Scanning Grating Microinterferometer for MEMS Metrology

Abstract

Quality control and metrology are critical to improved productivity and yield in MEMS design and production. This paper presents a micrograting interferometer for use in measuring MEMS devices. The sensor is also capable of making dynamic measurements, qualifying the functionality of the MEMS devices. The system employs a phase sensitive diffraction grating for interferometric axial resolution and a microfabricated lens for improved lateral resolution. The microinterferometer is capable of array implementation and can be used to increase the yield of MEMS manufacturing processes. The results generated by a single microinterferometer show good correlation with both analytic models and measurements of the MEMS devices by other metrology tools. The microinterferometer enables measurement of steady state vibration of MEMS devices as well as the development of surface vibration profiles. Initial results presented in this paper also demonstrate the ability to measure quantities such as part surface curvature, as well as reduce low frequency vibrational noise. The use of a deformable diffraction grating is proposed to further enhance the sensor’s capabilities.