Method of forming a metal interconnection of a semiconductor device, and metal interconnection formed by such method

Abstract

A metal interconnection of a semiconductor device, formed using a damascene process, has large grains and yet a smooth surface. First, a barrier layer and a metal layer are sequentially formed in an opening in an interlayer dielectric layer. A CMP process is carried out on the metal layer to form a metal interconnection remaining within the opening. Then, the metal interconnection is treated with plasma. The plasma treatment creates compressive stress in the metal interconnection, which stress produces hillocks at the surface of the metal interconnection. In addition, the plasma treatment process causes grains of the metal to grow, especially when the design rule is small, to thereby decrease the resistivity of the metal interconnection. The hillocks are then removed by a CMP process aimed at polishing the portion of the barrier layer that extends over the upper surface of the interlayer dielectric layer. Finally, a capping insulating layer is formed. The intentional forming of hillocks by the plasma treatment process at weak portions of the metal interconnection and the subsequent removal of the hillocks greatly reduces the possibility of any additional hillocks being produced at the surface of the metal interconnection, especially when the capping layer is formed.