Grain Sizes in Electroplated Thin Copper Interconnection Layers

Abstract

Grain sizes have been observed quantitatively at the surface of thin electroplated copper layers by employing a grain boundary etching technique. In conventional copper layers deposited on TaN barrier layers, the typical grain size in the as-deposited layer is at a thickness of . This size decreases rapidly with decreasing thickness and reaches for thick annealed layers, i.e., grain size is close to the thickness in such a layer. When lower stress layer is electroplated, however, the grain size in the annealed layer increases from for thick ( thick) and from in thick layers, respectively. Deposition of larger grain size copper layers is required in the electroplating of low-resistivity thin copper layers.