CN117109455A - Film thickness measuring device and method - Google Patents
Film thickness measuring device and method Download PDFInfo
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- CN117109455A CN117109455A CN202311221203.9A CN202311221203A CN117109455A CN 117109455 A CN117109455 A CN 117109455A CN 202311221203 A CN202311221203 A CN 202311221203A CN 117109455 A CN117109455 A CN 117109455A
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- 238000000034 method Methods 0.000 title claims description 19
- 238000005259 measurement Methods 0.000 claims abstract description 147
- 238000000572 ellipsometry Methods 0.000 claims abstract description 108
- 230000003287 optical effect Effects 0.000 claims abstract description 52
- 238000012545 processing Methods 0.000 claims abstract description 34
- 238000001514 detection method Methods 0.000 claims abstract description 31
- 230000010287 polarization Effects 0.000 claims abstract description 28
- 238000004364 calculation method Methods 0.000 claims abstract description 20
- 238000001228 spectrum Methods 0.000 claims description 57
- 238000002310 reflectometry Methods 0.000 claims description 15
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- 238000004458 analytical method Methods 0.000 claims description 2
- 239000010408 film Substances 0.000 description 94
- 239000010409 thin film Substances 0.000 description 26
- 238000006073 displacement reaction Methods 0.000 description 6
- 239000013078 crystal Substances 0.000 description 5
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- 238000012360 testing method Methods 0.000 description 3
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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
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Abstract
The application provides a film thickness measuring device, which comprises a sample stage, wherein the film thickness measuring device further comprises: the emission end is used for emitting incident light to a sample on the sample table, the incident light is formed by converging four lasers with different wavelengths, and the emission end can adjust the incident light into linearly polarized light; the receiving end is used for receiving emergent light formed by sample reflection, comprises a polarization detection component and a detection component, realizes detection of emergent light intensity under different azimuth angles by adjusting the polarization detection component, and obtains a group of light intensity values corresponding to the wavelengths of four lasers under each azimuth angle; and the processing component is used for respectively adopting an ellipsometry calculation method and a spectroscopic measurement calculation method according to the azimuth angle and the light intensity value to obtain the film thickness and the optical parameters of the sample, and comparing the film thicknesses calculated by the ellipsometry calculation method and the spectroscopic measurement calculation method to determine the film thickness value of the sample. The measuring device provided by the application can completely cover the measuring range of the film thickness.
Description
Technical Field
The application relates to the technical field of optical measurement, in particular to a thin film thickness measuring device and a thin film thickness measuring method.
Background
The detection of the optical film mainly comprises two aspects, namely film thickness and optical constant; in actual production preparation, it is also necessary to detect uniformity of thickness distribution of the thin film. In the measurement of film thickness and optical constants, ellipsometry and spectroscopic measurement are the most widely used technologies at present, but the ellipsometry and spectroscopic measurement are different in measurement range and precision of film thickness, different methods are needed to be adopted for measurement aiming at different film thicknesses at present, and the measurement steps are complex.
In the related art, a spectrophotometer is mostly used for spectrum measurement, and a reflection (or transmission) spectrum of a thin film is measured by the spectrophotometer, so that the reflectivity and the transmissivity of the thin film are calculated, and the thickness and the optical constant of the thin film are calculated. Ellipsometry can be performed by modulating polarized light incident on and reflected by a thin film using a laser, an LED lamp, a halogen lamp, or the like as a light source, and measuring the thickness and optical constant of the thin film. The spectrum measurement has a larger measurement range, but the measurement accuracy of measuring hundreds of nanometer films is poor, and the measurement requirement cannot be met; however, for ellipsometry, due to the periodic problem of film thickness, it is impossible to measure films with multiple periodic thicknesses, and there is a problem that, although there is a wide spectrum film thickness measuring device using a muller matrix, calibration needs to be performed on each device, and errors such as installation have a large influence on the measurement result.
Therefore, it is necessary to propose a technical solution to the problem of limited measurement range when the film thickness measurement method in the related art is used for measuring the film thickness.
Disclosure of Invention
The application aims to provide a technical scheme for solving the problem that the measurement range is limited when the film thickness is measured by a film thickness measurement method in the related art.
In view of the above problems, the present application provides a thin film thickness measuring apparatus, including a sample stage for carrying a sample, the thin film thickness measuring apparatus for detecting a thin film thickness and an optical constant of the sample, the thin film thickness measuring apparatus comprising:
the emission end is used for emitting incident light to a sample on the sample table, the incident light is formed by converging four lasers with different wavelengths, and the emission end can adjust the incident light into linearly polarized light;
the receiving end is used for receiving emergent light formed by sample reflection, comprises a polarization detection component and a detection component, realizes detection of emergent light intensity under different azimuth angles by adjusting the polarization detection component, and obtains a group of light intensity values corresponding to the wavelengths of four lasers under each azimuth angle;
and the processing component is used for respectively adopting an ellipsometry calculation method and a spectroscopic measurement calculation method according to the azimuth angle and the light intensity value to obtain the film thickness and the optical parameters of the sample, and comparing the film thicknesses calculated by the ellipsometry calculation method and the spectroscopic measurement calculation method to determine the film thickness value of the sample.
Further, the transmitting end includes:
the light source assembly comprises four laser transmitters, and the laser wavelengths emitted by the laser transmitters are different;
a beam splitter group including cascaded beam splitters for combining the laser light emitted by each laser emitter into a common beam;
and a polarizing assembly including a first polarizer rotatable in azimuth for converting the common light beam into linearly polarized light and for taking the common light beam converted into the linearly polarized light as incident light.
Further, the receiving end includes:
the polarization analysis assembly comprises a second polarizer and a third polarizer, the incident light forms emergent light after being reflected by the surface of the sample, and the emergent light sequentially passes through the second polarizer and the third polarizer, and the azimuth angles of the second polarizer and the third polarizer are adjustable;
a dichroic mirror group including three dichroic mirrors, each of which is aligned with the optical axis, and partially reflects and partially transmits the outgoing light passing through the dichroic mirrors to separate light of different wavelengths;
and the detection assembly comprises four detectors, wherein three detectors respectively receive the light beams reflected by the dichroic mirrors, and the remaining one detector receives the light beam transmitted by the last dichroic mirror and is used for detecting the light intensity of the received light beam.
Further, the second polarizer employs a magneto-optical modulation device.
Further, the processing component calculates ellipsometry parameters ψ and Δ by the following formula:
2ψ＝arccos(-s 1 /s 0 )
Δ＝arccos(s 2 /s 0 ·sin2ψ)
wherein s is 0 、s 1 、s 2 Representing stokes parameters, calculated by the following formula:
s 0-i ＝4×(a 0-i -a 4-i )
wherein a is 0-i 、a 2-i 、b 2-i 、a 4-i 、b 4-i For fourier coefficients, it is calculated by the following formula:
wherein I represents the detector number, N represents the total number of azimuth angles detected, I j Representing the intensity value, W, obtained by detector i during the j-th detection j Representing the azimuth angle of the second polarizer in the jth detection;
and the processing component obtains an ellipsometry measurement value of the film thickness of the sample and a corresponding optical constant through numerical inversion calculation according to the ellipsometry parameters psi and delta.
Further, the processing component calculates total reflection coefficients of the P light component and the S light component according to the light intensities of the S polarized light and the P polarized light, and the total reflection coefficients of the P light component and the S light component are expressed by the following formula:
wherein r is 1p ，r 1s The reflection coefficient of the P component and the reflection coefficient of the S component of the primary reflection respectively for the air/film interface, r 2p ，r 2s The reflection coefficient of the P component and the reflection coefficient of the S component, which are the primary reflections at the film/substrate interface, respectively, 2δ is the phase difference between adjacent reflected light beams, and is expressed by the following formula:
where lambda is the wavelength of light, n is the complex refractive index of the film,is the angle of refraction in the film;
the processing component also calculates a spectrum measurement value of the film thickness and a corresponding optical constant according to the calculated reflectivities of the film to four wavelengths.
Further, the processing component processes the light intensity data according to an ellipsometry principle to obtain ellipsometry parameters, and obtains ellipsometry results according to the ellipsometry parameters, wherein the ellipsometry results comprise ellipsometry values of the film thickness of the sample and corresponding optical constants;
the processing component is also used for processing the light intensity data according to a spectrum measurement principle, calculating the reflectivity of the sample film to the light beams with different wavelengths, and obtaining a spectrum measurement result according to the reflectivity, wherein the spectrum measurement result comprises a spectrum measurement value of the film thickness of the sample and a corresponding optical constant;
the processing component also compares the ellipsometry measurement result with the spectrum measurement result, when the ellipsometry measurement result and the spectrum measurement result are both in a thickness period range, the ellipsometry measurement result is output by the measurement result, and if the ellipsometry measurement result and the spectrum measurement result are more than one thickness period, the spectrum measurement result is output as the measurement result.
Further, the sample stage includes:
the object carrying plane is used for carrying a sample;
the five-dimensional adjusting platform is used for guaranteeing that the plane of the sample to be measured is perpendicular to the incident plane and adjusting the center of the object carrying plane to coincide with the incident optical axis;
the electric rotating platform drives the object carrying plane to rotate, so that the sample to be measured rotates, and circumference measurement is realized.
The application also provides a film thickness measuring method based on the film thickness measuring device, which comprises the following steps:
s1, setting an incident angle of incident light according to the refractive index range of a film on a sample;
s2, placing a sample substrate on a sample stage, sequentially adjusting the polarizing axes of the first polarizer to the P component and the S component, adjusting the sample stage and a receiving end to obtain proper signals, and recording the signals as a base line;
s3, placing the sample on a sample table, and aligning the center of the sample with the center of the sample table;
s4, adjusting the first polarizer to the third polarizer, collecting light intensity data, processing the light intensity data according to an ellipsometry principle to obtain ellipsometry parameters, and obtaining ellipsometry results according to the ellipsometry parameters, wherein the ellipsometry results comprise ellipsometry values of the film thickness of the sample and corresponding optical constants;
s5, adjusting the first polarizer to the third polarizer, collecting light intensity data, processing the light intensity data according to a spectrum measurement principle, calculating the reflectivity of the sample film to light beams with different wavelengths, and obtaining a spectrum measurement result according to the reflectivity, wherein the spectrum measurement result comprises a spectrum measurement value of the film thickness of the sample and a corresponding optical constant;
s6, comparing the ellipsometry measurement result with the spectrum measurement result, outputting the ellipsometry measurement value as the measurement result when the ellipsometry measurement value and the spectrum measurement value are both in a thickness period range, and outputting the spectrum measurement value as the measurement result if the ellipsometry measurement value and the spectrum measurement value are greater than one thickness period.
Further, the step S4 includes the following steps:
s41, controlling the polarizing axis of the first polarizer to form an angle of 45 degrees with the incident surface of incident light, and controlling the polarizing axis of the third polarizer to form an angle of 0 degrees with the incident surface;
s42, adjusting the second polarizer so that the initial polarization axis position of the second polarizer forms an angle of 0 DEG with the incident surface;
s43, changing the azimuth angle of the second polarizer by adopting magneto-optical modulation, and recording light intensity data once when the azimuth angle changes theta;
s44, processing the light intensity data according to an ellipsometry principle to obtain ellipsometry parameters, and obtaining ellipsometry measurement values of the film thickness of the sample and corresponding optical constants according to the ellipsometry parameters.
According to the above description, the application combines the spectroscopic measurement and the ellipsometry measurement, can completely cover the film thickness measurement range, can realize self calibration according to the ellipsometry measurement and the spectroscopic measurement results, and improves the measurement accuracy film thickness. And an automatic displacement structure is introduced into the design of the objective table, after the thickness of one point is measured, the distribution condition of the film can be rapidly obtained according to the light intensity at different positions, and the uniformity of the film is judged.
Drawings
FIG. 1 is a schematic diagram of a film thickness measuring apparatus according to an embodiment of the present application;
FIG. 2 is a schematic diagram of the structures of a transmitting end and a receiving end in a film thickness measuring device according to an embodiment of the present application;
FIG. 3 is a schematic diagram of a second polarizer in the film thickness measuring apparatus according to the embodiment of the present application;
FIG. 4 is a schematic diagram of a sample stage according to an embodiment of the present application;
FIG. 5 is a flowchart of a method for measuring film thickness according to an embodiment of the present application.
The film thickness measuring device 100, a sample stage 11, a transmitting end 12, a receiving end 13, a processing component 14, an object carrying plane 111, a five-dimensional adjustment platform 112, an electric rotating platform 113, an electric X-axis displacement platform 114, a light source component 121, a beam splitter group 122, a polarizing component 123, an analyzing component 131, a dichroic mirror group 132, a detecting component 133, a first polarizer 1231, a second polarizer 1311, a third polarizer 1312, a magneto-optical crystal 1311a and a controller 1311b.
Detailed Description
The present application will be described in detail below with reference to the specific embodiments shown in the drawings, but these embodiments are not limited to the present application, and structural, method, or functional modifications made by those skilled in the art based on these embodiments are included in the scope of the present application.
As shown in fig. 1, the present application provides a film thickness measuring device 100, which includes a sample stage 11, the sample stage 11 is used for carrying a sample, and the film thickness measuring device 100 is used for detecting the film thickness and optical constants of the sample. The film thickness measuring apparatus 100 further includes:
an emission end 12, the emission end 12 is used for emitting incident light to the sample on the sample stage 11, the incident light is formed by converging four laser beams with different wavelengths, and the emission end 12 can adjust the incident light into linearly polarized light;
the receiving end 13 is used for receiving emergent light formed by the reflection of the sample, the receiving end 13 comprises a polarization detection component 131 and a detection component 133, the polarization detection component 131 is adjusted to realize the detection of emergent light intensity under different azimuth angles, and a group of light intensity values corresponding to the wavelengths of four lasers are obtained under each azimuth angle;
the processing component 14 obtains the film thickness and the optical parameters of the sample by adopting the calculation methods of ellipsometry and spectrum measurement according to the azimuth angle and the light intensity value, and compares the film thickness calculated by the two methods to determine the film thickness value of the sample.
According to the above description, the embodiment of the application provides a thin film measuring device combining ellipsometry and spectroscopic measurement. The device provided by the embodiment of the application can measure parameters required by an ellipsometry measurement mode and a spectrum measurement mode at the same time, ensures that calculation parameters adopted by the ellipsometry measurement mode and the spectrum measurement mode are obtained by measurement under the same condition, can automatically judge the film thickness range by comparing calculation results of the ellipsometry measurement mode and the spectrum measurement mode, and can automatically verify the measurement result, thereby solving the problem that the ellipsometry measurement mode can have multiple solutions for measuring films with multiple period thicknesses.
As shown in fig. 2, as an alternative implementation, the emitting end 12 includes a light source assembly 121, a beam splitter group 122, and a polarizing assembly 123.
The light source assembly 121 includes four laser emitters, and the laser wavelengths emitted by the laser emitters are different. The thin film thickness measuring device 100 provided by the embodiment of the application adopts laser as a light source, has good collimation characteristic, does not need to adopt a lens and other structures, reduces the influence of chromatic dispersion on detection, and improves the detection precision.
Beam splitter group 122 includes cascaded beam splitters that combine the laser light emitted by each laser emitter into a common beam.
The polarizing assembly 123 comprises a first polarizer 1231, the first polarizer 1231 being rotatable in azimuth for converting the common light beam into linearly polarized light, which is incident on the sample surface.
As an alternative implementation, the receiving end 13 includes a polarization analyzing assembly 131, a dichroic mirror group 132, and a detecting assembly 133.
The polarization detection assembly 131 comprises a second polarizer 1311 and a third polarizer 1312, incident light is reflected by the surface of the sample to form emergent light, and the emergent light sequentially passes through the second polarizer 1311 and the third polarizer 1312, and the azimuth angles of the second polarizer 1311 and the third polarizer 1312 are adjustable;
the dichroic mirror group 132 includes three dichroic mirrors, each of which is aligned with the optical axis, and partially reflects and partially transmits the outgoing light passing through the dichroic mirrors to separate light of different wavelengths;
the detecting assembly 133 includes four detectors, three of which receive the light beams reflected by the respective dichroic mirrors, and the remaining one of which receives the light beam transmitted from the last dichroic mirror, for detecting the light intensity of the received light beam.
The processing component 14 can respectively adopt the calculation methods of ellipsometry and spectral measurement according to the azimuth angle and the light intensity value to obtain the film thickness and the optical parameter of the sample, and compare the film thicknesses calculated by the two methods to determine the film thickness value of the sample and the optical parameter corresponding to the film thickness value.
Specifically, for ellipsometry, the change of the polarization state of reflected light is measured through the same spectrum, if linear polarized light with a known polarization direction is reflected from the surface of a sample, the reflected light becomes elliptical polarized light, the polarization state of the elliptical polarized light depends on the incident angle, the incident direction of the linear polarized light and the reflection characteristic of the surface of the sample, two ellipsometry parameters ψ and Δ can be determined in ellipsometry, and the optical constants of the materials and the film thickness of the sample can be obtained by using the ellipsometry parameters ψ and Δ. Wherein, for the ellipsometry parameter ψ, tan ψ represents the ratio of the amplitude after the p light and s light reflection, and Δ represents the variation of the p light and s light phase difference.
As an alternative implementation, the processing component 14 may calculate the ellipsometry parameters ψ and Δ according to the following manner.
S11, adjusting the azimuth angle of the second polarizer 1311 piece to a j-th preset angle W j Each detector obtains a corresponding light intensity value I at the azimuth angle j Each detector obtains N light intensity values by detecting the light intensity at N different azimuth angles.
S12, constructing a light intensity expression formula, wherein the light intensity expression formula is as follows:
I i ＝a 0-i +a 2-i cos 2A+b 2-i sin2A+a 4-i cos4A+b 4-i sin4A
wherein I is i For the intensity of light obtained by different detectors, a 0-i 、a 2-i 、b 2-i 、a 4-i 、b 4-i Is a fourier coefficient;
s13, aiming at the ith detector, calculating Fourier coefficients according to a discrete periodic function Fourier coefficient formula according to the light intensity values corresponding to N different azimuth angles obtained through detection of the ith detector, wherein the discrete periodic function Fourier coefficient formula is expressed as follows:
wherein I represents the detector number, N represents the total number of azimuth angles detected, I j Representing the intensity value, W, obtained by detector i during the j-th detection j Representing the azimuth of the second polarizer 1311 in the jth detection.
S14, calculating Stokes parameters according to the Fourier coefficients. The stokes parameter can be calculated by the following formula:
s 0-i ＝4×(a 0-i -a 4-i )
and S15, calculating to obtain ellipsometry parameters psi and delta according to Stokes parameters.
The ellipsometry parameters ψ and Δ can be calculated by the following formula:
2ψ＝arccos(-s 1 /s 0 )
Δ＝arccos(s 2 /s 0 ·sin2ψ)
when only a single wavelength is used, the polarization instrument is an incomplete polarization instrument, only 3 Stokes parameters can be obtained, the positive and negative of delta cannot be judged, and meanwhile, the optical constants cannot be obtained by considering the measurement, the corresponding errors of the photoelectric detector and the like. The application adopts four-wavelength incident light formed by four lasers, and can obtain a group of ellipsometry parameters psi and delta for each wavelength, so that four groups of ellipsometry parameters psi and delta can be obtained. According to each group of ellipsometry parameters psi and delta, parameters such as film thickness, optical constant and the like of a sample to be measured can be obtained through numerical inversion calculation. And (3) carrying out mean processing on the film thickness calculated according to numerical inversion of four sets of ellipsometry parameters, and taking the mean value of the film thickness as a measurement result of the film thickness of the sample. Similarly, the optical constants calculated according to the numerical inversion of the four sets of ellipsometry parameters are processed as an average value, and the average value of the optical constants is used as an optical constant measurement result of the sample film.
As can be seen from the above description, the thin film thickness measuring device 100 according to the embodiment of the present application can obtain parameters such as the thin film thickness and the optical constant of the sample by using an ellipsometry method.
The thin film thickness measuring device 100 provided by the embodiment of the application can also obtain parameters such as the thin film thickness and the optical constant of a sample by utilizing a spectrum measuring mode.
As an alternative implementation manner, in spectrum measurement, measurement calibration needs to be performed on a film substrate, optical axes of a polarizing device are located on the same plane during calibration, light intensities of S polarized light and P polarized light are measured respectively, then a film sample is put on the film sample to obtain corresponding light intensity information, the light intensity information is obtained by a multi-beam flat plate interference theory, and total reflection coefficients of a P light component and an S light component are as follows:
wherein r is 1p ，r 1s The reflection coefficient of the P component and the reflection coefficient of the S component of the primary reflection respectively for the air/film interface, r 2p ，r 2s Respectively at the film/substrate interfaceThe reflection coefficient of the P component and the reflection coefficient of the S component of the primary reflection. 2 delta is the phase difference between adjacent reflected light beams and can be expressed by the following formula:
where lambda is the wavelength of light, n is the complex refractive index of the film,the thickness and optical constant of the film can be calculated by substituting the reflectivities of the four wavelengths obtained by measurement and calculation for the refraction angle in the film.
As can be seen from the above description, the thin film thickness measuring device 100 according to the embodiment of the present application can obtain the thin film thickness and the optical constant of the sample by one measurement and simultaneously using ellipsometry and spectrum measurement, and verify the measurement result according to the two methods, thereby improving the accuracy of measurement and the convenience of measurement. In this way, the film thickness measuring device 100 provided by the embodiment of the application can cover the thickness range of the complete film measurement, and can meet the film measurement requirement.
Specifically, in the case of measuring a film thickness of several hundred nanometers or more, the result of the spectroscopic measurement can be used as the film thickness. In the case of measuring a film thickness of several hundred nanometers or less, the result of ellipsometry may be taken as the thickness of the sample film.
And for the case that the ellipsometry can have multiple solutions due to the film periodicity problem, the application combines the spectroscopic measurement and the ellipsometry to realize self-calibration. Since the cycle number of the thickness is known, when the measured value of ellipsometry (hereinafter abbreviated as ellipsometry) and the measured value of spectroscopic measurement (hereinafter abbreviated as spectroscopic measurement) are both within one thickness cycle range, the measured result outputs the ellipsometry, and if the measured result is greater than one thickness cycle, the spectroscopic measurement is outputted as the measured result. In this way, an uncertainty value of the film thickness can be eliminated, and the film thickness measurement accuracy can be improved.
As an alternative implementation, in the thin film thickness measurement apparatus 100 provided in the embodiment of the present application, the second polarizer 1311 may use a magneto-optical modulation device.
In particular, a magneto-optical modulation device is shown in fig. 3. The magneto-optical modulation device includes a magneto-optical crystal 1311a and a controller 1311b.
The working principle of the magneto-optical modulation device is as follows: if a linearly polarized light propagates along the axial direction of the magneto-optical crystal, the controller is used for adjusting the voltage wound on the magneto-optical crystal, so that a direct-current magnetic field is generated along the optical axis direction, the polarization plane of the emergent light rotates by an angle W, the phenomenon is called magneto-optical effect, and the magneto-optical effect meets the following rules:
W＝VLB
wherein W is the rotation angle of the polarization plane of the light wave, V is Verdet constant, L is the length of the magneto-optical crystal, and B is the magnetic induction intensity. The current on the coil is changed by the controller to change the magnetic induction intensity B, so that the rotation angle W of the polarization plane of the light wave is enabled.
According to the above description, the present application controls the second polarizer 1311 by magneto-optical modulation, and reduces moving devices, so that the stability of operation can be increased and the measurement accuracy can be improved. In addition, the magneto-optical modulation mode is adopted, so that the azimuth angle adjustment is more convenient and quicker, and the measurement efficiency can be improved.
As an alternative implementation, in the embodiment of the present application, the design of the sample stage 11 introduces an automatically controlled X-axis (or Y-axis) and rotation structure, and in the actual test, each point of the film is moved to the incident surface by controlling the X-axis (or Y-axis) displacement and the rotation of the object carrying plane 111, so as to implement the film thickness measurement at each position.
The structure of the sample stage 11 is as shown in fig. 4, and the sample stage 11 includes: a carrying plane 111, a five-dimensional adjustment platform 112, an electric rotating platform 113 and an electric X-axis displacement platform 114.
Wherein the carrier plane 111 is used for carrying the sample.
The five-dimensional adjustment platform 112 is used for guaranteeing that the plane of the sample to be measured is perpendicular to the incident plane, and adjusting the center of the object carrying plane 111 to coincide with the incident optical axis.
The electric rotating platform 113 drives the object carrying plane 111 to rotate, so that the sample to be measured rotates, and circumference measurement is achieved.
The electric X-axis displacement platform 114 drives the object carrying plane 111 to move back and forth (or left and right), so that measurement at different positions from the center is realized.
As an alternative implementation, the thin film thickness measurement apparatus 100 provided in an embodiment of the present application includes a thin film uniformity test mode. In the film uniformity test mode, the device such as the five-dimensional adjustment platform 112, the electric rotation platform 113, the electric X-axis displacement platform 114 and the like are mutually matched after the zero position is automatically adjusted and the detection area is set, so that the sample stage 11 is driven to move, and therefore the film thickness measuring device 100 can scan each point in the detection area, record data, display film thickness distribution and calculate uniformity.
As an alternative implementation, the polarization axes of the first, second and third polarizers 1312 may be adjusted to the S-light plane, and the total reflectance of the S-light component may be obtained by using the formula, where the total reflectance is only related to the film thickness under the conditions that the optical constants (generally, the optical constants of the same sample are unchanged by default) and the wavelengths are known, so that the thickness distribution of the film can be rapidly obtained according to the change of the reflectance.
In order to further explain the thin film thickness measuring apparatus 100 according to the embodiment of the present application, as shown in fig. 5, the present application also provides a thin film thickness measuring method based on the thin film thickness measuring apparatus 100 described above.
First, a plane formed by incident light and a contact surface normal is defined as an incident surface, and a plane formed by reflected light and a contact surface normal vector is defined as a reflecting surface. In the discussion of polarized light, the vertical component S and the horizontal component P of the electric field are for both planes.
The film thickness measuring method comprises the following steps:
s1, setting the incident angle of incident light according to the refractive index range of the film on the sample.
S2, placing a sample substrate on the sample stage 11, sequentially adjusting the polarization axes of the first polarizer 1312 to the P component and the S component, adjusting the sample stage 11 and the receiving end 13, obtaining proper signals, and recording the signals as a base line.
S3, placing the sample on the sample table 11, and aligning the center of the sample with the center of the sample table 11.
S4, adjusting the first polarizer 1312 to the third polarizer 1312, collecting light intensity data, processing the light intensity data according to an ellipsometry principle to obtain ellipsometry parameters, and obtaining ellipsometry results according to the ellipsometry parameters, wherein the ellipsometry results comprise ellipsometry values of the film thickness of the sample and corresponding optical constants.
The step S4 includes the following steps:
s41, the polarization axis of the first polarizer 1231 is controlled to form an angle of 45 ° with the incident plane of the incident light, and the polarization axis of the third polarizer 1312 forms an angle of 0 ° with the incident plane.
S42, adjusting the second polarizer 1311 such that the initial polarization axis position of the second polarizer 1311 forms an angle of 0 ° with the incident surface.
S43, changing the azimuth angle of the second polarizer 1311 by magneto-optical modulation, and recording light intensity data once when the azimuth angle changes by θ.
S44, processing the light intensity data according to an ellipsometry principle to obtain ellipsometry parameters, and obtaining ellipsometry measurement values of the film thickness of the sample and corresponding optical constants according to the ellipsometry parameters.
S5, adjusting the first polarizer 1312 to the third polarizer 1312, collecting light intensity data, processing the light intensity data according to a spectrum measurement principle, calculating the reflectivity of the sample film to light beams with different wavelengths, and obtaining a spectrum measurement result according to the reflectivity, wherein the spectrum measurement result comprises a spectrum measurement value of the film thickness of the sample and a corresponding optical constant.
The step S5 includes the following steps:
and S51, adjusting the polarization axes of the first polarizer 1312 to the third polarizer into a p component and an S component in sequence.
S52, recording and processing light intensities corresponding to the four wavelengths, and calculating the reflectivity of the film to the light beams with the four wavelengths according to the light intensity by using a multi-beam flat-plate interference theory.
S53, calculating a spectrum measurement value of the film thickness and a corresponding optical constant according to the reflectances of the four wavelength light beams.
S6, comparing the ellipsometry measurement result with the spectrum measurement result, outputting the ellipsometry measurement value by the measurement result when the ellipsometry measurement value and the spectrum measurement value are both in a thickness period range, and outputting the spectrum measurement value as the measurement result if the distance between the ellipsometry measurement value and the spectrum measurement value is larger than one thickness period.
The above disclosure is illustrative of the preferred embodiments of the present application, but it should not be construed as limiting the scope of the application as will be understood by those skilled in the art: changes, modifications, substitutions, combinations, and simplifications may be made without departing from the spirit and scope of the application and the appended claims, and equivalents may be substituted and still fall within the scope of the application.
Claims (10)
1. A film thickness measuring apparatus comprising a sample stage for carrying a sample, the film thickness measuring apparatus for detecting a film thickness and an optical constant of the sample, the film thickness measuring apparatus comprising:
the emission end is used for emitting incident light to a sample on the sample table, the incident light is formed by converging four lasers with different wavelengths, and the emission end can adjust the incident light into linearly polarized light;
the receiving end is used for receiving emergent light formed by the reflection of the sample and comprises a polarization detection component and a detection component, the detection of the emergent light intensity under different azimuth angles is realized by adjusting the polarization detection component, and a group of light intensity values corresponding to the wavelengths of four lasers are obtained under each azimuth angle;
and the processing component is used for respectively adopting an ellipsometry calculation method and a spectrum measurement calculation method according to the azimuth angle and the light intensity value to obtain the film thickness and the optical parameters of the sample, and comparing the film thickness calculated by the ellipsometry calculation method and the spectrum measurement calculation method to determine the film thickness value of the sample.
2. A film thickness measuring apparatus according to claim 1, wherein,
the transmitting end comprises:
the light source assembly comprises four laser transmitters, and the laser wavelengths emitted by the laser transmitters are different;
a beam splitter group including cascaded beam splitters, which combine the laser emitted by each of the laser emitters into a common beam;
and a polarizing assembly including a first polarizer rotatable in azimuth for converting the common light beam into linearly polarized light and taking the common light beam converted into the linearly polarized light as incident light.
3. A film thickness measuring apparatus according to claim 1, wherein,
the receiving end comprises:
the polarization analysis assembly comprises a second polarizer and a third polarizer, wherein the incident light is reflected by the surface of the sample to form emergent light, and the emergent light sequentially passes through the second polarizer and the third polarizer, and the azimuth angles of the second polarizer and the third polarizer are adjustable;
a dichroic mirror group including three dichroic mirrors, each of which is aligned with an optical axis, and through which the outgoing light is partially reflected and partially transmitted to separate light of different wavelengths;
and the detection assembly comprises four detectors, wherein three detectors respectively receive the light beams reflected by the dichroic mirrors, the remaining one detector receives the light beam transmitted by the last dichroic mirror, and the detectors are used for detecting the light intensity of the received light beam.
4. A film thickness measuring apparatus according to claim 3, wherein,
the second polarizer adopts a magneto-optical modulation device.
5. A film thickness measuring apparatus according to claim 1, wherein,
the processing component calculates ellipsometry parameters ψ and Δ by the following formula:
2ψ＝arccos(-s 1 /s 0 )
Δ＝arccos(s 2 /s 0 ·sin 2ψ)
wherein s is 0 、s 1 、s 2 Representing stokes parameters, calculated by the following formula:
s 0-i ＝4×(a 0-i -a 4-i )
wherein a is 0-i 、a 2-i 、b 2-i 、a 4-i 、b 4-i For fourier coefficients, it is calculated by the following formula:
wherein I represents the detector number, N represents the total number of azimuth angles detected, I j Representing the intensity value, W, obtained by detector i during the j-th detection j Representing the azimuth angle of the second polarizer in the jth detection;
and the processing component obtains an ellipsometry measurement value of the film thickness of the sample and a corresponding optical constant through numerical inversion calculation according to the ellipsometry parameters psi and delta.
6. A film thickness measuring apparatus according to claim 1, wherein,
the processing component also calculates a total reflection coefficient of the P light component and the S light component from the light intensities of the S polarized light and the P polarized light, the total reflection coefficient of the P light component and the S light component being expressed by the following formula:
wherein r is 1p ，r 1s The reflection coefficient of the P component and the reflection coefficient of the S component of the primary reflection respectively for the air/film interface, r 2p ，r 2s The reflection coefficient of the P component and the reflection coefficient of the S component, which are the primary reflections at the film/substrate interface, respectively, 2δ is the phase difference between adjacent reflected light beams, and is expressed by the following formula:
where lambda is the wavelength of light, n is the complex refractive index of the film,is the angle of refraction in the film;
the processing component also calculates a spectrum measurement value of the film thickness and a corresponding optical constant according to the calculated reflectivity of the film to four wavelengths.
7. A film thickness measuring apparatus according to claim 1, wherein,
the processing component processes the light intensity data according to an ellipsometry principle to obtain ellipsometry parameters, and obtains ellipsometry results according to the ellipsometry parameters, wherein the ellipsometry results comprise ellipsometry values of the film thickness of the sample and corresponding optical constants;
the processing component is used for processing the light intensity data according to a spectrum measurement principle, calculating the reflectivity of the sample film to light beams with different wavelengths, and obtaining a spectrum measurement result according to the reflectivity, wherein the spectrum measurement result comprises a spectrum measurement value of the film thickness of the sample and a corresponding optical constant;
the processing component is also used for comparing the ellipsometry measurement result with the spectrum measurement result, when the ellipsometry measurement result and the spectrum measurement result are both in a thickness period range, the ellipsometry measurement result is output by the measurement result, and if the ellipsometry measurement result and the spectrum measurement result are more than one thickness period, the spectrum measurement value is output as the measurement result.
8. The film thickness measurement device of claim 1, wherein the sample stage comprises:
the object carrying plane is used for carrying a sample;
the five-dimensional adjusting platform is used for guaranteeing that the plane of the sample to be measured is perpendicular to the incident plane and adjusting the center of the object carrying plane to coincide with the incident optical axis;
the electric rotating platform drives the object carrying plane to rotate, so that the sample to be measured rotates, and circumference measurement is realized.
9. A film thickness measuring method, characterized in that the method is performed based on the film thickness measuring device according to any one of claims 1 to 8, the method comprising the steps of:
s1, setting an incident angle of incident light according to the refractive index range of a film on a sample;
s2, placing a sample substrate on a sample stage, sequentially adjusting the polarizing axes of the first polarizer to the P component and the S component, adjusting the sample stage and a receiving end to obtain proper signals, and recording the signals as a base line;
s3, placing the sample on a sample table, and aligning the center of the sample with the center of the sample table;
s4, adjusting the first polarizer to the third polarizer, collecting light intensity data, processing the light intensity data according to an ellipsometry principle to obtain ellipsometry parameters, and obtaining ellipsometry results according to the ellipsometry parameters, wherein the ellipsometry results comprise ellipsometry measurement values of the film thickness of the sample and corresponding optical constants;
s5, adjusting the first polarizer to the third polarizer, collecting light intensity data, processing the light intensity data according to a spectrum measurement principle, calculating the reflectivity of a sample film to light beams with different wavelengths, and obtaining a spectrum measurement result according to the reflectivity, wherein the spectrum measurement result comprises a spectrum measurement value of the film thickness of the sample and a corresponding optical constant;
s6, comparing the ellipsometry measurement result with the spectrum measurement result, outputting the ellipsometry measurement value as a measurement result when the ellipsometry measurement value and the spectrum measurement value are both in a thickness period range, and outputting the spectrum measurement value as a measurement result if the thickness period between the ellipsometry measurement value and the spectrum measurement value is larger than one thickness period.
10. The method for measuring a film thickness according to claim 9, wherein,
the step S4 includes the following steps:
s41, controlling the polarizing axis of the first polarizer to form an angle of 45 degrees with the incident surface of incident light, and controlling the polarizing axis of the third polarizer to form an angle of 0 degrees with the incident surface;
s42, adjusting the second polarizer so that the initial polarization axis position of the second polarizer forms an angle of 0 DEG with the incident surface;
s43, changing the azimuth angle of the second polarizer by adopting magneto-optical modulation, and recording light intensity data once when the azimuth angle changes theta;
s44, processing the light intensity data according to an ellipsometry principle to obtain ellipsometry parameters, and obtaining ellipsometry measurement values of the film thickness of the sample and corresponding optical constants according to the ellipsometry parameters.
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| CN202311221203.9A CN117109455A (en) | 2023-09-20 | 2023-09-20 | Film thickness measuring device and method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117760323A (en) * | 2024-02-22 | 2024-03-26 | 肇庆学院 | Device and method for detecting copper thickness uniformity of ultra-thick copper circuit board of new energy automobile |
| CN117928399A (en) * | 2024-03-22 | 2024-04-26 | 中国空气动力研究与发展中心超高速空气动力研究所 | Coaxial thermocouple insulating layer thickness measuring device and method based on polarized light imaging |
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2023
- 2023-09-20 CN CN202311221203.9A patent/CN117109455A/en not_active Withdrawn
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117760323A (en) * | 2024-02-22 | 2024-03-26 | 肇庆学院 | Device and method for detecting copper thickness uniformity of ultra-thick copper circuit board of new energy automobile |
| CN117760323B (en) * | 2024-02-22 | 2024-04-26 | 肇庆学院 | Device and method for detecting copper thickness uniformity of ultra-thick copper circuit board of new energy automobile |
| CN117928399A (en) * | 2024-03-22 | 2024-04-26 | 中国空气动力研究与发展中心超高速空气动力研究所 | Coaxial thermocouple insulating layer thickness measuring device and method based on polarized light imaging |
| CN117928399B (en) * | 2024-03-22 | 2024-05-28 | 中国空气动力研究与发展中心超高速空气动力研究所 | Coaxial thermocouple insulating layer thickness measuring device and method based on polarized light imaging |
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Application publication date: 20231124 |