Determination of Metallic Impurities in a Silicon Wafer by Local Etching and Electrothermal Atomic Absorption Spectrometry

An etching technique for the determination of the metallic impurities distribution in silicon wafers has been developed. An area of 10 mm∅ and 10 μm depth was etched by 100 μL of an etching solution with a HF and HNO₃ mixture. The acid matrix was evaporated on the wafer surface by IR lamp illumination and vacuum exhaust. Metallic impurities remaining on the wafer surface were redissolved into the collection solution, which was measured by electrothermal atomic absorption spectrometry (ET-AAS). The recovery invested by local etching/ET-AAS was within 95–112% for Fe, Cu and Ni. The detection limit (3σ) for Fe, Cu and Ni in silicon was 1 × 10¹³ atoms/cm³. To confirm the applicability, local etching was applied to evaluate the effects of metallic impurities in a gettering study and the electronic properties of semiconductor devices. It was found that local etching is a useful sample preparation technique for the analysis of metallic impurities in a specific area on a silicon wafer.

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