The use of ion implantation and annealing for the fabrication of strained silicon on thin SiGe virtual substrates

2004 ◽  
Vol 809 ◽  
Author(s):  
D. Buca ◽  
M.J. Mörschbächer ◽  
B. Holländer ◽  
M. Luysberg ◽  
R. Loo ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Rutherford Backscattering Spectrometry ◽  
Strain Relaxation ◽  
Chemical Vapor ◽  
Implantation Dose ◽  
Threading Dislocation ◽  
Misfit Dislocations ◽  
Dislocation Loops ◽  
Strained Si ◽  
Threading Dislocation Density

ABSTRACTStrain relaxed Si1−xGex layers are attractive virtual substrates for the epitaxial growth of strained Si. Tensile strained Si has attracted a lot of attention due its superior electronic properties. In this study, the strain relaxation of pseudomorphic Si1−xGex layers grown by chemical vapor deposition (CVD) on Si(100) substrates was investigated after He+ ion implantation and thermal annealing. The implantation induced defects underneath the SiGe/Si interface promote strain relaxation during annealing via preferred nucleation of dislocation loops which form misfit dislocations at the interface to the substrate. The amount of strain relaxation as well as the final threading dislocation density depend on the implantation dose and energy. Si1−xGex layers with thicknesses between 75 and 420 nm and Ge concentrations between 19 and 29 at% were investigated. The strain relaxation strongly depends on the layer thickness. Typically the structures show ≈70 % strain relaxation and threading dislocation densities in the low 106 cm−2 range. AFM investigations proved excellent surface morphology with an rms roughness of 0.6 nm. The samples were investigated by Rutherford backscattering spectrometry, ion channeling, transmission electron microscopy and atomic force microscopy.

Nanocavity Buffer Induced by Gas Ion Implantation in Silicon Substrate for Strain Relaxation of Heteroepitaxial Si1-xGex/Si Thin Layers

2007 ◽  
Vol 994 ◽  
Author(s):  
Mahfoudh Raïssi ◽  
Gabrielle Regula ◽  
Chokri Hadj Belgacem ◽  
Cyril Coudreau ◽  
Serge Nitsche ◽  
...  
Keyword(s):  
Ion Implantation ◽  
Strain Relaxation ◽  
Chemical Vapor ◽  
Sige Layer ◽  
Layer Growth ◽  
Thin Layers ◽  
Threading Dislocation ◽  
X Rays ◽  
Threading Dislocation Density ◽  
Dislocation Annihilation

AbstractTo weight the importance of a nanocavity buffer in a SiGe deposition substrate, some P type (001) FZ Si wafers are implanted (A samples) or not (B samples) at room temperature with 5×1016 He+ cm–2 at 10keV. They are annealed at 700°C for one hour to form a nanocavity layer close to the Si surface. Then, the wafers are carefully chemically cleaned in a clean room to remove both organic and metallic impurities from the surface. They are coated either by 210 nm (A) or 430 nm (B) Si1−xGex (x=0.20±0.02) alloy grown at 575°C for 0.42 hour by low pressure chemical vapor deposition (LP-CVD) with a growth rate of 8 to 17 nm.mn−1. Both kinds of samples are studied by cross section transmission electron microscopy, X-rays diffraction, Rutherford backscattering, atomic force microscopy and etch pit counts. The association of these techniques demonstrates that the thin SiGe layer which is deposited on sample A is fully relaxed and that the threading dislocation density (estimated to hardly reach 4×103cm−2) is at least one order of magnitude lower than what is obtained so far using ion implantation assistance in SiGe layer growth on Silicon. The roughness of the SiGe surface is low enough to stand a further Si epitaxy. Nevertheless, the mechanism involved responsible for the threading dislocation annihilation and/or confinement is still unclear.

Mechanism for the Reduction of Threading Dislocation Densities in Si0.82Ge0.18 Films on Silicon on Insulator Substrates

2001 ◽  
Vol 673 ◽  
Author(s):  
E.M. Rehder ◽  
T.S. Kuan ◽  
T.F. Kuech
Keyword(s):  
Dislocation Density ◽  
Chemical Vapor ◽  
Dislocation Core ◽  
Extensive Study ◽  
Silicon On Insulator ◽  
Dislocation Dynamics ◽  
Threading Dislocation ◽  
Misfit Dislocations ◽  
Threading Dislocation Density ◽  
Soi Substrates

ABSTRACTWe have made an extensive study of Si0.82Ge0.18 film relaxation on silicon on insulator (SOI) substrates having a top Si layer 40, 70, 330nm, and 10[.proportional]m thick. SiGe films were deposited with a thickness up to 1.2[.proportional]m in an ultrahigh vacuum chemical vapor deposition system at 630°C. Following growth, films were characterized by X-ray diffraction and a dislocation revealing etch. The same level of relaxation is reached for each thickness of SiGe film independent of the substrate structure. Accompanying the film relaxation is the development of a tetragonal tensile strain in the thin Si layer of the SOI substrates. This strain reached 0.22% for the 1.2[.proportional]m film on the 40nm SOI and decreases with SOI thickness. The Si thickness of the SOI substrate also effected the threading dislocation density. For 85% relaxed films the density fell from 7×106 pits/cm2 on bulk Si to 103pits/cm2 for the 40, 70, and 330nm SOI substrates. The buried amorphous layer of the SOI substrate alters the dislocation dynamics by allowing dislocation core spreading or dislocation dissociation. The reduced strain field of these dislocations reduces dislocation interactions and the pinning that results. Without the dislocation pinning, the misfit dislocations can extend longer distances yielding a greatly reduced threading dislocation density.

Thermal Mismatch Strain Relaxation Mechanisms and Hysteresis in Pb1−SnxSe-on-CaF2/Si Structures

1995 ◽  
Vol 379 ◽  
Author(s):  
H. Zogg ◽  
P. Müller ◽  
A. Fach ◽  
J. John ◽  
C. Paglino ◽  
...  
Keyword(s):  
Strain Relaxation ◽  
Structural Quality ◽  
Threading Dislocation ◽  
Misfit Dislocations ◽  
Thermal Mismatch ◽  
Mismatch Strain ◽  
Threading Dislocation Density ◽  
Deformation Hardening ◽  
Interaction Probability

ABSTRACTThe strain induced by the thermal mismatch in Pbl−xSnxSe and other IV–VI compound layers on Si(111)-substrates relaxes by glide of dislocations in the main <110> {001}-glide system. The glide planes are arranged with 3-fold symmetry and inclined to the (111)-surface. Despite a high threading dislocation density (> 107 cm−2) in these heavily lattice mismatched structures, the misfit dislocations move easily even at cryogenic temperatures and after many temperature cycles between RT and 77K. The cumulative plastic deformation after these cycles is up to 500%! Despite a pronounced deformation hardening occurs, the structural quality of the layer is only slightly adversely affected as regards additional threading dislocations created. The interaction probability between these dislocations is estimated to be about 10−5.

Nucleation of misfit and threading dislocations in GaSb/GaAs(001) heterostructure

1996 ◽  
Vol 54 ◽  
pp. 946-947
Author(s):  
W. Qian ◽  
M. Skowronski ◽  
R. Kaspi ◽  
M. De Graef
Keyword(s):  
Lattice Mismatch ◽  
Strain Relaxation ◽  
Threading Dislocation ◽  
Threading Dislocations ◽  
Misfit Dislocations ◽  
Extended Defects ◽  
Large Lattice ◽  
Threading Dislocation Density ◽  
Small Lattice ◽  
Large Lattice Mismatch

GaSb thin film grown on GaAs is a promising substrate for fabrication of electronic and optical devices such as infrared photodetectors. However, these two materials exhibit a 7.8% lattice constant mismatch which raises concerns about the amount of extended defects introduced during strain relaxation. It was found that, unlike small lattice mismatched systems such as InxGa1-xAs/GaAs or GexSi1-x/Si(100), the GaSb/GaAs interface consists of a quasi-periodic array of 90° misfit dislocations, and the threading dislocation density is low despite its large lattice mismatch. This paper reports on the initial stages of GaSb growth on GaAs(001) substrates by molecular beam epitaxy (MBE). In particular, we discuss the possible formation mechanism of misfit dislocations at the GaSb/GaAs(001) interface and the origin of threading dislocations in the GaSb epilayer.GaSb thin films with nominal thicknesses of 5 to 100 nm were grown on GaAs(001) by MBE at a growth rate of about 0.8 monolayers per second.

Reduced Pressure - Chemical Vapor Deposition of high Ge content (20% - 55%) SiGe virtual substrates

2004 ◽  
Vol 809 ◽  
Author(s):  
Y. Bogumilowicz ◽  
J.M. Hartmann ◽  
F. Laugier ◽  
G. Rolland ◽  
T. Billon ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Lattice Mismatch ◽  
Strain Relaxation ◽  
Chemical Vapor ◽  
Root Mean Square Roughness ◽  
Misfit Dislocations ◽  
Strained Si ◽  
Reduced Pressure ◽  
Pressure Chemical

ABSTRACTWe have studied the strain state, film and surface morphology of SiGe virtual substrates (Ge concentrations in-between 20% and 55%) grown by reduced pressure – chemical vapor deposition. The macroscopic degree of strain relaxation of those virtual substrates is equal to 97.2 ± 1.5%. The misfit dislocations generated to relax the lattice mismatch between Si and SiGe are mostly confined inside the graded layer. Indeed, the threading dislocations density obtained for Ge concentrations of 20% and 26% is indeed typically of the order of 7.5 ± 2.5 105 cm−2. Low surface root mean square roughness have been obtained, with values in-between 2 and 5 nm. In order to check the electronic quality of our layers, we have grown a MODFET-like heterostructure, with a buried tensile-strained Si channel 8 nm thick embedded inside SiGe 26%. We have obtained a well-behaved 2-dimensional electron gas in the Si channel, with electron sheet densities and mobilities at 1.45K of 5.4×1011 cm−2 and 212 000 cm2 V−1 s−1, respectively.

Role of Dislocation Interactions in Decreasing Mobile Threading Dislocation Density and Limiting Strain Relaxation in Si1-xGex Heteroepitaxial Films

1994 ◽  
Vol 356 ◽  
Author(s):  
Veronique T Gillard ◽  
William D Nix
Keyword(s):  
Dislocation Density ◽  
Late Stage ◽  
Strain Relaxation ◽  
Threading Dislocation ◽  
Misfit Dislocations ◽  
Si Substrates ◽  
Good Account ◽  
Dislocation Interactions ◽  
Threading Dislocation Density ◽  
Residual Strains

AbstractIn situ substrate curvature measurements obtained during isothermal annealing of Si1-xGex films grown on (001) Si substrates allow determination of the evolution of strain versus time in these films. By coupling the strain relaxation measurements with previous measurements of dislocation velocities in this system, the mobile threading dislocation density and its evolution in the course of strain relaxation can be determined. The results indicate that in the late stage of strain relaxation, the mobile threading dislocation density decreases significantly. Results obtained with samples of two different sizes show that this decrease in mobile dislocation density is not primarily associated with dislocations running out at the edges of the film but with dislocation interactions impeding their further motion. Furthermore, for films thinner than 500 nm the residual strains after annealing are significantly higher than the values predicted by the equilibrium theory of misfit dislocations. The measured residual strains are compared with predictions based on Freund’s treatment of the blocking of a moving threading segment by an orthogonal misfit dislocation in its path. We find that the blocking criterion gives a very good account of the residual strain in Si1-xGex films and that blocking of threading dislocations by other misfit dislocations appears to play an important role in the late stage of strain relaxation.

Lattice Engineering Using Lateral Oxidation of Alas: an Approach to Generate Substrates With New Lattice Constants

1998 ◽  
Vol 535 ◽  
Author(s):  
P.M. Chavarkar ◽  
L. Zhao ◽  
S. Keller ◽  
K.A. Black ◽  
E. Hu ◽  
...  
Keyword(s):  
Strain Relaxation ◽  
Local Strain ◽  
Epitaxial Layers ◽  
Threading Dislocation ◽  
Misfit Dislocations ◽  
Reactive Material ◽  
New Approach ◽  
Lattice Constants ◽  
Lateral Oxidation ◽  
Threading Dislocation Density

AbstractWe demonstrate a new approach to the growth of dislocation free lattice-mismatched materials on GaAs substrates using Al2O3 interlayers obtained by lateral oxidation of AlAs. This is achieved by generating relaxed low threading dislocation density InGaAs templates which are mechanically supported but epitaxially decoupled from the host GaAs substrate. This process uses the phenomena of relaxation of strained coherent hypercritical thickness (h > hcritical,) layer in direct contact with an oxidizing Al-containing semiconductor (i.e. AlAs or AlGaAs). 5000 Å In0.11Ga0.89As layers were then grown on the In0.2 Ga0.8As/Al2O3/GaAs template which acts as a pseudo-substrate (lattice-engineered substrate). The epitaxial layers are partially relaxed and have extremely smooth surface morphology. Further TEM micrographs of these epitaxial layers show no misfit dislocations or related localized strain fields at the In0.2Ga0.8As/Al2O3 interface. The absence of misfit dislocations or local strain contrast at the In0.2Ga0.8As/Al2O3 interface is attributed to both reactive material removal during the oxidation process and the porous nature of the oxide itself. We propose that the strain relaxation in In0.3Ga0.7As is enhanced due to the absence of misfit dislocations at the In0.2Ga0.8As/A12O3 interface.

Bandstructure Near Misfit Dislocations in Si Quantum Wells

1998 ◽  
Vol 4 (S2) ◽  
pp. 794-795
Author(s):  
P.E. Batson
Keyword(s):  
Quantum Wells ◽  
Conduction Band ◽  
Electron Mobility ◽  
Axial Strain ◽  
Strain Relaxation ◽  
Local Potential ◽  
Misfit Dislocations ◽  
High Electron ◽  
Strained Si ◽  
Growth Interface

High electron mobility structures have been built for several years now using strained silicon layers grown on SixGe(1-x) with x in the 25-40% range. In these structures, a thin layer of silicon is grown between layers of unstrained GeSi alloy. Matching of the two lattices in the plane of growth produces a bi-axial strain in the silicon, splitting the conduction band and providing light electron levels for enhanced mobility. If the silicon channel becomes too thick, strain relaxation can occur by injection of misfit dislocations at the growth interface between the silicon and GeSi alloy. The strain field of these dislocations then gives rise to a local potential variation that limits electron mobility in the strained Si channel. This study seeks to verify this mechanism by measuring the absolute conduction band shifts which track the local potential near the misfit dislocations.

Transition From Inclined to In-Plane 60° Misfit Dislocations in a Diffuse Interface

1993 ◽  
Vol 319 ◽  
Author(s):  
X. J. Ning ◽  
P. Pirouz
Keyword(s):  
Strain Relaxation ◽  
Classical Model ◽  
Diffuse Interface ◽  
Misfit Dislocations ◽  
Dislocation Loops ◽  
Boron Diffusion ◽  
Plan View ◽  
Transmission Electron ◽  
Mechanisms Of Formation ◽  
Film Substrate

AbstractDespite tremendous activity during the last few decades in the study of strain relaxation in thin films grown on substrates of a dissimilar material, there are still a number of problems which are unresolved. One of these is the nature of misfit dislocations forming at the film/substrate interface: depending on the misfit, the dislocations constituting the interfacial network have predominantly either in-plane or inclined Burgers vectors. While, the mechanisms of formation of misfit dislocations with inclined Burgers vectors are reasonably well understood, this is not the case for in-plane misfit dislocations whose formation mechanism is still controversial. In this paper, misfit dislocations generated to relax the strains caused by diffusion of boron into silicon have been investigated by plan-view and crosssectional transmission electron microscopy. The study of different stages of boron diffusion shows that, as in the classical model of Matthews, dislocation loops are initially generated at the epilayer surface. Subsequently the threading segments expand laterally and lay down a segment of misfit dislocation at the diffuse interface. The Burgers vector of the dislocation loop is inclined with respect to the interface and thus the initial misfit dislocations are not very efficient. However, as the diffusion proceeds, non-parallel dislocations interact and give rise to product segments that have parallel Burgers vectors. Based on the observations, a model is presented to elucidate the details of these interactions and the formation of more efficient misfit dislocations from the less-efficient inclined ones.

Transmission Electron Microscopy Studies of Strained Si CMOS

2005 ◽  
Vol 864 ◽  
Author(s):  
Qianghua Xie ◽  
Peter Fejes ◽  
Mike Kottke ◽  
Xiangdong Wang ◽  
Mike Canonico ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Scanning Transmission Electron Microscopy ◽  
Structural Information ◽  
Threading Dislocation ◽  
Misfit Dislocations ◽  
Strained Si ◽  
Thermal Budget ◽  
Transmission Electron ◽  
Scanning Transmission

AbstractIn this paper, various types of defects (both threading dislocation and misfit dislocations) in strained Si (sSi) have been analyzed by transmission electron microscopy (TEM). Germanium upper-diffusion has been studied by scanning transmission electron microscopy (STEM) for strained Si on SiGe/SOI. SGOI-devices processed using an optimized thermal budget show minimal Ge diffusion and minimal process related defects. Correlation between the device performance (such as leakage current and reliability) and structural information found in TEM has been established.

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