Improved planarization method using sandwiched hard layer (SHaL) CMP

CMP uniformity and planarity directly affect the Post-CMP TTV (Total Thickness Variation). Decreased TTV is necessary for successful patterning of devices. The trend in scaling down of device feature size requires smaller TTV and hence tighter CMP performances. The three layer pad stack with IC-1000/hard layer/foam layer (SHaL) was designed to improve the planarity with minimal deterioration of CMP uniformity. SHaL CMP process improves the planarity with negligible effect on uniformity. Reduced CMP time and less ILD oxide is achievable with the SHaL CMP process. Therefore preliminary tests show that improvements in post-CMP TTV can be achieved with reduced CoO. Further enhancements in the efficiency of the process is under investigation.