CN114509408A - Scattering measurement device and method - Google Patents

Scattering measurement device and method Download PDF

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Publication number
CN114509408A
CN114509408A CN202011289171.2A CN202011289171A CN114509408A CN 114509408 A CN114509408 A CN 114509408A CN 202011289171 A CN202011289171 A CN 202011289171A CN 114509408 A CN114509408 A CN 114509408A
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light
light intensity
prism
unit
illumination beam
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朱申磊
杨晓青
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Shanghai Micro Electronics Equipment Co Ltd
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Shanghai Micro Electronics Equipment Co Ltd
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G01B11/0608—Height gauges
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G01B11/0616—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating
    • G01B11/0641—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating with measurement of polarization
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/003—Light absorbing elements
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N2021/4735—Solid samples, e.g. paper, glass

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

The invention provides a scattering measurement device and a method, comprising the following steps: a light source for generating an illumination beam; a beam splitter for splitting the illumination beam into a first illumination beam and a second illumination beam; an objective lens which converges the first illumination beam to the substrate surface and collects light scattered by the substrate surface; an imaging unit that images a pupil of the objective lens to the detection unit; the reflecting unit is used for deflecting the optical axis of the second illuminating light beam, reflecting the second illuminating light beam and imaging the second illuminating light beam on the detecting unit through the imaging unit; wherein the reflection unit comprises at least one optical element, the presence of which in the reflection unit comprises a neutral absorbing material; the neutral absorption material refers to a material having a fluctuation rate of absorption rate smaller than a preset value in a preset wavelength band. The embodiment of the invention reduces the light intensity difference of the S polarized light and the P polarized light, solves the measurement error caused by the light intensity difference of the S polarized light and reduces the technical difficulty and the cost.

Description

Scattering measurement device and method
Technical Field
The present invention relates to scatterometry, and particularly to a scatterometry device and a scatterometry method.
Background
The scatterometry technique provides a non-contact, non-destructive, fast, high-precision, low-cost means for measuring the morphological parameters of semiconductors, and gradually becomes an important link of Advanced Process Control (APC), thus powerfully supporting the further development of technical nodes of 32nm and below. The measurement object of the scattering measurement technology is a semiconductor pattern structure with certain periodicity, mainly a photoresist dense line or a hole array and the like. The topographic structure parameters obtained by the scatterometry technique mainly include Height, CD (Critical Dimension topographic structure), SWA (Side-Wall Angle), OV (overlay), and the like.
In the prior art, a device structure is proposed, in which a reflection unit is disposed to introduce a monitoring optical path into an imaging optical path, so that the light intensity of the monitoring light can be used to normalize the light source fluctuation of the whole illumination light source, thereby reducing the measurement error caused by the illumination light fluctuation during the measurement of the reference light and the sample surface reflected light. However, the reflection unit may introduce reflectivity errors under different polarized lights, so that there is an error in the process of normalizing the light intensity of the signal light by the monitoring light.
Disclosure of Invention
Embodiments of the present invention provide a scattering measurement apparatus and method to reduce a difference between light intensities of S-polarized light and P-polarized light, solve a measurement error caused by the difference between the light intensities of the S-polarized light and the P-polarized light, and reduce technical difficulty and cost.
In a first aspect, an embodiment of the present invention provides a scatterometry device, including:
a light source for generating an illumination beam;
a beam splitter for splitting the illumination beam into a first illumination beam and a second illumination beam;
the objective lens converges the first illumination light beam to the surface of the substrate and collects light scattered by the surface of the substrate;
an imaging unit and a detection unit, the imaging unit imaging a pupil of the objective lens to the detection unit;
the reflecting unit is used for deflecting the optical axis of the second illuminating light beam, reflecting the second illuminating light beam and imaging the second illuminating light beam on the detecting unit through the imaging unit;
wherein the reflective unit comprises at least one optical element, the presence of at least one optical element in the reflective unit comprising a neutral absorbing material; the neutral absorption material refers to a material of which the fluctuation rate of the absorption rate in a preset wave band is less than a preset value.
Optionally, the optical element in the reflection unit includes a prism, and the prism includes at least two inclined reflection surfaces, and the at least two inclined reflection surfaces are used for deflecting the optical axis of the second illumination beam, and imaging the second illumination beam onto the detection unit through the imaging unit after reflecting the second illumination beam;
the prism includes the neutral absorbing material.
Optionally, the optical element in the reflection unit comprises a prism and at least one light intensity regulating element;
the prism comprises at least two inclined reflecting surfaces, and the at least two inclined reflecting surfaces are used for deflecting the optical axis of the second illuminating light beam and imaging the second illuminating light beam onto the detection unit through the imaging unit after reflecting the second illuminating light beam;
the at least one light intensity modulating element, including the neutral absorbing material, is located in a propagation path of the second illumination beam.
Optionally, the at least one light intensity modulating element comprises a first light intensity modulating element located on an optical path between the beam splitter and the prism.
Optionally, the at least one light intensity adjusting and controlling element includes a second light intensity adjusting and controlling element, the second light intensity adjusting and controlling element is located on one side of the at least one inclined reflecting surface, the second illumination light beam projected to the inclined reflecting surface penetrates through the inclined reflecting surface and the second light intensity adjusting and controlling element, and is reflected back to the prism by the second light intensity adjusting and controlling element far away from the surface of one side of the prism.
Optionally, the optical element in the reflection unit further includes an antireflection film, and the antireflection film is located between the second light intensity adjusting and controlling element and the inclined reflection surface of the prism.
Optionally, the at least one light intensity regulating element comprises a third light intensity regulating element located on an optical path between the beam splitter and the imaging unit.
Optionally, the light intensity regulating element is shaped as a parallel flat plate.
Optionally, the prism is a triangular prism.
Optionally, the optical element in the reflection unit further includes a total reflection film on a side of at least one of the inclined reflection surfaces.
Optionally, the absorbance of the neutral absorbing material has a volatility of less than 5% in the 400nm to 700nm wavelength band.
Optionally, the neutral absorbing material comprises neutral gray glass.
In a second aspect, an embodiment of the present invention provides a method for a scatterometry device based on the first aspect, including:
the light intensity regulation and control of the monitoring light are realized by changing the optical path of the second illumination beam in the neutral absorption material.
Optionally, the optical element in the reflection unit includes a prism, and the prism includes at least two inclined reflection surfaces, and the at least two inclined reflection surfaces are used for deflecting the optical axis of the second illumination beam and imaging the second illumination beam onto the detection unit through the imaging unit after being reflected; the prism comprises the neutral absorbing material;
the light intensity regulation and control of the monitoring light is realized by changing the optical path of the second illumination beam in the neutral absorption material, and the method comprises the following steps:
and the light intensity regulation and control of the monitoring light is realized by changing the size of the prism.
Optionally, the optical element in the reflection unit comprises a prism and at least one light intensity regulating element; the prism comprises at least two inclined reflecting surfaces, and the at least two inclined reflecting surfaces are used for deflecting the optical axis of the second illuminating light beam and imaging the second illuminating light beam onto the detection unit through the imaging unit after reflecting the second illuminating light beam; said at least one light intensity modulating element comprises said neutral absorbing material in a propagation path of said second illumination beam;
the light intensity regulation and control of the monitoring light is realized by changing the optical path of the second illumination beam in the neutral absorption material, and the method comprises the following steps:
and the light intensity regulation and control of the monitoring light are realized by changing the thickness of the light intensity regulation and control element.
According to the embodiment of the invention, at least one optical element in the reflection unit comprises the neutral absorption material, and the optical element comprising the neutral absorption material is used for realizing light intensity modulation on the monitoring light spot, so that the light intensity attenuation of a specific proportion can be realized on a full-wave-band light source adopted for measurement. The scattering measurement device provided by the embodiment of the invention has the advantages of simple structure, simple implementation process and lower assembly difficulty, reduces the light intensity difference of S polarized light and P polarized light while realizing light intensity modulation, solves the measurement error caused by the polarized light intensity difference, and reduces the technical difficulty and cost.
Drawings
Fig. 1 is a schematic structural diagram of a scatterometry device according to an embodiment of the present invention;
FIG. 2 is a diagram of the detection of monitoring spots and signal spots of a horizontal marker using the scatterometry device of FIG. 1;
FIG. 3 is a diagram of the detection of monitoring spots and signal spots of a vertical square marker using the scatterometry device of FIG. 1;
FIG. 4 is a schematic view of a horizontal direction mark provided by an embodiment of the present invention;
FIG. 5 is a schematic view of a vertical orientation marker provided by an embodiment of the present invention;
FIG. 6 is a schematic structural diagram of another scatterometry device provided by an embodiment of the present invention;
FIG. 7 is a schematic diagram of a reflection unit of the scatterometry device shown in FIG. 6;
FIG. 8 is a graph of the internal transmittance of a neutral absorbent material of 1mm thickness;
FIG. 9 is a diagram of the detection of monitoring and signal spots obtained using the scatterometry device of FIG. 6;
FIG. 10 is a schematic view of another configuration of a reflection unit in the scatterometry device shown in FIG. 6;
FIG. 11 is a schematic view of another configuration of a reflection unit in the scatterometry device shown in FIG. 6;
fig. 12 is a schematic structural diagram of another scatterometry device according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention. It should be further noted that, for the convenience of description, only some of the structures related to the present invention are shown in the drawings, not all of the structures.
According to researches, reflectivity errors under different polarized lights can be introduced into the reflection unit, so that errors exist in the process of utilizing the monitoring light to normalize the light intensity of the signal light, the light intensity of the monitoring light is kept to be the same or nearly the same as the light intensity of the signal light, and the errors in the normalization process can be reduced.
Fig. 1 is a schematic structural diagram of a scatterometry device according to an embodiment of the present invention, and referring to fig. 1, the scatterometry device includes a light source 11, a beam splitter 15, an objective lens 16, an imaging unit 18, a detection unit 19, and a reflection unit 20. The light source 11 is used to generate an illumination beam. The beam splitter 15 is used to split the illumination beam into a first illumination beam and a second illumination beam. The objective lens 16 condenses the first illumination beam onto the surface of the substrate W and collects light scattered by the surface of the substrate W. The imaging unit 18 images the pupil of the objective 16 to the detection unit 19. The reflection unit 20 is configured to deflect the optical axis of the second illumination beam, reflect the second illumination beam, and image the second illumination beam onto the detection unit 19 through the imaging unit 18. The reflection unit 20 includes a prism 21, a total reflection film 23, and a medium-splitting film 17, the total reflection film 23 is located on one inclined reflection surface side of the prism 21, and the medium-splitting film 17 is located on the other inclined reflection surface side.
Exemplarily, the scatterometry device further includes an illumination collimation unit 12, an illumination mode switching unit 13, an illumination relay unit 14, and a processing unit 110. The illumination light beam generated by the light source 11 passes through the illumination collimating unit 12, the illumination mode switching unit 13, and the illumination relay unit 14 in this order, and then is projected onto the beam splitter 15. The illumination mode switching unit 13 and the illumination relay unit 14 can realize modulation of the illumination field of view, for example, realize S-polarized light and P-polarized light illumination. The processing unit 110 is connected to the detection unit 19 and is configured to process the image formed by the detection unit 19. According to the image processing requirement, the detection unit 19 needs to collect the monitoring light spot (as shown by the left light spot in fig. 2 and 3) at the same time as the signal light spot (as shown by the right light spot in fig. 2 and 3). In order to keep the light intensity of the monitoring light the same as or nearly the same as that of the signal light, the reflection unit 20 needs to modulate the light intensity of the monitoring light by plating a dielectric-splitting film 17 on the inclined reflection surface of the prism 21 (fig. 1 also illustrates another triangular prism on the side of the dielectric-splitting film 17 far away from the prism 21), and the splitting ratio of the dielectric-splitting film 17 is usually less than 10%. Thus, the light intensity of the monitoring light can be adjusted by the spectral ratio of the medium spectral film 17, and the light intensity of the monitoring light is kept the same as or nearly the same as that of the signal light.
Fig. 2 is a monitoring light spot and signal light spot detection diagram of a horizontal mark acquired by using the scatterometry device shown in fig. 1, fig. 3 is a monitoring light spot and signal light spot detection diagram of a vertical square mark acquired by using the scatterometry device shown in fig. 1, fig. 4 is a schematic diagram of a horizontal mark provided in an embodiment of the present invention, fig. 5 is a schematic diagram of a vertical mark provided in an embodiment of the present invention, and referring to fig. 1 to fig. 5 in combination, a topography measurement mark (referred to as a mark for short) is generally a photoresist grating dense line. The topography measurement mark may be located in scribe lines or other blank areas of the silicon wafer. According to different compositions of the marking film system, different measurement configurations can be selected for measurement so as to achieve the optimal effect. The measurement configuration refers to the measurement light wave field, polarization state, illumination mode, etc. used for measurement. The horizontal direction mark W1 extends in the horizontal direction H, and the horizontal direction mark W1 is most sensitive only to measurement using P-polarized light. The vertical direction marker W2 extends in the vertical direction V, and the vertical direction marker W2 is most sensitive only when measured using S-polarized light. However, when the monitoring light is used by a user, the mark is randomly placed, so that the monitoring light to be modulated has both S-polarized light components and P-polarized light components. As can be seen from the monitoring light spot and the signal light spot detection diagrams shown in fig. 2 and 3, the reflected light intensities of the dielectric light-splitting film 17 corresponding to the S-polarized light and the P-polarized light will have a large difference at the interface with a large splitting ratio. This will cause it to have HV bias errors (i.e. measurement errors due to differences in the intensity of the polarized light) when making scatterometry measurements. The error is coupled with the nonlinear error of the detection unit 19, so that the light intensity is not regularly distributed, and the difficulty of algorithm measurement and calibration is high. In addition, the coating cost and the technical difficulty of forming the dielectric light-splitting film 17 are also large.
Fig. 6 is a schematic structural view of another scatterometry device according to an embodiment of the present invention, fig. 7 is a schematic structural view of a reflection unit in the scatterometry device shown in fig. 6, fig. 8 is a graph showing an internal transmittance of a neutral absorption material having a thickness of 1mm, and referring to fig. 6 to 8, the reflection unit 20 includes at least one optical element, and at least one optical element in the reflection unit 20 includes the neutral absorption material, which means a material having a absorption rate with a fluctuation smaller than a preset value in a preset wavelength band.
Fig. 9 is a monitoring light spot and signal light spot detection diagram obtained by using the scatterometry device shown in fig. 6, and referring to fig. 9, compared with the monitoring light spot and the signal light spot shown in fig. 2 and 3, the light intensity distribution of the monitoring light spot and the signal light spot obtained by using the scatterometry device shown in fig. 6 does not depend on the placing direction of the mark, that is, the mark is placed in any direction, and the monitoring light spot and signal light spot detection diagram shown in fig. 9 can be obtained.
The light intensity of the signal light spot and the light intensity of the monitoring light spot are greatly different due to factors such as the mark reflectivity, the absorption rate of the light path, the lens coating and the like, and the final scattering measurement result is influenced. In order to reduce the light intensity difference between the signal light spot and the monitoring light spot, in the embodiment of the present invention, at least one optical element in the reflection unit 20 includes a neutral absorption material, and the optical element including the neutral absorption material is used to modulate the light intensity of the monitoring light spot, so that the light intensity attenuation of a specific proportion can be realized for the full-band light source used for measurement. The scattering measurement device provided by the embodiment of the invention has the advantages of simple structure, simple implementation process and lower assembly difficulty, reduces the light intensity difference of S polarized light and P polarized light while realizing light intensity modulation, solves the measurement error caused by the polarized light intensity difference, and reduces the technical difficulty and cost.
Alternatively, referring to fig. 6 and 7, the optical element in the reflection unit 20 includes a prism 21, the prism 21 includes at least two inclined reflection surfaces 22, and the at least two inclined reflection surfaces 22 are used for deflecting the optical axis of the second illumination beam and imaging the second illumination beam onto the detection unit 19 through the imaging unit 18 after being reflected. Prism 21 comprises a neutral absorbing material. In embodiments of the present invention, the prism 21 may be formed using a neutral absorption material, so that the prism 21 may achieve a specific proportion of light intensity attenuation of the second illumination beam incident thereon over the full wavelength band of the light source.
Optionally, the absorbance of the neutral absorbing material has a volatility of less than 5% in the 400nm to 700nm wavelength band. The wave band of 400 nm-700 nm is a common wave band for scattering measurement, so a neutral material with low fluctuation rate of absorption rate in the wave band of 400 nm-700 nm can be selected.
With continued reference to fig. 8, the internal transmittance of the neutral absorbent material is relatively stable and has small fluctuation in the wavelength range of 400nm to 700nm, that is, the fluctuation in the absorbance of the neutral absorbent material is low, and the fluctuation in the absorbance of the neutral absorbent material is less than 2%, and thus, the neutral absorbent material is more preferable.
Alternatively, the neutral absorbing material may comprise neutral gray glass. The neutral gray glass is a glass material, and the neutral gray glass is used as a neutral absorption material, so that the optical performance of other glass optical elements in the existing scattering measurement device can be matched. In other embodiments, a material such as resin may be used as the neutral absorbent material, which is not limited in the embodiments of the present invention.
Optionally, with continued reference to fig. 7, the optical elements in the reflection unit 20 further include a total reflection film 23, that is, both the prism 21 and the total reflection film 23 are optical elements in the reflection unit 20. The total reflection film 23 is located on the side of at least one inclined reflection surface 22. The total reflection film 23 has a high reflectance, so that the reflectance of the inclined reflection surface 22 of the prism 21 can be increased, and since the total reflection film 23 does not have a difference in reflectance between S-polarized light and P-polarized light, the difference in reflectance between S-polarized light and P-polarized light can be reduced.
Alternatively, the prism 21 is a triple prism, and the triple prism 21 has a simple structure, and is easy to assemble and control light. In other embodiments, the prism 21 may be a pentaprism, for example.
Illustratively, the prism 21 is a triangular prism, the inclined reflective surface 22 of the prism 21 includes a first inclined reflective surface 221 and a second inclined reflective surface 222, there is one total reflection film 23 on the first inclined reflective surface 221 side, and there is another total reflection film 23 on the second inclined reflective surface 222 side. The total reflection film 23 may be formed on the inclined reflection surface 22 of the prism 21 by a plating method, for example.
Illustratively, the total reflection film 23 may be, for example, a metal film or a dielectric total reflection film.
Fig. 10 is another schematic structural diagram of the reflection unit in the scatterometry device shown in fig. 6, and referring to fig. 6 and 10, the optical elements in the reflection unit 20 include a prism 21 and at least one light intensity controlling member 24 (illustrated as one light intensity controlling member 24 in fig. 10). The prism 21 includes at least two inclined reflective surfaces 22, and the at least two inclined reflective surfaces 22 are used for deflecting the optical axis of the second illumination beam and imaging the second illumination beam onto the detection unit 19 through the imaging unit 18 after reflecting the second illumination beam. The light intensity controlling member 24 includes a neutral absorbing material, and the light intensity controlling member 24 is located on a propagation path of the second illumination beam, so that the light intensity controlling member 24 can achieve a specific ratio of light intensity attenuation of the second illumination beam incident thereon over a full wavelength band of the light source.
Optionally, referring to fig. 6 and 10, the at least one light intensity controlling element 24 includes a first light intensity controlling element 241, the first light intensity controlling element 241 is located on the optical path between the beam splitter 15 and the prism 21, the second illumination light beam emitted from the beam splitter 15 is incident into the prism 21 after passing through the first light intensity controlling element 241, and after being reflected by the at least two inclined reflecting surfaces 22 of the prism 21, passes through the first light intensity controlling element 241 again, and then is reflected to the imaging unit 18 by the beam splitter 15, and is imaged on the detecting unit 19 through the imaging unit 18. In the embodiment of the present invention, the at least one light intensity adjusting and controlling element 24 includes the first light intensity adjusting and controlling element 241, and the first light intensity adjusting and controlling element 241 is located on the light incident/emergent surface side of the prism 21, so that the first light intensity adjusting and controlling element 241 and the prism 21 are integrated in the same spatial region, the integration level is improved, and the assembly difficulty is reduced. Further, the first light intensity adjusting and controlling element 241 is disposed on the light incident/emergent surface side of the prism 21, the first light intensity adjusting and controlling element 241 is only located on the propagation path of the monitoring light, and is not located on the propagation path of the signal light, and the first light intensity adjusting and controlling element 241 is far away from the signal light, so that it can be ensured that the first light intensity adjusting and controlling element 241 only modulates the light intensity of the monitoring light, and the light intensity of the signal light is not affected. Further, when the first light intensity adjusting and controlling element 241 is disposed on one side of the light incident/emergent surface of the prism 21, the film layer at the inclined reflective surface 22 is not affected, so that the original film layer at the inclined reflective surface 22 and the manufacturing process of the original film layer are not affected.
Exemplarily, referring to fig. 10, the second illumination beam vertically irradiates to the first light intensity adjusting and controlling element 241, passes through the first light intensity adjusting and controlling element 241, propagates to the prism 21, is reflected by the first inclined reflective surface 221 of the prism 21, and then is projected to the second inclined reflective surface 222 of the prism 21, and exits from the prism 21 after changing the optical axis, vertically irradiates to the first light intensity adjusting and controlling element 241 again, and continues to propagate to the beam splitter 15 after passing through the first light intensity adjusting and controlling element 241.
Fig. 11 is another schematic structural diagram of the reflection unit in the scatterometry device shown in fig. 6, referring to fig. 6 and fig. 11, the at least one light intensity controlling element 24 includes a second light intensity controlling element 242, the second light intensity controlling element 242 is located on one side of the at least one inclined reflection surface 22, the second illumination light beam projected onto the inclined reflection surface 22 passes through the inclined reflection surface 22 and the second light intensity controlling element 242, and is reflected back into the prism 21 by a surface of one side of the second light intensity controlling element 242 away from the prism 21. In the embodiment of the present invention, the at least one light intensity controlling element 24 includes the second light intensity controlling element 242, and the second light intensity controlling element 242 is located at one side of the at least one inclined reflecting surface 22 of the prism 21, so that the second light intensity controlling element 242 and the prism 21 are integrated in the same spatial region, the integration level is improved, and the assembly difficulty is reduced. Further, the second light intensity adjusting and controlling element 242 is disposed on one side of the at least one inclined reflecting surface 22 of the prism 21, the second light intensity adjusting and controlling element 242 is only located on the propagation path of the monitoring light, and is not located on the propagation path of the signal light, and the second light intensity adjusting and controlling element 242 is far away from the signal light, so that it can be ensured that the second light intensity adjusting and controlling element 242 only performs light intensity modulation on the monitoring light, and the light intensity of the signal light is not affected.
Exemplarily, referring to fig. 11, the prism 21 is a triangular prism, the prism 21 in the reflection unit 20 includes a first inclined reflection surface 221 and a second inclined reflection surface 222, and the reflection unit 20 includes two second light intensity adjusting members 242, one of the second light intensity adjusting members 242 is located at a side of the first inclined reflection surface 221, and the other second light intensity adjusting member 242 is located at a side of the second inclined reflection surface 222. All the inclined reflecting surfaces 22 in the prism 21 are provided with the second light intensity adjusting and controlling member 242.
Optionally, referring to fig. 11, the optical elements in the reflection unit 20 further include an antireflection film 25, and the antireflection film 25 is located between the second light intensity adjusting and controlling element 242 and the inclined reflection surface 22 of the prism 21. In the embodiment of the present invention, an antireflection film 25 is further disposed between the second light intensity adjusting and controlling element 242 and the inclined reflecting surface 22 of the prism 21, when the second illumination light beam is projected onto the inclined reflecting surface 22, the transmittance of the second illumination light beam through the inclined reflecting surface 22 is increased by the antireflection film 25, and the second illumination light beam that has passed through the inclined reflecting surface 22 passes through the second light intensity adjusting and controlling element 242, is reflected by a surface of a side of the second light intensity adjusting and controlling element 242 away from the prism 21, and then passes through the second light intensity adjusting and controlling element 242 again and returns to the prism 21.
Exemplarily, referring to fig. 11, the optical element in the reflection unit 20 further includes a total reflection film 23, the total reflection film 23 is located on a side of the second light intensity regulating member 242 away from the prism 21, and since the second light intensity regulating member 242 is located on a side of the at least one inclined reflection surface 22, the total reflection film 23 is also located on a side of the at least one inclined reflection surface 22. The total reflection film 23 has a high reflectance, so that the reflectance of the second illumination beam on the surface of the second light intensity adjusting and controlling element 242 on the side away from the prism 21 can be improved, and the reflectance difference between the S-polarized light and the P-polarized light can be reduced because the total reflection film 23 has no difference in the reflectance of the S-polarized light and the P-polarized light.
It should be noted that, in other embodiments, the optical elements in the reflection unit 20 may further include a first light intensity adjusting and controlling element 241 and a second light intensity adjusting and controlling element 242, the first light intensity adjusting and controlling element 241 is located on the optical path between the beam splitter 15 and the prism 21, and the second light intensity adjusting and controlling element 242 is located on one side of the at least one inclined reflection surface 22.
Fig. 12 is a schematic structural diagram of another scatterometry device according to an embodiment of the present invention, and referring to fig. 12, the at least one light intensity controlling element 24 includes a third light intensity controlling element 243, and the third light intensity controlling element 243 is located on an optical path between the beam splitter 15 and the imaging unit 18. The second illumination beam reflected by the beam splitter 15 is projected onto the third light intensity control element 243, passes through the third light intensity control element 243, and then continuously propagates to the imaging unit 18, and is imaged on the detection unit 19 through the imaging unit 18. In the embodiment of the present invention, the third light intensity adjusting and controlling element 243 is only located on the propagation path of the monitoring light, but not located on the propagation path of the signal light, so as to ensure that the third light intensity adjusting and controlling element 243 only modulates the light intensity of the monitoring light, and does not affect the light intensity of the signal light.
It should be noted that in other embodiments, the optical element in the reflection unit 20 may further include a third light intensity controlling element 243, and at least one of the first light intensity controlling element 241 and the second light intensity controlling element 242. The first light intensity controlling member 241 is located on the optical path between the beam splitter 15 and the prism 21, the second light intensity controlling member 242 is located on the side of the at least one inclined reflecting surface 22, and the third light intensity controlling member 243 is located on the optical path between the beam splitter 15 and the imaging unit 18. In summary, at least one of the first light intensity controlling member 241, the second light intensity controlling member 242 and the third light intensity controlling member 243 may be selected to modulate the light intensity of the second illumination light beam.
Further, in another embodiment, when the prism 21 is provided to include a neutral absorption material, at least one of the first light intensity regulating member 241, the second light intensity regulating member 242, and the third light intensity regulating member 243 may be provided in the reflection unit 20, and the light intensity of the second illumination light beam is modulated by the prism 21 and the light intensity regulating member 24 together.
Alternatively, referring to any one of fig. 10 to 12, the light intensity controlling member 24 is shaped as a parallel flat plate. In the optical element, the manufacturing process of the parallel plate is the simplest, for example, the manufacturing process of the parallel plate is simpler than that of the prism 21, so that the manufacturing cost of the parallel plate is lower. The light intensity adjusting and controlling element 24 is shaped as a parallel flat plate, so that the cost of the scattering measurement device can be reduced, and the difficulty of light path control can be reduced.
Based on the same inventive concept, an embodiment of the present invention further provides a method based on the foregoing scatterometry device, and with reference to fig. 6 to 12, the method includes: the light intensity regulation and control of the monitoring light are realized by changing the optical path of the second illumination beam in the neutral absorption material. That is, when the light intensity of the monitoring light is different from the light intensity of the signal light, the optical path of the second illuminating light beam in the neutral absorbing material can be changed, so that the absorption degree of the neutral absorbing material to the second illuminating light beam is changed, the light intensity regulation of the monitoring light is realized, and the light intensity of the monitoring light is the same as or nearly the same as the light intensity of the signal light.
In the embodiment of the present invention, at least one optical element in the reflection unit 20 is made of a neutral absorption material, and the light intensity of the monitoring light is controlled by changing the optical path of the second illumination beam in the neutral absorption material, so that the light intensity attenuation of a specific proportion can be realized for the full-band light source used for measurement. The embodiment of the invention reduces the light intensity difference of S polarized light and P polarized light while realizing light intensity modulation, solves the measurement error caused by the light intensity difference of polarization, and reduces the technical difficulty and cost.
Alternatively, referring to fig. 6 and 7, the optical element in the reflection unit 20 includes a prism 21, the prism 21 includes at least two inclined reflection surfaces 22, the at least two inclined reflection surfaces 22 are used for deflecting the optical axis of the second illumination beam and imaging the second illumination beam onto the detection unit 19 through the imaging unit 18 after reflecting the second illumination beam, and the prism 21 includes a neutral absorption material. In this case, the scatterometry method may specifically be: the light intensity regulation of the monitoring light is realized by changing the size of the prism 21.
Illustratively, when the light intensity of the monitoring light is greater than the light intensity of the signal light, the size of the prism 21 is increased, the optical path length of the second illumination beam in the prism 21 is increased, the absorption degree of the second illumination beam by the prism 21 is increased, and the light intensity of the monitoring light is decreased, so that the light intensity of the monitoring light is the same as or nearly the same as the light intensity of the signal light. When the light intensity of the monitoring light is smaller than that of the signal light, the size of the prism 21 is reduced, the optical path of the second illuminating light beam in the prism 21 is reduced, the absorption degree of the prism 21 on the second illuminating light beam is reduced, and the light intensity of the monitoring light is increased, so that the light intensity of the monitoring light is the same as or nearly the same as that of the signal light.
Optionally, referring to fig. 10 to 12, the optical elements in the reflection unit 20 include a prism 21 and at least one light intensity adjusting and controlling element 24, the prism 21 includes at least two inclined reflection surfaces 22, and the at least two inclined reflection surfaces 22 are configured to deflect the optical axis of the second illumination beam and reflect the second illumination beam to be imaged 18 on the detection unit 19 through the imaging unit. At least one light intensity modulating element 24 comprises a neutral absorbing material located in the path of propagation of the second illumination beam. In this case, the scatterometry method may specifically be: the intensity control of the monitor light is realized by changing the thickness of the light intensity controlling member 24.
Illustratively, when the light intensity of the monitoring light is greater than the light intensity of the signal light, the thickness of the light intensity controlling member 24 is increased, the optical path length of the second illumination beam in the light intensity controlling member 24 is increased, the absorption degree of the second illumination beam by the light intensity controlling member 24 is increased, and the light intensity of the monitoring light is decreased so that the light intensity of the monitoring light is the same as or nearly the same as the light intensity of the signal light. When the light intensity of the monitoring light is smaller than that of the signal light, the thickness of the light intensity regulating element 24 is reduced, the optical path of the second illuminating light beam in the light intensity regulating element 24 is reduced, the absorption degree of the second illuminating light beam by the light intensity regulating element 24 is reduced, and the light intensity of the monitoring light is increased, so that the light intensity of the monitoring light is the same as or nearly the same as that of the signal light.
Illustratively, the light intensity modulating element 24 is shaped as a parallel flat plate. The light intensity control element 24 is shaped as a parallel flat plate, and each position of the light intensity control element 24 has the same thickness, so that the thickness of the light intensity control element 24 can be conveniently adjusted, and the difficulty in controlling the light path is reduced.
It should be noted that the light intensity controlling member 24 may include at least one of the first light intensity controlling member 241, the second light intensity controlling member 242, and the third light intensity controlling member 243, and the light intensity of the monitoring light may be the same as or nearly the same as the light intensity of the signal light by adjusting the thickness of at least one of the first light intensity controlling member 241, the second light intensity controlling member 242, and the third light intensity controlling member 243.
It should be noted that, in another embodiment, when the prism 21 is provided to include a neutral absorption material, at least one of the first light intensity controlling member 241, the second light intensity controlling member 242, and the third light intensity controlling member 243 may be provided in the reflection unit 20. At this time, the light intensity of the monitoring light is the same as or nearly the same as the light intensity of the signal light by at least one of adjusting the size of the prism 21, adjusting the thickness of the first light intensity controlling member 241, adjusting the thickness of the second light intensity controlling member 242, and adjusting the thickness of the third light intensity controlling member 243.
It is to be noted that the foregoing is only illustrative of the preferred embodiments of the present invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious modifications, rearrangements, combinations and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims (15)

1. A scatterometry device, comprising:
a light source for generating an illumination beam;
a beam splitter for splitting the illumination beam into a first illumination beam and a second illumination beam;
the objective lens converges the first illumination light beam to the surface of the substrate and collects light scattered by the surface of the substrate;
an imaging unit and a detection unit, the imaging unit imaging a pupil of the objective lens to the detection unit;
the reflecting unit is used for deflecting the optical axis of the second illuminating light beam, reflecting the second illuminating light beam and imaging the second illuminating light beam on the detecting unit through the imaging unit;
wherein the reflective unit comprises at least one optical element, the presence of at least one optical element in the reflective unit comprising a neutral absorbing material; the neutral absorption material refers to a material of which the fluctuation rate of the absorption rate in a preset wave band is less than a preset value.
2. The scatterometry device of claim 1, wherein the optical element in the reflection unit comprises a prism, the prism comprising at least two inclined reflection surfaces for deflecting the optical axis of the second illumination beam and imaging the second illumination beam onto the detection unit via the imaging unit after reflection;
the prism includes the neutral absorbing material.
3. The scatterometry device of claim 1, wherein the optical elements in the reflection unit comprise a prism and at least one intensity-modulating element;
the prism comprises at least two inclined reflecting surfaces, and the at least two inclined reflecting surfaces are used for deflecting the optical axis of the second illuminating light beam and imaging the second illuminating light beam onto the detection unit through the imaging unit after reflecting the second illuminating light beam;
the at least one light intensity modulating element, including the neutral absorbing material, is located in a propagation path of the second illumination beam.
4. A scatterometry device according to claim 3, characterized in that said at least one intensity-regulating element comprises a first intensity-regulating element located in the optical path between said beam splitter and said prism.
5. The scatterometry device of claim 3, wherein said at least one intensity control element comprises a second intensity control element, said second intensity control element being positioned on a side of at least one of said inclined reflective surfaces, wherein said second illumination beam projected onto said inclined reflective surface passes through said inclined reflective surface and said second intensity control element and is reflected by said second intensity control element back toward said prism from a side surface of said prism.
6. The scatterometry device of claim 5, wherein the optical elements in the reflection unit further comprise an anti-reflection coating between the second light intensity modulating element and the angled reflective surfaces of the prism.
7. A scatterometry device according to claim 3, characterized in that said at least one light intensity modulating element comprises a third light intensity modulating element, which is located in the optical path between said beam splitter and said imaging unit.
8. A scatterometry device according to claim 3, characterized in that the light intensity modulating element is shaped as a parallel flat plate.
9. A scatterometry device according to claim 2 or 3, characterized in that the prism is a triangular prism.
10. A scatterometry device according to claim 2 or 3, characterized in that the optical element in the reflection unit further comprises a total reflection film which is located on the side of at least one of the inclined reflection surfaces.
11. The scatterometry device of claim 1, wherein the absorbance of the neutral-absorbing material has a volatility of less than 5% in the 400-700 nm band.
12. The scatterometry device of claim 1, wherein the neutral-absorbing material comprises neutral-grey glass.
13. A method of scatterometry based measurement apparatus according to claim 1, comprising:
the light intensity regulation and control of the monitoring light are realized by changing the optical path of the second illumination beam in the neutral absorption material.
14. The method of claim 13, wherein the optical element in the reflection unit comprises a prism, and the prism comprises at least two inclined reflection surfaces, and the at least two inclined reflection surfaces are used for deflecting the optical axis of the second illumination beam and imaging the second illumination beam onto the detection unit through the imaging unit after reflection; the prism comprises the neutral absorbing material;
the light intensity regulation and control of the monitoring light is realized by changing the optical path of the second illumination beam in the neutral absorption material, and the method comprises the following steps:
and the light intensity regulation and control of the monitoring light is realized by changing the size of the prism.
15. The method of claim 13, wherein the optical elements in the reflection unit comprise a prism and at least one intensity-modulating element; the prism comprises at least two inclined reflecting surfaces, and the at least two inclined reflecting surfaces are used for deflecting the optical axis of the second illuminating light beam and imaging the second illuminating light beam onto the detection unit through the imaging unit after reflecting the second illuminating light beam; said at least one light intensity modulating element comprises said neutral absorbing material in a propagation path of said second illumination beam;
the light intensity regulation and control of the monitoring light is realized by changing the optical path of the second illumination beam in the neutral absorption material, and the method comprises the following steps:
and the light intensity regulation and control of the monitoring light are realized by changing the thickness of the light intensity regulation and control element.
CN202011289171.2A 2020-11-17 2020-11-17 Scattering measurement device and method Pending CN114509408A (en)

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