Atomic layer deposition has been employed to grow nanowires composed of ZnSe/CdSe superlattices. Growth of the nanowires was initiated using gold nanoparticles and the vapor-liquid-solid mechanism. High-resolution transmission electron microscopy shows that these structures are single crystals and the phase of alternating layers of ZnSe and CdSe is zinc blende. The (111) planes of ZnSe and CdSe are oriented at 60°.

Properties of copper films produced using atomic layer deposition (ALD) were characterized. Composition, morphology, and electrical properties of these films grown on glass, as well as Ta, TiN, and TaN on silicon wafers were examined. The resistivity of films thicker than about 60 nm was near bulk value. Films were deposited using a two-step ALD process in which copper(II)-1,1,1,5,5,5,-hexafluoroacetylacetonate hydrate and water vapor were introduced in the first step and a reducing agent was introduced in a subsequent step. Five reducing agents were evaluated, with the best results obtained using isopropanol or formalin. The optimum deposition temperature with isopropanol was about 260 °C, whereas it was about 300 °C with formalin. These films were also investigated as seed layers for electrodeposition of thicker Cu layers for possible interconnect applications. Excellent fills in high aspect ratio trenches were demonstrated.

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Electrochemical polishing (ECP) of copper using hydroxyethylidenediphosphonic acid (HEDP) has been investigated as an alternative to chemical mechanical polishing (CMP) for integration of low-k dialectrics in microelectronic devices. An optimal copper ECP process produces smooth polishing and a fast removal rate. For this investigation copper anodic polarisation curves in HEDP -phosphoric acid solutions were measured and copper ECP effects in various HEDP -phosphoric acid solutions were examined. Copper surface smoothing effects in various HEDP -phosphoric acid solutions were evaluated with atomic force microscopy. It was shown that HEDP and HEDP -phosphoric acid solutions have polarisation curves with a limited current plateau characteristic of ECP. Twenty to forty per cent of HEDP solutions had a maximum limiting current density of~80 A cm 2 2 . Adding phosphoric acid to HEDP solutions increased the limiting current to a maximum, beyond which further addition caused a decrease. An optimal ECP effect (removal rate1 . 8 mm min 2 1 , 80% reduction in mean roughness) was achieved with a solution of 30HEDPz30H 3 PO 4 z 40H 2 O (vol.-%). A higher removal rate was achieved by decreasing the concentration of phosphoric acid, but this resulted in a reduction of the smoothing effect. SE/455 J. Huo (huoj@ece.ogi.edu) and R. Solanki (solanki@ ece.ogi.edu) are in the