M. Redzheb

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.

On the mechanical and electrical properties of self-assembly-based organosilicate porous films

The effect of the replacement of Si–O–Si by Si–CH2–Si groups on the mechanical and electrical properties of silica-based hybrid sol–gel thin films is reported. For a reliable inference, two sets of organosilica films were synthesized – one consisting of a silica matrix decorated with methyl groups (Si–CH3) while the other further incorporating bridging methylene (Si–CH2–Si) functionalities. As a result, at the film density of 0.87 g cm−3, a higher Youngs modulus of 6.6 GPa was deduced for the film containing Si–CH2–Si groups compared to 5.3 GPa for the one with Si–O–Si functionalities. Concurrently, the introduction of the methylene bridging groups leads to a dielectric constant increase from 2.12 to 2.27. Furthermore, the type of surfactant, ionic or nonionic, employed as a templating agent has a negligible effect on the electrical properties and the reliability performance of the porous organosilica films.

Tuning the Properties of Periodic Mesoporous Organosilica Films for Low-k Application by Gemini Surfactants

Periodic mesoporous organosilica (PMO) thin films were synthesized by evaporation-induced self-assembly of 1,2-bis(triethoxysilyl)ethane and an ionic Gemini 16-12-16 surfactant under acidic conditions. The films were characterized by Fourier-transform infrared spectroscopy, grazing-incidence small-angle X-ray scattering, ellipsometric porosimetry, impedance measurements, and nanoindentation. The ease of control of the packing parameter in Gemini surfactants makes the PMO film templated by a Gemini an exciting first step towards small pore size PMO films with engineered mesostructures.

Periodic mesoporous organosilica films with a tunable steady-state mesophase

The mesophase formation in spin-coated periodic mesoporous organosilica (PMO) films aged at a controlled ambient humidity is investigated by time-resolved grazing-incidence small-angle X-ray scattering (GISAXS). The investigation demonstrates the existence of a tunable steady state in PMO spin-coated films. Thus, a film deposited at a relative humidity of 20 % has a lamellar mesophase, whereas a subsequent increase to 70 % leads to a phase transformation resulting in a P63 /mmc space group. On the other hand, an increase of the surfactant to organosilica molar ratio of between 0.26 and 0.31 results in films which at 70 % humidity form a mix of 2D and 3D hexagonal phases. A further increase of the surfactant amount leads to films with a 2D hexagonal phase. Finally, the different mesophases observed as a function of the solution aging emphasize the importance of the degree of polycondensation of the organosilica oligomers.

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 Youngs 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.

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

Advanced spin-on k 2.3 films with -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°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 but 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.