# US 2012/0236281 A1 · Source multiplexing illumination for mask inspection > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2012/0236281 A1 - Document ID: US20120236281A1 - Status: Published application - Kind: A1 - Application number: 13/419,157 - Filed: 2012-03-13 - Published: 2012-09-20 - Earliest claimed: 2011-03-16 - Assignees: KLA-Tencor Corporation - Inventors: Daimian Wang; Daniel Wack; Damon F. Kvamme; Tao-Yi Fu - Web page: https://patentgrep.com/patent/US20120236281A1 ## CPC - G03F 1/84: Inspecting - G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G) ## 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. ## Claims ### Claim 1 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. ### Claim 2 (depends on 1) The illumination system of claim 1, wherein the first set of mirrors is configured for reflecting radiations from a corresponding illumination source at grazing incidence. ### Claim 3 (depends on 1) The illumination system of claim 1, wherein the second set of mirrors is configured for reflecting radiations from a corresponding illumination source at grazing incidence. ### Claim 4 (depends on 1) The illumination system of claim 1, wherein the third set of mirrors is configured for reflecting radiations from a corresponding illumination source at near-normal incidence. ### Claim 5 (depends on 1) The illumination system of claim 1, wherein each of the plurality of illumination sources is a pulsed EUV source. ### Claim 6 (depends on 1) The illumination system of claim 1, further comprising: at least one aperture positioned on the common optical path. ### Claim 7 (depends on 1) The illumination system of claim 1, further comprising: an additional set of mirrors mounted to the outer surface of the base member, the additional set of mirrors positioned to be interleaved with the first set of mirrors, each one of the additional set of mirrors having a mirror surface generally facing away from the rotation axis and tilted away from the rotation axis by a predetermined angle different from the first predetermined angle, wherein the additional set of mirrors is configured for reflecting radiations from an illumination source to the common optical path. ### Claim 8 (depends on 1) The illumination system of claim 1, further comprising: an additional set of mirrors mounted to the inner surface of the base member, the additional set of mirrors positioned to be interleaved with the second set of mirrors, each one of the additional set of mirrors having a mirror surface generally facing toward the rotation axis and tilted toward the rotation axis by a predetermined angle different from the second predetermined angle, wherein the additional set of mirrors is configured for reflecting radiations from an illumination source to the common optical path. ### Claim 9 (depends on 1) The illumination system of claim 1, further comprising: an additional set of mirrors mounted to the end surface of the base member, the additional set of mirrors positioned to be interleaved with the third set of mirrors, each one of the additional set of mirrors having a mirror surface tilted by a predetermined angle with respect to the axis perpendicular to the rotation axis, wherein the predetermined angle is different from the third predetermined angle, and wherein the additional set of mirrors is configured for reflecting radiations from an illumination source to the common optical path. ### Claim 10 An illumination system, comprising: at least one illumination source; a base member rotatable about a rotation axis; and a conic mirror positioned on the base member, a center of axis of the conic mirror coinciding with the rotation axis; wherein the conic mirror is configured for receiving light from the at least one illumination source at grazing incidence and reflecting the light to an optical path. ### Claim 11 (depends on 10) The illumination system of claim 10, wherein the at least one illumination source includes a collection module configured for providing emission collection for the at least one illumination source. ### Claim 12 (depends on 11) The illumination system of claim 11, wherein the collection module is an ellipsoidal shaped module and the conic mirror is at least one of: a hyperbolical mirror or an ellipsoidal mirror. ### Claim 13 (depends on 11) The illumination system of claim 11, wherein the collection module is a parabolic shaped module and the conic mirror is a parabolic mirror. ### Claim 14 (depends on 10) The illumination system of claim 10, wherein the at least one illumination source includes a pulsed EUV source. ### Claim 15 (depends on 10) The illumination system of claim 10, further comprising: at least one aperture positioned on the optical path. ### Claim 16 An illumination system, comprising: an array of mirrors placed along a common optical axis; at least one light source corresponding to each particular mirror of the array of mirrors; and a control mechanism in communication with the array of mirrors, the control mechanism configured for positioning each particular mirror of the array of mirrors in a reflecting position when the at least one light source corresponding to the particular mirror emits a pulse of light. ### Claim 17 (depends on 16) The illumination system of claim 16, wherein the at least one light source includes a pulsed light source. ### Claim 18 (depends on 17) The illumination system of claim 17, wherein each particular mirror of the array of mirrors has an oscillation frequency the same as the pulse rate of its corresponding light source. ### Claim 19 (depends on 16) The illumination system of claim 16, wherein each particular mirror of the array of mirrors has a duty cycle no less than a reciprocal of the number of mirrors in the array. ### Claim 20 (depends on 16) The illumination system of claim 16, wherein each particular mirror of the array of mirrors includes at least one of: a MEMS type mirror or a resonant mirror.