Projection objective having adjacently mounted aspheric lens surfaces

A projection objective has at least five lens groups (G1 to G5) and has several lens surfaces. At least two aspheric lens surfaces are arranged so as to be mutually adjacent. These mutually adjacently arranged lens surfaces are characterized as a double asphere. This at least one double asphere (21) is mounted at a minimum distance from an image plane (0′) which is greater than the maximum lens diameter (D2) of the objective.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 6,707,616 discloses catadioptric optic projection objectives which include a plurality of aspheric lens surfaces. For example, the projection objective shown inFIG. 4includes 12 aspheric lens surfaces for 15 lenses. The manufacturing costs of aspheric lens surfaces with the accuracy required in microlithography are very high. Accordingly, these objectives are of little interest in the marketplace because of the many required aspheric lens surfaces.

U.S. Pat. No. 4,875,380 discloses an optical projection system especially for photolithography. The projection objective known from this publication includes five lens groups. The first, second, third and fifth lens groups each have only one lens. In part, the lenses are provided with aspheric lens surfaces. An aspheric object end mounted lens surface of the fifth lens group follows an aspheric lens surface mounted in the fourth lens group at the image end.

U.S. Pat. No. 6.104.472 discloses the adjacent mounting of aspheric lens surfaces in a projection objective. These aspheric lenses are supported so as to be displaceable in the radial direction. The projection objective is matched via the relative movement of the lenses. The aspheric lens surfaces are especially rotationally unsymmetrical because of the possibility of displacing the aspheres in radial direction with respect to each other. Because of the movable support of the aspheric lenses, this arrangement is not suitable of every projection objective because projection objectives designed especially for short wavelengths react sensitvely to the smallest position change of the individual lenses. Accordingly, the position stability, which is achievable because of the special support of the lenses, is not sufficient in order to reliably ensure a good imaging quality.

German patent publication 198 18 444 discloses a projection optic arrangement having a purely refractive projection objective which includes six lens groups G1to G6. In this projection objective, the lens groups G1, G3and G5have positive refractive power. The lens groups G2and G4have negative refractive power. To correct imaging errors, some lenses, especially in the fourth and fifth lens groups, have aspheric lens surfaces.

German patent publication 199 42 281.8 discloses additional projection exposure objectives which have six lens groups. The second lens group and the fourth lens group have negative refractive power. In the projection objectives known from this publication, lenses having aspheric lens surfaces are preferably arranged in the first three lens groups. A minimum number of spherical lens surfaces are arranged between the aspheric lens surfaces. This minimum spacing between the aspheric lens surfaces appears necessary so that the utilized aspheric lenses can develop their optimal effect.

From U.S. Pat. No. 4,871,237 it is already known to match an objective in dependence upon barometric pressure via the refractive index of a fill gas in the lens intermediate spaces. For example, spherical aberration, coma and other imaging errors can be corrected with a suitable combination of intermediate spaces.

U.S. Pat. No. 5,559,584 discloses introducing a protective gas into the intermediate spaces between a wafer and/or a reticle and the projection objective in a projection exposure system for manufacturing microstructured components.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a projection objective and a projection exposure system as well as a method for manufacturing microstructured components. These components are improved with respect to the imaging quality and the resolution capacity. Furthermore, it is an object of the invention to reduce manufacturing costs.

The projection objective of the invention defines a maximum lens diameter (D2) and includes: a plurality of lenses defining an object plane (0) and an image plane (0′); at least two of the lenses having respective mutually adjacent lens surfaces which are aspheric to define a double asphere; the double asphere being mounted at a distance from the image plane (0′) corresponding at least to the maximum lens diameter (D2); the lenses of the double asphere defining a mean lens diameter; and, the mutually adjacent lens surfaces being mounted at a spacing from each other which is less than half of the mean lens diameter.

In a projection objective having a plurality of lenses, the measure of arranging the double asphere at a spacing of at least the maximum lens diameter of the objective away from the image plane (especially the wafer plane), improves the imaging qualities of a projection objective in comparison to a projection objective without such double aspheres. In the above, at least two mutually adjacent mounted lens surfaces are aspheric and this is identified as a double asphere. The spacing between the aspheric lens surfaces of the double asphere is maximally half the lens diameter of the mean diameter of the double asphere. The numerical aperture can especially be increased in a refractive projection objective with the use of at least one double asphere in that the first convex form is shortened so that, at a constant length of the projection objective, the third convex form experiences an increase of the numerical aperture of approximately 0.03 to 0.05.

Especially in purely refractive projection objectives, the use of double aspheres with an arrangement in the first three lens groups has been shown to be especially advantageous.

In lithographic objectives, there are particular locations, which operate especially well on difficult to control aberrations, when these locations are aspherized. Precisely here it is purposeful to utilize especially the effectiveness at the corresponding location via a complex aspheric function. The region of the first restriction and the end of the second convex form as well as regions behind the diaphragm are predestined. Since the technical realization of complex aspheres is subjected to technical limits, the complex asphere functions are realized by means of double aspheres. In this way, a still more extensive correction is possible and the aspheres of the double asphere are technically realizable.

Furthermore, it has been shown to be advantageous to provide aspheric lens surfaces as aspheric lens surfaces of the double asphere. The radii of the aspheric lens surfaces of the best-fitting spherical lens surface (identified as the profile radius) differ very little. Preferably, the reciprocal values of the profile radius or radii of the double aspheres deviate less than 30% from each other. As a reference value, the reciprocal value of the larger radius in magnitude is applied.

It has been shown to be especially advantageous that the apex radii of the aspherical lens surfaces of the double aspheres differ by less than 30% with reference to the larger apex radius in magnitude.

In the area of microlithography, the developmental work is directed to increasing the resolution. On the one hand, the resolution can be increased by increasing the numerical aperture, utilizing ever smaller wavelengths and even by correcting the occurring imaging errors. For an increase of the image end numerical aperture, the last convex form of the objective arranged at the image end is increased. However, it is problematic that only a fixed pregiven space can be made available for the objective. Accordingly, in order to provide a larger numerical aperture, it is therefore necessary to save space in other regions of the objective.

It has been shown to be advantageous to provide the space needed for increasing the numerical aperture by shortening the first convex form. With the first convex form, especially the input telecentrics and the distortion are corrected. By utilizing double aspheres, it is possible to correct the input telecentrics as well as the distortion with ease and at a short distance. With the double asphere, a variable adjustment of the location is made available at a short distance. With the possibility of varying the location, the distortion can be corrected. Especially the input telecentrics is corrected because the angle can be flexibly influenced.

Corrective means has already been made available in the input region of the objective especially with the use of a double asphere in a refractive projection objective in the region of the first two lens groups, that is, up to and including the first lens group of negative refractive power. Accordingly, the corrective means, which is required in the third convex form, are reduced for ensuring a uniform or constant imaging quality.

Furthermore, by providing a double asphere in the forward region of the objective, especially up to the second restriction, the number of lenses is reduced. This operates advantageously on the manufacturing costs.

In purely refractive projection objectives, it has been shown to be advantageous to provide aspheric lens surfaces in the forward region of the objective ahead of the second restriction to improve the imaging quality. For example, for a numerical aperture of 0.83, the deviation from the wavefront of a spherical wave is reduced to less than 6 mλ with a field of 8×26 mm2referred to 248 nm.

The imaging characteristics of the objective can be changed because of fluctuations of the atmospheric pressure. In order to compensate for such pressure fluctuations, it has been shown to be advantageous to charge an intermediate space between two lens surfaces with pressure in a targeted manner so that pressure changes, especially of the atmospheric pressure, can be compensated. Furthermore, the targeted application of pressure can be used for a further reduction of imaging errors.

Furthermore, it has been shown to be advantageous to provide at least one of the end plates with a pressure manipulator so that a curvature of the plate or lens can be generated with a two-sided application of pressure of the particular lens or the particular plate. For a three-point support of the end plate and an application of pressure of the gas space, the three-waviness during operation is corrected in a targeted manner by means of the through-bending of the end plate. With an n-point support, an n-waviness can be corrected.

A force, which is directed in the z-direction, for curving the lens can be introduced via coaxially mounted actuators, especially, piezos. The force, which is introduced by the actuators, is directed to the lens center point.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Referring toFIG. 1, the principle configuration of a projection exposure system is described. The projection exposure system1includes an illuminating unit3and a projection objective5. The projection objective5includes a lens arrangement19having an aperture diaphragm AP. An optical axis7is defined by the lens arrangement19. Different lens arrangements are explained in greater detail hereinafter with respect toFIGS. 2to6. A mask9is mounted between the illuminating unit3and the projection objective5. The mask9is held in the beam path by means of a mask holder11. Such masks9, which are used in microlithography, have a micrometer-nanometer structure which is imaged demagnified on an image plane13by means of the projection objective5up to a factor of10, especially by the factor4. In the image plane13, a substrate15or a wafer is held. The substrate15or wafer is positioned by a substrate holder17.

The minimal structures, which can still be resolved, are dependent upon the wavelength λ of the light, which is used for the illumination, as well as in dependence upon the image side numerical aperture of the projection objective5. The maximum attainable resolution of the projection exposure system1increases with falling wavelength λ of the exposure illuminating unit3and with an increasing image end numerical aperture of the projection objective5.

The projection objective19shown inFIG. 2includes six lens groups G1to G6. This projection objective is designed for the wavelength 157 nm. The first lens group G1or first convex form is defined by the lenses L101to L103which are all biconvex lenses. This first lens group has positive refractive power. The last lens surface of this lens group G1, which is mounted at the image end, is aspherized. This lens surface is identified by AS1. The last lens of this lens group G1is a biconvex lens which can be clearly assigned to the first lens group.

The lens group G2or first constriction, which follows the lens group G1, includes the three lenses L104to L106. This lens group G2has negative refractive power and defines a restriction. An object end mounted lens surface AS2of the lens L104is aspheric. Furthermore, the image end mounted lens surface of lens L106is aspheric. A double asphere is formed by the two lens surfaces AS1and AS2.

The lens group G3has positive refractive power and is defined by the lenses L107to L111. The last lens surface of this lens group is the lens L111which is arranged at the image end and is aspherized. This lens group is a convex form.

The second lens group G4of negative refractive power continues from the third lens group. This lens group G4is defined by the lenses L112to L115. This lens group defines a constriction.

The fifth lens group G5has the lenses L116to L125and has positive refractive power and includes an aperture diaphragm AP which is mounted between the lens L119and the lens L120.

The sixth lens group G6is defined by the lenses or plates L126and L127. This objective is designed for the wavelength 157 nm having a spectral bandwidth of the illuminating source of 1.5 pm and the lenses L113to L115and L119for this objective are of sodium fluoride. With the use of a second material (here sodium fluoride), especially chromatic errors can be corrected. The chromatic transverse errors are significantly reduced because of the use of NaF in the first restriction. Even the chromatic longitudinal error is somewhat reduced. The largest individual contribution to correction of the chromatic longitudinal errors is achieved with the use of NaF in the lens group G5.

The positive lenses L116to L118of the lens group G5continue from the lens group G4and are of lithium fluoride. With the use of lithium fluoride at this location in the objective, especially the monochromatic correction is facilitated because only small individual refractive powers are needed for achromatization because of the larger dispersion distance of lithium fluoride and sodium fluoride than of calcium fluoride and sodium fluoride. The basic configuration does not differ so significantly from a chromatic objective because of the special material selection.

The two positive lenses, which are arranged after the diaphragm, are likewise of lithium fluoride and also make, as explained with respect to the lithium lenses mounted ahead of the diaphragm, an important contribution to the correction of the chromatic longitudinal error.

The lens L122, whose two surfaces run almost at a constant spacing to each other, comprises calcium fluoride. The lens is very significant for the monochromatic correction and has only a slight influence on the chromatic longitudinal error.

The last three lenses of the fifth lens group G5, L123to L125, are of lithium fluoride. These lenses supply a smaller but nonetheless very valuable contribution to the correction of the chromatic longitudinal error.

The sixth lens group includes the lenses or planar plates L126and L127which comprise calcium fluoride.

This objective is designed for illuminating a field of 8×26 mm. The structural length from position0to position0′ is 1,000 mm. The numerical aperture is 0.8. The precise lens data are set forth in Table 1.

The aspheric surfaces are in all embodiments described by the equation:P⁡(h)=δ·h·h1+1-(1+K)·δ·δ·h·h+C1⁢h4+…+Cn⁢h2⁢n+2⁢⁢δ=1/R
wherein: P is the arrow height as a function of the radius h (elevation to the optical axis7) with the aspheric constants C1to Cngiven in the Tables. R is the apex radius.

The projection objective shown inFIG. 3includes six lens groups G1to G6having the lenses L201to L225and a divided end plate (L226, L227). This objective is designed for the illumination wavelength 248 nm. The space required for this projection objective19amounts precisely to 1,000 mm from object plane0to image plane0′. At the image end, this objective19has a numerical aperture of 0.83. The field which can be exposed by this projection objective is 8×26 mm.

The first lens group G1includes the lenses L201to L204of which the lenses L201to203are biconvex lenses.

The first lens L204of the lens group G1has an aspheric form on the image end lens surface. This asphere is identified by AS1.

The second lens group G2includes the three lenses L205to L207. These lenses have a biconcave form and the lens surfaces of the lenses L205and L207, which face toward the respective bounding lens groups, are aspheric. The aspheric lens surface of the lens L205is identified by AS2. In this way, a double asphere is formed by the two mutually adjacent aspheric lens surfaces AS1and AS2. The last lens of the lens group G2is provided as aspheric on the side facing the wafer.

The third lens group includes the lenses L208to L212. With this lens group G3, a convex form is provided. The lens L211is made aspheric on the image end lens surface.

The fourth lens group G4is formed by the lenses L213to L215which are all configured to be biconcave. This lens group G4is the second lens group of negative refractive power. With this lens group, a restriction is formed.

The lens group G5includes the lenses L216to L225. An aperture diaphragm is mounted between the lenses L218and L219. The diaphragm curvature between the peripheral ray at the diaphragm at a numerical aperture of 0.83 and the intersect point of the chief ray with the optical axis is 30.9 mm. With this lens group, a convex form is provided.

The sixth lens group G6includes the lenses L226and L227and these lenses are configured as planar plates.

The precise lens data of this projection objective19are set forth in Table 2. For the same structural length of the objective from0to0′ of 1,000 mm compared toFIG. 2, the aperture is increased further to 0.83 with an excellent correction.

The projection objective shown inFIG. 4includes six lens groups having the lenses L301to L327. The objective is designed for the illuminating wavelength 248 nm and has a numerical aperture of 0.9.

The first lens group G1includes the lenses L301to L304. This lens group has a positive refractive power. The refractive power especially of lenses L302to L303is very low. The focal length of this lens at L302is 1077.874 mm and is −92397.86 mm at L303.

A lens group of negative refractive power G2continues from this last lens group and is formed by the three lenses L305to L307. The first lens surface of this lens group G2is arranged at the image end and is made aspheric and is identified by AS1. The lens surface of lens L305facing toward the lens surface AS1is made aspheric so that a double asphere is formed by the lens surfaces AS1and AS2. Between these aspheric lens surfaces AS1and AS2, there is a clearly recognizable spacing provided in contrast to the previous embodiment. In this double asphere, the equidistant arrangement of the surfaces AS1and AS2is no longer completely utilized and the double asphere opens somewhat toward the outside.

The next lens group G3has a positive refractive power and includes the lenses L308to L311. This lens group G3includes an aspheric lens surface and this aspheric lens surface is mounted on the image side on the lens L311.

The second lens group of negative refractive power G4includes the lenses L312to L315. The lens surface of the lens L314mounted at the image end is made aspheric.

The next lens group G5has a positive refractive power and includes the lenses L316to L325. The diaphragm AP is mounted between the lenses L319and L320. The two mutually adjacent lens surfaces of lenses L321and L322are aspheric and are identified as AS3and AS4. A double asphere is formed by these aspheres AS3and AS4. An air space is enclosed by the surfaces AS3and AS4. With this double asphere, especially the spherical aberration and the sine condition at high aperture are better decoupled and easily corrected.

The sixth lens group includes the lenses L326and L327which are configured as thick planar plates. The intermediate space defined by these planar plates is chargeable with an overpressure and an underpressure and/or with a gas for compensating fluctuations of the atmospheric pressure. For more extended correction possibilities, it can be provided that at least one of the planar plates with or without refractive power (that is, also as a lens which is clearly thinner) compensates n-waviness under pressure variation and point mounting. For a targeted deformation of the lens, piezo actuators can be provided on the outer periphery.

The structural length of this objective from object plane0to image plane0′ is 1139.8 mm. The numerical aperture at the image end amounts to 0.9 with an exposable field of 27.2 mm in the diagonal. The precise lens data are set forth in Table 3.

The projection objective19shown inFIG. 5includes six lens groups G1to G6. This projection objective is designed for a wavelength of 193 nm. The first lens group G1includes the lenses L401to L404. Already the first object end mounted lens surface of the lens L401is made aspheric. This asphere acts especially positively on dish-shaped traces and distortion with excellent entry telecentrics because this asphere is mounted at the location at which the best beam separation exists for the high-aperture lithographic objective.

The lens surface of lens L404, which is provided at the object end, is aspheric and is identified by AS1. A double asphere is formed by this lens surface AS1and the lens surface of the lens L405which is mounted at the image end and is likewise aspheric and is identified by AS2. This double asphere operates especially positively on dish-shaped traces while simultaneously providing good correction of the image errors caused by the high aperture. With increasing radial distance from the optical axis, the surfaces AS1and AS2of the double asphere have an increasing distance in the direction to the optical axis. This double asphere opens toward the outside and defines a complex corrective means with average beam separation.

The lens L404belongs already to the second lens group which includes the lenses L405to L407. This second lens group has a negative refractive power.

The first lenses L402to L405have an especially low refractive power fL402=1397.664 mm, fL403=509.911 mm, fL404=1371.145 mm and fL405=−342.044 mm. A further aspheric lens surface is provided at the image end on the lens L407.

The next lens group G3has a positive refractive power and includes the lenses L408to L413. The lens L409has, at the object end, an aspheric lens surface and the lens L413is provided with an aspheric lens surface at the image side. The aspheric lens L413has a positive influence on the coma of higher order and on the 45° structures. The air space, which is provided between the lenses L411and L412is virtually equidistant.

The lens group G4has a negative refractive power and is defined by the lenses L414to L416. The lens L415has an aspheric lens surface on the image side. This aspheric lens surface operates in a good mixture on aperture dependent and field dependent imaging errors, especially for objectives having a high aperture.

The next lens group G5is defined by the lenses L417to L427. A diaphragm AP is mounted between the lenses L420to L421. The lens surface of the lens L422, which follows the diaphragm AP, has an aspheric form. With this aspheric lens, it is possible to carry out the correction of the spheric aberration without influencing other imaging errors. For this purpose, it is, however, necessary with the presence of a clear diaphragm curvature, that the aspheric surface projects into the region of a slide diaphragm.

Furthermore, the mutually adjacent lens surfaces of the lenses L423and L424(identified by AS3and AS4) are made to have an aspheric form. With this follow-on double asphere, it is especially possible to have an excellent aplanar correction for highest numerical aperture. The simultaneous correction of the spheric aberration and the satisfaction of the sine condition is therefore possible.

The lens group G6is configured by the lenses L428to L429which are configured as planar plates. It can, in turn, be provided that the intermediate space between the planar parallel plates428and429are chargeable with a fluid.

Quartz glass is provided as a lens material. To reduce the chromatic aberration, the lenses L408and L409as well as L413can be made of calcium fluoride. To reduce the compaction effect because of the high radiation load, it can be provided that calcium fluoride be used as a material for the smaller one or for both planar parallel plates L428and L429. It is noted that, in this projection objective, the maximum diameter of the lens group G3has, with 398 mm, a greater maximum diameter than the lens group G5. This objective is very well corrected and the deviation from the wavefront of an ideal spherical wave is >=1.2 mλ referred to 193 nm. The spacing between object plane0and image plane0′ is 1188.1 mm and the exposable field is 8×26 mm. The precise lens data are set forth in Table 4.

The projection objective shown inFIG. 6includes the lens groups G1to G6with the lenses L501to L530. Planar plates are provided for L529and L530. This projection objective is designed for the wavelength 193 nm and has a numerical aperture of 0.9. The spacing between the object plane0and the image plane0′ is 1174.6 mm. The exposable field has a size of 8×26 mm. Viewed macroscopically, this projection objective does not differ from the projection objective shown in FIG.5. Again, especially the lenses L502and L503have a low refractive power. The lens L510is provided especially for the quadratic correction.

Apart from the planar parallel plates L529and L530, all lenses L501to L528are of quartz glass. This projection objective too is very well corrected and the deviation from the ideal wavefront of a spherical wave is <3.0 mλ referred to 193 nm. The lenses L510, L515, L522have a low refractive power. The precise lens data are set forth in Table 5. The effect of the aspheric surfaces corresponds principally to the effects described with respect to FIG.5. The effects are still greater because of the high numerical aperture of 0.9.

The projection objective shown inFIG. 7for the wavelength 157 nm includes six lens groups having lenses L601to L630with planar parallel plates L629and L630. The structural length of this projection objective from object plane0to image plane0′ is 997.8 mm. A field of 7×22 mm can be exposed. The numerical aperture of this objective is 0.9. Calcium fluoride is provided as a lens material. A further correction of chromatic errors is achievable with the use of barium fluoride as a lens material for the lenses L614to L617. The deviation from the wavefront of an ideal spherical wave is <1.8 mλ referred to 157 nm. Viewed macroscopically, the configuration of the projection objective shown inFIG. 7differs only slightly from the projection objective described with respect toFIGS. 5 and 6. For this reason, reference is made to the description with respect to FIG.5. The exact lens data are set forth in Table 6.

The projection objective shown inFIG. 8includes six lens groups G1to G6. The first lens group includes the lenses L701to L704. The lens L701at the object side and the lens L704at the image side have aspheric lens surfaces. This first lens group includes only lenses of positive refractive power which have approximately identical diameters.

The second lens group G2follows and has a negative refractive power and includes the lenses L705to L708. The lens L705has an aspheric lens surface on the side facing toward lens L704and this aspheric lens surface is identified by AS2. A double asphere21is formed by the two aspheric lens surfaces AS1and AS2. This double asphere is curved toward the wafer and opens slightly in the radial direction. Furthermore, the lens L708has an aspheric lens surface at the image end.

The third lens group G3has lenses L709to L714and has a positive refractive power. This lens group includes two aspheric lenses L710and L714. The air gap, which is formed between the lenses L712and L713, has an almost constant thickness.

The fourth lens group G4includes only two negative lenses L715and L716with which a restriction is formed. The lens L715is provided at the image side with an aspherical lens surface.

The fifth lens group has lenses L717to L727and has a positive refractive power. The diaphragm AP is mounted between the lenses L720and L721. In this lens group, a further double asphere21is provided which is formed by the two aspheric lens surfaces AS3and AS4of the lenses L723and L724. Further aspheric lens surfaces are on the lens L721on the object side and on lens L727on the image side.

The last lens group G6follows this lens group and is defined by the two planar parallel plates L728and L729. An intermediate space25is formed by the mutually adjacent surfaces of the planar plates L728and L729. The intermediate space25can be charged with pressure.

This projection objective is designed for the wavelength 193 nm and has a numerical aperture of 0.9. The distance between object plane0and image plane0′ is 1209.6 mm. A field of 10.5×26 mm can be exposed with this projection objective. The maximum deviation from the ideal wavefront of a spherical wave is 3.0 mλ referred to 193 nm. This deviation is determined by means of the program code CODE V. The precise lens data are set forth in Table 7.

InFIG. 9, a catadioptric projection objective is shown which is designed for the wavelength 157 nm. A field of 22×7 mm can be exposed with this projection objective. The numerical aperture is 0.8. All lenses in this projection objective are made of calcium fluoride. The first lens L801is provided with an aspheric lens surface on the image side. This aspheric lens supplies especially a valuable contribution to the correction of the distortion.

The radiation is deflected by mirror SP1and impinges on the lens L802of negative refractive power. The next lens L803is provided with an aspheric lens surface on the lens side on the image side in the beam path. This aspheric lens supplies an especially valuable contribution to the correction of the spherical aberration.

The radiation, which propagates from lens L803, is reflected back at the mirror SP2and passes the lenses L803and L802in the opposite sequence before it is directed via reflection at mirror SP3to the lens L804which is mounted on an optical axis common with the lens L801. An intermediate image Z1arises between the mirror SP3and lens L804. The next lenses L805and L806have aspheric lens surfaces AS1and AS2on the mutually adjacent surfaces. A double asphere is formed by these aspheres. Furthermore, the objective includes the lenses L807to L818. The lenses L812, L814, L816and L818are provided with aspheric surfaces on the image side and the lens L817has an aspheric lens surface on the object side. A double asphere is formed by the aspheric lens surfaces of the lenses L816and L817.

The subject matter of PCT/EP 00/13148, filed Dec. 22, 2000, is incorporated herein by reference.

TABLE 2M1159aREFRACTIVE½ FREELENSESRADIITHICKNESSESGLASSESINDEX AT 248.38 nmDIAMETER0infinite32.000000000Luft0.9999820054.410infinite0.750000000Luft0.9999820061.498L201359.20308592216.544139898SIO21.5083729862.894−367.8142850180.750000000Luft0.9999820063.342L202376.90658222916.424149202SIO21.5083729863.744−370.2668964350.750000000Luft0.9999820063.552L203623.86813330112.000921336SIO21.5083729862.201−558.9435396284.488271401Luft0.9999820061.489L204−593.88116379610.597937240SIO21.5083729860.233−258.275165583AS1.300130829Luft0.9999820059.503L205−195.528496730AS7.000000000SIO21.5083729859.067114.97081411227.465616009Luft0.9999820054.855L206−150.5930378927.000000000SIO21.5083729855.023203.78899007329.227930343Luft0.9999820059.359L207−116.8477569987.000000015SIO21.5083729860.888−1029423.850607139AS26.431412586Luft0.9999820074.043L208−433.33370632429.900058462SIO21.5083729889.733−145.8551785170.750000000Luft0.9999820093.351L209−740.439232493AS44.983538148SIO21.50837298108.655−155.9986814460.750000000Luft0.99998200111.280L210730.36945003838.596890643SIO21.50837298120.834−339.8308555520.750000000Luft0.99998200121.150L211159.41776824152.577878183SIO21.50837298112.765457732.591606731AS0.780542469Luft0.99998200110.299L212190.81201209423.738591831SIO21.5083729894.787115.67764395040.245663292Luft0.9999820077.717L213−412.1409765257.000000000SIO21.5083729876.256151.70109821427.102188582Luft0.9999820069.619L214−319.4875430807.000000000SIO21.5083729869.443236.70793319842.112032397Luft0.9999820070.193L215−105.9342592168.769693914SIO21.5083729871.068680.23146099417.681829203Luft0.9999820088.650L216−517.05686513236.235608441SIO21.5083729891.923−185.2717353910.764865888Luft0.99998200100.651L2172262.40279806844.431825566SIO21.50837298119.658−267.3297246178.198939895Luft0.99998200123.247L2181103.18679618940.827914599SIO21.50837298133.839−364.5939090458.280602730Luft0.99998200134.570infinite−3.250000000Luft0.99998200133.180L219620.77036631825.036239346SIO21.50837298134.241−1858.9439291570.750000000Luft0.99998200134.164L220329.63568668140.854820783SIO21.50837298132.227−1181.58127695531.972595866Luft0.99998200131.156L221−249.79913672910.000000000SIO21.50837298130.2296484.2629880045.619260320Luft0.99998200130.672L222−2574.68714100038.775298966SIO21.50837298130.696−254.6652555260.750000000Luft0.99998200130.891L223203.34174623025.409827006SIO21.50837298110.728463.4969735550.750000000Luft0.99998200108.517L224118.26309896737.247858671SIO21.5083729892.529191.0674274730.753637388Luft0.9999820084.037L225137.67138462524.859589811SIO21.5083729878.934507.5332717006.693359054Luft0.9999820074.624L226infinite55.768369688SIO21.5083729872.833infinite0.800000000Luft0.9999820035.729L227infinite4.000000000SIO21.5083729834.512infinite11.999970000Luft0.9999820031.851L228infinite0.0000000001.0000000013.602ASPHERIC CONSTANTSAsphere of Lens L204K−0.7780C1−1.91000417e−007C24.02870297e−011C3−5.55434626e−015C41.68245178e−019C52.20604311e−023C68.09599744e−027C70.00000000e+000C80.00000000e+000C90.00000000e+000Asphere of Lens L205K−0.4166C15.25344324e−008C21.26756433e−011C3−5.25489404e−015C47.04023970e−019C5−1.04520766e−022C62.06454806e−026C70.00000000e+000C80.00000000e+000C90.00000000e+000Asphere of Lens L207K−2116959451.7820C11.25171476e−007C2−1.53794245e−011C3−3.12532578e−016C42.00967035e−019C5−2.05026124e−023C67.81326379e−028C70.00000000e+000C80.00000000e+000C90.00000000e+000Asphere of Lens L211K0.0000C12.78321477e−009C25.89866335e−014C31.19811527e−017C4−7.81165149e−022C51.66111023e−026C6−1.60965484e−031C70.00000000e+000C80.00000000e+000C90.00000000e+000Refractive index and wavelength were determined in air.