Discrete Study of ALD TaN on Via and Line for Low Resistive and High Reliable Cu/Low-k Interconnects and Other Applications

Abstract

Atomic layer deposition (ALD) of TaN was intensively studied for barrier metal in Cu line and Cu via separately by utilizing single damascene (SD) structure. As a barrier metal for via, thin ALD TaN 0.7 nm is insufficient to suppress dissolution of Cu seed during electrochemical plating, resulting in poor filling property. While, thicker ALD TaN 2 nm formed high resistance layer at via bottom. Moderate thickness of ALD TaN 1 nm showed lower via resistance and longer EM lifetime than PVD TaN/Ta. Besides, 1 nm thick ALD TaN achieved comparable TDDB lifetime to PVD TaN/Ta due to excellent barrier property. On the other hand, a certain thickness of PVD Ta layer is required on ALD TaN for line structure to obtain requisite adhesion between barrier metal and Cu for good EM performance. However, thicker PVD Ta led to higher line resistance. PVD Ta 5 nm is ideal thickness on ALD TaN 1 nm to achieve low line resistance and long EM lifetime.