Lithographic apparatus, substrate holder and method of manufacturing

• US 7,110,085 B2
• Filed: 05/06/2004
• Issued: 09/19/2006
• Est. Priority Date: 05/06/2003
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Ottens, Joost Jeroen, Van Empel, Tjarko Adriaan Rudolf, Zaal, Koen Jacobus Johannes Maria
• Primary Examiner(s): MATHEWS, ALAN A
• Application Number:
  US10/839,720
• Publication Number:
  US 20040247361A1
• Time in Patent Office: 866 Days
• Field of Search: 355/53, 355/72, 355/73, 269/21
• US Class Current: 355/53
• CPC Class Codes: G03F 7/707 Chucks, e.g. chucking or un-chucking operations or structural details
• CPC Class Codes: G03F 7/70783 Handling stress or warp of chucks, masks or workpieces, e.g. to compensate for imaging errors or considerations related to warpage of masks or workpieces due to their own weight

Abstract

A lithographic projection apparatus including a radiation system for providing a projection beam of radiation; a support structure for supporting a patterning device, the patterning device serving to pattern the projection beam according to a desired pattern; a substrate holder having a plurality of protrusions, the extremities thereof defining a substantially flat plane of support for supporting a substantially flat substrate, the substrate holder provided with the ability to provide a pressing force for pressing the substrate against the extremities of the protrusions, the protrusions in an edge zone of the substrate holder arranged to provide a substantially flat overhanging of the substrate in relation to the pressing force of the pressing means; and a projection system for projecting the patterned beam onto a target portion of the substrate. The lithographic projection apparatus is characterized in that the protrusions in an off-edge zone of the substrate holder are distributed so as to provide a substantial equal supporting area for each protrusion of the plurality of protrusions, the supporting areas being defined by a Voronoi diagram distribution associated to the protrusions. The lithographic apparatus offers a substrate holder with a reduced overlay and focus error.

Claims

1. A lithographic projection apparatus comprising:

a radiation system for providing a projection beam of radiation;

a support structure for supporting a patterning device, said patterning device serving to pattern said projection beam according to a desired pattern to form a patterned beam;

a substrate holder comprising protrusions, each of said protrusions having an extremity, said extremities of said protrusions defining a substantially flat plane of support for supporting a substantially flat substrate, said substrate holder provided with a clamp to provide a pressing force for pressing said substrate against said extremities of said protrusions;

said protrusions in an edge zone of said substrate holder arranged to provide a substantially flat overhanging of said substrate in relation to said pressing force of said clamp; and

a projection system for projecting said patterned beam onto a target portion of said substrate, wherein said protrusions in an off-edge zone of said substrate holder are distributed so as to provide a substantially equal supporting area for said protrusions in said off-edge zone, said supporting area being defined by a Voronoi diagram distribution associated with at least a plurality of said protrusions.

2. A lithographic apparatus according to claim 1, wherein said substrate holder is a substantially circular structure for supporting a substantially circular substrate and wherein said protrusions are arranged in substantially concentric circles in a zone away from a central zone of said circular substrate holder;

wherein at least some concentric circles are non-equidistant.

3. A lithographic apparatus according to claim 2, wherein said protrusions are distributed in substantially equilateral triangular patterns.

4. A lithographic apparatus according to claim 1, wherein center protrusions are arranged according to a central protrusion and a surrounding first row of protrusions is arranged in a regular hexagonal shape.

5. A lithographic apparatus according to claim 4, wherein a second row of protrusions is arranged to have 12 protrusions oriented substantially symmetrical around said first row of protrusions.

6. A lithographic apparatus according to claim 2, wherein said substrate holder comprises a plurality of N openings, each of said N openings defining a second edge zone, wherein each concentric circle traversing said N second edge zones comprises an integer number of N protrusions.

7. A lithographic apparatus according to claim 6, wherein said plurality of N openings is arranged in an N/3 multiple of sets of three symmetrically configured openings.

8. A lithographic apparatus according to claim 6, wherein said substrate holder comprises a plurality of M notches, each of said M notches defining a third edge zone, wherein each concentric circle traversing said M third edge zones comprises an integer number of M protrusions.

9. A lithographic apparatus according to claim 8, wherein said plurality of M notches is arranged in an M/3 multiple of sets of three symmetrically configured notches.

10. A lithographic apparatus according to claim 1, wherein said substrate holder further comprises a wall for providing a leak seal and wherein said clamp is a vacuum system that forms a vacuum pressure between said substrate holder and said substrate.

11. A lithographic apparatus according to claim 10, wherein said vacuum pressure ranges from 0.1 to 0.9 bar with respect to ambient pressure.

12. A lithographic apparatus according to claim 11 wherein said vacuum pressure ranges from 0.5 to 0.2 bar with respect to ambient pressure.

13. A lithographic apparatus according to claim 10, wherein a radial distance x between said wall and a circle of protrusions nearest thereto satisfies a relationship 0.3<

x/d<

0.6, where d is a mutual radial separation of two circles of protrusions nearest to said wall.

14. A lithographic apparatus according to claim 1, wherein said edge zone is defined by at least one concentric circle of protrusions arranged nearest to an edge.

15. A lithographic apparatus according to claim 1, wherein said at least a plurality of said protrusions associated with said Voronoi diagram distribution is only located in said off-edge zone.

16. A lithographic apparatus according to claim 1, wherein said at least a plurality of said protrusions associated with said Voronoi diagram distribution includes protrusions located in said off-edge zone and protrusions located in said edge zone.

17. A substrate holder for a lithographic apparatus, comprising:

protrusions, each of said protrusions having an extremity, said extremities of said protrusions defining a substantially flat plane of support; and

a clamp to provide a pressing force for pressing said substrate against said extremities of said protrusions;

said protrusions in an edge zone of said substrate holder arranged to provide a substantially flat overhanging of the substrate in relation to said pressing force,

said protrusions in an off-edge zone of said substrate holder being distributed so as to provide a substantially equal supporting area for said protrusions in said off-edge zone, said supporting areas being defined by a Voronoi diagram distribution.

18. A method of manufacturing a substrate holder for a lithographic apparatus, comprising:

providing a plate for supporting a substantially flat substrate;

distributing a first plurality of supporting protrusions in an off-edge zone of the plate so as to provide a substantial equal supporting area for the first plurality of supporting protrusions, extremities of each protrusion of the first plurality of supporting protrusions defining a substantially flat plane of support;

arranging a second plurality of supporting protrusions in an edge zone of the plate so as to provide a substantially flat overhanging of the substrate in relation to a force pressing the substrate against the projections; and

calculating a supporting area distribution defined by a Voronoi diagram associated with the protrusions and keeping an area deviation of the supporting area distribution to a minimum.

19. A method according to claim 18, wherein the method further comprises:

a) calculating a height distribution of the substrate in correspondence with a pressure exerted on the substrate to press the substrate against the first plurality of distributions and to deform the protrusions locally in axial directions;

b) analyzing a focus error and an overlay error associated to the height distribution; and

c) redistributing the first plurality of supporting protrusions in areas wherein either or both of the focus and overlay error exceeds a predefined maximum value; and

d) repeating steps a–

c in an iterative way.

20. A method according to claim 19, wherein the height distribution is calculated in correspondence with a finite element analysis of a bending stiffness of the substrate.