Research On Precise Mechanism And Related Control Technologies Of Euvl Stage

Extreme Ultraviolet Lithography, which is called "one of the most promising next generation lithography technologies", is most likely to be the successor to optical lithograph for semiconductor fabrication below 45 nanometer node. Therefore, the technology of EUVL is becoming a hot point in international lithography field.Stage system is a key subsystem for lithography, besides, it is the basic torealize function and precision of lithography machine. Based on most of optical lithography stage technologies, the stage technology of EUVL is an integration of precise mechanics, mesurement, control, and vacuum technologes, and plays an important role in alignment and exposuring process.The report is proposed according to the requirments of 45 nm node commercial EUV lithography. Vaccum compatible stage structure and control strategy is investigated for high velocity and ultra precision mass production. Furthermore, simulations are made for the analysis of the proposed design. In addition, mounting device of projection optics is discussed, and an adjustable mounting device for the reflective mirrors is also developed.The report focuses on three issues: mechanism, control, and mirror mounting. Following contents are inluded:Structural design and simulation of EUVL stage. The characteristics of two non-contact stages, air bearing stage and magnetic leviated stage, are contrasted. Then, according to the requirements of 100wph throughput under 45nm node, both air bearing stage and magnetic leviated stage are proposed.many factors, such as friction force, disturbance of cable, and impact of vibration, are considered in the design. The mechanism is compact, ultra precise, stiff, and with good stability. Using finite element analysis software, static, transient, and modal analysises are explored for stepping and scanning. Based on the simulation results, some improvements are done by hollowing the structure. The optimized design has a lighter weight, smaller deformation. Furthermore, natural frequency of 1st mode is improved by 300hz higher.Control system design and analysis of EUVL stage. Based on the mechanism above designed, control model and strategies are built to realize both precise positioning and synchronous scanning. The contradiction of large displacement and ultra high precision is solved by coarse/fine dual stage method. Transfer value and synchronous compensation problems are emphasized in the design. Taking advantage of synchronization compensator, position compensation is fulfilled by using the fine reticle stage to compensate the deviation between position of the wafer stage and wafer stage. On the basis of the proposed control model, thereport examines the synchronization characteristics of wafer stage and reticle stage using MATLAB software. The simulation results illustrate that the compensator is effective to reduce the disturbance to synchronized control. The report also studys the contributions of environmental factors, such as vibration and heat, etc, and proposes some methods to control and compensate them.At last, an automated adjustable mounting system is developed according to the different shapes of the 6 projective mirrors. 5 degree-of-freedom alignment of each mirror can be obtained by adjusting the pize-actuated extensible legs in each mounting device. Strucural simulation results indicate that the design has proper layout, small deformation, and good stability.