Ru Barrier Research Articles

Thermal and Electrical Properties of PVD Ru(P) Film as Cu Diffusion Barrier

Thermal and electrical properties of physical vapor deposition (PVD) Ru(P) film deposited on porous ultra low-k (p-ULK) material as Cu diffusion barrier were studied. The phosphorous concentration can be tuned by adjusting Ar to PH 3 ratio of the sputtering gases. The leakage current depends on phosphorous concentration. Higher phosphorous content in Ru film has lower leakage current. No obvious phosphorous content dependence was observed when the amorphous Ru(P) film crystallized. The X-ray diffraction (XRD) graphs and energy dispersive spectrometer’s (EDS) atomic depth profiles show that the Ru(P) film deposited on p-ULK can effectively block Cu diffusion when the sample is subjected to 800 °C 5 min annealing. The phosphorous doped Ru film improves diffusion barrier properties and leakage current performance. The improved Ru(P) barrier capable of direct Cu plating could be a potential candidate for advanced metallization.

Galvanic Corrosion Control in Chemical Mechanical Polishing of Cu Interconnects with Ruthenium Barrier Metal Film

We investigated galvanic corrosion in Cu interconnects with ruthenium (Ru) barrier metal films that occurred in Cu chemical mechanical polishing (CMP) and Ru-CMP steps. When conventional CMP slurries were used in the same polishing conditions, severe dishing was found to occur in Ru barrier interconnects. This dishing was attributed to the electrochemical potential difference between Cu and Ru in the CMP slurries. Thus, we reduced this potential difference in the slurry from 400 to 2 mV, and we suppressed dishing just after Cu-CMP from 27 to 9 nm. As a result, by using Ru slurry with a controlled corrosion potential, we minimized final dishing after Ru-CMP to 25 nm which was lower than that of conventional Ta barrier interconnects.

Phosphorous doped Ru film for advanced Cu diffusion barriers

Copper diffusion barrier properties of phosphorous doped Ru film are studied. Phosphorous out-diffusion to Ru from underneath phosphosilicate glass (PSG) layer results in P doped Ru film. The doped Ru film improves copper barrier properties and has excellent thermal stability. XRD graph indicates that there is no copper silicide and ruthenium silicide formations after annealing at 550 °C for 30 min in vacuum. This result is consistant with AES depth profiles which show no Cu, Ru, O and Si inter-diffusion. The phosphorous doped Ru barrier also blocks oxygen's diffusion to copper from the PSG layer. The phosphorous doped Ru film could be an alternative Cu diffusion barrier for advanced Cu interconnects.

Study of Ru barrier failure in the Cu/Ru/Si system

The reaction mechanisms and related microstructures in the Cu/Si, Ru/Si, and Cu/Ru/Si metallization system were studied experimentally. With the help of sheet resistance measurements, x-ray diffraction, field-emission scanning electron microscopy, secondary ion mass spectroscopy, and transmission electron microscopy, the metallization structure with Ru barrier layer was observed to fail completely at temperatures around 700 °C, regardless of the Ru thickness because of the formation of polycrystalline Ru2Si3 followed by Cu3Si protrusions.

Highly (110)- and (111)-oriented BiFeO3 films on BaPbO3 electrode with Ru or Pt∕Ru barrier layers

Highly (110)- and (111)-oriented BiFeO3 (BFO) films were fabricated with BaPbO3 (BPO)∕Ru and BPO∕Pt∕Ru as electrode/barrier on Si substrates by rf-magnetron sputtering. The BPO∕Ru and BPO∕Pt∕Ru stacks both induce oriented BFO films and act as diffusion barriers. The (110)- and (111)-oriented BFO films possess excellent ferroelectric properties with only minor leakage. The values of remnant polarization are almost the same, about 42μC∕cm2, for (110)- and (111)-oriented BFO films. However, polarization measured under varying pulse widths demonstrates that the switching polarization in (111)-oriented BFO films is higher than in (110)-oriented films. Additionally, (111)-oriented BFO films exhibit better retention properties than (110)-oriented films.

Simulation and Experimental Results for Copper Deposition in a Moving Wafer Tool to Minimize Terminal Effects

Copper electrodepositon onto 200 mm silicon wafers containing a 30 nm ruthenium (Ru) barrier layer was studied using a novel horizontal research grade wafer processing tool. The wafer processing tool incorporates a virtual anode and a wafer holder that varies the wafer position vertically relative to the virtual anode opening during the plating process. The ability to change the distance between the wafer substrate and the virtual electrode opening during the plating process enables improved control of the dynamic current distribution across the wafer surface. The effect of the wafer position and wafer movement on the current distribution during the copper deposition process onto resistive Ru barrier layers is examined using numerical analysis. Experimental data for copper deposition onto the Ru barrier layer is compared with the simulation results.

Electrodeposition of Cu on Ru Barrier Layers for Damascene Processing

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Seedless Copper Electrochemical Deposition on Ultra-Thin Air Exposed TaN and Ru Barrier Layers

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Materials Characterization of Seedless Copper Electrochemical Deposition on Ultra-Thin Air Exposed TaN and Ru Barrier Layers

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Electrodeposition of Cu on Ru Barrier Layers for Damascene Processing

Superfilling of submicrometer trenches by direct copper electrodeposition onto physical vapor deposited and atomic layer deposited Ru barriers is demonstrated. The Cu nucleation and growth mode is found to be sensitive to the oxidation state of the Ru surface as well as the copper deposition parameters. Depending on the processing conditions, Cu deposition may or may not occur competitively with oxide reduction. Failure to remove the air-formed 3D oxide film results in Volmer-Weber (island) growth and consequently poor trench filling, as well as poor adhesion between Cu and Ru. In the case of thin resistive oxide-covered Ru seed layers, the “terminal effect” further exacerbates the difficulties in obtaining a compact, fully coalesced Cu film because the rate of Ru oxide reduction is decreased along with the density of Cu nuclei. In contrast, Cu deposition on a reduced “oxide-free” Ru surface results in more rapid coalescence involving the formation of a wetting Cu underpotential deposition layer. Electrochemical reduction of the oxidized Ru seed layer in a deaerated sulfuric acid solution, followed by rapid wet transfer to a Cu plating bath, enables robust superfilling of trenches and improved adhesion between Cu and Ru. Early film coalescence is favored by deposition at high overpotentials.

5 nm ruthenium thin film as a directly plateable copper diffusion barrier

Interfacial stability of electroplated copper on a 5nm ruthenium film supported by silicon, Cu∕(5nmRu)∕Si, was investigated using Rutherford backscattering and high-resolution analytical electron microscopy. Transmission electron microscopy (TEM) imaging shows that a 5nm Ru film is amorphous in contrast to the columnar microstructures of thicker films (20nm). Direct Cu plating on a 5nm Ru film yielded a homogeneous Cu film with over 90% plating efficiency. It is demonstrated that 5nm Ru can function as a directly plateable Cu diffusion barrier up to at least 300°C vacuum anneal. TEM reveals an interlayer between Ru∕Si, which expands at the expense of Ru upon annealing. Electron energy loss spectroscopy analyses show no oxygen (O) across the Cu∕(5nmRu)∕Si interfaces, thereby indicating that the interlayer is ruthenium silicide (RuxSiy). This silicidation is mainly attributed to the failure of the ultrathin Ru barrier at the higher annealing temperature.

Diffusion Studies of Copper on Ruthenium Thin Film

Diffusion studies were carried out on physical vapor deposited Cu/Ru(∼20 nm)/Si samples using secondary ion mass spectroscopy (SIMS) and transmission electron microscopy (TEM). Back side SIMS depth profiling revealed well-defined interfaces and showed that Cu interdiffusion was impeded by Ru thin film up to 450°C vacuum annealing. TEM showed a 20-22 nm Ru barrier layer with a columnar microstructure oriented vertically with respect to Si substrate. TEM results corroborate with SIMS data to indicate stability of the Ru film barrier for annealing temperatures up to 450°C. Direct Cu electroplating on ultrathin Ru barrier layers (<20 nm) was investigated in sulfuric acid. The electroplated Cu film is shiny, smooth, and without agglomeration under scanning electron microscopy. Excellent adhesion between interfacial layers was confirmed by the scribe-peel test. The interfacial characterization results indicate that Ru thin film is a promising candidate as a directly plateable Cu diffusion barrier.

Enhancement of EUV Reflective Multilayer Properties by the Insertion of a Ru Barrier Layer

Enhancement of EUV Reflective Multilayer Properties by the Insertion of a Ru Barrier Layer

Enhancement of Extreme Ultraviolet Reflective Multilayer Properties by the Insertion of Ru Barrier Layer

Extreme ultraviolet (EUV) reflective multilayers that contain a Ru barrier layer at the Mo-on-Si interface were deposited by multitarget magnetron sputtering. The microstructure, stacking quality, and optical properties of these multilayers were analyzed by X-ray diffraction (XRD), transmission electron microscope (TEM), and EUV reflectometry. The multilayers with a Ru barrier showed a more distinct Ru-on-Si interface and suppressed interfacial mixing during deposition. As a result, the peak reflectivity and Full width at half maximum (FWHM) were improved by 1.7% and 50%, respectively, as compared to the conventional Mo/Si multilayer structure.

Analysis of scattering lengths in Co/Cu/Co and Co/Cu/Co/Cu spin-valves using a Ru barrier.

We use uncoupled Co/Cu/Co and Co/Cu/Co/Cu spin-valve structures with a Ru barrier shifted through the top Co and Cu layer, respectively, to measure the longest of the electron mean free paths in Co and Cu as originally suggested by Parkin. From semiclassical transport calculations and careful analysis of the magnetoresistance data we conclude that the exponential behavior of DG is uniquely related to the longest of the Co and Cu mean free paths under the condition of effective spin-dependent filtering at the interfaces or in the bulk of the Co. In this regime we have compared l long in Co and Cu with bulk conductivities ~}l short 1l long !, yielding no strong evidence for bulk spin-dependent scattering in Co. @S0163-1829~96!02037-1#

Analysis of scattering lengths in Co/Cu spin-valves using a Ru barrier

The giant magnetoresistance of Co/Cu spin-valves containing a shifting Ru barrier has been investigated. The Boltzmann approach has been applied to predict how microscopic scattering lengths may be evaluated from the experiments. From the comparison of these data with the macroscopic conductivity no evidence could be found for a considerable contribution of bulk spin-dependent scattering.

RuO2 Thin Films as Bottom Electrodes for High Dielectric Constant Materials

ABSTRACTRuthenium dioxide (RuO2) thin films are evaluated as bottom electrode for dielectric SrTiO3. It was found that a RuO2 (50nm) / Ru (20nm) barrier layer on a Si substrate is effective as an oxygen barrier layer and as a metal diffusion barrier layer for sputter deposited SrTiO3 films at substrate temperature of 450°C. To test suitability for high temperature processes, RuO2/Ru electrodes were annealed in air at 600°C. 100nm-thiick RuO2 was sufficient to prevent oxygen diffusion. After annealing in the same condition, the leakage current of sputter deposited SrTiO3 (150nm) on RuO2(50nm) / Ru(50nm) was 7.6 × 10 −9 (A/cm2) at 2V.