Characteristics of Scholte wave and film characterization in layered thin film overlying substrate structures

The layered film-substrate structure is widely used in many fields such as microelectronic devices,but the ultrasonic measurement of film material parameters,especially the characterization of shear wave velocity,is a difficult problem.In this paper,the dispersion characteristics of Scholte wave at the liquid-solid interface and the acoustic pressure response generated by a pulse excitation are theoretically analyzed.The results show that the Scholte wave dispersion at the liquid-solid interface is closely related to the velocity distribution of the layered film-substrate structure.The thickness and shear wave velocity of each layer of the thin film material have a significant effect on the interface wave dispersion characteristics.Based on the dispersion properties of Scholte interface waves,a multi-parameter inversion characterization method for multilayer films is proposed.Firstly,the film parameter inversion is carried out for the theoretical signal,which verifies the feasibility of the method.Subsequent experiments on the excitation and acquisition of liquid-solid interface waves are carried out on different types of multilayer film material samples,and the film parameter inversion results of the experimental signals further verify the feasibility and effectiveness of the method.