A contactless thickness measurement of multilayer structure using terahertz time domain spectroscopy

In this paper, a technique is proposed to determine the thickness of individual layer of a multi-layered structure using reflection mode terahertz time domain spectroscopy. The multi-layered structure is modelled to get the overall reflection at the end face of the structure. A particle swarm algorithm is then used to determine the thickness of each layer, which provide the best agreement between reflection data obtained from the theoretical model and independent reflection data sets obtained by 3D full wave electromagnetic simulator.