Strain relaxation and threading dislocation density in helium-implanted and annealed Si1−xGex/Si(100) heterostructures

Cai, Jiahui; Mooney, P. M.; Christiansen, Silke; Chen, H.; Chu, J. O.; Ott, J. A.

doi:10.1063/1.1699488

Cited by 42 publications

(29 citation statements)

References 18 publications

(19 reference statements)

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“…In contrast to the (100) surface orientation, two of the {111} planes are ion implantation and annealing reported in the literature. 5,12,23,31 Yet, the absence of the relaxation for thin and low Ge content SiGe layers on (100) in contrast to the (011) system is not explained.…”

Section: Anisotropy Of Critical Condition For Layer Relaxationmentioning

confidence: 99%

“…It results in the formation of a strain relaxing network of misfit dislocations (MDs) at the SiGe/Si interface. 3,5 The validity of this analytical model proposed by Trinkaus et al 3 in 2000 was later on proven experimentally by in situ transmission electron microscopy by Hueging et al 13 and by computer simulations by Schwarz.…”

Section: Introductionmentioning

confidence: 96%

“…Extensive studies were devoted to the development of innovative methods capable to introduce and drive, in a controlled way, threading dislocations required for strain relaxation. 5,34 Special attention was dedicated to ion implantation and annealing processes. The role of the implanted ions is to create planar defects, i.e., platelets or {311} defects for He or Si ion implantation, respectively, as sources for mobile loop formation and the relaxation process is then thermally driven.…”

Section: Comparison Of Theory and Experimentsmentioning

confidence: 99%

“…1 Several methods use ion implantation as a mean to generate strain relaxation of SiGe layers. [2][3][4][5][6] As different strain types (tensile, compressive, biaxial, or uniaxial) modify in a specific way the material properties, i.e., carrier mobility, 7,8 dopant diffusion, 9 or dopant solubility, 10,11 the study of dislocation formation and control in Si(Ge) materials regained importance.…”

Section: Introductionmentioning

confidence: 99%

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Anisotropy of strain relaxation in (100) and (110) Si/SiGe heterostructures

Trinkaus

Buca

Minamisawa

et al. 2012

Journal of Applied Physics

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Plastic strain relaxation of SiGe layers of different crystal orientations is analytically analyzed and compared with experimental results. First, strain relaxation induced by ion implantation and annealing, considering dislocation loop punching and loop interactions with interfaces/surfaces is discussed. A flexible curved dislocation model is used to determine the relation of critical layer thickness with strain/stress. Specific critical conditions to be fulfilled, at both the start and end of the relaxation, are discussed by introducing a quality parameter for efficient strain relaxation, defined as the ratio of real to ideal critical thickness versus strain/stress. The anisotropy of the resolved shear stress is discussed for (001) and (011) crystal orientations in comparison with the experimentally observed anisotropy of strain relaxation for Si/SiGe heterostructures.

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Section: Anisotropy Of Critical Condition For Layer Relaxationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

Section: Comparison Of Theory and Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Anisotropy of strain relaxation in (100) and (110) Si/SiGe heterostructures

Trinkaus

Buca

Minamisawa

et al. 2012

Journal of Applied Physics

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“…Efficient relaxation of thin SiGe films with a thickness of 100-200 nm and Ge contents of up to 30% was demonstrated by ion implantation of H or He and subsequent annealing. [2][3][4][5][6][7] Its mechanism, however, is still under debate. Recently, Schwarz 8 simulated for a similar model system the dislocation dynamics during strain relaxation by assuming solely dislocation glide processes.…”

mentioning

confidence: 99%

Evolution of the defect structure in helium implanted SiGe∕Si heterostructures investigated by in situ annealing in a transmission electron microscope

et al. 2005

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The evolution of the He-implantation induced defect structure in SiGe/ Si heterostructures is observed during in situ annealing at 650 and 800°C within a transmission electron microscope. The He implantation and annealing results in the formation of He precipitates below the SiGe/ Si interface, which at first show a platelike shape and subsequently decay into spherical bubbles. The coarsening mechanism of the He bubbles is revealed as coalescence via movement of entire bubbles. The nucleation of dislocation loops at overpressurized He platelets and their propagation into the heterostructure could be observed as well. We found distinctly different velocities of the dislocations which we attribute to glide and climb processes. The in situ experiments clearly show that the He platelets act as internal dislocation sources and play a key role in the relaxation of SiGe layers. Since strained silicon is generally realized by epitaxial deposition of Si on relaxed SiGe layers, relaxed buffers in an adequate quality are required. Efficient relaxation of thin SiGe films with a thickness of 100-200 nm and Ge contents of up to 30% was demonstrated by ion implantation of H or He and subsequent annealing.2-7 Its mechanism, however, is still under debate. Recently, Schwarz 8 simulated for a similar model system the dislocation dynamics during strain relaxation by assuming solely dislocation glide processes. Here, we follow an analytical model proposed by Trinkaus et al. 9 where H / He implantation and annealing induces the formation of dislocation loops created at overpressurized He precipitates located underneath the SiGe/ Si heterointerface. These loops glide to the interface where subsequently one part unlaces up to the surface and creates two threading segments, whereas the lagging part in the interface forms a strain-relieving misfit dislocation segment. Driven by the misfit strain the two threading segments move apart and eventually annihilate with threading dislocations of opposite Burgers vector. As a consequence, efficient and "healthy" strain relaxation is observed. Measurements of the pressure within the platelike shaped He precipitates, which represent the initial stage of He precipitates, 10,11 revealed the shear stress to reach the critical value of dislocation formation. 12This indicates that He platelets may be capable to emit dislocations. In order to gain deeper insight into the relaxation mechanism of SiGe layers, we studied the evolution of the helium bubble structure as well as its interplay with nucleation and growth of dislocation loops utilizing in situ annealing investigations by transmission electron microscopy ͑TEM͒.Si 81 Ge 19 layers with a thickness of 170 nm were deposited onto Si ͑001͒ substrates by chemical vapor deposition. Helium was implanted with an energy of 37 keV at a dose of 1 ϫ 10 16 cm −2 resulting in a helium concentration profile with its maximum in a depth about double the layer thickness. These implant conditions are optimum with respect to high degree of relaxation and low th...

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