Industrial Czochralski n‐type Silicon Wafers: Gettering Effectiveness and Possible Bulk Limiting Defects
Tien T. Le, Yalun Cai, Zhongshu Yang, Ran Chen, Daniel Macdonald, AnYao Liu
Abstract
An assessment of the bulk material quality of industrial Czochralski (Cz) grown phosphorus‐doped n‐type silicon (Si) wafers along an ingot is reported. The minority charge carrier lifetimes of the Cz‐Si wafer bulk before and after phosphorous (POCl 3 ) diffusion gettering are assessed, by applying room‐temperature superacid surface passivation to avoid any additional gettering or hydrogenation effect. A substantial increase in the bulk lifetime of all of the n‐type Cz‐Si wafers along the ingot is observed, indicating the effectiveness of a gettering step for such wafers and the presence of getterable metallic impurities in these wafers. By experimentally monitoring the lifetime changes upon a gettering anneal and simulating the gettering kinetics based on different metal diffusivities, iron is identified to be a limiting defect, at least for the wafers from the tail part of the ingot. A dissolved iron concentration of is estimated from the bulk lifetimes of the tail wafers. This lifetime kinetics approach is also a demonstration of a new method to identify iron, or other getterable metals with moderate diffusivities such as chromium, in n‐type silicon wafers.