Fabrication Of Super-resolution Structure Of Electroconductive Materials By Direct Laser Writing

As a new processing technology,direct laser writing has made substantial application in the microelectronics industry.Microelectronics active devices need micro-nano conductive graphics to support their main optoelectronic functions,and the process of manufacturing micro-nano conductive graphics is very important.Common metals and conductive polymers are the main materials in conductive graphics,and their traditional micro-nano processing requires a variety of equipment,and the processes is very cumbersome.Femtosecond laser can initiate photophysical or photochemical reaction of materials at the laser focus,and has the ability to realize all kinds of high resolution graphics in one step.If femtosecond laser is applied to micro-nano manufacturing of conductive graphics,the traditional processing steps can be greatly simplified and the manufacturing cost can be reduced.However,the resolution of conductive structure in the current laser processing is low,so it is difficult to apply to microelectronic devices.The dual-beam laser processing can effectively break the diffraction limit,and its high processing resolution benefits from the high intensity of the depletion laser,but the side reaction caused by too high laser intensity limits the resolution to be further improved.Based on the above problems,femtosecond direct laser writing is used to directly prepare sub-micron size of common metal and conductive polymer from solution,and an efficient indirect depletion mode is proposed in dual-beam system to further improve the processing resolution to nanoscale.The main results are as follows:(1)Sub-micron copper wires are realized by two-photon absorption of femtosecond laser.By adjusting the ionic valence state,the optical absorption wavelength range of the solution is changed,and the solution absorbs energy of laser by two-photon absorption other than single-photon absorption.The two-photon absorption is enhanced by synthetizing copper clusters and the spontaneous reduction rate of copper is inhibited by the surfactant.The final copper wire has a width as low as 230 nm,and a conductivity of 8.19×104 S/m.Compared with similar researches,this method can effectively avoid strong photothermal effect and pave the way for direct laser writing of other common metals with superresolution structure.(2)The two-photon effect of femtosecond laser is used to realize the sub-micron organic conductive material poly(3,4-ethylene dioxthiophene,EDOT).The wire width of the PEDOT is as low as 140 nm,and the conductivity is 1.28×105 S/m,and the circuit is constructed based on the modified PEDOT nanowires.The electric field simulation of laser focus shows that the shape of the PEDOT material obtained by laser direct writing is determined by the electric field component in the X direction.This work realizes the superresolution direct laser writing of conductive polymers.(3)Because the conductive graphics fabricated by femtosecond laser is only with submicron resolution,the indirect depletion method is used to improve the processing resolution in dual-beam fabrication.Taking the triexciton fluorescence of quantum dots as an example,a theoretical model is established to describe the electron excitation process in the material under the excitation of the dual-beam.The second beam is used to deplete the intermediate state of the whole process to achieve the inhibition of triexciton.The indirect depletion under the same laser intensity can effectively improve the resolution.Based on this indirect depletion method,three indirect physical depletion methods are proposed for dual-beam super-resolution laser processing.This work provides an effective method for dual-beam super-resolution laser processing to further improve resolution.