Abstract:
An inspection microscope ( 1 ) having a light source ( 3 ) that emits light of a first wavelength below 400 nm for illumination of a specimen ( 13 ) to be inspected, and having an objective ( 11 ) that is composed of multiple optical components and has a numerical aperture and a focal length, and having a tube optical system ( 21 ) and an autofocus device ( 25 ) that directs light of a second wavelength onto the specimen ( 13 ), is disclosed. The inspection microscope ( 1 ) is characterized by the objective ( 11 ), which has an optical correction that eliminates the longitudinal chromatic aberrations with respect to the first and the second wavelength and whose optical components are assembled in cement-free fashion, the second wavelength being greater than 400 nm.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This invention claims priority of the German patent application 101 17 167.6-42 which is incorporated by reference herein. 
   FIELD OF THE INVENTION 
   The invention concerns an inspection microscope. The invention further concerns an objective used with the inspection microscope. 
   BACKGROUND OF THE INVENTION 
   In the semiconductor industry, inspection microscopes are used for the examination and inspection of wafers, masks, and semiconductor modules during the various phases of their production. Inspection microscopes are for the most part largely automated. This encompasses, inter alia, automatic transport and handling systems for the modules or wafers to be examined, as well as an automatic focusing capability. 
   Inspection microscopes are described, for example, in the German patent documents DE 39 17 260 “Wafer inspection device” and DE 197 42 802 C1 “Microscope stand for a wafer inspection microscope.” 
   The optical resolution capability of a microscope depends on the wavelength of the illuminating light and the numerical aperture of the objective. The smaller the feature to be resolved, the shorter the illuminating light wavelength that must be selected, since the numerical aperture of the objectives cannot be increased indefinitely. For dry objectives, numerical apertures of no more than 0.9 to 0.95 can be attained. The size of the features on wafers for highly integrated circuits necessitates the use of ultraviolet light. Illuminating wavelengths between 248 nm and 365 nm are common at present. 
   Standard objectives are operated in the visible region of the light spectrum, i.e. in the spectral region from 400 nm to 800 nm. Standard objectives are unsuitable for applications with ultraviolet light, since the transmittance of standard objectives decreases dramatically the further into the ultraviolet the selected wavelength lies. 
   An objective that is achromatic in both the visible and the ultraviolet region is disclosed in the Japanese Patent having publication number JP2000105340 A. This objective is made of at least three different types of glass that contain barium fluoride, the lens elements being assembled into several groups of which the first, second, and fourth have positive refractive power while the third group has negative refractive power. 
   Irradiation with extremely short-wave ultraviolet light results in damage both to standard objectives and to special objectives that were in fact manufactured for the ultraviolet region. In standard objectives this damage is attributable, inter alia, to phototropic effects in the glass that cause a diminution in transmittance due to chemical modification of the glass structure. Damage of this kind is often reversible. Objectives designed specifically for the ultraviolet region are usually fabricated from quartz glass or calcium fluoride. Glasses made of these materials exhibit high transmittance in the ultraviolet region and are not modified by ultraviolet light. Irreversible damage nevertheless also occurs in these special objectives just as in standard objectives, becoming evident as gradual clouding, decreased transmittance, and degraded resolution. These difficulties have hitherto not been completely understood. 
   An additional difficulty occurs when an inspection microscope is equipped with an autofocus system, in which an autofocus light beam is coupled into the beam path of the inspection microscope and focused by the objective. Focusing is then performed, for example, by ascertaining the contrast of the image of the light reflected from the component being examined, using a four-quadrant photodiode. Since the inspection microscope must be usable in both visible light and ultraviolet light, the wavelength of the autofocus light must not lie within those regions in order to prevent the measurement operation from being influenced by light of the autofocus system. Since the sensitivity of semiconductor detectors is highest in the red to infrared region of the spectrum, it is advantageous to select an autofocus wavelength in that region. The optical properties of objectives are generally different for light of differing wavelengths; this complicates evaluation of the autofocus system signals, which as a result are erroneous. 
   SUMMARY OF THE INVENTION 
   It is therefore the object of the invention to describe an inspection microscope that has an autofocus device and that solves the problem stated above. 
   The aforementioned object is achieved by an inspection microscope which comprises:
         a light source, emitting light of a first wavelength below 400 nm for illumination of a specimen to be inspected,   an objective that is composed of multiple optical components, wherein the objective has a numerical aperture and a focal length,   a tube optical system,   an autofocus device that directs light of a second wavelength onto the specimen, wherein the second wavelength is greater than 400 nm, wherein the objective shows an optical correction that eliminates the longitudinal chromatic aberrations with respect to the first and the second wavelength, and   a cement-free mounting of all optical components.       

   It is an additional object of the present invention to create an objective which shows constant optical properties over the long term. 
   The aforesaid object is achieved by an objective that transmits light of a first wavelength below 400 nm and light of a second wavelength above 400 nm and comprises:
         multiple optical components, wherein the objective has a numerical aperture as well as a magnification,   an optical correction that eliminates longitudinal chromatic aberrations with respect to the first and the second wavelength, and   a cement-free mounting of all optical components.       

   The invention has the advantage that the inspection microscope and objective according to the present invention allow a specimen under inspection to be examined using ultraviolet and deep ultraviolet light with no occurrence of damage to the inspection microscope as a result. In addition, it is possible to use a universal autofocus device whose light is transmitted even when standard objectives are utilized. 
   It has been recognized that the irreversible damage occurring even in special objectives is brought about as a result of chemical modifications of the optical cement between the individual lens elements upon irradiation with ultraviolet light and in particular upon irradiation with deep ultraviolet light. Objectives known from the existing art that are corrected for more than one wavelength have hitherto had lens elements cemented to one another or cemented lens element groups. The present invention completely resolves this difficulty, and moreover is configured in such a way that with collimated entry, the intersection distance for the autofocus light and for the illuminating light is at least largely identical, so that the autofocus device functions reliably. 
   In a preferred embodiment, the optical components are lens elements that are largely transparent to the first and to the second wavelength. They are preferably fabricated from calcium fluoride or quartz glass or barium fluoride or lithium fluoride or strontium fluoride. In a particularly preferred embodiment, adjacent lens elements are produced from calcium fluoride and quartz glass, respectively. 
   In a concrete embodiment, the first wavelength is 248 nm and the second wavelength is 903 nm. For high-resolution applications in particular, objectives having a numerical aperture that is greater than 0.8 and a high magnification are particularly advantageous. This means that the focal length of the objective is preferably less than 3.5 mm for a working distance exceeding 0.15 mm. 
   In the inspection of masks having pellicles, in which context large unobstructed working distances are important, objectives that have an unobstructed working distance of at least 7 mm with a numerical aperture of at least 0.5 to 0.55 are very particularly advisable. 
   It is very particularly advantageous, especially with regard to the physical size of the objective, if the aberrations are not all corrected exclusively in the objective, but rather if an overall correction is achieved by the coaction of the objective and tube optical system. Only the longitudinal chromatic aberration in terms of the first and second wavelengths must be corrected in the objective, since the beam path of the light of the autofocus device does not pass through the tube optics. The correction for light of the second wavelength is, in particular, in fact limited to the center of the image. 
   The tube optical system preferably also contains no optical cement, and is configured in such a way that as a result of the coaction of the tube optical system and the objective, the longitudinal chromatic aberration of the objective is compensated for in the region less than 10 nm above and below the first wavelength. It is moreover particularly advantageous to configure the tube optics in such a way that as a result of the coaction of the tube optical system and the objective, the transverse chromatic error of the tube optical system is compensated for in the region less than 10 nm above and below the first wavelength. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The subject matter of the invention is depicted schematically in the drawings and will be described below with reference to the Figures, in which: 
       FIG. 1  shows an embodiment of the inspection microscope; 
       FIG. 2  shows the internal construction of an embodiment of the objective according to the present invention; 
       FIG. 3  is a graphic depiction of the relative intersection distance of the objective as a function of wavelength; 
       FIG. 4  shows the internal construction of a further embodiment of the objective according to the present invention; 
       FIG. 5  shows the internal construction of a further embodiment of the objective according to the present invention; 
       FIG. 6  shows the internal construction of a further embodiment of the objective according to the present invention; 
       FIG. 7  shows the internal construction of a further embodiment of the objective according to the present invention; 
       FIG. 8  shows the internal construction of a further embodiment of the objective according to the present invention; and 
       FIG. 9  shows the internal construction of a tube optical system. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows an embodiment of inspection microscope  1  according to the present invention. A mercury lamp  5 , which emits an illuminating light beam  7  of a first wavelength in the region from 243 to 266 nm, serves as light source  3 . Illuminating light beam  7  is directed with the aid of a semitransparent mirror  9  to objective  11 , and there focused onto a specimen  13  to be inspected. Specimen  13  is located on an X-Y precision positioning stage  15  that is movable along the illuminating light axis for focusing and is driven by an electric motor  17 . Detected light  19  proceeding from the specimen passes via objective  11  and through semitransparent mirror  9  to tube optical system  21  which is assembled in cement-free fashion from multiple lens elements, and ultimately encounters a TV camera  23  whose image is displayed to the user on a monitor (not shown). The inspection microscope comprises an autofocus device  25  that, with the aid of a laser (not depicted), generates an autofocus light beam  27  of a second wavelength of 903 nm, which is coupled into the illuminating beam path with a dichroic beam splitter  28  and is focused by objective  11 . The autofocus light reflected from the specimen passes through objective  11  and via dichroic beam splitter  28  back to the autofocus device, where it is directed onto a four-quadrant photodiode (not shown) whose electrical signals are electronically evaluated in order to assess the position of specimen  13  relative to the focal plane of objective  11 . Autofocus device  25  controls electric motor  17  of precision positioning stage  13  in such a way that the surface of specimen  13  to be inspected lies in the focal plane of objective  11 . Objective  11  contains exclusively lens elements assembled in cement-free fashion, and possesses, with collimated light entry, the same intersection distance with respect to the first and second wavelengths. It has a 150× magnification with a numerical aperture of 0.9. The longitudinal chromatic aberration of objective  11  in the region from 238 nm to 258 nm is compensated for by the opposite longitudinal chromatic aberration in tube optical system  21 , and similarly for the transverse chromatic aberration. 
     FIG. 2  shows the internal configuration of an embodiment of objective  11  that contains twenty-one lens elements labeled with reference characters  29  through  69 . In combination with the tube optical system of 200 mm focal length shown in  FIG. 9 , objective  11  has a 150× magnification and a numerical aperture of 0.9. Lens elements  29 – 69  each have two boundary surfaces  71 – 153 , and are each manufactured of quartz glass or calcium fluoride. Air gaps are present between lens elements  29 – 69 . With collimated light entry, the objective has the same intersection distance of 0.418 mm for light of wavelengths 248 nm and 908 nm. The radii of curvature of boundary surfaces  71 – 153  of lens elements  29 – 69 , and lass of the individual lens elements and their spacings from one be gathered from the following table: 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
             
             
               Lens 
               Boundary 
                 
                 
                 
             
             
               element 
               surface 
               Radius/mm 
               Spacing/mm 
               Glass type 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               29 
               71 
               −1.0070 
               1.0200 
               QUARTZ GLASS 
             
             
               29 
               73 
               −1.0070 
               .2000 
             
             
               31 
               75 
               −5.1142 
               .7000 
               QUARTZ GLASS 
             
             
               31 
               77 
               116.3432 
               .0200 
             
             
               33 
               79 
               116.3432 
               2.1000 
               CAF2 
             
             
               33 
               81 
               −3.3054 
               .1000 
             
             
               35 
               83 
               13.0257 
               1.1000 
               QUARTZ GLASS 
             
             
               35 
               85 
               15.2835 
               .0200 
             
             
               37 
               87 
               15.2835 
               2.5000 
               CAF2 
             
             
               37 
               89 
               −6.3932 
               .5000 
             
             
               39 
               91 
               −63.2383 
               1.4000 
               QUARTZ GLASS 
             
             
               39 
               93 
               10.4603 
               .0200 
             
             
               41 
               95 
               10.4603 
               2.6000 
               CAF2 
             
             
               41 
               97 
               −15.0571 
               .2000 
             
             
               43 
               99 
               −71.0504 
               1.5000 
               QUARTZ GLASS 
             
             
               43 
               101 
               9.8492 
               .0200 
             
             
               45 
               103 
               9.8492 
               2.4000 
               CAF2 
             
             
               45 
               105 
               −58.9093 
               .1000 
             
             
               47 
               107 
               23.1720 
               2.9000 
               CAF2 
             
             
               47 
               109 
               −9.2663 
               .0200 
             
             
               49 
               111 
               −9.2663 
               1.5000 
               QUARTZ GLASS 
             
             
               49 
               113 
               23.9793 
               .1000 
             
             
               51 
               115 
               11.6587 
               3.4000 
               CAF2 
             
             
               51 
               117 
               −12.6456 
               .1000 
             
             
               53 
               119 
               −12.6456 
               1.5000 
               QUARTZ GLASS 
             
             
               53 
               121 
               2610.3417 
               .3000 
             
             
               55 
               123 
               30.6023 
               2.7000 
               CAF2 
             
             
               55 
               125 
               −9.9195 
               .0200 
             
             
               57 
               127 
               −9.9195 
               1.5000 
               QUARTZ GLASS 
             
             
               57 
               129 
               34.6720 
               .1000 
             
             
               59 
               131 
               7.0048 
               3.5000 
               CAF2 
             
             
               59 
               133 
               41.7404 
               1.8000 
             
             
               61 
               135 
               −27.4055 
               1.0000 
               QUARTZ GLASS 
             
             
               61 
               137 
               3.5732 
               .3000 
             
             
               63 
               139 
               4.0071 
               2.8000 
               CAF2 
             
             
               63 
               141 
               −7.1920 
               .0500 
             
             
               65 
               143 
               −9.8514 
               1.0000 
               QUARTZ GLASS 
             
             
               65 
               145 
               30.3842 
               5.5000 
             
             
               67 
               147 
               −1.7127 
               1.0000 
               CAF2 
             
             
               67 
               149 
               10.6695 
               .0500 
             
             
               69 
               151 
               4.0356 
               1.5000 
               QUARTZ GLASS 
             
             
               69 
               153 
               −18.3130 
               inf. 
             
             
                 
             
           
        
       
     
   
     FIG. 3  shows, in a graphic depiction, the relative intersection distance of objective  11  as a function of wavelength λ. It is evident that in the region a few nanometers around 248 nm, a low longitudinal chromatic aberration exists. In an inspection microscope, this longitudinal chromatic aberration is preferably compensated for using a specially designed tube optical system, so that even broad-band light used in aberration-free fashion. 
     FIG. 4  shows the internal configuration of a further embodiment of objective  11  that contains sixteen lens elements labeled with reference characters  155  through  185 . In combination with the tube optical system of 200 mm focal length shown in  FIG. 9 , objective  11  has a 63× magnification and a numerical aperture of 0.55. Lens elements  155 – 185  each have two boundary surfaces  187 – 249 , and are each manufactured of quartz glass or calcium fluoride. Air gaps are present between lens elements  155 – 185 . With collimated beam entry, the objective has the same intersection distance of 7.7 mm for light of wavelengths 248 nm and 903 nm. The working distance is 7.0 mm. The radii of curvature of boundary surfaces  187 – 249  of lens elements  155 – 185 , and the types of glass of the individual lens elements and their spacings from one another, may be gathered from the following table: 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
             
             
               Lens 
               Boundary 
                 
                 
                 
             
             
               element 
               surface 
               Radius 
               Spacing 
               Glass type 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               155 
               187 
               −31.8610 
               3.2000 
               QUARTZ 
             
             
               155 
               189 
               −8.9120 
               .3000 
             
             
               157 
               191 
               36.5170 
               5.3400 
               CAF2 
             
             
               157 
               193 
               −10.2030 
               .2400 
             
             
               159 
               195 
               −9.9220 
               2.0000 
               QUARTZ 
             
             
               159 
               197 
               20.1110 
               .2200 
             
             
               161 
               199 
               21.2920 
               6.0200 
               CAF2 
             
             
               161 
               201 
               −16.4330 
               .2000 
             
             
               163 
               203 
               44.0460 
               4.9000 
               CAF2 
             
             
               163 
               205 
               −16.5100 
               .3600 
             
             
               165 
               207 
               −15.6420 
               2.0000 
               QUARTZ 
             
             
               165 
               209 
               14.7420 
               .1700 
             
             
               167 
               211 
               15.1020 
               5.5000 
               CAF2 
             
             
               167 
               213 
               −29.4540 
               .2000 
             
             
               169 
               215 
               19.5190 
               5.0000 
               CAF2 
             
             
               169 
               217 
               −19.5190 
               .0800 
             
             
               171 
               219 
               −19.5200 
               2.0000 
               QUARTZ 
             
             
               171 
               221 
               8.8780 
               .5000 
             
             
               173 
               223 
               9.6970 
               5.8000 
               CAF2 
             
             
               173 
               225 
               −13.2430 
               .0700 
             
             
               175 
               227 
               −15.5050 
               2.0000 
               QUARTZ 
             
             
               175 
               229 
               plane surface 
               2.4010 
             
             
               177 
               231 
               −11.5420 
               1.8500 
               QUARTZ 
             
             
               177 
               233 
               48.0020 
               .2000 
             
             
               179 
               235 
               9.8410 
               3.2000 
               CAF2 
             
             
               179 
               237 
               plane surface 
               10.7500 
             
             
               181 
               239 
               −10.1470 
               1.6000 
               QUARTZ 
             
             
               181 
               241 
               −5.3040 
               .2300 
             
             
               183 
               243 
               −4.8080 
               1.1000 
               CAF2 
             
             
               183 
               245 
               4.8080 
               .0700 
             
             
               185 
               247 
               4.6630 
               1.4500 
               QUARTZ 
             
             
               185 
               249 
               7.1840 
               inf. 
             
             
                 
             
           
        
       
     
   
     FIG. 5  shows the internal configuration of a further embodiment of objective  11  that contains seventeen lens elements labeled with reference characters  251  through  282 . In combination with the tube optical system of 200 mm focal length shown in  FIG. 9 , objective  11  has a 150× magnification and a numerical aperture of 0.90. Lens elements  251  through  283  each have two boundary surfaces  285 – 351 , and are each manufactured of quartz glass or calcium fluoride. Air gaps are present between lens elements  251  through  283 . With collimated beam entry, the objective has the same intersection distance of 0.364 mm for light of wavelengths 248 nm and 903 nm. The working distance is 0.2 mm. The radii of curvature of boundary surfaces  285 – 351  of lens elements  251  through  283 , and the types of glass of the individual lens elements and their spacings from one another, may be gathered from the following table: 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
             
             
               Lens 
               Boundary 
                 
                 
                 
             
             
               element 
               surface 
               Radius 
               Spacing 
               Glass type 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               251 
               285 
               −1.3020 
               1.2200 
               QUARTZ GLASS 
             
             
               251 
               287 
               −1.3020 
               .2000 
             
             
               253 
               289 
               −4.4850 
               1.8800 
               CAF2 
             
             
               253 
               291 
               −2.8770 
               .1000 
             
             
               255 
               293 
               −25.3180 
               2.4000 
               CAF2 
             
             
               255 
               295 
               −3.9040 
               .0800 
             
             
               257 
               297 
               −3.8810 
               1.2000 
               QUARTZ GLASS 
             
             
               257 
               299 
               16.8000 
               .0310 
             
             
               259 
               301 
               16.8010 
               3.7000 
               CAF2 
             
             
               259 
               303 
               −7.4810 
               .5000 
             
             
               261 
               305 
               9.4200 
               4.1500 
               CAF2 
             
             
               261 
               307 
               −14.1090 
               .2000 
             
             
               263 
               309 
               −12.9970 
               1.5000 
               QUARTZ GLASS 
             
             
               263 
               311 
               8.4710 
               .0380 
             
             
               265 
               313 
               8.4720 
               4.1800 
               CAF2 
             
             
               265 
               315 
               −10.8320 
               .0350 
             
             
               267 
               317 
               −10.8320 
               1.5000 
               QUARTZ GLASS 
             
             
               267 
               319 
               7.5030 
               .6000 
             
             
               269 
               321 
               10.0000 
               3.3500 
               CAF2 
             
             
               269 
               323 
               −12.2530 
               .1000 
             
             
               271 
               325 
               18.1250 
               1.5000 
               QUARTZ GLASS 
             
             
               271 
               327 
               5.8690 
               .1000 
             
             
               273 
               329 
               5.9510 
               4.5300 
               CAF2 
             
             
               273 
               331 
               −8.0360 
               .0360 
             
             
               275 
               333 
               −8.0360 
               1.5000 
               QUARTZ GLASS 
             
             
               275 
               335 
               50.6020 
               .1000 
             
             
               277 
               337 
               6.3030 
               4.1000 
               CAF2 
             
             
               277 
               339 
               48.0020 
               1.2100 
             
             
               279 
               341 
               −8.1590 
               3.1000 
               QUARTZ GLASS 
             
             
               279 
               343 
               5.4540 
               3.8000 
             
             
               281 
               345 
               −3.3030 
               1.0000 
               CAF2 
             
             
               281 
               347 
               5.1430 
               .0500 
             
             
               283 
               349 
               4.6190 
               1.2000 
               QUARTZ GLASS 
             
             
               283 
               351 
               −17.7680 
               inf. 
             
             
                 
             
           
        
       
     
   
     FIG. 6  shows the internal configuration of a further embodiment of objective  11  that contains nineteen lens elements labeled with reference characters  353  through  389 . In combination with the tube optical system of 200 mm focal length shown in  FIG. 9 , objective  11  has a 150× magnification and an aperture of 0.90. Lens elements  353  through  389  each have two boundary surfaces  391 – 465 , and are each manufactured of quartz glass or calcium fluoride. Air gaps are present between lens elements  353  through  389 . With collimated beam entry, the objective has the same intersection distance of 0.42 mm for light of wavelengths 248 nm and 903 nm. The working distance is 0.2 mm. The radii of curvature of boundary surfaces  391 – 465  of lens elements  353  through  389 , and the types of glass of the individual lens elements and their spacings from one another, may be gathered from the following table: 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
             
             
               Lens 
               Boundary 
                 
                 
                 
             
             
               element 
               surface 
               Radius 
               Spacing 
               Glass type 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               353 
               391 
               −1.0070 
               .9600 
               QUARTZ GLASS 
             
             
                 
               393 
               −.9500 
               .1000 
             
             
               355 
               395 
               −5.4908 
               .7000 
               QUARTZ GLASS 
             
             
                 
               397 
               27.0607 
               .0200 
             
             
               357 
               399 
               27.0607 
               2.2000 
               CAF2 
             
             
                 
               401 
               −3.2531 
               .1000 
             
             
               359 
               403 
               −10.7848 
               1.2000 
               QUARTZ GLASS 
             
             
                 
               405 
               12.1721 
               .0200 
             
             
               361 
               407 
               12.1721 
               2.8000 
               CAF2 
             
             
                 
               409 
               −6.8280 
               .4000 
             
             
               363 
               411 
               −64.0972 
               1.5000 
               QUARTZ GLASS 
             
             
                 
               413 
               9.8461 
               .0200 
             
             
               365 
               415 
               9.8461 
               3.0000 
               CAF2 
             
             
                 
               417 
               −12.9844 
               .2000 
             
             
               367 
               419 
               101.2944 
               3.0000 
               CAF2 
             
             
                 
               421 
               −7.8870 
               .0200 
             
             
               369 
               423 
               −7.8870 
               1.5000 
               QUARTZ GLASS 
             
             
                 
               425 
               15.6216 
               .2000 
             
             
               371 
               427 
               11.8848 
               4.1000 
               CAF2 
             
             
                 
               429 
               −8.5251 
               .0200 
             
             
               373 
               431 
               −8.5251 
               1.5000 
               QUARTZ GLASS 
             
             
                 
               433 
               −140.7178 
               .2000 
             
             
               375 
               435 
               20.3658 
               3.3000 
               CAF2 
             
             
                 
               437 
               −9.4168 
               .0200 
             
             
               377 
               439 
               −9.4168 
               1.5000 
               QUARTZ GLASS 
             
             
                 
               441 
               93.5331 
               .1000 
             
             
               379 
               443 
               6.9040 
               4.7000 
               CAF2 
             
             
                 
               445 
               897.4094 
               1.9000 
             
             
               381 
               447 
               −11.6312 
               1.0000 
               QUARTZ GLASS 
             
             
                 
               449 
               3.7870 
               .3000 
             
             
               383 
               451 
               4.1771 
               2.8000 
               CAF2 
             
             
                 
               453 
               −6.0687 
               .0500 
             
             
               385 
               455 
               −6.9364 
               1.0000 
               QUARTZ GLASS 
             
             
                 
               457 
               −35.5321 
               5.8000 
             
             
               387 
               459 
               −1.7885 
               1.0000 
               CAF2 
             
             
                 
               461 
               5.0394 
               .0500 
             
             
               389 
               463 
               3.5153 
               1.7000 
               QUARTZ GLASS 
             
             
                 
               465 
               −17.9020 
               inf. 
             
             
                 
             
           
        
       
     
   
     FIG. 7  shows the internal configuration of a further embodiment of objective  11  that contains twenty lens elements labeled with reference characters  467  through  505 . In combination with the tube optical system of 200 mm focal length shown in  FIG. 9 , objective  11  has a 200× magnification and an aperture of 0.90. Lens elements  467  through  505  each have two boundary surfaces  507 – 587 , and are each manufactured of quartz glass or calcium fluoride. Air gaps are present between lens elements  467  through  505 . With collimated beam entry, the objective has the same intersection distance of 0.384 mm for light of wavelengths 248 nm and 903 nm. The working distance is 0.2 mm. The radii of curvature of boundary surfaces  507 – 587  of lens elements  467  through  505 , and the types of glass of the individual lens elements and their spacings from one another, may be gathered from the following table: 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
             
             
               Lens 
               Boundary 
                 
                 
                 
             
             
               element 
               surface 
               Radius 
               Spacing 
               Glass type 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               467 
               507 
               −1.3406 
               1.3417 
               QUARTZ GLASS 
             
             
                 
               509 
               −1.2832 
               .2000 
             
             
               469 
               511 
               −4.6344 
               2.0000 
               CAF2 
             
             
                 
               513 
               −3.0395 
               .1000 
             
             
               471 
               517 
               −19.1192 
               2.2000 
               CAF2 
             
             
                 
               519 
               −4.1705 
               .0500 
             
             
               473 
               521 
               −4.2122 
               1.2000 
               QUARTZ GLASS 
             
             
                 
               523 
               15.2410 
               .0500 
             
             
               475 
               525 
               15.2410 
               3.3201 
               CAF2 
             
             
                 
               527 
               −8.9154 
               .5000 
             
             
               477 
               529 
               9.9453 
               4.3403 
               CAF2 
             
             
                 
               531 
               −11.5633 
               .1570 
             
             
               479 
               533 
               −10.9741 
               1.5000 
               QUARTZ GLASS 
             
             
                 
               535 
               9.4708 
               .0500 
             
             
               481 
               537 
               9.4708 
               4.0274 
               CAF2 
             
             
                 
               539 
               −10.1508 
               .0500 
             
             
               483 
               541 
               −10.1508 
               1.5000 
               QUARTZ GLASS 
             
             
                 
               543 
               8.4705 
               .5016 
             
             
               485 
               545 
               10.8133 
               3.4593 
               CAF2 
             
             
                 
               547 
               −12.9233 
               .1000 
             
             
               487 
               549 
               11.9103 
               1.5000 
               QUARTZ GLASS 
             
             
                 
               551 
               6.1198 
               .0500 
             
             
               489 
               553 
               6.1198 
               4.2788 
               CAF2 
             
             
                 
               555 
               −9.7847 
               .0500 
             
             
               491 
               557 
               −9.7847 
               1.5000 
               QUARTZ GLASS 
             
             
                 
               559 
               92.3864 
               .1000 
             
             
               493 
               561 
               11.5539 
               3.8000 
               CAF2 
             
             
                 
               563 
               −62.2415 
               1.8263 
             
             
               495 
               565 
               −6.2817 
               1.0000 
               QUARTZ GLASS 
             
             
                 
               567 
               7.3680 
               .0500 
             
             
               497 
               569 
               6.8762 
               2.0000 
               CAF2 
             
             
                 
               571 
               −14.6005 
               .1151 
             
             
               499 
               573 
               −12.1375 
               1.0000 
               QUARTZ GLASS 
             
             
                 
               575 
               6.8053 
               9.0000 
             
             
               501 
               577 
               −3.6630 
               1.5000 
               QUARTZ GLASS 
             
             
                 
               579 
               −3.0606 
               .0500 
             
             
               503 
               581 
               −3.7004 
               1.0000 
               CAF2 
             
             
                 
               583 
               6.1983 
               .1993 
             
             
               505 
               585 
               7.5116 
               1.7000 
               QUARTZ GLASS 
             
             
                 
               587 
               −33.0000 
               inf. 
             
             
                 
             
           
        
       
     
   
     FIG. 8  shows the internal configuration of a further embodiment of objective  11  that contains twenty lens elements labeled with reference characters  589  through  623 . In combination with the tube optical system of 200 mm focal length shown in  FIG. 9 , objective  11  has a 63× magnification and an aperture of 0.90. Lens elements  589  through  623  each have two boundary surfaces  625 – 695 , and are each manufactured of quartz glass or calcium fluoride. Air gaps are present between lens elements  589  through  623 . With collimated beam entry, the objective has the same intersection distance of 0.417 mm for light of wavelengths 248 nm and 903 nm . The working distance is 0.2 mm. The radii of curvature of boundary surfaces  625 – 695  of lens elements  589  through  623 , and the types of glass of the individual lens elements and their spacings from one another, may be gathered from the following table: 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
             
             
               Lens 
               Boundary 
                 
                 
                 
             
             
               element 
               surface 
               Radius 
               Spacing 
               Glass type 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               589 
               625 
               −2.1244 
               1.7200 
               QUARTZ GLASS 
             
             
                 
               627 
               −2.1486 
               .1000 
             
             
               591 
               629 
               −4.6685 
               2.5000 
               CAF2 
             
             
                 
               631 
               −3.2430 
               .2000 
             
             
               593 
               633 
               −8.3322 
               1.2000 
               QUARTZ GLASS 
             
             
                 
               635 
               25.1850 
               .3268 
             
             
               595 
               637 
               43.3114 
               4.4000 
               CAF2 
             
             
                 
               639 
               −8.1452 
               .3000 
             
             
               597 
               641 
               16.8037 
               5.7000 
               CAF2 
             
             
                 
               643 
               −11.6783 
               .2968 
             
             
               599 
               645 
               −11.0103 
               1.8000 
               QUARTZ GLASS 
             
             
                 
               647 
               16.4439 
               .0500 
             
             
               601 
               649 
               16.4439 
               6.5000 
               CAF2 
             
             
                 
               651 
               −13.6015 
               .0500 
             
             
               603 
               653 
               −16.2615 
               1.8000 
               QUARTZ GLASS 
             
             
                 
               655 
               15.3763 
               .0500 
             
             
               605 
               657 
               15.3763 
               5.7500 
               CAF2 
             
             
                 
               659 
               −22.5022 
               .3000 
             
             
               607 
               661 
               14.5691 
               5.8000 
               CAF2 
             
             
                 
               663 
               −21.6045 
               .4808 
             
             
               609 
               665 
               −17.9557 
               1.8000 
               QUARTZ GLASS 
             
             
                 
               667 
               9.2065 
               .1088 
             
             
               611 
               669 
               9.3059 
               5.3000 
               CAF2 
             
             
                 
               671 
               −38.5138 
               .4000 
             
             
               613 
               673 
               21.6588 
               3.3000 
               CAF2 
             
             
                 
               675 
               −37.7818 
               .8000 
             
             
               615 
               677 
               −15.4376 
               1.9000 
               QUARTZ GLASS 
             
             
                 
               679 
               356.4300 
               3.8480 
             
             
               617 
               681 
               −7.5117 
               1.4000 
               QUARTZ GLASS 
             
             
                 
               683 
               15.5540 
               .1000 
             
             
               619 
               685 
               8.1444 
               2.8000 
               CAF2 
             
             
                 
               687 
               16.3383 
               1.4000 
             
             
               621 
               689 
               −13.4675 
               1.3000 
               CAF2 
             
             
                 
               691 
               8.6117 
               .1736 
             
             
               623 
               693 
               9.6434 
               2.5000 
               QUARTZ GLASS 
             
             
                 
               695 
               −33.000 
               inf. 
             
             
                 
             
           
        
       
     
   
     FIG. 9  shows the internal configuration of tube optical system  21 , which contains three lens elements labeled with reference characters  697  through  701 . Tube optical system  21  has a focal length of 200 mm at 248 nm. Lens elements  697  through  701  each have two boundary surfaces  703 – 713 , and are each manufactured of quartz glass or calcium fluoride. Air gaps are present between lens elements  697  through  701 . Tube optical system  21  contains no cement, and is configured in such a way that as a result of the coaction of tube optical system  21  and objective  11 , the longitudinal chromatic error of objective  11  is compensated for in the region 10 nm above and below the first wavelength. In addition, tube optical system  21  is embodied in such a way that as a result of the coaction of tube optical system  21  and objective  11 , the transverse chromatic error of tube optical system  21  is compensated for in the region less than 10 nm above and below the first wavelength. The radii of curvature of boundary surfaces  703 – 713  of lens elements  697  through  701 , and the types of glass of the individual lens elements and their spacings from one another, may be gathered from the following table: 
   
     
       
             
             
             
             
             
           
             
             
             
             
             
           
         
             
                 
             
             
               Lens 
               Boundary 
                 
                 
                 
             
             
               element 
               surface 
               Radius 
               Spacing 
               Glass type 
             
             
                 
             
           
           
             
                 
             
           
        
         
             
               697 
               703 
               174.9820 
               3.0000 
               Quartz glass 
             
             
                 
               705 
               −60.4200 
               12.1575 
             
             
               699 
               707 
               −44.6500 
               2.5000 
               CaF2 
             
             
                 
               709 
               76.1030 
               .1000 
             
             
               701 
               711 
               76.1030 
               3.0000 
               Quartz glass 
             
             
                 
               713 
               −191.4220 
               169.6484 
             
             
                 
             
           
        
       
     
   
   The invention has been described with reference to a particular embodiment. It is nevertheless self-evident that changes and modifications can be made without thereby leaving the range of protection of the claims recited hereinafter.