Metal wiring critical dimension shrink using ALD spacer in BEOL sub-50nm pitch

In advanced technology nodes, the BEOL requires advanced patterning techniques such as triple patterning (LELELE) and side wall image transfer techniques to form metal and via structures with pitches below 50nm. In this paper, we demonstrate metal critical dimension (CD) shrinkage using atomic layer deposition (ALD) enabled spacer layer to achieve sub-50 nm pitch. ALD spacer thickness is identified as the crucial parameter to achieve target CD. An optimization study correlating oxide thickness, final CD and electrical yield is presented. An optimized recipe that results in 50% shrinkage is identified with good electrical yield.