Robust Control Method Of Nano Manipulation Robot Inside SEM

The size of IC feature in the post-Molar era has entered the range where quantum effects are significant.Traditional silicon-based chip is approaching its performance limitation.However,the calculation speed of carbon-based chip is 3-5 times faster than that of silicon-based chip,which has the advantages of good thermal conductivity at room temperature,high upper limit of carrying current and fast frequency response.Thus,carbon nanotubes are one of the most promising materials to replace silicon.Both the bottom-up and the top-down processing methods for wafer-level carbon-based chips with semiconductor-type single-wall carbon nanotube(SWNT)as the building block present significant challenges.The nano-manipulation method is an effective complement to the mentioned processing techniques.Thus,there is a need for the nano manipulation robot which can operate SWNT in 3D at the wafer scale and in the complex structure.This paper proposes a motion control method with microscopic visual feedback for the three-dimensional motion precision control problem of the nano manipulation robot,which simplifies the three-dimensional motion into two-dimensional motion.A method is proposed for real-time detection of nano-scale displacements,which allows the detection of displacements in the resolution of the microscope.A control method combining feedforward and proportional-integral(PI)feedback based on the Prandtl-Ishlinskii(PI)inverse model is proposed.The output voltage is simultaneously regulated by proportionalintegral-derivative(PID).Thus optimizing the single-axis positioning accuracy of the nano manipulation robot.A robust controller based on hybrid adjustment of the weights of the input and output sensitivity functions is designed for the integrated suppression of disturbances in a nano-scale environment.The trajectory accuracy of the nano manipulation robot is optimized by two-axis robust controllers and an additional crosscoupling controller.The content of this research can be specifically divided into the following four parts.(1)A real-time measurement method of the displacement of the target based on the secondary electron image of the Scanning Electron Microscope(SEM)is proposed for the problem of measuring the nanoscale positioning accuracy of the nano manipulator.A nanoscale displacement measurement system for the nano manipulation robot was built,and the experiments of tracking target displacement measurement were conducted.And the image size of SEM is calibrated with a theoretical displacement measurement resolution better than 1 nm.(2)A comprehensive control method incorporating PI inverse model feedforward control,PI displacement feedback control based on image recognition,and output voltage PID stabilization control is proposed for the problem of controlling the accuracy of the sticky process in the stick-slip drive of the nano manipulation robot.The driving control platform of the nano manipulator was built,and the positioning accuracy reached 1.8nm.(3)For the problem of thermal interference of nano manipulation robot in the nanoscale environment,the thermal disturbances in the driving process of nano manipulation robot in vacuum are analyzed and build a thermal disturbance simulation platform.A robust controller based on hybrid adjustment of the weights of the input and output sensitivity functions was designed.The dry thermal disturbance is suppressed by the selection of the weight function.And the thermal interference suppression experiments were conducted.The positioning accuracy of the nano manipulation robot of 1.8 nm is guaranteed in the presence of thermal interference,and its repeatability is less than 3.6 nm.(4)A control scheme of two-axis robust control combined with cross-coupling control is proposed for the optimal control of the two-axis trajectory of the nano manipulation robot.The contour error of the typical trajectory of the nano manipulation robot are analyzed and the trajectory error is calculated based on the geometric contour error model.After optimizing the control of single-axis positioning accuracy with a robust controller,an additional cross-coupling controller is added to control the trajectory accuracy of the two axes.The experiments were carried out for both two-axis linear trajectories and circular trajectories.Compared with the previous work in the group,the average error of the linear trajectory of 1μm stroke is optimized by 75%,and the average error of the circular trajectory of 1μm diameter is optimized by 64%.