Polymethylsilsesquioxane Research Articles

Oil Wettability and Sliding Properties of Organic and Inorganic Hybrid Coating Films Prepared from Methyltriethoxysilane and Various Metal Alkoxides

The oil wettability and sliding property of polymethylsilsesquioxane (PMSQ) based organic inorganic hybrid coating films prepared from methyltriethoxysilane and various metal alkoxide were investigated. The wettability of oil increased in the order of PMSQ<Ta-<Ti-<Al-PMSQ, and was strongly affected by the surface roughness. The friction coefficient showed that Ti-PMSQ among hybrid coating films was the lowest value, which was found to be due to the presence and maintenance of the lubricating oil film during the sliding tests.

Ultralow-k nanoporous organosilicate dielectric films imprinted with dendritic spheres

Integrated circuits that have improved functionality and speed in a smaller package and that consume less power are desired by the microelectronics industry as well as by end users, to increase device performance and reduce costs. The fabrication of high-performance integrated circuits requires the availability of materials with low or ultralow dielectric constant (low-k: k <OR= 2.5; ultralow-k: k <OR= 2.0) because such dielectrics not only lower line-to-line noise in interconnect conductors, but also minimize power dissipation by reducing the capacitance between the interconnects. Here we describe the preparation of low- and ultralow-k nanoporous organosilicate dielectrics from blends of polymethylsilsesquioxane (PMSSQ) precursor with globular ethyl acrylate-terminated polypropylenimine dendrimers, which act as porogens. These dendrimers are found to mix well with the PMSSQ precursor and after their sacrificial thermal decompositions result in closed, spherical pores of <2.0 nm radius with a very narrow distribution even at high loading. This pore size and distribution are the smallest and the narrowest respectively ever achieved in porous spin-on dielectrics. The method therefore successfully delivers low- and ultralow-k PMSSQ dielectric films that should prove very useful in advanced integrated circuits.

ToF‐SIMS studies of nanoporous PMSSQ materials: kinetics and reactions in the processing of low‐K dielectrics for ULSI applications

AbstractDetailed investigations of spin‐on polymethylsilsesquioxane (PMSSQ)‐based low‐K materials were carried out by means of time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) to identify the reaction kinetics and mechanisms occurring during the manufacturing of nanoporous dielectrics for ULSI applications. Analysis of the static SIMS fingerprints led to the identification of key species related to the PMSSQ oligomers, as well to the observation of features related to the initial functionality of the precursor materials. The intensity variations of the key species with thermal curing reveal the polymerization kinetics of the dielectric precursors. In addition, thermal decomposition and volatilization of the polymethylmethacrylate–dimethylaminoethylmethacrylate copolymer (PMMA‐co‐DMAEMA) porogen was established based on the detection of fragments related to the different moieties of the copolymer molecule. Porogen degradation takes place via cleavage of the DMAEMA co‐monomer at low temperature, followed by volatilization of the residual PMMA‐enriched polymer upon annealing at higher temperature. Several complementary phenomena occurring during the formation of these complex systems can be evaluated by ToF‐SIMS, revealing major features crucial to materials development and the manufacturing of novel low‐dielectric‐constant (K) dielectrics. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Optical, dielectric and thermal properties of nanoscaled films of polyalkylsilsesquioxane composites with star-shaped poly(ε-caprolactone) and their derived nanoporous analogues

Nanoscaled films of poly(methylsilsesquioxane- co-ethylenylsilsesquioxane) (PMSSQ–BTMSE) and polymethylsilsesquioxane (PMSSQ) were prepared from the respective soluble prepolymers, and their thermal, optical, and dielectric properties were characterized. The PMSSQ–BTMSE nanofilm containing an ethylenyl bridge comonomer unit BTMSE was found to be thermally more stable than the nanofilm of PMSSQ, a representative polyalkylsilsesquioxane. Further, in comparison to the PMSSQ film the PMSSQ–BTMSE film exhibits a larger refractive index and a larger dielectric constant but a smaller out-of-plane thermal expansion coefficient, when both prepolymers are cured under the same conditions. These characteristics of PMSSQ–BTMSE films are due to the ethylenyl bridge provided by the BTMSE comonomer unit, which promotes the formation of a tighter, more perfect network structure in cured PMSSQ–BTMSE films. Composite films were prepared by solution-blending the pore generator (referred to as the porogen), a star-shaped poly(ε-caprolactone), with the soluble prepolymers then drying the resulting solution, and the nature of their curing reactions and extent of porogen calcination were investigated. It was found that the thermal curing and calcination processes of the composite films successfully produce PMSSQ–BTMSE and PMSSQ films containing pores that are about 400 nm in diameter. It was confirmed that the presence of these generated nanopores significantly reduces the refractive indices and the dielectric constants of the dielectric films but increases their out-of-plane thermal expansivity, depending on the initial porogen loading. The porosities of the nanoporous dielectric films were estimated from the measured refractive indices. The surface topographies of these films were also investigated, giving information about the sizes of the pores generated in the films. It was also found that prior to calcination the presence of the porogen increases the refractive index and dielectric constant of the composite dielectric films because of its inherent high polarizability, and also increases the thermal expansivity of MSSQ–BTMSE composite films but very slightly decreases the thermal expansivity of MSSQ composite films. It is demonstrated that PMSSQ–BTMSE films and the related nanometer scale nanoporous films are candidates for use as low and ultra-low dielectric interlayers in the fabrication of advanced microelectronic devices.

Pyrolysis of polymethylsilsesquioxane

AbstractChanges of the composition and structure of various samples of polymethylsilsesquioxane (PMSQ), pyrolyzed at different temperatures under flowing nitrogen, were investigated using thermogravimetric analysis, Raman and Fourier transform infrared spectroscopies, X‐ray photoelectron spectroscopy, elemental analysis, scanning electron microscopy, and transmission electron microscopy. The center of the Si2p peak could be used to estimate the extent of the pyrolysis of PMSQ. Two temperature domains correspond to important changes in the chemical composition of PMSQ. The former (Tp &lt; 500°C) is related to the conversion from a regular structure to an irregular structure and the latter (Tp &gt; 500°C) is associated with the organic– ceramic conversion. During the latter pyrolysis, flowing of the molten bulk occurred and then a final solid structure was obtained. The main product of PMSQ, pyrolyzed at 900°C, is silica, as well as some amount of silicon oxycarbide and traces of amorphous carbon. Based on the above analysis and observation, a conversion process from polysilsesquioxane to a ceramic is proposed. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1077–1086, 2002

Photoprobe Study of Siloxane Polymers. 3. Local Free Volume of Polymethylsilsesquioxane Probed by Photoisomerization of Azobenzene

We have investigated the local free volume and its thermal fluctuation in an amorphous polymethylsilsesquioxane (PMSQ) consisting only of T3 (CH3SiO3/2) and T2 (CH3Si(OH)O2/2) units using photoisomerization of azobenzene molecularly dispersed in the PMSQ films as a photoprobe over a wide temperature range (4−300 K). Photoisomerization profiles are discussed on the basis of three parameters, i.e., first-order plots, final cis fractions, and three-component analysis, for uncured and silanol-condensation-cured PMSQ's. The final cis fraction in the uncured PMSQ decreases markedly below 250 K, which has never been observed in linear polysiloxanes, MQ resins, or carbon-based polymers. The effect of low-molecular-weight components in the PMSQ was evaluated using fractionated PMSQ's by molecular weight. The effect of hydrogen bonding by a silanol group was also studied by temperature dependence of infrared spectra. These results suggest that the low-molecular-weight components with silanol groups fill local vacan...

Shrinkage-free ZrSiO 4-ceramics: Characterisation and Applications

Dense, shrinkage-free ZrSiO 4-ceramics can be produced by a reaction-bonding process using ZrSi 2, ZrO 2, and a polysiloxane as starting materials. Sinter shrinkage is compensated by the volume increase during oxidation of ZrSi 2. In addition, the use of a Si-containing so called low-loss-binder [polymethylsilsesquioxane (PMSS)] reduces shrinkage further. Near net-shape ceramic compacts can be produced by an embossing process. As the green bodies are extremely dense but not brittle, they can be mechanically machined. The reaction-bonding process has to be controlled in a way that first the pyrolysis of PMSS, followed by the oxidation of ZrSi 2, and finally the formation of ZrSiO 4 and the sintering to dense compacts take place. Due to the absence of shrinkage and the good mechanical properties obtained, these ceramics open up new applications in fields requiring high dimensional accuracy such as microsystem engineering or dentistry. ©

Preparation and properties of polysilsesquioxanes: Polysilsesquioxanes and flexible thin films by acid-catalyzed controlled hydrolytic polycondensation of methyl- and vinyltrimethoxysilane

Polymethylsilsesquioxane (PMS) and polyvinylsilsesquioxane (PVS) were prepared by acid-catalyzed controlled hydrolytic polycondensation of methyl- and vinyltrimethoxysilane (MTS and VTS), respectively. The spinnabilities and molecular weights of polysilsesquioxanes were easily controlled by the reaction conditions, such as the molar ratios of water, hydrochloric acid, and methanol to MTS or VTS; nitrogen flow rate; temperature; and stirring rate. PMS and PVS showed spinnability of more than 200 cm when their molecular weights were up to 42,000 (PMS) and 19,000 (PVS) Mw. Transparent, colorless, and flexible films of 0.02–0.10 mm thick were prepared by casting a 20 wt % acetone–methanol (V/V = 1) solution of PMS and PVS on a polymethylpentene shale, followed by heating at 80°C for 3 weeks. The tensile strength of the films, approximately 26 (PMS) and 17 (PVS) MPa, was found to be correlated with the structure of the polysilsesquioxanes. The surface contact angle and electroconductivity of films were also measured. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1017–1026, 1999

The effect of siloxane spin-on-glass and reaction bonded silicon oxycarbide coatings with a self-propagating interfacial reaction treatment (ASPIRE) in the synthesis of carbon/graphite fiber-reinforced aluminum metal matrix composites

Carbon fibers were treated with siloxane spin-on-glass and reaction bonded silicon oxycarbide coatings. The spin-on-glass (SOG) coatings were prepared by pyrolyzing solutions of polymethylsilsesquioxane (PMSO), polydimethoxysilane (PDSO), and poly(ethoxysilane)ethyltitanate copolymer (ESET). Since the flexibility of the coatings was found to be dependent on the concentration of the siloxane solution, only those of PMSO and PDSO below 1.25% were determined to be suitable for fiber coatings, and an alternative approach to the formation of a pliable silicon-based ceramic coating on the fibers was developed. Carbon fiber tows were impregnated by ethanolic solutions of organosilicon chlorides and fired at temperatures up to 900 °C to form a flexible reaction bonded silicon oxycarbide (RB–SiOC) coatings. Uncoated, SOG coated, and RB–SiOC coated carbon fibers were embedded in aluminum metal at 1000 °C. While both silica-based coatings protected the carbon surface, no wetting was observed, leading to fiber pull-out. When the coated fibers were treated with a mixture of Ti and B prior to immersion into the molten aluminum, complete wetting of the fibers occurred. In the presence of molten aluminum, the Ti/B coating enabled the exothermic formation of TiB2 and titanium aluminides, which facilitate wetting. This reaction is termed ASPIRE (Aluminum Self-Propagating Interfacial Reaction) and in combination with silicon-based ceramic coatings provides a scientific approach to the formation of stable carbon fiber/aluminum metal-matrix composites. The coated fibers and composites were characterized by scanning electron microscopy (SEM) with energy dispersive x-ray (EDX) analysis, and x-ray photoelectron spectroscopy (XPS).