Research On Beam Control In High-precision Laser Direct Writing

With the vigorous development of the information industry and put forward of "made in China 2025" strategy,enterprise expanding demand for semiconductor devices,countries have to chip in strategic industries,corporate demand for the quality of the semiconductor chip are also increasing.The key manufacturing process in chip production is lithography exposure.In this context,lithography technology has been developed rapidly.Laser direct writing technology is a kind of lithography technology which can control the direct exposure of laser beam on photoresist by changing the focus position.It is mainly used to fabricate nano-scale diffractive optical elements and mask for laser projection and exposure.It has high flexibility and can be used for lithography of grayscale mask,avoiding the random error caused by multiple overlays of traditional mask technology and effectively improving the machining precision.This subject mainly research the beam control technology in laser direct writing lithography system,key research beam shaping algorithm and the algorithm based on the research of experimental verification,the improved iterative Fourier annealing optimization algorithm design phase device to obtain the flat-topped beams.In practice,the use of phase modulation information combined with a spatial light modulator,the transition of incident gaussian beam and flat-topped beams,effectively improve the direct writing beams of light energy utilization ratio and improve the quality of photolithography line.It is of great significance to improve the precision of semiconductor components.The main research contents of this paper are as follows:This thesis introduces the basic principle of the common beam shaping algorithm in detail,and analyzes the theoretical performance of GS algorithm,SA algorithm and Fourier iteration algorithm.We propose an improved Annealing-Iterative Fourier optimization algorithm.Under the same optimization effect,the n?mber of iterations and the operation time is effectively reduced.In theory,the mean square error of modulation Sphere function and Rastrigin function can be as low as 1.94% and 3.98%.Designed beam shaping direct writing experiment system and applied the improved Annealing-Iterative Fourier optimization algorithm to gaussian incident beam shaping for uniform flat-topped beams,simulation of the mean square error as low as 3.94%.According to the proposed algorithm,the beam modulation is accomplished by the liquid crystal spatial light modulator.The phase modulation and phase measurement algorithm principle of SLM are analyzed.Measured the phase-gray characteristic curve of the SLM,which makes the SLM more accurate in modulating phase information.In terms of technology,the finite difference time domain method(FDTD)was adopted to build the same model as the actual direct writing system,and the appropriate thickness of the rubber layer is determined according to the simulation results.Then,multiple exposure and development experiments were carried out to study and optimize various experimental parameters in the process,so as to minimize the factors affecting the lithography quality of straight lines.Finally,set up the experimental device of laser direct writing for beam shaping to verify the modulation effect of flat-topped beam.It can be seen from the divergent flat-topped beam of the defocused surface that the shaping effect of the flat-topped beam is basically the same as the simulation result.From the line width of photolithography line with the trend of light intensity and line groove of morphology,the photolithography lines after modulation are not sensitive to light intensity fluctuation,lines have more sharp edges,the uniformity of the groove bottom have obvious improvement.