared with traditional mechanical dicing, multi beam laser grooving can get excellent dicing quality with acceptable die strength loss for low-k wafer.