An interconnection structure, along with methods of forming such, are described. The structure includes a dielectric layer, a first conductive feature disposed in the dielectric layer, and a conductive layer disposed over the dielectric layer. The conductive layer includes a first portion and a second portion adjacent the first portion, and the second portion of the conductive layer is disposed over the first conductive feature. The structure further includes a first barrier layer in contact with the first portion of the conductive layer, a second barrier layer in contact with the second portion of the conductive layer, and a support layer in contact with the first and second barrier layers. An air gap is located between the first and second barrier layers, and the dielectric layer and the support layer are exposed to the air gap.