Jan 2, 2020

Germanium Back‐Side Gettering of Gold in Silicon

A novel back‐side gettering technique was developed. The technique consists of applying germanium to the back side of a silicon wafer and then annealing in either a nitrogen or an oxygen ambient. The concentration profiles for gold before and after anneals were established to better than the part per million (ppm) level by using atomic absorption spectroscopy. The minority carrier lifetime of control and gettered samples was determined. The technique was found to be effective for the removal of gold from the active device region of a silicon wafer. The difference in activity coefficients for gold in silicon and gold in germanium is the theoretical basis for the gettering of gold from the silicon to the germanium on the back side. In addition to gettering gold from the front surface of the wafer, comparison was made of a germanium‐gettered wafer with a control wafer, showing that the application of germanium to the back side of a silicon wafer, followed by thermal annealing, is effective in preventing the formation of oxidation‐induced stacking faults (OISF) during high temperature oxidation.

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