Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/20—Exposure; Apparatus therefor
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/70483—Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
  • G03F7/7055—Exposure light control in all parts of the microlithographic apparatus, e.g. pulse length control or light interruption
  • G03F7/70583—Speckle reduction, e.g. coherence control or amplitude/wavefront splitting
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
  • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
  • G03F7/70—Microphotolithographic exposure; Apparatus therefor
  • G03F7/70058—Mask illumination systems

Definitions

• the invention relates to a system for reducing the coherence of a laser radiation emitting wavefronts, in particular for a projection objective in semiconductor lithography, a first partial beam being partially reflected by the laser beam impinging on a surface of a resonator body and a second partial beam entering the resonator body and after several total reflections at least approximately in the area of the entry point, it emerges from the resonator body and is passed on together with the first partial beam to an illumination plane.
• the invention also relates to a projection exposure system with a laser as a light source, an illumination system and a projection lens.
• the present invention has for its object to provide a system with which the lighting homogeneity can be improved even further.
• this object is achieved in that the resonator body is designed such that, in addition to the division into partial beams, the wave fronts of at least one partial beam are modulated during a laser pulse, the partial beams reflected on the resonator body and those entering the resonator body after the resonator body are superimposed and the resonator body is provided with a phase plate with different local phase distribution.
• the wave fronts of the laser radiation are also modulated according to the invention.
• a significant increase in lighting homogeneity can be achieved by averaging over several speckle distributions.
• the combination of temporally staggered wave fronts according to the invention, which is additionally modulated and thus receives different phase distributions, allows a very high degree of homogeneity to be achieved by means of averaged speckle patterns.
• a phase plate, which is attached in the resonator body, is suitable for this.
• the resonator body is designed as a prism with at least five corners. It was found that, in comparison to a resonator body with 3 corners, at the generally used wavelengths of the laser beams, in particular in the VUV range (vacuum ultraviolet spectral range) or shorter, deflection angles which are too steep result in the prism, so that it does not Total reflections occur, but partial exits with corresponding light losses.
• VUV range vacuum ultraviolet spectral range
• the resonator body with 3 corners at the generally used wavelengths of the laser beams, in particular in the VUV range (vacuum ultraviolet spectral range) or shorter, deflection angles which are too steep result in the prism, so that it does not Total reflections occur, but partial exits with corresponding light losses.
• VUV range vacuum ultraviolet spectral range
• the resonator body is designed as a prism with at least five corners. It was found that, in comparison to a resonator body with 3 corners, at the generally used wavelengths of the laser beams
• the thickness of the phase plate is different, then spatially offset wavefronts result. Different changes in thickness - in relation to a direction transverse to the beam direction - should occur at a distance which corresponds to the order of magnitude of the spatial coherence length of the laser radiation which should be modulated through.
• the phase plate is designed as a diffractive optical element (DOE) which is operated in the zeroth diffraction order.
• DOE diffractive optical element
• a diffractive optical element in the first or even a higher diffraction order is normally used.
• the diffractive optical element (DOE) in the zeroth diffraction order will be used, where the laser light passes through unbroken.
• Another option is to use a diffuser as a phase plate.
• the modulation of a wavefront according to the invention can also be achieved in that the resonator body, e.g. the prism with at least five corners is asymmetrical. This can e.g. by an asymmetrical, i.e. non-mirror-symmetrical formation of at least one side of the prism.
• Another solution, or a combination with an asymmetrical resonator body is that the beam guidance of the laser beam is selected such that the center of gravity beam hits the resonator body off-center. In this case, modulations of the wavefront are also created when the partial beam circulates in the resonator body.
• the possible uses can be increased further, since the angle dependency can be at least partially reduced.
• the entry angle can thus be varied through the divider layer and thus also the ratio of the reflected partial beam and that entering the resonator body Partial beam.
• the divider layer can be of different thicknesses and / or not homogeneous.
• a dielectric layer with a division ratio of 33: 67 or 1/3: 2/3 can advantageously be used as the divider layer.
• FIG. 1 shows a schematic structure of a projection exposure system with a light source, an illumination system and a projection lens
• FIG. 2 pentagonal prism as a resonator body with a phase plate
• FIG. 3a shows a cross section through the phase plate according to FIG. 2;
• FIG. 3b shows a cross section through a further embodiment of a phase plate
• Figure 4 shows a pentagonal prism with two asymmetrical sides
• Figure 5 shows a pentagonal prism with a divider layer on one surface.
• a projection exposure system 1 has a light source 2 in the form of a laser
• Illumination system 3 for illuminating a field in a Level 4, in which a structure-bearing mask 4a is arranged, and a projection objective 5 for imaging the structure-bearing mask 4a in level 4 onto a light-sensitive substrate 6.
• the projection lens 5 has a plurality of optical elements 7 in its housing 8.
• the projection exposure system 1 is used to produce semiconductor components, such as computer chips.
• a resonator body 9, 9 ' is arranged between the laser 2 and the illumination system 3 in order to reduce the, in particular temporal, coherence of a laser radiation 10 from the laser 2.
• FIG. 2 shows a pentagonal prism as resonator body 9
• a lambda / 2 plate 18 is used to adjust the degree of polarization (between unpolarized and linearly polarized) of the laser beam 10.
• the laser beam 10 impinging on a surface 11 of the prism 9 is divided into a first partial beam 10a which reflects on the surface 11 and a partial beam 10b which enters the resonator body 9 and there after several total reflections at the entry point again out of the resonator body 9 emerges and is combined there with the first partial beam 10a.
• Both partial beams are then fed to an illumination level, in this case level 4 with the structure-bearing mask.
• a phase plate 12 protrudes into the prism 9 is introduced into the prism 9 in such a way that the circulating partial beam 10b, which approximately meets perpendicularly with a front surface 13 of the phase plate 12, must penetrate it.
• the phase plate 12 causes a different local phase distribution.
• the phase plate 12 has a different thickness, as can be seen from the enlarged cross-sectional representations according to FIGS. 3a and 3b.
• the different thicknesses of the phase plate 12 vary in width s in the transverse direction to the beam direction. The greatest width s should be - depending on the laser used and its wavelength - in the order of the spatial coherence length of the laser radiation used.
• the value for s is between 0.05 and 1 mm, whereby a possible beam expansion increases the value accordingly.
• the base thickness of the phase plate b can be in the range of 500 ⁇ m.
• the distribution of the width differences s and the thickness differences a should be as random as possible, so that a relatively random phase distribution on the wavefront is also obtained.
• the optical path lengths differ locally and, in the case of the reunited partial beams 10a and 10b after the resonator body 9, correspondingly different partial beams are obtained, which are also modulated with respect to the wavefront.
• the individual pulses can be so short in their duration and in phase distribution that there is no longer any interference capability.
• the structure of the phase plate 12 is made tapered or prism-like, whereby an improved beam expansion is achieved.
• reflection angles are greater than 37 degrees, which means that total reflections occur inside.
• the exemplary embodiment shown was designed so that all total reflection angles are identical and are approximately 55 degrees.
• the crystal orientation of the CaF 2 prism 9 is selected such that the first (100) crystal plane forms an angle of 45 ° with the light entry plane of the entry or surface 11 and is perpendicular to the side surface 14.
• the second (100) crystal plane lies parallel to the side surface 14 of the prism 9.
• the --- intrinsic birefringence which is significant at the wavelength of 157 nm and 193 nm, does not affect the polarization of the circulating beam if the light at the entrance obex surface 11 is linearly polarized and the direction of oscillation of the electrical Field strength vector is parallel (p-polarized) or perpendicular (s-polarized) with respect to the plane of incidence.
• the light emerges from the prism 9 again in s or p polarization.
• the crystal orientation is not important and the prism 9 made of CaF 2 can be oriented as desired.
• a corresponding possibility consists in producing the block from MgF 2 (transparent at 157 nm and 193 nm, strongly birefringent). It is about. unpolarized Light at the entrance, then the crystal orientation with regard to the prism surfaces can also be chosen arbitrarily.
• the crystal orientation must be chosen so that the direction of oscillation of the incident electric field strength vector parallel to the fast ( Direction with extraordinary refractive index) or slow (direction with ordinary refractive index) crystal axis.
• a diffractive optical element can be used as the phase plate 12, which is optimized to the zero order of diffraction, in which incident light passes undeflected.
• a diffusing screen can also be used as the phase plate 12.
• FIG. 4 shows a prism in a pentagonal shape, an offset being present or the prism body being asymmetrical.
• one side namely the first side 15, on which the partial beams 10b impinge are shifted downward by the distance d.
• the distance d can be of the order of 0.1 mm.
• phase plate 12 (shown in dashed lines in FIG. 4) can also be used 2, which is even more variable with respect to the modulation of wave fronts.
• FIG. 5 shows an embodiment of a prism 9, also in a pentagonal shape, a divider layer 17 being applied to the entrance surface 11.
• the divider layer can e.g. a dielectric layer with a split ratio of 1/3: 2/3.
• the splitter layer has the task of influencing the entry angle of the partial beam 10b into the prism 9. This can be chosen according to the design and the material of the divider layer as desired.
• the divider layer also has a different thickness, modulation of the wavefront is also achieved in a manner similar to that of the phase plate (shown in broken lines in FIG. 5). The same is possible through an inhomogeneous or non-homogeneous formation of the divider layer.
• FIGS. 2, 4 and 5 for generating different wave fronts can be used both separately and in any combination with one another.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Exposure Of Semiconductors, Excluding Electron Or Ion Beam Exposure (AREA)
• Exposure And Positioning Against Photoresist Photosensitive Materials (AREA)
• Optical Elements Other Than Lenses (AREA)
• Diffracting Gratings Or Hologram Optical Elements (AREA)
• Lasers (AREA)

Priority Applications (4)

Applications Claiming Priority (2)

Publications (2)

Family

ID=34894863

Family Applications (1)

Country Status (5)

Cited By (6)

Families Citing this family (1)

Family Cites Families (9)

• 2005
  • 2005-02-22 US US10/590,537 patent/US7593095B2/en not_active Expired - Lifetime
  • 2005-02-22 EP EP05707555A patent/EP1721217A2/de not_active Withdrawn
  • 2005-02-22 KR KR1020067019720A patent/KR101109354B1/ko not_active Expired - Fee Related
  • 2005-02-22 JP JP2007500124A patent/JP4769788B2/ja not_active Expired - Fee Related
  • 2005-02-22 WO PCT/EP2005/001797 patent/WO2005083511A2/de not_active Ceased

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