Structural analysis of graphene-capped copper by spectroscopic ellipsometry for humidity reliability assessment

Abstract

Reliability of graphene-capped copper (Gr/Cu) against humidity is assessed by spectroscopic ellipsometry (SE). Changes in the volume fraction of crystalline Gr in a single-layer graphene (SLG) and a tri-layer graphene (TLG), and also Cu-oxide thicknesses under the Gr cap were characterized by SE before and after humidity reliability test. It was found that TLG has a higher moisture resistance than SLG with less changes in the crystalline Gr volume fraction and thickness than those of SLG, and it leads to the reduction in Cu-oxide thickness and the uniformity under the Gr-cap. The results were consistent with the analysis results by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy excluding variations due to differences in analysis areas of each method. Since detail structure changes such as Gr quality and thickness can be evaluated non-destructively, SE is considered as a promising method for the detail analysis of Gr/Cu structures.