Ultralow- $k$ Dielectric With Nanotubes Assisted Vertically Aligned Cylindrical Pores

An interlayer dielectric with an extremely low dielectric constant of 1.96 is demonstrated using SiO
₂
with vertically aligned cylindrical pores. Vertically grown carbon nanotubes are used as a template for the cylindrical pores to achieve high porosity while maintaining structural stability. Measurements show that an elastic modulus of 17.5 GPa can be maintained even at 65% porosity to provide sufficient mechanical strength for most back end of line processes. This represents a 94% improvement in mechanical stability compared with the state-of-the-art low-k dielectrics. The tradeoffs between dielectric constant and elastic modulus of different porous structures have also been studied to project the ultimate achievable k-value.