CN108981594A - It is declined based on optical fiber and swings the method for chamber measurement nano-level thin-membrane thickness - Google Patents
It is declined based on optical fiber and swings the method for chamber measurement nano-level thin-membrane thickness Download PDFInfo
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- CN108981594A CN108981594A CN201810854550.8A CN201810854550A CN108981594A CN 108981594 A CN108981594 A CN 108981594A CN 201810854550 A CN201810854550 A CN 201810854550A CN 108981594 A CN108981594 A CN 108981594A
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- optical fiber
- fiber
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- ring
- film sample
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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
Abstract
The invention discloses a kind of declined based on optical fiber swing chamber measurement nano-level thin-membrane thickness method, with change in film thickness, it is reflected back optical fiber by lens and declines and swing intracavitary loss and change therewith, the die-away time of pulse signal is caused to change, the ring-down time of corresponding standard film sample is obtained by detection according to the standard film sample of multiple groups known thickness, establish the linear relationship curve or linear relationship equation of film thickness and ring-down time, then the thickness of film sample to be measured is obtained according to the ring-down time of film sample to be measured and the linear relationship curve or linear relationship equation of combination film thickness and ring-down time that measure.Measuring system of the invention is compact-sized, and measurement process is simple, convenient and efficient, and measurement sensitivity is higher；Sound attenuation in wave distortion and compensated cavity is reduced using low gain and low noise Er-doped fiber；Cavity loss is compensated using erbium-doped fiber amplifier increases pulse peak number to improve the measurement accuracy of nano-level thin-membrane thickness.
Description
Technical field
The invention belongs to nano-level thin-membrane thickness measurement technique fields, and in particular to one kind is declined based on optical fiber and swings chamber measurement and receive
The method of meter level film thickness.
Background technique
With the extensive use of thin film technique and photoelectric device, the basis that optical thin film is widely used to weaponry is ground
Study carefully and the development and production of extraordinary device in.The status constantly updated and developed in face of weaponry and Novel Optoelectronic Device, essence
To optical thin film various parameters, more stringent requirements are proposed for close measurement.Film thickness is the key that in film design and technique manufacture
One of parameter, the especially rapid development of nano-level thin-membrane technology, so that precise measurement film thickness becomes thin film technique research
Hot issue in field causes the highest attention of technical staff.
Traditional calibrator mainly uses two class of transmission beam method and bounce technique, and wherein transmission beam method is that film to be measured is placed on light source
Between sensor, sensor receive light source issue light by film to be measured and with the organic molecule phase interaction of film to be measured
Used light, transmiting the intensity of optical attenuation and the thickness of the tested film passed through at this time has certain relationship；Bounce technique refers to biography
The light that sensor receives is the light that the light projection that light source issues is returned to film surface back reflection to be measured, is generally used for impermeable
Measured thin film that is bright, easily reflecting.By comparing two kinds of measurement methods, the reflected light signal of reflection method for measuring film thickness is found
Reception is a masty problem, i.e. sensor position placement is not easy to determine, simultaneously because reflection weak output signal, will lead to
Bad stability is measured, is easy to be affected, the design of whole system is made to become complicated, reliability reduces, application range also ten
It is point small, it can not achieve the thickness measure to transparent membrane.Unlike this, the light channel structure of transmission beam method is relatively simple, light source
Position between receiver is also easy determination, and the stability of system is also just guaranteed, and is based on fiber optic loop cavity ring-down spectroscopy skill
The highly sensitive advantage of art, the present invention devise a kind of method using transmission measurement nano-level thin-membrane thickness.
Summary of the invention
The present invention is that reflected light signal is weak in the prior art, system structure is complicated, reliability is low and application range is small for solution
The problem of and provide a kind of decline based on optical fiber and swing the method for chamber measurement nano-level thin-membrane thickness, this method declined by optical fiber ring cavity
The measurement that spectral technique realizes nano-level thin-membrane thickness is swung, by analyzing, studying the nano-level thin-membrane in the case where optical fiber declines and swings cavity configuration
The light decay of optical attenuation caused by thickness changes swings signal to realize the measurement of nano-level thin-membrane thickness.
The present invention adopts the following technical scheme that solve above-mentioned technical problem, is declined based on optical fiber and swings chamber measurement nano-level thin-membrane
The method of thickness, it is characterised in that: by passing sequentially through the first connected fiber coupler of optical fiber, 3.6km single mode optical fiber, er-doped light
Fiber amplifier, the second isolator, circulator and the second fiber coupler, which constitute optical fiber and decline, swings chamber, and the first fiber coupler successively leads to
It crosses optical fiber to connect with the first isolator and laser source, which passes sequentially through route and semiconductor laser modulator and number is believed
Number generator is connected, and the second fiber coupler is connected by optical fiber with photodetector, which passes through route and show
Wave device is connected, and the bypass ports of circulator are connected with the lens with optical fiber, and standard film sample or film sample to be measured are placed in
Before lens, semiconductor laser modulator, semiconductor laser modulation are accessed when digital signal generator generates a series of impulse waves
Device control laser source output power and wavelength, it is modulated after optical pulse train via the first isolator and the first fiber coupler
10% port be coupled in optical fiber loop, successively pass through 3.6km single mode optical fiber, erbium-doped fiber amplifier, the second isolator, ring
2. shape device, the optical signal 1. inputted by circulator port are projected from circulator port, optical signal after reflection is from circulator
2. port returns and 3. projects from circulator port, optical fiber, which declines, swings in chamber 90% output light through the second fiber coupler access the
One fiber coupler, optical fiber, which declines, to be swung in chamber 10% output light and accesses photodetection by optical fiber loop through the second fiber coupler
The output periodic sequence of device, the pulse that decays is converted into electric signal by photodetector, is eventually displayed on digital oscilloscope, with
Change in film thickness, be reflected back optical fiber by lens and decline and swing intracavitary loss and change therewith, when leading to the decaying of pulse signal
Between change, according to the standard film sample of multiple groups known thickness by detection obtain corresponding standard film sample decline swing when
Between, the linear relationship curve or linear relationship equation of film thickness and ring-down time are established, it is then to be measured thin according to measuring
The linear relationship curve or linear relationship equation of the ring-down time of membrane sample and combination film thickness and ring-down time obtain to
Survey the thickness of film sample.
Preferably, the erbium-doped fiber amplifier is by the Er-doped fiber of one section of low gain, pump laser and three ports
WDM coupler composition, Er-doped fiber, pump laser and the light pulse of WDM coupler output of low gain are connect respectively in WDM coupling
Three ports of clutch.
Compared with the prior art, the invention has the following beneficial effects:
1, the invention proposes a kind of declined based on optical fiber swing chamber measurement nano-level thin-membrane thickness method, this method can be real
The high-sensitivity measurement of existing nano-level thin-membrane thickness；
2, the present invention reduces sound attenuation in wave distortion and compensated cavity using low gain and low noise Er-doped fiber；
3, the present invention compensates cavity loss increase pulse peak number using erbium-doped fiber amplifier to improve nano-level thin-membrane
The measurement accuracy of thickness；
4, measuring system of the invention is compact-sized, and measurement process is simple, convenient and efficient, can carry out real-time measurement, and stone
English optical fiber has the advantages that electromagnetism interference, light-weight and core diameter are thick easy to process.
Detailed description of the invention
Fig. 1 is the optical path connection figure of nano-level thin-membrane thickness measurement system in the present invention.
In figure: 1- digital signal generator, 2- semiconductor laser modulator, 3- laser source, the first isolator of 4-, 5- first
Fiber coupler, 6-3.6km single mode optical fiber, 7- erbium-doped fiber amplifier, the second isolator of 8-, 9- circulator, 10- standard film
Sample or film sample to be measured, the second fiber coupler of 11-, 12- photodetector, 13- oscillograph, 14- optical fiber, 15- magnetic tape trailer
Fine lens.
Specific embodiment
Above content of the invention is described in further details by the following examples, but this should not be interpreted as to this
The range for inventing above-mentioned theme is only limitted to embodiment below, and all technologies realized based on above content of the present invention belong to this hair
Bright range.
Embodiment
It is declined based on optical fiber and swings the method for chamber measurement nano-level thin-membrane thickness, by passing sequentially through the first connected optical fiber of optical fiber 14
Coupler 5,3.6km single mode optical fiber 6, erbium-doped fiber amplifier 7, the second isolator 8, circulator 9 and the second fiber coupler 11
It constitutes optical fiber and declines and swing chamber, the first fiber coupler 5 passes sequentially through optical fiber and connect with the first isolator 4 and laser source 3, the laser source
3 pass sequentially through route is connected with semiconductor laser modulator 2 and digital signal generator 1, and the second fiber coupler 11 passes through light
Fibre is connected with photodetector 12, which is connected by route with oscillograph 13, and the bypass ports of circulator 9 connect
It is connected to the lens 15 with optical fiber, standard film sample or film sample to be measured 10 are placed in front of lens, and wherein Er-doped fiber is put
Big device 7 is made of the WDM coupler of the Er-doped fiber of one section of low gain, pump laser and three ports, the er-doped light of low gain
The light pulse of fine, pump laser and the output of WDM coupler is connect respectively in three ports of WDM coupler, when digital signal is sent out
Raw device 1 generates a series of impulse wave access semiconductor laser modulators 2, and semiconductor laser modulator 2 controls the output of laser source 3
Power and wavelength, it is modulated after optical pulse train be coupled to via 10% port of the first isolator 4 and the first fiber coupler 5
In optical fiber loop, successively passes through 3.6km single mode optical fiber 6, erbium-doped fiber amplifier 7, the second isolator 8, circulator 9, pass through ring
2. the input optical signal of 9 port of shape device 1. is projected from 8 port of circulator, 2. optical signal after reflection is returned from 9 port of circulator
It returns and is 3. projected from 9 port of circulator, optical fiber declines the output light for swinging in chamber 90% through the second fiber coupler 11 the first light of access
Fine coupler 5, optical fiber, which declines, to be swung in chamber 10% output light and accesses photodetector by optical fiber loop through the second fiber coupler 11
12, the output periodic sequence for the pulse that decays is converted into electric signal by photodetector 12, is eventually displayed in digital oscilloscope 13
On, it declines in optical fiber and swings the second intracavitary isolator for ensuring signal one-way transmission, avoid light source from damaging, with film thickness
Degree variation is reflected back optical fiber and is declined and swung intracavitary loss and change therewith, the die-away time of pulse signal is caused to change by lens
Become, the ring-down time of corresponding standard film sample is obtained by detection according to the standard film sample of multiple groups known thickness, is established
The linear relationship curve or linear relationship equation of film thickness and ring-down time, then according to the film sample to be measured measured
The linear relationship curve or linear relationship equation of ring-down time and combination film thickness and ring-down time obtain film sample to be measured
The thickness of product.
The principle of the present invention is based on fiber optic loop Research on Cavity Ring Down Spectroscopy, a series of impulse waves that digital signal generator generates
Semiconductor laser modulators modulate is transported into pulsed light by " analog-modulated input " port, is entered through the first fiber coupler
Optical fiber loop is declined by optical fiber and swings the intracavitary erbium-doped fiber amplifier of chamber, the second fibre optic isolater, circulator, anti-through film sample
It penetrates and is come out from one end of the second fiber coupler, access photodetector.In order to improve the measurement accuracy of ring-down time, it is necessary to
Increase pulse number.So with an erbium-doped fiber amplifier come the loss of compensated optical fiber loop.Pass through different length er-doped light
Fine Amplifier Experiment, it is found that laser can be generated by Er-doped fiber is too long, and Er-doped fiber is too short, and gain is inadequate, the pulse spacing compares
It is small.Therefore, the image intensifer and 980nm pump laser of the Er-doped fiber that length is 2m have been built in laboratory.In identical item
Under part, compared the decaying spectrum for the erbium-doped fiber amplifier (EDFA) for being placed on inside and outside of cavity, when EDFA be placed on it is intracavitary
When, the peak strength of pulse signal is bigger, more, is more advantageous to and detects ring-down time.With conventional CRD signal processing
It compares, optical fiber, which declines, to be swung the intracavitary system of swinging that declines with EDFA and be greatly improved to the raising of measured film thickness sensitivity.
Temporal analysis is usually to determine fiber optic loop by monitoring the Decay for the light pulse for being introduced into optical fiber circuit
Light loss in road.In FLRDS system, the pulsed light of modulation enters optical fiber loop by the first fiber coupler, then exists
It is repeatedly round-trip in optical fiber loop, in each two-way process, swings a small amount of light of cavity loss since optical fiber declines and can lose, result
It is that light in annular chamber is exponentially decayed at any time, optical cavity ring-down signal may be expressed as:
It=I0exp(-t/τ) (1)
Wherein I0For initial beam intensity, τ is the optical cavity ring-down time.
Damped exponential signals are obtained by the small amount of leakage light of the second coupler every time by photodetector detection record.?
Measured film thickness experiment in, optical fiber decline swing it is intracavitary decaying change with the variation of film thickness, when the loss in annular chamber
Lower, die-away time, τ was bigger.Therefore τ reflects the loss as caused by change in film thickness, and can be obtained by measurement τ.
The die-away time τ of optical cavity is defined as the time needed for light decay reduces to the 1/e of its initial strength, which is
In formula, d is the length of optical fiber ring cavity, and c is the light velocity, and n is the refractive index of optical fiber ring cavity, and A is each cavity-type BPM process
In total losses, decline including optical fiber and swing the loss that chamber inherent loss and camera lens are docked with high reflecting mirror surface.It is intracavitary in fiber annular,
The inherent loss of optic fiber ring-shaped cavity is damaged mainly from the scattering of the absorption of optical fiber ring cavity, the insertion loss of fiber coupler, optical fiber
The junction loss of consumption and optical fiber.
From experiment it can be seen that part energy can be to be measured when the light that light source issues penetrates film sample to be measured
Film sample is absorbed, some energy can be reflected by film sample to be measured, through the second coupler by photodetector
It detects.When film sample thickens, optical fiber, which declines, to be swung chamber energy and will reduce, correspondingly, optical fiber declines when film sample is thinning
Swinging chamber energy just will increase.Optical signal can be converted into electric signal by photodetector, then be shown by digital oscilloscope
Come, and then calculates the thickness of film sample to be measured by ring-down time.
Embodiment above describes basic principles and main features of the invention and advantage, the technical staff of the industry should
Understand, the present invention is not limited to the above embodiments, and the above embodiments and description only describe originals of the invention
Reason, under the range for not departing from the principle of the invention, various changes and improvements may be made to the invention, these changes and improvements are each fallen within
In the scope of protection of the invention.
Claims (2)
1. declined based on optical fiber swing chamber measurement nano-level thin-membrane thickness method, it is characterised in that: by pass sequentially through optical fiber be connected
First fiber coupler, 3.6km single mode optical fiber, erbium-doped fiber amplifier, the second isolator, circulator and the second fiber coupler
Optical fiber is constituted to decline and swings chamber, the first fiber coupler passes sequentially through optical fiber and connect with the first isolator and laser source, the laser source according to
Secondary to be connected by route with semiconductor laser modulator and digital signal generator, the second fiber coupler passes through optical fiber and photoelectricity
Detector is connected, which is connected by route with oscillograph, and the bypass ports of circulator are connected with optical fiber
Lens, standard film sample or film sample to be measured are placed in front of lens, when digital signal generator generates a series of pulses
Wave accesses semiconductor laser modulator, the output power and wavelength of semiconductor laser modulator control laser source, after modulated
Optical pulse train is coupled in optical fiber loop via 10% port of the first isolator and the first fiber coupler, successively passes through 3.6km
Single mode optical fiber, erbium-doped fiber amplifier, the second isolator, circulator, the optical signal 1. inputted by circulator port is from annular
2. device port is projected, 2. optical signal after reflection is returned from circulator port and 3. projected from circulator port, optical fiber, which declines, to be swung
90% output light accesses the first fiber coupler through the second fiber coupler in chamber, and optical fiber, which declines, swings in chamber 10% output light through the
Two fiber couplers access photodetector by optical fiber loop, and the output periodic sequence for the pulse that decays is converted by photodetector
At electric signal, be eventually displayed on digital oscilloscope, with change in film thickness, by lens be reflected back optical fiber decline swing it is intracavitary
Loss changes therewith, and the die-away time of pulse signal is caused to change, logical according to the standard film sample of multiple groups known thickness
It crosses detection and obtains the ring-down time of corresponding standard film sample, establish the linear relationship curve or line of film thickness and ring-down time
Sexual intercourse equation, then according to the ring-down time of the film sample to be measured measured and the line of combination film thickness and ring-down time
Sexual intercourse curve or linear relationship equation obtain the thickness of film sample to be measured.
2. according to claim 1 declined based on optical fiber swings the method for chamber measurement nano-level thin-membrane thickness, it is characterised in that: institute
It states erbium-doped fiber amplifier to be made of the WDM coupler of the Er-doped fiber of one section of low gain, pump laser and three ports, low increasing
Er-doped fiber, pump laser and the light pulse of WDM coupler output of benefit are connect respectively in three ports of WDM coupler.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201810854550.8A CN108981594A (en) | 2018-07-30 | 2018-07-30 | It is declined based on optical fiber and swings the method for chamber measurement nano-level thin-membrane thickness |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201810854550.8A CN108981594A (en) | 2018-07-30 | 2018-07-30 | It is declined based on optical fiber and swings the method for chamber measurement nano-level thin-membrane thickness |
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| CN201810854550.8A Pending CN108981594A (en) | 2018-07-30 | 2018-07-30 | It is declined based on optical fiber and swings the method for chamber measurement nano-level thin-membrane thickness |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002141274A (en) * | 2000-11-06 | 2002-05-17 | Tokyo Electron Ltd | Measuring apparatus for film thickness and its method |
| CN1414377A (en) * | 2001-10-18 | 2003-04-30 | Lg电子株式会社 | Method for investigating film and its device |
| CN107121080A (en) * | 2017-06-16 | 2017-09-01 | 东南大学 | A kind of method for measuring ordered porous nano film thickness |
-
2018
- 2018-07-30 CN CN201810854550.8A patent/CN108981594A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002141274A (en) * | 2000-11-06 | 2002-05-17 | Tokyo Electron Ltd | Measuring apparatus for film thickness and its method |
| CN1414377A (en) * | 2001-10-18 | 2003-04-30 | Lg电子株式会社 | Method for investigating film and its device |
| CN107121080A (en) * | 2017-06-16 | 2017-09-01 | 东南大学 | A kind of method for measuring ordered porous nano film thickness |
Non-Patent Citations (2)
| Title |
|---|
| A.H.M.SMETS等: "Bulk and surface defects in a-Si:H films studied by means of the cavity ring down absorption technique", 《JOURNAL OF NON-CRYSTALL INE SOLIDS》 * |
| 程瑞学: "基于光纤衰荡腔测量纳米级薄膜厚度的方法", 《激光技术》 * |
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Application publication date: 20181211 |