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Journal ArticleDOI

Oxidation rate enhancement of SiGe epitaxial films oxidized in dry ambient

28 Oct 2003-Applied Physics Letters (American Institute of Physics)-Vol. 83, Iss: 18, pp 3713-3715
TL;DR: In this paper, a study on thin oxides obtained by rapid thermal oxidation of Si1−xGex epitaxial layers was performed in dry O2 at 1000°C for times up to 600 s.
Abstract: We present a study on thin oxides obtained by rapid thermal oxidation of Si1−xGex epitaxial layers. The oxidation processes were performed in dry O2 at 1000 °C for times up to 600 s. Our data show an oxide growth rate enhancement with respect to pure Si. Except for a very small amount of GeO2 that is found at the surface, all the Ge is rejected towards the SiO2/SiGe interface, forming a Ge-enriched layer free of extended defects. The comparison of our results for dry processes with those reported in the literature for wet ambient supports the idea that the kinetics of SiGe oxidation is controlled by similar mechanisms in both cases, in contrast with models and interpretations so far proposed.
Citations
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Patent
16 Aug 2006
TL;DR: In this paper, a gate and a plurality of source/drain regions are formed on the silicon semiconductor substrate to form at least one pFET, and an interlevel dielectric layer is formed over the gate and the source/drains regions.
Abstract: A semiconductor method includes providing a silicon semiconductor substrate. A gate and a plurality of source/drain regions are formed on the silicon semiconductor substrate to form at least one pFET. A silicon-germanium layer is formed over the plurality of source/drain regions. The germanium is condensed from the silicon-germanium layer to form a plurality of source/drains in the plurality of source/drain regions by forming an oxide layer over the silicon-germanium layer. An interlevel dielectric layer is formed over the gate and the source/drain regions. A plurality of contacts is formed in the interlevel dielectric layer to the gate and the plurality of source/drain regions.

50 citations

Book
29 Mar 2010
TL;DR: In this article, a complete model for the oxidation of silicon germanium is proposed, which includes the participation of both silicon and germania atoms in the oxidation process and the replacement by silicon of germaniam in mixed oxides.
Abstract: We propose a complete model for the oxidation of silicon germanium. Our model includes the participation of both silicon and germanium atoms in the oxidation process and the replacement by silicon of germanium in mixed oxides. Our model is capable of predicting, as a function of time, the oxide thickness, the profile of the silicon in the underlying alloy, and the profile of germanium in the oxide. The parameters of the model vary with temperature, alloy composition, and oxidizing ambient. The model shows excellent agreement with published results, with model parameters following trends consistent with the physical phenomena hypothesized. The presence of germanium catalyzes both the silicon and the germanium oxidation rates, and all reaction rates increase with increasing temperature. The resulting effective oxidation rate is enhanced, with respect to the oxidation of pure silicon, at all germanium concentrations. Mixed oxides form only in the case of high germanium concentrations, but at high temperature...

23 citations

Journal ArticleDOI
TL;DR: In this article, the injection of Si self-interstitial atoms during dry oxidation at 815°C of very shallow SiGe layers grown on Si by molecular-beam epitaxy (MBE) has been investigated.
Abstract: The injection of Si self-interstitial atoms during dry oxidation at 815°C of very shallow SiGe layers grown on Si (001) by molecular-beam epitaxy (MBE) has been investigated. We first quantified the oxidation enhanced diffusion (OED) of two boron deltas buried into the Si underlying the oxidized SiGe layers. Then, by simulating the interstitial diffusion in the MBE material with a code developed on purpose, we estimated the interstitial supersaturation (S) at the SiGe∕Si interface. We found that S (a) is lower than that observed in pure Si, (b) is Ge-concentration dependent, and (c) has a very fast transient behavior. After such a short transient, the OED is completely suppressed, and the suppression lasts for long annealing times even after the complete oxidation of the SiGe layer. The above results have been related to the mechanism of oxidation of SiGe in which the Ge piles up at the SiO2∕SiGe interface by producing a thin and defect-free layer with a very high concentration of Ge.

20 citations

Journal ArticleDOI
TL;DR: In this paper, the pile-up effect was shown to occur at the oxidation interface, with the highest germanium content occurring at the same interface, and the proposed models may be used in nanostructuring of thin films of SiGe by oxidation and in the design of coreshell structures and transistors.
Abstract: Several fundamental aspects of the oxidation-induced redistribution of Ge in thin films of SiGe are studied. This includes the incorporation of Ge into the oxide and the formation of what is alternatively referred to as pile-up, snow-plow, or a germanium-rich layer. Experimental data from the present work shows longer oxidation times leading to an increase of Ge content in the pile-up region and eventually creating a single high Ge content pile-up layer by entirely consuming the initial SiGe layer. The pile-up effect was shown to occur at the oxidation interface, with the highest Ge content occurring at the same interface. For a given oxide thickness, the redistribution of Ge and the formation of a pile-up region was shown experimentally to be independent of temperature in the range between 800 °C and 1000 °C. Simulations using common models for the oxidation of Si and diffusion of Si in SiGe indicate that temperature does have an influence on the composition of the pile-up layer, though the range of achievable compositions is limited. The flux of Si due to diffusion of Si in SiGe relative to the oxidation-induced flux of Si out of the SiGe is integral to the formation and dimensions of a pile-up region. Two predictive relations were derived for describing the dynamics of oxidation of SiGe. The first relation is given for determining the pile-up layer thickness as a function of oxide thickness and the composition of the pile-up layer. The second relation assumes a limited supply of Si and is for determination of the minimum initial thickness of a SiGe layer to avoid oxidation of Ge. The validity of these equations was confirmed experimentally by RBS and XPS data from the present work. The proposed models may be used in nanostructuring of thin films of SiGe by oxidation and in the design of core-shell structures and transistors. This is all done with a focus on oxidation of epitaxial thin films (< 100 nm) of Si1-XGeX in dry O2 at 1 atm between 800 °C and 1000 °C.

17 citations

Journal ArticleDOI
TL;DR: In this paper, a modified technique to fabricate silicon-germanium on insulator (SGOI) starting with a sandwiched structure of Si ∕SiGe∕Si.
Abstract: We have developed a modified technique to fabricate silicon–germanium on insulator (SGOI) starting with a sandwiched structure of Si∕SiGe∕Si. By means of oxidation and annealing, relaxed SiGe-on-insulator (SGOI) with a Ge fraction of 34% has been produced. Our results indicate that oxidation of the silicon cap suppresses Ge loss at the initial stage of the SiGe oxidation and the subsequent annealing process homogenizes the Ge fraction and also reduces Ge enrichment under the oxide. It is found that the strain in the SiGe layer is almost fully relaxed at high oxidation temperature (∼1150°C) without generating any dislocations and crosshatch patterns that are commonly observed on the surface of a relaxed or partially relaxed SiGe layer on bulk Si substrate.

16 citations

References
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Book
01 Jan 1980

1,720 citations

Book ChapterDOI
TL;DR: In energy-filtering transmission electron microscopy (EFTEM), the zero-loss electrons or electrons passing an energy loss window of the electron energy-loss spectroscopy are used for image formation.
Abstract: Publisher Summary In energy-filtering transmission electron microscopy (EFTEM), the zero-loss electrons or electrons passing an energy-loss window of the electron energy-loss spectroscopy (EELS) are used for image formation. This can be achieved by using the scanning mode in a dedicated scanning transmission electron microscope (STEM) or in a TEM with a spectrometer behind the camera chamber or by using an imaging filter lens in the column of a TEM. The conventional TEM and STEM modes can be combined in this way with the mode of electron spectroscopic imaging (ESI) and electron spectroscopic diffraction (ESD), and different modes can be used to record an EELS spectrum. An EFTEM can therefore make full use of elastic and inelastic electron-specimen interactions. This chapter provides an overview of the physical background and the possibilities of EFTEM. The relevant physics of elastic and inelastic scattering is also discussed followed by the instrumentation of EFTEM. The theoretical approaches for understanding the contrast and examples of application are presented for ESI and for ESD.

391 citations

Journal ArticleDOI
TL;DR: In this paper, the authors studied the kinetics and mechanism of oxidation of SiGe alloys deposited epitaxially onto Si substrates by low-temperature chemical vapor deposition and demonstrated that Ge plays a purely catalytic role, i.e., it enhances the reaction rate while remaining unchanged itself.
Abstract: We have studied the kinetics and mechanism of oxidation of SiGe alloys deposited epitaxially onto Si substrates by low‐temperature chemical vapor deposition. Ge is shown to enhance oxidation rates by a factor of about 3 in the linear regime, and to be completely rejected from the oxide so that it piles up at the SiO2/SiGe interface. We demonstrate that Ge plays a purely catalytic role, i.e., it enhances the reaction rate while remaining unchanged itself. Electrical properties of the oxides formed under these conditions are presented, as well as microstructures of the oxide/substrate, Ge‐enriched/SiGe substrate, and SiGe/Si substrate interfaces, and x‐ray photoemission studies of the early stages of oxidation. Possible mechanisms are discussed and compared with oxidation of pure silicon.

315 citations

Journal ArticleDOI
TL;DR: It is demonstrated that the role of Ge is to suppress the formation of Si interstitials and that this is the rate limiting step in cases of rapid oxidation.
Abstract: The rates of oxidation of SiGe and of Si covered with a thin ‘‘marker’’ of Ge have been measured, and compared with rates of oxidation for pure Si, both for wet and dry ambient. It is shown that the presence of Ge at the SiO2/Si interface increases the rate of wet oxidation by a factor of about 2.5, while it does not affect the rate of dry oxidation. By decreasing the partial pressure of H2O sufficiently, the rate of wet oxidation can be decreased to match that of dry oxidation. In this case again, Ge has no effect on the rate. Contrary to what has been proposed before, Ge is being piled up at the interface both for fast and slow oxidation. We demonstrate that the role of Ge is to suppress the formation of Si interstitials and that this is the rate limiting step in cases of rapid oxidation. For slower oxidation, interstitials have considerably more time to diffuse away and thus their formation and/or diffusion is not rate limiting.

177 citations

Journal ArticleDOI
TL;DR: In this article, the oxidation of SiGe layers grown by molecular beam epitaxy was studied, and it was found that the Ge concentration in the SiGe layer played an important role in the formation of these Ge•Rich layers.
Abstract: The oxidation of SiGe layers grown by molecular beam epitaxy was studied. Auger depth profile showed that after oxidation, Ge was completely rejected from the oxide and Ge‐rich layers were formed. However, the Ge concentration in the SiGe layer was found to play an important role in the formation of these Ge‐Rich layers. For SiGe with Ge concentration below 50%, Si was preferentially oxidized and only one Ge‐rich layer was formed at the oxide/substrate interface. On the other hand, for SiGe with Ge concentration above 50%, two Ge‐rich layers were formed after oxidation with one at the oxide/substrate interface and the other at the oxide surface. X‐ray photoelectron spectroscopy studies showed that Ge at the oxide/substrate interface is in elemental form, while Ge at the oxide surface is in an intermediate oxidized state. A classical binary alloy oxidation theory is employed to explain the overall oxidation behavior qualitatively.

143 citations