New optomechanical technique for measuring layer thickness in MEMS processes

Dimensional metrology improvements are needed to achieve the fabrication of repeatable devices. This research presents a new optomechanical technique for measuring the thickness of a suspended material in two distinct microelectromechanical system (MEMS) fabrication processes. This technique includes design of test structure, choice of measurement tools, method of measurement, and computation of thickness. Two tools, the stylus profilometer and optical interferometer, are used to take measurements. Non-contact measurements are possible on structures as narrow as 5 μm. Local thickness measurements are achievable with combined standard uncertainty values of less than 10 mm. Benefits of using the new technique include greater likelihood of fabricating repeatable devices and more accurate measurements of material parameters. The proposed technique is also applicable for measuring layers that are thinner and made of materials other than the conventional suspended material used in this research