Study On Gap Control Of Immersion Flow Field

In this dissertation, the gap control of the immersion flow field in immersion lithography is systematically studied. Firstly, the demands of the immersion unit pose regulation are analyzed. The "spatial-planar" parallel mechanisms are employed as major models for the pose regulation and detection. The direct-inverse position analysis of the 3-PSP,3-PSR-O, and 3-P(PH) parallel mechanisms is carried out. Secondly, the feature boundaries of the 3-PSP and3-PSR-O parallel mechanisms are discussed respectively on the basis of the direct-inverse position analysis. Starting from the formation of the workspace boundary, a method based on the feature boundary and Boolean operations is raised, and applied for the workspace analysis of the "spatial-planar" parallel mechanisms. Thirdly, the hybrid serial-parallel mechanisms are employed to regulate the pose of the immersion unit and detect the gap parameters. The direct-inverse position models of the 3-PSP-P(PH) and 3-PSR-O-P(PH) hybrid serial-parallel mechanism are built, which can regulate the pose of the immersion unit and detect the parameters of the gap in a non-contact and precise way simultaneously. At last, a feedback control model based on the direct-inverse position solutions of the hybrid serial-parallel mechanism is proposed. An improved niche genetic algriothm is also adopted to optimize the position control of the branch driver module. Both simulation and prototype test are done to verify the effectiveness of this control model.The main contents of this dissertation are briefly stated as the followings:1. The demands of the immersion unit pose regulation, which are proposed to maintain the gap of the immersion flow field in the immersion lithography equipment, are fully analyzed. The existing 3-PSP mechanism and the novel 3-PSR-O and 3-P(PH) mechanism proposed in this paper all belong to the "spatial-planar" parallel mechanism. The direct-inverse position analysis as a basis of these three parallel mechanisms are derived respectively. By choosing proper geometric constraints, and introducing the mapping method, the solutions to the direct-inverse position problems of both the 3-PSP and 3-PSR-O are obtained with the coupled mixed-type parameters. All the six possible poses and the dual relationship among them are discussed in detail. Based on the 3-P(PH) parallel mechanism, a fast direct-inverse position analysis method is also proposed.2. A workspace analysis method based on the feature boundary and Boolean operations is presented. Comparing to the other "spatial-planar" parallel mechanisms with the same prismatic distribution and strokes, the workspace of the 3-P(PH) parallel mechanism is the largest and regarded as the basic workspace. On the basis of the direct-inverse postion solutions, the Jacobian matrix is employed to analyze the singularity of the 3-PSP parallel mechanism, while the geometric constraints are adopted in discussing the 6 types of singular poses for the 3-PSR-O parallel mechanism. The feature boundaries in the feature surfaces can be obtained respectively. By using the Boolean operation, the feature boundary divides the basic workspace into two parts: the reachable workspace and the unreachable workspace. The reachable workspace analysis based on the Boolean operation between the basic workspace and the feature boundary is much more efficient and convenient. On the other hand, this method also reveals the potential space which can be extended by varying the dimensions of the components in the moving plane.3. An improved niche genetic algriothm combined with pattern search is proposed. The algriothm is optimized in three aspects:â‘  niche classification; â‘¡ individuals generation; â‘¢ local search. The nondimensionalization of the real gene can avoid the distance deviation caused by the unit of the actual parameters, and the valley determination method can avoid the dependence on niche radius estimates. By introducing the penalty function to filter the new generated individuals, the repeated searching for the region can be reduced. Besides, the local search effiency is improved by the combination of the pattern search and genetic algriothm. These three improvements can enhance both the effiency and probability of the global optiamal individual searching process.4. The hybrid serial-parallel mechanism is employed to regulate the pose of the immersion unit and detect the parameters of the gap in a non-contact and precise way simultaneously. Then, a feedback control model based on the direct-inverse position solutions of the hybrid serial-parallel mechanism is proposed. An improved niche genetic algriothm is adopted to optimize the PID parameters of the position controller in each branch driver module. The pose tracking simulation models are established in the SimMechanics environment. The feedback control algriothm is executed on the 3-PSP-P(PH) prototype. The effectiveness of the control model is verified by both the simulation and the prototype test results. And the gap status varies within the accepted scope.