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

Effect of the C-bridge length on the ultraviolet-resistance of oxycarbosilane low-k films

The ultra-violet (UV) and vacuum ultra-violet (VUV) resistance of bridging alkylene groups in organosilica films has been investigated. Similar to the Si-CH3 (methyl) bonds, the Si-CH2-Si (methylene) bonds are not affected by 5.6 eV irradiation. On the other hand, the concentration of the Si-CH2-CH2-Si (ethylene) groups decreases during such UV exposure. More significant difference in alkylene reduction is observed when the films are exposed to VUV (7.2 eV). The ethylene groups are depleted by more than 75% while only about 40% methylene and methyl groups loss is observed. The different sensitivity of bridging groups to VUV light should be taken into account during the development of curing and plasma etch processes of low-k materials based on periodic mesoporous organosilicas and oxycarbosilanes. The experimental results are qualitatively supported by ab-initio quantum-chemical calculations

Enhanced Synthesis of the Exopolysaccharide Ethapolan by Acinetobacter sp. 12S Grown on a Mixture of Substrates

Earlier, we found that the synthesis of the microbial exopolysaccharide (EPS) ethapolan by Acinetobacter sp. 12S can be enhanced by growing this bacterium on a mixture of ethanol and glucose It should be noted that the cultivation of Acinetobacter sp. 12S on the substrate mixture was accompanied by the enhancement of the synthesis of not only the EPS but also the biomass. The aim of this work was to maximize the transformation of the substrate carbon into EPS. Among the factors studied that may influence the transformation efficiency were the effect of the inoculum, the concentration of carbon and nitrogen sources in the medium, the nature of the energy-deficient substrate, and the availability of sodium ions. MATERIALS AND METHODS Strains. The two bacterial strains used in this work were Acinetobacter sp. 12S (the ethapolan producer described earlier Cultivation conditions. The strains were grown in a liquid mineral medium Cells for inoculation were grown on nutrient agar for 2 days or in mineral K + medium with (a) 0.5 vol % ethanol, (b) 0.5 wt % glucose, or (c) 0.5 vol % ethanol + 0.5 wt % glucose for 16-24 h (i.e., to the exponential growth phase). The inoculum was grown at the Abstract -Enhanced synthesis of the exopolysaccharide ethapolan by Acinetobacter sp. 12S was observed when the bacterium was grown on a mixture of two energetically nonequivalent substrates (ethanol and glucose) taken in a molar proportion of 3.1 : 1. The efficiency of carbon transformation into EPSs was maximum when sodium ions were absent in the medium, the concentration of nitrogen source was reduced to 0.3-0.45 g/l, and the inoculum was grown on ethanol. Such conditions provided an increase in the maximum specific growth rate and its attainment in earlier cultivation terms. Molasses as a substitution for glucose was inefficient. The activities of the key enzymes of C 2 metabolism in Acinetobacter sp. 12S cells grown on the substrate mixture were 1.1 to 1.7 times lower than they were during growth on ethanol alone. The activity of isocitrate lyase in cells grown on the substrate mixture declined to an even greater extent (by 4-7 times), indicating that the role of the glyoxylate cycle in such cells is insignificant. Key words : intensification of exopolysaccharide synthesis, mixed substrate, key enzymes of C 2 and C 6 metabolism

Integrated cleanroom process for the vapor-phase deposition of large-area zeolitic imidazolate framework thin films

Robust and scalable thin-film deposition methods are key to realize the potential of metal-organic frameworks (MOFs) in electronic devices. Here, we report the first integration of the chemical vapor deposition (CVD) of MOF coatings in a custom reactor within a cleanroom setting. As a test case, the MOF-CVD conditions for the zeolitic imidazolate framework-8 are optimized to enable smooth, pinhole-free, and uniform thin films on full 200 mm wafers under mild conditions. The single-chamber MOF-CVD process and the impact of the deposition parameters are elucidated via a combination of in situ monitoring and ex situ characterization. The resulting process guidelines will pave the way for new MOF-CVD formulations and a plethora of MOF-based devices

Plasma induced damage mitigation in spin-on self-assembly based ultra low-k dielectrics using template residues

© 2017 Author(s). This paper describes an approach for the reduction of plasma-induced damage in self-assembly based porous ultra low-k organosilica dielectrics. The concept is based on retention of the partially decomposed sacrificial organic phase (template) into the pores of the low-k film during plasma exposure. The amount of the template residues can be controlled by varying the hard-bake process time. It is shown that those residues are uniformly distributed throughout the film in the form of pore wall coatings. After plasma processing, the remaining residues are removed by means of a UV cure. Plasma damage to the underlying organosilica matrix was assessed by exposure of the differently hard-baked low-k films to fluorine-rich Ar/SF6 plasma. The thickest coating, estimated to be around 0.4 nm, enables a nearly damage-free etch process without any carbon depletion or k-value degradation along with limited shrinkage induced by post-etch UV-curing (<4.5%). These results highlight the efficiency of a simple and scalable route for damage-free integration of highly porous self-assembly based low-k dielectrics.status: publishe

Metal barrier induced damage in self-assembly based organosilica low-k dielectrics and its reduction by organic template residues

© 2019 Elsevier B.V. This study describes the damage caused by physical vapor deposition of TaN/Ta barriers on porous self-assembled organosilica low-k dielectrics for IC applications. It is demonstrated that the ion bombardment associated with TaN layer sputtering strongly influences the metal species in-diffusion and modifies the bulk dielectric and pore sealing characteristics. The modulation of the pore structure via controlled decomposition of the organic template, prior to the barrier deposition step, allows to mitigate this damage. The reduction of open porosity, from nominal 39% down to 26%, is realized by partial retention of the sacrificial organic porogen phase in the pores of the low-k dielectric, resulting in the suppression of deep Ta penetration and in the recovery of pore sealing. This approach is successfully tested in a 45 nm half-pitch damascene vehicle. The compatibility of the organic template residues with the subsequent steps of the interconnects integration process flow, such as hard-mask deposition and patterning, are discussed.status: publishe