Micro-Raman measurement of thickness in microelectromechanical silicon structures

This paper presents a novel method of thickness measurement for microelectromechanical system ( MEMS) structures using micro-Raman spectroscopy. When heating by a constant power laser, the local temperature rise of a microscale structure depends on the thickness and thermal characteristics of the structure. The thickness information can then be evaluated by the temperature induced Raman shift. Theoretical analysis and simulation of this method are performed. The small spot size of the laser in micro- Raman spectroscopy enables thickness measurement with a high spatial resolution. This measurement method is confirmed by measuring the thickness of a MEMS single- crystalline silicon ( c- silicon) membrane. The measurement result also consists of that of scanning electron microscopy ( SEM) for the same sample. It has the advantages of being a non- contact and nondestructive process, no preparation, and spatial mapping aspects. The proposed method is also feasible for materials with a temperature sensitive Raman signal.