Preparation method of metal interconnection structure

The invention provides a preparation method of a metal interconnection structure, and the method comprises the steps: providing a semiconductor structure, and sequentially forming a first barrier layer, a low-K dielectric layer, a buffer layer and a hard mask layer on the surface of the semiconductor structure; a groove is formed through etching, and the metal interconnection layer is exposed out of the bottom of the groove; forming a diffusion inhibition layer on the inner wall of the groove; forming a main metal layer in the groove through an electrochemical plating process; performing a low-temperature thermal annealing process; performing a high-temperature thermal annealing process; and grinding to remove part of the main metal layer, part of the diffusion inhibition layer, the hard mask layer and the buffer layer. A high-temperature thermal annealing process is added after an electrochemical plating process and before a grinding process, so that crystal grains in a main metal layer can be recombined bef