Analysis And Correction Of The Distortion Error In A DMD Based Scanning Lithography System

The interests of using lithography in microfabrication are widely discussed nowadays because they provide the feasibility to fabricate light weight,integrated micro devices.However,the difficulties in photomask fabrication and their high maintenance costs restrict the development of micro-processing technology.Under this scenario,numbers of maskless lithography technologies are proposed.Among these technologies,DMD based digital lithography presents interesting benefits comparing with other alternatives.By introducing a DMD as a dynamic photomask(by selectively reflecting the incident light),DMD scanning lithography system is able to achieve multi-point parallel writing and large area processing.In this case,it is widely used in high-density production fabrication such as printed circuit board(PCB),touch-screen and et al.DMD based lithography system provides the feasibility to achieve multi-point parallel direct writing exposure.After complete the entire exposure process,the accumulated exposure point(the black rectangular in t5)on the substrate receives the whole energies from the micromirror,generating a final exposure pattern.Note that the high-resolution projection lens is one of the most important components in the whole DMD lithography system,and its main function is to project the mask pattern onto the lithographic substrate with a certain magnification.However,the distortion of the projection lens in a scanning lithography system not only deviates the vertical size(vertical to the scanning direction),but also deviates the center position of an accumulated exposure point from the ideal one.Under this scenario,a simulation on how the projection lens distortion influences the lithography patterns is proposed.Moreover,an imaging compensation method,demonstrate as a combination of changing the magnification of the photolithography lens with loading an appropriately designed mask on DMD,is provided.The maximum deviation of the accumulated exposure point centers is reduced from 4.3 ?m to 1.45 ?m,and the maximum size error is reduced from 0.4 ?m to 0.1 ?m with a 0.03% distortion projection lens by introducing the correction method.The effectiveness of the proposed correction method,which improves the lithography precision in any arbitrary lithography pattern,is demonstrated.