Synchronization Control Strategy And Method Of Step-and-scan Projection Lithography

Synchronization control between reticle stage and wafer stage is a keytechnology in a step-and-scan projection lithography system. The critical dimension,overlay and throughput of integrated circuit are determined by the synchronizationperformance between the reticle stage and wafer stage. In order to improve theperformance, a series of researches have been done in this dissertation. By theanalyses of synchronization error and its main causes, several technological solutionsare brought up. At the same time, controllers with good synchronization performanceare proposed. The validity of the controllers is verified both theoretically andexperimentally.The characteristics of synchronization error are analyzed in three differentaspects: the relationship between MA and frequency, the relationship between MSDand correlation of tracking errors, and the repetition of synchronization error.According to the analysis results, dynamic characteristics of control system, couplingbetween the coarse stage and fine stage, and the design of synchronization controllerare pointed out as the main factors influencing synchronization performance. Thedesign solutions of synchronization controller have been proposed.Third-order trajectory planning algorithms for step-move and scan–move ofstep-and-scan projection lithography system are investigated, which comply with themotion limitations. To improve the productivity of step-and-scan lithography, theoverlapping for step-move and scan-move of wafer stage, the overlapping forscan-move of reticle stage and delay time for synchronization of reticle stage andwafer stage are analyzed.The research objects of this dissertation are the reticle stage and wafer stage of astep-and-scan projection lithography system. Both the reticle stage and wafer stageare coarse-fine stages. The dynamics of a coarse-fine stage is analyzed base on itsstructure, and the dynamic model is simplified for control. A coarse-fine controller isdesigned, which gets the coarse stage to track the fine stage, and the coupling betweenthe coarse stage and the fine stage is reduced.The synchronized motion between two fine stages is regarded as thesynchronization between reticle stage and wafer stage. A synchronization controlmethod based on the iterative learning control is proposed in this dissertation. The stability of the system is improved by operating in closed loop, and the repeatabledisturbances are reduced to improve the synchronization performance.An experiment of the synchronization control of step-and-scan lithographysystem is implemented. The results demonstrate that the synchronization performanceof the simulated platform is gradually improved during the iterative process.