EP1483614A2 - Objectif lentille en cristal - Google Patents

Objectif lentille en cristal

Info

Publication number
EP1483614A2
EP1483614A2 EP03708221A EP03708221A EP1483614A2 EP 1483614 A2 EP1483614 A2 EP 1483614A2 EP 03708221 A EP03708221 A EP 03708221A EP 03708221 A EP03708221 A EP 03708221A EP 1483614 A2 EP1483614 A2 EP 1483614A2
Authority
EP
European Patent Office
Prior art keywords
lens
lenses
coating
optical
birefringence
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP03708221A
Other languages
German (de)
English (en)
Inventor
Aksel Goehnermeier
Alexandra Pazidis
Birgit Mecking
Christoph Zaczek
Daniel Kraehmer
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Carl Zeiss SMT GmbH
Original Assignee
Carl Zeiss SMT GmbH
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Carl Zeiss SMT GmbH filed Critical Carl Zeiss SMT GmbH
Publication of EP1483614A2 publication Critical patent/EP1483614A2/fr
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/708—Construction of apparatus, e.g. environment aspects, hygiene aspects or materials
    • G03F7/7095—Materials, e.g. materials for housing, stage or other support having particular properties, e.g. weight, strength, conductivity, thermal expansion coefficient
    • G03F7/70958—Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties
    • G03F7/70966—Birefringence
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/02—Optical elements characterised by the material of which they are made; Optical coatings for optical elements made of crystals, e.g. rock-salt, semi-conductors
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G02B5/3083—Birefringent or phase retarding elements
    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/70—Microphotolithographic exposure; Apparatus therefor
    • G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
    • G03F7/7055—Exposure light control in all parts of the microlithographic apparatus, e.g. pulse length control or light interruption
    • G03F7/70566—Polarisation control

Definitions

  • the invention relates to a lens according to the preamble of claim 1.
  • Such projection lenses are known from US 6,201,634. It is disclosed there that in the manufacture of fluoride crystal lenses the lens axes are ideally aligned perpendicular to the ⁇ l l l ⁇ crystal planes of the fluoride crystals in order to minimize the birefringence of the spam. US Pat. No. 6,201,634 assumes that fluoride crystals have no intrinsic birefringence.
  • the indexing of the crystal directions is given below between the characters " ⁇ " and “>", the indexing of the crystal planes between the characters “ ⁇ ” and “ ⁇ ”.
  • the crystal direction always indicates the direction of the surface normal of the corresponding crystal plane.
  • the crystal direction ⁇ 100> points in the direction of the surface normal of the crystal plane ⁇ 100 ⁇ .
  • the cubic crystals, to which the fluoride crystals belong have the main crystal directions ⁇ 110>, ⁇ 1 10>, ⁇ 1 10>, ⁇ 1 1 0>,
  • the main crystal directions ⁇ 110>, ⁇ T l0>, ⁇ 10>, ⁇ T ⁇ 0>, ⁇ 101>, ⁇ 10 ⁇ >, ⁇ T ⁇ l>, ⁇ T ⁇ T>, ⁇ 011>, ⁇ 0l l>, ⁇ 0l T> and ⁇ T T> are also equivalent to one another, so that crystal directions which point in one of these main crystal directions are given the prefix “(110) -”. Crystal planes which are perpendicular to one of these main crystal directions are accordingly given the prefix “(110 ) - ".
  • the main crystal directions ⁇ 111>, ⁇ TTT>, ⁇ TT 1>, ⁇ T 1 T>, ⁇ 11 T>, ⁇ T 11>, ⁇ 111> and ⁇ 11 1> are also equivalent to each other, so that in the following crystal directions, which point in one of these main crystal directions are given the prefix "(111) -”. Crystal planes which are perpendicular to one of these main crystal directions are accordingly given the prefix "(111) -". Statements that are made below regarding one of the above-mentioned main crystal directions always apply to the equivalent main crystal directions.
  • Projection objectives and microlithography projection exposure systems are, for example, from the patent application PCT / EP00 / 13148 by the applicant and the therein known writings known.
  • the exemplary embodiments of this application show suitable purely refractive and catadioptric projection objectives with numerical apertures of 0.8 and 0.9, at an operating wavelength of 193 nm and 157 nm.
  • the object of the invention is to provide projection objectives for a microlithography projection exposure system in which the influence of birefringence, in particular intrinsic birefringence, is significantly reduced.
  • claim 1 proposes to align the lens axes in fluoride crystal lenses so that they coincide with the ⁇ 100> crystal direction.
  • the lens axes coincide with a main crystal direction if the maximum deviation between the lens axis and the main crystal direction is less than 5 °.
  • Not all fluoride crystal lenses of the lens need to have such an alignment of the crystal planes.
  • Those lenses in which the lens axes are perpendicular to the ⁇ 100 ⁇ crystal planes are also referred to below as (100) lenses.
  • the alignment of the line The axis in the ⁇ 100> crystal direction has the advantage that the disruptive influence of intrinsic birefringence, which occurs when light propagates in the ⁇ 110> crystal direction, only becomes noticeable at higher opening angles of the light beams than for an alignment of the lens axis in ⁇ 111> crystal direction.
  • the opening angle means the angle between a light beam and the optical axis outside a lens and between the light beam and the lens axis inside a lens. Only when the opening angles come into the range of the angle between the ⁇ 100> crystal direction and the ⁇ 110> crystal direction, do the corresponding light rays feel the influence of birefringence.
  • the angle between the ⁇ 110> crystal direction and the ⁇ 100> crystal direction is 45 °.
  • the lens axis were oriented in the ⁇ 111> crystal direction, the disturbing influence of the intrinsic birefringence would be noticeable even at smaller opening angles, since the angle between the ⁇ 110> crystal direction and the ⁇ 111> crystal direction is only 35 °.
  • the disclosed approaches can of course also be used to reduce the disruptive influence of the birefringence.
  • the lens axis is given, for example, by an axis of symmetry of a rotationally symmetrical lens. If the lens has no axis of symmetry, the lens axis can be given by the center of an incident beam or by a straight line with respect to which the beam angles of all light rays within the lens are minimal.
  • refractive or diffractive lenses and correction slats with free-form correction surfaces are suitable as lenses.
  • Flat plates are also regarded as lenses if they are arranged in the beam path of the lens. The lens axis of a flat plate is perpendicular to the flat lens surface.
  • the lenses are preferably rotationally symmetrical lenses.
  • Lenses have an optical axis that runs from the object plane to the image plane.
  • the (100) lenses are preferably constructed centered around this optical axis, so that the lens axes also coincide with the optical axis.
  • the invention can advantageously be used in projection objectives for a microlithography projection exposure system, since extremely high demands are made on the resolution capability for these objectives.
  • the influence of birefringence also has a disruptive effect on test lenses, with which, for example, lenses for projection lenses are tested by measuring wave exposures with a large aperture.
  • opening angles which are greater than 25 °, in particular greater than 30 ° occur within the (100) lenses. It is precisely at these large opening angles that the invention comes into play in orienting the lens axes in the ⁇ 100> crystal direction. If the lens axes were oriented in the ⁇ 111> crystal direction, the light rays with opening angles greater than 25 °, in particular greater than 30 °, would feel the disruptive influence of birefringence more clearly if one of the correction measures described below is not used.
  • NA the numerical aperture on the image side
  • the opening angle which corresponds to the numerical aperture on the image side within a fluoride crystal lens, if the light beam is refracted at a flat interface. This is achieved by the lenses, which are arranged close to the image plane, collecting lens surfaces, flat lens surfaces or at most slightly have diverging lens surfaces if a more collecting lens surface follows in the light direction after the diverging lens surface.
  • the (100) lenses should therefore preferably be used in the area of the field planes.
  • the area in which the (100) lenses should be used can be determined via the ratio of the lens diameter to the diameter of the diaphragm.
  • the lens diameter of the (100) lenses is preferably at most 85%, in particular at most 80% of the diaphragm diameter.
  • the lens axis is preferably aligned in the direction of the ⁇ 100> crystal direction.
  • the intrinsic birefringence of a fluoride crystal lens is not only dependent on the opening angle of a light beam, but also on the azimuth angle of the light beam.
  • a birefringence distribution ⁇ n ( ⁇ L , ⁇ L ) can be assigned to each fluoride crystal lens, which is a function of the opening angle ⁇ L on the one hand and a function of the azimuth angle ⁇ L on the other.
  • the value of the birefringence ⁇ n indicates the ratio of the optical path difference for two mutually orthogonal linear polarization states to the physical beam path covered in the fluoride crystal in the unit [nm / cm] for a beam direction determined by the aperture angle ⁇ and the azimuth angle ⁇ L.
  • the intrinsic birefringence is therefore independent of the beam paths and the shape of the lens.
  • the optical path difference for a beam is obtained accordingly by multiplying the birefringence by the beam path covered.
  • the opening angle ⁇ L is determined between the beam direction and the lens axis, the azimuth angle ⁇ between the beam direction projected into the crystal plane perpendicular to the lens axis and a reference direction firmly linked to the lens.
  • the angular dependence of the birefringence distributions of the individual fluoride crystal lenses leads to the rays of a bundle of rays being in the image plane of the lens meets a pixel, experience angle-dependent optical path differences ⁇ OPL ( ⁇ R , ⁇ R ) for two mutually orthogonal linear polarization states.
  • the optical path differences ⁇ OPL are given as a function of the opening angle ⁇ R and the azimuth angle ⁇ R.
  • the opening angle ⁇ R of a beam is determined between the beam direction and the optical axis in the image plane, the azimuth angle ⁇ R between the beam direction projected into the image plane and a fixed reference direction within the image plane.
  • the objective now has at least two lenses or lens parts made of fluoride crystal, it is advantageous if the lens axes of these lenses or lens parts point in a main crystal direction and the lenses or lens parts are rotated relative to one another about the lens axes such that the distribution ⁇ OPL ( ⁇ R , ⁇ R ) of the optical path differences has significantly reduced values compared to an arrangement in which the lens axes point in the same main crystal direction and the lenses or lens parts are installed with the same orientation.
  • the twisted arrangement of the lenses can reduce the maximum value of the distribution ⁇ OPL ( ⁇ R , ⁇ R ) by up to 20%, in particular by up to 25%, compared to an identically oriented installation become.
  • Lens parts are to be understood as individual lenses, for example, which are blown together seamlessly to form a single lens.
  • lens parts denote the building blocks of a single lens, the lens axes of the lens parts each pointing in the direction of the lens axis of the individual lens.
  • the birefringence distribution ⁇ n ( ⁇ L , ⁇ ) of the lens has a k-fold azimuthal symmetry.
  • the birefringence distribution of a (100) lens in which the lens axis points in the ⁇ 100> crystal direction, shows a 4-fold azimuthal symmetry
  • the birefringence distribution in a (III) lens in which the lens axis is in the ⁇ 111> crystal direction has a 3-fold azimuthal symmetry
  • the birefringence distribution of an (HO) lens in which the lens axis points in the ⁇ 110> crystal direction, a 2-fold azimuthal symmetry.
  • the individual lenses or lens parts of a group are now rotated relative to each other about the lens axes by a predetermined angle of rotation ⁇ .
  • the angles of rotation ⁇ are measured between the reference directions of two lenses or lens parts.
  • the lens axes point in the same main crystal direction or an equivalent main crystal direction.
  • the reference directions of the lenses of a group are linked to the lenses in such a way that the birefringence distributions ⁇ n ( ⁇ L , ⁇ 0 ) have the same azimuthal course for a predetermined opening angle ⁇ 0 .
  • the azimuthal areas with maximum birefringence occur at the same azimuth angles for all lenses in a group.
  • the angles of rotation between two lenses are given as follows:
  • the tolerance of ⁇ 10 ° takes into account the fact that under certain circumstances the angles of rotation deviate from the theoretically ideal angles in order to be able to take other boundary conditions into account when adjusting the lens. A deviation from the ideal angle of rotation leads to a non-optimal azimuthal compensation of the optical path differences of the lenses of a group. However, this can be tolerated within certain limits.
  • the angle of rotation between these two lenses is ideally 45 °, or 135 °, 225 ° ...
  • the lenses of a group are determined, for example, by the fact that an outermost aperture beam of a bundle of rays within these lenses each has similar opening angles, the opening angles of the outermost aperture beam within these lenses advantageously being greater than 15 °, in particular greater than 20 °.
  • the outermost aperture beam is a beam that originates from an object point whose beam height in the diaphragm plane corresponds to the radius of the diaphragm and which therefore has an angle in the image plane in accordance with the numerical aperture on the image side.
  • the outermost aperture rays are used to define the groups because they usually have the largest aperture angles within the lenses and thus experience the greatest interference from birefringence. The determination of the optical path difference for two mutually orthogonal linear polarization states for the outermost aperture rays thus enables statements to be made about the maximum interference of a wavefront by the birefringence.
  • the outermost aperture beam covers the same beam path in each of these lenses.
  • the rotation of the lenses becomes particularly effective when the lenses are arranged adjacent to one another. It is particularly advantageous to divide a lens into two parts and to join the lens parts in a visually seamless manner, for example by wringing.
  • the projection lens has at least one group with (100) lenses and at least one group with (11) lenses. Good compensation is also possible if a group with (110) lenses is arranged inside the lens next to a group with (100) lenses.
  • birefringence not only has an absolute value, but also a direction.
  • the compensation of the disturbing influence The birefringence is optimal if the distribution of the optical path differences ⁇ OPL ⁇ ( ⁇ R , ⁇ R ), which is caused by the lenses or lens parts of all groups with (100) lenses, and the distribution of the optical path differences ⁇ OPL ( ⁇ R , 0 R ), which is caused by the lenses or lens parts of all groups with (111) lenses or (110) lenses, has similarly high maximum values.
  • Another advantageous way of reducing the disruptive influence of birefringence is to cover an optical element of the projection objective with a compensation coating.
  • each optical coating for example antireflection or mirror coatings, in addition to its properties with regard to reflection and transmission, also always entails optical path differences for two mutually orthogonal linear polarization states. These are different for s- and p-polarized light and also depend on the angle of incidence of the beam on the layer. So you have a birefringence dependent on the angle of incidence. For a bundle of rays whose center beam strikes the compensation coating at an angle of 0 °, the birefringence values and directions are rotationally symmetrical with respect to the center beam.
  • the compensation coating is now constructed in such a way that, with regard to the amount of birefringence, it exhibits a predetermined behavior as a function of the opening angle of the beams of a beam.
  • the distribution of the optical path differences ⁇ OPL ( ⁇ R , 0 R ) for two linear polarization states orthogonal to one another for a bundle of rays in the image plane of the projection lens is first determined.
  • the opening angle ⁇ R of a beam is determined between the beam direction and the optical axis in the image plane, the azimuth angle ⁇ R between the beam direction projected into the image plane and a fixed reference direction within the image plane.
  • the distribution of the optical path differences ⁇ OPL ( ⁇ R , 0 R ) for two mutually orthogonal linear polarization states describes all influences by intrinsic birefringence of fluoride crystal lenses, voltage birefringence, covering the optical elements with antireflection layers of lenses or mirror layers.
  • the effective birefringence distribution of the compensation coating is determined from the distribution of the optical path differences ⁇ OPL ( ⁇ R, ⁇ R ).
  • Refractive or diffractive lenses, plane plates or mirrors, for example, are used as optical elements.
  • the optical surfaces of the optical element are given by the optically used areas, that is to say usually the front and rear surfaces.
  • the element axis is given, for example, by an axis of symmetry of a rotationally symmetrical lens. If the lens has no axis of symmetry, the element axis can be given by the center of an incident beam or by a straight line, with respect to which the beam angles of all light rays within the lens are minimal.
  • the effective birefringence values depend on azimuth angles ⁇ p, which are related to a reference direction perpendicular to the element axis, and on opening angles ⁇ p, which are also related to the element axis.
  • a pair of values ( ⁇ , ⁇ R ) of a beam in the image plane corresponds to a pair of values ( ⁇ p, ⁇ F ) on the optical element.
  • the effective birefringence distribution of the compensation coating is now determined in such a way that the distribution of the optical path differences for two mutually orthogonal linear polarization states for the entire system including the compensation coating is significantly reduced compared to the distribution without the compensation coating.
  • the effective birefringence distribution can be influenced by the choice of material, the thickness curve and the evaporation angle for the individual layers of the compensation coating.
  • the layer design and the process parameters result from the use of layer design computer programs which determine the thickness curves of the individual layers and the process variables from the effective birefringence distribution, the specification of the materials and the geometry of the optical element.
  • the compensation coating can also be applied to several optical elements. This increases the degrees of freedom in the determination of the compensation layers, which in addition to the compensation should also ensure a high transmission of the coating.
  • the compensation coating can have a birefringence distribution with locally varying birefringence, so that regions with more or less phase splitting are generated.
  • the variation in birefringence here includes both variations in the absolute value of the phase splitting and variations in the direction, i.e. a directional dependency that e.g. is given by the alignment of the main axes, which describe the birefringent effect.
  • the birefringence distribution can, for example, be rotationally symmetrical to an element axis of the element covered with the coating.
  • a birefringence increasing or decreasing in a defined manner in the radial direction that is to say from the center to the edge of the optical element, can be provided.
  • the birefringence distribution is not rotationally symmetrical.
  • it can have an azimuthal modulation of the strength of the birefringence, in particular with a birefringence distribution which has a multiple-fold radial symmetry with respect to the element axis, in particular a 2-fold, 3-fold, 4-fold or 6-fold symmetry.
  • an cimuthal modulation of the birefringence properties of a substrate having intrinsic birefringence can be at least partially compensated for, for example a substrate made of ⁇ 110>, ⁇ 111> or ⁇ 100> -oriented fluoride single crystal.
  • a coating of at least one optical surface of an optical component of an optical system can also be designed as an anisotropic coating and can serve, for example, as a compensation coating.
  • Elements with an "anisotropic" coating can be useful independently of the other features of the invention and are explained in more detail below.
  • the invention can advantageously be used by designing the optical element with the compensation coating as an exchangeable element.
  • the optical element closest to the image plane is advantageously used.
  • the method provides that in a first step the distribution of the optical path differences ⁇ OPL ( ⁇ R , ⁇ R) for two mutually orthogonal linear polarization states for a bundle of rays in the image plane is determined. The influence of all optical elements of the lens including coatings is taken into account.
  • the optical element, which is coated with the compensation coating in a subsequent step, is also in the beam path of the beam.
  • the method described above is used to determine the effective birefringence distribution of a compensation coating and the resulting thickness profiles of the individual layers and the process parameters for producing the individual layers.
  • the optical element is removed from the beam path and coated with the compensation coating. If the optical surface of the optical element was already occupied, this layer is removed before the renewed covering.
  • the optical element with the compensation coating is reattached to the original location within the lens.
  • Calcium fluoride is preferably used as the material for the lenses in projection lenses, since calcium fluoride, when used together with quartz, is particularly suitable for color correction at a working wavelength of 193 nm, or provides sufficient transmission at a working wavelength of 157 nm.
  • the statements made here also apply to the fluoride crystals strontium fluoride or barium fluoride, since they are crystals of the same cubic crystal type.
  • the disruptive influence of intrinsic birefringence is particularly noticeable when the light rays within the lenses have large opening angles. This is the case for projection lenses that have a numerical aperture on the image side that is greater than 0.7, in particular greater than 0.8.
  • the intrinsic birefringence increases significantly as the working wavelength decreases.
  • the intrinsic birefringence at a wavelength of 193nm is more than twice as large, at a wavelength of 157nm more than five times as large as at a wavelength of 248nm.
  • the invention can therefore be used particularly advantageously if the light beams have wavelengths of less than 200 nm, in particular less than 160 nm.
  • the objective can be a purely refractive projection objective, which is arranged from a multiplicity of rotationally symmetrically around the optical axis. neten lenses, or a projection lens of the catadioptric lens type.
  • Such projection lenses can advantageously be used in microlithography projection exposure systems which, starting from the light source, comprise an illumination system, a mask positioning system, a structure-bearing mask, a projection lens, an object positioning system and a light-sensitive substrate.
  • This microlithography projection exposure system can be used to manufacture microstructured semiconductor components.
  • the invention also provides a suitable method for manufacturing lenses.
  • lenses or lens parts made of fluoride crystal, the lens axes of which point in a main crystal direction are arranged rotated about the lens axes in such a way that the distribution ⁇ OPL ( ⁇ R , ⁇ R ) has significantly reduced values in comparison with a lens arrangement in which the Lens axes of the fluoride crystal lenses point in the same main crystal direction and in which the lenses are arranged in the same orientation.
  • the method further provides for groups to be formed with (100) lenses and with (111) lenses or (HO) lenses and to use these in parallel.
  • the method is used, for example, in the case of a projection objective which comprises at least two fluoride crystal lenses in the ⁇ 100> orientation and at least two lenses in the ⁇ 111> orientation.
  • the position of the reference directions is also known from these lenses.
  • the method uses the inventive knowledge that by turning the fluoride crystal lenses around the optical axis, the maximum values of the distribution ⁇ OPL ( ⁇ R , ⁇ R ) of the optical path differences can be significantly reduced.
  • a bundle of rays originating from an object point is propagated through a projection objective and, based on the known optical properties of the fluoride crystal lenses, the distribution ⁇ OPL ( ⁇ R , ⁇ R ) in the image plane is determined.
  • the Angle of rotation between the fluoride crystal lenses changed until the birefringence has tolerable values.
  • the optimization step can also take into account other boundary conditions, such as the compensation of non-rotationally symmetrical lens errors by turning the lens.
  • the maximum value of the distribution ⁇ OPL ( ⁇ R ,) R ) can be reduced by up to 30%, in particular up to 50%, compared to a projection objective in which the fluoride crystal lenses are arranged in the same orientation.
  • the optimization process can also have an intermediate step.
  • the fluoride crystal lenses become groups with lenses, the lenses of one group for an outermost aperture beam, with the lenses being oriented in the same way, producing a similar optical path difference between two mutually orthogonal linear polarization states.
  • the lenses are then only rotated within the groups in order to reduce the optical path differences.
  • the (100) lenses can be rotated in such a way that the optical path differences caused by the (100) lenses are reduced, and then the (III) lenses can be rotated in such a way that the optical ones caused by the (111) lenses Path differences can be reduced.
  • the distribution of the fluoride crystal lenses on lenses with (100) -orientation and (III) -orientation must be such that the resulting (100) - distribution ⁇ OPL 10O (CC R , ⁇ R ) and the resulting (111) - Compensate for the distribution ⁇ OPL ⁇ ⁇ ( ⁇ R , ⁇ R ) to a large extent.
  • the invention also relates to a manufacturing method for a lens, in which in a first step a plurality of fluoride crystal plates are optically seamlessly joined to form a blank, and in a second step the lens is worked out of the blank by known manufacturing methods. As previously described for lenses or lens parts, the plates are arranged rotated relative to one another about the surface normal.
  • the ratio of the sum of the thicknesses of the (HO) panels to the sum of the thicknesses of the (100) panels should be 4.0 + 0.4.
  • the invention also relates to optical components with at least one “anisotropic” coating.
  • a coating of at least one optical surface of an optical component of an optical system can be designed as an anisotropic coating and, for example, serve as a compensation coating.
  • An “anisotropic” coating in the sense of this application is one Coating that shows a pronounced directional dependence of its optical effect on the direction of the electric field vectors of the incident radiation in the incident area.
  • An anisotropic coating can thus have a fast or a slow axis in a region under consideration, which axis corresponds to a preferred direction of the coating.
  • coatings with a birefringence distribution with a locally varying birefringence all known coating processes can be used with a suitable modification of the process control, in particular PVD processes such as electron beam evaporation or sputtering.
  • PVD processes such as electron beam evaporation or sputtering.
  • the coating material is applied to at least one area of the substrate surface or to an already existing coating at an occupancy angle, in particular a vapor deposition angle, which is so large that an anisotropic coating structure is produced.
  • the height distance between a material source and the substrates can be significantly reduced in order to achieve an oblique vapor deposition of coating material, in which typical vapor deposition angles can be in the range 30 ° to 40 ° or more.
  • the vapor deposition angle (coverage angle) is understood here to mean the angle between the direction of impact of coating material on the substrate surface and the surface normal of the substrate surface at the coating location.
  • a rotation of the substrate about a substrate axis of rotation is generated.
  • a planetary system is preferably used, in which each substrate is arranged on a substrate carrier, which has its own rotation about its substrate axis of rotation and a global rotation about one Main axis of rotation of the planetary system.
  • the substrate surface is now coated with the material from a material source at large coating angles.
  • the coating material is temporarily shaded during the rotation of the substrate in order to generate a coating time which is dependent on the radial position of the coating location in accordance with a predetermined radial time profile.
  • the shading can be carried out through one or more screens in such a way that small coating angles (e.g. ⁇ 30 ° to 35 °) are shaded so that the material is only or at least predominantly at very large evaporation angles (e.g. 40 ° or more) under selected directions hits the substrate surface.
  • the invention also relates to a method for producing a polarized optical element, ie an optical component or arrangement with a defined effect on the polarization state of the incident radiation, which can also be useful and protectable independently of the other features of the invention.
  • the polarization-optical element can be a delay element (retarder), for example.
  • the method provides for a change in the local birefringence distribution of a coating after the coating process has ended. This change can be carried out by subjecting the finished coating locally to an energy suitable for changing the morphology of the coating in accordance with a predetermined spatial distribution.
  • a subsequent local change in the layer properties can be provided in interference layer systems of all types (eg reflective layers, anti-reflective layers).
  • the areas to be energized can be determined, for example, with the help of one or more masks.
  • the morphology of a coating can be changed by thermal action. This is possible, for example, by irradiation with an infrared laser or another type of irradiation that generates sufficient thermal energy. Also a possible editing with an electronic ray beam is possible.
  • the energy can also be applied mechanically, for example with the aid of ion beams and / or heating stamps.
  • the subsequent processing of the layer structure makes it possible to set non-rotationally symmetrical birefringence distributions as a particular advantage, it possibly being possible to set properties very small-scale, for example with typical area sizes in the mm or cm range.
  • vapor-deposited layers in particular anisotropic layer systems, can be locally changed in their birefringence properties by laser radiation. In this way, a polarization filter with targeted local modulation of the phase splitting can be generated.
  • the subsequent change in the birefringence distribution also makes it possible to make targeted changes to their polarization-optical behavior on fully assembled optical systems, for example projection objectives for microlithography.
  • the optical system can first be assembled and measured using at least one component with an anisotropic coating or another non-equilibrium coating.
  • a desired effective birefringence distribution of the at least one compensation coating can be determined from the measurement result, which is required in order to optically polarize the system.
  • the optical element provided with the coating can be removed in order to make the subsequent changes in the layer properties locally by means of suitable energy input.
  • the optical system After installing the optical element modified in this way, the optical system then has the desired properties.
  • the invention thus also relates to a special manufacturing method for an optical system, in particular an optical system for microlithography.
  • Fig. 1 shows a section through a fluoride crystal block perpendicular to the
  • 3 shows a coordinate system for defining the opening angle and the azimuth angle
  • 5A-F show the birefringence distribution for (111) lenses in different
  • 6A-G show the birefringence distribution for (111) lenses in different representations, and the birefringence distribution for two (110) lenses rotated by 90 °, or for four (HO) lenses rotated by 45 °;
  • FIG. 7 shows the lens section of a refractive projection objective
  • FIG. 8 shows the lens section of a catadioptric projection objective
  • Figure 9 shows a microlithography projection exposure system in a schematic representation
  • FIG. 10 is a diagram showing the dependence of the phase splitting ⁇ PH caused by birefringence on the irradiation direction for a homogeneous and for an anisotropic compensation coating
  • FIG. 11 is a diagram showing the dependence of the phase splitting ⁇ PH caused by birefringence on the direction of irradiation for layers with different numbers of individual layers and different production conditions;
  • FIG. 14 schematically shows a manufacturing method for a polarizer with a subsequent change in the properties of an anisotropic coating.
  • Figure 1 shows schematically a section through a fluoride crystal block 3.
  • the section is chosen so that the ⁇ 100 ⁇ crystal planes 5 can be seen as individual lines, so that the ⁇ 100 ⁇ crystal planes 5 are perpendicular to the paper plane ,
  • the fluoride crystal block 3 serves as a blank or starting material for the (100) lens 1.
  • the (100) lens 1 is a biconvex lens with the lens axis EA, which is also the axis of symmetry of the lens.
  • the lens 1 is now worked out of the fluoride crystal block in such a way that the lens axis EA is perpendicular to the ⁇ 100 ⁇ crystal planes.
  • FIG. 2A a three-dimensional representation illustrates how the intrinic birefringence is related to the crystal directions when the lens axis EA points in the ⁇ 100> crystal direction.
  • a circular, plane-parallel plate 201 made of calcium fluoride is shown.
  • the lens axis EA points in the ⁇ 100> crystal direction.
  • the ⁇ 101>, ⁇ 1 1 0>, ⁇ 10 1> and ⁇ 110> crystal directions are also shown as arrows.
  • the intrinsic birefringence is schematically represented by four "lobes" 203, the surfaces of which indicate the amount of intrinsic birefringence for the respective beam direction of a light beam.
  • the maximum intrinsic birefringence results in the ⁇ 101> -, ⁇ 1 T ⁇ > -, ⁇ 10 1> - and ⁇ 110> - crystal directions, i.e. for light rays with an opening angle of 45 ° and an azimuth angle of 0 °, 90 °, 180 ° and 270 ° within the lens.
  • azimuth angles of 45 °, 135 °, 225 ° and 315 ° there are minimal values of the intrinsic birefringence.
  • the intrinsic birefringence disappears for an opening angle of 0 °.
  • FIG. 2B shows with a three-dimensional representation how the intrinic birefringence is related to the crystal directions when the lens axis EA points in the ⁇ 111> crystal direction.
  • a circular plane-parallel plate 205 made of calcium fluoride is shown.
  • the lens axis EA points in the ⁇ 111> crystal direction.
  • the ⁇ 011>, ⁇ 101> and ⁇ 110> crystal directions are also shown as arrows.
  • the intrinsic birefringence is schematically represented by three "lobes" 207, the surfaces of which indicate the amount of intrinsic birefringence for the respective beam direction of a light beam.
  • the maximum intrinsic birefringence results in the ⁇ 011> -, ⁇ 101> - and ⁇ 110> - crystal directions, i.e. for light rays with an opening angle of 35 ° and an azimuth angle of 0 °, 120 ° and 240 ° within the lens. For azimuth angles of 60 °, 180 ° and 300 ° there are minimal values of the intrinsic birefringence. The intrinsic birefringence disappears for an opening angle of 0 °.
  • FIG. 2C uses a three-dimensional representation to illustrate how the intrinsic birefringence is related to the crystal directions when the lens axis EA points in the ⁇ 110> crystal direction.
  • a circular plane-parallel plate 209 made of calcium fluoride is shown.
  • the lens axis EA points in the ⁇ 110> crystal direction.
  • the ⁇ 01 1>, ⁇ 10 1>, ⁇ 101> and ⁇ 011> crystal directions are also shown as arrows.
  • the intrinsic birefringence is schematically represented by five "lobes" 211, the surfaces of which indicate the amount of intrinsic birefringence for the respective beam direction of a light beam.
  • the maximum intrinsic birefringence results on the one hand in the direction of the lens axis EA, and on the other hand in the ⁇ 01 1>, ⁇ 10 1> -, ⁇ 101> - and ⁇ 011> - crystal directions, i.e. for light beams with an opening angle of 0 °, or with an opening angle of 60 ° and the four azimuth angles, which result from the projection of the ⁇ 0l T> -, ⁇ l ⁇ T> -, ⁇ 101> - and ⁇ 011> - crystal directions into the ⁇ 110 ⁇ crystal plane , Such high opening angles do not occur in crystal material, however, since the maximum opening angle is limited to less than 45 ° by the refractive index of the crystal.
  • the definition of the opening angle ⁇ and azimuth angle ⁇ is shown in FIG. 3.
  • the z axis points in the ⁇ 100> crystal direction
  • the x axis points in the direction that results from projecting the ⁇ 110> crystal direction in the ⁇ 100 ⁇ crystal plane.
  • the z axis is the lens axis and the x axis is the reference direction.
  • FIG. 4A shows the amount of intrinsic birefringence as a function of the opening angle ⁇ for the azimuth angle ⁇ ⁇ O 0 for a (100) lens.
  • the value for the intrinsic birefringence of 6.5nm / cm at the opening angle ⁇ 45 ° corresponds to the measured value.
  • the curve shape was determined according to the formulas known from crystal optics.
  • the fourfold azimuthal symmetry is obvious.
  • FIG. 4C shows the birefringence distribution ⁇ n ( ⁇ , ⁇ ) for individual beam directions in the ( ⁇ , ⁇ ) angular space for a (100) lens.
  • Each line represents the magnitude and direction for a beam direction defined by the opening angle ⁇ and the azimuth angle ⁇ .
  • the length of the lines is proportional to the amount of birefringence or the difference in the main axis lengths of the cutting ellipse, while the direction of the lines indicates the orientation of the longer main axis of the cutting ellipse.
  • the cut ellipse is obtained by cutting the index ellipsoid for the beam of direction ( ⁇ , ⁇ ) with a plane that is perpendicular to the beam direction and passes through the center of the index ellipsoid. Both the directions and the lengths of the lines show the four-fold distribution. The length of the lines and thus the birefringence is maximal at the azimuth angles 0 °, 90 °, 180 ° and 270 °.
  • FIG. 4D now shows the birefringence distribution ⁇ n ( ⁇ , ⁇ ) which results when two adjacent plane-parallel (100) lenses of the same thickness are arranged rotated by 45 °.
  • the resulting birefringence distribution ⁇ n ( ⁇ , ⁇ ) is independent of the azimuth angle ⁇ .
  • the longer main axes of the cutting ellipses are tangential.
  • the resulting optical path differences of two mutually orthogonal polarization states are obtained by comparing the birefringence values with the physical ones
  • ß + m-90 ° ⁇ 5 °, where n is the number of plane-parallel (100) lenses and m is an integer.
  • An almost rotationally symmetrical distribution of the optical path differences for two mutually orthogonal linear polarization states also results for any lenses, where all rays of a bundle of rays in the lenses each have similarly large angles and cover similarly long path lengths within the lenses. The lenses should therefore be grouped together in such a way that the rays meet the previously specified condition as well as possible.
  • the intrinsic birefringence is independent of the azimuth angle ⁇ .
  • the curve shape was determined according to the formulas known from crystal optics.
  • the threefold azimuthal symmetry is obvious.
  • FIG. 5C shows the birefringence distribution ⁇ n ( ⁇ , ⁇ ) for individual beam directions in the ( ⁇ , ⁇ ) angular space for a (111) lens in the representation already introduced with FIG. 4C. Both the directions and the lengths of the lines show the triple distribution. The length of the lines and thus the birefringence is maximum at the azimuth angles 0 °, 120 ° and 240 °. In contrast to a (100) lens, the orientation of the birefringence rotates by 90 ° if a beam passes through a lens instead of an azimuth angle of 0 ° with an azimuth angle of 180 °. Thus, for example, the birefringence can be compensated for by two identically oriented (11 l) lenses if the beam angles of a bundle of rays exchange their sign between the two lenses.
  • FIG. 5D now shows the birefringence distribution ⁇ n ( ⁇ , ⁇ ) which results when two adjacent plane-parallel (111) lenses of the same thickness are arranged rotated by 60 °.
  • the resulting birefringence distribution ⁇ n ( ⁇ , ⁇ ) is independent of the azimuth angle ⁇ .
  • the longer main axes of the cutting ellipses run radially.
  • the resulting optical path differences of two mutually orthogonal polarization states are obtained by multiplying the birefringence values by the physical path lengths of the rays within the (111) lenses.
  • rotationally symmetrical birefringence distributions are obtained if one arranges n plane-parallel (III) lenses of the same thickness in such a way that for the
  • k is the number of plane-parallel (111) lenses and 1 is an integer.
  • An almost rotationally symmetrical distribution of the optical path differences for two mutually orthogonal linear polarization states also results for any lenses if all beams of a bundle of rays in the lenses each have similarly large angles and cover similarly large path lengths within the lenses. The lenses should therefore be grouped together in such a way that the rays meet the previously specified condition as well as possible.
  • the intrinsic birefringence is independent of the azimuth angle ⁇ .
  • the curve shape was determined according to the formulas known from crystal optics.
  • FIG. 6D now shows the birefringence distribution ⁇ n ( ⁇ , ⁇ ) which results when two adjacent plane-parallel (HO) lenses of the same thickness are arranged rotated by 90 °.
  • FIG. 6E now shows the birefringence distribution ⁇ n ( ⁇ , ⁇ ) which results when the two plane-parallel (110) lenses of the same thickness in FIG. 6C are combined with two further plane-parallel (HO) lenses of the same thickness.
  • the angle of rotation between two of the (HO) lenses is 45 °.
  • the resulting birefringence distribution ⁇ n ( ⁇ , ⁇ ) is independent of the azimuth angle ⁇ .
  • the longer main axes of the cutting ellipses run radially, that is to say similarly to the distribution of FIG. 5C.
  • the resulting optical path differences of two mutually orthogonal polarization states are obtained by multiplying the birefringence values by the physical path lengths of the beams within the (HO) lenses. Also rotationally symmetrical birefringence distributions are obtained if 4-n plane-parallel (HO) lenses of the same thickness are arranged in such a way that ß
  • the intrinsic birefringence is independent of the azimuth angle ⁇ .
  • FIG. 7 shows the lens section of a refractive projection objective 611 for the wavelength 157 nm.
  • the optical data for this lens are summarized in Table 1.
  • the exemplary embodiment is taken from the applicant's patent application PCT / EP00 / 13148 and corresponds there to FIG. 7 or table 6.
  • All lenses of this lens are made of calcium fluoride crystal.
  • the numerical aperture of the lens on the image side is 0.9.
  • the imaging performance of this lens is corrected so well that the deviation from the wavefront of an ideal spherical wave is less than 1.8m ⁇ in relation to the wavelength of 157nm. Especially with these high-performance lenses, it is necessary to reduce interfering influences such as that of intrinsic birefringence as much as possible.
  • the opening angle ⁇ and beam paths RL of the outermost aperture beam 609 were calculated for the individual lenses L601 to L630.
  • the outermost aperture beam 609 is used because it results in almost the maximum opening angle within the lenses.
  • Table 2 In addition to the opening angles ⁇ and the path lengths RL L for the outermost aperture beam, Table 2 shows the optical path differences for two mutually orthogonal linear polarization states for different lens orientations.
  • the optical path differences are for (ll) lenses, (100) lenses and (HO) lenses. compiled, the azimuth angle ⁇ of the outermost edge ray within the lenses for a (III) lens 0 ° and 60 °, for a (100) lens 0 ° and 45 ° and for a (HO) lens 0 °, 45 ° , 90 ° and 135 °.
  • Table 2 shows that the opening angle ⁇ is greater than 25 ° for the lenses L608, L617, L618, L619, L627, L628, L629 and L630, and even greater than 30 ° for the lenses L618, L627, L628, L629 and L630 are.
  • the lenses L627 to L630 closest to the image plane are particularly affected by high opening angles.
  • the design of the projection lens ensures that the maximum opening angle of all light rays is less than 45 °.
  • the maximum opening angle for the outermost aperture beam is 39.4 ° for the L628 lens.
  • the use of two thick planar lenses L629 and L630 directly in front of the image plane was helpful.
  • the diameter of the aperture which is located between the lenses L621 and L622, is 270mm.
  • the diameter of the lens L618 is 207mm and the diameter of the lenses L627 to L630 are all less than 190mm.
  • the diameters of these lenses, which have high opening angles, are therefore less than 80% of the diaphragm diameter.
  • Table 2 shows that it is favorable for individual lenses with large opening angles to orient them in the (100) direction since the birefringence values are lower overall. This is due to the fact that with (100) lenses the influence of the ⁇ 110> crystal directions can only be felt at larger angles than with (III) lenses. For example with the L608, L609 and L617 lenses, the optical path differences are more than 30% lower.
  • both lenses have the same opening angle for the outermost aperture beam of 35.3 ° and similar beam paths of 27.3mm or 26.0mm. If both lenses were installed in the same orientation as (100) lenses, an op- table path difference of 30.7nm result. However, if you twist the two (100) lenses mutually by 45 °, the optical path difference is reduced to 20.9nm, i.e. by 32%. If both lenses were installed as (III) lenses with the same orientation, there would be an optical path difference of 34.6 nm. However, if you twist the two (III) lenses mutually by 60 °, the optical path difference is reduced to 13.6nm, i.e. by 61%.
  • the lens L629 into the lenses L6291 and L6292 and the lens L630 in the lenses L6301 and L6302 are split open, the lens L6291 being a (100) lens with a thickness of 9.15 mm, the lens L6292 being a (100) lens with a thickness of 13.11 mm, the lens L6301 being a (100) lens with a thickness of 8.33 mm and the lens L6302 is an (III) lens with a thickness of 12.9 mm.
  • the lenses L6291 and L6301 are rotated against each other by 45 °, the lenses L6292 and L6302 by 60 °. In this case, the resulting maximum optical path difference is 0.2 nm.
  • the lenses L6291 and L6292, as well as the lenses L6301 and L6302, can be joined optically seamlessly, for example by starting. This principle can also be used if the projection lens contains only one crystal lens. This is then broken down into at least two lenses, which are arranged rotated relative to one another. The assembly is possible by starting. Another possibility is to first connect individual plates of the desired crystal orientation optically seamless and in a further process step to manufacture the lens from the plates joined together.
  • lens L629 and L630 Another way to reduce the disruptive influence of intrinsic birefringence through lenses L629 and L630 is to split lens L629 into lenses L6293 and L6294 and lens L630 into lenses L6303 and L6304, lens L6293 then one (HO) lens with a thickness of 11.13mm, lens L6294 a (HO) lens with a thickness of 11.13mm, lens L6303 with a (110) lens with a thickness of 10.62mm and lens L6304 with a (HO) lens with a thickness of 10.62 mm is.
  • the lenses L6293 and L6294, as well as the lenses L6303 and L6304 are each rotated against each other by 90 °, the angle of rotation between the lens L6293 and L6303 being 45 °.
  • the resulting maximum optical path difference in this case is 4.2nm.
  • the lenses L6293 and L6294 like the lenses L6303 and L6304, can be joined optically seamlessly as lens parts, for example by means of wringing.
  • optical path differences for two mutually orthogonal linear polarization states are almost completely compensated for, which is caused by the highly stressed lenses L629 and L630, if each lens is split into three lens parts L6295, L6296 and L6297 or L6305, L6306 and L6307, the Lens L6295 then a (100) lens with a thickness of 4.45mm, lenses L6296 and L6297 (110) lenses with a thickness of 8.90mm, lens L6305 with a (100) lens with a thickness of 4.25mm and lenses L6306 and L6307 (HO ) Lenses are 8.49mm thick.
  • the lenses L6294 and L6304 are rotated against each other by 45 °, two of the lenses L6295, L6297, L6306 and L6307 by 45 °. In this combination, the resulting maximum optical path difference is reduced to less than 0.1 nm.
  • the lenses L6295 to L6297 like the lenses L6305 to L6307, can be joined optically seamlessly as lens parts, for example by cracking.
  • Another way to reduce the disruptive influence of intrinsic birefringence through lenses L629 and L630 is to combine two (HO) lenses with one (100) lens.
  • the two (HO) lenses are to be installed rotated by 90 ° to each other, while the angle of rotation between the (100) lens and the (HO) lenses is 45 o + m-90 °, where m is an integer.
  • the lens L629 is split into the lenses L6298 and L6299 and the lens L630 into the lenses L6308 and L6309, the lens L6298 then a (HO) lens with a thickness of 17.40 mm, the lens L6299 a (HO) lens with a thickness 4.87mm, the lens L6308 is a (HO) lens with a thickness of 12.53mm and the lens L6309 is a (lOO) lens with a thickness of 8.70mm.
  • the resulting maximum optical path difference is 3.1 nm.
  • the lenses L6298 and L6299, as well as the lenses L6308 and L6309, can be joined optically seamlessly as lens parts, for example by cracking.
  • FIG. 8 shows the lens section of a catadioptric projection objective 711 for the wavelength 157nm.
  • the optical data for this lens are summarized in Table 3.
  • the exemplary embodiment is taken from the applicant's patent application PCT / EP00 / 13148 and there corresponds to FIG. 9 or table 8.
  • the numerical aperture of the objective on the image side is 0.8.
  • the opening angles ⁇ and beam paths RL L of the upper outermost aperture beam 713 and the lower outermost aperture beam 715 were calculated for the individual lenses L801 to L817.
  • the upper and lower outermost aperture beams were calculated because the object field is remote from the axis and therefore the aperture beams are not symmetrical to the optical axis, as was the case for the outermost aperture beam of the exemplary embodiment in FIG. 7.
  • Table 4 shows the data for the top outermost aperture beam and in Table 5 for the bottom outermost aperture beam.
  • Table 4 and Table 5 summarize the optical path differences for two mutually orthogonal linear polarization states for different lens orientations; namely for (111) lenses, (100) lenses and (HO) lenses, the azimuth angle ⁇ L of the outermost edge ray within the lenses for a (111) lens 0 ° and 60 °, for a (100 ) Lens is 0 ° and 45 ° and for a (110) lens it is 0 °, 45 °, 90 ° and 135 °. 8th*
  • Table 4 and Table 5 show that the opening angles ⁇ for the lenses L815 to L817 are greater than 25 °. In this exemplary embodiment too, the lenses L815 to L817 closest to the image plane have large opening angles. The design of the lenses L815 to L817 ensures that the maximum opening
  • the maximum Opening angle for the outermost aperture beam is 30.8 ° for the L817 lens.
  • the diameter of the aperture which is located between the lenses L811 and L812, is 193mm.
  • the diameters of the lenses L815 to L817 are all less than 162mm.
  • the diameters of these lenses, which have high opening angles, are therefore smaller than 85% of the diaphragm diameter.
  • Table 4 and Table 5 show that it is favorable for lenses with large opening angles to orient them in the (100) direction, since the birefringence values are lower overall. For example, with lenses L815 to L817, the optical path differences are more than 20% lower.
  • the following is intended to show how the intrinsic birefringence can be largely compensated for by the parallel use of groups with mutually rotated (100) lenses and groups with mutually rotated (III) lenses.
  • the lenses L801 and L804 are combined into one group and the lenses L802 and L803 into another group, the angle of rotation between the lenses in each case being 60 °.
  • the lenses L808, L809 and L810 and the lenses L815, L816 and L817 are combined to form a group of three, the angle of rotation between two of these lenses being 40 °.
  • the Lenses L811, L812, L813 and L814 are combined in a group of four with a mutual angle of rotation of 30 °.
  • the lenses L801 and L804 are combined into one group and the lenses L802 and L803 into another group, the angle of rotation between the lenses in each case being 45 °.
  • the lenses L808, L809 and L810 as well as the lenses L815, L816 and L817 are combined to form a group of three, the angle of rotation between two of these lenses being 30 °.
  • the lenses L811, L812, L813 and L814 are combined into a group of four with a mutual angle of rotation of 22.5 °.
  • a maximum optical path difference for two mutually orthogonal linear polarization states of 7 nm is obtained if groups with (100) lenses are now combined with groups with (III) lenses.
  • the lenses L801 and L804 are combined into a group of (11 l) lenses, the angle of rotation between the lenses being 60 °.
  • the lenses L802 and L803 are combined into a group of (100) lenses, the angle of rotation between the lenses being 45 °.
  • the lenses L808, L809 and L810 are combined to form a group of three (100) lenses, the angle of rotation between two of these lenses being 30 °.
  • the lenses L815, L816 and L817 are combined to form a group of three (III) lenses, the angle of rotation between two of these lenses being 40 °.
  • the lenses L811, L812, L813 and L814 are combined into a group of four (100) lenses with an angle of rotation of 22.5 °.
  • the lens axes of the lenses L805 and L807 which are not combined into a group are oriented in the ⁇ 111> crystal direction, while the lens axis of the lens L806 is oriented in the ⁇ 100> crystal direction.
  • the groups can be arranged mutually rotated around the optical axis. These degrees of freedom of rotation cannot be rotationally symmetrical for compensation. exploit aberrations that are generated, for example, by the frame of the lenses.
  • the refractive objective 611 is intended to show in the following how the disruptive influence of birefringence effects can be significantly reduced by covering an optical element with a compensation coating 613.
  • the two lenses L629 and L630 which consist of calcium fluoride and thus show intrinsic birefringence, should be considered.
  • the two lenses have an (III) orientation and are rotated by 60 ° with respect to one another. This results in an almost rotationally symmetrical distribution of the optical path differences ⁇ OPL.
  • the maximum optical path difference ⁇ OPL is between 13.6 nm and 14.6 nm, depending on the azimuth angle ⁇ R.
  • the compensation coating 613 described in Table 6 is applied to the optical surface of the lens L630 facing the image plane O '.
  • the compensation coating 613 consists of 15 individual layers made of the materials magnesium fluoride (MgF2) and lanthanum fluoride (LaF3).
  • n and k in Table 6 indicate the real and imaginary parts of the refractive index.
  • the layer thicknesses are homogeneous and have no lateral thickness curve.
  • the evaporation angles during the coating are perpendicular to the optical surface of the L630 lens.
  • the compensation coating With the compensation coating, the resulting optical path difference is 1.1 nm and is therefore significantly reduced compared to the lens without a compensation coating.
  • the method can also be used to compensate for birefringence in an overall system, the causes of this birefringence being refraction, intrinsic birefringence and birefringence through the remaining layers.
  • the distribution of the optical path differences ⁇ OPL for one or more tufts of rays in the image plane is determined.
  • the necessary compensation layer is then calculated using a program for optimizing layers and applied, for example, to the system area closest to the image plane. It is advantageous if the optical element closest to the image plane can be exchanged. This also allows birefringence effects that only arise when the lens is in operation to be corrected.
  • the wringing can in particular by layers, for. B. made of quartz glass, are supported. It is important that there is no refraction or reflection at the joint that would be annoying.
  • Blanks are specified as exemplary embodiments, from which, for example, the lens L816 for the projection objective of FIG. 8 can be manufactured.
  • the lens L816 has a convex aspherical front surface with the apex radius 342.13mm and a concave spherical back surface with the apex radius 449.26mm.
  • the axial thickness is 37.3mm.
  • the lens material is calcium fluoride.
  • the lens diameter is 141mm.
  • the blank from which the lens is to be worked out requires at least a total thickness of 45mm and a diameter of 150mm.
  • the blank can consist of two (100) plates rotated by 45 ° (100) and two (13) plates rotated by 13 ° (13.5 mm), which are optically seamless.
  • the (100) plates and the (III) plates should each be arranged adjacent to one another.
  • HO eight (HO) plates with a thickness of 4.5 mm which are rotated relative to one another by 45 ° and four plates with a thickness of 2.25 rotated with respect to one another by 45 ° (100) are optically seamlessly joined, with four after each of two (110) plates (100) - plates follow.
  • the projection exposure system 81 has an illumination device 83 and a projection lens 85.
  • the projection objective 85 comprises a lens arrangement 819 with an aperture diaphragm AP, whereby through the Lens arrangement 89 an optical axis 87 is defined. Exemplary embodiments for the lens arrangement 89 are given in FIG. 6 and FIG. 7.
  • a mask 89 is arranged between the illumination device 83 and the projection lens 85 and is held in the beam path by means of a mask holder 811.
  • Such masks 89 used in microlithography have a micrometer-nanometer structure, which is imaged on the image plane 813 by means of the projection objective 85, for example reduced by a factor of 4 or 5.
  • a light-sensitive substrate 815 or a wafer positioned by a substrate holder 817 is held in the image plane 813.
  • the minimum structures that can still be resolved depend on the wavelength ⁇ of the light used for the illumination and on the numerical aperture of the projection lens 85 on the image side, the maximum achievable resolution of the projection exposure system 81 with decreasing wavelength ⁇ of the illumination device 83 and with increasing numerical aperture of the projection lens on the image side 85 rises.
  • resolutions of less than 150 nm can be realized. Therefore, effects such as intrinsic birefringence must also be minimized.
  • the invention has succeeded in greatly reducing the disruptive influence of intrinsic birefringence, particularly in the case of projection objectives with large numerical apertures on the image side.
  • the influence of the anisotropy of a compensation coating on the birefringence caused by the coating is explained with reference to FIG. 10.
  • the absolute amount and the direction of the birefringence caused by the layer are specified by the phase angle DPH of the phase splitting, that is to say by a difference in the wavefront between two mutually orthogonal, linear polarization states.
  • This parameter is suitable for describing the directional dependence of birefringence. 10 shows the dependence of the phase angle on the angle of incidence of the radiation, which corresponds to the opening angle ⁇ of the previous illustrations.
  • phase splitting is shown, which is caused by an anisotropic interference layer system (magnesium fluoride-lanthanum fluoride alternating layer package) is caused, which was evaporated at an evaporation angle of 40 °. This is compared to an isotropic layer system.
  • anisotropic interference layer system magnesium fluoride-lanthanum fluoride alternating layer package
  • the curves marked HOM in the middle indicate the measured values for the isotropic compensation coating 613 given in Table 6, the layer thicknesses of which are homogeneous and have no lateral course of thickness.
  • the solid line shows the ellipsometric measured values for radiation in a first plane perpendicular to the coating surface, which is referred to here as the 0 ° plane.
  • the dashed line indicates the values for the perpendicular 90 ° plane. It can be seen that the magnitude and direction of the phase splitting are essentially independent of the azimuth angle D. It is therefore an isotropic coating.
  • the radiation is in a plane perpendicular to the first plane (curve AN 90 °), thus changing the azimuth angle by 90 °, it is true the same amount of phase splitting before, but with a negative phase angle.
  • the direction of the phase splitting can be controlled with the help of an anisotropic coating by producing an anisotropic coating with a certain preferred direction, which is then to be aligned in a predetermined direction relative to the electric field vectors of the incoming radiation.
  • Fig. 11 it is explained that with anisotropic coatings the extent of the phase splitting, i.e. the strength of the birefringence, can be controlled specifically. Measured values are shown for the phase splitting depending on the opening angle winkel for different coatings.
  • the diamond symbols correspond to a MgF2 / LaF3 alternating layer package with 8 individual layers, which were evaporated at 150 ° C.
  • the square symbols correspond to a coating produced at the same temperature with 6 individual layers of these materials.
  • a comparison of the birefringent effect of these two layer systems shows that the absolute amount of the phase splitting that can be achieved increases with an increasing number of layers.
  • the triangle symbols correspond to a coating with 8 layers, which was coated at 250 °, i.e. significantly higher temperatures. Compared to the corresponding ⁇ -layer at 150 ° C, the phase splits are significantly lower.
  • the manufacture of a rotationally symmetrical anisotropic coating of a lens in a vapor deposition system with a planetary system is explained with reference to FIG. 12.
  • the planetary system has a main carrier (not shown) which can be rotated about a main axis of rotation 500, on the periphery of which a plurality of substrate carriers 502 which are rotatable about respective substrate carrier axes 501 are attached.
  • Each substrate carrier carries a substrate 503, which is designed as a biconvex lens in the example.
  • a material source 504 for vapor deposition material is arranged in the region of the main axis of rotation in order, for example, to alternately vaporize magnesium fluoride and lantan fluoride with the aid of an electron beam and to vaporize it onto the coating surface 505 of the substrate facing the material source.
  • the coating material symbolized by dashed lines strikes the respective coating locations at an evaporation angle (coating angle) 506, which is determined by the geometry of the system and the curvature of the coating surface.
  • a set of shading screens 511 is arranged between the material source 504 and the substrate, with which the part of the coating surface facing the material source can be completely shaded against the material flow, so that only the part of the coating surface facing away from the material source is coated under a large evaporation angle.
  • the oblique evaporation causes the layer material to grow in a columnar structure symbolized by oblique lines.
  • the direction of inclination is determined by the main dam direction.
  • the form of this morphology can be influenced by the coating temperature, the anisotropy being more pronounced at lower coating temperatures, for example between room temperature and approximately 90 ° C., than at higher coating temperatures, for example above 120 ° C., 150 ° C. or 200 ° C. It can be seen that an anisotropic coating which is rotationally symmetrical with respect to the axis of rotation 501 can be produced in this way, in which the normal direction (inclination direction of the coating material columns) points essentially in the radial direction.
  • diaphragms 511 ', 511 ", 511'” which show a substrate 503 ', 503 ", 503'” rotating behind them as they rotate about the axis of rotation 501 ', 501 ", 501” " shade from the material flow 520 represented by arrow symbols of the material source.
  • FIG. 13 (a) shows shading with a shading angle that is constant over the entire radius and that is measured in the circumferential direction of the rotation. This is achieved by means of an N-shaped “window” in the material flow.
  • This shading causes the coating time, ie the time that the rotating coating location lies within the material flow 520, to be essentially the same for all radial positions. This would be the case with flat substrate surfaces If the shading window is extended outwards, for example according to the dashed lines 515, there is a radial time profile in which the radial lying areas are shaded longer than radially outer areas. In this way, a compensation of geometry-related layer thickness reductions to the edge can be achieved, if necessary.
  • the rectangular window in FIG. 13 (b) has the effect that the radially inner regions are vaporized over longer time intervals and in more different directions than radially outer regions.
  • layers can optionally be produced, the layer thickness of which decreases more from the center to the edge than a decrease in thickness caused solely by the surface curvature.
  • the anisotropy on the other hand, will be more pronounced on the edge than in the middle.
  • a homogeneous layer thickness between the center and the edge can optionally be achieved in this way.
  • the geometry of the diaphragms 511 '"in FIG. 13 (c) has the effect that a central region 525 of the substrate 503'" remains constantly exposed to the material flow and is therefore coated essentially isotropically. In the remaining area there is a radial course with anisotropy and / or layer thickness changing in the radial direction.
  • the orientation of the main axis of the coating can be adjusted by a suitable choice of the orientation of the vapor deposition material with respect to the screens.
  • vapor deposition in a direction offset by 90 ° results in columnar structures which are oriented essentially tangentially.
  • a largely pore-free protective layer serving as a diffusion barrier can be applied, for example as the outermost layer of the coating. This can be made optically largely neutral by a suitable layer thickness, for example as a half-wave layer.
  • a method variant is explained on the basis of FIG. 15, which makes it possible to produce polarization-optically active components (eg retarders) with an almost freely selectable local birefringence distribution.
  • a substrate for example a plane-parallel plate 550
  • a polarization-optically active coating 551 the birefringent effect of which can be essentially homogeneous or anisotropic.
  • the coating has a non-equilibrium layer structure, which makes it possible to change the morphology of the layer and thus its birefringent properties in the area affected by targeted local energy input.
  • it can be an anisotropic coating 551 produced by oblique vapor deposition.
  • the layer is subjected locally to a predetermined distribution with an energy which is suitable for changing the morphology and thus the birefringence properties of the layer material.
  • high-energy radiation 552 for example an ion beam or a suitably expanded laser beam, is irradiated onto the coating through the opening 553 of a mask 554.
  • a diffusion-assisted change in the morphology is hereby induced, in which, for example, the columnar growth structures of an anisotropic layer coagulate and form a layer of greater density and less anisotropy.
  • phase splitting caused by a coating can be generated.
  • the area of uniform phase splitting can be very small, for example a few millimeters in size.
  • polarization masks i.e. polarizers or delay elements with a location-dependent effect
  • Initial coatings for the visible wavelength range can be generated, for example, by "cold vapor deposition", in which case the change in morphology can be generated by irradiation with high-energy laser light, for example from the UV range.
  • the starting layers must be stable against the working wavelength, where it is advisable to produce the starting coating at higher coating temperatures, for example between 100 ° and 152 °, which results in more thermally stable coatings
  • Larger energy inputs are carried out, for example with an infrared laser, by ion beams, electron beams or by suitable heating stamps.
  • the methods described are also suitable for producing polarizing phase shifting masks as components having a polarization-optical effect, in particular using at least one anisotropic coating.
  • areas in the immediate vicinity of structures to be imaged for example a line, can be covered with a spatially limited anisotropic coating in order to produce a favorable retarder effect.
  • PSM polarized phase shift masks
  • Wavelength and refractive index are given in relation to vacuum.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
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  • Engineering & Computer Science (AREA)
  • Environmental & Geological Engineering (AREA)
  • Epidemiology (AREA)
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  • Crystallography & Structural Chemistry (AREA)
  • Lenses (AREA)
  • Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)

Abstract

Objectif, en particulier objectif de projection pour une installation d'éclairage par projection pour la microlithographie, qui comporte au moins une lentille de cristal de fluorure. Il est possible d'obtenir une réduction de l'influence perturbatrice de la biréfringence lorsque cette lentille est une lentille (100) dotée d'un axe qui se trouve presque perpendiculaire par rapport aux plans cristallins {100} ou aux plans cristallins équivalents du cristal de fluorure. Dans des objectifs comportant au moins deux lentilles en cristal de fluorure, il est avantageux que lesdites lentilles soient déplacées angulairement l'une par rapport à l'autre. Les axes des lentilles en cristal de fluorure peuvent ainsi être orientés, outre dans le sens de cristal <100>, dans le sens de cristal <111> ou <110>. On obtient une réduction supplémentaire de l'influence perturbatrice de la biréfringence par l'utilisation simultanée de groupes à lentilles (100) déplacées angulairement les unes par rapport aux autres et de groupes de lentilles (111) ou (110) déplacées angulairement les unes par rapport aux autres. Une nouvelle réduction de l'influence perturbatrice de la biréfringence peut être obtenue par l'application d'une couche de compensation sur un élément optique.
EP03708221A 2002-03-12 2003-03-12 Objectif lentille en cristal Withdrawn EP1483614A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE10210782 2002-03-12
DE2002110782 DE10210782A1 (de) 2002-03-12 2002-03-12 Objektiv mit Kristall-Linsen
PCT/EP2003/002549 WO2003077007A2 (fr) 2002-03-12 2003-03-12 Objectif à lentille en cristal

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EP1483614A2 true EP1483614A2 (fr) 2004-12-08

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EP (1) EP1483614A2 (fr)
JP (1) JP2005520187A (fr)
CN (1) CN1653359A (fr)
AU (1) AU2003212341A1 (fr)
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WO (1) WO2003077007A2 (fr)

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US6970232B2 (en) 2001-10-30 2005-11-29 Asml Netherlands B.V. Structures and methods for reducing aberration in integrated circuit fabrication systems
US6995908B2 (en) 2001-10-30 2006-02-07 Asml Netherlands B.V. Methods for reducing aberration in optical systems
JP4333078B2 (ja) 2002-04-26 2009-09-16 株式会社ニコン 投影光学系、該投影光学系を備えた露光装置および該投影光学系を用いた露光方法並びにデバイス製造方法
US7075720B2 (en) 2002-08-22 2006-07-11 Asml Netherlands B.V. Structures and methods for reducing polarization aberration in optical systems
WO2004023172A1 (fr) 2002-09-03 2004-03-18 Carl Zeiss Smt Ag Methode d'optimisation pour un objectif a lentilles en cristal de fluorure et objectif pourvu de lentilles en cristal de fluorure
US7466489B2 (en) 2003-12-15 2008-12-16 Susanne Beder Projection objective having a high aperture and a planar end surface
JP2007518211A (ja) * 2004-01-16 2007-07-05 コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ 光学系
US7423727B2 (en) * 2005-01-25 2008-09-09 Asml Netherlands B.V. Lithographic apparatus and device manufacturing method
JP2008532273A (ja) * 2005-02-25 2008-08-14 カール ツァイス エスエムテー アクチエンゲゼルシャフト マイクロ・リソグラフィー投影露光装置のための光学システム
WO2007063136A2 (fr) * 2005-12-02 2007-06-07 Carl Zeiss Smt Ag Element optique pourvu d'un revetement birefringent
US7518797B2 (en) 2005-12-02 2009-04-14 Carl Zeiss Smt Ag Microlithographic exposure apparatus
DE102007058862A1 (de) 2007-12-06 2009-06-10 Carl Zeiss Smt Ag Optisches System, insbesondere für eine mikrolithographische Projektionsbelichtungsanlage
US9599787B2 (en) 2011-12-27 2017-03-21 Tera Xtal Technology Corporation Using sapphire lens to protect the lens module
DE102012206154A1 (de) 2012-04-16 2013-06-06 Carl Zeiss Smt Gmbh Optisches System für eine mikrolithographische Projektionsbelichtungsanlage sowie mikrolithographisches Belichtungsverfahren
DE102013108321B3 (de) * 2013-08-02 2014-10-23 Leibniz-Institut für Analytische Wissenschaften-ISAS-e.V. Fresnelsches-Parallelepiped

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Publication number Publication date
WO2003077007A2 (fr) 2003-09-18
CN1653359A (zh) 2005-08-10
WO2003077007A3 (fr) 2004-04-08
DE10210782A1 (de) 2003-10-09
JP2005520187A (ja) 2005-07-07
AU2003212341A1 (en) 2003-09-22
AU2003212341A8 (en) 2003-09-22

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