Study On The Mechanism Of Ductile Mode Grinding Of Silicon Wafers

Silicon wafers are the dominate substrates used for semiconductor manufacturing. Circuit elements are built in layers on silicon wafers by a series of processes such as oxidation, diffusion, ion implantation, deposition, etching, photolithography, CMP, metallization, and then, after electrical tests, dicing, assembly and package, IC chips are completed and may be installed directly in industry or comsumer products. The Continuous reduction of the device feature size and the transition to 300mm wafers underway lay increasingly stringent quality requirements for silicon wafers, including physical dimension, flatness, nanotopography, oxygen content, crystal defect particle and bulk resistivity. In order to manufacturing silicon wafers with high quality, low cost and high throughput, 300mm and 450mm silicon wafers preparation needs revolutionary machining technologies. Ductile mode grinding is a new technology for machining brittle and hard materials, by which, a crack-free surface could be realized. Ductile mode grinding is considered as the most promising technique for flattening and thinning silicon wafers. However, it is very difficult to achieve ductile mode grinding, because the state of the art grinding conditions can't assure that the grain depth of cut is below the critical depth of cut yet. At present, the 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 limits the application of grinding in silicon wafers machining. Therefore, it is critically important to investigate the mechanism of ductile mode grinding of silicon wafers.The brittle to ductile transition of single crystal silicon was studied by a novel single diamond grain grinding method. The shape of the grain cutting edges and crystal orientation on the brittle to ductile transition were analyzed. The critical depth of cut of single crystal silicon was investigated and the critical depth of cut for sharp and blunt diamond grains was obtained. The critical depth of cut for diamond grains in the grinding process with 3000# mesh diamond wheel was obtained as well.The surface topography of the diamond grinding wheel and the undeformed chip thickness were measured by using a 3D surface profiler based on scanning white light interferometry. The grain protrusion height, the static effective grain density, the width to depth ratio of the undeformed chip thickness and the grain cutting edge radii were analyzed. The grain depth of cut was studied and a model for grain depth of cut was proposed, which...