Etching A Meter-Scale Resist Grating With Plasma

With the wide application of meter-scale grating in high power laser system,large photolithography systems,etc.,more strict fabrication technology of meter scale grating is required.For the fabrication of meter-scale gratings,a relatively mature holographic-ion beam etching process has been developed by researchers in University of Science and Technology of China and Suzhou University.However,residual photoresist at the bottom of the grating grooves still appeared during the process of holographic lithography and development of the millimeter scale photoresist grating,which will probably degrade the diffraction quality of the grating after ion beam etching,because of uneven groove depth.In this paper,a trapezoidal diffusion structure was designed based on a plasma source with an output aperture of 40 mm,aiming at the problem of residual photoresist in the meter-scale photoresist gratings.The following research results are obtained.1.A new trapezoidal diffusion structure was proposed for a plasma source.The structure consists of two parts:a.trapezoidal hollow diffusion structure,which mainly plays the role of diffusion;b.Graphite barrier structure with an adjustable spacing,which aims to modulate the diffused plasma again and distribute it evenly.2.The trapezoidal diffusion structure was simulated by Fluent software,and the feasibility of the trapezoidal diffusion structure was theoretically verified.The simulation results show that the plasma is able to diffused to 600 mm 40 mm area after being modulated by trapezoidal diffusion structure,and the plasma distribution is uniform at 500 mm x40 mm.3.A series of plasma etching experiments were designed,and the effect of practical diffusion homogenization of the trapezoidal diffusion structure was verified by simulating the meter-scale grating with small-size grating array.The experimental results show that the output diameter is only ? 40 mm small plasma source plasma after trapezoidal diffusion structure modulation,can even output to 450 mm x40 mm area.Ionic etched photoresist raster lines etched with a±5%margin of error.The results show that the trapezoidal diffusion structure proposed in this paper can achieve uniform plasma diffusion.The plasma generated by a plasma source with an output aperture of only 40 mm can be uniformly diffused to a region of 450 mm × 40 mm.By using this trapezoidal diffusion structure and one-dimensional scanning etching,the plasma etching of meter-scale photoresist grating can be achieved,and the uniformity error of grating line etching is kept at ±5%,which meets the requirements of grating fabrication.