1230 Effect of porous structure on dielectric constant and stiffness of interlayer dielectric film between copper wirings

Porous low-k dielectrics are introduced for low-k dielectrics because of its ultra low-k dielectric constant. However, their poor mechanical strength and high coefficient of thermal expansion can cause cohesive failure of low-k dielectrics or interfacial failure between Cu/low-k dielectrics during thermal cycling or CMP(Chemical Mechanical Polishing) process. Especially, the damascene structure of the Cu interconnect can give rise to complex stress states and this causes a lot of issues during the fabrication process. Therefore, it is important to study the relationships between the porosity and the mechanical properties and, also, the porosity and the dielectric constant. In this paper, we studied the effect of the porosity in low-k dielectric film between copper wirings on the dielectric constant and the stiffness by numerical simulation. The effects of the shape and the porosity of pores in low-k dielectric film on the mechanical properties and the dielectric constant were discussed.