Self-formed Barrier Layer Research Articles

Self-forming barrier layer for carbon dioxide corrosion protection of mild steel in NaCl solution containing hydroxychavicol isolated from Piper betle L. leaf

Hydroxychavicol compound was isolated from Piper betle L. leaf and identified via preparative high performance liquid chromatography (Prep-HPLC) and nuclear magnetic resonance (NMR) spectroscopy. Hydroxychavicol compound was demonstrated to be a potential inhibitor for mild steel corrosion in carbon dioxide-containing environments due to the formation of a barrier layer on the steel surface. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) results indicated that the inclusion of hydroxychavicol in the aggressive environment made steel surfaces more homogeneous and smoother with a rough mean square roughness of 7.78 nm, whereas the steel surface was severely corroded in the blank solution. Moreover, X-ray photoelectron spectroscopy (XPS) results showed an enrichment of hydroxychavicol species combined with iron oxides and hydroxides on the mild steel surface. This can lead to the creation of a protective layer on the mild steel surface, thereby enhancing corrosion protection and localized inhibition. The work suggested a novel approach to isolate corrosion inhibitors from natural products, particularly agricultural by-products for mild steel in carbon dioxide and chloride ion environment with high inhibition performance.

Role of SnO2 Nanoparticles for a Self-Forming Barrier Layer on a Mild Steel Surface in Hydrochloric Acid Medium Containing Piper betle Leaf Extract.

The self-formation of a porous organic thin-film via corrosion inhibitor supports wide applications of carbon steel in industry. Unfortunately, serious damages could be concentrated to the pinhole and/or pore locations in the porous organic film, resulting in the localized corrosion even when an optimal concentration of organic corrosion inhibitors is used. In this work, SnO2 nanoparticles are used for producing the more robust barrier layer via the self-migration of nanoparticles, resulting in a higher corrosion resistance, smooth and uniform protective layer, as well as the existence of SnO2 in the protective layer that could directly affect the high inhibition performance. Therefore, the work suggests a new way to make a more robust thin film that could extend the use of organic corrosion inhibitors.

Effect of Different Ni Contents on Thermal Stability of Cu(Ni) Alloy Film

The effect of doping different contents of Ni on the thermal stability of Cu(Ni) alloy films has been investigated. Cu(Ni) films with different Ni contents were deposited on SiO2/Si substrates by magnetron sputtering, then annealed in vacuum at 350°C to 650°C for 0.5 h. X-ray diffraction analysis and resistance measurements revealed that high-resistance copper silicide was formed after annealing at 450°C for the Cu(Ni, 1.66 at.%) and Cu(Ni, 9.16 at.%) samples. However, no copper silicide was observed for Cu(Ni, 3.59 at.%) even after annealing at 650°C. Transmission electron microscopy provided evidence for a ∼ 25-nm self-formed barrier layer at the Cu/SiO2 interface with Cu(Ni, 3.59 at.%). The failure to form a diffusion barrier for the Cu(Ni, 1.66 at.%) sample resulted from its low Ni doping concentration, which was insufficient to produce such a self-formed layer during annealing. The barrier failure was caused by grain refinement due to the increased Ni content, providing diffusion channels for atom diffusion. The results clearly suggest that addition of an appropriate amount of Ni can improve the thermal stability of Cu(Ni)/SiO2/Si interconnect structure materials.

Co-precipitation of MnO and Cu in an ionic liquid as a first step toward self-formed barrier layers

Mixed MnO–Cu nanoparticles are synthesised in an ionic liquid, and the suspensions are spread and annealed directly on technological substrates to form films suitable for the metallisation of through-Si vias.

Editors' Choice—Interface Engineering Strategy Utilizing Electrochemical ALD of Cu-Zn for Enabling Metallization of Sub-10 nm Semiconductor Device Nodes

A novel interface engineering approach, utilizing electrochemical atomic layer deposition (e-ALD) of Cu(Zn) on a Ru liner, is presented for enabling the metallization of sub-10 nm interconnects in future semiconductor devices. Upon thermal treatment, Zn present in the e-ALD Cu layer at ∼0.8 at.% is shown to diffuse through the Ru liner and react with the SiO2 to form a Zn-silicate layer at the Ru-SiO2 interface. This ‘self-forming’ interfacial layer provides adhesion enhancement to the Ru-SiO2 interface and serves as a diffusion barrier retarding Cu diffusion into the SiO2 layer while enabling void-free gap-filling of high aspect ratio trench structures. Absorption Near-Edge Spectroscopy and Extended X-ray Absorption Fine Structure analyses confirm that the self-formed barrier layer is composed primarily of Zn2SiO4. The interface engineering approach utilizing Cu(Zn) presented herein offers several potential advantages over traditional Mn-based self-forming barrier approaches, i.e., scalability to narrower dimensions and minimal impact to interconnect resistance.

Self-forming barrier layer from CuMnTi alloy layer on SiO2 substrate

Advancement of large-scale integrated interconnect structure requires an ultra-thin and uniform diffusion barrier layer between Cu interconnect and insulating layers. As a promising alternative barrier to the conventional Ta/TaN, the self-forming barrier layer from the CuMnTi alloy layer was investigated in this work. In order to achieve the self-forming barrier layer, the CuMnTi alloy layer first was deposited on SiO2 substrate by magnetron sputtering. Second, the alloying elements were driven and migrated to the interface, and moreover, reacted with SiO2 to form the self-forming barrier layer. The self-forming barrier layer has a thickness of about 5nm. The annealing leads to an obvious decrease of resistivity from 50.10μΩcm to 4.23μΩcm for the CuMnTi alloy layer. The self-forming barrier can improve the adhesion of Cu interconnect layer and effectively prevent element diffusion between Cu interconnect and insulating SiO2 substrate.

A new field-assisted annealing approach for advanced Cu-Zr Alloy metallization

A new field-assisted annealing approach for Cu-Zr alloy metallization is proposed and investigated. Cu-Zr/SiO2/Si samples were vacuum-annealed at pressure of 2 × 10−3 Pa with (−20 V) and without field-assisted annealing for an hour in 250°C–400°C temperature range. Based on the XRD, TEM, XPS, and resistivity measurement results, we conclude that the dragging force for Zr atoms in field-assisted annealing samples to the interface shall be larger than that of samples without field-assisted annealing. As a consequence, by low concentration alloy atoms adding and FAA processing, the low Cu alloy film resistivity and thin self-forming barrier layer can be simultaneously obtained at lower temperature.

Interface Reaction Behavior between Mn and SiO<sub>2</sub> Formed by RF Sputter Deposition

The Present Work Investigated the Effects of Adsorbed Moisture in Substrates on the Growth of a Self-Forming Barrier Layer between Mn and SiO2. In Order to Control the Adsorbed Moisture, the Substrates of TEOS-SiO2/Si Were Pre-Annealed in Vacuum at Various Temperatures. Then, Mn Thin Films Were Deposited on the Substrate with or without Pre-Annealing. The Results of Interface Reaction after Additional Post-Annealing Indicated that an Interface Reaction Layer Becomes Thinner with Decreasing the Adsorbed Moisture in the SiO2Substrates.

Structure Analyses of Ti-Based Self-Formed Barrier Layers

Self-formed Ti-based barrier layer using Cu(Ti) alloy seed applied to 45-nm-node dual-damascene interconnects was reported to have sufficient barrier strength to prevent Cu diffusion into dielectrics. The constituent Ti compounds in the self-formed Ti-based barrier layers and the barrier structures in Cu(Ti)/dielectric samples were identified by X-ray photoelectron spectroscopy (XPS) analyses. Two types of SiOC with low dielectric constants, SiO2, and SiCN were used as dielectrics. The Ti-based barrier layers consisted mainly of amorphous Ti oxides such as TiO2, Ti2O3, and TiO, regardless of the dielectric. In addition to Ti oxides, barrier layers containing TiC, TiSi, and TiN were observed, depending on the dielectric. TiC and TiSi were in crystalline state. They were formed beneath the Cu(Ti) alloy films, and had orientation relationship with the crystalline Cu(Ti) alloy films. The amorphous Ti oxides were formed above the amorphous dielectric layers. The amorphous Ti oxides are believed to be formed continuously above the dielectric layers and prevent Cu diffusion into the dielectric layers.

Structure Analyses of Ti-Based Self-Formed Barrier Layers

Self-formed Ti-based barrier layer using Cu(Ti) alloy seed applied to 45-nm-node dual-damascene interconnects was reported to have sufficient barrier strength to prevent Cu diffusion into dielectrics. The constituent Ti compounds in the self-formed Ti-based barrier layers and the barrier structures in Cu(Ti)/dielectric samples were identified by X-ray photoelectron spectroscopy (XPS) analyses. Two types of SiOC with low dielectric constants, SiO2, and SiCN were used as dielectrics. The Ti-based barrier layers consisted mainly of amorphous Ti oxides such as TiO2, Ti2O3, and TiO, regardless of the dielectric. In addition to Ti oxides, barrier layers containing TiC, TiSi, and TiN were observed, depending on the dielectric. TiC and TiSi were in crystalline state. They were formed beneath the Cu(Ti) alloy films, and had orientation relationship with the crystalline Cu(Ti) alloy films. The amorphous Ti oxides were formed above the amorphous dielectric layers. The amorphous Ti oxides are believed to be formed continuously above the dielectric layers and prevent Cu diffusion into the dielectric layers.

Performance of Cu Dual-Damascene Interconnects Using a Thin Ti-Based Self-Formed Barrier Layer for 28 nm Node and Beyond

With continuous shrinkage of advanced ultralarge scale integrations (ULSI), the impact of line resistance on the devices has become more and more important. In order to achieve low resistance and high reliability of Cu interconnects, we have applied a thin Ti-based self-formed barrier layer using Cu–Ti alloy seed to 45 nm node dual-damascene interconnects and evaluated its performance. The microstructure analysis by transmission electron microscope and energy dispersive X-ray fluorescence spectrometer has revealed that 2-nm-thick Ti-based barrier layer is self-formed at the interface between Cu and low-k dielectrics. The line resistance and via resistance decrease significantly, compared with those of conventional Ta/TaN barrier system. The stress migration performance is also drastically improved using self-formed barrier process. These results suggest Ti-based self-formed barrier process is one of the most promising candidates for advanced Cu interconnects.

Graded composition and valence states in self-forming barrier layers at Cu–Mn/SiO2 interface

A self-forming diffusion barrier (SFB) layer was formed at Cu–Mn/SiO2 interface. Spatial variation of the chemical composition and valence state of the elements in the SFB was investigated in a subnanometer resolution using electron energy loss spectroscopy and transmission electron microscopy. The SFB was found to have a layered structure with graded compositions of nanocrystalline MnO and amorphous MnSiO3. The valence state of Mn was found to be +2 in the MnO layer and gradually increased to +3 in the MnSiO3 layer. The reported dielectric constant of the SFB could be explained by the observed composition and microstructure.

Analysis of dielectric constant of a self-forming barrier layer with Cu–Mn alloy on TEOS-SiO2

A Cu–Mn alloy film was deposited on SiO2 to self-form a diffusion barrier layer of MnOx at their interface. Transmission electron microscopy revealed that the barrier layer was formed not on the Cu alloy side but on the SiO2 side. Capacitance-voltage measurement revealed the decrease in the dielectric constant of the barrier layer from 11.4 to 5.1 with increasing annealing temperature. The obtained results indicated that the self-forming barrier layer with Cu–Mn is an excellent barrier layer without posing any negative influences on the interconnect line resistance and on the insulator capacitance.

Growth kinetics and thermal stability of a self-formed barrier layer at Cu-Mn∕SiO2 interface

A thin diffusion barrier was self-formed by annealing at an interface between a Cu-Mn alloy film and a SiO2 substrate. The growth of the barrier layer followed a logarithmic rate law, which represents field-enhanced growth mechanism in the early stage and self-limiting growth behavior in the late stage. The barrier layer was stable at 450 °C for 100 h and at 600 °C for 10 h. The interface diffusivity was estimated from the morphology change of the barrier layer at 600 °C and was found to be smaller than the grain-boundary diffusivity of bulk Cu.

Growth behavior of self-formed barrier at Cu–Mn∕SiO2 interface at 250–450°C

A diffusion barrier layer was self-formed at the interface between Cu–Mn alloy and tetraethylorthosilicate oxide layers at 250–450°C. No interdiffusion occurred across the self-formed barrier layer during annealing at these temperatures up to 100h. The growth of the barrier layer obeyed a logarithmic law and depended on manganese concentration. The barrier thickness could be controlled in the range of 2–8nm.

Self-forming diffusion barrier layer in Cu–Mn alloy metallization

Advancement of semiconductor devices requires the realization of an ultrathin diffusion barrier layer between Cu interconnect and insulating layers. The present work investigated the possibility of the self-forming barrier layer in Cu–Mn alloy thin films deposited directly on SiO2. After annealing at 450 °C for 30 min, a Mn containing amorphous oxide layer of 3–4 nm in thickness was formed uniformly at the interface. Residual Mn atoms were removed to form a surface oxide layer, leading to a drastic resistivity decrease of the film. No interdiffusion was detected between Cu and SiO2 within the detection limit of x-ray energy dispersive spectroscopy.