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Si is oxidized at temperatures lower than 500 degree Celsius by use of HN[O.sub.3] vapor to form Si[O.sub.2]/Si structure. The oxidation kinetics follows a parabolic law, indicating that diffusion of oxidizing species through Si[O.sub.2] is the rate determining step and Si[O.sub.2] layers formed at 350 degree Celsius follows the Poole-Frenkel mechanism and Si[O.sub.2] formed at 500 degree Celsius follows the Folwer-Nordheim mechanism.

Chemical oxidation of Si by use of HNO3 solutions (i.e., NAOS method) is investigated in view of its application to gate oxides. The results show that SiO2 layers of 0.7-1.4 nm thickness can be formed by the immersion of Si in HNO3 aqueous solutions and the SiO2 thickness can be controlled by changing the temperature of the HNO3 solutions.

Electrical characteristics and physical properties of 8–10 nm silicon dioxide (SiO2) films formed on Si (100) substrates by use of the nitric acid oxidation of Si method at ∼120 °C have been investigated. The atomic density of the SiO2 layer increases with the HNO3 concentration. Fourier transformed infrared absorption measurements show that the higher the HNO3 concentration, the higher the atomic density of the SiO2 layer. From the Fowler–Nordheim plots, the barrier height at the SiO2/Si interface is found to increase with the HNO3 concentration. The leakage current density flowing through the SiO2 layer decreases with the HNO3 concentration employed for the SiO2 formation. It is concluded that the higher atomic density leads to SiO2 band-gap widening and thus to the higher band discontinuity energy at the SiO2/Si interface, which in turn results in a decrease in the tunneling probability of charge carries through SiO2. The density of oxide fixed charges decreases with an increase in the HNO3 concentration. When postmetallization annealing is performed at 250 °C in hydrogen atmosphere on the SiO2 layer formed with 68 wt % HNO3, electrical characteristics become as good as those of a thermally grown SiO2 layer formed at 900 °C. [ABSTRACT FROM AUTHOR]

Si can be oxidized at temperatures between 350 and 500 °C by use of nitric acid (HNO3) vapor, resulting in 5–10 nm SiO2/Si structure. The oxidation kinetics follows a parabolic law, indicating that diffusion of oxidizing species (i.e., oxygen atoms generated by decomposition of HNO3 molecules) through SiO2 is the rate-determining step. The leakage current density flowing through the SiO2 layer formed at 350 °C follows the Poole-Frenkel mechanism, indicating the presence of trap states in the SiO2 band gap, and the trap energy is estimated to be 0.57 eV below the SiO2 conduction band. On the other hand, the leakage current density for the SiO2 layer formed at 500 °C follows the Fowler-Nordheim mechanism, showing the absence of trap states. [ABSTRACT FROM AUTHOR]

We have developed a room temperature formation method of silicon oxynitride (SiON) films by use of an electrochemical technique. Immersion of Si in potassium cyanide methanol solutions and application of 1–3 V to Si with respect to a reference platinum electrode form SiON films. At 1 V, decomposition of cyanide ions occurs, leading to Si nitridation, and subsequent air exposure forms SiON films with 4.2% concentration. At 2 and 3 V, on the other hand, oxidation and nitridation simultaneously proceed, resulting in the direct formation of SiON films with 0.8%–2.2% nitrogen concentration. X-ray photoelectron spectroscopy measurements show that nitrogen is present in the form of N-(Si)3 and Si-CN species. Relative dielectric constant of the SiON layers formed at 3 V is 5.1 with no heat treatment, and it decreases to 4.9 by a heat treatment at 700 °C. The leakage current density of the SiON films is relatively low (e.g., 1×10-6 A/cm2 at the gate bias of 1 V) in spite of the room temperature formation. [ABSTRACT FROM AUTHOR]

A formation method of ultrathin silicon oxynitride layers with high-nitrogen concentrations and good electrical characteristics has been developed. This method consists of nitridation by the use of nitrogen plasma generated by low-energy electron impact and chemical oxidation. Without annealing after the nitridation or oxidation, the metal-nitrided oxide-semiconductor diodes possess poor electrical characteristics with a high-density leakage current, a large flat band shift in the negative bias direction, and a large hysteresis in the capacitance-voltage curves. With annealing in nitrogen, on the other hand, the leakage current density is markedly decreased, the flat-band voltage shifts to nearly zero gate bias, and the hysteresis is eliminated. X-ray photoelectron spectroscopy measurements show that the electrical characteristics of the oxynitride layers containing only nitrogen atoms bound to one oxygen atom and two Si atoms each, O-N(-Si)[sub 2], as nitrogen species are excellent, while the electrical characteristics become poor when the oxynitride layers contain charged species, N-(Si)[sub 4, sup +] or high concentrations of nitrogen atoms bound to three Si atoms, N-(Si)[sub 3] or N-[Si(-O[sub 3])][sub 3]. Oxynitride layers in which nitridation is initially performed followed by chemical oxidation by immersion in nitric acid possess almost uniform nitrogen atomic concentration, N/(O+N), of 10-12% throughout the layer and high-relative dielectric constant, ε[sub r] of 5.2. This ε[sub r] is higher than that expected from the nitrogen concentration, indicating that nitrogen atoms have long-range interaction. When chemical oxide layers are initially formed and then nitridation is performed, the nitrogen concentration is lower (i.e., ∼8% for the surface region) and decreases with the depth, resulting in a lower ε[sub r] of 4.1. [ABSTRACT FROM AUTHOR]

Electrical characteristics and physical properties of silicon dioxide (Si[O.sub.2]) films formed on Si (100) substrates by use of the nitric acid oxidation of Si method are examined. The studies have shown that the higher atomic density has led to Si[O.sub.2] band-gap widening and thus to the higher band discontinuity energy at the Si[O.sub.2]/Si interface, which is turn has resulted in a decrease in the tunneling probability of charge carriers through Si[O.sub.2].

A room temperature method of silicon oxynitride (SiON) films is developed by using an electrochemical technique. The heat treatments have eliminated the hysteresis in the C-V curves but have increased a leakage current density probably due to the formation of interface states.

Presents a study which investigated the laser-generated plasma x-ray properties in the soft x-ray region. Experimental details; Results and discussion; Conclusions.