A method of measuring

Abstract

The application discloses a kind of measurement methods.Therein, measurement system includes: light source module, for providing visible light and near infrared light;Reflectance spectroscopy measurement module, for receiving the visible light reflected by the surface of sample to be measured and generating reflected spectrum;Spectral domain interferometry module, for receiving interference light and generating interference spectrum;Control module, control module is connected with reflectance spectroscopy measurement module and spectral domain interferometry module communication respectively, for receiving reflected spectrum and interference spectrum, and according to reflected spectrum and interference spectrum determines the film thickness and refractive index of sample to be measured.The technical scheme of the application can use spectral reflectance measurement principle, can also use spectral domain interferometry principle, can also be combined with both, ensure that different measurement modes are selected under different sample types to be measured, improve the accuracy of measurement system, and can flexibly respond to the measurement requirements of different types and thicknesses of samples to be measured.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of measurement, in particular to a measurement method. BACKGROUND

[0002] In the field of semiconductor industry, accurate film thickness and refractive index measurement is one of the core elements to guarantee the performance, yield and process stability of devices. Non-invasive optical measurement schemes include ellipsometry and spectroscopic reflectometry, the former mainly analyzes the polarization change after the interaction of the measuring beam and the sample, and the latter analyzes the intensity change of the reflected light in a specific waveband, and finally calculates the thickness and refractive index of the material through physical modeling.

[0003] For general thin film devices, the thickness of the film layer is usually from several nanometers to several microns, while the thickness of the substrate is between several hundred microns to several millimeters, and there is a difference of several orders of magnitude between the two. The system of the spectroscopic reflectometer is simple, but its performance is limited by the optical characteristics of the system itself, and it is difficult to handle such a wide thickness range in one measurement. SUMMARY

[0004] The present application provides a measurement method to solve the problem of large limitation and low accuracy of single measurement method in the prior art.

[0005] According to an aspect of the present application, a measurement system is provided, comprising:

[0006] A light source module is configured to provide visible light and near-infrared light, the near-infrared light including reference light and measurement light, and the visible light and the measurement light being incident on a sample to be measured;

[0007] A reflectance spectrum measurement module is configured to receive the visible light reflected by the surface of the sample to be measured and generate a reflectance spectrum;

[0008] A spectral domain interferometry measurement module is configured to receive interference light and generate an interference spectrum, wherein the interference light is generated by the interference of the reference light and the measurement light transmitted through the sample to be measured;

[0009] A control module is in communication with the reflectance spectrum measurement module and the spectral domain interferometry measurement module, respectively, and is configured to receive the reflectance spectrum and the interference spectrum, and determine the film thickness and the refractive index of the sample to be measured according to the reflectance spectrum and the interference spectrum.

[0010] Optionally, the reflectance spectrum measurement module includes a first beam splitter prism, a dichroic mirror and a visible light waveband spectrometer.

[0011] The visible light exits the light source module and passes through the first beam splitter prism and the dichroic mirror in sequence to reach the sample to be measured, and is reflected by the sample to be measured and exits the first beam splitter prism and the dichroic mirror in sequence to reach the visible light waveband spectrometer.

[0012] Optionally, the spectral domain interferometry module comprises a second beam splitter and an infrared spectrum analyzer, a third beam splitter and an infrared reflector;

[0013] The near-infrared light is split into reference light and measurement light by the second beam splitter after being emitted from the light source module; the reference light is reflected to the third beam splitter by the infrared reflector; the measurement light is incident on the sample to be measured and transmitted to the third beam splitter; the reference light and the measurement light generate interference light after interference at the third beam splitter, and then the interference light is emitted to the infrared spectrum analyzer.

[0014] According to another aspect of the present application, a measurement method is provided, which is applied to a measurement system, and the measurement method comprises:

[0015] receiving a reflection spectrum and / or an interference spectrum;

[0016] determining the film thickness and the refractive index of the sample to be measured according to the reflection spectrum and / or the interference spectrum.

[0017] Optionally, in the first measurement mode, the reflection spectrum is received, comprising:

[0018] obtaining the reflection spectrum, a reference spectrum, a reference reflectivity and a theoretical reflectivity; wherein the reference spectrum is a spectrum generated by the visible light reflected by the surface of the reference sample; the reference reflectivity is the reflectivity of the reference sample;

[0019] determining the film thickness and the refractive index of the sample to be measured according to the reflection spectrum, comprising:

[0020] determining the actual reflectivity according to the reflection spectrum, the reference spectrum and the reference reflectivity; wherein the reflection spectrum , the reference spectrum and the reference reflectivity and the actual reflectivity satisfy ;

[0021] determining the minimum value of according to the reflection spectrum; wherein λ is the wavelength; is the actual reflectivity; is the theoretical reflectivity; is the refractive index; is the film thickness;

[0022] determining the film thickness and the refractive index of the sample to be measured according to the minimum value.

[0023] Optionally, the sample to be measured comprises a thin film and a substrate arranged in a stack; the interference spectrum comprises a first interference signal and a second interference signal; the first interference signal is the interference signal of the thin film; the second interference signal is the interference signal of the substrate;

[0024] In the second measurement mode, the interference spectrum is received, comprising:

[0025] The first interference signal, the second interference signal and the measurement interference signal are acquired; wherein the measurement interference signal is an interference spectrum signal obtained after the reference light and the measurement light interfere without the sample to be measured;

[0026] The film thickness and the refractive index of the sample to be measured are determined according to the interference spectrum, comprising:

[0027] The film-free optical path difference, the first optical path difference and the second optical path difference are determined according to the second interference signal and the measurement interference signal;

[0028] The refractive index of the substrate at the first position and the thickness of the substrate are determined according to the film-free optical path difference, the first optical path difference and the second optical path difference; wherein the film-free optical path difference , the first optical path difference , the second optical path difference and the thickness of the substrate satisfy ; the refractive index of the substrate , the first optical path difference and the thickness of the substrate satisfy ;

[0029] The third optical path difference, the fourth optical path difference and the fifth optical path difference of the film are determined according to the first interference signal;

[0030] The refractive index of the film and the thickness of the film are determined according to the third optical path difference, the fourth optical path difference, the fifth optical path difference, the refractive index of the substrate and the film-free optical path difference.

[0031] Optionally, the refractive index of the film and the thickness of the film are determined according to the third optical path difference, the fourth optical path difference, the fifth optical path difference, the refractive index of the substrate and the film-free optical path difference, comprising:

[0032] The thickness of the substrate at the second position is determined according to the third optical path difference and the refractive index of the substrate;

[0033] The thickness of the film is determined according to the thickness of the substrate at the second position, the fourth optical path difference, the film-free optical path difference and the fifth optical path difference; wherein the thickness of the substrate at the second position , the fourth optical path difference , the film-free optical path difference , the fifth optical path difference and the thickness of the film satisfy ;

[0034] The refractive index of the film is determined according to the thickness of the film, the thickness of the substrate at the second position, the refractive index of the substrate and the fourth optical path difference; wherein the thickness of the film a thickness of the substrate at the second position a refractive index of the substrate a fourth optical path difference and a refractive index of the thin film satisfy .

[0035] Optionally, the sample to be measured includes a thin film and a substrate arranged in a stack; the reflection spectrum is a spectrum signal of the thin film; and the interference spectrum is an interference signal of the substrate.

[0036] In the third measurement mode, the reflection spectrum and the interference spectrum are received.

[0037] The film thickness and the refractive index of the sample to be measured are determined according to the reflection spectrum and the interference spectrum, including:

[0038] The reflection spectrum, the reference spectrum, the reference reflectivity and the theoretical reflectivity are obtained; the reference spectrum is a spectrum generated by visible light reflected by a surface of a reference sample; and the reference reflectivity is a reflectivity of the reference sample.

[0039] The thickness of the thin film and the refractive index of the thin film are determined according to the reflection spectrum, the reference spectrum signal, the reference reflectivity and the theoretical reflectivity.

[0040] The interference spectrum and the measurement interference signal are obtained; the measurement interference signal is an interference spectrum signal obtained after the reference light and the measurement light interfere without the sample to be measured.

[0041] The film-free layer optical path difference, the first optical path difference and the second optical path difference are determined according to the interference spectrum and the measurement interference signal.

[0042] The refractive index of the substrate is determined according to the film-free layer optical path difference, the first optical path difference and the second optical path difference.

[0043] A relationship between the refractive index of the substrate, the thickness of the thin film, the refractive index of the thin film, the thickness of the substrate and the theoretical interference model satisfies , the thickness of the thin film , the refractive index of the thin film , the interference spectrum , the thickness of the substrate and the theoretical interference model . ;

[0044] wherein λ is a wavelength; , , and are light intensity coefficients.

[0045] The film-free layer optical path difference and the interference spectrum are determined according to the theoretical interference model a minimum value;

[0046] determining the thickness of the substrate according to the minimum value .

[0047] The technical scheme of the present application, by setting up light source module, reflected spectrum measurement module, spectrum domain interference measurement module and control module in the measurement system, and then making the measurement system can use both the principle of spectral reflectance measurement, also can use the principle of spectral domain interference measurement, also can use both, ensure that different measurement methods are selected under different types of samples to be measured, improve the accuracy of the measurement system, can flexibly respond to the measurement requirements of different types and thickness of samples to be measured.

[0048] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present application, nor is it intended to limit the scope of the present application. Other features of the present application will become apparent from the following description. BRIEF DESCRIPTION OF DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0050] Figure 1 is a schematic diagram of the optical path of a measurement system according to an embodiment of the present application.

[0051] Figure 2 is a flowchart of a first measurement method according to an embodiment of the present application.

[0052] Figure 3 is a flowchart of a second measurement method according to an embodiment of the present application.

[0053] Figure 4 is a schematic diagram of a first measurement principle according to an embodiment of the present application.

[0054] Figure 5 is a flowchart of a third measurement method according to an embodiment of the present application.

[0055] Figure 6 is a schematic diagram of a second measurement principle according to an embodiment of the present application.

[0056] Figure 7 is a schematic diagram of an interference spectrum simulation result according to an embodiment of the present application.

[0057] Figure 8 is a schematic diagram of aFigure 7 Schematic diagram of the spatial domain results of Fourier transform.

[0058] Figure 9 4 is a flow chart of a fourth measurement method provided according to an embodiment of the present invention.

[0059] Figure 10 4 is a flow chart of a fifth measurement method provided according to an embodiment of the present invention.

[0060] Figure 11 A schematic diagram of a third measurement principle provided according to an embodiment of the present invention.

[0061] Figure 12 According to an embodiment of the present invention, a Interference diagram given by the theoretical model. DETAILED DESCRIPTION

[0062] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0063] It should be noted that the terms "first," "second," and the like in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or precedence. It should be understood that the numbers used in this way are interchangeable where appropriate so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to these processes, methods, products, or apparatus.

[0064] Figure 1 FIG. 1 is a schematic diagram of an optical path of a measurement system provided according to an embodiment of the present invention. Figure 1 As shown, the measurement system includes:

[0065] A light source module is used to provide visible light and near-infrared light; the near-infrared light includes reference light and measurement light; the visible light and measurement light are incident on the sample to be tested 6;

[0066] a reflection spectrum measurement module for receiving the visible light reflected by the surface of the sample 6 to be measured and generating a reflection spectrum;

[0067] a spectral domain interference measurement module for receiving the interference light and generating an interference spectrum; wherein the interference light is generated by the interference of the reference light and the measurement light transmitted through the sample 6 to be measured;

[0068] a control module in communication with the reflection spectrum measurement module and the spectral domain interference measurement module, for receiving the reflection spectrum and the interference spectrum, and determining the film thickness and the refractive index of the sample 6 to be measured according to the reflection spectrum and the interference spectrum.

[0069] The light source module can include a visible light source 1 and a near-infrared light source 3. The visible light source 1 can be used to emit visible light, and the visible light can be a wide-band parallel light beam in the visible light band. In some embodiments, the visible light source 1 can be a halogen lamp light source. The near-infrared light source 3 can be used to emit near-infrared light, and the near-infrared light can be a wide-band parallel light beam in the near-infrared band. In some embodiments, the near-infrared light can be a superluminescent diode light source. The near-infrared light includes reference light and measurement light with the same parameters, and the visible light and the measurement light are controlled to be incident on the sample 6 to be measured, and the reference light and the measurement light transmitted through the sample 6 to be measured interfere to generate interference light. It can be understood that the visible light source 1 and the near-infrared light source 3 cannot work at the same time, and only the visible light or the near-infrared light is incident on the sample 6 to be measured at a time, and cannot be incident at the same time.

[0070] The reflection spectrum measurement module can be used to generate a reflection spectrum, and the spectral domain interference measurement module can be used to generate an interference spectrum.

[0071] The control module is in communication with the reflection spectrum measurement module and the spectral domain interference measurement module, and can receive the reflection spectrum and the interference spectrum. The reflection spectrum can be a signal input by the reflection spectrum measurement module, and the interference spectrum can be a signal input by the spectral domain interference measurement module. The control module can analyze the thickness and the refractive index of the film layer by the reflection spectrum alone, by the interference spectrum alone, or by the reflection spectrum and the interference spectrum in combination.

[0072] It can be understood that the technical scheme of the embodiment of the present application fuses the spectral reflectance measurement method and the spectral domain interference measurement method in the measurement system, so there are three measurement modes in the embodiment of the present application, the first measurement mode can be a spectral reflectance mode, that is, the visible light source 1 is turned on, and the control module performs reflection spectrum collection and analysis alone; the second measurement mode can be a spectral domain interference mode, that is, only the near-infrared light source 3 is turned on, and the control module performs interference spectrum collection and analysis alone; the third measurement mode can be an integrated mode, that is, the visible light source 1 and the near-infrared light source 3 are turned on in sequence, and the collection and analysis of the reflection spectrum and the interference spectrum are performed respectively, and the thickness and the refractive index of each film layer are calculated comprehensively. The integrated mode can be used to measure the to-be-measured sample 6 with large thickness difference between film layers, and is more accurate than a single measurement mode.

[0073] The technical scheme of the embodiment of the present application sets the light source module, the reflection spectrum measurement module, the spectral domain interference measurement module and the control module in the measurement system, so that the measurement system can use the spectral reflectance measurement principle, the spectral domain interference measurement principle or a combination of the two, ensures that different measurement modes are selected under different types of to-be-measured samples, and improves the accuracy of the measurement system, so that the measurement demand of different types and thicknesses of to-be-measured samples can be flexibly met.

[0074] Optionally, continuing to refer to Figure 1 As shown in the figure, the reflection spectrum measurement module includes a first beam splitter 2, a dichroic mirror 5 and a visible light band spectrometer 10.

[0075] The visible light passes through the first beam splitter 2 and the dichroic mirror 5 in sequence to reach the to-be-measured sample 6 after being emitted from the light source module, and is emitted to the visible light band spectrometer 10 after being reflected by the to-be-measured sample 6 and passing through the dichroic mirror 5 and the first beam splitter 2 in sequence. The first beam splitter 2, the dichroic mirror 5 and the to-be-measured sample 6 are arranged in sequence on the visible light path, so that the visible light is reflected to the dichroic mirror 5 after being emitted from the visible light source 1 and passing through the first beam splitter 2, the dichroic mirror 5 transmits the visible light and reflects the near-infrared light, and then the visible light is transmitted to the to-be-measured sample 6 from the dichroic mirror 5; the to-be-measured sample 6 re-reflects the visible light to the dichroic mirror 5, and then the visible light is transmitted to the visible light band spectrometer 10 after passing through the dichroic mirror 5 and the first beam splitter 2 in sequence. In the embodiment of the present application, the film thickness and the refractive index of the to-be-measured sample 6 can be analyzed and solved by analyzing the spectrum in the visible light band spectrometer 10 by using the reflection spectrum measurement principle.

[0076] Optionally, continuing to refer to Figure 1 As shown in the figure, the spectral domain interference measurement module includes a second beam splitter 4 and an infrared band spectrometer 9, a third beam splitter 8 and an infrared reflector 7.

[0077] The near-infrared light is emitted from the light source module, passes through the second light splitting prism 4 to be split into reference light and measurement light; the reference light is reflected by the infrared reflector 7 to the third light splitting prism 8; the measurement light is incident on the sample 6 to be measured and transmitted to the third light splitting prism 8; the reference light and the measurement light are incident on the third light splitting prism 8 to generate interference light, and then the interference light is emitted to the infrared waveband spectrometer 9.

[0078] The second light splitting prism 4 and the infrared waveband spectrometer 9 are arranged on the light path of the near-infrared light, the near-infrared light is emitted from the near-infrared light source 3 to the second light splitting prism 4, the second light splitting prism 4 splits the near-infrared light into measurement light and reference light, the measurement light is incident on the sample 6 to be measured and transmitted to the infrared waveband spectrometer 9, and the reference light does not pass through the sample 6 to be measured and directly interferes with the measurement light to enter the infrared waveband spectrometer 9. The technical scheme of the embodiment of the present application detects and records the measurement light and the reference light according to the spectral domain interference principle, and analyzes and solves the film thickness and the refractive index of each film layer of the sample 6 to be measured.

[0079] The infrared reflector 7 and the third light splitting prism 8 are arranged on the light path of the reference light in sequence; the third light splitting prism 8 is also arranged on the light path of the measurement light and between the sample 6 to be measured and the infrared waveband spectrometer 9.

[0080] The third light splitting prism 8 functions to converge the reference light and the measurement light. The infrared reflector 7 functions to reflect the reference light to the third light splitting prism 8.

[0081] Specifically, after the second light splitting prism 4 splits the near-infrared light into reference light and measurement light, the reference light is incident on the infrared reflector 7, the infrared reflector 7 reflects the reference light to the third light splitting prism 8; the measurement light is incident on the dichroic mirror 5, the dichroic mirror 5 reflects the measurement light to the sample 6 to be measured, the measurement light penetrates the sample 6 to be measured and is incident on the third light splitting prism 8, the measurement light and the reference light intersect on the third light splitting prism 8 to generate interference, and then the interference light enters the infrared waveband spectrometer 9.

[0082] It can be understood that the compatibility of the system is ensured, and the light propagating on the first light splitting prism 2, the dichroic mirror 5, the sample 6 to be measured and the third light splitting prism 8 is coaxial. The technical scheme of the embodiment of the present application sets the visible light source, the first light splitting prism, the dichroic mirror, the visible waveband spectrometer, the near-infrared light source, the second light splitting prism, the infrared waveband spectrometer and the control module in the measurement system, so that the measurement system can use the spectral reflectance measurement principle, can use the spectral domain interference measurement principle, and can also use both, so as to ensure that different measurement methods are selected under different types of samples to be measured, and the accuracy of the measurement system is improved, and the measurement requirements of different types and thicknesses of samples to be measured can be flexibly met.

[0083] Based on the same inventive concept, Figure 2 is a flowchart of the first measurement method according to an embodiment of the present application, which is combined with Figure 1 and Figure 2 It is shown that the present embodiment provides a measurement method, which is applied to a measurement system, and the measurement method comprises the following steps:

[0084] S10, receiving a reflection spectrum and / or an interference spectrum.

[0085] Wherein, the reflection spectrum can be obtained from the visible band spectrometer 10 after the visible light source 1 is started, and the interference spectrum can be obtained from the infrared band spectrometer 9 after the near-infrared light source 3 is started.

[0086] It can be understood that the requirements for the reflection spectrum and the interference spectrum are different for different measurement modes. The reflection spectrum or the interference spectrum can be received according to the requirements, or the reflection spectrum and the interference spectrum can be received.

[0087] S11, determining the film thickness and the refractive index of the sample to be measured according to the reflection spectrum and / or the interference spectrum.

[0088] Specifically, the control module can analyze the thickness and the refractive index of the film layer through the reflection spectrum alone, analyze the thickness and the refractive index of the film layer through the interference spectrum alone, or analyze the film thickness and the refractive index through the reflection spectrum and the interference spectrum in combination.

[0089] The technical solution of the present embodiment can use the spectrum reflection measurement principle, the spectrum domain interference measurement principle, or a combination of the two, so as to select different measurement modes under different types of samples to be measured, improve the accuracy of the measurement system, and flexibly cope with the measurement requirements of different types and thicknesses of samples to be measured.

[0090] On the basis of the above-mentioned embodiments, Figure 3 is a flowchart of the second measurement method according to an embodiment of the present application, which is combined with Figure 1 and Figure 3 It is shown that the measurement method is suitable for the first measurement mode, and comprises the following steps:

[0091] S20, obtaining a reflection spectrum, a reference spectrum, a reference reflectivity, and a theoretical reflectivity. The reference spectrum is a spectrum generated by visible light reflected by the surface of a reference sample; and the reference reflectivity is the reflectivity of the reference sample.

[0092] The first measurement mode can be a spectral reflection mode, that is, the visible light source 1 is turned on, and the control module performs reflection spectrum acquisition and analysis alone. The first measurement mode can measure the thickness and refractive index of the film directly. The reference spectrum can be a reflection spectrum measured by replacing the position of the sample 6 to be measured with a reference sample and turning on the visible light source 1. The reference reflectivity can be the reflectivity of the reference sample, which is a known quantity. The theoretical reflectivity can be a function relationship of wavelength, thickness and refractive index.

[0093] S21, determining the actual reflectivity according to the reflection spectrum, the reference spectrum and the reference reflectivity. Wherein, the reflection spectrum , the reference spectrum and the reference reflectivity and the actual reflectivity satisfy the reference spectrum.

[0094] Wherein, the reflection spectrum , the reference spectrum and the reference reflectivity are known, the actual reflectivity is calculated according to the formula .

[0095] S22, determining the minimum value of according to the reflection spectrum. Wherein, λ is the wavelength; is the actual reflectivity; is the theoretical reflectivity; is the refractive index; is the film thickness.

[0096] Wherein, in order to further ensure the accuracy of the thickness and the refractive index, the actual reflectivity is combined with the theoretical reflectivity for fitting optimization, and the specific optimization method is to minimize the difference between the theoretical reflectivity and the actual reflectivity. The minimum value of the formula is obtained by .

[0097] S23, determining the film thickness and the refractive index of the sample to be measured according to the minimum value.

[0098] Wherein, when takes the minimum value, the corresponding thickness and refractive index are the optimal values.

[0099] Specifically, the basic measurement principle of the spectral reflection mode is to determine the thickness and reflectivity of the sample 6 to be measured by fitting the theoretical reflection spectrum with the actual reflection spectrum. Figure 4 is a first measurement principle diagram provided by the embodiment of the present application, as shown in Figure 4 , for the sample 6 to be measured, the reflected light is the interference superposition of the front and back surface reflected light. Based on this model, the expression of the theoretical reflectivity is: ; wherein, Fresnel reflection coefficient of air-film; Fresnel reflection coefficient of film-substrate; the value is ; wherein, and respectively correspond to the complex refractive index of air, film, and substrate; wherein, is the phase difference. Definition ; wherein, is the wavelength, is the thickness of the i-th layer. Based on the above theory, the theoretical reflectivity is a function of wavelength, refractive index, and thickness . Then, the thickness and reflectivity of the corresponding film layer are calculated according to the reflection spectrum, the reference spectrum, the reference reflectivity, and the theoretical reflectivity.

[0100] It can be understood that, since the spectral reflection principle can be limited by the optical characteristics of the respective system, it is difficult to process a wide range of thicknesses in one measurement, so this measurement method can be applied in a narrower film layer measurement process.

[0101] The technical scheme of the embodiment of the present application measures by using the spectral reflection method, continues to combine the theoretical reflectivity for fitting optimization after determining the actual reflectivity, and finally obtains the thickness and refractive index closest to the theoretical reflectivity, thereby ensuring the accuracy and accuracy of the calculation of the thickness and reflectivity of the film layer, and realizing high-speed measurement.

[0102] On the basis of the above embodiment, Figure 5 is a flowchart of a third measurement method provided by the embodiment of the present application, which is combined with Figure 1 and Figure 5 It is shown that the sample to be measured 6 includes a film and a substrate arranged in layers; the interference spectrum includes a first interference signal and a second interference signal; the first interference signal is the interference signal of the film; and the second interference signal is the interference signal of the substrate. The measurement method is applied in the second measurement mode, and includes:

[0103] S30, obtaining the first interference signal, the second interference signal, and the measurement interference signal. The measurement interference signal is an interference spectrum signal obtained after the reference light and the measurement light interfere without the sample to be measured.

[0104] Wherein, the sample to be measured 6 includes a film and a substrate arranged in layers. The second measurement mode can be a spectral domain interference mode, that is, only the near-infrared light source 3 is turned on, and the control module performs interference spectrum collection and analysis alone, so the thickness and refractive index of the film and the substrate need to be calculated one by one in the second measurement mode.

[0105] Wherein, Figure 6 According to the second measurement principle diagram provided by the embodiment of the present application, Figure 6The routes of the reference light and the measurement light are shown. When measuring the film layer thickness and the refractive index, the measurement light is only incident on the substrate, such as Figure 6 x1, the second interference signal can be the spectral signal collected at the incident position x1; when calculating the film thickness and the refractive index, the measurement light is incident on the film, such as x2, and the first interference signal can be the spectral signal collected at the incident position x2. The measurement interference signal can be the interference spectral signal obtained after the reference light and the measurement light interfere without the sample to be measured, which can be obtained in advance. In S31, the film-free optical path difference, the first optical path difference, and the second optical path difference are determined according to the second interference signal and the measurement interference signal.

[0106] For further reference Figure 7 , the film-free optical path difference OPD1 can be the optical path difference between the reference light W r and the measurement light W m0 . The first optical path difference OPD2(x1) can be the optical path difference between the measurement light W m1 transmitted after single reflection at the substrate boundary and the measurement light W m2 . The second optical path difference OPD3(x1) can be the optical path difference between the measurement light W m1 at the incident position x1 and the reference light W r .

[0107] For further reference , the optical path difference can be obtained by detecting the interference spectrum of the infrared spectrum spectrometer 9, and then performing Fourier transform to obtain the time-domain signal Figure 7 , in which the peak position corresponds to the optical path difference, and the amplitude of the peak is related to the reflection coefficient. An exemplary Figure 7 schematic diagram of the interference spectrum simulation result according to an embodiment of the present application is shown in Figure 8 , Figure 8 which is a spatial domain result schematic diagram of the Fourier transform of Figure 7 . From Figure 8 , the results of OPD2(x1) and OPD3(x1) can be clearly seen.

[0108] In S32, the refractive index of the substrate at the first position and the thickness of the substrate are determined according to the film-free optical path difference, the first optical path difference, the second optical path difference, and the thickness of the substrate. The film-free optical path difference , the first optical path difference , the second optical path difference , and the thickness of the substrate satisfy ; and the refractive index of the substrate , the first optical path difference , and the thickness of the substrate satisfy .

[0109] Wherein, according to the relationship between the film-free layer optical path difference, the first optical path difference and the second optical path difference, the refractive index of the substrate and the thickness of the film, the refractive index of the substrate and the thickness of the substrate are determined. The first position can be the x1 position in the figure, which is a single layer film layer.

[0110] The film-free layer optical path difference , the first optical path difference , the second optical path difference , and the thickness of the substrate satisfy ; then the thickness of the substrate , the first optical path difference , the second optical path difference can be determined. .

[0111] The refractive index of the substrate , the first optical path difference , and the thickness of the substrate satisfy ; then the thickness of the substrate , the first optical path difference can be determined. .

[0112] For example, as shown in Figure 6 , the reference light is W r , the measurement light is W m0 , and the film-free layer optical path difference OPD1 satisfies ; wherein, is the transmission distance of the reference light in air; is the transmission distance of the measurement light in air. The first optical path difference , the refractive index of the substrate , and the thickness of the substrate satisfy . The second optical path difference , the transmission distance of the reference light in air , the transmission distance of the measurement light in air , the refractive index of the substrate , and the thickness of the substrate satisfy , and after integrating the above formula, we get ; .

[0113] S33, determining a third optical path difference, a fourth optical path difference and a fifth optical path difference of the thin film according to the first interference signal.

[0114] Wherein, in combination Figure 6 As shown in the figure, after the measurement at x1 is completed, the measurement at x2 is continued. The third optical path difference can be the optical path difference between W m4 and W m5 . The fourth optical path difference can be the optical path difference between W m3 and W m4 . The fifth optical path difference can be the optical path difference between W r and W m4 .

[0115] S34, determining the refractive index of the thin film and the thickness of the thin film according to the third optical path difference, the fourth optical path difference, the fifth optical path difference, the refractive index of the substrate and the film-free layer optical path difference.

[0116] Wherein, the refractive index of the thin film and the thickness of the thin film are continuously calculated according to the relationship between the third optical path difference, the fourth optical path difference, the fifth optical path difference, the refractive index of the substrate, the film-free layer optical path difference, the refractive index of the thin film and the thickness of the thin film.

[0117] The technical scheme of the embodiment of the present application, when the spectral domain interference measurement method is used, obtains the thickness and refractive index information through direct analysis of the interference spectrum, without any numerical optimization, and thus high-speed measurement can be realized.

[0118] On the basis of the above embodiment, Figure 9 is a flowchart of a fourth measurement method provided by the embodiment of the present application, in combination Figure 1 , Figure 9 and Figure 6 , the measurement method comprises:

[0119] S40, obtaining the first interference signal, the second interference signal and the measurement interference signal.

[0120] S41, determining the film-free layer optical path difference, the first optical path difference and the second optical path difference according to the second interference signal and the measurement interference signal.

[0121] S42, determining the refractive index of the substrate at the first position and the thickness of the substrate according to the film-free layer optical path difference, the first optical path difference and the second optical path difference.

[0122] S43, determining the third optical path difference, the fourth optical path difference and the fifth optical path difference of the thin film according to the first interference signal.

[0123] S44, determining the thickness of the substrate at the second position according to the third optical path difference and the refractive index of the substrate.

[0124] Wherein, the thickness of the substrate at the x2 position can be calculated according to the third optical path difference, the refractive index of the substrate and the thickness of the substrate at the second position. In some embodiments, the third optical path difference , the refractive index of the substrate and the thickness of the substrate at the second position satisfy .

[0125] S45, the thickness of the thin film is determined according to the thickness of the substrate at the second position, the fourth optical path difference, the optical path difference of the film-free layer and the fifth optical path difference. Wherein, the thickness of the substrate at the second position , the fourth optical path difference , the optical path difference of the film-free layer , the fifth optical path difference and the thickness of the thin film satisfy .

[0126] Wherein, the thickness of the substrate at the second position , the fourth optical path difference , the optical path difference of the film-free layer , the fifth optical path difference and the thickness of the thin film satisfy ; accordingly, the thickness of the thin film at the x2 position .

[0127] S46, the refractive index of the thin film is determined according to the thickness of the thin film, the thickness of the substrate at the second position, the refractive index of the substrate and the fourth optical path difference. Wherein, the thickness of the thin film , the thickness of the substrate at the second position , the refractive index of the substrate , the fourth optical path difference and the refractive index of the thin film satisfy .

[0128] Wherein, the thickness of the thin film , the thickness of the substrate at the second position , the refractive index of the substrate , the fourth optical path difference and the refractive index of the thin film satisfy ; accordingly, the refractive index of the thin film .

[0129] In summary, the thickness and refractive index of the thin film, the thickness and refractive index of the substrate are calculated.

[0130] On the basis of the above embodiments, Figure 10is a flow chart of a fifth measurement method provided according to an embodiment of the present invention, combined with Figure 1 and Figure 10 As shown, the sample 6 to be measured includes a stacked film and a substrate; the reflection spectrum is the spectral signal of the film; and the interference spectrum is the interference signal of the substrate. This measurement method is applicable to the third measurement mode, including:

[0131] S50, obtaining a reflection spectrum, a reference spectrum, a reference reflectivity, and a theoretical reflectivity, wherein the reference spectrum is a spectrum generated by visible light reflected from the surface of the reference sample; and the reference reflectivity is the reflectivity of the reference sample.

[0132] The third measurement mode can be an integrated mode, which sequentially activates visible light source 1 and near-infrared light source 3 to collect and analyze the reflectance spectrum and interference spectrum, respectively, to comprehensively calculate the thickness and refractive index of the film and substrate. This third measurement mode is applicable when the thickness difference between the film and substrate is large. To ensure measurement accuracy, the third measurement mode integrates spectral reflectance and spectral domain interferometry.

[0133] S51. Determine the thickness and refractive index of the film according to the reflection spectrum, the reference spectrum signal, the reference reflectivity and the theoretical reflectivity.

[0134] The reflection spectrum can be the spectral signal of the thin film measured by the visible band spectrometer 10. The thin film of the sample to be measured 6 is transparent in the visible light band and the near infrared light band, and the substrate is opaque in the visible light band and transparent in the near infrared light band. In this measurement method, first turn on the visible light source 1, collect the spectral signal of the thin film, and calculate the thickness and refractive index of the thin film using the spectral reflection principle. The method in step S52 is the same as that in step S21 and step S22, using the reflection spectrum , reference spectrum and reference reflectivity Known, according to the formula Calculating actual reflectivity , and then determine the thickness and refractive index of the film of the sample 6 to be tested based on the actual reflectivity and theoretical reflectivity.

[0135] S52, obtaining an interference spectrum and measuring an interference signal, wherein the measured interference signal is an interference spectrum signal obtained after interference between the reference light and the measuring light when there is no sample to be measured.

[0136] After the reflection spectrum is collected, the near-infrared light source 3 is turned on and the visible light source 1 is turned off to collect the interference signal of the substrate. The interference spectrum is collected and the interference signal is measured using the principle of spectral domain interferometry.

[0137] S53, determining the film-free layer optical path difference, the first optical path difference and the second optical path difference according to the interference spectrum and the measured interference signal.

[0138] wherein, Figure 11 According to a third measurement principle provided by the embodiment of the present application, as shown in Figure 11 , the film layer optical path difference OPD1 can be the optical path difference between the reference light W r and the measurement light W m0 . The first optical path difference OPD2(x1) can be the optical path difference between the measurement light W SR0 and the measurement light W SR1 transmitted after single reflection of the thin film boundary. The second optical path difference OPD3(x1) can be the optical path difference between the measurement light W SR0 and the reference light W r .

[0139] S54, determining the refractive index of the substrate according to the film-free layer optical path difference, the first optical path difference and the second optical path difference.

[0140] wherein, the film-free layer optical path difference , the first optical path difference , the second optical path difference and the thickness of the substrate satisfy ; the refractive index of the substrate , the first optical path difference and the thickness of the substrate satisfy , and the refractive index of the substrate is obtained accordingly.

[0141] S55, establishing the relationship between the refractive index of the substrate, the thickness of the thin film, the refractive index of the thin film, the thickness of the substrate and the theoretical interference model. Wherein, the refractive index of the substrate , the thickness of the thin film , the refractive index of the thin film , the interference spectrum , the thickness of the substrate and the theoretical interference model satisfy ;

[0142] wherein, λ is the wavelength; , , and are the light intensity coefficients.

[0143] Wherein, the measuring beam is continuously moved to the double-layer position, and since the beam will inevitably be disturbed by the film in the third measuring mode, the Fourier analysis method is no longer suitable for realizing accurate thickness measurement. Therefore, the embodiment of the present application starts from a physical model, analyzes four main components in the interference signal, namely, the direct current signal, the interference signal between W m1 and W m2 , the interference signal between W m1 and W m3 , and the interference signal between W m1 and W m4 (or W m2 and W m3 ). The remaining high-order interference terms are ignored because their interference visibility is significantly lower than the above several terms, and then the refractive index of the substrate , the thickness of the film , the refractive index of the film , the interference spectrum and the thickness of the substrate satisfy ;

[0144] Wherein, λ is the wavelength; , , and are the light intensity coefficients.

[0145] Since , and are known, the interference spectrum theoretical model can be considered as a function of .

[0146] S56, the minimum value of is determined according to the theoretical interference model and the interference spectrum .

[0147] S57, the thickness of the substrate is determined according to the minimum value.

[0148] Wherein, the fitting optimization of is performed according to the theoretical interference model and the interference spectrum : when the difference between the theoretical interference model and the interference spectrum is minimum, that is, the takes the minimum value, the thickness of the substrate at this time is determined as the optimal thickness value. Figure 12 According to the interference schematic diagram given by the theoretical model based on provided by the embodiment of the present application, reference is made to Figure 12shown, Figure 12 based on theoretical model curve, the measurement results will be compared and analyzed with it during testing.

[0149] The technical solution of the embodiment of the present application designs a high-precision thin film and substrate measurement method based on a physical model. Compared with direct Fourier analysis, the measurement error caused by the thin film is minimized, and the measurement precision is improved.

[0150] It should be understood that the steps can be reordered, added, or deleted using the various forms of flow shown above. For example, each step described in the present application can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present application can be achieved, and this is not limited herein.

[0151] The above specific embodiments do not constitute a limitation on the scope of protection of the present application. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method of measurement, characterized by, The application is applied to a measuring system, the measuring system comprises: a light source module for providing visible light and near-infrared light; the near-infrared light comprises reference light and measuring light; the visible light and the measuring light are incident to a sample to be measured; a reflection spectrum measuring module for receiving the visible light reflected by the surface of the sample to be measured and generating a reflection spectrum; a spectral domain interference measuring module for receiving interference light and generating an interference spectrum; wherein the interference light is generated by interference between the reference light and the measuring light transmitted through the sample to be measured; a control module, which is in communication connection with the reflection spectrum measuring module and the spectral domain interference measuring module, respectively, for receiving the reflection spectrum and the interference spectrum, and determining the film thickness and the refractive index of the sample to be measured according to the reflection spectrum and the interference spectrum; the measuring method comprises: obtaining a reflection spectrum, a reference spectrum, a reference reflectivity and a theoretical reflectivity; wherein the reference spectrum is a spectrum generated by visible light reflected by the surface of a reference sample; the reference reflectivity is the reflectivity of the reference sample; determining an actual reflectance from the reflectance spectrum, the reference spectrum, and the reference reflectance; wherein the reflectance spectrum , the reference spectrum , and the reference reflectance , and the actual reflectance satisfy ; determined from the reflection spectrum is a minimum; wherein λ is the wavelength; is the actual reflectivity; is the theoretical reflectivity; is the refractive index; is the film thickness; determining the film thickness and the refractive index of the sample to be measured according to the minimum value; or, when the sample to be measured comprises a thin film and a substrate arranged in a stack; the interference spectrum comprises a first interference signal and a second interference signal; the first interference signal is the interference signal of the thin film; the second interference signal is the interference signal of the substrate, the measuring method comprises: obtaining the first interference signal, the second interference signal and a measuring interference signal; wherein the measuring interference signal is an interference spectrum signal obtained by interference between the reference light and the measuring light without the sample to be measured; determining a film-free layer optical path difference, a first optical path difference and a second optical path difference according to the second interference signal and the measuring interference signal; determining a refractive index of the substrate and a thickness of the substrate at the first position according to the filmless layer optical path difference, the first optical path difference and the second optical path difference; wherein the filmless layer optical path difference , the first optical path difference , the second optical path difference and the thickness of the substrate satisfy ; the refractive index of the substrate , the first optical path difference and the thickness of the substrate satisfy ; determining a third optical path difference, a fourth optical path difference and a fifth optical path difference of the thin film according to the first interference signal; determining the refractive index of the thin film and the thickness of the thin film according to the third optical path difference, the fourth optical path difference, the fifth optical path difference, the refractive index of the substrate and the film-free layer optical path difference; or, when the sample to be measured comprises a thin film and a substrate arranged in a stack; the reflection spectrum is the spectrum signal of the thin film; the interference spectrum is the interference signal of the substrate, the measuring method comprises: obtaining a reflection spectrum, a reference spectrum, a reference reflectivity and a theoretical reflectivity; determining the thickness of the thin film and the refractive index of the thin film according to the reflection spectrum, the reference spectrum signal, the reference reflectivity and the theoretical reflectivity; obtaining the interference spectrum and a measuring interference signal; determining a film-free layer optical path difference, a first optical path difference and a second optical path difference according to the interference spectrum and the measuring interference signal; determining the refractive index of the substrate according to the film-free layer optical path difference, the first optical path difference and the second optical path difference; establishing a relationship between the refractive index of the substrate, the thickness of the film, the refractive index of the film, the thickness of the substrate, and a theoretical interference model; wherein the refractive index of the substrate , the thickness of the film , the refractive index of the film , the interference spectrum , the thickness of the substrate , and the theoretical interference model satisfy ; where λ is the wavelength; 、 、 and is the light intensity coefficient; According to the theoretical interference model and the interference spectrum determined minimum; determining a thickness of the substrate from the minimum value .

2. The measurement method according to claim 1, characterized in that, determining the refractive index of the thin film and the thickness of the thin film according to the third optical path difference, the fourth optical path difference, the fifth optical path difference, the refractive index of the substrate and the film-free layer optical path difference, comprising: determining a thickness of the substrate at a second location based on the third optical path difference and a refractive index of the substrate; determining a thickness of the thin film according to the thickness of the substrate at the second position, the fourth optical path difference, the filmless layer optical path difference, and the fifth optical path difference; wherein the thickness of the substrate at the second position , the fourth optical path difference , the filmless layer optical path difference , the fifth optical path difference , and the thickness of the thin film satisfy ; determined from the thickness of the thin film, the thickness of the substrate at the second position, the refractive index of the substrate, and the fourth optical path difference; wherein the thickness of the thin film , the thickness of the substrate at the second position , the refractive index of the substrate , the fourth optical path difference , and the refractive index of the thin film satisfy .

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