Strategy of Insertion of Merge Features in a Sea of Wires SADP Integration

Abstract

SADP are one of the important patterning techniques for all the FEOL/BEOL levels in 7 nm technology node and beyond. In BEOL, not only the minimum features, but wide lines are also important for power distribution even in the thin wire levels. However, in the conventional SADP integration, insertion of wide features in the sea-of-wires area cannot be achieved easily. In this paper, various strategies are presented for creating merge features in SADP/SAQP integration. Firstly, using an add on lithography, the mandrel can be selectively merge or remove before the spacer deposition, as a result, merged mandrels or non-mandrels without touching others are created. On the other hand, a spacer cut lithography can be applied after the mandrel pull, then, there is a freedom to cut the spacer between the select features that will merge all the features in the area. Nevertheless, the undesired connections can be cut off by adding one more block-lithography. Therefore, it is possible to create any arbitrary shapes with this technique. The last block-lithography can also be eliminated by introducing pre-defined cuts in the mandrel cut or non-mandrel cut step.