Preliminary evaluation of interfacial stability of surface modified porous methyl silsesquioxane by ion implantation for copper metallization scheme

Thin films of ultra-low-κ materials such as porous methyl silsesquioxane (MSQ) (κ=2.2) were implanted with argon 1×10¹⁶ cm⁻² dose at energies varying from 20 to 50 keV at room temperature. This work shows that the surface hardness of the porous films can be improved five times as compared to the as-deposited porous films by implanting Ar with 1×10¹⁶ cm⁻² doses at 20 keV, sacrificing only a slight increase (∼9%) in dielectric constant (e.g., from 2.2 to 2.4). The hardness persists after 450 °C annealing. In this current work, an ion implantation strategy was pursued to create a SiO₂-like surface on MSQ. The effects of implantation parameters on the barrier property and bulk stability of MSQ were then studied. The results reveal one possible route to attain the “zero barrier thickness” requirement for interconnects systems.