Accurate Nondestructive Determination of Interfacial Oxide Layer Thickness on Si Wafers Using THz Inductive-Capacitive Resonant Metamaterial Spectroscopy

Abstract

We present a nondestructive technique to accurately measure interfacial oxide layer thickness using inductive-capacitive (LC) resonant metamaterial terahertz (THz) impedance spectroscopy. THz LC resonant metamaterials demonstrate high sensitivity to changes of the substrate’s effective relative permittivity/refractive index. This sensitivity is manifested by a change in the metamaterial’s natural resonating frequency. Utilizing this property, we built an analytical model and experimental tool to determine the interfacial oxide layer thickness. It is supported by 3D electromagnetic simulations and terahertz spectroscopic results, utilizing our highly sensitive arrowhead LC resonant metamaterial sensor. This method can detect changes in interfacial oxide layer thickness with an accuracy of 2 nm and sensitivity of 1200 GHz/RIU, which is one of the highest sensitivities to date for determining the interfacial dielectrics. We also demonstrate a complete correlation of the simulations with spectroscopic experiments, verified by measuring the real oxide thickness using a focused-ion beam. This nondestructive method enables accurate profiling of the interfacial oxide across the wafer.