Method and apparatus for measuring the thickness of multilayer thin films

Abstract

This invention provides a method and apparatus for measuring the thickness of multilayer thin films. The method includes the following steps: using the sample surface as the initial zero point, controlling the sample and optical detection module to approach each other at nanoscale steps along the Z-axis, collecting reflected light intensity information at each Z-axis height position to form a light intensity-z coordinate curve; analyzing the light intensity-z coordinate curve, extracting the peak position of the light intensity-z coordinate curve, and calibrating the peak position as the physical interface between each film layer; moving sequentially along the Z-axis to each physical interface, collecting the elliptic spectrum curve at each physical interface; obtaining the material information of each film layer, and constructing an elliptic model of each physical interface based on the material parameters of each film layer and the physical interface information; inputting the collected elliptic spectrum curve into the corresponding elliptic model, and calculating the thickness of each film layer. This invention has the beneficial effects of high interface positioning accuracy and accurate film thickness measurement, and can accurately measure the film thickness of ultrathin multilayer films.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit technology, and in particular to a method and apparatus for measuring the thickness of multilayer thin films. Background Technology

[0002] In semiconductor manufacturing, thin film thickness monitoring is crucial throughout core processes such as semiconductor mask fabrication and wafer processing, serving as a key quality control line to ensure the yield of final products. As the feature size of semiconductor devices continues to shrink to the nanometer scale, the structure of the film to be measured becomes increasingly complex, often involving multi-layer ultrathin film stacks. Furthermore, the optical constants (refractive index n, extinction coefficient k) between adjacent layers may be highly similar, posing a significant challenge to the accurate measurement of film thickness.

[0003] Currently, the mainstream thin film thickness measurement technologies in the industry mainly include spectroscopic ellipsometers and white light interferometry. Spectroscopic ellipsometers obtain the thin film thickness by measuring the polarization state change (Psi and Δ parameters) of reflected light and combining this with optical model inversion. This method is highly dependent on the accuracy of the optical model. When the film to be measured is a multilayer ultrathin structure, especially when the optical constants of adjacent layers are similar, traditional optical models can only obtain the overall information after multilayer coupling, making it difficult to effectively distinguish the interfaces between layers. When solving for the thickness parameters of multilayer thin films, model construction is difficult, and the spectral data inversion process suffers from severe ill-conditioned inverse problems (i.e., multiple solutions), making it difficult to guarantee the uniqueness and robustness of the measurement results, and significantly reducing measurement accuracy. White light interferometry uses the coherence peaks of the interference spectrum to locate the film interface. Since the optical path difference generated by ultrathin layers (usually less than 50 nm thick) is smaller than the coherence length of the light source, this method is difficult to effectively measure ultrathin layers and has a significant measurement blind zone.

[0004] Therefore, for ultrathin multilayer film systems, there is an urgent need to provide a method for measuring the thickness of multilayer thin films with higher detection accuracy. Summary of the Invention

[0005] The purpose of this invention is to provide a method and apparatus for measuring the thickness of multilayer thin films, so as to achieve high-precision measurement of the thickness of ultrathin multilayer films.

[0006] To achieve the above objectives, the present invention provides a method for measuring the thickness of a multilayer thin film, comprising the following steps: Using the sample surface as the initial zero point, the sample and the optical detection module are controlled to approach each other at a nanoscale step along the Z-axis, and the reflected light intensity information is collected at each Z-axis height position to form a light intensity-Z coordinate curve. Analyze the light intensity-z coordinate curve, extract the peak position of the light intensity-z coordinate curve, and mark the peak position as the physical interface between each film layer; Move sequentially along the Z-axis to each physical interface and collect the elliptic spectrum curves at each physical interface; Obtain material information for each membrane layer, and construct elliptic models of each physical interface based on the material parameters and physical interface information of each membrane layer. The collected elliptic spectrum curves are input into the corresponding elliptic model to calculate the thickness of each film layer.

[0007] In one embodiment, the step of obtaining material information for each film layer and constructing an elliptic model of each physical interface based on the material parameters and physical interface information of each film layer includes the following steps: Calculate the Z-axis height difference between the current physical interface and its adjacent physical interface below it, and mark the obtained Z-axis height difference as the initial thickness of the current film layer; Search the material library to obtain the initial material parameters for the corresponding membrane layer; Based on the physical interface information, initial thickness, initial refractive index, and initial extinction coefficient, an elliptic model of the current physical interface is constructed using a standard elliptic model.

[0008] In one embodiment, the step of inputting the acquired elliptic spectral curves into the corresponding elliptic model and calculating the thickness of each film layer includes: Input the collected elliptic spectrum curves into the elliptic model of the corresponding physical interface; The thickness of the film is obtained by nonlinear regression of the ellipsoidal spectral curve based on the ellipsoidal model and the Levenberg-Marquardt algorithm.

[0009] In one embodiment, the method further includes the step of performing confocal filtering on the reflected light to filter out unfocused light.

[0010] In one embodiment, the following steps are also included: The entire sample is scanned along the x-axis and y-axis directions to obtain the thickness of each film layer at different positions in the xY plane, generating a sample film layer thickness distribution map.

[0011] In one embodiment, The step size for controlling the sample to move closer to the optical detection module along the Z-axis is no greater than 1 nm. And / or, The scanning step size for scanning the sample along the x-axis and y-axis is no greater than 100 nm.

[0012] The aforementioned method for measuring the thickness of multilayer thin films involves collecting reflected light intensity information at different Z-axis height positions at the nanoscale to form a light intensity-z coordinate curve. The peak position of the light intensity-z coordinate curve is extracted and calibrated as the physical interface between each film layer. Furthermore, ellipsoidal spectral curves at each physical interface are collected, and ellipsoidal models of each physical interface are constructed based on the physical interface information and material parameters. Finally, the collected ellipsoidal spectral curves are input into the corresponding ellipsoidal models to calculate the thickness of each film layer. This multilayer thin film thickness measurement method utilizes the physical variation of reflected light intensity with Z-axis height. By identifying the light intensity peak, the physical interfaces between film layers are calibrated. The location of the physical interfaces does not rely on optical model inversion. Even for adjacent film layers with similar optical constants, accurate peeling and calibration can be achieved through spatial dimension response changes. The film interface positioning accuracy is high. Furthermore, the Z-axis scanning uses nanoscale step scanning, achieving nanometer-level resolution, which can effectively measure the thickness of ultrathin thin film layers. It can also accurately calibrate physical interfaces for various ultrathin and complex film systems such as mask substrates, mask plates, and wafer processing. Further, based on the accurate physical interface positioning results and multidimensional ellipsometry data, accurate initial boundary information and rich constraints are available when solving for thickness, effectively reducing the ambiguity (i.e., ill-conditioned inverse problem) in the optical model inversion process, effectively ensuring the uniqueness and robustness of the measurement results, and significantly improving measurement accuracy.

[0013] In summary, the above-mentioned method for measuring the thickness of multilayer thin films solves the technical problems of difficult interface positioning, insufficient measurement capability of ultrathin layers, and strong inversion ill-conditioning of traditional optical measurement methods by introducing high-precision scanning at the Z-axis nanoscale and joint analysis of multidimensional spectral data. It has the beneficial effects of high interface positioning accuracy and accurate film thickness measurement, and can accurately measure the film thickness of ultrathin multilayer films.

[0014] On the other hand, the present invention also provides a multilayer thin film thickness measurement device, comprising: an ellipsometer and a PZT driver. The ellipsometer includes an optical detection module, a sample stage, and a processor. The sample stage is located below the optical detection module and is used to support the sample to be tested. The PZT driver is connected to the optical detection module and / or the sample stage and is used to drive the sample stage and the optical detection module to step closer along the Z-axis. The optical detection module is used to detect the reflected light intensity information of the sample at different Z-axis height positions and the ellipsometric spectral curves at each physical interface of the sample. The processor is used to calibrate the physical interfaces between each film layer according to the reflected light intensity information of the sample at different Z-axis height positions and to calculate the thickness of each film layer according to the ellipsometric spectral curves at each physical interface.

[0015] The aforementioned multilayer thin film thickness measuring device is used to implement the aforementioned multilayer thin film thickness measuring method. This device can accurately calibrate the physical interfaces between the layers of the multilayer film and accurately measure the thickness of the ultrathin multilayer film.

[0016] In one embodiment, the ellipsometer further includes an aperture plate disposed in the detection optical path of the optical detection module for confocal filtering of reflected light and filtering out unfocused light.

[0017] In one embodiment, the movement step of the PZT driver is no greater than 1 nm.

[0018] In one embodiment, the step size of the sample stage moving along the x-axis and y-axis is no greater than 100 nm. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the principle of a multilayer thin film thickness measurement method according to one embodiment. Figure 2 This is a schematic diagram of the light intensity-z coordinate curve acquired by Z-axis scanning of a sample in one embodiment. Detailed Implementation

[0020] The present invention will be described more clearly and completely by way of embodiments and in conjunction with the accompanying drawings, but the present invention is not limited to the scope of the following embodiments.

[0021] This invention provides a method and apparatus for measuring the thickness of multilayer thin films. This method and apparatus offer advantages such as high accuracy in locating film interfaces and precise film thickness measurement. It can accurately measure the thickness of ultrathin multilayer films and can be used for film thickness measurement in various ultrathin multilayer film systems. It can also accurately measure the thickness of various ultrathin and complex film systems, such as mask substrates, mask plates, and wafer processing, meeting the high-precision film thickness measurement application requirements in the semiconductor field. For ease of explanation, the following embodiment uses the application of the multilayer thin film thickness measurement method and apparatus of this invention to measure the film thickness of a binary mask substrate comprising two film layers: a chromium layer and a photoresist layer.

[0022] Please see Figure 1 One embodiment of a multilayer thin film thickness measurement method includes the following steps: Step S11: Using the sample surface as the initial zero point, control the sample and the optical detection module to approach each other at a nanoscale step along the Z-axis, and collect the reflected light intensity information at each Z-axis height position to form a light intensity-Z coordinate curve.

[0023] Specifically, the sample is placed on the sample stage, with the sample surface as the initial zero point Z0. The sample stage is controlled to move upward along the Z-axis in nanoscale steps, or the optical detection module is controlled to move downward along the Z-axis in nanoscale steps. This brings the sample and the optical detection module closer together in nanoscale steps along the Z-axis, changing the axial position of the beam waist in the multilayer thin film under test. At each Z-axis height position, the reflected light intensity is collected, and the light intensity data at all Z-axis positions are recorded to form a light intensity-Z coordinate curve. Preferably, in one embodiment, the step size for controlling the sample and the optical detection module to move closer together along the Z-axis is no greater than 1 nm. This embodiment uses nanoscale Z-axis scanning, which can achieve a Z-axis scanning resolution of 1 nm or less, and can effectively measure ultrathin thin film layers with a thickness as low as 5 nm or even thinner.

[0024] Step S12: Analyze the light intensity-z coordinate curve, extract the peak position of the light intensity-z coordinate curve, and mark the peak position as the physical interface between each film layer.

[0025] Specifically, the light intensity-z coordinate curve is analyzed to identify local peaks (local maxima) where the light intensity varies with the Z-axis height. The locations of these identified local peaks are then labeled as the corresponding physical interfaces between film layers. For example... Figure 2 As shown, in this embodiment, three local peak positions Z0, Z1, and Z2 are identified. The three local peak positions correspond to the following: Z0: air / photoresist layer interface (sample surface), Z1: photoresist layer / chromium layer interface, and Z2: chromium layer / quartz substrate interface.

[0026] Step S13: Move sequentially along the Z-axis to each physical interface and collect the ellipsoidal spectral curves at each physical interface.

[0027] Specifically, based on the calibrated positions of each physical interface, the sample stage or optical detection module is moved to move the beam waist to positions Z0, Z1, and Z2 respectively, and complete ellipsoidal spectral curves (Psi curve and Δ curve) are collected at each position.

[0028] Step S14: Obtain the material information of each film layer, and construct the elliptic model of each physical interface based on the material parameters and physical interface information of each film layer. Specifically, step S14 includes the following steps: Step S141: Calculate the Z-axis height difference between the current physical interface and its adjacent physical interface below it, and mark the obtained Z-axis height difference as the initial thickness of the current film layer. Specifically, the Z-axis difference between adjacent interfaces is the initial thickness of the current film layer. For example, in this embodiment, (Z1-Z0) is the initial thickness of the photoresist layer, and (Z2-Z1) is the initial thickness of the chromium layer.

[0029] Step S142: Query the material library to obtain the initial material parameters of the corresponding film layer. Specifically, query the pre-stored material library to obtain the initial material parameters of the corresponding film layer. The initial material parameters may include, but are not limited to, the initial refractive index and the initial extinction coefficient.

[0030] Step S143: Based on the physical interface information, initial thickness, initial refractive index and initial extinction coefficient, construct the ellipsoidal model of the current physical interface using the standard ellipsoidal model.

[0031] Specifically, the physical interface information includes the position of each physical interface and the light intensity at each physical interface. In this embodiment, based on the physical interface information of each physical interface Z0, Z1, Z2, the initial thickness of the photoresist layer, the initial thickness of the chromium layer, and the obtained film material information at the physical interfaces of Z0, Z1, Z2, a photoresist layer elliptic model M0 and a chromium layer elliptic model M1 are constructed respectively.

[0032] Step S15: Input the acquired ellipsoidal spectral curves into the corresponding ellipsoidal model to calculate the thickness of each film layer. Specifically, step S15 includes the following steps: input the acquired ellipsoidal spectral curves into the ellipsoidal model of the corresponding physical interface; perform nonlinear regression on the ellipsoidal spectral curves based on the ellipsoidal model and the Levenberg-Marquardt algorithm to invert and obtain the thickness of the film layer.

[0033] In this embodiment, the elliptic spectral curves at the physical interfaces Z0 and Z1 are input into the elliptic model M0 to calculate the thickness of the photoresist layer, and the elliptic spectral curves at the physical interfaces Z1 and Z2 are input into the elliptic model M1 to calculate the thickness of the chromium layer. The thickness of the multilayer film is accurately solved by analyzing the variation trends of light intensity, Psi, and Δ, as well as the optical properties of the material. Since the physical positions of Z0, Z1, and Z2 have been accurately located in step S12, the initial thickness of each layer can be used as a strong constraint boundary for the inversion algorithm. Combined with material parameters and elliptic spectral curves, accurate initial boundary information and rich constraint conditions are available when solving for the thickness, which can significantly reduce the possibility of multiple solutions and effectively improve the convergence speed and accuracy of the inversion.

[0034] The aforementioned method for measuring the thickness of multilayer thin films involves collecting reflected light intensity information at different Z-axis height positions at the nanoscale to form a light intensity-z coordinate curve. The peak position of the light intensity-z coordinate curve is extracted and calibrated as the physical interface between each film layer. Furthermore, ellipsoidal spectral curves at each physical interface are collected, and ellipsoidal models of each physical interface are constructed based on the physical interface information and material parameters. Finally, the collected ellipsoidal spectral curves are input into the corresponding ellipsoidal models to calculate the thickness of each film layer. This multilayer thin film thickness measurement method utilizes the physical variation of reflected light intensity with Z-axis height. By identifying the light intensity peak, the physical interfaces between film layers are calibrated. The location of the physical interfaces does not rely on optical model inversion. Even for adjacent film layers with similar optical constants, accurate peeling and calibration can be achieved through spatial dimension response changes. The film interface positioning accuracy is high. Furthermore, the Z-axis scanning uses nanoscale step scanning, achieving nanometer-level resolution, which can effectively measure the thickness of ultrathin thin film layers. It can also accurately calibrate physical interfaces for various ultrathin and complex film systems such as mask substrates, mask plates, and wafer processing. Further, based on the accurate physical interface positioning results and multidimensional ellipsometry data, accurate initial boundary information and rich constraints are available when solving for thickness, effectively reducing the ambiguity (i.e., ill-conditioned inverse problem) in the optical model inversion process, effectively ensuring the uniqueness and robustness of the measurement results, and significantly improving measurement accuracy.

[0035] In summary, the above-mentioned method for measuring the thickness of multilayer thin films solves the technical problems of difficult interface positioning, insufficient measurement capability of ultrathin layers, and strong inversion ill-conditioning of traditional optical measurement methods by introducing high-precision scanning at the Z-axis nanoscale and joint analysis of multidimensional spectral data. It has the beneficial effects of high interface positioning accuracy and accurate film thickness measurement, and can accurately measure the film thickness of ultrathin multilayer films.

[0036] In one embodiment, the method further includes the step of performing confocal filtering on the reflected light to filter out off-focus light. Specifically, this embodiment forms a confocal optical system by setting a perforated plate in the reflected light path. The off-focus light is filtered out through the pinhole, ensuring that only reflected light from the beam waist position can efficiently pass through the pinhole to reach the detector, while the off-focus light is filtered out, thereby further enhancing the Z-axis resolution and improving the contrast of the interface signal.

[0037] In one embodiment, the method further includes the following steps: scanning the entire sample along the x-axis and Y-axis directions respectively to obtain the thickness of each film layer at different positions in the XY plane, and generating a film layer thickness distribution map of the sample. Specifically, after completing the single-point film layer thickness measurement, the sample stage is controlled to move the sample along the X-axis and Y-axis directions to perform a full-plate scan of the sample. Steps S11 to S15 are repeated at each detection point to obtain the thickness of each film layer at each detection point. After completing the full-plate scan detection, a film thickness distribution map of the sample to be tested is generated. This embodiment performs full-area film thickness uniformity detection on the sample, which can well meet the requirements of advanced semiconductor manufacturing for on-wafer uniformity monitoring. Further, in one embodiment, to ensure planar positioning accuracy, it is preferable that the scanning step size for scanning the sample along the x-axis and Y-axis directions is no greater than 100 nm.

[0038] This invention also provides a multilayer thin film thickness measurement device, comprising: an ellipsometer and a PZT driver. The ellipsometer includes an optical detection module, a sample stage, and a processor. The sample stage is located below the optical detection module and is used to hold the sample to be tested. The PZT driver is connected to the optical detection module and / or the sample stage and is used to drive the sample stage and the optical detection module to step closer together along the Z-axis. The optical detection module is used to detect the reflected light intensity information of the sample at different Z-axis height positions and the ellipsometric spectral curves at each physical interface of the sample. The processor is used to calibrate the physical interfaces between each film layer according to the reflected light intensity information of the sample at different Z-axis height positions, and to calculate the thickness of each film layer according to the ellipsometric spectral curves at each physical interface.

[0039] In one embodiment, the PZT driver has a step size of no more than 1 nm. The PZT driver can drive the sample and the optical detection module to move closer together along the Z-axis at the nanoscale, achieving a Z-axis scanning resolution of 1 nm or less. It can effectively measure ultrathin films with a thickness as low as 5 nm or even thinner.

[0040] In one embodiment, the step distance of the sample stage moving along the x-axis and Y-axis is no greater than 100 nm. Specifically, the sample stage can move the sample along the x-axis and Y-axis to perform a full-plate scan of the sample, generating a film thickness distribution map of the sample under test. This enables full-area film thickness uniformity detection of the sample, meeting the requirements of advanced semiconductor manufacturing for on-wafer uniformity monitoring. In this embodiment, the step distance of the sample stage moving along the x-axis and Y-axis is no greater than 100 nm, which can effectively ensure the positioning accuracy of planar scanning and can also accurately locate micro- and nano-structures (such as fine patterns on masks), enabling precise monitoring of on-wafer uniformity.

[0041] In one embodiment, the ellipsometer further includes an aperture plate disposed in the detection optical path of the optical detection module, used for confocal filtering of reflected light to filter out off-focus light. Specifically, the aperture plate is disposed in the reflected optical path of the ellipsometer, and is adjacent to the detector of the ellipsometer. Reflected light shines onto the detector through pinholes in the aperture plate. This embodiment forms a confocal optical system by setting an aperture plate in the reflected optical path, and filters out off-focus light through pinholes, ensuring that only reflected light from the beam waist position can efficiently pass through the pinholes to reach the detector, while defocused light is filtered out, thereby further enhancing Z-axis resolution and improving the contrast of interface signals.

[0042] Specifically, the working process of the multilayer thin film thickness measurement device in this embodiment is as follows: First, the sample is placed on the sample stage, with the sample surface as the initial zero point Z0. The sample stage is driven to move upward along the Z-axis at a nanoscale stepping speed by the PZT driver, or the optical detection module is driven to move downward along the Z-axis at a nanoscale stepping speed, so that the sample and the optical detection module approach each other at a nanoscale stepping speed along the Z-axis, changing the axial position of the beam waist in the multilayer thin film under test. At each Z-axis height position, the ellipsometer detector collects the reflected light intensity and records the light intensity data at all Z-axis positions, forming a light intensity-Z coordinate curve. Then, the processor extracts the peak position of the light intensity-Z coordinate curve based on the collected light intensity-Z coordinate curve and marks the peak position as the physical interface between each film layer. Then, the PZT driver drives the sample stage to move the sample, or drives the optical detection module to move, so that the beam waist moves to each physical interface, and complete ellipsometric spectral curves (Psi curve and Δ curve) are collected at each physical interface. After acquiring the ellipsoidal spectral curves at each physical interface, the processor obtains the material information of each film layer, constructs an ellipsoidal model of each physical interface based on the material parameters and physical interface information of each film layer, and inputs the acquired ellipsoidal spectral curves into the corresponding ellipsoidal models to calculate the thickness of each film layer. The multilayer thin film thickness measurement device in this embodiment is used to implement the above-described multilayer thin film thickness measurement method. This device can accurately calibrate the physical interfaces between the layers of a multilayer film and accurately measure the thickness of ultrathin multilayer films.

[0043] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the scope of the present invention.

Claims

1. A method for measuring the thickness of a multilayer thin film, characterized in that, Includes the following steps: Using the sample surface as the initial zero point, the sample and the optical detection module are controlled to approach each other at a nanoscale step along the Z-axis, and the reflected light intensity information is collected at each Z-axis height position to form a light intensity-Z coordinate curve. The light intensity-z coordinate curve is analyzed, the peak position of the light intensity-z coordinate curve is extracted, and the peak position is marked as the physical interface between each film layer; Move sequentially along the Z-axis to each physical interface and collect the elliptic spectrum curves at each physical interface; Obtain material information for each membrane layer, and construct elliptic models of each physical interface based on the material parameters and physical interface information of each membrane layer. The collected elliptic spectrum curves are input into the corresponding elliptic model to calculate the thickness of each film layer.

2. The method for measuring the thickness of a multilayer thin film according to claim 1, characterized in that, The steps of obtaining material information for each film layer and constructing an elliptic model of each physical interface based on the material parameters and physical interface information of each film layer include the following steps: Calculate the Z-axis height difference between the current physical interface and its adjacent physical interface below it, and mark the obtained Z-axis height difference as the initial thickness of the current film layer; Search the material library to obtain the initial material parameters for the corresponding membrane layer; Based on the physical interface information, the initial thickness, the initial refractive index, and the initial extinction coefficient, an elliptic model of the current physical interface is constructed using a standard elliptic model.

3. The method for measuring the thickness of a multilayer thin film according to claim 2, characterized in that, The step of inputting the acquired elliptic spectral curves into the corresponding elliptic model to calculate the thickness of each film layer includes: The collected elliptic spectral curves are input into the elliptic model of the corresponding physical interface; The thickness of the film is obtained by performing nonlinear regression on the elliptic spectral curve based on the elliptic model and the Levenberg-Marquardt algorithm.

4. The method for measuring the thickness of a multilayer thin film according to claim 1, characterized in that, It also includes the following steps: The reflected light is subjected to confocal filtering to filter out the unfocused light.

5. The method for measuring the thickness of a multilayer thin film according to claim 1, characterized in that, It also includes the following steps: The entire sample is scanned along the x-axis and y-axis to obtain the thickness of each film layer at different positions in the XY plane, generating a sample film layer thickness distribution map.

6. The method for measuring the thickness of a multilayer thin film according to claim 5, characterized in that, The step size for controlling the sample to move closer to the optical detection module along the Z-axis is no greater than 1 nm. And / or, The scanning step size for scanning the sample along the x-axis and y-axis is no greater than 100 nm.

7. A multilayer thin film thickness measuring device, characterized in that, include: An ellipsometer and a PZT driver, wherein the ellipsometer includes an optical detection module, a sample stage and a processor, and the sample stage is located below the optical detection module and is used to hold the sample to be detected; The PZT driver is connected to the optical detection module and / or the sample stage, and is used to drive the sample stage and the optical detection module to step closer together along the Z-axis direction; The optical detection module is used to detect the reflected light intensity information of the sample at different Z-axis height positions and the ellipsoidal spectral curves at each physical interface of the sample; the processor is used to calibrate the physical interfaces between each film layer according to the reflected light intensity information of the sample at different Z-axis height positions, and to calculate the thickness of each film layer according to the ellipsoidal spectral curves at each physical interface.

8. The multilayer thin film thickness measuring device according to claim 7, characterized in that, The ellipsometer also includes an aperture plate, which is disposed in the detection optical path of the optical detection module and is used to perform confocal filtering on the reflected light and filter out unfocused light.

9. The multilayer thin film thickness measuring device according to claim 7, characterized in that, The movement step of the PZT driver is no greater than 1 nm.

10. The multilayer thin film thickness measuring device according to claim 7, characterized in that, The step distance of the sample stage moving along the x-axis and y-axis is no greater than 100 nm.

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