Method and device for determining absorbance of light-transmitting flat part

Abstract

The invention relates to the field of optical measurement, and provides a method and equipment for determining the absorbance of a light-transmitting flat piece, the method is used for measuring the absorbance, and the method comprises the following steps: obtaining spectral data of reflected light of the light-transmitting flat piece collected by a spectral confocal measurement system; determining an upper surface focusing peak wavelength # imgabs0 # and an upper surface focusing peak value # imgabs1 # of the light-transmitting flat piece and a lower surface focusing peak wavelength # imgabs2 # and a lower surface focusing peak value # imgabs3 # of the light-transmitting flat piece according to the spectral data; the upper surface reflectivity # imgabs5 # corresponding to the upper surface focusing peak wavelength # imgabs4 # and the lower surface reflectivity # imgabs7 # corresponding to the lower surface focusing peak wavelength # imgabs6 # are determined; and according to the upper surface focusing peak value # imgabs 8 #, the lower surface focusing peak value # imgabs 9 #, the upper surface reflectivity # imgabs 10 # and the lower surface reflectivity # imgabs 11 #, the absorbance # imgabs 12 # of the light-transmitting flat piece is determined.

Description

Technical Field

[0001] The invention relates to the field of optical measurement, and in particular to a method and a device for determining the absorbance of a light-transmitting flat piece. Background Art

[0002] In academic research or industrial applications, it is necessary to evaluate the optical properties of materials. The absorbance directly reflects the material's absorption efficiency of light energy. Existing characterization methods are limited by the indirectness of the measurement method. According to the law of conservation of light energy, the absorbance A=1-TR. Spectrophotometers usually only directly measure the transmittance T. The reflectance R requires additional equipment such as an integrating sphere or an ellipsometer, which increases the complexity and cost of the experiment. Especially in the case of highly reflective materials (with metal film layers or translucent materials), the error is large. The transmittance of the traditional spectrophotometer transmission light path will be very low for rough surfaces or strong scattering surfaces. The single Lambert-Beer law is only valid in uniform, non-scattering, and low-absorption conditions. For highly absorbing materials such as thick silicon carbide and non-uniform porous structures, the low measurement signal-to-noise ratio leads to calculation errors.

[0003] By characterizing the absorbance, the light utilization efficiency of the material and the actual light energy absorption ratio can be evaluated, which can be used to evaluate the transparency of the material in non-contact measurement and detection.

[0004] Existing absorbance measurement equipment is costly, bulky, and relatively complex to operate. It requires professional technicians to use and is not suitable for rapid detection under on-site conditions of translucent flat parts processing. It is also difficult to integrate with the processing equipment of the translucent flat parts being measured. Therefore, it is impossible to detect the absorbance online during the processing process and is often used for offline detection. Summary of the invention

[0005] In view of this, the present invention provides a method for determining the absorbance of a light-transmitting flat member, comprising: Acquiring spectral data of reflected light from the light-transmitting flat piece collected by a spectral confocal measurement system; Determine the peak wavelength of the upper surface focusing of the light-transmitting flat member according to the spectral data , the upper surface focusing peak and the bottom surface of the transparent flat piece focuses the peak wavelength , bottom surface focusing peak ; Determine the wavelength corresponding to the peak focusing on the upper surface The reflectivity of the upper surface , corresponding to the peak wavelength of the bottom surface focus The reflectivity of the lower surface ; Focusing peak value based on upper surface , bottom surface focusing peak , upper surface reflectivity and the lower surface reflectivity Determining the absorbance of light-transmitting flat parts .

[0006] Optionally, determine the wavelength corresponding to the upper surface focusing peak The reflectivity of the upper surface , corresponding to the peak wavelength of the bottom surface focus The reflectivity of the lower surface ,include: The material of the light-transmitting flat piece determines the peak wavelength corresponding to the upper surface focus. Refractive index , corresponding to the peak wavelength of the bottom surface focus Refractive index ; Using the refractive index Determine the reflectivity of the upper surface , using the refractive index Determine the reflectivity of the lower surface .

[0007] Optionally, ; ; in is the refractive index of the ambient medium in the measurement environment where the light-transmitting flat piece is located.

[0008] Alternatively, the absorbance of the light-transmitting flat piece is determined as follows : ; ; ; in Based on the peak focus on the upper surface and the lower surface focusing peak Determine the focus peak ratio, Based on the reflectivity of the upper surface and the lower surface reflectivity Determine the influence factor of the focusing wavelength on the absorbance of the upper and lower surfaces.

[0009] Optionally, when determining the absorbance of the light-transmitting flat element The step further includes focusing the peak value of the upper surface using the spectrum of the light source and the lower surface focusing peak Make corrections.

[0010] Optionally, the light source spectrum is used to focus the peak on the upper surface and the lower surface focusing peak Make corrections, including: Determine the wavelength corresponding to the peak focusing wavelength on the upper surface in the light source spectrum Light intensity , corresponding to the peak wavelength of the bottom surface focus Light intensity ; Using light intensity Focus peak on upper surface Make corrections and use the light intensity Focus peak on bottom surface Make corrections.

[0011] Alternatively, the absorbance of the light-transmitting flat piece is determined as follows : ; ; ; in Based on the corrected upper surface focusing peak and the corrected lower surface focusing peak Determine the focus peak ratio, Based on the reflectivity of the upper surface and the lower surface reflectivity Determine the influence factor of the focusing wavelength of the upper and lower surfaces on the absorbance; Indicates the intensity of the light source Focus peak on bottom surface The result of the correction is Indicates the intensity of the light source Focus peak on upper surface The result of the correction.

[0012] Furthermore, in determining the absorbance After that, it also includes determining the transmittance as follows : ; in is the reflectivity pre-measured for the light-transmitting flat element.

[0013] Optionally, the spectral data is wavelength-intensity correspondence data, or pixel-intensity correspondence data, wherein the pixels correspond to the wavelengths one-to-one, and the intensity is any one of spectral illumination, brightness, grayscale value, and light intensity.

[0014] Correspondingly, the present invention also provides a device for determining the absorbance of a light-transmitting flat piece, comprising: a processor and a memory connected to the processor; wherein the memory stores instructions executable by the processor, and the instructions are executed by the processor so that the processor executes the above-mentioned method for determining the absorbance of a light-transmitting flat piece.

[0015] The technical solution provided in this application is based on the reflected light spectrum data collected by the spectral confocal measurement system for the transparent flat piece, extracting the upper and lower surface focusing peak wavelengths, as well as the upper and lower surface focusing peaks, and then analyzing the absorbance of the transparent flat piece according to the reflectivity of the upper and lower surfaces. The spectral confocal measurement system adopts a non-contact measurement method, which can realize the in-situ collection of reflected light spectrum data in the wafer processing environment and obtain the absorbance, thereby improving the flexibility of absorbance measurement and overcoming the limitations of traditional spectrophotometers in large-scale production and in-situ measurement; and the reflected light spectrum data has a high resolution, which can provide the accuracy of the absorbance measurement results, and can also meet the needs of real-time monitoring in modern production environments, achieve rapid response, and provide a certain reference for the optical properties of materials before and after processing.

[0016] The solution provided by this application does not require the construction of other projection systems and optical paths. The spectral confocal measurement system can be integrated in wafer processing equipment (such as thinning machines, chemical mechanical polishing equipment, etc.), and can quickly respond in the processing environment and measure the absorbance of the wafer in situ. Measuring absorbance using the method provided by this application does not require the use of commonly used transmittance measuring equipment such as spectrophotometers or infrared spectrometers. The spectral confocal measurement system has a simple structure and high integration, and is easier to integrate with processing equipment, which is conducive to online measurement or multi-sample measurement. It is not limited to the size of the sample, and can reduce costs. It can achieve rapid absorbance, transmittance and other material performance detection.

[0017] According to Beer-Lambert's law, the thickness of the medium through which light passes is proportional to the absorbance. When measuring the thickness of a light-transmitting flat piece, its corresponding absorbance can be determined. By measuring the thickness and absorbance of light-transmitting flat pieces of different thicknesses, a corresponding relationship model between absorbance and thickness can be established. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] Figure 1This is a flow chart of a method for determining the absorbance of a light-transmitting flat member in an embodiment of the present application; Figure 2 Spectral data of reflected light collected by the spectral confocal measurement system in the embodiment of the present application; Figure 3 It is the light source spectrum data of the spectral confocal measurement system in the embodiment of the present application; Figure 4 is the spectrum data of the demodulated reflected light in the embodiment of the present application; Figure 5 Schematic diagram of the light path of the transparent light-transmitting flat member in the embodiment of the present application. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments 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 creative work are within the scope of protection of the present invention.

[0021] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] The embodiment of the present invention provides a method for determining the absorbance of a light-transmitting flat member, which can be executed by an electronic device such as a computer or a server. Figure 1 As shown, this method includes the following operations: S1, obtain the spectral data of the reflected light of the transparent flat piece collected by the spectral confocal measurement system. According to the spectral confocal principle, for a transparent (transparent, semi-transparent) flat piece (which can be solid or liquid), different wavelengths have different focusing positions, and a focused wavelength is formed on the upper and lower surfaces of the flat piece. The spectrometer and other detectors receive and detect the spectral data of the reflected light of the focused wavelength. Figure 2 The spectral data collected at multiple different positions (the distance between the reflected light detector probe and the wafer) are shown, where the horizontal axis represents the wavelength of the reflected light and the vertical axis represents the light intensity. The spectral data in this scheme is the light intensity corresponding to different wavelengths.

[0023] S2, determine the peak wavelength λ of the upper surface of the transparent flat piece according to the spectral data top , upper surface focusing peak I TOP (λ top ) and the bottom surface of the transparent flat piece focuses the peak wavelength λ unter , bottom surface focusing peak I UNTER (λ unter ).

[0024] In some embodiments, the spectrum output by the spectrometer is wavelength-intensity correspondence data, wherein the intensity can be any one of spectral illumination, brightness, grayscale value, and light intensity. Figure 2 The following figure shows four spectral data curves Counts[au]2, Counts[au]3, Counts[au]4, and Counts[au]5. Each curve has two obvious peaks (characteristic peaks). The horizontal coordinate of the first peak point in any curve is the peak wavelength of the upper surface focus. , the vertical coordinate of the first peak point is the upper surface focusing peak ; The horizontal coordinate of the second peak point is the peak wavelength of the lower surface focus , the ordinate of the second peak point is the lower surface focusing peak For such a spectrum, the intensity peak and its corresponding focus peak wavelength can be directly obtained. The intensity peak in this embodiment is specifically the peak of the light intensity.

[0025] In some embodiments, the spectrum output by the spectrometer is pixel-intensity correspondence data, where the intensity can be any of spectral illumination, brightness, grayscale value, and light intensity. For such a spectrum, the intensity peak and its corresponding pixel are directly obtained. Since the pixel and the wavelength have a one-to-one correspondence, the corresponding wavelength can be obtained based on this correspondence. The correspondence between the pixel and the wavelength is determined by instrument calibration and calibration. For example, at the factory or after calibration using a standard light source, the physical position of each pixel will be associated with a specific wavelength value.

[0026] S3, determine the peak wavelength λ corresponding to the upper surface focus top The upper surface reflectivity R(λ top ), corresponding to the bottom surface focusing peak wavelength λ unter The lower surface reflectivity R(λ unter ).

[0027] Ideally, the reflectivity of the material surface Can be calculated according to the formula ; Represents the refractive index of the medium in which the material is located. Represents the refractive index of a material.

[0028] The refractive index is a function of wavelength. Taking SIC wafer as an example, its refractive index is: ; When the wavelength hour, .

[0029] Therefore, the reflectivity in this embodiment and reflectivity It is a function of wavelength. The reflectivity is different for different wavelengths. The reflectivity value is also related to the material of the light-transmitting flat piece. The specific value can be calculated using a mathematical model or queried in a database.

[0030] S4, based on the upper surface focusing peak I TOP (λ top ), the lower surface focusing peak I UNTER (λ unter ), upper surface reflectivity R(λ top ) and the lower surface reflectivity R(λ unter ) determines the absorbance ω of the light-transmitting flat piece.

[0031] Furthermore, after determining the absorbance, the transmittance T can be further calculated: ; in For the reflectivity pre-measured for the transparent light-transmitting flat member, for example, a single-wavelength light beam of a specific wavelength may be used to irradiate its surface, thereby determining the reflectivity value based on the reflected light.

[0032] Figure 5 The optical path diagram of a transparent flat piece is shown. The incident light is refracted and reaches the lower surface of the transparent flat piece, then reflects, and then reaches the upper surface without considering the refraction loss, and is detected by the spectrometer. Represents incident light, Indicates the light reflected from the upper surface, represents the outgoing light returning to the detector without considering the loss (ignoring further reflection on the upper surface), Represents the light refracted by the upper surface, represents the light reaching the lower surface, Indicates light reflected by the lower surface; Indicates the reflectivity of the upper surface of a transparent flat piece. Indicates the reflectivity of the lower surface of a transparent flat piece; Indicates the amount of incident light absorbed by the transparent flat piece. Indicates the amount of light reflected from the lower surface absorbed by the transparent flat piece. Indicates absorbance, Indicates light transmittance.

[0033] According to this optical path, we can know that: ; ; in , , Refers to the spectrum corresponding to of light intensity.

[0034] Therefore, the absorbance can be determined by using the signal intensity ratio of the upper and lower surface focused wavelengths detected by the spectral confocal detector. The upper and lower surface focused wavelength intensity ratio is

[0035] The ratio of the two peak light intensities is C ; because is the wavelength corresponding to the upper surface focus The upper surface focusing peak (peak light intensity) is is the wavelength corresponding to the focusing wavelength of the lower surface The upper surface focusing peak (peak light intensity) should be substituted into the optical path analysis calculation. , respectively calculate the corresponding reflectivity , , without considering the internal reflection, ,but ; From this we can get: ; in ; ; You can is called the focus peak ratio, It is called the influence factor of the focusing wavelength on the upper and lower surfaces on the absorbance. The absorbance can be calculated based on the focusing peak ratio and the influence factor. .

[0036] As a preferred embodiment, considering that the peak intensity of the focused wavelength is the characteristic reflection spectrum intensity after the light source spectrum is modulated, the peak intensity ratio of the wavelengths of the upper and lower surfaces needs to remove the influence of the light source spectrum, that is, the original spectrum needs to be demodulated and the collected data spectrum is divided by the light source spectrum. In step S4, the light source spectrum can be used to modulate the peak intensity of the upper surface focus. and the lower surface focusing peak Make corrections.

[0037] Furthermore, the light source spectrum is used to focus the peak on the upper surface. and the lower surface focusing peak Make corrections, including: Determine the wavelength corresponding to the peak focusing wavelength on the upper surface in the light source spectrum Light intensity , corresponding to the peak wavelength of the bottom surface focus Light intensity ; Using light intensity Focus peak on upper surface Make corrections and use the light intensity Focus peak on bottom surface Make corrections.

[0038] Figure 3 The light source spectrum is shown. The horizontal axis represents the wavelength of the light source, and the vertical axis represents the light intensity of the light source. The peak wavelength of the upper surface focus is extracted from the spectrum of the reflected light. and the bottom surface focusing peak wavelength Then, the corresponding light source intensity can be obtained according to the light source spectrum. and light intensity .

[0039] Specifically, the focused wavelength peak light intensity is the characteristic reflection spectrum intensity after light source spectrum modulation. Therefore, the upper and lower surface wavelength peak light intensity ratio needs to remove the influence of the light source spectrum, that is, the original spectrum needs to be demodulated and the collected data spectrum is divided by the light source spectrum.

[0040] ; represents the actual measured reflected light spectrum, Represents the light source spectrum.

[0041] For the original spectrum data that has not been removed, for samples of the same thickness, the light intensity ratio between the upper and lower surfaces deviates, resulting in a deviation in the absorbance calculation.

[0042] So we need to restore the unmodulated light intensity: ; ; After correction, the data without considering the spectral characteristics of the light source is corrected, and the peak light intensity ratio is ; Figure 4 Shown for Figure 2 The four spectra shown are the reflected light spectra after correction / demodulation, namely, the curves A, B, C and D corresponding to the spectra, where the abscissa represents the wavelength of the reflected light and the ordinate represents the light intensity. The corrected / demodulated lower surface focusing peak is , the corrected / demodulated upper surface focusing peak is .

[0043] Therefore, the corrected focus peak ratio can be calculated as follows: : ; but ; Among them, the influence factor of the focusing wavelength of the upper and lower surfaces on the absorbance is : ; but ; In one embodiment, step S3 determines the wavelength corresponding to the upper surface focusing peak. The reflectivity of the upper surface , corresponding to the peak wavelength of the bottom surface focus The reflectivity of the lower surface ,include: The material of the light-transmitting flat piece determines the peak wavelength corresponding to the upper surface focus. Refractive index , corresponding to the peak wavelength of the bottom surface focus Refractive index ; Using the refractive index Determine the reflectivity of the upper surface , using the refractive index Determine the reflectivity of the lower surface .

[0044] According to the calculation formula of reflectivity ; Available ; ; in is the refractive index of the ambient medium in the measurement environment where the light-transmitting flat piece is located.

[0045] Taking the wafer as an example, the same wafer (thickness remains unchanged) is measured, and the same position is measured using a spectral confocal probe (the measurement point remains unchanged, but the distance from the probe changes), and the actual data obtained is processed.

[0046] After calculation, the absorbance and related intermediate data results are shown in the following table ; Among them, the four rows of data represent the data measured and calculated at four distances. From the above data, it can be seen that at different measurement distances of the full range, for the same sample (thickness unchanged), the absorbance calculation results remain consistent. The error source is related to the upper surface focus peak. and the lower surface focusing peak Reading error, peak wavelength of upper surface focus and the bottom surface focusing peak wavelength The extraction error, as well as the absorption degree of different wavelengths by different glass materials of passive components such as dispersion lenses, cause different losses, resulting in different light intensities of each wavelength component, which in turn affects the focus peak ratio. The accuracy of the value.

[0047] As a comparative example, the transmittance T of the wafer is measured by the existing L950 spectrophotometer, which is 0.137 and the reflectivity is 0.20, according to , the absorbance can be calculated =0.663, which is consistent with the absorbance calculated according to the method provided in this application. The values ​​are basically consistent.

[0048] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0049] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0050] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0051] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0052] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for determining the absorbance of a light-transmitting flat member, characterized in that: include: Acquiring spectral data of reflected light from the light-transmitting flat piece collected by a spectral confocal measurement system; Determine the peak wavelength of the upper surface focusing of the light-transmitting flat member according to the spectral data , the upper surface focusing peak and the bottom surface of the transparent flat piece focuses the peak wavelength , bottom surface focusing peak ; Determine the wavelength corresponding to the peak focusing on the upper surface The reflectivity of the upper surface , corresponding to the peak wavelength of the bottom surface focus The reflectivity of the lower surface ; Focusing peak value based on upper surface , bottom surface focusing peak , upper surface reflectivity and the lower surface reflectivity Determining the absorbance of light-transmitting flat parts .

2. The method according to claim 1, characterized in that Determine the wavelength corresponding to the peak focusing on the upper surface The reflectivity of the upper surface , corresponding to the peak wavelength of the bottom surface focus The reflectivity of the lower surface ,include: The material of the light-transmitting flat piece determines the peak wavelength corresponding to the upper surface focus. Refractive index , corresponding to the peak wavelength of the bottom surface focus Refractive index ; Using the refractive index Determine the reflectivity of the upper surface , using the refractive index Determine the reflectivity of the lower surface .

3. The method according to claim 2, characterized in that: ； ； in is the refractive index of the ambient medium in the measurement environment where the light-transmitting flat piece is located.

4. The method according to claim 1, characterized in that The absorbance of the light-transmitting flat piece is determined as follows : ； ； ； in Based on the peak focus on the upper surface and the lower surface focusing peak Determine the focus peak ratio, Based on the reflectivity of the upper surface and the lower surface reflectivity Determine the influence factor of the focusing wavelength on the absorbance of the upper and lower surfaces.

5. The method according to claim 1, characterized in that In determining the absorbance of a light-transmitting flat piece The step further includes focusing the peak value of the upper surface using the spectrum of the light source and the lower surface focusing peak Make corrections.

6. The method according to claim 5, characterized in that Use the light source spectrum to focus the peak on the upper surface and the lower surface focusing peak Make corrections, including: Determine the wavelength corresponding to the peak focusing wavelength on the upper surface in the light source spectrum Light intensity , corresponding to the peak wavelength of the bottom surface focus Light intensity ; Using light intensity Focus peak on upper surface Make corrections and use the light intensity Focus peak on bottom surface Make corrections.

7. The method according to claim 6, characterized in that The absorbance of the light-transmitting flat piece is determined as follows : ； ； ； in Based on the corrected upper surface focusing peak and the corrected lower surface focusing peak Determine the focus peak ratio, Based on the reflectivity of the upper surface and the lower surface reflectivity Determine the influence factor of the focusing wavelength of the upper and lower surfaces on the absorbance; Indicates the intensity of the light source Focus peak on bottom surface The result of the correction is Indicates the intensity of the light source Focus peak on upper surface The result of the correction.

8. The method according to claim 1, characterized in that In determining the absorbance After that, it also includes determining the transmittance as follows : ； in is the reflectivity pre-measured for a transparent flat piece.

9. The method according to any one of claims 1 to 8, characterized in that The spectral data is wavelength-intensity correspondence data, or pixel-intensity correspondence data, wherein the pixels correspond to the wavelengths one-to-one, and the intensity is any one of spectral illumination, brightness, grayscale value, and light intensity.

10. A device for determining the absorbance of a light-transmitting flat element, characterized in that: include: A processor and a memory connected to the processor; wherein the memory stores instructions executable by the processor, and the instructions are executed by the processor so that the processor executes the method for determining the absorbance of a light-transmitting flat member as described in any one of claims 1-9.

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