Method of temperature compensation in high power focusing system for EUV LPP source
AssigneeASML Netherlands B.V.
InventorAlexander I. Ershov
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Abstract
Method of temperature compensating a focusing system in which a temperature of a thermal lens compensation plate is regulated based on an optical absorption of the thermal lens compensation plate with optical absorption being determined based at least in part on an expected end-of-lifetime value for focus lens optical absorption. A value representative of cumulative time in use of the focusing systems is determined and the temperature of the thermal lens compensation plate is increased to a temperature based at least in part on said cumulative time in use.
Claims3
A method of temperature compensating a focusing system, the method comprising the steps of:
- regulating a temperature of a thermal lens compensation plate to a first temperature, said first temperature being based on an optical absorption of said thermal lens compensation plate, said optical absorption having been determined based at least in part on an expected end-of-lifetime value for focus lens optical absorption for a final focus lens comprising part of said focusing system;
- determining a value representative of cumulative time in use of said focusing system;
- and
- adjusting said temperature of said thermal lens compensation plate to a second temperature higher than said first temperature, said second temperature having a value based at least in part on said cumulative time in use.
Dependencies are inferred from the claim text.