Study of pinholes in ultrathin SiO2 by C-AFM technique
TL;DR: In this paper, the authors correlated the electrical characteristics of ultrathin gate oxide with the presence of pinholes by C-AFM studies and showed that the improvement in the gate leakage current in thermally grown oxide is indeed due to the filling of pinhole by selective anodic oxidation.
About: This article is published in Thin Solid Films.The article was published on 2006-05-10. It has received 10 citations till now. The article focuses on the topics: Gate oxide & Oxide.
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TL;DR: The lithiation of SiO2-coated Si is studied in a controlled manner usingSiO2 coatings of different thicknesses grown on Si wafers via thermal oxidation to occur via rapid transport of Li along the SiO 2/Si interface radially outward from an existing pinhole, followed by the lithiation from the interface outwards.
Abstract: Silicon is a promising anode material for lithium-ion batteries because of its high capacity, but its widespread adoption has been hampered by a low cycle life arising from mechanical failure and t...
32 citations
TL;DR: In this article, the electrical and reliability properties of ultrathin silicon dioxide, grown by immersing silicon in nitric acid solution have been studied, and it is observed that the temperature, oxidation time, and concentration of the nitric acids solution play important roles in determining the thickness as well as the quality of the oxide.
Abstract: In this paper, electrical and reliability properties of ultrathin silicon dioxide, grown by immersing silicon in nitric acid solution have been studied. It is observed that the temperature, oxidation time, and concentration of the nitric acid solution play important roles in determining the thickness as well as the quality of the oxide. Prolonged exposure to nitric acid degrades the quality of the oxide. However, it was found necessary to reduce the oxidation temperature and the concentration of nitric acid to grow oxide of thickness 2 nm. In these conditions, the leakage current and fixed oxide charge in the chemical oxide were found to be too high. However, when this chemical oxidation was followed by anodic oxidation using ac bias, the electrical and reliability characteristics of metal-oxide-semiconductor (MOS) devices showed tremendous improvement. A MOSFETs with gate oxide grown by this technique have demonstrated low subthreshold slope, high transconductance and channel mobility. It is thus proposed that chemical oxidation followed by ac anodization can be a viable alternative low-temperature technique to grow thin oxides for MOS application.
9 citations
Cites background or methods from "Study of pinholes in ultrathin SiO2..."
...the surfaces of both thermal and chemical oxides using Atomic Force Microscopy [15]....
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...oxides grown by thermal oxidation at a temperature range of 700 ◦C–800 ◦C [15]....
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...This was verified by comparing the surfaces of both thermal and chemical oxides using Atomic Force Microscopy [15]....
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TL;DR: In this article, the effect of selective anodisation under ac bias on ultrathin (1.5-2.75-nm) silicon dioxide grown at two different temperatures, viz. 700 and 800°C, has been studied.
Abstract: In this paper the effect of selective anodisation under ac bias on ultrathin (1.5–2.75 nm) silicon dioxide grown at two different temperatures, viz. 700 °C and 800 °C have been studied. It is shown that ac anodisation is much more effective in improving the electrical properties of the ultrathin oxide compared to selective anodisation carried out under dc condition. Unlike dc anodisation, which only repairs the pinholes but does not improve the interfacial properties, ac anodisation is found to reduce the density of interface states. The parameters during ac anodisation, e.g. signal frequency and dc offset are found to have a major role in the degree of the improvement and have been optimised carefully. Best results have been obtained when ac anodisation has been carried out using a 260 mV peak-to-peak signal of frequency 5 kHz and dc offset of 70 mV.
7 citations
TL;DR: In this article , a pinhole-free silicon oxide (SiO x ) layer grown using dissolved ozone in deionized water (DI•O3) was demonstrated on a silicon wafer.
Abstract: The pinhole‐free silicon oxide (SiO x ) layer grown using dissolved ozone in deionized water (DI‐O3) is demonstrated. An ultrathin SiO x layer of thickness 1.53 nm ± 1.5% is grown on silicon wafer using 7 ppm DI‐O3. A four‐step methodology, including 25 wt% aq. tetramethylammonium hydroxide (TMAH) solution at 80 °C, is employed to magnify the pinhole signatures in the underlying silicon and visualized with dark‐field optical microscopy (DFOM) and scanning electron microscopy (SEM). The DFOM images show spots on the surface of wafer that originate from airborne particles, contamination, etc. SEM images reveal the absence of etch pits in silicon even after etching of SiO x /silicon in TMAH for 300 s. The minority carrier lifetime and interface states density in AlO x ‐capped SiO x /Si structure are ≥2 ms at carrier density of 1 × 1015 cm−3 and less than 2 × 1011 cm−2 eV−1, respectively.
2 citations
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TL;DR: In this paper, the leakage current of the SiO2 layer formed with 61 wt'% HNO3 at its boiling temperature of 113'°C has a 1.3 nm thickness with a considerably high density leakage current.
Abstract: Ultrathin silicon dioxide (SiO2) layers with excellent electrical characteristics can be formed using the nitric acid oxidation of Si (NAOS) method, i.e., by immersion of Si in nitric acid (HNO3) solutions. The SiO2 layer formed with 61 wt % HNO3 at its boiling temperature of 113 °C has a 1.3 nm thickness with a considerably high density leakage current. When the SiO2 layer is formed in 68 wt % HNO3 (i.e., azeotropic mixture with water), on the other hand, the leakage current density (e.g., 1.5 A/cm2 at the forward gate bias, VG, of 1 V) becomes as low as that of thermally grown SiO2 layers, in spite of the nearly identical SiO2 thickness of 1.4 nm. Due to the relatively low leakage current density of the NAOS oxide layer, capacitance–voltage (C–V) curves can be measured in spite of the ultrathin oxide thickness. However, a hump is present in the C–V curve, indicating the presence of high-density interface states. Fourier transformed infrared absorption measurements show that the atomic density of the SiO...
210 citations
IBM1
TL;DR: In this article, the rate of formation of very thin films thermally grown on [111] and [100] oriented silicon wafers was studied using ellipsometry to measure oxide thickness.
Abstract: The rate of formation of very thin films thermally grown on [111] and [100] oriented silicon wafers was studied using ellipsometry to measure oxide thickness. Film thicknesses from 10–300Aa were obtained by varying oxidation time, oxidation temperature (700°–1000°C), and oxygen concentration in O2‐N2 mixtures at 1 atm total pressure. The applicability of ellipsometry for such a study is discussed. Reproducibility of oxide films grown to thicknesses of 20–30Aa was approx. ±1.0Aa. Under otherwise equal conditions the oxide thickness grown differs for [100] and [111] oriented wafers. The pressure and temperature dependence of the linear rate constant, klin, show that the growth reaction is more complicated than was suggested earlier. In particular, a different pressure dependence for the two substrate orientations used indicates that several oxygen species participate in the rate determining steps.
96 citations
TL;DR: In this article, the formation of voids on the thermally grown (650 °C) ultrathin (∼1 nm) silicon oxide films on the Si(100) surface was investigated by using ultrahigh vacuum scanning tunneling microscopy.
Abstract: The formation of voids on the thermally grown (650 °C) ultrathin (∼1 nm) silicon oxide films on the Si(100) surface was investigated by using ultrahigh vacuum scanning tunneling microscopy. Voids form randomly on the ultrathin oxide film upon thermal annealing at 750 °C. In contrast to void formation observed on thicker (>5 nm) thermal silicon oxide films and that observed on ultrathin (∼1 nm) oxide films formed by room temperature O2 adsorption, the number of voids increases during annealing. We find that Si monomer creation and SiO production compete kinetically in the void formation process.
70 citations
67 citations
TL;DR: In this paper, the authors show that the effective tunnel mass of SiO2 employed as a fitting parameter in standard transfer-matrix multiple-scattering theory calculations increases strongly as the oxide thickness is decreased.
Abstract: Based on the results of three-dimensional atomistic tight-binding calculations, we argue that the effective tunnel mass of SiO2 employed as a fitting parameter in standard transfer-matrix multiple-scattering theory calculations increases strongly as the oxide thickness is decreased (we find more than 50% mass enhancement upon reduction of the oxide thickness from 4 to 1 nm). At least five factors, usually neglected in effective-mass-based calculations can contribute to this effect: the nonparabolicity of the complex bands in the gap of SiO2, the gradual (rather than abrupt) change of the electrostatic potential across the Si/SiO2 interface, a possible image force correction, the presence of native defects in the oxide, and the effective-mass approximation itself. Very good quantitative agreement between the theoretical predictions for the thickness dependence of the mass enhancement and corresponding results from transfer matrix fits to experimental currents is obtained if defect densities smaller than 10...
61 citations