Simple Method for Mapping Optical Defects in Insulating Silicon Carbide Wafers

We introduce a simple method for detecting and mapping optically-detectable defects in insulating silicon carbide wafers. A visible-light optical scanner can be used because insulating silicon carbide wafers are transparent to visible light. A standard page scanner is used, attached to a desktop computer. On-wafer resolution of 5.3 *mm is available (4800 lines/inch). This is adequate for characterizing defects in many silicon carbide wafers and higher-resolution scanners are becoming available. Sorting for transmission between 0.3 and 0.4 eliminates surface contamination (transmission < 0.2) and the major transmission peak near 0.78. Recent silicon carbide wafers have rather few optical defects, and the optical defect locations can be plotted within a circle representing the wafer periphery using available commercial plotting software. Scanning electron microscope and scanning optical microscope images are used to verify that defects detected optically this way correspond to voids and micropipes.