Impact of reducing resist stripping processes at elevated temperature on ULK and HM materials

Ultra low-k materials for interconnects in chip manufacturing require new or adapted procedures for integration into copper damascene metallization, including patterning processes. This work deals with the impact H2 containing stripping processes at elevated temperatures on porous ultra low-k materials and low-k hard mask/capping materials. Porous MSQ and SiO2 and a low-k hard mask have been prepared by spin on deposition (SOD) and for comparison dense SiOCH by PECVD deposition. Resist stripping was done with a downstream microwave discharge in an advanced strip passivation chamber (ASP) of Applied Materials using mixtures of H2/N2 and H2/He. Shrinkage (change of thickness) and electrical properties (k-value and field break down) were investigated. FTIR spectra were used to support the investigation. Ashing parameters, like time of plasma treatment, temperature and gas composition, have been characterized. It was found that the advantage of nitrogen admixture is the high rate of ashing, but shrinkage and impact on k-values will be higher than with He admixture. Helium admixture reduces shrinkage and k-values will be only slightly impacted, but stripping time has to be increased for resist removal.