Reducing Iron in Single Crystal Silicon Grown Using CZ Process

The metal iron, that is present in graphite hot zone components used in CZ silicon process, contaminates the crystal. To eliminate and reduce contamination, graphite components were coated with two protective layers including a first protective layer of silicon carbide and a second protective layer of silicon. The effectiveness of these coatings to prevent iron contamination was tested. At test temperature of 1100{degree sign}C and 900{degree sign}C, the Fe concentrations in the monitor wafer that was exposed to graphite sample with layers of silicon and silicon carbide coating was ten times lower. Several hot zone structural components were coated using this method and were used to grow single crystal silicon. The wafers from these crystals were tested for iron concentrations using standard SPV method and are found to be much lower when compared to wafers from crystals grown using only silicon carbide coated graphite components.