LOW THERMAL BUDGET IN-SITU SURFACE CLEANING FOR SELECTIVE SILICON EPITAXY

In this paper, we present a process which provides low thermal budget removal of carbon, oxygen, and chlorine from the silicon surface by an nealing the substrate in a vacuum ambient with water and oxygen partia l pressures less than 10(-9) Torr. Following the in situ clean, silico n was deposited epitaxially, and carbon, oxygen, and chlorine levels a t the epitaxy/substrate interface were quantified using secondary ion mass spectroscopy. It was demonstrated that these contaminants were re moved from the silicon surface with a 10 s anneal at temperatures as l ow as 750 degrees C. Both SiO2 patterned and bare silicon wafers were employed, and the patterns on the surface did not show any effect on t he in situ clean efficiency. The impact of chlorine as a contaminant w as 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 aft er in situ cleaning in vacuum. A defect analysis was performed using o ptical and scanning electron microscopy. A correlation was obtained be tween the defect density and the carbon levels at the epitaxy/substrat e 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 curre nt or transconductance.