Abstract: Thin films formed by atomic layer deposition (ALD) are being examined for a variety of chemical protection and diffusion barrier applications, yet their stability in various fluid environments is not well characterized. The chemical stability of titania and alumina thin films in air, 18 MΩ water, 1 M KCl, 1 M HNO3, 1 M H2SO4, 1 M HCl, 1 M KOH, and mercury was studied. Films were deposited at 150 °C using trimethylaluminum-H2O and tetrakis(dimethylamido)titanium-H2O chemistries for alumina and titania, respectively. A subset of samples were heated to 450 and 900 °C in inert atmosphere. Films were examined using spectroscopic ellipsometry, atomic force microscopy, optical microscopy, scanning electron microscopy, and X-ray diffraction. Notably, alumina samples were found to be unstable in pure water, acid, and basic environments in the as-synthesized state and after 450 °C thermal treatment. In pure water, a dissolution-precipitation mechanism is hypothesized to cause surface roughening. The stability of alumina films was greatly enhanced after annealing at 900 °C in acidic and basic solutions. Titania films were found to be stable in acid after annealing at or above 450 °C. All films showed a composition-independent increase in measured thickness when immersed in mercury. These results provide stability-processing relationships that are important for controlled etching and protective barrier layers.

Abstract: Using first-principles calculations and molecular dynamics simulations, we theoretically explored the potential applications of hexagonal boron nitride (h-BN) for H2/CH4 separation. The h-BN with appropriate pores possesses excellent H2/CH4 selectivity (>105 at room temperature). Furthermore, the adsorption energies (0.1 eV more or less) of both H2 and CH4 on the designed monolayer membranes are sufficiently low to prevent the blocking of the nanopores in a realistic separating process. Particularly, we demonstrate a highly promising membrane (h-BN with a triangular pore and a N9H9 rim) with a calculated diffusion barrier of 0.01 eV for H2 diffusion, and the simulated flux of H2 across the single layer is as large as 4.0 × 107 GPU at 300 K. Additionally, the estimated permeability of H2 significantly exceeds the industrially accepted standard for gas separation over a broad temperature range. Therefore, our results suggest that porous boron nitride nanosheets will be applicable as new membranes for gas se...

Abstract: A semiconductor diode includes a first semiconductor pattern including a first impurity, a first diffusion barrier pattern on the first semiconductor pattern, an intrinsic semiconductor pattern on the first diffusion barrier pattern, a second diffusion barrier pattern on the intrinsic semiconductor pattern, and a second semiconductor pattern including a second impurity on the second diffusion barrier pattern.

Abstract: A method of forming a hybrid bonding structure includes depositing an etch stop layer over surface of a substrate, wherein the substrate comprises a conductive structure, and the etch stop layer contacts the conductive structure. The method further includes depositing a dielectric material over the etch stop layer. The method further includes depositing a first diffusion barrier layer over the dielectric material. The method further includes forming an opening extending through the etch stop layer, the dielectric material and the diffusion barrier layer. The method further includes lining the opening with a second diffusion barrier layer. The method further includes depositing a conductive pad on the second diffusion barrier layer in the opening, wherein a surface of the first diffusion barrier layer is aligned with a surface of the conductive pad.

Abstract: The development of reliable bonding materials for PbTe-based thermoelectric modules that can undergo long-term operations at high temperature is carried out. Two cost-effective materials, Cu and Ag, are isothermally hot-pressed to PbTe-based thermoelectric materials at 550 °C for 3 h under a pressure of 40 MPa by the rapid hot-pressing method. Scanning electron microscopy, electron probe micro-analysis, and X-ray diffraction analysis are employed to identify intermetallic compounds, chemical reactions, and microstructure evolution after the initial assembly and subsequent isothermal aging at 400 °C and 550 °C. We find that Cu diffuses faster than Ag in PbTe. Neither Cu nor Ag is a good bonding material because they both react vigorously with Pb0.6Sn0.4Te. In order to be able to use Cu electrodes, it would be necessary to insert a diffusion barrier to prevent Cu diffusion into PbTe.

Abstract: A different mechanism was found for Cu transport through multi-transferred single-layer graphene serving as diffusion barriers on the basis of time-dependent dielectric breakdown tests. Vertical and lateral transport of Cu dominates at different stress electric field regimes. The classic E-model was modified to project quantitatively the effectiveness of the graphene Cu diffusion barrier at low electric field based on high-field accelerated stress data. The results are compared to industry-standard Cu diffusion barrier material TaN. 3.5 A single-layer graphene shows the mean time-to-fail comparable to 4 nm TaN, while two-time and three-time transferred single-layer graphene stacks give 2× and 3× improvements, respectively, compared to single-layer graphene at a 0.5 MV/cm electric field. The influences of graphene grain boundaries on Cu vertical transport through the graphene layers are explored, revealing that large-grain (10–15 μm) single-layer graphene gives a 2 orders of magnitude longer lifetime than ...

Abstract: Oxidation of ZrN ceramics from 973–1373 K under static conditions reveals parabolic rate behavior, indicative of a diffusion-controlled process. In-situ high temperature powder XRD found the oxidation mechanism begins with destabilization of ZrN through formation of a ZrN1−x phase with oxide peaks initially detected at around 773 K. The zirconium oxide layer was found to be monoclinic by in-situ XRD with no evidence of tetragonal or cubic polymorphs present to 1023 K. Bulk ceramic samples oxidized at 1173 and 1273 K underwent slower oxidation than those oxidized at 973 and 1073 K. This change in oxidation rate and hence mechanism was due to formation of a denser c-ZrO2 polymorph stabilized by nitrogen defects. This N-doped dense ZrO2 layer acts as a diffusion barrier to oxygen diffusion. However, at an oxidation temperature of 1373 K this layer is no longer protective due to increased diffusion through it resulting in grain boundary oxidation.

Abstract: We report on the diffusion barrier properties of chemical-vapor-deposition grown graphene, graphene oxide, and reduced graphene oxide (rGO) for copper metallization in integrated circuits. Single-layer graphene shows the best diffusion barrier performance among the three but it has poor integration compatibility, displaying weak adhesion and poor nucleation for Cu deposition on top of it. Within the allowable thermal budget in the back-end-of-line process, rGO in a range of 1 nm thickness shows excellent thermal stability with suitable integration compatibility at 400 °C for 30 min. The diffusion barrier property was verified through optical, physical, and chemical analyses. The use of an extremely thin rGO layer as a Cu barrier material is expected to provide an alternative route for further scaling of copper interconnect technology.

Abstract: In this study, the performance of Zr–Ti–Ni thin film metallic glass (TFMG) as a diffusion barrier between silicon and copper layers is reported. Three 5 nm TFMGs, deposited with or without nitrogen atmosphere, were prepared by magnetron sputtering sandwiched between Si substrate and 100 nm Cu. Rapid thermal annealing was conducted for 30 min at various temperatures between 500 and 800 °C to promote inter-diffusion of Cu and Si. Under transmission electron microscopy, there were no observable Cu–Si intermetallic compounds in the nitrogen-purged TFMG barrier annealed below 800 °C. The failure behaviors of TFMG characterized by the sheet resistance measurement and X-ray diffraction were in agreement. Compared to the sample without nitrogen purging, nitrogen atoms in TFMG were found to increase the failure temperature from 700 to 800 °C by retarding crystallization of TFMG and diffusion of copper. The failure mechanism of the barrier was also investigated in this work. Copper is confined at the interface between Cu and barrier layers and reacts with Ti to form new protective layer until full crystallization of TFMG. In conclusion, nitrogen purging could promote the performance of Zr-based TFMG as a diffusion barrier while preserving its amorphicity.

Abstract: Interconnect structures containing metal oxide embedded diffusion barriers and methods of forming the same. Interconnect structures may include an M x level including an M x metal in an M x dielectric, an M x+1 level above the M x level including an M x+1 metal in an M x+1 dielectric, an embedded diffusion barrier adjacent to the M x+1 dielectric; and a seed alloy region adjacent to the M x+1 metal separating the M x metal from the M x+1 metal. The embedded diffusion barrier may include a barrier-forming material such as manganese, aluminum, titanium, or some combination thereof. The seed alloy region may include a seed material such as cobalt, ruthenium, or some combination thereof.

Abstract: Bismuth ferrite (BiFeO3) thin films with Bi2O3 buffer layers were prepared on Si/SiO2/TiO2/Pt substrates by sol–gel-derived spin-coating method. The structural and electrical properties of BiFeO3 was effectively improved by adding a Bi2O3 buffer layers either at Pt/BiFeO3 interface or on BiFeO3 surface, also strongly depending on the positions and the annealing conditions of buffer layers. A 500°C-annealed Bi2O3 buffer layer could act as a Bi source for compensating Bi volatilization and a diffusion barrier for species from BiFeO3. A near stoichiometric BiFeO3 with less defects and substrate contamination was obtained by employing a 500°C-annealed Bi2O3 buffer layer in between Pt substrate and BiFeO3. The structure change in BiFeO3 led by such a buffer layer should result from the interfacial constraint between buffer layer and BiFeO3. Furthermore, this crystalline BiFeO3 specimen exhibited a highly (100)-textured, where this preferred orientation was attributed to the accumulation of Bi at Pt/BFO interface. Therefore, the Pt/500°C-annealed Bi2O3/BiFeO3/Pt thin film exhibited the good ferroelectric and magnetic properties. As compared to the usual method for controlling BiFeO3 composition by adding excess Bi, this study indicates the more advantages using a Bi2O3 buffer layer.

Abstract: A dielectric diffusion barrier is deposited on a substrate that has a via and an overlying trench etched into an exposed layer of inter-layer dielectric, wherein there is exposed metal from the underlying interconnect at the bottom of the via. In order to provide a conductive path from the underlying metallization layer to the metallization layer that is being formed over it, the dielectric diffusion barrier is formed selectively on the inter-layer dielectric and not on the exposed metal at the bottom of the via. In one example a dielectric SiNC diffusion barrier layer is selectively deposited on the inter-layer dielectric using a remote plasma deposition and a precursor that contains both silicon and nitrogen atoms. Generally, a variety of dielectric diffusion barrier materials with dielectric constants of between about 3.0-20.0 can be selectively formed on inter-layer dielectric.

Abstract: The advantages of graphene diffusion barrier are studied and benchmarked to the industry-standard barrier material TaN for the first time. Even when the wire width is scaled to 10 nm, the effective resistivity of the Cu interconnect is maintained near the intrinsic value of Cu using a 3 A single layer graphene (SLG) barrier. In the time dependent dielectric breakdown (TDDB) test, 4 nm multi-layer graphene (MLG) gives 6.5X shorter mean time to fail (MTTF) than 4 nm TaN. However, when the barrier thickness is reduced, 3 A single-layer graphene (SLG) gives 3.3X longer MTTF than 2 nm TaN, showing that SLG has better scaling potential. The influences of SLG grain size and various transfer methods are presented for further improving the SLG barrier performance.

Abstract: Zirconium nitride (ZrN) has the lowest bulk electrical resistivity and high thermal stability among group IV and V transition metal nitrides, which makes it a promising material for ULSI applications such as a diffusion barrier for Cu interconnects, contact metal in III-V semiconductor devices, and in high density memory structures. Plasma enhanced atomic layer deposition (PEALD) of conducting ZrN thin films using Zr[N(CH3)2]4 and forming gas (5% H2 + 95% N2) plasma is reported in this article. The growth per cycle (GPC) for every deposition was determined from analysis of dynamic in-situ spectroscopic ellipsometry (d-iSE) measurements. An experimental design is proposed for faster determination of ALD growth saturation curves. At substrate temperature of 150 °C, a GPC of 0.10 nm/cycle was observed for self-limiting ZrN PEALD growth. The electrical resistivity of ZrN films deposited on SiO2 substrate was found to be 559.5 ± 18.5 μΩ cm with negligible change in resistivity even after ∼1000 h exposure to ai...

Abstract: A method for a capacitive micromachined ultrasound transducer (cMUT) is provided. The method grows and patterns a diffusion barrier layer over a surface of a base layer. The diffusion barrier layer have different areas that allow different levels of diffusion penetration. A diffusion process is performed over the diffusion barrier layer such that a diffusion reactivated material reaches different depths into the base layer below the different areas. A anchor is formed using the diffusion reactivated material. The anchor has a lower portion below a major surface of the base layer and an upper portion above the major surface of the base layer. A cover layer is placed over the anchor and the base layer. At least one of the cover layer and the base layer includes a flexible layer, such that the cMUT electrodes are movable relative to each other to cause a change of the gap width.

Abstract: Ternary and amorphous tungsten silicon nitride (W–Si–N) thin films were grown by atomic layer deposition (ALD) using a sequential supply of a new fluorine-free, silylamide-based W metallorganic precursor, bis(tert-butylimido)bis(bis(trimethylsilylamido))tungsten(VI) [W(NtBu)2{N(SiMe3)2}2], and H2 plasma at a substrate temperature of 300 °C. Here, W(NtBu)2{N(SiMe3)2}2 was prepared through a metathesis reaction of W(NtBu)2Cl2(py)2 (py = pyridine) with 2 equiv of LiN(SiMe3)2 [Li(btsa)]. The newly proposed ALD system exhibited typical ALD characteristics, such as self-limited film growth and linear dependency of the film growth on the number of ALD cycles, and showed a high growth rate of 0.072 nm/cycle on a thermally grown SiO2 substrate with a nearly zero incubation cycle. Such ideal ALD growth characteristics enabled excellent step coverage of ALD-grown W–Si–N film, ∼100%, onto nanotrenches with a width of 25 nm and an aspect ratio ∼4.5. Rutherford backscattering spectrometry and X-ray photoelectron spectr...

Abstract: Atomic layer deposition (ALD) holds markedly high potential of becoming the enabling method for achieving the three-dimensional all-solid-state thin-film lithium ion battery (LiB). One of the most crucial components in such a battery is the electrolyte that needs to hold both low electronic conductivity and at least fair lithium ion conductivity being at the same time pinhole free. To obtain these desired properties in an electrolyte film, one necessarily has to have a good control over the elemental composition of the deposited material. The present study reports on the properties of ALD lithium aluminum oxide (LixAlyOz) thin films. In addition to LiB electrolyte applications, LixAlyOz is also a candidate low dielectric constant (low-k) etch stop and diffusion barrier material in nanoelectronics applications. The LixAlyOz films were deposited employing trimethylaluminum-O3 and lithium tert-butoxide-H2O for Al2O3 and Li2O/LiOH, respectively. The composition was aimed to be controlled by varying the pulsin...