Abstract: Magnesium oxide, MgO, has a number of features that make it useful in a variety of applications; however, it does not offer protection to magnesium alloys against thermal oxidation. Although the thin oxide films, formed at ambient and elevated temperatures, create a diffusion barrier, they are sensitive to environmental factors and often experience severe damage. The thick oxide morphologies, formed at high temperatures, do not block the outward ion diffusion or, at a certain growth stage, also the inward penetration of gaseous species, leading to nonprotective oxidation. While additions of common alloying elements generally increase the oxidation rate of Mg-based alloys, doping of MgO with reactive-element atoms essentially improves its protective behavior.

Abstract: Compared with rigid glass, manufacturing of Cu(In,Ga)Se2 (CIGS) solar cells on flexible stainless steel (SS) substrates has potential to reduce production cost because of the application of roll-to-roll processing. Up to now, high-efficiency cells on SS could only be achieved when the substrate is coated with a barrier layer (e.g. SiOx or Si3N4) for hindering the diffusion of impurities, especially Fe, into the CIGS layer. In this paper, the effect of these impurities on the electronic transport properties of the device is investigated. Using admittance spectroscopy, the presence of a deep defect level at around 320 meV is observed, which deteriorates the efficiency of the solar cells. Furthermore, it is shown that reducing substrate temperature during CIGS deposition is an effective alternative to a barrier layer for reducing diffusion of detrimental Fe impurities into the absorber layer. By applying a CIGS growth process for deposition at low substrate temperatures, an efficiency of 17.7%, certified by Fraunhofer Institute ISE, Freiburg, was achieved on Mo/Ti-coated SS substrate without an additional metal-oxide or metal-nitride impurity diffusion barrier layer. Copyright © 2012 John Wiley & Sons, Ltd.

Abstract: Semiconductor devices and a methods of fabricating the semiconductor devices are provided. The methods may include forming a pattern on a substrate, forming a capping dielectric layer on the pattern, and thermally processing the substrate. After thermally processing the substrate, the methods may further include forming a diffusion barrier layer by a nitride process that may include supplying nitrogen to the capping dielectric layer. The methods may also include forming an etching stop layer on the diffusion barrier layer, forming an inter-layer dielectric layer on the etching stop layer, and planarizing the inter-layer dielectric layer.

Abstract: A new beta gamma TiAl–4Nb–3Mn alloy was synthesized by powder metallurgy (PM) and coated with NiCrAlY powder by Air Plasma Spray (APS). The cyclic oxidation behavior of the coated beta gamma alloy was investigated between room temperature and 1000 °C for up to 800 cycles. During cyclic oxidation testing, a TiN layer formed at the interface between NiCrAlY and TiAl–4Nb–3Mn and the thickness of the TiN layer increased with the number of cycles. The outward Ti diffusion also resulted in the formation of titanium oxides on the coating top surface after 630 cycles. Inward diffusion of Ni led to the formation of an inner diffusion zone containing NiAlTi and a mixture of NiAlTi + TiAl. Due to the spallation of coating scales on the circumferential surface, weight loss was observed after 120 cycles although both the top and bottom surfaces of the specimens remain in contact with the substrate until 800 cycles. Due to inward and outward diffusion, half of the NiCrAlY coating was consumed after 800 cycles suggesting the need for diffusion barrier coating at the interface between the NiCrAlY coating and the TiAl–4Nb–3Mn alloy.

Abstract: Through-silicon vias (TSV) will speed up interconnections between chips. Manufacturable and cost-effective TSVs will allow faster computer systems. In this paper, we report the successful formation of seed layers for plating copper TSVs with aspect ratios greater than 25:1. Following the rapid atomic layer deposition (ALD) of a conformal insulating layer of silica inside the silicon vias, manganese nitride (Mn4N) is deposited conformally on the silica surface by chemical vapor deposition (CVD). Mn4N forms an effective copper diffusion barrier and provides strong adhesion between the silica and the subsequently-deposited copper. Conformal copper or copper-manganese alloy films are then deposited by an iodine-catalyzed direct-liquid-injection (DLI) CVD process. Diffusion of manganese during post-deposition annealing further enhances the barrier and adhesion properties at the copper/dielectric interface.

Abstract: Good ohmic contacts with low contact resistance, smooth surface morphology, and a well-defined edge profile are essential to ensure optimal device performances for the AlGaN/GaN high electron mobility transistors [HEMTs]. A tantalum [Ta] metal layer and an SiNx thin film were used for the first time as an effective diffusion barrier and encapsulation layer in the standard Ti/Al/metal/Au ohmic metallization scheme in order to obtain high quality ohmic contacts with a focus on the thickness of Ta and SiNx. It is found that the Ta thickness is the dominant factor affecting the contact resistance, while the SiNx thickness affects the surface morphology significantly. An optimized Ti/Al/Ta/Au ohmic contact including a 40-nm thick Ta barrier layer and a 50-nm thick SiNx encapsulation layer is preferred when compared with the other conventional ohmic contact stacks as it produces a low contact resistance of around 7.27 × 10-7 Ω·cm2 and an ultra-low nanoscale surface morphology with a root mean square deviation of around 10 nm. Results from the proposed study play an important role in obtaining excellent ohmic contact formation in the fabrication of AlGaN/GaN HEMTs.

Abstract: U-Mo alloys are being developed as low-enrichment uranium fuels under the Reduced Enrichment for Research and Test Reactor (RERTR) program. Significant reactions have been observed between U-Mo fuels and Al or Al alloy matrix. Refractory metal Zr has been proposed as barrier material to reduce the interactions. In order to investigate the compatibility and barrier effects between U-Mo alloy and Zr, solid-to-solid U-10wt.%Mo versus Zr diffusion couples were assembled and annealed at 600, 700, 800, 900, and 1000 °C for various times. The microstructures and concentration profiles due to interdiffusion and reactions were examined via scanning electron microscopy and electron probe microanalysis, respectively. Intermetallic phase Mo2Zr was found at the interface, and its population increased when annealing temperature decreased. Diffusion paths were also plotted on the U-Mo-Zr ternary phase diagrams with good consistency. The growth rate of interdiffusion zone between U-10wt.%Mo and Zr was also calculated under the assumption of parabolic diffusion and was determined to be about 103 times lower than the growth rate of diffusional interaction layer found in diffusion couples U-10wt.%Mo versus Al or Al-Si alloy. Other desirable physical properties of Zr as barrier material, such as neutron adsorption rate, melting point, and thermal conductivity, are presented as supplementary information to demonstrate the great potential of Zr as the diffusion barrier for U-Mo fuel systems in RERTR.

Abstract: The insertion of chemically vapor deposited graphene layers between Al metallization and Si substrates and between Au and Ni metal layers on Si substrates is shown to provide a significant reduction in spiking and intermixing of the metal contacts and reaction with the Si, where the bilayer graphene was transferred to the samples after the Cu-foil was etched. The graphene prevents reaction between Al and Si up to the temperatures of 700 °C and the intermixing of Au and Ni up to the temperatures of at least 600 °C. The outstanding performance of the graphene as a metal diffusion barrier will be very useful to improve the stability of the metallizations at elevated temperatures.

Abstract: Various embodiments provide semiconductor devices including a package structure and methods of forming the semiconductor devices. In one embodiment, the package structure can include a through-hole at least partially filled by one or more layers of material(s) to form a through-hole interconnect between semiconductor devices in the package structure. The through-hole can be filled by an insulating layer, a diffusion barrier layer, a metal interconnect layer, and/or a protective layer having a total thickness from the sidewall of the through-hole of less than or equal to the radius of the through-hole.

Abstract: A method of forming a fluorine-free tungsten diffusion barrier layer having a reduced resistivity, and a semiconductor device, and method for forming such semiconductor device, using the fluorine-free tungsten diffusion barrier layer.

Abstract: This disclosure relates to a transmission line for high performance radio frequency (RF) applications. One such transmission line can include a bonding layer configured to receive an RF signal, a barrier layer, a diffusion barrier layer, and a conductive layer proximate to the diffusion barrier layer. The diffusion barrier layer can have a thickness that allows a received RF signal to penetrate the diffusion barrier layer to the conductive layer. In certain implementations, the diffusion barrier layer can be nickel. In some of these implementations, the transmission line can include a gold bonding layer, a palladium barrier layer, and a nickel diffusion barrier layer.

Abstract: Bi2Te3 based thermoelectric devices typically use a nickel layer as a diffusion barrier to block the diffusion of solder or copper atoms from the electrode into the thermoelectric material. Previous studies have shown degradation in the efficiency of these thermoelectric devices may be due to the diffusion of the barrier layer into the thermoelectric material. In this work, Ni, Co, Fe, and Mn are intentionally doped into Cu0.01Bi2Te2.7Se0.3 in order to understand their effects on the thermoelectric material. Thermoelectric transport properties including the Seebeck coefficient, thermal conductivity, electrical resistivity, carrier concentration, and carrier mobility of Cu0.01Bi2Te2.7Se0.3 doped with 2 atomic percent M (M = Ni, Co, Fe, Mn) as Cu0.01Bi2Te2.7Se0.3M0.02 are studied in a temperature range of 5-525 K. It is seen that the introduction of Ni, Co, Fe, or Mn does not affect the overall figure of merit, and therefore demonstrates that the diffusion barrier is not leading to device degradation as pre...

Abstract: Dissociative chemisorption of H2 on the Al surface is a crucial step in the regeneration of promising hydrogen-storage materials such as alane and alanates. We show from first-principles calculations that transition metals such as V and Nb can act as effective catalysts for H2 interaction with Al(100). When located at subsurface sites, V and Nb can reduce the activation barrier for H2 dissociation by significantly larger values than the well-studied catalyst Ti. In addition, the binding energy of a H atom on the surface can be enhanced by as much as 0.4 eV when V or Nb is introduced in the sublayers of Al(100). The diffusion barrier for the adsorbed hydrogen is reduced by ∼0.1 eV, showing an increased hydrogen mobility. The mechanism of promoting the metal surface reactivity by subsurface alloying with transition metals proposed in this work may serve as a new possible scheme for catalytic reactions on the metal surface.

Abstract: MnO/MnSiO3-based layers were formed on porous SiCOH low-k dielectrics by Chemical Vapor Deposition (CVD) of Mn from Bisethylcyclopentadienyl manganese. The oxide phase formation is driven by the moisture desorbing from the low-k films. The silicate phase is defined by silanol groups chemisorbed on the low-k surface. The experimental results suggest that formation of thin Mn-based copper diffusion barrier (pore sealing) by CVD is limited to dielectrics having a pore size smaller than the Mn precursor molecules. In the case of larger pore sizes, Mn is deposited inside the dielectric on the pores surface and the layer cannot be a diffusion barrier. © 2012 The Electrochemical Society. [DOI: 10.1149/2.006206esl] All rights reserved.

Abstract: We investigate the stability, diffusion, and impurity concentration of nitrogen in intrinsic tungsten single crystal employing a first-principles method, and find that a single nitrogen atom is energetically favourable for sitting at the octahedral interstitial site. A nitrogen atom prefers to diffuse between the two nearest neighboring octahedral interstitial sites with a diffusion barrier of 0.72 eV. The diffusion coefficient is determined as a function of temperature and expressed as D(N) = 1.66 × 10−7 exp(−0.72/kT). The solubility of nitrogen is estimated in intrinsic tungsten in terms of Sieverts' law. The concentration of the nitrogen impurity is found to be 4.82 × 10−16 A−3 at a temperature of 600 K and a pressure of 1 Pa. A single nitrogen atom can easily sit in an off-vacancy-centre position close to the octahedral interstitial site. There exists a strong attraction between nitrogen and a vacancy with a large binding energy of 1.40 eV. We believe that these results can provide a good reference for the understanding of the behaviour of nitrogen in intrinsic tungsten.