Ultra-low Dielectric Constant Research Articles

High‐performance cross‐linked SiCOH/polyimide composite film with an ultralow dielectric constant at high frequency

AbstractUltralow‐k materials with promising comprehensive performance to meet the increasing requirements of high‐frequency communication are highly desired. Here, a cross‐linked porous polymer SiCOH, synthesized via simple sol–gel method, was used as the filler to prepare SiCOH/PI composite films by physically blending, which demonstrates ultralow dielectric constant at high frequency. Notably, only 2.5% of SiCOH in the composite can significantly reduce the dielectric constant of PI from 3.0 to an ultralow value of 1.7 in the 9.5–12.4 GHz, together with a low dielectric loss of 0.029. Additionally, the SiCOH/PI composite maintains a high tensile strength of 82.4 MPa and a tensile modulus of 1.82 GPa, which is comparable to pure PI film. While the glass transition temperature (Tg) increases to 370°C and the linear expansion coefficient is reduced to 30.7 ppm/°C, both of which are superior to those of pure PI film. Moreover, by introducing the hydrophobic SiCOH into PI, the contact angle of the composite films increased to 92.0°–99.0°. This simple and low‐cost method not only effectively lowers the dielectric constant of PI but also improves the thermal stability, mechanical properties, and hydrophobic ability, greatly boosts the practical application of PI in high‐frequency communication in the future.

Hierarchical microstructure changes of oriented poly(vinylidene fluoride) foam via supercritical carbon dioxide with increased piezoelectric performance

Light weight poly (vinylidene fluoride) (PVDF) has attracted wide attention for energy supply. In this work, oriented PVDF foams were prepared using supercritical carbon dioxide (CO2) physical foaming associated with a constraint mold. The corresponding micro-nanostructures and electrical performances were researched comprehensively. It reveals that the cell structure and molecular chains of PVDF foams are oriented due to the limitation of gas diffusion paths. Because of the realization of uniaxial stretching during cell growth, the β phase content is increased. Besides, after foaming, the regularity of the chain segments in amorphous region is improved, which is caused by the decrease in the quantity of free-volume cavities. The 1D-149 °C oriented PVDF foam exhibits a high voltage output (8 V), due to the ultralow dielectric constant (1.8) and high compressive strength. This study provides a theoretical foundation for the design of oriented PVDF foams, showing the potential of energy collector.

Remote plasma enhanced cyclic etching of a cyclosiloxane polymer thin film

The continuous evolution of chip manufacturing demands the development of materials with ultra-low dielectric constants. With advantageous dielectric and mechanical properties, initiated chemical vapor deposited (iCVD) poly(1,3,5-trimethyl-1,3,5-trivinyl cyclotrisiloxane) (pV3D3) emerges as a promising candidate. However, previous works have not explored etching for this cyclosiloxane polymer thin film, which is indispensable for potential applications to the back-end-of-line fabrication. Here, we developed an etching process utilizing O2/Ar remote plasma for cyclic removal of iCVD pV3D3 thin film at sub-nanometer scale. We employed in-situ quartz crystal microbalance to investigate the process parameters including the plasma power, plasma duration and O2 flow rate. X-ray photoelectron spectroscopy and cross-sectional microscopy reveal the formation of an oxidized skin layer during the etching process. This skin layer further substantiates an etching mechanism driven by surface oxidation and sputtering. Additionally, this oxidized skin layer leads to improved elastic modulus and hardness and acts as a barrier layer for protecting the bottom cyclosiloxane polymer from further oxidation.

Impact of hydrogenation on the stability and mechanical properties of amorphous boron nitride

Interconnect materials with ultralow dielectric constant, and good thermal and mechanical properties are crucial for the further miniaturization of electronic devices. Recently, it has been demonstrated that ultrathin amorphous boron nitride (aBN) films have a very low dielectric constant, high density (above 2.1 g cm−3), high thermal stability, and mechanical properties. The excellent properties of aBN derive from the nature and degree of disorder, which can be controlled at fabrication, allowing tuning of the physical properties for desired applications. Here, we report an improvement in the stability and mechanical properties of aBN upon hydrogen doping. With the introduction of a Gaussian approximation potential for atomistic simulations, we investigate the changing morphology of aBN with varying H doping concentrations. We found that for 8 at% of H doping, the concentration of sp 3-hybridized atoms reaches to a maximum which leads to an improvement of thermal stability and mechanical properties by 20%. These results will be a guideline for experimentalists and process engineers to tune the growth conditions of aBN films for numerous applications.

A facile in‐situ fabrication of black polyimide films with ultrahigh electrical properties

AbstractConsidering the ongoing evolution of flexible printed circuit boards and the importance of safeguarding the intellectual property of circuit designs, there exists an imperative demand for the development of a black film exhibiting exceptional electrical properties and remarkable light‐shielding capabilities. Consequently, this work employs a straightforward strategy to enhance the opacity of polyimide films by incorporating carbon black (CB) and manganese dioxide (MnO2) as black fillers using an in situ doping method. Rigorous tests are conducted, analyzing properties such as dielectric constant, dielectric loss, breakdown field strength, current density, and ferroelectric energy storage. The optimal ratio of CB to MnO2 (mass fraction) is determined as 1:5, with a total powder doping amount of 6 wt%, providing the best ratio relative to the matrix resin. This ratio ensures an optimal powder dispersion state, resulting in an outstanding breakdown field of 147.4 kV/mm and ultralow dielectric constants, measuring less than 3.78 at 103 Hz. This composite film is anticipated to find applications as a cutting‐edge material for electronic devices and the semiconductor industry.

Significantly Improve the Thermal Conductivity and Dielectric Performance of Epoxy Composite by Introducing Boron Nitride and POSS.

Dielectric materials with superb thermal and electrical properties are highly desired for high-voltage electrical equipment and advanced electronics. Here, we propose a novel strategy to improve the performance of epoxy composites by employing boron nitride nanosheets (BNNSs) and γ-glycidyl ether oxypropyl sesimoxane (G-POSS) as functional fillers. The resultant ternary epoxy composites exhibit high electrical resistivity (1.63 × 1013 Ω·cm) and low dielectric loss (<0.01) due to the ultra-low dielectric constants of cage-structure of G-POSS. In addition, a high thermal conductivity of 0.3969 W·m-1·K-1 is achieved for the epoxy composites, which is 114.66% higher than that of pure epoxy resin. This can be attributed to the high aspect ratio and excellent thermally conductive characteristics of BNNSs, promoting phonon propagation in the composites. Moreover, the epoxy composite simultaneously possesses remarkable dynamic mechanical properties and thermal stability. It is believed that this work provides a universal strategy for designing and fabricating multifunctional composites using a combination of different functional fillers.

A wide-bandgap graphene-like structure C6BN with ultra-low dielectric constant.

This study introduces a new wide-bandgap graphene-like structure, denoted as C6BN, achieved by incorporating an eight-electron BN pair, substantially modifying its electronic properties. Utilizing extensive density functional calculations, we comprehensively analyzed the stability, electronic structure, mechanical properties, and optical-electrical characteristics of C6BN. Our investigations reveal the material's exceptional thermodynamic, mechanical, and dynamic stability. Notably, the calculated wide bandgap of 2.81 eV in C6BN, supported by analyses of energy levels, band structures, and density of states, positions it as a promising two-dimensional wide-bandgap semiconductor. Additionally, C6BN exhibits isotropic mechanical features, highlighting its inherent flexibility. Remarkably, our calculations indicate an ultra-low dielectric constant (k = 1.67) for C6BN, surpassing that of well-established third-generation semiconductors. Further exploration into the thermoelectric properties of C6BN demonstrates its promising performance, as evidenced by calculations of thermal conductivity (κ), power factor (P), and Seebeck coefficient (S). In summary, our findings underscore the significant potential of the proposed C6BN structure as a flexible two-dimensional material poised to drive future advancements in electronic and energy-related technologies.

Lightweight polybenzoxazole aerogels with high compressive strength, ultralow dielectric constants, and excellent thermal stability

Three polybenzoxazole aerogels were prepared by using a two-step process through precursors. This new strategy avoids the drawback of directly preparing polymer aerogels from insoluble polymers.

Adjustable Plane Curvature of Covalent Organic Framework Enabling Outstanding Dielectric, Electret, and High‐Temperature Processing Properties

AbstractWith the rapid development of integrated circuits towards miniaturization and complexity, there is an urgent need for materials with low dielectric constant/loss and high processing temperatures to effectively prevent signal delay and crosstalk. With high porosity, thermal stability, and easy structural modulation, covalent organic frameworks have great potential in the field of low dielectric materials. However, the optimization of dielectric properties by modulating the conjugated/plane curvature structure of covalent organic frameworks (COFs) has rarely been reported. Accordingly, we herein innovatively prepare COF films with adjustable planar curvature, hence possessing ultralow dielectric constant (1.9 at 1 kHz), ultralow dielectric loss at 1 kHz (0.0029 at room temperature, 0.0052 at 200 °C), high thermal decomposition temperature (5 % weight loss temperature, 473 °C) and good hydrophobicity (water contact angle, 105.3°). Also, to the best of our knowledge, we are the first to report that the resulting COF film enables high surface potential (≈320 V) for one week, attributing to its intrinsic high porosity, thus presenting great potential in electret applications. Accordingly, this innovative work provides a readily available and scalable idea to prepare materials with comprehensively excellent dielectric and electret properties as well as high processing temperatures simultaneously for advanced electronic device applications.

Bioinspired construction of size adjustable hollow polydopamine microspheres for ultra-low dielectric polyimide composites

Polydopamine (PDA) has been extensively investigated due to its excellent adhesion ability and versatile chemical potential for secondary reactions. However, the potential application of hollow polydopamine microspheres (H-PDA) in the field of low-dielectric electronic packaging remains an unexplored area. Here, H-PDA microspheres with adjustable size were synthesized by a template-assisted approach, and the influence of size and content of H-PDA on the comprehensive performance of PI/H-PDA composites was explored in detail. The morphology observation revealed that the presence of H-PDA could be homogeneously dispersed in the PI matrix, and the PI/H-PDA composite containing 2 wt% H-PDA-800 achieved the lowest dielectric constant of 1.96 with a dielectric loss of 0.0123 at 1 MHz. It was attributed to the synergistic effects of nano-sized air bubbles from H-PDA and the dielectric confinement effect. Meanwhile, PI/H-PDA composites maintained high thermal stability (T5> 517 °C). In addition, the incorporation of H-PDA had a strengthening and toughening effect on PI composites, which can be explained by the sliding theory of macromolecular chains. This work offers a feasible strategy to obtain ultra-low dielectric constant of porous PI composites while maintaining good mechanical properties and thermal stability.

Ultralow-Dielectric-Constant Atomic Layers of Amorphous Carbon Nitride Topologically Derived from MXene.

Low-dielectric-constant materials such as silicon dioxide serving as interconnect insulators in current integrated circuit face a great challenge due to their relatively high dielectric constant of ≈4, twice that of the recommended value by the International Roadmap for Devices and Systems, causing severe parasitic capacitance and associated response delay. Here, novel atomic layers of amorphous carbon nitride (a-CN) are prepared via a topological conversion of MXene-Ti3 CNTx under bromine vapor. Remarkably, the assembled a-CN film exhibits an ultralow dielectric constant of 1.69 at 100 kHz, much lower than the previously reported dielectric materials such as amorphous carbon (2.2) and fluorinated-doped SiO2 (3.6), ascribed to the low density of 0.55g cm-3 and high sp3 C level of 35.7%. Moreover, the a-CN film has a breakdown strength of 5.6 MVcm-1 , showing great potential in integrated circuit application.

A superhydrophobic fluorinated-silica/polyimide nanofiber membrane with ultra-low dielectric constant

A superhydrophobic fluorinated-silica/polyimide nanofiber membrane with ultra-low dielectric constant

Structuring multiscale porous architecture in polyether sulfone films for ultra-low dielectric constant

Ultra-low dielectric constant materials possess a broad prospect for application in microelectronics devices and communication systems. The most efficient method for fabricating low dielectric constant materials is the incorporation of porous structure into the materials. However, it is vital and remains a great challenge to precisely control the size, distribution and number of pore structures for porous films to maintain comprehensive properties. Herein, a series of novel multiscale porous polyether sulfone-polyhedral oligomeric silsesquioxanes (PES-POSS) films with ultra-low dielectric constants were fabricated by solvent phase inversion approach. Specifically, the prepared PES-60%POSS (P60) films demonstrate an ultra-low dielectric constant and dielectric loss of 1.31 and 0.00078 at 1 kHz. Multiscale pores ranging from micron to nano and low molar polarization of POSS nano-hybrids are the key to its low dielectric properties of the resultant materials. Moreover, the interface enhancement by the covalent bonding of POSS and PES skeleton ensures that the composite hybrid films maintain reliable thermal and mechanical properties while possess low dielectric properties. The measurements of contact angle and water absorption show the PES-POSS films have favorable water resistance. That is beneficial to the dielectric stability and service life of films. In addition, the average transmissivity coefficient of P60 films in X-band is high up to 95.6%, which show the potential of application as an excellent wave transmitting material.

Highly Multifunctional Performances of Boron Nitride Nanosheets/Polydimethylsiloxane Composite Foams

Although this kind of hexagonal boron nitride (h-BN)-filled polydimethylsiloxane (PDMS) multifunctional composite foam has been greatly expected, its development is still relatively slow as a result of the limitation of synthetic challenge. In this work, a new foaming process of BNNSs-PDMS, alcohol, and water three-phase emulsion system is employed to synthesize a series of high-quality BNNSs/PDMS composite foams (BSFs) filled with highly functional and uniformly distributed BNNSs. As a result of well-bonded interfaces between the BNNSs and PDMS, enhanced multiple functions of BSFs appeared. The BSFs can show complete resilience at a compressive strain of 90% and only 3.99% irreversible deformation after 100,000 compressing-releasing hyperelastic cycles at a strain of 60%. On the basis of their outstanding shape-memory properties, the maximum voltage value of compression-driven piezo-triboelectric (CDPT) responses of the BSFs is up to ∼20 V. Depending on the remarkable super-elastic and CDPT performances, the BSFs can be used for sensitive sensing of temperature difference and electromechanical responses. Also, in the range of 12-40 GHz, the BSF materials display ultralow dielectric constants between 1.1 and 1.4 with proper dielectric loss tangent values of <0.3 and exhibit an enhanced and broadened sound adsorption capacity ranging from 500 to 6500 Hz. Although BSFs have high porosities of >65%, their thermal conductivities can still reach up to 0.407 ± 0.039 W m-1 K-1. Moreover, the BSF materials display favorable thermal stability, obviously reduced coefficient of thermal expansion, and good flame retardancy. All of these properties render the BSFs as a new category of excellent multifunctional material.

Three-dimensional inkjet printing and low temperature sintering of silica-based ceramics

The conventional LTCC fabrication route requires a series of costly molding equipment and a complicated manufacturing process. If it is achievable to fabricate ceramics using three-dimensional inkjet printing (IJP) technology, it is anticipated that LTCC components could be designed as a more efficient and flexible additive manufacturing route using IJP technology to co-print ceramic and conductive layers and co-fire them. This research represents the first attempt to utilize IJP technology in the field of LTCC, where we developed a stable SiO2-H3BO3 nanoceramic ink that can be continuously printed through a piezoelectric nozzle with an array of spray holes. The ink was supplemented with selected photosensitive resins to facilitate the curing of the printed layer under ultraviolet light irradiation. Green bodies are sintered at 950° for two hours to obtain ceramic sheets with good surface flatness and microscopic sintering degrees. The tested samples have an ultra-low dielectric constant (εr) of about 2.485 and a low dielectric loss (tan δ) of about 0.0038 (at 1 MHz), while being stable at high temperatures (< 400°) and high frequencies (< 10 GHz), indicating its ability to match the required dielectric properties required for microwave dielectric substrates.

Increasing porosity in hydrogen-bonded organic frameworks for low-κinterlayer dielectric

Herein, two HOFs with different porosities have been obtained by tuning the reaction temperature. The dielectric constant of HOF-FJU-57a at 298 K and 1 MHz is 2.18, which is the first example of an HOF with an ultra-low dielectric constant.

Fluorine-terminated functionalized liquid metal/silicon carbide binary nanoparticles for polyvinyl alcohol composite films with high in-plane thermal conductivity and ultra-low dielectric constant

Highly thermally conductive and low dielectric constant are among the most sought-after properties of flexible polymer-based thermal-management materials (TMMs). However, it remains a formidable challenge to develop efficient thermal dissipation materials with fascinating comprehensive performance. In this work, we present an interfacial engineering strategy using trifluoropropyltriethoxysilane (TFPTES) to act as a thermal linker at granular silicon carbide-liquid metal (SiC-LM) binary interfaces (SiC-LM@F) in the polyvinyl alcohol (PVA) matrix, in which the LMs merely partially anchored to the surface of binary filler by a controllable ball milling technology. The strong hydrogen bonding and/or compact “shoulder-to-shoulder” contact between the binary components and matrix interfaces confer an expressway for the propagation of interfacial phonons. For this, the developed PVA/SiC-LM@F composite film demonstrates a high in-plane TC of 10.2 W m−1 K−1 and ultra-low dielectric constant of 1.49 at 106 Hz at 40 wt% SiC-LM@F loading content, which is more superior to those of the other counterparts in this experiment. Additionally, the obtained PVA/SiC-LM@F composite film also reveals favorable tensile strength, excellent electric insulation, and efficient cooling capacity. This interfacial engineering strategy is expected to offer a versatile solution to the design and construction of advanced thermal-management materials (TMMs).

Cross-linked porous polyarylene ether nitrile films with ultralow dielectric constant and superior mechanical properties

Porous polymer materials with low dielectric constant, dielectric loss and excellent mechanical properties are expected to be widely used in the field of microelectronic devices. In this work, polyarylene ether nitrile containing trifluoromethyl and carboxyl groups (PEN) are designed and synthesized and then the cross-linked porous PEN films were successfully prepared by using 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF 4 ) as porogen and bisphenol-AF epoxy (BAFE) as crosslinker. Due to the introduction of low polarizability trifluoromethyl group and porous structures, porous PEN films show ultralow dielectric constants and hydrophobic surfaces with water contact angles greater than 100°. Moreover, benefiting from the construction of the cross-linked networks, porous low-dielectric PEN films are demonstrated to simultaneously possess excellent mechanical properties. They show excellent flexibility, which can be curled without breaking. Specially, PEN-E-20 film shows high thermal stability (T 5% = 486 °C), ultralow dielectric constant (1.47 at 1 MHz) and dielectric loss (0.004 at 1 MHz), superior mechanical properties (tensile strength of 67 MPa and tensile modulus of 2080 MPa). This strategy will provide a new idea for the design and preparation of flexible, ultralow dielectric materials. • The cross-linked porous PEN films with ultralow dielectric constant and superior mechanical properties were prepared. • The cross-linked networks were constructed to improve the performance of porous films. • The physical pore former EMIBF 4 was introduced to precisely control pore size and porosity.

Significantly Enhanced Porosity of Silicone Rubber Nanocomposite Foams via Cross-Linking Structure Regulation and Heterogeneous Nucleation by CNTs for Promising Ultralow-k Dielectrics

Ultralow-k materials with excellent thermal stability and good electrical insulation are urgently required taking into consideration the rapid development of 5G communication systems. Increasing the porosity of materials is the most effective way to reduce their dielectric constant. On this basis, with the help of cross-linking structure regulation and heterogeneous nucleation of CNTs, a polymethyl-vinyl siloxane (PMVS)/CNT foam with porosity up to 93.9% (density, 0.069 g/cm3) was fabricated via supercritical CO2 foaming. Therefore, promising dielectric properties were observed for the PMVS/CNT foam (0.5 wt % CNTs) with an ultralow dielectric constant (k = 1.52) and a low loss (tan δ = 0.0017) at 1 kHz. Additionally, the PMVS/CNT foams exhibited improved insulativity (RV > 1014 Ω·cm), prominent thermal stability (T5 > 444 °C), and good mechanical properties. These excellent PMVS/CNT foams afford a promising ultralow-k dielectric for modern integrated circuit development.

High‐strength ceramic foams with ultralow dielectric constant and loss in terahertz frequency region

AbstractSixth generation (6G) wireless networks operating in terahertz frequency region are significant solutions to the increasing number of telecommunication devices and the demand for faster data transmission. However, few dielectric materials exhibiting an ultralow relative dielectric constant (εr), loss tangent (tanδ), and high mechanical strength are found suited for 6G telecommunication. In this study, we developed lightweight ceramic foams by directly sintering glass hollow spheres. The effects of sintering temperatures on their mechanical performance, and terahertz optical and dielectric properties were systematically investigated. The final compositions of ceramic foams contain glass, cristobalite, quartz, and wollastonite. The crystalline content increases with increasing sintering temperature. The ceramic foams sintered at low temperatures of 700–850°C exhibit a high porosity ranging from 74.6% to 87.3%, ultralow εr ranging from 1.41 to 1.83, and tanδ of ∼0.011 at 0.5 THz, as well as high compressive strength ranging from 10.1 to 27.4 MPa, which could be promising materials for 6G telecommunication.