Ultrathin low temperature SiGe buffer for the growth of high quality Ge epilayer on Si(100) by ultrahigh vacuum chemical vapor deposition

Abstract

The authors report a method to grow high quality strain-relaxed Ge on a combination of low-temperature Ge seed layer on low temperature ultrathin Si0.8Ge0.2 buffer with thickness of 27.3nm by ultrahigh vacuum/chemical-vapor-deposition method without the need to use chemical mechanical polish or high temperature annealing. On 8in. Si wafer, the etch-pit density was 6×106cm−2. The root-mean-square surface roughnesses of Ge epitaxy by atomic force microscopy were 1.4 and 1.2nm for bulk Si and silicon-on-insulator substrates, respectively. Micro-Raman spectroscopy shows extremely uniform distribution of residual strain in the overgrown Ge epitaxy on 8in. wafers.

The influence of low-temperature Ge seed layer on growth of high-quality Ge epilayer on Si(100) by ultrahigh vacuum chemical vapor deposition

“…[10,13,14,18]). It is suggested that it is very difficult to fully relieve the strain in the Ge seed layer when growing at LT (300-400 1C).…”

“…As that has been systemically investigated by Nakatsuru et al [13] and Loh et al [14], SiGe buffer layer is employed to provide LT Ge nucleation sites, coalesce and annihilate dislocations, and absorb partially strain energy from mismatch of Ge to Si. With the help of SiGe buffer layer, Ge films have much lower TDD values and no thermal annealing is required.…”

“…To decrease TDD from 9 Â 10 8 to 2 Â 10 7 cm À2 , 10 cycles of thermal annealing was ex situ performed [9]. Recently, Nakatsuru et al [13] and Loh et al [14] reported a modified two-step growth approach, i.e., growing an ultra thin (2-30 nm) LT SiGe buffer layer prior to the deposition of LT Ge seed layer and HT Ge layer. With the help of LT SiGe layer to absorb partially misfit strain, provide Ge nucleation sites, and coalesce dislocations, the TDD can be reduced to 6 Â 10 6 cm À2 , without any thermal annealing.…”

“…[13,14], the influence of Ge content, thickness, and growth temperature of SiGe buffer layer on the quality of epitaxial Ge films were investigated. In this work, high-quality Ge epilayer on Si utilizing modified two-step approach by ultrahigh vacuum chemical vapor deposition (UHVCVD) was achieved with a surface RMS roughness of less than 1 nm and a TDD of 5 Â 10 5 cm À2 .…”

Edge misfit dislocations in the GeSi/Si(001) pair: Conditions and specific features of high-quantity generation

“…If we have an intermediate, partly relaxed layer [18][19][20] or a low-temperature seed layer with a large number of point defects [21][22][23], which was grown on the substrate prior to growing the main film, then such a layer will act as a source of threading dislocations, which will then penetrate into the next film layer as well. As soon as the film, as it grows on the preliminarily grown sublayer, reaches the thickness h c (601), favorable conditions for induced nucleation of complementary 601 MDs arise in the system; this then will lead to the formation of edge MDs at the interface between the film and the sublayer.…”