Enhanced strain relaxation in Si/Ge<i>x</i>Si1−<i>x</i>/Si heterostructures via point-defect concentrations introduced by ion implantation

Hull, R.; Bean, J. C.; Bonar, J. M.; Higashi, G. S.; Short, K. T.; Temkin, H.; White, Alice E.

doi:10.1063/1.102904

Cited by 87 publications

(35 citation statements)

References 19 publications

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“…Enhanced strain relaxation due to the introduction of point defects by Ge + ion implantation at 400°C or the implantation of dopants ͑B,As͒ was reported, however, without revealing the resulting microstructure. 7,8 The use of ion implantation for strain relaxation has several advantages: It is easy to use, is highly reproducible, is area-selective by the use of masks, and is fully compatible with existing Si technology. Therefore, there is interest in the development of an ion implantation method, which allows efficient strain relaxation after annealing at moderate temperatures while maintaining a high sample quality.…”

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confidence: 99%

Strain relaxation of pseudomorphic Si1−xGex∕Si(100) heterostructures after Si+ ion implantation

Holländer

Buca

Mörschbächer

et al. 2004

Journal of Applied Physics

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The strain relaxation of pseudomorphic Si 1−x Ge x layers ͑x = 0.21, . . . , 0.33͒ was investigated after low-dose Si + ion implantation and annealing. The layers were grown by molecular-beam epitaxy or chemical vapor deposition on Si͑100͒ or silicon-on-insulator. Strain relaxation of up to 75% of the initial strain was observed at temperatures as low as 850°C after implantation of Si ions with doses below 2 ϫ 10 14 cm −2 . We suggest that the Si implantation generates primarily dislocation loops in the SiGe layer and in the underlying Si which convert to strain relaxing misfit segments. Strained Si films grown on strain-relaxed SiGe buffer layers will soon be applied for advanced microelectronic devices since strained Si exhibits significantly enhanced carrier mobilities and therefore, yields to transistors with higher transconductance and drive currents.1,2 However, a key problem is the fabrication of thin strain relaxed SiGe buffer layers, which serve as virtual substrates for the growth of strained silicon. The standard approach is the growth of several micrometer thick, compositionally graded buffer layers. 3Recently, it was shown that He + ion implantation and subsequent thermal annealing can successfully be employed to relax the strain of thin pseudomorphic SiGe layer grown on Si͑100͒.4-6 The required He + implantation doses to achieve substantial strain relaxation during the subsequent annealing are in the range of 5 ϫ 10 15 cm −2 to 2 ϫ 10 16 cm −2 . These relatively high doses lead to long implantation times and limit throughput of wafers in production and form voids in the underlying silicon. Previously it was shown that strain relaxation can also be achieved by H + implantation and annealing.4 However, this method was only successful forSiGe layers with Ge concentrations below 25 at. %. Enhanced strain relaxation due to the introduction of point defects by Ge + ion implantation at 400°C or the implantation of dopants ͑B,As͒ was reported, however, without revealing the resulting microstructure. 7,8 The use of ion implantation for strain relaxation has several advantages: It is easy to use, is highly reproducible, is area-selective by the use of masks, and is fully compatible with existing Si technology. Therefore, there is interest in the development of an ion implantation method, which allows efficient strain relaxation after annealing at moderate temperatures while maintaining a high sample quality. It is important to use ions, which require only a low dose and avoid contamination or unintended doping by the implanted ions.In this work, we have investigated the strain relaxation of pseudomorphic Si 1−x Ge x layers induced by low dose Si + ion implantation at room temperature and subsequent annealing. We also provide a preliminary explanation for the mechanism of strain relaxation. The layers were grown by chemical vapor deposition (CVD) and solid-source molecular-beam-epitaxy (MBE) on Si͑100͒ and on siliconon-insulator (SOI) wafers. The samples were characterized using transmission electron microsco...

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confidence: 99%

Strain relaxation of pseudomorphic Si1−xGex∕Si(100) heterostructures after Si+ ion implantation

Holländer

Buca

Mörschbächer

et al. 2004

Journal of Applied Physics

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“…Kasper et al believe that the implementation of a complementary Si/GeSi modulation-doped field-effect transistor will depend on the successful application of ion implantation and annealing techniques [3]. Even though Hull et al [4] reported that implantation-induced point defects can substantially enhance the strain relaxation of metastable Si/GeSi heterostructures during the process of dopant-activation anneal, the n-type doping of strained GeSi layers by phosphorous implantation has been successfully performed and demonstrated by Lie et al without losing strain in the GeSi layer when the dose of implantation is low, i.e. no amorphized layer is formed [5].…”

Section: Introductionmentioning

confidence: 99%

Strain conservation in implantation-doped GeSi layers on Si(100)

Nicolet

1997

Metals and Materials

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Metastable pseudomorphic GeSi layers grown by chemical vapor deposition or by molecular beam epitaxy on Si(100) substrates were implanted at room temperature. The implantations were performed with 90 keV As ions to a dose of 1 • 10 ~3 cm -2 for Ge.0~Si~.,~2 layers and 70 keV BF2 ~ ions to a dose of 3• 10 ~ cm 2 for Ge..,~Sio~4 layers. The samples were subsequently annealed for short 10-40 s durations in a lamp furnace with a nitrogen ambient, or for a long 30 min period in a vacuum tube furnace. For Geo0,Si~,,~2 samples annealed for a 30 min-long duration at 700~ the dopant activation can only reach 50% without introducing significant strain relaxation, whereas samples annealed for short 40 s periods (at 850"C) can achieve more than 90% activation without a loss of strain. For Ge0.,Sio,4 samples annealed for either 40 s or 30 min at 800~ full electrical activation of the boron is exhibited in the GeSi epilayer without losing their strain. However, when annealed at 900~ the strain in both implanted and unimplanted layers is partly relaxed after 30 rain, whereas it is not visibly relaxed after 40 s.

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“…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%

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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Enhanced strain relaxation in Si/GexSi1−x/Si heterostructures via point-defect concentrations introduced by ion implantation

Cited by 87 publications

References 19 publications

Strain relaxation of pseudomorphic Si1−xGex∕Si(100) heterostructures after Si+ ion implantation

Strain relaxation of pseudomorphic Si1−xGex∕Si(100) heterostructures after Si+ ion implantation

Strain conservation in implantation-doped GeSi layers on Si(100)

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

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