Patent ID: 8163649

Claim:
A method for forming a copper interconnection structure, the method comprising the steps of: forming an insulating layer over a semiconductor substrate, the insulating layer including silicon (element symbol: Si), carbon (element symbol: C), hydrogen (element symbol: H) and oxygen (element symbol: O); forming a copper (element symbol: Cu) alloy layer including an additional element on the insulating layer in an atmosphere having a first volume concentration of oxygen (element symbol: O), forming a copper layer on the copper alloy layer; and applying a heat treatment so as to form a barrier layer at and adjacent to an interface between the insulating layer and the copper alloy layer, and so as to form an interconnection by unifying a part of the copper alloy layer with the copper (element symbol: Cu) in the copper layer; wherein the heat treatment is applied in an inert gas atmosphere having a second volume concentration of oxygen (element symbol: O) that is greater than the first volume concentration, and the heat treatment is applied at a temperature of not less than 300°C. and not more than 450°C.