Focusing and tilting adjustment system for lithography aligner, manufacturing apparatus or inspection apparatus

• US 5,825,043 A
• Filed: 10/07/1996
• Issued: 10/20/1998
• Est. Priority Date: 10/07/1996
• Status: Expired due to Fees

• Current Assignee: Nikon Precision Incorporated (Nikon Corporation)
• Original Assignee: Nikon Precision Incorporated (Nikon Corporation)
• Inventors: Suwa, Kyoichi
• Primary Examiner(s): Westin, Edward P.
• Assistant Examiner(s): PYO, KEVIN K
• Application Number:
  US08/727,695
• Time in Patent Office: 743 Days
• Field of Search: 250/548, 250/557, 250/201.2, 250/201.4, 355/53, 355/54, 355/55, 355/56, 356/399, 356/400, 356/401
• US Class Current: 250/548
• CPC Class Codes: G03F 7/70275 Multiple projection paths, e.g. array of projection systems, microlens projection systems or tandem projection systems
• CPC Class Codes: G03F 7/70341 Details of immersion lithography aspects, e.g. exposure media or control of immersion liquid supply chemical composition of immersion liquids G03F7/2041
• CPC Class Codes: G03F 7/70358 Scanning exposure, i.e. relative movement of patterned beam and workpiece during imaging
• CPC Class Codes: G03F 7/70641 Focus
• CPC Class Codes: G03F 7/70716 Stages
• CPC Class Codes: G03F 7/70808 Construction details, e.g. housing, load-lock, seals or windows for passing light in or out of apparatus
• CPC Class Codes: G03F 7/70866 of mask or workpiece
• CPC Class Codes: G03F 7/70875 Temperature, e.g. temperature control of masks or workpieces via control of stage temperature
• CPC Class Codes: G03F 7/70891 Temperature
• CPC Class Codes: G03F 9/70 for microlithography measuring printed patterns for monitoring overlay G03F7/70633 or focus G03F7/70641; projection system adjustment G03F7/70258; position control G03F7/70775
• CPC Class Codes: G03F 9/7026 Focusing

Abstract

Improvements in a focusing apparatus having an objective optical system for optically manufacturing a workpiece, forming a desired pattern on a surface of a workpiece or inspecting a pattern on a workpiece and used to adjust the state of focusing between the surface of the workpiece and the objective optical system. The focusing apparatus has a first detection system having a detection area at a first position located outside the field of the objective optical system, a second detection system having a detection area at a second position located outside the field of the objective optical system and spaced apart from the first position, and a third detection system having a detection area at a third position located outside the field of the objective optical system and spaced apart from each of the first and second positions. A calculator calculates a deviation between a first focus position and a target focus position and temporarily stores a second focus position at the time of detection made by the first detection system. A controller controls focusing on the surface of the workpiece on the basis of the calculated deviation, the stored second focus position and a third focus position when the area on the workpiece corresponding to the detection area of the first detection system is positioned in the field of the objective optical system by relative movement of the workpiece and the objective optical system.

Claims

1. A scanning exposure apparatus comprising:

(a) an imaging system for projecting an image of a pattern of a mask onto a substrate at an imaging field;

(b) a scanning mechanism for moving the mask and the substrate in a scanning direction relative to said imaging system;

(c) an adjusting system for adjusting a focus of the projected image on the substrate;

(d) a first detection system having a detection area at a first position located outside the imaging field of said imaging system and spaced apart from the imaging field in the scanning direction, said first detection system detecting the position of a principal surface of the substrate in a Z-direction;

(e) a second detection system having a detection area at a second position located outside the imaging field of said imaging system and spaced apart from said first position in a direction intersecting the scanning direction, said second detection system detecting the position of the principal surface of the substrate in the Z-direction;

(f) a third detection system having a detection area at a third position located outside the imaging field of said imaging system, spaced apart from the imaging field in a direction intersecting the scanning direction and also spaced apart from said second position in the scanning direction, said third detection system detecting the position of the principal surface of the substrate in the Z-direction;

(g) a calculator coupled to said first and second detection systems and calculating a deviation between the first Z-position detected by said first detection system and a target Z-position and storing the second Z-position detected by said second detection system at the time of detection by said first detection system; and

(h) a controller coupled to said adjusting system and to said calculator and to said third detection system and controlling said adjusting system on the basis of the calculated deviation, the stored second Z-position and the third Z-position detected by said third detection system when the area on the substrate corresponding to the detection area of said first detection system is positioned in the imaging field of said imaging system by movement of said scanning mechanism.

2. An exposure apparatus according to claim 1, wherein said scanning mechanism includes a mask stage for holding the mask, a substrate stage for holding the substrate, and a synchronizing drive system for moving said mask stage and said substrate stage at a speed ratio corresponding to a projection magnification of said imaging system.

3. An exposure apparatus according to claim 2, wherein said substrate stage includes an attraction portion for attracting a reverse surface of the substrate, and an auxiliary plate portion surrounding the substrate at a height approximately equal to the principal surface of the substrate when the substrate is supported on said attraction portion.

4. An exposure apparatus according to claim 3, wherein said second detection system and said third detection system are arranged to detect the position of a surface of said auxiliary plate portion in the Z-direction by at least one of the detection areas when a shot area of the substrate to be exposed by the pattern of the mask is at a peripheral portion of the substrate.

5. An exposure apparatus according to claim 4, wherein each of said first, second and third detection systems generates a Z-direction positional error value of one of the principal surface of the substrate and the auxiliary plate portion relative to predetermined reference Z-positions with respect to said first, second and third detection systems.

6. An exposure apparatus according to claim 5, wherein, if the predetermined reference Z-positions with respect to said first, second and third detection systems differ from each other, the differences between the reference Z-positions are detected by a calibration.

7. An exposure apparatus according to claim 4, wherein, if the scanning direction of the substrate is a Y-direction and if a direction perpendicular to each of the Y-direction and the Z-direction is an X-direction, said first detection system includes a first focus detector of a multi-point type having a plurality of detection areas in a row along the X-direction on the substrate over a range of a size of the imaging field of said imaging system in the X-direction.

8. An exposure apparatus according to claim 7, wherein said second detection system includes a plurality of second focus detectors having detection areas on opposite sides of the row of the plurality of detection areas of said multi-point focus detector in the X-direction, each of said second focus detectors separately detecting the Z-direction position of the principal surface of one of the substrate and the auxiliary plate portion at each of the detection areas.

9. An exposure apparatus according to claim 8, wherein said third detection system includes a plurality of third focus detectors on the opposite sides of the imaging field of said imaging system in the X-direction, each of said third focus detectors separately detecting the Z-direction position of the principal surface of one of the substrate and the auxiliary plate portion at each of the detection areas.

10. A projection exposure apparatus comprising:

(a) an imaging system for projecting an image of a mask pattern onto a substrate at a projection field;

(b) a movable stage mechanism for moving in intersecting X and Y directions to position the substrate with respect to the image of the projected mask pattern;

(c) an adjusting mechanism for adjusting a focus of the projected mask pattern image on the substrate;

d) a first detection system having a detection area at a first position located outside the projection field of said imaging system and spaced apart from the projection field in the Y direction, said first detection system detecting the position of a principal surface of the substrate in a Z direction;

(e) a second detection system having a detection area at a second position located outside the projection field of said imaging system and spaced apart from said first position in the X direction, said second detection system detecting the position of the principal surface of the substrate in the Z direction;

(f) a third detection system having a detection area at a third position located outside the projection field of said imaging system, spaced apart from the projection field in the X direction and also spaced apart from said second position in the Y direction, said third detection system detecting the position of the principal surface of the substrate in the Z direction;

(g) a calculator coupled to said first and second detection systems, and calculating a deviation between the first Z-position detected by said first detection system and a target Z-position and for storing the second Z-position detected by said second detection system at the time of detection made by said first detection system; and

(h) a controller coupled to said adjusting system and said calculator and said third detection system, and controlling said adjusting mechanism on the basis of the calculated deviation, the stored second Z-position and the third Z-position detected by said third detection system when the area on the substrate corresponding to the detection area of said first detection system is positioned in the projection field of said imaging system by said movable stage mechanism.

11. An exposure apparatus according to claim 10, wherein said first detection system includes a plurality of first focus detectors having a plurality of detection areas in a row along the X direction in a range according to a size of the projection field of said imaging system in the X direction, each of said first focus detectors separately detecting the Z-position of the principal surface of the substrate at each of the detection areas.

12. An exposure apparatus according to claim 11, wherein said second detection system includes two second focus detectors having two detection areas placed on opposite sides of the row of the plurality of detection areas of said first detection system, each of said second focus detectors separately detecting the Z-position of the principal surface of the substrate at each of the two detection areas.

13. An exposure apparatus according to claim 12, wherein said third detection system includes two third focus detectors placed on opposite sides of the projection field of said imaging system in the X direction, each of said third focus detectors separately detecting the Z-position of the principal surface of the substrate at each of the two detection areas.

14. An exposure apparatus according to claim 13, wherein said movable stage mechanism includes a mount portion for attracting a reverse surface of the substrate and an auxiliary plate portion which surrounds the substrate at a height substantially equal to the principal surface of the substrate when the substrate is supported on said mount portion, a surface of said auxiliary plate being detected by one of said two second focus detectors and one of said two third focus detectors.

15. A scanning exposure method in which a pattern of a mask is transferred onto a sensitive substrate by projecting a part of the mask pattern on the sensitive substrate through a projection system and by moving the mask and the sensitive substrate relative to a projection field of the projection system, the method comprising the steps of:

(a) mounting the sensitive substrate on a holder having an auxiliary plate portion surrounding the sensitive substrate at a height substantially equal to a height of a principal surface of the sensitive substrate;

(b) reading a focus error of an exposure area of the sensitive substrate on which area a part of the mask pattern is to be projected, the focus error of the exposure area being read before the exposure area reaches the projection field of the projection system during scanning movement of the holder and the sensitive substrate;

(c) detecting a focus error of the principal surface of a part of one of the sensitive substrate and the auxiliary plate portion by an exposure position focus detection system disposed apart from the projection field of the projection system in a direction perpendicular to the direction of said scanning movement when the exposure area on the sensitive substrate reaches the projection field; and

(d) adjusting the focus between the projection system and the sensitive substrate on the basis of the focus errors detected by said steps (b) and (c) so that the focus error of the exposure area on the sensitive substrate is corrected in the projection field of the projection system.

16. A method according to claim 15, applied to a projection aligner having a projection system having an effective working distance to the principal surface of the substrate of 20 mm or less.

17. A method according to claim 15, applied to an immersion projection exposure apparatus in which a space containing a projection optical path between the sensitive substrate and a transparent optical element disposed at an image plane side of the projection optical system is liquid filled.

18. A method according to claim 17, wherein the projection optical system has a working distance such that the thickness of the liquid between the sensitive substrate and the transparent optical element of said projection optical system is 2 mm or less.

19. A method according to claim 15, applied to a scanning exposure apparatus having a catadioptric projection system having a refractive optical material and a reflecting optical material, and in which a transparent optical element is disposed at an image plane side.

20. A method according to claim 19, wherein the transparent optical element disposed at the image plane side is a prism mirror having an emergent surface substantially parallel to the principal surface of the sensitive substrate.

21. A focusing apparatus provided in an apparatus having an objective optical system to control focusing between a surface of a workpiece and the objective optical system, said focusing apparatus comprising:

(a) a first detection system having a detection area at a first position located outside a field of said objective optical system, said first detection system detecting a position of the surface of the workpiece in the focusing direction;

(b) a second detection system having a detection area at a second position located outside the field of said objective optical system and spaced apart from said first position, said second detection system detecting the position of the surface of the workpiece in the focusing direction;

(c) a third detection system having a detection area at a third position located outside the field of said objective optical system and spaced apart from each of said first and second positions, said third detection system detecting the position of the surface of the workpiece in the focusing direction;

(d) a calculator coupled to said first and second detection systems, and calculating a deviation between the first focus position detected by said first detection system and a target focus position and for storing the second focus position detected by said second detection system at the time of detection made by said first detection system; and

(e) a controller coupled to said calculator and to said third detection system, and controlling focusing of the objective optical system on the surface of the workpiece on the basis of the calculated deviation, the stored second focus position and the third focus position detected by said third detection system when the area on the workpiece corresponding to the detection area of said first detection system is positioned in the field of said objective optical system by relative movement of the workpiece and the objective optical system.

22. A method of controlling focusing of an objective optical system onto a surface of a workpiece when the workpiece and a field of the objective optical system are moved relative to each other in X and Y directions, said method comprising the steps of:

(a) mounting the workpiece on a holder having an auxiliary plate portion surrounding the workpiece at a height substantially equal to a height of the surface of the workpiece;

(b) reading a focus error of a predetermined local portion of the surface of the workpiece before the local portion of the workpiece reaches the field of the objective optical system during movement of said holder and the workpiece in a predetermined moving direction;

(c) detecting a focus error of the surface of a part of one of the workpiece and the auxiliary plate portion by a first focus detection system disposed apart from the field of the objective optical system in a direction perpendicular to the moving direction when the local portion of the workpiece reaches the field; and

(d) controlling the focusing between the objective optical system and the workpiece on the basis of the focus errors detected by said steps (b) and (c) so that the focus error of the local portion of the workpiece is corrected in the field of the objective optical system.

23. A method according to claim 22, applied to at least one of a manufacturing instrument, a lithography exposure apparatus, a writing apparatus and an inspection apparatus having a small effective working distance such that a detecting beam of an oblique incident light type focus detector cannot be obliquely led to the surface of the workpiece immediately below the objective optical system.