Methods and systems disclosed herein use acoustic energy to determine a gap between a wafer and an integrated circuit (IC) processing system and/or determine a thickness of a material layer of the wafer during IC processing implemented by the IC processing system. An exemplary method includes emitting acoustic energy through a substrate and a material layer disposed thereover. The substrate is positioned within an IC processing system. The method further includes receiving reflected acoustic energy from a surface of the substrate and a surface of the material layer disposed thereover and converting the reflected acoustic energy into electrical signals. The electrical signals indicate a thickness of the material layer.