Creating air gap in multi-level metal interconnects using electron beam to remove sacrificial material

A method comprising:

• depositing a barrier layer on a structure;
• depositing a sacrificial layer on the barrier layer, the sacrificial layer being made of a sacrificial material having substantial thermal stability and decomposable by an electron beam;
• depositing a hard mask layer on the sacrificial layer;
• patterning and etching the barrier layer, the sacrificial layer, and the hard mask layer to form an opening;
• filling the opening with a metal material;
• and
• polishing and removing excess metal by a chemical mechanical planarization (CMP) process.

A device comprising:

• a barrier layer on a substrate;
• a hard mask layer;
• an air gap between the barrier layer and the hard mask layer, the air gap being formed by removing a sacrificial layer using an electron beam, the sacrifical layer being made of a sacrificial material having substantial thermal stability and decomposable by the electron beam;
• and
• a metallization layer through the barrier layer, the air gap, and the hard mask layer, the metallization layer being formed by a dual damascene process.