Study On The Grinding Performance Of Soft Abrasive Grinding Wheel For Silicon Wafer

Integrated circuit (IC) is the basic of modern information industry and information society. As the basic of IC development and the ideal substrate material for semiconductor chip, the silicon wafer surface quality directly affects the property, the yield and the lifetime of IC device. With the increasing size of the wafer and the shrinking of the device feature size, higher surface processing quality of wafer is demanded. Not only the extremely high flatness and minimum surface roughness are required, but no damage layer and no marks on the surface are also needed. At present, the ultra-precision grinding with fixed abrasive wheel is the main processing technology for manufacturing of large size wafers. However, traditional diamond wheel grinding would inevitably bring about surface/subsurface damages which will consequently affect the process time of the subsequent chemical mechanical polishing (CMP) procedure severely. Meanwhile, the CMP processing also has problems in its low efficiency, as well as the difficulty in handling the alkalescency or acidity slurry.Aiming at the problems in grinding of single crystal silicon wafer, based on adequate analysis of wafer chemo-mechanical grinding (CMG) technology with soft abrasive grinding wheel (SAGW), the grinding performances of different oxides SAGW are studied in this paper. The main research work is listed as follows:(1) The compositions of SAGW are designed, and the fabrication technology of SAGW is researched. Three kinds of cup-type silicon wafer SAGWs with Fe₂O₃, CeO₂ and MgO as the main material are respectively developed, and Fe₂O₃ and MgO SAGWs are first developed.(2) The experiments of solid phase chemical reaction between various abrasives/ additives of wheels and single crystal silicon powder are carried out in muffle furnace. X-Ray Diffraction experiments of reaction products are conducted. Solid phase chemical reaction in CMG with developed MgO SAGW and Fe₂O₃ SAGW are verified by experiments for the first time. The mechanism of material removal on wafer surface under the multi-energy field coupling action is analyzed and the generation principle of damage-free surface is studied.(3) The contrast grinding experiments of silicon wafer with the developed three kinds of SAGWs are carried out and the grinding performances are studied. Orthogonal experiments with optimal selected MgO SAGW are carried out, and the effects of different machining parameters (including rotation speed of wafer, rotation speed and feed speed of grinding wheel) in MgO SAGW processing on surface roughness and material removal rate are analyzed. Surface roughness (Ra=0.427nm) of grinded wafer with optimal selected machining parameters is closed to that of the polished wafer. The experiment results show that the grinding performance of MgO SAGW exhibits very good stability.(4) The surface and subsurface damage of wafer CMG with SAGW are detected and analyzed using optical microscope, 3D surface profiler, atomic force microscope, angle polishing methods and transmission electron microscope. The results show that the grinded wafer surface is super-smooth and has no defects such as scratch, grinding mask or dent. The depth of the uniformly distributed amorphous layer existing in subsurface is only about 20nm. Subsurface damages such as polycrystalline layer, microcracks, dislocations or stacking faults are not observed.