Self-aligned 8nm T2T as cell boundary in the middle-of-line

In order to achieve tight, 8 to 12 nm cell boundaries, Ru direct metal etch can be used to split a larger via into two opposite facing smaller vias and create a tight metal line tip-to-tip (T2T) at the cell boundary. This is obtained by self-aligning the Ru direct metal etch to the tightest metal layer above. This technique of splitting a via and creating a T2T with zero line extension is promising for cell boundary definition of complementary FET. In this work, we will discuss lithography overlay and via CD process window definition to achieve the improved morphological and electrical results. For 8 nm T2T, we have obtained a 55% leakage current yield. Additionally, for 10 and 12 nm T2T, a leakage current yield of above 90% was achieved.