Process Optimization Of Electrochemical Nanoimprinting On Semiconductor Wafer

With the continuous development of science and technology,semiconductor materials,as an important part of the advanced technology,have a great impact on the development of society.Micro-nano manufacturing technology of semiconductor is the technology of manufacturing micro-nano-scale semiconductor components.Electrochemical fabrication has a great pile of applications in the field of micro-nano fabrication of functional materials.The workpiece obtained by electrochemical fabrication has high precision and no residual stress,it can also fabricate threedimensional structure.In this thesis,we adopt the process route of nanoimprint which offers a mold-semiconductor processing,furthermore we uses electrochemical nanoimprinting(ECNL)to fabricate GaAs semiconductors,and optimizing the uniform pressure distribution.The main work and innovations of this thesis are summarized as follows:(1)Building an electrochemical nanoimprint experiment platform,compare the advantages and disadvantages of different devices,and finally determine the structural design plan,optimize the pressure uniformity problem in the nanoimprint process by adopting micro-motion feed and omnidirectional structure,and take the intensity examination of main force structure of the designed mechanical structure.(2)Using nanoimprinting to prepare rasters and array molds which is made of PMMA for electrochemical nanoimprinting,comparing the depth of the raster structure,the amount of depression and the overall warpage,it is determined that the holding temperature is 94～114℃ when PMMA is kept within the glass transition temperature range,plastic deformation can occur on the surface of the PMMA;comparing the integrity of the grating structure on the workpiece under different pressures,it is determined that the PMMA molecular chain can be reorganized after heating when the pressure is 9 N;comparing the flatness of the raster structure on the PMMA under different holding times,it is determined that when the holding time is 30 seconds,the temperature of the PMMA inner layer can reach the glass transition interval,reducing warpage deformation and improving processing quality.(3)Through theoretical analysis and experimental verification to study the distribution of the external pressure during the ECNL process,use COMSOL to conduct static simulation analysis to study the surface pressure distribution of semiconductor workpieces in electrochemical nanoimprinting,and use Hertz contact theory to predict the effect of elastic deformation area on GaAs and PMMA.The removal amount and structure etching depth increase with the increase of external pressure.However,when the pressure is too high,it will also produce hump defects in the center of the GaAs surface microstructure,and the defect size is similar to the size of the radius of the contact circle of PMMA produced by the contact deformation,and the final pressing pressure is determined to be 5 N.(4)Due to the flatness error of the PMMA impression itself and the parallelism error between the workpiece and the plane of the PMMA impression,it may lead to uneven distribution of the microstructure array after processing.The elastic substrate introduced in the ECNL process has good uniformity results in both the finite element simulation test and the actual processing test,which proves that the use of the flexible substrate can improve the overall uniformity of the imprinted array microstructure.