Methods are described for forming “air gaps” between adjacent copper lines on patterned substrates. The air gaps may be located between copper lines on the same layer. A sacrificial patterned dielectric layer is used as a template to form a layer of copper by physical vapor deposition in a substrate processing system (i.e. a mainframe). Without breaking vacuum, the copper is redistributed into the gaps with a copper reflow process. Dielectric material from the template is removed, again in the same mainframe, using a remote fluorine etch process leaving the gapfill copper as the structural material. A conformal capping layer (such as silicon carbon nitride) is then deposited (e.g. by ALD) to seal the patterned substrate before removing the patterned substrate from the mainframe.