Comparison of selective Ge growth in SiO2 trenches on Si(001) and on blanket Si(001) substrates: Surface roughness and doping

The authors investigate growth behavior, morphology, and doping of Ge grown selectively on silicon in submicron SiO2 trenches, in comparison with growth on blanket Si. Based on the surface morphology of Ge in trenches, it appears that lateral transport of Ge-containing species over the SiO2 surface extends on the order of similar to 100 mu m from the trench. For growth at 600 degrees C, preferential nucleation at trench edges leads to significant surface roughness. Contrary to behavior on blanket Si, reduction in growth temperature to 400 degrees C leads to increased Ge roughness in trenches. Finally, with very low temperature of 350 degrees C a very smooth surface in the trenches is achieved. Growth on blanket Si at this temperature is impractically slow, but is appreciable in the trenches; a discrepancy arising from the dominant supply of Ge-containing species migrating from the oxide. For boron and phosphorus-doped Ge inside the trenches, boron and phosphorus doping levels inside the trenches were about a half of those on blanket. (C) 2008 American Vacuum Society.