Controlling dislocation positions in silicon germanium (SiGe) buffer layers by local oxidation

The method of controlling dislocation positions via local oxidation of 80 nm thick Si0.8Ge0.2 buffer layer on Si substrate is investigated. The strained SiGe layer is locally exposed to oxidation by patterning Si3N4 mask layer on SiGe with perpendicularly crossing stripe patterns with <110> directions. The local oxidation of patterned SiGe regions leads to increased stress to the remaining SiGe either via Ge pileup or volume expansion during oxidation. The increased stress in the SiGe region underneath the oxide increases dislocation nucleation rate. The preferential nucleation of dislocations and subsequent propagation of dislocations through non-oxidized regions results in reduced threading dislocation density to 106–7/cm2, which is lower than that of the conventional constant composition SiGe buffer layer. Further reduction of threading dislocation density is expected by optimizing the oxidation conditions and pattern size and shape for local oxidation.