Effect of backside scratch direction on the Si die strength

The biaxial fracture strength of back-ground Si dies was measured using the ball-on-ring (BOR) test. A quarter of a wafer was divided into groups according to the angle of back-grinding scratches from the 〈110〉 direction in order to investigate the effect of this scratch angle on the die strength. As the scratch angle became larger, higher die strength was obtained. For example, when the scratch angle was larger than 34° the die strength was -60-70% higher than that when the angle was smaller than 11°. This is because the preferred fracture surface of Si is parallel to the 〈110〉 direction. The possible die strength improvement by an appropriate modification of the conventional back-grinding process was also compared against the additional backside finishing process such as polishing and etching.