Polycrystalline Cr2O3 films are prepared by normal pressure chemical vapour deposition (CVD), and electrical and optical properties of the films are investigated. The films are transparent from 800 to 1000 nm wavelength, and absorbing for wavelengths shorter than 800 nm. The optical band gap energy is Eopt = 2.98 to 3.09 eV for films formed at different substrate temperatures. The electrical conductivity σ of the films is from 1 × 10−2 to 2.5 × 10−3 S cm−1 at 500 K. The films are p‐type semiconducting. At temperatures higher than 500 K. the conduction is due to small polaron hopping. For temperatures lower than 500 K, a T−1/4 dependence of σT1/2 is found, which is attributed to variable‐range hopping.
The morphology of snow crystals growing at a low temperature has been experimentally studied. The habit and the morphological instability of the crystals vary remarkably with air pressure. In addition, the morphological instability of the crystals depends not only on air pressure but also on supersaturation, crystal size, the ratio of growth rates and the ratio of axial lengths. It is supposed from the experimental results that long prisms with small skeletal structures forming at low supersaturation are precipitating in polar regions.
We measured the spectrum of cesium emitted by a pulsed radio-frequency discharge in the region 1550 Å to 40 000 Å using concave grating spectrographs, Fabry-Perot interferometry, and Fourier transform spectroscopy. By varying the operating parameters of the discharge, we identified approximately 1700 of the more than 3000 spectral lines observed in this region as belonging to the spectrum of singly-ionized cesium (Cs II). Of these, 1683 were classified as transitions among 118 even and 165 odd energy levels. Partially or fully resolved hyperfine structure was analyzed for 579 lines.
In an attempt to predict the lifetime of a charcoal filter designed to remove gaseous organic compounds, a model was developed to simulate adsorption and desorption of multicomponent organic compounds in the filter. The model is composed of a mass balance equation and adsorption/desorption rate equations. When a charcoal filter is installed in a cleanroom airconditioning system, numerous types of organic compounds are competitively adsorbed onto adsorption sites (pores) of the activated carbon on the filter, which leads to displacement adsorption phenomenon. In order to consider this phenomenon in lifetime prediction, the adsorption/desorption rate equations are designed to express the concept that organic compounds of different types share or compete with each other for the limited number of adsorption sites. In this model, adsorption/desorption characteristics of each organic compound are represented by multiple parameters. A method was also proposed to estimate parameter values of organic compounds with unknown properties. In this method, the simulation model considers the total organic compound detected by means of gas chromatography (GC) analysis of cleanroom air sampled upstream of the charcoal filter. This newly developed simulation model was validated by comparing simulated and measured adsorption breakthrough curves for a multicomponent system. A charcoal filter with honeycomb-structure media was used in this validation. Simulated values were found to be in agreement with the measured values, which demonstrates that this simulation model is valid.
The influence of fluorine desorption from SiOF films deposited by biased ECR-CVD was studied. It was found that desorbed F atoms from the SiOF film react with Ti suicide film resulting in forming SiF4 gas. The evolution of SiF4 gas caused the peel-off of the films.
The technologies utilizing Fluorinated Silicon Oxide (FSG, k=3.6) and Hydrogen Silsesquioxane (HSQ, k=3.0) have been established for 0.25-µm and 0.1 8-µm generation ULSIs. However, low-k materials for the next generation ULSIs, which have a dielectric constant of less than 3.0, have not become mature yet. In this paper, we review process integration issues in applying FSG and HSQ, and describe integration results and device performance using Fluorinated Amorphous Carbon (a-C:F, k=2.5) as one of the promising low-k materials for the next generation ULSIs.
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