Innovative metrology method for the 3-dimensional measurement of MEMS structures

We introduce and demonstrate a new metrology method applicable for 3-dimensional (3D) measurements, based on common-path phase-shift interferometry. The method includes a unique optical setup in which wavefront modifications are applied over spatial regions of the wavefront reflected from an inspected object, and proprietary algorithm is used to fully reconstruct the reflected wavefront and thus the sample topography and reflectivity. This 3D measurement method was implemented into a measurement system, consisting of a measurement head integrated with a white-light microscope, using the latter as its imaging system. The system has sub nano-meter Z-axis accuracy, independent of the optical magnification. Other advantages of the technique are rapid real-time data acquisition, immunity to noise and vibration, small size, no moving parts, ability to work in various lateral magnifications, and versatile (reflectance or transmittance) optical imaging. The systemis small footprint, insensitivity to vibrations and operation simplicity, make it suitable to measure MEMS components in production environments and in conjunction with other probing systems.