New approach to the growth of low dislocation relaxed SiGe material

Abstract

In this growth process a new strain relief mechanism operates, whereby the SiGe epitaxial layer relaxes without the generation of threading dislocations within the SiGe layer. This is achieved by depositing SiGe on an ultrathin silicon on insulator (SOI) substrate with a superficial silicon thickness less than the SiGe layer thickness. Initially, the thin Si layer is put under tension due to an equalization of the strain between the Si and SiGe layers. Thereafter, the strain created in the thin Si layer relaxes by plastic deformation. Since the dislocations are formed and glide in the thin Si layer, no threading dislocation is ever introduced in to the upper SiGe material, which appeared dislocation free to the limit of the cross sectional transmission electron microscopy analysis. We thus have a method for producing very low dislocation, relaxes SiGe films with the additional benefit of an SOI substrate.

Experimental test for elastic compliance during growth on glass-bonded compliant substrates

“…Transmission electron microscopy observations have demonstrated a reduced dislocation density of films grown to many times their Matthews-Blakeslee 2 critical thickness h c on glass-bonded compliant substrates. [3][4][5] High-resolution x-ray diffraction ͑HRXD͒ measurements and atomic-force microscopy characterization were carried out on thick ͑3 m͒, highly mismatched ͑3%͒ In 0.45 Ga 0.55 As films grown simultaneously on conventional and the compliant substrates that are the focus of the present study. These measurements demonstrated a ϳ2ϫ reduction in the breadth of the film's strain distribution as determined by triplecrystal diffraction peak widths that decreased from 270Љ on a conventional substrate to 155Љ on the glass-bonded substrate.…”

“…There have been numerous descriptions in the literature of the effect of an ''elastically compliant substrate'' on film strain during growth. 3,4,[6][7][8][9][10][11][12][13] The strain in the film ⑀ f in terms of the film thickness h f , the template layer thickness h s , and the mismatch ⑀ 0 , between the film and substrate due to elastic compliance of the template layer is described by ⑀ f ϭ ⑀ 0 …”

“…1,[3][4][5] Compliant substrates consist of a thin ͑ϳ10 nm͒ ''template'' layer bonded to a thicker ''handle'' wafer by means of an intermediary glass layer in these studies. Transmission electron microscopy observations have demonstrated a reduced dislocation density of films grown to many times their Matthews-Blakeslee 2 critical thickness h c on glass-bonded compliant substrates.…”

InGaAs heteroepitaxy on GaAs compliant substrates: X-ray diffraction evidence of enhanced relaxation and improved structural quality

“…Two approaches to fabricating macroscopic compliant substrates have predominated. The first utilized a metal 7 or glass [8][9][10][11] media to join the template and handle. The second approach employed twist-bonded ͑TB͒ substrates, 12,13 in which the template was directly bonded to the handle with an intentional azimuthal angular misorientation .…”

“…Several studies utilizing transmission electron microscopy ͑TEM͒ have demonstrated a reduced dislocation density over sub-micron-sized areas of films when grown on glass-bonded [8][9][10] and twist-bonded 12,13 compliant substrates. There are comparatively little high-resolution x-ray diffraction ͑HRXD͒ data which measures the film relaxation behavior over macroscopic dimensions.…”