CN204612666U - A kind of position phase reinforced membranes thickness measurement system - Google Patents

Abstract

The utility model discloses a kind of position phase reinforced membranes method for measuring thickness and system.This system adopts broadband swept light source, measurement subcycle chamber and reference subcycle chamber is respectively arranged with in its optical path and reference path, utilize and measure light and the circulation of the high speed of reference light in two sub-torus (light velocity) light, accumulation measurement by magnification (enlargement factor equals to measure the light circulation level time of light and reference light) can be carried out mutually to the film position of the same lateral position of film sample to be measured, thus the sensitivity of enhanced film phase measurement.And, because this system is being carried out in the process of accumulation measurement by magnification mutually to film position, measuring beam irradiates the same lateral attitude in film sample to be measured all the time, thus be different from and utilize measuring beam multiple reflections and then ask for the spectrographic technique of reflectivity of optical thin film in film sample to be measured, this film position phase Enhancement Method can not sacrificial system to the horizontal resolution characteristic of film sample to be measured.

Description

A kind of position phase reinforced membranes thickness measurement system

Technical field

The utility model relates to optical coherence fields of measurement, is specifically related to a kind of position phase reinforced membranes thickness measurement system.

Background technology

The importance of thin film technique in modern science and technology and increasing severely day.In recent decades, the technology such as various photoelectric device, biosensor technique, Laser Devices, microelectronic component, liquid crystal display and integrated optics relies on the development of thin film technique all to a great extent.And along with the development of optical thin film design and thin film technique, needing several major optical parameters of Accurate Measurement optical thin film when preparing high performance optical thin film element, comprising: refractive index, thicknesses of layers, transmittance, reflectance and absorptance etc.Wherein the physical thickness of film is one of most basic parameter of film, and it can affect the final performance of whole optical element, thus how to improve existing film thickness detection technique, realizes measuring quickly and accurately being of great significance.

The measuring method of current thin film thickness mainly can divide by non optical method and optical means.Non optical method is mainly divided into probe scanning method, scanning electron microscope, atomic force microscope etc.

Probe scanning method, the method is also referred to as consistency profiles, and it measures the thickness of film by utilizing the surface of small mechanical probes (generally only having several micron) contact measured film.There is following deficiency in the method: needs the film thickness step for the preparation of using during test, the precision of the method is limited to the size of probe used in addition, and will the effect of integral smooth be had when surveying s and trying film surface profile, be similar to mathematical low-pass filtering, therefore prepared by undesirable sample to the roughness of high-frequency film and thin films step, good test effect cannot be obtained.The most important thing is that the method generally may bring unforeseen damage to the surface of film.

Scanning electron microscope can be used in the thickness detecting film, the method utilizes the very thin electron beam focused on as electron probe, the scanning of raster mode is done at tested film surface, and detect by detector the secondary electron that tested film surface excites by incident electron, then through amplifying and after data processing, the scanning electron image of a secondary high-amplification-factor can being obtained.Because the surface distributed of tested film is with the intensity of secondary electron and distribute relevant, therefore this scanning electron image can reflect the roughness distribution situation of tested film surface intuitively, and the horizontal and vertical resolution of the method can reach nanoscale.Although the method has as above said advantage, but because scanning electron microscope just utilizes stereoscopic technique and stereoscopic analysis technology indirectly to obtain the image with depth effect, therefore the pattern of the tested film surface of qualitative observation can only be used for, and its surface of sample that scanning electron microscope is suitable for needs conduction, when therefore nonconductor film being measured, need the plating metal on surface film at former film, destroy the primary morphology of film surface, introduce measuring error.

Atomic force microscope also can be applied to the measurement of film thickness, and the method can obtain film surface appearance by utilizing probe and film interatomic interaction force.The probe of usual atomic force microscope is placed on micro-cantilever, utilizes optical lever principle to measure the deformation of micro-cantilever under the interaction force of probe and film atom, thus records the pattern of film surface.Compared with scanning electron microscope, the sample surfaces that atomic force microscope is measured does not need conduction, and its lateral resolution and longitudinal frame can reach 0.1nm and 0.01nm, can observe molecule or atom intuitively.Although the method has above-mentioned said advantage, the horizontal and vertical sweep limit of the method generally only has micron dimension, and utilizes optical lever principle to measure the deformation of micro-cantilever, is easily subject to the impact of the factor such as optoelectronic noise, vibration.

Utilize scanning electron microscope and atomic force microscope to carry out the measurement of film thickness, also may bring unknown damage to the surface of film.Thus the thickness measure for film is more suitable for selecting optical means.Optical means at present for measured film thickness mainly contains spectroscopic methodology, Ellipsometric and optical thin film position phase method.

Spectroscopic methodology is based on the principle of interference of light, transmission (or reflection) according to light beam in film-substrate-film interface will cause twin-beam or multiple-beam interference, and therefore the film of different-thickness will have different spectral reflectivities (or transmissivity).Therefore, it is possible to carry out by the spectral characteristic detecting film the thickness that film is derived in inverting.The transmissivity of current thin film and reflectivity mainly adopt grating test analytic system to test.And according to different measuring requirement, comprise: single thin film, multilayer film, whether consider film absorption, how to select whether there are multiple extreme values etc. in rational dispersive model, spectrum, spectroscopic methodology can be subdivided into again extremum method, envelope method and full spectrum simulation method etc.Spectroscopic methodology needs by selecting suitable optimization method or using multiple method simultaneous, can realize comparatively high-precision measured film thickness.In addition, the method also requires that rete is thicker in produce certain interference oscillation, and can only be used for measuring weak absorbing film.

The measuring principle of Ellipsometric to be carried out the thickness of inverting derivation film.Ellipsometric not only may be used for recording parameters of film, also can be applied to the parameter asking for metal, semiconductor, deielectric-coating.When it is applied to the dielectric film thickness measured on high-selenium corn substrate, the method will an order of magnitude higher than optical interference method, even has the sensitivity of atomic level.But Ellipsometric exists a thickness cycle, within this cycle, only use Ellipsometric can record accurate film thickness value, if the scope measured exceedes this cycle, then the thickness of film will have multiple uncertain value.Therefore the film thickness scope of Ellipsometric measurement is generally from 1nm to 1 μm, and with the measured film thickness of about 10nm for the best.In addition, the method not only needs accurately to record reflective light intensity, and needs accurately to record analysis polarization intensity, and therefore mean the high-precision mobile optical device of needs, what improve system builds cost.Meanwhile, also it is pointed out that higher sensitivity means the impact being more easily subject to X factor, as the non-uniform Distribution of film refractive index.

Optical thin film position phase method refers to that utilizing interferometer to detect obtains interference signal to ask for reflection (or transmission) the position phase of film, because this reflection (or transmission) position is relevant with the thickness of film, therefore can carry out by recording this reflection (or transmission) position the exact value that film thickness is derived in inverting mutually.The method has following several advantage: 1. no matter be that transmission type thin-film or reflective film can detect its phase characteristics.2. the method is Dynamic Non-Destruction Measurement, can not produce destroy Optical Coatings Surface.3. measurement mechanism regulates simple, can realize Quick Measurement fully-automated synthesis even.4. detect spectral band wider.5. the whole apparatus structure of the method is simple, and cost is low, the very applicable rapid three dimensional imaging being applied to film thickness.The method is applicable to the high-acruracy survey being applied to thickness of multilayer film very much in addition, has had research group to utilize this optical thin film position phase method duplicature to be achieved to the Film thickness measurements of 80nm at present.But optical thin film position phase method is limited to the sensitivity (difference namely between film non-linear position phase maximal value and minimum value) of film non-linear position phase, the minimum Film thickness measurements that theory can accurately repeat to realize only has 0.18 μm.When the thickness of film is less than 0.18 μm, utilize the method to carry out measured film thickness and may bring larger error, error rate is greater than 1%.

Summary of the invention

The utility model, for the deficiency of optical thin film position phase method, discloses a kind of position phase reinforced membranes thickness measurement system.This system formed primarily of measured film thickness unit and sampling wave number drift correction unit.Measurement subcycle chamber and reference subcycle chamber is respectively arranged with in the optical path of measured film thickness unit and reference path, utilize and measure light and the circulation of the high speed of reference light in two sub-torus (light velocity) light, accumulation measurement by magnification (enlargement factor equals to measure the light circulation level time of light and reference light) can be carried out mutually to the film position of the same lateral position of film sample to be measured, thus the sensitivity of enhanced film phase measurement.And because this system is being carried out in the process of accumulation measurement by magnification mutually to film position, measuring beam irradiates the same lateral attitude in film sample to be measured all the time, thus be different from and utilize measuring beam multiple reflections and then ask for the spectrographic technique of reflectivity of optical thin film in film sample to be measured, this film position phase Enhancement Method can not sacrificial system to the horizontal resolution characteristic of film sample to be measured.

A kind of position phase reinforced membranes thickness measurement system, comprises broadband swept light source, the first broadband optical fiber coupler, measured film thickness unit, sampling wave number drift correction unit, high-speed data acquisition card and computing machine; Described measured film thickness unit comprises the second broadband optical fiber coupler, the 3rd broadband optical fiber coupler, the 4th broadband optical fiber coupler, the 5th broadband optical fiber coupler, the first Polarization Controller, the second Polarization Controller, the 3rd Polarization Controller, the 4th Polarization Controller, measures subcycle chamber, with reference to subcycle chamber, fibre delay line and the first high bandwidth balance photodetector;

Described broadband swept light source is connected with wave number drift correction unit input end of sampling with the second broadband optical fiber coupler input end respectively by the first broadband optical fiber coupler, and two output terminals of the second broadband optical fiber coupler connect the input end of the first Polarization Controller and the input end of the second Polarization Controller respectively, the output terminal of the first Polarization Controller is connected with one of them input end of the 3rd broadband optical fiber coupler, one of them output terminal of 3rd broadband optical fiber coupler connects the input end measuring subcycle chamber, the output terminal measuring subcycle chamber connects another input end of the 3rd broadband optical fiber coupler, another output terminal of 3rd broadband optical fiber coupler is connected with the input end of the 3rd Polarization Controller, and the output terminal of the 3rd Polarization Controller is connected with one of them input end of the 5th broadband optical fiber coupler, the output terminal of the second Polarization Controller is connected with one of them input end of the 4th broadband optical fiber coupler, one of them output terminal of 4th broadband optical fiber coupler connects the input end with reference to subcycle chamber, output terminal with reference to subcycle chamber connects another input end of the 4th broadband optical fiber coupler, another output terminal of 4th broadband optical fiber coupler is connected with the input end of fibre delay line, the output terminal of fibre delay line is connected with the input end of the 4th Polarization Controller, the output terminal of the 4th Polarization Controller is connected with another input end of the 5th broadband optical fiber coupler, two output terminals of the 5th broadband optical fiber coupler connect two input ends of the first high bandwidth balance photodetector respectively, electrical signal and the electrical signal of the first high bandwidth balance photodetector of sampling wave number drift correction unit are connected two input signal channels of high-speed data acquisition card respectively, and the output terminal of high-speed data acquisition card is connected with computing machine, the trigger pip output terminal of broadband swept light source is connected with high-speed data acquisition card trigger pip input end,

After the low-coherent light that broadband swept light source sends enters the first broadband optical fiber coupler, a part of light enters measured film thickness unit, and another part light enters sampling wave number drift correction unit; The low-coherent light entering measured film thickness unit is divided into two-way after the second broadband optical fiber coupler, wherein a road light enters the 3rd broadband optical fiber coupler after the first Polarization Controller, and another road light enters the 4th broadband optical fiber coupler after the second Polarization Controller; The light entering the 3rd broadband optical fiber coupler separates a part of light after the 3rd Polarization Controller, enters the 5th broadband optical fiber coupler; Another part light exported from the 3rd broadband optical fiber coupler enters the 3rd broadband optical fiber coupler for the second time after measuring subcycle chamber, the low-coherent light that second time enters the 3rd broadband optical fiber coupler is divided into two parts equally, arrives the 5th broadband optical fiber coupler respectively and enter the 3rd broadband optical fiber coupler for the third time along above-mentioned path; By that analogy, the low-coherent light entering the 3rd broadband optical fiber coupler for the N-1 time also arrives the 5th broadband optical fiber coupler along above-mentioned path and enters the 3rd broadband optical fiber coupler for the N time; Same, the light entering the 4th broadband optical fiber coupler separates a part of light successively after fibre delay line and the 4th Polarization Controller, enters the 5th broadband optical fiber coupler; Another part light exported from the 4th broadband optical fiber coupler enters the 4th broadband optical fiber coupler by reference to second time behind subcycle chamber, the low-coherent light that second time enters the 4th broadband optical fiber coupler is divided into two parts equally, arrives the 5th broadband optical fiber coupler respectively and enter the 4th broadband optical fiber coupler for the third time along above-mentioned path; By that analogy, the low-coherent light entering the 4th broadband optical fiber coupler for the N-1 time also arrives the 5th broadband optical fiber coupler along above-mentioned path and enters the 4th broadband optical fiber coupler for the N time; Above-mentioned all low-coherent lights entering the 5th broadband optical fiber coupler interfere, and interference signal detects via the first high bandwidth balance photodetector; System two unit detect the signal that obtains by high-speed data acquisition card synchronous acquisition, the Signal transmissions collected carries out data processing to the internal memory of computing machine; The trigger pip of high-speed data acquisition card is produced by broadband swept light source.

Described measurement subcycle chamber comprises the 5th Polarization Controller, the first band optical fiber circulator, the first boosting optical amplifier, the first acousto-optic frequency shifters, the first optical fiber collimator and the first lens;

The input end of the first acousto-optic frequency shifters is as the input end measuring subcycle chamber, and the output terminal of the 5th Polarization Controller is as the output terminal measuring subcycle; The output terminal of the first acousto-optic frequency shifters connects the input end of the first boosting optical amplifier, the output terminal of the first boosting optical amplifier is connected with the input end of the first band optical fiber circulator, first output terminal of the first band optical fiber circulator connects the input end of the first optical fiber collimator, second output terminal of the first band optical fiber circulator is connected with the input end of the 5th Polarization Controller, thus forms the measurement subcycle chamber in optical path;

The first acousto-optic frequency shifters is passed through from wherein a part of low-coherent light of the 3rd broadband optical fiber coupler outgoing, after first boosting optical amplifier and the first band optical fiber circulator, the first optical fiber collimator is entered from the first output terminal of the first band optical fiber circulator, after the first lens, film sample to be measured is injected from the low-coherent light of the first optical fiber collimator outgoing, the low-coherent light reflected from film sample to be measured is subsequently more successively through the first optical fiber collimator, first output terminal of the first band optical fiber circulator, the 3rd broadband optical fiber coupler is again entered after second output terminal and the 5th Polarization Controller, balancing a survey light is in the gain of measuring in subcycle chamber and loss, and this process will repeat N time, and measuring beam irradiates carrying out N time to the same lateral position of film sample to be measured, and the N realized measuring film position phase doubly amplifies.

Described reference subcycle chamber comprises the 6th Polarization Controller, the second band optical fiber circulator, the second boosting optical amplifier, the second acousto-optic frequency shifters, the second optical fiber collimator, the second lens and plane mirror;

The input end of the second acousto-optic frequency shifters is as the input end with reference to subcycle chamber, and the output terminal of the 6th Polarization Controller is as the output terminal with reference to subcycle; The output terminal of the second acousto-optic frequency shifters connects the input end of the second boosting optical amplifier, the output terminal of the second boosting optical amplifier is connected with the input end of the second band optical fiber circulator, first output terminal of the second band optical fiber circulator connects the input end of the second optical fiber collimator, second output terminal of the second band optical fiber circulator is connected with the input end of the 6th Polarization Controller, thus forms the reference subcycle chamber in reference path;

The second acousto-optic frequency shifters is passed through from wherein a part of low-coherent light of the 4th broadband optical fiber coupler outgoing, after second boosting optical amplifier and the second band optical fiber circulator, the second optical fiber collimator is entered from the first output terminal of the second band optical fiber circulator, after the second lens, plane mirror is injected from the low-coherent light of the second optical fiber collimator outgoing, the low-coherent light reflected from plane mirror is subsequently more successively through the second optical fiber collimator, first output terminal of the second band optical fiber circulator, the 4th broadband optical fiber coupler is again entered after second output terminal and the 6th Polarization Controller, balanced reference light is with reference to the gain in subcycle chamber and loss, and this process will repeat N time, and the low-coherent light of outgoing from reference subcycle chamber forms the secondary interference of respective cycle chamber level by with the low-coherent light of outgoing in measurement subcycle chamber.

Described sampling wave number drift correction unit comprises the 6th broadband optical fiber coupler, optical-fiber type Bragg diffraction gratings and the second high bandwidth balance photodetector;

One of them input end of 6th broadband optical fiber coupler is as the input end of sampling wave number drift correction unit, second high bandwidth balances the electrical signal of electrical signal as sampling wave number drift correction unit of photodetector, the output terminal of the 6th broadband optical fiber coupler is connected with the input end of optical-fiber type Bragg diffraction gratings, one of them input end that another one input end and second high bandwidth of the 6th broadband optical fiber coupler balance photodetector is connected, thus forms sampling wave number drift correction unit;

From wherein a part of low-coherent light of the first broadband optical fiber coupler outgoing after the 6th broadband optical fiber coupler, enter optical-fiber type Bragg diffraction gratings; The narrow band light of the specific wavelength reflected from optical-fiber type Bragg diffraction gratings, again through the 6th broadband optical fiber coupler, enters the second high bandwidth balance photodetector from another input end of the 6th broadband optical fiber coupler; This unit utilizes optical-fiber type Bragg diffraction gratings only to carry out reflecting this characteristic for the narrow-band spectrum of specific wavelength, the reflectance spectrum signal of different frequency sweep cycle is gathered by high-speed data acquisition card, and the entirety drift that the peak location contrasting reflectance spectrum between different frequency sweep cycle carrys out calculating sampling wave number is counted, thus realize the overall correction of drifting about of wave number of sampling between different frequency sweep cycle, greatly reduce the impact of system middle width strip swept light source electronic activation signal shake on film phase measurement stability.

Compared with background technology, the beneficial effect that the utility model has is:

1. utilize and measure light and the circulation of the high speed of reference light in two sub-torus (light velocity) light, accumulation measurement by magnification (enlargement factor equals to measure the light circulation level time of light and reference light) can be carried out mutually to the film position of the same lateral position of film sample to be measured, thus the sensitivity of enhanced film phase measurement.

2. because this system is being carried out in the process of accumulation measurement by magnification mutually to film position, measuring beam irradiates the same lateral attitude in film sample to be measured all the time, thus be different from and utilize measuring beam multiple reflections and then ask for the spectrographic technique of reflectivity of optical thin film in film sample to be measured, this film position phase Enhancement Method can not sacrificial system to the horizontal resolution characteristic of film sample to be measured.

3. the signal interference of measured film thickness unit main optical path (not comprising subcycle chamber) part is not owing to comprising subcycle chamber information, and can be arranged suitable fixing retardation values by the fibre delay line in main optical path.Thus the interference signal of main optical path part can be utilized to demarcate to the wave number of carrying out detecting light spectrum.Therefore, this system does not need additionally to arrange wave number and demarcates unit, simplifies the hsrdware requirements of system, reduces system cost.

4. utilize sampling wave number drift cells can measure the drift of interference signal sampling wave number between the different frequency sweep cycle of real time correction broadband swept light source, greatly reduce the shake of system middle width strip swept light source trigger pip to the impact of film phase measurement stability.

Accompanying drawing explanation

Fig. 1 is position described in the utility model phase reinforced membranes thickness measurement system structural representation;

Fig. 2 is the theoretical schematic diagram of the structural representation in measurement subcycle chamber described in the utility model and film position accumulation measurement by magnification mutually;

Fig. 3 is the structural representation with reference to subcycle chamber described in the utility model;

Fig. 4 is the structural representation of sampling wave number drift correction unit described in the utility model;

Fig. 5 is the signal processing flow figure of position described in the utility model phase reinforced membranes thickness measure;

Fig. 6 is the actual effect schematic diagram that the non-linear position of film described in the utility model accumulates amplification mutually.

Embodiment

Below in conjunction with drawings and Examples, the utility model is described further.

As shown in Figure 1, the utility model comprises broadband swept light source 1, first broadband optical fiber coupler 2, second broadband optical fiber coupler 3, first Polarization Controller 4, second Polarization Controller 5, the 3rd broadband optical fiber coupler 6, measurement subcycle chamber 7, the 4th broadband optical fiber coupler 8, balances photodetector 14, sampling wave number drift correction unit 15, high-speed data acquisition card 16, computing machine 17 with reference to subcycle chamber 9, the 3rd Polarization Controller 10, fibre delay line 11, the 4th Polarization Controller 12, the 5th broadband optical fiber coupler 13, first high bandwidth.

Broadband swept light source 1 is connected with wave number drift correction unit 15 input end of sampling with the second broadband optical fiber coupler 3 input end respectively by the first broadband optical fiber coupler 2, and two output terminals of the second broadband optical fiber coupler 3 connect the input end of the first Polarization Controller 4 and the input end of the second Polarization Controller 5 respectively.The output terminal of the first Polarization Controller 4 is connected with one of them input end of the 3rd broadband optical fiber coupler 6, one of them output terminal of 3rd broadband optical fiber coupler 6 connects the input end measuring subcycle chamber 7, the output terminal measuring subcycle chamber 7 connects another input end of the 3rd broadband optical fiber coupler 6, another output terminal of 3rd broadband optical fiber coupler 6 is connected with the input end of the 3rd Polarization Controller 10, and the output terminal of the 3rd Polarization Controller 10 is connected with one of them input end of the 5th broadband optical fiber coupler 13, the output terminal of the second Polarization Controller 5 is connected with one of them input end of the 4th broadband optical fiber coupler 8, one of them output terminal of 4th broadband optical fiber coupler 8 connects the input end with reference to subcycle chamber 9, output terminal with reference to subcycle chamber 9 connects another input end of the 4th broadband optical fiber coupler 8, another output terminal of 4th broadband optical fiber coupler 8 is connected with the input end of fibre delay line 11, the output terminal 11 of fibre delay line is connected with the input end of the 4th Polarization Controller 12, the output terminal of the 4th Polarization Controller 12 is connected with another input end of the 5th broadband optical fiber coupler 13.Two output terminals of the 5th broadband optical fiber coupler 13 connect two input ends of the first high bandwidth balance photodetector 14 respectively.Electrical signal and the electrical signal of the first high bandwidth balance photodetector 14 of sampling wave number drift correction unit 15 are connected two input signal channels of high-speed data acquisition card 16 respectively, and the output terminal of high-speed data acquisition card 16 is connected with computing machine 17.The trigger pip output terminal of broadband swept light source 1 is connected with high-speed data acquisition card 16 trigger pip input end.

After the low-coherent light that broadband swept light source 1 sends enters the first broadband optical fiber coupler 2, a part of light enters measured film thickness unit, and another part light enters sampling wave number drift correction unit 15.The low-coherent light entering measured film thickness unit is divided into two-way after the second broadband optical fiber coupler 3, wherein a road light enters the 3rd broadband optical fiber coupler 6 after the first Polarization Controller 4, and another road light enters the 4th broadband optical fiber coupler 8 after the second Polarization Controller 5.The light entering the 3rd broadband optical fiber coupler 6 separates a part of light after the 3rd Polarization Controller 10, enters the 5th broadband optical fiber coupler 13.Another part light exported from the 3rd broadband optical fiber coupler 6 enters the 3rd broadband optical fiber coupler 6 for the second time after measuring subcycle chamber 7, the low-coherent light that second time enters the 3rd broadband optical fiber coupler 6 is divided into two parts equally, arrives the 5th broadband optical fiber coupler 13 respectively and enter the 3rd broadband optical fiber coupler 6 for the third time along above-mentioned path.By that analogy, the low-coherent light entering the 3rd broadband optical fiber coupler 6 for the N-1 time also arrives the 5th broadband optical fiber coupler 13 along above-mentioned path and enters the 3rd broadband optical fiber coupler 6 for the N time.Same, the light entering the 4th broadband optical fiber coupler 8 separates a part of light successively after fibre delay line 11 and the 4th Polarization Controller 12, enters the 5th broadband optical fiber coupler 13.Another part light exported from the 4th broadband optical fiber coupler 8 enters the 4th broadband optical fiber coupler 8 by reference to second time behind subcycle chamber 9, the low-coherent light that second time enters the 4th broadband optical fiber coupler 8 is divided into two parts equally, arrives the 5th broadband optical fiber coupler 13 respectively and enter the 4th broadband optical fiber coupler 8 for the third time along above-mentioned path.By that analogy, the low-coherent light entering the 4th broadband optical fiber coupler 8 for the N-1 time also arrives the 5th broadband optical fiber coupler 13 along above-mentioned path and enters the 4th broadband optical fiber coupler 8 for the N time.Above-mentioned all low-coherent lights entering the 5th broadband optical fiber coupler 13 interfere, and interference signal detects via the first high bandwidth balance photodetector 14.System two unit detect the signal that obtains by high-speed data acquisition card 16 synchronous acquisition, the Signal transmissions collected carries out data processing to the internal memory of computing machine 17.The trigger pip of high-speed data acquisition card 16 is produced by broadband swept light source 1, and in figure, achievement unit is divided into optical fiber, and dot-and-dash line part is circuit connecting wire.

Be illustrated in figure 2 the theoretical schematic diagram of the structural representation in measurement subcycle chamber described in the utility model and film position accumulation measurement by magnification mutually; Measure subcycle chamber and comprise the 5th Polarization Controller 18, first band optical fiber circulator 19, first boosting optical amplifier 20, first acousto-optic frequency shifters 21, first optical fiber collimator 22, first lens 23, film sample to be measured 24.

The input end of the first acousto-optic frequency shifters 21 is as the input end measuring subcycle chamber 7, and the output terminal of the 5th Polarization Controller 18 is as the output terminal measuring subcycle 7.The output terminal of the first acousto-optic frequency shifters 21 connects the input end of the first boosting optical amplifier 20, the output terminal of the first boosting optical amplifier 20 is connected with the input end of the first band optical fiber circulator 19, first output terminal of the first band optical fiber circulator 19 connects the input end of the first optical fiber collimator 22, second output terminal of the first band optical fiber circulator 19 is connected with the input end of the 5th Polarization Controller 18, thus forms the measurement subcycle chamber 7 in optical path.

The first acousto-optic frequency shifters 21 is passed through from wherein a part of low-coherent light of the 3rd broadband optical fiber coupler 6 outgoing, after first boosting optical amplifier 20 and the first band optical fiber circulator 19, the first optical fiber collimator 22 is entered from the first output terminal of the first band optical fiber circulator 19, after the first lens 23, film sample 24 to be measured is injected from the low-coherent light of the first optical fiber collimator 22 outgoing, the low-coherent light reflected from film sample 24 to be measured is subsequently more successively through the first optical fiber collimator 23, first output terminal of the first band optical fiber circulator 19, the 3rd broadband optical fiber coupler 6 is again entered after second output terminal and the 5th Polarization Controller 18.Balancing a survey light is in the gain of measuring in subcycle chamber and loss, and this process will repeat N time, and thus as shown in the figure, measuring beam irradiates carrying out N time to the same lateral position of film sample to be measured, and the N realized measuring film position phase doubly amplifies.

Set forth to the theory of film position accumulation measurement by magnification mutually below, film sample to be measured for monofilm, now position phase reinforced membranes thickness measurement system detect the measurement interference signal obtained and can be expressed as on wavenumber domain:

$\begin{array}{c}{I}_{Measurement}\left(t\right)\∝2\underset{N}{\Σ}S\left(t\right)\·G_N\left(\right|z-{\mathrm{N\Δz}}^{\′}\left|\right)\\ \·\cos \[k\left(t\right)\left(z-{\mathrm{N\Δz}}^{\′}\right)+{\mathrm{N\ψ}}_n\left(t\right)+2\mathrm{\π}N\mathrm{\Δ}ft\],N=0,1,2,3,\mathrm{...},\end{array}---\left(1\right)$

In formula (1), S (t) represents the spectral power of the broadband swept light source of t, G _n(| z-N Δ z'|) represent the instantaneous coherence function secondary relative to circulation level of not sharing the same light.Z represents the optical path difference of main optical path (namely without the light path of two sub-torus), and k (t) represents the wave number of t, and N=0 represents the interference of light of the stellar interferometer main optical path part without subcycle chamber.As shown in Figure 2, in figure, a, b, c represent respectively with reference to zero optical path difference face, the upper surface position of film to be measured and the lower surface position of film to be measured between subcycle chamber and measurement subcycle chamber.Δ z' represents that its value can be tried to achieve by formula (2) with reference to the equivalent optical path amount of mismatch between subcycle chamber and measurement subcycle chamber:

Δz'＝Δz _RL+d' (2)

The group delay amount that d' in formula (2) is equivalent to film reflector position phase and measures subcycle chamber and introduce with reference to dispersion amount of mismatch between subcycle chamber.ψ _nt () comprises t and measures subcycle chamber and the non-linear partial ψ with reference to dispersion amount of mismatch between subcycle chamber _nsthe non-linear partial ψ of (t) and film reflector position phase _nf(t, d).Its value can be calculated by formula (3) and try to achieve:

ψ _n(t)＝ψ _nf(t,d)+ψ _ns(t) (3)

ψ from formula (3) _nf(t, d) is a non-linear position phase relevant with film thickness, next how introduction is accurately tried to achieve this non-linear position phase.

Fast discrete Fourier conversion is carried out to formula (1), successively the measurement interference signal that circulation level of not sharing the same light is secondary is windowed, and remove corresponding light circulation level time carrier frequency amount, then inverse Fourier transform is carried out again, can obtain corresponding to the secondary plural form interference signal of circulation level of not sharing the same light

I' _Measurement(t)∝S(t)·G _N(|z-NΔz'|)

(4)

·expj[k(t)(z-NΔz′)+Nψ _n(t)]

Solution parcel position is asked for this plural form interference signal and obtains the secondary interference signal position phase of corresponding light circulation level mutually,

In the not homogeneous of film sample is measured, broadband swept light source wave number k (t) that high-speed data acquisition card t collects is owing to being subject to the shake of broadband swept light source electronic activation signal, to more general form be had, as shown in formula (6):

$k(t+\mathrm{\ϵ})=\underset{n=0}{\overset{\mathrm{\∞}}{\Σ}}\frac{{\mathrm{\ϵ}}^n}{n!}{k}^{\left(n\right)}\left(t\right)---\left(6\right)$

Between ε represents that homogeneous is measured in formula (6), High speed data capture card shake the time delay that the wave number that causes samples due to broadband swept light source electronic activation signal.In order to minimize this time delay as far as possible, position phase reinforced membranes thickness measurement system introduces a sampling wave number drift correction unit constructed by broadband optical fiber coupler, high bandwidth balance photodetector and optical-fiber type Bragg diffraction gratings.Utilize the interference position phase of main optical path in addition, namely measured when N=0 interference spectrum position phase demarcate wave number sampling at equal intervals.Now

k(t)＝k ₀+γt (7)

K in formula ₀for initial wave number, γ is wave number linearization coefficient relevant to time t.Formula (7) is substituted in formula (5) and can be obtained

Join linearization is done to formula (8) and after deducting linearization part, the non-linear position phase that N doubly amplifies can be obtained thereupon,

In conjunction with formula (9) and (3), in order to can from non-linear position phase middle inverting draws N ψ _nf(t, d), needs use one piece of standard model (namely not introducing the sample of similar film reflector position phase) to draw N ψ _ns(t), thus accurately draw finally utilize the model shown in formula (10), the film thickness value different by iteration asks for minimum value ξ (d), thus obtains accurate film thickness value.

In formula (10) represent the theoretical value of the film reflector position phase non-linear partial relevant with film thickness, T _effectrepresent the efficient system sampling time.

Be illustrated in figure 3 the structural representation with reference to subcycle chamber described in the utility model; The 6th Polarization Controller 25, second band optical fiber circulator 26, second boosting optical amplifier 27, second acousto-optic frequency shifters 28, second optical fiber collimator 29, second lens 30, plane mirror 30 is comprised with reference to subcycle chamber.

The input end of the second acousto-optic frequency shifters 28 is as the input end with reference to subcycle chamber 9, and the output terminal of the 6th Polarization Controller 25 is as the output terminal with reference to subcycle 9.The output terminal of the second acousto-optic frequency shifters 28 connects the input end of the second boosting optical amplifier 27, the output terminal of the second boosting optical amplifier 27 is connected with the input end of the second band optical fiber circulator 26, first output terminal of the second band optical fiber circulator 26 connects the input end of the second optical fiber collimator 29, second output terminal of the second band optical fiber circulator 26 is connected with the input end of the 6th Polarization Controller 25, thus forms the reference subcycle chamber 9 in reference path.

The second acousto-optic frequency shifters 28 is passed through from wherein a part of low-coherent light of the 4th broadband optical fiber coupler 8 outgoing, after second boosting optical amplifier 27 and the second band optical fiber circulator 26, the second optical fiber collimator 29 is entered from the first output terminal of the second band optical fiber circulator 26, after the second lens 30, plane mirror 30 is injected from the low-coherent light of the second optical fiber collimator 29 outgoing, the low-coherent light reflected from plane mirror 30 is subsequently more successively through the second optical fiber collimator 29, first output terminal of the second band optical fiber circulator 26, the 4th broadband optical fiber coupler 8 is again entered after second output terminal and the 6th Polarization Controller 25.Balanced reference light is with reference to the gain in subcycle chamber and loss, and this process will repeat N time, and the low-coherent light of outgoing from reference subcycle chamber forms the secondary interference of respective cycle chamber level by with the low-coherent light of outgoing in measurement subcycle chamber.

Be illustrated in figure 4 the structural representation of sampling wave number drift correction unit described in the utility model; Sampling wave number drift correction unit comprises the 6th broadband optical fiber coupler 32, optical-fiber type Bragg diffraction gratings 33 and the second high bandwidth balance photodetector 34.

One of them input end of 6th broadband optical fiber coupler 32 is as the input end of sampling wave number drift correction unit 15, second high bandwidth balances the electrical signal of electrical signal as sampling wave number drift correction unit 15 of photodetector 34, the output terminal of the 6th broadband optical fiber coupler 32 is connected with the input end of optical-fiber type Bragg diffraction gratings 33, one of them input end that another one input end and second high bandwidth of the 6th broadband optical fiber coupler 32 balance photodetector 34 is connected, thus forms sampling wave number drift correction unit 15.In figure, achievement unit is divided into optical fiber, and dot-and-dash line part is circuit connecting wire.

From wherein a part of low-coherent light of the first broadband optical fiber coupler 2 outgoing after the 6th broadband optical fiber coupler 32, enter optical-fiber type Bragg diffraction gratings 33.The narrow band light of the specific wavelength reflected from optical-fiber type Bragg diffraction gratings, again through the 6th broadband optical fiber coupler 32, enters the second high bandwidth balance photodetector 34 from another input end of the 6th broadband optical fiber coupler 32.This unit utilizes optical-fiber type Bragg diffraction gratings only to carry out reflecting this characteristic for the narrow-band spectrum of specific wavelength, the reflectance spectrum signal of different frequency sweep cycle is gathered by high-speed data acquisition card, and the entirety drift that the peak location contrasting reflectance spectrum between different frequency sweep cycle carrys out calculating sampling wave number is counted, thus realize the overall correction of drifting about of wave number of sampling between different frequency sweep cycle, greatly reduce the impact of system middle width strip swept light source electronic activation signal shake on film phase measurement stability.

The signal processing flow figure of position described in the utility model phase reinforced membranes thickness measure as shown in Figure 5.First high-speed data acquisition card carries out synchronized sampling to the signal measured by measured film thickness unit and sampling wave number drift correction unit, thus obtain synchronized sampling measurement interference signal and for the overall drift-corrected narrow-band spectrum signal of wave number of sampling.The narrow-band spectrum signal utilizing signalling channel 2 to collect calculates the sampling wave number entirety drift of measuring interference signal between different frequency sweep cycle and counts, thus to drift about the correction of counting to measurement interference signal.Theory part as described above, subsequently Fourier transform, filtering of windowing carried out successively to the measurement interference signal after drift correction, remove the secondary carrier frequency amount of corresponding light circulation level and inverse Fourier transform, the measurement interference signal corresponding to the secondary plural form of circulation level of not sharing the same light can be obtained.Wherein main optical path interference signal (namely without the interference signal with reference to subcycle chamber and measurement subcycle chamber) can be regarded as the interference spectrum signal that light circulation level time is zero.And due to main optical path detection, what obtain is the interference spectrum with fixed light path difference, and the interference signal on main optical path thus can be utilized to demarcate wave numbers such as the interference signal through two sub-torus carry out.Then the interference signal solution parcel position that reciprocity wave number calibrated corresponding light circulation level is secondary is carried out linear fit mutually and is asked for non-linear position phase.In order to first the non-linear position of accurately trying to achieve film needs to use standard model I (namely not introducing the sample of similar film reflector position phase) to record the dispersion amount of excuse me, but I must be leaving now of system mutually, what utilize film sample to be measured to record subsequently corresponds to the dispersion amount of mismatch that the secondary non-linear position of circulation level of not sharing the same light deducts system mutually, finally try to achieve and be exaggerated N accurate film non-linear position phasor doubly, thus utilize above-mentioned theory model Exact Solution film thickness value.

If Fig. 6 is the actual effect schematic diagram that the non-linear position of film described in the utility model accumulates amplification mutually.After the measurement interference signal obtained this systematic survey carries out signal transacting as shown in Figure 5, N accurate film non-linear position phasor doubly can be amplified.N=1 near 1320 wave bands is respectively show in Fig. 6, the film non-linear position phasor of N=2 and N=3, the non-linear position of film obtains the amplification of corresponding light circulation level time multiple mutually, thus enhances the sensitivity (difference namely between film non-linear position phase maximal value and minimum value) of film phase measurement.

Claims (4)

1. a position phase reinforced membranes thickness measurement system, comprises broadband swept light source, the first broadband optical fiber coupler, measured film thickness unit, sampling wave number drift correction unit, high-speed data acquisition card and computing machine; Described measured film thickness unit comprises the second broadband optical fiber coupler, the 3rd broadband optical fiber coupler, the 4th broadband optical fiber coupler, the 5th broadband optical fiber coupler, the first Polarization Controller, the second Polarization Controller, the 3rd Polarization Controller, the 4th Polarization Controller, measures subcycle chamber, with reference to subcycle chamber, fibre delay line and the first high bandwidth balance photodetector;

It is characterized in that: described broadband swept light source is connected with wave number drift correction unit input end of sampling with the second broadband optical fiber coupler input end respectively by the first broadband optical fiber coupler, two output terminals of the second broadband optical fiber coupler connect the input end of the first Polarization Controller and the input end of the second Polarization Controller respectively, the output terminal of the first Polarization Controller is connected with one of them input end of the 3rd broadband optical fiber coupler, one of them output terminal of 3rd broadband optical fiber coupler connects the input end measuring subcycle chamber, the output terminal measuring subcycle chamber connects another input end of the 3rd broadband optical fiber coupler, another output terminal of 3rd broadband optical fiber coupler is connected with the input end of the 3rd Polarization Controller, and the output terminal of the 3rd Polarization Controller is connected with one of them input end of the 5th broadband optical fiber coupler, the output terminal of the second Polarization Controller is connected with one of them input end of the 4th broadband optical fiber coupler, one of them output terminal of 4th broadband optical fiber coupler connects the input end with reference to subcycle chamber, output terminal with reference to subcycle chamber connects another input end of the 4th broadband optical fiber coupler, another output terminal of 4th broadband optical fiber coupler is connected with the input end of fibre delay line, the output terminal of fibre delay line is connected with the input end of the 4th Polarization Controller, the output terminal of the 4th Polarization Controller is connected with another input end of the 5th broadband optical fiber coupler, two output terminals of the 5th broadband optical fiber coupler connect two input ends of the first high bandwidth balance photodetector respectively, electrical signal and the electrical signal of the first high bandwidth balance photodetector of sampling wave number drift correction unit are connected two input signal channels of high-speed data acquisition card respectively, and the output terminal of high-speed data acquisition card is connected with computing machine, the trigger pip output terminal of broadband swept light source is connected with high-speed data acquisition card trigger pip input end,

After the low-coherent light that broadband swept light source sends enters the first broadband optical fiber coupler, a part of light enters measured film thickness unit, and another part light enters sampling wave number drift correction unit; The low-coherent light entering measured film thickness unit is divided into two-way after the second broadband optical fiber coupler, wherein a road light enters the 3rd broadband optical fiber coupler after the first Polarization Controller, and another road light enters the 4th broadband optical fiber coupler after the second Polarization Controller; The light entering the 3rd broadband optical fiber coupler separates a part of light after the 3rd Polarization Controller, enters the 5th broadband optical fiber coupler; Another part light exported from the 3rd broadband optical fiber coupler enters the 3rd broadband optical fiber coupler for the second time after measuring subcycle chamber, the low-coherent light that second time enters the 3rd broadband optical fiber coupler is divided into two parts equally, arrives the 5th broadband optical fiber coupler respectively and enter the 3rd broadband optical fiber coupler for the third time along above-mentioned path; By that analogy, the low-coherent light entering the 3rd broadband optical fiber coupler for the N-1 time also arrives the 5th broadband optical fiber coupler along above-mentioned path and enters the 3rd broadband optical fiber coupler for the N time; Same, the light entering the 4th broadband optical fiber coupler separates a part of light successively after fibre delay line and the 4th Polarization Controller, enters the 5th broadband optical fiber coupler; Another part light exported from the 4th broadband optical fiber coupler enters the 4th broadband optical fiber coupler by reference to second time behind subcycle chamber, the low-coherent light that second time enters the 4th broadband optical fiber coupler is divided into two parts equally, arrives the 5th broadband optical fiber coupler respectively and enter the 4th broadband optical fiber coupler for the third time along above-mentioned path; By that analogy, the low-coherent light entering the 4th broadband optical fiber coupler for the N-1 time also arrives the 5th broadband optical fiber coupler along above-mentioned path and enters the 4th broadband optical fiber coupler for the N time; Above-mentioned all low-coherent lights entering the 5th broadband optical fiber coupler interfere, and interference signal detects via the first high bandwidth balance photodetector; System two unit detect the signal that obtains by high-speed data acquisition card synchronous acquisition, the Signal transmissions collected carries out data processing to the internal memory of computing machine; The trigger pip of high-speed data acquisition card is produced by broadband swept light source.

2. a kind of position according to claim 1 phase reinforced membranes thickness measurement system, is characterized in that: measure subcycle chamber and comprise the 5th Polarization Controller, the first band optical fiber circulator, the first boosting optical amplifier, the first acousto-optic frequency shifters, the first optical fiber collimator and the first lens;

The input end of the first acousto-optic frequency shifters is as the input end measuring subcycle chamber, and the output terminal of the 5th Polarization Controller is as the output terminal measuring subcycle; The output terminal of the first acousto-optic frequency shifters connects the input end of the first boosting optical amplifier, the output terminal of the first boosting optical amplifier is connected with the input end of the first band optical fiber circulator, first output terminal of the first band optical fiber circulator connects the input end of the first optical fiber collimator, second output terminal of the first band optical fiber circulator is connected with the input end of the 5th Polarization Controller, thus forms the measurement subcycle chamber in optical path;

The first acousto-optic frequency shifters is passed through from wherein a part of low-coherent light of the 3rd broadband optical fiber coupler outgoing, after first boosting optical amplifier and the first band optical fiber circulator, the first optical fiber collimator is entered from the first output terminal of the first band optical fiber circulator, after the first lens, film sample to be measured is injected from the low-coherent light of the first optical fiber collimator outgoing, the low-coherent light reflected from film sample to be measured is subsequently more successively through the first optical fiber collimator, first output terminal of the first band optical fiber circulator, the 3rd broadband optical fiber coupler is again entered after second output terminal and the 5th Polarization Controller, balancing a survey light is in the gain of measuring in subcycle chamber and loss, and this process will repeat N time, and measuring beam irradiates carrying out N time to the same lateral position of film sample to be measured, and the N realized measuring film position phase doubly amplifies.

3. a kind of position according to claim 1 phase reinforced membranes thickness measurement system, is characterized in that: comprise the 6th Polarization Controller, the second band optical fiber circulator, the second boosting optical amplifier, the second acousto-optic frequency shifters, the second optical fiber collimator, the second lens and plane mirror with reference to subcycle chamber;

The input end of the second acousto-optic frequency shifters is as the input end with reference to subcycle chamber, and the output terminal of the 6th Polarization Controller is as the output terminal with reference to subcycle; The output terminal of the second acousto-optic frequency shifters connects the input end of the second boosting optical amplifier, the output terminal of the second boosting optical amplifier is connected with the input end of the second band optical fiber circulator, first output terminal of the second band optical fiber circulator connects the input end of the second optical fiber collimator, second output terminal of the second band optical fiber circulator is connected with the input end of the 6th Polarization Controller, thus forms the reference subcycle chamber in reference path;

The second acousto-optic frequency shifters is passed through from wherein a part of low-coherent light of the 4th broadband optical fiber coupler outgoing, after second boosting optical amplifier and the second band optical fiber circulator, the second optical fiber collimator is entered from the first output terminal of the second band optical fiber circulator, after the second lens, plane mirror is injected from the low-coherent light of the second optical fiber collimator outgoing, the low-coherent light reflected from plane mirror is subsequently more successively through the second optical fiber collimator, first output terminal of the second band optical fiber circulator, the 4th broadband optical fiber coupler is again entered after second output terminal and the 6th Polarization Controller, balanced reference light is with reference to the gain in subcycle chamber and loss, and this process will repeat N time, and the low-coherent light of outgoing from reference subcycle chamber forms the secondary interference of respective cycle chamber level by with the low-coherent light of outgoing in measurement subcycle chamber.

4. a kind of position according to claim 1 phase reinforced membranes thickness measurement system, is characterized in that: sampling wave number drift correction unit comprises the 6th broadband optical fiber coupler, optical-fiber type Bragg diffraction gratings and the second high bandwidth balance photodetector;

One of them input end of 6th broadband optical fiber coupler is as the input end of sampling wave number drift correction unit, second high bandwidth balances the electrical signal of electrical signal as sampling wave number drift correction unit of photodetector, the output terminal of the 6th broadband optical fiber coupler is connected with the input end of optical-fiber type Bragg diffraction gratings, one of them input end that another one input end and second high bandwidth of the 6th broadband optical fiber coupler balance photodetector is connected, thus forms sampling wave number drift correction unit;

From wherein a part of low-coherent light of the first broadband optical fiber coupler outgoing after the 6th broadband optical fiber coupler, enter optical-fiber type Bragg diffraction gratings; The narrow band light of the specific wavelength reflected from optical-fiber type Bragg diffraction gratings, again through the 6th broadband optical fiber coupler, enters the second high bandwidth balance photodetector from another input end of the 6th broadband optical fiber coupler; This unit utilizes optical-fiber type Bragg diffraction gratings only to carry out reflecting this characteristic for the narrow-band spectrum of specific wavelength, the reflectance spectrum signal of different frequency sweep cycle is gathered by high-speed data acquisition card, and the entirety drift that the peak location contrasting reflectance spectrum between different frequency sweep cycle carrys out calculating sampling wave number is counted, thus realize the overall correction of drifting about of wave number of sampling between different frequency sweep cycle, greatly reduce the impact of system middle width strip swept light source electronic activation signal shake on film phase measurement stability.