Oxygen Segregation and Microscopic Inhomogeneity in Czochralski Silicon

In this paper, the origins of the microscopic impurity inhomogeneity in Czochralski (CZ) silicon are reviewed. The relevance of impurity segregation behavior and microscopic growth rate variations to the impurity microfluctuations are analyzed and discussed. The nature of the oxygen microfluctuations is studied in terms of its segregation behavior and its effects on precipitation. Spatially resolved infrared absorption and spreading resistance are used to study the oxygen microfluctuations induced by the melt thermal asymmetry, isolated by a manually controlled crystal growth. It is shown that oxygen segregates microscopically in the same manner as arsenic in silicon, that is, for oxygen. A quantitative analysis yields a value in the neighborhood of 0.3 for oxygen, which agrees well with the previous result based on a macroscopic analysis. Heat‐treatment experiments have shown that when CZ silicon exhibits microfluctuations in oxygen concentration the precipitation is not uniform; rather, the precipitation is enhanced in the high oxygen regions of the fluctuations. Such behavior can impede the formation of the denuded zone where the high oxygen regions meet the wafer surface, resulting in nonuniform denuded zone width across the wafer.

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