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:
(a) providing a plurality of reference marks distributed around the patterned portion in a peripheral portion of the patterning device and measuring positions of said marks relative to one another; (b) after a period of operation of the patterning device, measuring again the positions of said peripheral marks; and (c) by reference to the measured positions of the peripheral marks, calculating local positional deviations induced by thermal heating of the patterning device by said radiation beam at one or more positions of interest within the patterned portion of the patterning device.