Process Monitoring Techniques using Acoustic Waves

Process monitoring and control of semiconductor fabrication parameters, like film thickness, are important issues, limited at the present time by a lack of adequate sensors. In this paper, we outline the limitations of current film thickness technology and propose two new methods for nondestructive film thickness process monitoring: acoustic time domain reflectometry (TDR) and acoustic reflection coefficient phase measurements. Theoretical calculations and experimental measurements of different metal films are used to demonstrate the viability of these novel techniques