CN116136391A - Film thickness measuring device and method - Google Patents

Film thickness measuring device and method Download PDF

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Publication number
CN116136391A
CN116136391A CN202310257104.XA CN202310257104A CN116136391A CN 116136391 A CN116136391 A CN 116136391A CN 202310257104 A CN202310257104 A CN 202310257104A CN 116136391 A CN116136391 A CN 116136391A
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film
optical fiber
measured
film thickness
light source
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白蛟
杨昊崴
张建阳
陈俊光
宋江锋
石岩
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Institute of Materials of CAEP
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G01B11/0616—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating
    • G01B11/0625—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating with measurement of absorption or reflection
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/01—Arrangements or apparatus for facilitating the optical investigation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/55—Specular reflectivity

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  • General Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
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  • Pathology (AREA)
  • Length Measuring Devices By Optical Means (AREA)

Abstract

The invention discloses a thin film thickness measuring device and a thin film thickness measuring method, and relates to the technical field of optical measurement. The thin film thickness measuring device provided by the invention designs the objective lens probe of the shared light path of the incident light and the reflected light, can approximately focus the incident light of the light source optical fiber on the thin film to be measured, and controls the incident angle in a smaller range through the objective lens probe, thereby being beneficial to simplifying the reflection model and improving the measuring efficiency. In addition, the invention can shape the reflected light into the return light image distributed in the annular shape by adopting the objective lens probe, and the return light image is well matched with the converging end of the Y-shaped multi-core optical fiber, so that most of the reflected light enters the detection optical fiber, the reflected light can be effectively prevented from entering the light source optical fiber, the light energy utilization rate is greatly improved, and the measurement precision is remarkably improved.

Description

Film thickness measuring device and method
Technical Field
The invention relates to the technical field of optical measurement, in particular to a thin film thickness measuring device and a thin film thickness measuring method.
Background
The film can be used for protecting a substrate, catalyzing reaction, photoelectric conversion and the like, is widely applied to the manufacturing and processing processes of key devices such as solar cells, semiconductor chips and the like, and is very important for manufacturing process control and quality inspection. For film thickness measurement, besides the more direct step-type or section measurement method, more indirect physical property measurement methods are adopted, namely, the film thickness is reversely deduced through detection of physical properties of a certain aspect of the film, and the method comprises a weighing method, an electrical method, an optical method and the like, wherein the method is generally focused and studied by particularly taking advantages of non-contact, high resolution, high efficiency and the like of the optical method.
Optical methods typically reverse the thickness of the film to be measured by detecting reflection or transmission spectra, such as ellipsometry, spectrophotometry, integrating sphere, fiber optic spectroscopy, and the like. Ellipsometry has high sensitivity and wide range of measurable media, but has complex device, high cost and poor integrability. The spectrophotometry can realize multiplexing measurement of reflectivity and absorbance, but has the defects of dispersion effect, large light spot size, complex structure, high cost and the like. The integrating sphere method has simple principle and various illumination modes, but can generate contact damage, and the common integrating sphere has large size and inconvenient integration.
In contrast, the optical fiber spectroscopic method has more flexibility, obtains the spectral reflectivity of the film to be measured by comparing the reflection spectrums of the film to be measured and the standard mirror surface, and then solves the thickness of the film by comparing the spectral reflectivity with the theoretical spectral reflectivity, and the light source, the detector to be measured and the detector are connected through optical fibers (optical fiber coupler or Y-shaped multi-core optical fibers) without being limited by fixed space layout, so that the equipment integration level is high. However, the optical fiber spectroscopic method also has certain disadvantages, for example, when the optical fiber coupler is used for spectroscopic, larger light intensity loss is generated at the coupling point, when the Y-type multi-core optical fiber is used for spectroscopic, although the optical fiber loss is small, most of the light beams emitted from the end face of the optical fiber cannot return to the optical fiber under the condition that a focusing objective lens is not used, the light energy utilization rate is low, and because the numerical aperture of the optical fiber allows the reflected light beams in a larger angle range to enter the optical fiber, the incident angle range of the corresponding incident light is wider, the reflection model is more complex, and the solving efficiency of the film thickness is inevitably reduced. In the case of using the Y-type multi-core optical fiber and the focusing objective lens in combination, according to the optical conjugation principle, the light beam emitted from the end face of the light source optical fiber is projected onto the film through the focusing objective lens, and the light beam reflected from the film will still be mainly focused on the end face of the light source optical fiber, so that the end face of the detection optical fiber can only receive a small part of reflected light, and the problem of low light energy utilization rate is also caused.
In addition, the current solution method for the film thickness is also insufficient. The conventional reflection film thickness meter generally adopts the standard of known spectral reflectivity for comparison measurement, but because the spectral reflectivity is not only related to inherent optical characteristics, but also related to the incident angle in the measurement process, the standard known spectral reflectivity is often from other instruments such as a literature or a spectrophotometer, so that the incident angle when the reflection film thickness meter measures a film sample to be measured is often different from the incident angle when the standard known spectral reflectivity is obtained, and further a traceability error is generated when the absolute spectral reflectivity of the film sample to be measured is calculated by referring to the known spectral reflectivity, and a final film thickness error is caused.
Disclosure of Invention
The invention aims to provide a thin film thickness measuring device and a thin film thickness measuring method, which can improve the measuring accuracy while improving the measuring efficiency of the thin film thickness.
In order to achieve the above object, the present invention provides the following solutions:
a film thickness measuring apparatus comprising: the device comprises a light source, a Y-shaped multi-core optical fiber, an objective lens probe, a spectrometer and a processor;
the Y-shaped multi-core optical fiber comprises a light source optical fiber and a plurality of detection optical fibers;
one end of the light source optical fiber is connected with the light source; one end of each of the plurality of detection optical fibers is connected with the spectrometer; the other ends of the light source optical fibers and the other ends of the plurality of detection optical fibers form a converging end which is connected to the objective lens probe; the spectrometer is electrically connected with the processor.
Optionally, one ends of the plurality of detection optical fibers are connected to the spectrometer in a linear arrangement manner; the other ends of the plurality of detection optical fibers are circumferentially arrayed with the other end of the light source optical fiber as a center.
Optionally, the objective lens probe includes: the optical fiber comprises a first spherical lens, a first conical lens, a second spherical lens, a second conical lens, a fixed block, a cavity and an optical fiber interface;
the optical fiber interface, the first spherical lens, the first conical lens, the second spherical lens and the second conical lens are arranged along the same optical axis, and the first spherical lens, the first conical lens, the second spherical lens and the second conical lens are all fixed in the cavity through the fixing block.
Optionally, the objective lens probe includes: the optical fiber comprises a first spherical lens, a first conical lens, a second spherical lens, a fixed block, a cavity and an optical fiber interface;
the optical fiber interface, the first spherical lens, the first conical lens and the second spherical lens are arranged along the same optical axis, and the first spherical lens, the first conical lens and the second spherical lens are all fixed in the cavity by the fixing block.
Optionally, a slit structure is arranged on the spectrometer; the slit structure is parallel to the detection fibers which are arranged in a straight line so as to receive light rays in the detection fibers.
Optionally, the processor is a system or device in which an intelligent processing chip is implanted.
Optionally, the radius of the detection fiber is not smaller than the radius of the light source fiber.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects:
the thin film thickness measuring device provided by the invention designs the objective lens probe of the shared light path of the incident light and the reflected light, can approximately focus the incident light of the light source optical fiber on the thin film to be measured, and controls the incident angle in a smaller range through the objective lens probe, thereby being beneficial to simplifying the reflection model and improving the measuring efficiency. In addition, the invention can shape the reflected light into the return light image distributed in the annular shape by adopting the objective lens probe, and the return light image is well matched with the converging end of the Y-shaped multi-core optical fiber, so that most of the reflected light enters the detection optical fiber, the reflected light can be effectively prevented from entering the light source optical fiber, the light energy utilization rate is greatly improved, and the measurement precision is remarkably improved.
The invention also provides a film thickness measuring method which is applied to the film thickness measuring device; the film thickness measuring method comprises the following steps:
respectively acquiring a noise spectrum, a metal reflector reflection spectrum and a film reflection spectrum to be measured;
determining the relative spectral reflectivity of the film to be measured based on the noise spectrum, the metal reflector reflection spectrum and the film to be measured reflection spectrum;
presetting a metal reflector coating thickness d according to the incidence angle of the objective lens probe, the optical constant of the metal reflector and the metal reflector coating, and the thickness d of the metal reflector coating 1 Determining a theoretical spectral reflectance of the metal mirror;
determining the absolute spectral reflectance of the film to be measured based on the theoretical spectral reflectance of the metal reflector and the relative spectral reflectance of the film to be measured;
based on the optical constant of the film substrate to be detected and the film coating film of the film to be detected, the thickness d of the film is preset 2 Determining the theoretical spectral reflectivity of the film to be measured;
determining the fitting degree of the theoretical spectral reflectance of the film to be measured and the absolute spectral reflectance of the film to be measured;
when the fitting degree reaches a preset requirement, determining the preset film thickness d 2 The thickness of the film to be measured; specifically, the thickness d of the coating film of the preset metal reflector is used 1 And a preset film thickness d 2 Meanwhile, as a parameter, carrying out fitting degree optimization inversion solution to obtain the preset film thickness d when the fitting degree is optimal 2 The method comprises the steps of carrying out a first treatment on the surface of the Preset film thickness d when the fitting degree is optimal 2 The thickness of the film to be measured is obtained.
Optionally, the method includes respectively obtaining a noise spectrum, a reflection spectrum of the metal reflector, and a reflection spectrum of the film to be measured, specifically including:
under the condition that a light source is not turned on or a film to be measured is not placed, acquiring a plurality of groups of background noise signals within a set time, and carrying out average processing on the plurality of groups of background noise signals to obtain a noise spectrum;
placing a metal reflector at a position which is a preset distance away from an objective lens probe, and turning on a light source to obtain a first light intensity distribution signal; the first light intensity distribution signals are light intensity distribution signals of different wavelengths of the metal reflector in a set time after the light source is turned on;
carrying out average treatment on the first light intensity distribution signal to obtain a metal reflector reflection spectrum;
changing a metal reflector into a film to be detected, placing the film to be detected at a position which is a preset distance away from the objective lens probe, and turning on a light source to obtain a second light intensity distribution signal; the second light intensity distribution signals are light intensity distribution signals of different wavelengths of the film to be tested within a set time after the light source is turned on;
and carrying out average treatment on the second light intensity distribution signal to obtain a film reflection spectrum to be detected.
The technical effects achieved by the film thickness measuring method provided by the invention are the same as those achieved by the device provided by the invention, so that the detailed description is omitted here.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic diagram of a film thickness measuring apparatus according to the present invention;
FIG. 2 is a schematic diagram of the transmission of the optical path between the detection fiber, the objective lens probe and the object to be detected;
FIG. 3 is a schematic view of a first structure of an objective lens probe and an annular ring thereof according to the present invention;
FIG. 4 is a schematic view of a second structure of an objective lens probe and an annular ring thereof according to the present invention;
FIG. 5 is a schematic diagram of a flare image formed by an objective lens probe on the end face of a light source optical fiber when measuring different distances under different conditions provided by the invention, and a return image after being reflected to be measured; fig. 5 (a) is a schematic diagram of a spot image formed by the objective lens probe on the end face of the light source optical fiber and a return image after reflection to be measured when the distance 1 is measured in the case a, fig. 5 (B) is a schematic diagram of a spot image formed by the objective lens probe on the end face of the light source optical fiber and a return image after reflection to be measured when the distance 2 is measured in the case B, and fig. 5 (C) is a schematic diagram of a spot image formed by the objective lens probe on the end face of the light source optical fiber and a return image after reflection to be measured when the distance 3 is measured in the case C;
FIG. 6 is a schematic diagram of a return image 2 and the position of the image relative to the converging end of the Y-type multi-core optical fiber when measuring a distance 2;
FIG. 7 is a graph showing the radial distribution of return light energy when measuring distance 2 according to the present invention;
FIG. 8 is a schematic view of a thin film reflection model provided by the present invention;
FIG. 9 is a graph showing the difference of theoretical spectral reflectivities at different angles of incidence for the same predetermined thickness provided by the present invention;
FIG. 10 is a diagram of the noise spectrum, the reflection spectrum of the metal mirror surface, and the reflection spectrum of the film to be measured obtained by the present invention;
FIG. 11 is a schematic representation of the resulting spectral reflectance provided by the present invention.
Symbol description:
the device comprises a light source 11, a Y-type multi-core optical fiber 12, an objective lens probe 13, a spectrometer 14, a processor 15, a film to be tested 16, a first spherical lens 17, a first conical lens 18, a second spherical lens 19, a second conical lens 20, a fixed block 21 and an optical fiber interface 22.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention aims to provide a thin film thickness measuring device and a thin film thickness measuring method, which can improve the measuring accuracy while improving the measuring efficiency of the thin film thickness.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
As shown in fig. 1, the thin film thickness measuring apparatus provided by the present invention includes: a light source 11, a Y-shaped multi-core optical fiber 12, an objective lens probe 13, a spectrometer 14 and a processor 15.
The Y-type multi-core optical fiber 12 is used for transmission of light beams, and includes a light source 11 optical fiber and a plurality of detection optical fibers.
One end of the optical fiber of the light source 11 is connected to the light source 11. The light source 11 is configured to provide incident light having a broad spectrum of wavelengths to the optical fiber of the light source 11, and the wavelength range may cover ultraviolet, visible, and near infrared bands.
One end of each of the plurality of detection fibers is connected to the spectrometer 14, so that the spectrometer 14 detects the spectrum information of the reflected light received by the detection fibers. The other end of the light source 11 optical fiber and the other ends of the plurality of detection optical fibers are converged at the same port to form a converging end, the light source 11 optical fiber in the converging end is positioned at the center, and the detection optical fibers are annularly arranged at the periphery of the light source 11 optical fiber. The converging end is connected to the objective lens probe 13 to transmit the incident light of the light source 11 to the objective lens probe 13, and to receive the light (reflected light) from the objective lens probe 13 and transmit it to the spectrometer 14. As shown in fig. 2, the optical fiber of the light source 11 is used for transmitting incident light, and the detection optical fiber is used for transmitting reflected light. The spectrometer 14 is electrically connected with the processor 15, so that the processor 15 controls the spectrometer 14 in real time and reads the spectrum signals therein, and solves the thickness of the film 16 to be measured through an arithmetic program.
Further, in order to change the propagation directions of the incident light and the reflected light, the incident light of the optical fiber of the light source 11 is approximately converged on the film 16 to be measured, and the reflected light is shaped into a bessel annular light ring 23 to obtain an annular distribution return light image (as shown in fig. 5 and 6), so as to be received by the annular arrangement of the detection optical fibers, and the objective lens probe 13 adopted in the invention can adopt two different structures to realize imaging. One of the structures of the objective lens probe 13 is as follows: the optical fiber comprises a first spherical lens 17, a first conical lens 18, a second spherical lens 19, a second conical lens 20, a fixed block 21, a cavity and an optical fiber interface 22.
As shown in fig. 3, the optical fiber interface 22, the first spherical lens 17, the first conical lens 18, the second spherical lens 19, and the second conical lens 20 are disposed in the cavity along the same optical axis, and the first spherical lens 17, the first conical lens 18, the second spherical lens 19, and the second conical lens 20 are each fixed in the cavity by the fixing block 21. The fiber optic interface 22 is disposed on the cavity wall. In practical applications, the conical surface of the first axicon 18 and the conical surface of the second axicon 20 may be symmetrical along the second spherical lens 19, but this arrangement does not have a significant effect on the conical surface imaging of the axicon.
In another configuration of the objective lens probe 13, two conical lenses may only retain the first conical lens 18, for example, as shown in fig. 4, and the specific configuration is:
the optical fiber interface 22, the first spherical lens 17, the first conical lens 18 and the second spherical lens 19 are disposed in the cavity along the same optical axis, and the first spherical lens 17, the first conical lens 18 and the second spherical lens 19 are all fixed in the cavity by the fixing block 21. The optical fiber structure is disposed on the cavity wall.
However, in practical applications, different deformations may be used to achieve different effects of the annular spot, such as changing the direction of the conical surface of the first conical lens, or the first conical lens being placed to the right of the second spherical lens 19 (the right side here is with respect to the page display of fig. 4).
In practical application, the radius of the detection fiber is not smaller than the radius of the light source fiber, for example, when determining the radial distribution of return light energy when measuring the distance 2 as shown in fig. 5, the diameter of the light source 11 fiber may be 200nm, the outer diameter may be 220nm, the inner diameter of the outer ring receiving light is 120nm, and the outer diameter 320. At this time, as shown in fig. 7, energy is mainly concentrated between the inner and outer rings of the end face of the annular distribution detecting fiber, and this inner and outer rings can be used as an energy concentration region.
In addition, in the invention, the objective lens probe based on the combination of the conical lens and the spherical lens can collect point light on the surface of the film to be detected, then the point light returns to form an annular light beam, the annular light beam is well matched with the Y-shaped multi-core optical fiber, and the objective lens probe 13 is controlled in a range with a smaller incidence angle, so that the utilization rate of light energy is improved, and the film reflection model is simplified. The intermediate value in the range is approximately taken as the incident angle of the objective lens probe 13.
In fig. 6, a is an end face of the optical fiber of the light source 11, B is an end face of the detection optical fiber, and C is an end face of the converging end.
Further, in order to receive the reflected light from the alignment detection fiber to the maximum, the spectrometer 14 employed in the present invention is provided with a slit structure at the front end. The slit structure is parallel to the detection fibers which are arranged in a straight line so as to receive light rays in the detection fibers.
Further, the processor 15 employed in the present invention is a system or device, such as a computer, in which an intelligent processing chip is implanted.
The invention also provides a film thickness measuring method which is applied to the film thickness measuring device. The film thickness measuring method comprises the following steps:
s1: the noise spectrum, the metal mirror reflection spectrum and the film reflection spectrum to be measured are obtained respectively, as shown in fig. 10. The specific implementation process of the step can be as follows:
s1-1: under the condition that a light source is not turned on or a film (sample) to be detected is not placed, a processor is used for controlling a spectrometer to collect a plurality of groups of background noise signals within a certain time and carrying out average treatment to obtain a noise spectrum I 0 (λ)。
S1-2: and placing a metal reflector at a proper measuring distance in front of the objective lens probe, turning on a light source to generate wide-spectrum light, entering a light source optical fiber, approximately converging the light through the objective lens probe and making the light incident on the metal reflector, and shaping the reflected light into an annular light beam through the objective lens probe and projecting the annular light beam to the end face of the annularly arranged detection optical fiber.
S1-3: the light from the detection optical fibers which are arranged in a straight line is received by a spectrometer, a plurality of groups of light intensity distribution signals of different wavelengths of the metal reflecting mirrors within a certain time are obtained, and the average treatment is carried out to obtain a reflection spectrum I of the metal reflecting mirrors 1 (λ)。
S1-4: the metal reflector is replaced to be a film to be measured, the film is placed in front of the objective lens probe and has the same measuring distance as S1-2, wide-spectrum light is generated through the light source and enters the light source optical fiber, the light is approximately converged through the objective lens probe and is incident to the film to be measured, and the reflected light is shaped into annular light beams through the objective lens probe and is projected to the end face of the annularly arranged detection optical fiber.
S1-5: receiving light from the linear arrangement detection optical fiber by utilizing a spectrometer, and acquiring light intensity distribution signals of different wavelengths of the film to be detected in real time to obtain the reflection spectrum I of the film to be detected 2 (λ)。
S2: and determining the relative spectral reflectivity of the film to be measured based on the noise spectrum, the metal reflector reflection spectrum and the film to be measured reflection spectrum. The relative spectral reflectivity of the film to be measured is R 21 (λ)：R 21 (λ)＝(I 2 (λ)-I 0 (λ))/(I 1 (λ)-I 0 (λ))。
S3: according to the incidence angle of the objective lens probe, the optical constant of the metal reflector and the plating film of the metal reflector, the plating film thickness d of the metal reflector is preset 1 Determining the theoretical spectral reflectance R of a metallic mirror 1 (λ,d 1 ). The theoretical spectral reflectance differences for different angles of incidence at the same predetermined thickness are shown in fig. 9. Based on the thin film reflection model shown in fig. 8, the solution formula of the theoretical spectral reflectance of the metal mirror is as follows:
n O sinθ＝n 1 sinθ 1 ；
Figure BDA0004130035130000111
Figure BDA0004130035130000112
in FIG. 8 and the formula, n 0 Is the refractive index, k of air 0 Is the air extinction coefficient, n 1 To be measured of refractive index, k of film 1 For the extinction coefficient of the film to be measured, θ is the incident angle of the incident beam, θ 1 Is the refractive angle, r all-s For all s-polarized reflected beams, r 1s R in s polarization state 1 Value r 2s R in s polarization state 2 The value of the sum of the values,
Figure BDA0004130035130000121
r is the phase difference between adjacent reflected beams all-p The reflection coefficient, r, for all p-polarized reflected beams 1p R in p polarization 1 Value r 2p R in p polarization 2 The value lambda is the wavelength, h is the film thickness, R film For spectral reflectance of the film, R s For reflectivity in s-polarization, R p Is the reflectivity of the p-polarization state.
The above formula is a specific derivation process of the fresnel formula, and reference may be made to the relevant content of "engineering optics" specifically, and details are not described here again.
S4: and determining the absolute spectral reflectance of the film to be measured based on the theoretical spectral reflectance of the metal reflector and the relative spectral reflectance of the film to be measured. The absolute spectral reflectivity of the film to be measured is R 2 (λ)：R 2 (λ)＝R 21 (λ)×R 1 (λ,d 1 )。
S5: optical constant based on film substrate to be measured and film coating film to be measured, and preset film thickness d 2 Determining the theoretical spectral reflectance R of the film to be measured 2 reason (λ,d 2 )。
S6: and determining the fitting degree of the theoretical spectral reflectance of the film to be measured and the absolute spectral reflectance of the film to be measured. I.e. the preset film thickness d is solved by a computer 2 Theoretical spectral reflectance R of the film to be measured 2 reason (λ,d 2 ) By the absolute spectral reflectance R 2 (lambda) alignment.
S7: and when the fitting degree reaches the preset requirement, determining the preset film thickness d2 as the thickness of the film to be measured. Specifically, the thickness d of the metal reflector coating film is preset 1 And a preset film thickness d 2 Meanwhile, as a parameter, carrying out fitting degree optimization inversion solution to obtain the preset film thickness d when the fitting degree is optimal 2 . Preset film thickness d when the fitting degree is optimal 2 The thickness of the film to be measured is obtained.
Wherein, the coating thickness d of the metal reflector 1 Can be obtained by adopting SEM or step instrument, or the thickness d of the metal reflector coating film 1 And a preset film thickness d 2 And simultaneously, carrying out objective function optimization solving and obtaining as a parameter.
The resulting spectral reflectance is shown in FIG. 11, where d will be 1 And d 2 Simultaneously, as a parameter, carrying out optimization solution, and obtaining R 2 (lambda) and R 2 reason (λ,d 2 ) The sum variance of (2) is taken as an objective function, and d is finally obtained when the objective function is minimum 1 And d 2 。
In the method, the common metal reflecting mirror surface is utilized for comparison, and only the known film thickness parameter is needed or is used as one of optimization targets, so that the theoretical spectral reflectivity of the film to be measured under a specific incidence angle can be obtained, the relative spectral reflectivity of the film to be measured is corrected, the absolute spectral reflectivity of the film to be measured is obtained, and finally the thickness of the film to be measured is obtained through a fitting method.
Based on the above description, the present invention has the following advantages over the prior art:
1. according to the imaging characteristics of the conical lens and the spherical lens, the invention designs the objective lens probe of the common light path of the incident light and the reflected light, can shape the emergent light of the end face of the circular light source optical fiber to be approximately focused on the surface to be detected, has a smaller incident angle range, is beneficial to simplifying a reflection model, can shape the reflected light into a return light image distributed in an annular shape, is well matched with the converging end of the Y-shaped multi-core optical fiber, and most of the reflected light enters the end face of the detection optical fiber distributed in the annular shape, and prevents the reflected light from entering the end face of the light source optical fiber, so that the light energy utilization rate is greatly improved, the whole structure is simple, the modularized assembly is realized, and the integration is strong.
2. According to the invention, the metal reflecting mirror surface is adopted for comparison, and the theoretical spectral reflectivity corresponding to the incident angle of the device is obtained by utilizing the surface characteristics of the metal reflecting mirror surface, so that the more accurate absolute spectral reflectivity of the surface to be measured is obtained, the traceability of the measurement result is enhanced, and the measurement accuracy is improved.
3. The invention adopts the lens, the optical fiber, the metal reflector and other devices with lower cost, has strong operability in the measuring process, simple algorithm program and easy commercial development and popularization.
Furthermore, the film thickness measuring method described above may be implanted in a software functional unit in the form of a computer program. When implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored on a computer readable storage medium. Based on this understanding, the above-mentioned film thickness measuring method of the present invention may be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: various media capable of storing program codes, such as a U disk, a mobile hard disk, a read-only memory, a random access memory, a magnetic disk or an optical disk.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other.
The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to assist in understanding the methods of the present invention and the core ideas thereof; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.

Claims (9)

1. A film thickness measuring apparatus, comprising: the device comprises a light source, a Y-shaped multi-core optical fiber, an objective lens probe, a spectrometer and a processor;
the Y-shaped multi-core optical fiber comprises a light source optical fiber and a plurality of detection optical fibers;
one end of the light source optical fiber is connected with the light source; one end of each of the plurality of detection optical fibers is connected with the spectrometer; the other ends of the light source optical fibers and the other ends of the plurality of detection optical fibers form a converging end which is connected to the objective lens probe; the spectrometer is electrically connected with the processor.
2. The thin film thickness measuring apparatus according to claim 1, wherein one end of the plurality of the detection optical fibers is connected to the spectrometer in a straight line arrangement; the other ends of the plurality of detection optical fibers are circumferentially arrayed with the other end of the light source optical fiber as a center.
3. The film thickness measuring apparatus according to claim 1, wherein the objective lens probe includes: the optical fiber comprises a first spherical lens, a first conical lens, a second spherical lens, a second conical lens, a fixed block, a cavity and an optical fiber interface;
the optical fiber interface, the first spherical lens, the first conical lens, the second spherical lens and the second conical lens are arranged along the same optical axis, and the first spherical lens, the first conical lens, the second spherical lens and the second conical lens are all fixed in the cavity through the fixing block.
4. The film thickness measuring apparatus according to claim 1, wherein the objective lens probe includes: the optical fiber comprises a first spherical lens, a first conical lens, a second spherical lens, a fixed block, a cavity and an optical fiber interface;
the optical fiber interface, the first spherical lens, the first conical lens and the second spherical lens are arranged along the same optical axis, and the first spherical lens, the first conical lens and the second spherical lens are all fixed in the cavity by the fixing block.
5. The film thickness measuring apparatus according to claim 1, wherein the spectrometer is provided with a slit structure; the slit structure is parallel to the detection fibers which are arranged in a straight line so as to receive light rays in the detection fibers.
6. The thin film thickness measuring apparatus according to claim 1, wherein the processor is a system or device in which an intelligent processing chip is implanted.
7. The thin film thickness measuring apparatus according to claim 1, wherein a radius of the detection fiber is not smaller than a radius of the light source fiber.
8. A film thickness measuring method, characterized by being applied to the film thickness measuring apparatus according to any one of claims 1 to 7; the film thickness measuring method comprises the following steps:
respectively acquiring a noise spectrum, a metal reflector reflection spectrum and a film reflection spectrum to be measured;
determining the relative spectral reflectivity of the film to be measured based on the noise spectrum, the metal reflector reflection spectrum and the film to be measured reflection spectrum;
presetting a metal reflector coating thickness d according to the incidence angle of the objective lens probe, the optical constant of the metal reflector and the metal reflector coating, and the thickness d of the metal reflector coating 1 Determining a theoretical spectral reflectance of the metal mirror;
determining the absolute spectral reflectance of the film to be measured based on the theoretical spectral reflectance of the metal reflector and the relative spectral reflectance of the film to be measured;
based on the followingOptical constant of film substrate to be measured and film coating film to be measured, preset film thickness d 2 Determining the theoretical spectral reflectivity of the film to be measured;
determining the fitting degree of the theoretical spectral reflectance of the film to be measured and the absolute spectral reflectance of the film to be measured;
when the fitting degree reaches a preset requirement, determining the preset film thickness d 2 The thickness of the film to be measured; specifically, the thickness d of the coating film of the preset metal reflector is used 1 And a preset film thickness d 2 Meanwhile, as a parameter, carrying out fitting degree optimization inversion solution to obtain the preset film thickness d when the fitting degree is optimal 2 The method comprises the steps of carrying out a first treatment on the surface of the Preset film thickness d when the fitting degree is optimal 2 The thickness of the film to be measured is obtained.
9. The method according to claim 8, wherein the noise spectrum, the metal mirror reflection spectrum and the film reflection spectrum to be measured are obtained respectively, specifically comprising:
under the condition that a light source is not turned on or a film to be measured is not placed, acquiring a plurality of groups of background noise signals within a set time, and carrying out average processing on the plurality of groups of background noise signals to obtain a noise spectrum;
placing a metal reflector at a position which is a preset distance away from an objective lens probe, and turning on a light source to obtain a first light intensity distribution signal; the first light intensity distribution signals are light intensity distribution signals of different wavelengths of the metal reflector in a set time after the light source is turned on;
carrying out average treatment on the first light intensity distribution signal to obtain a metal reflector reflection spectrum;
changing a metal reflector into a film to be detected, placing the film to be detected at a position which is a preset distance away from the objective lens probe, and turning on a light source to obtain a second light intensity distribution signal; the second light intensity distribution signals are light intensity distribution signals of different wavelengths of the film to be tested within a set time after the light source is turned on;
and carrying out average treatment on the second light intensity distribution signal to obtain a film reflection spectrum to be detected.
CN202310257104.XA 2023-03-17 2023-03-17 Film thickness measuring device and method Pending CN116136391A (en)

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CN202310257104.XA CN116136391A (en) 2023-03-17 2023-03-17 Film thickness measuring device and method

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CN116136391A true CN116136391A (en) 2023-05-19

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