Abstract
HfO2 is investigated for its suitability to act as an oxygen and moisture barrier to prevent Cu oxidation in redistribution layers (RDLs) in 3D packaging technologies. HfO2 barriers of varying thicknesses were deposited via atomic layer deposition (ALD) on Cu surfaces and then stressed by (i) high temperature stress and (ii) humidity and thermal stress for 1000 h to ascertain the optimal thickness to prevent oxidation of the Cu. The thickness of the ALD HfO2 film was monitored by ellipsometry, while the extent of Cu oxidation was monitored by focus ion beam prepared SEM cross sections. It is found that ∼9 nm of HfO2 is sufficient to prevent Cu oxidation.
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