Chip-free singulation for medical application

Abstract

Singulation is one of the most damaging process steps in IC assembly because of the torque and force applied by the saw blade to abrade away silicon material on all 4 sides of the IC die. The removed material around the die creates a gap which allows the die to be freed from the wafer. If the abrasive singulation process is not controlled, the freed die may exhibit low mechanical strength due to chipping damage. This is particularly a problem because newer medical devices are designed with dimensions that are long and narrow in order to fit into small implantable or insertable products. Compared to the more square shaped IC dies, chipping is more of a problem on high aspect ratio dies because of the its susceptibility to resonance and vibration during blade dicing on the longer sides. For this paper, conventional dicing and Dice Before Grind (DBG) are compared. Mechanical test dies prepared from blank silicon wafers cut to >3.5 mm long 0.5 mm wide and 0.150 mm thick are prepared. High aspect ratios of 10:1 with various backside finishes will be compared for dicing quality and mechanical integrity. Using the proper grind wheels with the finer grit size, 100% yield for singulation resulting in higher strength devices can be obtained with good efficiency with dice before grind method.