publication . Thesis

Relaxation of strained silicon on virtual substrates

Parsons, Jonathan;
Open Access English
  • Country: United Kingdom
Abstract
The relaxation of variable thickness strained silicon layers on 20% and 50% germanium composition virtual substrates have been quantified using two independent methods. High resolution X-ray diffraction offers a means to measure relaxation directly, and a defect etching technique has been developed from which relaxation can be determined by the measurement of dislocation densities. Comparisons between the relaxation of tensile strained silicon in this work and compressively strained Si1−xGex in other works, suggest that strained silicon is unusually stable to relaxation. Observation of dislocation structures with defect etching and transmission electron microsco...
Subjects
free text keywords: TK, QC
Related Organizations
50 references, page 1 of 4

2.14 Cross-sectional diagram showing the forces acting on a nucleated halfloop dislocation, as used in the People and Bean critical thickness model. Adapted from People and Bean [1985]. . . . . . . . . . . . . . . . . . .

2.15 Graph showing the critical thickness regimes of Matthews and Blakelee (equation 2.13), and People and Bean (equation 2.15). . . . . . . . . .

2.16 Cross sectional view showing a threading dislocation (a) gliding towards an orthogonal misfit dislocation, marked by the cross with surrounding strain field in grey, (b) being forced to glide in a smaller channel region, h∗. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.17 Graph showing the Freund dislocation pinning regime (equation 2.16), together with the critical thickness of Matthews and Blakeslee (equation 2.13). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.18 Schematic representation of the modified Frank-Read process showning (a) a splitting reaction, (b) the Frank-Read mechanism closing a halfloop, (c) expanding half-loop to reach the surface, and (d) a pile-up formed by the expansion of dislocation half-loops along two glide-planes. Adapted from LeGoues et al. [1992] . . . . . . . . . . . . . . . . . . .

2.19 Schematic representation of a step graded virtual substrate, with misfit interfaces is arrowed. . . . . . . . . . . . . . . . . . . . . . . . . . . .

2.22 Simplified hard sphere representations of a face-centred cubic lattice showing (a) stacking of the {111} planes, and (b) a top-down view of the stacking sequence. Taken from Cottrell [1964]. . . . . . . . . . .

2.23 Simplified hard sphere representation of a cross section through a stacking fault (in grey) caused by one partial dislocation at point P, running into the plane of the page. Adapted from Kosevich [1979]. . . . . . . .

2.24 Schematic diagram of the formation of an extended stacking fault in a tensile strained layer. Adapted from Mar´ee et al. [1987]. . . . . . . . .

2.25 Cross-sectional view of a microtwin formed by the successive nucleation of 90◦ partial dislocations on adjacent glide-planes, which forms a step on the surface along its length. Adapted from Wegscheider and Cerva [1993]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5.25 Image of the defect etched surface of a 20.0nm strained silicon layer (LG20-7), showing dislocations pinned by stacking faults, three of which are indicated. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

5.26 Fraction of pinned dislocations which are pinned by orthogonal stacking faults for (a) linearly graded and (b) terrace graded samples. Lines are for guidance only. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108 6.13 Graphs to show the relaxation of strained silicon on 50% virtual substrates which are (a) linearly graded and (b) terrace graded, as measured by HRXRD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

6.14 XTEM image of a 8.2nm strained silicon layer (LG50-2), showing the presence of a stacking fault. . . . . . . . . . . . . . . . . . . . . . . . . 131

6.15 XTEM image of a 33.2nm strained silicon layer (LG50-6), showing the presence of a microtwin. . . . . . . . . . . . . . . . . . . . . . . . . . . 132 S. Amelinckx. Dislocations in Particular Structures. In F. R. N. Nabarro, editor, Dislocations in Solids, volume 2. North Holland Publishing, 1979.

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