Improved Furnace Contamination Test Wafers

An improved wafer structure for performing metal contamination evaluation in a furnace is proposed. The prior art (Monsanto) uses wafers from a standard (Czochralski) silicon ingot, one of which is oxidized in a known clean furnace to determine a base-line for contaminants in the ingot by counting oxygen induced stacking faults in the oxide after etching. Another wafer from the same ingot is then oxidized in the target furnace then etched and the faults are compared to the base-line to determine the relative cleanliness of the target furnace.