Photomask substrate, photomask substrate forming member, photomask substrate fabrication method, photomask, and exposing method that uses the photomask

• US 20100062350A1
• Filed: 11/09/2009
• Published: 03/11/2010
• Est. Priority Date: 05/09/2007
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Abe, Tetsuya, Kimura, Yukiyasu, Nitta, Yuhei
• Granted Patent: US 8,153,336 B2
• Time in Patent Office: Days
• US Class Current: 430/5
• CPC Class Codes: C03B 23/0252 by gravity only, e.g. sagging C03B23/035 takes precedence
• CPC Class Codes: G03F 1/60 Substrates
• 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
• CPC Class Codes: Y02P 40/57 Improving the yield, e-g- reduction of reject rates

Abstract

A photomask substrate with a substantially uniform thickness comprises: a first surface, which is a continuous curved surface whereon a mask pattern is to be formed; and a second surface. The first surface exhibits a square shape that comprises an opposing pair of first set sides and an opposing pair of second set sides and has support parts at end parts along the first set sides. When the photomask substrate is held such that the first surface is in a substantially vertical state, a reference plane that is parallel to a tangential plane of the first surface at the center point of the first surface is defined on the photomask substrate side that is closer to the first surface than to the second surface. At this time, a first distance in the thickness direction between the reference plane and the center point of the first surface is shorter than second distances in the thickness direction between the reference plane and the midpoints of the second set sides.

Claims

1. A photomask substrate that consists of a plate shaped member with a substantially uniform thickness, comprising:

a first surface, which is a continuous curved surface and whereon a mask pattern is to be formed; and

a second surface, which opposes the first surface;

wherein, the first surface exhibits a square shape that comprises an opposing pair of first set sides and an opposing pair of second set sides, which extend such that they communicate with the first set sides, and a support part, which is for supporting the photomask substrate at its end parts along the first set sides;

when the photomask substrate is held such that the first surface is in a substantially vertical state, the point at which the axis that passes through the center of gravity of the photomask substrate and extends in the thickness direction of the photomask substrate intersects the first surface is designated as a center point of the first surface; and

if a reference plane that is parallel to a tangential plane of the first surface at the center point is defined on the photomask substrate side that is closer to the first surface than to the second surface, then a first distance in the thickness direction between the reference plane and the center point of the first surface is shorter than second distances in the thickness direction between the reference plane and the midpoints of the second set sides.

2. A photomask substrate according to claim 1, wherein when the photomask substrate is held such that the first surface is substantially in the vertical state, the distances in the thickness direction between the reference plane and the portions of the second set sides on the first set sides are shorter than the second distances.

3. A photomask substrate according to claim 1, wherein when the photomask substrate is held such that the first surface is substantially in the vertical state, the distances in the thickness direction between the reference plane and any points along the first set sides are substantially the same.

4. A photomask substrate according to claim 1, wherein when the photomask substrate is held such that the first surface is substantially in the vertical state, the distances in the thickness direction between the reference plane and midpoints of the first set sides are substantially the same as the first distance.

5. A photomask substrate according to claim 1;

wherein when the photomask substrate is held such that the first surface is substantially in the vertical state, the distances in the thickness direction between the reference plane and the midpoints of the first set sides are shorter than the first distance.

6. A photomask substrate according to claim 1, wherein when the photomask substrate is held such that the first surface is substantially in the vertical state, the distances in the thickness direction between the reference plane and any points along the second set sides are substantially the same.

7. A photomask substrate according to claim 1, comprising:

marks for discriminating the first surface and the second surface.

8. A photomask substrate according to claim 1, wherein the substrate is made of quartz glass.

9. A photomask fabricated using the photomask substrate according to claim 1, wherein a mask pattern is formed on the first surface;

and the photomask is supported by an exposure apparatus at the support parts such that the exposure light is projected from the second surface side.

10. An exposing method that exposes a wafer with the mask pattern formed on the photomask according to claim 9, comprising the step of:

performing an exposure in the state wherein the support parts are supported by a photomask support member of the exposure apparatus such that the exposure light is projected from the surface on the side opposite the surface whereon the mask pattern of the photomask is formed, and the surface whereon the mask pattern is formed faces toward the wafer.

11. A photomask substrate forming member that shapes a plate shaped member, comprising:

a forming surface that is a continuous curved surface for shaping the plate shaped member that exhibits a square shape that comprises an opposing pair of first set sides and an opposing pair of second set sides, which extend such that they communicate with the first set sides;

wherein, the intersection point between the straight line that connects the midpoints of the first set sides and the straight line that connects the midpoints of the second set sides is designated as a center point of the forming surface; and

if a reference plane that is parallel to a tangential plane of the forming surface at the center point is defined on the forming surface side of the forming member spaced apart therefrom, then a first distance in the normal line direction of the tangential plane between the reference plane and the center point of the forming surface is shorter than the second distances in the normal line direction between the reference plane and the midpoints of the second set sides.

12. A photomask substrate forming member according to claim 11, wherein

the distances in the normal line direction between the reference plane and the portions of the second set sides on the first set sides are shorter than the second distances.

13. A photomask substrate forming member according to claim 11, wherein

the distances in the normal line direction between the reference plane and any points along the first set sides are substantially the same.

14. A photomask substrate forming member according to claim 11, wherein the distances in the normal line direction between the reference plane and midpoints of the first set sides are substantially the same as the first distance.

15. A photomask substrate forming member according to claim 11, wherein the distances in the normal line direction between the reference plane and the midpoints of the first set sides are shorter than the first distance.

16. A photomask substrate forming member according to claim 11, wherein the distances in the normal line direction between the reference plane and any points along the second set sides are substantially the same.

17. A photomask substrate forming member according to claim 11, wherein the photomask substrate forming member is made of graphite.

18. A photomask substrate fabricating method, comprising the steps of:

preparing a forming member according to claim 11;

preparing a plate shaped member with a substantially uniform thickness that comprises a first surface, whereon a mask pattern is to be formed, and a second surface, which opposes the first surface;

disposing the plate shaped member and the forming member in a heat treatment furnace in the state wherein the second surface of the plate shaped member is supported by a forming surface of the forming member; and

after heating the interior of the heat treatment furnace such that the temperature of the plate shaped member reaches a prescribed temperature, lowering the temperature of the plate shaped member.

19. A photomask substrate fabricating method, comprising the steps of:

preparing a plate shaped member with a substantially uniform thickness that comprises a first surface, whereon a mask pattern is to be formed, and a second surface, which opposes the first surface;

disposing the plate shaped member and the forming member in a heat treatment furnace in the state wherein end part areas along one set of sides of two sets of opposing sides that constitute the second surface of the plate shaped member are supported by support parts such that the plate shaped member is substantially horizontal; and

after heating the interior of the heat treatment furnace such that the temperature of the plate shaped member reaches a prescribed temperature, lowering the temperature of the plate shaped member.

20. A photomask substrate fabricating method according to claim 19, wherein the support member is made of graphite.

21. A photomask substrate fabricating method according to claim 19 or claim 20, wherein the plate shaped member is made of quartz glass.

22. A photomask substrate, wherein a first surface for forming a mask pattern is a rectangle with a diagonal line length of 1,200 mm or greater;

the thickness of the photomask substrate is 8 mm or greater;

the photomask substrate is held in the state wherein the first surface is substantially vertical; and

if a reference plane is defined as an arbitrary plane that is parallel to the vicinity of the center of the first surface and is located at a position that is sufficiently spaced apart from the first surface on the near side of the first surface, then distances from the vicinities of end parts of a first centerline, which is one of two centerlines that constitute the first surface, to the reference plane are longer by 30-100 μ

m than a distance from the vicinity of the center of the first centerline to the reference plane.

23. A photomask substrate according to claim 22, wherein the distances from any points in the vicinities of the first set sides, which are one set of sides parallel to the first centerline, to the reference plane are substantially the same.

24. A photomask substrate according to claim 22, wherein the distances from any points in an area in the vicinity of a second centerline, which is separate from the first centerline, of the two centerlines that constitute the first surface, to the reference plane are substantially the same.

25. A photomask substrate according to claim 22, wherein the distance from the vicinity of a center part of the second centerline to the reference plane is longer by 150-1500 μ

m than the distances from the vicinities of the end parts of the second centerline to the reference plane.

26. A photomask substrate according to any one claim of claim 22 through claim 25, wherein a second surface, which opposes the first surface, is substantially parallel to the first surface.

27. A photomask substrate according to any one claim of claim 22 through claim 25, comprising:

marks for discriminating the first surface and the second surface.

28. A photomask substrate according to claim 22, wherein the substrate is made of quartz glass.

29. A photomask fabricated using the photomask substrate according to claim 22, wherein a mask pattern is formed on the first surface;

and support portions, at which the photomask is supported by an exposure apparatus, are in the vicinities of first set sides.

30. An exposing method that performs an exposure using the photomask according to claim 29, comprising the step of:

performing an exposure in the state wherein the support portions are supported by a photomask support member of the exposure apparatus such that the surface whereon the mask pattern of the photomask is formed faces downward.

31. A photomask substrate forming member for forming a plate shaped member, comprising:

a forming surface for forming the plate shaped member;

wherein, the forming surface is a rectangle with a diagonal line length of 1,200 mm or greater; and

if a reference plane is defined as an arbitrary plane that is parallel to the vicinity of the center of the forming surface and is located at a position that is sufficiently spaced apart from the forming surface on the near side of the forming surface, then distances from the vicinities of end parts of a first centerline, which is one of two centerlines that constitute the forming surface, to the reference plane are longer by 30-100 μ

m than a distance from the vicinity of the center of the first centerline to the reference plane.

32. A photomask substrate forming member according to claim 31, wherein the distances from any points in the vicinities of the first set sides, which are one set of sides parallel to the first centerline, to the reference plane are substantially the same.

33. A photomask substrate forming member according to claim 31, wherein the distances from any points in an area in the vicinity of a second centerline, which is different from the first centerline, of the two centerlines that constitute the forming surface, to the reference plane are substantially the same.

34. A photomask substrate forming member according to claim 31, wherein the distance from the vicinity of a center part of the second centerline to the reference plane is longer by 150-1500 μ

m than the distances from the vicinities of the end parts of the second centerline to the reference plane.

35. A photomask substrate forming member according to claim 31, wherein the forming member is made of graphite.

36. A photomask substrate fabricating method, comprising the steps of:

preparing a forming member according to claim 31;

preparing a plate shaped member that a thickness of 8 mm or greater and wherein a surface for forming a mask pattern is a rectangle whose diagonal line length is 1,200 mm;

disposing the plate shaped member and the forming member in a heat treatment furnace in the state wherein the second surface of the plate shaped member is supported by a forming surface of the forming member; and

after heating the interior of the heat treatment furnace such that the temperature of the plate shaped member reaches a prescribed temperature, lowering the temperature of the plate shaped member.

38. A photomask substrate fabricating method according to claim 36, wherein the transparent plate shaped member is made of quartz glass and the support member is made of graphite.

37. A photomask substrate fabricating method, comprising the steps of:

preparing a plate shaped member that has a thickness of 8 mm or greater and wherein a surface for forming a mask pattern is a rectangle with a diagonal line length of 1,200 mm or greater;

disposing the plate shaped member and the forming member in a heat treatment furnace in the state wherein areas in the vicinities along one set of sides of two sets of opposing sides that constitute the lower surface of the plate shaped member are supported by support parts such that the plate shaped member is substantially horizontal; and

after heating the interior of the heat treatment furnace such that the temperature of the plate shaped member reaches a prescribed temperature, lowering the temperature of the plate shaped member.