A method for testing dielectric thin film based on mutual calibration of ellipsometry and ultraviolet-visible spectroscopy

Abstract

The application discloses a medium thin film testing method based on mutual calibration of ellipsometry and ultraviolet-visible spectrum, which comprises the following steps: firstly, fitting ellipsometry spectrum to obtain initial values of refractive index and extinction coefficient, comparing normal extinction coefficient dispersion model to determine abnormal wave band; secondly, fitting transmission spectrum, intercepting transmission spectrum refractive index and extinction coefficient corresponding to the ellipsometer abnormal wave band; then, calculating weighting factor and translation factor to calibrate transmission spectrum refractive index and extinction coefficient in the abnormal wave band; finally, correcting the ellipsometry spectrum of the abnormal wave band and re-fitting to obtain calibrated refractive index and extinction coefficient. The application adopts the above-mentioned medium thin film testing method based on mutual calibration of ellipsometry and ultraviolet-visible spectrum, applies the result of ultraviolet-visible spectrum to index specific wave band ellipsometry spectrum, realizes accurate fitting of refractive index and thickness, and thus improves medium thin film detection precision.

Description

Technical Field

[0001] The present invention relates to the technical field of dielectric thin film testing, and in particular to a dielectric thin film testing method based on mutual calibration of ellipsometry and ultraviolet-visible spectroscopy. Background Art

[0002] High-performance dielectric films have been widely used in fields such as high-energy lasers, aerospace, and photovoltaics. Achieving high-precision detection of the refractive index, extinction coefficient, and thickness of thin films is an important prerequisite for ensuring their optical performance.

[0003] Ellipsometer is a highly surface-sensitive, non-destructive method for measuring the refractive index, extinction coefficient, and thickness of dielectric thin films. The thickness can be measured in the range from sub-nanometer to several microns.

[0004] However, there are multiple solutions for fitting the refractive index, extinction coefficient, and thickness using ellipsometers. Furthermore, when the wavelength and incident angle satisfy the requirement that the phase difference Δ between s-light and p-light is an integer multiple of 2π, this will affect the decomposition calculation of the ratio of the Fresnel reflection coefficient amplitudes tan(Ψ) and the phase difference between s-light and p-light.

[0005] The calculation error of the abnormal band ellipsometric spectrum will affect the fitting results of the refractive index, extinction coefficient and thickness in the entire ellipsometric spectrum range.

[0006] The simultaneous fitting of multiple incident angles can improve the robustness of the ellipsometric spectrum fitting results. However, in order to reduce the interference of stray light from the back surface and sidewalls of the component, the test incident light angle of the ellipsometric spectrum is generally in the range of 45 to 75°, which makes it difficult to avoid the ellipsometric spectrum error caused by the phase difference of integer multiples of 2π.

[0007] UV-visible spectroscopy is another commonly used non-destructive dielectric thin film testing method, which uses the spectral envelope method to fit the refractive index and thickness of the film.

[0008] The fitting accuracy of UV-visible spectra is highly dependent on the number of peaks and valleys in the test spectrum. Therefore, it is generally used to test dielectric films with optical thicknesses ranging from a quarter wavelength to several microns, and it offers strong fitting robustness. However, when film thicknesses are subwavelength, the envelope method can only obtain a full-band refractive index dispersion trend, failing to produce accurate results. Summary of the Invention

[0009] The purpose of the present invention is to provide a dielectric thin film testing method based on mutual calibration of ellipsometry and ultraviolet-visible spectroscopy, which avoids the refractive index and thickness errors introduced by multiple solutions and phase interference and improves the accuracy of the test results.

[0010] To achieve the above object, the present invention provides a dielectric thin film testing method based on mutual calibration of ellipsometry and ultraviolet-visible spectroscopy, comprising the following steps:

[0011] S1. Fit the ellipsometry spectrum to obtain the initial values ​​of the refractive index and extinction coefficient, compare them with the normal extinction coefficient dispersion model, and determine the abnormal band;

[0012] S2. Fit the transmission spectrum and intercept the refractive index and extinction coefficient of the transmission spectrum corresponding to the abnormal band of the ellipsometer;

[0013] S3. Calculate the weighting factor and translation factor to calibrate the refractive index and extinction coefficient of the transmission spectrum in the abnormal band;

[0014] S4. Correct the ellipsometric spectrum in the abnormal band and refit to obtain the calibrated refractive index and extinction coefficient.

[0015] Preferably, S1 comprises the following steps:

[0016] S11. Use a double-sided polished, transparent material within the wavelength range of the incident light as the substrate;

[0017] S12. Prepare a dielectric film with a thickness of 100 nm by physical vapor deposition. The material and incident wavelength of the dielectric film must satisfy the requirements that its refractive index and extinction coefficient meet the normal dispersion model within the test wavelength range. Set the target material, deposition rate, vacuum degree in the cavity at the start of coating, oxygen pressure, and deposition temperature.

[0018] S13, using a single wavelength in-situ to monitor the thickness of the dielectric film, the monitoring wavelength is equal to the fitting wavelength, and the stop judgment method is the extreme point monitoring strategy;

[0019] S14, testing the amplitude ratio and phase difference of the transmission spectrum T and ellipsometric spectrum of the dielectric film within the incident wavelength range;

[0020] S15. Apply the Cauchy dispersion relation and the Urbach tail absorption model to fit the ellipsometric spectrum and obtain the extinction coefficient of the dielectric film. Compare it with the normal extinction coefficient dispersion model to determine the range of the abnormal band.

[0021] Preferably, in S2, the transmission spectrum is fitted using the Cauchy dispersion relation combined with the envelope method, and the refractive index and extinction coefficient of the transmission spectrum corresponding to the abnormal band of the ellipsometer are intercepted.

[0022] Preferably, in S3, the refractive index and extinction coefficient of the abnormal band calibration are obtained by calculating the weighting factor and translation factor that connect the end points of the refractive index splicing segment, and the linear weighted translation factor under the condition of S15 is found.

[0023] Preferably, in S4, the calibrated refractive index and extinction coefficient are used to calculate the amplitude ratio and phase difference of the ellipsometric spectrum corrected in the abnormal band, and the amplitude ratio and phase difference of the ellipsometric spectrum measured in the abnormal band are replaced, and the Cauchy dispersion relation and Urbach tail absorption are used to refit the ellipsometric spectrum to obtain the calibrated refractive index and extinction coefficient.

[0024] Preferably, in S14, when testing the transmission spectrum T, the dielectric film sample is placed vertically, the incident mode is normal incidence, the incident light step length is 1 nm, and the incident light angle is 90°;

[0025] When testing the amplitude ratio and phase difference of the ellipsometric spectrum, the dielectric film sample is vacuum adsorbed onto the sample stage, the incident light is linearly polarized light at an oblique incidence, the step size is 1nm, and the incident light angle is 55-65°.

[0026] Preferably, in S15, the refractive index n in the Cauchy dispersion relation satisfies:

[0027]

[0028] Among them, A n 、B n and C n is the Cauchy dispersion coefficient, which is determined by the dielectric film material, and λ is the wavelength of the incident light.

[0029] Preferably, in S15, the extinction coefficient k in the Urbach tail absorption model satisfies:

[0030]

[0031] Among them, A k 、B k and C k is the dispersion coefficient, which is determined by the dielectric film material, and λ is the wavelength of the incident light;

[0032] The abnormal band is the deviation of the extinction coefficient k dispersion curve fitting result from the Urbach tail absorption model.

[0033] Preferably, in S3, the refractive index and extinction coefficient obtained by fitting the transmission spectrum at both ends of the abnormal band are multiplied by the corresponding weighting factor and then added to the corresponding translation factor to obtain the corrected refractive index and extinction coefficient of the abnormal band. The calculation formula of the refractive index weighting factor is:

[0034]

[0035] The calculation formula of the extinction coefficient weighting factor is:

[0036]

[0037] The calculation formula of the refractive index shift factor is:

[0038]

[0039] The calculation formula of the extinction coefficient shift factor is:

[0040]

[0041] Among them, n e2 、n e1 is the refractive index obtained by ellipsometer fitting at both ends of the abnormal band, k e2 、k e1 is the extinction coefficient obtained by ellipsometer fitting at both ends of the abnormal band, n T2 、n T1 is the refractive index obtained by fitting the transmission spectrum at both ends of the abnormal band, k T2 、k T1 is the extinction coefficient obtained by fitting the transmission spectrum at both ends of the abnormal band.

[0042] Therefore, the present invention adopts the above-mentioned dielectric thin film testing method based on ellipsometry and ultraviolet-visible spectroscopy mutual calibration, and the beneficial effects are as follows:

[0043] The present invention corrects the local ellipsometer results by introducing a truncation method of spectral results; its advantages are low measurement cost, simple and reliable method, high correction accuracy, and wide applicability, that is, it is also applicable to other materials within the characterization wavelength range that meet one of the measurement conditions of the spectrometer and ellipsometer.

[0044] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is an overall flow chart of an embodiment of a dielectric thin film testing method based on mutual calibration of ellipsometry and ultraviolet-visible spectroscopy according to the present invention;

[0046] Figure 2 1 is a diagram illustrating the results of step S15 of an embodiment of a dielectric thin film testing method based on mutual calibration of ellipsometric and ultraviolet-visible spectroscopy according to the present invention, wherein (a) is the measured ellipsometric spectrum amplitude ratio Ψ and phase difference Δ, and (b) is the refractive index and extinction coefficient fitting results;

[0047] Figure 3 1 is a schematic diagram of the results of S2 of an embodiment of a dielectric thin film testing method based on ellipsometry and UV-visible spectroscopy mutual calibration of the present invention, wherein (a) is the fitting result of the measured transmission spectrum, and (b) is the fitting result of the refractive index and extinction coefficient;

[0048] Figure 4 is the refractive index correction result in S3 of an embodiment of a dielectric thin film testing method based on ellipsometry and ultraviolet-visible spectroscopy mutual calibration of the present invention;

[0049] Figure 5 is the ellipsometric spectrum correction result in S4 of an embodiment of a dielectric thin film testing method based on mutual calibration of ellipsometric and ultraviolet-visible spectroscopy of the present invention;

[0050] Figure 6It is the fitting result of the refractive index and extinction coefficient based on the mutual calibration of ellipsometry and ultraviolet-visible spectroscopy in S4 of an embodiment of a dielectric thin film testing method based on the mutual calibration of ellipsometry and ultraviolet-visible spectroscopy of the present invention. DETAILED DESCRIPTION

[0051] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0052] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0053] The present invention provides a high-precision dielectric thin film testing method for mutual calibration of ellipsometric and ultraviolet-visible spectra, including setting detection parameters and fitting models, locating abnormal bands, and mutual calibration of abnormal band spectra with refractive index as the link.

[0054] The ellipsometry method uses the ratio of the Fresnel reflection coefficients of p-light and s-light to obtain ρ, and calculates the amplitude ratio Ψ and phase difference Δ of the ellipsometry spectrum. Both are parameters of the refractive index and thickness of the dielectric film, the refractive index of the substrate, and the interface roughness. It is necessary to select an appropriate model to establish the relationship between the refractive index and wavelength, and increase the incident angle of the test light to improve the robustness of the fitting results. However, it is difficult to completely avoid the problem of multiple solutions. In addition, when the phase difference Δ of ρ reaches an integer of 2π, the phase difference Δ will jump by 2π, such as Figure 2 As shown, the amplitude of ρ, tan(Ψ), also shows large fluctuations due to calculations. In this range, the ellipsometry spectrum is abnormal.

[0055] When the minimum mean square error (MSE) strategy is used to fit the refractive index of the entire band, the measurement and calculation errors of the abnormal band will reduce the refractive index fitting accuracy of the entire band. The MSE definition mentioned in this invention is expressed as follows:

[0056]

[0057] Where n is the number of sampling points, m is the number of fitting parameters, N = cos(2Ψ), C = cos(2Ψ)sin(Δ), S = sin(2Ψ)sin(Δ), E represents the measured data, and G represents the model-generated data.

[0058] The UV-visible transmission spectrum uses the spectral envelope to calculate the refractive index and thickness of the film. The fitting accuracy depends on the number of peaks and valleys in the spectrum. When the thickness of the dielectric film is sub-wavelength, the envelope method can only obtain the dispersion trend of the refractive index in the entire band and cannot obtain accurate results.

[0059] Therefore, if Figure 1As shown, the present invention provides a high-precision dielectric thin film testing method based on the mutual calibration of ellipsometric and ultraviolet-visible spectroscopy. First, the Cauchy dispersion relation and the Urbach tail absorption model are applied to fit the film extinction coefficient corresponding to the ellipsometric spectrum, and compared with the normal extinction coefficient dispersion model to determine the range of the abnormal band; then, the full-band refractive index and extinction coefficient dispersion trend of the ultraviolet-visible transmission spectrum are combined with a weighting factor and a translation factor to correct the refractive index and extinction coefficient of the abnormal band, and then the ellipsometric spectrum Ψ and phase difference Δ of the abnormal band are solved; finally, the Cauchy dispersion relation and the Urbach tail absorption model are applied to fit the corrected ellipsometric spectrum to obtain accurate refractive index and film thickness, which specifically includes the following steps:

[0060] S1. Fit the ellipsometry spectrum to obtain the initial values ​​of the refractive index and extinction coefficient, compare them with the normal extinction coefficient dispersion model, and determine the abnormal band, including the following steps:

[0061] S11. Use a double-sided polished, transparent material within the wavelength range of the incident light as the substrate;

[0062] This embodiment requires certain requirements and special restrictions on the type of substrate, that is, the substrate must be transparent within the wavelength range of the incident light. The size of the substrate can be selected according to different needs. In this embodiment, double-sided polished substrate with a size of Φ50×3mm is selected. 2 The JGS1 quartz glass is used as the substrate and is transparent in the incident wavelength range of 300-1200nm.

[0063] S12. A dielectric film having a theoretical thickness of 100 nm is prepared by physical vapor deposition. In this embodiment, the number of film layers and the thickness of the dielectric film are not limited. However, the material of the dielectric film and the incident wavelength need to be subject to certain restrictions, that is, the refractive index and extinction coefficient of the dielectric film must meet the normal dispersion model within the test wavelength range.

[0064] In this example, a HfO2 monolayer film with a thickness of 100 nm was selected as the characterization object. It satisfies the normal dispersion in the incident wavelength range of 300-1200 nm. The target material is Hf target, the deposition rate is 0.23-0.25 nm / s, and the vacuum degree in the cavity at the beginning of the coating is 9.0×10 -4 Pa, oxygen pressure is 2.5×10 -2 Pa and deposition temperature were kept constant at 463–473 K.

[0065] S13. Use single wavelength in-situ to monitor the thickness of the dielectric film (HfO2 single layer film). The monitoring wavelength and the fitting wavelength are both 967.3 nm. The stop judgment method is the extreme point monitoring strategy.

[0066] S14. The transmission spectrum T of the test medium film (HfO2 single layer film) in the incident wavelength range of 300-1200nm and the amplitude ratio Ψ and phase difference Δ of the ellipsometric spectrum in the range of 300-1200nm.

[0067] When testing the transmission spectrum T, the dielectric thin film sample (HfO2 single layer film) is placed vertically, the incident mode is normal incidence, the incident light step length is 1nm, and the incident light angle is 90°, which can meet the transmission spectrum test of the single layer film of this thickness.

[0068] When testing the amplitude ratio and phase difference of the ellipsometric spectrum, the dielectric thin film sample (HfO2 monolayer film) is vacuum adsorbed onto the sample stage, the incident light is linearly polarized light at an oblique incidence, the step size is 1nm, and the incident light angle can be selected between 55-65°.

[0069] S15. In this embodiment, the wavelength range of the amplitude ratio Ψ and phase difference Δ of the ellipsometric spectrum is 300-1200 nm. The Cauchy dispersion relation and the Urbach tail absorption model are applied to fit the ellipsometric spectrum to obtain the extinction coefficient of the dielectric film (HfO2 monolayer film). The normal extinction coefficient dispersion model is compared to determine the range of the abnormal band. The refractive index and extinction coefficient of the abnormal band are intercepted, as shown in FIG. Figure 2 The difficulty lies in that the slopes at the two end points must be consistent with the slopes at the corresponding end points of the Cauchy dispersion model while retaining the most original ellipsometric data.

[0070] The main function of the UV-visible transmission spectrum is to provide reasonable initial values ​​of the refractive index and extinction coefficient, which are used to correct the amplitude ratio Ψ and phase difference Δ of the ellipsometric spectrum in the abnormal band. Therefore, the wavelength range of the incident light only needs to cover the abnormal band of the ellipsometric spectrum. For example, the incident wavelength range selected in this embodiment is 300-1200nm.

[0071] Among them, the refractive index n in the Cauchy dispersion relation satisfies:

[0072]

[0073] Among them, A n 、B n and C n is the Cauchy dispersion coefficient, which is determined by the dielectric film material, and λ is the wavelength of the incident light.

[0074] The extinction coefficient k in the Urbach tail absorption model satisfies:

[0075]

[0076] Among them, A k 、B k and C kis the dispersion coefficient, which is determined by the dielectric film material, and λ is the wavelength of the incident light;

[0077] The abnormal band is the deviation of the extinction coefficient k dispersion curve fitting result from the Urbach tail absorption model.

[0078] S2. Apply the Cauchy dispersion relation combined with the envelope method to fit the transmission spectrum and obtain the refractive index and extinction coefficient of the dielectric film (HfO2 monolayer film), such as Figure 3 As shown, the refractive index and extinction coefficient of the transmission spectrum corresponding to the abnormal band of the ellipsometer are intercepted.

[0079] S3. By calculating the weighting factor and translation factor that connect the end points of the refractive index splicing segment, the refractive index and extinction coefficient of the abnormal band calibration are obtained, and the linear weighted translation factor under the S15 condition is found to calibrate the refractive index and extinction coefficient of the transmission spectrum in the abnormal band.

[0080] like Figure 4 As shown, the refractive index and extinction coefficient obtained by fitting the transmission spectrum at both ends of the abnormal band in step S15 are multiplied by the corresponding weighting factor, and then added with the corresponding translation factor. The value is equal to the refractive index and extinction coefficient obtained by fitting the ellipsometric spectrum at both ends of the abnormal band, and the corrected refractive index and extinction coefficient of the abnormal band can be obtained.

[0081] The calculation formula of the refractive index weighting factor is:

[0082]

[0083] The calculation formula of the extinction coefficient weighting factor is:

[0084]

[0085] The calculation formula of the refractive index shift factor is:

[0086]

[0087] The calculation formula of the extinction coefficient shift factor is:

[0088]

[0089] Among them, n e2 、n e1 is the refractive index obtained by ellipsometer fitting at both ends of the abnormal band, k e2 、k e1 is the extinction coefficient obtained by ellipsometer fitting at both ends of the abnormal band, n T2 、n T1 is the refractive index obtained by fitting the transmission spectrum at both ends of the abnormal band, k T2 、k T1 is the extinction coefficient obtained by fitting the transmission spectrum at both ends of the abnormal band.

[0090] S4, correcting the ellipsometric spectrum of the abnormal wave band, and re-fitting to obtain the calibrated refractive index and extinction coefficient.

[0091] The amplitude ratio Ψ and phase difference Δ of the ellipsometric spectrum of the abnormal wave band are calculated by using the calibrated refractive index and extinction coefficient, and the amplitude ratio Ψ and phase difference Δ of the measured ellipsometric spectrum of the abnormal wave band are replaced, as shown in formula (3). Figure 5 The ellipsometric spectrum is re-fitted by using Cauchy dispersion relation and Urbach tail absorption to obtain the completed calibration of the refractive index and extinction coefficient, as shown in formula (4). Figure 6 Compared with the correction, the MSE decreases from 2.459 to 1.002, and the thickness result increases from 98.9 nm to 99.1 nm, which is closer to the thickness 99.2 nm obtained by X-ray reflectometer test.

[0092] Therefore, the present application adopts the above-mentioned medium thin film testing method based on the mutual calibration of ellipsometric and ultraviolet-visible spectrum, and aims at the problems in the existing non-destructive testing of medium thin film refractive index, such as the difficulty in decoupling the thickness and refractive index, and the inaccuracy of the specific wave band of the ellipsometric spectrum. The results of the ultraviolet-visible spectrum are used to index the ellipsometric spectrum of the specific wave band, so as to realize the accurate fitting of the refractive index and thickness, and improve the detection precision of the medium thin film.

[0093] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application but not to limit it. Although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can still be modified or replaced by the equivalent, and these modifications or replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A dielectric thin film testing method based on mutual calibration of ellipsometry and ultraviolet-visible spectroscopy, characterized in that: The following steps are involved: S1. Fit the ellipsometry spectrum to obtain the initial values ​​of the refractive index and extinction coefficient, compare them with the normal extinction coefficient dispersion model, and determine the abnormal band; S2. Fit the transmission spectrum and intercept the refractive index and extinction coefficient of the transmission spectrum corresponding to the abnormal band of the ellipsometer; S3. Calculate the weighting factor and translation factor to calibrate the refractive index and extinction coefficient of the transmission spectrum in the abnormal band; S4, correcting the ellipsometric spectrum of the abnormal band and refitting to obtain the calibrated refractive index and extinction coefficient; In S2, the Cauchy dispersion relation combined with the envelope method is used to fit the transmission spectrum, and the refractive index and extinction coefficient of the transmission spectrum corresponding to the abnormal band of the ellipsometer are intercepted; In S3, the refractive index and extinction coefficient of the anomalous band calibration are obtained by calculating the weighting factor and translation factor that connect the endpoints of the refractive index splicing segment, and finding the linear weighted translation factor that matches the slope at the corresponding endpoint of the Cauchy dispersion model while satisfying the most ellipsometric original data retention conditions; In S4, the calibrated refractive index and extinction coefficient are used to calculate the amplitude ratio and phase difference of the ellipsometric spectrum corrected in the anomalous band, and the amplitude ratio and phase difference of the ellipsometric spectrum measured in the anomalous band are replaced. The ellipsometric spectrum is refitted using the Cauchy dispersion relation and Urbach tail absorption to obtain the calibrated refractive index and extinction coefficient.

2. The dielectric thin film testing method based on mutual calibration of ellipsometry and ultraviolet-visible spectroscopy according to claim 1, characterized in that: S1 includes the following steps: S11. Use a double-sided polished, transparent material within the wavelength range of the incident light as the substrate; S12. Prepare a dielectric film with a thickness of 100 nm by physical vapor deposition. The material and incident wavelength of the dielectric film must satisfy the requirements that its refractive index and extinction coefficient meet the normal dispersion model within the test wavelength range. Set the target material, deposition rate, vacuum degree in the cavity at the beginning of coating, oxygen pressure, and deposition temperature. S13, using a single wavelength in-situ to monitor the thickness of the dielectric film, the monitoring wavelength is equal to the fitting wavelength, and the stop judgment method is the extreme point monitoring strategy; S14, testing the amplitude ratio and phase difference of the transmission spectrum T and ellipsometric spectrum of the dielectric film within the incident wavelength range; S15. Apply the Cauchy dispersion relation and the Urbach tail absorption model to fit the ellipsometric spectrum and obtain the extinction coefficient of the dielectric film. Compare it with the normal extinction coefficient dispersion model to determine the range of the abnormal band.

3. The dielectric thin film testing method based on mutual calibration of ellipsometry and ultraviolet-visible spectroscopy according to claim 2, characterized in that: In S14, when measuring the transmission spectrum T, the dielectric film sample is placed vertically, the incident light is normal incidence, the incident light step is 1 nm, and the incident light angle is 90°; When testing the amplitude ratio and phase difference of the ellipsometric spectrum, the dielectric film sample is vacuum adsorbed onto the sample stage, the incident light is linearly polarized light at an oblique incidence, the step size is 1 nm, and the incident light angle is 55-65°.

4. The dielectric thin film testing method based on mutual calibration of ellipsometry and ultraviolet-visible spectroscopy according to claim 3, characterized in that: In S15, the refractive index in the Cauchy dispersion relation satisfy: ； in, 、 and is the Cauchy dispersion coefficient, which is determined by the dielectric film material. is the wavelength of incident light.

5. The dielectric thin film testing method based on mutual calibration of ellipsometry and ultraviolet-visible spectroscopy according to claim 4, characterized in that: Extinction coefficient in the Urbach tail absorption model in S15 satisfy: ； in, 、 and is the dispersion coefficient, which is determined by the dielectric film material. is the wavelength of incident light; The abnormal band is the extinction coefficient The dispersion curve fitting results deviate from the Urbach tail absorption model.

6. The dielectric thin film testing method based on mutual calibration of ellipsometry and ultraviolet-visible spectroscopy according to claim 5, characterized in that: In S3, the refractive index and extinction coefficient obtained by fitting the transmission spectrum at both ends of the abnormal band are multiplied by the corresponding weighting factor and then added to the corresponding translation factor to obtain the corrected refractive index and extinction coefficient of the abnormal band. The calculation formula of the refractive index weighting factor is: ； The calculation formula of the extinction coefficient weighting factor is: ； The calculation formula of the refractive index shift factor is: ； The calculation formula of the extinction coefficient shift factor is: ； in, 、 is the refractive index obtained by ellipsometer fitting at both ends of the abnormal band, 、 is the extinction coefficient obtained by ellipsometer fitting at both ends of the abnormal band, 、 is the refractive index obtained by fitting the transmission spectrum at both ends of the abnormal band, 、 is the extinction coefficient obtained by fitting the transmission spectrum at both ends of the abnormal band.

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