Illumination system of a microlithographic projection exposure apparatus comprising a depolarizing element

摘要

The disclosure relates to an illumination system of a microlithographic projection exposure apparatus. The illumination system can include a depolarizer which in conjunction with a light mixing system disposed downstream in the light propagation direction at least partially causes effective depolarization of polarized light impinging on the depolarizer. The illumination system can also include a microlens array which is arranged upstream of the light mixing system in the light propagation direction. The microlens array can include a plurality of microlenses arranged with a periodicity. The depolarizer can be configured so that a contribution afforded by interaction of the depolarizer with the periodicity of the microlens array to a residual polarization distribution occurring in a pupil plane arranged downstream of the microlens array in the light propagation direction has a maximum degree of polarization of not more than 5%.

主权项

1. An illumination system, comprising:
a depolarizer; a light mixing system disposed downstream of the depolarizer in a light propagation direction of the illumination system; and a member upstream of the light mixing system in the light propagation direction, the member comprising a plurality of elements arranged with a periodicity, wherein:
the illumination system is a microlithographic illumination system;the depolarizer and the light mixing system are configured so that, during use of the illumination system, the depolarizer and the light mixing system in conjunction at least partially cause effective depolarization of polarized light that impinges on the depolarizer;the depolarizer is configured so that, during use of the illumination system, the depolarizer produces mutually orthogonal polarization states in a plane perpendicular to an optical axis of the illumination system;the mutually orthogonal polarization states produced by the depolarizer during use of the illumination system have a distribution that does not have any periodicity;during use of the illumination system, the light has a residual polarization distribution in a plane downstream of the member in the light propagation direction; anda contribution to the residual polarization distribution due to the interaction of the depolarizer with the periodicity of the plurality of elements is not more than 5%.