The control factors controlling the growth of native silicon oxide on silicon (Si) surfaces have been identified. The coexistence of oxygen and water or moisture is required for growth of native oxide both in air and in ultrapure water at room temperature. Layer-by-layer growth of native oxide films occurs on Si surfaces exposed to air. Growth of native oxides on n-Si in ultrapure water is described by a parabolic law, while the native oxide film thickness on n+-Si in ultrapure water saturates at 10 Å. The native oxide growth on n-Si in ultrapure water is continuously accompanied by a dissolution of Si into the water and degrades the atomic flatness at the oxide-Si interface, producing a rough oxide surface. A dissolution of Si into the water has not been observed for the Si wafer having surface covered by the native oxide grown in air. Native oxides grown in air and in ultrapure de-ionized water have been demonstrated experimentally to exhibit remarkable differences such as contact angles of ultrapure water drops and chemical binding energy. These chemical bond structures for native oxide films grown in air and in ultrapure water are also discussed.

Native silicon (Si) oxide growth on Si (100) wafers in air and in ultrapure water at room temperature requires coexistence of water and oxygen in the air and ultrapure water ambients. The growth rate data on n-, n+-, and p+-Si (100) in air indicate layer-by-layer growth of an oxide. The growth rate on n-Si (100) in ultrapure water may be governed by a parabolic law. For native oxide growth in ultrapure water, the number of Si atoms dissolved in ultrapure water is over one order of magnitude larger than the number of Si atoms contained in the grown native oxide film. The structural difference between the native oxide film in air and in ultrapure water is also discussed.

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Interface defects generated by negative-bias temperature stress (NBTS) in an ultrathin plasma- nitrided SiON/Si(100) system were characterized by using D2 annealing, conductance-frequency measurements, and electron-spin resonance measurements. D2 annealing was shown to lower negative-bias temperature instability (NBTI) than H2 annealing. Interfacial Si dangling bonds (Pb1 and Pb0 centers), whose density is comparable to an increase in interface trap density, were detected in a NBTS-stressed sample. The NBTI of the plasma-nitrided SiON/Si system was thus shown to occur through Pb depassivation. Furthermore, the nitridation was shown to increase the Pb1/Pb0 density ratio and modify the Pb1 structure. Such a predominance and structural modification of Pb1 centers are presumed to increase NBTI by enhancing the Pb–H dissociation. Although we suggest that NBTS may also induce non-Pb defects, nitrogen dangling bonds do not seem to be included in them.

This paper shows that a structural transition layer of SiO2 exists at an SiO~/Si interface prepared by thermal oxidation of St. Using a newly developed grazing-incidence x-ray diffraction of synchrotron radiation, the transition layer density (2.4 g/cm 3) is found to be lower than the immediate bulk SiO2 density (2.6 g/cm3), and its thickness is approximately 7 nm. Electrical properties of the SiO2 films are examined by using Fowler-Nordheim tunneling electrons which are injected from the polycrystalline silicon gate electrode into the SiO2 film. The injected charge-to-breakdown (Qbd) rapidly degrades when the SiO2 film thickness decreases below approximately 7 nm due to dielectric breakdown in the transition layer. Based on theoretical analysis, the mechanism of the dielectric breakdown in the transition layer is proposed to be St-St bond formations via hypervalent Si atoms and a replacement reaction of an oxygen atom with an electron. Introduction of nitrogen atoms into the transition layer improves the Qbd degradation of thin SiQ films, because the St-St bond formation is suppressed by stress relaxation in the transition layer.With the down-scaling of gate dielectric films to less than 10 nm in thickness, there are new reliability concerns for the dielectric films in metal oxide semiconductor (MOS) integrated circuits. Time-dependent dielectric breakdown (TDDB) is one major reliability issue. When Fowler-Nordhelm (F-N) tunneling electrons are injected from a polycrystalline silicon gate electrode into an SiO2 film (gate injection), the TDDB characteristics of the MOS structure rapidly degrade with decreasing SiO2 film thickness. 1-3 When the F-N tunneling electrons are injected in the Si substrate (substrate injection), the TDDB characteristics are much better than for the gate injection. 3-5 It is also reported that the TDDB characteristics for gate injection are significantly improved by the introduction of nitrogen (N) atoms into the SiQ film. 6-8 These reports suggest that the TDDB characteristics strongly depend on the SiO2 film structure. However, the asymmetric properties and improvement of the TDDB characteristics have not been fully discussed on the basis of structural analyses. The purpose of this work is to study how and why the TDDB characteristics depend on the SiO2 film structure.The dielectric breakdown properties of SiO2 films have been extensively studied in the last few decades. According to those studies, the constant-current TDDB measurement is one of the most suitable means of evaluating the reliability of SiO2 films. 9 The Qbd, which is defined as the injected charge-to-breakdown in the constant current TDDB measurement, quantitatively indicates the reliability of SiQ films. Many samples are examined in the TDDB measurements, and the cumulative failures of TDDB are statistically investigated as a function of Qbd. The cumulative failures are classified into two groups. One is time-dependent breakdowns in the short time range of the TDDB plots, which indicate metallic impurities. The other ...