Research On Optimized Scheme Of Generation Quality Of Patterns In Scanning Lithography System Based On DMD

The interests of using DMD digital lithography as a new mask-less lithography have been widely discussed nowadays.For instance,it not only improves the production efficiency and reduces the production cost,but also provides a broad prospect in the field of lithography compare to single point laser direct writing technique.With the improvement in DMD drive technology,a high frame frequency of more than 20k-Hz is achieved.Note that such high frequency outfits the feasibility of the continuous rolling scanning exposure mode.Under this scenario,DMD digital lithography is widely used in various fields such as printed circuit board,chip fabrication,bioassays,drug-delivery,cell carriers,tissue-engineering and so on.Although the laser digital scanning photolithography technology based on DMD has the advantages of high flexibility,low cost and high efficiency,the lithography system usually leads to inconsistent scribing width of the lithography pattern caused by the inhomogeneity of the system illumination due to the difficulty of component design and system setup and adjustment.The resolution of Digital Micro-mirror Device(DMD)scanning lithography is limited in the transverse direction(the scanning direction is vertical)as a result of the compacted size of the DMD micro-mirror and the low magnification of the projection lens.Above-stated restrictions lead to an unsatisfactory saw-tooth edge after the lithography process within all directions except for the scanning orientation.Therefore,this dissertation focuses on the research of DMD digital scanning lithography system and puts forward some solutions to the above problems:(1)The scanning lithography system based on DMD(digital micro mirror device)in fact is a multi-point parallel direct writing exposure process.After each column of DMD micro mirrors scanning,an accumulated exposure point is formed on the lithographic substrate.In this paper,an analysis model of energy accumulation for rolling exposure mode is constructed,and the relation between the non-uniformity of light source illumination and the lateral(Vertical to scanning direction.)dimension of each accumulated exposure point is analyzed.According to the analysis results and combining with the arbitrary encoding characteristics of DMD micro mirror,energy compensation data is superimposed on the exposure data.An energy compensation electronic template matched with the non-uniformity of the light source energy is formed and solidified in the DMD display pattern to modulate the lateral dimension of the accumulated exposure point.The uniformity of the photolithography pattern line width is guaranteed.(2)The resolution of Digital Micro-mirror Device(DMD)scanning lithography is limited in the transverse direction(the scanning direction is vertical)as a result of the compacted size of the DMD micro-mirror and the low magnification of the projection lens.Above-stated restrictions lead to an unsatisfactory saw-tooth edge after the lithography process within all directions except for the scanning orientation.In order to smooth the edge,an optimized sub-pattern construction method,described as the combination of wobulation techniques and the continuous scanning lithography process,is proposed.Afterward,lithography experiments were implemented by introducing the wobulation techniques within the DMD scanning lithography system.At this point,the edge of the lithography pattern is appropriately smoothed.The effectiveness of the above-mentioned method which improves the edge smoothness of the lithography pattern is demonstrated.