THE GETTERING OF TRANSITION-METALS BY OXYGEN-RELATED DEFECTS IN SILICON

A study has been made of the gettering efficiency of a variety of transition metals (Ni, Cu, Co, Fe, and Pd) by a range of oxygen-related defect distributions generated in Czochralski-grown silicon wafers of various initial oxygen concentrations at two stages of a simulated CMOS process. An extension and variation of the palladium getter test was used to monitor gettering efficiencies. Cu and Ni were found to be the easiest to getter with Co and Pd progressively more difficult. Co was found to interact with the other metals and affect their ability to be gettered. A gettering threshold (for the amount of precipitated oxygen) was observed which varies from metal to metal but is in all cases very low and very steep. Complete gettering of all metals tested was observed in a wafer with an initial (Oi) of 6.45 × 1017 cm−3 after a portion of the CMOS simulation was complete. The amount of oxygen precipitated under these conditions is well below the level at which oxygen precipitates are visible by etching techniques or x-ray topography and not reliably measurable by FTIR. No indication was found that bulk stacking faults are necessary for effective gettering. Some indication of a decrease in gettering efficiency with increasing precipitation or processing time was found. X-ray topography and further etching experiments were performed to help shed light on the mechanisms of gettering in the variety of cases investigated. © 1990, The Electrochemical Society, Inc. All rights reserved.