Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B3/00—Simple or compound lenses
• • 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
  • G03F7/70216—Mask projection systems
  • G03F7/70233—Optical aspects of catoptric systems, i.e. comprising only reflective elements, e.g. extreme ultraviolet [EUV] projection systems
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B17/00—Systems with reflecting surfaces, with or without refracting elements
  • G02B17/02—Catoptric systems, e.g. image erecting and reversing system
  • G02B17/06—Catoptric systems, e.g. image erecting and reversing system using mirrors only, i.e. having only one curved mirror
  • G02B17/0647—Catoptric systems, e.g. image erecting and reversing system using mirrors only, i.e. having only one curved mirror using more than three curved mirrors
  • G02B17/0657—Catoptric systems, e.g. image erecting and reversing system using mirrors only, i.e. having only one curved mirror using more than three curved mirrors off-axis or unobscured systems in which all of the mirrors share a common axis of rotational symmetry
• • 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
  • G03F7/70216—Mask projection systems
  • G03F7/70275—Multiple projection paths, e.g. array of projection systems, microlens projection systems or tandem projection systems

Definitions

• the invention relates to a microlithography objective according to the preamble of claim 1, a projection exposure system according to claim 18 and a chip production method according to claim 19.
• Wavelength of the incident light and NA denotes the image-side, numerical aperture of the system.
• the reflectivity of the multilayer layers used is currently at most in the range of approximately 70%, so that a requirement is met
• a projection objective for EUV microlithography is to use as few optical components as possible in order to achieve a sufficient light intensity.
• the beam path within a projection lens is free of shading or obscuring.
• the projection objectives should not have mirrors with transmissive areas, in particular openings, since such transmissive areas lead to shadowing.
• the lens has no mirrors with transmissive areas, the lens has an obscuration-free beam path and the exit pupil of the lens is free of shadowing.
• no shading device has to be arranged in the aperture diaphragm of such shading-free systems or in planes conjugated to the aperture diaphragm.
• Schwarzschild mirror systems is that structures of a certain size can only be imaged to a limited extent.
• the exit pupil is defined as the image of the aperture diaphragm, imaged by the lens part that lies in the beam path between the aperture diaphragm and the image plane.
• 6-mirror systems for microlithography are known from the documents US-A-5 153 898, EP-A-0 252734, EP-A-0947 882, US-A-5686728, EP 0 779 528, US 5 815 310, WO 99/57606 and US 6 033 079 become known.
• Such systems 6-mirror systems have an image-side numerical aperture ⁇ 0.3, which leads to a resolution limit in the range of 30 nm when using X-ray light with a wavelength of 10 to 30 nm.
• a microlithography projection lens with eight mirrors is from the US
• a first object of the invention is to provide a projection lens which is suitable for lithography with short EUV wavelengths in the range from 10 to 30 nm and which is different from those known to date
• EUV microlithography projection systems are characterized by a large numerical aperture and improved possibilities of image correction.
• Another object of the invention is to use for lithography
• Wavelengths ⁇ 193 nm a microlithography projection lens to specify, which has both a large aperture and is easy to manufacture.
• the first object is achieved by a microlithography projection objective for EUV lithography with a wavelength in the
• Range 10 to 30 nm solved by the fact that the microlithography projection lens comprises eight mirrors instead of the four or six mirrors.
• Objective provides both a sufficient light intensity, as well as a sufficiently large numerical aperture to meet the requirements for high resolution, as well as sufficient options for image correction.
• the numerical aperture of the projection objective on the image side is greater than 0.2.
• the image-side numerical aperture of the projection system according to the invention is advantageously limited to NA ⁇ 0.5.
• the projection lens is designed such that at least one in the beam path of the projection lens between the object field and the image field
• the useful area of a mirror is understood to mean the part of a mirror in which the light rays that are guided through the projection objective strike.
• the distance of the useful area is the distance of the point of incidence of the main beam of the central field point from the optical axis.
• the diaphragm is arranged in the light path between the first and third mirrors, preferably on or near the first or on or near the second mirror ,
• “near” is understood to mean a distance of the diaphragm from the respective closest mirror, which is less than 1/10 of the distance from the preceding mirror to the respective mirror close to the diaphragm.
• near S2 means that:
• the radius of curvature of at least one mirror is chosen to be larger than the overall length of the projection objective.
• the overall length of the system is understood to mean the distance from the object to be imaged to its image in the present application. It is particularly advantageous if this is for the
• Microlithography projection lens designed such that the The main beam angle on the object is smaller than twice the value of the aperture NAO on the object. This is advantageous because it reduces shading effects on the masks.
• the first intermediate picture at. a system with two intermediate images is preferably formed between the second and third mirrors.
• the projection lens is designed such that the second intermediate image between the sixth and seventh mirrors in the beam path is trained. It is particularly preferred if in a system with two
• the angle of incidence of the main beam of the field point which lies on the axis of symmetry in the middle of the object field, is less than 20 ° on all mirrors.
• At least one of the eight mirror surfaces is spherical.
• the mirror or mirrors of the objective are spherical, the useful area of which is the most distant from the optical axis of the projection objective, since the interferometric testability of off-axis aspheres lies far outside the optical axis The further the useful area is from the optical axis, the more difficult the useful area becomes.
• the sixth mirror is the mirror with the most distant useful area. In such an embodiment, this is advantageously spherically shaped for the sake of easier interferometric testability.
• the invention also provides a projection exposure system, the projection exposure system including an illumination device for illuminating a ring field and a projection lens according to the
• Invention includes.
• Figure 1 the definition of the useful area of a mirror
• Figure 2 the shape of the field in the object or image plane of the
• Figure 3 a first embodiment of an inventive
• Figure 5 a second embodiment of an inventive
• 6A-6H Usable areas of the S1-S8 of the second embodiment.
• Figure 7 the basic structure of a
• FIG. 1 shows what is mentioned in the present application
• Usable area and diameter of the usable area is to be understood.
• FIG. 1 shows, by way of example, a field in the shape of a kidney for an illuminated field 1 on a mirror of the projection objective.
• a shape is expected for the useful area when using the objective according to the invention in a microlithography projection exposure system.
• the enveloping circle 2 completely surrounds the kidney shape and coincides with the edge 10 of the kidney shape at two points 6, 8.
• the envelope circle is always the smallest circle that encompasses the useful area.
• the diameter D of the useful area then results from the diameter of the enveloping circle 2.
• FIG. 2 shows the object field 11 of a projection exposure system in the object plane of the projection objective, which is imaged with the aid of the projection objective according to the invention in an image plane in which a light-sensitive object, for example a wafer, is arranged.
• the shape of the image field corresponds to that of the object field. With reduction lenses, as are often used in microlithography, the image field is reduced by a predetermined factor compared to the object field.
• the object field 11 has the shape of a segment of a ring field.
• the segment has an axis of symmetry 12.
• the axes spanning the object or image plane namely the x-axis and the y-axis, are shown in FIG. As from a figure
• the axis of symmetry 12 of the ring field 11 runs in the direction of the y-axis.
• the y-axis coincides with the scan direction of an EUV projection exposure system, which is designed as a ring field scanner.
• the x direction is then the direction that is perpendicular to the scan direction within the object plane.
• the unit vector x in the direction of the x axis is also shown in FIG. 12.
• the optical axis HA of the system extends in the z direction.
• the object is imaged in the object plane 100 into the image plane 102, in which, for example, a wafer can be arranged, by the projection objective.
• the projection objective according to the invention comprises a first mirror S1, a second mirror S2, a third mirror S3, a fourth mirror S4, a fifth mirror S5, a sixth mirror S6, a seventh mirror S7 and an eighth mirror S8.
• all mirrors S1, S2, S3, S4, S5, S6, S7 and S8 are designed as aspherical mirrors.
• the system comprises an intermediate image Z1 between the fifth S5 and the sixth S6 mirror.
• the y and z directions of the right-handed x, y, z coordinate system are also shown in FIG.
• the z-axis runs parallel to the optical axis HA and the orientation of the z-axis points from the object plane 100 to the image plane 102.
• the y-axis runs parallel to the symmetry axis 12 of the object field 11.
• the object field 11 is shown in FIG.
• the orientation of the y-axis is from the optical axis HA to
• the system is centered on the optical axis HA and on the image side, i.e. in the image plane 102 telecentric.
• Image-side telecentricity is understood to mean that the main beam CR is at an angle of close to or approximately 90 ° to the
• Image plane 102 meets.
• the main beam CR is reflected on the fourth mirror S4 in such a way that it runs away from the optical axis.
• the characteristic quantities are defined as the scalar product between the unit vector x in the direction of the x-axis and the vector product of a unit vector n j before having the direction of the th i-to mirror the incident principal ray, and a unit vector ni after which the direction of the main beam reflected at the i-th mirror, that is
• the main beam CR incident on the mirror is reflected in the positive or negative y direction, it being important to note whether the main beam CR is incident from the direction of the object plane 100 or from the direction of the image plane 102. It holds that C j > 0 when the main beam strikes the mirror from the direction of the object plane 100 and in the direction of the negative y-
• C; ⁇ 0 applies if the main beam comes from the direction of the Object plane 100 strikes the mirror and is reflected in the direction of the positive y-axis.
• C;> 0 applies when the main beam hits the mirror from the direction of the image plane 102 and is reflected in the direction of the positive y-axis, and
• C j ⁇ 0 applies when the main beam hits the mirror from the direction of the image plane 102 and in the direction the negative y-
• the angle of incidence of the main beam CR is the central one
• Field point on the respective mirror surface in the exemplary embodiment according to FIG. 3 is less than 26 °.
• the angles of incidence of the main radiator of the central field point are shown in Table 1 below:
• Table 1 Angle of incidence of the main beam of the central field point for the embodiment according to. Figure 3
• NA 0.4 on the image side
• NAO 0.1
• the maximum main beam angle on the object is only 6.1 ° with the specified object-side numerical aperture NAO of 0.1 and is thus significantly smaller than the maximum main beam angle of 13 ° on the object according to US Pat. No. 5,686,728.
• the physical aperture is located on the second mirror S2. This allows a minimal separation of the beams in the front part of the lens, which reduces the angles of incidence to S1, S2 and S3. Furthermore, this has the effect that the useful area of S3 lies directly below the optical axis and almost mirror image of the useful area S1, in contrast, for example, to the 8-mirror lens shown in US Pat. No. 5,686,728 for wavelengths> 126 nm. This measure also reduces the angles of incidence on S4 and S5, since the distance of the beam from the optical axis between S4 and S5 becomes minimal.
• the useful areas of the individual mirror segments are shown in FIGS. 4A-4H. 4A is the useful area on mirror S1, in FIG. 4B the useful area on mirror S2, in FIG. 4C the useful area on mirror S3, in FIG. 4D the useful area on mirror S4, in FIG. 4E the useful area on mirror S5, in FIG. 4F the usable area on mirror S6, in
• FIG. 4G shows the useful area on mirror S7 and in FIG. 4H the useful area on mirror S8 of the embodiment of an 8-mirror lens according to FIG. 3.
• all useful areas of the mirrors S1 to S8 are free from shading or obscuration. This means that the beam path of a light bundle that passes through the lens from the object plane to the image plane and that maps the object field in the object plane into the image field in the image plane is free from shading or obscuration.
• the radii of curvature become at least one of the mirrors
• S2 to S4 selected as large, preferably larger than the overall length of the Projection objectives that drift distances are as large as possible and the beam paths from S1 to S2 and from S3 to S4 are almost parallel. The same applies to the beam paths from S2 to S3 and from S4 to S5. This also results in minimal separation of the beam.
• the wavefront has a maximum fms value of less than 0.030 ⁇ .
• the distortion is corrected to a maximum value of 1 nm via the scanning slot and has the form of a third degree polynomial, so that the dynamic distortion averaged over the scanning process is minimized.
• Image field curvature is corrected by taking the Petzval condition into account.
• FIG. 5 shows a second embodiment of an 8-mirror lens according to the invention with mirrors S1, S2, S3, S4, S5, S6, S7 and S8.
• the same components as in Figure 3 are given the same reference numerals.
• the x-axis, the y-axis and the z-axis as well as the characteristic quantities are defined as in the description of FIG. 3.
• the characteristic quantities C j as defined in the description of FIG. 3, the following applies: 0 ⁇ 0, C 2 ⁇ 0, C 3 ⁇ 0, C 4 > 0, C 5 ⁇ 0, C 6 > 0, C 7 > 0, C 8 ⁇ 0.
• the mirror be made spherical with the axis remote useful area.
• the embodiment according to FIG. 5 has two intermediate images Z1, Z2.
• mirrors S1, S2, S3, S4, S5 as well as S7 and S8 are aspherical, while mirror S6 with the useful area furthest from the axis is spherical.
• the mirror S6 is shaped as an asphere, it would be difficult to test with on-axis inspection optics. It is therefore spherically shaped in accordance with the invention.
• the angles of incidence of the main beam of the central field point are shown in Table 3 below:
• Table 3 Angle of incidence of the main beam of the central field point for the exemplary embodiment according to FIG. 5
• FIGS. 6A-6H The useful areas of the individual mirror segments are shown in FIGS. 6A-6H. 6A is the useful area on mirror S1 in FIGS. 6A-6H. 6A is the useful area on mirror S1 in FIGS. 6A-6H. 6A is the useful area on mirror S1 in FIGS. 6A-6H.
• FIGS. 6A-6H all useful areas of the mirrors S1 to S8 are free from shading or obscuration. This means that the beam path of a light bundle that passes through the objective from the object plane to the image plane and that maps the object field in the object plane into the image field in the image plane is free from shading or obscuration.
• the distances between the useful areas of the mirrors are advantageously kept small in order to generate small angles of incidence on the mirrors. Since these can be varied as required by appropriate scaling, these distances are given here by their size ratio to the overall length of the mirrors.
• Table 5 shows the ratios of the distances between the useful areas divided by the overall length for all mirrors of the two exemplary embodiments:
• FIG. 7 shows a projection exposure system for microlithography with an 8-mirror projection objective 200 according to the invention.
• the lighting system 202 can, as for example in EP 99106348.8 with the title “Lighting system, in particular for EUV lithography” or US serial no. 09 / 305,017 with the title “Illumination System particulary for EUV-Lithography", the disclosure content of which is fully incorporated in the present application.
• Such a lighting system comprises an EUV light source 204.
• the light from the EUV light source is collected by the collector mirror 206.
• the reticle 212 is illuminated with the aid of a first mirror 207 comprising raster elements - so-called field honeycombs - and a second mirror 208 comprising raster elements - so-called pupil honeycombs - and a mirror 210.
• the light reflected by the reticle 212 is imaged onto a carrier 214 comprising a light-sensitive layer by means of the projection objective according to the invention.
• the projection lens presented is characterized by a high aperture with a shading-free or obscuration-free beam path. This leads to a shadow-free exit pupil.

Landscapes

• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Optics & Photonics (AREA)
• Lenses (AREA)

Applications Claiming Priority (5)

Publications (1)

Family

ID=26007445

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (44)

Family Cites Families (12)

• 2001
  • 2001-10-19 EP EP01982439A patent/EP1327172A1/de not_active Withdrawn
  • 2001-10-19 KR KR10-2003-7004654A patent/KR20030045817A/ko active IP Right Grant
  • 2001-10-19 WO PCT/EP2001/012110 patent/WO2002033467A1/de active Application Filing
  • 2001-10-19 JP JP2002536594A patent/JP2004512552A/ja active Pending
• 2003
  • 2003-04-18 US US10/418,515 patent/US7177076B2/en not_active Expired - Fee Related
• 2006
  • 2006-11-02 US US11/592,065 patent/US7372624B2/en not_active Expired - Fee Related
• 2008
  • 2008-02-06 US US12/012,825 patent/US7508580B2/en not_active Expired - Fee Related

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events