Method for Forming Interconnect Structure

A device comprising:

• a gate structure over a substrate, wherein the gate structure comprises:
• a gate dielectric layer over the substrate;
• and
• a gate electrode over the gate dielectric layer;
• a contact plug over the gate electrode and in a first dielectric layer;
• a bottom metal line in contact with the contact plug and in a first inter-metal dielectric layer;
• a top metal line over the bottom metal line and in a second inter-metal dielectric layer;
• a second dielectric layer over the second inter-metal dielectric layer;
• a first barrier layer on a bottom and sidewalls of an opening in the second dielectric layer, wherein the first barrier layer is of a first thickness;
• a second barrier layer over the first barrier layer, wherein the second barrier layer is of a second thickness greater than the first thickness;
• and
• a pad over the second barrier layer.

A device comprising:

• a first drain/source region and a second drain/source region in a substrate and between a first isolation region and a second isolation region;
• a gate structure in a first dielectric layer and over the substrate, wherein the first drain/source region and the second drain/source region are on opposite sides of the gate structure;
• a contact plug over the gate structure and in the first dielectric layer;
• a first metal line in contact with the contact plug and in a first inter-metal dielectric layer;
• a second metal line over the first metal line and in a second inter-metal dielectric layer, wherein the second metal line is electrically coupled to the first metal line through a plurality of vias and metal lines;
• a second dielectric layer over the second inter-metal dielectric layer;
• a first barrier layer on a bottom and sidewalls of an opening in the second dielectric layer;
• a second barrier layer over the first barrier layer, wherein:
• a thickness of the second barrier layer is greater than a thickness of the first barrier layer;
• and
• the first barrier layer and the second barrier layer are formed of two different materials;
• and
• a pad over the second barrier layer.