Estimating and Controlling Droplet Displacement Induced by Local Plasma Force
ASML is the global leader in photolithography equipment. With advent of EUV Lithography technology, it is possible to create microchips with smaller transistors and with greater precision. As EUV Lithography technology matures, customers expect ever higher productivity from these machines. This thesis analyzes a phenomenon called Local Force, which can negatively affect the system's productivity. Additionally, this thesis proposes a method to correct for the disturbances caused by the Local Force.
A set of four experiments are proposed to characterize the nature of the Local Force. These experiments demonstrate linear relation between the amount of EUV produced and the droplet displacement and impact on the upstream droplets. Additionally the experiments identify a process window in which the droplet displacement would not affect system performance.
These findings were then used to a develop Kalman predictor and a feedforward algorithm which can compensate for the disturbances produced by the Local Force. Using data from a real machine in conjunction with a high fidelity simulation, it is shown that the algorithm can maintain the L2Dx position within the process window.