Position detector and microlithography apparatus comprising same
First Claim
1. A position detector for measuring the position of a workpiece having alignment marks, comprising:
- (a) an illumination optical system for illuminating the alignment marks with an alignment light flux, the illumination optical system comprising an illumination aperture stop;
(b) an imaging optical system that receives the alignment flux from the alignment marks and forms an image of the alignment marks, the imaging optical system comprising an imaging aperture stop;
(c) a phase plate positionable conjugate to the illumination aperture stop and having a phase-shift region and defining a phase-plate aperture, the phase plate providing a phase shift between a portion of the alignment flux from the alignment marks transmitted through the phase-shift region that corresponds to an image of the illumination aperture stop and a portion of the alignment flux transmitted through the phase-plate aperture; and
(d) a selector operable with the phase plate for selecting a phase-contrast image of the alignment marks.
1 Assignment
0 Petitions
Accused Products
Abstract
Position detectors are disclosed for reliable, high-accuracy detection of alignment marks on a wafer, including alignment marks consisting of small phase steps. The position detector comprises a phase plate located conjugate to an aperture stop. The phase plate produces a phase shift between the undiffracted light flux from the alignment marks and the diffracted light flux and a phase-contrast image is of the alignment marks is formed. The phase plate is switchable or insertable so that a bright-field image is also obtainable. Bright-field images and phase-contrast images are directly viewable or are received by one or more image sensor. A signal processor receives image signals from the image sensors and determines the position of the alignment marks. The sensor then provides a position signal that is used to move the wafer and reticle into alignment.
22 Citations
29 Claims
-
1. A position detector for measuring the position of a workpiece having alignment marks, comprising:
-
(a) an illumination optical system for illuminating the alignment marks with an alignment light flux, the illumination optical system comprising an illumination aperture stop; (b) an imaging optical system that receives the alignment flux from the alignment marks and forms an image of the alignment marks, the imaging optical system comprising an imaging aperture stop; (c) a phase plate positionable conjugate to the illumination aperture stop and having a phase-shift region and defining a phase-plate aperture, the phase plate providing a phase shift between a portion of the alignment flux from the alignment marks transmitted through the phase-shift region that corresponds to an image of the illumination aperture stop and a portion of the alignment flux transmitted through the phase-plate aperture; and (d) a selector operable with the phase plate for selecting a phase-contrast image of the alignment marks. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 21)
-
-
10. A position detector for measuring the position of a workpiece having alignment marks, comprising:
-
(a) an illumination optical system for illuminating the alignment marks with an alignment light flux, the illumination optical system comprising an illumination aperture stop; (b) a switchable mirror that is insertable to receive the alignment flux from the alignment marks; (c) a bright-field optical system, selectable by the switchable mirror, that receives the alignment flux and comprises an imaging optical system and an imaging aperture stop for forming a bright-field image; (d) a phase-contrast optical system, selectable by the switchable mirror, that receives the alignment flux and comprises an imaging system and a phase plate for forming a phase-contrast image; (e) a selector for switching between bright-field imaging and phase-contrast imaging and that controls the switchable mirror. - View Dependent Claims (11, 12, 13)
-
-
14. A position detector for measuring the position of a workpiece having alignment marks, comprising:
-
(a) an illumination optical system for illuminating the alignment marks with an alignment light flux, the illumination optical system comprising an illumination aperture stop; (b) a bright-field optical system comprising an imaging optical system and an imaging aperture stop for forming a bright-field image of the alignment marks; (c) a phase-contrast optical system comprising an imaging optical system and a phase plate for forming a phase-contrast image; (d) a beamsplitter that receives the alignment flux from the alignment marks and directs the alignment flux to the bright-field optical system and the phase-contrast optical system. - View Dependent Claims (15, 16, 17, 18, 19, 20)
-
-
22. An exposure device for exposing a sensitized substrate to patterns on a reticle, comprising:
-
(a) a position detector comprising; (1) an illumination optical system that illuminates alignment marks on the substrate with an alignment flux, the illumination system comprising an illumination aperture stop; (2) an imaging system that receives the alignment flux and forms an image of the alignment marks; (3) an imaging detector that receives the image and provides an image signal; (4) a phase plate located conjugate to the illumination aperture stop and defining a phase-shift region and phase-plate aperture, the phase plate providing a phase shift between a portion of the alignment flux from the alignment marks transmitted through the phase-shift region that corresponds to an image of the aperture stop and a portion of the alignment flux transmitted through the phase-plate aperture; and (5) a selector that inserts and withdraws the phase plate to switch between bright-field imaging and phase-contrast imaging; (b) an illumination system for illuminating the reticle; (c) a projection system for forming an image of the reticle on the substrate; and (d) a stage for translating the substrate. - View Dependent Claims (23)
-
-
24. An apparatus for observing a wafer, comprising:
-
(a) an illumination optical system comprising an illumination aperture stop, the illumination optical system producing an alignment flux that illuminates the wafer; (b) an imaging system that forms an image of the wafer, the imaging system comprising an imaging aperture stop and a phase plate, the imaging aperture stop and the phase plate being located conjugate to the illumination aperture stop, the phase plate defining a phase-shift region and a phase-plate aperture, the phase plate providing a phase shift between a portion of the alignment flux from the alignment marks transmitted through the phase-shift region that corresponds to an image of the illumination aperture stop and a portion of the alignment flux transmitted through the phase-plate aperture; and (c) a selector for controlling the insertion of the phase plate. - View Dependent Claims (25)
-
-
26. A method for exposing a sensitized substrate having alignment marks corresponding to patterns on a reticle, comprising:
-
(a) exposing the reticle with an exposure flux and forming an image of the reticle on the substrate with the exposure flux; (b) illuminating the alignment marks with an alignment flux; (c) obstructing a diffracted portion of the alignment flux at a imaging aperture plane and forming a bright-field image of the alignment marks with an unobstructed portion; (d) determining a conjugate location to the imaging aperture plane; (e) phase-shifting an undiffracted portion of the alignment flux relative to a diffracted portion at the conjugate location; (f) forming a phase-contrast image of the alignment marks with the undiffracted and diffracted portions after phase-shifting; and (g) selecting the bright-field image or the phase-contrast image of the alignment marks; (h) adjusting the relative positions of the reticle and the sensitized substrate based on the selected image; and (i) exposing the sensitized substrate to the pattern on the reticle. - View Dependent Claims (27, 28, 29)
-
Specification