A reflective method for measuring the transmittance of a thin film in situ in real time and a device therefor

Abstract

The application discloses a reflective method for measuring transmittance of a thin film in real time and in situ and a device thereof. The application adds a reflecting surface, and only needs to measure light intensity reflectivity R of the thin film and light intensity reflectivity R' of the thin film-reflecting surface, so that the transmittance of the thin film can be directly calculated through a formula without establishing a precise optical model and complex fitting. The reflected light of the thin film and the light reflected back by the reflecting surface do not interfere and do not involve superposition of amplitudes, but only superposition of light intensities. The transmittance can be obtained by only obtaining the light intensity. The transmittance of the thin film is measured by the method of measuring reflectivity twice. In the process of measuring the transmittance by the reflective method, the thickness of the thin film and the optical properties of the film do not need to be known in advance, and the reflective method is very suitable for real-time in-situ measurement and monitoring of the growth process of the thin film. All optical elements of the reflective method are on one side of the thin film, the incident light can have a range of angles much larger than that of an ellipsometer, and the reflective method is easy to integrate with other film manufacturing equipment.

Description

TECHNICAL FIELD

[0001] The present application relates to optical thin film measurement technology, and in particular to a reflection method for real-time in-situ measurement of thin film transmittance and a device thereof. BACKGROUND

[0002] Thin films are widely used in modern photonic and optoelectronic technology fields such as photovoltaics, storage, chips, etc. They can be used to manufacture various optoelectronic devices, chips and instruments. The properties of thin films, such as material properties, thickness, etc. and uniformity, are crucial to the performance of optoelectronic devices and chips. The optical properties of materials can be characterized by measuring transmittance or absorbance, and the transmittance of different materials will be different. In addition, real-time in-situ measurement of the growth process of optical thin films can study the kinetic process of film forming technology, which is crucial to understanding and optimizing device function.

[0003] Optical measurement methods have the characteristics of non-contact, high measurement accuracy and non-destructive, and are widely used in the measurement and detection of thin film properties in the fields of semiconductors, optical coating, new energy materials, etc. Optical measurement methods are mainly divided into two types: reflection and transmission. The film thickness meter and ellipsometer based on the reflection system use the thin film interference principle to study the properties of the thin film, such as film thickness and material complex refractive index, by measuring the reflected light of the thin film structure. The film thickness and material complex refractive index can be further calculated to obtain the transmittance or absorbance of the thin film structure. The physical nature of such reflection system instruments (ellipsometer and film thickness meter) is to use the amplitude superposition interference of many reflected lights at the interface of different materials. The interference spectrum of the reflected light of the thin film measured by the film thickness meter must know one of the film thickness and material complex refractive index, and the other parameter is obtained by fitting the interference spectrum. Although the probe of such film thickness meter is small (about 30mm 2 ), it is easy to integrate. However, during the growth process of thin film materials, the film thickness and material properties change with time, so the film thickness meter cannot realize real-time in-situ measurement of the growth process of the thin film. In addition, for a single wavelength light source, the film thickness meter cannot obtain the material complex refractive index at a single wavelength by formula fitting. The ellipsometer based on the measurement of the change of the polarization state of the reflected light of the thin film uses an accurate optical model and complex calculation to simultaneously solve the film thickness and material complex refractive index, and can realize real-time in-situ measurement of the thin film. However, such reflection ellipsometer needs to use a large inclined light incidence (about 70°), which makes the whole optical system large and not easy to integrate.

[0004] Film thickness gauges and ellipsometers based on reflective systems neglect the transmitted light portion, making it impossible to directly measure the transmittance of thin films. Instruments such as spectrophotometers based on transmission systems can directly measure the transmittance or absorbance of thin films in real time. This type of transmission system requires incident light from one side of the sample and measured transmitted light from the other side. This transmission configuration makes the entire measurement system bulky and difficult to integrate, especially for equipment where the sample is solid and requires extreme temperature conditions, such as large-area coating machines, spin coaters, and vacuum heating / cooling coating systems [molecular beam epitaxy (MBE) equipment and electron beam evaporation (Ebeam) equipment]. In summary, obtaining a small, easily integrated method and apparatus for real-time, in-situ measurement of the transmittance (or absorbance) of thin film structures remains a significant challenge. Summary of the Invention

[0005] To address the problems of large equipment size, difficulty in integration, and inability to measure thin film properties in real time in situ in the existing technologies, this invention proposes a reflective method and apparatus for real-time in-situ measurement of thin film transmittance.

[0006] One object of the present invention is to provide a reflective method for real-time in-situ measurement of thin film transmittance.

[0007] The reflective method for real-time in-situ measurement of thin film transmittance of the present invention includes the following steps:

[0008] a) Erecting the equipment:

[0009] The thin film to be measured is placed on a transparent substrate, with the environment above the film; the transmittance T of the substrate is measured. s ≥5%; An incident light path and an outgoing light path are set on the thin film; the light source is coupled to the incident light path, and the end of the outgoing light path is coupled to a detector or spectrometer, which is connected to a computer;

[0010] b) Measure the light reflectance R of the thin film:

[0011] 1) The light source emits a light beam, which is incident on the thin film through the incident light path. The intensity of the light incident on the thin film is I0.

[0012] 2) When incident light strikes the interface between the environment and the thin film, part of the light is reflected back into the environment and part of the light is refracted into the thin film.

[0013] 3) The portion of light refracted into the thin film is reflected and refracted at the interface between the thin film and the substrate;

[0014] 4) Light reflected at the interface between the thin film and the substrate will be reflected back and forth between the upper and lower interfaces of the thin film and then refracted into the environment and the substrate; light refracted at the interface between the thin film and the substrate will be transmitted from the lower surface of the substrate.

[0015] 5) The reflected light of the film is received by the detector or spectrometer through the exit light path; the reflected light of the film includes the light reflected by the interface between the environment and the film to the environment and the light reflected by the interface between the film and the substrate and then refracted by the interface between the environment and the film to the environment;

[0016] 6) The detector or spectrometer measures the intensity I of the reflected light of the film R , and further obtains the light intensity reflectivity R of the film:

[0017] R = I R / I0 (1)

[0018] c) Measuring the light intensity reflectivity R' of the film-reflection surface:

[0019] 1) A reflection surface with a known reflectivity is arranged below the substrate, the amplitude reflectivity of the reflection surface is r0, and the light intensity reflectivity R0 of the reflection surface is |r0| 2 ≥ 5%; the distance from the lower surface of the film to the reflection surface exceeds the interference length of the light source;

[0020] 2) The intensity of the transmitted light of the lower surface of the substrate is I T = I0×T×T s , T is the light intensity transmittance of the film, and T s is the light intensity transmittance of the substrate;

[0021] 3) The reflection surface reflects the transmitted light of the lower surface of the substrate back to the substrate, and the light reflected back to the substrate is transmitted to the environment through the film again, at this time, the transmitted light passes through the film and the substrate twice, and the intensity I' of the light transmitted by the substrate and then reflected by the reflection surface and then transmitted to the environment through the film is: R

[0022] I' R = I0×T×T s ×R0×T×T s = I0×R0×T 2 ×T s 2 (2)

[0023] 4) The reflected light of the film and the light reflected back by the reflection surface are received by the detector or spectrometer through the exit light path together, the detector or spectrometer measures the total light intensity I RR , and further obtains the light intensity reflectivity R' of the film-reflection surface:

[0024] R' = I RR / I0 (3)

[0025] d) Calculating the transmittance T of the film:

[0026] ​1) After adding the reflecting surface under the substrate, the light detected by the detector or spectrometer is composed of two parts: the reflected light of the film and the light reflected back by the reflecting surface, the distance from the lower surface of the film to the reflecting surface exceeds the interference length of the light source, the two parts of light do not interfere, only the superposition of intensity, without amplitude superposition;

[0027] 2) The total light intensity I measured by the detector or spectrometer is: RR

[0028] I RR R R = I0x R + I0x R0x T 2 x T s 2 (4)

[0029] 3) The transmittance T of the film is obtained as:

[0030]

[0031] wherein, R = I R / I0 is the light intensity reflectance of the film, which has been obtained in 6) of step b); R' is the light intensity reflectance of the film-reflecting surface, which has been obtained in 4) of step c); R0 is the light intensity reflectance of the reflecting surface, which is a known quantity; T s is the transmittance of the substrate, which is a known quantity; only the light intensity reflectance R of the film and the light intensity reflectance R' of the film-reflecting surface need to be measured, and the transmittance of the film is directly calculated by using formula (5); the reflected light of the film and the light reflected back by the reflecting surface do not interfere, without amplitude superposition, only the superposition of light intensity, and the transmittance of the film can be directly calculated by measuring the light intensity; during the measurement, the thickness of the film and the optical properties of the film do not need to be known in advance, realizing real-time in-situ measurement and monitoring of the growth process of the film.

[0032] wherein, in 2) of step a), the first angle θ1 satisfies 0°≤θ1<90°.

[0033] In 1) of step c), the reflecting surface can be in close contact with the substrate or not, and the distance d between the reflecting surface and the lower surface of the substrate is less than 500 mm. The distance from the lower surface of the film to the reflecting surface is greater than the interference length L = λ 2 / (Δλ) of the light source, λ is the central wavelength of the light source, and Δλ is the spectral width of the light source.

[0034] ​​​In 1) and 2) of step d), the light directly reflected by the film to the environment and the light reflected by the reflecting surface and then transmitted by the film to the environment do not interfere with each other, but only superimpose in intensity, which is completely different from the amplitude superposition in the film thickness meter and ellipsometer of the reflection system, and the two have different physical natures.

[0035] In 3) of step d), when the reflectivity of the reflecting surface and the transmittance of the substrate are both high, R0≥95% and T s ≥95%, the transmittance of the film is simplified as T=(R'-R) 1 / 2 Further, the method of the present application can measure the transmittance or transmittance spectrum of a single-layer film or a multi-layer film, thereby reflecting the optical properties of the film material; when measuring the transmittance or transmittance spectrum of a multi-layer film, the multi-layer film is equivalent to a single-layer film. The light source uses a multi-wavelength light source to directly measure the transmittance spectrum; the light source uses a monochromatic light source to measure the transmittance at one wavelength. In the process of measuring the transmittance by the reflection method, the thickness of the film and the optical properties of the film do not need to be known in advance, which is very suitable for real-time in-situ measurement and monitoring of the growth process of the film. In addition, all optical elements of the incident light path and the exit light path of the reflection method are on one side of the film, the angle θ1 of the incident light satisfies 0°≤θ1<90°, and the range of the angle can be much larger than that of the ellipsometer, which is easy to integrate with other film manufacturing equipment.

[0036] Another object of the present application is to provide a reflection device for real-time in-situ measurement of the transmittance of a film.

[0037] The reflection device for real-time in-situ measurement of the transmittance of a film of the present application comprises a film, a substrate, a light source, an incident light path, an exit light path, a detector or a spectrometer, a computer and a reflecting surface; wherein the film is arranged on the light-transmitting substrate, and the environment is above the film; the transmittance T s of the substrate is ≥5%; the incident light path and the exit light path are arranged above the film; the light source is coupled to the incident light path, the end of the exit light path is coupled to the detector or the spectrometer, and the detector or the spectrometer is connected to the computer;

[0038] In the measurement of the light intensity reflectance of the film, the light source emits a light beam which is incident on the film through an incident light path; the incident light is incident on the interface between the environment and the film, a part of the light is reflected into the environment, and a part of the light is refracted into the film; the light refracted into the film is reflected and refracted by the interface between the film and the substrate; the light reflected by the interface between the film and the substrate is reflected back and forth by the upper and lower interfaces of the film, and is refracted into the environment and the substrate; the light refracted by the interface between the film and the substrate is transmitted from the lower surface of the substrate; the reflected light of the film is received by a detector or a spectrometer through an exit light path, and the reflected light of the film includes the light reflected by the interface between the environment and the film to the environment and the light reflected by the interface between the film and the substrate and then refracted by the interface between the environment and the film to the environment, and the detector or the spectrometer measures the intensity I of the reflected light of the film R , and further obtains the light intensity reflectance R of the film;

[0039] In the measurement of the light intensity reflectance of the film-substrate, a substrate with a known reflectance is arranged below the substrate, the amplitude reflectance of the substrate is r0, and the light intensity reflectance R0 of the substrate is |r0| 2 ≥ 5%; the distance from the lower surface of the film to the substrate exceeds the interference length of the light source; the intensity of the transmitted light from the lower surface of the substrate is I T = I0×T×T s , T is the light intensity transmittance of the film, and T s is the light intensity transmittance of the substrate; the substrate reflects the transmitted light from the lower surface of the substrate back to the substrate, and the light reflected back to the substrate is transmitted to the environment through the film again, at this time, the transmitted light passes through the film and the substrate twice, and the light transmitted from the substrate to the environment is reflected by the substrate and then transmitted to the environment through the film; the reflected light of the film and the light reflected back by the substrate are received by a detector or a spectrometer through an exit light path; at this time, the light detected by the detector or the spectrometer is composed of two parts: the reflected light of the film and the light reflected back by the substrate, the distance from the lower surface of the film to the substrate exceeds the interference length of the light source, the two parts of light do not interfere, and do not involve the superposition of amplitudes, but only the superposition of light intensities; the detector or the spectrometer measures the total light intensity I RR , and further obtains the light intensity reflectance R' of the film-substrate; the transmittance T of the film is calculated by the measured light intensity reflectance R of the film and the light intensity reflectance R' of the film-substrate.

[0040] The light source uses a multi-wavelength light source to directly measure the transmittance spectrum; or the light source uses a monochromatic light source to measure the transmittance of only one wavelength.

[0041] The incident light path and the emergent light path adopt a fiber transmission system or a free space transmission system; when the fiber transmission system is adopted, the incident light path adopts an incident fiber and the emergent light path adopts an emergent fiber; when the free space transmission system is adopted, the incident light path adopts a first lens and the emergent light path adopts a second lens; in the incident light path, the incident light is collimated by the first lens and then enters the upper surface of the film through a light splitting element; in the emergent light path, the emergent light is collected by the second lens after passing through the light splitting element and is coupled to a detector or a spectrometer; and the light splitting element adopts a light splitting prism or a light splitting mirror.

[0042] The distance d between the reflecting surface and the lower surface of the substrate is less than 500 mm.

[0043] The reflecting surface adopts a mirror or a reflecting film.

[0044] Further, the application also includes a moving device, and the reflecting surface is placed on the moving device; when the light intensity reflectivity of the film is measured, the reflecting surface is moved out from under the substrate by the moving device; when the light intensity reflectivity of the film-reflecting surface is measured, the reflecting surface is placed under the substrate by the moving device.

[0045] Advantages of the application:

[0046] The application adds a reflecting surface, and only needs to measure the light intensity reflectivity R of the film and the light intensity reflectivity R' of the film-reflecting surface to directly calculate the transmittance of the film by a formula, without the need to establish a precise optical model and complex fitting; the reflected light of the film and the light reflected back by the reflecting surface do not interfere, do not involve the superposition of amplitudes, only involve the superposition of light intensities, and only the light intensity needs to be obtained to obtain the transmittance, so that the transmittance of the film is measured by the method of measuring the reflectivity twice; in the process of measuring the transmittance by the reflecting method, the thickness of the film and the optical properties of the film do not need to be known in advance, and the reflecting method is very suitable for real-time in-situ measurement and monitoring of the growth process of the film; all optical elements of the reflecting method are on one side of the film, the angle θ1 of the incident light satisfies 0°≤θ1<90°, the angle range can be much larger than the angle range of an ellipsometer, and the reflecting method is easy to integrate with other film manufacturing equipment. The application has the characteristics of rapidness (~ms), simplicity, small size, easy integration and low cost, and has important application prospects in optical film measurement and real-time detection of the growth process of the film, and is very beneficial to film equipment which is not friendly to integrated transmissive devices, such as a coating machine, a spin coater, an MBE, an Ebeam and the like. Therefore, the method and device provided by the application can be widely applied to industrial application fields such as semiconductors, optical coating and new energy materials. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 FIG. 1 is a schematic diagram of an embodiment of the reflecting device for real-time in-situ measurement of the transmittance of the film according to the application;

[0048] Figure 2 This is a schematic diagram of a second embodiment of the reflective device for real-time in-situ measurement of thin film transmittance of the present invention;

[0049] Figure 3 This is a schematic diagram of an embodiment of the reflective method for real-time in-situ measurement of thin film transmittance of the present invention;

[0050] Figure 4 The following is a result diagram obtained from an embodiment of the reflective method for real-time in-situ measurement of thin film transmittance according to the present invention, wherein (a) is a comparison diagram of the reflectance spectrum or transmittance spectrum of perovskite thin films experimentally measured by the prior art and the present invention with and without reflective surfaces, and (b) is a comparison diagram of the light intensity transmittance spectrum of perovskite thin films calculated by the prior art and the method of the present invention. Detailed Implementation

[0051] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0052] The incident and outgoing optical paths employ either fiber optic systems or free-space optical systems.

[0053] Example 1

[0054] In this embodiment, an optical fiber system is used.

[0055] like Figure 1 As shown, the reflective device for real-time in-situ measurement of thin film transmittance in this embodiment includes: a thin film, a substrate, a light source, an incident optical fiber, an outgoing optical fiber, a spectrometer, a computer, and a reflective surface; wherein, the thin film is disposed on a light-transmitting substrate, and the environment is on the thin film; the transmittance T of the substrate is... s ≥5%; An incident fiber and an exit fiber are placed on the thin film; the light source is connected to one end of the incident fiber, and the end of the exit fiber is connected to a spectrometer, which is connected to a computer via a data cable; the distance from the lower surface of the thin film to the reflecting surface exceeds the interference length of the light source. The incident fiber and the exit fiber have a common port, which is fixed by a five-axis fiber optic holder. The five-axis fiber optic holder adjusts the three-dimensional position (xyz) of the fiber on the thin film and adjusts the pitch of the fiber to make the fiber perpendicular to the surface of the thin film.

[0056] Example 2

[0057] In this embodiment, a free-space light system is used.

[0058] like Figure 2As shown, the reflective device for measuring the transmittance of the thin film in real time in situ of the embodiment comprises: a thin film, a substrate, a light source, a first lens, a second lens, a light splitting prism, a spectrometer, a computer and a reflecting surface; wherein the thin film is arranged on the light-transmitting substrate, and the environment is on the thin film; the first lens is used for the incident light path, and the second lens is used for the exit light path; in the incident light path, the incident light is collimated by the first lens, is split by the light splitting prism and is turned, in the exit light path, the exit light transmits through the light splitting prism, is reflected by the reflecting mirror and is collected by the second lens to be coupled to the spectrometer; the spectrometer is connected to the computer. The light splitting prism is partially reflective and partially transmissive.

[0059] The reflective method for measuring the transmittance of the thin film in real time in situ of the embodiment comprises the following steps:

[0060] a) erecting the measuring device:

[0061] arranging the thin film to be measured on the light-transmitting substrate, and the environment is on the thin film; the complex refractive index of the environment is n1, the complex refractive index of the thin film is n2 (unknown), the thickness of the thin film is h (unknown), the complex refractive index of the substrate is n3, and the transmittance of the substrate is ≥5%; arranging the incident light path and the exit light path above the thin film; coupling the light source to the incident light path, and coupling the end of the exit light path to the spectrometer; connecting the spectrometer to the computer through the data line;

[0062] b) measuring the light intensity reflectance R of the thin film, as shown in the left graph in Figure 3

[0063] 1) the light source emits a light beam, which is incident on the thin film through the incident light path, and the light intensity incident on the thin film is I0;

[0064] 2) the incident light is incident on the interface between the environment and the thin film at a first angle θ1, a part of the light is reflected into the environment at the first angle θ1, and a part of the light is refracted into the thin film at a second angle θ2, the first angle θ1 and the second angle θ2 satisfy the refraction law n1sin(θ1) = n2sin(θ2);

[0065] 3) the part of the light refracted into the thin film is reflected and refracted at the interface between the thin film and the substrate, the reflection angle and the refraction angle are the second angle θ2 and the third angle θ3 respectively, the second angle θ2 and the third angle θ3 satisfy the refraction law n1sin(θ1) = n2sin(θ2) = n3sin(θ3);

[0066]

[0067] 4) the light reflected at the interface between the thin film and the substrate is reflected back and forth by the upper and lower interfaces of the thin film, and is refracted into the environment and the substrate; the light refracted at the interface between the thin film and the substrate is transmitted from the lower surface of the substrate;

[0068] ​​5) The reflected light of the film is received by the spectrometer through the exit light path; the reflected light of the film includes the light reflected to the environment by the interface between the environment and the film and the light reflected by the interface between the film and the substrate and then refracted to the environment by the interface between the environment and the film;

[0069] 6) The spectrometer measures the intensity of the reflected light as I R , and further calculates the light intensity reflectivity of the film as:

[0070] R = I R / I0 (1);

[0071] c) Measure the light intensity reflectivity R' of the film-reflection surface, as shown in the right graph in FIG. 2: Figure 3

[0072] 1) A reflection surface with a known reflectivity is arranged below the substrate, the amplitude reflectivity of the reflection surface is r0, and the light intensity reflectivity R0 = |r0| of the reflection surface is greater than or equal to 5%; the distance from the lower surface of the film to the reflection surface exceeds the interference length of the light source; 2

[0073] 2) The intensity of the transmitted light of the lower surface of the substrate is I T = I0x T x T s , T is the light intensity transmittance of the film, and T s is the light intensity transmittance of the substrate;

[0074] 3) The reflection surface reflects the transmitted light of the lower surface of the substrate back to the substrate, and the light reflected back to the substrate is transmitted to the environment through the film again, at this time, the transmitted light passes through the film and the substrate twice, and the light transmitted to the environment through the film and the substrate after being reflected by the reflection surface is the intensity I' of the light reflected back by the reflection surface:

[0075] R

[0076] I' R = I0x T x T s x R0x T x T s = I0x R0x T 2 x T 2 (2)

[0077] 4) A reflection surface is added below the substrate, and the reflected light of the film and the light reflected back by the reflection surface are received by the spectrometer through the exit light path, and the total light intensity measured by the spectrometer is I RR , and further calculates the light intensity reflectivity R' of the film-reflection surface as:

[0078] R' = I RR / I0 (3)

[0079] d) Calculate the transmittance T of the film: ​​​​

[0080] 1) At this time, the light measured by the spectrometer consists of two parts: the light reflected from the thin film and the light reflected back from the reflecting surface. The distance from the lower surface of the thin film to the reflecting surface exceeds the interference length of the light source. These two parts of light do not interfere with each other, but are only superimposed in intensity, without involving the superposition of amplitude.

[0081] 2) Adding a reflective surface beneath the substrate, the total light intensity I measured by the spectrometer RR for:

[0082] I RR = I R + I′ R = I0×R + I0×R0×T 2 ×T s 2 (4)

[0083] 3) The transmittance T of the thin film is obtained as follows:

[0084]

[0085] Where R = I R / I0 is the light intensity reflectivity of the thin film, obtained from step b) 6); R′ is the light intensity reflectivity of the thin film-reflective surface, obtained from step c) 4); R0 is the light intensity reflectivity of the reflective surface, a known quantity; T s Let R be the transmittance of the substrate, and R be a known quantity; only the light intensity reflectance R of the thin film and the thin film need to be measured separately.

[0086] - The light intensity reflectance R′ of the reflective surface is used to calculate the transmittance of the film using formula (5). The reflected light of the film and the light reflected back from the reflective surface do not interfere with each other and do not involve the superposition of amplitudes. They are only superpositions of light intensity. The transmittance of the film can be directly calculated by measuring the light intensity. During the measurement process, it is not necessary to know the thickness and optical properties of the film in advance, so as to realize real-time in-situ measurement and monitoring of the growth process of the film.

[0087] Furthermore, in step a) 5), the complex amplitude reflectivity r of the thin film satisfies:

[0088]

[0089] Where k0 is the vacuum wave vector, r 12 and r 23 These represent the complex amplitude reflectivity at the interface between the environment and the thin film, and at the interface between the thin film and the substrate, respectively. 12 and t 21 The complex amplitude transmittance at the interface between the environment and the thin film, and at the interface between the thin film and the substrate, can be obtained from Fresnel's formula. Their values ​​are related to the angle of incidence and the refractive index of the material.

[0090] The first term of equation (6) is the reflection of the incident light at the interface between the environment and the film; the second term is the part of the light in the film that is reflected back and forth by the two interfaces and then refracted into the environment. The two terms interfere with each other to form the interference spectrum of the film. The film thickness measurement instrument based on the film interference method measures the film thickness based on the measurement of the reflection spectrum of equation (6). However, this method ignores the transmitted light part E t and cannot measure the transmission spectrum.

[0091] Figure 4 A comparison between the transmission spectrum of the perovskite film measured by the present application and the transmission spectrum of the perovskite film measured by the existing spectrophotometer transmission method is shown in FIG. 2. The sample is a perovskite film with a thickness of about 330 nm. The substrate under the perovskite film is glass with a thickness of 1 mm, and the distance d between the reflecting surface and the lower surface of the substrate is about 50 μιη. When there is no mirror under the substrate, the measured reflection spectrum of the perovskite film is shown by the dashed line in the upper part of FIG. 2(a), which is an interference spectrum curve with absorption. When there is a mirror, the measured reflection spectrum of the perovskite film-mirror is shown by the short dashed line in the upper part of FIG. 2(b). In the long-wave band (λ > 780 nm), the absorption of the perovskite material is very small, and a large amount of light reaches the mirror below, so that the light reflected by the mirror is very strong, resulting in a large reflection rate (about 80%) measured by the device in the long-wave band. Figure 4 The transmission spectrum of the perovskite film measured by the existing spectrophotometer transmission method is shown by the solid line in FIG. 2(b). The results of the transmission spectrum of the perovskite film measured by the present application and the transmission spectrum of the perovskite film measured by the existing spectrophotometer transmission method have basically the same trend in the long-wave band, and the absorption edges are basically coincident. The reflection spectrum of the perovskite film-mirror basically reflects the absorption spectrum of the perovskite film. In the short-wave band (λ < 760 nm), the perovskite material has a strong absorption, and a small amount of light reaches the mirror below, so that the mirror has little effect, resulting in that the measured light is mainly the light reflected by the upper and lower interfaces of the film, and the reflection rate in the short-wave band is obviously small (about 20%). Moreover, there is an interference oscillation. The film thickness can be measured by fitting the interference oscillation spectrum with equation (6) to be h = 320 nm, which has a very small deviation from the actual thickness of the perovskite (330-320) / 330 ≈ 3%. Figure 4 Figure 4 The light intensity transmittance T of the perovskite film is calculated by equation (5) and is shown by the short dashed line in FIG. 2(b). From the transmittance spectrum of the perovskite film measured by the present application and the transmittance spectrum of the perovskite film measured by the existing spectrophotometer transmission method have basically the same trend in the long-wave band, and the absorption edges are basically coincident. The reflection spectrum of the perovskite film-mirror basically reflects the absorption spectrum of the perovskite film. In the short-wave band (λ < 760 nm), the perovskite material has a strong absorption, and a small amount of light reaches the mirror below, so that the mirror has little effect, resulting in that the measured light is mainly the light reflected by the upper and lower interfaces of the film, and the reflection rate in the short-wave band is obviously small (about 20%). Moreover, there is an interference oscillation. The film thickness can be measured by fitting the interference oscillation spectrum with equation (6) to be h = 320 nm, which has a very small deviation from the actual thickness of the perovskite (330-320) / 330 ≈ 3%.

[0092] The light intensity transmittance T of the perovskite film is calculated by equation (5) and is shown by the short dashed line in FIG. 2(b). From Figure 4 the transmittance spectrum of the perovskite film measured by the present application and the transmittance spectrum of the perovskite film measured by the existing spectrophotometer transmission method have basically the same trend in the long-wave band, and the absorption edges are basically coincident. The reflection spectrum of the perovskite film-mirror basically reflects the absorption spectrum of the perovskite film. In the short-wave band (λ < 760 nm), the perovskite material has a strong absorption, and a small amount of light reaches the mirror below, so that the mirror has little effect, resulting in that the measured light is mainly the light reflected by the upper and lower interfaces of the film, and the reflection rate in the short-wave band is obviously small (about 20%). Moreover, there is an interference oscillation. The film thickness can be measured by fitting the interference oscillation spectrum with equation (6) to be h = 320 nm, which has a very small deviation from the actual thickness of the perovskite (330-320) / 330 ≈ 3%. Figure 4As can be seen in (b), the short dashed line and the transmittance spectrum of the perovskite film measured by spectrophotometer transmission method (solid line) coincide very well, especially in the perovskite absorption edge part. The absorbance of the material can be calculated by the formula log(l / T). The transmittance and thickness of the perovskite film can be measured simultaneously by the fiber-optic reflection device proposed in the present application. Here, a single-layer film structure is shown, but the transmittance spectrum of a multi-layer film structure can also be measured by the fiber-optic reflection device proposed in the present application, because the absorption of a multi-layer film can be equivalent to the absorption of a single-layer film. This reflection method for measuring the transmittance of a film and the device thereof are used to measure the properties of a film material and detect the kinetic process of the growth of a film material.

[0093] Finally, it should be noted that the purpose of the disclosed embodiments is to help further understand the present application, but those skilled in the art can understand that various replacements and modifications are possible without departing from the spirit and scope of the present application and the appended claims. Therefore, the present application should not be limited to the disclosed embodiments, and the scope of the present application is defined by the scope of the claims.

Claims

1. A reflective method for measuring the transmittance of a thin film in real time in situ, characterized in that, The reflection method comprises the following steps: a) setting up a device; The film to be measured is arranged on a light-transmitting substrate, with the environment above the film; the substrate has a transmittance T s ≥ 5%; an incident light path and an emergent light path are arranged above the film; a light source is coupled to the incident light path, and the end of the emergent light path is coupled to a detector or a spectrometer, which is connected to a computer; b) measuring the light intensity reflectance R of the film: 1) the light source emits a light beam, which is incident on the film through an incident light path, and the light intensity incident on the film is I0; 2) the incident light is incident on the interface between the environment and the film at a first angle θ1, part of the light is reflected into the environment, and part of the light is refracted into the film; 3) the part of the light refracted into the film is reflected and refracted by the interface between the film and the substrate; 4) the light reflected at the interface between the film and the substrate is reflected back and forth by the upper and lower interfaces of the film and is refracted into the environment and the substrate; the light refracted at the interface between the film and the substrate is transmitted from the lower surface of the substrate; 5) the reflected light of the film is received by a detector or a spectrometer through an exit light path; the reflected light of the film includes the light reflected by the interface between the environment and the film into the environment and the light reflected by the interface between the film and the substrate and then refracted by the interface between the environment and the film into the environment; 6) The intensity of the reflected light I is measured by a detector or a spectrometer R The reflectivity of the film R is further obtained as R = I R / I0 (1) c) measuring the light intensity reflectance R' of the film-reflection surface: 1) a reflective surface of known reflectivity is placed under the substrate, the amplitude reflectivity of the reflective surface being r0, the light intensity reflectivity of the reflective surface being R0 = |r0| 2 ≥ 5%; the distance of the lower surface of the film to the reflective surface exceeds the interference length of the light source; 2) the intensity of the transmitted light of the lower surface of the substrate is I T = I0x T x T s , T is the light intensity transmittance of the thin film, T s is the light intensity transmittance of the substrate; 3) the reflective surface reflects the transmitted light from the lower surface of the substrate back into the substrate, the light reflected back into the substrate is transmitted through the film to the environment, at this time the transmitted light passes through the film and the substrate twice, the intensity of the light transmitted through the film to the environment after the light from the lower surface of the substrate is reflected by the reflective surface is I' R is: I′ R = I0 x T x T s x R0 x T x T s = I0 x R0 x T 2 x T s 2 (2) 4) The reflected light from the film and the light reflected from the reflecting surface together are received by a detector or a spectrometer via the exit light path, and the detector or the spectrometer measures the total light intensity I RR Further, the light intensity reflectivity R' of the film-reflecting surface is obtained as follows: R' = I RR / I0 (3) d) calculating the transmittance T of the film: 1) after the reflection surface is added below the substrate, the light detected by the detector or the spectrometer is composed of two parts: the reflected light of the film and the light reflected back by the reflection surface, the distance from the lower surface of the film to the reflection surface exceeds the interference length of the light source, and the two parts of light do not interfere, but only the superposition of intensity, without involving amplitude superposition; 2) Total light intensity I measured by the detector or spectrometer RR is: I RR = I R + I′ R = I0x R + I0x R0x T 2 x T s 2 (4) 3) the transmittance T of the film is obtained as: where R = I R R0is the reflectivity of the reflecting surface, which is a known quantity; T s is the transmittance of the substrate, which is a known quantity; only the light intensity reflectivity of the film R and the light intensity reflectivity of the film-reflecting surface R' need to be measured respectively, and the transmittance of the film is directly calculated by using formula (5); the reflected light of the film and the reflected light of the reflecting surface do not interfere, do not involve the superposition of amplitude, and are only the superposition of light intensity, so that the transmittance of the film can be directly calculated by only measuring the light intensity; in the measurement process, the thickness of the film and the optical properties of the film do not need to be known in advance, and the growth process of the film is realized in real time and in situ.

2. The reflective method of claim 1, wherein, In step b) 2), the first angle θ1 satisfies 0°≤θ1<90°.

3. The reflective method of claim 1, wherein, In step c) 1), the reflection surface is in close contact with or not in close contact with the substrate, and the distance between the reflection surface and the lower surface of the substrate is less than 500 mm.

4. The reflective method of claim 1, wherein, In 3) of step d), when the reflectivity of the reflecting surface and the transmittance of the substrate satisfy R0≥ 95% and T s ≥ 95%, the transmittance of the thin film is simplified to T = (R' - R) 1 / 2 .

5. The reflective method of claim 1, wherein, The light source uses a multi-wavelength light source to directly measure the transmittance spectrum; Or, the light source uses a monochromatic light source to measure the transmittance of one wavelength.

6. The reflective method of claim 1, wherein, The film is a single-layer film or a multi-layer film, and the transmittance or transmittance spectrum of the single-layer film or the multi-layer film is measured, thereby reflecting the optical properties of the film; when the transmittance or transmittance spectrum of the multi-layer film is measured, the multi-layer film is equivalent to a single-layer film.

7. A reflective device for measuring the transmittance of a thin film in real time in situ, characterized in that The reflection device comprises a thin film, a substrate, a light source, an incident light path, an exit light path, a detector or a spectrometer, a computer and a reflecting surface; wherein the thin film is arranged on the light-transmitting substrate, and the environment is above the thin film; the transmittance T of the substrate is ≥5%; the incident light path and the exit light path are arranged above the thin film; the light source is coupled to the incident light path, the end of the exit light path is coupled to the detector or the spectrometer, and the detector or the spectrometer is connected to the computer. s ≥5%; the incident light path and the exit light path are arranged above the thin film; the light source is coupled to the incident light path, the end of the exit light path is coupled to the detector or the spectrometer, and the detector or the spectrometer is connected to the computer. In the measurement of the light intensity reflectivity of the thin film, the light source emits a light beam which is incident on the thin film through an incident light path; the incident light is incident on the interface between the environment and the thin film, a part of the light is reflected into the environment, and a part of the light is refracted into the thin film; the light refracted into the thin film is reflected and refracted by the interface between the thin film and the substrate; the light reflected by the interface between the thin film and the substrate is reflected back and forth by the upper and lower interfaces of the thin film, and is refracted into the environment and the substrate; the light refracted by the interface between the thin film and the substrate is transmitted from the lower surface of the substrate; the reflected light of the thin film is received by a detector or a spectrometer through an exit light path, the reflected light of the thin film includes the light reflected by the interface between the environment and the thin film to the environment and the light reflected by the interface between the thin film and the substrate and then refracted by the interface between the environment and the thin film to the environment, and the detector or the spectrometer measures the intensity I of the reflected light of the thin film R , and further obtains the light intensity reflectivity R of the thin film; In the measurement of the transmittance of the thin film, a reflecting surface with known reflectance is arranged under the substrate, the amplitude reflectance of the reflecting surface is r0, and the light intensity reflectance of the reflecting surface is R0=|r0| 2 ≥5%; the intensity of the transmitted light of the lower surface of the substrate is I T =I0×T×T s , T is the light intensity transmittance of the thin film, T s is the light intensity transmittance of the substrate; the reflecting surface reflects the transmitted light from the lower surface of the substrate back to the substrate; the light reflected back to the substrate is refracted to the environment again, at this time, the transmitted light passes through the thin film and the substrate twice, and the light transmitted to the substrate after being reflected by the reflecting surface and then transmitted to the environment through the thin film is the light reflected back by the reflecting surface; the reflected light of the thin film and the light reflected back by the reflecting surface are received by the detector or the spectrometer through the exit light path; at this time, the light measured by the detector or the spectrometer is composed of two parts: the reflected light of the thin film and the light reflected back by the reflecting surface, the distance from the lower surface of the thin film to the reflecting surface exceeds the interference length of the light source, the two parts of light do not interfere, do not involve the superposition of amplitude, and are only the superposition of light intensity, the detector or the spectrometer measures the total light intensity I RR , and further obtains the light intensity reflectance R' of the thin film-reflection surface; the transmittance T of the thin film is calculated through the obtained light intensity reflectance R of the thin film and the light intensity reflectance R' of the thin film-reflection surface.

8. The reflective device of claim 7, wherein, The light source uses a multi-wavelength light source to directly measure the transmittance spectrum; or, the light source uses a monochromatic light source to measure the transmittance of one wavelength.

9. The reflective device of claim 7, wherein, The incident light path and the exit light path use a fiber transmission system or a free space transmission system; when the fiber transmission system is used, the incident light path uses an incident fiber, and the exit light path uses an exit fiber; When the free space transmission system is used, the incident light path uses a first lens, and the exit light path uses a second lens; in the incident light path, the incident light is collimated by the first lens, then passes through a light splitting element to be incident on the upper surface of the film; in the exit light path, the exit light passes through the light splitting element and is collected by the second lens to be coupled to the detector or the spectrometer.

10. The reflective device of claim 7, wherein, It also includes a moving device, and the reflection surface is placed on the moving device; when the light intensity reflectance of the film is measured, the reflection surface is moved out from below the substrate by the moving device; when the light intensity reflectance of the film-reflection surface is measured, the reflection surface is set below the substrate by the moving device.

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