Research On3-DOF Displacement Measurement And Error Propagation Analysis Of Compensation System

With the rapid development of the semiconductor manufacturing industry, thelithographic exposure equipment for production of integrated circuit (IC) is requiredto provide high productivity, low ‘critical dimension’(CD) and high overlay.However the requirement of design and assembly is becoming more and morecritical by the conflict of high acceleration and high positioning accuracy. To solvethis problem, balance mass is introduced. The main purpose of it is to weaken thevibration of the machine to achive high positioning accuracy during the highacceleration. Due to the compliexity of compensation system, and the large numbersof motion chains, the error of each part must be analyzed and make uncertainevalution so that the most influnce source can be found. And error compensationshould be taken to improve the measurement accuracy of wafer stage.This paper takes the compensation system as the research object which consistsof balance mass, long stoke and short stroke, building the3degree offreedom(3-DOF) displacement measurement model and error propagation model.The effect of each error is analyzed, and simulation and experiments have beencarried out to verification. The main reaserch work as belowings:(1)Based on the machine architecture of compenastion system and the layout ofmeasuring sensors, the3-DOF displacement meaurement models of balance masswith respect to support frame, long stroke with respect to balance mass and shortstroke with respect to long stroke are built, finaly the position of wafer stage in thereference coordinate system is obtained. Besides, taking the misalignment error intoaccount, the mathmatical model of balance mass measurement system is calibrated.(2)Based on the multi-body system and instrument precision theory, an errorpropagation model of compenastion system combined with the effects of the variouserror sources is bulit. By analyzing the effect of each error, the influneces of eacherror in6-DOF displcement of support frame, balance mass, long stroke have beengiven in the form of geometric error vector. And the uncertainty assessment modelfor measurement results of balance mass and long stroke are built.(3)By reference to relevant information and experiments, the value of severalparameters in motion chain is obtained, and the displacement measurementuncertainty evaluation results of balance mass and long stroke are calculated.Besides, the dynamic simulation is carried out to get the dynamic error of H driverto provide computing-related parameters for subsequent error propagation(4)Experiments are carried out to evaluate the validity of the3-DOF displacment of balance mass, the resluts indicate that this method will satisfied therequirement of accuracy with the error in x, y, and Rz less than35μm,35μm and17μrad respectively in the0~10mm stroke.(5)The uncertainty evaluation of compensation system have been evaluatedaccording to MeteCaro method. The displacement of wafer stage in the base stagecoordinate system was evaluated, within the95%probability, the reslut and theexpanded uncertainty in x and y directions: x=(165.000±0.064)mm，y=(195.000±0.054)mm。In summary, this paper proposed the3-DOF displacment measurement modelof compensation system, the effect of motion chains in6-DOF caused by each errorand the combined effects of the various error sources are calculated. The results canbe used for measuring system error compensation to improve the measurementaccuracy of wafer stage.