Low Dielectric Constant Materials Research Articles

Crystal structure and dielectric properties of Ln2Ti2SiO9 (Ln = Pr and Nd)

Low loss and high dielectric constant materials are essentially desired for wide varieties of applications in electronics and communication technology. Herein the structure and dielectric properties of two titanosilicates, Ln2Ti2SiO9, for Ln = Pr3+ and Nd3+ are reported. Both materials are isostructural and have layered structure with layers of [LnTi2SiO9]3- and Ln3+ ions. Electrical properties of both have been analyzed by using the temperature and frequency dependent permittivity, loss, conductivity and modulus data. At room temperature, appreciable relative permittivity (35 for Nd2Ti2SiO9 and 22 for Pr2Ti2SiO9 over the frequency range of 100Hz to 5MHz) and low dielectric loss (like 0.007-0.03 at 100Hz and 10-4-10-3 at 1MHz). Analysis of dc-conductivity data of both compounds indicate that the conduction in both materials is due to the correlated barrier hopping (CBH) of polarons. The relaxation peak of modulus spectra indicates more non-Debye like relaxation in Pr2Ti2SiO9 than that in Nd2Ti2SiO9, and that is possibly due to increased correlation in the dynamics of hopping polarons in Pr2Ti2SiO9.

Non-contact near-field cavity perturbation method for quantitative dielectric measurement and metallic defect inspection

Low dielectric constant (low-k) materials are essential in electronic industry aiming at new generation high-speed communications. Dielectric constant of these materials are measured by standard procedures and instruments with conventional contact configuration. Non-contact and in-situ techniques for low-k dielectric measurement are highly demanded in practice and worth of investigation. We hereby proposed a near-field microwave probe (NFMP) to accurately measure dielectric constant of low-k samples in a non-contact manner with a quantitative electromagnetic (EM) cavity perturbation theory. An NFMP set was designed, optimized by finite-element method (FEM) and fabricated with handy materials in the lab. Frequency response of the NFMP was tested experimentally and further used for subsequent frequency displacement analysis. Various low-k samples were tested by the non-contact NFMP set and dielectric constant were extracted based on the field perturbation theory. The relative error was obtained less than 0.5 % for low-k materials. The NFMP was then fixed on a micrometer stage and worked in a line-scan mode to inspect conductive defects in a low-k substrate. Both surface and subsurface defects were inspected by analyzing displaced central frequencies. The NFMP system is promising to facilitate quantitative and non-contact dielectric property measurement in electronics.

The Recent Advances of Polymer-POSS Nanocomposites With Low Dielectric Constant.

This study provides a comprehensive overview of the preparation methods for polyhedral oligomeric silsesquioxane (POSS) monomers and polymer/POSS nanocomposites. It focuses on the latest advancements in using POSS to design polymer nanocomposites with reduced dielectric constants. The study emphasizes exploring the potential of POSS, either alone or in combination with other materials, to decrease the dielectric constant and dielectric loss of various polymers, including polyimides, bismaleimide resins, poly(aryl ether)s, polybenzoxazines, benzocyclobutene resins, polyolefins, cyanate ester resins, and epoxy resins. In addition, the research investigates the impact of incorporating POSS on improving the thermal properties, mechanical properties, surface properties, and other aspects of these polymers. The entire study is divided into two parts, discussing systematically the role of POSS in reducing dielectric constants during the preparation of POSS composites using both physical blending and chemical synthesis methods. The goal of this research is to provide valuable strategies for designing a new generation of low dielectric constant materials suitable for large-scale integrated circuits in the semiconductor materials domain.

Peptide Orientation Strongly Affected by the Nanoparticle Size as Revealed by Sum Frequency Scattering Spectroscopy.

The orientation of proteins at interfaces has a profound effect on the function of proteins. For nanoparticles (NPs) in a biological environment, protein orientation determines the toxicity, function, and identity of the NP. Thus, understanding how proteins orientate at NP surfaces is a critical parameter in controlling NP biochemistry. While planar surfaces are often used to model NP interfaces for protein orientation studies, it has been shown recently that proteins can orient very differently on NP surfaces. This study uses sum frequency scattering vibrational spectroscopy of the model helical leucine-lysine (LK) peptide on NPs of different sizes to determine the cause for the orientation effects. The data show that, for low dielectric constant materials, the orientation of the helical LK peptide is a function of the coulombic forces between peptides across different particle volumes. This finding strongly suggests that flat model systems are only of limited use for determining protein orientation at NP interfaces and that charge interactions should be considered when designing medical NPs or assessing NP biocompatibility.

Polymeric electronic materials for microelectronics manufacturing: A review

This review paper is part of a series of papers dedicated to the centenary celebration of the American Chemical Society Division of Polymeric Materials: Science and Engineering which has been the scientific home of many polymer scientists and engineers in the semiconductor industry. It is a review of parts of the research and development of advanced polymeric electronic materials for the fabrication and manufacturing of modern integrated circuits at the International Business Machines Corporation. This paper covers three types of advanced polymeric electronic materials: (1) photoresist materials used to “print” integrated circuits on silicon wafers, (2) on-chip low dielectric constant (low-κ) materials to insulate electrically conducting copper wires and (3) photo-patternable on-chip low-κ materials which function both as a photoresist and as an on-chip low-κ material. The photoresist materials are thin film imaging material systems of bilayer photoresist materials for 248 nm lithography and trilayer photoresist materials for 193 nm lithography. The low-κ dielectric material part focuses on fundamental understanding of plasma-induced damage to nanoporous organosilicate low-κ dielectric materials and the design of damage-resistant low-κ dielectric materials. Finally, the photo-patternable low-κ dielectric materials part describes the design and the development of dual-functional photo-patternable low-κ dielectric materials for both 193 nm and 248 nm lithography patterning of semiconductor Back-End-Of-the-Line. Several of these materials have been adopted for high-volume manufacturing of semiconductor chips for some of the most popular electronic devices in the world today.

Polybenzoxazine/organosilicon composites with low dielectric constant and dielectric loss

The evolution of electronic communication technology raises higher requirements for low dielectric constant (low-k) materials. For this, a benzoxazine functional organosilicon (HP-aptes) with dense Si—O—Si crosslinking networks and large sterically hindered tert-butyl groups was prepared by the sol–gel method. Then, a series of polybenzoxazine composites (PPHP) were prepared from intrinsically low dielectric constant bis-functional benzoxazine monomer (P-aptmds) and HP-aptes. The double crosslinking networks of polybenzoxazine and organosilicon further increased the crosslinking density and decreased the dipole density of composites, which endowed the composites with enhanced low-k properties. When the content of HP-aptes is 30% (mass), the crosslinking density was 2.05 × 10−3 mol·cm−3, while that of PP-aptmds was 3.31 × 10−3 mol·cm−3. In addition, the dielectric constant and dielectric loss of PPHP composite at 1 MHz could reach 2.61 and 0.0056, respectively.

Autonomous hydrogel locomotion regulated by light and electric fields.

Autonomous robotic functions in materials beyond simple stimulus-response actuation require the development of functional soft matter that can complete well-organized tasks without step-by-step control. We report the design of photo- and electroactivated hydrogels that can capture and deliver cargo, avoid obstacles, and return without external, stepwise control. By incorporating two spiropyran monomers with different chemical substituents in the hydrogel, we created chemically random networks that enabled photoregulated charge reversal and autonomous behaviors under a constant electric field. In addition, using perturbations in the electric field induced by a dielectric inhomogeneity, the hydrogel could be attracted to high dielectric constant materials and autonomously bypasses the low dielectric constant materials under the guidance of the electric field vector. The photo- and electroactive hydrogels investigated here can autonomously perform tasks using constant external stimuli, an encouraging observation for the potential development of molecularly designed intelligent robotic materials.

The characterization of low-k thin films and their fracture analysis in a WLCSP device

The IC industry implements low dielectric constant (low-k) materials in copper/low-k interconnects to reduce the RC delay and crosstalk noises. As low-k dielectrics are weaker than traditional SiO2, measuring their mechanical properties is important for numerical simulations to evaluate the structural integrity of a package with low-k materials. In this study, we fabricated freestanding samples of low-k thin film with/without pre-cracks on both sides using lithography and exfoliation for uniaxial tension and coefficient of thermal expansion tests. The tension tests revealed that the average fracture toughness and Young's modulus of the low-k film are 1.41 MPa·m1/2 and ∼2.5 GPa, respectively. Using the measured mechanical properties, we performed a fracture analysis by a 2D finite element model for the low-k material in a wafer-level chip-size package under thermal loading. The computational results showed that the critical microcrack in the low-k layer occurs near the solder balls, where the KI increases rapidly with crack length and exceeds KIC. The results are consistent with the experimental findings in literature. The present methods can help evaluate the integrity of low-k material in a package and improve reliability.

Preparation of high‐performance hyperbranched polybenzoxazine with low dielectric constant

AbstractA high‐performance hyperbranched polybenzoxazine with low dielectric constant was prepared. A hyperbranched benzoxazine (HTTr‐d) was synthesized from 1,1,1‐tris(4‐hydroxyphenyl) ethane, 1,12‐dodecanediamine and paraformaldehyde through an A2 + B3 approach with p‐tertbutyl phenol as an end‐capping reagent. After thermal curing, hyperbranched polybenzoxazine (PHTTr‐d) was obtained. For comparison, trifunctional polybenzoxazine (PTr‐s) with long alkyl groups was also synthesized. The introduction of long alkyl chains can effectively reduce the dielectric constants of polybenzoxazines. Due to the presence of tertiary butyl groups and the forming of hyperbranched structure, the dielectric constant of PHTTr‐d was 2.59 at 1 MHz, which was lower than 2.68 of PTr‐s. Compared with PTr‐s, PHTTr‐d exhibited higher thermal stability with the glass transition temperature (Tg) of 197 °C. These results indicated that the hyperbranched polybenzoxazine has potential application as a low dielectric constant material in the field of electronic information.

High Thermal Stability and Low Dielectric Constant of BCB Modified Silicone Resins.

Based on the excellent physical properties and flexible molecular modifiability, modified silicone resins have received favorable attention in the field of microelectronics, and recently a number of modified silicone resins have appeared while few breakthroughs have been made in low dielectric constant (low-k) materials field due to the limitations of structure or the curing process. In this work, functional silicone resin with different BCB contents was prepared with two monomers. The resins showed low dielectric constant (k = 2.77 at 10 MHz) and thermal stability (T5% = 495.0 °C) after curing. Significant performance changes were observed with the increase in BCB structural units, and the functional silicone obtained does not require melting and dissolution during processing because of good fluidity at room temperature. Moreover, the mechanical properties of silicone resins can be also controlled by adjusting the BCB content. The obtained silicone resins could be potentially used in the field of electronic packaging materials.

Dielectric and mechanical properties of TiO2/polyimide composites with low dielectric constant

AbstractWith the advent of 5G era, the high millimeter‐wave frequency band, poor signal penetration and large loss make 5G communication more dependent on low dielectric constant materials. Therefore, the research and development of low dielectric polymer materials has become a hot spot in recent years. With its good chemical corrosion resistance, thermal stability, high dispersion and high mobility, titanium dioxide (TiO2) as a high function fine inorganic material is doped in polymer systems to improve the electrical properties of polymer composites. In recent years, a large number of studies have used spherical TiO2 nanoparticles doped on the polymer matrix, however, there is almost no research on doping nanolinear TiO2 nanoparticles on the polymer matrix. Here, TiO2 nanowires were prepared by hydrothermal method, and the prepared TiO2 nanowires were added to polyimide (PI). TiO2/PI monolayer and three‐layer composite films with good dielectric and mechanical properties were prepared by in‐situ polymerization. Fourier transform infrared spectoscopy, scanning electron microscopy and X‐ray diffraction were used to characterize the structure and test the properties of the composites. During the initiation process, the thermal initiation reaction of the composite membrane was completed. The composite film with good mechanical properties and excellent dielectric properties were obtained by adding titanium oxide nanowires, which can meet the requirements of its use in the field of microelectronic devices.

Additive manufacturing substrate for patch antenna using variable infill Poly Lactic acid

A low dielectric constant substrate for patch antenna using additive manufacturing air gap technique is prepared. This work can tune the desirable value of the dielectric constant and loss tangent of patch substrate by optimizing the various factors involved in 3D printing. The prototype is based on PLA Pro + filament to check the variation in dielectric constant and loss tangent. The performance of the 3D printer used has also been examined for the proposed substrate. This technique helps to create low dielectric constant materials for the high-frequency range of operation of RF communication devices. The prototype's experimental results demonstrate that the 80% Linearly infilled sample (L-80) outperforms the 100% Linearly infilled sample (L-100) in terms of average loss tangent, which has improved by 45.07% on average from 8.5 to 12.5 GHz. At higher frequency ranges of 10.86 to 12.5 GHz, the dielectric constant of the L-80 sample outperforms the L-100 sample in terms of a lower desirable dielectric constant (εr) range (2.0≤εr≤2.2). The dielectric constant results for the above frequency range show that the L-80 sample is 3 to 5 times better than L-100. The average improvement in the dielectric constant for 8.5 to 9.0 GHz is nearly 31.84%.

Low-Voltage Stretchable Electroluminescent Loudspeakers with Synchronous Sound and Light Generation.

Stretchable sound-in-displays, which can generate synchronous sound and light directly from the display without a separate speaker, allow immersive audio and visual perception even on curved surfaces. In stretchable sound-in-displays, alternating current electroluminescent (ACEL) devices have been used as light-emitting sources owing to their high brightness and stability. However, stretchable ACEL devices that use low dielectric constant (κ) materials require a high operating voltage for generating light and sound. Herein, we demonstrate a stretchable ACEL loudspeaker with a low operating voltage using stretchable high-κ dielectrics and strain-insensitive electrodes. Our device exhibits 87.7 cd/m2 of luminance and 79.70 dB of sound pressure level at an operating voltage of 120 V and 10 kHz. As the next platform of wearable devices, the suggested ACEL loudspeaker exhibits high-quality synchronous light and sound generation performance even under various types of mechanical deformation, such as finger flexion and wrist bending.

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.

Comprehensive Study of the Chemical, Physical, and Structural Evolution of Molecular Layer Deposited Alucone Films during Thermal Processing

Thermal processing of molecular layer deposited (MLD) hybrid inorganic–organic alucone thin films produced porous and low-k materials. Alucone films were deposited by MLD using trimethyl aluminum and ethylene glycol at 120 °C. Changes in the film density and thickness during annealing were monitored using in-situ X-ray reflectivity and were compared to atomic layer deposited (ALD) alumina films. The chemical evolution of the as-deposited and annealed alucone films during post-deposition heating with and without UV was probed using infrared spectroscopy, Rutherford backscattering, nuclear reaction analysis, and 15N spectroscopy, providing a detailed understanding of the induced changes. The concentration of OH groups decreased after depositing 1 nm of alumina capping layer as a barrier to moisture uptake, which also decreased the etch rate in CF4/O2 plasma. The lowest dielectric constant of the processed alucone films (kmin = 4.75) was 25% lower than the lowest values measured in ALD alumina counterparts (kmin = 6.7). Large thickness decreases for alucone films were observed at ∼200 °C of anneal temperatures. Removal of retained organic components by thermal processing of MLD films is demonstrated to be a promising and versatile route to porous thin films for a wide range of applications including low dielectric constant materials.

Polyimides with low dielectric constants and dissipation factors at high frequency derived from novel aromatic diamines with bistrifluoromethyl pendant groups

Fan-out wafer-level packaging (FOWLP) urgently demands low dielectric constant and dissipation factor interlayer dielectric materials to mitigate high transmission losses at high frequencies.

A low dielectric constant material synergized by calix[4]arene and benzocyclobutene units

A novel low-kmaterial (Dkis as low as 2.23) was prepared from functionalized 4-tert-butylcalix[4]arene with different numbers of benzocyclobutene (BCB) units (2 or 4) and spacers (–(CH2)3– or –(CH2)6–).

Design and synthesis of novel phenolphthalein-based poly (aryl ether) resin containing isopropyl groups

With the rapid development of 5G technology, low dielectric constant materials present a widespread application prospect in microelectronic devices. Poly (aryl ether) resins have been widely used in this field due to their excellent thermal stability, mechanical properties and electrical insulation properties, however, reducing its dielectric constant remains a challenge. In this study, novel phenolphthalein poly (aryl ether ketone) containing isopropyl groups and fluorene groups was successfully synthesized with high molecular weight via SN2 aromatic nucleophilic polycondensation reaction. At lower frequencies ranging from 10 Hz to 1 MHz and higher frequencies from 10 GHz to 42 GHz, the films exhibit the intrinsic dielectric constant in the range of 2.4–2.7. The resin has good thermal stability, mechanical properties and insulation properties. Thus, the functional poly (aryl ether ketone) possesses attractive potential applications in the field of high-performance flexible electronic packaging materials.

Light weight, low dielectric constant, super-robust polylactide film based on stress-induced cavitation aided by crystallization

Exploiting pollution-free and highly efficient pore-forming method for low dielectric constant biodegradable materials remains a challenge in green electronics field. As biodegradable polylactide (PLA) exhibits good electric insulation, herein a facile “casting-thermal stretching” approach via stress-induced cavitation aided by crystallization is reported to obtain porous PLA films. The extensional stress and optical purity have vital influence on determining the hierarchical structures (oriented crystallites and porous structure). Hence the PLA with the highest optical purity (>99%) has the best comprehensive properties: When the DR reaches 6.6 (PLA99–6.6), the PLA99–6.6 film exhibits light weight (0.99 g/cm3), low dielectric constant (2.48 at 1 kHz), low dielectric loss (4.6 × 10−3 at 1 kHz), super robustness (tensile strength of 185.9 MPa, Young's modulus of 4.5 GPa and tensile strain of 12.4%) and excellent durability under high temperature and humidity condition, which have great potential application in green electronics.

High-performance and low-dielectric cyanate ester resin optimized by regulating the structure of linear polyhydroxy ether modifier

Cyanate ester resin (CE) is an ideal candidate for low dielectric constant (low-k) materials in the microelectronic industry, however the incoordination among mechanical, thermal and low-k properties greatly restricts their practical applications. Herein, two kinds of fluorinated polyhydroxy ether (PHE) with or without polyhedral oligomeric silsesquioxane (FPHE, FPHE-POSS) were designed and synthesized by regulating the structure of the linear PHE chains, to modify CE resin for elevating its comprehensive performances. Results reveal that FPHE can improve the mechanical properties and reduce the k of CE resin to some extent owing to its weakly polarizable flexible chains. Whereas FPHE-POSS can not only enlarge the optimization effects from FPHE, but also significantly improve thermostability simultaneously due to the extra-contribution of the heat-resistant rigid skeleton (POSS). Especially, FPHE-POSS6/CE possesses lower k values (2.48, 1 MHz), superior impact strength (24.59 kJ/m2, increased by 65.0 %) and higher glass transition temperature (307.6°C, increased by 18.8°C) as compared with pure CE resin. This work proposed a facile strategy to break through the incoordination among dielectric, thermal, and mechanical properties of CE resin via using weak-polarizable and flexible-rigid linear oligomer, which could be a guidance for advanced researches.