CN104375385A - Wave aberration measure apparatus and method for lithographic projection lens system - Google Patents
Wave aberration measure apparatus and method for lithographic projection lens system Download PDFInfo
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- CN104375385A CN104375385A CN201410185411.2A CN201410185411A CN104375385A CN 104375385 A CN104375385 A CN 104375385A CN 201410185411 A CN201410185411 A CN 201410185411A CN 104375385 A CN104375385 A CN 104375385A
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Abstract
The invention discloses a wave aberration measure apparatus and a method for a lithographic projection lens system. The apparatus mainly consists of an excimer laser, a beam-expanding prism, a light-uniformizing focusing objective lens system, an optical fiber coupling objective lens, multimode fiber, an imaging objective lens, an illumination mask plate, a collimating objective lens and a Hartmann-Shack wavefront sensor; a square light spot is obtained by using the beam-expanding prism to perform beam expanding on a narrow and long rectangular light spot output by the excimer laser, and the square light spot is coupled into the multimode fiber after passing through the light-uniformizing focusing objective lens system and the optical fiber coupling objective lens; after passing through the imaging objective lens, a divergent spherical wave ejected from the multimode fiber is imaged on the illumination mask plate and generates multiple spherical waves; the spherical waves carry the wave aberration information after passing through a projection objective lens system and then form a plane wave after passing through the collimating objective lens; the plane wave is divided into multiple sub-beams by a microlens array of the Hartmann-Shack wavefront sensor; and the sub-beams are focused on a detector of the Hartmann-Shack wavefront sensor, so that the wave aberration information of the projection objective lens system is measured.
Description
Technical field
The present invention relates to field of optical measuring technologies, particularly relate to a kind of photoetching projection objective lens system wave aberration measurement mechanism and method.
Background technology
21 century is the information economy era, developed country's growth of the national economic very most of relevant with integrated circuit.Integrated circuit has become basic, strategic industry concerning a national national economy, national defense construction, people's lives and information security.Chip from single transistor to today, the development of integrated circuit is a constantly microminiaturization, integrated process, and this will give the credit to the continuous progress of optical lithography techniques.
As the projection objective system of litho machine core component, its wave aberration size directly affects the resolution of optical patterning quality and litho machine.In order to improve the resolution of litho machine, in litho machine, exposure wavelength constantly reduces, and numerical aperture of projection objective improves constantly, and various resolution enhance technology makes process factor constantly reduce.Meanwhile, lithographic objective is also huger and complicated, and such as, the optical element quantity of state-of-the-art deep UV projection photoetching objective lens is more than 20 in the world at present, and this gives optical design, processing, detects and debug and all bring great challenge.The complicacy of projection objective system and accuracy, require that projection objective system is in the detection of processing, links that is integrated and exposure all must carry out wave aberration.Especially debug the stage in the system integration, it is the integrated important guarantee of final objective system high precision that wave aberration detects.
Projection lens of lithography machine system wave aberration detection method mainly contains based on interference of light principle with based on Shack-Hartmann wavefront sensor two kinds.Wherein, method based on interference of light principle has point-diffraction interferometer (PDI) and the line diffraction interferometer (LDI) of diffraction type, the lateral shearing interferometer (LSI) of shearing-type, double grating shearing interferometer (DLSI), crossed grating shearing interferometer (CGLSI) and digital Taibo interferometer (DTI).Method based on Shack-Hartmann wavefront sensor mainly contains the iPot that NIKON adopts.
The technology adopting PDI to carry out the detection of system wave aberration described in detail by document " Phase-shifting point-diffraction interferometry at193nm " (Appl.Opt., 2000,29 (31): 5768 ~ 5772).Wherein, PDI adopts the spherical wave of micropore diffraction generation as with reference to light, is realized the measurement of system wave aberration by grating phase shift.But 0.75 is reached for the deep UV projection objective system image-side numerical aperture (NA) towards 100nm node, in order to produce enough high-quality reference diffraction wavefront, require that micro-pore diameter is very little, this will make energetic transmittance very low, affect measuring accuracy.Simultaneously grating is arranged in convergent beam and carries out phase shift, will bring error to measurement result.Document " A newon-machine measurement system to measure wavefront aberration ofprojection optics with hyper-NA " (Proc.SPIE, 2006,6154:615424) describe the technology adopting LDI to carry out the detection of system wave aberration in detail.The cylindrical wave that LDI adopts slit diffraction to produce, as with reference to light, solves PDI and adopts the problem that micropore energetic transmittance is very low, energy is improved greatly.But LDI can only measure the wave aberration information in certain direction, in order to realize the perfect measurement of system wave aberration, needing to carry out twice measurement in 2 orthogonal directions, like this in the process adjusting slit and grating, error will be brought to measurement.Equally, the same with PDI, the grating that LDI adopts also will bring error to final measurement.
Shearing-type interferometer, as US Patent No. 7352475, does not need reference wavefront, but test wavefront and the dislocation of himself (shearing) wavefront is interfered, and realizes the detection of system wave aberration.Owing to not needing micropore or slit, therefore can obtain very large energetic transmittance, there is higher precision.But in shearing interferometer, grating is arranged in convergent beam or divergent beams, will bring error to measurement result.
Document " High numerical aperture Hartmann wavefront sensor withpinhole array extended source " (Proc.SPIE, 2012,8550:85503M) describe the technology adopting the method for hole array and Shack-Hartmann wavefront sensor to carry out the measurement of system wave aberration in detail.Wherein, by the hole array by square mode arrangement integrated on the object plane of projection objective system, it is before the diffracted wave of 0.1875 that diffraction produces NA, after projection objective system, plane wave front is converted to by before divergent wave, final employing Shack-Hartmann wavefront sensor register system wave aberration information with collimator objective.But adopt this device, need a NA to be the collimator objective of 0.75, at 193nm wave band, NA reaches the collimator objective of 0.75, bulky, expensive, be also difficult to accurately demarcate its wave aberration simultaneously.
Summary of the invention
In view of this, the object of the invention is to, overcome the defect that prior art exists, a kind of new photoetching projection objective lens system wave aberration measurement mechanism and method are provided, technical matters to be solved makes it pass through integrated microwell array in the image planes of projection objective system, Shack-Hartmann wavefront sensor is adopted to carry out the measurement of projection objective system wave aberration, can while ensureing high energetic transmittance, effectively reduce the numerical aperture of collimator objective, thus improve the problem that bulky, the expensive and wave aberration of collimator objective is difficult to accurately demarcate.
The object of the invention to solve the technical problems realizes by the following technical solutions.According to a kind of photoetching projection objective lens system wave aberration measurement mechanism that the present invention proposes, this device comprises: excimer laser, prism beam expander, even smooth focusing objective len system, coupling fiber object lens, multimode optical fiber, image-forming objective lens, lighted mask, collimator objective and Shack-Hartmann wavefront sensor, wherein, described excimer laser, described prism beam expander, described even smooth focusing objective len system and described coupling fiber object lens are set in turn in one end of described multimode optical fiber, the long and narrow rectangular light spot exported from described excimer laser obtains square focus spot after described prism beam expander expands, and described square focus spot is coupled in described multimode optical fiber after described even smooth focusing objective len system and described coupling fiber object lens, described image-forming objective lens is set gradually at the other end of described multimode optical fiber, described lighted mask, described collimator objective and described Shack-Hartmann wavefront sensor, be imaged onto after described image-forming objective lens on described lighted mask by the divergent spherical wave of described multimode optical fiber outgoing and produce multiple spherical wave, these spherical waves carry its wave aberration information after projection objective system to be measured, the plane wave carrying wave aberration information is become again after described collimator objective, described plane wave is divided into multiple beamlet by the microlens array of described Shack-Hartmann wavefront sensor, these beamlets focus on the detector of described Shack-Hartmann wavefront sensor, record the wave aberration information of described projection objective system to be measured.
The object of the invention to solve the technical problems also can be applied to the following technical measures to achieve further.
Aforesaid photoetching projection objective lens system wave aberration measurement mechanism, wherein said prism beam expander comprises: the first prism beam expander, the second prism beam expander and the 3rd prism beam expander; Described first prism beam expander, described second prism beam expander and described 3rd prism beam expander vary in size, and material is identical, and the right-angle prism that the angular dimension of three drift angles is corresponding consistent respectively; Wherein the enlargement ratio X of each right-angle prism meets following relation:
In formula, n is the refractive index of prism, n
0the refractive index of medium residing for prism, the long and narrow rectangular light spot exported from described excimer laser after described first prism beam expander, described second prism beam expander and described 3rd prism beam expander expand, obtains described square focus spot successively, wherein, first inclined-plane of described first prism beam expander is towards described excimer laser, first right-angle surface of described first prism beam expander is towards the second inclined-plane of described second prism beam expander, described second prism beam expander second right-angle surface corresponding with described first right-angle surface is towards the 3rd inclined-plane of described 3rd prism beam expander, described 3rd prism beam expander three right-angle surface corresponding with described first right-angle surface and described second right-angle surface is towards described even smooth focusing objective len system, between wherein said first right-angle surface and described second inclined-plane, and the angle between described second right-angle surface and described 3rd inclined-plane is acute angle, make the long and narrow rectangular light beam sent from described excimer laser successively from described first inclined-plane, described second inclined-plane and described 3rd inclined-plane oblique incidence, and successively from described first right-angle surface, described second right-angle surface and described 3rd right-angle surface vertical exit.
Aforesaid photoetching projection objective lens system wave aberration measurement mechanism, described square focus spot after wherein expanding energy after described even smooth focusing objective len system becomes being uniformly distributed of flat-top and focuses on described coupling fiber object lens, is coupled in described multimode optical fiber after described coupling fiber object lens.
Aforesaid photoetching projection objective lens system wave aberration measurement mechanism, the length of wherein said multimode optical fiber is the coherent length that the size of the modal dispersion that the light beam after by described multimode optical fiber is produced is greater than described light beam self.
Aforesaid photoetching projection objective lens system wave aberration measurement mechanism, wherein said lighted mask is positioned in the image planes of described projection objective system to be measured, the front focus of described collimator objective is positioned at the described object plane of projection objective system to be measured and the point of intersection of optical axis, makes to have little numerical aperture NA by the light beam of described projection objective system outgoing to be measured
o, its size is NA
o=NA
i/ M, wherein M and NA
ibe respectively enlargement ratio and the image-side numerical aperture of described projection objective system to be measured.
Aforesaid photoetching projection objective lens system wave aberration measurement mechanism, wherein between described image-forming objective lens and described lighted mask, be also provided with diffuser, increased by light beam angle of divergence after described diffuser of described image-forming objective lens outgoing, and be irradiated to more equably on described lighted mask.
Aforesaid photoetching projection objective lens system wave aberration measurement mechanism, is wherein provided with multiple circular micropore on described lighted mask, and spherical wave produces multiple close to desirable incoherent spherical wave through these circular micropore diffraction.
Aforesaid photoetching projection objective lens system wave aberration measurement mechanism, the multiple described circular micropore on wherein said lighted mask is arranged in microwell array region according to hexagonal mode; Described lighted mask comprises: substrate, metallic film and anti-reflection film, the material of described substrate is fused quartz, two of described substrate relative surfaces are coated with described metallic film and described anti-reflection film respectively, optical density (OD) (OD) value of described metallic film is greater than 6, and described circular micropore on described metallic film, etches formation by the mode of focused ion beam (FIB); Wherein, the diameter d of described circular micropore meets following formula:
In formula, λ is lighting light wave wavelength, NA
ifor the numerical aperture of described projection objective system image space to be measured; Interval S between adjacent two described circular micropores is the condition of zero according to illumination coherence factor, is determined by following formula:
In formula, λ is lighting light wave wavelength, and b is the diameter of the light source irradiating described lighted mask, and L is the distance of described diffuser to described lighted mask; The radius R in described microwell array region is determined by following formula:
In formula, λ is lighting light wave wavelength, a for the cycle of microlens array described in described Shack-Hartmann wavefront sensor, f be the focal length of described collimator objective.
Aforesaid photoetching projection objective lens system wave aberration measurement mechanism, the multiple described circular micropore on wherein said lighted mask is that random alignment is in microwell array region; Described lighted mask comprises: substrate, metallic film and anti-reflection film, the material of described substrate is fused quartz, two of described substrate relative surfaces are coated with described metallic film and described anti-reflection film respectively, optical density (OD) (OD) value of described metallic film is greater than 6, and described circular micropore on described metallic film, etches formation by the mode of focused ion beam (FIB); Wherein, the diameter d of described circular micropore meets following formula:
In formula, λ is lighting light wave wavelength, NA
ifor the numerical aperture of described projection objective system image space to be measured; The radius R in described microwell array region is determined by following formula:
In formula, λ is lighting light wave wavelength, a for the cycle of microlens array described in described Shack-Hartmann wavefront sensor, f be the focal length of described collimator objective.
The object of the invention to solve the technical problems also realizes by the following technical solutions.According to a kind of photoetching projection objective lens system wave aberration measuring method that the present invention proposes, the method comprises the following steps:
1) the first prism beam expander, the second prism beam expander and the 3rd prism beam expander, is adjusted, make the long and narrow rectangular light beam sent from excimer laser successively from the inclined-plane oblique incidence of described first prism beam expander, described second prism beam expander and described 3rd prism beam expander, and successively from the right-angle surface vertical exit of described first prism beam expander, described second prism beam expander and described 3rd prism beam expander, by selecting the refractive index of each prism beam expander, make, from the light beam of described 3rd prism beam expander outgoing, there is square energy distribution, obtain square focus spot;
2), by even smooth focusing objective len system making the energy of the described square focus spot after expanding become being uniformly distributed of flat-top and focus on coupling fiber object lens, being coupled in multimode optical fiber by regulating described coupling fiber object lens;
3), select the length of appropriate described multimode optical fiber, the size of the modal dispersion that light beam is produced after described multimode optical fiber is greater than the coherent length of described light beam self;
4), by image-forming objective lens, the divergent spherical wave by described multimode optical fiber outgoing is imaged onto on lighted mask, diffuser is added between described image-forming objective lens and described lighted mask, make to be increased by the angle of divergence of the light beam of described image-forming objective lens outgoing, and be irradiated on described lighted mask more equably;
5), described lighted mask is regulated, be located in the image planes of projection objective system to be measured, thus making spherical wave diffraction after described lighted mask produce multiple close to desirable incoherent spherical wave, these spherical waves carry its wave aberration information after described projection objective system to be measured; Regulate collimator objective, make its front focus be positioned at the described object plane of projection objective system to be measured and the point of intersection of optical axis, thus make these described spherical waves carrying wave aberration information after described collimator objective, become the plane wave carrying wave aberration information;
6), by the wavefront information of plane wave described in Shack-Hartmann wavefront sensor record, integration obtains measurement result W
t.
7), by described measurement result W
tdeduct the systematic error W that described collimator objective and described Shack-Hartmann wavefront sensor are introduced
s, obtain the wave aberration information W=W of described projection objective system to be measured
t-W
s.
The present invention compared with prior art has obvious advantage and beneficial effect.By technique scheme, a kind of photoetching projection objective lens system wave aberration measurement mechanism of the present invention and method at least have following advantages and beneficial effect: photoetching projection objective lens system wave aberration measurement mechanism of the present invention and method, can realize the integrated quick high accuracy debuging system wave aberration in process of photoetching projection objective lens exposure optical system and detect.Obtain high-quality incoherent illumination light wave by microwell array, while guarantee spherical wave quality, improve the homogeneity arriving energy on Shack-Hartmann wavefront sensor and energy distribution thereof, effectively improve measuring speed and precision.
Above-mentioned explanation is only the general introduction of technical solution of the present invention, in order to technological means of the present invention can be better understood, and can be implemented according to the content of instructions, and can become apparent to allow above and other object of the present invention, feature and advantage, below especially exemplified by preferred embodiment, and coordinate accompanying drawing, be described in detail as follows.
Accompanying drawing explanation
Fig. 1 is the schematic diagram that a preferred embodiment of a kind of photoetching projection objective lens system of the present invention wave aberration measurement mechanism is measured for projection objective system wave aberration.
Fig. 2 is the schematic side view of the lighted mask of microwell array regular array of the present invention.
Fig. 3 is the schematic top plan view of the lighted mask of microwell array regular array of the present invention.
Fig. 4 is the schematic side view of the lighted mask of microwell array random arrangement of the present invention.
Fig. 5 is the schematic top plan view of the lighted mask of microwell array random arrangement of the present invention.
10: excimer laser 20: prism beam expander
21: the first prism beam expander 22: the second prism beam expanders
23: the three prism beam expanders 30: even smooth focusing objective len system
40: coupling fiber object lens 50: multimode optical fiber
60: image-forming objective lens 67: diffuser
70: lighted mask 71: substrate
72: metallic film 73: circular micropore
74: anti-reflection film 75: microwell array region
80: collimator objective 90: Shack-Hartmann wavefront sensor
100: projection objective system
Embodiment
For further setting forth the present invention for the technological means reaching predetermined goal of the invention and take and effect, below in conjunction with accompanying drawing and preferred embodiment, to a kind of photoetching projection objective lens system wave aberration measurement mechanism proposed according to the present invention and its embodiment of method, structure, method, step, feature and effect thereof, be described in detail as follows.
The present invention is the detection adopting Shack-Hartmann wavefront sensor method to carry out projection lens of lithography machine system wave aberration, referring to shown in Fig. 1, is the schematic diagram that a preferred embodiment of a kind of photoetching projection objective lens system of the present invention wave aberration measurement mechanism is measured for projection objective system wave aberration.Photoetching projection objective lens system wave aberration measurement mechanism of the present invention is primarily of the excimer laser 10 producing illuminating bundle, for the prism beam expander 20 that laser beam expands, non-uniform lighting light beam is played to the even smooth focusing objective len system 30 of even light and focussing force, illuminating bundle is coupled into the coupling fiber object lens 40 in multimode optical fiber, the multimode optical fiber 50 of transmission and reduction illuminating bundle coherence, the light beam of multimode optical fiber outgoing is imaged onto the image-forming objective lens 60 that lighted mask gets on, produce the lighted mask 70 of the incoherent spherical wave of high-quality, the collimator objective 80 converting plane wave front before divergent wave to and the Shack-Hartmann wavefront sensor 90 that is used for detecting wavefront aberration information are formed.
Wherein, excimer laser 10, prism beam expander 20, even smooth focusing objective len system 30 and coupling fiber object lens 40 are set in turn in one end of multimode optical fiber 50, the long and narrow rectangular light spot exported from excimer laser 10 obtains square focus spot after prism beam expander 20 expands, and square focus spot is coupled in multimode optical fiber 50 after even smooth focusing objective len system 30 and coupling fiber object lens 40.Image-forming objective lens 60 is set gradually at the other end of multimode optical fiber 50, lighted mask 70, collimator objective 80 and Shack-Hartmann wavefront sensor 90, be imaged onto after image-forming objective lens 60 on lighted mask 70 by the divergent spherical wave of multimode optical fiber 50 outgoing and produce multiple spherical wave, these spherical waves carry its wave aberration information after projection objective system 100 to be measured, become the plane wave carrying wave aberration information through collimator objective is after 80s again, plane wave is divided into multiple beamlet by the microlens array of Shack-Hartmann wavefront sensor 90, these beamlets focus on the detector of Shack-Hartmann wavefront sensor 90, thus record the wave aberration information of projection objective system 100 to be measured.
As shown in Figure 1, prism beam expander 20 of the present invention comprises: the first prism beam expander 21, second prism beam expander 22 and the 3rd prism beam expander 23.Wherein, the first prism beam expander 21, second prism beam expander 22 and the 3rd prism beam expander 23 vary in size, and material is identical, and the right-angle prism that the angular dimension of three drift angles is corresponding consistent respectively, the enlargement ratio X of each right-angle prism meets following relation:
In formula, n is the refractive index of prism, n
0the refractive index of medium residing for prism.The long and narrow rectangular light spot exported from excimer laser 10 obtains square focus spot successively after the first prism beam expander 21, second prism beam expander 22 and the 3rd prism beam expander 23 expand.
Wherein, first inclined-plane of the first prism beam expander 21 is towards excimer laser 10, first right-angle surface of the first prism beam expander 21 is towards the second inclined-plane of the second prism beam expander 22, second prism beam expander 22, second right-angle surface corresponding with aforementioned first right-angle surface is towards the 3rd inclined-plane of the 3rd prism beam expander 23, and the 3rd prism beam expander 23 three right-angle surface corresponding with aforementioned first right-angle surface and the second right-angle surface is towards even smooth focusing objective len system 30.Wherein between the first right-angle surface and the second inclined-plane, and second angle between right-angle surface and the 3rd inclined-plane be acute angle, make the long and narrow rectangular light beam that sends from excimer laser 10 successively from aforementioned first inclined-plane, the second inclined-plane and the 3rd inclined-plane oblique incidence, and successively from aforementioned first right-angle surface, the second right-angle surface and the 3rd right-angle surface vertical exit.
Square focus spot after the present invention expands energy after even smooth focusing objective len system 30 becomes being uniformly distributed of flat-top and focuses on coupling fiber object lens 40, is coupled in multimode optical fiber 50 after coupling fiber object lens 40.
The size of the modal dispersion that the length of multimode optical fiber 50 of the present invention should make the light beam after by multimode optical fiber 50 produce is greater than the coherent length of light beam self.
Lighted mask 70 of the present invention is positioned in the image planes of projection objective system 100 to be measured, the front focus of collimator objective 80 is positioned at the object plane of projection objective system 100 to be measured and the point of intersection of optical axis, has little numerical aperture NA like this by the light beam of projection objective system 100 to be measured outgoing
o, its size is NA
o=NA
i/ M, wherein M and NA
ibe respectively enlargement ratio and the image-side numerical aperture of projection objective system 100 to be measured.
The present invention is also provided with for expanding the illuminating bundle angle of divergence and the diffuser 67 increasing illuminating bundle homogeneity between image-forming objective lens 60 and lighted mask 70, increased by light beam angle of divergence after diffuser 67 of image-forming objective lens 60 outgoing, and be irradiated to more equably on lighted mask 70.
The present invention is provided with multiple circular micropore 73 on lighted mask 70, and spherical wave produces multiple close to desirable incoherent spherical wave through these circular micropore 73 diffraction.
Refer to shown in Fig. 2 and Fig. 3, Fig. 2 is the schematic side view of the lighted mask of microwell array regular array of the present invention.Fig. 3 is the schematic top plan view of the lighted mask of microwell array regular array of the present invention.In one embodiment of this invention, the multiple circular micropore 73 on lighted mask 70 of the present invention is arranged in microwell array region 75 according to hexagonal mode, and lighted mask 70 comprises: substrate 71, metallic film 72 and anti-reflection film 74.Wherein, the material of substrate 71 is fused quartz, two of substrate 71 relative surfaces are coated with metallic film 72 and anti-reflection film 74 respectively, optical density (OD) (OD) value of metallic film 72 is greater than 6, and circular micropore 73 on metallic film 72, etches formation by the mode of focused ion beam (FIB).The diameter d of each circular micropore 73 meets following formula:
In formula, λ is lighting light wave wavelength, NA
ifor the numerical aperture of projection objective system 100 image space to be measured.Interval S between adjacent two circular micropores 73 is the condition of zero according to illumination coherence factor, is determined by following formula:
In formula, λ is lighting light wave wavelength, and b is the diameter of the light source irradiating lighted mask 70, and L is the distance of diffuser 67 to lighted mask 70.The radius R in microwell array region 75 is determined by following formula:
In formula, λ is lighting light wave wavelength, and a is the cycle of microlens array in Shack-Hartmann wavefront sensor 90, and f is the focal length of collimator objective 80.
Refer to shown in Fig. 4 and Fig. 5, Fig. 4 is the schematic side view of the lighted mask of microwell array random arrangement of the present invention.Fig. 5 is the schematic top plan view of the lighted mask of microwell array random arrangement of the present invention.In another embodiment of the invention, the multiple circular micropore 73 on lighted mask 70 of the present invention be random alignment in microwell array region 75, lighted mask 70 comprises: substrate 71, metallic film 72 and anti-reflection film 74.Wherein, the material of substrate 71 is fused quartz, two of substrate 71 relative surfaces are coated with metallic film 72 and anti-reflection film 74 respectively, optical density (OD) (OD) value of metallic film 72 is greater than 6, and circular micropore 73 on metallic film 72, etches formation by the mode of focused ion beam (FIB).The diameter d of each circular micropore 73 meets following formula:
In formula, λ is lighting light wave wavelength, NA
ifor the numerical aperture of projection objective system 100 image space to be measured.The radius R in microwell array region 75 is determined by following formula:
In formula, λ is lighting light wave wavelength, and a is the cycle of microlens array in Shack-Hartmann wavefront sensor 90, and f is the focal length of collimator objective 80.
The present invention, on the one hand, by arranging (arranging by hexagonal mode or random fashion arrangement) microwell array in the image planes of projection objective system 100 to be measured, diffraction produces the incoherent spherical wave that numerical aperture NA is 0.75, improves the homogeneity of energetic transmittance and energy distribution.On the other hand, by collimator objective 80 being arranged at the object space of projection objective system 100 to be measured, make its numerical aperture NA only have 0.1875, thus improve the problem that bulky, the expensive and wave aberration of collimator objective 80 is difficult to accurately demarcate.Wherein, microwell array adopts hexagonal mode to arrange, and the arrangement of circular micropore 73 can be made compacter, and energetic transmittance is higher.And microwell array adopts random fashion arrangement, the coherence before the energy uniformity before micropore diffracted wave can being improved further and reducing diffracted wave further.
The method that the present invention utilizes said apparatus to measure projection lens of lithography machine system wave aberration mainly comprises the following steps:
1) the first prism beam expander 21, second prism beam expander 22 and the 3rd prism beam expander 23, is adjusted, make the long and narrow rectangular light beam that sends from excimer laser 10 successively from the inclined-plane oblique incidence of the first prism beam expander 21, second prism beam expander 22 and the 3rd prism beam expander 23, and successively from the right-angle surface vertical exit of the first prism beam expander 21, second prism beam expander 22 and the 3rd prism beam expander 23, by selecting the refractive index of each prism beam expander, make, from the light beam of the 3rd prism beam expander 23 outgoing, there is square energy distribution, obtain square focus spot.
2), by even smooth focusing objective len system 30 making the energy of the square focus spot after expanding become being uniformly distributed of flat-top and focus on coupling fiber object lens 40, being coupled in multimode optical fiber 50 by regulating coupling fiber object lens 40.
3), select the length of appropriate multimode optical fiber 50, the size of the modal dispersion that light beam is produced after multimode optical fiber 50 is greater than the coherent length of light beam self.
4), by image-forming objective lens 60, the divergent spherical wave by multimode optical fiber 50 outgoing is imaged onto on lighted mask 70, diffuser 67 is added between image-forming objective lens 60 and lighted mask 70, make to be increased by the angle of divergence of the light beam of image-forming objective lens 60 outgoing, and be irradiated to more equably on lighted mask 70.
5), lighted mask 70 is regulated, be located in the image planes of projection objective system 100 to be measured, thus making spherical wave diffraction after lighted mask 70 produce multiple close to desirable incoherent spherical wave, these spherical waves carry its wave aberration information after projection objective system 100 to be measured; Regulate collimator objective 80, make its front focus be positioned at the object plane of projection objective system 100 to be measured and the point of intersection of optical axis, thus make these spherical waves carrying wave aberration information become the plane wave carrying wave aberration information through collimator objective is after 80s.
6), by Shack-Hartmann wavefront sensor 90 record the wavefront information that plane wave carries, integration obtains measurement result W
t.
7), by measurement result W
tdeduct the systematic error W that collimator objective 80 and Shack-Hartmann wavefront sensor 90 are introduced
s, obtain the wave aberration information W=W of projection objective system 100 to be measured
t-W
s.
The above, it is only preferred embodiment of the present invention, not any pro forma restriction is done to the present invention, although the present invention discloses as above with preferred embodiment, but and be not used to limit the present invention, any those skilled in the art, do not departing within the scope of technical solution of the present invention, when the method and technology contents that can utilize above-mentioned announcement are made a little change or be modified to the Equivalent embodiments of equivalent variations, in every case be the content not departing from technical solution of the present invention, according to any simple modification that technical spirit of the present invention is done above embodiment, equivalent variations and modification, all still belong in the scope of technical solution of the present invention.
Claims (10)
1. a photoetching projection objective lens system wave aberration measurement mechanism, it is characterized in that, this device comprises: excimer laser (10), prism beam expander (20), even smooth focusing objective len system (30), coupling fiber object lens (40), multimode optical fiber (50), image-forming objective lens (60), lighted mask (70), collimator objective (80) and Shack-Hartmann wavefront sensor (90);
Wherein, described excimer laser (10), described prism beam expander (20), described even smooth focusing objective len system (30) and described coupling fiber object lens (40) are set in turn in one end of described multimode optical fiber (50), the long and narrow rectangular light spot exported from described excimer laser (10) obtains square focus spot after described prism beam expander (20) expands, and described square focus spot is coupled in described multimode optical fiber (50) after described even smooth focusing objective len system (30) and described coupling fiber object lens (40);
Described image-forming objective lens (60) is set gradually at the other end of described multimode optical fiber (50), described lighted mask (70), described collimator objective (80) and described Shack-Hartmann wavefront sensor (90), after described image-forming objective lens (60), the multiple spherical wave of the upper generation of described lighted mask (70) is imaged onto by the divergent spherical wave of described multimode optical fiber (50) outgoing, these spherical waves carry its wave aberration information after projection objective system to be measured (100), the plane wave carrying wave aberration information is become again after described collimator objective (80), described plane wave is divided into multiple beamlet by the microlens array of described Shack-Hartmann wavefront sensor (90), these beamlets focus on the detector of described Shack-Hartmann wavefront sensor (90), record the wave aberration information of described projection objective system to be measured (100).
2. photoetching projection objective lens system wave aberration measurement mechanism according to claim 1, is characterized in that wherein said prism beam expander (20) comprising: the first prism beam expander (21), the second prism beam expander (22) and the 3rd prism beam expander (23); Described first prism beam expander (21), described second prism beam expander (22) and described 3rd prism beam expander (23) vary in size, and material is identical, and the right-angle prism that the angular dimension of three drift angles is corresponding consistent respectively; Wherein the enlargement ratio X of each right-angle prism meets following relation:
In formula, n is the refractive index of prism, n
0the refractive index of medium residing for prism; The long and narrow rectangular light spot exported from described excimer laser (10) after described first prism beam expander (21), described second prism beam expander (22) and described 3rd prism beam expander (23) expand, obtains described square focus spot successively;
Wherein, first inclined-plane of described first prism beam expander (21) is towards described excimer laser (10), first right-angle surface of described first prism beam expander (21) is towards the second inclined-plane of described second prism beam expander (22), described second prism beam expander (22) second right-angle surface corresponding with described first right-angle surface is towards the 3rd inclined-plane of described 3rd prism beam expander (23), described 3rd prism beam expander (23) three right-angle surface corresponding with described first right-angle surface and described second right-angle surface is towards described even smooth focusing objective len system (30), between wherein said first right-angle surface and described second inclined-plane, and the angle between described second right-angle surface and described 3rd inclined-plane is acute angle, make the long and narrow rectangular light beam sent from described excimer laser (10) successively from described first inclined-plane, described second inclined-plane and described 3rd inclined-plane oblique incidence, and successively from described first right-angle surface, described second right-angle surface and described 3rd right-angle surface vertical exit.
3. photoetching projection objective lens system wave aberration measurement mechanism according to claim 1, it is characterized in that the energy after described even smooth focusing objective len system (30) of the described square focus spot after wherein expanding becomes being uniformly distributed of flat-top and focuses on described coupling fiber object lens (40), be coupled in described multimode optical fiber (50) after described coupling fiber object lens (40).
4. photoetching projection objective lens system wave aberration measurement mechanism according to claim 1, is characterized in that the length of wherein said multimode optical fiber (50) is the coherent length that the size of the modal dispersion that the light beam after by described multimode optical fiber (50) is produced is greater than described light beam self.
5. photoetching projection objective lens system wave aberration measurement mechanism according to claim 1, it is characterized in that wherein said lighted mask (70) is positioned in the image planes of described projection objective system to be measured (100), the front focus of described collimator objective (80) is positioned at the described object plane of projection objective system to be measured (100) and the point of intersection of optical axis, makes to have little numerical aperture NA by the light beam of described projection objective system to be measured (100) outgoing
o, its size is NA
o=NA
i/ M, wherein M and NA
ibe respectively enlargement ratio and the image-side numerical aperture of described projection objective system to be measured (100).
6. photoetching projection objective lens system wave aberration measurement mechanism according to claim 1, it is characterized in that wherein between described image-forming objective lens (60) and described lighted mask (70), being also provided with diffuser (67), increased by light beam angle of divergence after described diffuser (67) of described image-forming objective lens (60) outgoing, and be irradiated to more equably on described lighted mask (7).
7. photoetching projection objective lens system wave aberration measurement mechanism according to claim 6, it is characterized in that wherein on described lighted mask (70), being provided with multiple circular micropore (73), spherical wave produces multiple close to desirable incoherent spherical wave through these circular micropore (73) diffraction.
8. photoetching projection objective lens system wave aberration measurement mechanism according to claim 7, is characterized in that the multiple described circular micropore (73) on wherein said lighted mask (70) is arranged in microwell array region (75) according to hexagonal mode; Described lighted mask (70) comprising: substrate (71), metallic film (72) and anti-reflection film (74), the material of described substrate (71) is fused quartz, two of described substrate (71) relative surfaces are coated with described metallic film (72) and described anti-reflection film (74) respectively, the optical density value of described metallic film (72) is greater than 6, and described circular micropore (73) on described metallic film (72), etches formation by the mode of focused ion beam;
Wherein, the diameter d of described circular micropore (73) meets following formula:
In formula, λ is lighting light wave wavelength, NA
ifor the numerical aperture of described projection objective system to be measured (100) image space;
Interval S between adjacent two described circular micropores (73) is the condition of zero according to illumination coherence factor, is determined by following formula:
In formula, λ is lighting light wave wavelength, and b is the diameter of the light source irradiating described lighted mask (70), and L is the distance of described diffuser (67) to described lighted mask (70);
The radius R of described microwell array region (75) is determined by following formula:
In formula, λ is lighting light wave wavelength, and a is the cycle of microlens array described in described Shack-Hartmann wavefront sensor (90), and f is the focal length of described collimator objective (80).
9. photoetching projection objective lens system wave aberration measurement mechanism according to claim 7, is characterized in that the multiple described circular micropore (73) on wherein said lighted mask (70) is that random alignment is in microwell array region (75); Described lighted mask (70) comprising: substrate (71), metallic film (72) and anti-reflection film (74), the material of described substrate (71) is fused quartz, two of described substrate (71) relative surfaces are coated with described metallic film (72) and described anti-reflection film (74) respectively, the optical density value of described metallic film (72) is greater than 6, and described circular micropore (73) on described metallic film (72), etches formation by the mode of focused ion beam;
Wherein, the diameter d of described circular micropore (73) meets following formula:
In formula, λ is lighting light wave wavelength, NA
ifor the numerical aperture of described projection objective system to be measured (100) image space;
The radius R of described microwell array region (75) is determined by following formula:
In formula, λ is lighting light wave wavelength, and a is the cycle of microlens array described in described Shack-Hartmann wavefront sensor (90), and f is the focal length of described collimator objective (80).
10. a photoetching projection objective lens system wave aberration measuring method, it is characterized in that, the method comprises the following steps:
1), adjust the first prism beam expander (21), second prism beam expander (22) and the 3rd prism beam expander (23), make the long and narrow rectangular light beam sent from excimer laser (10) successively from described first prism beam expander (21), the inclined-plane oblique incidence of described second prism beam expander (22) and described 3rd prism beam expander (23), and successively from described first prism beam expander (21), the right-angle surface vertical exit of described second prism beam expander (22) and described 3rd prism beam expander (23), by selecting the refractive index of each prism beam expander, make, from the light beam of described 3rd prism beam expander (23) outgoing, there is square energy distribution, obtain square focus spot,
2), by even smooth focusing objective len system (30) making the energy of the described square focus spot after expanding become being uniformly distributed of flat-top and focus on coupling fiber object lens (40), being coupled in multimode optical fiber (50) by regulating described coupling fiber object lens (40);
3), select the length of appropriate described multimode optical fiber (50), the size of the modal dispersion that light beam is produced after described multimode optical fiber (50) is greater than the coherent length of described light beam self;
4), by image-forming objective lens (60), the divergent spherical wave by described multimode optical fiber (50) outgoing is imaged onto on lighted mask (70), diffuser (67) is added between described image-forming objective lens (60) and described lighted mask (70), make to be increased by the angle of divergence of the light beam of described image-forming objective lens (60) outgoing, and be irradiated on described lighted mask (70) more equably;
5) described lighted mask (70), is regulated, be located in the image planes of projection objective system to be measured (100), thus making spherical wave diffraction after described lighted mask (70) produce multiple close to desirable incoherent spherical wave, these spherical waves carry its wave aberration information after described projection objective system to be measured (100); Regulate collimator objective (80), make its front focus be positioned at the described object plane of projection objective system to be measured (100) and the point of intersection of optical axis, thus make these described spherical waves carrying wave aberration information become the plane wave carrying wave aberration information after described collimator objective (80);
6), recorded the wavefront information of described plane wave by Shack-Hartmann wavefront sensor (90), integration obtains measurement result W
t.
7), by described measurement result W
tdeduct the systematic error W that described collimator objective (80) and described Shack-Hartmann wavefront sensor (90) are introduced
s, obtain the wave aberration information W=W of described projection objective system to be measured (100)
t-W
s.
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