Analysis of the Leakage Current Origin in Thin Strain Relaxed Buffer Substrates

This paper describes the impact of various defect types on the junction leakage in highly doped drain junctions, fabricated on strained silicon/relaxed silicon–germanium virtual substrates. The substrates were fabricated with a thin buffer-layer scheme, using a carbon-doped layer to induce a high relaxation degree of the virtual substrate. Threading dislocations, carbon-induced defects, and residual implantation damage each have a distinct effect on the junction leakage, generation lifetime, and high-temperature behavior of the diodes. It is shown that threading dislocations degrade the junction quality at room temperature. However, the high-temperature behavior of these junctions is diffusion-dominated. When present in the depletion region, carbon-induced defects cause a large generation current inside the diodes, a behavior that is dominant in the full temperature range investigated . Implantation damage influences the leakage in silicon junctions but is of minor importance in junctions with a large amount of threading dislocations or carbon-induced defects. While increasing the thermal anneal budget has a large relative influence on the silicon junctions, this effect is less pronounced for the junctions, showing that defects associated with threading dislocations or carbon-induced defects are not as easily removed as damage resulting from the n-well implantation.