Low dielectric organic materials have been studied extensively, however, the relationship and regularity between the molecular structure and the dielectric properties is still not clear and barely reported. In this study, we report the synthesis of three polyimides (PPy6F, mBPPy6F and mTPPy6F) containing the same diphenylpyridine core structure but different side-chains with varied number of benzene rings. The polyimides PPy6F, mBPPy6F and mTPPy6F which contain one, two and three benzene rings in the pendant group, respectively, show intrinsic dielectric constant k values of 2.81 (PPy6F), 2.61 (mBPPy6F) and 2.44 (mTPPy6F). The reason for the reduced k value with increasing number of benzene rings in the pendant group is discussed through the investigation of morphology, density and water absorption properties of these polyimides. This discovery provides us with a new and easy strategy to obtain lower dielectric polymers. Polyimide mTPPy6F shows excellent comprehensive properties, with a high glass transition temperature (Tg) of 342 °C, a 5 wt% loss temperature (Td,5%) of 551 °C, tensile strength of 105 MPa, low moisture absorption of only 0.61% and good solubility in common organic solvents.

Intrinsic low dielectric constant polyimides: relationship between molecular structure and dielectric properties

Low dielectric polymers play an important role in replacing traditional inorganic dielectric materials in advanced electronic manufacturing due to their excellent physical and chemical properties. Herein we report the preparation and characterization of two novel low-k dielectric polymers by introducing adamantane into benzocyclobutene. Because the adamantyl group has low polarizability and can increase the free volume of the polymer, both polymers showed low dielectric constants (2.5) and low dielectric loss ( 350 °C), high storage modulus and good thermal stability (Td > 400 °C in nitrogen). Especially, the p-Ada-TVS-BCB polymer showed a low coefficient of thermal expansion (41 μm m−1 °C−1). All of these good properties are in accord with the requirement of the interconnect fabrication of Cu metallization using the damascene process. Both of the polymers are suitable for the utilization in the electronic packing industry.

Adamantyl-based benzocyclobutene low-k polymers with good physical properties and excellent planarity

A novel class of lamellar structured polyhedral oligomeric silsesquioxane/bisphenol Z (POSS/BPZ) polybenzoxazine (PBz) nanocomposites was successfully designed by a facile one-step copolymerization technique. The chemical structures of the monomer and resulting polymer were characterized by Fourier transform infrared (FTIR) spectroscopy, 1H, 13C, DEPT-135, 29Si NMR (nuclear magnetic resonance) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The desired cross-linked lamellae structural arrangement of POSS/BPZ polybenzoxazine (PBz) nanocomposites was confirmed by transmission electron microscopy (TEM). The BPZ-PBz and POSS-PBz layers were self-assembled by intermolecular hydrogen bonding in such a way as to form the lamellar structure during ring opening polymerization. An advantage of this lamellar structure is that 30% POSS/BPZ polybenzoxazine composite exhibits an ultra low-k value of 1.7 at 1 MHz as well as high thermal stability.

Design of lamellar structured POSS/BPZ polybenzoxazine nanocomposites as a novel class of ultra low-k dielectric materials

A series of fluorinated polyimide/POSS hybrid polymers (FPI-4-FPI-16) were prepared via a facile synthetic route using 2,2'-bis(trifluoromethyl)benzidine, 4,4'-oxydiphthalic dianhydride and monofunctional POSS as starting materials. The hybrid polymers showed excellent solubility and film formation ability. Flexible and robust hybrid films could be conveniently obtained via solution-casting. The hybrid films demonstrated low dielectric constants and high thermal stability. Their dielectric constants were in the range of 2.47-2.92 at 1 MHz measured for their capacitance, and were tunable and decreased with an increase of POSS content. Their 10% weight loss temperatures were in the range of 539-591℃ and the weight residual at 800℃ ranged from 48% to 53% in nitrogen atmosphere. These hybrid films also possessed good mechanical properties and hydrophobic characteristics. This work could provide a potential strategy for the preparation of fluorinated polyimide/POSS hybrid polymers.

Fluorinated polyimide/POSS hybrid polymers with high solubility and low dielectric constant

POSS (polyhedral oligomeric silsesquioxane) reinforced polyurethane (PU) based polybenzoxazine (PBz) nanocomposites were prepared as an interlayer low k dielectric material for microelectronics applications based on the concept of polarization and porosity of the composite. The hydroxyl terminated benzoxazine (OH–Bz) materials containing a less polar long aliphatic chain and hydroxyl terminated nanoporous POSS (OH–POSS) material were synthesized and copolymerized with hexamethylenediisocyante (HMDI) to obtain POSS–Bz–PU nanocomposites. Dielectric analysis of different concentrations of POSS reinforced PU–PBz nanocomposites indicates that the incorporation of POSS into the polymer matrix significantly reduced the value of the dielectric constant. Despite this, the reduction of dielectric constant by reinforcement is limited up to 30% POSS–PU–PBz (k = 1.94) and beyond this concentration the reverse trend was observed which might be due to the increasing density of the resulting composites by agglomeration of POSS nanoparticles. The SEM images of 40% POSS–PU–PBz composites evidently support the agglomerate formation of POSS particles. Besides, the thermal stability of the resulting POSS reinforced PU–PBz nanocomposites also increased to an appreciable extent.

Dielectric and thermal behaviors of POSS reinforced polyurethane based polybenzoxazine nanocomposites

The novel ultra low dielectric constant poly(ether ether ketone) hybrid films in which nanoscale phosphotungstic acid (PWA) clusters were grafted onto the side chains of poly(ether ether ketone) containing (3-trifluoromethyl) phenyl groups and carboxyl groups (PEEK–CF3–COOH) in the presence the silane coupling agent γ-aminopropyltriethoxysilane (KH-550) were prepared and characterized. The chemical structures of the PWA/PEEK–CF3–COOH hybrid films were confirmed by FT-IR spectroscopy and 1H-NMR. The analysis of wide-angle X-ray diffraction (WAXD) indicated that the PWA clusters could not form crystalline structures in the PEEK–CF3–COOH matrix, and the investigation of the scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) (W-mapping) revealed that the PWA particles were well dispersed in the PEEK–CF3–COOH matrix with nanoscale. The influence of the incorporation of PWA particles by side chain grafting reaction on the properties of PEEK–CF3–COOH was studied. The dielectric constants of the PWA/PEEK–CF3–COOH hybrid films were remarkably lower than that of the neat PEEK–CF3–COOH film and the lowest value their dielectric constant could achieve was as low as 1.96 (1 MHz) when the content of grafted PWA reached 10 wt%. Meanwhile, the hybrid films still retain the excellent thermal and mechanical properties as well as the good transparency.

Ultra low dielectric constant hybrid films via side chain grafting reaction of poly(ether ether ketone) and phosphotungstic acid

A series of novel amorphous poly(aryl ether ketone) random copolymers containing rigid bulky pendant adamantyl groups and different length symmetrical alkyl side chains were synthesized and charact...

The influence of different length of symmetrical alkyl side chains on the dielectric constant of soluble poly(aryl ether ketone) copolymers

The invention belongs to the technical field of organic chemistry, and more specifically relates to a novel (4-(1-adamantyl))phenyl hydroquinone bisphenol monomer which contains adamantyl groups and is used for preparing functional poly(aryl ether) polymers and to a preparation method for the same. (4-(1-adamantyl))phenyl hydroquinone is prepared by the following steps that: 1-bromoadamantane and antifebrin undergo a Fiedel-Crafts alkylation reaction so as to obtain para-adamantyl antifebrin; acetyl is removed under acidic condition so as to obtain hydrochloride of para-adamantyl aniline; the obtained hydrochloride is subjected to a diazo reaction first and couples with benzoquinone next so as to obtain (4-(1-adamantyl))benzoquinone; and the (4-(1-adamantyl))benzoquinone undergoes a reduction reaction so as to obtain the target product (4-(1-adamantyl))phenyl hydroquinone. According to the invention, the synthetic route of the product is simple; monomers of the raw materials are stable at room temperature; the prepared product has broad application prospects in preparing electronic packaging materials and gas perm-selective membranes which have excellent thermal performance, a low dielectric constant and low water absorption.

Jinyu Ba

Papers

Ultra low dielectric constant hybrid films via side chain grafting reaction of poly(ether ether ketone) and phosphotungstic acid

The influence of different length of symmetrical alkyl side chains on the dielectric constant of soluble poly(aryl ether ketone) copolymers

(4-(1-adamantyl))phenyl hydroquinone and preparation method thereof