Microlithographic projection exposure apparatus

Abstract

The disclosure relates to a microlithographic projection exposure apparatus, such as are used for the production of large-scale integrated electrical circuits and other microstructured components. The disclosure relates in particular to coatings of optical elements in order to increase or reduce the reflectivity.

1 . Microlithographic projection exposure apparatus having an optical element ( 36 ), on which there is an antireflection coating ( 32 ) in order to reduce the reflectivity,
 characterised in that   the antireflection coating ( 32 ) is configured so that the transmission coefficients of the antireflection coating for mutually orthogonal polarisation states ( 42   p ,  42   s ) differ from one another by no more than 10%, preferably by no more than 3%, more preferably by no more than 1% over an incidence angle range of from 0° to 70°, and   in that the projection exposure apparatus comprises means ( 50 ) for homogenising an intensity distribution.   
     
     
         2 . Microlithographic projection exposure apparatus having an optical element, on which there is a reflection coating in order to increase the reflectivity,
 characterised in that   the reflection coating is configured so that the reflection coefficients of the coating for mutually orthogonal polarisation states differ from one another by no more than 10%, preferably by no more than 3%, more preferably by no more than 1% over an incidence angle range of from 0° to 70°, and   in that the projection exposure apparatus comprises means for homogenising an intensity distribution.   
     
     
         3 . Microlithographic projection exposure apparatus having a plurality of optical elements, on which there is an antireflection coating in order to reduce the reflectivity,
 characterised in that   the antireflection coatings are configured so that the transmission coefficients of the plurality of antireflection coatings differ from one another by no more than 10%, preferably by no more than 3%, more preferably by no more than 1% in respect of the total effect for mutually orthogonal polarisation states over an incidence angle range of from 0° to 70°, and   in that the projection exposure apparatus comprises means for homogenising an intensity distribution.   
     
     
         4 . Microlithographic projection exposure apparatus having a plurality of optical elements, on which there is a reflection coating in order to increase the reflectivity,
 characterised in that   the reflection coatings are configured so that the reflection coefficients of the plurality of reflection coatings differ from one another by no more than 10%, preferably by no more than 3%, more preferably by no more than 1% in respect of the total effect for mutually orthogonal polarisation states over an incidence angle range of from 0° to 70°, and   in that the projection exposure apparatus comprises means for homogenising an intensity distribution.   
     
     
         5 . Projection exposure apparatus according to one of the preceding claims, in that the means for homogenising an intensity distribution comprise a grey filter with a locally varying grey value. 
     
     
         6 . Projection exposure apparatus according to  claim 5 , characterised in that the grey filter is a transmissive optical element with a locally varying transmission factor. 
     
     
         7 . Projection exposure apparatus according to  claim 5  preceding claims, characterised in that the grey filter is a reflective optical element with a locally varying reflection factor. 
     
     
         8 . Projection exposure apparatus according to one of  claims 5  to  7 , in that the grey filter does not affect the phase distribution of projection light passing through. 
     
     
         9 . Projection exposure apparatus according to one of the preceding claims, characterised in that the means for homogenising an intensity distribution comprise adjustable aperture elements, which are arranged in an illumination system of the projection exposure apparatus. 
     
     
         10 . Projection exposure apparatus according to one of the preceding claims, characterised in that the means for homogenising an intensity distribution are arranged in or in the vicinity of a field or pupil plane. 
     
     
         11 . Projection exposure apparatus according to one of the preceding claims, characterised in that the coating is configured so that the coating generates a phase difference which is less than λ/10 between orthogonal polarisation states, where λ is the wavelength of the projection light used in the projection exposure apparatus. 
     
     
         12 . Projection exposure apparatus according to  claim 10 , characterised in that the means comprise local and non-axisymmetric surface deformations. 
     
     
         13 . Projection exposure apparatus according to  claim 10 , characterised in that the means are configured so that they homogenise only variations in the intensity distribution due to one or more coatings. 
     
     
         14 . Optical element of a microlithographic projection exposure apparatus, having a support material and an antireflection coating applied thereon, which comprises a plurality of layers,
 characterised in that   the transmission coefficients of the antireflection coating for mutually orthogonal polarisation states ( 42   p ,  42   s ) differ from one another by no more than 1% over an incidence angle range of from 0° to 70°, and in that none of the layers has a refractive index of less than 1.35 for the operating wavelength for which the antireflection coating is configured.   
     
     
         15 . Optical element according to  claim 14 , characterised in that the antireflection coating has six layers, counting from the support material, the first, third and fifth layers having a higher refractive index than the support material and the second, fourth and sixth layers having a lower refractive index than the support material, and the first layer having an optical thickness of between 1.2 and 1.5 λ/4, the second layer between 0.35 and 0.65 λ/4, the third layer between 1.2 and 1.5 λ/4, the fourth layer between 1.5 and 2.4 λ/4, the fifth layer between 0.4 and 0.9 and the sixth layer between 0.1 and 1.1 λ/4, where λ is the operating wavelength. 
     
     
         16 . Optical element according to  claim 14  or  15 , characterised in that the higher refractive index lies between 1.60 and 1.92 and the lower refractive index lies between 1.37 and 1.44. 
     
     
         17 . Optical element of a microlithographic projection exposure apparatus, having a support material and an antireflection coating applied thereon, which comprises a plurality of layers,
 characterised in that   the antireflection coating reflects s-polarised light less than p-polarised light in an incidence angle range comprising at least 100, which lies between 0° and 60°.   
     
     
         18 . Optical element of a microlithographic projection exposure apparatus, having a support material and an antireflection coating applied thereon, characterised in that the antireflection coating reflects s-polarised light less than p-polarised light at least in an incidence angle range of between 40° and 50°. 
     
     
         19 . Optical element according to  claim 18 , characterised in that the antireflection coating has four layers, counting from the support material, the first and third layers having a higher refractive index than the support material and the second and fourth layers having a lower refractive index than the support material, and the first layer having an optical thickness of between 1.6 and 2.2 λ/4, the second layer between 0.8 and 1.5 λ/4, the third layer between 1.2 and 1.5 λ/4, and the fourth layer between 0.9 and 1.1 λ/4, where λ is the operating wavelength. 
     
     
         20 . Optical element according to  claim 19 , characterised in that the antireflection coating reflects s-polarised light less than p-polarised light at least in an incidence angle range of between 50° and 60°. 
     
     
         21 . Optical element according to  claim 20 , characterised in that the antireflection coating has eight layers, counting from the support material, the first, third, fifth and seventh layers having a higher refractive index than the support material and the second, fourth, sixth and eighth layers having a lower refractive index than the support material, and the first layer having an optical thickness of between 1.5 and 2.4 λ/4, the second layer between 1.7 and 2.1 λ/4, the third layer between 0.8 and 1.5 λ/4, the fourth layer between 1.6 and 2.1 λ/4, the fifth layer between 1.3 and 1.8, the sixth layer between 1.2 and 1.5 λ/4, the seventh layer between 1.2 and 1.5 λ/4 and the eighth layer between 0.9 and 1.1 λ/4, where λ is the operating wavelength. 
     
     
         22 . Optical element according to  claim 19  or  20 , characterised in that the higher refractive index lies between 1.60 and 1.92 and the lower refractive index lies between 1.37 and 1.44. 
     
     
         23 . Optical element according to one of  17  to  22 , characterised in that within the incidence angle range, there is a subrange in which s-polarised light is reflected less than p-polarised light by 0.2%. 
     
     
         24 . Optical element according to  claim 23 , characterised in that within the incidence angle range, there is a subrange in which s-polarised light is reflected less than p-polarised light by 0.5%. 
     
     
         25 . Optical element of a microlithographic projection exposure apparatus, having a support material and an antireflection coating applied thereon, which comprises a plurality of layers,
 characterised in that   the antireflection coating reflects s-polarised light less than p-polarised light in an incidence angle range comprising at least 10°, which lies between 0° and 70°, and in that none of the layers has a refractive index of less than 1.35 for the operating wavelength for which the antireflection coating is configured.   
     
     
         26 . Optical element of a microlithographic projection exposure apparatus, having a support material and an antireflection coating applied thereon, which comprises a plurality of layers,
 characterised in that   the transmission coefficients of the antireflection coating for mutually orthogonal polarisation states ( 42   p ,  42   s ) differ from one another by no more than 0.2% over an incidence angle range of from 0° to 60°.   
     
     
         27 . Optical element according to  claim 25 , characterised in that the antireflection coating has seven layers, counting from the support material, the first, third, fifth and seventh layers having a lower refractive index than the support material and the second, fourth and sixth layers having a higher refractive index than the support material, and the first layer having an optical thickness of between 0.96 and 1.44 λ/4, the second layer between 0.4 and 0.91 λ/4, the third layer between 0.2 and 0.4 λ/4, the fourth layer between 0.59 and 1.1 λ/4, the fifth layer between 1.06 and 1.24, the sixth layer between 1.06 and 1.2 λ/4 and the seventh layer between 1.0 and 1.2 λ/4, where λ is the operating wavelength. 
     
     
         28 . Optical element of a microlithographic projection exposure apparatus, having a support material and an antireflection coating applied thereon, which comprises at least four layers,
 characterised in that   counting from the support layer, the second-outermost layer has an optical thickness of more than 1.2 λ/4 and the third-outermost layer has an optical thickness of between 0.8 and 1.5 λ/4, where λ is the operating wavelength.   
     
     
         29 . Optical element according to  claim 28 , characterised in that the antireflection coating comprises at least 6 layers. 
     
     
         30 . Optical element of a microlithographic projection exposure apparatus, having a support material and an antireflection coating applied thereon,
 characterised in that   counting from the support layer, the second-outermost layer has an optical thickness of more than 1.2 λ/4 and the third-outermost layer has an optical thickness of between 0.8 and 1.5 λ/4, where λ is the operating wavelength.   
     
     
         31 . Optical element of a microlithographic projection exposure apparatus, having a support material and an antireflection coating applied thereon, which comprises a plurality of layers,
 characterised in that   the phases of mutually orthogonal polarisation states ( 42   p ,  42   s ) differ from one another by no more than 8° in magnitude after passing through the antireflection coating over an incidence angle range of from 0° to 70°.   
     
     
         32 . Optical element according to  claim 31 , characterised in that the phases of mutually orthogonal polarisation states ( 42   p ,  42   s ) differ from one another by no more than 2° in magnitude after passing through the antireflection coating over an incidence angle range of from 0° to 50°. 
     
     
         33 . Optical element according to  claim 31  or  32 , characterised in that the antireflection coating has eight layers, counting from the support material, the first, third, fifth and seventh layers having a higher refractive index than the support material and the second, fourth, sixth and eighth layers having a lower refractive index than the support material, and the first layer having an optical thickness of between 1.8 and 2.6 λ/4, the second layer between 0.05 and 0.4 λ/4, the third layer between 0.3 and 1.4 λ/4, the fourth layer between 0.05 and 0.4 λ/4, the fifth layer between 0.05 and 0.4, the sixth layer between 0.8 and 1.5 λ/4, the seventh layer between 1.2 and 1.5 λ/4 and the eighth layer between 0.9 and 1.1 λ/4, where λ is the operating wavelength. 
     
     
         34 . Optical element of a microlithographic projection exposure apparatus, having a support material and an antireflection coating applied thereon, which comprises a plurality of layers,
 characterised in that   the phase of s-polarised light is less than the phase of p-polarised light after passing through the antireflection coating over an incidence angle range of at least 20°.   
     
     
         35 . Optical element according to one of  claims 31  to  34 , characterised in that the antireflection coating has eight layers, counting from the support material, the first, third, fifth and seventh layers having a higher refractive index than the support material and the second, fourth, sixth and eighth layers having a lower refractive index than the support material, and the first layer having an optical thickness of between 0.4 and 0.85 λ/4, the second layer between 0.3 and 0.55 λ/4, the third layer between 0.3 and 0.55 λ/4, the fourth layer between 1.15 and 1.7 λ/4, the fifth layer between 1.9 and 2.5, the sixth layer between 1.7 and 1.8 λ/4, the seventh layer between 0.5 and 0.95 λ/4 and the eighth layer between 1.15 and 1.4 λ/4, where λ is the operating wavelength. 
     
     
         36 . Optical element of a microlithographic projection exposure apparatus, having a support material and an antireflection coating applied thereon, which comprises a plurality of layers,
 characterised in that   at least three layers have an optical thickness of less than 0.4 λ/4, where λ is the operating wavelength of the projection exposure apparatus.   
     
     
         37 . Optical element of a microlithographic projection exposure apparatus, having a support material and an antireflection coating applied thereon, which comprises a plurality of layers,
 characterised in that   at least two first layers have an optical thickness of less than 0.4 λ/4 and at least two second layers, which are different from the first layers, have an optical thickness of less than 0.6 λ/4, where λ is the operating wavelength of the projection exposure apparatus.   
     
     
         38 . Microlithographic projection exposure apparatus having a plurality of optical elements, on which there is an antireflection coating in order to reduce the reflectivity, at least one first antireflection coating having a reflectivity which is greater for s-polarised light than for p-polarised light within a first incidence angle range,
 characterised in that   at least one second antireflection coating has a reflectivity which is less for s-polarised light than for s-polarised light within a second incidence angle range, the at least one first antireflection coating and the at least one second antireflection coating being arranged in the beam path so that they at least partially compensate for the polarisation-dependent differences in the reflectivity.   
     
     
         39 . Projection exposure apparatus according to  claim 38 , characterised in that at least some light rays, which strike the at least one first antireflection coating with incidence angles lying within the first incidence angle range, strike the at least one antireflection coating with incidence angles lying within the second incidence angle range.