Development of multi-wire EDM slicing method for silicon ingot
INSTRUCTIONS The diameter of silicon wafer becomes larger in order to increase the number of chips per one wafer. For such a larger diameter silicon ingot is mainly sliced by using multi-wire method, in which a long thin wire is used with slurry. In this method, several hundreds of wafers could be sliced at the same time. However there are still problems remained, such as large cracks, slurry treatment, contamination and so on. Therefore, we proposed a new slicing method of monocrystalline silicon ingot using wire electrical discharge machining (wire-EDM), and showed the possibility of wire EDM slicing for monocrystalline silicon ingot [1]. However, the efficiency of wafer slicing by the commerciallyavailable wire-EDM compared to multi-wire saw method is very low, because the number of sliced wafer was only one per one process in the conventional wire-EDM method. Therefore, a multi-wire EDM slicing equipment was newly developed with a single wire and a multi-EDM power supply unit in order to increase the efficiency of wafer slicing [2-4]. In this report, machining characteristics for mono-crystalline silicon ingot using this newly developed multiwire EDM slicing equipment was discussed. Besides, the possibility of applying this technique to silicon ingot for solar cell was also investigated.
Improving -wire electro-discharge machining operation of polished silicon wafer by conductive coating ICOMM 2014 No.72
Micro-Wire Electro-discharge machining (-WEDM) is a nonconventional machining technology which is extensively used for metal based micro fabrication process. This is a non-contact machining process where material removal is taken place by electro-thermal action. -WEDM process is difficult to be applied for semiconductor material like Silicon (Si). In this paper a new approach is proposed for machining polished Si (p-type, resistivity 1-50 -cm) wafer. In this method, initially Si workpiece is coated with a conductive material (gold for this study) and then -WEDM operation is carried out. Finally, after WEDM operation, the conductive layer is removed from the polished Si substrate without damaging the substrate. WEDM process stability was found to be improved (up to 60 times for certain machining condition) if coated Si wafer is used as compared to uncoated Si workpiece. Material removal rate was also found to be increased by a good margin (~ 100% maximum) for coated Si wafer. Overall this new method of -WEDM operation of polished Si wafer has been found to be more efficient and useful.
Tradeoffs and limitations in statistically based image reconstruction problems.
TRADEOFFS AND LIMITATIONS IN STATISTICALLY BASED IMAGE RECONSTRUCTION PROBLEMS