Ultra-low-k materials and chemical mechanical planarization (CMP)

The need for ultra-low-k (ULK) materials in back-end-of-line integration is presented, in the context of the overall drive for performance enhancement and size scaling in semiconductor circuits. This is followed by an overview of dielectric materials, and the steady decrease in k-value, culminating in ULK materials. The impact of chemical mechanical planarization consumables on ULK films is discussed, along with details of how such degradation is characterized. This leads to a presentation of the unique challenges of ULK films incorporated into multilayer damascene Cu interconnects, including reliability and mechanical strength considerations. The chapter concludes with an outlook on dielectric constant scaling.