First pass study of surface modified porous low-k by ion implantation for zero thickness barrier requirement of Cu/MSQ/Si stacks in copper metallization scheme

摘要

Low-kappa dielectrics have to meet stringent requirements in material properties in order to be successfully integrated.A particularly difficult challenge for material development is to obtain a combination of low dielectric constant with good thermal and mechanical properties.Incorporation of low dielectric constant materials such as porous silica based materials as a replacement to conventional dielectrics like SiO_2 and use of Cu metallization schemes has become a necessity as critical dimensions of devices decrease.This paper is focused on the challenges in developing materials with low dielectric constant but strong thermo mechanical properties.Thin films of Ultra-Low kappa materials such as porous Methyl Silsesquioxane(MSQ)(kappa=2.2)were implanted with argon 1x10~(16)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 x 10~(16)cm~(-2)doses at 20 keV,sacrificing only a slight increase(approx 9%)in dielectric constant(e.g.,from 2.2 to 2.4).The hardness persists after 450 deg C annealing.In this current work,an ion implantation strategy was pursued to create a SiO_2-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.