The invention discloses a metal interconnection structure and a manufacturing method thereof. The method comprises steps: firstly, forming a first intermetallic interconnect wire in a first intermetallic dielectric layer on a substrate; forming a covering layer on the first intermetallic connecting wire; forming a second intermetallic dielectric layer on the covering layer; carrying out a first etching process to remove part of the second intermetallic dielectric layer to form an opening; performing a plasma processing process; and carrying out a second etching process to remove part of the covering layer.