SiSiO2 interface characterization by ESCA

A low temperature thermal cleaning method for Si molecular beam epitaxy (MBE) is proposed. This method consists of wet chemical treatment to eliminate carbon contaminants on Si substrates, thin oxide film formation to protect the clean Si surface from contamination during processing before MBE growth, and desorption of the thin oxide film under UHV. The passivative oxide can be removed at temperatures below 800~ It is confirmed that Si epitaxial growth can take place on substrates cleaned by this method and that high quality Si layers with dislocations of fewer than 100/cm ~ and high mobility comparable to good bulk materials are formed. Surface cleanliness, the nature of thin passivative oxide films, and cleaning processes are also studied by using such surface analytic methods as Auger elec tron spectroscopy, reflection high energy electron diffraction, and x-ray photoelectron spectroscopy.Si molecular beam epitaxy (Si-MBE) has been shown to produce device quality epitaxial Si films. This can, however, be obtained only when a clean silicon substrate surface is prepared before epitaxial growth. That is, contaminants on the substrate, such as oxide and carbide, prevent layer growth and become the main causes of crystal defects in the epitaxial layers. In order to provide clean surfaces and eliminate defect origins at interfaces, high temperature thermal etching at about 1200~ prior to epitaxial growth has been commonly used in an ultrahigh vacuum (UHV) (1-5). However, this technique causes undesirable impurity diffusion and changes the designed impurity concentration profile within th.e Si substrate. Furthermore, crystal defects, such as dislocations and stacking faults, tend to increase and slip lines are often generated across the Si substrate during high temperature treatment. Thus, it is important to find a low temperature surface cleaning method in which the temperature can be lowered to below 900~ Several studies have reported low temperature surface cleaning techniques. The methods used include ion sputtering (6, 7), laser annealing (8, 9), "galliation," in which the substrate is exposed to a gallium vapor beam at about 800~ substrate temperature in UHV (10), and exposure to a Si beam (11). Ion sputtering, however, produces undesirable radiation damage at the surface and point defects often remain even after annealing. Galliation is effective in removing silicon oxide, but complete removal of Ga atoms from the Si surface and no Ga diffusion into the Si substrate have not yet been fully confirmed. Also, for the ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 54.245.13.81

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“…The peak intensity ratio obtained is about 0.22, and the estimated oxide thickness is approximately 6.4~, using Eq. [14] in Ref. (14).…”

Section: Resultsmentioning

confidence: 99%

Low Temperature Surface Cleaning of Silicon and Its Application to Silicon MBE

Ishizaka

Shiraki

1986

J. Electrochem. Soc.

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1,629

433

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“…where \ is the mean free path of the Si2p photoelectrons, which is 23 A , in Si [17] and 34.9 A , in Si 4 + [17]. | is the photoionization cross section for the Si2p level electron, which is assumed to be equal [18,19] for the bulk and for the oxide layer.…”

Section: The X-ray Photoelectron Spectroscopy (Xps)mentioning

confidence: 99%

Creation of nanostructures to study the topographical dependency of protein adsorption

Galli

Coen

Hauert

et al. 2002

Colloids and Surfaces B: Biointerfaces

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Nanostructures of sizes comparable to protein dimensions are created on Si and Ti surfaces by local anodic oxidation (LAO) using the atomic force microscope (AFM). The characterization of the surface by X-ray photoelectron spectroscopy (XPS) reveals that this method assures a modification of the topography of the surface without a change of its chemical composition. Surfaces structured by LAO therefore represent ideal systems to study the dependence of protein adsorption on topography. We are able to visualize the created nanostructures with an AFM and successively adsorb the proteins in situ, rinse and image the new surface. The densities of adsorbed proteins on the nanostructured and neat surfaces are compared and we find that the protein arrangement depends on the underlying nanostructures, showing that proteins can ''sense'' the topography of surfaces at the nanometer scale. This result can be considered as the nanoscale analogous of the adsorption found for cell systems on micrometer structures.

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“…2(b)], a chemical shift component from the oxide layer ͑Si 41 ͒ was identified and a small amount of peak intensity from the intermediate oxidation states suggested the presence of an abrupt SiO 2 ͞Si interface [3,21]. Assuming the escape depth of the photoelectron through the oxide layer to be 3.5 nm [13,22], the film thickness was estimated to be 0.63 nm. This estimation means that oxidation of the fourth layer had begun [23], which coincides with the phase of the SREM oscillation [ Fig.…”

mentioning

confidence: 99%

Kinetics of Initial Layer-by-Layer Oxidation of Si(001) Surfaces

Watanabe¹,

Kato²,

Uda³

et al. 1998

Phys. Rev. Lett.

288

146

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Layer-by-layer oxidation of Si(001) surfaces has been studied by scanning reflection electron microscopy (SREM). The oxidation kinetics of the top and second layers were independently investigated from the change in oxygen Auger peak intensity calibrated from the SREM observation. A barrierless oxidation of the first subsurface layer, as well as oxygen chemisorption onto the top layer, occurs at room temperature. The energy barrier of the second-layer oxidation was found to be 0.3 eV. The initial oxidation kinetics are discussed based on first-principles calculations.[S0031-9007(97)04959-4] PACS numbers: 81.65. Mq, Oxidation of Si surfaces is important for technological application of electronic devices [1][2][3]. Although many kinds of surface analyses have been used to study oxygen adsorption kinetics onto Si surfaces [4][5][6][7][8][9], the oxidation kinetics of subsurface layers, which determine oxide film growth, have not been studied in detail. This is because of the difficulty of experimentally and independently analyzing the oxidation processes of specific subsurface layers. In this Letter we used scanning reflection electron microscopy (SREM [10]) combined with Auger electron and x-ray photoelectron spectroscopy (AES and XPS) to investigate the initial oxidation of Si(001) surfaces. Our combined analysis has a great advantage for observing layer-by-layer oxidation of subsurface layers, as well as the step and terrace configurations buried with oxide layers. We report, for the first time, reaction barriers of the uppermost and second layer oxidations, and discuss our experimental results based on first-principles calculations.Our experiments were carried out using an ultrahighvacuum surface analysis system that performs SREM, AES, and XPS [11]. This system is equipped with a thermal field emission electron gun, a precision energy analyzer (a spherical capacitor analyzer), and a conventional x-ray source (Mg Ka excitation). A 30-keV electron beam with a 2-nm diameter was used for the SREM with a low incident angle of about 2 ± to the surface. The AES measurement could be performed simultaneously by using the electron gun for SREM at an incident angle and detection angle of about 2 ± and 73 ± to the sample surface, respectively. The XPS was performed with a 60 ± takeoff angle with respect to the normal to the surface. A Si(001)-͑2 3 1͒ surface was prepared by flash heating with a direct current. Oxidation of the surfaces was carried out by introducing molecular oxygen into the analysis chamber. Since the electron gun and the energy analyzer were independently evacuated, the AES measurement could be performed under oxygen pressure on the order of 10 26 Torr.As we previously reported, since SREM images of SiO 2 ͞Si systems are obtained by recording the intensity change in reflection spots from a crystal Si substrate covered with an amorphous oxide layer, the interfacial structure can be observed without the need to remove the SiO 2 overlayer [12][13][14]. Figures 1(a)-1(d) show SREM images of Si(001) surfaces...

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SiSiO2 interface characterization by ESCA

Cited by 177 publications

References 31 publications

Low Temperature Surface Cleaning of Silicon and Its Application to Silicon MBE

Low Temperature Surface Cleaning of Silicon and Its Application to Silicon MBE

Creation of nanostructures to study the topographical dependency of protein adsorption

Kinetics of Initial Layer-by-Layer Oxidation of Si(001) Surfaces

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