Abstract: We demonstrate 10 nm half-pitch (HP) Ruthenium interconnects filled by atomic layer deposition (ALD). The resistivity and the cross-sectional area of Ruthenium interconnects were determined via the Matthiessen's rule method. We find that the resistivity of Ru was rather independent of the cross-sectional area of the interconnect, increasing from 12 µΩcm for larger lines to 15–17 µΩcm for cross-sectional areas of 200–300 nm2. 10 nm HP Ru lines showed no electromigration failures at 5 MA/cm2 and 300°C during 1000 hours. Time-dependent dielectric breakdown measurements indicated that Ruthenium does not require a diffusion barrier on both dense and porous low-κ dielectrics.

Abstract: Two-dimensional monolayers are attractive for applications in metal-ion batteries because of their low ion-diffusion barrier and volume expansion. In this work, we carry out a first-principles study on electrochemical and structural properties of two-dimensional (2D) oxide monolayers and investigate their applications in metal-ion batteries. 2D transition-metal oxide monolayers (MO2; M = Mn, Co, and Ni) with various ion-intercalation densities are systematically studied. Our calculations show that Li and Na atoms can easily be transported on the surfaces of the monolayers with low diffusion barriers because of the long binding distance. We find that Li2MO2 and Na2MO2 are stable because of negative intercalation energies and unsaturated specific energies. We show that MnO2 has the lowest diffusion barrier, highest specific capacity, and smallest lattice expansion under Li-intercalation, but lowest cell voltage. We also find that CoO2 shows the largest cell voltages in a wide range of ion-intercalation densities and smallest lattice expansion under Na-intercalation, and NiO2 only gives the highest cell voltage in Li2NiO2 and has the largest volume expansion. We further show that Li and Na atoms in Li2MO2 and Na2MO2 move from stable-adsorption sites to metastable sites on the surfaces of oxide monolayers to reduce lattice expansion, leading to reduced cell voltages. It is expected that metal-ion batteries with particular applications and performances can be achieved in the design of these oxide monolayers.

Abstract: This paper explores the possibility of using Ag paste containing silicon carbide particles (SiC-p) as a novel high-temperature die-attachment solution for the design of power devices. The bonding structure used in this research was composed of silicon dies and a direct bonded copper (DBC) substrate. A SiC-p/microporous Ag composite structure was prepared by sintering a Ag microflake paste containing 2 wt% sub-micron SiC-p under mild conditions (250 °C and 0.4 MPa for 30 min). In addition to the Ag paste, the surface metallization of the DBC substrate was also evaluated in this research. Ag metallization layers deposited by electroplating and sputtering were compared, along with samples also containing a titanium (Ti) diffusion barrier layer between Cu and Ag. The results indicated that the SiC-p-containing Ag sinter paste showed better stability in storage tests than the paste without SiC-p at the temperatures such as 150, 250 and 350 °C. Additionally, the Ti diffusion barrier layer played an active role in preventing the oxidation of Cu and inter-diffusion between Cu and Ag during use at high temperatures exceeding 250 °C. The joint bonded by SiC-p-containing Ag paste on DBC substrate with Ti barrier layer exhibited excellent stability up to 1000 h at 150 and 250 °C.

Abstract: Copper/SiO2/Si metal-oxide-semiconductor (MOS) devices both with and without a MnSiO3 barrier layer at the Cu/SiO2 interface have been fabricated in an ultrahigh vacuum X-ray photoelectron spectroscopy (XPS) system, which allows interface chemical characterization of the barrier formation process to be directly correlated with electrical testing of barrier layer effectiveness. Capacitance voltage (CV) analysis, before and after tube furnace anneals of the fabricated MOS structures showed that the presence of the MnSiO3 barrier layer significantly improved electric stability of the device structures. Evidence of improved adhesion of the deposited copper layer to the MnSiO3 surface compared to the clean SiO2 surface was apparent both from tape tests and while probing the samples during electrical testing. Secondary ion mass spectroscopy (SIMS) depth profiling measurements of the MOS test structures reveal distinct differences of copper diffusion into the SiO2 dielectric layers following the thermal anneal d...

Abstract: The initial oxidation process of the Ti(0001) surface is investigated based on the diffusion of oxygen with a potential barrier by first-principles methods. The results show that oxygen molecules can dissociate freely at the Ti surface without an energy barrier and oxygen atoms are chemisorbed on the face-centered cubic (FCC) site of the surface. At low oxygen coverage on the surface, the nearest-neighbor oxygen can assist the diffusion of oxygen from the surface into the sublayer, due to the decrease in the energy barrier. Based on the analysis of the adsorption energy and diffusion barrier, the double-layer model of oxygen adsorption is proposed. With this model, the change in work function is analyzed by following the increase in adsorbed oxygen from 0 to 200%, and is consistent with the experimental results.

Abstract: Indium (In) out-diffusion through high-k oxides severely undermines the thermal reliability of the next generation device of III-V/high-k based metal oxide semiconductor (MOS). To date, the microscopic mechanism of In diffusion is not yet fully understood. Here, we utilize angle resolved X-ray photoelectron spectroscopy (ARXPS) and density functional theory (DFT) to explore In diffusion in high-k oxide HfO2. Our ARXPS results confirm the In diffusion through as-prepared and annealed HfO2 grown on InP substrate. The theoretical results show that the In diffusion barrier is reduced to ∼0.88 eV in the presence of oxygen vacancies (VO), whereas this barrier is as high as ∼4.78 eV in pristine HfO2. Fundamentally, we found that the high feasibility of In diffusion is owing to In nonbonding with its neighboring atoms. These findings can be extended to understand the In diffusion in other materials in addition to HfO2.

Abstract: It is known that individual metal atoms on insulating ionic films can occur in several different (meta)stable charge states, which can be reversibly switched in a controlled fashion. Here we show that the diffusion of gold adatoms on NaCl thin films depends critically on their charge state. Surprisingly, the anionic species has a lower diffusion barrier than the neutral one. Furthermore, for the former we observe that the diffusion atop a bilayer of NaCl is strongly influenced by the interface between NaCl and the underlying copper substrate. This effect disappears for a trilayer of NaCl. These observations open the prospect of controlling the diffusion properties of individual metal atoms on thin insulating films.

Abstract: To enable the continued scaling of integrated circuits, the semiconductor industry faces ongoing struggles to implement better low-dielectric-constant (low-k) materials within the interconnect system. One of the biggest challenges to integrating new dielectrics is overcoming the low-k death curve—that is, the fatal falloff in mechanical properties associated with the low material densities required to achieve low k values. It is shown that amorphous hydrogenated boron carbide (a-BC:H) films exhibit Young's modulus (E) values between two and ten times greater than those of state-of-the-art Si-based dielectric materials across a wide range of k values. In particular, optimized a-BC:H films with moderate k values in the range of 3–4, in addition to possessing outstanding stiffness (E ≈ 100–150 GPa), simultaneously exhibit excellent electrical properties (leakage current of 5 MV cm–1). Films in this range also demonstrate resistance to Cu diffusion to at least 600 °C, as well as chemical stability and etch properties suitable for low-k diffusion barrier/etch stop applications.

Abstract: Memory stack structures are formed through an alternating stack of insulating layers and sacrificial material layers. Backside recesses are formed by removal of the sacrificial material layers selective to the insulating layers and the memory stack structures. An electrically conductive, amorphous barrier layer can be formed prior to formation of a metal fill material layer to provide a diffusion barrier that reduces fluorine diffusion between the metal fill material layer and memory films of memory stack structures. The electrically conductive, amorphous barrier layer can be an oxygen-containing titanium compound or a ternary transition metal nitride.

Abstract: We disclose a method of applying a sculptured layer of material on a semiconductor feature surface using ion deposition sputtering, wherein a surface onto which the sculptured layer is applied is protected to resist erosion and contamination by impacting ions of a depositing layer. A first protective layer of material is deposited on a substrate surface using traditional sputtering or ion deposition sputtering, in combination with sufficiently low substrate bias that a surface onto which the layer is applied is not eroded away or contaminated during deposition of the protective layer. Subsequently, a sculptured second layer of material is applied using ion deposition sputtering at an increased substrate bias, to sculpture a shape from a portion of the first protective layer of material and the second layer of depositing material. The method is particularly applicable to the sculpturing of barrier layers, wetting layers, and conductive layers upon semiconductor feature surfaces.

Abstract: For double MgO-based p-MTJ spin-valves with a top Co2Fe6B2 free layer ex-situ annealed at 400 °C, the insertion of a nanoscale-thickness Fe diffusion barrier between the tungsten (W) capping layer and MgO capping layer improved the face-centered-cubic (f.c.c.) crystallinity of both the MgO capping layer and tunneling barrier by dramatically reducing diffusion of W atoms from the W capping layer into the MgO capping layer and tunneling barrier, thereby enhancing the TMR ratio and thermal stability (Δ). In particular, the TMR ratio was extremely sensitive to the thickness of the Fe barrier; it peaked (154%) at about 0.3 nm (the thickness of only two atomic Fe layers). The effect of the diffusion barrier originated from interface strain.

Abstract: The authors investigate the interdiffusion damage of Cu/TiN stacks deposited on Si(001) substrates by low-temperature unbalanced direct current magnetron sputtering. Pristine and diffusion-annealed samples are examined by x-ray diffraction, four-point-probe resistivity measurements, scanning electron microscopy, energy-dispersive x-ray spectroscopy, and atom probe tomography. Two relevant diffusion processes are identified. The local diffusion of Cu through defects and grain boundaries in the TiN layer leads to the formation of the η″-Cu3Si phase at the barrier/substrate interface. Three-dimensional reconstructions obtained by atom probe tomography additionally reveal the outward diffusion of Si atoms from the substrate through the TiN bulk toward the Cu top layer, eventually also resulting in the formation of a discontinuous Cu3Si surface layer.

Abstract: The ability to precisely control interfaces of atomic layer deposited (ALD) zinc oxysulfide (Zn(O,S)) buffer layers to other layers allows precise tuning of solar cell performance. The O K- and S K-edge X-ray absorption near edge structure (XANES) of ∼2–4 nm thin Zn(O,S) films reveals the chemical and structural influences of their interface with ZnO, a common electrode material and diffusion barrier in solar cells. We observe that sulfate formation at oxide/sulfide interfaces is independent of film composition, a result of sulfur diffusion toward interfaces. Leveraging sulfur’s diffusivity, we propose an alternative ALD process in which the zinc precursor pulse is bypassed during H2S exposure. Such a process yields similar results to the nanolaminate deposition method and highlights mechanistic differences between ALD sulfides and oxides. By identifying chemical species and structural evolution at sulfide/oxide interfaces, this work provides insights into increasing thin film solar cell efficiencies.

Abstract: The amorphous W/WN bi-layer with excellent thermal stability was successfully prepared by hot-filament chemical vapor deposition method on SiO2/Si substrate. It was found that the W/WN bi-layer is technological importance because of its low resistivity and good diffusion barrier properties between Cu and Si up to 700 °C for 30 min. The thermal stability was evaluated by X-ray diffractometer (XRD) and scanning electron microscope. The XRD results show that the Cu3Si phase was formed by Cu diffusion through W/WN barrier for the 800 °C annealed sample. The formation of the Cu–Si compounds denotes the failure of the W/WN diffusion barrier with rapid increase in sheet resistance of the film. The microstructure of the interface between W/WN and Cu reflects the stability and breakdown of the barriers. The failure of this amorphous barrier occurs with heat treatment when the deposited amorphous barrier material crystallizes. The major part of Cu diffusion in polycrystalline structure with disordered grain boundaries is controlled by grain boundaries. AFM results indicated a rapid increase in surface roughness at the diffusion barrier failure temperature. It was found that the grain size plays an important factor to control the thermally stability of the W/WN bi-layer.

Abstract: A novel approach to prepare a coating system containing an in situ grown Cr2O3 diffusion barrier between a nickel top layer and 310SS was reported. Cold spraying was employed to deposit Ni(O) interlayer and top nickel coating on the Cr-contained stainless steel substrate. Ni(O) feedstock was prepared by mechanical alloying of pure nickel powders in ambient atmosphere, acting as an oxygen provider. The post-spray annealing was adopted to grow in situ Cr2O3 layer between the substrate and nickel coating. The results revealed that the diffusible oxygen can be introduced into nickel powders by mechanical alloying. The oxygen content increases to 3.25 wt.% with the increase of the ball milling duration to 8 h, while Ni(O) powders maintain a single phase of Ni. By annealing the sample in Ar atmosphere at 900 °C, a continuous Cr2O3 layer of 1-2 μm thick at the interface between 310SS and cold-sprayed Ni coating is formed. The diffusion barrier effect evaluation by thermal exposure at 750 °C shows that the Cr2O3 oxide layer effectively suppresses the outward diffusion of Fe and Cr in the substrate effectively.

Abstract: This work deals with a double-layer coating for the corrosion protection of stainless steel (SS) structures used in molten fluoride salt reactors for energy production. It aims to mitigate the dissolution of chromium from stainless steel structures into the molten salts. On 304SS substrates, three coating layers consisting of NiCoCrAlY, Ni(O), and the nickel layer on the top were deposited by cold spraying. The Ni(O) coating was made by using a powder containing active oxygen and prepared by mechanical-alloyed pure Ni powders in ambient atmosphere. The Al 2 O 3 diffusion barrier was evolved by annealing the cold-sprayed coating system in argon at temperatures ranging from 800 to 1000 °C at the interface between NiCoCrAlY and Ni(O) layers. During the annealing, the Al 2 O 3 layer formed with a growth following a parabolic law, resulting from the reaction of the oxygen in the Ni (O) layer with the aluminium in the NiCoCrAlY layer. The coating test conducted at 900 °C for 100 h in argon showed that the Al 2 O 3 layer changed little during annealing and could effectively prevent the diffusion of Fe and Cr from the SS substrate to the upper Ni layer.