The ultra fine dynamics of MEMS as revealed by the Polytec micro system analyzer

摘要

Polytec presents its latest Micro System Analyzer for dynamic characterization of MEMS. Polytec continues to advance laser Doppler vibrometry since its introduction as a MEMS characterization tool in the 1990's and has introduced the first confocal vibrometer microscope with the Micro System Analyzer in 20051. Laser vibrometer out-of-plane resolution down to 0.2 pm / root 15.6 Hz is achieved by combination of highly sensitive Doppler shift measurement, digital decoding techniques and FFT signal analysis. Laser spot sizes less than 750 nm are measured for a high magnification 100X microscope objective and compared to theoretical limitations. The theoretical determination of the lateral resolution limit is discussed in detail with the implication that measurement of objects a couple orders of magnitude smaller (<10nm) can be measured. Example measurements that illustrate the unique measurement capabilities are performed on Sandia comb drive resonators and RF switches. New measurements on the Sandia comb drive show clear advances in resolution, including the ability to place and focus the measurement beam on very tiny structures such as a 2 micron comb finger. High Frequency measurements of comb drive deflection are made out to 2MHz. Furthermore, examples of stroboscopic in-plane response measurements show resolution better than 0.01 pixel. Transient response measurements are taken to determine critical performance parameters on an RF MEMS device developed by XComWireless. This includes measurements of snap down voltage, settling time, resonant frequency and three dimensional deflection shapes of transient time response.