US Patent 9490202 Self-aligned airgap interconnect structures

Devices and methods for forming a self-aligned airgap interconnect structure includes etching a conductive layer to a substrate to form conductive structures with patterned gaps and filling the gaps with a sacrificial material. The sacrificial material is planarized to expose a top surface of the conductive layer. A permeable cap layer is deposited over the conductive structure and the sacrificial material, Self-aligned airgaps are formed by removing the sacrificial material through the permeable layer.