Research On Related Technology Of Dual-frequency Laser Scanning Tip Measurement System

With the development of high performance and high integration of electronic products,The market advancements demand the increasing super-smooth surfaces of parts.The manufacture of computer hard drives and large scale integrated circuits require chips and discs with nano-scale surface accuracy or angstrom dimension surface ripple and roughness,and their profiles can be detected quickly and accurately.In the paper,the development of nano-detection technologies at home and abroad firstly are studied.A dual-frequency laser heterodyne interferometer with scanning tip measurement system is adopted,and it combines both the dual-frequency laser scanning tip module,data processing module and 3D-scanning stage module.The principle of each sub-system modules are introduced,and the setting process of preset point is hard studied to obtain the judgment basis of preset points.The integration design of 3D-scanning system is particularly studied that it includes the driving mode,components,micro displacement output mode,etc.The Zdirection drive core device is simulated by finite element method,and the design scheme is optimized.The measurement stability and error of the designed Z-direction drive device are experimentally measured.In the experiment,the distance between the tip and sample is changed by controlling the driving voltage in the Z-direction.On this basis,the repeatability experiment of the displacement-voltage relationship of the Zdirection scanning platform is carried out.The results show that the variance of repeated measurement is less than 0.0190?m.The linearity relationship between the displacement and the driving voltage has good performance on the Z-direction scanning stage.The dynamic contact model of tip and sample in the dual-frequency laser scanning tip system is analyzed by nonlinear finite element simulation.The simulation results show that the 1st harmonic amplitude of tip vibration can characterize the surface morphology of sample,and the 2nd harmonic amplitude of tip vibration can be used as the basis of contact between the tip and sample characteristics.The influence of change the tip radius and driving forces on tip vibration has also studied,the simulation results also show that the 1st and 2nd harmonic amplitudes of tip vibration are approximate linear change respectively.The experimental study on the contact between the tip and sample is carried out by using the dual-frequency laser scanning tip measurement system.The experimental results show that the vibration tip contacts the sample when the z-direction fretting distance reaches 62.9nm,and the change of 2nd harmonic amplitude of tip is approximately linear change.Accordingly,the z-direction fretting distance corresponding to the preset point of the tip can be set between 62.9nm-67.6nm.The results of simulation and experiment also show that the measurement system can detect the morphologies of nano-scale samples.