1. An optical system, comprising:
a plurality of elements arranged to image radiation at a wavelength \u03bb from an object surface to an image surface, the elements including mirror elements, each mirror element having a reflective surface positioned at a path of the radiation,
wherein:
at least one first mirror element of the plurality of mirror elements is a pupil mirror having a pupil mirror surface arranged at or near to a pupil surface of the optical system;
at least one second mirror element of the plurality of mirror elements is a highly loaded mirror having a mirror surface arranged at a position where at least one of a largest value of a range of angles of incidence and a largest value of an average angle incidence of all remaining mirrors occurs, the at least one second mirror element being different from the at least one first mirror element;
the pupil mirror surface is formed by a reflective coating designed as a one-dimensionally graded coating including a multilayer stack of layers of different materials, the layers having a geometrical layer thickness which varies according to a first grading function in a first direction of the coating and which is substantially constant in a second direction perpendicular to the first direction; and
the mirror surface of the highly loaded mirror is coated with a reflective mirror coating designed as a graded coating according to a second grading function.
2. The optical system of claim 1, wherein the position andor a variation of geometric film thickness of layers of the mirror coating of the highly loaded mirror is adapted to the one-dimensionally graded pupil mirror coating such that non-uniformities of radiation intensity in the image field caused by the one-dimensionally graded pupil mirror coating are at least partly compensated by the graded coating of the highly loaded.
3. The optical system of claim 1, wherein the pupil mirror surface is arranged at a position where the condition P(M)\u22670.95 is fulfilled and the mirror surface of the highly loaded mirror is arranged at a position where the condition P(M)<0.95 is fulfilled, wherein
P(M)=D(SA)(D(SA)+D(CR)),
where D(SA) is a diameter of a subaperture of a ray bundle originating from a field point in the object surface on a respective surface M and D(CR) is a maximum distance of chief rays of an effective object field imaged by the optical system measured in a meridional plane of the optical system.
4. The optical system of claim 1, wherein the highly loaded mirror is a pupil mirror positioned at or close to another optically conjugate pupil surface of the projection objective.
5. The optical system of claim 4, wherein the graded coating of the highly loaded mirror is optimized to compensate at least partially for illumination inhomogeneities caused by the one-dimensionally graded coating of the other pupil mirror.
6. The optical system of claim 1, wherein the plurality of elements define a meridional plane and wherein the first direction is in the meridional plane.
7. The optical system of claim 1, wherein the plurality of elements define a meridional plane and the elements are symmetric with respect to the meridional plane.
8. The optical system of claim 1, wherein a path of radiation through the optical system has an average angle of incidence, \u03b8avg, of rays on each location of a reflective surface, and the first grading function is adapted to the average angle of incidence, \u03b8avg, at the pupil mirror surface such that a local geometrical layer thickness of the layers of the multilayer stack varies substantially proportional to the average angle of incidence, \u03b8avg, in the first direction.
9. The optical system of claim 1, wherein a path of radiation through the optical system has a range of angles of incidence, \u0394\u03b8, of rays on each location of a reflective surface, and the first grading function is adapted to the range of angles of incidence, \u0394\u03b8, at the pupil mirror surface such that a local geometrical layer thickness of the layers of the multilayer stack varies substantially proportional to the range of angles of incidence, \u0394\u03b8, in the first direction.
10. The optical system of claim 1, wherein the first grading function is adapted to a range of angles of incidence, \u0394\u03b8, andor an average angle of incidence, \u03b8avg, at each location of the pupil mirror surface such that an absolute value of a local reflectivity of the pupil mirror surface in the first direction varies by no more than 30%.
11. The optical system of claim 1, wherein the first grading function is a linear function.
12. The optical system of claim 1, wherein the first grading function is defined such that a local geometrical layer thickness of the layers of the multilayer increases monotonically from one side of the pupil mirror to an opposite side of the pupil mirror along the first direction.
13. The optical system of claim 1, wherein the first grading function is a parabolic function.
14. The optical system of claim 1, wherein the mirror coating of the highly loaded mirror is designed according to a rotationally symmetric second grading function symmetric to a rotation center.
15. The optical system of claim 14, wherein the rotationally symmetric second grading function is a parabolic function.
16. The optical system of claim 1, wherein a local geometrical film thickness d(x, y) of the layers of the multilayer stack deviates by \u03bb100 from a grading function according to
d(x,y)=d0\xb7max(0,fac(x,y)),
where
fac(x,y)=c0+c1y\xb7y+c2\xb7r(x,y)2,
with
r(x,y)=\u221a{square root over (x2+y2)},
where y is a coordinate in the first direction, x is a coordinate in the second direction, d0 is a nominal thickness measured in a z direction normal to the reflective surface perpendicular to the x and y direction in a local coordinate system of the reflective surface.
17. The optical system of claim 16, wherein the conditions 0.9\u2266c0\u22661.2 and c1y\u22660.1 and |c2|\u226610\u22125 hold for a nominal thickness d0=6.9 nm.
18. The optical system of claim 1, wherein at least one mirror has a coating with uniform thickness.
19. The optical system of claim 1, wherein all remaining mirrors except for the highly loaded mirror have a coating with uniform thickness.
20. The optical system of claim 1, wherein the optical system is a purely reflective optical system designed for EUV wavelength 13 nm<\u03bb<14 nm and has an image-side numerical aperture NA of about 0.3 or more.
21. The optical system of claim 1, wherein 0.3\u2266NA\u22660.4.
22. The optical system of claim 1, wherein the optical system comprises at least three mirrors and is designed for EUV wavelength 13 nm<\u03bb<14 nm and has an image-side numerical aperture NA>0.25, where an overall transmission T is 0.08 or more.
23. The optical system of claim 22, wherein 0.3\u2266NA\u22660.4.
24. The optical system of claim 1, wherein the optical system has an even number of mirrors.
25. The optical system of claim 24, wherein the optical system has six mirrors.
26. The optical system of claim 1, wherein the optical system comprises three or more mirrors, an average reflectivity Rmean integrated over the entire utilized area of the reflective mirror surface being at least 60% on each mirror.
27. The optical system of claim 26, wherein the optical system has an even number of mirrors.
28. The optical system of claim 27, wherein the optical system has six mirrors.
29. The optical system of claim 1, wherein at least one of the elements is a reflective element that has a rotationally asymmetric surface positioned in the path of the radiation, wherein the rotationally asymmetric surface deviates from a best-fit rotationally symmetric surface by about \u03bb or more at one or more locations.
30. The optical system of claim 29, wherein the best-fit rotationally asymmetric surface deviates by about 0.1\u03bb or less from a surface corresponding to the equation:
Z
=
cr
2
1
+
1
–
(
1
+
k
)
\u2062
c
2
\u2062
r
2
+
\u2211
j
=
2
\u03b1
\u2062
C
j
\u2062
X
m
\u2062
Y
n
\u2062
\u2062
where
j
=
(
m
+
n
)
2
+
m
+
3
\u2062
n
2
+
1
,
z is the sag of the surface parallel to an axis, c is the vertex curvature and k is the conical constant, Cj is the coefficient of the monomial xmyn, and \u03bb is an integer.
31. The optical system of claim 30, wherein \u03bb is 66.
32. The optical system of claim 30, wherein m consists of even integers.
33. The optical system of claim 30 wherein m+n\u226710.
34. The optical system of claim 29, wherein the rotationally asymmetric surface deviates from the best-fit rotationally symmetric surface by about 10\u03bb or more at the one or more locations.
35. The optical system of claim 29, wherein at least one of the reflective elements that has a rotationally asymmetric surface has a reflective surface coated with a graded coating.
36. A projection-exposure system, comprising:
an illumination system configured to receive radiation from a primary light source and to illuminate a pattern in an object surface of a projection objective; and
a projection objective,
wherein the project-exposure system is configured to be used in microlithography, and the projection objective comprises an optical system according to claim 1.
37. A projection-exposure system according to claim 36, wherein the primary light source emits EUV radiation at a wavelength 13 nm<\u03bb<14 nm.
38. A method, comprising:
illuminating a mask having a pattern with radiation having a wavelength \u03bb; and
using an optical system according to claim 1 to project an image of the pattern onto a photosensitive substrate arranged in the vicinity of the image plane of a projection objective formed.
39. The optical system according to claim 1, configured as a projection objective for microlithography having a resolution of less than 1 \u03bcm.
40. An optical system comprising:
a plurality of elements arranged to image radiation at a wavelength \u03bb from an object surface to an image surface, the elements including mirror elements having a reflective surface positioned at a path of radiation,
wherein:
at least one of the mirror elements is a pupil mirror having a pupil mirror surface arranged at or near to a pupil surface of the optical system;
the pupil mirror surface is formed by a reflective coating designed as a one-dimensionally graded coating including a multilayer stack of layers of different materials; and
the layers have a geometrical layer thickness which varies according to a first grading function in a first direction of the coating and which is substantially constant in a second direction perpendicular to the first direction.
41. An optical system comprising:
a plurality of elements arranged to image radiation at a wavelength \u03bb from an object surface to an image surface, the elements including mirror elements having a reflective surface positioned at a path of radiation,
wherein:
at least one first mirror element of the plurality of mirror elements is a pupil mirror having a pupil mirror surface arranged at or near to a pupil surface of the optical system;
at least one second mirror element of the plurality of mirror elements being a highly loaded mirror, the at least one second mirror being different from the at least one first mirror element;
the pupil mirror surface is formed by a reflective coating designed as a one-dimensionally graded coating including a multilayer stack of layers of different materials;
the layers have a geometrical layer thickness which varies according to a first grading function in a first direction of the coating and which is substantially constant in a second direction perpendicular to the first direction; and
the mirror surface of the highly loaded mirror is coated with a reflective mirror coating designed as a graded coating according to a second grading function.
42. An optical system comprising:
a plurality of elements arranged to image radiation at a wavelength \u03bb from an object surface to an image surface, the elements including mirror elements having a reflective surface positioned at a path of radiation;
wherein the mirror elements include a mirror element having a maximum value for the range of the angles of incidence, \u0394\u0398, in a first direction, this mirror element is coated with a reflective coating designed as a one-dimensionally graded multilayer coating including a multilayer stack of layers of different materials, the layers have a geometrical layer thickness which varies according to a first grading function in a first direction of the coating and which is substantially constant in a second direction perpendicular to the first direction.
43. An optical system comprising:
a plurality of elements arranged to image radiation at a wavelength \u03bb from an object surface to an image surface, the elements including mirror elements having a reflective surface positioned at a path of radiation;
wherein the mirror elements include a mirror element having a maximum value for a variation, \u0394\u0398avg, of an average angle of incidence, this mirror element is coated with a reflective coating designed as a one-dimensionally graded multilayer coating including a multilayer stack of layers of different materials, the layers have a geometrical layer thickness which varies according to a first grading function in a first direction of the coating and which is substantially constant in a second direction perpendicular to the first direction.
44. An optical system comprising:
a plurality of elements arranged to image radiation at a wavelength \u03bb from an object surface to an image surface, the elements including mirror elements having a reflective surface positioned at a path of radiation;
where the mirror elements include a first pupil mirror positioned at or close to a first pupil surface and a second pupil mirror positioned at or close to a second pupil surface optically conjugate to the first pupil surface, and the first and second pupil mirror each have a reflective coating designed as a graded coating having a geometrical layer thickness which varies according to a grading function in at least one direction of the mirror coating.
45. An optical system comprising:
a plurality of elements arranged to image radiation at a wavelength \u03bb from an object surface to an image surface, the elements including mirror elements having a reflective surface positioned at a path of radiation;
wherein the optical system includes at least one reflective freeform surface and at least one reflective surface is coated with a graded coating having a geometrical layer thickness which varies according to a grading function in at least one direction of the mirror coating, and
the optical system is a microlithographic projection objective.
46. The optical system according to claim 45, wherein at least one reflective freeform surface is coated with a graded coating.
47. An optical system comprising:
a plurality of elements arranged to image radiation at a wavelength \u03bb from an object surface to an image surface, the elements including a first mirror and a second mirror,
wherein:
the optical system has an intermediate image plane between the first and second mirrors along an optical path of the image radiation from the first mirror to the second mirror;
the first mirror is upstream of the intermediate image plane along the optical path;
the first mirror is a pupil mirror;
each of the first and second mirrors has a reflective coating having a geometrical layer thickness which varies in at least one direction of the mirror coating; and
the optical system is a microlithographic projection objective.
48. The optical system of claim 47, wherein the second mirror is a pupil mirror.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A hitch coupler, comprising:
a frame member including a plurality of vertically spaced apart plates extending outwardly from the frame member;
a pin member slidably received within apertures disposed on the vertically spaced apart plates, the pin member moveable between an extended position and a retracted position, wherein the pin member includes a pin housing having a hollow interior;
a guide slot vertically disposed on the pin housing having upper and lower ends and an offset portion disposed therebetween;
a guide member extending from the frame member, wherein the guide member is slideably received in the guide slot of the pin housing to guide the pin member between the extended position and the retracted position; and
a biasing mechanism disposed within the hollow interior of the pin housing, the biasing mechanism operably coupled to a portion of the frame member at a first end and operably coupled to a lower portion of the pin housing at a second end, wherein the biasing mechanism is adapted to bias the pin member towards the extended position, and wherein the biasing mechanism is configured to impart torsional force on the pin housing.
2. The hitch coupler of claim 1, wherein torsional force imparted on the pin housing by the biasing mechanism is adapted to rotate the pin housing such that the guide member aligns with the upper end of the guide slot when the pin member is in the extended position, and further wherein the torsional force imparted on the pin housing by the biasing mechanism is adapted to rotate the pin housing such that the guide member aligns with the lower end of the guide slot when the pin member is in the retracted position.
3. The hitch coupler of claim 1, further comprising:
a handle member having a connecting portion, the connecting portion coupled to an upper portion of the pin housing such that the connecting portion is partially disposed within the hollow interior of the pin housing, wherein the guide member abuts the connecting portion of the handle member to retain the pin member in the extended position.
4. The hitch coupler of any one of claim 3,
wherein the handle member is pivotally coupled to the upper portion of the pin housing, and wherein the handle portion is configured to be engaged by a user to move the pin member between the extended and retracted positions.
5. The hitch coupler of claim 1, further comprising:
a relief slot disposed at the lower end of the guide slot, wherein the relief slot is configured to engage a portion of the guide member when the pin member is in the retracted position to retain the pin member in the retracted position.
6. The hitch coupler of claim 1, wherein the biasing mechanism comprises a spiral torsion spring.
7. The hitch coupler of claim 6, further comprising:
a first boss member disposed on an underside of the guide member, wherein the first end of the spiral torsion spring is coupled to the first boss member.
8. The hitch coupler of claim 7, further comprising:
a second boss member disposed in a lower portion of the hollow interior of the pin housing, wherein the second end of the spiral torsion spring is coupled to the second boss member.
9. A hitch coupler, comprising:
a frame member including a top plate, a bottom plate and a middle plate disposed between the top plate and the bottom plate, each plate extending outwardly from the frame member and each plate further including a pin receiving aperture disposed thereon;
a pin member having a pin housing and a handle portion, the pin housing slidably received within the pin receiving apertures such that the pin member is slideable between an extended position and a retracted position;
a guide slot disposed along the pin housing having an upper end and a lower end and an offset portion disposed between the upper end and the lower end;
a guide member extending laterally from the top plate, wherein the guide member is configured to be slidably received within the guide slot of the pin housing; and
a biasing mechanism disposed within a hollow interior of the pin housing, the biasing mechanism operably coupled to a portion of the guide member at a first end and operably coupled to a lower portion of the pin housing at a second end, wherein the biasing mechanism is adapted to bias the pin member towards the extended position, and wherein the biasing mechanism is configured to impart a torsional force on the pin housing.
10. The hitch coupler of claim 9, wherein the torsional force imparted on the pin housing by the biasing mechanism is adapted to rotate the pin housing such that the guide member aligns with the upper end of the guide slot when the pin member is in the extended position, and wherein the torsional force imparted on the pin housing by the biasing mechanism is adapted to rotate the pin housing such that the guide member aligns with the lower end of the guide slot when the pin member is in the retracted position.
11. The hitch coupler of claim 9, further comprising:
a handle member pivotally coupled to an upper portion of the pin housing such that a portion of the handle member is disposed within the hollow interior of the pin housing and abuts the guide member when the pin member is in the extended position to retain the pin member in the extended position.
12. The hitch coupler of claim 9, wherein the lower end of the guide slot comprises a relief slot adapted to engage a portion of the guide member when the pin member is in the retracted position to retain the pin member in the retracted position.
13. The hitch coupler of claim 12, wherein the relief slot comprises an angled top surface.
14. The hitch coupler of claim 13, further comprising:
a protrusion disposed on the guide member having a mating angled surface relative to the angled top surface of the relief slot.
15. The hitch coupler of claim 9, wherein the biasing mechanism comprises a spiral torsion spring.
16. A hitch coupler, comprising:
a frame member having a plurality of pin receiving apertures disposed thereon;
a pin member having a pin housing slidably received within the pin receiving apertures such that the pin member is slideable between an extended position and a retracted position;
a guide slot disposed vertically along the pin housing having an upper end and a lower end and an offset portion disposed between the upper end and the lower end;
a guide member extending from the frame member into a hollow interior of the pin housing, wherein a portion of the guide member is configured to be slidably received within the guide slot of the pin housing; and
a biasing mechanism disposed within the hollow interior of the pin housing, the biasing mechanism operably coupled to a portion of the guide member at a first end and operably coupled to a lower portion of the pin housing at a second end, wherein the biasing mechanism is adapted to bias the pin member towards the extended position, and wherein the biasing mechanism is configured to impart a torsional force on the pin housing.
17. The hitch coupler of claim 16, wherein the torsional force imparted on the pin housing by the biasing mechanism is adapted to rotate the pin housing such that the guide member aligns with the upper end of the guide slot when the pin member is in the extended position, and wherein the torsional force imparted on the pin housing by the biasing mechanism is adapted to rotate the pin housing such that the guide member aligns with the lower end of the guide slot when the pin member is in the retracted position.
18. The hitch coupler of claim 16, further comprising:
a first boss member disposed on an underside of the guide member, wherein the first end of the biasing mechanism is coupled to the first boss member.
19. The hitch coupler of claim 18, further comprising:
a second boss member disposed in a lower portion of the hollow interior of the pin housing, wherein the second end of the biasing mechanism is coupled to the second boss member.
20. The hitch coupler of claim 19, wherein the second boss member comprises a cross-shaped configuration.