Low Thermal Budget In Situ Surface Cleaning for Selective Silicon Epitaxy

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Abstract
In this paper, we present a process which provides low thermal budget removal of carbon, oxygen, and chlorine from the silicon surface by annealing the substrate in a vacuum ambient with water and oxygen partial pressures less than 10−9 Torr. Following the in situ clean, silicon was deposited epitaxially, and carbon, oxygen, and chlorine levels at the epitaxy/substrate interface were quantified using secondary ion mass spectroscopy. It was demonstrated that these contaminants were removed from the silicon surface with a 10 s anneal at temperatures as low as 750°C. Both patterned and bare silicon wafers were employed, and the patterns on the surface did not show any effect on the in situ clean efficiency. The impact of chlorine as a contaminant was also studied, and no effect on the in situ cleaning efficiency was observed. Surface roughness was quantified by atomic force microscopy, which revealed that surface roughness on Si〈;100〉 did not increase after in situ cleaning in vacuum. A defect analysis was performed using optical and scanning electron microscopy. A correlation was obtained between the defect density and the carbon levels at the epitaxy/substrate interface. However, electrical device characterization did not show any correlation between different in situ clean temperatures and the n‐channel metal‐oxidation‐silicon field effect transistor leakage current or transconductance.

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