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Ru capping process was demonstrated on 48nm-pitch Cu damascene interconnect with area selective deposition technique of Ru CVD. Ru nucleation and film continuity were optimized by process including wet cleaning and dry surface treatments. Physical analysis and line leakage electrical test were conducted to evaluate Ru capping layer for different process conditions.

Historically, complementary metal-oxide-semiconductor (CMOS) technology was driven by geometrical scaling of the front-end-of-line (FEOL) transistor but it has slowed down significantly in recent years. On the other hand, back-end-of-line (BEOL) interconnects are projected to continue scaling aggressively to meet power, performance and area targets in advanced nodes. In this paper, we will introduce and review BEOL interconnect options targeting sub-7nm metal pitch with an emphasis on materials and process technologies.

Fe–Pd alloy films have been prepared by electrochemical deposition from an alkaline electrolyte containing Fe sulfate, Pd chloride and 5-sulfosalicylic acid onto polycrystalline titanium substrates. The as-deposited films were nanocrystalline and magnetically soft (coercivity ∼ 25 Oe). L10 Fe–Pd films with a (1 1 1) preferred orientation were obtained by post-deposition thermal annealing of films with composition about 37 at% Fe in an (Ar + 5% H2) gas flow at 500 °C. Such films exhibit hard magnetic properties, with a coercivity up to 1880 Oe, and a slightly anisotropic magnetic response, with a larger in-plane remanence. Preliminary magnetic investigations support magnetization switching through pinning of domain walls. Keywords: Fe–Pd, Electrodeposition, L10

Adherent copper films were electrochemically grown onto the native oxide surfaces of Si wafers modified by the adsorption of polyamidoamine (PAMAM) dendrimers. Metallic nuclei of copper grow at isolated nucleation sites, associated with adsorbed dendrimers, and film coalescence can be observed above a metal thickness of about 10,000 monolayers (∼2.5 μm). Film microstructure depends on the deposition mode; higher coverage and better adhesion were obtained by galvanostatic control of the deposition process. It is hypothesized that reduction of Cu2+ ions complexed with functional groups of the chemisorbed dendrimer leads to the formation of metallic copper nuclei, and that metal films grow from these nuclei. Further improvement of this process may open the way to the direct integration of metal electrodeposition with silicon microfabrication processes and selective deposition by dendrimer patterning.

Co-rich Co-Pt films (thickness 5 - 1000 nm) were electrodeposited under galvanostatic conditions onto (0001)-oriented ruthenium seed layers. The films grow mainly with a hexagonal close packed structure, with the c axis oriented perpendicular to the film plane. The growth occurs epitaxially on top of the Ru seed, and thin films reproduce the grain size and morphology of the seed layer. Thick films grow with a columnar microstructure; the extent of coarsening of the column diameter depends on the growth rate and becomes negligible for current densities above 50 mA/cm2. The films exhibit a perpendicular magnetic anisotropy, and the magnetic properties depend on thickness and growth rate. Films grown at low rate present lower coercivity; the high coercivity observed in films grown at high rate is attributed to the formation of defects during growth. At large thickness, the magnetic properties are dominated by the demagnetizing fields.

Electrodeposition of epitaxial Fe films on GaAs(001) and GaAlAs (001) substrates prepared using different chemical etching methods was investigated. GaAlAs surfaces etched with 2% ammonia solution can promote the growth of oriented cubes, suggesting the oriented growth of Fe(001). Fe on GaAlAs appears to grow through two different growth modes, which are interpreted as two-dimensional 2D followed by 3D growth. GaAs surfaces etched with HCl present a different nucleation and growth mode from that obtained using ammonia etching. This results in a larger nucleation density and promotes the growth of continuous films and smaller grain sizes.

Electrochemical deposition of materials with hard magnetic properties in the as-deposited state is essential for the efficient integration of micro-magnetic components into MEMS devices. Here we discuss the growth process and the microstructure-magnetic properties correlation for two Co-rich alloys, Co–Ni–P and Co–Pt. Under suitable synthesis conditions, these materials exhibit perpendicular anisotropy and hard magnetic properties in the as-deposited state; in addition, such properties are maintained up to several micrometer film thickness through close control of the film microstructure. In the case of Co–Ni–P films we achieved a saturation magnetization of 1.21 T (963 emu/cm 3 ), perpendicular coercivity up to 188 kA/m (2.36 kOe) at a thickness of 10 μm, and energy products up to 4.2 kJ/m 3 . Co-rich Co–Pt films were grown on several substrates – Cr, Cu(0 0 1), Cu(1 1 1), and Ru(0 0 0 1) – in order to control magnetic anisotropy and achieve optimum hard magnetic properties. Cu(1 1 1) contributes to stabilize the hexagonal hcp phase at high current density yielding excellent hard magnetic properties, although only in films thicker than 100 nm; saturation magnetization in these films was about 1.04 T (828 emu/cm 3 ). Perpendicular coercivities up to 485.6 kA/m (6.1 kOe) were obtained in 1 μm thick film deposited at 50 mA/cm 2 . Ru(0 0 0 1) seed layers provide an appropriate interface structure to further facilitate the epitaxial growth of hcp films, yielding hard magnetic properties and perpendicular coercivity with a squareness ∼1 in films as thin as 10 nm. The hard magnetic properties were only marginally compromised at large film thickness. Deposition at higher current density (50 mA/cm 2 ) favored markedly improved hard magnetic properties. The Co–Pt films on Ru exhibited perpendicular anisotropy with anisotropy constant up to 1.2 MJ/m 3 . The electrodeposition process was further extended to fill lithographically patterned hole arrays (850 nm diameter, center-to-center distance 2550 nm and about 700 nm thick resist), yielding arrays of micron-sized hard magnetic cylinders with perpendicular coercivity of 361 kA/m (4.54 kOe) and high squareness.

An oligo(phenylene ethynylene) (OPE) molecule with a nitro side group has exhibited electrical switching with memory and thus has potential for use in molecular electronic devices. However, different research groups have reported different electrical behaviors for this molecule. In addition to variations among test structures, differences in local molecular environments could be partially responsible for the differences in the reported results. Thus, we tested four variations of a nitro-OPE/dodecanethiol monolayer in the same type of nanowell test device to study how the environment of the nitro-OPE affects the observed electrical behavior. We found that the density of the nitro-containing molecules in the device altered the observed electrical switching behavior. Further, we found a positive correlation between the disorder of the monolayer and the observed electrical switching behavior. This correlation is consistent with suggestions that nitro molecule switching may depend on a conformational change of the molecule, which may be possible only in a disordered monolayer.

In order to realize molecular electronic devices, molecules with electrically interesting behavior must be identified. One molecule that has potential for use in devices is an oligo(phenylene ethynylene) (OPE) molecule with nitro sidegroup(s). These “nitro” molecules have been reported to show electrical switching with memory behavior, as well as negative differential resistance (NDR). However, different research groups testing the nitro molecules in different test beds have observed different electrical behaviors. In this work, we assembled two different nitro monolayers: one completely composed of nitro molecules and the second a mixed matrix where nitro molecules were separated by dodecanethiol molecules. We used scanning tunneling microscopy to image each of the monolayers and observed that the nitro molecules were effectively inserted into the ordered dodecanethiol monolayer. We tested the electrical behavior of the pure monolayer, as well as the mixed monolayer, in our nanowell test device. The nanowell devices were fabricated on micron-size gold lines patterned on oxide-coated silicon wafers. The gold lines were covered with a silicon dioxide layer, through which a nanometer size well was milled. This nanowell device was filled with a self-assembling monolayer of organic molecules, and capped with titanium and gold. The nanowell electrical results showed switching with memory for the pure nitro monolayer, but not for the mixed monolayer. This switching behavior consisted of a molecule starting in a high conductivity state and switching to a low conductivity state upon application of a threshold voltage. The high conductivity state could only be returned by application of an opposite threshold voltage.

We tested the electrical characteristics of an oligo(phenylene ethynylene) (OPE) molecule with one nitro side group, an OPE with two nitro side groups, and an OPE with no nitro side groups in our nanowell device. The OPE molecule with nitro side group(s) showed switching behavior with memory as well as nonreversible negative differential resistance (NDR). Current-voltage (I‐V) characteristics showed a high conductivity state that switched to a low conductivity state upon the application of a threshold voltage. This low state held until the opposite threshold voltage was applied and the device switched back to the high conductivity state. The OPE with no nitro side groups did not show memory or NDR. In this work, we report the complete switching behavior observed including the device yield, average threshold voltage, and the average high to low current ratios.

We report a new organic−inorganic hybrid templating approach to synthesize micrometers-long, 50−230 nm diameter single-crystal nanorods of lead telluride. Lead telluride nanorods were synthesized using tellurium nanotubes as consumable templates. The nanorod aspect ratio is tunable by altering the reaction parameters during tellurium nanotube synthesis

The electrochemical nucleation and growth of Au from a Au sulfite electrolyte onto dodecanethiol-modified Au surfaces is investigated by a combination of microscopy and chronoamperometry methods. The self-assembled dodecanethiol monolayers are continuous but exhibit defects in correspondence of the Au grain boundaries and on top of Au terraces. Nucleation of Au films occurs initially at these defect sites, but only a small fraction of these nuclei survive an initial competition process. The remaining nuclei expand through three-dimensional progressive nucleation followed by diffusion-limited growth. The resulting Au films exhibit microstructures which are widely different from those observed in the electrochemical growth of Au on Au and that depend on the applied potential: while at low overpotentials the film grows as an assembly of hemispherical clusters, at intermediate overvoltages the films are smooth and at high overvoltages become dendritic. Metal growth onto self-assembled monolayer-modified substrates can thus provide an alternative method for controlling film morphology for a wide range of applications.

We report on the synthesis and characterization of nanofibrous structures of vanadium oxide V 2 O 5 by anodic electrodeposition. The electrodeposits are thick layers of several micrometers consisting of fibers with length in the micrometer range and a width of about 10 nm. At variance with available reports, the vanadium oxide nanofibers were obtained without the use of templates or additives. Electrochemical synthesis was performed in aqueous solutions containing VOSO 4 and Na 2 SO 4 . The observed sponge-like structure, and consequent large surface area, with strong entanglement of the nanofibers are potentially important material ' features for applications such as gas sensors, lithium batteries, and catalysis.

We investigate the influence of chloride Cl - ions in a broad range of chloride concentrations on the kinetics and mechanism of copper electrodeposition from sulfate-based acidic electrolytes. Chloride ions influence copper deposition through two competitive effects: at low Cl - concentration (few mM), chloride ions depolarize the Cu reduction process, while higher Cl - concentrations induce complexation of copper species and cause a cathodic polarization of the deposition process. Cu reduction proceeds through two parallel mechanisms, a direct two-step reduction and a chloride-mediated route, whose relative importance depends on the amount of chloride present. A transition between these two mechanisms can be identified both by steady-state and impedance methods; however, the chloride concentration at which it occurs depends on the time scale probed by the two techniques. Impedance measurements further demonstrate that the presence of chlorides changes the double-layer structure.

We present a study of the effect of chloride anion additions on the electrochemical nucleation and growth of copper on n-Si(100) from acidic sulfate solutions. Chloride additions in the millimolar range depolarize copper reduction, while additions in the 100 mM range and above have the opposite effect. Chlorides have no effect on the nucleation and growth mode. Deposition at constant potential in the presence of small amounts of chloride leads to an increased deposition overpotential, but contrary to the predictions of nucleation theory, this results in a lower density of nuclei with larger size. We hypothesize that adsorption of chlorides on the copper islands enhances surface diffusion processes which lead to island coarsening through Ostwald ripening. Morphological changes during deposition are possible at room temperature due to the high values of diffusivities at the electrolyte/ solid interface.

CoNiP alloy films have been grown by electrodeposition from a chloride bath under galvanostatic control. Film growth, structure, composition, magnetic properties, and morphology have been found to depend significantly on deposition current density. Hard magnetic films were successfully grown at the current density of 7 mA/cm 2 with thickness up to 10 μm, at which a perpendicular coercivity of 188 kA/m was achieved. The magnetic hardness and perpendicular anisotropy of these films are the combined result of a microstructure composed of columnar grains and of a hexagonal phase oriented with the c axis perpendicular to the film plane. Preliminary investigations of magnetization reversal processes suggest the presence of pinning sites located probably at grain boundaries.

We present a study of the magnetic properties and magnetization processes in hard Co-Pt (Pt∼20at.%) films. Co-rich Co-Pt films, with thickness t ranging from 5nm up to 2μm, were prepared by electrodeposition on (0001)-oriented Ru underlayers. All samples displayed strong perpendicular magnetic anisotropy and high coercivity. Virgin magnetic domain structures for varying thickness were investigated by magnetic force microscopy (MFM). The observed increase of domain width with film thickness is well understood by full two-dimensional micromagnetic computations with no adjustable parameters. The easy-axis magnetization process, as observed by measuring virgin curves by magnetometry and imaging the corresponding magnetization configurations by MFM in variable field, consists of two stages separated by a well-defined critical field, marking the onset of domain wall propagation. A thorough analysis of the out-of-plane angular dependence of the switching field points out that unpinning of domain walls is the dom...

Co-rich Co–Pt alloys were electrodeposited from an amino-citrate-based solution on a Si (011)∕Cu(111)∕Ru(0001) seed layer. Such a template provides an appropriate interface structure for the growth of a (0002)-oriented hexagonal phase, stabilized at larger thickness by the electrolyte chemistry, providing for a columnar structure with no detectable grain coarsening. This results in as-deposited Co–Pt films exhibiting perpendicular anisotropy (anisotropy constant up to 1.2MJ∕m3) and hard magnetic properties (coercivity up to 358.2kA∕m) in a wide thickness range, from 5to2000nm. Crystalline, magnetoelastic, and interface effects are discussed as possible origins of the observed perpendicular anisotropy.

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Co-rich Co–Pt films were grown by electrodeposition from an amino-citrate based electrolyte on Si(011)∕Cu(111)∕Ru(0001) templates. The Ru(0001) surface provides an interface which induces the growth of an oriented hexagonal phase, thereby yielding hard magnetic properties and perpendicular anisotropy in films as thin as 10nm. Increase in film thickness only marginally compromises the hard magnetic properties probably due to the limited coarsening of the microstructure, oriented columnar growth, and magnetic grain isolation. The deposition current density plays an important role in optimizing microstructure and hard magnetic properties. Perpendicular squareness close to 1 and coercivities as high as 4.5kOe were obtained in thin as-deposited Co–Pt films.

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Co-Pt (Pt ∼ 20 atom %) alloy films were electrochemically grown at constant current density on Cr seed layers in order to study the influence of the Cr surface on their morphology and magnetic properties. The Cr seed layer favors the growth of a hexagonal close-packed phase, as revealed by X-ray diffraction. Morphological investigation using a scanning electron microscope revealed the electrocrystallization of Co-Pt on Cr to be proceeding through the nucleation and growth of three-dimensional (3D) clusters with columns growing outward in all directions from isolated nucleation centers. The 3D growth is likely due to the presence of a thin oxide layer on the Cr seed. At lower current density, individual micrometer-sized clusters were formed with distinct hexagonally shaped faces. Increasing current density results in a finer grain microstructure. At early stages of growth and low current density, the clusters exhibit a faceted morphology similar to that of the substrate. Samples prepared at higher current density or with larger thickness show larger coercivities, reaching values as high as 3490 Oe (278 kA/m) and 2275 Oe (181 kA/m) in the perpendicular and parallel directions, respectively, for a 500-nm-thick film deposited at 50 mA/cm 2 .