The Mechanism of Oxidation of SiGe.
IBM1
TL;DR: In this article, the authors studied the oxidation mechanism of SiGe alloys, prepared by UHV/CVD, and found that Si is completely rejected from the oxide and to pile up at the oxide/substrate interface.
Abstract: We have studied the oxidation mechanism of SiGe alloys, prepared by UHV/CVD. Ge is found to be completely rejected from the oxide and to pile up at the oxide/substrate interface. In the case of thick SiGe layers, this can give rise to very heavily concentrated layers of SiGe (up to 80% Ge) several hundreds of angstroms thick between the oxide and the substrate. The oxidation of Si then proceeds by Si diffusing though the Ge-rich layer. When only a thin layer of Ge is present on top of Si at the start, it acts as a marker, moving, unchanged, with the SiO2/Si interface. The rate of oxidation is enhanced in this case. The atomic motion and chemical reactions involved in the process are discussed and possible mechanisms are described to explain the data. Oxidation of a SiGeB sample is also discussed and compared with the previous case.
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IBM1
TL;DR: In this article, the authors discuss the growth and properties of pseudomorphic Si/sub 1-x/Ge/sub x/ structures and then focus on their applications, especially the Si-sub 1 -x/ge/sub X/-base heterojunction bipolar transistor (HBT).
Abstract: Advanced epitaxial growth techniques permit the use of pseudomorphic Si/sub 1-x/Ge/sub x/ alloys in silicon technology. The smaller bandgap of these alloys allows for a variety of novel band-engineered structures that promise to enhance silicon-based technology significantly. The authors discuss the growth and properties of pseudomorphic Si/sub 1-x/Ge/sub x/ structures and then focus on their applications, especially the Si/sub 1-x/Ge/sub x/-base heterojunction bipolar transistor (HBT). They show that HBTs in the Si/sub 1-x/Ge/sub x/ system allow for the decoupling of current gain and intrinsic base resistance. Such devices can be made by using a variety of techniques, including molecular-beam epitaxy and chemical vapor deposition. The authors describe the evolution of fabrication schemes for such HBTs and describe the DC and AC results obtained. They show that optimally designed HBTs coupled with advanced bipolar structures can provide performance leverage. >
428 citations
TL;DR: In this paper, a detailed review of a full SiGe HBT BiCMOS process is presented, with a description of a 12-bit Digital-to-Analog Converter.
Abstract: For pt. I, see ibid., vol. 3, p. 455-68 (1995). This part focuses on process integration concerns, first described in general terms and then detailed through an extensive review of both simple non-self-aligned device structures and more complex self-aligned device structures. The extension of SiGe device technology to high levels of integration is then discussed through a detailed review of a full SiGe HBT BiCMOS process. Finally, analog circuit design is discussed and concluded, with a description of a 12-bit Digital-to-Analog Converter presented to highlight the current status of SiGe technology. >
240 citations
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
IBM1
TL;DR: In this paper, a high-quality dielectric system for use with Si/sub 1-x/Ge/sub x/ alloys was presented, where the buffer layer and the deposited oxide prevent the accumulation of Ge at the oxide-semiconductor interface and thus keep the interface state density within acceptable limits.
Abstract: The authors present a high-quality dielectric system for use with Si/sub 1-x/Ge/sub x/ alloys. The system employs plasma-enhanced chemical vapor deposited (PECVD) SiO/sub 2/ on a thin (6-8-nm) layer of pure silicon grown epitaxially on the Si/sub 1-x/Ge/sub x/ layer. The buffer layer and the deposited oxide prevent the accumulation of Ge at the oxide-semiconductor interface and thus keep the interface state density within acceptable limits. The Si cap layer leads to a sequential turn-on of the Si/sub 1-x/Ge/sub x/ channel and the Si cap channel as is clearly observed in the low-temperature C-V curves. The authors show that this dual-channel structure can be designed to suppress the parasitic Si cap channel. The MOS capacitors are also used to extract valence-band offsets. >
88 citations
TL;DR: In this paper, the reaction layers between silicon carbide continuous fibers and a calcium aluminosilicate glass-ceramic (anorthite composition) matrix in hot-pressed composites have been characterized both structurally and chemically using high-resolution, field-emission scanning transmission electron microscopy.
Abstract: The reaction layers between silicon carbide continuous fibers (Nicalon) and a calcium aluminosilicate glass-ceramic (anorthite composition) matrix in hot-pressed composites have been characterized both structurally and chemically using high-resolution, field-emission scanning transmission electron microscopy. Chemical compositions at 10-nm spacings, with a resolution of ∼5 nm, were collected across the fiber-matrix interface zone. The reaction sequence in the material is silicon carbide (fiber)—carbon (in this case, graphite)—silica-rich glass—anorthite. The composition of the carbon layer is constant across its width; the interfaces between the four phases are planar. This morphology and the chemical gradients observed are consistent with the simple, ‘carbon-condensed’ oxidation displacemetn reaction, SiC + O2→ SiO2+ C, being responsible for interface phase formation in the composites. The planar interfaces indicate that the rate-limiting process in the interface formation reaction is the diffusion of oxygen through the matrix and silica glass layer; a corollary of this conclusion is that the diffusion of silicon through the carbon layer is a relatively faster process.
75 citations
References
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Book•
01 Jan 1986
TL;DR: In this paper, a review of passivation-related instability in modern silicon devices is presented, and the effects of Radiations on the Si-SiO2 interface are discussed.
Abstract: Volume 1. Part 1. The Physics of Silicon Passivation. Part II. General Electrical Aspects of the Si-SiO2 structure. Part III. Electrical Phenomena in the Bulk of SiO2. Volume 2. Part IV. Electrical Phenomena at the Si-SiO2 interface. Part V. A Review of Passivation-Related Instabilities in Modern Silicon Devices. Part VI - The Effects of Radiations. Author Index for vols. 1 and 2. Subject Index for Vols. 1 and 2.
94 citations
TL;DR: In this paper, a survey of some features of silicon oxidation is given, in particular the stress at the Si/SiO2 interface, and an explanation of the absence of large macroscopic stresses is suggested.
Abstract: A survey is given of some features of the oxidation of silicon. In particular, the stress at the Si/SiO2, interface is discussed, and an explanation of the absence of large macroscopic stresses is suggested. The explanation given by Deal and Grove (1965) for the linear rate of growth of the oxide film at moderate thicknesses has to be abandoned for oxidation in O2, but perhaps not in water vapour. Transport numbers in anodization are discussed. Following observations by Rochet et al., we discuss the conditions for formation of amorphous and crystalline films.
76 citations
TL;DR: In this article, a model of viscoelastic flow in SiO2, layers grown on silicon substrates is introduced to explain various phenomena, such as interstitial and vacancy concentrations in silicon during oxidation, and related to the oxidation stacking fault length.
Abstract: Models of viscoelastic flow in SiO2, layers grown on silicon substrates are introduced to explain various phenomena. Experimental data are first presented: stresses in the layer and substrate, measured during the growth at about 1000°C or at room temperature (20°C); density of the oxides grown at a temperature less than 1000°C; and values of the viscosity of the oxide. Models of stress distribution inside the oxide layer are then discussed, as a function of temperature and oxide growth rate, and related to stresses at the steps, jogs and nuclei of the Si-SiO2, interface, which are able to break Si-Si bonds in silicon. This explains the value of the interface stresses in the oxide. Values of the interstitial and vacancy concentrations in silicon during oxidation are then reviewed, and related to the oxidation stacking fault length and to the change in the diffusivity of dopants. Hu's model of the interstitial and vacancy generation at the interface is then discussed.
69 citations
TL;DR: In this paper, a number of measured SiO2, film and Si-SiO2 interface properties are reported, as well as the variation of the these properties with oxidation temperature and Si substrate orientation.
Abstract: The commonly accepted linear-parabolic oxidation model for the thermal oxidation of Si includes two rate processes in the steady state: a reaction between Si and oxidant at the Si-SiO2, interface and transport of oxidant through the SiO2, film. Based on available data, it is argued that the former process seems dominant for thin-film growth in dry O2. A number of measured SiO2, film and Si-SiO2, interface properties are reported, as well as the variation of the these properties with oxidation temperature and Si substrate orientation. These properties include refractive index, density, intrinsic stress, interface fixed oxide charge and interface trapped charge. It is also observed that all of these properties display similar oxidation-temperature and inert-anneal behaviour together with a complex orientation dependence. Through the use of a modified form for the interface reaction, a better understanding is obtained of both the origin of these measured properties, and of new oxidation data taken o...
34 citations
TL;DR: In this article, the authors deal with the modeling of thermal oxidation of silicon based on stress relaxation by viscous flow, and an analysis of the anomalously high rate of dry oxidation occurring at low thickness is given.
Abstract: This paper deals with the modelling of thermal oxidation of silicon based on stress relaxation by viscous flow. An analysis of the anomalously high rate of dry oxidation occurring at low thickness is given. This initial regime is attributed to a reduced diffusivity in the vicinity of the Si-SiO2, interface due to the presence of high compressive stress. A model of oxidation based on stress-dependent diffusivity, namely the stress-state model, is then described. The model makes it possible to obtain the oxidation kinetics over a wide range of temperature. Moreover, the influence of stress both on the parabolic and linear kinetic constants is discussed. Finally, the effects of intrinsic oxidation stress on the structural properties of thermal oxides are also described. In particular, the role of growth temperature on densification phenomena is emphasized.
25 citations