Study On Femtosecond Laser Controlled Silicon Surface Forming Based On Phase Field Model

Microcantilever probes are widely used in microsensors and atomic force microscopes due to its unique mechanical,electrical and optical properties.Microcantilever probes are manufactured by controlling the morphology of silicon-based surfaces.Currently,micro-cantilever probes are prepared by low-pressure chemical vapor deposition,sputtering,and chemical etching.However,the above methods all have problems such as unstable molding,complicated manufacturing processes,and low molding efficiency.Based on above problems,this paper innovatively proposes a method that uses femtosecond laser irradiate the surface morphology of silicon,and change the aspect ratio of silicon surface to control the surface morphology,then enriching the manufacturing method of cantilever beam probe.This thesis mainly studies the surface morphology of femtosecond laser control silicon based on theoretical model derivation,numerical simulation and experimental verification.Firstly,based on the phase field model,the theoretical model that femtosecond laser irradiate silicon is derived,and the numerical simulation and calculation are carried out for the model.Further study the control law of the various parameters on the surface morphology of silicon substrate.Finally,the phase field model theory of the surface morphology is verified by experiments.The main research contents of this thesis are listed as follows:(1)Conducting phase field model study that silicon-based surface morphology irradiated by femtosecond laser.Firstly,according to the mechanism of the thermophoretic motion of silicon atoms that induced by femtosecond laser to establish corresponding phase field model framework.Secondly,the variation of potential energy of silicon atoms in the temperature field is discussed.The studies show that varying potential energy generate driving forces and push silicon atoms migrating from low temperature locations to high temperatures location.Finally,a mathematical model of the surface morphology induced by femtosecond is derived based on the phase field model.(2)Based on the theory of phase field model,the formation of the surface morphology of silicon based on the variation of various parameters is studied.In the phase field model,the evolution process of the surface morphology of silicon is simulated,and the corresponding molding law is studied.Based on the numerical simulation of the phase field model,the influence of the power of the femtosecond laser,the thermal conductivity of the material and the thermal conductivity of the cantilever beam contact material on the aspect ratio of the silicon substrate was studied.This thesis study forming law by change of the aspect ratio of silicon surface,which laid a foundation for controlling the micro-cantilever probe with high aspect ratio.(3)The numerical simulation of the phase field model of the silicon irradiated by femtosecond laser was carried out,and then the corresponding experimental research be carried out.Experiments show that the surface morphology of the experimentally formed silicon-based surface and the surface morphology simulated by the phase-field model remain basically the same in morphology and aspect ratio under the same femtosecond laser parameters.The above research verifies the correctness of the numerical simulation of the phase field model of the surface morphology of the silicon-based surface controlled by femtosecond laser.