Supercritical CO2 for ULK/Cu integration

Supercritical CO₂ (SC CO₂) processing was investigated for porous ultra low-k dielectric (ULK) and copper for successful Back End Of Line (BEOL) integration. The introduction of specific additives into a SC CO₂ and careful control of the process parameters lends this technique to a wide range of applications: 1. Stripping: Potentially able to replace both dry ash and wet clean steps to give a single fully compatible process for ULK/Cu. The main current limitation is the removal of resins hardened during dielectric etch. 2. Cleaning: SC CO₂ is a unique candidate for a dry-in/dry-out process able to clean surface and pores of ULK materials. The removal of Cu rich residues was demonstrated with a chelating agent dissolved in SC CO₂. 3. Curing of ULK: Contamination by water and organics can significantly damaged ULK material and these can be eliminated by processing in SC CO₂. Furthermore, by introducing a suitable additive, hexamethyldisilazane (HMDS), subsequent uptake of water was prevented.