The impact of diamond particles on the susceptibility of silicon chips to flexural fracture

It was investigated in the present work how diamond or silicon particles resulting from wafer-grinding or wafer-dicing influence the susceptibility of silicon chips to flexural fracture. Silicon particles, which result from the grinding or chipping damage of silicon wafers, were found to be unimportant in determining the susceptibility of silicon chips to flexural fracture, regardless of the size of the particles. However, diamond particles resulting from the wearing-off of a diamond-embedded grinding wheel, were found to have a serious impact on chip cracking potential under a fixed flexural load of 20 N. When the diamond particles have a diameter of about 12 μm, corresponding to the maximum size of diamond particles embedded in the grinding wheel, they result in deep defects which cause preferential sites for crack initiation during three point bending. On the other hand, when the diamond particles have a diameter much smaller than 8 μm, they are unable to cause defects leading to crack initiation. Instead, such small diamond particles result in chip cracking failure only under the limited condition where they cause defect lines running parallel to the orientation of grinding marks on the back surface of chips and are subjected to maximum biaxial tension under a bending load Polishing was very effective for the minimization of interaction between diamond particles (smaller than 8μm) and grinding marks. On the other hand, in a case of large diamond particles which cause defects deeper than 6μm (corresponding to 3% of total chip thickness), polishing was not so effective. Thus, chip cracking failure under a flexural load is suppressed most effectively by the proper control of the maximum size of the diamond particles embedded in the grinding wheel.