The properties of an Ir ͑5 nm͒ / TaN ͑5 nm͒ stacked layer as a copper diffusion barrier on Si have been investigated. Ir/ TaN bilayer barriers were prepared at room temperature by magnetron sputtering followed by in situ Cu deposition for diffusion tests. Thermal annealing of the barrier stacks was carried out in vacuum at high temperatures for 1 h. X-ray diffraction patterns, cross sectional transmission electron microscopy images, and energy-dispersive spectrometer line scans on the samples annealed at 600°C revealed no Cu diffusion through the barrier. The results indicate that the Ir/ TaN bilayer is an effective diffusion barrier for copper metallization.

RE 5 La, Pr, Tb, Tm, and Y) ceramics prepared by conventional solid-state processing has been examined. The phase and structure analysis was carried out using powder X-ray diffraction (XRD) and transmission electron microscopy. Electron diffraction and Rietveld structure refinement of XRD data indicated that (Sr 2 RE 2 )(RE 6 )(SiO 4 ) 6 O 2 (RE 5 La, Pr, Tb, and Y) has a typical oxyapatite-type structure, A I 4 A II 6 (BO 4 ) 6 O 2 in space group P6 3 /m (No. 176), where the A I site is shared equally and randomly by Sr and RE ions, A II is occupied by RE ions only, and B is occupied by Si. As the metaprism twist angle in this lanthanide series should increase as the size of RE decreases, the unrealistically low metaprsim twist angle for (Sr 2 Tm 2 )(Tm 6 )(SiO 4 ) 6 O 2 suggested that the hexagonal metric of apatite might not be sustained and the symmetry reduced to monoclinic, space group P2 1 /m (No. 11), in order to compensate for the shorter Tm-O bond length. The P2 1 /m model for (Sr 2 Tm 2 )(Tm 6 )(SiO 4 ) 6 O 2 also yields a better fit and improvement in bond valence as compared with P6 3 /m model. P. Davies-contributing editor

The crystal structure and microwave dielectric properties of apatite‐type LiRE9(SiO4)6O2 ceramics (RE = La, Pr, Nd, Sm, Eu, Gd, and Er) have been investigated. The densification of lithium apatites has been greatly improved with the addition of 1 wt% LiF. Selected area electron diffraction and X‐ray diffraction (XRD) Rietveld analysis confirm that these compounds belong to the P63/m (No. 176) space group with hexagonal crystal symmetry. The porosity‐corrected relative permittivity was found to decrease with decreasing ionic polarizability of RE3+ ions. Relationships between the structural parameters and microwave dielectric properties have been examined. The observed variation in the quality factor of LiRE9(SiO4)6O2 + 1 wt% LiF ceramics (RE = La, Pr, and Nd) was correlated with average cation covalency (%). The temperature coefficient of resonant frequency was found to depend on the bond valence sum of cations. LiEr9(SiO4)6O2 + 1 wt% LiF ceramics showed good microwave dielectric properties with εr = 12.8, Qu × f = 13000 GHz and τf = +17 ppm/°C. All the compositions showed low coefficient of thermal expansion with thermal conductivity in the range 1.3–2.8 W (m K)−1.

The tungsten piperidylhydrazido complex Cl 4 ͑CH 3 CN͒W͑N-pip͒ ͑1͒ was used for film growth of tungsten carbonitride ͑WN x C y ͒ by metal-organic chemical vapor deposition ͑CVD͒ in the absence and presence of ammonia ͑NH 3 ͒ in H 2 carrier. The microstructure of films deposited with NH 3 was x-ray amorphous between 300 and 450°C. The chemical composition of films deposited with NH 3 exhibited increased N levels and decreased C levels over the entire deposition temperature range ͑300-700°C͒ as compared to films deposited without NH 3. As determined by x-ray photoelectron spectroscopy, W is primarily bonded to N and C for films deposited at 400°C, but at lower deposition temperature the binding energy of the W-O bond becomes more evident. The growth rates of films deposited with NH 3 varied from 0.6 Å / min at 300°C to 4.2 Å / min at 600°C. Over 600°C, the growth rate decreased when using NH 3 presumably due to parasitic gas phase reactions that deplete the precursor. Diffusion barrier properties were investigated using Cu/ WN x C y / Si stacks consisting of 100 nm Cu deposited at room temperature by reactive sputtering on a 20 nm WN x C y film deposited at 400°C by CVD. X-ray diffraction and cross-sectional transmission electron microscopy were used to determine the performance of the diffusion barrier. Cu/ WN x C y / Si stacks annealed under N 2 at 500°C for 30 min maintained the integrity of both Cu/ WN x C y and WN x C y / Si interfaces.

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