Improvement of mechanical integrity of ultra low k dielectric stack and CMP compatibility

This paper reports about examinations on mechanical integrity improvement which were done to enable the integration of aerogel as ultra low k (ULK) dielectric into copper damascene technology. Our work focussed on the increase of the adhesive strength between the dielectrics aerogel and the cap layer material PECVD silicon nitride and on ensuring successful CMP process and post-treatment to achieve optimum copper damascene architectures. An argon plasma pre-treatment showed best potential for improvement of adhesive strength. Investigations were performed to find optimum process conditions of this treatment and to verify the impact on the porous ULK material. Furthermore, compatibility of CMP and post-CMP-cleaning chemicals with the ULK material was shown and a ULK compatible CMP process was developed. Finally, complete and defect-free damascene structures were manufactured.