We have been developing novel ultra-low-A porous silica by use of a surfactant self-assembly technology. Our porous silica films include periodic type and disordered (nonperiodic) type in terms of pore structure. In order to put these porous silica films into practical use in the next-generation microelectronics, it is necessary to increase the mechanical strength as well as to decrease the dielectric constant of the film. To lower the dielectric constant, we have developed the pore size control technologies by the vapor-phase tetraethoxysilane (TEOS) treatment to stabilize the porous structure and by employing the different alkyl chains of surfactant molecules. The mechanical properties of the porous silica films could be reinforced independently of the dielectric constant by the vapor-phase tetramethyl-cyclo-tetra-siloxane (TMCTS) treatment. By this treatment, porous silica films with the elastic modulus of 8 GPa and dielectric constant of 2 can be achieved simultaneously, and ultra-low-fc'Cu damascene with sufficient mechanical strength was demonstrated.
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