Imaging EUV optical unit for imaging an object field onto an image field

Abstract

The imaging EUV optical unit (10) serves to image the object field (5) onto the image field (11). The optical unit includes a plurality of mirrors (M1 to M6) for guiding EUV imaging light (16) having a wavelength shorter than 30 nm along an imaging beam path from the object field (5) to the image field (11). The plurality of mirrors includes at least two NI mirrors (M5, M6) and at least two GI mirrors (M1 to M4). The total transmittance of the plurality of mirrors (M1 to M6) is greater than 10%. This results in an imaging EUV optical unit with improved usability for EUV projection exposure apparatuses.

Description

Technical Field

[0001] This patent application claims the priority of German patent application DE102022206110.1, the content of which is incorporated herein by reference.

[0002] The present invention relates to an imaging EUV optical unit for imaging an object field into an image field. Furthermore, the present invention relates to an optical system having such an imaging optical unit, a projection exposure apparatus having such an optical system, a method for manufacturing a microstructured or nanostructured component using such a projection exposure apparatus, and a microstructured or nanostructured component manufactured by said method.

Background Art

[0003] Projection optical units of the type mentioned at the beginning are known from WO2018 / 010960A1, DE102015209827A1, DE102012212753A1, US Patent Application Publication No. 2010 / 0149509, and US Patent No. 4,964,706. The technical article "Polarization dependence of multilayer reflectance in the EUV spectral range" by F. Scholze et al., Proc. of SPIE, Vol. 6151 615137-1 to -8 discloses reflection data measured using an EUV reflectometer. DE102011075579A1 discloses a mirror and a microlithographic projection exposure apparatus having such a mirror. DE102015226529A1 discloses an imaging optical unit for imaging an object field into an image field, and a projection exposure apparatus having such an imaging optical unit.

Summary of the Invention

[0004] The object of the present invention is to develop an imaging EUV optical unit of the type described at the beginning so that its usability for an EUV projection exposure apparatus is improved.

[0005] According to the present invention, this object is achieved by an imaging EUV optical unit having the features specified in claim 1.

[0006] According to the present invention, it has been recognized that when using at least two NI mirrors and at least two GI mirrors in an imaging EUV optical unit, a design with a surprisingly high total transmittance of more than 10% becomes available. For a given light source power using EUV, a total transmittance of more than 10% enables an increased EUV throughput to the image field, and thus an improved exposure power. Alternatively, for a given required exposure power to the image field, it is possible to use a reduced power supply.

[0007] The imaging EUV optical unit may comprise at least four GI mirrors.

[0008] The total transmittance or overall transmittance of the imaging EUV optical unit may be greater than 11%, may be greater than 12%, may be greater than 13%, may be greater than 14%, and may also be greater than 15%. The overall transmittance of the imaging EUV optical unit may be at least 11.8%. The overall transmittance is usually less than 20% due to the number of mirrors and the individual transmittances of the imaging light guiding mirrors, which are usually 80% or less.

[0009] The imaging EUV optical unit may have a numerical aperture on the image side of less than 0.5, particularly less than 0.4. The numerical aperture on the image side may be greater than 0.25 and may be greater than 0.3.

[0010] The average wavefront aberration RMS may be less than 200 mλ (λ: wavelength of the light used), may be less than 100 mλ, and may also be less than 50 mλ. This wavefront aberration RMS is usually greater than 5 mλ.

[0011] The object field of the imaging EUV optical unit may be located on the object plane. The image field of the imaging EUV optical unit may be located on the image plane. The object plane may extend parallel to the image plane. The object plane may extend at an angle different from 0° with respect to the image plane.

[0012] The embodiment according to claim 2 in particular enables the use of the last mirror upstream of the image field, which defines the largest possible image-side numerical aperture using the relatively small angle of incidence present there and its mirror dimensions.

[0013] It has been found that the number of NI-GI mirrors according to claims 3 and 4 is an advantageous combination of high total transmittance and good imaging quality at the same time.

[0014] It has been found that the mirror pairs according to claim 5 complement each other in terms of their beam shaping effect. Specifically, the imaging EUV optical unit may comprise two sets of such GI mirror pairs, and their deflection effects cancel each other out such that the deflection effect of the second GI mirror pair has a subtractive effect with respect to the deflection effect of the first GI mirror pair. As a result, what can be achieved overall is that the total deflection effect of the NI mirrors on the imaging light is relatively small, and as a result, the angle between the object plane and the image plane is small, and the design in which the object plane preferably extends parallel to the image plane remains available.

[0015] The embodiment having the intersection region according to claim 6 enables the dispersion of the angle of incidence on the mirrors of the imaging EUV optical unit whose reflectivity is optimized, in particular with respect to the absolute angle of incidence on the mirror surface and / or with respect to the smallest possible incident angular bandwidth on the mirror. Such an embodiment in particular ensures a high-reflection coating on the mirror. Alternatively, such an intersection region may not be present in the case of the imaging EUV optical unit.

[0016] This applies in particular to the configuration of the intersecting imaging beam path section according to claim 7, which enables a small angle of incidence on the penultimate NI mirror.

[0017] The entrance pupil according to claim 8 enables the use of an illumination optical unit in the imaging light beam path upstream of the object field. In this case, the mirror of the illumination optical unit arranged at the entrance pupil becomes the last EUV light guiding mirror upstream of the object field. The loss of reflectivity due to an intervening transmission optical unit, which is required in other cases, is eliminated.

[0018] The advantages of the optical system according to claim 9 or 10, the projection exposure apparatus according to claim 11, the manufacturing method according to claim 12, and the microstructured or nanostructured component according to claim 13 correspond to the advantages already described above with respect to the projection optical unit according to the invention. An alternative illumination light input coupling is possible with the optical system according to claim 10, which can meet the corresponding installation space requirements. The EUV light source of the projection exposure apparatus can be embodied such that a use wavelength of 13.5 nm or less, less than 13.5 nm, less than 10 nm, less than 8 nm, less than 7 nm, for example 6.7 nm or 6.9 nm, occurs. Use wavelengths of less than 6.7 nm, in particular on the order of 6 nm, are also possible.

[0019] Specifically, a semiconductor component, for example a memory chip, can be manufactured using this projection exposure apparatus.

[0020] Hereinafter, at least one exemplary embodiment of the invention will be described based on the drawings.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

[0022] In the following description, first, the basic components of the microlithographic projection exposure apparatus 1 are described by way of example with reference to FIG. 1. The basic structure of the projection exposure apparatus 1 and its components should not be construed as restrictive here.

[0023] One embodiment of the illumination system 2 of the projection exposure apparatus 1 has, in addition to a light source or radiation source 3, an illumination optical unit 4 for illuminating an object field 5 within an object plane 6. In an alternative embodiment, the light source 3 may also be provided as a module separate from the rest of the illumination system. In that case, the illumination system does not include the light source 3.

[0024] The reticle 7 disposed in the object field 5 is exposed. The reticle 7 is held by a reticle holder 8. The reticle holder 8 is displaceable by a reticle displacement drive mechanism 9, particularly in the scanning direction.

[0025] For the purpose of explanation, a Cartesian xyz coordinate system is shown in FIG. 1. The x - direction extends perpendicular to the plane of the drawing and into the depth of the drawing. The y - direction extends horizontally, and the z - direction extends vertically. The scanning direction extends in the y - direction in FIG. 1. The z - direction extends perpendicular to the object plane 6.

[0026] The projection exposure apparatus 1 includes a projection optical unit or imaging optical unit 10. The projection optical unit 10 serves to image the object field 5 onto an image field 11 of an image plane 12. The image plane 12 extends parallel to the object plane 6. Alternatively, an angle different from 0° between the object plane 6 and the image plane 12 is also possible.

[0027] The structure on the reticle 7 is imaged onto a photosensitive layer of a wafer 13 disposed in the region of the image field 11 of the image plane 12. The wafer 13 is held by a wafer holder 14. The wafer holder 14 is displaceable by a wafer displacement drive mechanism 15, particularly in the y - direction. The displacement of the reticle 7 by the reticle displacement drive mechanism 9 on one hand and the displacement of the wafer 13 by the wafer displacement drive mechanism 15 on the other hand may be performed in synchronization with each other.

[0028] The radiation source 3 is an EUV radiation source. The radiation source 3 emits, in particular, EUV radiation 16, which is hereinafter also referred to as the used radiation or the illumination radiation. Specifically, the used radiation has a wavelength in the range of 5 nm to 30 nm. The radiation source 3 can be a plasma source, for example an LPP (laser-produced plasma) source or a GDPP (gas-discharge-produced plasma) source. It can also be a synchrotron-based radiation source. The radiation source 3 can be a free electron laser (FEL).

[0029] The illumination radiation 16 emitted from the radiation source 3 is focused by the condenser 17. The condenser 17 can be a condenser having one or more reflecting surfaces of an ellipsoid and / or a hyperboloid. The illumination radiation 16 can be incident on at least one reflecting surface of the condenser 17 at a grazing incidence (GI), i.e., an incident angle greater than 45°, or at a normal incidence (NI), i.e., an incident angle less than 45°. The condenser 17 can be structured and / or coated, firstly, to optimize its reflectivity for the used radiation and, secondly, to suppress stray light.

[0030] Downstream of the condenser 17, the illumination radiation 16 propagates through the intermediate focus of the intermediate focus plane 18. The intermediate focus plane 18 can correspond to the boundary between the radiation source module comprising the radiation source 3 and the condenser 17 and the illumination optical unit 4.

[0031] The illumination optical unit 4 comprises a first facet mirror 19. When the first facet mirror 19 is arranged on the surface of the illumination optical unit 4 that is optically conjugate to the object plane 6, this facet mirror is also referred to as the field facet mirror. The first facet mirror 19 comprises a number of individual first facets 20, which are hereinafter also referred to as field facets. Only some of these facets are illustrated exemplarily in FIG. 1.

[0032] The first facet 20 may be embodied as a macroscopic facet, in particular as a rectangular facet, or as a facet having an arcuate edge contour or an edge contour that is part of a circle. The first facet 20 may be embodied as a planar facet or, alternatively, as a facet having a convex or concave curvature.

[0033] As is known, for example, from DE102008009600A1, the first facet 20 itself may in each case be composed of a number of individual mirrors, in particular a number of micromirrors. The first facet mirror 19 may in particular be formed as a microelectromechanical system (MEMS system). For details, reference is made to DE102008009600A1.

[0034] The deflection mirror US is located between the intermediate focus of the intermediate focal plane 18 in the beam path of the illumination optical unit 4 and the first facet mirror 19. This deflection mirror US may be embodied as a planar mirror, but alternatively may also have a beam shaping effect.

[0035] In the beam path of the illumination optical unit 4, a second facet mirror 21 is arranged downstream of the first facet mirror 19. If the second facet mirror 21 is arranged at the pupil plane of the illumination optical unit 4, it is also referred to as a pupil facet mirror. The second facet mirror 21 may also be arranged at a distance from the pupil plane of the illumination optical unit 4. In that case, the combination of the first facet mirror 19 and the second facet mirror 21 is also referred to as a mirror reflector. Mirror reflectors are known from US Patent Application Publication No. 2006 / 0132747, EP1614008B1, and US Patent No. 6,573,978.

[0036] The second facet mirror 21 comprises a plurality of second facets 22. In the case of a pupil facet mirror, the second facets 22 are also referred to as pupil facets.

[0037] The second facet 22 may likewise be a macroscopic facet, which may have, for example, circular, rectangular, or hexagonal boundaries, or alternatively may be a facet composed of micromirrors. In this regard as well, DE102008009600A1 is likewise referred to.

[0038] The second facet 22 may have a planar reflective surface, or alternatively, a convex or concave curved reflective surface.

[0039] As a result, the illumination optical unit 4 forms a dual-facet system. This basic principle is also referred to as a fly-eye condenser (fly-eye integrator).

[0040] It may be advantageous not to arrange the second facet mirror 21 exactly in a plane optically conjugate to the pupil plane of the projection optical unit 10. Specifically, the pupil facet mirror 22 may be arranged to be inclined with respect to the pupil plane of the projection optical unit 10, for example, as described in DE102017220586A1.

[0041] The individual first facets 20 are imaged onto the object field 5 using the second facet mirror 21 and optionally using an imaging optical assembly in the form of a transmission optical unit not shown in FIG. 1.

[0042] The transmission optical unit may comprise exactly one mirror, but alternatively may also comprise two or more mirrors, which are arranged in series in the beam path of the illumination optical unit 4. The transmission optical unit may in particular comprise one or two normal incidence mirrors (NI mirrors) and / or one or two grazing incidence mirrors (GI mirrors). The illumination optical unit 4 has exactly three mirrors in the embodiment shown in FIG. 1, namely, downstream of the condenser 17, specifically, the deflection mirror US, the first facet mirror 19, and the second facet mirror 21.

[0043] The second facetted mirror 21 is the last beam shaping mirror or the actually last mirror for the illumination radiation 16 in the beam path upstream of the object field 5 to such an extent that a transmission optical unit downstream of the second facetted mirror 21 becomes unnecessary. An example of an illumination optical unit 4 without a transmission optical unit is disclosed in FIG. 2 of WO2019 / 096654A1.

[0044] The imaging of the first facetted mirror 20 onto the object plane 6 using the second facetted mirror 22 or using the second facetted mirror 22 and the transmission optical unit is mostly only an approximate imaging.

[0045] The projection optical unit 10 comprises a plurality of mirrors, namely six mirrors M1 to M6 (see FIG. 2), which are sequentially numbered according to their order in the beam path of the projection exposure apparatus 1.

[0046] In the example shown in FIG. 1, the projection optical unit 10 comprises six mirrors M1 to M6. Alternative examples with four, five or other numbers of mirrors Mi are equally possible.

[0047] The projection optical unit 10 is a non-obscured optical unit. None of the mirrors M1 to M6 includes a passage opening for the illumination radiation 16.

[0048] The projection optical unit 10 has an image-side numerical aperture of 0.33. Depending on the embodiment of the projection optical unit 10, the image-side numerical aperture may be in the range of, for example, 0.25 to 0.4. Depending on the embodiment, the projection optical unit 10 may also adopt different values for the image-side numerical aperture.

[0049] The reflective surface of mirror Mi is embodied as a freeform surface without an axis of rotational symmetry. Alternatively, the reflective surface of mirror Mi can be designed as an aspherical surface having exactly one axis of rotational symmetry of the reflective surface shape. Similar to the mirrors of the illumination optical unit 4, mirror Mi can have a highly reflective coating for the illumination radiation 16. These coatings can be designed, for example, as multilayer coatings having alternating layers of molybdenum and silicon. In particular, ruthenium coatings are also possible as coatings for mirrors with oblique incidence (GI mirrors).

[0050] The projection optical unit 10 provides a size reduction in a ratio of 4:1 in the x-direction, i.e., the direction perpendicular to the scanning direction y. Furthermore, the projection optical unit 10 provides an inversion of the image in this x-direction. Thus, the imaging scale β in the x-direction x is -4.00.

[0051] In the scanning direction y, the projection optical unit 10 also provides a size reduction of 4:1 here, but in this case without image inversion (β y = +4.00)

[0052] The projection optical unit 10 may also have an anamorphic design in an alternative embodiment. In that case, different imaging scales β in the x-direction and y-direction x , β y are provided. The two imaging scales β of the projection optical unit 7 x , β y are preferably (β x , β y ) = (+ / -4, + / -8).

[0053] Other imaging scales are likewise possible. Imaging scales with the same sign in the x-direction and y-direction are also possible.

[0054] The image field 11 has a spread of 26 mm in the x-direction and a spread of 2.5 mm in the y-direction.

[0055] The image field may also have a partial annular shape embodiment.

[0056] Alternatively, the image field may also have a rectangular embodiment.

[0057] The number of intermediate image planes in the x-direction and the number of intermediate image planes in the y-direction in the beam path between the object field 5 and the image field 11 are different in the case of the projection optical unit 10. In the yz-plane, the projection optical unit 10 has an intermediate image at the intermediate image plane 24 between the mirror M3 and the mirror M4, as shown in the meridional sectional view according to FIG. 2. Imaging scale β x When = -4.00, in the imaging direction perpendicular thereto, the projection optical unit 10 has no intermediate image. Examples of projection optical units with different numbers of such intermediate images in the x-direction and the y-direction are known from US Patent Application Publication No. 2018 / 0074303. Alternatively, the projection optical unit 10 may also be designed without intermediate images or with the same number of intermediate images in the x-direction and the y-direction.

[0058] To form an illumination channel for illuminating the object field 5 in each case, one of the pupil facets 22 is assigned to exactly one of the field facets 20 in each case. Specifically, this can create illumination according to the Koehler principle. The far field is decomposed into a number of object fields 5 using the field facets 20. The field facets 20 generate a plurality of intermediate focal images on the respective assigned pupil facets 22.

[0059] The field facets 20 are imaged onto the reticle 7 by the respective assigned pupil facets 22 so as to overlap each other for the purpose of illuminating the object field 5. The illumination of the object field 5 is particularly uniform as much as possible. Preferably, it has a uniformity error of less than 2%. The uniformity of the field can be achieved by superimposing different illumination channels.

[0060] The illumination of the entrance pupil of the projection optical unit 10 can be geometrically defined by the arrangement of the pupil facets. The intensity distribution of the entrance pupil of the projection optical unit 10 can be set by selecting an illumination channel, in particular a subset of the pupil facets that conduct light. The intensity distribution is also referred to as the illumination setting or illumination pupil filling.

[0061] Similarly favorable pupil uniformity in the regions of the plurality of sections of the illumination pupil of the illumination optical unit 4, which is illuminated as defined, may be achieved by redistribution of the illumination channels.

[0062] Further aspects and details of the illumination of the object field 5, in particular of the entrance pupil of the projection optical unit 10, will be explained below.

[0063] The projection optical unit 10 may in particular have a concentric entrance pupil. It may be achievable as in the embodiment of the projection optical unit 10 according to FIG. 2.

[0064] The projection optical unit 10 has an entrance pupil EP (see FIG. 1), which is located in the range of 1500 mm to 2000 mm upstream of the object field 5 of the beam path in both the x - direction and the y - direction, in particular in the range of 1800 mm to 2200 mm. The arrangement plane of this entrance pupil is shown as EP in FIG. 1. Thus, when the pupil facet mirror 21 is arranged approximately 2 m upstream of the object field 5 in the beam path of the illumination or imaging light 16, the pupil facet mirror 21 satisfies the position condition of "arrangement within the region of the entrance pupil of the projection optical unit".

[0065] The entrance pupil may also be inaccessible in the case of an alternative embodiment of the projection optical unit 10, and as a result, the arrangement plane of the pupil facet mirror 21 will be imaged onto the entrance pupil using further components of the illumination optical unit 4.

[0066] In principle, the entrance pupil of the projection optical unit 10 cannot be accurately illuminated using the pupil facet mirror 21. When imaging the projection optical unit 10 that images (image) the opening rays telecentrically to the center of the pupil facet mirror 21 on the wafer 13, the opening rays often do not intersect at a single point. However, it is possible to find an area where the distance between the required pair of opening rays is minimized. This area corresponds to the entrance pupil or an area in the real space conjugate thereto. Specifically, this area has a finite curvature.

[0067] The projection optical unit 10 may have entrance pupils with different postures in the tangential beam path and the sagittal beam path. In this case, imaging elements, particularly the optical component part of the transfer optical unit, must be provided between the second facet mirror 21 and the reticle 7. By using this optical element, the different positions of the entrance pupil in the tangential direction and the entrance pupil in the sagittal direction can be taken into account.

[0068] In the arrangement of the components of the illumination optical unit 4 shown in FIG. 1, the pupil facet mirror 21 is arranged to be inclined with respect to the object plane 5. The second facet mirror 21 is further arranged to be inclined with respect to the arrangement plane defined by the first facet mirror 19.

[0069] Further details regarding the projection optical unit 10 will be described later in this specification with reference to FIG. 2.

[0070] The projection optical unit 10 has two NI mirrors (mirrors for normal incidence; normal incidence mirrors), that is, the last two mirrors M5 and M6 in the imaging beam path of the projection optical unit 10. The imaging light 16 is incident on these two NI mirrors M5 and M6 at an incident angle of less than 45°. The maximum incident angle of the imaging light 16 incident on each NI mirror may be less than 40°, less than 35°, less than 30°, less than 25°, less than 20°, less than 15°, or less than 10°.

[0071] The other mirrors M1 to M4 of the projection optical unit 10 are GI mirrors (mirrors for oblique incidence, oblique incidence mirrors). These mirrors M1 to M4 have an incident angle of the illumination light 16 to the mirror larger than 45° in each case. The minimum incident angle incident on each GI mirror may be larger than 50°, may be larger than 55°, may be larger than 60°, may be larger than 65°, may be larger than 70°, may be larger than 75°, or may be larger than 80°.

[0072] Information regarding reflection by a GI mirror (oblique incidence mirror) can be found in WO2012 / 126867A. Further information regarding the reflectance of a NI mirror (normal incidence mirror) can be found in DE10155711A.

[0073] None of the mirrors M1 to M6 have a through aperture, and the mirrors are used in a reflection mode within a continuous region without a gap in each case.

[0074] FIG. 2 shows the reflection surfaces of the calculated mirrors M1 to M6. The used reflection surfaces of the mirrors M1 to M6 are supported in a known manner by a mirror body (not shown).

[0075] The total transmittance of the projection optical unit 10, which appears as the product of the respective reflectances of the mirrors M1 to M6 with respect to the illumination light 16 along the imaging beam path passing through the projection optical unit 10, is a value of 15.12% for the projection optical unit 10 according to FIG. 2. Thus, on average, each of the mirrors M1 to M6 has a reflectance of 73%.

[0076] The first two mirrors M1 and M2 in the imaging beam path of the projection optical unit 10 are a pair of consecutive GI mirrors, and their deflection effects are additive. Thus, the two subsequent mirrors M3 and M4 in the imaging beam path of the projection optical unit 10 are a pair of consecutive GI mirrors, and their deflection effects are additive. These two pairs, M1, M2 on one hand and M3, M4 on the other hand, have deflection effects that are opposite in meaning to each other. That is, the deflection effect of the second GI mirror pair M3, M4 has a subtractive effect on the deflection effect of the first GI mirror pair M1, M2.

[0077] In the yz plane, the first pupil plane of the projection optical unit 10 is located between the mirror M2 and the mirror M3 in the beam path of the imaging light. The second pupil plane in the yz plane is at the same location as the pupil plane of the xz plane, which is perpendicular to the yz plane, adjacent to the reflection of the imaging light 16 at the mirror M6 in the imaging beam path. In the case of the projection optical unit 10, the aperture can be restricted by an aperture stop, and the aperture stop can restrict the imaging beam path, especially on the edge side, and may be attached to the mirror M6. If necessary, internal obscuration may also be defined at the mirror M6 using an appropriate stop portion.

[0078] The y-direction offset between the central field point of the object field 5 and the central field point of the image field 11 is approximately 3570 mm in the case of the projection optical unit 10.

[0079] The z-direction distance between the mirror M5 and the image field 11 is 140 mm.

[0080] The distance between the object field 5 and the image field 11 is 2600 mm in a direction perpendicular to the object field.

[0081] The object plane 6 and the image plane 12 extend parallel to each other.

[0082] The entire projection optical unit 10 can be accommodated within a cube with edge lengths in the xyz directions of 860 mm, 4011 mm, and 1993 mm.

[0083] The imaging beam path of the projection optical unit 10 includes an intersection region 25 where two imaging beam path sections of the imaging beam path intersect. The first of these intersecting imaging beam path sections is the section between mirror M4 and mirror M5. The second of these intersecting imaging beam path sections is the section between mirror M6 and image field 11.

[0084] Mirrors M1 to M6 are coated with a coating that optimizes the reflectivity of mirrors M1 to M6 for imaging light 16. Particularly in the case of GI mirrors, this may be a lanthanum coating, a boron coating, or a boron coating with a top layer of lanthanum, or a ruthenium coating. Other coating materials, particularly lanthanum nitride and / or B4C, may also be used. For mirrors M1 to M4 for oblique incidence, for example, a coating containing a single layer of boron or lanthanum can be used. In particular, the high-reflection layers of mirrors M5 and M6 for normal incidence can be configured as multilayers, and the successive layers can be made of different materials. Alternating material layers can also be used. A typical multilayer can have 50 double layers, each made of a layer of boron and a layer of lanthanum. Layers containing lanthanum nitride and / or boron, particularly B4C, may also be used.

[0085] Table 1 below is a summary of the parameters of the projection optical unit 10. In addition to the data already described above, Table 1 also specifies the angle (5.20°) of the chief ray of the central field point with respect to the z-axis, as well as the usable étendue and the average wavefront aberration RS of the projection optical unit.

[0086]

Table 1

[0087] Tables 2a and 2b below are summaries of the parameters "maximum incident angle", "spread of the reflecting surface in the x direction", "spread of the reflecting surface in the y direction", and "maximum mirror diameter" of mirrors M1 to M6 of the projection optical unit 10.

Table 2

[0088]

Table 3

[0089] The four GI mirrors M1 to M4 have a minimum incident angle of the imaging light 16 of 66.6° and a maximum incident angle of 83.5°. The two NI mirrors M5 and M6 have a minimum incident angle of 2.9° and a maximum incident angle of 27.3°. The maximum incident angle is less than 10°, particularly less than 6°, at the last mirror M6.

[0090] The minimum incident angle is greater than 70°, and further greater than 73°, at the last two GI mirrors M3 and M4. The minimum incident angle is greater than 75° at the last GI mirror M4.

[0091] The mirror with the smallest spread of the reflection surface in the x direction is mirror M1, and its spread is less than 250 mm. The mirror with the smallest spread of the reflection surface in the y direction is mirror M5, with a spread of less than 240 mm. The spread of mirrors M3 and M5 in the y direction is less than 250 mm. All of the mirrors M1 to M6 have a spread of the reflection surface in the x / y direction greater than 200 mm.

[0092] The largest mirror is mirror M6, which is substantially circular and has a diameter of 860 mm.

[0093] The mirrors M1 to M6 are embodied as free-form surfaces that cannot be described by a rotationally symmetric function. Other embodiments of the projection optical unit 10 are possible in which at least one of the mirrors M1 to M6 is embodied as a rotationally symmetric aspherical surface. It is also possible for all of the mirrors M1 to M6 to be embodied as such aspherical surfaces.

[0094] The free-form surface can be described by the following free-form surface formula (Equation 1).

Equation

[0095] The following applies to the parameters of this formula (1).

[0096] Z is the sagittal height of the freeform surface at points x, y, where x 2 +y 2 =r 2 Here, r is the distance from the reference axis (x = 0; y = 0) of the freeform surface equation.

[0097] In the freeform surface equation (1), C1, C2, C3... represent the coefficients of the freeform surface series expansion as powers of x and y.

[0098] In the case of a conical base region, c x , c y are constants corresponding to the vertex curvature of the corresponding aspherical surface. Thus, c x = 1 / R x (1 / RDX) and c y = 1 / R y (1 / RDY) apply. k x and k y (CCX, CCY) each correspond to the conic constant of the corresponding aspherical surface. Thus, equation (1) describes a bi-conical freeform surface.

[0099] Alternative freeform surfaces can be generated from a rotationally symmetric reference surface. Such a freeform surface for the reflective surface of a mirror in the projection optical unit of a microlithographic projection exposure apparatus is known from U.S. Patent Application Publication No. 20070058269.

[0100] Alternatively, the freeform surface can also be described using a two-dimensional spline surface. This example is a Bézier curve or a non-uniform rational basis spline (NURBS). As an example, the two-dimensional spline surface can be described by a grid of points in the xy plane and associated z values, or by these points and the associated gradients. Depending on each type of spline surface, the completed surface is obtained by interpolation between grid points using, for example, polynomials or functions having specific properties with respect to its continuity and differentiability. An example of this is an analytical function.

[0101] The optical design data of the reflecting surfaces of the mirrors M1 to M6 of the projection optical unit 10 can be collected from still other tables below.

[0102] Table 3 specifies the surface origin of each mirror surface and the coordinates of an area of the object field 5 with respect to the xyz coordinate system of the image field 11.

[0103] The first column specifies the distance of each mirror or the object field 5 from the coordinate origin at the center of the image field 11 in the y direction (first column) and the z direction (second column).

[0104] The other columns of Table 3 further specify the tilt values of the respective surfaces of the mirrors M1 to M6 or the object field 5 with respect to the x-axis, y-axis, and z-axis. In the embodiment according to FIG. 2, neither the object field 5 nor the image field 11 is tilted with respect to the x-axis and extends parallel to each other.

[0105] Table 4 tabulates, for each of the mirrors M1 to M6, the parameters RDX, RDY, CCX, CCY, and the values of the coefficients C1, C2, C3... of the series expansion of the freeform surface according to the above formula (1) arranged according to the powers of x and y.

[0106] Table 5 tabulates the reflectivities of the mirrors M1 to M6 and the total transmittance or overall transmittance of the projection optical unit 10, which is 15.4584%.

[0107] Table 6 shows the aperture data of the aperture stop AS of the projection optical unit 10 arranged in the area of the mirror M6. This aperture is defined by a polygon, and its x and y values are specified in Table 6.

[0108] A mirror with different signs for the values RDX and RDY has a saddle point type or a minimax basic shape. [Table 4]

[0109] [Table 5]

[0110] [Table 6-1] [Table 6-2] [Table 6-3] [Table 6-4] [Table 6-5] [Table 6-6] [Table 6-7] [Table 6-8]

[0111] [Table 7]

[0112]

Table 8

[0113] Figure 3 shows a further embodiment of the projection optical unit or imaging optical unit 27, which can be used in the projection exposure apparatus 1 instead of the projection optical unit 10 of the embodiment according to FIG. 2. With respect to FIGS. 1 and 2, in particular with respect to FIG. 2, the components and functions corresponding to those already described above are denoted by the same reference numerals, and the detailed description thereof is omitted.

[0114] Starting from the object field 5, the beam path of the projection optical unit 27 first passes through three GI mirrors M1, M2, and M3, whose deflection effects are added, so that a total deflection effect slightly larger than 90° is produced on the imaging light 16. Over the subsequent path of the beam path, the imaging light 16 is reflected by three further GI mirrors M4, M5, and M6, whose deflection effects are opposite to the deflection effects of the mirrors M1 to M3, and their deflection effects are added. This total deflection effect of the mirrors M4 to M6 is approximately 60°. Thus, the projection optical unit 27 has a total of six GI mirrors.

[0115] Thereafter, the imaging light 16 is reflected by the NI mirror M7 and subsequently by the last NI mirror M8, and the NI mirror M8 determines the numerical aperture on the image side of the projection optical unit 27. None of the mirrors M1 to M8 includes a passage aperture for the imaging light 16.

[0116] The pupil plane that can be used for the aperture stop AS is located between the mirrors M7 and M8 in the beam path of the imaging light 16.

[0117] Similar to the case of the projection optical unit 10, the second last mirror of the projection optical unit 27 is located on the opposite side of the beam path section between the last aperture limiting mirror (M6 / M8) and the image field 11 with respect to the other mirrors of the projection optical units 10 and 27 within the beam path of the imaging light 16 (mirror M5 of the projection optical unit 10; mirror M7 of the projection optical unit 27).

[0118] The following table is a summary of the parameters and optical design of the projection optical unit 27. Regarding its structure, these tables correspond to those already described above with respect to FIG. 2.

Table 9

[0119]

Table 10

[0120]

Table 11

[0121]

Table 12

[0122]

Table 13

[0123]

Table 14-1

Table 14-2

Table 14-3

Table 14-4

Table 14-5

Table 14-6

Table 14-7

Table 14-8

Table 14-9

[0124]

Table 15

[0125] FIG. 4 shows a further embodiment of the projection optical unit or imaging optical unit 28, which can be used in the projection exposure apparatus 1 instead of the projection optical unit 10 of the embodiment according to FIG. 2. With respect to FIGS. 1 to 3, in particular with respect to FIGS. 2 and 3, the components and functions corresponding to those already described above are denoted by the same reference numerals, and the detailed description thereof is omitted.

[0126] In the beam path of the imaging light 16 downstream of the object field 5, the projection optical unit 28 first has three GI mirrors M1, M2, M3, and the deflection effects thereof are added so that a total deflection effect slightly exceeding 90° is produced. This is followed by two further GI mirrors M4 and M5, and the deflection effects thereof are further added and are opposite to the deflection effects of the GI mirrors M1 to M3. The total deflection effect of the GI mirrors M4 and M5 is approximately 75°. This is followed by two further NI mirrors M6 and M7, and their basic arrangement is equivalent to the two penultimate mirrors of the projection optical units 10 and 27 described above. Thus, the projection optical unit 28 has five GI mirrors M1 to M5 and two NI mirrors M6 and M7.

[0127] In the case of the projection optical unit 28, the chief ray CR of the central field point starting from the object field 5 proceeds in another half space extending to the right of the perpendicular N in FIG. 4 in relation to the perpendicular N of this central field point in the object field 5 and also initially in relation to the plane (xN) formed by each perpendicular N and the axis parallel to the x-axis.

[0128] As a result, first, the illumination / imaging beam path section 28a between the last component 28b of the illumination optical unit 4 shown as a mirror in FIG. 4 and the object field 5, and second, the illumination / imaging light beam path section 28c between the first two mirrors M1 and M2 of the projection optical unit 28 will intersect within the intersection region 28d. Thus, the illumination / imaging beam path section 28a between one of several last components of the illumination optical unit 4 (component 28b) and the object field 5, and the illumination / imaging beam path section 28c (the beam path section between the mirrors M1 and M2) between the object field 5 and one of several first components of the imaging optical unit 28 intersect within the intersection region 28d.

[0129] In addition, compared to the other mirror M2ff, the mirror M1 is located in the other half-space in relation to this xN plane.

[0130] The following table is a summary of the parameters and optical design of the projection optical unit 28. Regarding its structure, these tables correspond to those already described above with respect to FIG. 2.

Table 16

[0131]

Table 17

[0132]

Table 18

[0133]

Table 19

[0134]

Table 20

[0135]

Table 21-1

Table 21-2

Table 21-3

Table 21-4

Table 21-5

Table 21-6

Table 21-7

Table 21-8

Table 21-9

Table 21-10

Table 21-11

[0136]

Table 22

[0137]

Table 23

[0138] FIG. 5 shows a further embodiment of the projection optical unit or the imaging optical unit 29, which can be used in the projection exposure apparatus 1 in place of the projection optical unit 10 of the embodiment according to FIG. 2. With respect to FIGS. 1 to 4, in particular with respect to FIGS. 2 to 4, components and functions corresponding to those already described above are denoted by the same reference numerals, and detailed description thereof is omitted.

[0139] First, there are five GI mirrors M1 to M5, and then there are two further NI mirrors M6 and M7. The basic structure of the projection optical unit 29 corresponds to the basic structure of the projection optical unit 28 according to FIG. 4. The projection optical unit 29 has a significantly larger spread in the y direction than the projection optical unit 28. As a result, in the case of the projection optical unit 29, in particular, the y-direction distance between the mirror M3 and the mirror M4 is significantly larger than in the case of the projection optical unit 28 according to FIG. 4.

[0140] The following table is a summary of the parameters and optical design of the projection optical unit 29. Regarding its structure, these tables correspond to those already described above with respect to FIG. 2.

Table 24

[0141]

Table 25

[0142]

Table 26

[0143]

Table 27

[0144]

Table 28

[0145]

Table 29-1

Table 29-2

Table 29-3

Table 29-4

Table 29-5

Table 29-6

Table 29-7

Table 29-8

Table 29-9

[0146]

Table 30

[0147]

Table 31

[0148] FIG. 6 shows a further embodiment of the projection optical unit or the imaging optical unit 30, which can be used in the projection exposure apparatus 1 instead of the projection optical unit 10 of the embodiment according to FIG. 2. With respect to FIGS. 1 to 5, in particular with respect to FIGS. 2 to 5, the components and functions corresponding to those already described above are denoted by the same reference numerals, and detailed description thereof is omitted.

[0149] The basic mirror structure of the projection optical unit 30 corresponds to the basic mirror structure of the projection optical unit 28 according to FIG. 4, particularly with regard to the arrangement of the GI mirrors. The substantial difference is that in the projection optical unit 30 according to FIG. 6, the second last NI mirror M6 is arranged on the same side as the other mirrors M1 to M5 in relation to the partial beam path section between the last mirror M7 and the image field 11. Therefore, the projection optical unit 30 according to FIG. 6 does not have an intersection region corresponding to the intersection region 25 existing in the projection optical units according to FIGS. 2 to 5.

[0150] In the case of the projection optical unit 30, the chief ray CR of the central field point starting in the object field 5 proceeds in another half-space extending to the right of the perpendicular N in FIG. 6 in relation to the perpendicular N of this central field point in the object field 5 and also initially in relation to the plane (xN) formed by each perpendicular N and the axis parallel to the x-axis.

[0151] As a result, firstly, the illumination / imaging beam path section 30a between the last component 30b of the illumination optical unit 4 shown as a mirror in FIG. 6 and the object field 5, and secondly, the illumination / imaging light beam path section 30c between the first two mirrors M1 and M2 of the projection optical unit 30 will intersect within the intersection region 30d. Thus, the illumination / imaging beam path section 30a between one of the last components (component 30b) of the illumination optical unit 4 and the object field 5 and the illumination / imaging beam path section 30c (the beam path section between the mirrors M1 and M2) between the object field 5 and one of the first components of the imaging optical unit 30 intersect within the intersection region 30d.

[0152] In addition, compared to the other mirror M2ff, the mirror M1 is located in the other half-space in relation to this xN plane.

[0153] The following table is a summary of the parameters and optical design of the projection optical unit 30. Regarding its structure, these tables correspond to those already described above with respect to FIG. 2.

Table 32

[0154]

Table 33

[0155]

Table 34

[0156]

Table 35

[0157]

Table 36

[0158]

Table 37-1

Table 37-2

Table 37-3

Table 37-4

Table 37-5

Table 37-6

Table 37-7

Table 37-8

Table 37-9

[0159]

Table 38

[0160]

Table 39

[0161] FIG. 7 shows a further embodiment of the projection optical unit or imaging optical unit 31, which can be used in the projection exposure apparatus 1 in place of the projection optical unit 10 of the embodiment according to FIG. 2. With respect to FIGS. 1 to 6, in particular with respect to FIGS. 2 to 6, the components and functions corresponding to those already described above are denoted by the same reference numerals, and the detailed description thereof is omitted.

[0162] In the case of the projection optical unit 31, the chief ray CR of the central field point starting in the object field 5 proceeds in another half space extending to the right of the perpendicular N in FIG. 7 in relation to the perpendicular N of this central field point in the object field 5 and also initially in relation to the plane (xN) formed by this perpendicular N and the axis parallel to the x-axis.

[0163] As a result, firstly, the illumination / imaging beam path section 32 between the last component 33 of the illumination optical unit 4 shown as a mirror in FIG. 7 and the object field 5, and secondly, the illumination / imaging light beam path section 34 between the first two mirrors M1 and M2 of the projection optical unit 31 intersect in the intersection region 35. Thus, the illumination / imaging beam path section 32 between one of some of the last components of the illumination optical unit 4 (component 33) and the object field 5 intersects with the illumination / imaging beam path section 34 between the object field 5 and one of some of the first components (mirrors M1 and M2) of the imaging optical unit 31 in the intersection region 35.

[0164] In addition, compared to the other mirror M2ff, the mirror M1 is located in the other half space in relation to this xN plane.

[0165] In other respects, the projection optical unit 31 according to FIG. 7 has a correspondence relationship with the projection optical unit 28 according to FIG. 4 with respect to the arrangement of the GI mirrors M1 to M5, and has a correspondence relationship with the projection optical unit 30 according to FIG. 6 with respect to the arrangement of the subsequent NI mirrors M6 and M7.

[0166] According to the embodiments of the projection optical unit described above, the projection optical unit may have a different number of NI mirrors and / or GI mirrors, for example exactly two GI mirrors or exactly three GI mirrors. Three or more NI mirrors, for example three or four NI mirrors, are also possible.

[0167] To manufacture microstructured or nanostructured components, the projection exposure apparatus 1 is used as follows. First, a reflective mask 7 or a reticle and a substrate or wafer 13 are provided. Thereafter, the structure on the reticle 7 is projected onto the photosensitive layer of the wafer 13 using the projection exposure apparatus 1. Subsequently, the microstructures or nanostructures on the wafer 13, and thus the microstructured components, are manufactured by developing the photosensitive layer.

Claims

1. An imaging EUV optical unit (10;27;28;29;30;31) for imaging an object field (5) onto an image field (11), - A plurality of mirrors (M1-M6; M1-M7; M1-M8) are provided to guide EUV imaging light (16) with a wavelength shorter than 30 nm along the imaging beam path from the object field (5) to the image field (11), - The plurality of mirrors (M1-M6; M1-M7; M1-M8) include at least two NI mirrors (M5, M6) and at least two GI mirrors (M1-M4; M1-M6; M1-M5), - An imaging EUV optical unit (10; 27; 28; 29; 30; 31) having a total transmittance of the plurality of mirrors (M1-M6; M1-M7; M1-M8) greater than 10%.

2. The imaging EUV optical unit according to claim 1, characterized in that the last two mirrors (M5, M6; M7, M8; M6, M7) in the imaging beam path are NI mirrors.

3. The imaging EUV optical unit according to claim 1 or 2, characterized in that the imaging optical unit comprises exactly two NI mirrors (M5, M6; M7, M8; M6, M7).

4. The imaging EUV optical unit according to claim 1 or 2, characterized in that the imaging optical unit comprises exactly four GI mirrors (M1 to M4), exactly five GI mirrors (M1 to M5), or exactly six GI mirrors (M1 to M6).

5. The imaging EUV optical unit according to claim 1 or 2, characterized in that the imaging optical unit comprises at least one pair of consecutive GI mirrors (M1, M2; M3, M4; M1-M3; M4-M6; M4, M5) in which the deflection effects are added together.

6. The imaging EUV optical unit according to claim 1 or 2, characterized in that two imaging beam path sections intersect within an intersection region (25) between two consecutive mirrors (M3, M4; M6, M7; M5, M6) and / or between the mirrors (M6; M8; M7) and the image field (11) of the EUV optical unit (10).

7. The two intersecting imaging beam path sections are - The imaging beam path section, -- The mirrors (M4; M6; M5) upstream of the second-to-last NI mirror (M5; M7; M6) in the imaging beam path, -- The second to last mirror (M5; M7; M6) in the imaging beam path and The imaging beam path section between, and - Imaging beam path section between the last mirror (M6; M8; M7) in the imaging beam path and the image field (11) The imaging EUV optical unit according to claim 2, characterized in that it is the same as described above.

8. The imaging EUV optical unit according to claim 1 or 2, characterized by an entrance pupil in the imaging beam path upstream of the object field (5).

9. - An illumination optical unit (4) for illuminating the object field (5) with imaging light (16), - The imaging optical unit (10) according to claim 1 or 2 and An optical system equipped with [the following features].

10. The illumination / imaging beam path section (28a; 30a; 32) between one of the last few components (28b; 30b; 33) of the illumination optical unit (4) and the object field (5), The illumination / imaging beam path section (28c; 30c; 34) between the object field (5) and one of the first several components (M2) of the imaging optical unit (28; 30; 31) is, The optical system according to claim 9, characterized in that it intersects within the intersection region (28d; 30d; 35).

11. A projection exposure apparatus comprising the optical system described in claim 9 and an EUV light source (3).

12. - A method step of providing a reticle (7) and a wafer (13), - A method of projecting the structure on the reticle (7) onto the photosensitive layer of the wafer (13) using the projection exposure apparatus described in claim 9, - A method for generating a microstructure or nanostructure on the wafer (13) A method for manufacturing structural components, including [a specific component].

13. A structural component manufactured according to the method of claim 12.

Images