Reflection-type method and device for real-time in-situ measurement of film transmittance

Abstract

The invention discloses a reflective method and a reflective device for real-time in-situ measurement of film transmittance. By adding the reflecting surface, the transmittance of the thin film can be directly calculated through a formula only by respectively measuring the light intensity reflectivity R of the thin film and the light intensity reflectivity R'of the thin film-reflecting surface, and a precise optical model and complex fitting do not need to be established; reflected light of the thin film and light reflected back by the reflecting surface do not interfere with each other, amplitude superposition is not involved, only light intensity superposition is achieved, the transmittance can be obtained only by obtaining the light intensity, and the transmittance of the thin film is measured through the method of measuring the reflectivity twice. In the process of measuring the transmittance by using the reflection-type method, the thickness and the optical property of the film do not need to be known in advance, so that the method is very suitable for measuring and monitoring the growth process of the film in real time in situ; according to the reflection type method, all optical elements are arranged on one side of the thin film, the available angle range of incident light is far larger than the angle range of an ellipsometer, and the ellipsometer can be easily integrated with other film manufacturing equipment.

Description

Technical Field

[0001] The invention relates to an optical thin film measurement technology, and in particular to a reflection method and a device for real-time in-situ measurement of thin film transmittance. Background Art

[0002] Thin films are widely used in modern photonics and optoelectronics fields such as photovoltaics, storage, and chips. They can be used to manufacture various optoelectronic devices, chips, and instruments. The properties of thin films, such as material properties, thickness, 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 kinetics of the film-making process, which is crucial for understanding and optimizing device functions.

[0003] Optical measurement methods are non-contact, highly accurate, and non-destructive. They are widely used in the measurement and detection of thin film properties in the fields of semiconductors, optical coatings, new energy materials, etc. There are two main types of optical measurement methods: reflection and transmission. Film thickness meters and ellipsometers based on reflection systems use the principle of thin film interference to measure the reflected light of thin film structures to study the properties of thin films, such as film thickness and the complex refractive index of the material. The transmittance or absorbance of the film structure can be further calculated based on the film thickness and the complex refractive index of the material. The physical essence of this reflection system instrument (ellipsometer and film thickness meter) is to use the amplitude superposition interference of many reflected lights at the interface of different materials. When using a film thickness meter to measure the interference spectrum after the film is reflected, one of the parameters, the film thickness and the complex refractive index of the material, must be known, and the other parameter can be obtained by fitting the interference spectrum through a formula. Although the probe of this film thickness meter is very small (about 30mm 2 ), which is easy to integrate. However, during the growth of thin film materials, the film thickness and material properties change over time, so the film thickness meter cannot achieve real-time in-situ measurement of the film growth process. In addition, for a single-wavelength light source, it is impossible to fit it with a formula, and the film thickness meter cannot obtain the complex refractive index of the material at a single wavelength. The ellipsometer is based on measuring the change in the polarization state of the reflected light of the film, using precise optical models and complex calculations to simultaneously solve the film thickness and the complex refractive index of the material, thereby achieving real-time in-situ measurement of the film. However, this reflective ellipsometer requires a large oblique light incidence (about 70°), which makes the entire optical system bulky and difficult to integrate.

[0004] Film thickness meters and ellipsometers based on reflection systems ignore the transmitted light part and cannot directly measure the transmittance of the film. Instruments such as spectrophotometers based on transmission systems can directly measure the transmittance or absorbance of the film in real time. This transmission system requires incident light from one side of the sample and measurement of the transmitted light from the other side of the sample. This transmission configuration makes the entire measurement system bulky and difficult to integrate, especially for equipment with entities under the sample and requiring extreme temperature changes, such as large-area coaters, spin coaters, vacuum heating / cooling coating equipment [molecular beam epitaxy (MBE) equipment and electron beam evaporation (Ebeam) equipment], etc. In summary, it is still a huge challenge to obtain a method and device that is small in size, easy to integrate, and can measure the transmittance (or absorbance) of a thin film structure in real time in situ. Summary of the invention

[0005] In view of the problems in the above prior art that the equipment is large in size, difficult to integrate and cannot measure the film properties in real time in situ, the present invention proposes a reflective method and device for real-time in situ measurement of film transmittance.

[0006] An 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 comprises the following steps:

[0008] a) Installation equipment:

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

[0010] b) Measure the light intensity reflectivity R of the film:

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

[0012] 2) The incident light is incident on the interface between the environment and the film, part of the light is reflected into the environment, and part of the light is refracted into the film;

[0013] 3) The part of light refracted into the film is reflected and refracted by the interface between the film and the substrate;

[0014] 4) The light reflected at the interface between the film and the substrate will be reflected back and forth by the upper and lower interfaces of the film, and then 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;

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

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

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

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

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

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

[0021] 3) The reflective surface reflects the transmitted light from the lower surface of the substrate back to the substrate. The light reflected back to the substrate is then transmitted to the environment through the film. At this time, the transmitted light passes through the film and the substrate twice. The light transmitted from the substrate to the substrate is reflected by the reflective surface and then transmitted to the environment through the film. The intensity I′ of the light reflected back by the reflective surface R for:

[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 from the reflective surface are received by a detector or a spectrometer through the outgoing light path. The detector or spectrometer measures the total light intensity I RR , and further obtain the light intensity reflectivity R′ of the film-reflecting surface:

[0024] R′=I RR / I0 (3)

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

[0026] 1) After adding a reflective surface under the substrate, the light measured by the detector or spectrometer consists of two parts: the reflected light of the film and the light reflected back by the reflective surface. The distance from the bottom surface of the film to the reflective surface exceeds the interference length of the light source. These two parts of light do not interfere with each other, but only superposition of intensities, without involving amplitude superposition;

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

[0028] I RR = I R + I′ R = I0×R + I0×R0×T 2 ×T s 2 (4)

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

[0030]

[0031] Where R = I R / I0 is the light intensity reflectivity of the film, which has been obtained in step b) 6); R′ is the light intensity reflectivity of the film-reflecting surface, which has been obtained in step c) 4); R0 is the light intensity reflectivity of the reflecting surface, which is a known quantity; T s is the transmittance of the substrate, which is a known quantity. It is only necessary to measure the light intensity reflectance R of the film and the light intensity reflectance R′ of the film-reflecting surface respectively, and use formula (5) to directly calculate the transmittance of the film. The reflected light of the film and the light reflected back from the reflecting surface do not interfere with each other, and do not involve the superposition of amplitudes, but only the superposition of light intensities. It is only necessary to measure the light intensity to directly calculate the transmittance of the film. During the measurement process, it is not necessary to know the thickness of the film and the 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.

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

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

[0034] In step d) 1) and 2), since the distance from the lower surface of the film to the reflecting surface exceeds the interference length of the light source, the light directly reflected by the film into the environment and the light reflected by the reflecting surface and then transmitted through the film into the environment do not interfere with each other, but are simply a superposition of intensities, which is completely different from the amplitude superposition in the film thickness meter and ellipsometer of the reflective system, and the two are physically different in nature.

[0035] In step d) 3), 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 to T = (R'-R) 1 / 2 . Furthermore, the method of the present invention 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 film. The light source adopts a multi-wavelength light source to directly measure the transmittance spectrum; the light source adopts a monochromatic light source to measure the transmittance of one wavelength. In the process of measuring the transmittance using this reflective method, there is no need to know the thickness of the film and the optical properties of the film 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 outgoing light path of the reflective method are on one side of the film, and the angle θ1 of the incident light satisfies 0°≤θ1<90°. The angle range that can be taken is much larger than the angle range of the ellipsometer, and it is easy to integrate with other film-making equipment.

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

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

[0038] When measuring the light intensity reflectivity of a film, a light beam emitted by a light source is incident on the film through an incident light path; the incident light is incident on the interface between the environment and the film, part of the light is reflected into the environment, and part of the light is refracted into the film; the part of the light refracted into the film is reflected and refracted by the interface between the film and the substrate; the light reflected at the interface between the film and the substrate will be reflected back and forth by the upper and lower interfaces of the film, and then 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; the reflected light of the film is received by a detector or a spectrometer through an outgoing light path. The reflected light of the film includes the light reflected from the interface between the environment and the film to the environment and the light reflected from the interface between the film and the substrate and then refracted from the interface between the environment and the film to the environment. The detector or the spectrometer measures the intensity I of the reflected light of the film R , and further obtain the light intensity reflectivity R of the film;

[0039] When measuring the light intensity reflectivity of the film-reflecting surface, a reflecting surface with a known reflectivity is set under the substrate, the amplitude reflectivity of the reflecting surface is r0, and the light intensity reflectivity of the reflecting surface is R0 = |r0| 2 ≥5%; the distance from the lower surface of the film to the reflecting surface exceeds the interference length of the light source; the intensity of the transmitted light on the lower surface of the substrate is I T =I0×T×T s , T is the light intensity transmittance of the 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, and the light reflected back to the substrate is then transmitted to the environment through the film. At this time, the transmitted light passes through the film and the substrate twice, and the light transmitted from the substrate to the substrate, reflected by the reflecting surface, and then transmitted to the environment through the film is the light reflected back by the reflecting surface; the reflected light of the film and the light reflected back by the reflecting surface are received by the detector or spectrometer through the outgoing light path; at this time, the light measured by the detector or spectrometer consists 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, and there is no superposition of amplitudes, only the superposition of light intensities. The detector or spectrometer measures the total light intensity I RR , and further obtain the light intensity reflectivity R′ of the film-reflecting surface; the transmittance T of the film is calculated by measuring the light intensity reflectivity R of the film and the light intensity reflectivity R′ of the film-reflecting surface.

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

[0041] The incident light path and the outgoing light path adopt an optical fiber transmission system or a free space transmission system; when the optical fiber transmission system is adopted, the incident light path adopts an incident optical fiber, and the outgoing light path adopts an outgoing optical fiber; when the free space transmission system is adopted, the incident light path adopts a first lens, and the outgoing light path adopts a second lens. In the incident light path, the incident light is collimated by the first lens and then incident on the upper surface of the film through a beam splitter. In the outgoing light path, the outgoing light is collected by the second lens after passing through the beam splitter and coupled to a detector or a spectrometer. The beam splitter adopts a beam splitter prism or a beam splitter.

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

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

[0044] Furthermore, the present invention also includes a moving device, and the reflective surface is placed on the moving device; when measuring the light intensity reflectivity of the film, the reflective surface is moved out from under the substrate by the moving device, and the reflective surface is not set under the substrate; when measuring the light intensity reflectivity of the film-reflective surface, the reflective surface is set under the substrate by the moving device.

[0045] Advantages of the present invention:

[0046] By adding a reflective surface, the present invention only needs to measure the light intensity reflectivity R of the film and the light intensity reflectivity R′ of the film-reflective surface respectively, and the transmittance of the film can be directly calculated through 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 reflective surface do not interfere with each other, and do not involve the superposition of amplitudes, but only the superposition of light intensities. The transmittance can be obtained by only obtaining the light intensity, and the transmittance of the film is measured by measuring the reflectivity twice; in the process of measuring the transmittance by the reflective method, it is not necessary to know the thickness of the film and the optical properties of the film in advance, and it is very suitable for real-time in-situ measurement and monitoring of the growth process of the film; all the optical elements of the reflective method are on one side of the film, the angle θ1 of the incident light satisfies 0°≤θ1<90°, the angle range is much larger than the angle range of the ellipsometer, and it is easy to integrate with other film-making equipment. The present invention has the characteristics of fast (~ms), simple, small size, easy integration, low cost, etc., and has important application prospects in optical thin film measurement and real-time detection of thin film growth process, especially for thin film equipment that is not friendly to integrated transmission devices, such as coaters, spin coaters, MBE, Ebeam, etc. Therefore, the method and device proposed by the present invention can be widely used in industrial application fields such as semiconductors, optical coatings and new energy materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 It is a schematic diagram of a first embodiment of a reflective device for real-time in-situ measurement of thin film transmittance according to the present invention;

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

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

[0050] Figure 4 The results are obtained according to 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 reflection spectrum or transmission spectrum of the perovskite film experimentally measured without and with a reflective surface between the prior art and the present invention, and (b) is a comparison diagram of the light intensity transmission spectrum of the perovskite film calculated by the prior art and the method of the present invention. DETAILED DESCRIPTION

[0051] The present invention will be further described below through specific embodiments in conjunction with the accompanying drawings.

[0052] The incident light path and the outgoing light path adopt an optical fiber system or a free space optical system.

[0053] Embodiment 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 film transmittance in this embodiment includes: a film, a substrate, a light source, an incident optical fiber, an output optical fiber, a spectrometer, a computer and a reflective surface; wherein the film is arranged on a light-transmitting substrate, and the film is above the environment; the substrate transmittance T s ≥5%; an incident optical fiber and an output optical fiber are arranged on the film; a light source is connected to one end of the incident optical fiber, the end of the output optical fiber is connected to a spectrometer, and the spectrometer is connected to a computer via a data cable; the distance from the lower surface of the film to the reflection surface exceeds the interference length of the light source. The incident optical fiber and the output optical fiber have a common port, which is fixed by a five-axis optical fiber clamp, which adjusts the three-dimensional position (xyz) of the optical fiber on the film, and adjusts the pitch of the optical fiber so that the optical fiber is perpendicular to the surface of the film.

[0056] Embodiment 2

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

[0058] like Figure 2As shown, the reflective device for real-time in-situ measurement of film transmittance of this embodiment includes: a film, a substrate, a light source, a first lens, a second lens, a beam splitter, a spectrometer, a computer and a reflective surface; wherein the film is arranged on a light-transmitting substrate, and the film is on the environment; the first lens is used for the incident light path, and the second lens is used for the outgoing light path; in the incident light path, the incident light is collimated by the first lens, and then split and deflected by the beam splitter; in the outgoing light path, the outgoing light passes through the beam splitter, and is collected by the second lens after being reflected by the reflector and coupled to the spectrometer; the spectrometer is connected to the computer. The beam splitter is partially reflective and partially transmissive.

[0059] The reflective method for real-time in-situ measurement of film transmittance of this embodiment includes the following steps:

[0060] a) Set up the measuring device:

[0061] The film to be measured is placed on a transparent substrate, with the environment above the film; the complex refractive index of the environment is n1, the complex refractive index of the film is n2 (unknown), the thickness is h (unknown), the complex refractive index of the substrate is n3, and the transmittance of the substrate is ≥5%; an incident light path and an outgoing light path are set above the film; a light source is coupled to the incident light path, the end of the outgoing light path is coupled to a spectrometer, and the spectrometer is connected to a computer via a data cable;

[0062] b) Measure the light intensity reflectivity R of the film, such as Figure 3 As shown in the middle left picture:

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

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

[0065] 3) The part of light refracted to the film is reflected and refracted by the interface between the 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)=

[0066] n2sin(θ2)=n3sin(θ3);

[0067] 4) The light reflected at the interface between the film and the substrate will be reflected back and forth by the upper and lower interfaces of the film, and then 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;

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

[0069] 6) The intensity of the reflected light measured by the spectrometer is I R , the light intensity reflectivity of the film is further calculated as:

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

[0071] c) Measure the light intensity reflectivity R' of the film-reflecting surface, such as Figure 3 As shown in the middle right picture:

[0072] 1) A reflective surface with known reflectivity is set under the substrate, the amplitude reflectivity of the reflective surface is r0, and the light intensity reflectivity of the reflective surface is R0 = |r0| 2 ≥5%; the distance from the lower surface of the film to the reflecting surface exceeds the interference length of the light source;

[0073] 2) The intensity of the transmitted light on the lower surface of the substrate is I T =I0×T×T s , T is the light intensity transmittance of the film, T s is the light intensity transmittance of the substrate;

[0074] 3) The reflective surface reflects the transmitted light from the lower surface of the substrate back to the substrate. The light reflected back to the substrate is then transmitted through the film to the environment. At this time, the transmitted light passes through the film and the substrate twice. The substrate is transmitted to the substrate, reflected by the reflective surface, and then passes through the film.

[0075] The intensity of the light transmitted to the environment, that is, the light reflected back from the reflective surface, is I' R for:

[0076] I′ R = I0×T×T s ×R0×T×T s = I0×R0×T 2 ×Ts 2 (2)

[0077] 4) Add a reflective surface under the substrate. The reflected light of the film and the light reflected back from the reflective surface are received by the spectrometer through the outgoing light path. The total light intensity measured by the spectrometer is I RR , the light intensity reflectivity R′ of the film-reflecting surface is further calculated 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 reflected light of the film and the light reflected back from the reflective surface. The distance from the lower surface of the film to the reflective surface exceeds the interference length of the light source. These two parts of light do not interfere with each other, but only superposition of intensities, without involving amplitude superposition;

[0081] 2) Add a reflective surface under the substrate, and 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 film is obtained as:

[0084]

[0085] Where R = I R / I0 is the light intensity reflectivity of the film, which has been obtained in step b) 6); R′ is the light intensity reflectivity of the film-reflecting surface, which has been obtained in step c) 4); R0 is the light intensity reflectivity of the reflecting surface, which is a known quantity; T s is the transmittance of the substrate, which is a known quantity; we only need to measure the light intensity reflectivity R and the film

[0086] -The light intensity reflectivity R′ of the reflecting 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 reflecting surface do not interfere with each other, and do not involve the superposition of amplitudes, but only the superposition of light intensities. 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 of the film and the optical properties of the film in advance, so that real-time in-situ measurement and monitoring of the film growth process can be achieved.

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

[0088]

[0089] Where k0 is the vacuum wave vector, r 12 and r 23 are the complex amplitude reflectivity of the interface between the environment and the film and the interface between the film and the substrate, respectively, t 12 and t 21 are the complex amplitude transmittances at the interface between the environment and the film and the interface between the film and the substrate, respectively. These quantities can be obtained from the Fresnel formula, and their values ​​are related to the incident angle and the refractive index of the material.

[0090] The first term of formula (6) is the reflection of the incident light by 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. These two terms interfere with each other to form the interference spectrum of the film. The film thickness measuring instrument based on the thin film interference method measures the film thickness by measuring the reflection spectrum based on formula (6). However, this method ignores the transmitted light part E t , the transmission spectrum cannot be measured.

[0091] Figure 4 The comparison chart of the transmission spectrum of the film measured by the optical fiber reflection method of the present invention and the transmission spectrum of the film measured by the existing spectrophotometer transmission method is given in FIG. The test sample is a perovskite film with a thickness of about 330nm. The substrate under the perovskite film is glass with a thickness of 1mm, and the distance d between the reflective surface and the lower surface of the substrate is about 50μm. When no reflector is set under the substrate, the reflection spectrum of the perovskite film is measured as follows Figure 4 As shown by the dashed line in the upper figure (a), this is an interference spectrum curve with absorption. When the complex refractive index of the perovskite material is known, the thickness of the film can be obtained by fitting this curve using formula (6). When there is a reflector, the reflectance spectrum of the perovskite film-reflector is measured as Figure 4 As shown by the short dashed line in the upper middle figure. In the long-wave band (λ>780nm), the perovskite material absorbs very little, and a lot of light reaches the reflector below, so the light reflected by the reflector is very strong, resulting in the reflectivity measured by the device being very high in the long-wave band (~80%). The existing results of using a spectrophotometer to measure the transmission spectrum of perovskite films are Figure 4 Indicated by a solid line. The results of measuring the transmission spectrum of the film using the optical fiber reflection method of the present invention and the results of measuring the transmission spectrum of the perovskite film using the existing spectrophotometer transmission method have basically the same trend in the long-wave band, and the absorption edges basically overlap. The reflection spectrum of the perovskite film-reflector can basically reflect the absorption spectrum of the perovskite film. In the short-wave band (λ<760nm), the perovskite material has a strong absorption, and very little light reaches the reflector below, so the effect of the reflector is very small, resulting in the measured light being mainly the light reflected by the upper and lower interfaces of the film, and the reflectivity in the short-wave band is significantly reduced (~20%). There is also interference oscillation. Fitting the interference oscillation spectrum with formula (6) can measure the film thickness to be approximately h=320nm, which has a 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 using formula (5), as Figure 4 (b) is shown by the short dashed line. Figure 4As can be seen in (b), the short dashed line and the transmittance spectrum result (solid line) of the perovskite film measured by the spectrophotometer transmission method overlap well, especially the perovskite absorption edge. The absorbance of the material can be calculated using the formula log(1 / T). The optical fiber reflection device proposed in the present invention can simultaneously measure the transmittance and film thickness of the perovskite film. What is shown here is a single-layer film structure. The transmittance spectrum of a multi-layer film structure can also be measured using the optical fiber reflection device proposed in the present invention, because the absorption of a multi-layer film can be equivalent to the absorption of a single film. This reflective method for measuring the transmittance of a thin film and its device are used to measure the properties of thin film materials and detect the kinetic process of the growth process of thin film materials.

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

Claims

1. A reflective method for real-time in-situ measurement of thin film transmittance, characterized in that: The reflective method comprises the following steps: a) Installation equipment: The film to be measured is placed on a transparent substrate, with the environment above the film; the substrate transmittance T s ≥5%; an incident light path and an outgoing light path are arranged on the film; a light source is coupled to the incident light path, an end of the outgoing light path is coupled to a detector or a spectrometer, and the detector or the spectrometer is connected to a computer; b) Measure the light intensity reflectivity R of the film: 1) The light source emits a light beam, which is incident on the film through the incident light path. The light intensity incident on the film is I0; 2) The incident light is incident on the interface between the environment and the film, part of the light is reflected into the environment, and part of the light is refracted into the film; 3) The part of 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 will be reflected back and forth by the upper and lower interfaces of the film, and then 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 via an outgoing light path; the reflected light of the film includes light reflected from the interface between the environment and the film to the environment and light reflected from the interface between the film and the substrate and then refracted from the interface between the environment and the film to the environment; 6) The detector or spectrometer measures the intensity of the reflected light from the film. R , and further obtain the light intensity reflectivity R of the film: R=I R / I0 (1) c) Measure the light intensity reflectivity R' of the film-reflecting surface: 1) A reflective surface with known reflectivity is set under the substrate, the amplitude reflectivity of the reflective surface is r0, and the light intensity reflectivity of the reflective surface is R0 = |r0| 2 ≥5%; the distance from the lower surface of the film to the reflecting surface exceeds the interference length of the light source; 2) The intensity of the transmitted light on the lower surface of the substrate is I T =I0×T×T s , T is the light intensity transmittance of the 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 to the substrate. The light reflected back to the substrate is then transmitted to the environment through the film. At this time, the transmitted light passes through the film and the substrate twice. The light transmitted from the substrate to the substrate is reflected by the reflective surface and then transmitted to the environment through the film. The intensity I′ of the light reflected back by the reflective surface R for: I′ R = I0×T×T s ×R0×T×T s = I0×R0×T 2 ×T s 2 (2) 4) The reflected light of the film and the light reflected back from the reflective surface are received by a detector or a spectrometer through the outgoing light path. The detector or spectrometer measures the total light intensity I RR , and further obtain the light intensity reflectivity R′ of the film-reflecting surface: R′ = I RR / I0 (3) d) Calculate the transmittance T of the film: 1) After adding a reflective surface under the substrate, the light measured by the detector or spectrometer consists of two parts: the reflected light of the film and the light reflected back by the reflective surface. The distance from the bottom surface of the film to the reflective surface exceeds the interference length of the light source. These two parts of light do not interfere with each other, but only superposition of intensities, without involving amplitude superposition; 2) The total light intensity I measured by the detector or spectrometer RR for: I RR = I R + I′ R = I0×R + I0×R0×T 2 ×T s 2 (4) 3) The transmittance T of the film is obtained as: Where R = I R / I0 is the light intensity reflectivity of the film, which has been obtained in step b) 6); R′ is the light intensity reflectivity of the film-reflecting surface, which has been obtained in step c) 4); R0 is the light intensity reflectivity of the reflecting surface, which is a known quantity; T s is the transmittance of the substrate, which is a known quantity. It is only necessary to measure the light intensity reflectance R of the film and the light intensity reflectance R′ of the film-reflecting surface respectively, and use formula (5) to directly calculate the transmittance of the film. The reflected light of the film and the light reflected back from the reflecting surface do not interfere with each other, and do not involve the superposition of amplitudes, but only the superposition of light intensities. It is only necessary to measure the light intensity to directly calculate the transmittance of the film. During the measurement process, it is not necessary to know the thickness of the film and the 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.

2. The reflective method according to claim 1, wherein: In step a) 2), the first angle θ1 satisfies 0°≤θ1<90°.

3. The reflective method according to claim 1, wherein: In step c) 1), the reflective surface is in close contact or loose contact with the substrate, and the distance between the reflective surface and the lower surface of the substrate is less than 500 mm.

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

5. The reflective method according to claim 1, wherein: The light source adopts a multi-wavelength light source to directly measure the transmittance spectrum; Alternatively, a monochromatic light source is used as the light source and the transmittance of one wavelength is measured.

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

7. A reflective device for real-time in-situ measurement of thin film transmittance, characterized in that: The reflective device comprises: a film, a substrate, a light source, an incident light path, an outgoing light path, a detector or a spectrometer, a computer and a reflective surface; wherein the film is arranged on a light-transmitting substrate, and the film is above the environment; the substrate transmittance T s ≥5%; an incident light path and an outgoing light path are arranged on the film; a light source is coupled to the incident light path, an end of the outgoing light path is coupled to a detector or a spectrometer, and the detector or the spectrometer is connected to a computer; When measuring the light intensity reflectivity of a film, a light beam emitted by a light source is incident on the film through an incident light path; the incident light is incident on the interface between the environment and the film, part of the light is reflected into the environment, and part of the light is refracted into the film; the part of the light refracted into the film is reflected and refracted by the interface between the film and the substrate; the light reflected at the interface between the film and the substrate will be reflected back and forth by the upper and lower interfaces of the film, and then 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; the reflected light of the film is received by a detector or a spectrometer through an outgoing light path. The reflected light of the film includes the light reflected from the interface between the environment and the film to the environment and the light reflected from the interface between the film and the substrate and then refracted from the interface between the environment and the film to the environment. The detector or the spectrometer measures the intensity I of the reflected light of the film R , and further obtain the light intensity reflectivity R of the film; When measuring the transmittance of a thin film, a reflective surface with a known reflectivity is set under the substrate. The amplitude reflectivity of the reflective surface is r0, and the light intensity reflectivity of the reflective surface is R0 = |r0| 2 ≥5%; the intensity of the transmitted light on the lower surface of the substrate is I T =I0×T×T s , T is the light intensity transmittance of the 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 into the environment, at this time the transmitted light passes through the film and the substrate twice, the light transmitted from the substrate to the substrate, reflected by the reflecting surface, and then transmitted to the environment through the film is the light reflected back by the reflecting surface; the reflected light of the film and the light reflected back by the reflecting surface are received by the detector or spectrometer together through the outgoing light path; at this time the light measured by the detector or spectrometer consists 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, and do not involve the superposition of amplitudes, only the superposition of light intensities, the detector or spectrometer measures the total light intensity I RR , and further obtain the light intensity reflectivity R′ of the film-reflecting surface; the transmittance T of the film is calculated by the obtained light intensity reflectivity R of the film and the light intensity reflectivity R′ of the film-reflecting surface.

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

9. The reflective device according to claim 7, wherein: The incident light path and the outgoing light path adopt an optical fiber transmission system or a free space transmission system; when the optical fiber transmission system is adopted, the incident light path adopts an incident optical fiber, and the outgoing light path adopts an outgoing optical fiber; When a free space transmission system is used, the first lens is used for the incident light path and the second lens is used for the outgoing light path. In the incident light path, the incident light is collimated by the first lens and then incident on the upper surface of the film through the beam splitter. In the outgoing light path, the outgoing light is collected by the second lens after passing through the beam splitter and coupled to a detector or a spectrometer.

10. The reflective device according to claim 7, wherein: It also includes a moving device, on which the reflecting surface is placed; when measuring the light intensity reflectivity of the film, the reflecting surface is moved out from under the substrate by the moving device; when measuring the light intensity reflectivity of the film-reflecting surface, the reflecting surface is set under the substrate by the moving device.

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