Invention Grant
- Patent Title: Position measurement with illumination profile having two diametrically opposed off-axis radiation
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Application No.: US15439833Application Date: 2017-02-22
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Publication No.: US09970747B2Publication Date: 2018-05-15
- Inventor: Justin Lloyd Kreuzer , Arie Jeffrey Den Boef , Simon Gijsbert Josephus Mathijssen
- Applicant: ASML Netherlands B.V. , ASML Holding N.V.
- Applicant Address: NL Veldhoven NL Veldhoven
- Assignee: ASML Netherlands B.V.,ASML Holding N.V.
- Current Assignee: ASML Netherlands B.V.,ASML Holding N.V.
- Current Assignee Address: NL Veldhoven NL Veldhoven
- Agency: Sterne, Kessler, Goldstein & Fox P.L.L.C.
- Main IPC: G01B9/02
- IPC: G01B9/02 ; G01B11/14 ; G03F7/20 ; G03F9/00

Abstract:
An apparatus (AS) measures positions of marks (202) on a lithographic substrate (W). An illumination arrangement (940, 962, 964) provides off-axis radiation from at least first and second regions. The first and second source regions are diametrically opposite one another with respect to an optical axis (O) and are limited in angular extent. The regions may be small spots selected according to a direction of periodicity of a mark being measured, or larger segments. Radiation at a selected pair of source regions can be generated by supplying radiation at a single source feed position to a self-referencing interferometer. A modified half wave plate is positioned downstream of the interferometer, which can be used in the position measuring apparatus. The modified half wave plate has its fast axis in one part arranged at 45° to the fast axis in another part diametrically opposite.
Public/Granted literature
- US20170160075A1 Position Measurement with Illumination Profile having Regions Confined to Peripheral Portion of Pupil Public/Granted day:2017-06-08
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