WO2010037434A1

WO2010037434A1 - Field facet mirror for use in an illumination optic of a projection illumination system for euv microlithography

Info

Publication number: WO2010037434A1
Application number: PCT/EP2009/004449
Authority: WO
Inventors: Adrian Staicu
Original assignee: Carl Zeiss Smt Ag
Priority date: 2008-09-30
Filing date: 2009-06-19
Publication date: 2010-04-08
Also published as: DE102008049585A1

Abstract

The invention relates to a field fact mirror for use in an illumination optic in a projection illumination system for EUV microlithography for transferring a structure of an object disposed in an object field into an image field. The field facet mirror has a plurality of field facts (18) having reflective surfaces (22). The reflective surfaces (22) of the field facets (18) are each formed by a face wall of a base facet body. The base facet body is bounded by two opposite spherical side walls. The result is a field facet mirror ensuring that high requirements are met for uniform object field illumination and simultaneously high EUV throughput.

Description

Field facet mirror for use in illumination optics of a projection exposure system for EUV microlithography

The invention relates to a field facet mirror for use in a lighting optical system of a projection exposure apparatus for EUV microlithography according to the preamble of claim 1. Furthermore, the invention relates to a method for producing such a field facet mirror, an illumination optics with such a field facet mirror, a lighting system with such Illumination optics, a projection exposure system with such an illumination system, a method for producing a microstructured or nanostructured component using such a projection exposure apparatus and a microstructured or nanostructured component produced by such a production method.

Such a field facet mirror is known from WO2007 / 128407A.

On the one hand, such field facet mirrors are intended to provide uniform illumination of the object field and, on the other hand, to lead the greatest possible share of the illumination light provided by an EUV light source to the object field. The facets of the field facet mirror receive a shape and an aspect ratio which are adapted to the object field to be illuminated. With regard to the simultaneous provision of a uniform object field illumination, in particular even if the illumination light provided by the EUV light source does not have a uniform intensity distribution over the illumination beam, and a high EUV throughput, there is still room for improvement in the known field facet mirrors. It is therefore an object of the following invention to further develop a field facet mirror of the type mentioned at the beginning in such a way that guaranteeing a uniform object field illumination with simultaneously high EUV throughput meets high requirements.

This object is achieved by a field facet mirror with the features specified in claim 1.

The facet main body according to the invention has two opposite spherical side walls, that is, two opposite side walls, which are designed as ball gap sections. According to the invention, it has been recognized that spherical sidewalls for a faceted base body offer the possibility of producing these sidewalls with processing methods which are known and tested from the manufacture of lenses. It is then possible to produce the facet main body with high accuracy of the spherical configuration of the side walls. This creates the possibility of an exact arrangement of adjacent facet main bodies to one another, which in turn leads to the possibility of a high occupation density of the field facet mirror in a main reflection plane. The main reflection plane of the field facet mirror is the plane in which the reflection surfaces of all facets of the field facet mirror are arranged.

A facet shape according to claim 2 is well adapted to a bow or partial ring shape of an object field to be illuminated.

Facets with side walls of the facet base body according to claim 3 can be packed on the one hand very tight and on the other hand allow a displacement of the two adjacent facet base relative to each other along the spherical surface of the two facing each other Side walls. This allows new degrees of freedom in the relative positioning of the field facets of the field facet mirror to each other.

Field facets according to claim 4 can be produced with one and the same processing tool for the production of the spherical side walls.

Facet mirrors according to claim 5 can be tightly packed on the one hand and on the other hand can be tightly packed between other field facets and yet tilt-adjusted around the center.

Field facets according to claim 6 can also be adapted to more exotic object field shapes or to other requirements, for example for intensity control of the illumination light.

At least two of the field facets can be tilted by more than 1 ° about an axis perpendicular to the base plane of the field facet mirror, ie perpendicular to the main reflection surface of the field facet mirror. The boundary condition that has been met so far, according to which the projection of field facet edges in the direction of a normal of a usually present carrier plate of the known field facet mirrors is identical, identical in terms of both size and shape as well as orientation, becomes thereby given up. Due to the new degree of freedom of the tilting, for example, a precompensation of a possible rotation of the images of individual field facets due to the imaging conditions relative to one another is achievable when they are superposed on the object field. Such a rotation of the faceted images results, as was recognized according to the invention, due to different paths of the illumination light guided channel-by-channel over the field facets through the illumination optics. This can also lead to ner variation of the magnification of the field facets come to the object field. When imaging onto the object field, the rotation of the facet images without precompensation leads to the undesired effect of the edge scattering of the object field illumination, since the images of the field facets superimposed on the object field no longer match the different real facet surfaces, especially on the edge. The field facets can be arranged side by side on a carrier plate. This support plate then runs usually parallel to the base plane of the field facet mirror. The tilted arrangement of the field facets represents a degree of freedom previously discarded due to supposed steric accommodation problems of the field facets, which in particular reduces or completely avoids a marginal scattering of the object field illumination observed in the previously known assignment geometries of field facets on the field facet mirror. By tilting the field facets to one another, this variation of the magnification can also be precompensated. The inventive degree of freedom of tilting the field facets about an axis perpendicular to the main reflection plane also facilitates a design in which tilt angles about axes that lie in the main reflection plane and to a large mismatch between the surface of the projection of the reflection surfaces tilted field facets on the Main reflection level on the one hand and the real reflection surface on the other hand lead, are avoided. It is then possible to use field facets having a more favorable aspect ratio relative to their occupancy with respect to occupancy of the field facet mirror, without resulting in disturbing edge-side scattering in the field illumination. In addition, effectively increases the degree of filling of the object field and thus the transportable optical conductivity. This is particularly true for sources with high light conductance or for lighting systems that offer differently filled lighting pupils without loss of light, important. In addition, a corresponding assignment of field facets tilted about the tilt axis perpendicular to the main reflection plane leads to the illumination angles predetermined by association with pupil facets of a pupil facet mirror for the possibility of ensuring intensity monitoring of the illumination light with minimized losses taking place at the edges of the object field. Such field facets can be used in a projection exposure apparatus, within which an object is displaced continuously or stepwise during a projection exposure in an object displacement direction.

A partial ring or arc shape of the field facets according to claim 8 allows a well-adapted illumination of a corresponding partial ring or arcuate object field. Such an object field form can be well imaged with a downstream projection optics of the projection exposure apparatus designed as mirror optics.

An arrangement of the tilting axis according to claim 9 ensures that tilting of the respective field facet only slightly changes the occupancy requirement of this field facet in the main reflection plane, since tilting leads at best to a slight deviation of the position of the arcuate or partially ring-shaped side edges of the facet Reflection surface leads. With a tilting about this tilting axis, practically only the end faces of the facet reflection surfaces leading or following in the circumferential direction about the pitch circle or arc shape are displaced.

Field facets according to claim 10 can be compared to field facets with lower partial ring thickness finished with lower production costs. Accompanied by this minimum partial ring thickness or with this minimum radial extent of the reflection surface of the respective field facet a strength of the respective field facet body which is easier to handle for the production of the field facets. In addition, the mutual relative shading of the field facets may be smaller with increasing width.

A further tilting degree of freedom according to claim 11 tilted field facets ensure a desired variability in the assignment of the field facets to pupil facets of a pupil facet mirror of an illumination optics of the EUV projection exposure apparatus. A predetermined and well-mixed assignment of the pupil facets of the pupil facet mirror assigned to the field facets is possible. As the tilting axis for the further tilting degree of freedom, an axis is selected whose tilt leads to the smallest possible deviation of a surface of a field facet projected onto the main reflection plane from the real reflection surface of the field facet.

A field facet mirror according to claim 12, for which various embodiments are specified according to the invention, increases the EUV light throughput within a projection exposure apparatus equipped with such a field facet mirror.

A manufacturing method according to claim 13 allows efficient production of field facet groups with side walls of adjacent facet bodies having the same radius of curvature.

A fabrication method according to claim 14 is adapted to facet block arrays of field facet mirrors. A manufacturing method according to claim 15 enables exact alignment of the combined within a facet block field facets.

The advantages of an illumination optics according to claim 16, an illumination system according to claim 17, a projection exposure apparatus according to claim 18, a manufacturing method according to claim 19 and a microstructured component according to claim 20 correspond to those which have already been discussed above with reference to the field facet mirror according to the invention.

An embodiment of the invention will be explained in more detail with reference to the drawing. In this drawing show:

1 shows schematically a projection exposure apparatus for the EUV

Microlithography, wherein an illumination optics in Meridi- onalschnitt is shown;

FIG. 2 shows a plan view of a field facet mirror of the illumination optics according to FIG. 1; FIG.

Fig. 3 shows schematically an enlarged detail according to detail

III in Figure 2;

Fig. 4 enlarges and perspectively a single one of the field facets of the field facet mirror of Fig. 2;

5 to 8 respectively in plan view different embodiments of group-wise arranged field facets for use in Feldfa cettenspiegel according to Figure 2 and examples of their adjacent arrangement;

9 shows a meridional section comparable to FIG. 1, rotated by 180 ° about an x axis and rotated by 90 ° about a z axis, at the edge of an object field illuminated by the illumination optics at the location of an intensity monitoring sensor;

10 shows a plan view of the object field, wherein the edge illumination thereof is highlighted for different illumination directions;

11 shows, in a representation similar to FIG. 10, a superimposition of the illumination of the object field on the basis of a predetermined test point pattern on the field facets in an arrangement according to FIG. 2;

FIG. 12 schematically shows a representation of two adjacent field facets arranged tilted relative to one another for representing possible tilt angles; FIG.

13 schematically shows a sequence in the production of a field facet mirror with field facets, wherein mutually facing side walls of adjacent facet main bodies are the same

Have radius of curvature.

FIG. 1 schematically shows a projection exposure apparatus 1 for EUV microlithography. The light source 2 is an EUV radiation source. This may be an LPP (Laser Produced Plasma) radiation source or a DPP (Discharge Produced Plasma) radiation source. The light source 2 emits EUV useful radiation 3 having a wavelength in the range between 5 nm and 30 nm. The useful radiation 3 is also referred to below as illumination or imaging light.

The illumination light 3 emitted by the light source is first collected by a collector 4. Depending on the type of light source 2, this may be an ellipsoidal mirror or a nested collector. After the collector 4, the illumination light 3 passes through a Zwischenfokusebene 5 and then strikes a field facet mirror 6, which will be explained in detail below. From the field facet mirror 6, the illumination light 3 is reflected toward a pupil facet mirror 7. By way of the facets of the field facet mirror 6 on the one hand and the pupil facet mirror 7 on the other hand, the illuminating light bundle is divided into a plurality of illumination channels, wherein each illumination channel is assigned exactly one facet pair with a field facet or a pupil facet.

A subsequent optical system 8 arranged downstream of the pupil facet mirror 7 guides the illumination light 3, ie the light of all illumination channels, to an object field 9. The field facet mirror 6, the pupil facet mirror 7 and the sequential optics 8 are components of an illumination optical system 10 for illuminating the object field 9. The object field 9 is arcuate or partially circular, as will be explained below. The object field 9 lies in an object plane 1 1 of a projection optics 12 of the projection exposure apparatus 1 arranged downstream of the illumination optics 10. A structure arranged in the object field 9 is mounted on a reticle (not shown in the drawing). The projection lens 12, ie on a mask to be projected, is imaged onto an image field 13 in an image plane 14 using the projection optics 12. At the location of the image field 13, a wafer, likewise not shown in the drawing, is arranged, onto which the structure of the reticle for producing a microstructured or nanostructured component, for example a semiconductor chip, is transmitted.

The follower optics 8 between the pupil facet mirror 7 and the object field 9 has three further EUV mirrors 15, 16, 17. The last EUV mirror 17 in front of the object field 9 is designed as a grazing incidence mirror. In alternative embodiments of the illumination optics 10, the sequential optics 8 may also have more or fewer mirrors or even be dispensed with altogether. In the latter case, the illumination light 3 is guided by the pupil facet mirror 7 directly to the object field 9.

To facilitate the representation of positional relationships, an xyz coordinate system is used below. In FIG. 1, the x direction runs perpendicular to the plane of the drawing into it. The y-direction runs in the figure 1 to the right and the z-direction is in the figure 1 down. Insofar as a Cartesian coordinate system is likewise used in FIGS. 2 et seq., This in each case spans the reflection surface of the illustrated component. The x-direction is then in each case parallel to the x-direction in FIG. 1. An angular relationship of the y-direction of the individual reflection surface to the y-direction in FIG. 1 depends on the orientation of the respective reflection surface.

FIG. 2 shows the field facet mirror 6 more in detail. This has a total of four columns Sl, S2, S3, S4, which are numbered from left to right in Figure 2, arranged individual field facets 18. The two middle columns S2, S3, are separated by a space 19, which extends in the y-direction and has a constant x-Aussteckung. The installation space 19 corresponds to a far-field shadowing of the illumination light beam, which is structurally conditioned by the structure of the light source 2 and the radiator 4. The four facet slits Sl to S4 each have a y-propagation which ensures that all four facet slits S 1 to S 4 lie within a circularly limited far field 20 of the illumination light 3. With the boundary of the far field 20, the edge of a support plate 21 for the field facets 18 coincides.

Reflecting surfaces 22 of the field facets 18 have, with respect to a projection on the xy plane, that is to say with respect to a main reflection plane of the field facet mirror 6, a congruent arc or partial ring shape which is similar to the shape of the object field 9.

The object field 9 has an x / y aspect ratio of 13/1. The x / y aspect ratio of the field facets 18 is greater than 13/1. Depending on the embodiment, the x / y aspect ratio of the field facets 18 is 26/1, for example, and is usually greater than 20/1.

Overall, the field facet mirror 6 has 416 field facets 18. Alternative embodiments of such field facet mirrors 6 may have numbers of field facets 18 ranging from a few tens to, for example, a thousand.

The reflection surfaces 22 of the field facets 18 have a displacement in the y direction of about 3.4 mm. The extent of the field facets 18 in the y direction is in particular greater than 2 mm. The totality of all 416 field facets 18 has a packing density of 73%. The packing density is defined as the sum of the illuminated reflection surfaces 22 of all field facets 18 in relation to the surface illuminated on the carrier plate 21 as a whole.

FIG. 3 shows an enlarged detail of the field facet mirror 6 in an end region of the facet slit S1. Adjacent ones of the field facets 18 are arranged tilted by more than 1 ° about an axis which is perpendicular to the main reflection plane of the field facet mirror 6, ie parallel to the z-axis in FIG.

This is shown in FIG. 2 using the example of the second field facet 18 ₂ in the facet column S ₂ from below in comparison to the third field facet 18 ₃ in the column S 4 from below. These two field facets 18 ₂ , 18 ₃ are tilted relative to one another about an axis 23, which is perpendicular to the plane of the drawing of FIG. 2, ie perpendicular to the main reflection plane of the field facet mirror 6, by a tilt angle Kz of approximately 2 °. A larger tilt angle Kz is possible. This causes the field facet 18 ₂ over the field facet I8 ₃ on the left edge, ie in the negative x direction, while the field facet 18 ₃ over the field facet 18 ₂ by the same amount at the right edge, ie in the positive x direction , Corresponding projections between adjacent field facets 18 can be seen in the detail enlargement of FIG. The tilt angles Kz between adjacent ones of the field facets 18 vary in the range between ± 2.5 °.

The tilting axes 23, by means of which the tilt angle Kz of respectively adjacent field facets 18 is defined relative to one another, lie centrally between the two Ring centers, which are assigned to these two partially annular field facets 18. The adjacent field facets 18 are thus tilted relative to each other about the axis 23, which coincides to a good approximation with the ring centers. The tilting of adjacent field facets 18 relative to one another about the axis 23 defined by the position of the respective ring centers of these field facets 18 is also referred to below as tilting Z. This tilt Z is in each case associated with a tilt angle Kz.

FIG. 4 shows details of the structure of one of the field facets 18. In the x-direction, the reflection surface 22 has an extension of approximately 60 mm. The facet base 24 continues away from the reflection surface 22 in the manner not shown in FIG. 4.

The reflection surface 22 carries a reflectivity-enhancing multilayer (multilayer) coating with alternating molybdenum and silicon layers.

The facet base 24 is of two substantially perpendicular to the y-axis, opposing spherical side walls 27, 28 convex / concave, so convex on one side and concave on the other side, bounded. The two side walls 27, 28 are thus formed as spherical surface sections. The side wall 27 facing the observer of FIG. 4 is convex and the opposite side wall 28 facing away from the observer of FIG. 4 is concave.

If one limits oneself to such a configuration of a facet main body 24, in which the side walls 27, 28 are spherical surfaces displaced in parallel, then projections of the reflection surfaces 22 of such facet main bodies 24 are on a base plane xy, which are represented by the arrangement tion of the field facets 18 is clamped next to each other, limited by parallel shifted pitch circles. The direction of the radially extending parallel displacement of the inner pitch circle defined by the concave side wall 28 to the outer pitch circle defined by the convex side wall 27 is individual for each of the field facets 18. An angle between these parallel shift directions and the y-axis corresponds to the respective tilt angle Kz.

The reflection surface 22 is designed as one of a total of four end walls of the facet main body 24. The reflection surface 22 may be flat or, according to given imaging specifications, curved, e.g. spherical, aspherical or free-form surface.

FIG. 4 shows a further tilting possibility of adjacent field facets 18 relative to one another, namely a tilting about a further tilting axis 25 parallel to the y axis, which is also referred to below as tilting Y. The tilting axis 25 runs parallel to a radius that is predetermined by the partial ring shape of the reflection surface 22 of the field facet 18. Due to the tilt Y, an angle deviation of a normal N results on the tilted reflection surface (see 22 ') in FIG.

Deviation by one tilt angle Ky is greatly exaggerated in FIG. Such a tilt Y can be used for the correct alignment of the reflection surface 22 of the respective field facet 18 or also in connection with the fabrication of the field facet mirror 6. In principle, it is possible to bring about an association of the respective field facet 18 with the associated pupil facet of the pupil facet mirror 7 via the tilt Y. As an alternative to tilting by a tilt angle Kz, as described in connection with FIG. 2, it is also possible to tilt the field facets 18 about a tilting axis 26 (see FIG. 4) which is also parallel to the z-axis ., Through a center 27a of the reflection surface 22 extends. Such tilting about the tilting axis 26 also leads to a tilting Z of the field facet 18.

FIG. 5 shows again schematically the tilting of adjacent field facets 18 about the respective tilt axes 23 defined for them. In the figure 5 sections of two adjacent columns Sx and Sy are shown. A total of four field facets 18i to 18 _{4 of} the column Sx, whose index is numbered from top to bottom, and a total of three field facets 18 ₅ to 18 _{7 of} the column Sy, whose index is also numbered from top to bottom, are shown in FIG. The field facets IS ₁ to 18 ₇ each again have a bow or partial ring shape.

Not all of the field facets 18] to 18 ₇ have a partial ring shape which is congruent with respect to their projection onto the main reflection plane xy of the field facet mirror 6. Thus, the field facet 18 ₂ covers a larger circumferential angle than the field facet IS ₁ arranged above it and has a greater extent in the x direction than the field facet 18 ₁ .

Mutually facing side walls 27, 28 of the field facets IS ₁ to 18 ₄ on the one hand and the field facets I 8 ₅ to 18 ₇ on the other hand each have the same radius of curvature.

Effective tilt angles Kz of the field facets 18 ₅ to 18 ₇ relative to one another are indicated in FIG. 5 by arrows 29. Three of the illustrated arrows 29 represent extensions of mid-symmetry radii of the respective field facet 18 ₅ to 18 ₇ represents. When respective center symmetry radius is the coincident radius of the concave or convex side walls 28, 27 of the field facet 18. This symmetry are radii in the drawing also by the reference numeral 29 marked. Also shown is a representative tilt axis 23.

The radii of curvature of some of the side walls 27, 28 of the field facets 18 are indicated in FIG. 5 by dashed circles.

FIG. 6 shows a further arrangement of adjacent field facet mirrors IS ₁ to 18 g within a facet column Sx. The spherically concave side wall 28 _{8 of} the field facet 18 ₈ shown at the bottom in FIG. 6 has a radius of curvature with the amount R ₁ , starting from a center 30 g. The spherically convex side wall 27g of the field facet 18g has a radius of curvature, also with the amount Ri, starting from a center 3O _7, 18 ₈ displaced in the positive y direction about a center thickness Mz of the facet base body 24 ₈ of the field facet to the center 3O ₈ is arranged. The center 3O ₇ is at the same time the center for the curvature of the concave spherical side wall 28 _{7 of} the field facet 18 ₇ , which is adjacent to the field facet 18 ₈ . Correspondingly, the other side walls 27i to 27 ₇ and 28] to 28 _{6 of} the other field facets 18i to 18g shown in FIG. 6 are also centered by centers 30] to 3O ₇ , which in each case are spaced from one another by the distance Mz from the positive y direction , Are defined.

In the embodiment according to FIG. 6, therefore, all side walls 27 ₁ to 27 ₈ , 28 ₁ to 28 _{8 have} the same radius of curvature Ri in magnitude. The side walls 27 _X , 28 _{X of} one of the facet mirrors 18 _X do not run concentrically in the embodiment according to FIG but the curvature Center points 3O _{x of} the two side walls 27 _X , 28 _{X of} the respective field facet mirror 18 _X are offset by the thickness of the reflection surface in the y-direction to each other.

FIG. 7 shows an alternative embodiment of field facets 18 arranged adjacent to a column S _x. In FIG. 7 four field facets 18i to 18 ₄ are shown one above the other. Two of the four field facets 18 shown in FIG. 7, namely the field facets 18 ₂ and 18 _4, have opposite side walls 27 ₂ , 28 ₂ and 27 ₄ , 28 ₄ , respectively, which have different radii of curvature R ₂ , Ri and are concentric. This is illustrated in more detail in FIG. 7 on the basis of the curvature of the side walls 27 ₂ , 28 _{2 of} the field facet 18 ₂ . The spherical concave side wall 28 ₂ has a radius of curvature of the amount Ri, starting from a center 3O ₂ . Starting from the same center 3O ₂ , the spherically convex side wall 27 _{2 of} the field facet 18 _{2 has} a radius of curvature with magnitude R ₂ , where R _{2 is} greater than Ri.

The other two field facets 18i shown in Figure 7, I8 ₃ have convex / concave side walls 27 _1, 28], and 27 _3, 28 _3, having various radii of curvature and are also not run concentrically. The arrangement of the facets 18 _X in the column Sx according to Figure 7 is such that in each case a Feldfacette 18 with concentrically designed side walls 27, 28 with a Feldfacette 18 with non-concentrically designed side walls 27, 28 also have different radii of curvature alternates.

Figure 8 shows a facet column Sx with field facets 18] to I8 ₄ , the opposite side walls 27, 28 are not designed concentric. In addition, centers over which the spherical side walls 27, 28 of the field facets 18 ₁ to 18 ₄ are defined according to Figure 8, occasionally offset in the x direction against each other. The reflection surfaces of the field facets 18 ₁ to 18 ₄ according to FIG. 8 in each case form partial rings with circumferentially varying y-strength. The y-strength of the reflection surface 22 of the field facet 18 ₄ in FIG. 8 increases continuously from left to right. The y-strength of the reflection surface 22 Feldfacette 18 ₂ in Figure 8 decreases continuously from left to right. Strengths of the field facets 18 ₁ to 18 ₄ in the y-direction are greatly exaggerated in FIG. Dashed lines in the figure 8 at an acute angle to the x axis extending lines are indicated, the tilt angle K _{z of} the field facets I8 ₁ , 18 ₂ and I8 ₃ represent.

Subsequently, lighting conditions in the area of the object field 9 and in the area of the object plane 11 will be explained with reference to FIGS. 9 to 11. In a detection plane 31, which is spaced from the object plane 11 by a distance Δz and lies in the beam direction of the illumination light 3 in front of the object plane 11, a detection device 32 with two EUV intensity sensors 33 is arranged, one of which is shown schematically in FIG. FIG. 9 shows an enlarged view of the edge of the object field 9 with positive x values.

For illumination of the object field 9, this can be used independently of an illumination angle within the numerical aperture NA of the illumination light 3 up to an x value X _n for the projection exposure. In the case of irradiation from direction -NA, in the sensor 33 shown in FIG. 9 the object field 9 shadows the object field 9 at x values which are greater than X _n . In order for the sensor 33 to still be acted upon by the beam direction -NA, the illumination light beam in the object plane 11 must be in x-direction. Direction an extension to x. Have _NA , where x is valid. _NA > X _n - So that illumination light 3, which arrives on the sensor 33 shown in FIG. 9 exactly in the z-direction (v _x = 0), an illumination must take place in the object plane 11 up to the value X ₀ , where: Xo > X. _NA - For illumination light incident at illumination angle + NA to reach sensor 33 shown in FIG. 9, illumination must take place in object plane 11 up to the x value x _{+ NA} , where: x _{+ NA} > X ₀ .

This is illustrated schematically in FIG. 10, which illustrates the illumination of the object field 9 beyond its edge at the values ± x _n . The corners of the object field illumination required in the x direction are shown with different dot representations, so that an illumination of the sensor 33 is ensured during the irradiations from the illumination directions -NA, V _x = 0 and + NA. The corners to the illuminating direction -NA, which have the smallest x distance to the usable field edge x _N for positive x values, have the largest x distance to the usable field edge -x _n for negative x values. At the corners to the illumination direction + NA this is exactly the opposite. The vertices to the illumination direction v _x = 0 have the same x distance to the usable field boundaries ± x _n on both sides of the object field 9.

Correspondingly, the field facets 18, the shape of which is superimposed on the object field 9, must have different extents in the x-direction depending on the angle of illumination, ie depending on their assignment to the respective pupil facets of the pupil acetate mirror 7, thus illuminating without loss of light as a function of the illumination angle each of the sensors 33 is just fulfilled. These necessary for the illumination of the sensors 33 different extents of the field facets 18th In the x-direction, certain asymmetry of the field facets 18 about the mean symmetry radius in the x-direction is achieved by an asymmetry targeted in the x-direction.

The illumination of the sensors 33 is thus achieved independently of the tilt angle Kz by adapting the azimuthal extent of the individual field facets 18 to both sides of the center symmetry radius 29. Measured by the center symmetry radius, the field facets 18 have an unequal x-extension on both sides and an unequal extent in the azimuthal direction about the respective tilting axis 23.

FIG. 10 illustrates in an insert the shape of the projection surfaces of such asymmetrized field facets 18a, 18b and 18c. All three field facets 18a to 18c have one and the same central symmetry radius 29. On the basis of this, the field facet 18a shown at the top in FIG. 10 sweeps to the right a larger azimuth angle than to the left. The field facet 18b shown in the middle in FIG. 10 passes over a larger azimuth angle to the left than to the right. The field facet 18c, which is shown at the bottom in FIG. 10, covers approximately the same azimuth angle in both directions. It should be noted that all three field facets 18a to 18c have the same tilt angle K _z .

FIG. 11 shows the superimposition of field facets 18 tilted relative to one another in the object field 9 with tilt Z. The superimposition of selected illumination points AP on the one hand in the region of the center of the respective field facet 18 and on the other hand in the region of the two sides of the field facets 18. FIG. 11 shows that identical positions are present on the different field facets 18 The arrangement of Figure 2 in the object field 9 in the region of the edges of the object field 9 are superimposed on the same positions.

An undesirable scattering, that is to say a deviation of the images of the same facet point of different facets in the object plane 11, does not take place.

This practically perfect superposition of the images of the field facets 18 in the object field 9 is a direct consequence of the fact that the projection surfaces of the reflection surfaces 22 of the different field facets 18 differ to the base plane xy in at least one of the following parameters: size of the reflection surfaces 22, shape of the reflection surfaces 22, orientation of the reflection surfaces 22. This difference leads to a precompensation, so that the individual image of the different reflection surfaces 22 in the object field 9 with the tilting, the resulting change in size and the resulting change in shape exactly to that shown in the figure 11 , perfect superposition of the field facets 18 in the object field 9 leads.

Figure 12 illustrates the possibilities of tilting two field facets 18i, 18 ₂ , whose side walls 27], 28 ₂ facing each other are arranged concentrically with the same radius of curvature. Any tilt on the surface defined thereby around a center O is possible. The associated tilting axis can run in any direction. It is only necessary that this tilting axis passes through the center O.

FIG. 13 schematically shows the sequence of a method for producing a facet mirror 6 in the manner of that of FIG individual green field facets 34 are produced with spherical side walls 27, 28 (see method step 35, in which a spherical grinding wheel 36 for producing the side walls 28 is indicated). In a method step 37, the individual raw field facets 34 are then assigned to a field facet stack 38, in which side walls 27, 28 of adjacent facet main bodies 24, which are assigned to one another in each case, have the same radius of curvature.

The individual reflection surfaces 22 of the raw field facets 34 are individually processed, ie optically polished and provided with the reflection multilayer.

After the assignment in step 37 and before the individual processing (step 39), a block of the raw field facets 34 is assembled in a method step 40 (step 40a) and then a base 41 of the block of the raw field facets 34 to a flat reference surface ground. After the individual processing 39, a grouping of the field facets 18 is then combined to form a facet block 42, wherein the reference surface 41 is applied to a planar counter surface 43 of a mirror holding structure 44.

As a result of the above-described arrangement variants of the field facets 18 of the field facet mirror 6, a transfer of the illumination light 3, which was reflected by the field facet mirror 6 to illuminate the object field 9, is maximized.

To produce a microstructured or nanostructured component, the projection exposure apparatus 1 is used as follows: First, the reticle and the wafer are provided. Subsequently, a structure projected on the reticle onto a photosensitive layer of the wafer with the aid of the projection exposure apparatus 1. By developing the photosensitive layer, a microstructure is then produced on the wafer and thus the microstructured component.

The projection exposure apparatus 1 is designed as a scanner. The reticle is thereby continuously displaced in the y-direction during the projection exposure. Alternatively, an embodiment as a stepper is possible in which the reticle is displaced stepwise in the y-direction.

In the arrangement of Figure 7 is a Kippjustage for example the

Field facet 18 ₂ possible without affecting the other field facets 18 _l5 18 _3, 18 ₄ must be shifted to the center 3O _2.

Claims

claims

1. field facet mirror (6) for use in an illumination optical system of a projection exposure apparatus (1) for EUV microlithography for

Transmission of a structure of an object arranged in an object field (9) into an image field (13), having a plurality of field facets (18) with reflection surfaces (22), characterized in that the reflection surfaces (22) of the field facets (18) are each by a End wall of a facet base body (24) are formed, wherein the facet base body (24) of two opposing spherical side walls (27, 28) is limited.

2. field facet mirror according to claim 1, characterized in that the facet base body of the two opposite, spherical side walls (27, 28) is convex / concave limited.

3. facet mirror according to claim 1 or 2, characterized in that the two mutually facing side walls (27 _X , 28 _y ) of adjacent facet base body (24) have the same radius of curvature and are concentric with each other.

4. facet mirror according to one of claims 1 to 3, characterized in that the two opposite side walls (27 _X , 28 _X ) of the facet base body (24) of the field facets (18) have the same radius of curvature (Ri) and not are executed concentrically.

5. facet mirror according to one of claims 1 to 3, characterized in that the two opposite side walls (27 _X , 28 _X ) of the facet base body (24) one of the field facets (18) have different radius of curvature (Ri, R ₂ ) and are concentrically executed.

6. facet mirror according to one of claims 1 to 3, characterized in that the two opposite side walls (27 _X , 28 _X ) of the facet base body (24) are not concentric, wherein the reflection surface (22) has a partial ring with varying in the circumferential direction Strength forms.

7. Facet mirror according to one of claims 1 to 6, characterized in that at least two of the field facets (18) about an axis (23; 26) perpendicular to a main Refiexionsfläche the Feldfacettenspiegels (6) are tilted by more than 1 degree to each other ,

8. field facet mirror according to claim 7, characterized in that projections of the field facets (18) on the main reflection plane have a partial ring shape.

9. field facet mirror according to claim 8, characterized in that the tilting axis (23) through a center of a ring on which the partial ring shape adjacent field facets (18) is arranged, and perpendicular to the plane predetermined by this ring (xy).

10. field facet mirror according to claim 8 or 9, characterized in that the field facets (18) in a projection on the main Reflection level, a thickness of the partial ring of at least 2 mm, in particular a thickness of 3.4 mm.

11. field facet mirror according to one of claims 8 to 10, character- ized in that at least two of the field facets (18) are tilted to each other about an axis (25) which extends parallel to a radius of the sub-ring.

12. field facet mirror (6) for use in a projection exposure apparatus (1) for EUV microlithography for transmitting a structure of an object arranged in an object field (9) into an image field (13) with a plurality of field facets (18), which are arranged such that a transfer of illumination light (3) for illuminating the object field (9) which has been reflected by the field facet mirror (6) is maximized.

13. A method for producing a field facet mirror (6) according to one of claims 1 to 12, comprising the following steps:

Producing individual raw field facets (34) with faceted basic bodies (24) with spherical side walls (27, 28),

Assigning the individual raw field facets (34) to a field facet stack (38), in which respective mutually associated side walls (27, 28) of adjacent facet base bodies (24) have the same radius of curvature, - individual processing (39) of the individual reflection surfaces (22) the field facets,

Assembling a group of the processed field facets (18) into a facet arrangement on the field facet mirror (6).

14. The method according to claim 13, characterized in that when assembling the arrangement of the field facets (18) a group-wise arrangement to Feldfacettenblöcken (42).

15. The method according to claim 13 or 14, characterized in that after the assignment and prior to individual processing a raw facet block composed (40a) and a base surface (41) of the raw facet block is ground to a flat reference surface.

16. Illumination optics with a field facet mirror (6) according to one of claims 1 to 12.

17. Illumination system with an illumination optics (10) according to claim 16 and an EUV light source (2).

18. Projection exposure system with an illumination system according to claim 17 and a projection optical system (12) for imaging the object field (9) in the image field (13).

19. Method for producing a microstructured component with the following method steps:

Providing a reticle and a wafer, projecting a structure on the reticle onto a photosensitive layer of the wafer with the aid of the projection exposure apparatus according to claim 18,

Creating a microstructure on the wafer.

20. A microstructured component produced by a method according to claim 19.