Fabrication Of High Aspect Ratio Copper Micro Column Array Based On THB Photoresist

Metal micro column array structure has the advantages of large specific surface area,good electrochemical characteristics and good energy storage performance.It is widely used in many industrial fields.Micro electroforming technology has the advantages of high machining precision and mass production.It has been one of the main manufacturing methods of metal micro column array.In this paper,a square copper micro column array with a width of 50μm and a depth width ratio of 6 was fabricated,In order to solve the problems of difficult photoresist removal and poor adhesion between micro column and substrate,a method of using dissolvable THB photoresist and enhancing adhesion by chemical etching is proposed.Firstly,the process parameters of THB photoresist were studied.Then,the method of chemical etching to enhance the adhesion between the micro column and the substrate was studied.Finally,the fabrication experiment of copper micro column array was carried out.The specific research contents of this paper are as follows:(1)In order to solve the problems of high aspect ratio copper micro column fracture and incomplete removal of photoresist between columns after SU-8 photoresist removal,THB-151 N photoresist which can remove the photoresist by dissolving was proposed.In order to obtain a photoresist master mold with uniform and controllable thickness and good dimensional accuracy,the uniform parameters,pre baking parameters,exposure parameters and development parameters of THB-151 N photoresist were explored in this paper.Using the optimized process parameters,the pre fabrication of copper micro column array structure with width of 50μm and depth width ratio of 2 was completed.(2)In order to solve the problem of poor adhesion between the metal micro column array structure with small width and high aspect ratio with the substrate,a method of chemical etching with acidic copper chloride solution to increase the bonding area of casting layer is proposed.The qualitative measurement experiment of interface adhesion was carried out.The experimental results show that compared with no pretreatment,the falling off rate of micro columns after chemical etching is reduced from 92.6% to 2.8%.The bonding strength between the casting layer and the substrate has been greatly improved.The method verifies the effectiveness of this method.(3)In order to study the effect of different experimental parameters on the side erosion amount,the chemical etching experiment of acidic copper chloride solution was carried out.The results show that the contour length decreases with the increase of Cu Cl2 concentration.With the increase of HCl concentration,the contour length increases gradually.With the increase of temperature,the contour length increases,but the increasing range decreases gradually.With the increase of etching time,the contour length increases gradually.(4)In order to obtain better etching parameters and predict the etching results of micro columns with other widths under different etching conditions,the chemical etching process of micro column structure was simulated by cellular automata algorithm.The simulation model was established,the etching cell rules were designed,and the simulation parameters were modified by the experimental results.Then,the model was verified by using 50μm micro column structure.The relative error between the experimental results and the simulation results is less than 10%,which verifies the accuracy of the model.(5)Based on the above research results,a copper micro column array with a height of300μm and a length and width of 50μm×50μm was fabricated by micro electroforming process.After the photoresist was removed,the micro column did not fall off from the substrate.Finally,the average side length of the top of the micro column is 56.7μm and the average height is 302.4μm,which meet the manufacturing requirements of the copper micro column array.