Research On Modeling And Effect Mechanism Of Focused Ion Beam Induced Deposition

Focused ion beam induced deposition is an additive manufacturing technology in micro/nano field with advantages such as high precision,prominent local effect and easy to control,which is widely used in mask repair,IC circuit modification,construction of micro-electro-mechanical system and preparation of micro sensors and actuators.In the process of focused ion beam induced deposition,the size of additive structure is difficult to calculate due to the complex interaction between incident beam,sample surface and deposition structure.Meanwhile,there are many sophisticated effects in the additive process,making the morphology of additive structure more difficult to predict.In this paper,the complex interaction among the particles involved in the reaction process of focused ion beam induced deposition are considered,and the process model of focused ion beam induced deposition is established.The process model can accurately calculate the precursor gas concentration within the reaction area and the dynamically capture the contour of additive structure under different process parameters and working conditions.Next,the reliability and accuracy of the process model are verified by reproducing various effects from the perspectives of experiments and simulations.Finally,on this basis,the process model is used to replace the experiment,so as to play its predictive role and realize the process parameters optimization for complex functional micro/nano structures,providing process parameters guidance and optimization for the preparation of complex chiral optical metamaterials.The superiority reduces the cost of experimental trial and error,and successfully realizes the fabrication of the target chiral optical metamaterials.The optical characteristics in the visible frequency domain is calculated by the finite-difference time-domain method to verify the working performance of optical metamaterials.The main content of this paper is as followed:(1)Based on the gas kinetic theory and Fick’s diffusion law,a precursor gas concentration calculation module is established.In the module,the effects of precursor gas adsorption,diffusion,decomposition,and desorption are comprehensively considered,and the accurate calculation of the number of precursor gas molecules in the reaction area of focused ion beam induced deposition is realized,and the influence of process parameters on the processing of micro-nano structure of focused ion beam induced deposition in terms of precursor gas factors is quantitatively explained.Using this module,the concentration distribution of precursor gas in the reaction area of focused ion beam induced deposition is simulated under different working conditions,and the physical law between the process parameters and the concentration of precursor gas is revealed.(2)The Continuous Cellular Automata is introduced to establish the process model of focused ion beam induced deposition,and the numerical simulation algorithm of focused ion beam induced deposition is developed.The model accurately describes the number and distribution of various particles involved in the reaction process of focused ion beam induced deposition in the form of flux.At the same time,on the basis of a deep understanding of the physical process of focused ion beam induced deposition,the cell space,types and conversion principles are established,and the precise prediction of the processing morphology of the additive of focused ion beam induced deposition is realized.In view of the shadow effect,secondary effect and other phenomena commonly occurring in the process of focused ion beam induced deposition,the process model reproduces these complex effects,which provides help to understand the physical laws behind the effects.(3)Experiments on complex effects of focused ion beam induced deposition are carried out.Due to the complex reaction process of focused ion beam induced deposition and the uncertainty of reaction cross section between gas molecules,incident ions and substrate atoms,there are empirical parameters in the process model.On the basis of a few experiments,the empirical parameters in the process model are calibrated,and the simulation prediction results under other process parameters are calculated.The accuracy of the process model is verified by the consistency between the experimental results and the simulation results,and the correctness of the physical laws in the process model for the occurrence of effects is proved,and the process methods to avoid or use these effects are proposed.(4)An error adaptive ion beam path planning tool is developed to optimize the processing mode in focused ion beam induced deposition.The tool realizes the stable control of the distance between ion beam pixels and the free adjustment of the dwell time.In the process model,using the ion beam path planning provided by the tool,the numerical simulation of asymmetric deposition between micro-nano structure arrays and complex nano-helix structures are successfully realized.The effects of secondary effects and thermal effects are mainly considered,and the process defects are overcome,providing the optimal process parameter group and processing conditions for experimental processing.(5)On the basis of the optimal process parameter group and processing conditions,the preparation of complex chiral optical metamaterials in the visible light domain is realized through experiments,and the structure selection and characteristic size range of chiral optical metamaterials are expanded.The operating frequency band and optical properties of optical metamaterials are calculated using the finite-difference time-domain method,and the physical laws between the characteristic size and optical properties of materials are revealed,It provides a new idea for the preparation of optical metamaterials with tunable properties.To sum up,in this paper,a focused ion beam induced deposition process model is established.The accuracy and reliability of the process model are verified by experiments and simulation methods.The process model is used to provide parameter optimization guidance for the preparation of micro/nano complex functional structures,which lays an engineering practical foundation for a deeper understanding of focused ion beam induced deposition and expanding it to a wider application field.