JP2005524985A - Lens made of crystalline material - Google Patents

Abstract

The present invention relates to a method for producing an optical blank (1) comprising an objective lens, in particular a projection objective lens for a microlithographic projection exposure apparatus or a crystalline material as a precursor for producing a lens part. In this method, first, the orientation of the first crystal direction (3) oriented within a certain crystal structure is determined. The optical blank (1) is then processed so that the first crystal direction (3) is essentially perpendicular to the optical rough plane (7) of the optical blank (1). Next, the marking is placed on the optical blank (1) or the holding frame of the optical blank (1) that has a certain relationship with the second crystal direction (11) that takes an angle different from zero with respect to the first crystal direction (3). Applied.

Description

  The present invention relates to a method for producing an optical blank made of a crystal material and an optical blank. The optical blank is used as a precursor for manufacturing a lens or lens part. Accordingly, the present invention also relates to a method of manufacturing a lens or lens part made of a crystalline material, as well as the lens or lens part. This type of lens or lens part is used in an objective lens, in particular a projection objective for a microlithographic projection exposure apparatus. The invention therefore also relates to an objective lens, in particular a projection objective for a microlithographic projection exposure apparatus.

  A method for producing an optical blank made of fluoride crystals is known from US Pat. No. 6,201,634. A lens for a projection objective for a microlithographic projection exposure apparatus is manufactured from the optical blank. The lens axis of the lens is preferably oriented in the <111> crystal direction. The <111> crystal orientation is selected according to US Pat. No. 6,201,634 so that the disturbing effects of stress birefringence are minimized.

  In general, a birefringent lens separates unpolarized light into two light beams having different polarization states and different diffusion rates and directions. When a birefringent lens is used for the objective lens, the birefringent lens causes a reduction in resolution unless the corresponding corrective action is taken. The birefringence effect in the lens is caused by, for example, stress birefringence conditioned by the lens manufacturing method or mechanical stress. Birefringence plays a role in crystal optics in particular. Anisotropic crystals are birefringent.

  However, isotropic crystals such as cubic fluoride crystals also have intrinsic birefringence that becomes noticeable, especially at vacuum ultraviolet (VUV) wavelengths (<200 nm). Cubic fluoride crystals such as calcium fluoride and barium fluoride are preferably lens materials for projection objectives having an operating wavelength in the wavelength region. Therefore, the advantageous birefringence of the crystal is corrected by favorable measures at the wavelength.

  In the following, since the unique name of the crystal direction plays a role, first, some notations are introduced for the crystal direction, the crystal plane, and the lens name in which the lens axis indicates a certain crystal direction.

  The direction of the crystal direction is indicated between the symbols “<” and “>”, and the direction of the crystal plane is indicated between the symbols “{” and “}”. In this case, the crystal direction always indicates the direction of the plane normal of the corresponding crystal plane. Therefore, the crystal direction <100> indicates the direction of the plane normal of the crystal plane {100}. Cubic crystals belonging to fluoride crystals have main crystal directions <110>, <1￣10>, <1￣1￣0>, <101>, <101￣>, <1￣01>, <1 ￣01￣, <011>, <01￣1>, <011￣>, <01￣1￣>, <111>, <1￣1￣1￣>, <1￣1￣1>, <1 ￣11￣>, <11￣1￣>, <1￣11>, <11￣1>, <111￣>, <100>, <010>, <001>, <1￣00>, <01￣ 0>, <001￣>. (In this specification, the upper bar in the notation of crystal is attached above the number in front of it.)

  The main crystal directions <100>, <010>, <001>, <1￣00>, <01￣0>, <001￣> are equivalent to each other based on the symmetry of the cubic crystal. The prefix “(100)” is attached to the following crystal directions that face the direction. The crystal plane perpendicular to the main crystal direction is given “(100)” as a prefix corresponding thereto. The lens whose lens axis is parallel to the main crystal direction is prefixed with “(100)”.

  Main crystal directions <110>, <1￣10>, <1￣10>, <1￣1￣0>, <101>, <101￣>, <1￣01>, <1￣01￣>, < 011>, <01￣1>, <011￣>, and <011￣> are similarly equivalent to each other, and therefore, the following crystal direction facing the main crystal direction is prefixed with “(110)”. . The crystal plane perpendicular to the main crystal direction is prefixed with “(110)” correspondingly. A lens whose lens axis is parallel to the main crystal direction is prefixed with “(110)”.

  Main crystal directions <111>, <1￣1￣1￣>, <1￣1￣1>, <1￣11￣>, <11￣1￣>, <1￣11>, <11￣1>, <111￣> are similarly equivalent to each other, and therefore the prefix “(111)” is attached to the following crystal directions facing the main crystal direction. The crystal plane perpendicular to the main crystal direction is prefixed with “(111)” correspondingly. A lens whose lens axis is parallel to the main crystal direction is prefixed with “(111)”.

  Hereinafter, the indication corresponding to one of the main crystal directions always applies to the equivalent main crystal direction.

  J. et al. Burnett et al., "Intrinsic birefringence in calcium fluoride and barium fluoride" (Physical Review B, Volume 64 (2001), 241102-1 to 241102-4). It is known to have birefringence. Intrinsic birefringence in this case strongly depends on the fluoride crystal lens and the material orientation in the direction of light. The intrinsic birefringence has the greatest effect on the rays that the lens transmits along the (110) crystal direction. The measurements presented here are: (11.8 ± 0.4) nm / cm at wavelength λ = 156.1 nm and wavelength λ = 193. At the time of light diffusion in the (110) crystal direction for calcium fluoride crystals. It shows that birefringence of (3.6 ± 0.2) nm / cm appears at 09 nm and (0.55 ± 0.07) nm / cm appears at a wavelength λ = 253.65 nm. Calcium fluoride, on the other hand, has no intrinsic birefringence as predicted by theory due to light diffusion in the (100) and (111) crystal directions. Therefore, intrinsic birefringence is strongly direction dependent and obviously increases with decreasing wavelengths.

  J. et al. In Burnett et al.'S paper "The trouble with calcium fluoride" (spie's omagazine, March 2002, pages 23-25, https://omagazine.com/fromThemagn. The angular dependence of intrinsic birefringence in a fluoride crystal with a crystal structure is shown. The intrinsic birefringence of the light beam in this case depends on the opening angle and the azimuth angle of the light beam. From FIG. 4, intrinsic birefringence is four times the azimuth symmetry when the lens axis is in the (100) crystal direction, and three times the azimuth angle when the lens axis is in the (111) crystal direction. It is clear that when the lens axis is oriented in the (110) crystal direction, it has double azimuth symmetry. The interfering twist of the two fluoride crystal lenses around the lens axis can reduce the disturbing effects of intrinsic birefringence. A rotation angle of 45 ° is advantageous in the case of two lenses whose lens axes are in the (100) crystal direction, and a rotation angle of 60 in the case of two lenses whose lens axes are in the (111) crystal direction. Is advantageous, and in the case of two lenses whose lens axes are oriented in the (110) crystal direction, a rotation angle of 90 ° is convenient. The simultaneous use of the paired (100), (111), and (110) lenses can reduce the optical path difference for two mutually orthogonal polarization states. Further, according to FIG. 2 of the above paper, since the birefringence with respect to the crystal direction which can be compared with that of barium fluoride and calcium fluoride has opposite symbols, the simultaneous use of the calcium fluoride lens and the barium fluoride lens is also possible. Corrections to the disturbing effects of intrinsic birefringence occur.

  Projection objectives and microlithographic projection exposure apparatuses are known, for example, from International Patent Application Publication No. WO 01/50171 A1 (US Patent Application No. 10/177580) and references cited therein. The embodiment of this application is a purely refractive and catadioptric projection objective with numerical apertures of 0.8 and 0.9 at drive wavelengths of 193 nm and 157 nm. Calcium fluoride is used as the lens material.

  Applicant's unpublished patent application PCT / EP02 / 05050 includes various corrections to reduce the disturbing effects of intrinsic birefringence, for example in the embodiments of WO 01/50171 A1 (US patent application Ser. No. 10/177580). A method is described. In particular, a parallel use of (111) lenses or (110) and (100) lenses made of the same fluoride crystal and the use of a correction coating are disclosed. The disclosure content of this application will be fully incorporated into this application.

  The correction method described above for reducing the disturbing effects of birefringence is based on the use of lenses that are thereby twisted about one another around the lens axis. The angle of rotation between the two lenses in this case depends, for example, on which crystal direction the lens axis of the lens is oriented. In the case of a lens manufactured by the method described in US Pat. No. 6,201,634, the lens axis is, for example, oriented in the (111) crystal direction. In order to reduce the disturbing effects of intrinsic birefringence, a convenient 60 ° rotation angle occurs between the two (111) lenses in this case. The rotation angle is in this case related to the crystal structure of both lenses. However, this crystal structure cannot be seen from the outside of one lens.

  The object of the present invention is to present here a manufacturing method for an optical blank made of a crystalline material as a precursor for manufacturing a lens or lens part. This method subsequently takes into account that when lenses or lens parts made from said optical blanks are used in an objective lens, they can be twisted to each other by a predetermined angle with respect to their crystal structure.

  This subject includes a method for manufacturing an optical blank made of the crystalline material according to claim 1, a method for manufacturing an optical blank according to claim 13, a lens or a lens portion made of the crystalline material according to claims 16 and 18, Solved by the lens or lens portion according to Item 28, 32, the objective lens according to Claim 33, 37, the microlithographic projection exposure apparatus according to Claim 39, and the method of manufacturing a semiconductor element according to Claim 40. .

  Preferred embodiments of the invention result from the features of the dependent claims.

  In order to allow the rotation angle to be adjusted between the lens or lens part and the reference direction of the objective lens or between the two lenses or lens parts in the objective lens, a predetermined rotation angle with respect to the crystal structure of the lens or lens part, It is advantageous if each lens or each lens part or their holding frame has a marking that is in constant relation with the crystal structure of the lens or lens part.

  The lens portion is, for example, an individual lens in which individual lenses are optically seamlessly connected. Quite generally, the lens portion represents a component of an individual lens.

  Preferred crystals for optical blanks as starting material are cubic fluoride crystals such as calcium fluoride, barium fluoride or strontium fluoride.

  A number of molding and surface treatment process steps are required until the lens or lens part has its final shape. Since the lens or lens part is made of a crystalline material, a single crystal block or a single crystal ingot, which can be manufactured by the method described in US Pat. No. 6,201,634, for example, is generally used as a starting material. An optical blank is first finished from a single crystal block, for example by cutting and grinding. The precursor of the lens or lens part is called an optical blank. One or more lenses or lens parts can be finished from the optical blank. When finishing multiple lenses or lens parts from an optical blank, the optical blank is cut into individual optical blanks by sawing, so that the individual optical blanks can perform optical measurements on the thus treated plane. Grinding and / or polishing in another processing step. The optical blank thus treated then forms individual material disks in the form of cylinders.

  Here, the optical blank is advantageously processed so that its plane normal has an optical rough plane facing the first crystal direction oriented within a constant crystal structure. Advantageously, this is the main crystal direction, for example the <100>, <111> or <110> crystal direction. Therefore, it is necessary to first determine the direction of the first crystal direction with an optical blank. This determination can be performed on the optical blank in this case before the optical blank is cut into individual optical blanks. It is also possible to first make a division and then make a decision on each individual optical blank. The optical blank is processed by cutting and grinding so that the first crystal direction is substantially perpendicular to the optical rough plane. Preferably, the angular deviation between the first crystal direction and the optical rough plane is less than 5 °. The optical rough plane is in this case the front or back side of the material disk.

  In the next step, markings are applied on the optical blank or its holding frame which are in a fixed relationship with the second crystal direction having an angle different from 0 ° with respect to the first crystal direction. The second crystal direction may likewise be the main crystal direction or the crystal direction oriented within a certain crystal structure, for example the <331> crystal direction or the <511> crystal direction.

  The marking may be, for example, a dot or line sculpture with an outer cylindrical body of an optical blank or a holding frame fixedly connected to the optical blank. The holding frame may in this case consist of metal, ceramic or glass-ceramic.

  A certain relationship between the second crystal direction and the marking is, for example, the projection of the second crystal direction onto a plane in which the marking is perpendicular to the first crystal direction and the plane normal is directed to the first crystal direction. Can be manufactured by indicating a reference direction. Thus, in the case of a cylindrical optical blank having a symmetry axis essentially facing the first crystal direction, the reference direction preferably intersects the symmetry axis. The marking is in this case, for example, the intersection of the outer cylinder of the optical blank or its holding frame with the reference direction. The marking thereby also determines the orientation angle of the projected second crystal direction relative to the coordinate system associated with the optical blank. The azimuth angle is determined as the angle between the reference direction and the coordinate axis that stands on the axis of symmetry at right angles and intersects the axis of symmetry.

  In determining the first crystal direction, the optical blank can be exposed from a certain direction by measuring radiation, in particular X-ray measuring radiation. The measurement radiation is reflected by a crystal plane belonging to the first crystal direction, for example, by a {111} crystal plane, and becomes a corresponding Bragg reflection. Since the wavelength of the measurement radiation and the material of the optical blank are known, the target angle of the incident and emission measurement radiation with respect to the first crystal direction is known based on Bragg's reflection law. The optical blank is now adjusted relative to the Bragg measurement array until a Bragg reflection is detected relative to the first crystal direction. From the relative orientation of the measurement array and the optical blank, the orientation in the first crystal direction is determined here with reference to the plane normal of the optical rough plane of the optical blank. If the plane normal of the optical rough plane does not coincide with the first crystal direction, the optical blank is processed until the angular deviation is less than ± 5 °, for example by grinding.

  In an advantageous embodiment, the optical blank is pivotally supported about an axis perpendicular to the optical rough plane of the optical blank. The Bragg reflection is now determined for various rotation angles, which in the simplest case are 0 ° and 90 °.

  The reference direction can be similarly determined by evaluation of the Bragg reflection. In this case, the measurement radiation is reflected by the crystal plane belonging to the second crystal direction.

  Alternatively, the position in the reference direction can be determined by the Laue method.

  Based on birefringence in a lens made from an optical blank, the maximum is when the projection of the light beam onto a plane perpendicular to the first crystal direction extends parallel to the reference direction, eg in the case of two mutually orthogonal linear polarization states It is desirable to select the reference direction so as to produce the optical path difference. When using the intertwist of lenses as a correction method to reduce the disturbing influence of intrinsic birefringence, it is easy to adjust the rotation angle based on the marking rule. It is also possible to mark a reference direction in which the light ray produces a minimum optical path difference if the projection of the light ray onto a plane perpendicular to the first crystal direction extends parallel to the reference direction.

  When the first crystal direction is the <100> crystal direction or the <111> crystal direction or a crystal direction equivalent to these crystal directions, the projection of the second crystal direction onto a plane perpendicular to the first crystal direction is Conveniently parallel to the projection of the <110> crystal direction or equivalent crystal direction onto the same plane. That is, a light beam extending parallel to the <110> crystal direction or an equivalent crystal direction produces the maximum optical path difference in the case of two mutually orthogonal polarization states in the cubic fluoride crystal.

  When the first crystal direction is oriented in the <111> crystal direction or an equivalent crystal direction, it is desirable that the second crystal direction is oriented in the <331> crystal direction or an equivalent crystal direction.

  When the first crystal direction is the <100> crystal direction or a crystal direction equivalent thereto, it is desirable that the second crystal direction is the <511> crystal direction or a crystal direction equivalent thereto.

  Since the measurement radiation that determines the Bragg reflections can cause material loss in the area of the optical coarse plane, it is advantageous to excise the material area of the optical blank that is transmitted by the measurement radiation.

  This method advantageously makes it possible to produce optical blanks as starting objects for the production of lenses or lens parts for objective lenses.

  Here, when a lens or a lens part is manufactured from the optical blank prepared as described above, the optical plane of the lens or the lens part is a plane normal line whose lens axis is substantially parallel to the direction of the first crystal direction or an optical rough plane. It is processed so that it is directed parallel to. Preferably, the angular deviation between the first crystal direction and the lens axis is less than 5 °. The curved lens surface of the lens is produced by grinding and polishing the optical rough surface of the optical blank. If this is a rotationally symmetric plane, the lens axis is the axis of symmetry. When the plane is not rotationally symmetric, the lens axis can be a straight line that minimizes the radiation angle of the center of the incident light beam or all the rays inside the lens. Examples of lenses include refractive or diffractive lenses or correction plates having free-form correction surfaces. A flat plate is regarded as a lens when the flat plate is arranged in the optical path of the objective lens. In that case, the lens axis of the flat plate is positioned at right angles to the surface of the planar lens.

  It should be noted that if a pre-installed reference direction marking is lost in the production of a lens or lens part made of an optical blank, this reference direction marking is transferred to the lens or lens part or their holding frame.

  For example, in a lens or lens part used in a high performance optical system such as a projection objective for microlithography, the angle between the lens axis and the first crystal direction even if the angular deviation is less than 5 °. Deviation plays a role. It is therefore desirable to determine this angular deviation very accurately. In that case, for example, an X-ray diffraction measurement method is used. Furthermore, it is advantageous if not only the magnitude of the angle but also the orientation of the first crystal axis is known. The orientation can be explained by the deviation direction. The deviation direction is a perpendicular direction on the lens axis and occurs as a projection of the first crystal direction onto a plane placed perpendicular to the lens axis. The deviation direction is then marked on the lens or lens part, for example on the periphery of the lens. Alternatively, the marking may be mounted on the lens or the holding frame of the lens part. If the lens or lens part or their holding frame already has a reference direction marking, the angle with the symbol can be determined between the reference direction and the deviation direction and indicated to the lens or lens part. For example, the angle values can be stored in a data bank in which the lens or lens portion material data and manufacturing data are organized.

  In an alternative manner, the lens or lens part can first be manufactured from an optical blank made of crystalline material and marked with a second crystal orientation. In that case, a lens is produced from the optical blank, for example by grinding and polishing the lens surface. In this case, the surface is processed so that the lens axis is parallel to the first crystal direction, preferably the main crystal direction. In the next step, a marking is applied on the lens or lens part or their holding frame which has a fixed relationship with the second crystal direction having an angle different from 0 ° with respect to the first crystal direction. In this case, the second crystal direction is similarly the main crystal direction or the crystal direction oriented within a certain crystal structure, for example, the <331> crystal direction or the lens axis when the lens axis faces the <111> crystal direction. Is oriented in the <100> crystal direction, it will be in the <511> crystal direction.

  The marking may be, for example, a dot or line sculpture on the outer cylinder of the lens or lens part or a holding frame to which the lens or lens part is fixed. The holding frame may in this case consist of metal, ceramic or glass-ceramic.

  The constant relationship between the second crystal direction and the marking is, for example, a reference that is a projection of the second crystal direction onto a plane in which the marking is perpendicular to the lens axis and the plane normal is directed to the lens axis. It can be formed by indicating the direction. Preferably, the reference direction intersects the lens axis. The marking is in this case, for example, the intersection of a reference direction with the outer cylinder or holding frame of the lens or lens part. The marking thereby also defines the azimuth angle of the projected second crystal direction relative to the coordinate system associated with the lens or lens part.

  For the determination of the reference direction, the method already shown with an optical blank can be applied. In the measurement of Bragg reflection, it is advantageous if the position of the lens is adjustable, so that the measurement radiation is incident on a curved lens surface at a certain location. It is advantageous if the measurement radiation is incident on the area of the lens apex, especially when the measurement is performed at various rotational positions of the lens.

  The second crystal direction is selected so that the incident measurement radiation and the reflected radiation considered for determining the first crystal direction or the reference direction are not disturbed by the lens shape so as not to be disturbed by the self-shading process on the concave lens surface. It is advantageous.

  Preferred crystalline materials for use as objective lenses for low sub-200 nm wavelengths are cubic fluoride crystals such as calcium fluoride, barium fluoride or strontium fluoride.

  Intrinsic birefringence in cubic fluoride crystals has a significant effect at wavelengths below 200 nm that require appropriate corrective action. For this reason, the determination of the reference direction and the determination of the deviation direction which is necessary in some cases are first advantageous for the use. Advantageously, a lens or lens part with a reference direction and possibly a deviation direction marking is used for an objective lens in which the interfering twist of the lens or lens part reduces the disturbing influence of birefringence around its lens axis. . Marking depending on the crystal orientation essentially simplifies the standardized twisting of the individual lenses. Based on the theoretically predictable birefringence properties of fluoride crystals and known correction methods, the individual lenses of the objective lens or the objective lens are clearly reduced so that the disturbing influence of birefringence on the imaging performance of the objective lens is clearly reduced. The rotation angle between the lens parts can be determined.

  It is particularly advantageous to take into account the amount of angle between the first crystal direction known for each lens and the lens axis and the deviation direction in the determination of the rotation angle.

  A single determination and marking of the deviation direction is advantageous when the optical action of the lens or lens part essentially depends on the angular deviation between the first crystal direction and the lens axis. Affecting the effect on the imaging performance of the objective lens such that a favorable twist of the lens around its lens axis by a predetermined value causes a correction action by the cooperation of several mutually twisted lenses or lens parts. Can do. Thereby, a lens or lens part having an angular deviation between the first crystal direction and the lens axis can also be used. This greatly facilitates the production of lenses or lens parts from crystalline material, since finishing tolerances can be neglected.

  In this case, the objective lens may be a purely refractive projection objective consisting of a number of rotationally symmetrical lenses arranged around the optical axis, or a catadioptric objective type projection objective.

  A projection objective of this kind is advantageously a microlithography starting from a light source and comprising an illumination system, a mask positioning system, a mask carrying a pattern, a projection objective, an object positioning system and a photosensitive substrate. It can be used in a projection exposure apparatus.

  With this microlithographic projection exposure apparatus, a finely structured semiconductor element can be manufactured.

  The present invention will be described in more detail with reference to the drawings.

  As an embodiment, the manufacture of a calcium fluoride lens whose lens axis is essentially oriented in the <111> crystal direction will be described. This production method can, however, also be applied to the production of lenses made of other crystalline materials having a cubic crystal structure, for example barium fluoride or strontium fluoride. Further, the direction of the lens axis may be <100> or <110> crystal direction. This method is advantageous for the production of plane parallel lenses or lenses or lens parts having curved surfaces.

  An optical blank is first produced as a precursor for the production of the lens. 1 and 2 are optical blanks 1 of this kind produced by the method according to the invention in schematic representation. FIG. 1 is a cross-sectional view of the optical blank 1 taken along line AA in the plan view of FIG.

  In the first step, the orientation of the optical blank 1, in this case the calcium fluoride disk, in the <111> crystal direction 3 is determined. The <111> crystal direction 3 is in this case perpendicular to the {111} crystal plane 5 some of which are shown in FIG. This determination can be made with high accuracy, for example by a crystallographic method, for example by calculation of a cleaved surface or production of an etching groove. This improved orientation determination is achieved by X-ray diffraction. A convenient instrument for this is a clinometer arrangement using monochromatic X-ray irradiation. The occurrence of Bragg reflection for the {111} crystal plane 5 is determined by a known table value from the literature. The tabular value indicates the incident angle required in this case according to the reflection display. In the measurement, the calcium fluoride disk rotates around an axis that is perpendicular to the calcium fluoride disk. Thereby, deviations of the <111> crystal direction from the plane normal of the calcium fluoride disk for various rotation angles are obtained. It is advantageous to determine the deviation at at least two rotational positions. In this embodiment, the measurement is performed at 0 ° and 90 °. In order to increase the measurement accuracy, the measurement may additionally be performed at 180 ° and 270 ° or another intermediate angle.

  In the second step, the calcium fluoride disk is processed so that the plane normal of the calcium fluoride disk is parallel to the direction of the <111> crystal direction 3 so that the <111> crystal direction 3 is essentially perpendicular. Located on the optical rough plane 7. The measured deviation is in this case used as the basis for the orientation correction, ie the basis for the constant machining of the calcium fluoride disk by cutting and grinding. The plane normal of the calcium fluoride disk after this processing step is directed to the <111> crystal direction with a deviation of less than 5 °.

In the third step, a reference direction 9 having a fixed relationship with another crystal direction is determined by the calcium fluoride disk. When the plane normal of the calcium fluoride disk is the <111> crystal direction 3, three crystal directions <110>, <011>, <101> collected around the <111> crystal direction due to the symmetry of the three waveforms. Or <100>, <010>, <001> are conveniently identified. Therefore, if a ray extends in the <110> crystal direction or equivalent crystal direction in a calcium fluoride lens, the ray is maximum for two mutually orthogonal linear polarization states based on intrinsic birefringence. This is interesting because it causes the optical path difference. If the light beam extends in the <100> crystal direction or an equivalent crystal direction, the light beam does not cause an optical path difference. The three crystal directions <110>, <011>, and <101> all have an angle of 35 ° with the <111> crystal direction, and the three crystal directions <100>, <010>, and <001> have an angle of 55 °. is there. For physical reasons, X-ray reflections on (110) or (100) crystal planes cannot be measured with crystals having a calcium fluoride structure. Therefore, it is necessary to use Bragg reflection of another crystal plane having a certain relationship with the (100) or (110) crystal plane. For example, (331) Bragg reflection can be used. The three crystal directions <331>, <133>, and <313> each have an angle of 22 ° together with the <111> crystal direction. In FIG. 1, a <331> crystal direction 11 standing at a right angle to a {331} crystal plane 13 on which some are written is shown. (331) Bragg reflection appears in calcium fluoride at less than 38 ° for monochromatic copper Kα ₁ -radiation (8048 eV). This results in an incident angle of 16 ° and a detection angle of 60 ° relative to the reference plane defined by the surface 7 of the calcium fluoride disk. When the disc is rotated 360 ° around the plane normal, the Bragg reflection can be measured at three rotation angles. This indicates that one of the three important (331) crystal plane direction vectors is at the entrance surface of the Bragg measurement. The projections of the three (331) crystal directions onto the disk surface 7 are parallel to the projections of the three crystal directions <110>, <011>, and <101>. That is, if the crystallographic directions <331>, <133>, and <313> are determined, the crystallographic directions <110>, <011>, and <101> are also determined. The source and detector must be oriented accordingly in the possible deviation of the surface normal from the <111> crystal direction.

  In FIG. 2, the reference direction 9 is directed to the direction of the projected <331> crystal direction projected onto a plane perpendicular to the <111> crystal direction. The reference direction additionally intersects with the symmetry axis 17 of the optical blank 1.

  Alternatively, the crystal orientation can be determined from a Laue image. Unlike the measurement of Bragg reflection by monochromatic X-ray irradiation, the Laue method works with “white” or broadband X-ray light. In the case of white X-ray light, Bragg reflection of various crystal plane groups can be obtained, thereby producing a Laue image peculiar to the material. When the <111> crystal direction is parallel to the incident direction, the Laue image is generated with three symmetries. If the <111> crystal direction is displaced several degrees from the disc normal, the result is a slightly distorted image. Accurate analysis of the Laue image can be used to determine the deviation of the <111> crystal direction from the disk normal, for example by appropriate software. The evaluation of this image can further determine three crystal directions <110>, <011>, <101>, or <100>, <010>, <001> and thereby determine the orientation of the disk. .

  In a fourth step, at least one marking 15 that marks the reference direction 9 is applied to the optical blank 1. After all, the marking 15 has a certain relationship with the <331> crystal direction 11. The marking 15 can be performed, for example, by engraving, etching or labeling. The cylindrical peripheral edge of the optical blank 1 is used for the marking 15. Alternatively, the marking may be attached to a frame to which the optical blank 1 is attached.

  In the fifth step, a lens is manufactured from this optical blank 1. 3 and 4 show the lens 31 manufactured from the optical blank 1 in the schematic display. In this case, the lens 31 is held by the holding frame 33. FIG. 3 shows the lens 31 gripped in the cross-sectional view along the line BB written in the plan view of FIG.

  In this case, the lens 31 is manufactured so that the lens axis 35 is parallel to the <111> crystal direction 3. In this case, the marking 15 applied in advance is not broken when the optical blank 1 is processed. This is possible because many processing steps such as grinding or polishing are performed only on the upper and lower sides of the lens, but not on the cylindrical periphery. However, when the peripheral portion of the calcium fluoride disk is also processed, for example, turned, it is necessary to transfer the marking to the holder of the calcium fluoride disk with sufficient accuracy, and attach the marking to the cylindrical peripheral portion again after the processing is completed.

  Further, a marking 37 in the reference direction 9 is attached to the holding frame 33.

  In another embodiment, the lens is manufactured from an optical blank consisting of cubic fluoride crystals, such as calcium fluoride, on the surface of the optical blank whose <111> crystal orientation is essentially perpendicular. The marking is then applied after the lens has been manufactured.

  In the first step, a lens made of an optical blank is manufactured such that the lens axis faces the <111> crystal direction.

  In the second step, a reference direction is determined. In this case, the same method as previously described in the manufacture of the optical blank is applied. However, in that case, it should be noted that the point of incidence of X-rays on the lens surface is precisely adjusted to high and low. Therefore, the lens mounting surface can be adjusted to be high or low. Thereby, when various points are measured on the curved lens surface, it can follow the curved contour of the lens. In addition, it should be noted that curvature may cause shadows of incident or exiting light rays. The generation of shadows can be avoided by the choice of a convenient Bragg reflection and the resulting measurement shape.

  In the case of a plane parallel plate, the method can be applied to each point on the surface based on a goniometer structure.

  It should be noted that in the processing of optical blanks and lenses, irradiation of calcium fluoride with X-rays can generate color centers. The penetration depth of Cu-Kα radiation is about 30 μm in the case of calcium fluoride. In order to avoid the presence of color centers, X-ray analysis is advantageously performed only on optical blanks or lenses that are subsequently subjected to corresponding material ablation. In the case of irradiation with Cu-Kα radiation, this means an ablation of at least 30 μm.

  5 and 6 show another embodiment of the lens 51 according to the present invention in a schematic display. FIG. 5 shows a lens 51 with a cross-sectional view taken along the line CC in the plan view of FIG.

  In this case, the calcium fluoride lens 51 is not a (111) lens but a (100) lens. However, the lens axis 53 does not accurately face the <100> crystal direction 55 and appears in the <100> crystal direction 55 having a deviation angle δ from the lens axis 53. In this case, the <100> crystal direction 55 is positioned on the {100} crystal plane 57 at a right angle.

  In addition to the amount of the angle δ, it is also important to determine the deviation direction 63. The deviation direction 63 is obtained as a projection of the <100> crystal direction 55 onto a plane perpendicular to the lens axis 53.

  The deviation direction 63 preferably intersects the lens axis 53. A marking 65 for displaying the deviation direction 63 is attached on the lens 51. The marking may be attached to a holding frame (not shown in FIGS. 5 and 6). In FIG. 6, the marking 65 indicates the intersection of the outer cylindrical body of the lens 51 and the deviation direction 63.

  The orientation of the <100> crystal direction 55 relative to the lens axis 53 can be determined by determining the Bragg reflection of the <100> crystal direction 55 at various rotational positions of the lens 51. In this case, the lens 51 is rotated around its lens axis 53. It is advantageous to determine the deviation at at least two rotational positions. In this embodiment, the measurement is performed at 0 ° and 90 °. In order to increase the measurement accuracy, the measurements are additionally performed at 180 ° and 270 °.

  Alternatively, the deviation between the <100> crystal direction 55 and the lens axis 53 can also be determined by the measurement radiation incident by the Laue method being incident in the direction of the lens axis 53.

  In addition to the marking 65, the lens 51 further has a marking 67. The marking 67 is in a fixed relationship with the <511> crystal direction 59 located perpendicular to the {511} crystal plane 61. The marking displays the intersection of the outer cylindrical body of the lens 51 and the reference direction 69. The reference direction 69 is obtained as a projection of the <511> crystal direction 59 onto a plane perpendicular to the lens axis 53. Further, the reference direction 69 intersects the lens axis 53. The <511> crystal direction 59 is adopted because the projection of the <511> crystal direction 59 onto a plane perpendicular to the lens axis 53 extends parallel to the corresponding <011> crystal direction projection. The <011> crystal direction is marked because a light beam entering through the lens 51 in parallel with that direction produces the maximum optical path difference for two orthogonal polarization states based on intrinsic birefringence.

  Since the rotation angle of the lens can be adjusted around its lens axis with reference to the reference direction associated with the objective lens, only one marking is sufficient. Since the lens 51 has the marking 67 in the reference direction 69, the angle between the reference direction 69 and the deviation direction 63 can be determined instead of the marking 65 in the deviation direction 63, and can be instructed to the lens. For example, the angle can be arranged together with the deviation angle, for example, in a data bank in which material data and manufacturing data of the lens 51 are stored. Thereby the angle and the deviation angle are provided to the optimization method.

  FIG. 7 is a first embodiment of the objective lens 71 according to the present invention in a schematic display. The objective lens focuses the object OB on the image IM. Illustrated are lenses 73, 75, 77 and 79. The lens axes of the lenses 73, 75, 77, and 79 are oriented in the direction of the optical axis OA. The lenses 73 and 75 are (111) lenses made of calcium fluoride, and the lenses 77 and 79 are (100) lenses. In order to correct the disturbing effects of intrinsic birefringence, the lenses are each arranged twisted around their lens axis, so that for external rays 81 and rays extending along the optical axis OA. The difference in optical path difference between the two orthogonal polarization states of the corresponding optical path difference is minimized. The rotation angle between the (111) lenses 73 and 75 is 60 °. The rotation angle can be easily adjusted by the present invention because the lenses 73 and 75 have markings 83 and 85 indicating the reference directions 87 and 89, respectively. Reference directions 87, 89 are projections of each <331> crystal direction onto a plane that stands perpendicular to each lens axis. The rotation angle between the (100) lenses 77 and 79 is not precisely 45 ° because in this case, the <100> crystal direction is not precisely directed to the direction of each lens axis. Deviation directions 95, 97 are indicated by markings 91, 93. In optimizing the rotation angle between the lenses 77 and 79, the magnitude and orientation of the deviation are taken into account. The rotation angle calculated between the lenses 77 and 79 can be easily adjusted by the markings 99 and 101. The markings indicate reference directions 103, 105 that are projections of each <511> crystal direction onto a plane that stands perpendicular to each lens axis.

  Hereinafter, in an objective lens having a known optical design, an optimization method is possible in which the orientation of the lens axis of each lens can be determined in the direction of the main crystal direction marked, and on the other hand, the rotation angle between the lenses can be determined. explain. The plurality of lenses of the objective lens are made of birefringent fluoride crystals. The birefringent nature of the lens is known. For example, the influence of intrinsic birefringence can be theoretically estimated according to the opening angle and the azimuth angle of the light beam when the material orientation based on the coordinate system of the lens is known in addition to the crystal material. However, the birefringence properties can also be determined by measuring with a lens. Since the birefringent nature of the lens and the optical design of the objective lens are known, the optical path difference for two mutually orthogonal linear polarization states where the light rays occur inside the objective lens is known. This optical path difference is used below as an optimization amount whose absolute value should be minimized. In a similar manner, optimization can be performed on the total luminous flux of individual rays. The degree of freedom possible for this optimization is the orientation of the lens axis relative to the rotation angle of the individual lenses and the main crystal direction. On the other hand, it is convenient when the lens axis indicates the main crystal direction, and on the other hand, the rotation angle between the lenses takes only discrete values depending on the direction of each lens axis.

  Three degrees of freedom are provided for lens axis orientation. The lens axis can then be oriented in the (100), (111) or (110) crystal direction.

  Lenses whose lens axes are the same or equivalent to the main crystal direction are grouped into individual groups. Each group has at least two lenses.

  The discrete rotation angle of a group of lenses depends on the orientation of the lens axis.

For a group with n (100) lenses, the following reference value for the rotation angle:
γ = (90 ° / n) + m · 90 ° ± 10 ° (where m is an arbitrary integer) is generated.

  If this group contains two (100) lenses, the angle of rotation between the two lenses is ideally 45 °, or 135 °, 225 °. . . become.

For a group with n (111) lenses, the following reference value for the rotation angle:
γ = (120 ° / n) + m · 120 ° ± 10 ° (where m is an arbitrary integer) is generated.

For a group with n (110) lenses, the following reference value for the rotation angle:
γ = (180 ° / n) + m · 180 ° ± 10 ° (where m is an arbitrary integer) is generated.

  This provides discrete rotation angles and discrete crystal orientations between the lenses as degrees of freedom.

  Within this parameter space, the combination of rotation angle and crystal orientation can be found for individual lenses where the amount of optimization takes a minimum value or falls below a certain threshold.

  For each objective lens, there is one optimal solution where the optical path difference between two mutually orthogonal polarization states takes a minimum value for the total luminous flux.

  However, it is very expensive to determine the optimal solution when the objective has a large number of lenses, as is particularly true for the objective 8 in FIG. FIG. 8 shows a lens cross section of the catadioptric projection objective 8 when the wavelength is 157 nm. The optical data of this objective lens is summarized in Table 1. This embodiment is read from International Patent Application Publication WO 01/50171 A1 (US Patent Application No. 10/177580) and corresponds to FIG. 9 or Table 8 therein. Reference is made to International Patent Application Publication No. WO 01/50171 A1 (US Patent Application No. 10/177580) for a more detailed description of the mode of operation of the objective lens 8. All the lenses of this objective lens are made of calcium fluoride crystals. The numerical aperture on the image side of the objective lens is 0.8.

By the way, although not unconditional, an optimal solution and an optimization method for finding a sufficiently good solution for actual use of an objective lens are known. A very similar mathematical task setting known in the literature is the “traveling salesman problem” involving finding the shortest possible route through the indicated city for a given map. The following methods known from the literature under the name can be used in the optimization:
1. Monte Carlo survey 1. Simulated cooling ("simulated annealing")
3. Threshold acceptance (“Threshold accepting”)
4). 4. Simulated cooling including intermediate heating Genetic algorithm

Four degrees of freedom (FGH) are provided for each lens in the first embodiment for correction of the disturbing effects of intrinsic birefringence:
FGH1: (111) lens with a rotation angle of 0 ° FGH2: (111) lens with a rotation angle of 60 ° FGH3: (100) lens with a rotation angle of 0 ° FGH4: (100) lens with a rotation angle of 45 ° Individual lens rotation angle Are related to a certain reference direction in the object plane O in this case.

An optimum crystal orientation of the lens axis and a lens L801 that is based on a certain reference direction in the object plane O by Monte Carlo investigation and setting of four degrees of freedom FGH1 to FGH4 for the projection objective lens 8 in FIG. The rotation angle β _{L of} L817 was determined. Table 2 shows the crystal direction of the lens axis and the rotation angle β _L with respect to the lenses L801 to L817. Also shown are the optical path differences of two mutually orthogonal polarization states for the upper and lower outermost aperture rays for each lens. Both outermost aperture rays start in this case from the object point at the center of the object field and each have one angle relative to the optical axis OA corresponding to the image-side numerical aperture at the image plane O ′. The resulting maximum optical path difference is 5 nm.

  Other degrees of freedom of optimization are obtained when assigning lenses to individual groups. In this case, the lens axes of one group of lenses are oriented in the same main crystal direction. Within one group, the lenses are now twisted together so that the distribution of the optical path difference between the two orthogonal linear polarization states caused by one group is approximately rotationally symmetric. The angle of rotation between the individual groups can now be arbitrarily adjusted here, in order to be corrected by said additional degrees of freedom or production limited additional aberrations.

  In the embodiment of Table 2, the lenses L801 and L814 form a first group having (100) lenses, and both lenses are arranged twisted by a rotation angle of 45 ° relative to each other.

  Lenses L802, L804, L807, and L812 form a second group having (111) lenses. In this case, the lenses L802 and L807 and the lenses L804 and L812 form one subgroup, in which the lenses are not twisted with respect to each other, or at most have a rotation angle γ = 1 · 120 ° ± 10 °. (Wherein l is an integer). Both subgroups are twisted with respect to each other by an angle of 60 °, so that the rotation angle between the two lenses of the various subgroups is γ = 60 ° + m · 120 ° ± 10 ° (wherein , M is an arbitrary integer).

  Lenses L803, L805, and L815 form a third group having (100) lenses. In this case, the lens L803 and the lenses L805 and L815 form one subgroup, in which the lenses are not twisted with respect to each other, or at most have a rotation angle γ = l · 90 ° ± 10 ° (formula Where l is an integer). Both subgroups are twisted with respect to each other by an angle of 45 °, so that the rotation angle between the two lenses of the various subgroups is γ = 45 ° + m · 90 ° ± 10 ° (where , M is an arbitrary integer).

  Lenses L808, L809, and L811 form a fourth group having (100) lenses. The lens L808 and the lenses L808 and L809 each form one subgroup in this case, within which the lenses are not twisted together or have a rotation angle γ = l · 90 ° ± 10 ° at most (formula Where l is an integer). Both subgroups are twisted with respect to each other by an angle of 45 °, so that the rotation angle between the two lenses of the various subgroups is γ = 45 ° + m · 90 ° ± 10 ° (where , M is an arbitrary integer).

  Lenses L816 and L817 form a fifth group having (111) lenses, and both lenses are arranged twisted relative to each other by a rotation angle of 60 °.

In the second embodiment, 8 degrees of freedom are provided for each lens:
FGH1: (111) lens with rotation angle 0 ° FGH2: (111) lens with rotation angle 60 ° FGH3: (100) lens with rotation angle 0 ° FGH4: (100) lens with rotation angle 45 ° FGH5: (110) lens FGH6: (110) lens with a rotation angle of 0 ° FGH7: (110) lens with a rotation angle of 90 ° FGH8: (110) lens With a rotation angle of 135 °

  The number of degrees of freedom improves the optimization result, but the optimization cost also increases exponentially. The other degrees of freedom are caused by fine step differences in the rotation angle.

  Of course, the optimization method may be implemented with fine discrete rotation angles.

  Optimization birefringence measurement data, lens or mirror surface data and / or lens material inhomogeneities may be considered in the optimization. By this method, all the generated interference amounts are grasped, and an objective lens state that provides a good imaging quality as a whole is calculated using the degree of freedom.

  In particular, the recognition of the magnitude and orientation of the deviation between the marking of the deviation direction and the respective lens axis for each lens of the objective lens and the principal crystal direction indicated allows the effects caused by the deviation in the optimization to be taken into account. To do. In the case of a lens whose lens axis is precisely oriented in the (100), (111) or (110) crystal direction, for example, γ = 45 ° + m · 90 ° with respect to two (100) lenses. There is always an equivalent rotation angle that results from. Here, when one deviation appears between each lens axis and the main crystal direction shown for both (100) lenses, the natural number m can be used as a degree of freedom for optimization. The natural number m may be the values 1, 2, 3 in this case. Since the deviation direction and the reference direction are marked, the rotation angle thus determined can be precisely adjusted.

  The following describes the optimization method in each step:

  In the first step, a target function is calculated for an objective lens whose lens birefringence properties are known. This target function is a measure of the disturbing effects of birefringence. As the target function, for example, an optical path difference between two mutually orthogonal linear polarization states of the outermost aperture light beam can be used. It is also possible to determine the maximum value or the average value of the distribution of the optical path difference of the light flux as the target function. A lens rotation angle, crystal orientation, and a target function of the objective lens state are stored.

  For the target function, there is a threshold that can tolerate a reduction in the disturbing effects of birefringence.

  In a second step, it is tested whether the target function is below a threshold value. If below the threshold, the method is interrupted. If not below the threshold, the third step follows.

  In the third step, the rotation angle between the lenses and the crystal orientation inside the objective lens are changed here according to a predetermined degree of freedom, and one of the methods, for example the Monte Carlo method, is used.

  After the third step, the method starts again at the first step and the number of loops that are transmitted is determined. If the number of permeating loops exceeds the maximum number, the method is similarly interrupted.

  In other words, the method is interrupted when it falls below a certain threshold or when a predetermined number of loops is exceeded. If the maximum number of loops is exceeded, a ranking list can be generated in which, for example, the resulting objective function is indicated by the attached objective function.

  The principle structure of the microlithographic projection exposure apparatus will be described with reference to FIG. The projection exposure apparatus 111 includes a light source 113, an illumination apparatus 115, a mask 117 that carries a pattern, a projection objective lens 119, and a substrate to be exposed 121. The illumination device 115 collects light from the light source 113 in accordance with, for example, each operating wavelength KrF laser or ArF laser, and illuminates the mask 117. In this case, the exposure process provides predetermined illumination distribution uniformity and predetermined illumination of the entrance pupil of the objective lens 119. The mask 117 is held in the optical path by the mask holder 113. The mask 113 used for such microlithography has a micrometer-nanometer structure. As a mask for carrying the pattern, a driven micromirror array or a programmable LCD array may be used as an alternative to the so-called reticle. The mask 117, that is, a partial area of the mask is imaged on the substrate 121 positioned by the substrate holder 125 using the projection objective lens 119. The projection objective lens 119 is, for example, a catadioptric objective lens shown in FIG. In this case, the individual lenses 127 of the projection objective are arranged twisted together to minimize the disturbing influence of birefringence or other effects. It is easy to adjust the rotation angle of the lens with the markings attached according to the invention. The substrate 121 is typically a silicon wafer with a photosensitive coating, so-called resist. Next, a semiconductor element is manufactured from the substrate to be exposed in another processing step.

It is sectional drawing of the optical blank in a model display. It is the optical blank of FIG. 1 by the top view in a model display. It is sectional drawing of the hold | gripped lens in a model display. FIG. 4 is a grasped lens of FIG. 3 in a schematic view. It is sectional drawing of another embodiment of the lens in a model display. FIG. 6 is the lens of FIG. 5 in a schematic view. It is an objective lens in schematic perspective display. It is lens sectional drawing of a projection objective lens. It is the projection exposure apparatus in a model display.

Claims (40)

As a precursor for the production of objective lenses (71, 8), in particular lenses (31, 51, 73, 75, 77, 79) or lens parts for projection objectives for microlithographic projection exposure apparatus (111) A method for producing an optical blank (1) comprising a crystalline material,
a) determining the orientation of the first crystal direction (3) oriented within a constant crystal structure;
b) processing the optical blank (1) such that the first crystal direction (3) is essentially perpendicular to the optical rough plane (7) of the optical blank (1);
c) providing the marking (15) on the optical blank (1) or the holding frame of the optical blank (1), the marking (15) being at an angle different from zero with respect to the first crystal direction (3) Providing a marking in a fixed relationship with the second crystal direction (11).   The marking (15) indicates a reference direction (9) perpendicular to the first crystal direction (3), and the second crystal direction to a plane in which the reference direction (9) is placed perpendicular to the first crystal direction (3) The method of claim 1, which is a projection of (11).   The method according to claim 1 or 2, wherein the first crystal direction (3) is determined by measuring the direction of Bragg reflection of the first crystal plane group (5) belonging to the first crystal direction (3).   The first crystal direction (3) is a measurement direction of Bragg reflection of the crystal plane group (5) at a plurality of measurement positions twisted with respect to an axis (17) perpendicular to the optical rough plane (7) of the blank. The method of claim 3, which is determined by comparing.   The first crystal direction (3) is directed to a <100> crystal direction, a <111> crystal direction, a <110> crystal direction, or a crystal direction equivalent to the crystal direction, according to any one of claims 1 to 4. The method described.   6. The method according to any one of claims 1 to 5, wherein the crystalline material is calcium fluoride, strontium fluoride or barium fluoride.   7. The method according to claim 1, wherein the reference direction (9) is determined by measuring the direction of Bragg reflection of the crystal plane group (13) belonging to the second crystal direction (11).   The method according to claim 1, wherein the reference direction is determined by the Laue method.   A ray whose projection onto a plane perpendicular to the first crystal direction (3) is parallel to the reference direction (9) produces a maximum or minimum optical path difference for two mutually orthogonal linear polarization states. 9. The method according to any one of items 8.   The first crystal direction (3) faces the <100> crystal direction or the crystal direction equivalent to the <100> crystal direction or the <111> crystal direction or the crystal direction equivalent to the <111> crystal direction. 3. The projection of the second crystal direction (11) onto the plane perpendicular to 3) is parallel to the projection of the <110> crystal direction or equivalent crystal direction onto the plane perpendicular to the first crystal direction. 10. The method according to any one of items 9.   The first crystal direction (3) faces the <111> crystal direction or equivalent crystal direction, and the second crystal direction (11) faces the <331> crystal direction or equivalent crystal direction, or the first crystal direction 10. (3) is a <100> crystal direction or a crystal direction equivalent thereto, and the second crystal direction (11) is a <511> crystal direction or a crystal direction equivalent thereto. The method described.   12. The method according to any one of claims 2 to 11, wherein a material region of the optical blank (1) that is transmitted by the Bragg measurement radiation is ablated. Objective lens (71, 8) with an optical rough plane (7) essentially perpendicular to the first crystal direction (3), in particular a projection objective lens (31) for a microlithographic projection exposure apparatus (111). 51, 73, 75, 77, 79) or an optical blank (1) of crystalline material as a starting product for the production of lens parts,
The marking (15) in which the optical blank (1) or the holding frame of the optical blank (1) has a fixed relationship with the second crystal direction (11), which is an angle different from zero with respect to the first crystal direction (3). Optical blank with.   The marking (15) indicates the direction of the reference direction (9) perpendicular to the first crystal direction (3), the second crystal direction (9) to the plane where the reference direction (9) is perpendicular to the first crystal direction (3) ( The optical blank (1) according to claim 13, which is a projection of 11).   The optical blank (1) according to claim 13 or 14, produced by the method according to any one of claims 1 to 12.   d) molding a lens (31) or lens part, wherein the direction of the first crystal direction (3, 55) is essentially parallel to the lens axis (35, 53). The manufacturing method of the lens (31, 51, 73, 75, 77, 79) or lens part which consists of an optical blank (1) as described in any one. e) determining an angular deviation between the lens axis (53) and the first crystal direction (55);
f) A step of determining a deviation direction (63, 95, 97) perpendicular to the lens axis (53), wherein the deviation direction (63, 95, 97) is a first to a plane perpendicular to the lens axis (53). Determining a projection of the crystal orientation (55);
g) marking the lens (51, 77, 79) or the lens part or the holding frame of the lens (51, 77, 79) or lens part with the deviation direction (63, 95, 97) and / or the reference direction (69 And determining the angle between the deviation direction (63, 95, 97) and indicating the angle to the lens (51, 77, 79) or lens part. a1) lenses (31, 51, 73, 75, 77) in which the direction of the first crystal direction (3, 55) oriented within a constant crystal structure is essentially parallel to the lens axis (35, 53) 79) or molding the lens part;
b1) Marking (15, 37, 67, 83, 85, 99, 101) on the lens (31, 51, 73, 75, 77, 79) or the lens portion or the holding frame (33) of the lens (31) or the lens portion. ), Wherein the marking (15, 37, 67, 83, 85, 99, 101) is at a second crystal direction (11, 59) and a step of providing a lens (31, 51, 73, 75, 77, 79) or a lens portion made of a crystalline material, characterized in that it has a step of being provided in a fixed relationship.   The marking (15, 37, 67, 83, 85, 99, 101) indicates the direction of the reference direction (9, 69, 87, 89, 103, 105) perpendicular to the lens axis (35, 53), and the reference direction 19. The method according to claim 18, wherein (9, 69, 87, 89, 103, 105) is a projection of the second crystal direction (11, 59) onto a plane perpendicular to the lens axis (35, 53).   The lens axis (35, 53) is essentially a <100> crystal direction or a crystal direction equivalent to a <100> crystal direction or a <111> crystal direction or a crystal direction equivalent to a <111> crystal direction or a <110> crystal direction The method according to claim 18 or 19, wherein the crystal orientation is equivalent to a <110> crystal orientation.   21. A method according to any one of claims 18 to 20, wherein the crystalline material is calcium fluoride, strontium fluoride or barium fluoride.   The position of the reference direction (9, 69, 87, 89, 103, 105) is determined by measuring the direction of Bragg reflection of the crystal plane group (13, 61) belonging to the second crystal direction (11, 59). The method according to any one of claims 18 to 21.   The method according to any one of claims 18 to 22, wherein the position of the reference direction (9, 69, 87, 89, 103, 105) is determined by the Laue method.   Rays whose projections on a plane perpendicular to the first crystal direction (3, 55) are parallel to the reference direction (9, 69, 87, 89, 103, 105) are for two mutually orthogonal linear polarization states 24. A method as claimed in any one of claims 18 to 23 which produces a maximum or minimum optical path difference.   The first crystal direction (3, 55) faces the <100> crystal direction or the crystal direction equivalent to the <100> crystal direction or the <111> crystal direction or the crystal direction equivalent to the <111> crystal direction, and the first crystal The projection of the second crystal direction (11, 59) onto the plane perpendicular to the direction is parallel to the projection of the <110> crystal direction or equivalent crystal direction onto the plane perpendicular to the first crystal direction (3, 55). 25. A method according to any one of claims 18 to 24.   When molding the lens (31, 51, 73, 75, 77, 79) or lens part, the material region of the lens (31, 51, 73, 75, 77, 79) or lens part through which the Bragg measurement radiation has been transmitted 26. A method according to any one of claims 22 to 25, wherein the method is ablated. c1) determining an angular deviation between the lens axis (53) and the first crystal direction (55);
d1) A step of determining a deviation direction (63, 95, 97) perpendicular to the lens axis (53), wherein the deviation direction (63, 95, 97) is a first to a plane perpendicular to the lens axis (53). Determining a projection of the crystal orientation (55);
e1) The deviation direction (63, 95, 97) is marked on the lens (51, 77, 79) or lens part or the holding frame of the lens (51, 77, 79) or lens part and / or the reference direction (69 ) And the deviation direction (63, 95, 97) and determining the angle to the lens (51, 77, 79) or lens part. The method according to one item. An objective lens (71, 8), in particular a lens (31, 51, 73, 75, 77, 79) or a lens part for a projection objective for a microlithographic projection exposure apparatus (111),
The lens (31, 51, 73, 75, 77, 79) or the lens portion is made of a crystalline material,
The lens axis (35, 53) of the lens (31, 51) or lens part is essentially in the direction of the first crystal direction (3, 55), and the lens (31, 51) or lens part or the lens (31) Alternatively, the holding frame (33) of the lens portion has a marking (15, 37,) having a fixed relationship with the second crystal direction (11, 59), which is an angle different from zero with respect to the first crystal direction (3, 55). 67, 83, 85, 99, 101).   The markings (15, 37, 67, 83, 85, 99, 101) indicate the direction of the reference direction (9, 69, 87, 89, 103, 105) perpendicular to the first crystal direction (3, 55); 29. The reference direction (9, 69, 87, 89, 103, 105) is a projection of the second crystal direction (11, 59) onto a plane perpendicular to the first crystal direction (3, 55). Lens (31, 51, 73, 75, 77, 79) or lens part.   30. A lens (31, 51, 73, 75, lens, according to claim 28 or 29, wherein the lens (31, 51, 73, 75, 77, 79) or lens part is manufactured according to any one of claims 18 to 27. 77, 79) or lens part.   The lens (51, 77, 79) or the lens portion or the holding frame of the lens or the lens portion is perpendicular to the optical axis (53) and in a first crystal direction (55) to a plane perpendicular to the optical axis (53). 31) Lens (51, 77, 79) according to any one of claims 28 to 30, having another marking (65, 91, 93) that marks the deviation direction (63, 95, 97) that is a projection of). ) Or lens part. An objective lens (71, 8), in particular a lens (51, 77, 79) or lens part for a projection objective for a microlithographic projection exposure apparatus (111),
The lens (51, 77, 79) or lens portion is made of a crystal material, and the lens axis (53) of the lens (51, 77, 79) or lens portion is essentially in the direction of the first crystal direction (55). The lens (51, 77, 79) or the lens part or the holding frame of the lens or lens part mark the deviation direction (63, 95, 97) perpendicular to the optical axis (53) and the optical axis (53) Lens or lens part with markings (65, 91, 93), which is a projection of the first crystal direction (55) onto a plane perpendicular to the surface.   32. At least one lens (73, 75, 77, 79, L801-L817, 127) or an objective lens (71, 8, 119) comprising at least one lens part according to any one of claims 28 to 31. Projection objective, especially for a microlithographic projection exposure apparatus (111).   At least two lenses (73, 75, 77, 79, L801 to L817, 127) or each of the lens parts to have a predetermined rotation angle between two reference directions (87, 89, 103, 105), respectively. 32. At least two lenses (73, 75, 77, 79, L801-L817, 127) or lens portions according to any one of claims 28 to 31 arranged in a twisted manner about its lens axis. The objective lens according to 33 (71, 8, 119).   At least two lenses (73, 75, 77, 79, L801 to L817, 127) or a lens portion is made of a fluoride crystal having a cubic crystal structure, and the rotation angle is determined based on the birefringence characteristics of the fluoride crystal. Objective lens (71, 8, 119) according to claim 34.   At least two lenses (77, 79) or lens portions each have one angular deviation between the lens axis and the first crystal direction, and the rotational angle depends on the birefringence characteristics of the fluoride crystal. 36. Objective lens (71) according to claim 35, determined under consideration.   The at least two lenses (77, 79) or each of the lens portions are arranged to be twisted around their lens axes so as to have a predetermined rotation angle between two deviation directions (95, 97) each. Objective lens (71), in particular for a projection objective for a microlithographic projection exposure apparatus, comprising at least two lenses (77, 79) or a lens part.   At least two lenses (77, 79) or each of the lens parts cause disturbances in the optical imaging performance of the objective lens based on the deviation between the lens axis and the first crystal direction, with individual disturbances inherent The objective lens (71) according to claim 37, wherein the rotation angle is determined so as to be corrected to.   39. An illumination system (115) for illuminating a mask (117) carrying a pattern and imaging the mask (117) carrying the pattern on a photosensitive substrate (121). A microlithographic projection exposure apparatus (111), comprising the objective lens (119) according to Item.   40. A method of manufacturing a semiconductor device by a microlithographic projection exposure apparatus (111) according to claim 39.

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