Method of forming a relaxed semiconductor buffer layer on a substrate with a large lattice mismatch
A method of forming a relaxed silicon-germanium layer for use as an underlying layer for a subsequent, overlying tensile strain silicon layer, has been developed. The method features initial growth of a underlying first silicon-germanium layer on a semiconductor substrate, compositionally graded to feature the largest germanium content at the interface of the first silicon-germanium layer and the semiconductor substrate, with the level of germanium decreasing as the growth of the graded first silicon-germanium layer progresses. This growth sequence allows the largest lattice mismatch and greatest level of threading dislocations to be present at the bottom of the graded silicon-germanium layer, with the magnitude of lattice mismatch and threading dislocations decreasing as the growth of the graded silicon-germanium layer progresses. In situ growth of an overlying silicon-germanium layer featuring uniform or non-graded germanium content, results in a relaxed silicon-germanium layer with a minimum of dislocations propagating from the underlying graded silicon-germanium layer. In situ growth of a silicon layer results in a tensile strain, low defect density layer to be used for MOSFET device applications.
Chartered Semiconductor Manufacturing Ltd.
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Jin Ping Dong Kyun Liang Choo
Liu Sohn Hsia