A scalable low-k/Cu interconnect technology using self-assembled ultra-low-k porous silica films

A novel ultra-low-k porous silica film was developed by use of a self-assembly technology. A periodic hexagonal porous silica film and disordered porous silica film were formed by self-assembling surfactants and acidic silica derived from tetraethoxysilane (TEOS) on a Si substrate. The properties of the periodic porous film such as porosity, pore diameter and resulting dielectric constant can be controlled by the alkyl chain length of the surfactant and the molecular ratio of surfactant/Si. The mechanical properties of the porous silica film can be reinforced by introducing tetramethyl-cyclo-tetra-siloxane (TMCTS) treatment without increasing the dielectric constant. The elastic modulus of 8 GPa and dielectric constant of 2 were achieved for the porous silica film. Ultra-low-k/Cu damascene integration was demonstrated for 45 nm BEOL technology.