Development Of The Grinding Wheel For Low-damage Grinding Of Silicon Crystal

Silicon is widely used in integrated circuit (IC) manufacturing industry and photovoltaic industry. Through a series of process, silicon crystals processed to meet the requirements of the wafers; the grinding process is an important part of the silicon crystal machining process. Diamond grinding wheels and other hard-abrasives grinding wheels were widely used in ultra-precision grinding of the silicon crystals. These wheels will inevitably introduce grinding marks and scratches on the silicon crystal surface, and generate cracks in the silicon sub-surface. The damages introduced in grinding would affect the IC performance and the strength of the silicon, therefore the necessary follow-up process must to be adopted to eliminate the damages. How to eliminate the silicon surface layer cracks and grinding marks, reduce the depth of sub-surface damage introduced by grinding, ultimately, to replace the subsequent damage eliminating process, processing the surface with low-damage is the main direction of the silicon crystal grinding.A new type of silicon MCG wheel was developed on the basis of in-depth analysis of the silicon mechanical chemical grinding (MCG). This paper proposed a new MCG wheel recipe, designed its preparation process, and suggested a dressing plane with two steps. The silicon wafer chemical mechanical grinding tests was done with VG401MK11silicon ultra-precision grinding machines; optical microscopy, scanning electron microscopy, three-dimensional surface profiler, atomic force microscopy, transmission electron microscopy, flatness instrument and other instruments were used to detect the surface morphology of the silicon surface defects, surface roughness, subsurface damage and flatness. The experiments show that the new MCG wheel machined silicon wafers with diameter of150mm, can be obtained surface quality as perfect as CMP silicon. MCG silicon surface is quite smooth, with the surface roughness of0.3nm, flatness of less than1um. It is found that the silicon sub-surface layer only with a few nanometers thick amorphous layer, and without any other form damages. The material removal rate did not change with the processing time; however the spindle speed impacted it significant. Observing morphology of the residues on the silicon surface after grinding, detecting the residues, the silicon surface before and after the MCG wheel grinding by XRD, the removal mechanism of silicon chemical mechanical grinding was studied, the theoretical model of silicon low-damage grinding was improved.