787A new systematical method which enables us to describe an electron gas in terms of bosons is developed. This boson corresponds to an "exciton", i. e. a pair of an electron outside the Fermi sphere and a hole inside. The formalism is particularly suitable to the system at high density, as suggested by Sawada's discussion of the same system. As a straightforward application, the effect of electron exchange on the plasma frequency is calculated. The result coincides with that of a Hartree-Fock treatment.

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The effect of plasma treatment and a dielectric diffusion barrier on electromigration (EM) performance was examined. The characteristics and adhesion properties at the interface between copper (Cu) and the dielectric diffusion barrier were also investigated by scanning transmission electron microscopy–electron energy loss spectrometry (STEM–EELS). The existence of oxygen at the interface after hydrogen (H2) plasma treatment, which has a large pre-exponential factor, causes a large EM drift velocity. Ammonium (NH3) plasma treatment can reduce the Cu oxide completely, resulting in an improvement in EM performance. On the other hand, the dielectric diffusion barrier of SiCxNy, which has a better adhesion property then SiCx, reduces EM drift velocity and provides a larger activation energy. The reduction of CuOx completely by plasma treatment is essential and the selection of dielectric diffusion barrier is important to improve the EM performance of Cu damascene interconnects.

In order to realize the effective dielectric constant (k eff)=2.4 for 32 nm-node copper(Cu) dual-damascene(DD) interconnects, a spin-on-dielectric(SOD) SiOC (k=2.0) as the inter-level dielectric and plasma-induced damage restoration treatment were successfully demonstrated. It was obtained that good via resistance and stress-induced voiding (SiV) reliability. In addition, CoW-cap and thin SiC (k=3.5) and dual hard mask process using a metal layer was proposed to reduce the capacitance of dielectric diffusion barrier and protection layers in hybrid(PAr/SiOC) inter-layer dielectric(ILD) structure. As for the metallization, a self-formed MnSi x O y barrier technology was applied in hybrid ILD structure. Drastic reduction of via resistance and excellent electromigration and SiV performance were obtained for the first time in hybrid ILD structure.

Silicon carbide (SiC) coating is one of the countermeasures for the prevention of oxidation and hydrogen embrittlement of fuel claddings because SiC has high resistance of oxidation and hydrogen permeation. Hydrogen permeation and oxidation experiments for the cladding materials with SiC coatings were conducted in unirradiated conditions. The sputtering method was employed to make SiC coatings. In the hydrogen permeation experiment, 316 type of stainless steel (SS316) was used as a base material of the coating. SS316 with SiC coatings showed hydrogen permeation reduction by one order of magnitude. In the oxidation experiments, Zircaloy 4 (Zry-4) and SS316 were used as base materials of the coatings. The weight gain of the Zry-4 specimens with a SiC coating decreased by about one-fifth compared to the uncoated ones at 750 • C and 1200 • C. This phenomenon was observed for SS316 at 750 • C as well. The peel-off of the coating was observed in several experiments, and it is considered that the peel-off was caused by the difference of the thermal expansions between coatings and base materials. Thicker coatings showed better oxidation resistance, but thinner coatings showed more tolerance of peel-off.

A 32 nm BEOL with PVD CuMn seedlayer and conventional PVD-TaN/Ta liner was fully characterized by fundamental, integrated, and reliability methods. CuMn was confirmed to have fundamental advantages over CuAl, such as higher electromigration (EM) reliability for the same Cu line resistance (R). Both low R and high reliability (EM, SM, and TDDB) were achieved. Improved extendibility of CuMn relative to CuAl was also supported by studies of alloy interactions with advanced liner materials Ru and Co, and by enhancement of ultra-thin TaN barrier performance.

1395It is pointed out that a uniform superfluid solution of He 3 -He 4 at low temperature will show the phase separation when rotated. The normal He 3 rich fluid occupies the central region of a vortex line, the radius of which is determined as a function of the He 3 concentrations in the absence of rotation. The dispersion relation is derived for waves associated with the oscillations of the phase boundary.