Polybenzoxazole Film Research Articles

Chemical and Morphological Modifications Induced by Argon Plasma Treatments on Fluorinated Polybenzoxazole Films.

Fluorinated photodefinable polymers are widely employed as re-distribution layers in wafer-level packaging to produce microelectronic devices because of their suitable low dielectric constant and moisture absorption, high mechanical toughness, thermal conductivity and stability, and chemical inertness. Typically, fluorinated photodefinable polybenzoxazoles (F-PBOs) are the most used in this field. In the present work, we investigated by atomic force microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy the morphological and chemical modifications induced by Ar plasma treatments on F-PBO films. This process, used to remove surface contaminant species, as well as increase the polymeric surface roughness, to improve the adhesion to the other components during electronic packaging, is a crucial step during the manufacturing of some microelectronic devices. We found that argon plasma treatments determine the wanted drastic increase of the polymer surface roughness but, in the presence of a patterned silver layer on F-PBO, needed for the fabrication of electric contacts in microelectronic devices, also induce some unwanted formation of silver fluoride species.

Nanoparticle-Catalyzed Green Chemistry Synthesis of Polybenzoxazole.

Enabling catalysts to promote multistep chemical reactions in a tandem fashion is an exciting new direction for the green chemistry synthesis of materials. Nanoparticle (NP) catalysts are particularly well suited for tandem reactions due to the diverse surface-active sites they offer. Here, we report that AuPd alloy NPs, especially 3.7 nm Au42Pd58 NPs, catalyze one-pot reactions of formic acid, diisopropoxy-dinitrobenzene, and terephthalaldehyde, yielding a very pure thermoplastic rigid-rod polymer, polybenzoxazole (PBO), with a molecular weight that is tunable from 5.8 to 19.1 kDa. The PBO films are more resistant to hydrolysis and possess thermal and mechanical properties that are superior to those of commercial PBO, Zylon. Cu NPs are also active in catalyzing tandem reactions to form PBO when formic acid is replaced with ammonia borane. Our work demonstrates a general approach to the green chemistry synthesis of rigid-rod polymers as lightweight structural materials for broad thermomechanical applications.

Highly Efficient AuPd Catalyst for Synthesizing Polybenzoxazole with Controlled Polymerization

Summary Using nanoparticles (NPs) to catalyze chemical reactions for the formation of functional polymers with controlled polymerization is an important field of chemical research. In this article, we report an AuPd NP system as an active and stable catalyst to catalyze one-pot reaction of formic acid, 1,5-diisopropoxy-2,4-dinitrobenzene, and terephthaldehyde, leading to the controlled polymerization and the formation of polybenzoxazole (PBO) (Mw = 3.6 kDa). The one-pot reaction is AuPd NP size and composition dependent, and 8-nm Au39Pd61 NPs are the best catalyst for the polymerization. The highly pure PBO shows excellent thermal stability up to 600°C and improved chemical and mechanical stability under challenging environmental conditions compared with commercial PBO (Zylon, Mw = 40 kDa). The reported NP-catalyzed one-pot reaction to polymerization is not limited to the formation of PBO but can be extended as a general approach to rigid polymers that are important for ballistic fiber, anti-flame, and smart-textile applications.

Integration of Photodefinable Polybenzoxazole as Intermetal Dielectric for GaAs HBT Technology

Polybenzoxazole (PBO) is a polymer dielectric that has excellent mechanical, physical, and electrical characteristics and that is used for various semiconductor thin film applications. The PBO has low dielectric constant, and has good thermal stability and thermo-oxidative resistance. Furthermore, the PBO material can be applied by spin-coating and can be cured at temperature of <300oC, which is significantly lower than many other spin-on dielectric materials. These characteristics make PBO suitable for use in many semiconductor technologies and applications that require the processing temperatures not to exceed 300oC, such as GaAs hetero-junction bipolar transistor (HBT) technology. The PBO material is easily processed, and can be made photodefinable by adding photoactive compounds, and therefore be patterned on semiconductor wafers. By using a photodefinable PBO dielectric material, there will not be any need to perform patterning by dry-etch process steps that are typically performed in GaAs technologies.In this study, photodefinable PBO has been integrated as intermetal dielectric in GaAs HBT technology. Process module optimization and integration studies were performed and the PBO results and process flow were compared to those of dry-etch polyimide, which is typically used as intermetal dielectric in GaAs technology. The photodefinable PBO is shown to allow the intermetal dielectric process flow to be simplified and the number of processes and equipments to be reduced. Results show that PBO has more planarity than polyimide, when coated on GaAs HBT wafers, which typically have significant topography. The PBO photolithography coat, expose, and develop processes were optimized in order to obtain the desired dielectric thickness and the required via dimension and sidewall profile, in addition to removing the PBO from the die street. The PBO thermal curing process was performed at 300oC, while ashing was performed to remove any PBO residue in the vias and streets. Figure 1 shows the FIB/SEM images of GaAs wafer after deposition of Metal 1 and coated with photodefinable, after via expose and develop, after cure, and after ash. Figure 2 shows the GaAs HBT wafer with (a) dry-etch polyimide and (b) photodefinable PBO used as intermetal dielectric. These results show that the photodefinable PBO film is compatible with, is suitable for, and can be integrated as intermetal dielectric in GaAs HBT technology.

Synthesis and photoluminescence properties of polybenzoxazoles containing perylenebisimide functionalized graphene nanosheets via stacking interactions

The stable acidic dispersion of reduced graphene oxide (RGO) is prepared by a non-covalent functionalization method using perylenebisimide-modified fluorinated poly(hydroxyamide) (PTCDA-6FPHA). Then a series of RGO–polybenzoxazole (PBO) composites were prepared by a solution blending method in MSA. The change of perylenebisimide absorption peaks in the UV-Vis absorption spectra indicates that π–π stacking indeed occurs between graphene and perylene rings. The conjugation between functionalized RGO and PBO molecular chains increases the conjugation degree of the composite, since the PTCDA-6FPHA-containing perylene rings have a high π-electron delocalization degree. The energy gap of RGO–PBO composite is 2.72 eV with the absorption edge at 456 nm. The corresponding data of pure PBO film are 2.78 eV and 446 nm, respectively. Moreover, the intensity of the two emission peaks at 442 and 467 nm in the PL emission spectra of RGO–PBO decreases rapidly along with the increase of RGO–PBO ratio. The intensity of the weak emission peak at 622 nm increases with the increase of the RGO–PBO ratio. This behavior can be attributed to the energy transfer between benzoxazole chromophore units and functionalized RGO. Meanwhile, the RGO–PBO composite has outstanding thermal stability.

Design and preparation of porous polybenzoxazole films using the tert-butoxycarbonyl group as a pore generator and their application for patternable low-k materials

The continuous advance of the device performance in microelectronics requires the development of the lower dielectric constant (low-k) materials. We target the development of a next generation low-k material based on poly(p-phenylene benzobisoxazole) (PPBO) films due to their low k value, remarkable mechanical toughness, excellent thermal stability, extremely low coefficient of thermal expansion and chemical inertness. In order to overcome the poor processability caused by the insolubility in organic solvents, the tert-butoxycarbonyl (t-Boc) group was introduced into the PPBO precursor (t-Boc-prePBO). The obtained t-Boc-prePBO shows excellent solubility in common organic solvents and fine films were successfully prepared. The thermal treatment of the t-Boc-prePBO film produces the PPBO film, which was completely characterized using IR. The low dielectric constant (k) value of 2.37 was achieved in the PPBO film. Scanning electron microscopy revealed the formation of a pore structure that plays an important role in the low k value of the film. The porous PPBO film also showed a good mechanical strength (16.0 MPa) and remarkably high thermal conductivity (0.445 W m−1 K−1). Furthermore, the t-Boc functionalization enabled micropatterning using a photolithographic technique. Such a patternable film with a low k value, mechanical toughness, and high thermal conductivity is a promising candidate for the next generation low-k materials. Our calculation revealed that a k value could be lowered to 1.98 by controlling the film morphology, the value that satisfies the requirement of the International Technology Roadmap for Semiconductors (ITRS 2009).

Photodefinable Polybenzoxazole as Interlevel Dielectric and Buffer Layer for GaAs HBT Technology

Polybenzoxazole (PBO) has been investigated and used as interlevel dielectric and buffer layer for GaAs hetero-junction bipolar transistor (HBT) technology. The polymer film is applied by spin-coating, and is photosensitive and photodefinable. These film characteristics allow the simplification of the process flow and allow the elimination of various steps that are typically used to define the vias, streets, and bonding pads. Additionally, this PBO film can be cured at low temperature (>250oC) and the resulting film has good characteristics against moisture absorption and is stable thermally. Furthermore, the film has good planarity and gapfill characteristics, and has excellent mechanical properties. Results show that GaAs device wafers fabricated with this film as interlevel dielectric has good electrical characteristics. When used as buffer layer, the PBO film is shown to be effective in mechanically protecting the underlying devices and interconnections. The use of photodefinable PBO will result in improvement in device quality and reliability, in addition to in significant reduction in capital and consumable cost, and reduction in cycle time of wafers manufactured. All the above characteristics make this PBO film to be well-suited as interlevel dielectric and buffer layer for and compatible with GaAs HBT technology.

Corrosion and Adhesion Properties of a Low-CTE Polybenzoxazole Film

The corrosion and adhesion properties between conductive silver pastes and a novel, solutionprocessable low-CTE polybenzoxazole (PBO) film were studied. In this study, a polyester and an epoxy resin were used as the binders of conductive pastes. The pastes were coated on the PBO film, then thermally cured. The samples obtained were cut using the SAICAS slant-cut method to analyze the corrosion caused by the corrosive gases and to measure the interfacial peel force. The system using epoxy resin as the paste binder showed excellent corrosion resistance and adhesion properties. The results revealed that PBO film is a promising candidate in the area of new insulation materials having not only heat resistance, low CTE, and low water absorption but also corrosion resistance and good adhesion.

Strongly Fluorescent and Thermally Stable Functional Polybenzoxazole Film: Excited-State Intramolecular Proton Transfer and Chemically Amplified Photopatterning

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTStrongly Fluorescent and Thermally Stable Functional Polybenzoxazole Film: Excited-State Intramolecular Proton Transfer and Chemically Amplified PhotopatterningSanghyuk Park, Sehoon Kim, Jangwon Seo, and Soo Young ParkView Author Information School of Materials Science and Engineering, Seoul National University, ENG 445, Seoul 151-744, Korea Cite this: Macromolecules 2005, 38, 11, 4557–4559Publication Date (Web):May 5, 2005Publication History Received4 January 2005Revised17 April 2005Published online5 May 2005Published inissue 1 May 2005https://doi.org/10.1021/ma050009rCopyright © 2005 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views995Altmetric-Citations53LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (144 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Absorption,Fluorescence,Hydroxyls,Manufacturing,Thin films Get e-Alerts

Synthesis and properties of polybenzoxazole–clay nanocomposites

A novel polybenzoxazole (PBO)/clay nanocomposite has been prepared from a PBO precursor, polyhydroxyamide (PHA) and an organoclay. The PBO precursor was made by the low temperature polycondensation reaction between isophthaloyl chloride (IC) and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane with an inherent viscosity of 0.5 dl/g. The organoclay was formed by a cation exchange reaction between a Na +-montorillonite (Na +-Mont) clay and an ammonium salt of dodecylamine. The PHA/clay was subsequently thermal cured to PBO/clay. Both X-ray diffraction and transmission electron microscope analyzes showed that the organoclay was dispersed in the PBO matrix in a nanometer scale. The in-plane coefficient of thermal expansion (CTE) of PBO/clay film decreased with increasing amounts of organoclay. The CTE of PBO/clay film containing 7 wt% clay was decreased by 21% compared to the pure PBO film. Both of the glass transition temperature ( T g) and the thermal decomposition temperature of PBO/clay increased with increasing amounts of organoclay. The thermal decomposition temperature and the T g of PBO/clay containing 7 wt% clay increased to 12 and 16 °C, respectively.

Thermal Conversion of Hydroxy-Containing Imides to Benzoxazoles: Polymer and Model Compound Study

A series of hydroxy-containing polyimides, containing pendent hydroxyl groups ortho to the heterocyclic imide nitrogen, were prepared via the solution condensation of aromatic dianhydrides with bisaminophenols. The polyimides were found to undergo thermal conversion to polybenzoxazoles upon heating between 350 and 500 °C under nitrogen or vacuum. The thermal conversion was accompanied by loss of carbon dioxide. No other volatile byproducts were detected by IR or NMR. Structures were confirmed by IR, solid-state NMR, and elemental analysis. Polybenzoxazole films, obtained by the thermolysis of solvent-cast poly(amic acid) or polyimide solutions, displayed excellent solvent resistance and good thermal stability. Insolubility of the polybenzoxazoles in all solvents tested indicates possible cross-linking. No crystallinity was observed by X-ray diffraction. Due to the insolubility of the resulting polybenzoxazoles, model compound reactions were also investigated. In the vapor phase at 400 °C, N-(2-hydroxyphenyl)phthalimide underwent intramolecular thermal conversion to 2-phenylbenzoxazole in 83% yield, emulating the polyimide reactions. Thermal conversion of N-(2-hydroxyphenyl)phthalimide in the melt at 400 °C resulted in the formation of intermolecular reaction products. The intermolecular reactions may be a source of possible cross-links, which would explain the insolubility of the polybenzoxazoles.

Unexpected thermal conversion of hydroxy-containing polyimides to polybenzoxazoles

An aromatic polyimide containing pendent hydroxyl groups ortho to the heterocyclic imide nitrogen was found to rearrange to a polybenzoxazole, with quantitative loss of carbon dioxide, upon heating above 400°C in an inert atmosphere. A hydroxy-containing polyimide film based on 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 3,3′-dihydroxy-4,4′-diaminobiphenyl (HAB) was prepared and converted to a fully aromatic polybenzoxazole by heating at 500°C for 1 h under nitrogen. The resulting polybenzoxazole film was found to be amorphous by small angle X-ray scattering (SAXS). The film also displayed excellent solvent resistance and good thermal stability by thermogravimetric analysis with 5% weight loss in nitrogen occurring at 625°C. A hydroxy-containing imide model compound was also found to undergo thermal conversion to a bisbenzoxazole when heated above 400°C under nitrogen.

Synthesis and Second-Order Nonlinear Optical Properties of Tricyanovinylated Polybenzoxazole

We have developed the second-order nonlinear optically (NLO) active polybenzoxazole as a new thermally stable NLO polymeric system. This polybenzoxazole was synthesized by direct polycondensation of diacid monomer containing N-phenyl pendant with 2,2-bis(3-amino-4-hydroxyphenyl)- 1,1,1,3,3,3-hexafluoropropane using phosphorus pentoxide/methanesulfonic acid as a condensing agent and solvent, followed by a post-substitution of tricyanovinyl group. The resultant polybenzoxazole had a glass transition temperature of about 180°C and an initial decomposition temperature of about 300°C. Electro-optic coefficient of this polybenzoxazole film poled at 1.5 MV cm -1 was 34 pm V -1 (at 633 nm), and its NLO activity was quite stable at 100°C during long period.

A study of novel heat‐resistant polymers: Preparation of photosensitive fluorinated polybenzoxazole precursors and physical properties of polybenzoxazoles derived from the precursors

AbstractA series of novel photosensitive polybenzoxazole precursors were prepared from polycondensation of 2,2‐bis(3,3′‐amino‐4,4′‐hydroxyphenyl)hexafluoropropane with photosensitive dicarboxylic acid chlorides such as p‐phenylenediacryloyl chloride and benzophenone‐4,4′‐dicarboxylic chloride. The precursors are soluble in common organic solvents owing to the presence of perfluoromethyl groups in the chain structure, and insolubilized in the solvents on irradiation with the light. Polybenzoxazole patterns with high resolution as well as high aspect ratio were reproduced by baking the precursor patterns at 300°C. The pattern shrinkage on the conversion to polybenzoxazole was slight. The polybenzoxazole films offered good heat‐resistance up to 400°C in addition to good electrical properties.