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Liquid crystal alignment with a photo-crosslinkable and solvent-soluble polyimide film
(2000-05-15)
Lee, WC
;
Hsu, CS
;
Wu, ST
;
應用化學系
;
Department of Applied Chemistry
A new photo-crosslinkable and solvent-soluble polyimide containing cinnamate side chains (PICA) was developed for aligning nematic liquid crystals (LCs). Good LC alignment was achieved by exposing a long-wave linearly polarized ultraviolet (LPUV) light to the PICA film. The LC alignment direction is found perpendicular to the polarization axis of the incident LPUV light. The uniform alignment of LC molecules induced by PICA Films remains intact after being heated at 85 degreesC for 450 hours. A small pretilt angle on the PICA film was generated by the double exposure method.
Mechanical properties of clay-polyimide (BTDA-ODA) nanocomposites via ODA-modified organoclay
(2000-11-15)
Tyan, HL
;
Wei, KH
;
Hsieh, TE
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Clay-polyimide [3,3', 4,4'-benzophenone tetracarboxylic dianhydride-4,4'-oxydianiline (BTDA-ODA)] nanocomposites were synthesized from ODA-modified montmorillonite (organoclay) and poly(amic acid). The layered silicates of organoclay were intercalated by polyimide (BTDA-ODA), as confirmed by X-ray diffraction and by transmission electron microscopy, and the tensile mechanical properties of the nanocomposites were measured. It was found that the modulus and the maximum stress of these organoclay/BTDA-ODA nanocomposites were much higher than those of pure BTDA-ODA: a twofold increase in the modulus and a one-half-fold increase in the maximum stress in the case of 7/93 organoclay-BTDA-ODA. In addition, the elongation-for-break of organoclay/BTDA-ODA nanocomposites is even slightly higher than that of pure BTDA-ODA, which is a sharp contrast to that of conventional inorganics-filled polymer composites. (C) 2000 John Wiley & Sons, Inc.
Effect of montmorillonite on thermal and moisture absorption properties of polyimide of different chemical structures
(2001-08-15)
Tyan, HL
;
Wu, CY
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The thermal properties and the moisture absorption of three types of polyimide/montmorillonite nanocomposite were investigated: 3,3 ' ,4,4 ' -biphenyl tetracarboxylic dianhydride-4,4 ' -oxydianiline (BPDA-ODA); pyromellitic dianhydride-ODA (PMDA-ODA); and 3,3 ' ,4,' -benzophenone tetracarboxylic dianhydride-ODA (BTDA-ODA). The inhibition effect on in-plane coefficients of thermal expansion (CTE) and moisture absorption of these polyimide nanocomposites by layered silicates from montmorillonite was found to decrease with the crystallinity in the pristine polyimides. The largest reduction, 30% in in-plane CTE occurred in the case of amorphous BTDA-ODA containing 5 wt % montmorillonite as compared with that of pure BTDA-ODA, while the reduction in in-plane CTE was 20% for the case of semicrystalline BPDA-ODA. The maximum reduction in moisture absorption, 43%, also took place for the case of 3/97 ODA-Mont/BTDA-ODA as compared with that of pure BTDA-ODA, whereas the semicrystalline 1/99 PPD-Mont/BPDA-ODA showed a 30% reduction as compared with that of pure BPDA-ODA. (C) 2001 John Wiley & Sons, Inc.
Sensitivity of the photo-crosslinkable polyimide for liquid crystal alignment
(2001-10-01)
Lee, WC
;
Hsu, CS
;
Wu, ST
;
應用化學系
;
Department of Applied Chemistry
Two methods were developed for enhancing the photosensitivity of the cinnamates-contained polyimide (PICA), One is to increase the content of cinnamate side chain in PICA main chain and another is to blend some photosensitizer into PICA films. Our experimental results show that increasing the rate of photo-dimerization decreases the alignment ability of the PICA films. Using the molecular simulation method, we successfully describe the photoalignment mechanism of the PICA films. It is also found that photo-induced LC alignment ability of the PICA film could be enhanced through choosing a proper coating solvent.
Curing of polyimide and the effect of the TEOS SiO2 barrier layer on the electromigration of sputtered Cu with polyimide passivation
(2002-01-01)
Hung, HY
;
Chiou, BS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The curing process of polyimide and the electromigration of copper films with polyimide (PI) passivation are studied. Thermal analysis of polyimide suggests that imidization completes at similar to200degreesC with an endothermic reaction associated with the breaking of the C-OH and N-H bonds as revealed by Fourier transformation infrared spectroscopy (FTIR). Although there is 89.8% weight loss when PI is heated from 20 degreesC to 200 degreesC, outgassing of PI passivation is still observed at higher temperatures. Carbon, nitrogen, and oxygen atoms diffuse into Cu during thermal processing of PI/Cu films. The tetraethyl orthosilicate (TEOS) SiO2 films are used as the barrier layer between PI and Cu to retard the poisoning of Cu. The effect of TEOS SiO2 film on electromigration of Cu is investigated.
Electroluminescence characteristics of aromatic polyimides by vapor deposition polymerization
(2003)
Hsu, SC
;
Whang, WT
;
Chen, SC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Light emitting polyimide (PI) thin films are successfully prepared from two kinds of diamines: 2,5-Bis(4-aminophenyl)-1,3,4-oxadiazole (BAO) and 4,4'-(9-Fluorenylidene)dianiline (BAPF) reacting with 4,4'-(Hexafluoroisopropylidene)diphthalic anhydride (6FDA) by vapor deposition polymerization (VDP). We succeed to reduce the thickness of the thin polyimide film to 150 Angstrom, and the threshold voltage of BAO-6FDA and BAPF-6FDA PI light-emitting diodes to 4.5 V and 6.5 V respectively. The root mean square of the surface roughness of the BAO-6FDA and BAPF-6FDA PI films are 8.8 Angstrom and 4.7 Angstrom respectively. But that of the BAO-6FDA film from wet coating process is 37.1 Angstrom. Apparently, VDP process is the better way to produce smooth polyimide film. The BAO-6FDA LED film emits a broader electroluminscence (EL) band, covering the full range of visible light (400 nm to 700 nm), than the BAPF-6FDA LED. However, the electroluminescence efficiency of BAPF-6FDA LED device is better than BAO-6FDA LED device. It is due to the better balance on the hole and electron injection in the former and better intermolecular charge transfer.
The synthesis and morphology characteristic study of BAO-ODPA polyimide/TiO2 nano hybrid films
(2003-04-01)
Chiang, PC
;
Whang, WT
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Hybrid nanocomposite films of titanium dioxide (TiO2) in polyimide (PI) from 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole (BAO) and 4,4'-1-oxydiphthalic anhydride (ODPA) have been successfully fabricated by an in situ sol-gel process. These nanocomposite films exhibit fair good optical transparency up to 40 wt% of TiO2 Content. X-ray diffraction spectroscopy shows three sharp peaks in pure BAO-ODPA PI. It results from the intermolecular regularity. However, the intermolecular regularity in the hybrid film is disrupted by the introduction of TiO2 nanoparticles with no sharp peak in XRD spectra. Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) results confirm the formation of TiO2 particles in PI matrix. The surface Ti content is much lower than the theoretical bulk content in all hybrid films. The ratio of the former to the latter increases with the TiO2 content and levels off at TiO2 wt% greater than or equal to 20. Transmission electron microscope (TEM) images show that the TiO2 phase is well dispersed in the polymer matrix. The size of the TiO2 phase increases from 10 to 40 nm when the TiO2 content is 5-30 wt%, respectively. (C) 2003 Elsevier Science Ltd. All rights reserved.
Effects of underlayer dielectric on the thermal characteristics and electromigration resistance of copper interconnect
(2003-12-01)
Chin, YL
;
Chiou, BS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effects of underlayer dielectric on the thermal characteristics and electromigration resistance of copper interconnects are investigated. It is shown that the thermal impedance of metal lines on polyimide is about three times that of metal lines on plasma-enhanced chemical vapor deposition of tetraethylorthosilicate (PETEOS) oxide. The open-circuit failure occurs after 75 s stressing at a current density of 1.4 x 10(7) A/cm(2) for polyimide underlayer specimens due to the high joule heating effect which causes the extreme temperature rise at, interconnects. Hence, decomposition of polyimide occurred which further accelerated the breakdown of interconnects. The thermal impedance is one of the major factors causing the electrical resistance to change during the electromigration (EM) test. The activation energies for electromigration of Cu are 0.87 eV for SiO2/Cu/PI2610 and 0.65 eV for SiO2/Cu/SiO2. After 500 thermal cycles, both the mean time-to-failure (MTF) and activation energy E-a decrease for EM, and lognormal standard deviation increases. At 225degreesC, the MTF of SiO2/Cu/PI2610 is about two times longer than that of SiO2/Cu/SiO2.
Effects of titania content and plasma treatment on the interfacial adhesion mechanism of nano titania-hybridized polyimide and copper system
(2004-06-03)
Chiang, PC
;
Whang, WT
;
Wu, SC
;
Chuang, KR
;
材料科學與工程學系
Nano-titania (TiO2) incorporated into polyimide (PI) matrix can significantly enhance the adhesion strength for PI/TiO2 hybrid film and copper system. Surface modifications by various plasma treatments (Ar, Ar/N-2 and Ar/O-2) were also applied in this study to improve the adhesion strength. The Ar/N2 plasma treatment is regarded as the more effective way in promoting the adhesion strength. The maximum adhesion value of 9.53 N/cm was obtained for the PI/TiO2-1 wt% hybrid film with Ar/N-2 plasma treatment. It is enhanced about 10 times as large as pristine PI. Furthermore, by Ar/O-2 plasma treatment, a weak boundary of copper oxide was formed at the interlayer between PI/TiO2 hybrid film and copper which decreases the adhesion strength. The effects of plasma treatment and content of nanosized TiO2 on the adhesion strength between PI/TiO2 hybrid film and copper system were studied. Atomic force microscope and contact angle analyses were used to measure the changes in surface morphology and surface energy as a result of plasma treatment. Besides, the interfacial states of peeled-off polymer side and copper side were investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Based on the result of XPS spectra, the peeled-off failure mode between PI/TiO2 hybrid film and copper was proposed in this study. (C) 2004 Elsevier Ltd. All rights reserved.
Polyimide and polyhedral oligomeric silsesquioxane nanocomposites for low-dielectric applications
(2005-01-06)
Lee, YJ
;
Huang, JM
;
Kuo, SW
;
Lu, JS
;
Chang, FC
A novel polyimide (PI) hybrid nanocomposite containing polyhedral oligomeric silsesquioxane (POSS) with well defined architecture has been prepared by copolymerization of octakis(glycidyldimethylsiloxy)octasilsesquioxane (Epoxy-POSS), 4,4'-oxydianiline diamine (ODA), and 4,4'-carbonyldiphthalic anhydride (BTDA). In these nanocomposite materials, the equivalent ratio of the Epoxy-POSS and ODA are adjustable, and the resultant PI-POSS nanocomposites give variable thermal and mechanical properties. More importantly, we intend to explore the possibility of incorporating POSS moiety through the Epoxy-POSS into the polyimide network to achieve the polyimide hybrid with lower dielectric constant (low-k) and thermal expansion. The lowest dielectric constant achieved of the POSS/PI material (PI-10P) is 2.65 by incorporating 10 wt% Epoxy-POSS (pure PI, k = 3.22). In addition, when contents of the POSS in the hybrids are 0, 3, 10 wt% (PI-0P, PI-3P, PI-10P), and the resultant thermal expansion coefficients (TEC) are 66.23, 63.28, and 58.25 ppm/degreesC, respectively. The reduction in the dielectric constants and the resultant thermal expansion coefficients of the PI-POSS hybrids can be explained in terms of creating silsesquioxane cores of the POSS and the free volume increase by the presence of the POSS-tethers network resulting in a loose PI structure. (C) 2004 Elsevier Ltd. All rights reserved.

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