Method for measuring film thickness in situ, reference spectrum generation method and device

Abstract

The present invention provides a method for measuring a film thickness in situ, a reference spectrum generation method and a device. The reference spectrum generation method comprises: obtaining a spectrum calculation model which is provided with a first-type layer and a second-type layer, wherein the second-type layer is located between the first-type layer and a wafer film; determining spectral parameters of the first-type layer, the second-type layer, the wafer film and a wafer substrate; and using the spectral parameters and the spectral calculation model to calculate reference spectra at different given thicknesses of the wafer film.

Description

Method for measuring film thickness in-situ, reference spectrum generation method and device TECHNICAL FIELD

[0001] The present application relates to the field of wafer parameter measurement, in particular to a method for measuring film thickness in-situ, a reference spectrum generation method and a device. BACKGROUND

[0002] In wafer manufacturing, with the upgrading of process technology and the reduction of wire and gate size, the requirement of lithography technology on the flatness of wafer surface is higher and higher, and CMP (chemical mechanical polish) technology has been widely used in wafer in recent decades. CMP has very high requirements on polishing accuracy, and in order to meet the accuracy requirements, accurate thickness measurement of wafer film is needed. Due to the complex CMP processing environment, the existing technology cannot realize optical non-contact in-situ real-time measurement of wafer film, and can only use offline measurement and other end-point measurement after the wafer is taken out from the CMP, and the end-point measurement can only detect the grinding end-point and cannot perform real-time measurement.

[0003] In the implementation of the present application, there are various media between the wafer and the probe, such as glass, PU, polishing liquid, etc. Under the influence of these media, the reflectivity spectrum will be "deformed", and the theoretical spectrum of the measured film (wafer film) in the prior art cannot accurately describe this "deformation" phenomenon, resulting in that the prior art cannot accurately measure the accurate thickness of the measured film, and thus since CMP has been applied in the semiconductor manufacturing and processing industry, in-situ measurement of wafer film thickness during processing has not been realized. SUMMARY

[0004] Therefore, the present application provides a reference spectrum generation method for measuring film thickness in-situ, comprising:

[0005] Obtaining a spectrum calculation model with first type layer and second type layer parameters, wherein the second type layer is located between the first type layer and the wafer film;

[0006] Determining the spectrum parameters of the first type layer, the second type layer, the wafer film and the wafer substrate;

[0007] Calculating the reference spectrum under different given thicknesses of the wafer film by using the spectrum parameters and the spectrum calculation model.

[0008] Optionally, determining the spectrum parameters of the second type layer comprises:

[0009] acquire a measured spectrum of a wafer surface in a first type layer state and a second type layer state, wherein the wafer comprises a wafer substrate and a wafer film, and parameters of the wafer substrate and the wafer film are known parameters measured in advance;

[0010] generate a theoretical spectrum of the wafer in the second type layer state according to the spectrum calculation model and a given spectrum parameter of the second type layer;

[0011] determine the spectrum parameter of the second type layer according to the theoretical spectrum and the measured spectrum.

[0012] Optionally, the determining of the spectrum parameter of the second type layer according to the theoretical spectrum and the measured spectrum comprises:

[0013] matching the plurality of theoretical spectra with the measured spectrum, and screening a theoretical spectrum with a matching degree higher than a threshold value;

[0014] determining the spectrum parameter of the second type layer according to the theoretical spectrum with the matching degree higher than the threshold value.

[0015] Optionally, the reference spectrum comprises a curve of wavelength and reflectivity.

[0016] Optionally, the spectrum parameter comprises a refractive index n1 of the first type layer, a refractive index n2 of the wafer film, a refractive index n3 of the wafer substrate, a refractive index n4 of the second type layer, and a thickness d4 of the second type layer.

[0017] Optionally, the spectrum calculation model comprises: R = r·r *

[0018] wherein r is a total reflection coefficient determined based on n1, n2, n3, n4 and d4, r * represents a conjugate complex number of r, and R is reflectivity.

[0019] Optionally, the total reflection coefficient r is calculated in the following manner:

[0020] calculating reflection coefficients of interfaces of each layer by using n1, n2, n3 and n4;

[0021] calculating a phase thickness θ of the wafer film by using n2, wavelength λ and thickness d2 of the wafer film;

[0022] calculating a phase thickness α of the second type layer by using n4, wavelength λ and thickness d4;

[0023] calculating the total reflection coefficient r by using the reflection coefficients of the interfaces of each layer, the phase thickness α and the phase thickness θ.

[0024] Optionally, the reflection coefficients of the interfaces of the layers include a reflection coefficient r2 of an interface between the wafer film and the wafer substrate, a reflection coefficient r3 of an interface between the first type of layer and the second type of layer, and a reflection coefficient r4 of an interface between the second type of layer and the wafer film.

[0025] Optionally, the calculating the reflection coefficients of the interfaces of the layers includes:

[0026] calculating the reflection coefficient r2 of the interface between the wafer film and the wafer substrate using n2 and n3;

[0027] calculating the reflection coefficient r3 of the interface between the first type of layer and the second type of layer using n1 and n4;

[0028] calculating the reflection coefficient r4 of the interface between the second type of layer and the wafer film using n2 and n4.

[0029] Optionally, the calculating the total reflection coefficient r includes:

[0030] calculating the equivalent interface reflection coefficient r using θ, r2 and r4 等效 ;

[0031] calculating the total reflection coefficient r using α, r3 and r 等效 .

[0032] The application also provides a method for in-situ measuring film thickness, comprising:

[0033] acquiring a measured spectrum during grinding of the wafer film;

[0034] matching the measured spectrum with a reference spectrum library obtained by the above method;

[0035] acquiring a wafer film thickness corresponding to the reference spectrum matched with the measured spectrum as a real-time detection result.

[0036] The application also provides a method for end-point detection of wafer film grinding, comprising:

[0037] using the above method for in-situ measuring film thickness to monitor whether the thickness of the wafer film reaches a target thickness in real time;

[0038] stopping grinding when the thickness of the wafer film reaches the target thickness.

[0039] Correspondingly, the application also provides an electronic device, comprising a processor and a memory connected to 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 above method.

[0040] The reference spectrum generation method and device provided in the application introduce the spectrum parameters of two near-surface layers in the spectrum model, and the spectrum calculated under different given wafer film thicknesses reflects the deformation phenomenon, which is consistent with the situation of the measured spectrum. The reference spectrum library generated by the scheme can be used to measure the thickness of the wafer film, which can improve the accuracy. According to the actual needs, the reference spectrum generated by the scheme can be used to measure the thickness of the wafer film in situ and in real time in the CMP environment, thereby greatly improving the efficiency and precision of semiconductor manufacturing and processing.

[0041] The application also provides another reference spectrum generation method for in-situ measurement of film thickness, comprising:

[0042] Obtaining a spectrum calculation model, wherein the spectrum calculation model includes parameters of a surface equivalent layer and a wafer, and the surface equivalent layer is used to simulate at least a layer formed by matter between bulk water and the wafer film surface of the wafer film surface;

[0043] Determining the spectrum parameters of the surface equivalent layer, the wafer film and the wafer substrate;

[0044] Calculating reference spectra under different given thicknesses of the wafer film by using the spectrum parameters and the spectrum calculation model.

[0045] Optionally, the spectrum parameters of the surface equivalent layer are determined, comprising:

[0046] Obtaining a measured spectrum under the condition that the wafer surface has a surface equivalent layer, wherein the wafer includes a wafer substrate and a wafer film, and the parameters of the wafer substrate and the wafer film are known parameters measured in advance;

[0047] Generating theoretical spectra under different given spectrum parameters of the surface equivalent layer by using the spectrum calculation model;

[0048] Determining the spectrum parameters of the surface equivalent layer according to the theoretical spectra and the measured spectrum.

[0049] Optionally, the spectrum parameters of the surface equivalent layer are determined according to the theoretical spectra and the measured spectrum, comprising:

[0050] Matching a plurality of theoretical spectra with the measured spectrum, and screening out theoretical spectra with a matching degree higher than a threshold value;

[0051] Determining the spectrum parameters of the surface equivalent layer according to the theoretical spectrum with the matching degree higher than the threshold value.

[0052] Optionally, the reference spectrum includes a wavelength-reflection rate corresponding relationship curve.

[0053] Optionally, the spectrum parameters include the refractive index n1 of the surface equivalent layer, the refractive index n2 of the wafer film and the refractive index n3 of the wafer substrate.

[0054] Optionally, the spectrum calculation model comprises: R = r·r *

[0055] wherein r is a total reflection coefficient determined based on n1, n2 and n3, r * represents a conjugate complex number of r, and R is reflectivity.

[0056] Optionally, the total reflection coefficient r is calculated in the following manner:

[0057] The reflection coefficient of the interface of each layer is calculated using n1, n2 and n3;

[0058] The phase thickness θ of the wafer film is calculated using n2, wavelength λ and thickness d2;

[0059] The total reflection coefficient r is calculated using the reflection coefficient of the interface of each layer and the phase thickness θ.

[0060] Optionally, the reflection coefficient of the interface of each layer comprises the reflection coefficient r1 of the interface between the surface equivalent layer and the wafer film, and the reflection coefficient r2 of the interface between the wafer film and the wafer substrate.

[0061] Optionally, calculating the reflection coefficient of the interface of each layer comprises:

[0062] The reflection coefficient r1 of the interface between the surface equivalent layer and the wafer film is calculated using n1 and n2;

[0063] The reflection coefficient r2 of the interface between the wafer film and the wafer substrate is calculated using n2 and n3.

[0064] Optionally, the surface equivalent layer is further used to simulate bulk water on the surface of the wafer film, and layers formed by the bulk water and various media between the bulk water and the spectrum collection end.

[0065] The application further provides another method for measuring the thickness of a film in situ, comprising:

[0066] Obtaining a measured spectrum during the grinding of the wafer film;

[0067] Matching the measured spectrum with a reference spectrum library obtained using the above method;

[0068] Obtaining the thickness of the wafer film corresponding to the reference spectrum matched with the measured spectrum as a real-time detection result.

[0069] The application further provides another end-point detection method for the grinding of a wafer film, comprising:

[0070] Using the above method for measuring the thickness of a film in situ to monitor whether the thickness of the wafer film reaches a target thickness in real time;

[0071] When the thickness of the wafer film reaches the target thickness, the grinding is stopped.

[0072] Correspondingly, the application provides an electronic device, comprising 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 make the processor execute the above method.

[0073] The reference spectrum generation method provided by the application introduces a surface equivalent layer structure and parameters of the layer in the spectrum model, and the medium between the wafer film in the grinding scene and the spectrum measurement end is simulated through the surface equivalent layer, so that the spectrum calculated under different given wafer film thicknesses reflects the deformation phenomenon, which is consistent with the situation of the measured spectrum. The reference spectrum library generated by the present scheme can be used to measure the thickness of the wafer film, which can improve the accuracy. BRIEF DESCRIPTION OF DRAWINGS

[0074] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0075] Fig. 1 is a schematic diagram of the in-situ measurement of film thickness in the embodiment of the present application;

[0076] Fig. 2 is a comparison diagram of the reference spectrum and the measured spectrum in the embodiment of the present application;

[0077] Fig. 3 is a plurality of reference spectrum curves in the embodiment of the present application;

[0078] Fig. 4 is a comparison diagram of the theoretical spectrum curve and the measured spectrum curve in the embodiment of the present application. DETAILED DESCRIPTION

[0079] The technical solutions of the present application will be described in detail below with reference to the drawings. Obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0080] In addition, the technical features involved in different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0081] The embodiment of the present application provides a reference spectrum generation method for in-situ measurement of film thickness, which can be executed by a computer or a server or other electronic device, comprising the following operations:

[0082] obtaining a spectrum calculation model, wherein parameters of a surface equivalent layer and the wafer are included in the spectrum calculation model, and the surface equivalent layer is used to simulate a layer formed by matter between bulk water and a wafer film surface of the wafer film.

[0083] spectrum parameters of the surface equivalent layer, the wafer film and the wafer substrate are determined. The spectrum parameters of the surface equivalent layer can be calculated by theoretical calculation. The spectrum parameters of the wafer film and the wafer substrate are generally known or can also be measured. The reference spectrum under different given thicknesses of the wafer film is calculated by using the spectrum parameters and the spectrum calculation model. The reference spectrum can be the corresponding relationship data of wavelength and reflectivity, which can be expressed by a curve, that is, the reference spectrum can be the corresponding relationship curve of wavelength and reflectivity. In the embodiment, the corresponding relationship of wavelength and reflectivity can be deformed according to actual needs, and other different forms of changes or variations can be made on the basis of the above description for those skilled in the art. All embodiments cannot be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the present application.

[0084] As shown in FIG. 1, the final measurement object in the application scenario faced by the embodiment of the present application is a wafer 1, which includes a wafer substrate and a wafer film. The wafer 1 is in a state to be ground or ground, and there is bulk water between the ground surface of the wafer film and the polishing pad 2, which can be a polishing liquid or water, and there is also matter between the bulk water and the wafer film. In the orientation shown in FIG. 1, the bulk water is located between the lower surface of the wafer 1 and the polishing pad 2, and the matter is located between the bulk water and the lower surface of the wafer 1. These matters can be one matter, such as air, or multiple matters.

[0085] The matter between the bulk water and the wafer film will affect the spectrum of the reflected light of the wafer film. In order to avoid this influence, a surface equivalent layer is set to simulate the layer formed by the matter between the wafer film and the bulk water in an embodiment, and the related parameters of the surface equivalent layer are introduced when the spectrum calculation model is constructed.

[0086] There are also multiple media between the bulk water and the spectrum collection end. In the orientation shown in FIG. 1, there is one or more sealing layers 3 and air layers 4 under the bulk water, and the reflected light of the wafer film surface of the wafer 1 passes through multiple media to the spectrum collection end 5, which will all affect the spectrum. In order to avoid the influence of the media between the bulk water and the wafer film and the media between the bulk water and the spectrum collection end on the spectrum, a surface equivalent layer is set to simulate the multiple media layers between the wafer film and the spectrum collection end in an embodiment, and the related parameters of the surface equivalent layer are introduced when the spectrum calculation model is constructed.

[0087] It should be noted that since the surface equivalent layer simulates at least two different media, the values of the related parameters are different from the parameter values of the simulated media, and should be equivalent to the joint action of multiple media.

[0088] For example, assuming that the wafer film surface in the measurement scene is a polishing liquid, and the polishing liquid and the wafer film include an air layer, the parameters of the surface equivalent layer in this embodiment can specifically include a refractive index, which is not equal to the refractive index of the polishing liquid or the air refractive index.

[0089] The spectral calculation model is specifically a set of calculation formulas, and the values of the spectral parameters can be substituted into the calculation formulas to calculate the reflectivity corresponding to the spectral parameters. Specifically, the spectral calculation model can be expressed in the following manner: f(x)=R, where x represents the spectral parameters, and R represents the reflectivity. The spectral parameters at least include the wavelength λ and the thickness d2 of the wafer film, and in this embodiment, the parameters of the surface equivalent layer are also included.

[0090] Each reference spectrum corresponds to a different d2, such as the curve shown in FIG. 2, where the relatively smooth curve is the curve of the reference spectrum, which is a curve fitted by calculating the reflectivity corresponding to d2 taking the value of 700 nm and the wavelength λ taking the value range of 400-800 nm by using the method. The 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.

[0091] Regarding the spectral parameters, in one embodiment, the refractive index n1 of the surface equivalent layer, the refractive index n2 of the wafer film, and the refractive index n3 of the wafer substrate are specifically included.

[0092] For example, the spectral calculation model can be specifically: R=r·r *

[0093] where r is the total reflection coefficient determined based on n1, n2 and n3, r * represents the conjugate complex number of r, and R is the reflectivity.

[0094] In one embodiment, the total reflection coefficient r is calculated in the following manner:

[0095] The reflection coefficients of the interfaces of each layer are calculated using n1, n2 and n3; the phase thickness θ of the wafer film is calculated using n2, the wavelength λ and the 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.

[0096] Further, the reflection coefficients of the interfaces of each layer include the reflection coefficient r1 of the interface between the surface equivalent layer and the wafer film, and the reflection coefficient r2 of the interface between the wafer film and the wafer substrate.

[0097] The reflection coefficient of the interface of each layer is calculated by calculating r1 using n1 and n2, and calculating r2 using n2 and n3.

[0098] As an example, r can be calculated as follows:

[0099] where i is the imaginary unit, and e is the natural constant.

[0100] Further, r1 and r2 are calculated as follows:

[0101] θ is calculated as follows:

[0102] Regarding the above calculation formulas, simple modifications can also be made according to actual needs, such as adding preset coefficients or weights in some calculation formulas, and other different forms of changes or variations can also be made by those skilled in the art based on the above description. Here, it is not necessary and impossible to exhaust all calculation formulas. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

[0103] The reference spectrum calculated in the embodiment is used for comparison with the measured spectrum of the wafer in the online state (grinding state or to-be-ground state). The set of reference spectra of different wafer film thicknesses is referred to as a reference spectrum library.

[0104] The reference spectrum generation method provided in the embodiment introduces a surface equivalent layer structure and parameters of the layer in a spectrum model. All media between the wafer film and the spectrum measurement end in the grinding scene are simulated by the surface equivalent layer. The spectrum calculated under different given wafer film thicknesses reflects the deformation phenomenon, which is consistent with the situation of the measured spectrum. The reference spectrum library generated by the present scheme can be used to measure the thickness of the wafer film, and the accuracy can be improved.

[0105] Regarding the spectrum parameters of the surface equivalent layer, in one embodiment, a method for determining the spectrum parameters of the surface equivalent layer is provided, including:

[0106] The measured spectrum under the condition that the wafer surface has a surface equivalent layer is obtained, wherein the wafer includes a wafer substrate and a wafer film, and the parameters of the wafer substrate and the wafer film are known parameters measured in advance;

[0107] The spectral calculation model is used to generate theoretical spectra of the surface equivalent layer with different given spectral parameters. The spectral calculation model and the generation method of the theoretical spectrum can refer to the above-mentioned embodiments about the reference spectrum. The difference between the process of generating the reference spectrum is that the spectral parameters of the wafer film and the wafer substrate are fixed values, and the spectral parameters of the surface equivalent layer are multiple given values.

[0108] 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 film, and the refractive index n3 of the wafer substrate, wherein n2 and n3 are known, and multiple n1 are given in the embodiment, denoted as [n 1i , n 1j ].

[0109] The thickness d2 of the wafer film in the embodiment is a known fixed value, and the spectral calculation model is used to calculate multiple theoretical spectra corresponding to [n 1i , n 1j ].

[0110] The spectral parameters of the surface equivalent layer are determined according to the theoretical spectrum and the measured spectrum. Specifically, multiple theoretical spectra can be matched with the measured spectrum, and the theoretical spectra with a matching degree higher than a threshold value are screened out, and the corresponding refractive index is denoted as [n 1j , n 1k ]. If a high enough threshold value is set, a theoretical spectrum matching the measured spectrum can also be obtained, and the corresponding refractive index is denoted as n 1p .

[0111] Therefore, one value can be selected from [n 1j , n 1k ] as the spectral parameter of the surface equivalent layer, or n 1p as the spectral parameter of the surface equivalent layer.

[0112] The embodiment generates theoretical spectra with multiple given spectral parameters of the surface equivalent layer, and determines the value of the spectral parameter of the surface equivalent layer by matching with the measured spectrum, which has high accuracy.

[0113] The embodiment also provides a method for measuring the film thickness in situ. The reference spectrum (reference spectrum library) obtained based on the above-mentioned method is used for online detection, and the method needs to be executed by an electronic device such as a computer or a server, and includes the following operations:

[0114] The measured spectrum is obtained during the grinding process of the wafer film. There is bulk water on the surface of the wafer film during the grinding process, and there is at least another medium between the bulk water and the collection end of the measured spectrum.

[0115] The measured spectrum is matched with the reference spectrum library. By comparing all the reference spectra with the measured spectrum one by one, one reference spectrum most similar to the measured spectrum is determined. There are various methods for calculating the similarity of two spectra, and various indicators for measuring the similarity or matching degree, such as the similarity method, the nonlinear regression method, and the FFT method, etc.

[0116] The wafer film thickness corresponding to the reference spectrum matched with the measured spectrum is obtained as the real-time detection result. The curve with obvious fluctuations in the ordinate in FIG. 2 is the curve of the measured spectrum. It is assumed that the measured spectrum is determined to have the highest similarity with the reference spectrum in FIG. 2, and since the thickness corresponding to the reference spectrum is 700 nm, the real-time monitoring result is that the wafer film thickness is 700 nm.

[0117] The embodiment also provides an endpoint detection method for wafer film grinding, which is based on the above online detection method for real-time control of grinding. The method needs to be executed by an electronic device such as a computer or a server, and includes the following operations:

[0118] In the wafer grinding process, the above method for in-situ measurement of film thickness is used to monitor whether the thickness of the wafer film reaches the target thickness in real time; and the grinding is stopped when the thickness of the wafer film reaches the target thickness.

[0119] The embodiment of the present application provides another reference spectrum generation method for in-situ measurement of film thickness, which can be executed by an electronic device such as a computer or a server, and includes the following operations:

[0120] A spectrum calculation model with parameters of the first type layer and the second type layer is obtained, wherein the second type layer is located between the first type layer and the wafer film. The final measurement object in the application scenario faced by the embodiment of the present application is a wafer, which includes a wafer substrate and a wafer film. The wafer is in a state to be ground or is in a ground state. The grinding surface of the wafer film is covered with bulk water, which can be a polishing liquid or water, etc. There are various media between the bulk water and the wafer film. The media in direct contact with the bulk water is generally air (forming the first type layer), and there is another medium (forming the second type layer) between the air layer and the wafer film.

[0121] The first type layer and the second type layer will affect the spectrum of the wafer film reflected light. In order to avoid the influence of the media between the bulk water and the wafer film on the spectrum, the embodiment sets two layers to simulate the layers formed by the various media between the wafer film and the bulk water, and introduces the related parameters of the two layers when constructing the spectrum calculation model.

[0122] The spectral parameters of the first type layer, the second type layer, the wafer film and the wafer substrate are determined. The first type layer can be regarded as a layer formed by air, and thus its spectral parameters can be taken as those of air. The spectral parameters of the second type layer can be calculated by theoretical calculation. The spectral parameters of the wafer film and the wafer substrate are usually known or can also be measured.

[0123] The reference spectrum under different given thicknesses of the wafer film is calculated by using the spectral parameters and the spectral calculation model. The reference spectrum can be the corresponding relationship data of wavelength and reflectivity, and can be expressed by a curve, that is, the reference spectrum can be the corresponding relationship curve of wavelength and reflectivity. In the embodiment, the corresponding relationship of wavelength and reflectivity can be deformed according to actual needs by those skilled in the art, and other different forms of changes or variations can also be made by those skilled in the art on the basis of the above description. All the embodiments cannot be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the present application.

[0124] The spectral calculation model is a set of calculation formulas. The reflectivity corresponding to the spectral parameters can be calculated by substituting the values of the spectral parameters into the calculation formulas. Specifically, the spectral calculation model can be expressed as f(x)=R, where x represents the spectral parameters, and R represents the reflectivity. The spectral parameters at least include the wavelength λ and the thickness d2 of the wafer film, and in the embodiment, the spectral parameters of the first type layer and the second type layer are also included.

[0125] The thickness d2 of the wafer film has a plurality of different given values. The curves calculated under different values of d2 are all different. The present method calculates the reflectivity R corresponding to the given wavelength λ range for different given d2, so as to obtain the reference spectrum corresponding to different d2. FIG. 3 shows the curves of four spectra with d2 being 100 nm, 300 nm, 500 nm and 700 nm.

[0126] Regarding the spectral parameters, in one embodiment, the spectral parameters specifically include the refractive index n1 of the first type layer, the refractive index n2 of the wafer 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.

[0127] As an example, the spectral calculation model can be specifically as follows: R=r·r *

[0128] wherein r is the total reflection coefficient determined based on n1, n2, n3, n4 and d4, r * is the conjugate complex number of r, and R is the reflectivity. According to the above model, R under each λ corresponding to each given d2 can be calculated, and thus the reference spectrum data is obtained.

[0129] In one embodiment, the total reflection coefficient r is calculated in the following way:

[0130] The reflection coefficients of the interfaces of the layers are calculated using n1, n2, n3, n4; the phase thickness θ of the wafer film is calculated using n2, wavelength λ and thickness d2 of the wafer film; the phase thickness α of the second type of 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 the layers, phase thickness α and phase thickness θ.

[0131] Further, the reflection coefficients of the interfaces of the layers include the reflection coefficient r2 of the interface between the wafer film and the wafer substrate, the reflection coefficient r3 of the interface between the first type of layer and the second type of layer, and the reflection coefficient r4 of the interface between the second type of layer and the wafer film.

[0132] The reflection coefficients of the interfaces of the layers are calculated in the following way: the reflection coefficient r2 of the interface between the wafer film and the wafer substrate is calculated using n2 and n3; the reflection coefficient r3 of the interface between the first type of layer and the second type of layer is calculated using n1 and n4; and the reflection coefficient r4 of the interface between the second type of layer and the wafer film is calculated using n2 and n4.

[0133] The total reflection coefficient r is calculated in the following way: the equivalent interface reflection coefficient r 等效 is calculated using θ, r2 and r4; and the total reflection coefficient r is calculated using α, r3 and r 等效 .

[0134] As an example, the reflection coefficient can be calculated in the following way:

[0135] The phase thickness θ can be calculated in the following way:

[0136] The phase thickness α can be calculated in the following way:

[0137] The equivalent interface reflection coefficient r 等效 can be calculated in the following way:

[0138] The total reflection coefficient r can be calculated in the following way:

[0139] where i is the imaginary unit and e is the natural constant.

[0140] The above calculation formulae can also be simply modified according to actual needs, such as adding preset coefficients or weights in some calculation formulae, and other different forms of changes or variations can be made by those skilled in the art based on the above description. All calculation formulae do not need to be exhausted here. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

[0141] Regarding the spectral parameters of the second type of layer, in one embodiment, a method for determining the spectral parameters of the second type of layer is provided, including the following operations:

[0142] The measured spectrum of the wafer surface under the condition of the first type of layer and the second type of layer is obtained, the wafer includes a wafer substrate and a wafer film, and the parameters of the wafer substrate and the wafer film are known parameters measured in advance.

[0143] The theoretical spectrum under different given spectral parameters of the second type of layer is generated by using a spectrum calculation model. The difference from the process of generating the reference spectrum is that the spectral parameters of the wafer film and the wafer substrate are fixed values, and the spectral parameters of the second type of layer are multiple given values.

[0144] The spectral parameters of the second type of layer are determined according to the theoretical spectrum and the measured spectrum.

[0145] Specifically, the parameters involved in the spectrum calculation model include the refractive index n1 of the first type of layer, the refractive index n2 of the wafer film, the refractive index n3 of the wafer substrate, the refractive index n4 of the second type of layer, and the thickness d4 of the second type of layer, wherein n1, n2 and n3 are known, multiple n4 are given in the embodiment, denoted as [n 4i , n 4j ], and multiple d4 are given, denoted as [d 4i , d 4j ].

[0146] In the embodiment, the thickness d2 of the wafer film is a known fixed value, and multiple theoretical spectra corresponding to [n 1i , n 1j ] and [d 4i , d 4j ] are calculated by using the spectrum calculation model.

[0147] The multiple theoretical spectra can be matched with the measured spectrum, and the theoretical spectra with a matching degree higher than a threshold are screened out, the corresponding refractive index is denoted as [n 1j , n 1k ], and the corresponding thickness is denoted as [d 4j , d 4k ]; if a high enough threshold is set, a theoretical spectrum matching the measured spectrum can also be obtained, the corresponding refractive index is denoted as n 1p , and the corresponding thickness is denoted as d4p .

[0148] Thus, one value in [n 1j , n 1k ] and [d 4j , d 4k ] can be selected as the spectral parameter of the second type layer, or n 1p and d 4p are the spectral parameters of the second type layer. Figure 4 shows the curve of the theoretical spectrum (dotted line) and the curve of the measured spectrum (solid line), and if the similarity of the two curves is considered to be high enough, the thickness and refractive index of the second type layer of the theoretical spectrum are determined as the result.

[0149] The embodiment generates a theoretical spectrum based on the given spectral parameters of the second type layer, and determines the value of the spectral parameters of the second type layer by matching the theoretical spectrum with the measured spectrum, which is accurate.

[0150] The embodiment also provides a method for measuring the film thickness in situ, which is based on the reference spectrum (reference spectrum library) obtained by the above method under different given wafer film thicknesses for online detection. The method needs to be executed by an electronic device such as a computer or a server, and includes the following operations:

[0151] The measured spectrum is obtained during the grinding process of the wafer film.

[0152] The measured spectrum is matched with the reference spectrum library. By comparing all the reference spectra with the measured spectrum one by one, a reference spectrum most similar to the measured spectrum is determined. There are various methods for calculating the similarity of the two spectra, and various indicators for measuring the similarity or matching degree, such as the similarity method, the nonlinear regression method, and the FFT method, etc.

[0153] The wafer film thickness corresponding to the reference spectrum matched with the real-time spectrum is obtained as the real-time detection result.

[0154] The embodiment also provides an end point detection method for wafer film grinding, which is based on the above online detection method for real-time control of grinding. The method needs to be executed by an electronic device such as a computer or a server, and includes the following operations:

[0155] During the grinding process of the wafer, the above method for measuring the film thickness in situ is used to monitor whether the thickness of the wafer film reaches the target thickness in real time; and the grinding is stopped when the thickness of the wafer film reaches the target thickness.

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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 generating a reference spectrum for in-situ measurement of film thickness, characterized in that, include: Obtain a spectral calculation model with parameters of 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; Determine the spectral parameters of the first type of layer, the second type of layer, the wafer thin film, and the wafer substrate; The reference spectra for different given wafer thin film thicknesses are calculated using the spectral parameters and the spectral calculation model.

2. The method according to claim 1, characterized in that, Determining the spectral parameters of the second type of layer includes: Measured spectra of a wafer surface having a first type of layer and a second type of layer are obtained, 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; Using the aforementioned spectral calculation model, theoretical spectra are generated for different given spectral parameters of the second type layer; The spectral parameters of the second type of layer are determined based on the theoretical spectrum and the measured spectrum.

3. The method according to claim 2, characterized in that, Determining the spectral parameters of the second type layer based on the theoretical spectrum and the measured spectrum includes: Multiple theoretical spectra are matched with measured spectra, and theoretical spectra with a matching degree higher than a threshold are selected. The spectral parameters of the second type of layer are determined based on the theoretical spectra with a matching degree higher than the threshold.

4. The method according to claim 1, characterized in that, The spectral parameters 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.

5. The method according to claim 4, characterized in that, The spectral calculation model includes: R = r·r * Where r is the total reflection coefficient determined based on n1, n2, n3, n4, and d4. * Let r be the conjugate complex number, and R be the reflectivity.

6. The method according to claim 5, characterized in that, The total reflection coefficient r is calculated as follows: Calculate the reflection coefficient of the interface of each layer 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; The total reflection coefficient r is calculated using the reflection coefficients, phase thickness α, and phase thickness θ of each layer's interface.

7. The method according to claim 6, characterized in that, 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.

8. The method according to claim 7, characterized in that, Calculating the reflection coefficient of each layer's interface includes: The reflection coefficient r2 at the interface between the wafer thin film and the wafer substrate is calculated using n2 and n3; The reflection coefficient r3 at the interface between the first type layer and the second type layer is calculated using n1 and n4; The reflection coefficient r4 at the interface between the second type layer and the wafer thin film is calculated using n2 and n4.

9. The method according to claim 7, characterized in that, The total reflectance r is calculated, including: Calculate 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.

10. A method for generating a reference spectrum for in-situ measurement of film thickness, characterized in that, include: A spectral calculation model is obtained, which includes parameters of a surface equivalent layer and a wafer. The surface equivalent layer is used to simulate at least the layer formed between the bulk water on the wafer thin film surface and the material on the wafer thin film surface. Determine the spectral parameters of the surface equivalent layer, wafer thin film, and wafer substrate; The reference spectra for different given wafer thin film thicknesses are calculated using the spectral parameters and the spectral calculation model.

11. The method according to claim 10, characterized in that, Determining the spectral parameters of the surface equivalent layer includes: 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; Using the aforementioned spectral calculation model, theoretical spectra are generated under different given surface equivalent layer spectral parameters; The spectral parameters of the surface equivalent layer are determined based on the theoretical spectrum and the measured spectrum.

12. The method according to claim 11, characterized in that... Determining the spectral parameters of the surface equivalent layer based on the theoretical spectrum and the measured spectrum includes: Multiple theoretical spectra are matched with measured spectra, and theoretical spectra with a matching degree higher than a threshold are selected. The spectral parameters of the surface equivalent layer are determined based on the theoretical spectra with a matching degree higher than the threshold.

13. The method according to claim 10, characterized in that, The spectral parameters 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.

14. The method according to claim 13, characterized in that, The spectral calculation model includes: R = r·r * 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.

15. The method according to claim 14, characterized in that, The total reflection coefficient r is calculated as follows: Calculate the reflection coefficients of the interfaces of each layer using n1, n2, and n3; The phase thickness θ of the wafer thin film is calculated using n2, wavelength λ, and thickness d2; The total reflection coefficient r is calculated using the reflection coefficients of the interfaces of each layer and the phase thickness θ.

16. The method according to claim 15, characterized in that, 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.

17. The method according to claim 16, characterized in that, Calculating the reflection coefficient of each layer's interface includes: The reflection coefficient r1 at the interface between the surface equivalent layer and the wafer thin film is calculated using n1 and n2; The reflection coefficient r2 at the interface between the wafer thin film and the wafer substrate is calculated using n2 and n3.

18. The method according to any one of claims 10-17, characterized in that, The surface equivalent layer is also used to simulate bulk water on the surface of a wafer thin film, and a layer formed by various media between the bulk water and the spectral acquisition end.

19. The method according to claim 1 or 10, characterized in that, The reference spectrum includes a curve showing the relationship between wavelength and reflectivity.

20. A method for in-situ measurement of film thickness, characterized in that, include: Measured spectra were obtained during the grinding process of wafer thin films; The measured spectra are matched with a reference spectral library obtained using the method described in any one of claims 1-19; The wafer thin film thickness corresponding to the reference spectrum that matches the measured spectrum is obtained as the real-time detection result.

21. A method for detecting the endpoint of wafer thin film grinding, characterized in that, include: Using the method for in-situ film thickness measurement as described in claim 20, the thickness of the wafer thin film can be monitored in real time to see if the target thickness has been reached. Grinding stops when the wafer film thickness reaches the target thickness.

22. An electronic device, characterized in that, include: 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 method as described in any one of claims 1-21.

23. A chemical mechanical polishing apparatus, characterized in that, Used for chemical mechanical polishing of wafer thin films, and for measuring the thickness of wafer thin films using the method of claim 20 and / or for endpoint detection of chemical mechanical polishing using the endpoint detection method of claim 21.

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