In order to clarify the relationship between Al line reliability and film microstructure, especially grain boundary structure and crystal texture, we have tested three kinds of highly textured Al lines, namely, single-crystal Al line, quasi-single-crystal Al line and hypertextured Al line, and two kinds of conventional Al lines deposited on TiN/Ti and on SiO2. Consequently, the empirical relation between the electromigration (EM) lifetime of Al line † and the (111) full width at half maximum (FWHM) value ω is described by † ∝ ω-2 [1]. This improvement of Al line reliability results from as following reasons; firstly, homogeneous microstructure and high activation energy of 1.28eV for the single-crystal Al line (ω=0.18°); secondly, sub-grain boundaries which consisted of dislocation arrays found in the quasi-single-crystal Al line (ω=0.26°) has turned out to be no more effective mass transport paths because dislocation lines are perpendicular to the direction of electron wind. Although there exist plural grain boundary diffusion paths in the newly developed hypertextured Al line (ω=0.5°) formed by using an amorphous Ta-Al underlayer {1], the vacancy flux along the line has been suppressed to the same order of magnitude of single crystal line. It has been clarified that the decrease of FWHM value has promoted the formation of sub-grain boundaries and low-angle boundaries with detailed orientation analysis of individual grains in the hypertextured film. The longer EM lifetime for the hypertextured Al line is considered to be due to the small grain boundary diffusivities for these stable grain boundaries, and this diffusivity reduction resulted in the suppression of void/hillock pair in the Al lines. These results have confirmed that controlling texture and/or grain boundary itself is a promising approach to develop reliable Al lines which withstand higher current densities required in future ULSIs.

A tight-binding type self-consistent band calculation is performed to study the magnetic properties of the ordered TPt (T identical to V, Cr, Mn, Fe, Co and Ni) alloys with CuAu structure within the Hartree-Fock approximation of the Hubbard model for their spin polarisation. Global features of their ground-state magnetic properties such as phase stability and local moments are explained successfully. The characteristic tetragonality of the lattice is argued from the calculated uniaxial pressures to be a consequence of the spin polarisation.

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The thermal oxidations of a sputtered TaN film and the properties of an oxidized TaN (TaNO) film were investigated. By oxidation at around 600°C in dry oxygen, conductive TaN converts into an amorphous insulator which develops, after subsequent annealing at about 800°C, to a mixed compound consisting of main hcp Ta2O5 and amorphous nitride phases. The oxidation is controlled by a diffusion process. Capacitance measurements yield a relative dielectric constant of about 20. The dielectric breakdown strength is more than 2×106 V/cm. The TaNO film was found to be very suitable as a capacitor-forming material for microwave GaAs ICs in conformity with a self-align Au/TaN/WN/GaAs gate FET process.