Method for in-situ measurement of film thickness and chemical mechanical planarization device

Abstract

The present invention provides a method for in-situ measurement of film thickness and a chemical mechanical planarization device, the method comprising: on the basis of a reflection spectrum of a wafer film and an equivalent light source spectrum, generating an actually measured spectrum, the equivalent light source spectrum being data of the correspondence relationship between wavelength and light intensity generated by using reflected light passing through a planarization solution and a dielectric layer between the planarization solution and a collimating light source probe; matching the actually measured spectrum with a reference spectrum library; and obtaining a wafer film thickness corresponding to a reference spectrum matching the actually measured spectrum and using said thickness as a measurement result.

Description

Methods for in-situ film thickness measurement and chemical mechanical polishing equipment Technical Field

[0001] This invention relates to the field of wafer parameter measurement, specifically to a method for in-situ measurement of film thickness and a chemical mechanical polishing device. Background Technology

[0002] Chemical Mechanical Polishing (CMP) is a global surface planarization technique used in semiconductor manufacturing to reduce the impact of wafer thickness variations and surface topography. The CMP process involves pressing the wafer against a polishing pad using a support head. Polishing is achieved through the relative motion between the wafer and the pad, aided by abrasive particles in a polishing slurry. Some polishing processes require removing transparent or translucent monolayers from the wafer (the wafer includes the substrate and the monolayer formed on it). Controlling the thickness of these monolayers during polishing is crucial for CMP; it determines whether the film has been planarized to the desired flatness or thickness, or when the required amount of material has been removed. Therefore, accurate and real-time acquisition of monolayer thickness variations is essential for adjusting polishing pressure and duration, precisely controlling the polishing endpoint, and preventing over- or under-polishing.

[0003] In in-situ measurement of wafer film thickness using optical non-contact reflectance methods, various media, such as air, glass, PU, ​​and polishing fluid, exist between the wafer and the probe. In wafer film thickness measurement within multilayer dielectric structures, the degree and manner of influence of each different dielectric layer on the wafer reflectance spectrum vary. Furthermore, multiple media significantly increase the modeling difficulty and interfere with the theoretical reflectance spectrum model. Therefore, avoiding the influence of excessive dielectric layers on the theoretical reflectance spectrum model is a crucial technical problem that urgently needs to be solved.

[0004] Since CMP was applied to the semiconductor manufacturing and processing industry, it has not yet been possible to measure wafer thin film thickness in situ during processing. Summary of the Invention

[0005] In view of this, this application provides a method for in-situ measurement of film thickness, comprising:

[0006] The measured spectrum is generated based on the reflection spectrum of the wafer thin film and the equivalent light source spectrum. The equivalent light source spectrum is the data on the relationship between wavelength and light intensity generated by the reflected light through the polishing slurry and the dielectric layer between the polishing slurry and the collimating light source probe.

[0007] The measured spectra are matched with the reference spectral library;

[0008] The wafer thin film thickness corresponding to the reference spectrum that matches the measured spectrum is obtained as the detection result.

[0009] Optionally, before generating the measured spectrum based on the reflection spectrum of the wafer thin film and the equivalent light source spectrum, the method further includes:

[0010] Acquire the reflected light emitted by the collimated light source probe and reflected by the reflector after passing through the dielectric layer;

[0011] The reflected light is used to generate the equivalent light source spectrum.

[0012] Optionally, the medium layer includes a light-transmitting sealing layer disposed on the polishing disc and polishing pad, and a bulk water layer formed by the polishing liquid.

[0013] Optionally, the reference spectral library is a collection of reference spectra generated using a spectral calculation model for a given wafer thin film thickness. The spectral calculation model includes the spectral parameters of the wafer and the spectral parameters of the near-surface layer formed by the bulk water on the wafer thin film surface and the material between the wafer thin film surface and the material.

[0014] Optionally, the spectral parameters of the wafer include the spectral parameters of the wafer thin film and the spectral parameters of the wafer substrate.

[0015] Optionally, the spectral parameters of the wafer thin film include the refractive index n2 of the wafer thin film, and the spectral parameters of the wafer substrate include the refractive index n3 of the wafer substrate.

[0016] Optionally, the near-surface layer is a surface equivalent layer used to simulate the bulk water and the material between the wafer thin film surface and the wafer thin film surface.

[0017] Optionally, the spectral parameters of the surface equivalent layer include the refractive index n1′ of the surface equivalent layer.

[0018] Optionally, before matching the measured spectrum with the reference spectral library, the method further includes:

[0019] Obtain the spectral calculation model;

[0020] Determine the spectral parameters of the surface equivalent layer, wafer thin film, and wafer substrate;

[0021] The reference spectra for different given wafer thin film thicknesses are calculated using the spectral parameters and the spectral calculation model.

[0022] Optionally, the near-surface layer includes a first type of layer and a second type of layer, wherein the second type of layer is located between the first type of layer and the wafer thin film.

[0023] Optionally, the spectral parameters of the first type of layer include the refractive index n1 of the first type of layer, and the spectral parameters of the second type of layer include the refractive index n4 of the second type of layer and the thickness d4 of the second type of layer.

[0024] Optionally, before matching the measured spectrum with the reference spectral library, the method further includes:

[0025] Obtain the spectral calculation model;

[0026] Determine the spectral parameters of the first type of layer, the second type of layer, the wafer thin film, and the wafer substrate;

[0027] The reference spectra for different given wafer thin film thicknesses are calculated using the spectral parameters and the spectral calculation model.

[0028] This application also provides a method for endpoint detection in wafer thin film grinding, including:

[0029] Using the above-mentioned method for in-situ film thickness measurement, the thickness of the wafer thin film can be monitored in real time to see if it reaches the target thickness.

[0030] Grinding stops when the wafer film reaches the target thickness.

[0031] Accordingly, this application provides an electronic device, characterized in that it includes: a processor and a memory connected to the processor; wherein the memory stores instructions executable by the processor, the instructions being executed by the processor to cause the processor to perform the above-described method.

[0032] This application also provides a chemical mechanical polishing apparatus, comprising:

[0033] A light-transmitting channel connects the polishing disc and polishing pad;

[0034] A sealing layer is encapsulated on the light-transmitting channel, and the sealing layer and the polishing liquid on the polishing pad form an in-situ measurement environment;

[0035] A collimated light source probe is used to emit collimated light into the light transmission channel and receive reflected light from the surface of the wafer thin film;

[0036] A measuring device for performing the above method.

[0037] Optionally, the sealing layer includes a first sealing layer encapsulated on the light-transmitting channel of the polishing pad and a second sealing layer encapsulated on the light-transmitting channel of the polishing disc.

[0038] Optionally, the material of the first sealing layer includes PU; the material of the second sealing layer includes glass.

[0039] According to the in-situ measurement method and equipment provided in the embodiments of the present invention, the light emitted by the collimated light source probe through the light transmission channel of the polishing liquid is equivalent to the equivalent light source spectrum. The measured spectrum is obtained by using the equivalent light source, avoiding the influence of several dielectric layers in the measurement environment on the spectrum. By matching the measured spectrum with the reference spectral library, the wafer thin film thickness is obtained, realizing in-situ measurement under chemical mechanical polishing environment, and the measurement results are highly accurate.

[0040] Based on actual needs, this solution can be used to measure the thickness of wafer thin films in situ and in real time under CMP environment, thereby significantly improving the efficiency and accuracy of semiconductor manufacturing and processing. Attached Figure Description

[0041] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0042] Figure 1 is a schematic diagram of the in-situ measurement of film thickness in an embodiment of the present invention;

[0043] Figure 2 is a flowchart of the in-situ film thickness measurement method in an embodiment of the present invention;

[0044] Figure 3 is a comparison diagram of the measured spectrum and a theoretical spectrum in an embodiment of the present invention;

[0045] Figure 4 is a comparison diagram of the measured spectrum and another theoretical spectrum in an embodiment of the present invention. Detailed Implementation

[0046] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0047] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0048] As shown in Figure 1, an embodiment of the present invention provides a chemical mechanical polishing apparatus, comprising:

[0049] Light-transmitting channel 4, which connects polishing disc 6 and polishing pad 2;

[0050] A sealing layer 3 is encapsulated on the light-transmitting channel 4. The sealing layer 3 can be one or more layers; in this embodiment, there are two sealing layers: a first sealing layer encapsulated on the light-transmitting channel of the polishing pad 2, and a second sealing layer encapsulated on the light-transmitting channel of the polishing disk 6. When there are multiple sealing layers 3, the materials can be the same or different. In this embodiment, the material of the first sealing layer includes PU (polyurethane), and the material of the second sealing layer includes glass.

[0051] The collimating light source probe 5 is used to emit collimated light into the light transmission channel 4 and receive reflected light from the surface of the wafer thin film. The wafer 1 includes a wafer thin film and a wafer substrate. In the orientation shown in Figure 1, the lower surface of the wafer 1 is the surface of the wafer thin film. During polishing, there is a polishing fluid (bulk water) between the surface of the wafer thin film and the polishing pad 2.

[0052] The reflected light from the surface of the wafer thin film passes sequentially through the bulk water, the sealing layer 3, and the air or other environmental media in the light-transmitting channel 4 before entering the collimated light source probe 5.

[0053] A measuring device is used for in-situ film thickness measurement. In the environment shown in Figure 1, the measuring device determines the thickness of the wafer thin film on wafer 1 based on the reflected light collected by the collimated light source probe 5. As shown in Figure 2, the in-situ film thickness measurement method performed by the measuring device includes the following operations:

[0054] S1, a measured spectrum is generated based on the reflection spectrum of the wafer thin film and the equivalent light source spectrum. The equivalent light source spectrum is the data on the relationship between wavelength and light intensity generated by the reflected light passing through the polishing slurry and the dielectric layer between the polishing slurry and the collimating light source probe. The reflection spectrum is the data on the relationship between wavelength and light intensity, and the measured spectrum is the data on the relationship between wavelength and reflectivity. In this embodiment, the light emitted from the collimating light source probe 5 through the light transmission channel 4 through the polishing slurry is equivalent to the equivalent light source spectrum.

[0055] Specifically, before placing wafer 1, with polishing slurry added to polishing pad 2, a reflector is placed on polishing pad 2. The collimated light source probe 5 emits light into the light transmission channel 4 and reaches the reflector. The light reflected by the reflector passes through the polishing slurry (bulk water), the sealing layer 3, and the air and enters the collimated light source probe 5. The equivalent light source spectrum is obtained based on the reflected light passing through multiple dielectric layers.

[0056] The structure of the polishing equipment determines the various media layers through which the reflected light passes. In the structure shown in Figure 1, the media layers through which the reflected light passes include a light-transmitting sealing layer 3 (first sealing layer and second sealing layer) disposed on the polishing disc and polishing pad, and a bulk water layer formed by the polishing fluid. In other embodiments, there may be more or fewer layers in the light-transmitting channel, and the light source spectrum generated by the reflected light passing through various media layers is the equivalent light source spectrum.

[0057] S2, matching the measured spectrum with a reference spectral library. The reference spectral library is a collection of reference spectra corresponding to different wafer thin film thickness values; the reference spectra are data showing the correspondence between wavelength and reflectance. By comparing each reference spectrum with the measured spectrum, the reference spectrum most similar to the measured spectrum is determined. There are various methods for calculating the similarity between two spectra, and various metrics for measuring similarity or matching degree, such as similarity methods, nonlinear regression methods, and FFT methods, etc.

[0058] The reference spectrum can be measured data, such as the spectrum collected for a wafer thin film of known thickness, where the thickness of the wafer thin film can be a measurement value obtained using non-spectral, contact, or non-contact instruments and methods.

[0059] S3, obtain the wafer thin film thickness corresponding to the reference spectrum that matches the measured spectrum as the detection result. The reference spectrum and the measured spectrum can be expressed by a curve, that is, the reference spectrum and the measured spectrum can be a curve showing the correspondence between wavelength and reflectivity. In this embodiment, the art can modify the correspondence between wavelength and reflectivity according to actual needs. For those skilled in the art, other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. However, obvious variations or modifications derived therefrom are still within the protection scope of this invention.

[0060] Assuming the wafer film thickness corresponding to the reference spectrum that matches the measured spectrum is 700 nm, the detection result is that the wafer film thickness is 700 nm.

[0061] According to the in-situ measurement method and equipment provided in the embodiments of the present invention, the light emitted by the collimated light source probe through the light transmission channel of the polishing liquid is equivalent to the equivalent light source spectrum. The measured spectrum is obtained by using the equivalent light source, avoiding the influence of several dielectric layers in the measurement environment on the spectrum. By matching the measured spectrum with the reference spectral library, the wafer thin film thickness is obtained, realizing in-situ measurement under chemical mechanical polishing environment, and the measurement results are accurate.

[0062] Regarding the reference spectrum, in one embodiment, it is data generated using a spectral calculation model that includes the spectral parameters of the wafer and the spectral parameters of the near-surface layer formed by the bulk water on the wafer thin film surface and the material between the wafer thin film surface and the surface.

[0063] The spectral calculation model is specifically a set of formulas. By substituting the values ​​of the spectral parameters into these formulas, the reflectance corresponding to those spectral parameters can be calculated. Specifically, the spectral calculation model can be expressed as: f(x) = R, where x represents the spectral parameter and R represents the reflectance. The spectral parameters include at least the wavelength λ and the thickness d² of the wafer thin film. Given or having determined all the spectral parameters, the corresponding reflectance can be calculated.

[0064] This method calculates the reflectance R corresponding to a given wavelength λ range for different given d2, thereby obtaining the reference spectrum corresponding to different d2.

[0065] Furthermore, the wafer includes a wafer thin film and a wafer substrate. Specifically, the spectral parameters of the wafer thin film may include the refractive index n2 of the wafer thin film, and the spectral parameters of the wafer substrate may include the refractive index n3 of the wafer substrate.

[0066] In one embodiment, the near-surface layer is a surface equivalent layer used to simulate the bulk water and the material between the wafer thin film surface and the wafer thin film surface, i.e., when the presence of material between the wafer thin film surface and the bulk water is recognized, these materials are regarded as a layer of material.

[0067] In this embodiment, the spectral parameters of the surface equivalent layer include the refractive index n1′ of the surface equivalent layer.

[0068] Accordingly, the reference spectrum can be calculated as follows:

[0069] Obtain the spectral calculation model;

[0070] Determine the spectral parameters of the surface equivalent layer, wafer thin film, and wafer substrate;

[0071] Reference spectra for different given wafer thin film thicknesses are calculated using spectral parameters and spectral calculation models.

[0072] Specifically, the spectral calculation model in this embodiment includes parameters of the surface equivalent layer and the wafer. The surface equivalent layer is used to simulate the layer formed between the bulk water on the wafer thin film surface and the material on the wafer thin film surface.

[0073] Determine the spectral parameters of the surface equivalent layer, wafer thin film, and wafer substrate. The spectral parameters of the surface equivalent layer can be calculated theoretically. The spectral parameters of the wafer thin film and wafer substrate are usually known, or can be measured.

[0074] The substance between the bulk water and the wafer thin film surface can be a single substance, such as air, or it can be a multilayered substance, which can affect the spectrum of light reflected from the wafer thin film. To avoid this effect, this embodiment sets up a surface equivalent layer to simulate the substance between the wafer thin film and the bulk water, and the relevant parameters of the surface equivalent layer are introduced when constructing the spectral calculation model.

[0075] Regarding the spectral parameters, in one embodiment, they specifically include the refractive index n1′ of the surface equivalent layer, the refractive index n2 of the wafer thin film, and the refractive index n3 of the wafer substrate.

[0076] For example, a specific spectral calculation model could be: R = r·r *

[0077] Where r is the total reflection coefficient determined based on n1′, n2, and n3, r * Let r be the conjugate complex number, and R be the reflectivity.

[0078] In one embodiment, the total reflection coefficient r is calculated as follows:

[0079] The reflection coefficients of the interfaces of each layer are calculated using n1′, n2, and n3; the phase thickness θ of the wafer thin film is calculated using n2, wavelength λ, and thickness d2; and the total reflection coefficient r is calculated using the reflection coefficients of the interfaces of each layer and the phase thickness θ.

[0080] Furthermore, the reflection coefficients of each layer's interface include the reflection coefficient r1 of the interface between the surface equivalent layer and the wafer thin film, and the reflection coefficient r2 of the interface between the wafer thin film and the wafer substrate.

[0081] The calculation of the reflection coefficients of the interfaces of each layer includes: calculating r1 using n1′ and n2, and calculating r2 using n2 and n3.

[0082] As an example, r can be calculated as follows:

[0083] Where i is the imaginary unit and e is the natural constant.

[0084] Furthermore, r1 and r2 are calculated as follows:

[0085] θ is calculated as follows:

[0086] The above calculation formulas can be modified in simple ways according to actual needs, such as adding preset coefficients or weights to one of the formulas. For those skilled in the art, other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all the calculation formulas here. However, any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

[0087] The reference spectrum calculated in this embodiment is used to compare with the measured spectrum of the wafer in the online state (grinding state or waiting to be ground state). The collection of reference spectra with different wafer thin film thicknesses is called the reference spectrum library.

[0088] The reference spectrum generation method provided in this invention introduces a surface equivalent layer structure and its parameters into the spectral model. This surface equivalent layer is used to simulate the bulk water on the wafer thin film surface and the material between the wafer thin film in the grinding scenario. The spectra calculated for different given wafer thin film thicknesses reflect the deformation phenomenon, which is consistent with the situation observed in the measured spectra. Using the reference spectrum library generated by this scheme to measure the thickness of wafer thin films can improve the accuracy.

[0089] Regarding the spectral parameters of the surface equivalent layer, one embodiment provides a method for determining the spectral parameters of the surface equivalent layer, including:

[0090] Obtain the measured spectrum of a wafer surface with an equivalent surface layer, wherein the wafer includes a wafer substrate and a wafer thin film, and the parameters of the wafer substrate and the wafer thin film are known parameters that have been measured in advance;

[0091] Using a spectral calculation model, theoretical spectra are generated for different given surface equivalent layers with varying spectral parameters. The spectral calculation model and the method for generating the theoretical spectra can be referenced in the above-described embodiment regarding the reference spectrum. The difference lies in the fact that the spectral parameters of the wafer thin film and wafer substrate are fixed values, while the spectral parameters of the surface equivalent layer are multiple given values.

[0092] Specifically, the parameters involved in the spectral calculation model include the refractive index n1′ of the surface equivalent layer, the refractive index n2 of the wafer thin film, and the refractive index n3 of the wafer substrate, where n2 and n3 are known. In this embodiment, multiple n1′ are given, denoted as [n 1i ′,n 1j ′).

[0093] In this embodiment, the thickness d2 of the wafer thin film is a known fixed value. Multiple values ​​corresponding to [n] are calculated using a spectral calculation model. 1i ′,n 1j The theoretical spectrum of ′].

[0094] The spectral parameters of the surface equivalent layer are determined based on theoretical and measured spectra. Specifically, this can involve matching multiple theoretical spectra with measured spectra, selecting those with a matching degree higher than a threshold, and denoting the corresponding refractive index as [n]. 1i ′,n 1j If a sufficiently high threshold is set, a theoretical spectrum that matches the measured spectrum may also be obtained, with the corresponding refractive index denoted as n. 1p ′.

[0095] Therefore, in [n] 1i ′,n 1j Choose a value from '] as the spectral parameter of the surface equivalent layer, or n 1p The '' is used as the spectral parameter of the surface equivalent layer. In Figure 3, the curve with obvious fluctuations in the vertical axis is the curve of the measured spectrum, and the curve with relatively smooth fluctuations in the vertical axis is the curve of the theoretical spectrum. If the similarity between these two curves is considered to be high enough, the refractive index of the surface equivalent layer of the theoretical spectrum can be determined.

[0096] This embodiment generates a theoretical spectrum by providing the spectral parameters of multiple surface equivalent layers, and determines the value of the spectral parameters of the surface equivalent layers by matching them with the measured spectra. This solves the problem of the difficulty in measuring the spectral parameters of near-surface layers and achieves high accuracy.

[0097] In one embodiment, the near-surface layer includes a first type of layer and a second type of layer, wherein the second type of layer is located between the first type of layer and the wafer thin film, i.e., when it is known that there are substances on the wafer thin film surface and the water, these substances are regarded as two layers of substances.

[0098] In this embodiment, the spectral parameters of the first type of layer include the refractive index n1 of the first type of layer, and the spectral parameters of the second type of layer include the refractive index n4 of the second type of layer and the thickness d4 of the second type of layer.

[0099] Accordingly, the reference spectrum can be calculated as follows:

[0100] Obtain the spectral calculation model;

[0101] Determine the spectral parameters of the first type layer, the second type layer, the wafer thin film, and the wafer substrate;

[0102] Reference spectra for different thicknesses of thin films on a given wafer are calculated using spectral parameters and spectral calculation models.

[0103] Specifically, the spectral calculation model of this embodiment has first-type layer and second-type layer parameters. In this embodiment, it is considered that there are multiple layers between the bulk water and the wafer thin film. The medium that is in direct contact with the bulk water is generally air (forming the first-type layer). There is another medium between the air layer and the wafer thin film (forming the second-type layer).

[0104] The first and second types of layers can affect the spectrum of light reflected from the wafer thin film. To avoid this effect, this embodiment uses two layers to simulate the layers formed by various media between the wafer thin film and bulk water, and the relevant parameters of the two layers are incorporated into the constructed spectral calculation model.

[0105] For example, the first type of layer can be regarded as an air-formed layer, so its spectral parameters can be taken according to the values ​​of air. The spectral parameters of the second type of layer can be calculated theoretically.

[0106] The spectral calculation model is specifically a set of formulas. Substituting the values ​​of the spectral parameters into these formulas allows for the calculation of the reflectance corresponding to those spectral parameters. Specifically, the spectral calculation model can be expressed as: f(x) = R, where x represents the spectral parameter and R represents the reflectance. The spectral parameters include at least the wavelength λ and the thickness d2 of the wafer thin film. In this embodiment, it also includes the spectral parameters of the first and second type layers.

[0107] The thickness d2 of the wafer thin film can be given by multiple different values. The curves calculated for different values ​​of d2 are different. This method calculates the reflectivity R corresponding to a given wavelength λ range for different given d2, thereby obtaining the reference spectrum corresponding to different d2.

[0108] Regarding the spectral parameters, in one embodiment, they specifically include the refractive index n1 of the first type layer, the refractive index n2 of the wafer thin film, the refractive index n3 of the wafer substrate, the refractive index n4 of the second type layer, and the thickness d4 of the second type layer.

[0109] For example, a specific spectral calculation model could be:

[0110] R = r·r *

[0111] Where r is the total reflection coefficient determined based on n1, n2, n3, n4, and d4. * Let R be the conjugate complex number of r, and R be the reflectance. Based on the above model, R can be calculated for each given d², corresponding to each λ, thus obtaining the reference spectral data.

[0112] In one embodiment, the total reflection coefficient r is calculated as follows:

[0113] The reflection coefficients of the interfaces of each layer are calculated using n1, n2, n3, and n4; the phase thickness θ of the wafer thin film is calculated using n2, wavelength λ, and wafer thin film thickness d2; the phase thickness α of the second type layer is calculated using n4, wavelength λ, and thickness d4; and the total reflection coefficient r is calculated using the reflection coefficients of the interfaces of each layer, phase thickness α, and phase thickness θ.

[0114] Furthermore, the reflection coefficients of the interfaces of each layer include the reflection coefficient r2 of the interface between the wafer thin film and the wafer substrate, the reflection coefficient r3 of the interface between the first type layer and the second type layer, and the reflection coefficient r4 of the interface between the second type layer and the wafer thin film.

[0115] The calculation of the reflection coefficients at the interfaces of each layer includes: calculating the reflection coefficient r2 at the interface between the wafer thin film and the wafer substrate using n2 and n3; calculating the reflection coefficient r3 at the interface between the wafer thin film and the wafer substrate using n1 and n4; and calculating the reflection coefficient r4 at the interface between the wafer thin film and the wafer substrate using n2 and n4.

[0116] Calculate the total reflection coefficient r, including: calculating the equivalent interface reflection coefficient r using θ, r2, and r4. 等效 Using α, r3 and r 等效 Calculate the total reflection coefficient r.

[0117] As an example, the reflection coefficient can be calculated as follows:

[0118] The phase thickness θ can be calculated as follows:

[0119] The phase thickness α can be calculated as follows:

[0120] The equivalent interface reflection coefficient r can be calculated as follows: 等效 :

[0121] The total reflection coefficient r can be calculated as follows:

[0122] Where i is the imaginary unit and e is the natural constant.

[0123] The above calculation formulas can be modified in simple ways according to actual needs, such as adding preset coefficients or weights to one of the formulas. For those skilled in the art, other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all the calculation formulas here. However, any obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

[0124] Regarding the spectral parameters of the second type layer, one embodiment provides a method for determining its spectral parameters, including:

[0125] Measured spectra of wafer surfaces with first-type and second-type layers are obtained. The wafer includes a wafer substrate and a wafer thin film. The parameters of the wafer substrate and the wafer thin film are known parameters that have been measured in advance.

[0126] Using a spectral calculation model, theoretical spectra are generated for different given spectral parameters of the second type layer. Unlike the process of generating reference spectra, where the spectral parameters of the wafer thin film and wafer substrate are fixed values, the spectral parameters of the second type layer are multiple given values.

[0127] The spectral parameters of the second type layer are determined based on theoretical and measured spectra.

[0128] Specifically, the parameters involved in the spectral calculation model include the refractive index n1 of the first type layer, the refractive index n2 of the wafer thin film, the refractive index n3 of the wafer substrate, the refractive index n4 of the second type layer, and the thickness d4 of the second type layer. Here, n1, n2, and n3 are known, and this embodiment provides multiple n4 values, denoted as [n...]. 4i n 4j ], and multiple d4, which is [d 4i d 4j ].

[0129] In this embodiment, the thickness d2 of the wafer thin film is a known fixed value. Multiple values ​​corresponding to [n] are calculated using a spectral calculation model. 1i n 1j ] and [d 4i d 4j The theoretical spectrum of ].

[0130] Multiple theoretical spectra can be matched with measured spectra, and the theoretical spectra with a matching degree higher than a threshold can be selected. The corresponding refractive index is denoted as [n]. 1j n 1k The corresponding thickness is denoted as [d]. 4j d 4k If a sufficiently high threshold is set, a theoretical spectrum that matches the measured spectrum may be obtained, with the corresponding refractive index denoted as n. 1p The corresponding thickness is denoted as d. 4p .

[0131] Therefore, in [n] 1j n 1k ] and [d 4j d 4k In the diagram, one value is selected as the spectral parameter of the second type layer, or n. 1p and d 4p The spectral parameters of the second type of layer are shown in Figure 4. The curves of the theoretical spectrum (dashed line) and the curves of the measured spectrum (solid line) are shown. If the similarity between the two curves is considered to be high enough, the thickness and refractive index of the second type of layer in the theoretical spectrum can be determined.

[0132] This embodiment generates a theoretical spectrum using the given spectral parameters of the second type layer, and determines the value of the spectral parameters of the second type layer by matching them with the measured spectrum. This solves the problem of the difficulty in measuring the second type layer and has high accuracy.

[0133] This embodiment also provides an endpoint detection method for wafer thin film grinding. Based on the above-mentioned online detection method, the grinding is controlled in real time. This method needs to be executed by electronic devices such as computers or servers, and can be specifically executed by the above-mentioned measuring equipment, including the following operations:

[0134] During the wafer grinding process, the above-mentioned method for in-situ real-time measurement of film thickness is used to monitor whether the thickness of the wafer thin film has reached the target thickness; grinding is stopped when the thickness of the wafer thin film reaches the target thickness.

[0135] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0136] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in one or more blocks of the flowchart illustrations and / or one or more blocks of the block diagrams.

[0137] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means that implement the functions specified in one or more flowcharts and / or one or more block diagrams.

[0138] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions, which execute on the computer or other programmable apparatus, provide steps for implementing the functions specified in one or more flowcharts and / or one or more block diagrams.

[0139] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for measuring film thickness in situ, characterized by, The method comprises the following steps: generating a measured spectrum according to the reflection spectrum of the wafer film and an equivalent light source spectrum, wherein the equivalent light source spectrum is generated by using the wavelength and light intensity corresponding relationship data of the reflection light of the polishing liquid and the medium layer between the polishing liquid and the collimated light source probe; matching the measured spectrum with a reference spectrum library; obtaining the wafer film thickness corresponding to the reference spectrum matched with the measured spectrum as a detection result.

2. The method of claim 1, wherein, Before generating the measured spectrum according to the reflection spectrum of the wafer film and the equivalent light source spectrum, the method further comprises the following steps: obtaining the reflection light of the medium layer emitted by the collimated light source probe and reflected by the reflector; generating the equivalent light source spectrum by using the reflection light.

3. The method of claim 1, wherein, The medium layer comprises a light-transmitting sealing layer arranged on the polishing disc and the polishing pad, and a bulk water layer formed by the polishing liquid.

4. The method of claim 1, wherein, The reference spectrum library is a set of reference spectra generated by using a spectrum calculation model for a given wafer film thickness, wherein the spectrum calculation model comprises the spectrum parameters of the wafer and the spectrum parameters of a near-surface layer formed by the substance between the bulk water on the wafer film surface and the wafer film surface.

5. The method of claim 4, wherein, The spectrum parameters of the wafer comprise the spectrum parameters of the wafer film and the spectrum parameters of the wafer substrate.

6. The method according to claim 5, characterized in that, The spectrum parameters of the wafer film comprise the refractive index n2 of the wafer film, and the spectrum parameters of the wafer substrate comprise the refractive index n3 of the wafer substrate.

7. The method of claim 4, wherein, The near-surface layer is a surface equivalent layer for simulating the substance between the bulk water on the wafer film surface and the wafer film surface.

8. The method of claim 7, wherein, The spectrum parameters of the surface equivalent layer comprise the refractive index n1' of the surface equivalent layer.

9. The method of claim 8, wherein, Before matching the measured spectrum with the reference spectrum library, the method further comprises the following steps: obtaining the spectrum calculation model; determining the spectrum parameters of the surface equivalent layer, the wafer film and the wafer substrate; calculating the reference spectrum under different given wafer film thicknesses by using the spectrum parameters and the spectrum calculation model.

10. The method of claim 4, wherein, The near-surface layer comprises a first type layer and a second type layer, wherein the second type layer is located between the first type layer and the wafer film.

11. The method of claim 10, wherein, The spectrum parameters of the first type layer comprise the refractive index n1 of the first type layer, and the spectrum parameters of the second type layer comprise the refractive index n4 of the second type layer and the thickness d4 of the second type layer.

12. The method of claim 10, wherein, Before matching the measured spectrum with the reference spectrum library, the method further comprises the following steps: obtaining the spectrum calculation model; determining the spectrum parameters of the first type layer, the second type layer, the wafer film and the wafer substrate; calculating the reference spectrum under different given wafer film thicknesses by using the spectrum parameters and the spectrum calculation model.

13. An end point detection method for wafer thin film grinding, characterized by, The method comprises the following steps: using the method for in-situ measurement of film thickness according to any one of claims 1-12 to monitor whether the thickness of the wafer film reaches a target thickness in real time; stopping grinding when the thickness of the wafer film reaches the target thickness.

14. An electronic device, comprising: The method comprises the following steps: a processor and a memory connected with the processor; wherein the memory stores instructions executable by the processor, and the instructions are executed by the processor to enable the processor to perform the method according to any one of claims 1-13.

15. A chemical mechanical polishing apparatus characterized by comprising: The method comprises the following steps: a light-transmitting channel penetrating through the polishing disc and the polishing pad; a sealing layer encapsulating the light transmission channel, the sealing layer and the polishing liquid on the polishing pad forming an in-situ measurement environment; a collimated light source probe for emitting collimated light to the light transmission channel and receiving reflected light from the wafer film surface; a measurement device for performing the method of any one of claims 1-13.

16. The apparatus of claim 15, wherein, The sealing layer includes a first sealing layer encapsulating the light transmission channel of the polishing pad and a second sealing layer encapsulating the light transmission channel of the polishing pad.

17. The device according to claim 16, characterized in that, The material of the first sealing layer includes PU; and the material of the second sealing layer includes glass.

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