The results of time-dependent density functional theory (TD-DFT) calculations of the transition energies and oscillator strengths of the excited states of formaldehyde, benzene, ethylene, and methane are reported. The local DFT (LDFT) transition energies tend to be smaller than experimental values by 0.1-1.3 eV. Inclusion of nonlocal (NLDFT) (gradient corrected) effects made the calculated energies larger than the LDFT values and thus made the energies closer to the experimental values for formaldehyde, ethylene, and methane. For benzene, no significant change in the calculated transition energies due to the addition of nonlocal effects was observed. The TD-DFT oscillator strengths are much better than those found at the configuration interaction singles (CIS) level. The agreement between the calculated TD-DFT values and the experimental values for the oscillator strengths is quite good, at least semiquantitative at both the LDFT and NLDFT levels.

We have calculated the linear absorption coefficients of various resist polymers using the mass absorption coefficients at 13 nm and the density obtained from the graph-theoretical treatment derived by Bicerano. The values indicate that the transmittance at 13 nm of conventional resists used in 193-nm, 248-nm and 365-nm lithography is about 30% when the thickness is 3000 Å and 60–70% when it is 1000 Å. This shows that conventional resists are suitable for an EUVL (extreme ultraviolet lithography) thin-layer resist (TLR) process using a hard-mask layer, but their large photoabsorption makes them unsuitable for a single-layer resist (SLR) process. To design polymers that are suitable for an SLR process, we further calculated the absorption of about 150 polymers. The results suggest that the introduction of aromatic groups into a polymer not only reduces the absorption at 13 nm but also increases the etching resistance.

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 ...

We clarify the mechanism of leakage current through the nanoscale ultrathin silicon dioxide (SiO2) layer in a metal-insulator-semiconductor structure based on the multiple scattering theory when technologically important phosphorus doped polycrystalline silicon is adopted as the gate electrode. We also derive an analytic expression for the direct tunneling current, and show that its measurement presents an excellent opportunity to determine the effective mass of an electron in the SiO2.

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