DE102017203571A1 - OPTICAL ARRANGEMENT FOR A LITHOGRAPHIC SYSTEM AND METHOD FOR OPERATING A LITHOGRAPHIC SYSTEM - Google Patents

Abstract

Optical arrangement for a lithographic system, which has a beam path for imaging lithographic structures, with a wavefront manipulator arranged in the beam path, which is irradiated during operation of the lithography of a beam extending in the beam path along a transmission direction and which is adapted to an optical path length for to adjust the beam, the wavefront manipulator having
a segmented optical element with segments arranged transversely to the transmission direction, wherein at least one segment is arranged such that changes in the position of the segment relative to the radiation beam passing through the segment changes the optical path length for the radiation beam.

Description

The present invention relates to an optical arrangement for a lithography system with a wavefront manipulator and to a method for operating a lithography system.

Microlithography is used to fabricate microstructured devices such as integrated circuits. The microlithography process is performed with a lithography system having an illumination system and a projection system. The image of a mask (reticle) illuminated by means of the illumination system is projected onto a photosensitive layer (photoresist) coated in the image plane of the projection system substrate, for example a silicon wafer, by the projection system to the mask structure on the photosensitive coating of the substrate transferred to.

When imaging the lithographic micro- or nanostructures onto the wafer surface, it is usually not the entire wafer that is exposed, but only a narrow area. As a rule, the wafer surface is exposed piece by piece or slitwise. Both the wafer and the mask are scanned step by step and moved against each other antiparallel. The exposure area is often a rectangular area.

Current light wavelengths for DUV systems are currently 248 nm, 193 nm and occasionally 157 nm. In order to achieve even higher lithographic resolutions, radiation up to soft X-radiation is used. For 13.5 nm light, for example, radiation sources and optics can be fabricated for lithographic purposes.

Current lithography systems achieve a resolution in the nanometer range. In order to be able to produce complex structures, it is necessary to expose individual wafers several times in several process steps. It depends on an exact match of the structures to be imaged of a mask with already existing structures. Although known projection optics achieve a very high imaging quality, temporally variable operating conditions occur, in particular in the operation of a lithography system, which are reflected in part in time-varying aberrations. For example, a local heating of a lens leads to mechanical stresses in the lens, which on the one hand lead to a deformation of the lens body and on the other hand can also cause locally changed optical properties of the lens material.

Aberrations of optical systems are also called aberrations. One way to describe the aberrations of an optical system, the so-called Zernike polynomials dar. Different Zernike polynomials describe different aberrations. The function value of a Zernike polynomial indicates the deviation of the actual wavefront of radiation from an ideal wavefront.

With a targeted change of the wavefront of the radiation, it is therefore possible to obtain an ideal wavefront and thus obtain an ideal optical system. This can be achieved by specifically adjusting the optical path length of individual light beams or light bundles. As a result, an undesired curvature of the wavefront can be compensated.

For example, in an optical element, the refractive index can be changed locally for individual light bundles. One way to accomplish this is by locally heating a glass plate through. Such devices are for example from DE 199 56 353 C1 or from the WO 2013 044 936 A1 known.

However, such systems are not suitable for making a fast adaptation, since a control process with such systems takes at least several seconds.

Against this background, an object of the present invention is to provide an improved optical arrangement for correcting the wavefront of radiation in a lithography system.

Accordingly, an optical arrangement for a lithography system is proposed. The lithographic system has a beam path for imaging lithographic structures, wherein a wavefront manipulator is arranged in the beam path, which is irradiated in the operation of the lithographic system by a beam extending in the beam path along a transmission direction. The wavefront manipulator is configured to set an optical path length for the beam. For this purpose, the wavefront manipulator has a segmented optical element with segments arranged transversely to the transmission direction, wherein at least one segment is arranged such that changes in the position of the segment relative to the radiation beam passing through the segment changes the optical path length for the beam.

An additional aspect of this application relates to an optical arrangement for a lithography system, which comprises a beam path for imaging has lithographic structures, wherein in the beam path, a wavefront manipulator is arranged, which is irradiated in the operation of the lithographic system by a beam extending in the beam path along a transmission direction. The wavefront manipulator is configured to set an optical path length for the beam. For this purpose, the wavefront manipulator has a segmented optical element with segments arranged transversely to the transmission direction, wherein at least one segment can be heated with the aid of a corresponding heating device such that the optical path length for the beam passing through the segment changes as the segment changes in temperature.

The embodiments and features described for the optical arrangement for a lithography system with a movable segment wavefront manipulator apply correspondingly to this additional aspect.

A corresponding optical arrangement makes it possible to compensate for a wave front that runs in an undesired manner and to achieve an improved imaging performance. In particular, it is possible to achieve a wavefront correction particularly quickly, for example within fractions of a second. In particular, the respective beam carries a lithographic information, so then includes useful light. The light beams of the beam preferably have a wavelength between 150 and 200 nm.

For the material of the segments, absorption at wavelengths of 248 nm or 193 nm is preferably not more than 5%. Absorption rates at the stated wavelengths for projection light of less than 1% are particularly preferred. The material of the segments or of the optical element has a transparency of at least 95% for the projection light, preferably at the wavelength 193 nm. In particular, the transparency is at least 99%, more preferably at least 99.5%.

The segments are arranged side by side transversely to the transmission direction. Transverse to the transmission direction means, for example, that two segments do not overlap in the transmission direction and / or have no intersection such that a light beam emerges from a Ausstrahlseite from a first segment and irradiated on a Einstrahlseite of a transversely arranged adjacent to the first segment second segment. Each segment has a Einstrahlseite and a Ausstrahlseite. The Einstrahlseite is, for example, the substantially the light source facing surface of a segment. The Ausstrahlseite is the Einstrahlseite opposite and substantially away from the light source surface of the segment. It is possible that a side surface of a segment, which connects the Einstrahlseite with the Ausstrahlseite, sections facing the light source and / or may be remote. Transverse juxtaposed segments may overlap with their side surfaces such that there are configurations in which a beam of light radiates into the first segment via the inflow side thereof beyond the side surface of the first segment out of the first segment and over the side surface of the second segment radiates into the second segment and finally radiates over the Ausstrahlseite the second segment of this. For example, transverse to one another may also mean that the segments are arranged in one plane.

It can be said that in embodiments the projections of the segments of a respective optical element in the transmission direction do not overlap.

The segments can form a coherent body in a certain position relative to one another, which forms the segmented optical element in a basic form. The segmented optical element is obtained, for example, by dividing the basic shape, such as a wedge-shaped glass plate. One can speak of a segmented Alvarez "lens".

Preferably, the segments are not offset along the transmission direction. By way of example, adjoining segments are arranged in a conforming and displaceable manner relative to one another. The projection light with lithographic information is particularly incident on a plurality of juxtaposed segments of the segmented optical element.

The arrangement of the segments in the beam path can also be described as follows with respect to the projection light during operation of the lithography system. Each light beam of the projection light traverses along the irradiation direction only at most the irradiation sides of two segments and a radiating side of a segment of a single segmented optical element or the radiating sides of two segments and a radiating side of a segment of a single segmented optical element. This means in particular that it can also be provided that the wavefront manipulator comprises a plurality of segmented optical elements arranged one behind the other in the transmission direction, wherein each light beam does not radiate two segments of each segmented optical element in full thickness, measured along the propagation direction of the light beam. In other words, a ray of light shines through sections through two segments of a segmented optical element, at least one of these segments only partially, measured on the thickness of the segment along the transmission direction. In this case, a light beam is defined, for example, as an arbitrarily small subset of the projection light to be selected. For example, it can be said that a light beam illuminates, in a plane perpendicular to its direction of propagation, a contiguous area of 0.01 mm ² to 0.1 mm ² or the area of a circle with a radius of 1 μm.

A lithography system is in particular designed to image lithographic structures, for example, onto a wafer coated with a photoresist. However, the term lithography system also includes other devices, such as devices for measuring lithographic structures (verification) or devices for measuring and repairing lithography masks. In the following, the optical arrangement will be described with reference to a lithography system which is used for exposing wafers, without this being a limitation of the possibility of use.

The lithography system comprises a light source, for example a laser, which emits projection light, as well as an imaging optic. The imaging optics has a beam path. Beams of light passing through the beam path contribute to the image. The course of the light rays in the imaging optics is influenced by various optical elements, such as lenses and / or mirrors. Furthermore, screens may be provided which limit the beam path in particular laterally. The lithographic structure to be imaged may be predetermined, for example, by a lithography mask which is arranged in the beam path and is irradiated in an exposure by the projection light.

The projection light comprises a plurality of light beams, wherein a plurality of light beams can also be combined to form a beam. In the present case, a radiation beam comprises in particular a plurality of light beams emanating from a field point. A field point is a point in a field plane of the beam path. A field plane is defined by the fact that in this plane the image or an intermediate image of the structure to be imaged is generated during the operation of the lithography system. The field level can also be referred to as the image plane. One would obtain an image of the lithography mask if one attached a projection screen in the field plane. The beams propagate along the beam path and illuminate surfaces on subsequent optical elements, which can be referred to as a subaperture, for example. Instead of lighting, you can also say that it is irradiated. The subaperture may be different for each optical element irradiated by a beam. It may also be different on the incident surface and on the radiating surface of an optical element.

The light source side arranged surfaces of the segments of the segmented optical element are preferably arranged in the region of a field plane. Such an arrangement may, for example, be referred to as a near-field arrangement of the wavefront manipulator. A near-field arrangement can be defined as follows. Each bundle of rays emanating from a field point of the field plane illuminates a subaperture with a subaperture diameter SAD on a surface of a subsequent optical element. All beams originating from the field level together illuminate an optically used region with the maximum diameter DFP on the surface of the subsequent optical element. The area can be categorized using the ratio SAD / DFP. A ratio of 0 describes the field plane, a ratio of 1 the pupil plane. For example, an area with a ratio between 0 and 0.5, preferably between 0 and 0.25, can be described as close to the field. For example, a region in which the ratio SAD / DFP lies within a predetermined interval, for example between 0 and 0.5, preferably between 0 and 0.25, can apply as the field-near region along the transmission direction.

It is also conceivable arrangement of the segments in a near-pupil area. Then the range is given by means of an interval for the ratio SAD / DFP, e.g. between 0.5 and 1, preferably between 0.75 and 1.

Preferably, all surfaces of the respective segment irradiated by the projection light are within a corresponding range, e.g. close to the field or close to the pupil.

The light beams of the beam each have an individual direction in which they move. Overall, one can assign the beam to a direction which is referred to herein as Durchstrahlrichtung and includes all directions propagate into the individual light beams of the beam. The transmission direction can change, in particular during an irradiation on and during an emission from an optical element. Furthermore, the transmission direction can also change within an optical element, for example when the optical element has a refractive index varying along the transmission direction.

Light can be described as an electromagnetic wave. The wave nature of the light can be described as a propagating vibration of the electric and magnetic fields. Such a wave may be mathematically written, for example, as a sine function, with the argument of the function being referred to as the phase of the wave. When such an electromagnetic wave propagates in space, a wavefront can be defined. The wave front of an electromagnetic wave includes all those points that have the same phase. The wavefront thus forms an area in space that shifts along the propagation direction. If the electromagnetic wave has more than one period, then several consecutive wavefronts result. For example, the wavefront of an electromagnetic wave radiated isotropically from a point source forms a spherical surface that grows in the radial direction. In a plane wave, the wavefront is a flat surface that propagates in a straight line perpendicular to the surface in space, provided there are no disturbances in the optical properties of the irradiated volume.

The wavefront is locally always perpendicular to the propagation direction of an electromagnetic wave. In a beam emanating from a field point, the wavefront forms a section of a spherical surface. If the beam passes through an optical element, the propagation direction can change. For example, in a perfect converging lens, all light rays or bundles of rays meet at the focal point. With reference to the wavefront, this means that the wavefronts of different radiation beams converge towards the focal point, where the wavefronts overlap in phase. If the convergent lens has errors, such as local deformations, this can lead to delays that portion of the electromagnetic wave of the beam, which transmits the deformation. This leads to a phase shift of the portion of the electromagnetic wave and thus to a local deformation of the wavefront with respect to the ideal course. Such a deformation can be compensated or corrected with a wavefront manipulator. In the above example, for example, it would be possible to delay correspondingly the further portions of the electromagnetic wave of the beam that did not transilluminate the defect of the condenser lens. Thus, the wavefront of the beam is brought back into its intended form.

It should be noted that the wavefront of adjacent beams may also be intentionally different. This is the case, for example, when using phase-changing lithography masks. In the case of this type of mask, in the case of binary structures, the phase of adjacent areas is rotated by 180 °, for example, so that destructive interference results when the beams are superimposed. In this way, a contrast in the exposure can be increased.

The wavefront manipulator is adapted to adjust the phase of each beam individually and independently of the other beams. This is accomplished by adjusting the optical path length of the beam or electromagnetic wave describing the beam as it passes through the wavefront manipulator. The optical path length for classical media is a function of the refractive index n of the medium and the geometric path length traversing the electromagnetic wave in the medium. For example, the optical path length β for a glass plate having a refractive index n1 and a thickness d along the irradiation direction may be given as the product of these quantities: β = n1 · d. In general, for an electromagnetic wave propagating in the x-direction, the optical path length along the path through which it passes can be represented as an integral according to equation (1): $$\mathrm{\beta }={\displaystyle \int \text{n}\left(\text{x}\right)\cdot \text{dx}}$$

Here, n (x) is a function indicating the value of the refractive index of the medium at the position x for the electromagnetic wave. For vacuum, n (x) ≡ 1, where equation (1) gives the geometric path length in this case.

The wavefront manipulator is presently implemented as a segmented optical element. This may for example be a segmented glass plate with plane-parallel Einstrahl- and Ausstrahlseiten, a segmented lens with a predetermined type curved surface of the Einstrahl- and / or Ausstrahlseite such as convex or concave, or it may also be a segmented into segments Body act whose Einstrahl- and / or Ausstrahlseite is formed by a free-form surface. A free-form surface has no symmetry, in particular within the area illuminated by the projection light.

The segmented optical element is preferably made of a transparent material for the projection light. For example, it may be made of quartz glass and / or monocrystalline calcium fluoride. The segmented optical element is divided into segments. For example, the segmented optical element is divided into strips for this purpose. The segmented optical element can be obtained, for example, by sawing a previously integral optical element.

Such a segmented optical element makes it possible to arrange and position individual segments independently of the other segments. For example, individual segments of the segmented optical element are arranged at different positions in the optical arrangement, wherein different segments are arranged side by side transversely to the transmission direction. The segmented optical element may in particular be arranged in a basic form. With respect to the individual segments of the segmented optical element, this basic arrangement is also referred to as the home position or zero position in this application.

At least one of the segments is arranged to be movable. This means that the segment can be brought into a different position from the zero position. For this purpose, the segment is fixed, for example, in a movable version. By a deflection of the socket then the segment can be deflected as a whole. In this case, a deflection may comprise a displacement along a specific axis, a rotation about a specific axis or even a combination thereof. The deflection takes place along a deflection direction, which also includes rotations about an axis.

A beam illuminates the area defined by the subaperture of the beam on the segmented optical element and transmits a certain volume of the segmented optical element. This volume can be referred to as Durchstrahlvolumen. The transmission volume is a partial volume of the total volume encompassed by the segmented optical element. The Durchstrahlvolumen may be completely in one segment or it may include partial volumes of several juxtaposed segments.

In the present case, the Durchstrahlvolumen comprises at least a partial volume of the movably arranged segment. The portion of the beam that passes through this sub-volume may also be referred to as a sub-beam. Due to a deflection of the segment, which takes place relative to the beam, it is therefore achieved that the partial beam passes through another subvolume of the segment. If the optical properties of the segment are different in different sub-volumes, a targeted change in particular of the optical path length for the sub-beam can be achieved by a deflection of the movable segment. It is clear that the partial beam may also comprise the entire beam.

The optical arrangement for a lithography system can also comprise other optical elements in addition to the wavefront manipulator. For example, one or more lenses can be provided for each beam, which effect beam shaping of the respective beam, for example, focus or collimate it to a small area. This may allow advantageous implementations of the wavefront manipulator.

According to one embodiment of the optical arrangement for a lithography system, a geometric path length which traverses the beam in the segment and / or a refractive index along the path irradiated by the beam in the segment are adjustable in dependence on the position of the segment relative to the beam.

Thus, advantageously, the optical path length of the beam according to equation (1) can be adjusted. For example, for this purpose, the segment has a thickness which varies along the direction of deflection along the transmission direction. Furthermore, the segment may have a variable refractive index along the direction of deflection.

According to a further embodiment of the optical arrangement for a lithography system, the movably arranged segment of the segmented optical element is movable independently of the further segments of the segmented optical element.

According to a further embodiment of the optical arrangement for a lithography system, a segment of the segmented optical element is displaceable along a displacement direction and the displacement direction encloses an angle of greater than 0 °, in particular between 45 ° and 90 °, with the transmission direction.

The displacement direction corresponds to the deflection direction when the displacement is a displacement along the axis given by the displacement direction. Because the displacement direction encloses an angle greater than 0 ° with the transmission direction, it is ensured that the volume of the segment irradiated by the radiation beam is changed by a displacement. Such a displacement along a displacement direction is clearly defined by the specification of the deflection in the case of a known displacement direction. This can be for example a length in cm or in mm. In particular, can while the zero position can be used as the zero point for the deflection. The segment may then have, for example, a deflection of +4 cm or a deflection of -15 mm.

In accordance with a further embodiment of the optical arrangement for a lithography system, the wavefront manipulator is set up to correct for tilting, spherical aberration, coma, astigmatism, distortion and / or curvature of field.

Imaging errors are due to imperfect properties of optical elements that are unavoidable in the operation of the lithography system. Any aberration can be described with reference to the wavefront of the projection light by coefficients of so-called Zernike polynomials. For example, a first order Zernike polynomial describes a tilt of the wavefront. A tilt of the wavefront against the desired state causes an offset of the pixel, which is imaged by the relevant beam. Therefore, distortion of an image as a whole can be described by first-order Zernike polynomials with individual coefficients for each ray bundle.

According to a further embodiment of the optical arrangement for a lithography system, an area between two segments of the segmented optical element of the wavefront manipulator is parallel to the radiation beam.

In this embodiment, it is advantageously ensured that unwanted refraction and / or other undesired influence on the propagation of the beam, for example due to a transmission of a side surface of a segment that is not the irradiation side or the emission side of the segment, are minimized.

Geometrically, this is fulfilled if a surface segment of the area between two segments has a normal vector which is perpendicular to the local transmission direction of the projection light or of the beam.

According to a further embodiment of the optical arrangement for a lithography system, an area between two segments of the segmented optical element of the wavefront manipulator is formed opaque.

By way of example, the region can be an edge between two segments, through which part of the projection light strikes the segmented optical element when it is irradiated. An edge may cause the light that strikes it to be scattered so that it exits the segmented element at a different location and at a different angle than adjacent light that does not hit the edge. This leads to an increase in scattered light, which can lead to loss of contrast for the image. An edge can also lead to a local change in the optical path length, which leads to an edge in the wavefront and can degrade the imaging quality.

By the term opaque is meant that the light incident on the opaque area is at least partially absorbed. For example, the area for this purpose is treated with an absorbent coating or a separate absorber is attached. Alternatively, it can also be provided that the light is deflected, for example reflected, onto an absorber surface arranged laterally of the beam path. This alternative embodiment has the advantage that the absorber surface can be cooled more easily.

In this embodiment, it is thus avoided that beam portions which would radiate or radiate onto the area between two segments are absorbed and thus do not contribute to an exposure. Thus, the resolution of the lithographic image can be improved.

This embodiment may be advantageous because, for example, at the boundary of a segment, curvatures may occur in the surface of the segment. Furthermore, for example, from the production of the segmented optical element locally changed optical properties, lattice defects and / or other damage and changes in the structure of the material may occur, which are predominantly in the material close to the cut surface.

According to a further embodiment of the optical arrangement for a lithography system, a radiation beam emanates from a field point which corresponds to a pixel of an image of the lithographic structure. The beam illuminates a subaperture on the segmented optical element and there are at least two segments in the area defined by the subaperture.

This embodiment makes it possible to correct for the beam at least one tilt of the wavefront.

In that two segments lie in the area determined by the subaperture, it is meant that at least a partial area of the irradiation sides of these two segments corresponds to a corresponding part of the subaperture.

According to a further embodiment of the optical arrangement for a lithography system There are a number of segments in the area defined by the subaperture, the number of segments being at least as large as the order of the function with which the course of the wavefront along an axis can be described.

In the above example, a straight line, for example along the x-axis, can be described, as this requires at least two parameters. These parameters are a y-intercept and a slope. In order to correct a wavefront having higher order aberrations, there is preferably a correspondingly higher number of segments in the subaperture.

According to a further embodiment of the optical arrangement for a lithography system, the wavefront manipulator has a plurality of segmented optical elements which are arranged one after the other along the beam path in the transmission direction.

Along the beam path arranged in the transmission direction one after the other means that all segmented optical elements are irradiated by the projection light in a sequential sequence, wherein the segments of each individual segmented optical element are arranged side by side transversely to the transmission direction. Such an arrangement makes it possible to multiply correct the wavefront of a beam. However, this does not exclude that other optical elements such as lenses, mirrors and / or diaphragms can be arranged between segmented optical elements.

For example, if a beam has a tilt of the wavefront in the x-direction and in the y-direction, a segmented optical element whose segments are wedge-shaped and lined up next to one another along the x-direction can correct the tilt only in the x-direction. Therefore, if, after this segmented optical element, another segmented optical element, whose segments are aligned along the y-direction, is irradiated by the beam, the tilt of the wavefront in the y-direction can also be corrected by this second segmented optical element. With the aid of movable segments with a curved surface, further tilting can be corrected.

Thus, with an arrangement according to this embodiment, complex two-dimensional optical path length distributions can be generated for each beam. This makes it possible to correct even higher-order aberrations in two dimensions.

According to a further embodiment of the optical arrangement for a lithography system, a plurality of segmented optical elements arranged one behind the other in the beam path are present, the segments of which are displaceable along a direction of displacement. The displacement direction of the segments includes with the transmission direction an angle greater than 0 °, preferably from 45 ° to 90 °.

This makes it possible to provide a two-dimensional distribution of optical path lengths for the projection light and / or beam in the beam path by the displacement of different segments of different segmented optical elements.

According to a further embodiment of the optical arrangement for a lithography system, the wavefront manipulator is arranged in a field-near position in the beam path.

According to a further embodiment of the optical arrangement for a lithography system, a heating device is provided, which is set up to produce a local temperature change in associated segments.

With such a heater, it is possible to cause a local temperature change in individual segments. The refractive index of most materials is temperature dependent. Therefore, by a targeted temperature change, a targeted refractive index change can be achieved. Furthermore, most materials have a temperature-dependent expansion coefficient not equal to zero. Then, by changing the temperature, the claimed volume of the material also changes. This is a geometric path length of a light beam, which radiates through the affected area, customizable. Thus, the advantage with such a heating device is that the optical path length can be adjusted locally in a targeted manner and without a mechanical change in position of a segment.

Such a heating device may for example be formed by a conductive coating which heats up by means of a current flow. This coating may be applied to one of the irradiated areas of a segment or, alternatively or additionally, to a side surface of the segment. The heating device may also be an optical heating device which, for example, injects infrared radiation laterally into a segment. The injected infrared radiation is at least partially absorbed by the material, resulting in a local temperature change.

In the example with strip-shaped segmented optical elements, for example, a displacement of a segment relates to all the ray bundles in whose subaperture the segment lies. There may be situations where this is undesirable. Then, the embodiment with such a heater offers the possibility of setting the optical path length specifically for only one beam without a displacement of the segment.

According to a further embodiment of the optical arrangement for a lithography system, the wavefront manipulator has two segmented optical elements. The segments of a respective segmented optical element are arranged side by side transversely to the transmission direction. The segmented optical elements are arranged one behind the other in the transmission direction and enclose or form a cavity-free volume. Furthermore, one segment of the one segmented optical element corresponds to a corresponding segment of the other segmented optical element, which are in surface contact with one another in the transmission direction. By shifting the corresponding segments in opposite directions, the optical path length for the beam passing through the two segments is variable.

Two such corresponding segments are irradiated in particular by the same radiation beams during operation of the lithographic system.

For example, the segments of the segmented optical elements are formed as wedge segments whose thickness is perpendicular to the transmission direction, that is, the geometric path length, depends on the position. If one selects a Cartesian coordinate system whose z-axis points in the direction of transmission, the segments are displaceably arranged in the x-direction and one surface irradiated by the projection light lies in the xy-plane, then, for example, one wedge segment has one in the positive x-direction increasing thickness and the other wedge segment has an increasing in the negative direction x thickness. The two wedge segments are in contact with each other, wherein the contact surface is opposed by the surface irradiated by the projection light and lying in the x-y plane and not in the x-y plane, but has a gradient along the x direction. If the two wedge segments are displaced relative to one another, for example one wedge segment is displaced in the positive x-direction and the other wedge segment is displaced in the negative x-direction, the result is an overall increased optical path length in the transmission direction for the beam (s) that comprise these two segments by radiation.

• Durchstrahlen der optischen Anordnung mit Projektionslicht; und
• Einstellen einer Position eines beweglichen Segments eines segmentierten optischen Elements eines Wellenfrontmanipulators zur Korrektur einer Aberration einer Wellenfront des Projektionslichts.

According to a further aspect of the invention, a method for operating a lithography system with an optical arrangement, in particular according to one of the aforementioned embodiments is proposed. The method comprises the steps:

• Radiating the optical assembly with projection light; and
• Adjusting a position of a movable segment of a segmented optical element of a wavefront manipulator to correct an aberration of a wavefront of the projection light.

Throughput of the optical arrangement is achieved, for example, by arranging the optical arrangement in a beam path of the lithography system. Furthermore, a light source of the lithography system emits the projection light. The material of the optical elements which are part of the optical arrangement is predominantly transparent to the projection light, or at least substantially transparent.

The adjustment of the position of the movable segment is realized, for example, by displacement of the segment. For this purpose, the segment can be movably mounted and controlled by a dedicated actuator.

• Erfassen der Wellenfront des Projektionslichts mit einem Wellenfrontsensor;
• Berechnen von Koeffizienten von Zernike-Polynomen derart, dass eine Linearkombination der Zernike-Polynome mit dem berechneten Koeffizienten der erfassten Wellenfront entspricht;
• Berechnen von einzustellenden Positionen von Segmenten von segmentierten optischen Elementen mit Hilfe der berechneten Koeffizienten derart, dass die erfasste Wellenfront korrigiert wird; und
• Ansteuern von den Segmenten zugeordneten Aktuatoren zu Einstellung der berechneten Position eines jeden Segments.

According to one embodiment of the method, this further comprises the steps:

• Detecting the wavefront of the projection light with a wavefront sensor;
• Calculating coefficients of Zernike polynomials such that a linear combination of the Zernike polynomials with the calculated coefficient corresponds to the detected wavefront;
• Calculating positions to be set of segments of segmented optical elements using the calculated coefficients such that the detected wavefront is corrected; and
• Driving actuators associated with the segments to adjust the calculated position of each segment.

The lithography system preferably has a device for detecting the wavefront of the projection light. This could be for example a Hartmann-Shack sensor. Furthermore, the lithography system can have devices for electronic data processing, such as computers. These computers can be set up to perform the calculations. Furthermore, a computer program product is proposed which is based on a program-controlled device causes the implementation of the method as explained above.

A computer program product, such as a computer program means may, for example, be used as a storage medium, e.g. Memory card, USB stick, CD-ROM, DVD, or even in the form of a downloadable file provided by a server in a network or delivered. This can be done, for example, in a wireless communication network by transmitting a corresponding file with the computer program product or the computer program means.

The embodiments and features described for the proposed device apply accordingly to the proposed method.

Further possible implementations of the invention also include not explicitly mentioned combinations of features or embodiments described above or below with regard to the exemplary embodiments. The skilled person will also add individual aspects as improvements or additions to the respective basic form of the invention.

• 1 zeigt eine schematische Ansicht einer Ausführungsform einer DUV-Lithographieanlage mit einer optischen Anordnung mit einem Wellenfrontmanipulator;
• 2 zeigt eine erste Ausführungsform eines Wellenfrontmanipulators mit einem segmentierten optischen Element aufweisend ein beweglich angeordnetes Segment;
• 3a zeigt eine perspektivische Ansicht des Wellenfrontmanipulators, bei dem das beweglich angeordnete Segment verschoben ist;
• 3b zeigt eine perspektivische Ansicht einer Ausführungsform des beweglich angeordneten Segments in zwei Positionen A und B;
• 4 zeigt einen Querschnitt einer weiteren Ausführungsform eines beweglich angeordneten Segments, wobei das Segment Teilvolumina mit unterschiedlichen Brechungsindizes aufweist;
• 5 zeigt ein schematisches Beispiel einer Korrektur einer Wellenfront mittels eines Wellenfrontmanipulators;
• 6 zeigt eine Ausführungsform einer Projektionsoptik einer Lithographieanlage mit einer optischen Anordnung;
• 7 zeigt einen Querschnitt einer weiteren Ausführungsform eines segmentierten optischen Elements;
• 8 zeigt eine schematische Ansicht einer zweiten Ausführungsform eines Wellenfrontmanipulators mit zwei segmentierten optischen Elementen;
• 9 zeigt einen Querschnitt einer dritten Ausführungsform eines Wellenfrontmanipulators mit zwei segmentierten optischen Elementen;
• 10 zeigt eine perspektivische Ansicht einer vierten Ausführungsform eines Wellenfrontmanipulators mit einem Infrarotlaser;
• 11 zeigt ein Ablaufschema einer Ausführungsform eines Verfahrens zum Betreiben einer Lithographieanlage mit einer optischen Anordnung; und
• 12 zeigt einen schematischen Querschnitt einer Ausführungsform eines segmentierten optischen Elements.

Further advantageous embodiments and aspects of the invention are the subject of the dependent claims and the embodiments of the invention described below. Furthermore, the invention will be explained in more detail by means of preferred embodiments with reference to the attached figures.

• 1 shows a schematic view of an embodiment of a DUV lithography system with an optical arrangement with a wavefront manipulator;
• 2 shows a first embodiment of a wavefront manipulator with a segmented optical element comprising a movably arranged segment;
• 3a shows a perspective view of the wavefront manipulator, in which the movably arranged segment is shifted;
• 3b shows a perspective view of an embodiment of the movably arranged segment in two positions A and B;
• 4 shows a cross-section of another embodiment of a movably arranged segment, wherein the segment has partial volumes with different refractive indices;
• 5 shows a schematic example of a correction of a wavefront by means of a wavefront manipulator;
• 6 shows an embodiment of a projection optics of a lithographic system with an optical arrangement;
• 7 shows a cross section of another embodiment of a segmented optical element;
• 8th shows a schematic view of a second embodiment of a wavefront manipulator with two segmented optical elements;
• 9 shows a cross section of a third embodiment of a wavefront manipulator with two segmented optical elements;
• 10 shows a perspective view of a fourth embodiment of a wavefront manipulator with an infrared laser;
• 11 shows a flowchart of an embodiment of a method for operating a lithography system with an optical arrangement; and
• 12 shows a schematic cross section of an embodiment of a segmented optical element.

In the figures, identical or functionally identical elements have been given the same reference numerals, unless stated otherwise.

1 shows a schematic view of a DUV lithography system 100 which is a beam shaping and illumination system 102 and a projection system 104 includes. DUV stands for "deep ultraviolet" (English: deep ultraviolet, DUV) and refers to a wavelength of the working light (also called useful radiation) between 30 and 250 nm. The beam shaping and illumination system 102 and the projection system 104 can be arranged in a vacuum housing and / or surrounded by a machine room. For example, evacuation devices for producing a vacuum and / or drive devices for mechanically operating or adjusting the optical elements are provided in the machine room. Furthermore, electrical controls and the like may be provided in this engine room.

The DUV lithography system 100 has a DUV light source 106 on. As a DUV light source 106 For example, an ArF excimer laser can be provided, which radiation 108 in the DUV range at, for example, 193 nm emitted.

This in 1 illustrated beam shaping and illumination system 102 directs the DUV radiation 108 on a lithography mask 120 , The lithography mask 120 is formed as a transmissive optical element and can outside the systems 102 . 104 be arranged. The lithography mask 120 has lithographic structures, which by means of the projection system 104 reduced to a wafer 124 or the like. Here is the wafer 124 in the image plane of the projection system 104 arranged.

The projection system 104 has several lenses 128 and / or mirrors for imaging the lithographic mask 120 on the wafer 124 on. This can be individual lenses 128 and / or mirrors of the projection system 104 symmetrical to the optical axis 126 of the projection system 104 be arranged. It should be noted that the number of lenses and mirrors of the DUV lithography system 100 is not limited to the number shown. There may also be more or fewer lenses and / or mirrors. Furthermore, the mirrors are usually curved at their front for beam shaping.

The illustrated lithography system 100 points in the beam path of the projection system 104 is predetermined, in particular an optical arrangement 110 with a wavefront manipulator 112 on. The projection light 108 radiates on the way to the wafer 124 the optical arrangement 110 and the wavefront manipulator 112 , The projection light 108 In particular, it can be divided into radiation beams 114, which extend along a transmission direction 116 propagate in the beam path.

An air gap between the last lens 128 and the wafer 124 can be through a liquid medium 132 be replaced, which has a refractive index> 1. The liquid medium may be, for example, high purity water. Such a structure is also referred to as immersion lithography and has an increased photolithographic resolution.

2 shows an embodiment of a wavefront manipulator 112 with a segmented optical element 218 which is a movably arranged segment 222 having. The illustrated wavefront manipulator 112 For example, in an optical arrangement 110 as the wavefront manipulator 112 be used (see 1 ). The segmented optical element 218 is in the example of 2 formed as a glass plate with a wedge shape, wherein the wedge in the direction of displacement 238 tapers. The wedge shape is for the sake of clarity in the 2 not shown. An illustration of a wedge-shaped segment 222 is shown in FIG 3b given. The segmented optical element 218 has a plurality of segments 220 on, their light source side surfaces 221 in this example form a layer. In the 2 For reasons of clarity, it is only a segment surface 221 hatched and marked. The segments 220 are transverse to the direction of radiation 116 arranged side by side. The segments 220 of the segmented optical element 218 are in this representation in the zero position. The movably arranged segment 222 is in the 2 as a movable segment 222 is formed and is displaceable along the displacement direction 238.

Furthermore, in the 2 a picture frame 232 with field points 234 shown (in the 2 is just a field point). From the field point 234 goes a ray of light 114 out, which is in the direction of radiation 116 propagates. The ray bundle 114 Illuminates a subaperture 236 on the segmented optical element 218. The subaperture 236 lies in the representation of 2 completely on the Einstrahlseite the movably arranged segment 222 , Moreover, in the 2 the one from the projection light 108 spanned projection light cone 108 shown. The projection light cone 108 includes all the rays coming from the field points of the image field 232 out. The projection light cone 108 Illuminates one in the 2 circular area 226 on the segmented optical element 218 , After passing through the segmented optical element 218 the projection light cone is planted 108 continues and illuminates a surface 228, which may be, for example, a Einstrahlseite another optical element (not shown). That from the field point 234 outgoing beams 114 illuminates one in the area 228 located further Subapertur 230 , In the illustrated situation, the light beams of the beam diverge 114 , which is why the subaperture 230 a larger area than the subaperture 236 ,

In the example of FIG. 2 can be by means of a shift of the slidably disposed segment 222 an optical path length for the beam 114 to adjust. In this way it is possible to see the wavefront of the beam 114 relative to the other beams of the projection light cone 108 to correct.

In a preferred embodiment, the segmented optical element 218 such in segments 220 split that subaperture 236 of the beam 114 at least two of the segments 220 illuminated (see, for example 8th ). Furthermore, it is preferred that the other segments 220 are movably arranged.

Deviating from the presentation of 2 is it possible for the segmented optical element 218 in other ways into segments 222 is divided. In addition, the segmented optical element 218 not necessarily given in a rectangular basic form.

3a shows the segmented optical element of 2 , wherein the movably arranged segment 222 in this representation, from the zero position along the direction of displacement 238 and relative to the beam 114 is moved. In the 3a are also from the beam 114 illuminated subaperture 236 as well as the area 236 ' drawn, which in the zero position of the segment 222 from the beam 114 would be illuminated.

3b shows a perspective view of an embodiment of the movably arranged segment 222 in two positions A and B. The segment 222 of the 3b has a wedge shape, that is, it is in the transmission direction 116 having a position-dependent geometric thickness. The movably arranged element 222 is along the direction of displacement 238 slidably arranged. The segment 222 is in the illustrated positions A and B relative to the beam 114 postponed. The of the beam 114 Illuminated subaperture 236 is drawn in both positions. If a refraction of the light is neglected, the beam passes through 114 in the segment 222 a volume 302 . 304 which is determined by the geometric thickness of the segment 222 at the position of the subaperture 236 along the transmission direction 116 and the subaperture 236 itself is defined. By the displacement of the wedge-shaped segment 222 from the position shown in Fig. A to the position shown in Fig. B, a reduced geometric path length for the beam becomes 114 in the segment 222 reached. As a result, the optical path length is reduced and a wavefront can be the segment 222 go through faster. The optical and geometric path length in volume 302 ( 3b : A) is for the ray bundle 114 greater than in volume 304 ( 3b : B). In this respect, a wavefront manipulation occurs when moving 238 of the transparent segment 222 ,

4 shows a cross section through a further embodiment of a movably arranged segment 422 , which is a segment of a segmented optical element 218 (please refer 2 . 3a or 3b ) can be. In this embodiment, the segment has two partial volumes 402 and 404 which differ in their refractive index for the projection light. In the present case, the partial volume 402 a refractive index n1 which is smaller than a refractive index n2 of the sub-volume 404. Depending on the position on the inflow side of the segment 422 a light beam passes through different areas in the segment 422 , This is in the 4 by means of three beams of light 410 . 420 . 430 shown.

The light rays pass through different geometric distances 412 . 423 , 432 in the subvolume 404 with refractive index n2 and different geometric distances 414 . 424 . 434 in the subvolume 402 with refractive index n1. Therefore, the optical path length of the three light beams 410 . 420 . 430 differently. This is in the 4 represented by arrows of different lengths, which are the segment 422 irradiated light rays 416 . 426 . 436 represent. The optical path length for the light beam 410 is the lowest, which is why this is the segment 422 goes through faster and therefore by the longest arrow 416 is represented. The same applies to the two other light beams 420 and 430 with the corresponding arrows 426 and 436 , At a given Einstrahlposition, by the subaperture 236 (please refer 2 . 3a . 3b ) is defined by a shift of the segment 422 thus the optical path length for a light beam or a beam 114 be set. As a result, the respective wavefront of the incoming light rays 410 . 120 . 430 changed.

It should be noted that a representation of the refraction of the light beams was deliberately omitted in order to clarify the actual effect of adjusting the optical path length.

Except the illustrated division of the segment 422 in volumes 402 . 404 with different refractive indices, further divisions are possible, for example a discretized structure in which the interface between the volumes 402 , 404 is represented by a step function. Also, more than two different volumes 402 . 404 conceivable or also gradients of the refractive index within a segment 422 ,

5 shows a schematic example of a correction of a wavefront of the projection light 108 by means of a wavefront manipulator 218 which is here as a segmented optical element 218 is trained. In the middle illustration of the 5 If you look in the possible direction of displacement on the juxtaposed segments 220 of which only one is provided with the corresponding reference numeral. In this illustration, it can be clearly seen that the light-source-side segment surfaces 221 (in the figure is only one surface 221 referred) do not have to lie in one plane, but rather also over an area 500 along the transmission direction 108 can be distributed. The area 500 results from the condition that the wavefront manipulator 218 in a near-field position in the beam path of the lithography system 100 should be arranged. This is then fulfilled when the individual segment surfaces 221 the segments 220 are arranged in a near-field position. In the below described 6 Field levels and corresponding positions are explained in more detail.

In the 5 Two diagrams (top and bottom view) are shown, which have an x-axis and a phase axis, which is denoted by Δφ. The x-axis corresponds to a cross-sectional position of the on the Wellenfronmanipulator 218 incident projection light 108 , The phase axis represents the coefficient of tilt of the wavefront of the projection light 108 relative to the ideal or desired wavefront at the position of the wavefront manipulator 218 in the beam path. In the example, the course of the tilt of the wavefront 506 . 508 are described by a function whose amplitude is proportional to x ³ . For negative x-values, Δφ is less than 0, which means that the wavefront leads the target position. For positive x-values, Δφ is greater than 0, which means that the wavefront is retarded with respect to the target position. Such a course of the wavefront causes a distortion of the image.

Furthermore, in the 5 a coordinate system x, z drawn, which shows the orientation of the wavefront manipulator 218 relative to the projection light 108 represents. The x-position should coincide with the x-position in the phase diagrams. Due to the arrangement of the segments of the wavefront manipulator shown 218 can be a weakening of the phase difference 506 can be achieved over the desired phase curve. After passing through the wavefront manipulator 218 has the projection light 108 a reduced amount of phase difference 508 to an ideal course of the wavefront. The segments 220 the segmented optical element 218 are designed such that a geometric path length of the projection light 108 can be adjusted depending on the x-position.

In this example, the correction was made with a total of twelve segments 220 reached. For a better correction, more segments are advantageous. In particular, in this example, correction is shown only along the x-axis. It is understood that this correction by a corresponding arrangement of the wavefront manipulator 218 is also possible along any other axis. By arranging a plurality of segmented optical elements 218 Furthermore, a higher resolution and / or a combined correction along more than one axis can be achieved in the beam path in succession (see, for example, FIG 8th ).

6 shows an embodiment of a projection optics 600 a lithography system 100 with an optical arrangement 610 , The optical design of the projection optics 600 corresponds with the exception of the optical arrangement 610 of the 34 of the US 8,289,619 B2 , which are hereby incorporated by reference ("incorporation by reference"). The optical arrangement 610 especially in all in the US 8,289,619 B2 catadioptric projection optics are used. In the plane 602 is an image plane in this example 602 , which field points 604 . 606 having. From every field point 604 . 606 goes a ray of light 614 . 616 out. The projection optics 600 is set to the field points 604 . 606 the picture plane 602 reduced to a wafer 624 map. For this purpose, the projection optics includes 600 a variety of unspecified lenses and mirrors. The projection optics 600 also has an optical arrangement 610 with a wavefront manipulator 612 on. For example, it may be provided that the wavefront manipulator one of 2 . 3a . 4 . 5 . 8th in the optical arrangement 610 to use. Every ray bundle 614 . 616 Illuminates a subaperture on the wavefront manipulator 610 , In the 6 is also a pupil level 620 located. This is distinguished by the fact that every ray of light 614 . 616 the pupil plane 620 irradiated in the full diameter. The subaperture of each ray bundle 614 . 616 corresponds to the pupil level 620 therefore, the diameter of the projection light cone.

A near-field position can be defined as follows. Each of a field point 604, 606 of a field level 602 outgoing beams 614 . 616 illuminated at the segment surface 221 a subaperture with a subaperture diameter SAD. All from the field level 602 outgoing beams 614 . 616 lighting together on the segment surfaces 221 an optically used area with the maximum diameter DFP. The area can be categorized using the ratio SAD / DFP. A ratio of 0 describes the field level 602 , a ratio of 1 the pupil level. For example, an area with a ratio between 0 and 0.5, preferably between 0 and 0.25, can be described as close to the field.

In the 6 is in particular the wavefront manipulator 612 arranged in a field near position. This is characterized in that the diameter of a subaperture SAD of a beam 614 . 616 on the wavefront manipulator 612 constitutes only a fraction, eg less than 50%, of the diameter of the optically used region DFP. The closer the wavefront manipulator 612 at the frame 602 is arranged, the better the wavefront of individual field points 604 . 606 correct individually. Because then the subaperture of a field point 604 . 606 on the wavefront manipulator 612 becomes smaller, should a lateral extent of the segments shrink, so that nevertheless a larger number of segments lie in the sub-aperture and thus higher-order aberrations can be corrected. It is understood that the surfaces of the individual optical segments not necessarily a level, but, as in 5 can also be distributed in a certain range, as long as they are still in the near-field position. You can also use the entire lens or the projection optics 600 as an optical arrangement with a wavefront manipulator 612 conceive. However, it is also the use of a dedicated optical arrangement 610 as it is in the 6 is indicated, possible. It is also conceivable that one of the projection lenses is used by a segmentation as wavefront manipulator.

Deviating from the 6 are also optical configurations conceivable that have no reflective element or at least have a folding mirror and / or at least one pupil mirror.

7 shows a cross section of another embodiment of a segmented optical element 718 , The segmented optical element 718 has segments in this embodiment 720 on, their contact surfaces 706 . 708 parallel to the marginal rays of an incident beam 114 are set up. This is schematic for the segment 704 shown. The ray bundle 114 is from a field point 234 of the image field 232 radiated. In addition, the segmented optical element has 718 opaque structures 710 on, which is an irradiation of projection light on the of the contact surfaces 706 . 708 on the irradiation side of the segmented optical element 718 formed edges prevented. With such an embodiment, therefore, an influence of the contact surfaces 706 . 708 on the projection light 108 minimized. Notwithstanding the illustrated embodiment of the opaque structures 710 are further arrangements possible. The opacity can be suitably adjusted and take into account the wavelength of the projection light used. For example, the side surface 708 . 706 each coated with a UV-absorbing material.

8th shows a schematic view of another embodiment of the wavefront manipulator 112 with two segmented optical elements 820 and 830 , each segment 821 and 831 include. Furthermore, in the 8th a ray of light 114 shown, which is along a transmission direction 116 propagates. The transmission direction 116 is shown here parallel to the z-axis of a Cartesian coordinate system. The two segmented optical elements 820 . 830 each point in the direction of radiation 116 rectangular segments 821, 831 on, the orientation of the segments 821 . 831 orthogonal to each other is selected. The segments 821 the segmented optical element 820 run along the y-direction and the segments 831 the segmented optical element 830 run along the x-direction. The segments 821 . 831 are, for example, according to the segments 222 of the 2 or 422 of the 4 educated. The segments 821 . 831 a respective segmented optical element 820 . 830 are each transverse to the direction of radiation 116 arranged side by side. This arrangement has the consequence that a light beam or beam 114 along the transmission direction 116 just one segment 821 . 831 a respective segmented optical element 820 . 830 irradiated. In the example of 8th are the segments 821 . 831 the segmented optical elements 820 . 830 each arranged in the xy plane. Exemplary is each a light source side segment surface 823 . 833 the two segmented optical elements 820 . 830 characterized. In the presentation of the 8th lie all segment surfaces 823 the segmented optical element 820 in one plane and all segment surfaces lie 833 the segmented optical element 830 in a plane. Deviating from this representation, it is possible that the segment surfaces 823, 833 of a respective segmented optical element 820 . 830 do not lie in one plane, as in the example 5 is shown.

Each of the segmented optical elements 820 . 830 has at least one movable segment 824 . 834 on. The moving segments 824 . 834 are along a shift direction 828 . 838 slidably arranged. The ray bundle 114 shines on a subaperture 826 of the first segmented optical element 820 and radiates this. As can be seen in the figure, the subaperture 826 covers part of the irradiation side of the two segments 822 and 824 , By a shift of the movably arranged segment 824 along the direction of displacement 828 can therefore be part of the beam 114 be set from the other part different optical path. Thus, a curved wavefront along the x-direction can be corrected (see, eg 5 ).

After the beam 114 the first segmented optical element 820 radiates, it radiates on a Subapertur 836 of the second segmented optical element 830 one in which the two segments 832 and 834 are located. By a shift of the movably arranged segment 834 along the direction of displacement 838 can now for in the y-direction different partial beams of the beam 114 a different optical path length can be set. Thus, a curvature of the wavefront in the y direction can be corrected.

With this embodiment, it is therefore possible to achieve a wavefront correction along several axes. More than two segmented optical elements are preferred 820 . 830 used, the displacement directions are arranged at further angles to each other and are sequentially irradiated. In particular, the segmented optical elements 820 830 into a larger number of segments 821 . 831 as shown here, preferably each individual segment 821 . 831 is movably arranged. Overall, this results in the possibility of manipulating or correcting even complex two-dimensionally curved wavefronts.

9 shows a cross section of a third embodiment of a wavefront manipulator 900 with two segmented optical elements 910 . 920 , The 9 shows the wavefront manipulator 900 in three different states A, B, C. The segmented optical elements 910 . 920 of the wavefront manipulator 900 These embodiments are each made of wedge segments 910 . 920 assembled and form a cavity-free volume. The segments 910 . 920 are each along a direction of displacement 912 . 922 slidably arranged. In this case, a shift takes place such that the segments 910 . 920 each touching each other flat on the side facing each other. The individual segments 910 . 920 of a respective segmented optical element are transverse to the direction of radiation 116 (corresponds to the beam direction of the light beam 114 ) arranged side by side, which is in side view of 9 is not recognizable. In the presentation of the 9 are the individual segments 910 . 920 one after the other into the image plane and / or out of the image plane. As before, this arrangement has the effect that the light beam 114 just one segment 910 . 920 of each segmented optical element radiates through and successively first the segment 910 of the first segmented optical element and then the segment 920 of the second segmented optical element, as will be explained below.

It is also a ray of light 114 shown on the segment 910 of the first segmented optical element. The light beam 114 then goes through a light path 914 in the segment 910 and then a light path 924 in the segment 920 , In the three representations A, B, C of 9 the segments 910, 920 are shown in different positions. As a result, the light path changes in each case 914 . 924 of the light beam 114 in the respective segment 910 , 920 and thus the optical path length that this must cover. Present is by a shift of the segments 910 . 920 relative to each other, therefore, the optical path length for the light beam 114 set.

In a further embodiment, for example, only the segments 920 movable while the segments 910 are not movable and / or the first optical element is not segmented.

These as well as other embodiments of the wavefront manipulator 900 For example, they are suitable for use in projection optics 104 of the 1 or 600 of the 6 ,

10 shows a fourth embodiment of a wavefront manipulator 112 , The wavefront manipulator 112 has a segmented optical element 218 with segments 220 on and a laterally arranged infrared laser 1020 , In the 10 was on a representation of the projection light 108 and / or a beam 114 waived.

The infrared laser 1020 is equipped to infrared radiation 1030 to radiate in a predeterminable direction. In the example of 10 The infrared laser 1020 emits an infrared ray beam 1030 on an aperture 1040 , which is a partial area of the inflow side of the segment 222 is a. The infrared radiation 1030 is made of the material of the segment 222 in the area of the aperture 1040 at least partially absorbed, whereby the material heats up. This allows a targeted change in the optical properties of the segment 222 in the area of the aperture 1040 be achieved. For example, the refractive index of the material may change, or due to thermal expansion, the respective geometric optical path length of a light beam will change as it passes through the aperture 1040.

The infrared laser 1020 is further adapted to the infrared beam to further areas 1050 of the segment 222 to judge. It is also possible, deviating from the presentation, to cover several areas 1040 . 1050 is irradiated simultaneously. Furthermore, more infrared lasers 1020 be provided on more segments 220 the segmented optical element 218 radiate. In addition, the infrared lasers 1020 also different from in the 10 be arranged shown position. In addition to the change in the optical path length at the aperture 1040 Due to the possible displacement of the segment, therefore, a further change can be made by the heat input and the thereby variable optical property of the infrared-irradiated part of the segment.

11 shows a schematic flow diagram of a method for operating a lithography system 100 with an optical arrangement 112 with a wavefront manipulator 114 . 112 . 610 . 112 . 900 (please refer 1 . 2 . 6 . 8th . 9 ). The illustrated method comprises the steps of radiating through 1110 the optical arrangement 112 with the wavefront manipulator 114 . 112 . 610 . 112 . 900 with projection light 108, as well as the setting 1120 a position of a movable segment 222 a segmented optical element 218 of the wavefront manipulator 114 . 112 . 610 , 112, 900, leaving an aberration of the wavefront of the projection light 108 is corrected.

The radiating 1110 comprises a blasting of the projection light 108 through a light source 106 , passing the projection light 108 in a beam forming and illumination system 102 and a projection optics 104 , In addition, the process step of the transmission comprises 1110 in particular the sub-process steps of a detection 1111 the wavefront of the projection light 108 with a wavefront sensor, a computation 1112 of coefficients of Zernike polynomials such that a linear combination of the Zernike polynomials with the calculated coefficient of the detected wavefront corresponds, as well as a computation 1113 of positions of segments to be set 220 of segmented optical elements 218 such that the detected wavefront is corrected.

A capture 1111 The wavefront can be done in particular with a device designed for this purpose, for example a wavefront sensor such as a Hartmann-Shack sensor. The calculation 1112 The coefficients of the Zernike polynomials can be carried out by means of a computer or computer program designed for this purpose, for example using an optimization algorithm. Also the calculation 1113 the position of the segments to be set 220 to correct the wavefront can be performed by a dedicated computer. For this purpose, the computer comprises, for example, a memory unit in which the effect of a change in position of each individual segment 220 stored on the wavefront.

The process step of setting 1120 a position of a movably arranged segment 222 includes, for example, a driving 1121 of the actuator assigned to the segment 222, so that the segment 222 is brought into the calculated position.

The method may comprise further method steps not shown here. Advantageously, this method is performed in a kind of control loop, so that several hundred or thousand control steps are performed within one second. A high temporal resolution makes it possible, in particular, to effectively correct disturbances with very small time constants, such as, for example, vibrations of the lithography system, which lead to small local deformations of optical elements.

12 shows a schematic cross section of an embodiment of a segmented optical element 1200, which, for example, in a wavefront manipulator 112 . 612 . 900 Can be used. The peculiarity of this embodiment is that the three segments shown 1210 . 1220 . 1230 are each individually shaped, wherein they touch with their inclined side surfaces 1213, 1223, 1233 in this example, and that the Einstrahlseiten 1211 , 1221, 1231 do not form a flat surface with each other. A respective angle of attack α1-α6 of the side surfaces 1213 . 1223 . 1233 the segments 1210 . 1220 . 1230 is preferably chosen so that a respective side surface 1213 . 1223 . 1233 parallel to a middle, that is to say an averaged, direction of incidence of incident light rays 1214 . 1215 . 1216 and / or a radiation beam. This becomes an effect of the side surfaces 1213 . 1223 . 1233 effectively minimized to the propagation of the projection light.

There are also three light beams 1214 . 1215 . 1216 which illuminate different areas or positions on the segmented optical element 1200 and irradiate the segmented optical element 1200 along different paths. The rays of light 1214 . 1215 . 1216 each have an individual propagation direction. The light beam 1214 For example, runs obliquely to a solder (shown dotted) on the Einstrahlseiten 1211 . 1221 . 1231 the segments 1210 . 1220 . 1230 ,

The first ray of light 1214 falls diagonally on the Einstrahlseite 1211 of the first segment 1210 , becomes when radiating into the first segment 1210 Broken in the direction of the Lot and occurs obliquely over the Ausstrahlseite 1212 from the first segment 1210 out, where he is broken away from the Lot. Since here the Einstrahlseite 1211 and the broadcast side 1212 are parallel to each other, the light beam 1214 has after passing through the segment 1210 the same direction of propagation that he already had before the radiation.

The second light beam 1215 falls perpendicular to the Einstrahlseite 1221 of the middle segment 1220 and therefore will not be broken when irradiated. Due to the non-rectangular arrangement of the side surface 1223 relative to the Einstrahlseite 1221 the ray of light falls 1215 on the side surface 1223 of the segment 1220 , Therefore, the light beam occurs 1215 over the side surface 1223 from the segment 1220 out and over the side surface 1233 of the outer segment 1230 into this one. Finally, the beam of light shines 1215 over the broadcast side 1232 from the outer segment 1230 out. The light beam 1215 Thus, two segments 1220, 1230 of the segmented optical element 1200 partially penetrate.

The third light beam 1216 radiates perpendicular to the inflow side 1231 of the third segment 1230 a, this radiates and radiates on the Ausstrahlseite 1232.

For reasons of clarity, a representation of movably arranged segments was dispensed with in this exemplary embodiment. It is understood, however, that the statements made on the other embodiments are also applicable to this embodiment.

Although the present invention has been described with reference to embodiments, it is variously modifiable. For example, a non-linear movement of the segments is conceivable. It is also possible to use circular strips as segments which are rotatable about a common center relative to each other. The segments of an optical element can in principle be arranged movably at different locations in the beam path. One can then speak of a distributed Alvarez arrangement. Particularly suitable as transparent materials for the segments are quartz glass or CaF ₂ .

LIST OF REFERENCE NUMBERS

100

lithography system

102

Beam forming and lighting system

104

projection system

106

light source

108

projection light

110

optical arrangement

112

Wavefront manipulator

114

ray beam

116

By beam direction

120

lithography mask

124

wafer

128

lens

132

high refractive liquid

218

segmented optical element

220

segments

221

light source side segment surface

222

movably arranged segment

226

Illuminated surface on the segmented optical element

228

Illuminated surface on a subsequent optical element

230

subaperture

232

field

234

field point

236

subaperture

236 '

illuminated area before moving

238

shift direction

302

irradiated volume with geometric path length 1

304

irradiated volume with geometric path length 2

402

Partial volume with refractive index n1

404

Partial volume with refractive index n2

410

first light beam

412

geometric path length of the first light beam in refractive index n2

414

geometric path length of the first light beam in refractive index n1

416

transmitted first light beam

420

second light beam

422

Segment with partial volumes with different refractive indices

423

geometric path length of the second light beam in refractive index n2

424

geometric path length of the second light beam in refractive index n1

426

transmitted second light beam

430

third light beam

432

geometric path length of the third light beam in refractive index n2

434

geometric path length of the third light beam in refractive index n1

436

transmitted third light beam

500

Area

506

Phase difference of the wavefront in front of the wavefront manipulator

508

Phase difference of the wavefront after the wavefront manipulator

600

projection optics

602

field

604

field point

606

field point

610

optical arrangement,

612

Wavefront manipulator

614

ray beam

616

ray beam

620

pupil

624

wafer

704

segment

706

contact area

708

contact area

710

opaque structure

718

segmented optical element

720

segments

820

segmented optical element

821

segments

822

slidably arranged segment

823

light source side segment surface

824

slidably arranged segment

826

subaperture

828

shift direction

830

segmented optical element

831

segments

832

slidably arranged segment

833

light source side segment surface

834

slidably arranged segment

836

subaperture

838

shift direction

900

Wavefront manipulator

910

first wedge segment

912

Displacement direction of the first wedge segment

914

geometric path length in the first wedge segment

920

second wedge segment

922

Displacement direction of the second wedge segment

924

geometric path length in the second wedge segment

1020

infrared laser

1030

Infrared radiation beam

1040

Aperture of infrared beam on the segment

1050

further possible radiation surfaces for the infrared beam

1110

Process step (radiography)

1111

Procedural step (capture)

1112

Procedural step (calculation)

1113

Procedural step (calculation)

1120

Procedural step (setting)

1121

Procedural step (driving)

1210

first segment

1211

Einstrahlseite

1212

jetting side

1213

side surface

1214

beam of light

1215

beam of light

1216

beam of light

1220

second segment

1221

Einstrahlseite

1222

jetting side

1223

side surface

1230

third segment

1231

Einstrahlseite

1232

jetting side

1233

side surface

α1 - α6

angle of attack

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19956353 C1 [0008]
• WO 2013044936 A1 [0008]
• US 8289619 B2 [0105]

Claims (17)

Optical arrangement (110, 610) for a lithography system (100), which has a beam path for imaging lithographic structures, with a wavefront manipulator (112, 612, 900) arranged in the beam path, which in the operation of the lithography system (100) differs from one in the Beam path extending beam (114, 614, 616) is irradiated along a transmission direction (116) and which is adapted to adjust an optical path length for the beam (114, 614, 616), wherein the wavefront manipulator (112, 612, 900) : a segmented optical element (218, 718, 820, 830) with segments (220, 720, 821, 831) arranged transversely to the transmission direction (116), wherein at least one segment (222, 422, 822, 824, 832, 834, 910, 920) is movably arranged such that when the position of the segment (222, 422, 822, 824, 832, 834, 910, 920) relative to which the segment (222, 422, 822, 824, 832, 834 , 910, 920) radiating beams (114, 614, 616) changes the optical path length for the beam (114, 614, 616). Optical arrangement (110, 610) for a lithography system (100) according to Claim 1 wherein a geometric path length traversing the beam (114, 614, 616) in the segment (222, 422, 822, 824, 832, 834, 910, 920) and / or a refractive index along that of the beam (114, 614, 616) in the segment (222, 422, 822, 824, 832, 834, 910, 920) depending on the position of the segment (222, 422, 822, 824, 832, 834, 910, 920) relative to the beam (114, 614, 616) are adjustable. Optical arrangement (110, 610) for a lithography system (100) according to Claim 1 or 2 wherein the movably arranged segment (222, 422, 822, 824, 832, 834, 910, 920) of the segmented optical element (218, 718, 820, 830) is independent of the further segments (220, 720, 821, 831) the segmented optical element (218, 718, 820, 830) is movable. An optical arrangement (110, 610) for a lithography apparatus (100) according to any one of the preceding claims, wherein a segment (222, 422, 822, 824, 832, 834, 910, 920) of the segmented optical element (218, 718, 820, 830) along a displacement direction (238, 828, 838, 912, 922) is displaceable and the displacement direction (238, 828, 838, 912, 922) with the transmission direction (116) forms an angle greater than 0 °. Optical arrangement (110, 610) for a lithography system (100) according to Claim 4 wherein the wavefront manipulator (112, 612, 900) is adapted to correct for tilt, spherical aberration, coma, astigmatism, distortion and / or curvature of the field. An optical arrangement (110, 610) for a lithography system (100) according to any one of the preceding claims, wherein a surface (706, 708) between two segments (220, 720, 821, 831) of the segmented optical element (218, 718, 820, 830) of the wavefront manipulator (112, 612, 900) is parallel to the beam (114, 614, 616). An optical arrangement (110, 610) for a lithography system (100) according to any one of the preceding claims, wherein an edge (710) between two segments (220, 720, 821, 831) of the segmented optical element (218, 718, 820, 830) of the wavefront manipulator (112, 612, 900) is opaque. An optical arrangement (110, 610) for a lithography apparatus (100) according to any one of the preceding claims, wherein a beam (114, 614, 616) emanates from a field point (234, 604, 606) corresponding to a pixel of an image of the lithographic structure wherein the beam (114, 614, 616) illuminates a subaperture (236, 826, 836) on the segmented optical element (218, 718, 820, 830) and wherein at least two segments (220, 720, 821, 831) in the area defined by the subaperture (236, 826, 836). Optical arrangement (110, 610) for a lithography system (100) according to one of the preceding claims, wherein the wavefront manipulator (112, 612, 900) has a plurality of segmented optical elements (218, 718, 820, 830) arranged one behind the other along the beam path are. Optical arrangement (110, 610) for a lithography system (100) according to Claim 9 , wherein a plurality of segmented optical elements (218, 718, 820, 830) arranged in succession in the beam path along the transmission direction (116) are present, the segments (220, 720, 821, 831) of which are along a displacement direction (238, 828, 838) , 912, 922) are displaceable and the displacement direction (238, 828, 838, 912, 922) with the transmission direction (116) encloses an angle greater than 0 °. An optical arrangement (110, 610) for a lithography system (100) according to one of the preceding claims, wherein the wavefront manipulator (112, 612, 900) is arranged in a field-near position in the beam path. An optical arrangement (110, 610) for a lithography system (100) according to any one of the preceding claims, wherein a heating device (1020) is provided, which is adapted to associated segments (220, 720, 821, 831) cause a local temperature change. An optical arrangement (110, 610) for a lithography system (100) according to any one of the preceding claims, wherein the wavefront manipulator (112, 612, 900) comprises two segmented optical elements (218, 718, 820, 830), characterized in that: Segments (910, 920) of a respective segmented optical element (218, 718, 820, 830) are arranged side by side transversely to the direction of radiation (116); the segmented optical elements (218, 718, 820, 830) are arranged one behind the other in the transmission direction (116) and enclose a cavity-free volume; a segment (910) of the one segmented optical element (218, 718, 820, 830) corresponds to a corresponding segment (920) of the other segmented optical element (218, 718, 820, 830), which in the transmission direction (116) in one Surface contact stand; and by a displacement of the corresponding segments (910, 920) in respectively opposite direction (912, 922), the optical path length for the beam (114, 614, 616) which passes through the two segments (910, 920) is variable. Optical arrangement (110, 610) for a lithography system (100), which has a beam path for imaging lithographic structures, with a wavefront manipulator (112, 612, 900) arranged in the beam path, which in the operation of the lithography system (100) differs from one in the Beam path extending beam (114, 614, 616) is irradiated along a transmission direction (116) and which is adapted to adjust an optical path length for the beam (114, 614, 616), wherein the wavefront manipulator (112, 612, 900) : a segmented optical element (218, 718, 820, 830) having segments (220, 720, 821, 831) juxtaposed transversely of the direction of radiation (116), wherein a heater (1020) is provided which is arranged in associated segments (220, 720, 821, 831) cause a local temperature change for adjusting the optical path length for the respective segment radiating beam (114, 614, 616). Optical arrangement for a lithography system according to Claim 14 , further comprising the features according to claims 1-13. Method for operating a lithography system (100) with an optical arrangement (110, 610) according to one of the Claims 1 to 15 method comprising the steps of: irradiating (1110) the optical assembly (110, 610) with projection light (108); and adjusting (1120) a position of a movable segment (222, 422, 822, 824, 832, 834, 910, 920) of a segmented optical element (218, 718, 820, 830) of a wavefront manipulator (112, 610, 900) Correction of an aberration of a wavefront of the projection light (108). Method for operating a lithography system (100) with an optical arrangement (110, 610) according to Claim 16 further comprising the steps of: detecting (1111) the wavefront of the projection light (108) with a wavefront sensor; Calculating (1112) coefficients of Zernike polynomials such that a linear combination of the Zernike polynomials with the calculated coefficient corresponds to the detected wavefront; Calculating (1113) positions of segments (220, 720, 821, 831) of segmented optical elements (218, 718, 820, 830) to be adjusted such that the detected wavefront is corrected; and driving (1121) actuators associated with the segments (220, 720, 821, 831) to adjust the calculated position of each segment (222, 422, 822, 824, 832, 834, 910, 920).

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