Laser grooving characterization for dicing defects reduction and its challenges

Blade sawing has been widely used in semiconductor industry and it is the most conventional process in semiconductor manufacturing to produce singulated ICs. This well established dicing technique poses challenges to process next generation of wafer when the wafer fabrication technology is fast scaling down in node size to 90-, 45-, 32-and 22-nm where low-k dielectric is used. ILD (Inter-Layer Dielectric) and metal layers peelings, cracks, chipping, and delamination are the most common dicing defects observed on low-k wafer processed by the traditional blade sawing techniques. This paper presents an experimental study to improve the dicing performance and quality on processing low-k wafer by using a combination of laser grooving process and traditional blade sawing technique. Some low-k wafers were used as test vehicles. The laser process outcomes and responses are governed by the changes of process input parameters such as laser power, repetition rate, grooving feed speed, defocus amount and street index. The effects of the process parameters on the laser kerf geometry, grooving edge quality and defects are evaluated by using optical microscopy and scanning electron microscopy (SEM). Experimental results have shown that the dicing quality produced by using a combination of laser grooving and blade sawing technique can significantly minimize the dicing defects. It is one of the potential solutions to address the quality and yield issues in low-k wafer dicing. The key challenges of laser grooving and recommended future development works are discussed.