Experimental Investigations On Ultrathin Slit Dicing Of Silicon Wafers

The thickness of dicing blade turns thinner and thinner with the development of integrated circuit (IC). Diamond blades with hubs are widely used in the fabrication of ICs. Diamond grits are electroplated within the metal bond using complicated processes to fabricate the diamond blades. The diamond blades have ultrathin thickness and good stability. However, the ultrathin diamond blades used domestically are mainly imported overseas, which is cost-ineffective for the domestic production of IC industries. In this study, three kinds of ultrathin diamond blades were developed to overcome the dependence for overseas products. Dicing experiments were conducted to verify the validity of developed three kinds of ultrathin diamond blades. Optimal dicing parameters were obtained after experiments.The width and chipping size induced by developed diamond blades were affected by the mesh size and concentration of diamond grits, dicing mode, characteristics of crystalline planes, as well as dicing processes consisting of depth of cut, wheel and table speeds. High-speed dicing was carried out on4-in.(100) silicon (Si) wafers using an ultra-precision DISCO-DHD641cutter to confirm the effects of dicing processes on the dicing results. Optimal dicing width was achieved using higher wheel speed and lower depth of cut and table speed. The stiffness of blade and maximum unreformed chip thickness both have influence on the width of slits. The chipping width is consistent with the variation of maximum unreformed chip thickness calculated by the overall dicing parameters. The minimum widths of slit and chipping of29.4and2μm, respectively, are achieved, corresponding to a relative width of slit of1.18. The optimal fabrication conditions for ultrathin diamond blades are as follows:the size of diamond grits varies from2to6μm, the length ranges from650to780μm, thickness of blade changes from20to25μm, and the type of bond is hard.The topography of diamond grits on the three developed blades were characterized prior to and after dicing. The wear mechanism of diamond grits during dicing consists of pull out, cracking, and worn flatness. The minimum width of chipping was achieved using the diamond blade with minimum size of grits distributing uniformly within the blade. Cobalt element was observed, which is identified by X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The introduction of cobalt increased the stiffness of diamond blades.