A new detection technique of crystalline defects by sheet resistance measurement on multicrystalline silicon wafers

Abstract

The mapping of crystalline defect density on the whole area of a 10 × 10 cm2 multicrystalline silicon (mc-Si) wafer is a long and difficult task if one uses the conventional techniques of chemical delineation followed by optical or electron microscopy. We have demonstrated the feasibility of a new procedure which proved less time consuming and well adapted to mc-Si wafer quality test automation. This new method is based on the measurement of the sheet resistance variation resulting from defective zones etched by a chemical which is sensitive to crystalline defects. Previously, with special process experimentation, we have shown that the best sensitivity to extended crystalline defects in mc-Si material is supported by ‘Secco etch’. This chemical sensitivity to crystalline defects was applied to the development of a new technique for dislocation and defect density mapping. Using an automated four-probe test bench, we have extracted the sheet resistance variation mapping of an mc-Si wafer before and after Secco etching. We have successfully correlated this mapping to the physical image of crystalline defect density and grain boundaries distribution on the whole mc-Si wafer.