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A theory for the y-ray background involving cosmic-ray interactions at high redshifts has been re-examined using improved computational techniques and more realistic radiation fields. Comparison with observations shows good overall agreement but a possible discrepancy in the 10-100 MeV range.

The dual damascene (DD) formation process for sub 0.2 µm feature size devices has been investigated. The via-first DD process, where via holes are first formed, followed by trench formation, used the antireflection film in via holes after the trench pattern lithography process. In subsequential trench etch process, crownlike etch residues of SiO2 were formed around via holes due to etch inhibiting effect of antireflection films in via holes. A spin-on-glass (SOG) film is filled in via holes as a sacrificial film before trench pattern lithography was used. It could eliminate the crownlike etch residues because of the absence of an antireflection film in via holes. Moreover, it could give via holes a rounded profile at their top edges. This DD process used for fabricating films with no etch residues and rounded via holes reduces the aspect ratio of via holes and was confirmed to be effective for subsequential metal filling process.

In this study, we propose a simulation model to clarify the mechanism of microtrench generation in the etching process of a wiring trench on a silicon dioxide (SiO 2 ) layer using a high-pressure etching gas. Furthermore, the validity of the simulation model is clarified by a comparison with the experimental result. The trench etching process can be expressed by a transportation model outside the trench where radicals and ions are transported from the plasma to the surface of the SiO 2 layer, a transportation model inside the trench where radicals and ions are transported to the trench bottom, and a surface reaction model for the SiO 2 layer where the etching behavior of fluorine reaching the trench bottom is modeled. In the transportation model outside the trench, the measurement values for the density of reactive radical species in the plasma, electron temperature, and electron density should be used. In the transportation model inside the trench, the insulation layer characteristic and the behavior of radicals and ions in the trench with the aspect ratio of the trench should be considered. The surface reaction model of the SiO 2 layer can use the etching rate for the blanket of the SiO 2 layer and the real ion energy should be considered. Moreover, the simulation results obtained using this model correspond well to the experimental results, and the validity of the proposed model is shown.

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