Nanoporous Organosilicate Thin Films Research Articles

Thermal conductivity-structure-processing relationships for amorphous nano-porous organo-silicate thin films

While numerous thermal conductivity investigations of amorphous dielectrics have been reported, relatively few have attempted to correlate to the influence of processing conditions and the resulting atomic structure. In this regard, we have investigated the influence of growth conditions, post deposition curing, elemental composition, atomic structure, and nano-porosity on the thermal conductivity for a series of organo-silicate (SiOCH) thin films. Time-domain thermoreflectance (TDTR) was specifically utilized to measure thermal conductivity while the influence of growth conditions and post deposition curing on composition, mass density, atomic structure, and porosity were examined using nuclear reaction analysis (NRA), Rutherford backscattering spectroscopy (RBS), Fourier-transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR), ellipsometric porosimetry (EP), and positronium annihilation lifetime spectroscopy (PALS). Analytical models describing the thermal conductivity dependence on mass density and vol% porosity were found to generally over-predict the measured thermal conductivity, but improved agreement was obtained when considering only the heat carrying network density determined by FTIR. Ashby’s semi-empirical relation, which assumes only 1/3 of the heat carrying bonds are aligned to the heat transport direction, was also found to reasonably describe the observed trends. However, the thermal conductivity results were best described via a model proposed by Sumirat (J Porous Mater 9:439 (2006)) which considers the effect of both vol% porosity and phonon scattering by nanometer sized pores. Post-deposition curing was additionally observed to increase thermal conductivity despite an increase in nano-porosity. This effect was attributed to an increase in the Si–O–Si network bonding produced by the cure.

Effects of e-beam curing on glass structureand mechanical properties of nanoporous organosilicate thin films

AbstractStructural characterization techniques, including solid-state nuclear magnetic resonance and Fourier transform infrared spectroscopies, were used in conjunction with mechanical testing to study the effects of thermally activated electron bombardment curing on organosilicate thin films. The electron beam process produced significant improvements in elastic modulus and fracture resistance while still preserving low dielectric constant. Detailed and quantitative analysis was used to elucidate fundamental curing effects on glass structure, including changes in film composition and local bond rearrangements. Enhancements in fracture properties with curing are shown to be due to increased network bond density resulting from changes in network connectivity coupled with moderate film densification.

Exploration of endocrine-disrupting chemicals on estrogen receptor α by the agonist/antagonist differential-docking screening (AADS) method: 4-(1-Adamantyl)phenol as a potent endocrine disruptor candidate

We established a novel screening method to survey endocrine-disrupting chemicals by means of in silico docking calculations. Endocrine disruptors target the human nuclear receptor, which bind a chemical in a pocket presenting in the ligand-binding domain (LBD). The LBD alters its conformation, depending upon the binding of either agonist or antagonist. We discovered that the chemicals can be differentiated into either agonist or antagonist by the docking calculations of the chemical for the LBD. We used the crystal structures of both agonist-bound LBDs and antagonist-bond LBDs as templates in the docking calculations, and estimated binding energies to discriminate between agonist and antagonist bindings. This agonist/antagonist differential-docking screening (AADS) method predicted, for example, 4-(1-adamantyl)phenol as an agonist of the human estrogen receptor α (hERα). Indeed, this compound, one of the essential raw materials for nanoporous organosilicate thin films, was confirmed to exhibit strong agonist activity in the reporter-gene assay for hERα with a high binding affinity. The AADS method is an approach that appears to foresee both the binding ability and the agonist/antagonist function of chemicals for the target nuclear receptors.

Surfactant-controlled damage evolution during chemical mechanical planarization of nanoporous films

The integration of nanoporous organosilicate thin films involving chemical mechanical planarization (CMP) is a significant challenge due the evolution of defects in the films during CMP in the form of cracking and delamination. This study shows that small changes in CMP electrolyte chemistry and surfactant additions can have dramatic effects on crack growth rates in the films. Crack growth rates were sensitive to the type of electrolyte and decreased in the presence of electrolytes that caused crack tip blunting. Growth rates were also sensitive to nonionic surfactant additions where molecular structure and weight were demonstrated to be important variables. An optimized blend of surfactants and electrolytes can significantly retard defect evolution due to molecular bridging. Surfactant self-assembly and resulting molecular bridging were characterized by in situ atomic force microscopy and used to quantify the molecular bridging observed.

Molecular‐Controlled Fracture and Release of Templated Nanoporous Organosilicate Thin Films

Molecular‐Controlled Fracture and Release of Templated Nanoporous Organosilicate Thin Films

Synchrotron X-ray Reflectivity Studies on Nanoporous Low Dielectric Constant Organosilicate Thin Films

Spatially resolved, quantitative, non-destructive analysis using synchrotron x-ray reflectivity (XR) with subnano-scale resolution was successfully performed on the nanoporous organosilicate thin films for low dielectric applications. The structural information of porous thin films, which were prepared with polymethylsilsesquioxane and thermally labile 4-armed, star-shaped poly(e-caprolactone) (PCL) composites, were characterized in terms of the laterally averaged electron density profile along with a film thickness as well as a total thickness. The thermal process used in this work caused to efficiently undergo sacrificial thermal degradation, generating closed nanopores in the film. The resultant nanoporous films became homogeneous, well-defined structure with a thin skin layer and low surface roughness. The average electron density of the calcined film reduced with increase of the initial porogen loading, and finally leaded to corresponding porosity ranged from 0 to 22.8% over the porogen loading range of 0-30 wt%. In addition to XR analysis, the surface and the inner structures of films are investigated and discussed with atomic force and scanning electron microscopy images.

Effect of UV Pretreatment on the Nanopore Formation within Organosilicate Thin Films

We have investigated the low-temperature cure process to realize nanoporous organosilicate thin films at temperature below by adding a small amount of photoacid generator (PAG) followed by UV irradiation. The Gemini surfactant, which decomposes in the temperature range from , was used as a pore-generating material (porogen) for organosilicate matrix. The UV pretreatment in the presence of PAG lowers the condensation temperature of poly(methyl silsesquioxane) matrix and leads to the fast matrix vitrification enabling the addition of increased amount of porogens. Because the full vitrification of the matrix by UV pretreatment in the presence of PAG below the decomposition temperature of porogens prevents the pore collapse, the porosity up to 35.5% was achieved with an average pore size of , as measured from X-ray reflectivity as well as ellipsometric porosimetry. It is shown that both dielectric constant and refractive index continue to decrease to 2.0 and 1.26, respectively. The present experimental system demonstrates that porogens with low degradation temperature can be successfully incorporated to realize nanoporous films without pore collapse. Consequently, this process can widen the choice of porogens to prepare nanoporous films.

Thermally Stable Antireflective Coatings Based on Nanoporous Organosilicate Thin Films

Thermally stable nanoporous organosilicate thin films were realized by the microphase separation of pore-generating polymers mixed with an organosilicate matrix to be antireflective coatings (ARCs), for which a thin film with a refractive index (n) of 1.23 for zero reflection is required. The refractive index of such nanoporous organosilicate films can be tuned from 1.39 down to 1.23 by incorporating nanopores within the films. With a nanoporous single layer with n approximately 1.23, the light transmittance of the glass above 99.8% was achieved in the visible range (lambda approximately 550 nm). To overcome the limitation on the narrow wavelength for high transmittance imposed by a single antireflective nanoporous thin film, bilayer thin films with different refractive indices were prepared by placing a high refractive index layer with a refractive index of 1.45 below the nanoporous thin film. UV-vis transmittance of a glass coated with the bilayer films was compared with nanoporous single-layer films and it is demonstrated that the novel broadband antireflection coatings in a wide range of visible wavelength can be easily obtained by the organosilicate bilayer thin films described in this study. Also, ARCs developed in this study demonstrate excellent AR durability owing to the hydrophobic nature of the organosilicate matrix.

Synchrotron X-ray Scattering Study of the Mechanism of Nanopore Generation in Nanoporous Organosilicate Thin Films Imprinted with a Reactive Six-Armed Porogen

In situ grazing incidence small-angle X-ray scattering analysis was successfully performed during the thermal processing of film blends of polymethylsilsesquioxane (PMSSQ) precursor and triethoxysilyl-terminated six-arm poly(epsilon-caprolactone) (mPCL6) porogen. In addition, thermogravimetric analysis of the films was carried out in a nitrogen atmosphere. These measurements provide important information about the structures of the blend films and of the resulting porous films. In particular, they are used in this paper to establish the mechanism of the formation of imprinted pores within the blend films. During the heating run, the sacrificial thermal degradation of the porogen component commenced at 320 degrees C, generating pores in the resulting cured PMSSQ films. Only very limited porogen aggregation occurred during the blend film formation process (spin-coating and subsequent drying), and these porogen aggregates were of relatively small size and narrow size distribution. The observed restriction of the formation of such porogen aggregates was found to result from the favorable hybridization reaction of the porogen's reactive end groups with the reactive functional groups of the PMSSQ precursor, which competes with aggregation via reaction between the porogen molecules. The average radius (or half-size) of the porogen aggregates was in the range 2.45-3.98 nm, depending on the porogen loading (10-40 wt %). The porogen aggregates retained their size and size distribution until thermal degradation, which resulted in the imprinting of nanopores in the cured PMSSQ films with size and size distribution corresponding to those of the porogen aggregates. The porosities of the resulting nanoporous films were in the range 12.4-41.7%, depending on the initial porogen loading.

Nanoporous Organosilicate Thin Films Prepared with Covalently Bonded Adamantylphenol Pore Generators

A new class of nanoporous organosilicate thin films with balanced mechanical and low dielectric properties has been designed and prepared using covalently bonded adamantylphenols as pore-generating (porogen) materials. The adamantylphenol groups were grafted or bridged to poly(methyl silsesquioxane) (PMSSQ) polymers through propyl linkers and the thermal decomposition of such porogens through the cleavage of covalent bonds during curing was confirmed by FT-IR, TGA, and GC-MS. One of the nanoporous thin films examined in this study contains nanopores, less than 10 nm, within the films with 18% porosity, as characterized by X-ray reflectivity, ellipsometry, and nitrogen sorption analysis. Elastic modulus of a nanoporous film measured by a nanoindenter was significantly increased to 5.5 GPa, while maintaining the dielectric constant of 2.3, which is due to the partial formation of silica structure by the decomposition of residual propenyl groups after the bond cleavage of porogens and also due to the enhance...

Scattering Studies of Nanoporous Organosilicate Thin Films Imprinted with Reactive Star Porogens

ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTScattering Studies of Nanoporous Organosilicate Thin Films Imprinted with Reactive Star PorogensB. Lee, W. Oh, J. Yoon, Y. Hwang, J. Kim, B. G. Landes, J. P. Quintana, and M. ReeView Author Information National Research Lab for Polymer Synthesis & Physics, Pohang Accelerator Laboratory, Center for Integrated Molecular Systems, Department of Chemistry, Polymer Research Institute, and Division of Molecular and Life Sciences, and School of Environmental Science & Engineering, Pohang University of Science & Technology, Pohang 790-784, Republic of Korea; Department of Analytical Sciences-Materials Characterization, 1897 Building, Dow Chemical Company, Midland, Michigan 48667; and DND-CAT Synchrotron Research Center, Building 432A/A-008, Argonne National Laboratory, 9700 S. Case Ave., Argonne, Illinois 60439-4857 Cite this: Macromolecules 2005, 38, 22, 8991–8995Publication Date (Web):September 30, 2005Publication History Received30 January 2005Revised15 September 2005Published online30 September 2005Published inissue 1 November 2005https://doi.org/10.1021/ma0501951Copyright © 2005 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views391Altmetric-Citations46LEARN 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 (308 KB) Get e-AlertsSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Grazing incidence small angle scattering,Insulators,Scattering,Thin films,X-rays Get e-Alerts

Investigation on hexamethyldisilazane vapor treatment of plasma-damaged nanoporous organosilicate films

Hexamethyldisilazane (HMDS) vapor treatment of plasma-damaged nanoporous organosilicate thin films has been studied as a function of treatment temperature in this work. Although, the HMDS vapor treatment facilitated incorporation of methyl (CH 3) groups subsequent to the removal of free hydroxyl (OH) groups in the damaged films at treatment temperature as low as 55 °C, the bonded OH groups were not removed. More significantly, detailed analysis of the results reveals that HMDS vapor modified only the surface of the plasma-damaged samples and not the entire film as expected. This is attributed to the formation of a thin solid layer on the surface, which effectively prevents penetration of HMDS vapors into the bulk. The Fourier transform-infrared (FT-IR) absorption and dielectric constant measurements confirm that the vapor treatment assists only partial curing of the plasma-damaged films. Alternative processes of curing the films with HMDS dissolved in supercritical carbon dioxide (SCCO 2) as a medium of reaction in static and pulsed modes were also attempted and the results are presented in this paper.

Supercritical CO2extraction of porogen phase: An alternative route to nanoporous dielectrics

We present a supercritical CO2(SCCO2) process for the preparation of nanoporous organosilicate thin films for ultralow dielectric constant materials. The porous structure was generated by SCCO2extraction of a sacrificial poly(propylene glycol) (PPG) from a nanohybrid film, where the nanoscopic domains of PPG porogen are entrapped within the crosslinked poly(methylsilsesquioxane) (PMSSQ) matrix. As a comparison, porous structures generated by both the usual thermal decomposition (at approximately 450 °C) and by a SCCO2process for 25 and 55 wt% porogen loadings were evaluated. It is found that the SCCO2process is effective in removing the porogen phase at relatively low temperatures (<200 °C) through diffusion of the supercritical fluid into the phase-separated nanohybrids and selective extraction of the porogen phase. Pore morphologies generated from the two methods are compared from representative three-dimensional (3D) images built from small-angle x-ray scattering (SAXS) data.