Characterization of piezoelectric films and mems devices by scanning interferometer

Abstract

In recent years the increasing demand of MEMS and piezoelectric technology has driven the research in that particular field, a measuring method for displacement with very high resolution will be required. Piezoelectricity is the ability of some materials, which exhibit the deformation of material proportional to an applied voltage, and vice versa. The displacement due to deformation can be in subÅngström range. A modulated laser interferometer will be adopted to carry out such small displacement in the study.

In this report, a scanning interferometer is developed based on a modulated Mach-Zehnder interferometer to study the piezoelectric material and MEMS device. The main concept here is that a slow modulation is introduced to an ordinary interferometer, whereas enables the simultaneous measurement of the vibration signal Vout and the reference signal Vp-p, thus real time calibration can be realized compare to other methods. Accurate measurement of the maximum intensity change corresponding to the small vibration at the most sensitive quarter-wavelength point can be achieved by measuring the envelope amplitude of the modulated vibration signal.

The resolution of the system is up to 10-2 Å and it is highly sensitive due to its high resolution. In order to ensure the stability and accuracy of scanning interferometer, it is crucial to adjust and align all optical apparatus to maximize its performance and reliability. Several approaches will be developed and compared to improve the reading’s stability and reliability.