Lithographic apparatus, device manufacturing method and device manufacturing thereby

• US 20040263846A1
• Filed: 04/16/2004
• Published: 12/30/2004
• Est. Priority Date: 08/24/2000
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Kwan, Yim Bun Patrick
• Granted Patent: US 7,289,212 B2
• Time in Patent Office: Days
• US Class Current: 356/399
• CPC Class Codes: G03F 7/70716 Stages
• CPC Class Codes: G03F 7/70725 control
• CPC Class Codes: G03F 9/7053 Non-optical, e.g. mechanical, capacitive, using an electron beam, acoustic or thermal waves

Abstract

The X, Y and Rx positions of a mask stage are measured using two optical encoder-reading heads measuring displacements of respective grid gratings mounted on the mask stage. The grid gratings are preferably provided on cut-away portions of the mask table so as to be coplanar with the pattern on the mask itself. Measurements of the table position in the other degrees of freedom can be measured with capacitative or optical height sensors.

Claims

1. A lithographic projection apparatus comprising:

a support structure for supporting a patterning device, the patterning device serving to pattern a beam of radiation according to a desired pattern;

a substrate table for holding a substrate;

a projection system for projecting the patterned beam onto a target portion of the substrate; and

a displacement measuring system for measuring the position of a moveable object comprising one of said support structure and said substrate table in at least two degrees of freedom, said displacement measuring system comprising at least one grid grating mounted on said moveable object and at least one sensor head for measuring displacements of said grid grating in two degrees of freedom.

2. Apparatus according to claim 1 wherein said displacement measuring;

system comprises two grid gratings mounted on said moveable object at spaced apart locations and two sensor heads each for measuring displacements of a respective one of said grid gratings.

3. Apparatus according to claim 1 wherein said grid grating is incorporated directly into the main body of said moveable object.

5. Apparatus according to claim 1 wherein said moveable object is moveable in a first direction for scan imaging and said grid grating has a length in said first direction greater than or equal to the range of motion of said moveable object in said first direction.

6. Apparatus according to claim 1 wherein the or each said grid grating is positioned so as to be substantially coplanar with the functional surface of said patterning device supported by said support structure or a substrate held by said substrate table.

7. Apparatus according to claim 1 wherein said displacement measuring, system further comprises a memory for storing correction information representing differences between said grid grating and an ideal grid grating and a data processing unit for correcting measurements output by said sensor head.

8. Apparatus according to claim 1 wherein said displacement measuring system further comprises one or more capacitive or optical sensors for measuring the position of said moveable object in degrees of freedom not measured by said grid grating and sensor head.

9. Apparatus according to claim 1 wherein the or each grid grating includes a reference mark detectable by the respective sensor head for defining a reference position of said moveable object.

10. Apparatus according to claim 1 wherein said sensor head comprises an encoder head.

11. Apparatus according to claim 1 wherein said displacement measuring system further comprises an interpolator for interpolating the output of the or each sensor head.

12. Apparatus according to claim 1, wherein the support structure comprises a mask table for holding a mask.

13. Apparatus according to claim 1, wherein the radiation system comprises a radiation source.

4. A lithographic projection apparatus comprising:

a support structure for supporting a patterning device, the patterning device serving to pattern a beam of radiation according to a desired pattern;

a substrate table for holding a substrate;

a projection system for projecting the patterned beam onto a target portion of the substrate; and

a displacement measuring system for measuring the position of a moveable object comprising one of said support structure and said substrate table in at least two degrees of freedom, said displacement measuring system comprising at least one grid grating mounted on a reference frame and at least one sensor head mounted on said moveable object for measuring displacement of said moveable object relative to said grid grating in two degrees of freedom.

14. A device manufacturing method comprising:

projecting a patterned beam of radiation onto a target portion of a layer of radiation-sensitive material on a substrate;

measuring displacements of one of a support structure for a patterning device for patterning the beam of radiation and a substrate table for holding the substrate, in at least two degrees of freedom using at least one grid grating mounted thereon and at least one sensor head.

15. A device manufactured according to the method of claim 14.

20. A method according to claim 14, wherein said measuring displacements further comprises measuring a displacement in a z-direction perpendicular to a plane substantially parallel to a surface of the target portion.

16. A method of calibrating a lithographic projection apparatus comprising:

providing a reference pattern to a patterning device held in a moveable support structure, said reference pattern having a plurality of reference marks at pre-calibrated positions in at least a scanning direction of the lithographic projection apparatus;

holding an image sensor on a substrate table at a constant position relative to the projection lens;

positioning said support structure so as to project an image of each of said reference marks in turn onto said transmission image sensor; and

measuring the position of said support structure in at least a first degree of freedom when each of the reference marks is projected onto said image sensor.

17. A method according to claim 16 wherein said image sensor is positioned under a center line of the projection system.

18. A method according to claim 16 wherein the image sensor is positioned at an extreme position of the exposure field of the projection lens.

19. A method according to claim 16, wherein the position of said moveable support structure is measured using at least one grid grating mounted thereon and at least one sensor head.