1. A manufacturing method of a semiconductor structure, comprising: providing a semiconductor substrate comprising semiconductor devices; depositing a copper diffusion barrier layer on the semiconductor substrate; forming a copper composite layer on the copper diffusion barrier layer; decomposing the copper composite at corresponding positions, where copper interconnection is to be formed, into copper according to the shape of the copper interconnection; and etching off the undercomposed copper composite and the copper diffusion barrier layer underneath, to interconnect the semiconductor devices.