DE102005033564A1 - Projective lens for e.g. optical interferometer, has correction surface compensating non-rotation symmetrical aberration, where plane is pupil plane or pupil near plane of lens, and another plane is field plane or field near plane of lens - Google Patents

Abstract

The lens has an optical unit (114) that is angularly vertical to a primary optical axis and defines a plane perpendicular to the axis. A correction surface (111a) is arranged in another plane and non-rotationally symmetrical to the axis, and partially compensates non-rotation symmetrical aberration. One of the planes is a pupil plane or pupil near plane of the lens, and another plane is field plane or field near plane of the lens. Independent claims are also included for the following: (1) a micro lithographic projection illumination arrangement including a projective lens (2) a method for lithographically producing a micro-structured component (3) a micro-structured component produced according to a method for producing a micro-structured component (4) a digital projection system including a projective lens (5) an optical interferometer including a projective lens.

Description

The This invention relates to an optical system, and more particularly to imaging systems in a microlithographic projection exposure apparatus, a digital projection system or an optical interferometer.

In Such optical systems often require optical surfaces in the optical system Light passage at an angle to such as the realization of a semitransparent mirror, typically arranged at an angle of 45 ° to the beam path becomes. Thus the predominant Light path before and after such an inclined surface by optical elements can extend to the primary optical axis of the system are rotationally symmetric, are conventionally made of two prisms composite beam splitter cube (so-called "beam splitter cubes ") used. However, these have a large volume of material in the light path, what in terms of the cost of the material (e.g., calcium fluoride), Absorption losses and caused by material inhomogeneities Aberration is disadvantageous.

As an alternative to beam splitter cube is for example US 4,953,960 the use of obliquely arranged (also typically at an angle of 45 °) arranged beam splitter plates. However, these have the disadvantage that they introduce non-rotationally symmetric aberrations into the system. The primary aberrations caused by such an inclined optical element are coma and astigmatism.

In order to correct the image defect caused by an inclined element, US 5,490,013 proposed a combination of four plane plates which are each rotated in pairs by ± 45 ° about two axes of rotation which are perpendicular to the optical axis of the basic system and perpendicular to each other (the basic system comprising the system without these inclined plane plates). The special application of this correction principle in a lithography objective is described, for example, in US Pat US 5,251,070 described.

Furthermore, for example US 6,611,383 Systems are known in which a beam splitter in the vicinity of the aperture diaphragm or a pupil is formed such that the two planar surfaces of the beam splitter form an angle. The rotation of the two surfaces relative to each other is carried out about the same axis about which each of these two surfaces is rotated with respect to the beam path.

The above approaches each achieve a partial or complete correction of the primary non-rotationally symmetric Image defects. Especially with extremely high-opening lithography lenses not only cause the primary aberrations caused by decentration, but also higher-order aberrations an impairment the picture quality.

US 6,590,718 B2 discloses in a reduction objective, in particular for microlithography, inter alia, the use of a polarization beam splitter plate, which is wedge-shaped for the correction of low-order astigmatism.

to Compensation of remaining higher-order aberrations has a surface this polarization beam splitter plate targeted aspherization ( "Targeted aspherization ") which are non-rotationally symmetric, but symmetrical to the meridional plane of the system is formed.

Out US 6,597,511 B2 It is known that in an illumination system of a microlithographic projection exposure apparatus which illuminates an off-axis object field for a catoptric or catadioptric projection objective in the reticle plane, one of the optical elements of the illumination system is aligned asymmetrically with respect to the optical axis for the purpose of telecentricity adaptation, this optical element being located in the vicinity of the field. or reticle plane or a plane conjugate thereto is arranged. This optical element may be formed as a decentered spherical lens, as a rotationally symmetrical aspherical lens or with a freeform surface.

Of Furthermore, free-form surfaces are also used in polarization-influencing optical elements made of birefringent or optically active Material exist and a thickness-dependent polarization-rotating As in the case of optically active materials, e.g. in PCT application PCT / EP2005 / 000320 (registered on 14.01.2005).

Out US 2004/0075894 A1 is known in a catadioptric reduction objective a multirange lens ("multi-region lens "), which are arranged immediately adjacent to two folding mirrors and is formed with areas of different radii of curvature such that they have a first lens area associated with the one folding mirror and a second lens area associated with the other folding mirror wherein the refractive power of these two lens areas is different is.

Out US 6,268,903 B1 For example, a method of adjusting an optical projection apparatus is known in which, based on the measurement of aberrations of the projection device together with a correction element located at a predetermined position, the surface shape of the correction element suitable for correcting these aberrations is calculated, whereupon the correction element is processed accordingly and again is arranged at its predetermined position.

task It is the object of the present invention to provide inclined optical elements also in precise optical systems can be used, which only a very small Tolerance regarding have non-rotationally symmetric aberrations, such as in a microlithography projection exposure apparatus, a digital projection system or an optical interferometer.

These Task becomes according to the characteristics the independent one claims solved.

• – eine primäre optische Achse, welche eine von einer Mehrzahl der optischen Elemente des optischen Systems aufgespannte Symmetrieachse ist;
• – wenigstens ein zu dieser primären optischen Achse schrägstehendes optisches Element, durch dessen Schnittpunkt mit der primären optischen Achse eine erste, zur primären optischen Achse senkrechte Ebene definiert wird; und
• – wenigstens eine in einer zweiten Ebene angeordnete Korrekturfläche, welche durch das schrägstehende optische Element verursachte, nicht-rotationssymmetrische Abbildungsfehler wenigstens teilweise kompensiert und nicht-rotationssymmetrisch zu der primären optischen Achse ist;
• – wobei eine Ebene von der ersten und der zweiten Ebene eine Pupillenebene oder pupillennahe Ebene des optischen Systems ist und die andere Ebene von der ersten und der zweiten Ebene eine Feldebene oder feldnahe Ebene des optischen Systems ist.

An optical system according to the invention comprises:

• A primary optical axis which is an axis of symmetry subtended by a plurality of the optical elements of the optical system;
• At least one optical element inclined to said primary optical axis, by the intersection of which with the primary optical axis a first plane perpendicular to the primary optical axis is defined; and
• At least one correction surface arranged in a second plane, which is caused by the oblique optical element, is at least partially compensated for non-rotationally symmetric aberrations and is non-rotationally symmetrical to the primary optical axis;
• Wherein one plane of the first and second planes is a pupil plane or pupil-near plane of the optical system and the other plane of the first and second planes is a field plane or near-field plane of the optical system.

in the For the purposes of the present application, the term "primary optical Axis "designating the Reference axis used, with respect the one "inclined optical element "tilted is. Under "primary optical Axis "is included in the context of the present application, the majority of the optical elements to understand the symmetry axis formed. In other words, the "primary optical Axis "one each straight line or a succession of straight line sections, through the centers of curvature the rotationally symmetrical optical components runs.

The Formulation that the one level of the first and the second Plane a pupil plane or pupil-near plane of the optical system is and the other level of the first and the second level one Field level or near-field level of the optical system is in the Meaning of the present application so that according to the invention also deviations from the exact positioning in a pupil plane or a Field level, ie "pupil-near" or "field-near" positioning, possible and are encompassed by the present application. It should under a pupil-close Level "one level be understood, whose distance from the nearest pupil plane along the primary optical axis maximum 20% of the distance from the nearest Field level along the primary optical axis is. Accordingly, under a "near field Level "one level be understood, whose distance from the nearest field level along the primary optical axis maximum 20% of the distance from the nearest Pupil plane along the primary optical axis is.

In the context of the invention, it has surprisingly been found that a compensation of the non-rotationally symmetric aberrations introduced by an inclined element into the system need not occur as close as possible to the origin of these aberrations or to a location optically conjugated to this origin. Rather, it is advantageous if the non-rotationally symmetric aberration used to compensate for the non-rotationally symmetric imaging aberration caused by an inclined optical element is then arranged adjacent to a field plane if the oblique optical element is located near a pupil plane. On the other hand, the said correction surface then arranged at least immediately adjacent to a pupil plane when the inclined optical element is located in a field plane. In this case, it has been found, in particular, that it is also possible to compensate for aberrations up to high order by using a single non-rotationally symmetrical correction surface.

With other words, as a place for one is the non-rotationally symmetric Aberration compensating correction surface substantially a "Fourier transformed Place "or a Fourier-transformed Plane (i.e., pupil plane to field plane or field plane to pupil plane) advantageous.

• – eine primäre optische Achse, welche eine von einer Mehrzahl der optischen Elemente des optischen Systems aufgespannte Symmetrieachse ist;
• – wenigstens ein zu dieser primären optischen Achse schrägstehendes optisches Element, durch dessen Schnittpunkt mit der primären optischen Achse eine erste, zur primären optischen Achse senkrechte Ebene definiert wird; und
• – wenigstens eine in einer zweiten Ebene angeordnete Korrekturfläche, welche durch das schrägstehende optische Element verursachte, nicht-rotationssymmetrische Abbildungsfehler wenigstens teilweise kompensiert und nicht-rotationssymmetrisch zu der primären optischen Achse ist;
• – wobei die zweite Ebene im Wesentlichen eine Fouriertransformierte Ebene zu der ersten Ebene ist.

According to another approach, therefore, an optical system according to the invention comprises:

• A primary optical axis which is an axis of symmetry subtended by a plurality of the optical elements of the optical system;
• At least one optical element inclined to said primary optical axis, by the intersection of which with the primary optical axis a first plane perpendicular to the primary optical axis is defined; and
• At least one correction surface arranged in a second plane, which is caused by the oblique optical element, is at least partially compensated for non-rotationally symmetric aberrations and is non-rotationally symmetrical to the primary optical axis;
• - wherein the second plane is substantially a Fourier transformed plane to the first plane.

there either the first level can essentially be a field level and the second level will be essentially a pupil level, or the first level can be essentially one pupil level and the second Level essentially be a field level.

erfüllt. Hierbei ist vorzugsweise das schrägstehende optische Element derart im Abbildungsstrahlengang angeordnet, dass für das Verhältnis einer Strahlhöhe y₁ eines Hauptstrahls eines radial maximal von der primären optischen Achse entfernten Feldpunktes zu einer Strahlhöhe y₂ eines Randstrahls des Feldpunktes auf der primären optischen Achse die Bedingung |y₂/y₁| > 2, bevorzugt |y₂/y₁| > 3, und noch bevorzugter |y₂/y₁| > 5 erfüllt ist. Bei dieser pupillennahen Positionierung bewirkt das schrägstehende optische Element (z.B. eine Strahlteilerplatte) hauptsächlich Fehler in der Pupillenabbildung des optischen Systems, die teilweise auch durch die Freiheitsgrade rotationssymmetrischer optischer Wirkflächen kompensiert werden können, sowie nicht-rotationssymmetrische Verzeichungs- und Telezentriefehler, die besonders gut durch eine erfindungsgemäße Korrekturfläche in der Nähe der Objekt- oder einer Zwischenbildebene korrigierbar sind.According to a preferred embodiment, in the case where the beam splitter plate is arranged close to the pupil, the non-rotationally symmetric correction surface is arranged in the imaging beam path in such a way that the condition D ₁ <D _{2 is} satisfied, where D _{1 is} the diameter of a light beam used for the optical imaging, which originates from an object point arranged in the center of the object field, at which non-rotationally symmetrical correction surface is, and where D _{2 is} the total diameter used for the optical imaging on the non-rotationally symmetrical correction surface. Preferably, this is the condition

Fulfills. In this case, the oblique optical element is preferably arranged in the imaging beam path in such a way that for the ratio of a beam height y _{1 of} a main beam to a beam height y _{2 of} an edge beam of the field point on the primary optical axis, the field | y is predominantly radially remote from the primary optical axis ₂ / y ₁ | > 2, preferably | y ₂ / y ₁ | > 3, and more preferably | y ₂ / y ₁ | > 5 is fulfilled. In this pupil near positioning causes the inclined optical element (eg a beam splitter plate) mainly errors in the pupil image of the optical system, which can be partially compensated by the degrees of freedom of rotationally symmetric optical active surfaces, as well as non-rotationally symmetric distortion and telecentricity errors, which are particularly well Correction surface according to the invention in the vicinity of the object or an intermediate image plane can be corrected.

According to one Another approach is preferably the inclined optical element arranged in the imaging beam path such that in the first Plane the marginal rays of a for the optical image used light beam, which of a in the center of the object field arranged object point goes out, in Are substantially parallel to each other. Preferably, the Sine of the angle between the respective marginal ray and the primary optical Axis smaller in size than 0.2, preferably less than 0.1.

According to one preferred embodiment indicates the non-rotationally symmetric correction area the only symmetry is a mirror symmetry with respect to a meridional plane of the imaging system.

According to one another preferred embodiment is non-rotationally symmetric Correction surface one Freeform surface.

The non-rotationally symmetric correction surface can according to a another preferred embodiment in terms of primary optical axis a 4-fold Have symmetry.

According to a further embodiment, the non-rotationally symmetrical correction surface is a To roidfläche or has a toric basic shape. Such a toric basic shape causes a good correction of the primary astigmatism caused by the beam splitting plate, since the different cutting widths in the meridional and sagittal sections can be influenced separately. Especially in applications or systems with lower accuracy requirements (eg digital projector), the correction surface can be a purely toric surface.

The non-rotationally symmetric correction surface can in particular be described by a polynomial winding according to coordinates in two coordinate directions lying perpendicular to the reference axis (eg x and y), which has a maximum occurring order for which the condition 4 <n <∞ is satisfied. The term "maximum occurring order" of the polynomial winding is understood to mean the highest exponent sum occurring in the development terms of the polynomial winding (ie the sum of the exponent in the powers with respect to the coordinates x and y) at which the polynomial winding terminates (ie one with the Term x ³ y ⁴ breaking polynomial winding has the maximum occurring order 7).

According to one another embodiment are at least two non-rotationally symmetric in an imaging system correction surfaces available. This is particularly advantageous for manufacturing reasons, for example, there are two free-form surfaces with smaller deviations make easier from a rotationally symmetric basic shape let as a freeform surface with greater deviation, since the IBF process (IBF = "Ion Beam Figuring ") only relatively small material removal allowed.

According to one embodiment is the sloping optical element a beam splitter plate.

The inclined optical element can e.g. also a plan wedge with two with each other including an angle plane surfaces be.

In An application of the invention comprises the inclined optical element a coating on that for incident light one from the polarization state or from the angle of incidence dependent Transmission causes, or a coating, one of the polarization state or dependent on the angle of incidence delay between mutually perpendicular polarization states causes.

Also in such applications, it is necessary that the relevant Plate as support surface at least an area having a significantly different from zero angle to the beam path forms. The weakening and / or delay can be used in particular to the homogeneity of the illuminance in the picture to improve, for example, due to apodization effects impaired can be. Apodization effects can due to polarization influences occur when imaging with high-open bundles, or you can the sequence of different lengths the passed glass paths for different field bundles be. In the first case, the plane plate with the coating is preferably near the Pupil of the optical system arranged. In the second case is the Planplatte preferably near the Object or an intermediate image arranged, and the coating is preferably additional laterally structured so that the attenuation differences due different glass paths can be compensated just.

In Another application of the invention is the inclined optical element for compensation of non-rotationally symmetric aberrations of the imaging system to the beam path decentered and / or order an axis perpendicular to the Meridionalebene axis rotatable.

One Another application of the invention is based on that a optical system due to manufacturing errors of surfaces, defects at the mechanical contact surfaces, static or thermally-induced refractive index inhomogeneities in the glass etc. non-rotationally symmetric May have errors leading to non-rotationally symmetric errors in the Lead picture.

These aberrations can be selectively influenced, ie in particular be reduced by rotating a tilted plate arranged in the optical system by small angular amounts by a predetermined zero position, or by an inclined plate by forces acting outside the optically used range (by actuators in means of FEM calculations simulatable manner) selectively deformed. By setting external forces, the plate can then be deliberately "bent", whereby a deflection symmetrical with respect to the plate normal also influences non-rotationally symmetric aberrations, since the plate is oblique to the beam path, thus allowing defined amounts to be determined by the slanted plate caused astigmatism and that caused by the slanted plate verur create coma that counteract production-related errors. In this case, the present invention can be used to eliminate as completely as possible the influence of this slanted plate (ie the generated by the inclined plate non-rotationally symmetric aberrations) in the force-free, undeformed state of the slanted plate.

The Invention further relates to a microlithographic projection exposure apparatus, a method for the microlithographic production of microstructured Devices, a microstructured device, a digital projection system and an optical interferometer.

Further Embodiments of the invention are the description and the dependent claims to remove.

The Invention is described below with reference to the accompanying drawings illustrated embodiments explained in more detail.

It demonstrate:

1 - 3 in each case a meridional overall section through a complete catadioptric projection objective according to different embodiments of the invention;

4 - 5 each an enlarged section of the presentation 1 ;

6 a schematic representation for explaining the basic structure of a microlithography projection exposure apparatus; and

7 a schematic diagram for explaining the basic structure of a digital projector according to another application of the present invention.

According to 1 is the basic structure of an imaging system in the form of a catadioptric microlithography projection objective 100 according to an embodiment of the present invention.

The projection lens 100 serves for imaging a mask which can be positioned in an object plane OP on a photosensitive layer which can be positioned in an image plane IP in a microlithography projection exposure apparatus. The microlithography projection exposure apparatus whose basic structure is still with reference to 6 is explained in more detail, used according to the embodiment as a light source F ₂ laser (wavelength about 157 nm), but can also for other operating wavelengths, for example, when using an argon-fluoride (ArF) laser about a working wavelength of 193 nm, when using of a krypton-fluoride laser (KrF) has a working wavelength of about 248 nm.

The design data of the projection lens 100 are listed in Table 1, wherein the first column is the sequence number of a refractive or otherwise marked surface, the second column of the radius of the surface in mm, the third column the distance of the surface to the subsequent surface in mm and the fourth and fifth column indicates the material or the refractive index of the optical component.

The areas of the projection lens specified in Table 2 100 are each aspherically curved, the curvature of these surfaces being given by the following aspherical formula:

there P are the height of the arrow the area concerned parallel to the primary optical axis, h is the radial distance from the primary optical Axis, r the radius of curvature the area concerned, K is the conic constant and C1, C2, ... the aspheric constants listed in Table 2.

The projection lens 100 has a first catadioptric subsystem 110 and a second dioptric subsystem 120 on. Through the first subsystem 110 an intermediate IMI is generated whose approximate Location in 1 is indicated by the arrow labeled "IMI" and that by the second subsystem 120 is imaged in the image plane IP.

In 1 Also indicated is a primary optical axis OA, which in the context of the present application means the symmetry axis formed by the plurality of optical elements, ie a straight line or succession of straight line sections which runs through the centers of curvature of the rotationally symmetrical optical components.

The first subsystem 110 comprises a group of refractive lenses along the primary optical axis OA 111 to 113 , Following in the light propagation direction, a plane-parallel beam splitter plate 114 is arranged. The beam splitter plate 114 in the exemplary embodiment has a thickness of 10 mm and is made of a transparent material at working wavelength material, in the embodiment of calcium fluoride (CaF ₂ ). The beam splitter plate 114 is arranged at an angle of 45 ° to the primary optical axis OA.

The projection lens 100 has four coordinate system decentrations or coordinate system rotations which occur (with reference to the design data listed in Table 1) at the areas Nos. 10, 12, 23 and 27. Here, each coordinate system decentering or coordinate system rotation defines a new (offset and / or rotated) coordinate system in which the surfaces following the respective surface are defined. The decentration data used for the quantitative description of these coordinate system decentrations are given in Table 3. Dislocation following areas are located along the z axis of the new coordinate system, which is valid until a new coordinate system decentration occurs. The coordinate system decentering itself takes place at the relevant surface by displacement of the axes X, Y and Z and tilting ("tilt") by the angles α, β and γ, each with the values given in Table 3.

On the beam splitter plate 114 follows a group of refractive lenses 115 and 116 as well as a concave mirror 117 , That from the concave mirror 117 reflected light is after re-crossing the lenses 115 . 116 at the beam splitter plate 114 partially reflected, and the reflected light component strikes after passing through a refractive lens 118 on a folding mirror 119 after which the intermediate IMI is generated. The second subsystem 120 includes lenses in a purely refractive structure 121 to 137 , by which the intermediate image "IMI" is mapped into the image plane IP.

The beam splitter plate 114 serves in the projection lens 100 according to 1 to divide the concave mirror 117 leading and the concave mirror 117 returning beam path. The use of the beam splitter plate 114 has the advantage over the likewise possible use of a beam splitter cube that the disadvantages associated with a beam splitter cube (material costs, absorption losses, aberrations caused by material inhomogeneities) can be largely avoided. However, as already explained, the beam splitter plate introduces non-rotationally symmetrical aberrations into the system. This from the beam splitter plate 114 aberrations caused include both errors of the image geometry (distortion, telecenter deviations) and wavefront errors (astigmatism caused by the beam splitter plate, coma caused by the beam splitting plate and higher order aberrations).

For compensation of the beam splitter plate 114 caused aberration is in the beam path of the first subsystem 110 a non-rotationally symmetric correction surface 111 provided, on the light entry surface of the first, following the object plane lens 111 ,

The non-rotationally symmetric to the primary optical axis OA correction surface 111 is a free-form surface that can be quantitatively described using a polynomial winding in the general form in equation (2):

In this case, z (x, y) denotes the arrow height z as a function of the surface coordinates x and y. The first summand on the right side of equation (2) represents the usual vertex shape of a conic, where k is the conic parameter and the base radius is given by 1 / c. The second summand on the right side of equation (2) is a general polynomial winding in x and y with powers n and m that can run independently to infinity, counting over the indices m and n (ie the exponents are in the powers of x and y).

The occurring development _coefficients C _mn in the polynomial winding according to equation (2) are for the embodiment according to 1 in Table 4, in each case the value of C _mn for a pair of values of m (= power in x) and n (= power in y). In this case, in Table 4, for example, the value C _{23 is} denoted by X2Y3, the value C ₄₂ is denoted by X4Y2, etc.

It It should be noted that, of course, different options to describe the same inventive area, e.g. a rotation and / or a reference point change of the reference coordinate system each result in different terms.

As can be seen from Table 4, the general polynomial winding of equation (1) is for the non-rotationally symmetric correction surface 111 only terms for which m is even (ie only even powers appear in X). Furthermore, the polynomial winding contains terms up to the maximum order (n + m) _max = 6. It has been found that for n + m ≤ 6 in most cases or applications a sufficiently good correction is achieved.

It can be seen that, in the above embodiment, the non-rotationally symmetrical correction surface according to the invention 111 the basic form can be well approximated by a torus. This toric part is expressed by the fact that, in a good approximation, the horizontal and the vertical section are excellent cuts. Total results for the correction surface 111 According to the embodiment in the lowest approximation, a rotationally symmetric component and in a next higher approximation, a fairly pronounced toric component. In addition, there are even higher proportions / orders that represent a departure from the toric basic form. The toric basic shape effects a good correction of the primary astigmatism caused by the beam splitter plate, since the correction surface according to the invention separately influences the different cutting widths in the meridional and sagittal sections. In addition, it can be seen that the use of even higher orders in the general polynomial winding for additional correction also leads to higher-order aberrations, so that overall the quality of the correction is further improved. Nevertheless, in applications or systems with lower accuracy requirements (eg digital projector), a purely toric surface may also be suitable as a correction surface.

How out 1 can be seen, there is the correction surface 111 along the primary optical axis OA of the projection lens 100 in the immediate vicinity of the object plane OP of the projection objective 100 , The beam splitter plate 114 however, in the immediate vicinity is a pupil plane of the projection objective 100 , The preferred positions of the non-rotationally symmetric correction surface 111 on the one hand and the beam splitter plate 114 On the other hand, explained in more detail below.

First, the proximity of the correction surface 111 As far as the object plane is concerned, it is definable in accordance with a suitable quantitative criterion that between bundles of rays emanating from different object points, at the location of the correction surface 111 is a small bundle overlap or, in other words, a good separation of different "subapertures." Here, "subaperture" on a surface is the portion of that surface used by a single beam, more precisely the diameter of the light beam used for optical imaging at the respective one Surface understood.

bevorzugt

und noch bevorzugter

erfüllt. Im Ausführungsbeispiel gemäßHere, with reference to the enlarged illustration, the position of the non-rotationally symmetric correction surface 111 according to 4 , preferably satisfies the condition D ₁ <D ₂ , where D _{1 is} the diameter of the light beam used for the optical imaging of an object point arranged in the center of the object field on the non-rotationally symmetrical surface 111 and D _{2 is} the total diameter used for optical imaging on the non-rotationally symmetric surface 111 is. More preferred here is the condition

prefers

and more preferably

Fulfills. In the embodiment according to

1 is

Unlike the correction area 111 is the beam splitter plate 114 not "close to the field", but arranged "close to the pupil", ie at a position where the field beams of the individual object points overlap comparatively strongly The beam splitter plate 114 Thus, it is preferably located where almost collimated radiation beams are present, ie the marginal rays of the radiation beams are substantially parallel to one another.

For a quantitative description of the preferred position of the beam splitter plate 114 can with reference to the enlarged view in 5 the criterion be used, according to which the beam splitter plate 114 is arranged in the imaging beam path such that a distance "a1" between the marginal rays of a light beam used for the optical imaging, which emanate from an object point arranged in the center of the object field, at a light entrance surface of the beam splitter plate 114 at least 50%, preferably at least 70%, more preferably at least 90% of the distance "a2" between the outermost edge beams used for optical imaging at the light entry surface of the beam splitter plate 114 is.

According to another approach, the beam splitter plate 114 arranged in the imaging beam path such that for the ratio of a beam height y _{1 of} a main beam of a radially maximally distant from the primary optical axis field point to a beam height y2 of a marginal beam of the field point on the primary optical axis, the condition | y ₂ / y ₁ | > 2, preferably | y ₂ / y ₁ | > 3, and more preferably | y ₂ / y ₁ | > 5 is fulfilled.

Generally is according to the invention then, when the sloping optical element is located in a pupil plane, for compensation the one by a tilted optical element caused non-rotationally symmetric aberration used, non-rotationally symmetric correction area at least immediately adjacent to a field plane (i.e., the object plane or an optically conjugate plane, ie an intermediate image plane) arranged.

The good correction effect of the non-rotationally symmetrical correction surface which can be achieved according to the invention in such "near-field positions" can be attributed, according to a possible explanatory model, to the possibility of selectively influencing field-dependent aberrations at such positions 114 insofar advantageous as the beam splitter plate 114 in pupil-near positioning mainly errors in the pupil imaging of the imaging system, which can be partially compensated by the degrees of freedom of the rotationally symmetric correction surfaces, as well as distortion and telecentricity causes, which are particularly well corrected by the inventive correction surface in the vicinity of the object or an intermediate image plane.

Conversely, the correction surface 111 preferably then arranged at least in the immediate vicinity of a pupil plane when the beam splitter plate 114 at least in the immediate vicinity of a field plane or a plane optically conjugated thereto, ie an intermediate image plane (with the above criteria being able to be used analogously for a quantitative description).

For the quantitative description of in the projection lens 100 Existing aberrations are listed in Table 5 for distortion, telecentricity, and wavefront errors. In each case, in the first column ("XOB") the X coordinate of an object point (in mm) in the object plane, in the second column ("YOB") in each case the Y coordinate of the object point (in mm) in the object plane, in the third column ("VZX") the distortion of the principal ray in the direction of the X-coordinate (in mm) in the image plane, in the fourth column ("VZY") the distortion of the principal ray in the direction of the Y-coordinate (in mm) in the image plane, in the fifth column ("TZI"), the telecentricity error (angle of the principal ray to the optical axis of the fundamental system (in mrad) and in the sixth column ("WFE") the mean square wavefront error in the exit pupil (in mm) In this case, the principal ray is to be understood as meaning the ray passing through the center of the aperture diaphragm from an object point.

In 2 is a projection lens 200 represented according to a second embodiment of the invention. The design data of the projection lens 200 are listed in Table 6, with areas of the projection lens specified in Table 7 200 aspherically curved. The projection lens 200 also has four coordinate system decentrations, the decentration data used to quantitatively describe these coordinate system decentrations are given in Table 8. In to the projection lens 100 analogous way are for the non-rotationally symmetric correction surface 211 the development _coefficients C _mn occurring in the polynomial winding according to equation (2) are given in Table 9. For the quantitative description of in the projection lens 200 Existing aberrations are listed in Table 10 for distortion, telecentricity, and wavefront errors.

The projection lens 200 In the basic structure (ie, except for the quantitative design-specific values) corresponds to the projection objective 100 out 1 , wherein corresponding elements are provided with increased by one hundred reference numerals.

The projection lens 200 is different from the projection lens 100 in that the beam splitter plate 214 of the projection lens 200 has a thickness of 20 mm, which is twice as thick as the beam splitter plate 114 of the projection lens 100 , so that the individual design parameters of the other optical components of the projection lens 200 , in particular the non-rotationally symmetrical correction surface 211 , are adjusted accordingly.

In 3 is a projection lens 300 shown according to a third embodiment of the invention. The design data of the projection lens 300 are listed in Table 11, with areas of the projection lens specified in Table 12 300 aspherically curved. The projection lens 300 also has four coordinate system decentrations, the decentration data used to quantitatively describe these coordinate system decentrations are given in Table 13. In to the projection lens 100 respectively. 200 analogously, the development _coefficients C _mn in the polynomial winding according to equation (2) in Table 14 are given for the non-rotationally symmetrical correction _surfaces . For the quantitative description of in the projection lens 300 Existing aberrations are listed in Table 15 for distortion, telecentricity, and wavefront errors.

The projection lens 300 corresponds again in the basic structure (ie, except for the quantitative design-specific values) the projection lens 100 out 1 , wherein corresponding elements are provided with increased by two hundred reference numerals. The projection lens 200 differs, however, from the projection lens 100 in that not only one but two non-rotationally symmetric correction surfaces 311 . 312a are provided, which in each case at the light entry surfaces of the lenses 311 and 312 are provided. The beam splitter plate 314 points like the beam splitter plate 114 from 1 a thickness of 10mm.

The in the projection lens 300 from 3 taking place "division" of the compensation by beam splitter plate 314 caused non-rotationally symmetric aberrations on the two non-rotationally symmetric correction surfaces 311 . 312a on the one hand results in a further improvement of the correction.

A Another consequence of the "division" of the compensation on two non-rotationally symmetric correction surfaces is that the Deviation of this non-rotationally symmetric Correction surfaces of a rotationally symmetrical basic shape can be reduced. This is manufacturing technology advantageous, since that for the production in particular suitable IBF process (IBF = "Ion Beam Figuring") allows only relatively small material removal, so that there are two freeform surfaces with minor deviations from a rotationally symmetric basic shape easier to produce than a freeform surface with greater deviation.

According to others embodiments can There are also two or more non-rotationally symmetric correction surfaces be whose preferred positions each at least in the Near one Field level, i. the object plane OP or an intermediate image plane IMI, lie. Suitable "near-field" positions can turn be determined on the basis of the criteria described above.

Based on 6 describes the basic structure of a microlithography projection exposure apparatus. According to 6 has a projection exposure system 600 a lighting device 601 and a projection lens 602 on. The projection lens 602 includes a merely schematically indicated lens arrangement 603 with an aperture stop AP, whereby through the lens arrangement 603 an optical axis OA is defined. Between the lighting device 601 and the projection lens 602 is a mask 604 arranged by means of a mask holder 605 is held in the beam path. Such masks used in microlithography 604 have a structure in the micrometer to nanometer range, by means of the projection lens 602 for example, by a factor of 4 or 5 reduced to an image plane IP is mapped. In the image plane IP is a through a substrate holder 607 positioned photosensitive substrate 615 , or a wafer held. The still resolvable minimum structures depend on the wavelength λ of the light used for the illumination and on the image-side numerical aperture of the projection objective 602 with the maximum achievable resolution of the projection exposure system 600 with decreasing wavelength λ of the illumination device 601 and with the image-side numerical aperture of the projection lens 602 increases.

In 7 In order to explain a further application of the present invention, the basic structure of a digital projector in the form of an LCOS (Liquid Crystal On Silicon) projector is illustrated 7 in a known manner, a light source 701 , a lighting system 702 , a pre-polarizer 703 , a polarization beam splitter (PBS = "polarization beam splitter") 704 , an LCOS device 705 , a clean-up 906 and a projection lens 707 on. Examples of digital projectors are about US 6,234,634 B1 and US 6,447,120 B2 known.

The use of the polarization beam splitter 704 in the form of a plane-parallel plate also has advantages in the digital projector 700 compared to the use of a beam splitter cube or prism systems, inter alia, a shorter glass path and a reduction of contrast losses due to stress birefringence leads to lower thermal problems and a reduced space and weight. The use of the beam splitter plate also introduces non-rotationally symmetric aberrations, the dominating aberrations in turn being the astigmatism caused by the beam splitter plate and the coma caused by the beam splitter plate. In order to correct these aberrations, at least one non-rotationally symmetrical correction surface is thus also arranged in the beam path in accordance with the invention, which is caused by the obliquely arranged beam splitter 704 caused aberrations at least partially compensated.

TABELLE 2 – ASPHÄRISCHE KONSTANTEN ZU FIG. 1

TABELLE 3 – DEZENTRIERUNGSANGABEN ZU FIG. 1

TABELLE 4 – FREIFORMFLÄCHE ZU FIG. 1

TABELLE 5 – VERZEICHNUNG, TELEZENTRIE UND WELLENFRONTFEHLER ZU FIG. 1

TABELLE 6 – DESIGNDATEN ZU FIG. 2

TABELLE 7 – ASPHÄRISCHE KONSTANTEN ZU FIG. 2

TABELLE 8 – DEZENTRIERUNGSANGABEN ZU FIG. 2

TABELLE 9 – FREIFORMFLÄCHE ZU FIG. 2

TABELLE 10 – VERZEICHNUNG, TELEZENTRIE UND WELLENFRONTFEHLER ZU FIG. 2

TABELLE 11 – DESIGNDATEN ZU FIG. 3

TABELLE 12 – ASPHÄRISCHE KONSTANTEN ZU FIG. 3

TABELLE 13 – DEZENTRIERUNGSANGABEN ZU FIG. 3

TABELLE 14 – FREIFORMFLÄCHEN ZU FIG. 3

TABELLE 15 – VERZEICHNUNG, TELEZENTRIE UND WELLENFRONTFEHLER ZU FIG. 3

Although the invention has also been described with reference to specific embodiments, numerous variations and alternative embodiments will be apparent to those skilled in the art, eg, by combining and / or replacing features of individual embodiments. Accordingly, it will be understood by those skilled in the art that such variations and alternative embodiments are intended to be embraced by the present invention, and the scope of the invention is limited only in terms of the appended claims and their equivalents. TABLE 1 - DESIGN DATA FOR FIG. 1

TABLE 2 - ASPHARICAL CONSTANTS FOR FIG. 1

TABLE 3 - DECENTRATION DETAILS FOR FIG. 1

TABLE 4 - FREQORM AREA FOR FIG. 1

TABLE 5 - DIRECTORY, TELECENTRIC AND SHAFT FRONT FAULT TO FIG. 1

TABLE 6 - DESIGN DATA FOR FIG. 2

TABLE 7 - ASPHARICAL CONSTANTS FOR FIG. 2

TABLE 8 - DECENTRATION DETAILS FOR FIG. 2

TABLE 9 - FREE-FORM SURFACE TO FIG. 2

TABLE 10 - DIRECTORY, TELECENTRIC AND SHAFT FRONT ERROR FOR FIG. 2

TABLE 11 - DESIGN DATA FOR FIG. 3

TABLE 12 - ASPHARIC CONSTANTS FOR FIG. 3

TABLE 13 - DECENTRATION DETAILS FOR FIG. 3

TABLE 14 - FREE-FORM SURFACES FOR FIG. 3

TABLE 15 - DIRECTORY, TELECENTRIC AND SHAFT FRONT ERROR FOR FIG. 3

Claims (38)

Optical system ( 100 . 200 . 300 ) having • a primary optical axis (OA) which is an axis of symmetry subtended by a plurality of the optical elements of the optical system; At least one optical element inclined to this primary optical axis (OA) ( 114 . 214 . 314 ) whose intersection with the primary optical axis defines a first plane perpendicular to the primary optical axis (OA); and at least one correction surface arranged in a second plane ( 111 . 211 . 311 . 312a ), which by the oblique optical element ( 114 . 214 . 314 ), non-rotationally symmetric aberrations at least partially compensated and non-rotationally symmetric to the primary optical Ach is; Wherein one plane of the first and second planes is a pupil plane or near-pupil plane of the optical system and the other plane of the first and second planes is a field plane or near-field plane of the optical system. Optical system ( 100 . 200 . 300 ) having • a primary optical axis (OA) which is an axis of symmetry subtended by a plurality of the optical elements of the optical system; At least one optical element inclined to this primary optical axis (OA) ( 114 . 214 . 314 ) whose intersection with the primary optical axis defines a first plane perpendicular to the primary optical axis (OA); and at least one correction surface arranged in a second plane ( 111 . 211 . 311 . 312a ), which by the oblique optical element ( 114 . 214 . 314 ) is at least partially compensated for and non-rotationally symmetric to the primary optical axis; Wherein the second level is substantially a Fourier transformed plane to the first level. Optical system according to claim 1 or 2, characterized characterized in that the first level is substantially a pupil plane of the optical system and the second level is essentially one Field level of the optical system is. Optical system according to one of claims 1 to 3, characterized in that the non-rotationally symmetrical correction surface ( 111 . 211 . 311 ) is arranged in the imaging beam path such that the condition

prefers

and more preferably

is satisfied, where D _{1 is} the diameter of a light beam used for the optical imaging, which emanates from an object point arranged in the center of the object field, at the non-rotationally symmetrical correction surface (FIG. 111 . 211 . 311 D _{2 is} the total diameter used for the optical imaging on the non-rotationally symmetric correction area (FIG. 111 . 211 . 311 ). Optical system according to claim 4, characterized that the particular condition for all the non-rotationally symmetric one present in the optical system correction surfaces Fulfills is. Optical system according to one of the preceding claims, characterized in that the oblique optical element ( 114 . 214 . 314 ) is arranged in the imaging beam path such that in the first plane the marginal rays of a light beam used for the optical imaging, which emanates from an object point arranged in the middle of the object field, are substantially parallel to one another. Optical system according to claim 6, characterized that the sine of the angle between the respective marginal ray and the primary smaller in terms of optical axis than 0.2, preferably less than 0.1. Optical system according to one of the preceding claims, characterized in that the oblique optical element ( 140 ) is arranged in the imaging beam path such that in the first plane for the ratio of a beam height y _{1 of} a main beam of a radially maximally remote from the primary optical axis field point to a beam height y _{2 of} a marginal ray of the field point on the primary the condition | y ₂ / y ₁ | > 2, preferably | y ₂ / y ₁ | > 3, and more preferably | y ₂ / y ₁ | > 5 is fulfilled. Optical system according to claim 1 or 2, characterized characterized in that the first level is essentially a field level of the optical system and the second level is essentially one Pupil plane of the optical system is. Optical system according to one of the preceding claims, characterized in that the non-rotationally symmetrical correction surface ( 111 . 211 . 311 . 312a ) as a single symmetry a mirror symmetry with respect to a meridional plane of the optical system ( 100 . 800 ) having. Optical system according to one of the preceding claims, characterized in that the non-rotationally symmetrical correction surface ( 111 . 211 . 311 . 312a ) is a freeform surface. Optical system according to one of the preceding claims, characterized in that the non-rotationally symmetrical correction surface ( 111 . 211 . 311 . 312a ) has a 4-fold symmetry with respect to the primary optical axis. Optical system according to one of the preceding claims, characterized in that the non-rotationally symmetrical correction surface ( 111 . 211 . 311 . 312a ) is a toroidal surface. Optical system according to one of claims 1 to 12, characterized in that the non-rotationally symmetrical correction surface ( 111 . 211 . 311 . 312a ) is a surface deviating from a toroidal surface. Optical system according to one of the preceding claims, characterized in that the non-rotationally symmetrical correction surface ( 111 . 211 . 311 . 312a ) is describable by a general polynomial winding having an order n for which the condition 4 <n <∞ is satisfied. Optical system according to one of the preceding claims, characterized in that it has precisely one such non-rotationally symmetrical correction surface ( 111 . 211 ) having. Optical system according to one of claims 1 to 15, characterized in that it comprises at least two non-rotationally symmetrical correction surfaces ( 311 . 312a ) having. Optical system according to claim 17, characterized that there are more than two non-rotationally symmetric correction surfaces having. Optical system according to one of the preceding claims, characterized in that the non-rotationally symmetrical correction surface ( 111 . 211 . 311 . 312a ) is formed on a refractive element of material substantially transparent to light of a working wavelength, the working wavelength being less than 250 nm, preferably less than 200 nm, and more preferably less than 160 nm. Optical system according to one of claims 1 to 18, characterized in that the non-rotationally symmetric correction surface on a reflective element is formed. Optical system according to one of the preceding claims, characterized in that an optically active surface of the inclined optical element ( 114 . 214 . 314 ) at an angle of at least 15 °, preferably at least 30 °, and more preferably substantially 45 ° to the primary optical axis. Optical system according to one of the preceding claims, characterized in that the oblique optical element ( 114 . 214 . 314 ) is arranged symmetrically with respect to the meridional plane of the optical system. Optical system according to one of the preceding claims, characterized in that the oblique optical element ( 114 . 214 . 314 ) is a beam splitter plate. Optical system according to one of claims 1 to 22, characterized in that the oblique optical element ( 114 ) is a plan wedge with two planar surfaces enclosing an angle. Optical system according to one of claims 1 to 22, characterized in that the inclined optical element has a coating which is one of the incident light Polarization state and / or dependent on the angle of incidence transmission and / or delay between mutually perpendicular polarization states causes. Optical system according to one of claims 1 to 22, characterized in that the inclined optical element for compensation of non-rotationally symmetric Abbildfehler of the optical system to the beam path decentered and / or is rotatable about an axis perpendicular to the Meridionalebene axis. Optical system according to one of claims 1 to 22, characterized in that the inclined optical element targeted to compensate for aberrations of the optical system is deformable. Optical system according to one of the preceding claims, characterized characterized in that it is an imaging system, in particular an imaging system a microlithography projection exposure machine. Optical system according to claim 28, characterized that it is essentially telecentric object and image plane side is. Optical system according to claim 28 or 29, characterized characterized in that one for imaging by means of the optical system object field is a rectangular field. Optical system according to one of claims 28 to 30, characterized in that the optical system is a catadioptric System with at least one geometric beam splitter. Optical system according to one of claims 28 to 31, characterized in that it is a picture-side numerical Aperture (NA) of at least 0.8, preferably at least 1.0 more preferably at least 1.2. Optical system according to one of the preceding claims, characterized marked that it is for a Working wavelength less than 250 nm, preferably less than 200 nm, and more preferably less than 160 nm is designed. Microlithographic projection exposure equipment, which comprises an optical system according to one of the preceding claims. Process for the microlithographic production of microstructured components comprising the following steps: 606 ) to which is at least partially applied a layer of a photosensitive material; • Providing a mask ( 604 ) having structures to be imaged; Providing a projection exposure apparatus ( 600 ) according to claim 34; • projecting at least part of the mask ( 604 ) to a region of the layer using the projection exposure apparatus ( 600 ). Microstructured device that works by a method according to claim 35 is made. Digital projection system, characterized that it is an optical system according to one of claims 1 to 33 has. Optical interferometer, characterized that it is an optical system according to one of claims 1 to 33 has.