Method for predicting the lifespan of extreme UV pellicles

Abstract

This invention provides a method for predicting the lifespan of an extreme ultraviolet pellicle using its transmittance. [Solution] The present invention provides a method for predicting the lifetime of an extreme ultraviolet pellicle, comprising the steps of: a) obtaining transmittance data of an extreme ultraviolet pellicle in a wavelength band from the infrared region to the ultraviolet region; b) obtaining complex refractive index data of an extreme ultraviolet pellicle in a wavelength band from the infrared region to the ultraviolet region; c) performing optical modeling using the transmittance data and the complex refractive index data to obtain information on the relationship between the density and transmittance of the extreme ultraviolet pellicle according to the wavelength; and d) measuring the transmittance of an extreme ultraviolet pellicle to at least one measurement beam having a wavelength belonging to the wavelength band from the infrared region to the ultraviolet region, extracting an estimated density of the extreme ultraviolet pellicle based on the measured transmittance and the information on the relationship between density and transmittance obtained in step c), thereby predicting the remaining lifetime of the extreme ultraviolet pellicle.

Description

Technical Field

[0001] The present invention relates to a method for predicting the life of an extreme ultraviolet pellicle, and more particularly, to a method for predicting the life of an extreme ultraviolet pellicle using the transmittance of the extreme ultraviolet pellicle.

Background Art

[0002] In extreme ultraviolet lithography, extreme ultraviolet light is used to transfer the pattern of a photomask onto a substrate (wafer). The extreme ultraviolet pellicle serves to protect the photomask from particle contamination and damage. Maintaining the integrity of the photomask and ensuring optimal performance in the semiconductor manufacturing process is of great importance.

[0003] One of the main problems in the working environment of extreme ultraviolet lithography is hydrogen in the extreme ultraviolet chamber. Hydrogen can move freely within the chamber. Extreme ultraviolet light can generate hydrogen radicals from hydrogen. Hydrogen radicals are highly chemically reactive. Silicone, carbon nanotubes (CNTs), etc. that make up the pellicle film of the extreme ultraviolet pellicle are vulnerable to etching by hydrogen radicals.

[0004] Etching by hydrogen radicals poses a serious threat to the performance of the pellicle. The life of the pellicle is directly affected by the time it is exposed to hydrogen radicals.

[0005] Currently, the life of an extreme ultraviolet pellicle is mainly predicted by a method of measuring changes in the transmittance of extreme ultraviolet light. However, such an approach has limitations. Extreme ultraviolet light is absorbed by various substances within the scanner environment. The transmittance of extreme ultraviolet light can be affected by chamber conditions and the material properties of the pellicle film. Also, since the transmittance of extreme ultraviolet light does not react sensitively to the degree of etching of the pellicle film, it is difficult to accurately predict the life.

[0006] Typically, the thickness of a thin film can be determined by optical spectroscopic modeling using elliptical spectroscopy. However, for transparent thin films with very low reflectivity, such as pellicle films, it is extremely difficult to obtain a valid signal using elliptical spectroscopy. In particular, the thickness of free-standing films, which are not supported by a substrate, cannot be determined by optical spectroscopic modeling using measurements by elliptical spectroscopy. Therefore, lifetime prediction based on thickness and density measurements using elliptical spectroscopy is also difficult to apply. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Korean Registered Patent Publication No. 10-1948416 [Patent Document 2] Korean Registered Patent Publication No. 10-0252937 [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] The present invention aims to provide a novel method that can more accurately predict the lifespan of extreme ultraviolet pellicles. [Means for solving the problem]

[0009] To achieve the above objective, the present invention provides a method for predicting the lifetime of an extreme ultraviolet pellicle, comprising the steps of: a) obtaining transmittance data of an extreme ultraviolet pellicle in a wavelength band from the infrared region to the ultraviolet region; b) obtaining complex refractive index data of an extreme ultraviolet pellicle in a wavelength band from the infrared region to the ultraviolet region; c) performing optical modeling using the transmittance data and the complex refractive index data to obtain information on the relationship between the density and transmittance of the extreme ultraviolet pellicle according to the wavelength; and d) measuring the transmittance of an extreme ultraviolet pellicle to at least one measurement beam having a wavelength belonging to the wavelength band from the infrared region to the ultraviolet region, extracting an estimated density of the extreme ultraviolet pellicle based on the measured transmittance and the information on the relationship between density and transmittance obtained in step c), thereby predicting the remaining lifetime of the extreme ultraviolet pellicle.

[0010] Furthermore, the present invention provides a method for predicting the lifetime of an extreme ultraviolet pellicle, wherein the wavelength band of step a) includes a wavelength band of 190 nm to 200 μm.

[0011] Furthermore, the present invention provides a method for predicting the lifetime of an extreme ultraviolet pellicle, wherein the wavelength band of step a) includes a wavelength band of 190 nm to 1000 nm.

[0012] Furthermore, the present invention provides a method for predicting the lifetime of an extreme ultraviolet pellicle, wherein step a) includes a-1) acquiring transmittance data in the wavelength band of 770 nm to 200 μm using an FT-IR spectrometer, and a-2) acquiring transmittance data in the wavelength band of 190 nm to 1000 nm using a UV-Vis spectrophotometer.

[0013] Furthermore, the present invention provides a method for predicting the lifetime of an extreme ultraviolet pellicle, wherein step b) includes b-1) attaching the pellicle film of the extreme ultraviolet pellicle to a substrate, and b-2) obtaining complex refractive index data of the extreme ultraviolet pellicle using an elliptic spectrometer.

[0014] Furthermore, the present invention provides a method for predicting the lifetime of an extreme ultraviolet pellicle, wherein step c) is a step using the intensity transfer matrix method.

[0015] Furthermore, the present invention provides a method for predicting the lifetime of an extreme ultraviolet pellicle, wherein step d) includes d-1) selecting at least one measurement beam, d-2) measuring the transmittance of the extreme ultraviolet pellicle to the selected measurement beam, d-3) extracting an estimated density of the extreme ultraviolet pellicle based on the transmittance measured in step d-2) and information obtained in step c) regarding the relationship between the density and transmittance of the extreme ultraviolet pellicle, and d-4) predicting the remaining lifetime based on the estimated density extracted in step d-3).

[0016] Furthermore, the present invention provides a method for predicting the lifetime of an extreme ultraviolet pellicle, wherein step d-1) includes a step of identifying the absorption mode that contributes most significantly to the absorption amount of the pellicle film; a step of determining the full width at half maximum of the absorption mode; a step of selecting an outer wavelength range of the full width at half maximum, based on the full width at half maximum of the absorption mode; and a step of selecting the wavelength of the measurement beam from the selected outer wavelength range of the full width at half maximum.

[0017] The present invention also provides a method for predicting the lifetime of an extreme ultraviolet pellicle, wherein the step of selecting the wavelength of the measurement beam includes a linear characterization step of identifying wavelengths in the selected wavelength range outside the full width at half maximum that have a linear relationship with respect to density change in the transmission, and a wavelength selection step of selecting the wavelength at which the linear relationship is most clearly expressed as the wavelength of the measurement beam. [Effects of the Invention]

[0018] According to the present invention, the lifespan of extreme ultraviolet pellicles can be predicted more accurately. This helps prevent contamination of photomasks and contributes to maintaining the yield of the lithography process. [Brief explanation of the drawing]

[0019] [Figure 1] It is a flowchart of a method for predicting the lifetime of an extreme ultraviolet pellicle according to an embodiment of the present invention. [Figure 2] It is a diagram showing an example of an extreme ultraviolet pellicle. [Figure 3] It shows the transmittance of a carbon nanotube pellicle film measured using an FT-IR spectrometer and a UV-Vis spectrophotometer. [Figure 4] It is the result of optical modeling by applying density and thickness information from the complex refractive index to the transmittance data in FIG. 3. [Figure 5] It is a graph showing the relationship between transmittance and relative density depending on wavelength. [Figure 6] It is a distribution diagram of transmittance depending on relative density and wavelength. [Figure 7] It is a flowchart of steps for predicting the remaining lifetime of an extreme ultraviolet pellicle. [Figure 8] It is a flowchart of a step for selecting a measurement beam.

Embodiments for Carrying Out the Invention

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and can be embodied in various forms. However, this embodiment is provided to make the disclosure of the present invention complete and to fully inform those with ordinary knowledge of the scope of the invention. The same reference numerals in the figures refer to the same elements.

[0021] FIG. 1 is a flowchart of a method for predicting the lifetime of an extreme ultraviolet pellicle according to an embodiment of the present invention.

[0022] As shown in Figure 1, a method for predicting the lifetime of an extreme ultraviolet pellicle according to one embodiment of the present invention includes the steps of obtaining transmittance data of the extreme ultraviolet pellicle (S1), obtaining complex refractive index data of the extreme ultraviolet pellicle (S2), obtaining information on the relationship between the density and transmittance of the extreme ultraviolet pellicle according to wavelength (S3), and predicting the remaining lifetime of the extreme ultraviolet pellicle (S4).

[0023] First, we will explain the step (S1) of obtaining transmittance data of an extreme ultraviolet pellicle in the wavelength range from the infrared region to the ultraviolet region.

[0024] In this step (S1), the wavelength band to be measured is set to include at least the visible light region and the ultraviolet region.

[0025] For example, a wavelength range including 190 nm to 200 μm can be selected as the wavelength range for obtaining transmittance data. Preferably, a wavelength range including 190 nm to 1000 nm can be selected as the wavelength range for obtaining transmittance data.

[0026] This range allows for a thorough evaluation of the pellicle's transmittance and enables the analysis of the performance of extreme ultraviolet pellicles under other wavelength conditions that are more accurately and easily evaluated, rather than using extreme ultraviolet light.

[0027] Equipment such as FT-IR spectrometers (Fourier Transform Infrared Spectrometers) and UV-Vis spectrophotometers (Ultraviolet-Visible Spectrophotometers) can be used to measure transmittance data.

[0028] FT-IR spectrometers are primarily used to measure transmittance data in the wavelength range of 770 nm to 200 μm, while UV-Vis spectrophotometers are primarily used to measure transmittance data in the range of 190 nm to 1000 nm. In this way, the transmittance characteristics of extreme ultraviolet pellicles can be acquired over a wide wavelength range through multiple pieces of equipment.

[0029] Figure 2 shows an example of an extreme ultraviolet pellicle. As shown in Figure 2, the extreme ultraviolet pellicle 1 includes a pellicle frame 20 and a pellicle film 10.

[0030] In this invention, the transmittance of the extreme ultraviolet pellicle refers to the transmittance of the pellicle film 10.

[0031] The pellicle film 10 may have a multilayer structure including a core layer and a capping layer (or coating layer). The core layer can be composed of a variety of materials with high transmittance to extreme ultraviolet light, such as carbon nanotubes, silicone, metal silicide, and graphene, and the capping layer may be made of a material capable of protecting the core layer from hydrogen radicals, such as a silicone compound or metal silicide. The pellicle film may also have a single-layer structure.

[0032] In the case of a multilayer structure, the transmittance can be measured at each layering step. That is, by measuring the transmittance of the core layer, the transmittance of the multilayered pellicle thin film consisting of a "core layer + capping layer" can be measured. By analyzing this using the intensity transfer matrix method, the transmittance of the core layer and the capping layer can be obtained. By obtaining the transmittance of individual layers from the transmittance of the thin film in the multilayered structure, the density and thickness of the core layer and the capping layer can also be modeled.

[0033] Figure 3 shows the transmittance of the carbon nanotube pellicle film measured using an FT-IR spectrometer and a UV-Vis spectrophotometer.

[0034] Next, we will describe the step (S2) of obtaining complex refractive index data of extreme ultraviolet pellicles in the wavelength range from the infrared region to the ultraviolet region.

[0035] Complex refractive index data can be obtained through optical analysis processes using data measured with spectroscopic ellipsometry, Fourier transform infrared spectrometers, and UV-Vis spectrophotometers. Complex refractive index data appears as a spectrum corresponding to the wavelength of light. This data represents the inherent physical properties of the material.

[0036] Elliptic spectroscopy is an analytical method that investigates the optical and structural properties of a material by using information on the change in polarization ratio according to the complex refractive index and thickness (path of light) of the medium after light incident on the material is reflected or transmitted from its surface.

[0037] This step includes the step of attaching the pellicle film of the extreme ultraviolet pellicle to a substrate (S21) and the step of obtaining complex refractive index data of the extreme ultraviolet pellicle using an elliptic spectrometer (S22).

[0038] To obtain complex refractive index data for a transparent thin film with an absorption coefficient k close to 0 using an elliptic spectrometer, a substrate is always necessary. Therefore, it is necessary to separate the freestanding pellicle film from the pellicle frame and attach it to a substrate. Smooth and transparent substrates such as silicone, sapphire, and glass are mainly used. The substrate must have a flat surface and be free of defects. The pellicle film can be attached to the substrate by methods such as wet transfer, dry transfer, or vapor deposition.

[0039] Ellipsometric spectrometers only provide indirect information based on the polarization ratio (amplitude ratio Ψ, phase difference Δ) between a circularly polarized beam incident on the surface of a material and the reflected elliptically polarized beam. Therefore, ellipsometric modeling is necessary to obtain information about the physical properties and thickness of the pellicle film from the measured spectrum. Through this process, complex refractive index data of extreme ultraviolet pellicles can be obtained.

[0040] For example, using an elliptic spectrometer, a circularly polarized beam is incident at an angle between 61° and 70° in 1° increments. The reflected beam is then analyzed to determine the polarization ratio, including the phase difference and amplitude ratio between the P-wave and S-wave. After that, complex refractive index data that satisfies the measured polarization ratio can be obtained through an optical modeling process with pellicle film thickness, refractive index n, and absorption coefficient k as variables.

[0041] Furthermore, complex refractive index data can be obtained by measuring transmittance and reflectance using other equipment besides the elliptic spectrometer, such as an FT-IR spectrometer (Fourier Transform Infrared Spectrometer) or a UV-Vis spectrophotometer.

[0042] To obtain precise and reliable data on complex refractive index, we acquire data using all of the above-mentioned methods, including the polarization ratio method and the transmittance and reflectance methods, and ensure accuracy and reliability through cross-validation.

[0043] Figure 4 shows the results of optical modeling the transmittance data from Figure 3 by applying density and thickness information from the complex refractive index. The optical modeling results and the transmittance measurement results are in close agreement.

[0044] Next, we will describe step (S3), in which optical modeling is performed using transmittance data and complex refractive index data to obtain information on the relationship between the density and transmittance of the extreme ultraviolet pellicle according to the wavelength.

[0045] In this step, for example, as shown in Figure 5, a graph can be obtained showing the relationship between transmittance and relative density at various wavelengths. In Figure 5, the X-axis represents relative density and the Y-axis represents transmittance. 0.65 represents a transmittance of 65%. EUV stands for extreme ultraviolet light, and DUV stands for deep ultraviolet light. As can be seen from Figure 5, the shorter the wavelength (e.g., 280 nm), the more rapidly the transmittance decreases as the relative density decreases. Conversely, the longer the wavelength (e.g., 750 nm), the less the transmittance is affected by changes in relative density. However, it can be confirmed that the transmittance of extreme ultraviolet light is not significantly affected by changes in relative density. Therefore, extreme ultraviolet light is unsuitable for measuring relative density.

[0046] Furthermore, as shown in Figure 6, a transmittance distribution map corresponding to relative density and wavelength can also be obtained. The X-axis represents wavelength, with wavelengths increasing from left to right. The Y-axis represents relative density. Transmittance is represented by color. White indicates high transmittance, and black indicates low transmittance. This graph shows the change in transmittance according to relative density and wavelength in a two-dimensional map format.

[0047] Transmittance is defined as a function of complex refractive index, density, and thickness. Therefore, by measuring the transmittance of an extreme ultraviolet pellicle under irradiation with a complex refractive index, information on the density and thickness of the pellicle film can be extracted. Conversely, transmittance data can also be extracted using thickness and density information as variables. In other words, with complex refractive index data secured, density and thickness information can be obtained based on transmittance information.

[0048] In this step, an optical model is set up, and the simulation results using the optical model are compared with the actually measured transmittance data. The parameters of the optical model are then adjusted to minimize the difference. The parameters of the optical model may include transmittance, complex refractive index, density, and thickness.

[0049] Once the optical model is optimized through the optimization process, the relationship between the density and transmittance of the pellicle film is analyzed. Then, a mathematical model illustrating the relationship between the density and transmittance of the pellicle is developed.

[0050] The Intensity Transfer Matrix Method (ITMM) can be used for this type of optical modeling. The Intensity Transfer Matrix Method is a mathematical method for modeling the propagation of light in an optical system. Each layer is represented by a transfer matrix, and the transfer matrix of each layer is multiplied to calculate the transfer matrix of the entire system. Then, the transmittance is calculated from the transfer matrix of the entire system. The measured transmittance is compared with the model's predictions, and the predicted density and thickness are adjusted accordingly.

[0051] Next, we will describe the step (S4) of predicting the remaining lifespan of the extreme ultraviolet pellicle.

[0052] As shown in Figure 7, step (S4) includes the steps of selecting at least one measurement beam (S41), measuring the transmittance of the extreme ultraviolet pellicle to the selected measurement beam (S42), extracting the estimated density (S43), and predicting the remaining lifetime (S44).

[0053] As shown in Figure 8, the step of selecting at least one measurement beam (S41) includes the steps of: identifying the absorption mode that contributes most significantly to the absorption amount of the pellicle film (S411); determining the full width at half maximum (FWHM) of the absorption mode (S412); selecting the wavelength range outside the FWHM (S413); linear characterization (S414); and wavelength selection (S415).

[0054] The step of identifying the absorption mode that contributes most significantly to the absorption of the pellicle film (S411) is the process of analyzing the degree to which a material absorbs light at a specific wavelength. In this step, first, the absorption spectrum of the material is measured by spectroscopic analysis. Then, the most distinct absorption peak (wavelength band with high absorption) is identified in the absorption spectrum. This peak reflects the absorption mode associated with electronic transitions, vibrations, or rotational modes within the material.

[0055] Absorption modes include electronic absorption mode, vibrational absorption mode, rotational absorption mode, Raman absorption mode, plasmon absorption mode, resonance absorption mode, phonon absorption mode, and magnetic absorption mode. For example, when carbon nanotubes (CNTs) are used as the material for the pellicle film, the absorption mode may be plasmon absorption mode.

[0056] The step (S412) of determining the full width at half maximum (FWHM) of the absorption mode in question is a process of measuring the width of the absorption peak in the absorption spectrum. In this step, first, the maximum value of the absorption peak is determined. Then, the absorptivity (or absorbance) corresponding to half of the maximum value is calculated. Two wavelengths corresponding to this half-absorptivity value are determined, and the difference between them is calculated. This difference is the full width at half maximum (FWHM), which represents the width of the absorption mode in question.

[0057] The step of selecting the outer wavelength range for the full width at half maximum (FWHM) (S413) is a step in which the outer region of the FWHM, which is less affected by absorption modes, is selected based on the FWHM calculated in the previous step (S412). The selection of this region is aimed at selecting wavelengths in which the density information of the core layer can be expressed by a linear function rather than an exponential function, while selecting wavelengths in which absorption by the coating layer is extremely small.

[0058] In the absorption wavelength band, transmittance increases exponentially as density decreases, making it difficult to intuitively grasp the density value from transmittance data. For example, when carbon nanotubes are used as the pellicle film, the central value in the absorption wavelength band is approximately 280 nm. As shown in Figure 7, the transmittance for light at a wavelength of 280 nm changes exponentially.

[0059] The linear characterization step (S414) is a step that analyzes the relationship between transmittance and relative density in the wavelength range outside the full width at half maximum. In this step, wavelengths in which transmittance and density have a linear relationship are identified. A linear relationship means that the change in transmittance due to a change in density increases or decreases at a constant rate. This is advantageous for simplifying the predictive model and improving its accuracy.

[0060] In the wavelength selection step (S415), the wavelength at which the linear relationship is most clearly observed is selected. This wavelength serves as a reference for effectively monitoring the density change of the pellicle film. For example, as shown in Figure 7, 550 nm, which falls outside the absorption wavelength band and shows a linear relationship between transmittance and density, can be selected as the wavelength of the measurement beam.

[0061] Step (S42) of measuring the transmittance of the extreme ultraviolet pellicle to the selected measurement beam involves passing the measurement beam of the selected wavelength through the pellicle film, measuring the intensity of the light after it has passed through the pellicle film, and calculating the transmittance by calculating the ratio of the intensity of the transmitted beam to the intensity of the original beam.

[0062] The step of extracting the estimated density (S43) is a step in which the estimated density is extracted using the relationship between the transmittance calculated in the previous step (S42), the transmittance obtained in step S3, and the density of the pellicle film.

[0063] In the step of predicting the remaining life (S44), the estimated density extracted in the previous step (S43) is used to determine how much the pellicle has deteriorated in its current state. Then, the time required to reach the critical density at which the pellicle loses its function is calculated. This time is the remaining life of the pellicle. The remaining life can be calculated by taking into account environmental conditions such as the intensity of extreme ultraviolet radiation and the concentration of hydrogen radicals, as well as the degradation rate of the pellicle film.

[0064] When a pellicle film consists of multiple layers made of different materials, the density change of each layer can be determined using transmittance data acquired with measurement beams of different wavelengths. In this case, using at least as many measurement beams as there are layers in the pellicle film is advantageous for accurate measurement. For example, if the pellicle film consists of two layers, two or more measurement beams with different wavelengths can be used. Using as many transmittance data points as possible relative to the number of layers is advantageous in that it increases reliability.

[0065] However, layers that do not affect transmittance can be excluded from the number of layers. For example, if the pellicle film includes a coating layer and a core layer, and the coating layer does not affect the transmittance of the measurement beam, but only the core layer affects the transmittance, then only one measurement beam can be used.

[0066] Even when the pellicle film consists of multiple materials, it is advantageous to use transmittance data equal to or greater than the number of materials. If it includes multiple layers, and each layer consists of multiple materials, then a number of transmittance data points must be obtained that takes into account both the number of layers and the number of materials.

[0067] As described above with reference to the drawings and embodiments, a person skilled in the art will understand that various modifications and changes can be made to the present invention without departing from the technical idea of ​​the invention as described in the following claims. [Explanation of symbols]

[0068] 1. Extreme UV pellicle 10 Pellicle membrane 20 Pellicle Frames

Claims

1. a) A step of obtaining transmittance data of an extreme ultraviolet pellicle in the wavelength range from the infrared region to the ultraviolet region, b) A step of obtaining complex refractive index data of an extreme ultraviolet pellicle in the wavelength range from the infrared region to the ultraviolet region, c) Perform optical modeling using the transmittance data and the complex refractive index data to obtain information regarding the relationship between the density and transmittance of the extreme ultraviolet pellicle according to the wavelength, A method for predicting the lifetime of an extreme ultraviolet pellicle, comprising the steps of: d) measuring the transmittance of the extreme ultraviolet pellicle to at least one measurement beam having a wavelength in the wavelength band from the infrared region to the ultraviolet region; extracting an estimated density of the extreme ultraviolet pellicle based on the measured transmittance and information on the relationship between density and transmittance obtained in step c); thereby predicting the remaining lifetime of the extreme ultraviolet pellicle.

2. The method for predicting the lifetime of an extreme ultraviolet pellicle according to claim 1, wherein the wavelength band of step a) includes a wavelength band of 190 nm to 200 μm.

3. The method for predicting the lifetime of an extreme ultraviolet pellicle according to claim 1, wherein the wavelength band of step a) includes a wavelength band of 190 nm to 1000 nm.

4. The above step a) is, a-1) A step of acquiring transmittance data in the wavelength band from 770 nm to 200 μm using an FT-IR spectrometer, a-2) A method for predicting the lifetime of an extreme ultraviolet pellicle according to claim 1, comprising the step of acquiring transmittance data in the wavelength band of 190 nm to 1000 nm using a UV-Vis spectrophotometer.

5. The aforementioned step b) is, b-1) A step of attaching the pellicle film of the extreme ultraviolet pellicle to the substrate, b-2) A method for predicting the lifetime of an extreme ultraviolet pellicle according to claim 1, comprising the step of obtaining complex refractive index data of the extreme ultraviolet pellicle using an elliptic spectrometer.

6. The method for predicting the lifetime of an extreme ultraviolet pellicle according to claim 1, wherein step c) is a step using the intensity transfer matrix method.

7. The aforementioned step d) is, d-1) The step of selecting at least one measurement beam, d-2) A step of measuring the transmittance of the extreme ultraviolet pellicle to the selected measurement beam, d-3) A step of extracting an estimated density of the extreme ultraviolet pellicle based on the transmittance measured in step d-2) and the information obtained in step c) regarding the relationship between the density and transmittance of the extreme ultraviolet pellicle, d-4) A method for predicting the lifetime of an extreme ultraviolet pellicle according to claim 1, comprising the step of predicting the remaining lifetime based on the estimated density extracted in step d-3).

8. The aforementioned step d-1) is, The steps include identifying the absorption mode that contributes most significantly to the absorption amount of the pellicle membrane, The steps include determining the full width at half maximum of the absorption mode, A step of selecting a wavelength range outside the full width at half maximum (FWHM) based on the full width at half maximum (FWHM) of the absorption mode, A method for predicting the lifetime of an extreme ultraviolet pellicle according to claim 7, comprising the step of selecting the wavelength of the measurement beam from a selected outer wavelength range of full width at half maximum.

9. The step of selecting the wavelength of the measurement beam is, A linear characteristic evaluation step that identifies wavelengths in the selected wavelength range outside the full width at half maximum where the transmittance has a linear relationship with the density change, A method for predicting the lifetime of an extreme ultraviolet pellicle according to claim 8, comprising a wavelength selection step of selecting the wavelength at which the linear relationship is most clearly expressed as the wavelength of the measurement beam.

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