Illumination system of a microlithographic projection exposure apparatus

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 depolariser; a light mixing system disposed downstream of the depolarizer in a light propagation direction; and a member arranged upstream of the light mixing system in the light propagation direction, the member comprising a plurality of elements arranged with a periodicity;
wherein during use:
the depolarizer in conjunction with the light mixing system at least partially causes effective depolarisation of polarised light impinging on the depolariser;the depolariser produces a succession of mutually orthogonal polarisation states during use;the succession of mutually orthogonal polarisation states is periodic over its cross-section and can be described by a depolarisation period;the depolarisation period is adapted to the periodicity of the elements of the member so that at least two light beams which impinge on mutually adjacent elements of the member at positions whose spacing from each other corresponds to the periodicity of the elements of the member bear mutually orthogonal polarisation states;a contribution due to interaction of the depolariser with the periodicity of the elements of the member to a residual polarisation distribution occurring in a pupil plane, which is arranged in the illumination system downstream of the member in the light propagation direction, has a maximum degree of polarisation of not more than 5%; andthe illumination system is configured to be used in a microlithographic projection exposure apparatus.