SiGe growth on patterned Si(001) substrates: Surface evolution and evidence of modified island coarsening

Zhang, Jianjun; Stoffel, M.; Rastelli, Armando; Schmidt, Oliver G.; Jovanović, Vladimir; Nanver, L.K.; Bauer, G.

doi:10.1063/1.2802555

Cited by 69 publications

(89 citation statements)

References 22 publications

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“…This step enables not only further processing steps for which each island has to be addressed but leads also to a narrow distribution of island properties such as shape, size, and composition. 9,11 Due to the larger lattice constant of Ge ͑about 4.2% larger than that of Si for pure Ge͒, dome or barn-shaped islands form in the pits during growth on silicon substrate, depending on the number of monolayers deposited. 9 Domes as well as barns are multifaceted islands; domes with an aspect ratio of 0.2 contain ͕001͖, ͕105͖, ͕113͖, and ͕15 3 23͖ facets, whereas the steeper barns ͑aspect ratio of 0.32͒ additionally show ͕111͖, ͕20 4 23͖, and ͕23 4 20͖ facets.…”

Section: Introductionmentioning

confidence: 99%

X-ray investigation of buried SiGe islands for devices with strain-enhanced mobility

Hrauda¹,

Zhang²,

Stangl³

et al. 2009

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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In this work self-organized SiGe islands are used as stressors for Si capping layers, which later act as carrier channels in field effect transistors. To be able to address individual islands and to obtain a sufficiently narrow distribution of their properties, the SiGe islands are grown by molecular beam epitaxy on prepatterned Si substrates, with a regular two-dimensional array of pits. This combination of lithographic patterning and self-assembled island growth combines the advantages of both approaches and leads to very homogeneous island shape, size, and chemical composition. For processing, 4in. wafers are used, and fields with pit periods between 600 and 1000nm are defined by optical lithography. After growth of a Si buffer layer several monolayers of Ge are deposited, leading to island formation (dome or barn shaped) in the pits. Subsequent Si capping is performed at a low substrate temperature of 300°C to avoid intermixing and shape changes of the buried islands. The Ge distribution in the buried islands and the strain distribution in the islands and the surrounding Si matrix are assessed by x-ray diffraction experiments, combined with three-dimensional model simulations using finite elements. Tensile strain values in the Si cap up to 8×10−3 can be achieved using this approach, which is difficult to achieve using other methods without introduction of dislocations.

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Section: Introductionmentioning

confidence: 99%

X-ray investigation of buried SiGe islands for devices with strain-enhanced mobility

Hrauda¹,

Zhang²,

Stangl³

et al. 2009

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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“…Consequently, some years ago a templated selfassembly of semiconductor nanostructures was introduced, [30][31][32][33][34][35][36][37] combining growth on patterned substrates for the definition of an initial two-dimensionally periodic island layer with subsequent vertical ordering due to the strain fields of the buried quantum dots in a multidot layer system. 38,39 So far, in particular, three-dimensionally ordered structures of InAs/GaAs ͑Ref. 40͒ and SiGe/Si ͑Refs.…”

Section: Introductionmentioning

confidence: 99%

X-ray diffraction investigation of a three-dimensional Si/SiGe quantum dot crystal

et al. 2009

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High-resolution x-ray diffraction was employed to study the structural properties of a three-dimensional periodic arrangement of SiGe quantum dots in a Si matrix. Using extreme ultraviolet lithography at a synchrotron source a two-dimensional array of pits ͑period 90ϫ 100 nm 2 ͒ was defined and transferred into a ͑001͒ Si wafer by reactive ion etching. By molecular-beam epitaxy SiGe islands of about 30 nm diameter and 3 nm height were grown into the pits. Subsequent deposition of Si spacer layers of 10 nm thickness and SiGe island layers results in a three-dimensionally periodic arrangement of quantum dots, mediated by the strain fields of the buried dots. Their so far unmatched structural perfection is assessed by coplanar x-ray diffractometry using synchrotron radiation. Reciprocal-space maps around the ͑004͒ and ͑224͒ reciprocal-lattice maps were recorded and analyzed to get quantitative information on the disorder of the dot positions and to obtain the mean Ge content of the dots. In addition, information on the strain fields was deduced from the analysis of the diffraction data. Together with atomic force microscopy data on the island shape and size distribution, a complete structural characterization is achieved.

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“…Due to the statistical nature of the growth process if deposited on planar Si substrates, such islands usually exhibit a rather broad size distribution. By growing Ge islands on two-dimensionally pit-patterned Si substrates, the island size distribution is much narrower [2][3][4][5]. Furthermore such islands can be addressed individually if necessary, e.g.…”

Section: Introductionmentioning

confidence: 99%

“…• C. For more details on the MBE growth see [5]. Whereas the deposition of 5 to 6 ML Ge results in dome-shaped islands, depositing more than 8 ML results in barns.…”

Section: Introductionmentioning

confidence: 99%

X-ray diffraction study of the composition and strain fields in buried SiGe islands

Hrauda

Zhang

Stoffel

et al. 2009

Eur. Phys. J. Spec. Top.

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Abstract.We report on studies of strain and composition of two-dimensionally ordered SiGe islands grown by molecular beam epitaxy using high resolution x-ray diffraction. To ensure a small size distribution of the islands, pit-patterned 4 (001) Si wafers were used as substrates. The Si wafers were patterned by optical lithography and reactive ion etching. The pits for island growth are ordered in regular 2D arrays with periods ranging from 500 to 1000 nm along two orthogonal 110 directions. After the growth of a Si buffer layer, 5 to 9 monolayers of Ge are deposited, leading to the formation of islands with either dome-or barn shape, depending on the number of monolayers deposited. The Si capping of the islands is performed at low temperatures (300• C) to avoid intermixing and thus strain relaxation. Information on the surface morphology obtained by atomic force microscopy (AFM) was used to set up models for three-dimensional Finite Element Method (FEM) simulations of the islands including the patterned Si substrate. In the model, special attention was given to the non uniform distribution of the Ge content within the islands. The FEM results served as an input for calculating the diffracted x-ray intensities using kinematical scattering theory. Reciprocal space maps around the vicinity of symmetric (004) and asymmetric (113) and (224) Bragg peaks were recorded in coplanar geometry. Simulating different germanium gradients leads to altered scattered intensity distribution and consequently information on this quantity is obtained for both dome-and barn-shaped islands as well as on the strain fields.

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SiGe growth on patterned Si(001) substrates: Surface evolution and evidence of modified island coarsening

Cited by 69 publications

References 22 publications

X-ray investigation of buried SiGe islands for devices with strain-enhanced mobility

X-ray investigation of buried SiGe islands for devices with strain-enhanced mobility

X-ray diffraction investigation of a three-dimensional Si/SiGe quantum dot crystal

X-ray diffraction study of the composition and strain fields in buried SiGe islands

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