US Patent 7790601 Forming interconnects with air gaps

Disclosed is a process of an integration method to form an air gap in an interconnect. On top of a metal wiring layer on a semiconductor substrate is deposited a dielectric cap layer followed by a sacrificial dielectric layer and pattern transfer layers. A pattern is transferred through the pattern transfer layers, sacrificial dielectric layer, dielectric cap layer and into the metal wiring layer. The presence of the sacrificial dielectric layer aids in controlling the thickness and profile of the dielectric cap layer which in turn affects reliability of the interconnect.