Simulation Study On The Self-assembly Process For Thin-film Optoelectronic Devices Integration

The integration of optical devices on silicon substrate is a hotspot in the field of optoelectronic integration.It is easy to be affected by the sticking effect by using the traditional method of pick-and-place assembly for the integration of optical micro components.The non-contact characteristics of the self-assembly technology can overcome the defects of the sticking effect,and it is expected to achieve higher integration efficiency.In the self-assembly technique driven by capillary force,the optimal design of the geometry of the binding sites is one of the key factors to improve the successful rate of self-assembly technology.Based on the simulation analysis,the effects of different sizes and shapes of the binding sites on the self-assembly of thin-film photodetectors are predicted.In the self-alignment process driven by capillary forces,the capillary action between the device and the substrate is the key factor to realize the precise positioning and orientation of the micro components.Therefore,by analyzing the capillary force and torque in the process of self-alignment,the self-alignment effect of the device can be predicted effectively.In this thesis,the simulation model of the self-alignment process of the thin-film photodetector is established by the finite element analysis software Surface Evolver.Through the simulation analysis,we find that when the size of the binding site is larger,the capillary force and torque of the adhesive to the device is larger.Therefore,we predict that when the size of the binding site is larger,the alignment effect of the device is better.For the different binding site shapes,the capillary effect of the adhesive is also different.In the three different binding site shapes designed in this article,the capillary force and torque of the binding site of the circle and the triangle(angle point to the interior)are larger.Therefore,we predict that when the shape of the binding sites are circle and triangle(angle point to the interior),the alignment effect of the device is better.In the process of self-alignment,the device is easily affected by fluid turbulence.In this thesis,according to the maximum capillary force of device in the process of self-alignment,we analyze the ability of the device with different sizes and shapes of the binding sites to resist the fluid disturbance.In the simulation using Surface Evolver,the shape of different binding sites should be remodeled,the process is complicated.Through the simplified model,the self-alignment effect of different binding site shapes can be unified analysis.Based on the simplified model,this paper analyzes the self-alignment effect of the devices with different two ends spacing and different shapes by using MATLAB.Through the analysis,the prediction results show that the self-alignment effect of the device is better when the distance between the two ends of the binding site is larger,but the alignment effect will not be improved obviously after the space is increased to a certain extent.Considering the fact that thin-film devices may need to distinguish between positive and negative poles,the two ends of the binding site are designed into asymmetric shapes and complementary shapes.Through the analysis,it is predicted that complementary shapes can be better to avoid the appearance of positive and negative inversion in the process of self-alignment.Based on the simulation analysis,this thesis predicts the effects of different sizes and shapes of the binding sites on the self-alignment of thin-film photodetectors.These conclusions can provide references for the fabrication and assembly of practical devices,which can improve the design efficiency and assembly efficiency.