Non-contact Mode SPM System Design by Integrating MEMS Electro-static Micro-probe & Laser Doppler Interferometer

This research made a non-contact vibration mode scanning probe microscope. The system operation principle was firstly by placing the microprobe in perpendicular to the sample surface, and using signal generator to deliver a sinusoidal drive voltage, then the microprobe would vibrate due to the Coulomb electrostatic force generated by the electrodes on the microprobe. The working frequency is right at the natural resonant frequency of the microprobe. Then let the sample carried by a Z-stage move up. When the sample gets closer to the microprobe, then the vibration amplitude of the microprobe would be reduced and which can be determined by a laser Doppler interferometer, because the Van Der Waal´s force between the sample and microprobe would become larger. Thus one can detect the surface profile of the sample, by moving and holding the tip on a constant height, then the probe vibration amplitude is proportion to the surface profile that can be determined by a laser Doppler interferometer, and the topographic data can be obtained by recording the amplitude of vibration history.