The elimination of surface cross-hatch from relaxed, limited-area Si1−xGex buffer layers

Abstract

The influence of lateral dimensions on the relaxation and surface topography of linearly graded Si1−xGex buffer layers has been investigated. A dramatic change in the relaxation mechanism has been observed for depositions on Si mesa pillars of lateral dimensions 10 μm and below. Misfit dislocations are able to extend unhindered and terminate at the edges of the growth zone, yielding a surface free of cross-hatch. For lateral dimensions in excess of 10 μm orthogonal misfit interactions occur and relaxation is dominated by the modified Frank–Read (MFR) mechanism. The stress fields associated with the MFR dislocation pile-ups result in a pronounced cross-hatch topography.

Strain-balanced Si/SiGe short period superlattices: Disruption of the surface crosshatch

“…In conclusion, we have demonstrated that inserting strain-balanced Si/SiGe superlattices ͑with the SiGe layers being elastically relaxed͒ inside SiGe virtual substrates provides an alternate to, for example, limited area epitaxy 19 or vicinal substrates 20 for reducing the surface roughness, by disrupting the surface crosshatch. Moreover, some filtering of the threading dislocations by those strain-balanced superlattices has also been demonstrated in transmission electron microscopy.…”

Epitaxial growth of CdTe on (211) silicon mesas formed by deep reactive ion etching

“…Growth on isolated mesas allows threading dislocations propagating through the layer to reach mesa boundaries and exit the mesa surface. Similar techniques have been applied successfully to other materials systems, including GaAs on Si, 2,3 In x Ga 1Àx As on GaAs, 4,5 Si x Ge 1Àx on Si, [5][6][7][8][9] ZnSe on GaAs, 10,11 and Hg x Cd 1Àx Te on Zn x Cd 1Àx Te. 12 For these systems, a combination of annealing to set dislocations into motion and the proximity of mesa sidewalls that act as dislocation sinks has resulted in a reduction in dislocation density at the top of the mesas.…”

SiGe pMOSFETs Fabricated on Novel SiGe Virtual Substrates Grown on 10um x 10um Pillars

“…The edges of the pillars are suitable sites for the nucleation of dislocations. This reduces the amount of cross-hatch and improves wafer surface planarity [6].…”

“…This is achieved by growing such layers on top of microscopic pillars [6][7], as shown in figure 1. The edges of the pillars are suitable sites for the nucleation of dislocations.…”

“…However, the use of such a technique is limited by the formation of cross hatch patterns on the surface of the relaxed SiGe virtual substrates, formed by the stress fields associated with the SiGe buffer layer as it adapts to the different lattice constant of the silicon substrate wafer [6].…”