• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
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    • 专利摘要:
    A metrology apparatus for determining a characteristic of a structure manufactured on a substrate comprising an illumination branch for illuminating the structure with radiation and a detection branch for guiding a portion of the scattered radiation towards a sensor suitable for recording radiation impinging on the sensor, the detection branch comprising an optical element for capturing a portion of the scattered radiation excluding radiation from the specular reflection, the detection branch further comprising a reception unit for receiving reference radiation being coherent with respect to the radiation that illuminates the structure, the detection branch is configured to guide the reference radiation to the sensor for interfering, on the sensor, with the scattered radiation that is captured by the optical element.
    公开号:NL2021848A
    申请号:NL2021848
    申请日:2018-10-22
    公开日:2018-11-06
    发明作者:Tomas Tenner Vasco；Fitzgerald De Boer Johannes；Jeffrey Den Boef Arie
    申请人:Stichting Vu；Stichting Nederlandse Wetenschappelijk Onderzoek Inst；Univ Amsterdam；Asml Netherlands Bv；
    IPC主号:
    专利说明:

    Octrooicentrum
    Θ 2021848
    (21) Aanvraagnummer: 2021848 © Aanvraag ingediend: 22 oktober 2018 @ Int. CL:
    G03F 7/20 (2018.01) © Voorrang:
    april 2018 EP 18166312.1 (41) Aanvraag ingeschreven:
    november 2018 © Aanvraag gepubliceerd:
    november 2018 (71) Aanvrager(s):
    Stichting VU te Amsterdam.
    Stichting Nederlandse Wetenschappelijk Onderzoek Instituten te Utrecht.
    Universiteit van Amsterdam te Amsterdam.
    ASML Netherlands B.V. te Veldhoven.
    © Uitvinder(s):
    Vasco Tomas Tenner te Amsterdam.
    Johannes Fitzgerald de Boer te Amsterdam. Arie Jeffrey den Boef te Veldhoven.
    (74) Gemachtigde:
    ir. A.J. Maas te Veldhoven.
    © Holographic metrology apparatus.
    (57) A metrology apparatus for determining a characteristic of a structure manufactured on a substrate comprising an illumination branch for illuminating the structure with radiation and a detection branch for guiding a portion of the scattered radiation towards a sensor suitable for recording radiation impinging on the sensor, the detection branch comprising an optical element for capturing a portion of the scattered radiation excluding radiation from the specular reflection, the detection branch further comprising a reception unit for receiving reference radiation being coherent with respect to the radiation that illuminates the structure, the detection branch is configured to guide the reference radiation to the sensor for interfering, on the sensor, with the scattered radiation that is captured by the optical element.
    NL A 2021848
    Deze publicatie komt overeen met de oorspronkelijk ingediende stukken.
    Holographic metrology apparatus.
    Integrated circuits are often manufactured by means of a manufacturing process in which layers are formed on top of each other on a substrate by means of several process steps. One of the process steps is photolithography which may use electromagnetic radiation in the deep ultraviolet (DUV) spectral range or in the extreme ultraviolet (EUV) spectral range. The substrate is often a Silicon wafer. The smallest dimensions of the manufactured structures are in the nanometer range.
    During the manufacturing process there is a need to inspect the manufactured structures and/or to measure characteristics of the manufactured structures. Suitable inspection and metrology apparatuses are known in the art. One of the known metrology apparatuses is a scatterometer and, for example, by a dark field scatterometer.
    Patent application publication US2016/0161864A1, patent application publication US2010/0328655A1 and patent application publication US2006/0066855A1 discus embodiments of a photolithographic apparatus and embodiments of a scatterometer. The cited documents are herein incorporated by reference. There is a need for improved metrology apparatuses for inspecting and/or measuring characteristics of structures on a substrate.
    According to the invention, a metrology apparatus is disclosed for determining a characteristic of a structure manufactured on a substrate. The metrology apparatus uses the principles of holography to measure a complex radiation field of radiation scattered by the structure. The metrology apparatus comprises an illumination branch for illuminating the structure with radiation. The metrology apparatus comprises a detection branch for guiding a portion of the scattered radiation towards a sensor suitable for recording radiation impinging on the sensor. The detection branch comprises an optical element for capturing a portion of the scattered radiation excluding radiation from the specular reflection. The detection branch further comprises a reception unit for receiving reference radiation being coherent with respect to the radiation that illuminates the structure. The detection branch is configured to guide the reference radiation to the sensor for interfering, on the sensor, with the scattered radiation that is captured by the optical element.
    The above metrology apparatus is a holographic setup and at the sensor an image is formed that is the result of interference between the reference radiation and a portion of the radiation scattered by the structure. Based on one or more images formed on the sensor, a complex field of radiation can be determined that comprises information about the scattered radiation. The optical element, and optional further optics, that guide the radiation towards the sensor contains aberrations that degrade the image formation on the camera. If the characteristics of the optical element are known, it is relatively easy to back-propagate the measured complex field of the scattered radiation towards the complex field that is scattered by the structure on the substrate. Having knowledge of the complex field of the scattered radiation is advantageous because it provides more information that can be used to determine characteristics of the structure on the substrate. For example, in European patent application EP18158745.2, filed on February 27, 2018, it has been disclosed how phase information of the scattered radiation can be used to determine overlay errors between structures of different layers on the substrate. European patent application EP18158745.2 is hereby incorporated by reference.
    In an embodiment, the optical element is not shared with the illumination branch.
    Optionally, the sensor is arranged in a pupil plane of the optical element, or in a plane conjugate with the pupil plane. Optionally, the sensor is arranged in a field plane of the optical element. Optionally, the sensor is arranged in a plane that is configured in between the pupil plane of the optical element and the field plane.
    In an embodiment, the optical element has a low Numerical Aperture (NA). Optionally, the NA of the optical element is lower than 0.3, optionally, lower than 0.2. Optionally, the optical element is a piano convex lens. The piano convex lens is isoplanatic and has relatively high aberrations. Optionally, the optical element is a piano asphere. The piano asphere is non-isoplanatic and has relatively low aberrations.
    In an embodiment, the optical element has a high Numerical Aperture (NA). Optionally, the NA of the optical element is higher than 0.5, optionally, higher than 0.65, optionally, higher than 0.8.
    In an embodiment, lhe metrology apparatus has a beam splitter that is configured to split a received radiation beam into a first beam with illumination radiation and into a second beam of reference radiation. Optionally, the metrology apparatus comprises a delay element in the optical path of the first beam or the second beam for controlling a phase difference between the first beam and the second beam.
    Optionally, the metrology apparatus comprises a radiation sources being configured to generate a beam of temporal and spatial coherent, or temporal and spatial partially coherent, or temporal coherent and spatially partially incoherent electromagnetic radiation. This beam of radiation is provided to the beam splitter.
    Optionally the radiation has a wavelength in the visible wavelength range. Optionally, the radiation has a wavelength in the Infrared wavelength range. Optionally, the radiation has a wavelength in the Ultraviolet wavelength range. Optionally, the radiation has a wavelength in the deep ultraviolet (DUV) wavelength range. Optionally, the radiation has a wavelength in the extreme ultraviolet (EUV) wavelength range. Optionally, the radiation source is configured to generate radiation at a controllable wavelength. Optionally, the radiation source comprises a filtering unit for generating the radiation of a controllable wavelength from radiation having a broadband spectral distribution.
    Optionally, the metrology apparatus comprises a processing unit for determining a characteristic of the structure on the substrate. The processing unit being coupled to the sensor for receiving a signal comprising information about radiation impinging on the sensor. Optionally, the processing unit being configured to correct for aberrations of the optical element. Optionally, the processing unit being configured to correct for the aberration in the pupil plane of the optical element.
    Optionally, the metrology tool performs different measurements with radiation at different wavelengths and the processing unit being configured to use the different measurements to determine the structure on the substrate.
    Figure 1 presents an embodiment of a metrology apparatus 100. The metrology apparatus comprises a sensor 102 which may be a pixelated image sensor that is being configured to register an image of impinging radiation. Optionally, the metrology apparatus comprises a filter 104 that is configured to filter the radiation that impinges on the sensor 102. The filter 104 may be a polarizing filter.
    Radiation 119 of (at least a portion of) a non-zero diffraction order of radiation scattered by a structure 118 on a substrate is guided along a detection branch from the structure 118 towards the sensor 102. In general radiation 119 is not the radiation of the specular reflection and if the document refers to non-zero diffraction order, one may also read radiation that excludes the specular reflected radiation. The detection branch also comprises a beam splitter 106 which allows the ( partial ) transmission of radiation 119 towards the sensor 102 and which reflects reference radiation 126 towards the sensor 102 as well. The detection branch at least comprises one optical element 120 that captures a portion of radiation scattered by the structure 118. In an embodiment, the optical element 120 captures a non-zero diffraction order of the scattered radiation. The optical element 120 may also capture multiple non-zero diffraction orders. The zeroth diffraction order (not shown in the figure) is reflected by the structure 118 at a reflection angle that is equal to the angle of incidence of illumination radiation 114. The detection branch may comprise a further optical element 108. The optical element 120 and the further optical element 108 may be refractive or reflective elements such as lenses or mirrors. Also a combination of lenses and mirrors can be used. Embodiments of the optical element 120 are discussed previously. The sensor 102 may be arranged in a pupil plane, or a plane conjugate with the pupil plane, of the optical element. In another embodiment, the sensor 102 may be arranged in the field plane of optical element 120.
    The metrology apparatus also comprises an illumination branch which illuminates the structure 118 on the substrate. The illumination branch comprises a illumination radiation reception unit 112 that receives, for example, from a glass fiber 110 the illumination radiation. The illumination radiation reception unit 112 transmits the illumination radiation 114 towards a mirror 116 which reflects the illumination radiation
    114 towards the structure 118. In the drawn embodiment the illumination radiation impinges on the structure 118 at a non-zero angle of incidence. In another embodiment the illumination radiation impinges on the structure 118 at a non-zero angle of incidence and an optical axis of the detection branch has a nonzero angle with respect to a normal to the substrate on which the structure 118 is present. In the embodiment of Figure 1, optical element 120 is not shared with the illumination branch of the metrology apparatus.
    The metrology apparatus also comprises a reference illumination reception unit 124 which may receive reference radiation from, for example, a glass fiber 122. The reference radiation 126 is transmitted by the illumination reception unit 124 towards a mirror 128 which reflects the illumination radiation 126 towards element beam splitter 106. The reference radiation is coherent with respect to the illumination radiation 114.
    The sensor 102 may be coupled to a processing unit 132. The sensor 102 provides a signal 130 that represents information of the radiation that impinges on the sensor 102. Optional tasks of processing unit 132 have been discussed above.
    In order to generate the illumination radiation and the reference radiation that are coherent with respect to each other, the metrology apparatus may comprise a beam splitting arrangement 200 as presented in Figure 2. A source 202 may provide a beam of radiation 222. This may be coherent radiation having a sufficient spatial coherence length and having sufficient temporal coherence. In general the radiation is one of temporal and spatial coherent, or temporal and spatial partially coherent, or temporal coherent and spatially partially incoherent electromagnetic radiation. The beam of radiation 222 is provided towards a beam splitter 220. In between the source 202 and the beam splitter 220 a filter unit 224 may be provided. The filter unit may be provided with interchangeable or controllable filters that allow the transmission of radiation of a single wavelength or only in a narrow spectral range towards the beam splitter 220. From the beam splitter two beams of radiation are transmitted.
    One of the beams of radiation may be the reference radiation and another one of the beams of radiation may be the illumination radiation. In the example of Figure 2 beam 204 comprises illumination radiation which may be coupled by unit 206 into a glass fiber 208 that may be coupled to glass fiber 110 of Figure 1.
    The other beam of radiation that is transmitted by the beam splitter 220 is transmitted towaids a mirror 210 with a triangular cross-sec tion. In the example of Figure 2 this beam of radiation is the reference radiation 212. A first surface of mirror 210 reflects the reference radiation towards a mirror 218 that is formed by a recess in a material. The cross sectional shape of the recess is triangular as well. The mirror 218 reflects the reference radiation at a slightly different position back to a second surface of mirror 210. The second surface reflects the reference radiation 212 towards a unit that couples the reference radiation into a fiber 214 which may be coupled to glass fiber 122 of Figure 1. . By translating the recessed mirror 218 in the directions indicated by arrow 216 a controllable time delay (=phase difference) between the illumination beam and reference beam can be realized. Also other means can be used to introduce the controllable time delay, such as, for example, by an optical wedge that can be moved in and out the beam. In the above embodiments of Figures 1 and 2, glass fibers 110, 112, 208, 214 are used to transport radiation from the beam splitting arrangement towards the reception units 112, 124. The use of glass fibers is not essential. Also other means may be used to transport or transmit the radiation towards the reception units 112, 124. In an embodiment, the beam splitting arrangement 200 is completely integrated with the arrangement shown in Figure 1 such that the radiation for illuminating the structure is transmitted directly to the structure 118 on the substrate and such that the reference radiation is transported directly to the beam splitter 106 or the sensor 102.
    It is to be noted that the embodiments of Figures 1 and 2 are example of possible setups. The skilled person may come up with variation that have still the same functionality and are within the spirit of the invention.
    A further embodiment is disclosed in the subsequent numbered clause:
    1. A metrology apparatus for determining a characteristic of a structure manufactured on a substrate comprising
    - an illumination branch for illuminating the structure with radiation,
    - a detection branch for guiding a portion of the scattered radiation towards a sensor suitable for recording radiation impinging on the sensor, the detection branch comprising an optical element for capturing a portion of the scattered radiation excluding radiation from the specular reflection, the detection branch further comprising a reception unit for receiving reference radiation being coherent with respect to the radiation that illuminates the structure, the detection branch is configured to guide the reference radiation to the sensor for interfering, on the sensor, with the scattered radiation that is captured by the optical element.
    权利要求:
    Claims (2)
    [1]
    CONCLUSION
    A lithography apparatus comprising:
    an illumination device adapted to provide a radiation beam;
    5 a carrier constructed for supporting a patterning device, which patterning device is capable of applying a pattern in a section of the radiation beam to form a patterned radiation beam;
    a substrate table constructed to support a substrate; and a projection device adapted to project the patterned radiation beam onto a
    The target area of the substrate, characterized in that the substrate table is adapted to position the target area of the substrate in a focal plane of the projection device.
    1/2 ns
    [2]
    2/2
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    引用文献:
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    法律状态:
    优先权:
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