Method for fabricating metal interconnection of semiconductor device

In a method for fabricating a metal interconnection of a semiconductor device, a lower interconnection and a lower insulation layer are formed over a semiconductor substrate. An etch stop layer is formed over the lower insulation layer. An upper insulation layer is formed over the etch stop layer. A first via hole is formed to expose the etch stop layer corresponding to the lower interconnection. A second via hole exposing the lower interconnection is formed by a primary etching process that selectively removes the etch stop layer exposed by the first via hole. A chemical cleaning process is performed on the second via hole, wherein polymer is formed over the surface of the lower interconnection during the chemical cleaning process. The polymer is removed from the second via hole by a secondary etching process using vaporized gas.