US 2012/0236281 A1Published application

Source multiplexing illumination for mask inspection

AssigneeKLA-Tencor Corporation

InventorsDaimian Wang, Daniel Wack, Damon F. Kvamme, Tao-Yi Fu

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Abstract

Methods and systems for source multiplexing illumination for mask inspection are disclosed. Such illumination systems enable EUV sources of small brightness to be used for EUV mask defect inspection at nodes below the 22 nm. Utilizing the multiple plane or conic mirrors that are either attached to a continuously rotating base with different angles or individually rotating to position for each pulse, the reflected beams may be directed through a common optical path. The light may then be focused by a condenser to an EUV mask. The reflected and scattered light from the mask may then be imaged by some imaging optics onto some sensors. The mask image may be subsequently processed for defect information.

Claims20

Dependent claims

An illumination system, comprising:

a base member rotatable about a rotation axis, the base member defining at least an outer surface, an inner surface and an end surface;
at least one of:
a first set of mirrors mounted to the outer surface of the base member, each one of the first set of mirrors having a mirror surface generally facing away from the rotation axis and tilted away from the rotation axis by a first predetermined angle;
a second set of mirrors mounted to the inner surface of the base member, each one of the second set of mirrors having a mirror surface generally facing toward the rotation axis and tilted toward the rotation axis by a second predetermined angle;
and
a third set of mirrors mounted to the end surface of the base member, each one of the third set of mirrors having a mirror surface tilted by a third predetermined angle with respect to an axis perpendicular to the rotation axis;
wherein the first set of mirrors, the second set of mirrors and the third set of mirrors are configured for reflecting radiations from a plurality of illumination sources to a common optical path.

4 more elements

Dependencies are inferred from the claim text.