Chemical composition, pore structure and mechanical properties of porous organosilicate low-k films with terminal and bridging organic groups are studied. It is shown that BTMSE based low-k films with alkyl bridge between the Si atoms have non-uniform pore structure with internal voids (ink-bottle like pores) while the films with terminal alkyl groups have pores with cylindrical shape. All studied spin-on deposited films have better mechanical properties than PECVD films with similar chemical composition and porosity. The best mechanical properties showed alkyl bridged low-k films. Moreover, the Young's modulus increases with BTMSE content because of higher concentration of bridging bonds. Porous organosilicate glasses (OSG) have many different applications such as catalysts, adsorbents, trapping agents, drug delivery agents, stationary phases in chromatography and chemical sensors. 1One of the most important applications of porous OSG films is related to interconnects in advanced ULSI (ultra large-scale integration) devices where they are used as insulators with low dielectric constant. Modern ICs can be made very compact, incorporating up to several billions transistors and other electronic components in an area of about 1 cm 2 . All transistors and other IC components have to be electrically interconnected to provide the proper functionality. The width of the conducting lines that connect different transistors in a circuit is becoming very small; in 2008, it dropped below 100 nm, and now is of the order of a few tens of nm. In parallel, the interconnect delay is becoming an increasing limitation factor of the overall signal propagation delay. The low dielectric constant materials are needed to reduce capacitance (C) between the metal (Cu) conductors. Together with low resistivity (R) of metal wires, low-k materials improve ULSI device performance by decreasing RC delay, cross talk noise and power consumption in interconnects.2 Different types of organosilicate films deposited by plasma enhanced chemical vapor deposition (PECVD) and spin-on glass (SOG) technology have been developed during the last 20 years. Using of appropriate precursors allows to control the chemical composition and porosity of these films. PECVD is currently the method of choice in microelectronic industry because this technique is easily integrated in the existing device manufacturing process.3 PECVD precursors (normally different types of organosilanes) are transferred to the reaction chamber where Si wafer is located on a heated pedestal. Quality of the deposited films depends on plasma characteristics and pedestal temperature. In the modern interconnect technology, the dielectric layer is deposited by PECVD and patterned first before the metal deposition using lithography and plasma etching. Lithography and plasma etching define the structure of interconnect wiring by forming certain patterns in the dielectric film. Then copper should fill the patterns in the dielectric film by superfilling electrodeposition and after chemicalmechanica...

Organosilicate glass-based porous low dielectic constant films with different ratios of terminal methyl to bridging organic (methylene, ethylene and 1,4-phenylene) groups are spin-on deposited by using a mixture of alkylenesiloxane with organic bridges and methyltrimethoxysilane, followed by soft baking at 120–200 °C and curing at 430 °C. The films’ porosity was controlled by using sacrificial template Brij® L4. Changes of the films’ refractive indices, mechanical properties, k-values, porosity and pore structure versus chemical composition of the film’s matrix are evaluated and compared with methyl-terminated low-k materials. The chemical resistance of the films to annealing in oxygen-containing atmosphere is evaluated by using density functional theory (DFT). It is found that the introduction of bridging groups changes their porosity and pore structure, increases Young’s modulus, but the improvement of mechanical properties happens simultaneously with the increase in the refractive index and k-value. The 1,4-phenylene bridging groups have the strongest impact on the films’ properties. Mechanisms of oxidative degradation of carbon bridges are studied and it is shown that 1,4-phenylene-bridged films have the highest stability. Methylene- and ethylene-bridged films are less stable but methylene-bridged films show slightly higher stability than ethylene-bridged films.

Surfactant-templated organosilicate glass (OSG) based low-k films are deposited by using tetraethyl orthosilicate/methyltriethoxysilane (TEOS/MTEOS) mixture with different ratio and spin-on technology with the goal of understanding the effects of terminal methyl groups on chemical and structural properties. It is shown that despite of constant surfactant concentration these films have quite different properties when the changing of CH3/Si ratio. The most important changes are related to change of their hydrophilicity, change of mechanical properties, the pore size and to the shift of Si–CH3 peak position in Fourier transform infrared (FTIR) spectra. The films are becoming hydrophobic if they are deposited from sols with CH3/Si ratio higher than 0.2. The Young’s modulus gradually decreases with increasing the terminal methyl groups concentration in the films. The pore size increases with concentration of methyl groups and changes from cylindrical to ink-bottle shape. The nature of SiCH3 peak shift is explained by using molecular mechanics simulation. It is shown that the reason of this shift is change of dπ–pπ hybridization in Si–O–Si bonds, which is affected by presence of CH3 group.

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