In-situ thickness measurement of epoxy molding compound in semiconductor package products using a Terahertz-Time of Flight System

Abstract

Refractive index and thickness of an epoxy molding compound (EMC) were successfully measured without any advance knowledge of properties of material using the Terahertz-Time of Flight System (THz-TFS). The theoretical analysis for calculation of the refractive index and thickness of EMC was conducted considering two time-delay values of emission and detection mode (normal reflection mode and transmission mode). By combining two time-delay values from the normal reflection and transmission modes, the refractive index of EMC could be directly deduced without any parameter of the properties of specimen. The thickness of EMC mold could be simultaneously calculated by using only THz time-delay values. The thickness measurement results using THz-TFS were verified with the thickness measured through scanning electron microscopy (SEM).