Michael John Spaulding

Simple, Calibrated Analysis and Mapping of SiC Wafer Defects by Birefringence Imaging

This paper presents a method to obtain repeatable SiC wafer defect maps from a birefringence imaging system with a built-in calibration/reference scale. Digital processing of the image is performed using tabletop optical scanner and commercial image processing software. From the scanned image, a quantitation strategy is applied to normalize the light intensity (and indirectly the degree of optical polarization rotation) in order to scale the magnitude of the defect. The defects have then been binned by intensity and using a threshold approach, the defects known to deteriorate device parameters can be isolated and mapped. Examples of the analysis provided will include PVT growth, watering and develop wafer/epi/device correlations.

Comparison of Chlorine Based In Situ Etching of 4H SiC Substrates

Gas phase etching of 4H SiC n+ substrates was performed utilizing chlorine containing etch chemistries in a hot wall CVD system. Carbon and silicon vapor were added to explore selective etching reactions on the wafer surface. The impact of the etch on the bare wafer surface as a function of temperature and etch chemistry is investigated. Selection of the etch chemistry and temperature are critical to ensure a smooth etched surface on which to begin epitaxial deposition. Etching also influences defect propagation from the substrate into the epitaxial layer. The results show etch chemistry reactions will influence the conversion of micropipes in the epi buffer layer.