Experimental Study On Single Diamond Grain Grinding Of Silicon Wafers

Single crystal silicon wafers are the dominate substrates used for semiconductor manufacturing. There are increasingly stringent working accuracy and surface quality requirements of silicon wafers in order to meet the IC manufacturing demands. Ductile mode grinding is a new technology in recent years, and it is considered as the most promising technique of flattening and thinning silicon wafers. However, it is comparatively difficult to achieve ductile mode grinding, because its precondition is that the grain depth of cut should below the critical depth of cut. At present, the character and condition of brittle to ductile transition of single crystal silicon, the critical depth of cut, material removal mechanism and surface formation mechanism of ductile mode grinding of silicon wafers, as well as the boundary conditions allowing a ductile grinding process are only insufficiently clarified, which limit the application of grinding in silicon wafers machining.As a simplified mode, single diamond grain grinding has already been one of the most important methods in studying ductile mode grinding. Aim at the disadvantages of single diamond grain grinding experiments in existence, a scratching experiment at a low speed is designed combining the condition of lab, and a novel single diamond grain grinding method is developed. Through analyzing and comparing the relative merits and feasibility of various wafer surface layer damage measurement methods, the decision methods for the realization of grinding wafers in ductile mode are determined with different damage forms and abundant experiments. The surface topography and defects of silicon wafers are measured by SEM. To study the subsurface cracks of silicon wafers caused by grinding accurately and to estimate if it achieves ductile mode grinding, an improved angle polishing method is presented. In order to identify the grinding mode, it is capable of measuring whether there are subsurface cracks of silicon wafers by using a 3D surface profiler based on scanning white light interferometry. The microstructure of surface layer damages of silicon wafers after grinding is measured by TEM and Raman microspectroscopy. Bases on the single diamond grain grinding method, the brittle to ductile transition of single crystal silicon is studied. The shape of the grain cutting edges and crystal orientation on the brittle to ductile transition are analyzed. The critical depth of cut of single crystal silicon is investigated and the critical depth of cut with both blunt and sharp diamond grains is obtained. With the rotation grinding method, the critical depth of cut with diamond grains in the grinding process with 3000# mesh diamond wheel is obtained as well.