Resistivity of thin copper interconnection layers

Resistivity is observed quantitatively in a thin electroplated copper layer. A resistivity of 2.6 mu Omega(.)cm is observed in a 600-nm-thick as-deposited copper layer by conventional electroplating. This resistivity increases rapidly with decreasing thickness and reaches 7.8 mu Omega(.)cm at a thickness of 75 nm. This rapid increase is mainly due to the increase in the orientation ratio of the copper (111)/(200). The resistivity in the as-deposited layer is maintained at 2.2 mu Omega(.)cm in a 75 nm low resistivity layer with a low orientation ratio. Such a low-resistivity thin layer is electroplated practically by newly developed process. The preparation of a low-stress seed layer is also required in this electroplating process.