Alignment method for used in chemical mechanical polishing process

Abstract

A method of alignment for a chemical mechanical polishing includes previously patterning a primary zero alignment mark on a surface of a wafer. A first dielectric layer is deposited on the wafer for isolation. Then, an etching is used to etch the first dielectric layer using a photoresist as a mask. First conductive plugs are formed in the first dielectric layer. Next, a first conductive layer is formed on the surface of the first dielectric layer and on the tungsten plugs. Thus, the first non-zero alignment mark pattern is formed on the surface of the first conductive layer and aligned to the first conductive plugs. Next, a second non-zero alignment mark pattern is thus formed on the surface of a second conductive layer and aligned to the a second conductive plugs. By repeating the aforementioned method, odd non-zero alignment mark patterns will be formed over the first non-zero alignment mark pattern, and even non-zero alignment mark patterns will be formed over the second non-zero alignment mark pattern. Therefore, the present invention save space to put non-zero alignment marks in multilevel interconnection and planarization processes.