In-situ Plasma Process Monitoring System and Its Monitoring Method

Abstract

The present invention discloses an in-situ plasma process monitoring system and a monitoring method thereof. For the elements contained in etching film layers of different materials, according to the NIST database, the standard wavelength and intensity information of the characteristic spectral lines corresponding to each element are obtained to establish a simulated spectral library corresponding to different etching film layers, and the measured plasma spectrum is preliminarily matched with the simulated spectra in the simulated spectral library. For the successfully matched spectral lines, pixel-intensity information is extracted from the measured plasma spectrum, the peak position is fitted to obtain the peak position center pixel value, and combined with the standard wavelength value of the already matched simulated spectrum in the simulated spectral library, a dispersion relationship function between the wavelength of the spectrometer and the pixel is fitted. Finally, the reflected spectrum is processed according to the new dispersion relationship function to obtain the accurate reflected light wavelength. Furthermore, in the real-time monitoring of the plasma, real-time wavelength calibration of the spectrometer is realized, the accurate reflected light wavelength is obtained, and the etching rate and etching depth are accurately calculated.

Description

Technical Field

[0001] The present invention relates to the technical field of plasma process manufacturing, and particularly relates to an in-situ plasma process manufacturing monitoring system and a monitoring method thereof. Background Art

[0002] In the process of real-time monitoring of the endpoint of plasma etching by using the IEP (Interferometry Endpoint) method, it is necessary to use the etching rate obtained by real-time calculation to monitor the etching process, so that the etching stops at the target depth. In the calculation process of the etching rate, the accuracy of the reflected light wavelength directly affects the accuracy of the etching rate obtained by real-time calculation, thus having an important impact on the yield of the final etching process.

[0003] There are two common methods to improve the accuracy of the reflected light wavelength: one is to use a laser or an LED lamp as the incident light source and directly calibrate the wavelength with the incident light source without wavelength correction; the other is as disclosed in Chinese Patent (CN106876236B), which discloses a method of correcting the incident light wavelength by using the relevant spectral lines of plasma emission spectrum. Specifically, by measuring a specific spectral line in the plasma emission spectrum, comparing the wavelength obtained by the spectrometer with the standard wavelength to obtain a wavelength correction amount, and using this correction amount to correct the wavelength of the reflected light measured by the spectrometer.

[0004] For the first method, on the one hand, since the incident light source is placed around the etching machine, the increase in ambient temperature will affect the wavelength of the incident light source. On the other hand, after the light emitted by the incident light source enters the etching chamber, due to the continuous processes of ionization, recombination, charge exchange, radiative transition, etc. of the plasma during the etching process, a higher temperature is generated, so it will also affect the wavelength of the incident light.

[0005] For the second method of improving the accuracy of the reflected light wavelength, the spectrometer will perform a wavelength calibration during factory production, that is, the pixels of the detector are mapped to the wavelength information of the required wavelength band. However, due to the complex environment around the etching chamber where the spectrometer is located, which is different from the environment during the factory calibration of the spectrometer, and the spectrometer will inevitably vibrate during the entire transportation process, there will be deviations if the reflected light wavelength directly measured by the spectrometer is used to calculate the etching rate. This method corrects the reflected light wavelength by comparing the wavelength value of a single spectral line measured by the spectrometer with the wavelength of the standard plasma characteristic spectral line. However, since the wavelength band generally covered by a spectrometer is 200nm - 900nm, and the spectrum of the reflected light can also cover a wide wavelength band of 200nm - 900nm, if a single fixed correction amount is used to correct the spectral line wavelengths of the entire wavelength band, for example, using the wavelength correction amount obtained from the 700nm emission spectral line to correct the 800nm reflected spectral line, it may not introduce too much error. However, if this correction amount is used to correct the 300nm reflected spectral line, due to the non-linear correspondence between the wavelength and the detector pixel points, it may bring a large error.

[0006] The information disclosed in this background art section is only intended to enhance the overall understanding of the present invention and should not be regarded as an admission or any form of suggestion that this information is prior art well-known to those of ordinary skill in the art. Summary of the Invention

[0007] To overcome the defects of the prior art, there is provided an in-situ plasma process monitoring system and its monitoring method to solve the problem that the traditional method for improving the accuracy of the reflected light wavelength has poor effect in plasma etching depth monitoring.

[0008] To achieve the above object, there is provided an in-situ plasma process monitoring method, including the following steps:

[0009] Select multiple etching film layers, where the etching film layers are film layers of known materials and the materials of the multiple etching film layers are different;

[0010] Based on the materials of the etching film layers, obtain the standard wavelength and intensity information of the characteristic spectral lines of the target elements in the etching film layers from the NIST atomic and molecular database;

[0011] Select multiple spectral lines with relatively high intensities from the characteristic spectral lines of the target elements to establish the simulated spectrum corresponding to the etching film layer, and then form a simulated spectrum library of different etching film layers;

[0012] During the real-time monitoring of the etching of an etching film layer, turn off the incident light source and use a spectrometer to measure the plasma emission spectrum of the etching film layer;

[0013] Based on the wavelength, intensity, and spectral line shape, match the simulated spectrum corresponding to the etching film layer in the simulated spectrum library with the plasma emission spectrum to determine the wavelength calibration characteristic spectral line;

[0014] Extract the pixel-intensity relationship of each successfully matched characteristic peak from the plasma emission spectrum;

[0015] Perform a relationship fitting of the pixel position and intensity of the successfully matched characteristic peaks in the plasma emission spectrum to obtain the central position pixel value of the spectrum of the characteristic peaks;

[0016] Perform a fitting of the central position pixel values of multiple characteristic peaks with the wavelengths of the simulated spectra matched in the simulated spectrum library to obtain the dispersion relationship function of pixel and wavelength;

[0017] Turn on the incident light source and use a spectrometer to measure the reflection spectrum of the etching film layer;

[0018] Based on the dispersion relationship function, convert the pixel values of the reflection spectrum measured by the spectrometer into wavelength values to obtain the standard values of the reflection spectrum wavelengths.

[0019] According to the standard values of the reflected light wavelengths obtained by real-time calibration, the refractive index of the etching film layer, and the etching time, calculate the etching rate and etching depth in real time.

[0020] Further, at least select three characteristic spectral lines of the elements corresponding to the etching film layer to construct the simulated spectrum corresponding to the etching film layer.

[0021] Further, perform a peak position curve fitting on the pixel position and intensity relationship of each characteristic peak in the plasma emission spectrum to obtain the central position pixel value of the spectrum of the characteristic peak.

[0022] Further, the peak position curve fitting is a peak position curve fitting such as Gaussian curve fitting, or linear interpolation to take the full width at half maximum, Lorentz curve fitting, etc.

[0023] Further, perform a polynomial curve fitting on the central position pixel value of the spectrum of the characteristic peak and the wavelengths of the corresponding simulated spectra in the simulated spectrum library to obtain the dispersion relationship function.

[0024] The present invention provides an in-situ plasma process monitoring system, including:

[0025] A storage module for storing a simulated spectrum library of different etching film layers;

[0026] An acquisition module for acquiring the plasma emission spectrum of an etching film layer;

[0027] A matching module for matching the simulated spectrum corresponding to the etch film layer in the simulated spectrum library with the plasma emission spectrum based on wavelength, intensity, and spectral line shape, connected to the storage module and the acquisition module;

[0028] An extraction module for extracting the pixel-intensity relationship of each successfully matched characteristic peak from the plasma emission spectrum, connected to the matching module;

[0029] A first fitting module for fitting the relationship between the pixel position and intensity of the successfully matched characteristic peaks in the plasma emission spectrum to obtain the central position pixel value of the spectrum of the characteristic peaks, connected to the extraction module;

[0030] A second fitting module for fitting the central position pixel values of multiple characteristic peaks with the wavelengths of the simulated spectral lines matched in the simulated spectrum library to obtain a dispersion relationship function between pixels and wavelengths, connected to the first fitting module;

[0031] A calculation module for converting the pixel values of the reflection spectrum measured by the spectrometer into wavelength values based on the dispersion relationship function and calculating the standard value of the reflection spectrum wavelength, connected to the second fitting module;

[0032] A second calculation module for calculating the etch rate and etch depth in real time according to the standard value of the reflection light wavelength obtained by real-time calibration, the refractive index of the etch film layer, and the etch time used, connected to the first calculation module.

[0033] The beneficial effect of the present invention is that the in-situ plasma process monitoring method of the present invention selects at least three target element spectral lines of different materials for different etch film layers, obtains the characteristic spectral line wavelengths from the NIST database of the National Institute of Standards and Technology of the United States to synthesize characteristic spectral lines, and then establishes a simulated spectrum library containing multiple etch film layers. Then, according to the spectrometer calibrated at the factory, the measured plasma spectrum is preliminarily matched with the simulated spectrum. For the successfully matched spectral lines, pixel-intensity information is obtained through the spectrometer, the peak position is Gaussian-fitted to obtain pixel values, combined with the standard wavelength values on NIST, polynomial fitting is performed to obtain a new dispersion relationship function. Finally, the reflection spectrum is processed according to the new dispersion relationship function to obtain an accurate reflection wavelength. The in-situ plasma process monitoring method of the present invention can perform real-time calibration and accurately correct the reflection light wavelength during the process of monitoring the etch endpoint using the IEP method, so as to obtain accurate etch rate and etch depth, which is more conducive to real-time online monitoring of the etch endpoint of plasma etching. Description of the Drawings

[0034] Other features, objects, and advantages of the present application will become more apparent from the following detailed description of non-limiting embodiments read in conjunction with the accompanying drawings:

[0035] Figure 1 It is a schematic diagram of the matching between the database simulation spectrum and the plasma emission spectrum of the embodiment of the present invention.

[0036] Figure 2 It is a schematic flowchart of the in-situ plasma process monitoring method of the embodiment of the present invention. Detailed Embodiments

[0037] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only for explaining the relevant invention and not for limiting the invention. Additionally, it should be noted that for the sake of description, only parts related to the invention are shown in the drawings.

[0038] It should be noted that, without conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0039] Referring to Figure 1 and 2 As shown, the present invention provides an in-situ plasma process monitoring method, including the following steps:

[0040] S1: Select a plurality of etched film layers, where the etched film layers are film layers of known materials and the materials of the plurality of etched film layers are different.

[0041] S2: Based on the elements contained in the etched film layers, obtain the standard wavelength and intensity information of the characteristic spectral lines corresponding to the target elements from the NIST Atomic and Molecular Database.

[0042] The NIST Atomic and Molecular Database is a Web-based physical property database of the National Institute of Standards and Technology (NIST) of the United States.

[0043] Specifically, for example, for the SiN film layer, the target elements (i.e., characteristic elements) are Si and N, and then the standard characteristic wavelengths and intensity information of the target elements are obtained from the NIST Atomic and Molecular Database.

[0044] S3: Select multiple characteristic element standard spectral lines with relatively high intensities from the characteristic spectral lines of the target elements in the etched film layers to construct a simulation spectrum. Further, establish a simulation spectrum library for different etched film layers.

[0045] Select multiple spectral lines with relatively high intensities from the characteristic spectral lines of the target elements, establish the simulation spectrum corresponding to the etched film layer, and obtain a simulation spectrum library for different etched film layers.

[0046] Specifically, select at least three elemental characteristic spectral lines from the characteristic standard spectral lines of the elements corresponding to the etched film layer (refer to the elemental characteristic standard spectral lines pointed by the vertical black arrows in Figure 1 , Figure 1 ) to construct a simulated spectrum.

[0047] S4: During the real-time monitoring of the etching of an etched film layer, turn off the incident light source and use a spectrometer to measure the plasma emission spectrum of an etched film layer.

[0048] S5: Based on the wavelength, intensity, and spectral line shape, match the simulated spectrum 1 corresponding to an etched film layer in the simulated spectrum library with the plasma emission spectrum 2 to determine the wavelength calibration characteristic spectral line.

[0049] S6: From the plasma emission spectrum measured by the spectrometer, extract the pixel-intensity relationship of each successfully matched characteristic peak.

[0050] S7: Fit the relationship between the pixel position and intensity of the successfully matched characteristic peaks in the plasma emission spectrum to obtain the pixel value of the central position of the spectrum of the characteristic peaks.

[0051] Specifically, fit the pixel position-intensity relationship of each characteristic peak in the plasma emission spectrum through peak position curve fitting to obtain the pixel value of the central position of the spectrum of the characteristic peaks.

[0052] Among them, the peak position curve fitting can use peak position curve fitting such as Gaussian curve fitting, or linear interpolation to take the full width at half maximum, Lorentz curve fitting, etc.

[0053] S8: Fit the pixel values of the central positions of multiple characteristic peaks with the wavelengths of the simulated spectra matched in the simulated spectrum library to obtain the dispersion relationship function between pixels and wavelengths.

[0054] Specifically, perform a fifth-order polynomial curve fitting on the pixel values and the wavelengths of the simulated spectra corresponding to the plasma emission spectrum 2 in the NIST Atomic and Molecular Database to obtain the dispersion relationship function.

[0055] S9: Turn on the incident light source and use a spectrometer to measure the reflection spectrum of an etched film layer.

[0056] S10: Based on the dispersion relationship function, convert the pixel values of the reflection spectrum measured by the spectrometer into wavelength values to obtain the standard values of the reflection light wavelengths.

[0057] S11: According to the standard values of the reflection light wavelengths obtained by real-time calibration, the refractive index of the etched film layer, and the etching time, calculate the etching rate and etching depth in real time.

[0058] The present invention provides an in-situ plasma process monitoring system, including a storage module, an acquisition module, a matching module, an extraction module, a first fitting module, a second fitting module, a first calculation module, and a second calculation module. The matching module is connected to the storage module and the acquisition module. The extraction module is connected to the matching module. The first fitting module is connected to the extraction module. The second fitting module is connected to the first fitting module. The first calculation module is connected to the second fitting module. The second calculation module is connected to the first calculation module.

[0059] Among them, the storage module is used to store the simulated spectral libraries of different etched film layers.

[0060] The acquisition module is used to acquire the plasma emission spectrum of an etched film layer.

[0061] The matching module is used to match the simulated spectrum corresponding to the etched film layer in the simulated spectral library with the plasma emission spectrum based on wavelength, intensity, and spectral line shape.

[0062] The extraction module is used to extract the relationship between the pixel and intensity of each successfully matched characteristic peak from the plasma emission spectrum.

[0063] The first fitting module is used to fit the relationship between the pixel position and intensity of the successfully matched characteristic peaks in the plasma emission spectrum to obtain the pixel value of the central position of the spectrum of the characteristic peaks.

[0064] The second fitting module is used to fit the pixel values of the central positions of multiple characteristic peaks with the wavelengths of the simulated spectra matched in the simulated spectral library to obtain the dispersion relationship function between pixels and wavelengths.

[0065] The first calculation module is used to convert the pixel values of the reflected spectrum measured by the spectrometer into wavelength values based on the dispersion relationship function, and calculate the standard value of the reflected light wavelength.

[0066] The second calculation module is used to calculate the etching rate and etching depth in real time according to the standard value of the reflected light wavelength obtained by real-time calibration, the refractive index of the etched film layer, and the etching time.

[0067] The in-situ plasma process monitoring method of the present invention, for the elements contained in the etching film layers of different materials, establishes a simulated spectral library corresponding to different etching film layers according to the standard wavelength and intensity information of the characteristic spectral lines corresponding to each element obtained from the NIST database, and preliminarily matches the plasma spectrum measured by the spectrometer with the characteristic spectral lines in the simulated spectral library. For the successfully matched spectral lines, pixel-intensity information is extracted from the plasma spectrum measured by the spectrometer, the peak position is fitted to obtain the peak position center pixel value, and the calibration relationship coefficient between the new spectrometer wavelength and the pixel is fitted in combination with the already matched standard wavelength value in the simulated spectral library. Finally, the reflected spectrum is processed according to the new calibration dispersion relationship function to obtain the accurate reflected light wavelength, and then during the real-time monitoring of plasma etching, the real-time wavelength calibration of the spectrometer is realized, the reflected light wavelength is accurately obtained, and the etching rate and etching depth are accurately calculated.

[0068] The above description is only the preferred embodiment of the present application and the explanation of the applied technical principles. Those skilled in the art should understand that the scope of the invention involved in the present application is not limited to the technical solution formed by the specific combination of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the technical solutions formed by mutually replacing the above features with the technical features (but not limited to) having similar functions disclosed in the present application.

Claims

1. An in-situ plasma process monitoring method, characterized in that, Including the following steps: Select a plurality of etching film layers, where the etching film layers are film layers of known materials, and the materials of the plurality of etching film layers are different; Based on the material of the etching film layer, obtain the standard wavelength and intensity information of the characteristic spectral lines of the target elements in the etching film layer from the NIST atomic and molecular database; Select multiple spectral lines with relatively high intensities from the characteristic spectral lines of the target elements to establish the simulated spectrum corresponding to the etching film layer, and then form a simulated spectrum library of different etching film layers; During the real-time monitoring of the etching of an etching film layer, turn off the incident light source and use a spectrometer to measure the plasma emission spectrum of the etching film layer; Based on wavelength, intensity, and spectral line shape, match the simulated spectrum corresponding to the etching film layer in the simulated spectrum library with the plasma emission spectrum to determine the wavelength calibration characteristic spectral line; Extract the pixel-intensity relationship of each successfully matched characteristic peak from the plasma emission spectrum; Fit the pixel position-intensity relationship of the successfully matched characteristic peaks in the plasma emission spectrum to obtain the central position pixel value of the spectrum of the characteristic peak; Fit the central position pixel values of multiple characteristic peaks with the wavelengths of the simulated spectra matched in the simulated spectrum library to obtain the dispersion relationship function of pixel and wavelength; Turn on the incident light source and use a spectrometer to measure the reflection spectrum of the etching film layer; Based on the dispersion relationship function, convert the pixel values of the reflection spectrum measured by the spectrometer into wavelength values to obtain the standard values of the reflection spectrum wavelengths; According to the standard values of the reflected light wavelengths obtained by real-time calibration, the refractive index of the etching film layer, and the etching time, calculate the etching rate and etching depth in real time.

2. The in-situ plasma process monitoring method according to claim 1, characterized in that Select at least three characteristic spectral lines of the elements corresponding to the etching film layer to construct the simulated spectrum corresponding to the etching film layer.

3. The in-situ plasma process monitoring method according to claim 1, wherein Fit the pixel position-intensity relationship of each characteristic peak in the plasma emission spectrum through peak position curve fitting to obtain the central position pixel value of the spectrum of the characteristic peak.

4. The in-situ plasma process monitoring method according to claim 3, wherein The peak position curve fitting is Gaussian curve fitting, or linear interpolation to take the full width at half maximum, or Lorentz curve fitting peak position curve fitting.

5. The in-situ plasma process monitoring method according to claim 1, wherein Fit the central position pixel value of the spectrum of the characteristic peak with the wavelength of the simulated spectrum corresponding in the simulated spectrum library through polynomial curve fitting to obtain the dispersion relationship function.

6. An in-situ plasma process monitoring system, characterized in that, Including: A storage module for storing a simulated spectrum library of different etching film layers; An acquisition module for acquiring the plasma emission spectrum of an etching film layer; A matching module for matching the simulated spectrum corresponding to the etching film layer in the simulated spectrum library with the plasma emission spectrum based on wavelength, intensity, and spectral line shape, connected to the storage module and the acquisition module; An extraction module for extracting the pixel-intensity relationship of each successfully matched characteristic peak from the plasma emission spectrum, connected to the matching module; A first fitting module for fitting the pixel position-intensity relationship of the successfully matched characteristic peaks in the plasma emission spectrum to obtain the central position pixel value of the spectrum of the characteristic peak, connected to the extraction module; A second fitting module for fitting the pixel values at the central positions of multiple said characteristic peaks with the wavelengths of the simulated spectral lines matched in the simulated spectral library to obtain a dispersion relationship function between pixels and wavelengths, which is connected to the first fitting module; A first calculation module for converting the pixel values of the reflection spectrum measured by the spectrometer into wavelength values based on the dispersion relationship function and calculating the standard value of the reflection spectrum wavelength, which is connected to the second fitting module; A second calculation module for calculating the etching rate and etching depth in real time according to the standard value of the reflected light wavelength obtained by real-time calibration, the refractive index of the etched film layer, and the etching time used, which is connected to the first calculation module.

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