EP1327172A1

EP1327172A1 - 8-mirrored microlithographic projector lens

Info

Publication number: EP1327172A1
Application number: EP01982439A
Authority: EP
Inventors: Hans-Jürgen Mann; Wilhelm Ulrich; Günther SEITZ
Original assignee: Carl Zeiss AG
Current assignee: Carl Zeiss SMT GmbH
Priority date: 2000-10-20
Filing date: 2001-10-19
Publication date: 2003-07-16
Also published as: US20070047069A1; US20080137183A1; US7177076B2; WO2002033467A1; US7508580B2; KR20030045817A; US7372624B2; JP2004512552A; US20040012866A1

Abstract

The invention relates to a microlithographic projector lens for EUV-lithography with a wavelength in the range 10 - 30 nm, an incident aperture diaphragm and an emergent aperture diaphragm for the transformation of an object field in an object plane into an image field in an image plane. The invention is characterised in that the microlithographic projector lens comprises a first, second, third, fourth, fifth, sixth, seventh and eighth mirror (51-58) and the beam path from the object plane (100) to the image plane (102) is free from obscuration.

Description

8-mirror microlithography projection lens

The invention relates to a microlithography objective according to the preamble of claim 1, a projection exposure system according to claim 18 and a chip production method according to claim 19.

Lithography with wavelengths <193 nm, in particular EUV lithography with λ = 11 nm or λ = 13 nm, are discussed as possible techniques for imaging structures <130 nm, particularly preferably <100 nm. The resolution of a lithographic

Systems is described by the following equation:

^FLSS? = *. ^' WA

where k1 is a specific parameter of the lithography process, λ die

Wavelength of the incident light and NA denotes the image-side, numerical aperture of the system.

For imaging systems in the EUV area, essentially reflective systems with multilayer layers are available as optical components.

Mo / Be systems are preferred as multilayer coating systems at λ = 11 nm and Mo / Si systems at λ = 13 nm.

The reflectivity of the multilayer layers used is currently at most in the range of approximately 70%, so that a requirement is met

A projection objective for EUV microlithography is to use as few optical components as possible in order to achieve a sufficient light intensity. On the other hand, in order to achieve the highest possible resolution, it is necessary for the system to have the largest possible aperture on the image side.

For lithography systems, it is advantageous if the beam path within a projection lens is free of shading or obscuring. In particular, the projection objectives should not have mirrors with transmissive areas, in particular openings, since such transmissive areas lead to shadowing. If the lens has no mirrors with transmissive areas, the lens has an obscuration-free beam path and the exit pupil of the lens is free of shadowing. Furthermore, no shading device has to be arranged in the aperture diaphragm of such shading-free systems or in planes conjugated to the aperture diaphragm. The disadvantage of systems with a shaded exit pupil, e.g. so-called

Schwarzschild mirror systems is that structures of a certain size can only be imaged to a limited extent. The exit pupil is defined as the image of the aperture diaphragm, imaged by the lens part that lies in the beam path between the aperture diaphragm and the image plane.

4-mirror systems for microlithography are known for example from US 5,315,629 or EP 0 480 617 B1. However, such systems only allow a numerical aperture of NA = 0.1 on the image side with a sufficient field size of at least 1.0 mm scan slot width. The resolution limit is when using X-ray light with a

Wavelength from 10 to 30 nm then in the range of 70 nm.

6-mirror systems for microlithography are known from the documents US-A-5 153 898, EP-A-0 252734, EP-A-0947 882, US-A-5686728, EP 0 779 528, US 5 815 310, WO 99/57606 and US 6 033 079 become known. Such systems 6-mirror systems have an image-side numerical aperture <0.3, which leads to a resolution limit in the range of 30 nm when using X-ray light with a wavelength of 10 to 30 nm.

Another disadvantage of both the 4- and 6-mirror systems is that they provide only a few possibilities for correcting non-imaging errors.

A microlithography projection lens with eight mirrors is from the US

5,686,728 became known. This projection objective has a high numerical aperture NA = 0.55 on the image side. However, the projection lens known from US Pat. No. 5,686,728 is only suitable for wavelengths greater than 126 nm, since for example the angle of incidence of the main beam of the field point, which lies on the axis of symmetry in the middle of the object field, is so large that this 8-mirror system is not can be operated in the EUV wavelength range from 10 to 30 nm. A further disadvantage of the system according to US Pat. No. 5,686,728 is that all eight mirrors are aspherical and that the main beam angle on the object has a value of 13 ° with a numerical aperture of 0.11 on the object side.

A first object of the invention is to provide a projection lens which is suitable for lithography with short EUV wavelengths in the range from 10 to 30 nm and which is different from those known to date

EUV microlithography projection systems are characterized by a large numerical aperture and improved possibilities of image correction.

Another object of the invention is to use for lithography

Wavelengths <193 nm a microlithography projection lens to specify, which has both a large aperture and is easy to manufacture.

According to the invention, the first object is achieved by a microlithography projection objective for EUV lithography with a wavelength in the

Range 10 to 30 nm solved by the fact that the microlithography projection lens comprises eight mirrors instead of the four or six mirrors.

The inventors have surprisingly recognized that such

Objective provides both a sufficient light intensity, as well as a sufficiently large numerical aperture to meet the requirements for high resolution, as well as sufficient options for image correction.

In order to achieve the highest possible resolution, in an advantageous embodiment the numerical aperture of the projection objective on the image side is greater than 0.2.

In order to keep the angle of incidence of the main beam of the field point, which lies on the axis of symmetry and in the center of the object field, low, the image-side numerical aperture of the projection system according to the invention is advantageously limited to NA <0.5.

In order to force the beam in the direction of the optical axis (HA) and to avoid the occurrence of useful areas remote from the axis, it is provided in a particularly advantageous embodiment that the projection lens is designed such that at least one in the beam path of the projection lens between the object field and the image field

Intermediate image of the object field is formed. In the present application, the useful area of a mirror is understood to mean the part of a mirror in which the light rays that are guided through the projection objective strike. In the present application, the distance of the useful area is the distance of the point of incidence of the main beam of the central field point from the optical axis.

In order to keep the angles of incidence on the first mirrors of the projection objective according to the invention low, it is provided in a particularly advantageous embodiment of the invention that the diaphragm is arranged in the light path between the first and third mirrors, preferably on or near the first or on or near the second mirror , In the present application, “near” is understood to mean a distance of the diaphragm from the respective closest mirror, which is less than 1/10 of the distance from the preceding mirror to the respective mirror close to the diaphragm.

For example, "near S2" means that:

BS, <1/10 S1S2 where BS _{2 is} the distance from the diaphragm to the second mirror and S1S2 is the

Distance from the first and second mirrors. Such an arrangement permits minimal separation of the beam bundles in the front lens part, which reduce the angles of incidence on the first, second and third mirrors. Furthermore, such an arrangement of the diaphragm means that the useful area of the third mirror lies directly below the optical axis and is almost a mirror image of the useful area of the first mirror S1. This property also reduces the angles of incidence on the fourth and fifth mirrors, since the distance of the beam from the optical axis between the fourth and fifth mirrors is minimal. To generate small angles of incidence on the mirrors, it is also advantageous if the distances between the useful areas of the mirrors are kept small. Since these can be varied as required by appropriate scaling, these distances are characterized in the present application by their size ratio to the overall length of the lens. It is particularly advantageous if the relation

Amount of the distance of the useful area <0.3 * overall length

prefers

Amount of the distance of the useful area <0.25 * overall length

is satisfied, since this creates particularly small angles.

In a further developed embodiment of the invention, the radius of curvature of at least one mirror is chosen to be larger than the overall length of the projection objective. The overall length of the system is understood to mean the distance from the object to be imaged to its image in the present application. It is particularly advantageous if this is for the

Radius of curvature of the second, third and ^" fourth mirrors applies, so that the beam paths from the first to the second and from the third to the fourth mirror are almost parallel. This configuration results in minimal separation of the beams and large drift distances are generated. Under drift distance in the present

Understand the distance between the vertices between two successive mirrors in the optical beam path. This contributes to low angles of incidence on the mirrors.

In a further developed embodiment of the invention that is

Microlithography projection lens designed such that the The main beam angle on the object is smaller than twice the value of the aperture NAO on the object. This is advantageous because it reduces shading effects on the masks.

It is particularly advantageous if the projection lens has two

Has intermediate images. The first intermediate picture at. a system with two intermediate images is preferably formed between the second and third mirrors. This means that the first, second, third and fourth mirrors have a useful area close to the axis. In order to ensure a useful area close to the axis for as many of the mirrors as possible in the subsequent lens part, including the fifth, sixth, seventh and eighth mirrors, it is advantageously provided that the projection lens is designed such that the second intermediate image between the sixth and seventh mirrors in the beam path is trained. It is particularly preferred if in a system with two

Intermediate images the angle of incidence of the main beam of the field point, which lies on the axis of symmetry in the middle of the object field, is less than 20 ° on all mirrors.

In an embodiment of the invention with two intermediate images, at least one of the eight mirror surfaces is spherical.

It is particularly advantageous if the mirror or mirrors of the objective are spherical, the useful area of which is the most distant from the optical axis of the projection objective, since the interferometric testability of off-axis aspheres lies far outside the optical axis The further the useful area is from the optical axis, the more difficult the useful area becomes. In a system with two intermediate images between the second and third mirrors and between the sixth and seventh mirrors, the sixth mirror is the mirror with the most distant useful area. In such an embodiment, this is advantageously spherically shaped for the sake of easier interferometric testability.

In addition to the projection lens, the invention also provides a projection exposure system, the projection exposure system including an illumination device for illuminating a ring field and a projection lens according to the

Invention includes.

The invention will be described below using the exemplary embodiments.

Show it:

Figure 1: the definition of the useful area of a mirror

Figure 2: the shape of the field in the object or image plane of the

objective

Figure 3: a first embodiment of an inventive

Projection lenses with eight mirrors with an intermediate image

4A-4H: Usable areas of the mirrors S1-S8 of the first

Embodiment.

Figure 5: a second embodiment of an inventive

Projection lenses with seven aspherical Mirror and a spherical mirror and two intermediate images

6A-6H: Usable areas of the S1-S8 of the second embodiment.

Figure 7: the basic structure of a

Projection exposure system with such a lens

FIG. 1 shows what is mentioned in the present application

Usable area and diameter of the usable area is to be understood.

FIG. 1 shows, by way of example, a field in the shape of a kidney for an illuminated field 1 on a mirror of the projection objective. Such a shape is expected for the useful area when using the objective according to the invention in a microlithography projection exposure system. The enveloping circle 2 completely surrounds the kidney shape and coincides with the edge 10 of the kidney shape at two points 6, 8. The envelope circle is always the smallest circle that encompasses the useful area. The diameter D of the useful area then results from the diameter of the enveloping circle 2.

FIG. 2 shows the object field 11 of a projection exposure system in the object plane of the projection objective, which is imaged with the aid of the projection objective according to the invention in an image plane in which a light-sensitive object, for example a wafer, is arranged. The shape of the image field corresponds to that of the object field. With reduction lenses, as are often used in microlithography, the image field is reduced by a predetermined factor compared to the object field. The object field 11 has the shape of a segment of a ring field. The segment has an axis of symmetry 12. Furthermore, the axes spanning the object or image plane, namely the x-axis and the y-axis, are shown in FIG. As from a figure

2, the axis of symmetry 12 of the ring field 11 runs in the direction of the y-axis. At the same time, the y-axis coincides with the scan direction of an EUV projection exposure system, which is designed as a ring field scanner. The x direction is then the direction that is perpendicular to the scan direction within the object plane. Also shown in FIG. 12 is the unit vector x in the direction of the x axis.

The optical axis HA of the system extends in the z direction.

FIG. 3 shows a first exemplary embodiment of a projection lens which can be used in the EUV range with λ = 10 to 30 nm and is distinguished by a small angle of incidence on all mirrors.

The object is imaged in the object plane 100 into the image plane 102, in which, for example, a wafer can be arranged, by the projection objective. The projection objective according to the invention comprises a first mirror S1, a second mirror S2, a third mirror S3, a fourth mirror S4, a fifth mirror S5, a sixth mirror S6, a seventh mirror S7 and an eighth mirror S8. In the figure

3, all mirrors S1, S2, S3, S4, S5, S6, S7 and S8 are designed as aspherical mirrors. The system comprises an intermediate image Z1 between the fifth S5 and the sixth S6 mirror. The y and z directions of the right-handed x, y, z coordinate system are also shown in FIG. The z-axis runs parallel to the optical axis HA and the orientation of the z-axis points from the object plane 100 to the image plane 102. The y-axis runs parallel to the symmetry axis 12 of the object field 11. The object field 11 is shown in FIG. The orientation of the y-axis is from the optical axis HA to

Object field 11. Furthermore, in FIG. 3, for the first mirror S1 N unit vectors n and drawn ^after _1, which indicate the direction of the main beam CR before and after reflection on the first mirror. The main beam CR starts from an object point on the axis of symmetry 12 in the middle of the object field 11 shown in FIG. 2 and extends to the image field. The result for the other mirrors S2 to S8

Unit vectors in an analogous manner.

The system is centered on the optical axis HA and on the image side, i.e. in the image plane 102 telecentric. Image-side telecentricity is understood to mean that the main beam CR is at an angle of close to or approximately 90 ° to the

Image plane 102 meets. The main beam CR is reflected on the fourth mirror S4 in such a way that it runs away from the optical axis.

As a characteristic variable C; the following inequalities result for the mirrors: C ^ O, C ₂ <0, C ₃ > 0, C ₄ <0, C ₅ <0, C ₆ > 0

C ₇ <0, C ₈ > 0. The characteristic quantities are defined as the scalar product between the unit vector x in the direction of the x-axis and the vector product of a unit vector n _j ^before having the direction of the th i-to mirror the incident principal ray, and a unit vector ni ^after which the direction of the main beam reflected at the i-th mirror, that is

C _j = x ^• (n _j ^or xni ^πach ),

Are defined. The size C _j clearly shows whether one is on one

The main beam CR incident on the mirror is reflected in the positive or negative y direction, it being important to note whether the main beam CR is incident from the direction of the object plane 100 or from the direction of the image plane 102. It holds that C _j > 0 when the main beam strikes the mirror from the direction of the object plane 100 and in the direction of the negative y-

Axis is reflected. C; <0 applies if the main beam comes from the direction of the Object plane 100 strikes the mirror and is reflected in the direction of the positive y-axis. C;> 0 applies when the main beam hits the mirror from the direction of the image plane 102 and is reflected in the direction of the positive y-axis, and C _j <0 applies when the main beam hits the mirror from the direction of the image plane 102 and in the direction the negative y-

Axis is reflected.

In order to keep the light losses and the coating-induced wavefront aberrations within the mirror system as low as possible, the angle of incidence of the main beam CR is the central one

Field point on the respective mirror surface in the exemplary embodiment according to FIG. 3 is less than 26 °. The angles of incidence of the main radiator of the central field point are shown in Table 1 below:

Table 1: Angle of incidence of the main beam of the central field point for the embodiment according to. Figure 3

The 8-mirror objective shown in FIG. 3 has an aperture of NA = 0.4 on the image side and a scan slot width of 1 mm. The following measures were taken to minimize the angle of incidence on the individual mirrors: The main beam angle on the object 100 is minimized, the Objective aperture NAO = 0.1 This minimizes the angle of incidence on the first mirror. The maximum main beam angle on the object is only 6.1 ° with the specified object-side numerical aperture NAO of 0.1 and is thus significantly smaller than the maximum main beam angle of 13 ° on the object according to US Pat. No. 5,686,728.

The physical aperture is located on the second mirror S2. This allows a minimal separation of the beams in the front part of the lens, which reduces the angles of incidence to S1, S2 and S3. Furthermore, this has the effect that the useful area of S3 lies directly below the optical axis and almost mirror image of the useful area S1, in contrast, for example, to the 8-mirror lens shown in US Pat. No. 5,686,728 for wavelengths> 126 nm. This measure also reduces the angles of incidence on S4 and S5, since the distance of the beam from the optical axis between S4 and S5 becomes minimal. The useful areas of the individual mirror segments are shown in FIGS. 4A-4H. 4A is the useful area on mirror S1, in FIG. 4B the useful area on mirror S2, in FIG. 4C the useful area on mirror S3, in FIG. 4D the useful area on mirror S4, in FIG. 4E the useful area on mirror S5, in FIG. 4F the usable area on mirror S6, in

FIG. 4G shows the useful area on mirror S7 and in FIG. 4H the useful area on mirror S8 of the embodiment of an 8-mirror lens according to FIG. 3. As can be clearly seen from FIGS. 4A-4H, all useful areas of the mirrors S1 to S8 are free from shading or obscuration. This means that the beam path of a light bundle that passes through the lens from the object plane to the image plane and that maps the object field in the object plane into the image field in the image plane is free from shading or obscuration.

Furthermore, the radii of curvature become at least one of the mirrors

S2 to S4 selected as large, preferably larger than the overall length of the Projection objectives that drift distances are as large as possible and the beam paths from S1 to S2 and from S3 to S4 are almost parallel. The same applies to the beam paths from S2 to S3 and from S4 to S5. This also results in minimal separation of the beam.

The wavefront has a maximum fms value of less than 0.030 λ. The distortion is corrected to a maximum value of 1 nm via the scanning slot and has the form of a third degree polynomial, so that the dynamic distortion averaged over the scanning process is minimized. The

Image field curvature is corrected by taking the Petzval condition into account.

The exact data of the lens according to FIG. 3 are given in Code-V format in Table 2 in the Appendix.

FIG. 5 shows a second embodiment of an 8-mirror lens according to the invention with mirrors S1, S2, S3, S4, S5, S6, S7 and S8. The same components as in Figure 3 are given the same reference numerals. In particular, the x-axis, the y-axis and the z-axis as well as the characteristic quantities are defined as in the description of FIG. 3. For the characteristic quantities C _j , as defined in the description of FIG. 3, the following applies: 0 ^ 0, C ₂ <0, C ₃ <0, C ₄ > 0, C ₅ <0, C ₆ > 0, C ₇ > 0, C ₈ <0.

In order to achieve the manufacture of an 8-mirror objective with as little effort as possible and to ensure that it can be checked interferometrically, it is provided with this objective that the mirror be made spherical with the axis remote useful area. In order to keep the angles of incidence low and to force the beam in the direction of the optical axis and thus to limit the occurrence of useful areas remote from the axis, the embodiment according to FIG. 5 has two intermediate images Z1, Z2.

In the exemplary embodiment shown in FIG. 5 with two intermediate images, mirrors S1, S2, S3, S4, S5 as well as S7 and S8 are aspherical, while mirror S6 with the useful area furthest from the axis is spherical. The system has an aperture of NA = 0.4 on the image side. On the basis of the exemplary embodiment in FIG. 5, it is clear that the first intermediate image between S2 and S3 ensures that the first four mirrors S1, S2, S3, S4 have a useful area close to the axis. This cannot be guaranteed to this extent in the rear high-aperture lens part by the second intermediate image Z2 alone. The sixth mirror S6 therefore has an axis-distant useful area. If the mirror S6 is shaped as an asphere, it would be difficult to test with on-axis inspection optics. It is therefore spherically shaped in accordance with the invention. The angles of incidence of the main beam of the central field point are shown in Table 3 below:

Table 3: Angle of incidence of the main beam of the central field point for the exemplary embodiment according to FIG. 5

The useful areas of the individual mirror segments are shown in FIGS. 6A-6H. 6A is the useful area on mirror S1 in FIG

6B the useful area on mirror S2, in FIG. 60 the useful area on mirror S3, in FIG. 6D the useful area on mirror S4, in FIG. 6E the useful area on mirror S5, in FIG. 6F the useful area on mirror S6, in FIG. 6G the useful area on mirror S7 and in FIG. 6H the useful area on mirror S8 in accordance with the embodiment of an 8-mirror lens

Figure 5 shown. As can be clearly seen from FIGS. 6A-6H, all useful areas of the mirrors S1 to S8 are free from shading or obscuration. This means that the beam path of a light bundle that passes through the objective from the object plane to the image plane and that maps the object field in the object plane into the image field in the image plane is free from shading or obscuration.

The exact data of the objective according to FIG. 5 are shown in Code V format in Table 4 in the Appendix.

In both embodiments of the invention, the distances between the useful areas of the mirrors are advantageously kept small in order to generate small angles of incidence on the mirrors. Since these can be varied as required by appropriate scaling, these distances are given here by their size ratio to the overall length of the

Objective characterized. Table 5 shows the ratios of the distances between the useful areas divided by the overall length for all mirrors of the two exemplary embodiments:

Table 5: Distances between usable areas in relation to the overall length

FIG. 7 shows a projection exposure system for microlithography with an 8-mirror projection objective 200 according to the invention. The lighting system 202 can, as for example in EP 99106348.8 with the title "Lighting system, in particular for EUV lithography" or US serial no. 09 / 305,017 with the title "Illumination System particulary for EUV-Lithography", the disclosure content of which is fully incorporated in the present application. Such a lighting system comprises an EUV light source 204. The light from the EUV light source is collected by the collector mirror 206. The reticle 212 is illuminated with the aid of a first mirror 207 comprising raster elements - so-called field honeycombs - and a second mirror 208 comprising raster elements - so-called pupil honeycombs - and a mirror 210. The light reflected by the reticle 212 is imaged onto a carrier 214 comprising a light-sensitive layer by means of the projection objective according to the invention.

The invention thus for the first time specifies a projection lens with eight mirrors, which can be used in the EUV- Characterized wavelength range with λ = 11 to 30 nm and represents a compact projection lens that is particularly advantageous from a constructional and manufacturing point of view.

In addition, the projection lens presented is characterized by a high aperture with a shading-free or obscuration-free beam path. This leads to a shadow-free exit pupil.

Appendix: Tables 2 and 4

Table 2 (exemplary embodiment in FIG. 3)

ELEMENT RADXIS OU-K-HMESSH

NUMBER BXCKE AKT oa3acr INF 437.8550

51 A <1> -248.1062 2ia.Λαα2 REH. APSπURBTEND 91.-5283 0.0000

P. 2 A 25 193.6511 91.5770 RE.

S 3 A {3D -23Q. S805 133.7182 REFL

§4 AC4) 619.7098 ^• 320.2546 REFL

S 5 AC5) -169.8751 39S.39S8 RER.

S 6 A «202.7900 280.0000 EFL

-S 7 Aζ7) -293.6734 85.8365 REFL S 8 A 8) 326.9836 308.4810 REH.

FIG 3- F 55.0127

ASPHASIC CONSTANTS

CCURV) Y 4 6 8 10

Z a + CA) Y + (B} Y + CÖY + C∑ÖY

2 2 1/2

1 + 1-Q - MO CCURV) Y)

12 14 lfi 18 20

+ CΞ) Y + CF3Y + CG) Y + CH) Y + CQ

ASPHERE OSO A S O e F G 3

AC 1) -0.00123747 o.oooooo 2.31212E-09 -1.20823E-14 5.14612E-19 -3.39768E-23

2.27258E-27 -4.42780E-32 0.000006 + 00 Q.00Q00E + αθ Q.OOOOOE + 00

AC 2) 0.00016948 0.000000 -1.89814E-Q8 -2.29358E-13 -4.85183E-19 1.15028E-20

-4.21257E-24 S .69674E-28 o.αooαoE + oo Q.QQQOQE3-00 O.OQOOOε + 00

A 3) -0.00011398 o.ooαooα 6.S3150E-09 - * € 7300E-14 -1.83359E-13 5.15096E-23

-6-74819E-28 2.3848SE-32 0Λ3O0OOE + Q0 O.QOOOOE + 00 α.αooαα & fαo

A D 0.00052128 0.000000 1.3Q245E-09 2.58343E-15 -1.56164E-19 2.66615E-24

-3.14527S-29 2.αai97E-34 Q „0OQOOE * 00 O.QOOOOE + 00 O.OOOOOE + OO

AC 5) -0.00182108 0.000000 -1-.19681E-09 -5.88576E-1S 1.80550E-19 -2..S11-.3E-24

6.43317E-3Q 3.29849E-36 Q.0OO0QE + 00 o.αooooε + oo Q.OOOOOEfOO

A <6D -0.00107055 o.oooooo 2.53003E- B -1.45839E-12 7.48859E-17 -1.38858E-21

1.34840E-28 6.67275E-31 O. QOOαOE + OO o.αoθQQE + oα α.OOOOOE + O

AC 71 0.00584900 o.oooooo 5.51082E-O8 9.2S821S-13 -4.97336E-16 -6.35635E-20

-9.50902E-24 -1.7095SE-26 O. QQOQOE- OO Q.QOOOOE + 00 O.flOOOOE + 00

A 8) 0.0O289780 0.000000 4.07773E-10 3.17817E-15 2.239Q3E-2Q 1.620475-25-

1.06923E-3O 3.3937SE-35 α.αθOOOE-s-00 O.αOOQOE + QQ α. oooooE + oo

Table 4 (exemplary embodiment in FIG. 5)

ELEMENT RAÖIUS DIAMETER NUMBER S-PIECE ART

OBJECT INF 346.0618

APPEARING PANEL 174.4481 o.oooo-

≤.l ACD -596, 9226 174.6201 REH. • S2 AG) 1258.0118 302.7847 REFL S3 AC3} -560.6789 376.8895 REFL ■ 34 A J 502.0689 132-.7627 REFL

.SS AC55 -548.1913 251.5133 REFL S6 369.9668 C 1025.6939 825.4854 REH. t ⁷ A Ω -318.8926 93.3960 REH.

AC7) 349.2051 327.8538 REFL

IMAGE INF 56.5279

ASPHERE CONSTANTS OURVjY 4 S 8 10

2 = + CA} Y + CB} + COY + oDY

2 2 1/2 1 + l-Orf-K) CCURV) Y)

ASPHERIC CURV

A 1} -0.00077091 o.oooooo- 1.74667E-09 3-.88463E-14 2.31479E-19 -1.93103E-23

A 23 0.00069673 0.000000 -3.24472E-1Q 2.27H2E-15 7.69172E-21 7.043-0QE-26

AC 3) -0.00095818 0.000000 -8.63211E-11 -3.33704E-16 3.53842E-21 -2.98818E-26

A 4) 0.00013409 0.000000 5.05967E- 9 1.60649E-13 -2.50451E-18 -6.77033E-22

AC 5} 0.00174877 0.000000 -1.31567E-09 7.S14 ^Q 7E-15 -1.05690E-19 2.09186E-24

AC 6) 0.00451027 0.000000 7.10441E-08 ^• 3..63352E-12 -1.83737E-17 1.18169E-20

A 7) 0.00267159 Q.QOOQOO 2.02896E-10 2-44899E-15 2.34247E-20 2.04113E-2S

REFERENCE WAVELENGTH = 13.0 NM IMAGE DIMENSIONS FROM = -0.25

B-OJBSEX.ΪSE APERTUR = »0.40

Claims

Patent claims

1. Microlithography projection lens for EUV lithography with a wavelength in the range 10 - 30 nm for imaging an object field in an object plane into an image field in an image plane, characterized in that the microlithography projection lens has a first (S1), a second ( S2), a third (S3), a fourth (S4), a fifth (S5), a sixth (S6), a seventh (S7) and an eighth mirror (S8), with a beam path from the object plane to the image plane is that is free of obscuration.

2. Microlithography projection lens for EUV lithography according to claim 1, characterized in that the projection lens has a shadow-free exit pupil.

3. Microlithography projection lens for EUV lithography according to one of claims 1 to 2, characterized in that the projection lens has a diaphragm (B) between the object plane and the image plane.

4. Microlithography projection lens for EUV lithography according to claim 3, characterized in that the aperture (B) is circular or almost circular.

5. Microlithography projection system according to one of claims 3 to 4, characterized in that the aperture (B) is preferably arranged on or near the first mirror (S1) or on or near the second mirror (S2). Microlithography projection system according to one of claims 1 to 5, wherein the object field represents a segment of a ring field with an axis of symmetry which is perpendicular to an optical axis (HA), an object point being defined on the axis of symmetry in the middle of the object field, from which a main ray (CR) emanates, which runs to the image field, a right-handed coordinate system with an x, a y and a z axis being defined for the microlithography-lithography projection lens, with the z-axis running parallel to the optical axis and the orientation of the z-axis points from the object field to the image field, with the y-axis running parallel to the symmetry axis and the orientation of the y-axis from the optical axis to

Object field has, for each mirror i (i = 1 to 8) a characteristic size C _; which is ^the ^scalar product of a _unit vector -th mirror reflected main ray is defined, so

C _j = x • ( n _j ^v ° ^r xni ^naoh ),

where for the first mirror (S1) C ₁ > 0 applies, where for the second mirror (S2) C ₂ < 0 applies, where for the fifth mirror (S5) C ₅ < 0 applies, and where for the sixth mirror

(S6) C ₆ > 0 applies.

7. Microlithography projection lens according to one of claims 1 to 6, characterized in that the mirrors (S1, S2, S3, S4, S5, S6, S7, S8) are arranged centered with respect to an optical axis (HA).

8. Microlithography projection lens according to one of claims 1 to 7, characterized in that the image-side numerical aperture NA > 0.2.

9. Microlithography projection lens according to claim 8, characterized in that the image-side numerical aperture NA is <0.5.

10. Microlithography projection lens according to one of claims 1 to 9, characterized in that at least one intermediate image of the object field is formed in the beam path of the projection lens between the object field and the image field.

11. Microlithography projection lens according to one of claims 1 to 10, characterized in that the image field represents a segment of a ring field, the segment having an axis of symmetry and an extent perpendicular to the axis of symmetry and the extent being at least 20, preferably at least 25 mm.

12. Microlithography projection lens according to one of claims 1 to 11, characterized in that the sine of the angle of incidence of the main beam of the field point, which lies on the axis of symmetry and in the center of the object field, at Object field is smaller than twice the value of the object-side aperture NAO.

13. Microlithography projection lens according to one of claims 1 to 12, characterized in that the angle of incidence of the

Main ray of the field point, which lies on the axis of symmetry and in the center of the object field, is <45°, preferably <26°, in particular <20° on all mirrors.

14. Microlithography projection lens according to one of claims 1 to 13, characterized in that each of the eight mirrors (S1, S2, S3, S4, S5, S6, S7, S8) comprises a useful area onto which the rays from the lens Object passes through to the image, hits, and that for each mirror the distance of the useful area to the optical axis is at most 30%, preferably at most 25%, of the overall length.

15. Microlithography projection lens device according to one of claims 1 to 14, characterized in that the lens is telecentric on the image side.

16. Microlithography projection lens according to one of claims 1 to 15, characterized in that the first mirror (S1), the third mirror (S3) and the fourth mirror (S4) are concave.

17. Microlithography projection lens according to one of claims 1 to 16, characterized in that the sixth mirror (S6) and the eighth mirror (S8) are concave.

18. Microlithography projection lens according to one of claims 1 to 17, characterized in that the second mirror (S2) is concave.

19. Microlithography projection lens according to one of the claims

1 to 18 characterized in that the seventh mirror (S7) is convex and the eighth mirror (S8) is concave.

20. Microlithography projection lens according to one of the claims

1 to 19, characterized in that for the third mirror (S3) C ₃ > 0 applies, for the fourth mirror (S4) C ₄ < 0 applies, for the seventh mirror (S7) C ₇ < 0 applies, and for the eighth mirror (S8) C ₈ > 0 applies.

21. Microlithography projection lens according to one of claims 6 to 20, characterized in that the main beam (CR) reflected on the fourth mirror (S4) extends away from the optical axis (HA).

22. Microlithography projection lens according to one of claims 1 to 21, characterized in that the amount of the radius of curvature of at least one mirror is greater than the overall length of the projection lens.

23. Microlithography - projection lens, according to claim 22, characterized in that the amount of the radius of curvature of the second (S2) and/or the third (S3) and/or the fourth mirror (S4) is greater than the overall length of the projection lens.

24. Microlithography projection lens according to one of claims 1 to 23, characterized in that at least one drift path, which is formed between two mirrors of the lens, is longer than 70% of the overall length of the projection lens.

25. Microlithography projection lens according to one of claims 1 to 23, characterized in that the sum of the amounts of all

Drift distances between two mirrors of the lens that follow one another in the optical beam path and the distance from the object plane to the apex of the first mirror (S1) and the distance from the last mirror (S8) in the optical beam path to the image plane are at least 2.5 times that

Length of the projection lens is.

26. Microlithography projection lens according to one of claims 1 to 25, characterized in that the fifth mirror (S5) is concave.

27. Microlithography projection lens according to one of claims 1 to 26, characterized in that the sixth mirror (S6) is convex.

28. Microlithography projection lens according to one of claims 1 to 27, characterized in that exactly one intermediate image (Z^) is formed between the object field and the image field.

29. Microlithography projection system according to one of claims 1 to 19, characterized in that for the third mirror (S3) C ₃ < 0 applies, for the fourth mirror (S4) C ₄ > 0 applies, for the seventh mirror (S7) C ₇ > 0 applies, and for the eighth mirror (S8) C ₈ < 0 applies.

30. Microlithography projection lens according to one of claims 1 to 19 or claim 29, characterized in that the microlithography projection lens comprises three subsystems, the first subsystem images the object field in a first intermediate image of the object field, the second subsystem the first intermediate image of the object field into a second intermediate image of the object field and the third subsystem maps the second intermediate image of the object field into the image field.

31. Microlithography projection lens according to claim 30, characterized in that each subsystem comprises at least two mirrors.

32. Microlithography projection lens according to one of claims 30 to 31, characterized in that the first subsystem has the first and second mirrors (S1, S2), the second subsystem has the third, fourth, fifth and sixth mirrors (S3, S4, S5, S6) and the third subsystem includes the seventh and eighth mirrors (S7, S8).

33. Microlithography projection lens according to one of claims 1 to 19 or according to one of claims 29 to 32, characterized in that the sixth mirror (S6) is concave.

34. Microlithography projection lens according to one of claims 1 to 19 or according to one of claims 29 to 33, characterized in that the fifth mirror (S6) is convex.

35. Microlithography projection lens according to one of claims 1 to 34, characterized in that at least one of the eight mirrors (S1, S2, S3, S4, S5, S6, ^" S7, S8) is spherical.

36. Microlithography projection lens according to claim 35, characterized in that seven of the eight mirrors are aspherical and one mirror is spherical, the mirror being spherical whose useful area is at the greatest distance from the optical axis.

37. Microlithography projection lens according to claim 35, characterized in that the sixth mirror (S6) is spherical.

38. Projection exposure system, characterized in that the projection exposure system

- a source for generating EUV radiation,

- an illumination device which partially collects the radiation generated by the source and forwards it to illuminate a ring field, - a structure-bearing mask on a carrier system, this

Mask lies in the plane of the ring field,

- a projection lens according to one of claims 1 to 37, wherein this projection lens images the illuminated part of the structure-bearing mask into an image field, - a light-sensitive substrate on a carrier system, this light-sensitive substrate lying in the plane of the image field of the projection lens.

39. Method for chip production with a projection exposure system according to claim 38.