Decomposition Of Polyimide Research Articles

Fabrication of a Bilayer Structure of Cu and Polyimide To Realize Circuit Microminiaturization and High Interfacial Adhesion in Flexible Electronic Devices.

With commercialization of the fifth-generation mobile communication system and the further spread of the Internet of Things, industrial innovation is arriving with new business fields related to concepts such as high-speed communication, self-driving vehicles, and remote medicine. One of the challenges is the realization of flexible devices with high-definition circuits, which requires new fabrication techniques for Cu films on polymer substrates to meet demands and an understanding of Cu/polymer interfacial nanostructure to assure product quality. We have developed a promising technique for the fabrication of Cu film on polyimide (PI), which consists mainly of very simple semiconductor device processes. This technique allows for control of the Cu thickness with nanometer precision to form miniaturized Cu circuits with potential advantages in terms of interfacial adhesion and material/production costs. The Cu/PI interfaces fabricated by conventional vapor deposition and the new technique are systematically analyzed using synchrotron hard X-ray photoelectron spectroscopy, scanning transmission electron microscopy, and time-of-flight secondary ion mass spectroscopy. With conventional vapor deposition, it was discovered that evaporated Cu atoms decompose the PI and an oxidation layer with a thickness of several nanometers that deteriorates the interfacial adhesion could be visualized at the Cu/PI interface. With the new technique, the decomposition of PI and interfacial oxidation are significantly suppressed. Furthermore, the proposed technique can be broadly applied to the investigation of metal/polymer interfaces fabricated by polymer coating on a metal substrate, which has so far been impossible.

Preparation and characterization of a polyimide nanofoam through grafting of labile poly(propylene glycol) oligomer

AbstractPreparation of a polyimide nanofoam (PI‐F) for microelectronic applications was carried out using a polyimide precursor synthesized from poly[(amic acid)‐co‐(amic ester)] and grafted with a labile poly(propylene glycol) (PPG) oligomer. Polyimide precursor was synthesized by partial esterification of poly(amic acid) (PAA) derived from pyromellitic dianhydride (PMDA) and 4,4′‐oxydianiline (ODA). The precursor was then grafted with bromide‐terminated poly(propylene glycol) in the presence of K2CO3 in hexamethylphosphoramide and N‐methylpyrrolidone, imidized at 200°C in nitrogen and the product was subsequently decomposed in air at 300°C to eliminate the labile PPG oligomer to produce PMDA/ODA polyimide nanofoam. Nuclear magnetic resonance spectroscopy (1H‐NMR) and Fourier transform infrared spectroscopy (FT‐IR) techniques were used to characterize the formation of polyimide precursor and extent of grafting of PPG with polyimide. The results of thermogravimetric analysis (TGA) showed three step decomposition of nanofoam with the removal of PPG at 350°C and decomposition of polyimide at around 600°C. The polyimide nanofoams were also characterized by small angle X‐ray scattering (SAXS), field‐emission scanning electron microscopy (FE‐SEM) and transmission electron microscopy (TEM). The morphology showed nanophase‐separated structures with uniformly distributed and non‐interconnected pores of 20–40 nm in size. Dynamic mechanical analysis (DMA) indicated higher storage modulus for the foamed structure compared to the pure PI with reduction in loss tangent for the former system. Copyright © 2004 John Wiley & Sons, Ltd.

Anisotropic Decomposition of Polyimide Molecules Induced by Irradiation of Linearly Polarized UV Light

We have investigated the anisotropic decomposition of polyimide (poly[bis(4,4′-oxydiphenylene)-dimetylmetyl-pyromellitimide]) molecules induced by exposure to linearly polarized ultraviolet light (LPUVL) of wavelength ∼ 300 nm. The decomposition of the polyimide molecule was monitored by measuring the polarized infrared (IR) absorption spectra as a function of LPUVL exposure. We propose an empirical equation that describes the relation between the orientational distribution of polyimide chains and LPUVL exposure. We consider two decomposition rates β/ and β⊥ for the polyimide chains oriented parallel and perpendicular to the polarization direction of LPUVL, respectively. By taking account of the increase of the decomposition rates around 30 J·cm−2, the IR absorption data could be reproduced with β/β⊥ = 1.23 ± 0.02. The decomposition rate β/ is (4.5 ± 1.0) × 10−3J−1·cm2 for the LPUVL exposure range up to -30 J·cm−2, and (1.6 ± 0.1) × 10−2 J−1·cm2 beyond -30 J·cm−2.

Controlled Rate Thermogravimetry: New usefulness of controlled rate thermogravimetry revealed by decomposition of polyimide

Curves obtained by controlled rate TG of polyimide film in air are quite different from those obtained by conventional constant rate heating TG. A two step mass loss was observed during the constant rate heating TG, while mass loss proceeded as a single step process in the controlled rate TG. To elucidate the cause for this difference, kinetic analysis was made, and it was found that the reaction mechanism in a lower temperature range is different from those in a higher temperature range. The lower temperature decomposition is a single step process, and the higher temperature decomposition is a two-step process. The reason for the difference is that only the low temperature single step process is observed in the controlled rate TG, while both reactions are observed in the constant heating rate TG along with the temperature increase. This speculation was confirmed by isothermal TG. These facts show us another usefulness of controlled rate TG. To analyze the three types of TG data together, the Friedman—Ozawa method was used, and it is demonstrated to be the most appropriate and reliable.

Oxidation of Cu in contact with preimidized polyimide

We have investigated interface formation and degradation at the junction of preimidized polyimide and Cu by means of scanning Auger and secondary electron microscopies, and x-ray photoelectron spectroscopy. Our approach has been to spin on ultrathin (tens of Å) polyimide overlayers onto Cu substrates, cure the polyimide while in contact with the Cu in an inert atmosphere, and then expose the interface to different environments. We found that only a very small amount of oxidation occurs during the curing process itself. This result is expected on the basis of the preimidization step prior to contact with Cu. The limited amount of oxidation appears to be due to the formation of a Cu–amine complex at the interface. Storage in vacuum leaves the interface abrupt and no further oxidation occurs. However, exposure to room-temperature air or high humidity at 85 °C causes more extensive Cu oxidation to occur. In the case of exposure to high humidity at 85 °C, metal oxidation is accompanied by Cu outdiffusion and polyimide decomposition. The interface degradation process after curing appears to be driven by absorption of water, and the primary degradation reaction product is CuO.

Excimer Laser Applications: Polymer Etching and Metal Deposition

AbstractExcimer laser induced ablative decomposition of polyimide and poly(methylmethacrylate) at high fluences (> 1 J/cm2) is discussed. It is shown that 0.4 μm sized features can be imaged in polyimide using ArF laser pulses. Preliminary results from experiments in which copper particles (<1 μm in size) have been deposited by exposing thin films of a copper formate and glycerol paste to KrF laser radiation are presented.

The Effect of the Polymer Coating on Residual Current of Mos Devices

The influence of polyimides on seniconductor devices has been studied by measuring the residual current in an MOS test device in which the gate position was0 incompletely covered by the gate electrode. Residual currents were found to be a function of the heat-treatment temperature of the coated polyamic acid. At first the residual current decreased with increasing heat-treatment temperature, untill a minimum value was reached, then it increased with temperature. These phenomena are d'iscussed with respect to the physical and chemical properties of the polyimide, e. g. flowing temperature, adhesion characteristics, decomposition temperature, impurities, and amount of unreacted amidic acid groups. Unreacted amidic acid groups and decomposition of polyimide caused a high residual current, while good adhesion of the polyimide to the MOS device brought about a low residual current.