Research On The Trigger Mechanism Of A 3D Resonant Nano Probe

Nano measurement technology is one of the basic subjects of nano science and technology. With the development of super finishing and superfine processing, the feature sizes of MEMS, super precision optical devices, etc., are miniaturized with the coming new era of nano technology. For the true three dimensional (3D) measurement of these micro/nano structures, the resolution of nanometer (even sub-nanometer), and the measuring force of micro Newton (even nano Newton), are necessary. Currently, the true 3D measurement from several hundred of micrometers to several millimeters has made some progress, but there is no mature technology yet. As the key technology of micro/nano 3D measurement,3D nano trigger positioning technology is not only the basis to realize the true 3D measurement of micro devices, etc., but also one of the research difficulties of micro/nano three Coordinate Measuring Machine (CMM) at home and abroad.In order to fulfill the research requirements and overcome the technical bottlenecks of micro/nano CMM, based on the analysis and summary of domestic and foreign research situation of micro/nano CMM,3D nano resonant trigger method is proposed in this paper. And, based on this method,3D nano resonant trigger probes and measurement and positioning systems developed, which can realize the 3D trigger measurement of micro inner hole with high resolution. The main researches and results are summarized as follows.(1) Trigger mechanism of the 3D nano resonant trigger probe is analyzed. Based on interface mechanical theory, the dynamic contact mechanism between the 3D resonant trigger probe and sample surface is analyzed, and the mechanical models of the interactions in X(Y) and Z directions are constructed. According to the established mechanical models, influences to the motion of the probe from interface forces, such as van der Walls force, capillary force, etc. and their resultant force, are analyzed and simulated.(2) 3D nano resonant trigger probe is developed. Based on optical fiber tapering technology and Taguchi method with two steps, an integrated optical fiber micro-sphere is fabricated, of which the two-dimensional (2D) diameter is less than 80 μm,2D roundness error is less than 0.70 μm,2D offset distance between the micro-sphere center and the fiber stylus central line is less than 0.65 μm, and true sphericity is about 0.50 μ m. Due to the high sensitivity of resonant parameters (resonant amplitude, resonant frequency or resonant phase) to micro forces, and combined with the integrated optical fiber micro-sphere, quartz tuning fork, PVDF and double-ended tuning fork are used as micro force sensor to build the 3D resonant trigger probe respectively. The significant feature of the probe is that, it works in tapping mode (TM) in Z direction, and in friction mode (FM) in X and Y directions. Measurement systems based on are researched. According to some characteristic tests about noise level, sensitivity, trigger resolution, repeatability, etc., it can be gotten that in the all three directions (X, Y and Z), the trigger resolutions of the systems are in sub-nanometer magnitude, the repeatability errors are in tens of nanometer magnitude, and the measuring forces of the system based on quartz tuning fork are between tens of micro-Newton and hundreds of micro-Newton, while the system based on PVDF are in sub-micro-Newton level.(3) 3D nano resonant trigger measurement and positioning systems are developed. Using the above constructed probes based on quartz tuning fork and PVDF respectively, and combined with a 3D nano positioning stage, a feedback control module and a signal processing circuit,3D resonant trigger measurement and positioning systems are constructed. For the 3D resonant trigger measurement and positioning system, the overall mechanical structure, the phase feedback control circuit based on phase lock loop (PLL), and the control and test procedures based on VC++, are designed successively.(4) Characteristic tests of the 3D nano resonant trigger measurement and positioning systems are completed. It is obtained by characteristic tests (such as test of circumferential force curves, etc.) that in all measuring directions of the quartz tuning fork system, the resolutions are in nanometer/sub-nanometer magnitude, the repeatability errors and the single point trigger repeatability errors in X and Y directions are both in tens of nanometer magnitude. Calibration method of probe’s equivalent diameter is designed, and the corresponding orientation calibration procedure is written based on VC++. Synthetic standard inside dimension using standard gauge group is tested in eight directions, which are directions at 0 degree angle,45 degree angle,90 degree angle.135 degree angle,180 degree angle,225 degree angle,270 degree angle and 315 degree angle. Based on the calibrated values, measurement results of the micro inner hole are corrected and compensated. According to the comparison result, the imaged dimensioning values are basically consistent with the calibrated values. Using the quartz tuning fork system, trigger measurement of micro inner hole with eight and more points is realized.