Key Techniques Research For Maskless Lithography System Based On DMD

With the rapid development of electronic information industry,the demand of the integrated circuit industry shows a trend of explosive growth,and lithography technology has become the core technology in the field of integrated circuit(IC)manufacturing industry nowadays.In recent years,digital light processing(DLP)projectors based on digital micromirror device(DMD)have been widely used for their advantages of high contrast,high brightness,high efficiency,and secondary development.At present,there are still many problems in the practical production and application of maskless lithography based on DMD.This paper mainly focuses on the lens distortion correction in the DMD maskless lithography process,the large-area image lithography and projection image splicing and other issues.In this paper,through the study of the projection principle of the entire maskless lithography system,the causes of lens distortion are clarified,and the problem of how to achieve the distortion correction of the projected image is discussed.Two different distortion correction schemes are proposed based on whether the measurement data of the projection angle of incidence and the pixel offset have been obtained or not.If no measurement data is obtained,an camera can be used to achieve image acquisition,and the likelihood estimation algorithm can be used to optimize the calibration process of the camera and reduce the intermediate error,and finally the distortion correction of the projected image can be achieved by completing projector calibration.If the measurement data has been obtained,the reconstruction of the relationship between the distorted variable and the pixel coordinate can be performed by interpolation,and after the pixel-by-pixel projection corresponding to the distorted variable value is calculated,the pre-distortion processing of the exposure image is performed.In order to improve the efficiency of large-area image exposure,after contrasting with the traditional exposure scheme,this paper proposes a large-area distributed stepped projection method after deeply understanding the deficiencies of the scanning projection and the stepped projection.Through the use of multiple DMD lenses and according to the distribution of DMD and DMD size,the picture is pre-filled and the key frame information of the step frame is recorded,and the reading of the control instruction and the transmission of the area image are performed by the auxiliary device,thereby improving the exposure throughput.Aiming at the problems of picture mosaic between multiple DMD and different image frames,this paper proposes a method of image stitching based on DMD gray modulation technology.In the splicing process,grayscale gradation processing is performed on overlapping mosaic regions of the cut exposure subgraphs,so as to ensure that the overlapping degree of the exposure pattern overlaps with that of the non-overlapping area,thereby achieving smooth splicing.Finally,combined with the experimental project of this paper,using DLP6500 as an experimental platform,a projection lens distortion correction experiment platform and a large-area step exposure experiment platform were built.A host computer control software based on Qt and Open CV was designed and programmed to verify the image distortion correction and large-area exposure scheme proposed in this paper.The feasibility of the scheme was further confirmed by measuring the distortion and actually verifying the actual image to be exposed.