Impact of UV wavelength and curing time on the properties of spin-coated low-k films

Advanced spin-on k 2.3 films with similar to 40% porosity were enabled by liquid phase self-assembly (LPSA) mechanism on Si substrates. UV-assisted thermal template removal is investigated as a faster alternative to the conventional thermal process. The as-deposited films were exposed to narrow-band UV light of 172 nm, 222 nm, 254 nm or 185/254 nm at 400 degrees C for different time. The optical, mechanical, chemical and electrical properties of the resulting films are discussed in this work. Photons with wavelength of about 172 nm from one side are detrimental to the electrical and chemical properties of the low-k films hut from the other side notably improve the porous low-k mechanical properties. Exposure to 222 nm light as short as 3 min, is more efficient in terms of template removal when compared to 2h thermal cure, while in both cases similar mechanical and electrical properties are reported. UV-cure using 254 nm or dual band 254/185 nm photons seem to have a minor contribution to the template removal efficiency for the applied doses. Higher doses are necessary in order to better understand the effective contribution of these photon energies. Finally, the HF etching mechanism is discussed

Laser anneal of oxycarbosilane low-k film

Submilisecond laser anneal has been experimentally investigated for porogen removal and its ability to improve the mechanical strength in oxycarbosilane ultra low-k films compromised due to the introduction of porosity. We report the occurrence of extensive bond rearrangements inferred from Fourier-transform infra-red (FTIR) spectroscopy, elastic recoil detection (ERD) and spectroscopic ellipsometry (SE) in the energy range of 1.4-8 eV. The laser anneal affects most notably the organic content of the organosilicate matrix leading to depletion and reorganization. Nevertheless, the tested conditions reveal a processing window which allows for 13% improvement of Young’s modulus as compared to the reference film, annealed in a conventional furnace at 400°C for 2 h, while not impacting the relative dielectric constant of 2.25

Catalyst preparation for CMOS-compatible silicon nanowire synthesis

Metallic contamination was key to the discovery of semiconductor nanowires, but today it stands in the way of their adoption by the semiconductor industry. This is because many of the metallic catalysts required for nanowire growth are not compatible with standard CMOS (complementary metal oxide semiconductor) fabrication processes. Nanowire synthesis with those metals which are CMOS compatible, such as aluminium and copper, necessitate temperatures higher than 450 C, which is the maximum temperature allowed in CMOS processing. Here, we demonstrate that the synthesis temperature of silicon nanowires using copper based catalysts is limited by catalyst preparation. We show that the appropriate catalyst can be produced by chemical means at temperatures as low as 400 C. This is achieved by oxidizing the catalyst precursor, contradicting the accepted wisdom that oxygen prevents metal-catalyzed nanowire growth. By simultaneously solving material compatibility and temperature issues, this catalyst synthesis could represent an important step towards real-world applications of semiconductor nanowires.Comment: Supplementary video can be downloaded on Nature Nanotechnology websit

Biomass production of site selective 13C/15N nucleotides using wild type and a transketolase E. coli mutant for labeling RNA for high resolution NMR

Characterization of the structure and dynamics of nucleic acids by NMR benefits significantly from position specifically labeled nucleotides. Here an E. coli strain deficient in the transketolase gene (tktA) and grown on glucose that is labeled at different carbon sites is shown to facilitate cost-effective and large scale production of useful nucleotides. These nucleotides are site specifically labeled in C1′ and C5′ with minimal scrambling within the ribose ring. To demonstrate the utility of this labeling approach, the new site-specific labeled and the uniformly labeled nucleotides were used to synthesize a 36-nt RNA containing the catalytically essential domain 5 (D5) of the brown algae group II intron self-splicing ribozyme. The D5 RNA was used in binding and relaxation studies probed by NMR spectroscopy. Key nucleotides in the D5 RNA that are implicated in binding Mg2+ ions are well resolved. As a result, spectra obtained using selectively labeled nucleotides have higher signal-to-noise ratio compared to those obtained using uniformly labeled nucleotides. Thus, compared to the uniformly 13C/15N-labeled nucleotides, these specifically labeled nucleotides eliminate the extensive 13C–13C coupling within the nitrogenous base and ribose ring, give rise to less crowded and more resolved NMR spectra, and accurate relaxation rates without the need for constant-time or band-selective decoupled NMR experiments. These position selective labeled nucleotides should, therefore, find wide use in NMR analysis of biologically interesting RNA molecules

Oxygen chemiluminescence in He plasma as a method for plasma damage evaluation

We propose a method for evaluating the hydrophilisation degree of low-k films upon plasma damage. The evaluation is based on optical emission spectroscopy analysis of O* emission during He plasma exposure of sample in question. The O* is presumably desorbed from damaged low-k film by vacuum-ultraviolet radiation from He plasma. The new method correlates well with other methods for plasma damage characterization such as Fourier Transform Infrared Spectroscopy and Water-Vapor Ellipsometric Porosimetry. The presented method gives a unique opportunity to assess the degree of hydrophilisation of low-k films immediately after processing. (C) 2008 Elsevier B.V. All rights reserved.status: publishe

Damage reduction and sealing of low-k films by combined He and NH3 plasma treatment

Modification of chemical vapor deposition low-k films upon sequential exposure to helium plasma and then ammonia plasma is characterized using various methods. The He plasma emits extreme ultraviolet (EUV) photons creating O-2 vacancies, which impacts surface reactive sites and induces localized chemical modifications in the first surface monolayers. The subsequent NH3 plasma treatment provides complete sealing of the low-k surface. The depth of the modification, which is a factor of merit of the sealing process, is limited because of the high absorption coefficient of silica-based low-k materials in the range of EUV emission. (C) 2007 The Electrochemical Society.status: publishe

Quantum transport in ultrathin CoSi2 polycrystalline films

Quantum transport in ultrathin CoSi2 polycrystalline films was studied for the first time. The temperature corrections to the conductivity of these films and their anomalous magnetoresistance have been observed and investigated. It is shown that they are determined by the effects of interaction and weak localization with the strong spin-orbit and spin scattering taken into account. Unlike the epitaxial crystalline films reported previously our films including one with the thickness larger than 10 nm show no superconductivity down to the lowest temperature (0.2 K). In the thinnest film we used an unusual dimensional crossover from one dimensional behavior of quantum corrections to two dimensional have been observed with lowering temperature, supposedly due to changes of the characteristic correlation length in the sample, which consisted of meandrous conducting paths caused by the presence of pin-holes. (C) 1997 Published by Elsevier Science Ltd.X11sciescopu

Improvement of cohesion strength in ULK OSG materials by pore structure adjustment

© 2015 Elsevier B.V. All rights reserved. In this study cohesion strength in low-k dielectric films was enhanced by tuning the pore structure. The correlation between the average size of pores in ultra-low-k materials and cohesion energy was demonstrated by performing a 4-point bending test on multi-layer structures including TaN/Ta metal barrier. Spin-on organosilica films prepared with different templating surfactants were used to alleviate porosity- pore size coupling, which revealed the particular role of pore size with respect to material toughness. The paper also discusses aspects of material design at precursor level.status: publishe