Next-generation Microelectronic Devices Research Articles

High-temperature ferromagnetism and strong π-conjugation feature in two-dimensional manganese tetranitride

Two-dimensional (2D) magnetic materials have attracted tremendous research interest because of the promising application in the next-generation microelectronic devices. Here, by the first-principles calculations, we propose a two-dimensional ferromagnetic material with high Curie temperature, manganese tetranitride MnN4 monolayer, which is a square-planar lattice made up of only one layer of atoms. The structure is demonstrated to be stable by the phonon spectra and the molecular dynamic simulations, and the stability is ascribed to the π–d conjugation between π orbital of N=N bond and d orbital of Mn. More interestingly, the MnN4 monolayer displays robust 2D ferromagnetism, which originates from the strong exchange couplings between Mn atoms due to the π–d conjugation. The high critical temperature of 247 K is determined by solving the Heisenberg model using the Monte Carlo method.

Interfacial thermal conductance of BP/MoS2 van der Waals heterostructures: An insight from the phonon transport

Recently, two-dimensional (2D) van der Waals (vdW) heterostructures have attracted a great deal of attention due to their outstanding properties and are considered an alternative for the next generation of microelectronic devices. The interfacial thermal transport properties of these heterostructures are of great importance for their practical applications. Herein, we investigate the effect of temperature and three different vacancy defects on the interfacial thermal conductance (ITC) of BP/MoS2 vdW heterostructures by using molecular dynamics. The results show that its ITC increases by 167% when the temperature increases from 100 to 350 K. In addition, a strong dependence of the ITC on the concentration of the Mo vacancy defects is also found. In this study, phonon dispersion relations, phonon density of states, and phonon participation rates are used to analyze the physical mechanisms of interfacial thermal transport behavior. Interestingly, the Mo vacancy defects will cause the phonon density of states to shift towards lower frequencies, and the number of low-frequency phonons will increase with increasing defect concentration. In particular, the Mo vacancy defects will lead to phonon non-localization features in the low-frequency range of 4–6 THz, which is significantly different from the phonon participation rate of the system with the introduction of the S vacancy defects and the double S vacancy defects. These findings could provide theoretical support for thermal conductance manipulation of devices based on BP/MoS2 vdW heterostructures.

Novel, flexible, and transparent thin film polyimide aerogels with enhanced thermal insulation and high service temperature

Due to their high service temperature, excellent thermal insulation, and nanoporous morphology, polyimide (PI) aerogels have the potential capability to be used in the next generation of microelectronic devices and flexible electronics.

Miniaturized high-performance metallic 1T-Phase MoS2 micro-supercapacitors fabricated by temporally shaped femtosecond pulses

The recent development of wearable and portable microelectronic devices requires energy storage devices to be miniaturized; micro-supercapacitors (MSCs), as one of the most outstanding candidates, have great potential in future electronic devices. However, in the miniaturization of MSCs, the maintenance of electrochemical performance remains a key challenge. Herein, this study proposes a simple, one-step, mask-free and high-resolution fabrication method for high-performance 1T MoS2 MSCs in atmosphere. The method involves the direct writing of restacked 1T MoS2 films by a temporally shaped femtosecond laser. Specifically, femtosecond laser pulses are temporally shaped to control the transient electron temperature and material absorption for achieving high-resolution fabrication. Excellent electrode material properties and ultrashort ion transfer distance enable the MSCs to exhibit optimal performances with an ultrahigh power density (14 kW cm−3), ultrahigh energy density (15.6 mWh cm−3) and large areal capacitance (36 mF cm−2). Notably, such miniaturized MSCs in a 100 × 100 μm2 area own superior frequency responses (1221 Hz) and time constant (0.82 ms), which are suitable for AC line filters and other high-power demanded electronic devices. This method successfully solves the problem of maintaining performance in the miniaturization of MSCs, allowing next-generation microelectronic devices to be developed.

Magnetic origami creates high performance micro devices

Self-assembly of two-dimensional patterned nanomembranes into three-dimensional micro-architectures has been considered a powerful approach for parallel and scalable manufacturing of the next generation of micro-electronic devices. However, the formation pathway towards the final geometry into which two-dimensional nanomembranes can transform depends on many available degrees of freedom and is plagued by structural inaccuracies. Especially for high-aspect-ratio nanomembranes, the potential energy landscape gives way to a manifold of complex pathways towards misassembly. Therefore, the self-assembly yield and device quality remain low and cannot compete with state-of-the art technologies. Here we present an alternative approach for the assembly of high-aspect-ratio nanomembranes into microelectronic devices with unprecedented control by remotely programming their assembly behavior under the influence of external magnetic fields. This form of magnetic Origami creates micro energy storage devices with excellent performance and high yield unleashing the full potential of magnetic field assisted assembly for on-chip manufacturing processes.

Integrating Superwettability within Covalent Organic Frameworks for Functional Coating

Summary Despite the availability of a variety of skeletons for covalent organic frameworks (COFs), control of pore-surface wettability remains undeveloped, which could immensely expand their overall versatility. Herein, we contribute an effective strategy for imparting superwettability on COFs by chemically coating the pore surface with perfluoroalkyl groups to confer them with superhydrophobicity. Taking advantage of controllable modification, the resultant COFs retain the porosity and crystallinity of the pristine COFs. Benefiting from the bulk superhydrophobicity of the COF crystals and the feasibility of COF synthesis, they can be used as a coat or in situ integrated within various substrates; once applied, this renders them superhydrophobic. Given the modular nature, this protocol is compatible with the development of various specific wettabilities in COFs, which thereby constitutes a step for expanding the scope of COF applications and provides many opportunities for the processing of advanced materials and devices.

Metal–Organic Framework-Inspired Metal-Containing Clusters for High-Resolution Patterning

We report the preparation of discrete nanometer-scale zinc-based clusters and use them to form sub-15 nm structures by means of extreme ultraviolet lithography. By taking advantage of a metal-containing building unit derived by a metal–organic framework—MOF-2, we found the 3-methyl-phenyl-modified Zn-mTA cluster that formed is well-defined with controlled size and structure and demonstrates extremely high solubility. Progress in recent years in metal–organic frameworks has created a rich variety of metal-containing structures that are useful for numerous applications. Substitution of the bridging ligands with monovalent ligands produces a discrete metal–organic cluster that strongly interacts with soft X-rays at a wavelength of 13 nm. Here we describe the design, preparation, computational modeling, and physical characterization of these new materials. Such metal-containing structures may form the basis of photoresists that enable the next generation of microelectronic devices.

Gap-Fill Characteristics and Film Properties of DMDMOS Fabricated by an F-CVD System

The deposition process for the gap-filling of sub-micrometer trenches using DMDMOS, (CH3)2Si(OCH3)2, and CxHyOz by flowable chemical vapor deposition (F-CVD) is presented. We obtained low-k films that possess superior gap-filling properties on trench patterns without voids or delamination. The newly developed technique for the gap-filling of submicrometer features will have a great impact on IMD and STI for the next generation of microelectronic devices. Moreover, this bottom up gap-fill mode is expected to be universal in other chemical vapor deposition systems.

Effect of a Multi-Step Gap-Filling Process to Improve Adhesion between Low-K Films and Metal Patterns

A multi-step deposition process for the gap-filling of submicrometer trenches using dimethyldimethoxysilane (DMDMOS), (CH3)2Si(OCH3)2, and CxHyOz by plasma enhanced chemical vapor deposition (PECVD) is presented. The multistep process consisted of pre-treatment, deposition, and post-treatment in each deposition step. We obtained low-k films with superior gap-filling properties on the trench patterns without voids or delamination. The newly developed technique for the gapfilling of submicrometer features will have a great impact on inter metal dielectric (IMD) and shallow trench isolation (STI) processes for the next generation of microelectronic devices. Moreover, this bottom up gap-fill mode is expected to be universally for other chemical vapor deposition systems.

Micrometer-Scale Ordering of Silicon-Containing Block Copolymer Thin Films via High-Temperature Thermal Treatments.

Block copolymer (BCP) self-assembly is expected to complement conventional optical lithography for the fabrication of next-generation microelectronic devices. In this regard, silicon-containing BCPs with a high Flory-Huggins interaction parameter (χ) are extremely appealing because they form high-resolution nanostructures with characteristic dimensions below 10 nm. However, due to their slow self-assembly kinetics and low thermal stability, these silicon-containing high-χ BCPs are usually processed by solvent vapor annealing or in solvent-rich ambient at a low annealing temperature, significantly increasing the complexity of the facilities and of the procedures. In this work, the self-assembly of cylinder-forming polystyrene-block-poly(dimethylsiloxane-random-vinylmethylsiloxane) (PS-b-P(DMS-r-VMS)) BCP on flat substrates is promoted by means of a simple thermal treatment at high temperatures. Homogeneous PS-b-P(DMS-r-VMS) thin films covering the entire sample surface are obtained without any evidence of dewetting phenomena. The BCP arranges in a single layer of cylindrical P(DMS-r-VMS) nanostructures parallel-oriented with respect to the substrate. By properly adjusting the surface functionalization, the heating rate, the annealing temperature, and the processing time, one can obtain correlation length values larger than 1 μm in a time scale fully compatible with the stringent requirements of the microelectronic industry.

High Performance Amorphous Multilayered ZnO-SnO<sub>2</sub> Heterostructure Thin-Film Transistors: Fabrication and Characteristics

Multilayered ZnO- heterostructure thin films consisting of ZnO and layers are produced by alternating the pulsed laser ablation of ZnO and targets, and their structural and field-effect electronic transport properties are investigated as a function of the thickness of the ZnO and layers. The performance parameters of amorphous multilayered ZnO- heterostructure thin-film transistors (TFTs) are highly dependent on the thickness of the ZnO and layers. A highest electron mobility of , a low subthreshold swing of a 0.22 V/dec, a threshold voltage of 1 V, and a high drain current on-to-off ratio of are obtained for the amorphous multilayered ZnO(1.5nm)-(1.5 nm) heterostructure TFTs, which is adequate for the operation of next-generation microelectronic devices. These results are presumed to be due to the unique electronic structure of amorphous multilayered ZnO- heterostructure film consisting of ZnO, , and ZnO- interface layers.

Characterization of ZnO–SnO2 nanocomposite thin films deposited by pulsed laser ablation and their field effect electronic properties

ZnO–SnO2 nanocomposite thin films were produced using pulsed laser ablation of pie-shaped ZnO–SnO2 oxides target, and their field effect electronic transport properties investigated as a function of annealing temperature. The films have a nanocomposite structure consisting of ZnO and SnO2 nanoparticles. The amorphous ZnO–SnO2 nanocomposite thin films, as oxide semiconductors, exhibited excellent electronic transport properties with saturation mobility of around 16.9cm2/Vs, turn-on voltage of ~−1V, subthreshold swing of 0.22V/decade, and high drain current on-to-off ratio of over 1010, enough to operate for next-generation microelectronic devices. These results are presumed due to the unique electronic structure of amorphous nanocomposite coupled with two heavy-metal Zn and Sn cations having spherically symmetric s-orbitals.

(Super)hydrophobic and Multilayered Amphiphilic Films Prepared by Continuous Assembly of Polymers

AbstractThe continuous assembly of polymers (CAP) is used to fabricate tailored nanocoatings on a wide variety of substrates. Ring‐opening metathesis polymerization (ROMP) is used to mediate the CAP process (CAPROMP) to assemble specifically designed macromolecules into nanoengineered crosslinked films. Different films composed of single or multiple macromolecules are used to tune the surface wetting characteristics on various planar substrates, including porous substrates such as filter paper and cotton, and non‐porous subtrates such as aluminium foil and glass. By judicious selection of the macromolecules, these substrates, which are hydrophilic in nature, can be rendered (super)hydrophobic. The robustness of the ROMP catalysts and the reinitiation ability of the CAPROMP approach allow the production of layered multicomponent amphiphilic films with on‐demand switchable wettability. Such functional nanocoatings can be potentially applied as self‐cleaning surfaces, as waterproof woven fabrics, and for the next generation of microelectronic devices.

Design and preparation of stress-free epitaxial BaTiO3 polydomain films by RF magnetron sputtering

Domain structures of BaTiO3 thick films grown on (100) SrTiO3 single-crystal substrates were engineered using an RF magnetron sputtering deposition process. By tuning the sputtering power and cooling rate and using an off-axis sputtering technique to prepare conducting perovskite oxide bottom electrode with heteroepitaxial quality, we have deposited epitaxial tetragonal single-domain and polydomain BaTiO3 films with a self-assembled three-domain architecture. The electrical properties and microstructure of the BaTiO3 films were characterized, and a c/a1/a2 cellular polydomain structure was clearly observed in as-grown films by optical microscopy. Such a polydomain structure was a consequence of a complete relaxation of misfit stresses of the film. Engineering of this self-assembled microstructure has great potential in providing large, field-tunable pyroelectric and electromechanical responses in next-generation microelectronic devices and micro-electro-mechanical systems (MEMS).

Band gap opening of graphene by doping small boron nitride domains

Boron nitride (BN) domains are easily formed in the basal plane of graphene due to phase separation. With first-principles calculations, it is demonstrated theoretically that the band gap of graphene can be opened effectively around K (or K') points by introducing small BN domains. It is also found that random doping with boron or nitrogen is possible to open a small gap in the Dirac points, except for the modulation of the Fermi level. The surface charges which belong to the π states near Dirac points are found to be redistributed locally. The charge redistribution is attributed to the change of localized potential due to doping effects. The band opening induced by the doped BN domain is found to be due to the breaking of localized symmetry of the potential. Therefore, doping graphene with BN domains is an effective method to open a band gap for carbon-based next-generation microelectronic devices.

Local flow boiling heat transfer characteristics in silicon microchannel heat sinks using liquid crystal thermography

The next generation of microelectronic devices will require better heat management through new technologies such as microchannel heat sinks. The present study focuses on the experimental investigation of onset of boiling and flow boiling heat transfer characteristics in a silicon microchannel heat sink. The microchannel heat sink consists of a rectangular silicon chip in which 45 rectangular microchannels were chemically etched with a depth of 276 μm, width of 225 μm, and a length of 16 mm. Experiments are carried out for mass fluxes ranging from 341 to 531 kg/m 2 s and heat fluxes from 55.5 to 154.2 kW/m 2 using FC-72 as the working fluid. The present study focuses on the characteristics of boiling incipience in microchannels including the effect of mass and heat fluxes. It provides a first qualitative and quantitative local experimental data on the position of the incipient boiling. The boiling incipience and temperature thermal maps for the heat sink surface are provided from a localized measured data using Un-encapsulated thermochromic liquid crystals (TLC). This measuring technique is also used to determine the local heat transfer coefficient for saturated flow boiling. The heat transfer coefficient decreases sharply at low exit quality and then it remains almost constant as the exit quality increases. Two-phase heat transfer coefficient asymptotic models and correlations in microchannels underpredict the data in the nucleate boiling regime.

Electroplating of Cu(Ag) thin films for interconnect applications

Electromigration effects in interconnect metallizations cause a need for materials with superior resistance against electromigration failure but with adequate electrical properties. In principle, Cu(Ag) alloys are potential candidates to become an interconnect material of the next generation of microelectronic devices. Therefore, in the following paper the electroplating of such Cu(Ag) alloys from a sulfuric acid electrolyte solution with varying silver content in a home built deposition tool is presented. Besides the general deposition characteristics, the growth mode of the films and the deposition into trenches will be discussed. The investigations show that Cu(Ag) alloys can be deposited with adequate homogeneity of the film thickness by electroplating. Furthermore, the electrical resistivity is low enough to assure a use of these films for interconnect applications. However, distinct island growth and insufficient trench filling capabilities lead to the fact that the additive composition needs to be optimized for Cu(Ag) thin film electroplating.

Structure of a thin barrier film deposited from tetrakis-(dimethylamino)-titanium onto a Si(100)-2×1 substrate

The formation and structure of a thin film deposited using tetrakis-(dimethylamino)-titanium [Ti(N(CH 3) 2) 4, TDMAT] as a precursor onto a Si(100)-2×1 substrate at ultrahigh vacuum (UHV) conditions was investigated by a combination of surface analytical techniques. The effects of surface temperature and pressure of the precursor molecules on the deposition rate are correlated with the monolayer chemistry of the precursor. The titanium carbonitride (TiC x N y ) thin films produced by thermal deposition of TDMAT onto Si(100)-2×1 at 593 K are continuous and smooth with a root-mean-square (RMS) roughness of <2 nm, having a thickness with a lower limit of 4.7±0.4 nm, and a stoichiometry of approximately x= y=1. In addition, it was determined that the lower limit of the sputtering rate for TiC x N y was ∼0.016 nm s −1 under the conditions used here. These films hold great promise as barrier materials in next-generation microelectronic devices.

Optimal Control of Transient Enhanced Diffusion

Transient enhanced diffusion of boron inhibits the formation of ultrashallow junctions needed in the next-generation of microelectronic devices. Reducing the junction depth using rapid thermal annealing with high heating rates comes at a cost of increasing sheet resistance. The focus of this study is to design the optimal annealing temperature program that gives the minimum junction depth while maintaining satisfactory sheet resistance. Comparison of different parameterizations of the optimal trajectories shows that linear profiles gave the best combination of minimizing junction depth and sheet resistance. Worst-case robustness analysis of the optimal control trajectory motivates improvements in feedback control implementations for these processes

Optimal control of rapid thermal annealing in a semiconductor process

This study focuses on the optimal control of rapid thermal annealing (RTA) used in the formation of ultrashallow junctions needed in next-generation microelectronic devices. Comparison of different parameterizations of the optimal trajectories shows that linear profiles give the best combination of minimizing junction depth and sheet resistance. Worst-case robustness analysis of the optimal control trajectory motivates improvements in feedback control implementations for these processes. This is the first time that the effects of model uncertainties and control implementation inaccuracies are rigorously quantified for RTA.