Effect of Bridging and Terminal Alkyl Groups on Structural and Mechanical Properties of Porous Organosilicate Films

Abstract

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...

Impact of VUV photons on SiO2 and organosilicate low-k dielectrics: General behavior, practical applications, and atomic models

“…In the case of spin-on deposition the film composition quite well reproduces composition of the precursor solution. 56 The porogen molecules form agglomerated states that allow formation of porous structure after the curing. The matrix/porogen phase separation was studied for spin-on deposited films polymethysilsesquioxane (PMSSQ) for the low-k matrix andpolymethylmethacrylate-co-dimethylaminoethylacrylate (PMMA-co-DMAEMA) as the porogen, which is volatilized to leave nanopores in the matrix in ref.…”

Analytical Study of Porous Organosilicate Glass Films Prepared from Mixtures of 1,3,5- and 1,3-Alkoxysilylbenzenes

“…A further increase of porogen does not change porosity but it increases the pore size. The presented EP data shows that an unusual property of benzene-bridged samples in comparison with alkylene-bridged and methyl-terminated materials [34,35] is their very small pore size. The pore radius value is constant and equal to 0.81 nm until a porogen concentration lower than 30% (Figure 13b).…”

“…The pore radius value is constant and equal to 0.81 nm until a porogen concentration lower than 30% (Figure 13b). The adsorption-desorption isotherms do not have a hysteresis loop (Figure 12a), which suggests the quasi-cylindrical shape of micropores without internal voids [34,35]. The small pore size can make them more attractive for the integration in ULSI interconnects because of better compatibility with ultrathin barrier layers [36].…”

Design of Ultrastiff Organosilicate Hybrid Glasses

“…We can increase the stiffness by means of specific geometrical features without causing a significant increase in density, as opposed to previous approaches solely increasing cross link density which will always increase network density. [7][8][9][10][11][12][13] This achievement is expected to have significant implications for the ubiquitous use of such hybrid glasses in device and energy technologies. We also interpret the effectiveness of both network connectivity and precursor geometry through the topological and geometrical constraints they impose on the network to enforce structural rigidity.…”