Low Dielectric Constant Polyimide Research Articles

Nanoporous low-? polyimide films prepared from poly(amic acid)s with grafted poly(methylmethacrylate)/poly(acrylamide) side chains

Copolymers of poly[N,N′-(1,4-phenylene)-3,3′4,4′-benzophenonetetra-carboxylic amic acid] (PAmA) with grafted poly(methylmethacrylate) (PMMA) and poly(acryamide) (PAAM) side chains (PMMA-g-PAmA and PAAM-g-PAmA, respectively) were synthesized by thermally-induced graft copolymerization of methylmethacrylate (MMA) and acrylamide (AAM) with the ozone-pretreated PAmA in N-methyl-2-pyrrolidone (NMP) solutions. The graft copolymers were characterized by elemental analysis, X-ray photoelectron spectroscopy (XPS), thermogravimetric (TG) analysis, and differential scanning calorimetry (DSC). Nanoporous low dielectric constant (low-κ) polyimide (PI) films were obtained by thermal imidization of the PAmA graft copolymers under reduced argon pressure, followed by thermal decomposition of the side chains in air. The nanoporous PI films were characterized by density, scanning electron microscopy (SEM) and dielectric constant measurements. Nanoporous PI films with porosities in the range 4–15% and pore sizes in the range 30–60 nm were obtained. Dielectric constants as low as 2.3 and 2.5 were obtained for the nanoporous PI films prepared from the PMMA-g-PAmA and PAAM-g-PAmA copolymers, respectively.

Nanoporous Polyimides Derived from Highly Fluorinated Polyimide/Poly(propylene Oxide) Copolymers

Porous, low dielectric constant polyimide films have been made by a “nanofoam” approach. The pore sizes generated in the polymer films are in the tens of nanometers range, hence the term “nanofoams...

Photo-Induced Large Area Growth of Dielectrics With Excimer Lamps

ABSTRACTIn this paper, UV-induced large area growth of high dielectric constant (Ta2O5, TiO2and PZT) and low dielectric constant (polyimide and porous silica) thin films by photo-CVD and sol-gel processing using excimer lamps, as well as the effect of low temperature UV annealing, are discussed. Ellipsometry, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), UV spectrophotometry, atomic force microscope (AFM), capacitance-voltage (C-V) and current-voltage (I-V) measurements have been employed to characterize oxide films grown and indicate them to be high quality layers. Leakage current densities as low as 9.0×10−8 A·cm−2and 1.95×10−7 A·cm−2at 0.5 MV/cm have been obtained for the as-grown Ta2O5 films formed by photo-induced sol-gel processing and photo-CVD, respectively – several orders of magnitude lower than for any other as-grown films prepared by any other technique. A subsequent low temperature (400°C) UV annealing step improves these to 2.0×10−9A·cm−2and 6.4×10−9A·cm−2, respectively. These values are essentially identical to those only previously formed for films annealed at temperatures between 600 and 1000°C. PZT thin films have also been deposited at low temperatures by photo-assisted decomposition of a PZT metal-organic sol-gel polymer using the 172 nm excimer lamp. Very low leakage current densities (10−7A·cm2) can be achieved, which compared with layers grown by conventional thermal processing. Photo-induced deposition of low dielectric constant organic polymers for interlayer dielectrics has highlighted a significant role of photo effects on the curing of polyamic acid films. I-V measurements showed the leakage current density of the irradiated polymer films was over an order of magnitude smaller than has been obtained in the films prepared by thermal processing. Compared with conventional furnace processing, the photo-induced curing of the polyimide provided both reduced processing time and temperature. A new technique of low temperature photo-induced sol-gel process for the growth of low dielectric constant porous silicon dioxide thin films from TEOS sol-gel solutions with a 172 nm excimer lamp has also been successfully demonstrated. The dielectric constant values as low as 1.7 can be achieved at room temperature. The applications investigated so far clearly demonstrate that low cost high power excimer lamp systems can provide an interesting alternative to conventional UV lamps and excimer lasers for industrial large-scale low temperature materials processing

Photo-induced Large Area Growth Of Dielectrics With Excimer Lamps

AbstractIn this paper, UV-induced large area growth of high dielectric constant (Ta2O5, TiO2and PZT) and low dielectric constant (polyimide and porous silica) thin films by photo-CVD and sol-gel processing using excimer lamps, as well as the effect of low temperature LW annealing, are discussed. Ellipsometry, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), UV spectrophotometry, atomic force microscope (AFM), capacitance-voltage (C-V) and current-voltage (I-V) measurements have been employed to characterize oxide films grown and indicate them to be high quality layers. Leakage current densities as low as 9.0×10−8 Acm−2 and 1.95×10−7 Acm−2 at 0.5 MV/cm have been obtained for the as-grown Ta2O5 films formed by photo-induced sol-gel processing and photo-CVD. respectively - several orders of magnitude lower than for any other as-grown films prepared by any other technique. A subsequent low temperature (400°C) UV annealing step improves these to 2.0×10−9 Acm−2 and 6.4× 10−9 Acm−2, respectively. These values are essentially identical to those only previously formed for films annealed at temperatures between 600 and 1000°C. PZT thin films have also been deposited at low temperatures by photo-assisted decomposition of a PZT metal-organic sol-gel polymer using the 172 nm excimer lamp. Very low leakage current densities (10−7 A/cm2) can be achieved, which compared with layers grown by conventional thermal processing. Photo-induced deposition of low dielectric constant organic polymers for interlayer dielectrics has highlighted a significant role of photo effects on the curing of polyamic acid films. I-V measurements showed the leakage current density of the irradiated polymer films was over an order of magnitude smaller than has been obtained in the films prepared by thermal processing. Compared with conventional furnace processing, the photo-induced curing of the polyimide provided both reduced processing time and temperature, A new technique of low temperature photo-induced sol-gel process for the growth of low dielectric constant porous silicon dioxide thin films from TEOS sol-gel solutions with a 172 nm excimer lamp has also been successfully demonstrated. The dielectric constant values as low as 1.7 can be achieved at room temperature. The applications investigated so far clearly demonstrate that low cost high power excimer lamp systems can provide an interesting alternative to conventional UV lamps and excimer lasers for industrial large-scale low temperature materials processing.

Low loss multilayer microstrip line for monolithic microwave integrated circuits applications

This paper describes the multilayer microstrip structure using low dielectric constant polyimide as a buffer layer between the microstrip conductor and the GaAs substrate to reduce dissipation loss, especially for very high impedance microstrip lines. The new structure provides about half the dissipation loss and about 40% higher characteristic impedance in comparison to the conventional microstrip line on GaAs substrate having the same conductor widths. An empirical formula for the equivalent dielectric constant compatible with commercial computer-aided design tools was developed to design monolithic microwave integrated circuits (MMICs) using this medium. The multilayer microstrip structure is compatible with ITT's 4′ MSAG® process which uses polyimide for crossovers and scratch protection. The present structure has great potential in realizing low loss and wideband matching networks including low noise, high power, and high efficiency amplifiers, and passive components on GaAs substrate with improved insertion loss and bandwidth performance, and three-dimensional MMICs. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 441–454, 1998

Low dielectric constant polyimides derived from 1,3-bis(4-aminophenyl)adamantane

This work describes the synthesis of new adamantane-based polyimides by reaction of 1,3-bis(4-aminophenyl)adamantane (4) with various aromatic tetracarboxylic dianhydrides (5). The films have low dielectric constants ranging from 2.76 to 2.92. The poly(amic-acid)s 6 have inherent viscosities of 0.98∼1.42 dL/g. The polyimide 7 d is soluble in o-chlorophenol, m-cresol, chloroform and cyclohexanone. The inherent viscosity and number-average molecular weight of polyimide 7 d is 0.61 dL/g and 45 000, respectively. The films from 7 have tensile strengths of 69.7-110.8 MPa, elongation to breakage values of 2.1∼11.3%, and initial moduli of 2.0-2.3 GPa. Dynamic mechanical analysis (DMA) reveals that most polyimides 7 have two transitions. However, another subglass transition appears at 300°C in the extremely rigid polyimide 7 a . The glass transition temperatures of most polyimides 7, except 7 e and 7 f , exceed 360 °C according to DMA and DSC.

Low dielectric constant polyimides derived from 1,3-bis(4-aminophenyl)adamantane

Low dielectric constant polyimides derived from 1,3-bis(4-aminophenyl)adamantane

Photo-induced deposition of low dielectric constantpolyimide film for interlayer dielectric applications

The photo-assisted conversion of polyamic acid spun onto Si substrates into thin polyimide films at low temperature using a 172 nm excimer lamp is reported. Current-voltage measurements showed that the leakage current densities in the polymer were over an order of magnitude less than those obtained in films prepared by conventional thermal processing.

Fibers from a low dielectric constant fluorinated polyimide: Solution spinning and morphology control

Control of the internal morphology of wet-spun fibers from a fluorinated polyimide has been achieved by varying the rate of polymer coagulation through adjustments in nonsolvent/solvent miscibility and precipitation strength of the coagulation bath. Filament internal morphologies ranged from very porous or sponge-like to fully solid. Intermediate structures included fibers containing a spongy core with a nonporous skin, sponge-like fibers containing large voids, and a relatively solid material containing randomly spaced small voids. The cross-sectional shape of the fiber is dependent upon the coagulation process as well as the volume contraction of the initial extrudate. Drawn fibers (3×) retained the original asspun cross-sectional shape and also lost porosity. Mechanical properties of poly(6FDA-4BDAF) fibers have an inverse relationship to filament porosity. Maximum modulus and break strength for drawn fibers is approximately 6 CPa and 200 MPa, respectively. Asspun mechanical properties were dependent upon the processing conditions and have moduli between 0.4–3.0 Gpa and break strengths of 10–160 MPa. A dielectric constant of 2.50 for nonporous films was measured over a frequency range between 1.0 MHz to 1.8 GHz, showing little dispersion. © 1997 John Wiley & Sons, Inc.

Optical Properties of Low Dielectric Constant Polyimides and Effects of Orientation

AbstractControl of the refractive index in low dielectric constant polyimides through modification of chemistry and structure was investigated. The optical refractive indices of several low dielectric constant polyimides were measured, and the effects of orientation on optical anisotropy were determined. Refractive index in these polyimides was found to decrease with increasing fluorine content due primarily to the low electronic polarizability of the fluorine-carbon bonds. In zone drawn polyimides, refractive index was found to increase substantially in the direction of the draw, but decrease substantially normal to the draw direction. This was explained in terms of the preferential alignment of the polymer chains.