Method of operating a patterning device and lithographic apparatus

摘要

A lithographic reticle is illuminated to transfer a pattern to a substrate, inducing distortions due to heating. The distortions are calculated using reference marks in a peripheral portion of the reticle and measuring changes in their relative positions over time. A plurality of cells are defined for which a system of equations can be solved to calculate a dilation of each cell. In an embodiment, each equation relates positions of pairs of marks to dilations of the cells along a line (s, s1, s2) connecting each pair. Local positional deviations can be calculated for a position by combining calculated dilations for cells between at least one measured peripheral mark and the position. Corrections can be applied in accordance with the result of the calculation. Energy may be applied to the patterning device (for example by thermal input or mechanical actuators) to modify a distribution of the local positional deviations.

主权项

1. A method of operating a patterning device, the patterning device having a patterned portion which in operation is illuminated with a radiation beam so as to impart a pattern to the radiation beam in its cross-section, the method comprising:
measuring a position of each of a plurality of reference marks, the plurality of reference marks being on the patterning device and distributed around the patterned portion in a peripheral portion of the patterning device; by reference to the measured positions of the reference marks, calculating a local positional deviation, induced by thermal heating of the patterning device by said radiation beam, at a position of interest within the patterned portion of the patterning device; repeating the measuring and calculating a plurality of times, each measuring and calculating occurring after a period of operation of the patterning device; and updating the calculated local positional deviation, separately from the calculating the local positional deviation the plurality of times, between successive measurements of the plurality of times for use of the updated local positional deviation in modifying a parameter of an exposure operation between the successive measurements, in accordance with a mathematical model of predicted future progression of thermal heating.