Method for acquiring complex refractive index distribution morphology of film, and device

Abstract

A method for acquiring a complex refractive index distribution morphology of a film, and a device. The method comprises: S101, collecting interferograms of a reference area and a sample under test; S102, on the basis of the obtained interferograms, by means of a recovery algorithm, determining a normalized light intensity image and an optical path difference image of said sample relative to the reference area; S103, establishing a measurement model on the basis of a reflective film transmission equation; S104, determining a relationship between a measured reflection coefficient and optical path difference of an area under test of said sample relative to the reference area and the measurement model; and S105, on the basis of the measured reflection coefficient and optical path difference of the area under test of the film relative to the reference area and the relationship, calculating a complex refractive index distribution morphology of the film under test. The method is used for solving the problem in the prior art of limitation of film interference and an extinction coefficient of an absorption material.

Description

A method and device for obtaining the complex refractive index distribution morphology of a thin film

Technical field

[0001] The present invention belongs to the technical field related to optical complex refractive index measurement, and more specifically, relates to a method and device for obtaining the distribution morphology of the complex refractive index of a thin film. [Background Technology]

[0002] Currently, the measurement of the refractive index of optical materials has become particularly important in industries such as optics, new energy, and integrated circuits. The increasing requirements for optical thin film manufacturing in these industries have promoted the widespread use and in-depth research of the refractive index measurement of optical materials.

[0003] Optical phase measurement has the general advantages of being non-destructive, highly efficient, and having high lateral resolution. However, due to the influence of multiple reflections and the extinction coefficient of absorbing materials, optical phase measurement is not suitable for measuring the complex refractive index of materials under all conditions.

[0004] [Summary of the invention]

[0005] In response to the above defects or improvement needs of the prior art, the present invention provides a method and device for obtaining the complex refractive index distribution morphology of a thin film, which is used to solve the limitations of the prior art regarding thin film interference and the extinction coefficient of the absorbing material.

[0006] To achieve the above object, according to one aspect of the present invention, a method for obtaining the complex refractive index distribution morphology of a thin film is provided, the method comprising the following steps:

[0007] S101, collecting interference patterns of the reference area and the sample to be tested;

[0008] S102, determining a normalized light intensity map and an optical path difference of the sample to be tested relative to the reference area by a restoration algorithm based on the obtained interference pattern;

[0009] S103, establishing a measurement model based on a reflective thin film transmission equation;

[0010] S104, determining a relationship between the measured reflection system and optical path difference of the test area of ​​the test sample relative to the reference area and the measurement model;

[0011] S105 , calculating the complex refractive index distribution morphology of the film to be measured based on the measured reflectance and optical path difference of the film to be measured relative to the reference area and the relationship.

[0012] Furthermore, the interference image of the sample to be tested is acquired by acquiring an image sequence of the sample to be tested in real time based on the optical path system, or by calling and obtaining the image sequence from a storage medium storing the image sequence of the sample to be tested acquired based on the optical path system.

[0013] Furthermore, the optical path system includes a white light source, a filter, a first lens, a field stop, an aperture stop, a second lens and a beam splitter arranged in sequence along the optical path. The optical path system also includes a microscope objective and an electric translation stage, and the microscope objective is located between the beam splitter and the electric translation stage; the optical path system also includes a tube lens and a wavefront sensor, and the tube lens is located between the beam splitter and the wavefront sensor.

[0014] Furthermore, the electric translation stage is used to drive the sample to be tested to move in the horizontal or vertical direction.

[0015] Furthermore, the formula corresponding to the relationship is:

[0016] Where R and They represent the measured reflection coefficient and optical path difference of the area to be measured relative to the reference area, r is the reflection coefficient of the area to be measured, and r0 is the reflection coefficient of the reference area.

[0017] Furthermore, boundary a and boundary b represent the boundaries between the film and the incident medium and substrate, respectively. Because the incidence is perpendicular, the relationship between the electric field Ea and magnetic field Ha at boundary a and the electric field Eb at boundary b is: η r =y0n r

[0018] Where n r ,y0 and M r They represent the complex refractive index, optical admittance and film-related characteristic matrices respectively, q is used to represent the number of film layers, and m represents the substrate.

[0019] Furthermore, the multilayer film structure is regarded as a single-layer surface, and the admittance y is obtained, which represents the ratio of the magnetic field to the electric field, and is expressed as:

[0020] The complex reflection coefficient expression is:

[0021] The present invention also provides a method system for obtaining the complex refractive index distribution morphology of a thin film. The system includes a memory and a processor. The memory stores a computer program. When the processor executes the computer program, it executes the method for obtaining the complex refractive index distribution morphology of a thin film as described above.

[0022] The present invention also provides a computer-readable storage medium for storing computer-readable programs or instructions. When the program or instructions are executed by a processor, the method for obtaining the complex refractive index distribution morphology of the thin film as described above can be implemented.

[0023] In general, compared with the prior art, the above technical solutions conceived by the present invention have the following beneficial effects:

[0024] 1. After obtaining the original phase and light intensity distribution, the present invention first obtains the initial complex refractive index distribution based on the model of the reflective thin film transmission equation. After obtaining the target complex refractive index distribution morphology model, the model outliers are removed, thereby improving the accuracy of the obtained target complex refractive index distribution, that is, maximally restoring the complex refractive index distribution of the measured sample.

[0025] 2. The acquisition method is simple, easy to implement and has good flexibility.

[0026] 3. The present invention determines the relationship between the measurement results and the model of the reflective thin film transmission equation, and then based on the formula corresponding to the relationship and the measurement results, the complex refractive index distribution morphology of the thin film sample to be measured can be obtained.

Brief Description of the Drawings

[0027] FIG1 is a flow chart of a method for obtaining a thin film complex refractive index distribution profile provided by the present invention;

[0028] FIG2 is a schematic structural diagram of an embodiment of an optical path system provided by the present invention;

[0029] FIG3 is a schematic diagram of the reflective thin film transmission equation model in S103 in FIG1 ;

[0030] FIG4 is a schematic structural diagram of an embodiment of a device for determining the complex refractive index distribution profile of a thin film provided by the present invention;

[0031] FIG5 is a schematic structural diagram of an embodiment of a device for measuring the complex refractive index distribution profile of a thin film provided by the present invention.

[0032] In all the drawings, the same reference numerals are used to represent the same elements or structures, wherein: 10-optical path system, 11-white light source, 12-filter, 13-first lens, 14-field diaphragm, 15-aperture diaphragm, 16-second lens, 17-beam splitter, 18-microscope objective, 110-tube lens, 111-wavefront sensor, 112-electric translation stage, 19-sample to be measured, 400-complex refractive index distribution morphology determination device, 401-interference image acquisition unit, 402-light intensity map and optical path difference map recovery unit, 403-thin film transmission equation model determination unit, 404-target complex refractive index distribution model determination unit, 500-complex refractive index distribution morphology measurement device, 501-processor, 502-memory, 503-display. [Specific implementation method]

[0033] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0034] Referring to FIG1 , the present invention provides a method for obtaining the complex refractive index distribution morphology of a thin film, the method mainly comprising the following steps:

[0035] S101 , collecting interference patterns of the reference area and the sample 19 to be tested.

[0036] The interference image of the sample 19 to be tested in step S101 can be acquired by acquiring an image sequence of the sample 19 to be tested in real time based on the optical path system, or by calling and acquiring the image sequence of the sample 19 to be tested from a storage medium storing the image sequence of the sample to be tested acquired based on the optical path system.

[0037] In one embodiment, as shown in FIG2 , an optical system 10 includes a white light source 11, a filter 12, a first lens 13, a field stop 14, an aperture stop 15, a second lens 16, and a beam splitter 17, which are sequentially arranged along the optical path. The optical system 10 also includes a microscope objective 18 and a motorized translation stage 112. The microscope objective 18 is located between the beam splitter 17 and the motorized translation stage 112. The optical system 10 also includes a tube lens 110 and a wavefront sensor 111. The tube lens 110 is located between the beam splitter 17 and the wavefront sensor 111. The sample to be measured is placed on the motorized translation stage 112 and is located on the light-emitting side of the microscope objective 18.

[0038] The principle of the optical path system 10 collecting the interference pattern of the sample to be tested is as follows: the white light source 11 is used to generate an incident light source, which is adjusted by the filter 12, the first lens 13, the field stop 14, the aperture stop 15 and the second lens 16 to generate a collimated monochromatic light source. The collimated monochromatic light source is reflected by the beam splitter 17 to the microscope objective lens 18 and then converges onto the sample to be tested. The light irradiated on the sample to be tested is reflected again to the microscope objective lens 18 and transmitted to the tube lens 110 to be magnified and imaged on the wavefront sensor 111.

[0039] The electric translation stage 112 is used to move the sample to be tested in a horizontal or vertical direction.

[0040] The interference image of the sample to be tested and the reference area refers to the interference image of the sample to be tested and the reference area obtained by the electric translation stage 112 driving the sample to be tested to move horizontally. The electric translation stage 112 moves vertically to adjust the focus.

[0041] S102 , determining a normalized light intensity map and an optical path difference map of the sample to be tested relative to the reference area by using a restoration algorithm based on the obtained interference map.

[0042] S103, establishing a measurement model based on the reflective thin film transmission equation.

[0043] As shown in Figure 3, boundary a and boundary b represent the boundaries between the film and the incident medium and substrate, respectively. Because the incidence is perpendicular, the relationship between the electric field Ea and magnetic field Ha at boundary a and the electric field Eb at boundary b is: η r =y0n r

[0044] Where n r ,y0 and M r They represent the complex refractive index, optical admittance and film-related characteristic matrices respectively, q is used to represent the number of film layers, and m represents the substrate.

[0045] Considering the multilayer film structure as a single-layer surface, the admittance y can be obtained, which represents the ratio of the magnetic field to the electric field and is expressed as:

[0046] The complex reflection coefficient expression is:

[0047] S104, determining the relationship between the measured reflection system and optical path difference of the test area of ​​the test sample relative to the reference area and the measurement model, wherein the formula corresponding to the relationship is:

[0048] Where R and They represent the measured reflection coefficient and optical path difference of the area to be measured relative to the reference area, r is the reflection coefficient of the area to be measured, and r0 is the reflection coefficient of the reference area.

[0049] S105 , calculating the complex refractive index distribution morphology of the film to be measured based on the measured reflectance and optical path difference of the film to be measured relative to the reference area and the relationship.

[0050] After obtaining the original phase and light intensity distribution, the acquisition method provided by the present invention first obtains the initial complex refractive index distribution based on the reflective thin film transmission equation model, obtains the target refractive index distribution morphology model, and then removes the model outliers, thereby improving the accuracy of the obtained target complex refractive index distribution, that is, maximally restoring the complex refractive index distribution of the measured sample.

[0051] In order to better implement the complex refractive index distribution morphology determination method in the embodiment of the present invention, on the basis of the complex refractive index distribution morphology determination method, correspondingly, as shown in Figure 4, the present invention also provides a complex refractive index distribution morphology determination device 400, which includes an interference image acquisition unit 401, a light intensity map and optical path difference map recovery unit 402, a thin film transmission equation model determination unit 403 and a target complex refractive index distribution morphology determination unit.

[0052] The interference image acquisition unit 401 is used to acquire an interference pattern of the sample to be measured, wherein the interference pattern includes interference patterns of the measured area and the reference area. The interference pattern acquisition unit includes all interferometric measurement methods that can simultaneously image a light intensity image and an optical path difference image, including but not limited to transverse shearing interferometry, holography, and diffraction phase imaging.

[0053] The light intensity map and optical path difference map restoration unit 402 is used to determine the normalized light intensity map and optical path difference map of the sample to be tested relative to the reference area based on a restoration algorithm.

[0054] The thin film transmission equation model determination unit 403 is used to analyze the thin film sample and determine the relationship between the light beam reflected by the thin film sample and the incident light beam.

[0055] The target complex refractive index distribution profile determination unit is used to determine the initial value of the complex refractive index distribution profile based on the reflective film transmission matrix model and based on the relationship between the reflective film transmission matrix and the measured results, and remove outliers to obtain the target complex refractive index distribution profile.

[0056] The device can implement the above-mentioned method for obtaining the complex refractive index distribution morphology of the thin film. The specific implementation principles of the above-mentioned various units can be found in the response content of the above-mentioned method for obtaining the complex refractive index distribution morphology of the thin film, and will not be repeated here.

[0057] In another embodiment, referring to FIG5 , a complex refractive index distribution profile measurement device 500 is provided, comprising a processor 501, a memory 502, and a display 503. In some embodiments, the memory 502 may be an internal storage unit of the complex refractive index distribution profile measurement device 500, such as a hard disk or memory of the complex refractive index distribution profile measurement device. In other embodiments, the memory may also be an external storage device of the complex refractive index distribution profile measurement device, such as a plug-in hard disk, a smart media card (SMC), a secure digital (SD) card, a flash card, etc., equipped on the complex refractive index distribution profile measurement device.

[0058] The memory may also include both an internal storage unit of the complex refractive index distribution profile measurement device and an external storage device. The memory is used to store application software for installing the complex refractive index distribution profile measurement device and various data.

[0059] In some embodiments, the processor 501 may be a central processing unit (CPU), a microprocessor, or other data processing chip, configured to execute program codes stored in a memory or process data, such as the complex refractive index distribution profile determination method of the present invention.

[0060] In some embodiments, the display 503 can be an LED display, a liquid crystal display, a touch-sensitive liquid crystal display, or a QLED (Organic Light-Emitting Diode) touchscreen. The display is used to display information about the complex refractive index distribution topography measurement device and to display a visual user interface. The components of the complex refractive index distribution topography measurement device communicate with each other via a system bus.

[0061] In some embodiments of the present invention, when the processor executes the complex refractive index distribution topography model determination program in the memory, the following steps may be implemented:

[0062] Collecting interference patterns of the reference area and the sample to be tested;

[0063] Determine a normalized light intensity map and an optical path difference map of the sample to be tested relative to a reference area based on a recovery algorithm;

[0064] Establish a measurement model based on the reflective thin film transmission equation;

[0065] Determine the relationship between the measured results and the measurement model based on the reflective thin film transmission equation;

[0066] Based on the measurement results and the established model, the complex refractive index distribution morphology of the thin film sample to be tested is determined and outliers are removed.

[0067] It should be understood that, when the processor executes the complex refractive index distribution profile model determination program in the memory, in addition to the above functions, it can also implement other functions. For details, please refer to the description of the corresponding method embodiment above.

[0068] Furthermore, the embodiment of the present invention does not specifically limit the type of complex refractive index distribution profile measurement device mentioned, and the complex refractive index distribution profile measurement device can be a complex refractive index distribution profile measurement device for photovoltaic devices, semiconductor devices, optical devices, etc. Exemplary embodiments of a portable complex refractive index distribution profile measurement device include but are not limited to a portable complex refractive index distribution profile measurement device equipped with IOS, Android, Microsoft or other operating systems. The above-mentioned portable complex refractive index distribution profile measurement device can also be other portable complex refractive index distribution profile measurement devices, such as a laptop computer with a touch-sensitive surface (e.g., a touch panel). It should also be understood that in some other embodiments of the present invention, the complex refractive index distribution profile measurement device may not be a portable complex refractive index distribution profile measurement device, but a desktop computer with a touch-sensitive surface (e.g., a touch panel).

[0069] Accordingly, an embodiment of the present application also provides a computer-readable storage medium, which is used to store computer-readable programs or instructions. When the program or instructions are executed by a processor, it can implement the method for obtaining the complex refractive index distribution morphology of the thin film provided by the above-mentioned method embodiments.

[0070] A method system for obtaining the complex refractive index distribution morphology of a thin film includes a memory and a processor. The memory stores a computer program. When the processor executes the computer program, the method for obtaining the complex refractive index distribution morphology of a thin film as described above is executed.

[0071] Those skilled in the art will appreciate that all or part of the process steps for implementing the above-described method embodiments can be accomplished by instructing related hardware (e.g., a processor, a controller, etc.) through a computer program, and the computer program can be stored in a computer-readable storage medium, such as a magnetic disk, an optical disk, a read-only memory, or a random access memory.

[0072] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for obtaining the complex refractive index distribution morphology of a thin film, characterized in that: The acquisition method comprises the following steps: S101, collecting interference patterns of the reference area and the sample to be tested; S102, determining a normalized light intensity map and an optical path difference of the sample to be tested relative to the reference area by a restoration algorithm based on the obtained interference map; S103, establishing a measurement model based on a reflective thin film transmission equation; S104, determining the relationship between the measured reflection system and optical path difference of the tested area of ​​the tested sample relative to the reference area and the measurement model; S105, calculating the complex refractive index distribution morphology of the film to be tested based on the measured reflectance and optical path difference of the film to be tested area relative to the reference area and the relationship.

2. The method for obtaining the complex refractive index distribution morphology of a thin film according to claim 1, characterized in that: The interference image of the sample to be tested is collected in real time based on the optical path system. The interference image is obtained by calling a storage medium storing the image sequence of the sample to be tested collected based on the optical path system.

3. The method for obtaining the complex refractive index distribution morphology of a thin film according to claim 2, characterized in that: The optical path system includes a white light source, a filter, a first lens, a field stop, an aperture stop, a second lens and a beam splitter which are sequentially arranged along the optical path. The optical path system also includes a microscope objective and an electric translation stage, wherein the microscope objective is located between the beam splitter and the electric translation stage. The optical path system also includes a tube lens and a wavefront sensor, wherein the tube lens is located between the beam splitter and the wavefront sensor.

4. The method for obtaining the complex refractive index distribution morphology of a thin film according to claim 2, characterized in that: The electric translation stage is used to drive the sample to be tested to move in the horizontal or vertical direction.

5. The method for obtaining the complex refractive index distribution morphology of a thin film according to claim 1, characterized in that: The formula corresponding to the relationship is: In the formula, R and They represent the measured reflection coefficient and optical path difference of the area to be measured relative to the reference area, r is the reflection coefficient of the area to be measured, and r0 is the reflection coefficient of the reference area.

6. The method for obtaining the complex refractive index distribution morphology of a thin film according to claim 5, characterized in that: Boundary a and boundary b represent the boundaries between the film and the incident medium and substrate, respectively. Because the incidence is vertical, the relationship between the electric field Ea and magnetic field Ha at boundary a and the electric field Eb at boundary b is: or r =y0n r Where n r ,y0 and M r They represent the complex refractive index, optical admittance and characteristic matrix related to the film, q is used to represent the number of film layers, and m represents the substrate.

7. The method for obtaining the complex refractive index distribution morphology of a thin film according to claim 6, characterized in that: The multilayer film structure is regarded as a single-layer surface, and the admittance y is obtained, which represents the ratio of the magnetic field to the electric field, and the expression is: The complex reflection coefficient expression is:

8. A method and system for obtaining the complex refractive index distribution morphology of a thin film, characterized in that: The system includes a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the method for acquiring the complex refractive index distribution morphology of the thin film according to any one of claims 1 to 7 is executed.

9. A computer-readable storage medium, characterized in that: The computer-readable storage medium is used to store computer-readable programs or instructions. When the programs or instructions are executed by the processor, the method for obtaining the complex refractive index distribution morphology of the thin film described in any one of claims 1 to 7 can be implemented.

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