Mechanistic Study of Plasma Damage and CH4 Recovery of Low k Dielectric Surface

A mechanistic study was performed to investigate plasma damage and CFL, recovery of porous carbon-doped oxide (CDO) low k surfaces. First the nature of damage was examined for different plasma treatments in a standard RIE chamber then followed by a study using a downstream hybrid plasma source with separate ions and atomic radicals to investigate their respective roles in the plasma process. Plasma damage was found to be a complicated phenomenon involving both chemical and physical effects, depending on chemical reactivity and the energy and mass of the plasma species. Moisture uptake after plasma damage was found to be a major reason to cause dielectric constant increase. The CFL plasma treatment was found to be promising in repairing oxygen ashing damages by formation of a carbon-rich polymer layer. However, sp² carbons on the top polymer layer seemed to limit the penetration of plasma CH₄ and thus full recovery of low k damage.