English: The subject of this image is a silicon integrated circuit wafer. At the center of the image is a light triangle. This triangle is a pyramid-shaped area of Al-Si alloy caused by high-temperature processing (450°C annealing) of the wafer after Aluminum deposition and etching. The 1-1-1 orientation of the silicon wafer enables the alloying to descend into the wafer perpendicular to the surface of the wafer. The alloyed area has a different index of refraction than than the other silicon substrate and is highlighted by the Nomarski Differential Interference Contrast microscopy (DIC). Note that the features are visible because of the aluminum had previously been etched away with acid to enable this microscopic analysis.