Rapid Scanning Of Silicon Carbide Wafers Using Prior Scientific's Purefocus 850 Autofocus

By Simon Bush, Prior Scientific

PureFocus 850 Autofocus: Benefits for Wafer Inspection
The PureFocus 850 is highly effective for wafer inspection and has been used with particular success for analysis of defect selective etching. The PureFocus 850 has enabled STMicroelectronics, the multinational electronics and semiconductor manufacturer, to overcome a number of challenges associated with traditional autofocus systems and reduce scanning time per sample. STMicroelectronics has used the PureFocus 850 with automatic image recognition software to analyze the quality of Silicon Carbide wafers at their manufacturing facility in Sweden.

When wafer quality is analyzed through defect-selective etching, it creates etch pits on the Silicon Carbide wafer surface, and the morphology, number, and distribution of these pits indicate the type and location of potential defects within a sample. Traditional laser autofocus systems analyze signals reflected from the center of the field of view to calculate the optimal focus position. If the sample surface is not flat, however, peripheral areas of the image may still be out of focus.