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JP-2026074505-A - Optical property evaluation device

JP2026074505AJP 2026074505 AJP2026074505 AJP 2026074505AJP-2026074505-A

Abstract

[Problem] To provide an optical property evaluation device for evaluating the optical properties of a light-transmitting member. [Solution] The optical properties evaluation device consists of a light source 10, a photodetector 20, a focusing optical system 30, and an evaluation unit 40. The light source 10 is capable of emitting divergent light. The photodetector 20 is capable of detecting the light intensity distribution of light incident on the detection surface. The focusing optical system 30 causes the light beam from the light source 10 to be incident on the light-transmitting member 1 at a predetermined incident angle to form an irradiation spot having a predetermined shape and size on the light-transmitting member 1, and causes the reflected light from the light-transmitting member 1 to be incident on the detection surface of the photodetector 20 to form an image of the light source. The evaluation unit 40 evaluates the reflected light and scattered light from the light-transmitting member 1 based on the light intensity distribution detected by the photodetector 20. [Selection Diagram] Figure 1

Inventors

  • 三宅 明

Assignees

  • 株式会社トヤマ

Dates

Publication Date
20260507
Application Date
20241021

Claims (8)

  1. An optical properties evaluation apparatus for evaluating the optical properties of a light-transmitting member, wherein the optical properties evaluation apparatus is A light source capable of emitting divergent light, A photodetector capable of detecting the light intensity distribution of light incident on the detection surface, A focusing optical system for causing a light beam from the light source to be incident on a light-transmitting member at a predetermined incident angle to form an illumination spot having a predetermined shape and size on the light-transmitting member, and causing the reflected light from the light-transmitting member to be incident on the detection surface of a photodetector to form an image of the light source, An evaluation unit that evaluates reflected and scattered light from a light-transmitting member based on the light intensity distribution detected by the photodetector, An optical properties evaluation apparatus characterized by comprising the following:
  2. In the optical property evaluation apparatus according to claim 1, The aforementioned focusing optical system consists of a focusing mirror that focuses divergent light from a light source onto the detection surface of a photodetector. The aforementioned focusing mirror causes the light beam, which is in the process of converging from the focusing mirror, to be incident on a light-transmitting member at a predetermined incident angle, thereby forming an illumination spot on the light-transmitting member. An optical properties evaluation apparatus characterized by the following features.
  3. In the optical property evaluation apparatus according to claim 1, The aforementioned focusing optical system comprises a first focusing mirror that focuses divergent light from a light source to a predetermined intermediate focusing point, and a second focusing mirror that focuses divergent light emitted from the intermediate focusing point onto the detection surface of a photodetector. The first focusing mirror causes the light beam, which is converging before the intermediate focusing point or diverging after the intermediate focusing point, to be incident on the light-transmitting member at a predetermined incident angle, thereby forming an illumination spot on the light-transmitting member. The second focusing mirror causes reflected light from the light-transmitting member to be incident on the detection surface of the photodetector to form an image of the light source. An optical properties evaluation apparatus characterized by the following features.
  4. An optical property evaluation apparatus according to claim 1, characterized in that the evaluation unit separates reflected light and scattered light within a predetermined range based on the light intensity distribution detected by a photodetector, and calculates the reflected light intensity and scattered light intensity, or the reflectance and scattering rate, of a light-transmitting member by integrating the separated light intensity distributions within the predetermined range.
  5. In the optical property evaluation apparatus according to claim 1, the focusing optical system comprises an angle aperture having an aperture that cuts out divergent light from a light source within a predetermined range, The angle-reducing aperture can change the incident angle of the light beam incident on the light-transmitting member by changing the position of its opening. An optical properties evaluation apparatus characterized by the following features.
  6. In the optical property evaluation apparatus according to claim 1, the focusing optical system comprises an angle aperture having an aperture that cuts out divergent light from a light source within a predetermined range, The optical properties evaluation apparatus is characterized in that the angle aperture can change the size of the illumination spot formed on the light-transmitting member by changing the size of its opening, or the shape of the illumination spot formed on the light-transmitting member by changing the shape of its opening.
  7. An optical property evaluation apparatus according to claim 1, further comprising a transmitted light detector capable of detecting the light intensity of transmitted light from a light-transmitting member incident on a detection surface, The evaluation unit evaluates the transmitted light intensity or transmittance of the light-transmitting member based on the light intensity of the transmitted light detected by the transmitted light detector. An optical properties evaluation apparatus characterized by the following features.
  8. In the optical property evaluation apparatus according to any one of claims 1 to 7, The aforementioned light source is a plasma light source capable of emitting divergent light of extreme ultraviolet wavelengths. The light-transmitting material is a pellicle used in extreme ultraviolet lithography. An optical properties evaluation apparatus characterized by the following features.

Description

This invention relates to an optical property evaluation apparatus, and more particularly to an optical property evaluation apparatus for evaluating the optical properties of a light-transmitting member. Conventionally, in semiconductor lithography, pellicles made of thin resin films have been used as dust covers for photomasks. When exposing a semiconductor wafer, the pellicle has high transmittance to excimer laser ultraviolet light from the light source, allowing the laser to pass through the pellicle and transfer the photomask pattern to the semiconductor wafer. Since the photomask and pellicle are positioned at a distance from each other and outside the depth of focus of the projection optical system, the image of foreign matter adhering to the pellicle is blurred and not transferred to the semiconductor wafer. Thus, pellicles are useful in preventing manufacturing defects in semiconductor wafers caused by foreign matter. In recent years, the miniaturization of semiconductor circuit patterns has progressed in line with the increasing sophistication and speed of communication systems. Extreme ultraviolet (EUV) light sources are used to form these microcircuits. Unlike visible light, EUV light has an extremely short wavelength and is absorbed by resin thin films, making it impossible to use resin thin films as pellicles. Therefore, materials with excellent EUV transparency are necessary. Furthermore, EUV light sources generate high-temperature plasmas of around 300,000 Kelvin instantaneously by irradiating materials such as xenon or tin with laser light. Such EUV light sources require an increase in numerical aperture (NA) to further miniaturize semiconductor circuit patterns. Specifically, EUV light sources with an NA of 0.25 are known, and even higher NAs of 0.33 are available. Further increases in NA are progressing, with EUV light sources of 0.55 now appearing. Development is underway to create new pellicle materials that can withstand the exposure environment of such EUV light sources and possess excellent EUV transparency. As an apparatus for inspecting pellicles, for example, Patent Document 1 is known. The pellicle inspection apparatus of Patent Document 1 includes an illumination optical system that focuses a solid-state laser light source, which generates a laser beam with a wavelength of 355 nm (the third harmonic of a YAG laser), onto the pellicle, and an objective lens having an optical axis perpendicular to the pellicle. It also includes a focusing optical system that focuses scattered light emitted from foreign matter present on the pellicle, and a detection system that detects the scattered light focused by the focusing optical system. By providing a photodetector that receives specularly reflected light from the pellicle, contamination formed on the pellicle can also be detected. Furthermore, there are known devices for inspecting photomasks irradiated with EUV light from an EUV light source, such as the one described in Patent Document 2. In the device for inspecting photomasks described in Patent Document 2, the photomask is irradiated with EUV light from an EUV light source, and the EUV light reflected from the photomask is guided through a projection lens to the image sensor of an EUV camera so that the photomask forms an image on the image sensor. The EUV light then passes through a pellicle placed between the projection lens and the image sensor. That is, the pellicle is placed after the imaging optical system to prevent contaminants from inside the EUV camera from reaching the image sensor. Japanese Patent Publication No. 2015-204339Japanese Patent Publication No. 2024-125210 Figure 1 is a schematic diagram illustrating the optical property evaluation apparatus of the present invention.Figure 2 is a schematic diagram illustrating the light incident on the detection surface of the photodetector of the optical property evaluation apparatus of the present invention.Figure 3 is a graph illustrating the light intensity distribution detected by the photodetector of the optical property evaluation apparatus of the present invention.Figure 4 is a schematic diagram illustrating the focusing optical system of the optical property evaluation apparatus of the present invention.Figure 5 is a schematic diagram illustrating an example in which an angular aperture is provided in the focusing optical system of the optical property evaluation apparatus of the present invention.Figure 6 is a schematic diagram illustrating the aperture of the angular diaphragm aperture of the focusing optical system of the optical characteristic evaluation apparatus of the present invention.Figure 7 is a schematic diagram illustrating the difference in the size of the illumination spot in response to the difference in the size of the aperture for the angular diaphragm of the focusing optical system of the optical characteristic evaluation apparatus of the present invention.Figure 8 is a schematic diagram illustrating