Patent ID: 7361452

Claim:
A method for forming a metal line, comprising: stacking a lower insulating layer, a lower metal layer and an upper insulating layer; patterning a first photosensitive film on the upper insulating layer; using the patterned first photosensitive film as a mask, etching the upper insulating layer until at least a portion of the lower metal layer is exposed; filling an etched portion of the upper insulating layer with a nitride film; patterning a second photosensitive film over the lower metal layer and the nitride film; using the second photosensitive film as a mask, etching the lower metal layer until the lower insulating layer is exposed to form a lower metal line pattern; depositing an IMD (Inter Metal Dielectric) layer on the lower metal line pattern, including the sidewalls of the lower metal line pattern, the lower insulating layer, and the nitride film, thereby forming an air gap within the IMD layer between lines in the lower metal line pattern; planarizing the IMD layer to expose the nitride film; removing the nitride film, thereby forming a contact hole in the IMD layer exposing an upper surface of the lower metal line pattern; filling the contact hole with a conductive material; depositing an upper metal line over the conductive material.