Optical position assessment apparatus and method

• US 20060092419A1
• Filed: 10/28/2004
• Published: 05/04/2006
• Est. Priority Date: 10/28/2004
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Gui, Cheng-Qun
• Granted Patent: US 7,388,663 B2
• Time in Patent Office: Days
• US Class Current: 356/401
• CPC Class Codes: G03F 7/70216 Mask projection systems
• CPC Class Codes: G03F 7/70425 Imaging strategies, e.g. for increasing throughput or resolution, printing product fields larger than the image field or compensating lithography- or non-lithography errors, e.g. proximity correction, mix-and-match, stitching or double patterning
• CPC Class Codes: G03F 9/7088 Alignment mark detection, e.g. TTR, TTL, off-axis detection, array detector, video detection

Abstract

A lithographic apparatus comprises a substrate table that supports a substrate having alignment marks on a surface thereof. The apparatus further comprises a frame moveable relative to the substrate to provide for a scanning or stepping mode of operation. An array of projection systems is disposed across the frame for projecting respective patterned beams onto a target portion of the substrate. A plurality of alignment mark detectors are attached to the frame and are moveable with respect to the frame using respective linear drive mechanisms. A position sensor is associated with each alignment mark detector for determining the position of the detector relative to the frame. A control system is responsible for both initial positioning of the detectors above alignment mark patterns on the substrate, and for dynamic alignment of the frame and substrate during a lithographic process.

Claims

1. A lithographic apparatus, comprising:

an illumination system that produces a beam of radiation;

a pattern generating device that patterns the beam;

a substrate table that supports a substrate having alignment marks provided on a surface thereof;

a frame moveable relative to the substrate;

one or more projection systems coupled to the frame, wherein the one or more projection systems are capable of projecting the patterned beam onto a target portion of the substrate;

one or more alignment mark detectors coupled to the frame and moveable with respect to the frame; and

a position sensor associated with each of the one or more alignment mark detectors, wherein the position sensor determines the position of the one or more alignment mark detectors relative to at least one of the frame and the one or more projection system.

2. The apparatus of claim 1, wherein:

the frame is moveable relative to the substrate along a first axis in a plane substantially parallel to a plane of the substrate; and

the one or more alignment mark detectors are movable relative to the frame along a second axis substantially perpendicular to the first axis and in a plane parallel to the plane of the substrate.

3. The apparatus of claim 2, wherein the one or more alignment mark detectors have a range of movement sufficient to provide coverage of substantially a whole dimension of the substrate in the direction of the second axis.

4. The apparatus of claim 1, wherein the one or more alignment mark detectors comprise:

an illumination system that supplies an alignment beam of radiation;

a projection system that projects the alignment beam onto an alignment target portion of the substrate; and

a sensor that detects radiation reflected from the substrate.

5. The apparatus of claim 1, wherein each of the position sensors comprise:

a laser interferometer.

6. The apparatus of claim 5, wherein the laser interferometer comprises:

a reflector or mirror surface fixed relative to the associated alignment mark detector; and

a laser and a radiation detector fixed relative to the frame.

7. The apparatus of 1, wherein each of the position sensors comprise:

a linear grating system.

8. The apparatus of 1, further comprising

a linear motor associated with each of the one or more alignment mark detectors that provides linear movement of a respective one of the alignment mark detectors relative to the frame.

9. The apparatus of 1, further comprising:

a controller that controls position of the one or more alignment mark detectors based on at least one of operator inputs and feedback from respective ones of the position sensors.

10. The apparatus of 1, further comprising:

an alignment controller that receives an output from the one or more alignment mark detectors and, based on the received signals, adjusts at least one of (i) the position of the substrate relative to the frame, (ii) a scanning speed of the substrate, and (iii) the patterned beam generated by each of the one or more projection systems.

11. The apparatus of 1, wherein at least five of the one or more alignment mark detectors and respective position sensors are used.

12. A method, comprising:

determining approximate positions of alignment marks provided on a surface of a substrate; and

moving one or more alignment mark detectors relative to at least one of (i) a frame that is moveable relative to the substrate and (ii) one or more projection systems, the one or more alignment mark detectors being moved to positions at which the alignment marks can be detected.

13. The method of claim 12, wherein the step of moving one or more alignment mark detectors comprises:

monitoring an output of one or more detector position sensors to provide detector position feedback, the one or more position sensors being fixed to at least one of the frame and the alignment mark detectors.

14. The method of claim 12, wherein the step of moving one or more alignment mark detectors comprises:

applying drive signals to a linear drive mechanism associated with each of the one or more alignment mark detectors.

15. The method of claim 14, wherein each of the one or more linear drive mechanisms utilize a linear motor.