CN108426530B - Device and method for simultaneously measuring thickness and refractive index of thin film - Google Patents
Device and method for simultaneously measuring thickness and refractive index of thin film Download PDFInfo
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- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/45—Refractivity; Phase-affecting properties, e.g. optical path length using interferometric methods; using Schlieren methods
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- 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
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Abstract
本发明公开了一种薄膜厚度与折射率同时测量的装置及测量方法，属于光学测量领域。具体包括宽谱光源输出模块、窄线宽激光光源输出模块、膜厚测量探头模块、解调干涉仪模块以及采集与控制模块五部分。本发明将窄线宽激光光源输出模块的输出信号直接输入到解调干涉仪模块中，满足干涉信号共光路的同时避免了膜厚测量探头模块中激光透射光以及激光多次反射光对干涉信号质量的影响；通过控制膜厚测量探头尾纤的长度避免了膜厚测量探头模块中宽谱光透射光对特征信号峰识别的干扰。本发明实现不需标定样品标定即可对薄膜的厚度及折射率进行非接触测量，具有自校准、测量结果可溯源、稳定性高、特征信号识别简单等优点。
The invention discloses a device and a measurement method for simultaneously measuring film thickness and refractive index, belonging to the field of optical measurement. Specifically, it includes five parts: a broad-spectrum light source output module, a narrow linewidth laser light source output module, a film thickness measurement probe module, a demodulation interferometer module, and an acquisition and control module. The present invention directly inputs the output signal of the narrow linewidth laser light source output module into the demodulation interferometer module, which satisfies the common optical path of the interference signal and avoids the interference signal caused by the laser transmission light and the laser multiple reflection light in the film thickness measurement probe module. The influence of quality; by controlling the length of the pigtail fiber of the film thickness measurement probe, the interference of the broad-spectrum transmitted light in the film thickness measurement probe module to the identification of characteristic signal peaks is avoided. The invention realizes the non-contact measurement of the thickness and the refractive index of the thin film without the need for sample calibration, and has the advantages of self-calibration, traceability of measurement results, high stability, simple identification of characteristic signals, and the like.
Description
Technical Field
The invention belongs to the field of optical measurement, and particularly relates to a device and a method for simultaneously measuring the thickness and the refractive index of a film.
Background
With the vigorous development of material science and technology, in order to meet the urgent needs in the fields of microelectronics, optoelectronics, new energy and the like, films are widely applied in the fields of optical engineering, mechanical engineering, communication engineering, bioengineering, aerospace engineering, chemical engineering, medical engineering and the like. The thickness of the film is not only one of the key parameters in the film production, but also determines the application performance of the film in the fields of mechanics, electromagnetism, photoelectricity, optics and the like. Accurate measurement of film thickness has been one of the important links in film production and application.
In 1941, n.schwartz et al proposed a contact probe Method (n.schwartz, r.brown, "a Stylus Method for evaluating changes in Surface profile of an object," in transaction of the observation Vacuum Symposium and Second International convergence (permamon, new york,1941), which has the advantages of good stability, high resolution, large measurement range, etc.; however, the probe method includes a probe based on mechanical movement, and thus, a secondary process is required for measuring the thin film, and the thin film is damaged to some extent by the movement of the probe on the surface of the thin film. Therefore, the non-contact measurement method can quickly replace the contact measurement method for measuring the thickness of the thin film.
In 2013, maxidc et al, university of aerospace, Nanjing, disclose an ultrasonic film thickness measuring instrument and a measuring method thereof (Chinese patent application number: 201310198294.9), wherein ultrasonic pulses are emitted to the surface of an oil film to generate resonance, and the thickness of the oil film is measured by measuring the relevant characteristics of the reflected pulses; however, the method is only suitable for the measurement of the liquid mode, different models need to be established for films with different thickness ranges, and the demodulation difficulty is high.
Optical measurement has the advantage of high accuracy and is beginning to be widely used in the field of film thickness measurement. In 2012, the great company of the Beijing east photoelectric technology Co., Ltd discloses a film thickness measuring device and method (Chinese patent application No. 201210080754.2), which adopts a mode of combining a space optical path and an optical fiber optical path, performs light splitting treatment on a color light source through a prism to irradiate the surface of a film, and measures the thickness of the film by measuring the characteristics of different reflected lights. The method expands the frequency spectrum range of the sampling point of the device for measuring the film thickness and improves the resolution ratio.
As a part of optical measurement methods, white light interferometry has been developed in the field of film thickness measurement because of its absolute measurement advantage. The basic principle of the white light interferometry is as follows: the method comprises the steps that a scanning mirror is connected to the tail end of one arm of a white light interferometer to serve as a sensing arm, the length of the other arm is fixed to serve as a reference arm, the length of the sensing arm is changed by moving the scanning mirror, when the optical path of light transmitted in the sensing arm is matched with the optical path of light transmitted in the reference arm, the maximum interference peak value occurs, and the measurement of relevant parameters is achieved by identifying the position of the peak value. In 2008, Peter j.de Groot et al of Zygo corporation, usa, discloses a Scanning interferometry for film thickness and surface measurement (US Patent 7448799), which adopts a film thickness measuring method based on white light interference principle, and utilizes a fourier transform method to extract two peak values from an interference light intensity map, the method is not affected by film thickness, and is suitable for measuring films with thicknesses greater than and less than the light source coherence length. In 2014, jia herian, university of Shandong, et al, disclose a system for measuring film thickness by a broad-spectrum optical interference method (Chinese patent application number: 201410290494.1), in which a Fabry-Perot interferometer is formed between a reflector and a collimator, and the thickness of a film to be measured can be obtained by measuring the cavity length of the Fabry-Perot before and after the film to be measured is placed under the reflector.
In 2017, the subject group of the applicant of the invention provides a common-path self-calibration film thickness measuring device and a measuring method (Chinese patent application No. CN201710277954.0), the method utilizes a common-path wide-spectrum optical interferometer and a laser interferometer to realize the measurement of the film thickness, has the advantages of common path, no need of calibrating devices and the like, but the method can not eliminate the influence of laser transmission light, causes the cracking of laser interference signals and influences the thickness measuring precision; in the same year, the applicant of the present invention has proposed a polarization-multiplexing common-path self-calibration film thickness measurement apparatus and measurement method (chinese patent application No. CN201710277939.6), which can further eliminate the influence of transmitted light on the measurement result on the basis of the original advantages, but the apparatus construction is complicated.
The invention provides a device and a method for simultaneously measuring the thickness and the refractive index of a film, which can simultaneously realize the non-contact measurement of the thickness and the refractive index of the film. The design of the differential structure in the film thickness measuring probe module reduces the influence of the film thickness measuring probe on the external environment, the output signal of the narrow linewidth laser output module is directly input into the demodulation interferometer module, the interference signal common light path is met, the influence of laser transmission light and laser multiple reflection light in the film thickness measuring probe module on the quality of the interference signal is avoided, and the film thickness tracing precision is improved; the interference of the wide-spectrum light transmission light in the film thickness measuring probe module on the characteristic signal peak is avoided by controlling the length of the tail fiber of the film thickness measuring probe, and the accuracy of characteristic signal identification is improved. The invention can be widely used in the field of film production and other fields needing high-precision measurement of the thickness of the film.
Disclosure of Invention
The invention aims to provide a device and a method for simultaneously measuring the thickness and the refractive index of a thin film, which can measure the thickness and the refractive index of the thin film without calibrating a calibration sample, and have the advantages of self calibration, traceable measurement result, high stability, strong anti-interference capability and simple characteristic signal identification.
The purpose of the invention is realized by the following technical scheme:
a device for simultaneously measuring the thickness and the refractive index of a thin film comprises a wide-spectrum light output module 1, a narrow-linewidth laser output module 2, a film thickness measuring probe module 3, a demodulation interferometer module 4 and an acquisition and control module 5; the modules respectively comprise the following components:
the broad spectrum light output module 1 is composed of a broad spectrum light source 101 and a 1 st isolator 102.
The narrow linewidth laser output module 2 is composed of a narrow linewidth laser light source 201 and a 2 nd isolator 202.
The film thickness measuring probe module 3 includes a 1 st measuring probe 301 and a 2 nd measuring probe 302.
The demodulation interferometer module 4 is composed of a demodulation interferometer module 4 consisting of a 1 st Faraday mirror 401, a 2 nd Faraday mirror 402, a 1 st collimating mirror 403, a 2 nd collimating mirror 404, a 3 rd collimating mirror 405, a 4 th collimating mirror 406, a 1 st demodulation interferometer coupler 407, an optical path scanning device 408, a 2 nd demodulation interferometer coupler 409, a 5 th collimating mirror 410, a 6 th collimating mirror 411, a 7 th collimating mirror 412, an 8 th collimating mirror 413, a 3 rd Faraday mirror 414 and a 4 th Faraday mirror 415.
The acquisition and control module 5 is composed of a computer 501, a data acquisition card 502, a 1 st photodetector 503, a 2 nd photodetector 504, a 3 rd photodetector 505 and a 4 th photodetector 506.
The output light of the broad spectrum light output module 1 is divided into two paths by the 1 st beam splitting coupler 6, and the two paths of the output light respectively enter the 1 st measuring probe 301 and the 2 nd measuring probe 302 of the film thickness measuring probe module 3 through the 1 st circulator 10 and the 2 nd circulator 13 to measure related parameters; the return light via the 1 st and 2 nd measurement probes 301 and 302 enters the relevant wavelength inputs of the 1 st and 2 nd wavelength division multiplexers 8 and 9 through the 1 st and 2 nd circulators 10 and 13; the output light of the narrow linewidth laser output module 2 is divided into two paths by a second beam splitting coupler 7 and respectively enters the relevant wavelength input ends of a 1 st wavelength division multiplexer 8 and a 2 nd wavelength division multiplexer 9; two beams of light respectively combined by the 1 st wavelength division multiplexer 8 and the 2 nd wavelength division multiplexer 9 are input into the demodulation interferometer module 4, and optical path matching is respectively realized through scanning of the 1 st demodulation interferometer 4A and the 2 nd demodulation interferometer 4B in the demodulation interferometer module 4; the interference signals with different wavelengths are separated by a 3 rd wavelength division multiplexer 11 and a 4 th wavelength division multiplexer 12 and then input into the acquisition and control module 5.
The half-spectrum width of a wide-spectrum light source 101 in the wide-spectrum light output module 1 is more than 45nm, and the fiber output power is more than 2 mW; the half-spectral width of the narrow-linewidth laser light source 201 in the narrow-linewidth laser output module 2 is less than 1pm, and the fiber output power is greater than 2 mW; the wide spectrum light source 101 and the narrow line width laser light source 201 have different central wavelengths, and the spectrums of the two have no overlapped part in the half-spectrum width;
the 1 st measuring probe 301 and the 2 nd measuring probe 302 in the film thickness measuring probe module 3 can simultaneously realize transmission and reflection of transmission light, and the reflectivity of the transmission light is between 20% and 80%; the emergent rays of the 1 st measuring probe 301 and the 2 nd measuring probe 302 are overlapped with each other; when the device to be measured is placed and measured, the device to be measured is respectively vertical to the emergent rays of the 1 st measuring probe 301 and the 2 nd measuring probe 302; the 1 st measuring probe 301 is connected with the output end 10c of the 1 st circulator 10, and the 2 nd measuring probe 302 is connected with the output end 13c of the 2 nd circulator 13;
the length difference of the tail fibers of the 1 st measuring probe 301 and the 2 nd measuring probe 302 in the film thickness measuring probe module 3 is larger than the optical path scanning range of the optical path scanning device 408 in the demodulation interferometer module 4;
an output end 8c of a 1 st wavelength division multiplexer 8 in the demodulation interferometer module 4 is connected with a 4a input end of a 1 st demodulation interferometer coupler 407, a 4c output end of the 1 st demodulation interferometer coupler 407 is connected with a 1 st collimating mirror 403, a 2 nd collimating mirror 404 is connected with a 1 st Faraday mirror 401, a 4d output end of the 1 st demodulation interferometer coupler 407 is connected with a 5 th collimating mirror 410, and a 6 th collimating mirror 411 is connected with a 3 rd Faraday mirror 414; the output end 9c of the 2 nd wavelength division multiplexer 9 is connected with the input end 4g of the 2 nd demodulation interferometer coupler 409, the output end 4e of the 2 nd demodulation interferometer coupler 409 is connected with the 4 th collimating mirror 406, the 3 rd collimating mirror 405 is connected with the 2 nd Faraday mirror 402, the output end 4f of the 2 nd demodulation interferometer coupler 409 is connected with the 8 th collimating mirror 413, and the 7 th collimating mirror 412 is connected with the 4 th Faraday mirror 415; the 1 st demodulation interferometer 4A is composed of a 1 st demodulation interferometer coupler 407, a 1 st collimator mirror 403, a 2 nd collimator mirror 404, a 1 st faraday mirror 401, a 1 st forward movable optical mirror 408a, a 1 st reverse movable optical mirror 408b, a 5 th collimator mirror 410, a 6 th collimator mirror 411, and a 3 rd faraday mirror 414; the 2 nd demodulation interferometer coupler 409, the 3 rd collimator mirror 405, the 4 th collimator mirror 406, the 2 nd faraday mirror 402, the 2 nd forward movable optical mirror 408c, the 2 nd reverse movable optical mirror 408d, the 7 th collimator mirror 412, the 8 th collimator mirror 413, and the 4 th faraday mirror 415 constitute a 2 nd demodulation interferometer 4B; optical parameters of the 1 st collimating mirror 403, the 2 nd collimating mirror 404, the 3 rd collimating mirror 405, the 4 th collimating mirror 406, the 5 th collimating mirror 410, the 6 th collimating mirror 411, the 7 th collimating mirror 412 and the 8 th collimating mirror 413 are consistent; optical parameters of the 1 st Faraday mirror 401, the 2 nd Faraday mirror 402, the 3 rd Faraday mirror 414 and the 4 th Faraday mirror 415 are consistent;
the optical parameters of the 1 st forward movable optical mirror 408a, the 2 nd forward movable optical mirror 408b, the 1 st reverse movable optical mirror 408c and the 2 nd reverse movable optical mirror 408d of the optical path scanning device 408 in the demodulation interferometer module 4 are consistent; the scanning range L of the table top of the position scanning device 408 can meet the requirement that when the film thickness measuring probe module is not inserted into a film to be measured, the 1 st demodulation interferometer 4A and the 2 nd demodulation interferometer 4B can both realize the optical path matching of light reflected by the surfaces of different probe lenses; the 1 st demodulation interferometer 4A and the 2 nd demodulation interferometer 4B share the same position scanning device 408; when the 1 st forward movable optical mirror 408a and the 2 nd forward movable optical mirror 408c are located at the zero point position, the 1 st reverse movable optical mirror 408b and the 2 nd reverse movable optical mirror 408d have the maximum displacement L, and when the 1 st reverse movable optical mirror 408b and the 2 nd reverse movable optical mirror 408d are located at the zero point position, the 1 st forward movable optical mirror 408a and the 2 nd forward movable optical mirror 408c have the maximum displacement L; during scanning, the 1 st forward movable optical mirror 408a, the 2 nd forward movable optical mirror 408b, the 1 st reverse movable optical mirror 408c, and the 2 nd reverse optical mirror 408d have the same displacement;
the 1 st photoelectric detector 503 in the acquisition and control module 5 is connected with the 11a output end of the 3 rd wavelength division multiplexer 11, and the 2 nd photoelectric detector 504 is connected with the 11b output end of the 2 nd wavelength division multiplexer 11; the 3 rd photodetector 505 is connected to the 12a output terminal of the 3 rd wavelength division multiplexer 12, and the 4 th photodetector 506 is connected to the 12b output terminal of the 3 rd wavelength division multiplexer 12. The photodetector transmits the collected signal to the computer 501 through the data acquisition card 502, and the computer 501 is also responsible for driving the position scanning device 408 to complete the optical path scanning.
The optical interferometry is the distance measurement method with the highest precision at present, but the laser interferometry cannot realize the measurement of absolute quantity due to the longer coherence length of the laser light source. White light interferometry uses a broad spectrum light source with low coherence. Because the coherence length of the low coherence light source is very small, the shape of the interference fringe output after interference is a sinusoidal oscillation modulated by a gaussian envelope, and the fringe has a main maximum value corresponding to the position where the optical path difference between the two arms of the interferometer is zero. Because of the harsh requirement on the optical path difference of two arms of the interferometer, the position of the central fringe provides a good-quality reference position for the measurement of the physical quantity, and the absolute quantity of the change of the measured physical quantity can be obtained according to the change of the position of the central fringe. Thus, the measurement of the physical quantity in the white light interferometry system is converted into a measurement of the change in the position of the central fringe of the interference signal. The invention adopts the design of double light sources, as shown in figure 5, in the scanning process of the position scanning device, white light interference signals and laser interference signals are recorded simultaneously, and the actual moving distance of the position scanning device can be calibrated with high precision by reading the number of the fringes of the laser interference signals.
The invention discloses a device and a method for simultaneously measuring the thickness and the refractive index of a film, which take the example that the distance between a first measuring probe 301 and a second measuring probe is measured by returning light when the film to be measured is not inserted as an example:
the 1 st measurement probe 301 internal reflected light 311 and the 2 nd measurement probe 302 external surface reflected light 312 are divided into two paths by the 1 st demodulation interferometer coupler 407: one path enters a reflection system consisting of a 1 st collimating mirror 403, a 1 st forward movable mirror 408a, a 2 nd collimating mirror 404 and a 1 st Faraday mirror 401 to generate 311 'and 312' reflected lights; one way into the reflection system consisting of the 5 th collimator mirror 410, the 1 st backward movable mirror 408b, the 6 th collimator mirror 411, and the 3 rd faraday mirror 414, generates 311 "and 312" reflected light. Under the control of the computer 501, the position scanning device 408 drives the 1 st forward movable mirror 408a and the 1 st backward movable mirror 408b to perform optical path scanning, and as shown in fig. 6, the process of generating the wide-spectrum optical interference signal is as follows:
(1) when the optical path difference between the two arms is equal to 2H, the light 311' in the scanning arm is matched with the light 312 "in the fixed arm, and a 1 st maximum white light interference signal 331 is generated.
(2) When the optical path difference between the two arms is equal to 0, the light 311 'and 311 ″ and the light 312' and 312 ″ in the scanning arm and the fixed arm are matched, and a dominant large white light interference signal 332 is generated.
(3) When the optical path difference between the two arms is equal to-2H, the light 312' in the scanning arm matches the light 312 "in the fixed arm, and a 2 nd maximum white light interference signal 333 is generated.
(4) By extracting the position of the central fringe of the white light interference signal, the absolute difference of the scanning distance between the major maximum and the minor maximum is obtained by utilizing the tracing characteristic of the laser interference signal, and further the absolute optical path between the 1 st measuring probe 301 and the 2 nd measuring probe 302 is obtained.
The method for measuring the thickness of the opaque film 303 to be measured based on the wide-spectrum light interference measurement method comprises the following steps:
(1) when the opaque film to be measured 303 is not inserted, the optical path position scanning device 408 is driven to perform optical path scanning, so that optical path matching is performed between the reflected light 311 inside the 1 st measuring probe 301 and the reflected light 312 of the light emitted by the 1 st measuring probe 301 on the outer surface of the 2 nd measuring probe 302, and optical path matching is performed between the reflected light 321 inside the 2 nd measuring probe 302 and the reflected light 322 of the light emitted by the 2 nd measuring probe 302 on the outer surface of the 1 st measuring probe 301; the acquisition and control module 5 demodulates and records the related parameters to obtain the optical path H between the two measuring probes;
(2) inserting the opaque film to be measured 303 between the 1 st measuring probe 301 and the 2 nd measuring probe 302, so that the opaque film to be measured 303 is perpendicular to the emergent rays of the 1 st measuring probe 301 and the 2 nd measuring probe 302; driving the optical path position scanning device 408 to perform optical path scanning, so that optical path matching is performed between the internal reflected light 413 of the 1 st measuring probe 301 and the reflected light 314 of the light emitted by the 1 st measuring probe 301 on the front surface 303a of the opaque film to be measured, and optical path matching is performed between the internal reflected light 323 of the 2 nd measuring probe 302 and the reflected light 324 of the light emitted by the 2 nd measuring probe 302 on the rear surface 303b of the opaque film to be measured; demodulating and recording related parameters by the acquisition and control module 5 to respectively obtain the optical path double H1 of the 1 st measuring probe 301 and the front surface 303a of the opaque film to be measured and the optical path double H2 of the 2 nd measuring probe 302 and the front surface 303b of the opaque film to be measured;
(3) opaque to be measuredThe thickness d1 of the film 303 can be determined by the two measurements described above, i.e.
The method for measuring the thickness and the refractive index of the transparent film 304 to be measured comprises the following steps:
(1) when the transparent film to be measured 304 is not inserted, the optical path position scanning device 408 is driven to perform optical path scanning, so that the optical path matching is performed between the internal reflected light 311 of the 1 st measuring probe 301 and the reflected light 312 of the light emitted by the 1 st measuring probe 301 on the outer surface of the 2 nd measuring probe 302, and the optical path matching is performed between the internal reflected light 321 of the 2 nd measuring probe 302 and the reflected light 322 of the light emitted by the 2 nd measuring probe 302 on the outer surface of the 1 st measuring probe 301; demodulating and recording related parameters through the acquisition and control module 5 to obtain a double optical path H between the two measuring probes;
(2) inserting a transparent film 304 to be measured between the 1 st measuring probe 301 and the 2 nd measuring probe 302, wherein the transparent film 304 to be measured is vertical to the emergent rays of the 1 st measuring probe 301 and the 2 nd measuring probe 302; driving the optical path position scanning device 408 to perform optical path scanning, so that the internal reflected light 315 of the 1 st measuring probe 301, the reflected light 316 of the emergent light of the 1 st measuring probe 301 on the front surface 304a of the transparent film to be measured, and the reflected light 317 of the emergent light of the 1 st measuring probe 301 on the rear surface 304b of the transparent film to be measured are respectively subjected to optical path matching, and the internal reflected light 325 of the 2 nd measuring probe 302, the reflected light 326 of the emergent light of the 2 nd measuring probe 302 on the rear surface 304b of the transparent film to be measured, and the reflected light 327 of the emergent light of the 2 nd measuring probe 302 on the front; the acquisition and control module 5 demodulates and records the related parameters to respectively obtain a double optical path H3 between the 1 st measuring probe 301 and the front surface 304a of the transparent film to be measured, a double optical path H4 between the 1 st measuring probe 301 and the rear surface 304b of the transparent film to be measured, a double optical path H5 between the 2 nd measuring probe 302 and the rear surface 304b of the transparent film to be measured, and a double optical path H6 between the 2 nd measuring probe 302 and the front surface 304a of the transparent film to be measured;
(3) the thickness d2 of the transparent film 304 can be determined by the above two measurements, i.e., d2 ═ 1/2[ H- (H3+ H5)](ii) a When the air refractive index is 1, the transparent film to be measuredThe refractive index n of 304 can be determined by the two measurements described above, i.e.
The invention has the beneficial effects that:
according to the invention, the narrow linewidth laser light source is directly input into the demodulation interferometer, so that the influence of laser transmission light and laser multiple reflection on the quality of an interference signal is further avoided, and the accuracy of tracing the thickness of the film is improved;
the invention avoids the interference of the wide-spectrum light transmission light in the film thickness measuring probe module on the identification of the characteristic signal peak by controlling the length of the tail fiber of the film thickness measuring probe, reduces the identification difficulty and further improves the accuracy of the identification of the characteristic signal.
The invention adopts the design of double probes, and can simultaneously measure the thickness of the film and the refractive index of the film in a non-contact manner;
the double-light-source common-light-path and differential light path structure design can further reduce the influence of external environment disturbance on the film thickness measurement result;
drawings
FIG. 1 is a schematic diagram of an apparatus for simultaneously measuring film thickness and refractive index;
FIG. 2 is a diagram of the internal optical path of the measurement probe module when no film to be measured is loaded;
FIG. 3 is a diagram of the internal optical path of the measurement probe module when loading an opaque film to be measured;
FIG. 4 is a diagram of the internal optical path of the measurement probe module when the transparent film to be measured is loaded;
FIG. 5 is a schematic diagram illustrating the tracing principle of laser interference signals;
FIG. 6 is a schematic diagram of a distance measurement method based on the principle of white light interference when a thin film to be measured is not loaded.
Detailed Description
The following further describes embodiments of the present invention with reference to the accompanying drawings:
the first embodiment is as follows:
the general technical scheme of the invention is shown in figure 1. The wide-spectrum light output module 1 consists of a wide-spectrum light source 101 with the central wavelength of 1310nm and a 1 st isolator 102 with the working wavelength of 1310nm, wherein the wide-spectrum light source 101 is used as a measurement light source and is mainly used for realizing absolute measurement of the thickness of a thin film; the narrow linewidth laser output module is composed of a narrow linewidth laser light source 201 with the wavelength of 1550nm and a No. 2 isolator 202 with the working wavelength of 1550nm, and the narrow linewidth frequency stabilization laser light source 103 is used as a light path correction light source and is mainly used for tracing the measurement of the thickness of a thin film. Light emitted by a wide-spectrum light source 101 respectively enters a beam splitting coupler 2 with a splitting ratio of 3dB through a 1 st isolator 102 and is equally divided into two paths, and the two paths respectively enter a film thickness measuring probe module 3 through a 1 st circulator 10 with a working wavelength of 1310nm and a 2 nd circulator 13 with a working wavelength of 1310 nm; the ratio of the reflectivity and the transmissivity of the lens end faces of the 1 st measuring probe 301 and the 2 nd measuring probe 302 is 50:50, and measuring light returned from the 1 st measuring probe 401 and the 2 nd measuring probe 402 respectively enters the 1 st wavelength division multiplexer 8 with the working wavelength of 1310nm and the 1550nm and the related wavelength input ends of the 2 nd wavelength division multiplexer 9 with the working wavelength of 1310nm and 1550nm through the 1 st circulator 11 with the working wavelength of 1310nm and the 2 nd circulator 13 with the working wavelength of 1310 nm; the output light of the narrow linewidth laser output module 2 with the wavelength of 1550nm is divided into two paths by the second beam splitting coupler 2 and respectively enters the relevant wavelength input ends of the first wavelength division multiplexer 8 with the working wavelength of 1310nm and 1550nm and the second wavelength division multiplexer 9 with the working wavelength of 1310nm and 1550 nm; two beams of light respectively combined by a 1 st wavelength division multiplexer 8 with the working wavelength of 1310nm and 1550nm and a 2 nd wavelength division multiplexer 9 with the working wavelength of 1310nm and 1550nm are input into the demodulation interferometer module 4, and optical path matching is respectively realized through scanning of a 1 st demodulation interferometer 4A and a 2 nd demodulation interferometer 4B in the demodulation interferometer module 4; a3 rd wavelength division multiplexer 11 with the working wavelength of 1310nm and 1550nm and a 4 th wavelength division multiplexer 12 with the working wavelength of 1310nm and 1550nm are used for separating a white light measuring beam with the central wavelength of 1310nm and a laser correction beam with the wavelength of 1550nm and then are obtained by a 1 st photoelectric detector 503, a 2 nd photoelectric detector 504, a 3 rd photoelectric detector 505 and a 4 th photoelectric detector 506. The photodetector transmits the collected signals to the computer 501 through the data acquisition card 502 for demodulation, and the computer 501 is also responsible for driving the position scanning device 408.
When the film to be measured is not inserted, the output light of the wide-spectrum light output module 1 is split by the 1 st beam splitting coupler 6 with the splitting ratio of 3dB, and the light enters the film thickness measuring probe module 3 through the 1 st circulator 11 with the working wavelength of 1310nm and the 2 nd circulator 13 with the working wavelength of 1310nm respectively. As shown in FIG. 2, the reflected light beams 311 from the inner surface of the lens of the 1 st measurement probe 301 and 312 from the outer surface of the lens of the 2 nd measurement probe 302 pass through the 1 st circulator 11 with the operating wavelength of 1310nm and enter the relevant wavelength input ends 8a and 8b of the 1 st wavelength division multiplexer 8 with the operating wavelength of 1310nm and 1550 nm; the reflected light beams 321 reflected by the 2 nd measuring probe 302 self lens and the reflected light beams 322 reflected by the 1 st measuring probe 301 lens are input to the relevant wavelength input ends 9a and 9b of the 2 nd wavelength division multiplexer 9 with the working wavelength of 1310nm and 1550nm through the 2 nd circulator 13 with the working wavelength of 1310 nm; the output light of the narrow linewidth laser output module 2 is split by a 2 nd beam splitter coupler 7 with the splitting ratio of 3dB and then is respectively input to a 1 st wavelength division multiplexer 8 with the working wavelength of 1310nm and 1550nm and a related wavelength input end of a 2 nd wavelength division multiplexer 9 with the working wavelength of 1310nm and 1550 nm; the optical signal is input into the 1 st demodulation interferometer 4A after being combined by the 1 st wavelength division multiplexer 8 with the working wavelength of 1310nm and 1550 nm; the optical signals are combined by a 2 nd wavelength division multiplexer 9 with the working wavelength of 1310nm and 1550nm and then input into a 2 nd demodulation interferometer 4B; the transmission mode of the light beam in the 1 st demodulation interferometer 4A is as follows: the 1 st wavelength division multiplexer 8 with the working wavelength of 1310nm and 1550nm inputs the optical signal into the 1 st demodulation interferometer coupler 407 with the splitting ratio of 3dB and divides the optical signal into two beams: one beam is transmitted by the 1 st forward movable mirror 408a and reflected by the 1 st faraday mirror 401, the other beam is transmitted by the 1 st backward movable mirror 408b and reflected by the 3 rd faraday mirror 414, when the 1 st forward optical scanning mirror 408a and the 1 st backward movable mirror 408b move, the optical path of the reflected light 411 and the reflected light 412 are completely matched, a wide-spectrum optical interference fringe is formed on the 1 st photodetector 503, and a laser interference fringe is formed on the 2 nd photodetector 504; the transmission mode of the light beam in the 2 nd demodulation interferometer 6B is as follows: the 2 nd wavelength division multiplexer 9 with the working wavelength of 1310nm and 1550nm inputs the optical signal into the 2 nd demodulation interferometer coupler 409 with the splitting ratio of 3dB and divides the optical signal into two beams: one beam is transmitted by the 2 nd forward movable mirror 408c and reflected by the 2 nd faraday mirror 402, the other beam is transmitted by the 2 nd reverse movable mirror 408d and reflected by the 4 th faraday mirror 415, when the 2 nd forward optical scanning mirror 408c and the 2 nd reverse movable optical mirror 408d move, the optical path of the reflected light 321 and the reflected light 322 are completely matched, a wide-spectrum light interference fringe is formed on the 3 rd photodetector 505, a laser interference fringe is formed on the 4 th photodetector 506, and the double optical path H between the two measuring probes can be obtained by demodulating a white light interference signal.
When the opaque film to be measured 303 is measured, as shown in fig. 3, a light beam 313 reflected by the inner surface of the lens of the 1 st measurement probe 301 and a light beam 314 reflected by the front surface 303a of the opaque film to be measured are inputted to the 1 st demodulation interferometer 4A; the light beam 323 reflected by the inner surface of the lens of the 2 nd measuring probe 302 and the light beam 324 reflected by the rear surface 303B of the film to be measured are inputted to the 2 nd demodulation interferometer 4B. The transmission mode of the light beam in the 1 st demodulation interferometer 4A is as follows: inputting an optical signal into a 1 st demodulation interferometer coupler 407 with a splitting ratio of 3dB by a 1 st wavelength division multiplexer 8 with working wavelength of 1310nm and 1550nm to be split into two beams, wherein one beam is transmitted by a 1 st forward movable reflecting mirror 408a and reflected by a 1 st Faraday reflecting mirror 401, the other beam is transmitted by a 1 st reverse movable reflecting mirror 408b and reflected by a 3 rd Faraday reflecting mirror 414, when the 1 st forward optical scanning reflecting mirror 408a and the 1 st reverse movable optical reflecting mirror 408b move, the optical path of the reflected light 313 and the reflected light 314 are completely matched, a wide-spectrum optical interference fringe is formed on a 1 st photoelectric detector 503, and a laser interference fringe is formed on a 2 nd photoelectric detector 504; the transmission mode of the light beam in the 2 nd demodulation interferometer 6B is as follows: an optical signal is input to a 2 nd demodulation interferometer coupler 409 with a splitting ratio of 3dB by a 2 nd wavelength division multiplexer 9 with working wavelengths of 1310nm and 1550nm and is split into two beams, one beam is transmitted by a 2 nd forward movable mirror 408c and reflected by a 2 nd Faraday mirror 402, the other beam is transmitted by a 2 nd backward movable mirror 408d and reflected by a 4 th Faraday mirror 415, and when the 2 nd forward optical scanning mirror 408c and the 2 nd backward movable optical mirror 408d move, the reflected light is reflected323 and the reflected light 324 are perfectly matched in optical path, forming a wide spectrum optical interference fringe on the 3 rd photodetector 505 and a laser interference fringe on the 4 th photodetector 506. By demodulating the wide-spectrum light interference signal and the narrow-line-width laser interference signal, a double optical path length H1 between the 1 st measurement probe 301 and the front surface 303a of the opaque film to be measured and a double optical path length H2 between the 2 nd measurement probe 302 and the rear surface 303b of the opaque film to be measured are obtained, respectively. Thus, the opaque film thickness d1 is determined by the two measurements described above, i.e.
When the transparent film to be measured 304 is measured, as shown in fig. 4, a reflected beam 315 from the inner surface of the lens of the 1 st measurement probe 301, a reflected beam 316 from the front surface 304A of the transparent film to be measured, and a reflected beam 317 from the rear surface 304b of the transparent film to be measured are inputted into the 1 st demodulation interferometer 4A; the light beam 325 reflected from the lens inner surface of the 2 nd measuring probe 302, the light beam 326 reflected from the transparent film-to-be-measured rear surface 304B, and the light beam 327 reflected from the transparent film-to-be-measured front surface 304a are inputted to the 2 nd demodulation interferometer 6B. The transmission mode of the light beam in the 1 st demodulation interferometer 4A is as follows: inputting an optical signal into a 1 st demodulation interferometer coupler 407 with a splitting ratio of 3dB by a 1 st wavelength division multiplexer 8 with working wavelength of 1310nm and 1550nm to be split into two beams, wherein one beam is transmitted by a 1 st forward movable reflecting mirror 408a and reflected by a 1 st Faraday reflecting mirror 401, the other beam is transmitted by a 1 st reverse movable reflecting mirror 408b and reflected by a 3 rd Faraday reflecting mirror 414, when the 1 st forward optical scanning reflecting mirror 408a and the 1 st reverse movable optical reflecting mirror 408b move, the reflected light 315, the reflected light 316 and the reflected light 317 respectively generate complete optical path matching, a wide spectrum optical interference fringe is formed on a 1 st photoelectric detector 503, and a laser interference fringe is formed on a 2 nd photoelectric detector 504; the transmission mode of the light beam in the 2 nd demodulation interferometer 6B is as follows: the optical signal is input to a 2 nd demodulation interferometer coupler 409 with a splitting ratio of 3dB by a 2 nd wavelength division multiplexer 9 with working wavelength of 1310nm and 1550nm and is split into two beams, one beam is transmitted by a 2 nd forward movable mirror 408c and reflected by a 2 nd Faraday mirror 402, and the other beam is transmitted by a 2 nd backward movable mirror 408d,When the 4 th faraday mirror 415 reflects and the 2 nd forward optical scanning mirror 408c and the 2 nd backward movable optical mirror 408d move, the optical path of the reflected light 325, the reflected light 326 and the reflected light 327 respectively completely match, a wide-spectrum optical interference fringe is formed on the 3 rd photodetector 505, and a laser interference fringe is formed on the 4 th photodetector 506. Demodulating the wide-spectrum light interference signal and the narrow-line-width laser interference signal to respectively obtain a double optical path H3 between the 1 st measuring probe 301 and the front surface 304a of the transparent film to be measured, a double optical path H4 between the 1 st measuring probe 301 and the rear surface 304b of the transparent film to be measured, a double optical path H5 between the 2 nd measuring probe 302 and the rear surface 304b of the transparent film to be measured, and a double optical path H6 between the 2 nd measuring probe 302 and the front surface 304a of the transparent film to be measured; the thickness d2 of the transparent film (304) to be measured can be determined by the two measurements described above, i.e.
When the refractive index of air is 1, the refractive index n of the transparent film (304) to be measured can be determined by the above two measurements, i.e.
Example two:
a device for simultaneously measuring the thickness and the refractive index of a thin film comprises a wide-spectrum light output module 1, a narrow-line width laser output module 2, a film thickness measuring probe module 3, a demodulation interferometer module 4, an acquisition and control module 5 and the like;
the output light of the broad spectrum light output module 1 is divided into two paths by the 1 st beam splitting coupler 6 and enters the 1 st measuring probe 301 and the 2 nd measuring probe 302 of the film thickness measuring probe module 3 through the 1 st circulator 10 and the 2 nd circulator 13 respectively; returning light via the 1 st and 2 nd measurement probes 301 and 302 enters the relevant wavelength inputs of the 1 st and 2 nd wavelength division multiplexers 8 and 9 through the 1 st and 2 nd circulators 10 and 13, respectively;
the output light of the narrow linewidth laser output module 2 is divided into two paths by a second beam splitting coupler 7 and respectively enters the relevant wavelength input ends of a 1 st wavelength division multiplexer 8 and a 2 nd wavelength division multiplexer 9; the two beams of light respectively combined by the 1 st wavelength division multiplexer 8 and the 2 nd wavelength division multiplexer 9 are input into the demodulation interferometer module 4 and pass through the 1 st demodulation interferometer 4A and the 2 nd demodulation interferometer 4B in the demodulation interferometer module 4; interference signals with different wavelengths are separated by the 3 rd wavelength division multiplexer 11 and the 4 th wavelength division multiplexer 12 and then input into the acquisition and control module 5.
The light sources in the wide-spectrum light output module 1 and the narrow-line width laser output module 2 are characterized in that: the half-spectrum width of the wide-spectrum light source 101 is larger than 45nm, and the fiber output power is larger than 2 mW; the half-spectrum width of the narrow-line-width laser light source 201 is less than 1pm, and the fiber output power is more than 2 mW; the wide-spectrum light source 101 and the narrow-line-width laser light source 201 have different center wavelengths, and the spectrums of the two have no overlapping portion within a half-spectrum width.
The film thickness measuring probe module 3 consists of a 1 st measuring probe 301 and a 2 nd measuring probe 302; the 1 st measuring probe 301 and the 2 nd measuring probe 302 can simultaneously realize the transmission and reflection of the transmission light, and the reflectivity of the transmission light is between 20% and 80%; the emergent rays of the 1 st measuring probe 301 and the 2 nd measuring probe 302 are overlapped with each other; when the device to be measured is placed and measured, the device to be measured is respectively vertical to the emergent rays of the 1 st measuring probe 301 and the 2 nd measuring probe 302; the 1 st measurement probe 301 is connected to the output 10c of the 1 st circulator 10, and the 2 nd measurement probe 302 is connected to the output 13a of the 2 nd circulator 13.
The film thickness measuring probe module 3 is characterized in that the length of the tail fiber of the film thickness measuring probe is as follows: the difference between the lengths of the tail fibers of the 1 st measuring probe 301 and the 2 nd measuring probe 302 is larger than the optical path scanning range of the optical path scanning device 408 in the demodulation interferometer module 4.
The demodulation interferometer module 4 is composed of a 1 st Faraday reflector 401, a 2 nd Faraday reflector 402, a 1 st collimator 403, a 2 nd collimator 404, a 3 rd collimator 405, a 4 th collimator 406, a 1 st demodulation interferometer coupler 407, an optical path scanning device 408, a 2 nd demodulation interferometer coupler 409, a 5 th collimator 410, a 6 th collimator 411, a 7 th collimator 412, an 8 th collimator 413, a 3 rd Faraday reflector 414 and a 4 th Faraday reflector 415; the output end 8c of the 1 st wavelength division multiplexer 8 is connected with the 4a input end of the 1 st demodulation interferometer coupler 407, the 4c output end of the 1 st demodulation interferometer coupler 407 is connected with the 1 st collimating mirror 403, the 2 nd collimating mirror 404 is connected with the 1 st Faraday mirror 401, the 4d output end of the 1 st demodulation interferometer coupler 407 is connected with the 5 th collimating mirror 410, and the 6 th collimating mirror 411 is connected with the 3 rd Faraday mirror 414; the output end 9c of the 2 nd wavelength division multiplexer 9 is connected with the input end 4g of the 2 nd demodulation interferometer coupler 409, the output end 4e of the 2 nd demodulation interferometer coupler 409 is connected with the 4 th collimating mirror 406, the 3 rd collimating mirror 405 is connected with the 2 nd Faraday mirror 402, the output end 4h of the 2 nd demodulation interferometer coupler 409 is connected with the 8 th collimating mirror 413, and the 7 th collimating mirror 412 is connected with the 4 th Faraday mirror 415; a 1 st demodulation interferometer coupler 407, a 1 st collimator mirror 403, a 2 nd collimator mirror 404, a 1 st Faraday mirror 401, a 1 st forward movable optical mirror 408a, a 1 st reverse movable optical mirror 408b, a 5 th collimator mirror 410, a 6 th collimator mirror 411, a 3 rd Faraday mirror 414, and a 1 st demodulation interferometer 4A; a 2 nd demodulation interferometer coupler 409, a 3 rd collimator mirror 405, a 4 th collimator mirror 406, a 2 nd faraday mirror 402, a 2 nd forward movable optical mirror 408c, a 2 nd reverse movable optical mirror 408d, a 7 th collimator mirror 412, an 8 th collimator mirror 413, a 4 th faraday mirror 415, and a 2 nd demodulation interferometer 4B; optical parameters of the 1 st collimating mirror 403, the 2 nd collimating mirror 404, the 3 rd collimating mirror 405, the 4 th collimating mirror 406, the 5 th collimating mirror 410, the 6 th collimating mirror 411, the 7 th collimating mirror 412 and the 8 th collimating mirror 413 are consistent; optical parameters of the 1 st faraday mirror 401, the 2 nd faraday mirror 402, the 3 rd faraday mirror 414, and the 4 th faraday mirror 415 are consistent.
The optical path scanning device 408 in the demodulation interferometer module 4 is characterized in that: optical parameters of the 1 st forward movable optical mirror 408a, the 2 nd forward movable optical mirror 408b, the 1 st reverse movable optical mirror 408c, and the 2 nd reverse movable optical mirror 408d are identical; the optical path scanning range L of the position scanning device 408 can satisfy that when the film thickness measurement probe module 4 is not inserted into the film to be measured, the 1 st demodulation interferometer 4A and the 2 nd demodulation interferometer 4B can both realize optical path matching of light reflected by different probe lens surfaces; the 1 st demodulation interferometer 4A and the 2 nd demodulation interferometer 4B share the same position scanning device 408; when the 1 st forward movable optical mirror 408a and the 2 nd forward movable optical mirror 408c are located at the zero point position, the 1 st reverse movable optical mirror 408b and the 2 nd reverse movable optical mirror 408d have the maximum displacement L, and when the 1 st reverse movable optical mirror 408b and the 2 nd reverse movable optical mirror 408d are located at the zero point position, the 1 st forward movable optical mirror 408a and the 2 nd forward movable optical mirror 408c have the maximum displacement L; during scanning, the 1 st forward movable optical mirror 408a, the 2 nd forward movable optical mirror 408b, the 1 st reverse movable optical mirror 408c, and the 2 nd reverse optical mirror 408d have the same displacement.
The method for measuring the thickness of the opaque film comprises the following steps:
(1) when the opaque film to be measured 303 is not inserted, the optical path position scanning device 408 is driven to perform optical path scanning, so that optical path matching is performed between the reflected light 311 inside the 1 st measuring probe 301 and the reflected light 312 of the light emitted by the 1 st measuring probe 301 on the outer surface of the 2 nd measuring probe 302, and optical path matching is performed between the reflected light 321 inside the 2 nd measuring probe 302 and the reflected light 322 on the outer surface of the 1 st measuring probe 301 and the light emitted by the 2 nd measuring probe 302; demodulating and recording related parameters through the acquisition and control module 5 to obtain a double optical path H between the two measuring probes;
(2) inserting the opaque film to be measured 303 between the 1 st measuring probe 301 and the 2 nd measuring probe 302, so that the opaque film to be measured 303 is perpendicular to the emergent rays of the 1 st measuring probe 301 and the 2 nd measuring probe 302; driving the optical path position scanning device 408 to perform optical path scanning, so that optical path matching is performed on the reflected light 313 inside the 1 st measuring probe 301 and the reflected light 314 of the light emitted by the 1 st measuring probe 301 on the front surface 303a of the opaque film to be measured, and optical path matching is performed on the reflected light 323 inside the 2 nd measuring probe 302 and the reflected light 324 of the light emitted by the 2 nd measuring probe 302 on the rear surface 303b of the opaque film to be measured; the related parameters are demodulated and recorded through the acquisition and control module 5, and a double optical path H1 of the No. 1 measuring probe 301 and the front surface 303a of the opaque film to be measured and a double optical path H2 of the No. 2 measuring probe 302 and the front surface 303b of the opaque film to be measured are respectively obtained;
(3) the thickness d1 of the opaque film 303 to be measured can be determined by the above two measurements, i.e.
A device and a method for simultaneously measuring the thickness and the refractive index of a film comprise the following steps:
(1) when the transparent film to be measured 304 is not inserted, the optical path position scanning device 408 is driven to perform optical path scanning, so that the optical path matching is performed between the internal reflected light 311 of the 1 st measuring probe 301 and the reflected light 312 of the light emitted by the 1 st measuring probe 301 on the outer surface of the 2 nd measuring probe 302, and the optical path matching is performed between the internal reflected light 321 of the 2 nd measuring probe 302 and the reflected light 322 of the light emitted by the 2 nd measuring probe 302 on the outer surface of the 1 st measuring probe 301; demodulating and recording related parameters through the acquisition and control module 5 to obtain a double optical path H between the two measuring probes;
(2) inserting the transparent film 304 to be measured between the 1 st measuring probe 301 and the 2 nd measuring probe 302, so that the transparent film 304 to be measured is perpendicular to the emergent rays of the 1 st measuring probe 301 and the 2 nd measuring probe 302; driving the optical path position scanning device 408 to perform optical path scanning, so that the internal reflected light 315 of the 1 st measuring probe 301, the reflected light 316 of the emergent light of the 1 st measuring probe 301 on the front surface 304a of the transparent film to be measured, and the reflected light 317 of the emergent light of the 1 st measuring probe 301 on the rear surface 304b of the transparent film to be measured are respectively subjected to optical path matching, and the internal reflected light 325 of the 2 nd measuring probe 302, the reflected light 326 of the emergent light of the 2 nd measuring probe 302 on the rear surface 304b of the transparent film to be measured, and the reflected light 327 of the emergent light of the 2 nd measuring probe 302 on the front; the related parameters are demodulated and recorded by the acquisition and control module 5, and a double optical path H3 between the 1 st measuring probe 301 and the front surface 304a of the transparent film to be measured, a double optical path H4 between the 1 st measuring probe 301 and the rear surface 304b of the transparent film to be measured, a double optical path H5 between the 2 nd measuring probe 302 and the rear surface 304b of the transparent film to be measured, and a double optical path H6 between the 2 nd measuring probe 302 and the front surface 30ab of the transparent film to be measured are respectively obtained;
(3) when the refractive index of air is 1, the thickness d2 of the transparent film 304 to be measured can be determined according to the aboveIs determined by two measurements, i.e.
The refractive index n of the transparent film 304 can be determined by the two measurements described above, i.e.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
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