Method for Establishing Single-Wavelength Beam Thickness Measurement Reference Database, Measurement Method and Equipment

Abstract

The present invention provides a method, a measurement method and a device for establishing a reference database for single-wavelength beam thickness measurement. The method for establishing the reference database includes: obtaining the reflectivity of a wafer thin film at different thicknesses, where the thickness is a given value, and the corresponding reflectivity is a value calculated through a mathematical model. The reflectivity is the reflectivity of the wafer thin film to light of a specific wavelength, and the reflectivity shows periodic changes with the change of the thickness; determining the trend information of the change of the reflectivity with the thickness; and establishing a reference database for measuring the thickness of the wafer thin film by a single-wavelength beam according to the different thicknesses, the corresponding reflectivities and the trend information.

Description

Technical Field

[0001] The present invention relates to the field of wafer feature measurement, and particularly to a method for establishing a reference database for single-wavelength beam thickness measurement, a measurement method, and a device. Background Art

[0002] In the polishing EPD (End Point Detection) process based on optical measurement methods, there are two methods for measuring the thickness of the wafer thin film: The first method is to invert the film thickness through the spectral characteristic information of multiple wavelengths in the spectrometer at different film thicknesses, which is simply referred to as the multi-wavelength beam measurement method; the second method is under a single-wavelength light source, by converting the received optical intensity signal of the reflected light into an electrical signal, thereby judging the relative thickness of the wafer thin film, which is simply referred to as the single-wavelength beam measurement method.

[0003] However, when performing EPD end point detection on a CMP (Chemical Mechanical Polishing) machine tool, since there is no peak characteristic information for small film thicknesses in the wide spectral wavelength range, and the spectral shape changes with the film thickness are less obvious than those for large film thicknesses, it is difficult for the multi-wavelength beam measurement method to obtain accurate film thickness information at small film thicknesses.

[0004] The defect of the single-wavelength beam method is that since the output electrical signal shows periodic changes with the film thickness value, this method can only obtain relative measurement values of the film thickness and cannot obtain the absolute value of the film thickness. Summary of the Invention

[0005] In view of this, the present application provides a method for establishing a reference database for single-wavelength beam thickness measurement, including:

[0006] Obtaining the reflectivity of the wafer thin film at different thicknesses, where the thickness is a given value, and the corresponding reflectivity is a value calculated by a mathematical model. The reflectivity is the reflectivity of the wafer thin film to light of a specific wavelength, and the reflectivity shows periodic changes with the change of the thickness;

[0007] Determining the trend information of the change of the reflectivity with the thickness;

[0008] Establishing a reference database for measuring the thickness of the wafer thin film by a single-wavelength beam according to the different thicknesses, the corresponding reflectivities, and the trend information.

[0009] Optionally, each piece of data in the reference database includes the thickness, the reflectivity, and the trend information of the reflectivity. The trend information is used to indicate the change trend of the reflectivity value in one piece of data compared with the reflectivity in another piece of data with a larger adjacent thickness.

[0010] Optionally, in the reference database, two different thicknesses correspond to the same reflectivity and different trend information.

[0011] Optionally, the number of the reference databases is one or two. Each of the same reference databases has unique trend information, and the trend information is used to indicate the change trend of the reflectivity value in each piece of data in the reference database compared with the reflectivity in another piece of data with a larger adjacent thickness.

[0012] Optionally, when there are two reference databases, the two reference databases have different trend information, and different thicknesses in the two reference databases correspond to the same reflectivity.

[0013] Optionally, determining the trend information of the change of the reflectivity with the thickness includes:

[0014] Starting from the reflectivity corresponding to the maximum thickness within a specific thickness range, one by one, compare the reflectivity corresponding to the next smaller thickness with the reflectivity corresponding to the previous larger thickness;

[0015] When the reflectivity corresponding to the smaller thickness is greater than the reflectivity corresponding to the larger thickness, determine that the trend of the reflectivity corresponding to the smaller thickness is rising;

[0016] When the reflectivity corresponding to the smaller thickness is less than the reflectivity corresponding to the larger thickness, determine that the trend of the reflectivity corresponding to the smaller thickness is falling.

[0017] Optionally, after obtaining the reference database, it further includes:

[0018] Use a conversion coefficient to convert the reference database into a reference database applicable to the multilayer film environment.

[0019] This application also provides a thickness measurement method for the wafer thin film polishing process, including:

[0020] During the polishing process of the wafer thin film, obtain the electrical signal corresponding to the light intensity of the reflected light of the wafer thin film for a single-wavelength beam , and at the same time determine the trend information of the change of the electrical signal with the thickness;

[0021] According to the electrical signal and the calibration coefficient calculate the reflectivity of the wafer thin film for the single-wavelength beam , and the reflectivity changes periodically with the thickness;

[0022] According to the thickness at the previous moment , the reflectivity and the trend information, match in a pre-established reference database to obtain the thickness at the current moment , where the reference database includes the reflectivity corresponding to different thicknesses and the trend information of the change of reflectivity with thickness.

[0023] Optionally, before calculating the reflectivity, it further includes:

[0024] Collect the electrical signal corresponding to the light intensity of the reflected light of a single-wavelength beam for a wafer thin film with a known thickness ;

[0025] Calculate the reflectivity of the wafer thin film for the single-wavelength reflected light according to the thickness ;

[0026] Calculate the calibration coefficient according to the reflectivity and the electrical signal ;

[0027] Optionally, the electrical signal is a voltage signal, and the calibration coefficient ; the reflectivity

[0028] Optionally, determining the trend information of the change of the electrical signal with thickness includes:

[0029] Compare the electrical signal collected at the current moment with the electrical signal collected at the previous moment , where the thickness of the wafer thin film at the current moment is less than the thickness of the wafer thin film at the previous moment;

[0030] Obtain the trend information according to the comparison result, where if then the trend information indicates a decrease, and if then the trend information indicates an increase.

[0031] Optionally, obtaining the thickness at the current moment includes:

[0032] Determine a set of data including the thickness in the reference database;

[0033] Match two sets of data according to the reflectivity in the set of data;

[0034] According to the trend information of determine a set of data from the two sets of data to obtain the thickness ​​​​

[0035] Correspondingly, the present application provides an apparatus for establishing a reference database for single-wavelength beam thickness measurement, including: a processor and a memory connected to the processor; wherein, the memory stores instructions executable by the processor, and when the instructions are executed by the processor, the processor is caused to execute the above-mentioned method for establishing a reference database for single-wavelength beam thickness measurement.

[0036] Correspondingly, the present application provides a thickness measurement apparatus for the wafer thin film polishing process, including: a processor and a memory connected to the processor; wherein, the memory stores instructions executable by the processor, and when the instructions are executed by the processor, the processor is caused to execute the above-mentioned thickness measurement method for the wafer thin film polishing process.

[0037] The method and apparatus for establishing a reference database for single-wavelength beam thickness measurement provided by the present application analyze the known wafer thin film thickness and the corresponding reflectivity, determine the trend information of the reflectivity changing with the thickness, and establish a reference database for measuring the wafer thin film thickness by single-wavelength beam according to different thicknesses and the corresponding reflectivity and trend information. The trend information is consistent with the trend of the electrical signal measured by the single-wavelength beam. According to this reference database, during the single-wavelength beam measurement process, by using the two kinds of information of the measured electrical signal and its trend, a unique thickness value can be matched in any thickness period in the reference database, so that the single-wavelength beam measurement method can measure the absolute thickness of the wafer thin film.

[0038] The thickness measurement method and apparatus for the wafer thin film polishing process provided by the present application analyze the electrical signal measured by the single-wavelength beam, determine the trend information of the electrical signal changing with the thickness of the wafer thin film during the polishing process, calculate the reflectivity based on a pre-determined calibration coefficient, and in the pre-established reference database, by combining the thickness information at the previous moment, and the two kinds of information of the reflectivity and the trend of the electrical signal, a unique thickness value can be matched in the reference database, so that the single-wavelength beam measurement method can measure the absolute thickness of the wafer thin film during the polishing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0040] Figure 1 It is a flowchart of the method for establishing a reference database for single-wavelength beam thickness measurement in an embodiment of the present application;

[0041] Figure 2 Schematic diagram of reflectivity and thickness data in the embodiments of the present application;

[0042] Figure 3 Flow chart of the single-wavelength beam measurement method in the embodiments of the present application. Detailed implementation manners

[0043] The technical solutions of the present invention will be described clearly and completely below with reference to the accompanying drawings. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0044] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0045] An embodiment of the present invention provides a method for establishing a single-wavelength beam thickness measurement reference database. This method can, before performing a single-wavelength beam measurement, calculate, by an electronic device such as a computer or a server, a database for measuring the absolute thickness of a wafer thin film using a single-wavelength beam, that is, the reference database. As Figure 1 shown, this method includes the following operations:

[0046] S1A. Obtain the reflectivity of the wafer thin film at different thicknesses. The wafer thin film may specifically be a silicon dioxide layer on the surface of a silicon-based wafer. The reflectivity in this solution refers to the reflectivity of the wafer thin film to light of a specific wavelength, and the specific wavelength is the wavelength of the light used in the single-wavelength beam measurement method. The thickness and the corresponding reflectivity may be data calculated by a theoretical spectral model. The user can give a thickness value according to the measurement requirements and calculate the corresponding reflectivity using the theoretical spectral model.

[0047] According to the theoretical calculation results, it can be known that the reflectivity changes periodically with the change of the thickness, and the relationship between the two is a periodic function relationship.

[0048] According to the thin film optical principle, in an air environment, the following relationship exists between the film thickness of the wafer and the reflectivity:

[0049] ;

[0050] where R represents the reflectivity, A, B, and are all coefficients related to the refractive index of the wafer surface material and can be obtained by substituting relevant parameters. Among them, the phase difference . n1 represents the refractive index, h represents the thickness of the wafer thin film, represents the incident light wavelength, Indicates the refraction angle between the incident light and the surface of the optical thin film.

[0051] From the above relationship, it can be seen that in the environment of a single-layer film, the film thickness - reflectivity curve changes in a sine - cosine law, and its relational expression can be simplified as:

[0052] ;

[0053] Where represents the reflectivity, d represents the thickness, , A and B are constants.

[0054] As Figure 2 shown, in one embodiment, the correspondence between the reflectivity R and the thickness d is a quasi - sine function relationship. Given that the period of the reflectivity R is T = 220nm, and the user intends to measure the absolute thickness near the endpoint of CMP using a single - wavelength light beam (the endpoint thickness in this embodiment is 0), and the thickness range is at least half a period, such as any range exceeding 110nm, like 0 - 200nm, 0 - 1000nm, etc.

[0055] As an example, for all thickness values in the range of 0 - 200nm, the corresponding reflectivities R0 - R200 are calculated. Among them, the reflectivities of data point a and data point b are the same as Ri. Since the reflectivity shows periodic changes and different thicknesses within one period may correspond to the same reflectivity, when only the reflectivity can be measured or calculated, a unique thickness value cannot be obtained.

[0056] S2A, determine the trend information of the reflectivity changing with the thickness, where the trend is specifically increasing or decreasing. Taking Figure 2 the data points a and b as an example, if the thickness da of data point a is greater than the thickness db of data point b, and in the application scenario, the thickness of the measurement object changes from right to left, then the trend of the reflectivity Ri at point a is decreasing, and the trend of the reflectivity Ri at data point b is increasing. In response to this phenomenon, comparing the reflectivity corresponding to the current thickness with the reflectivity corresponding to a previous given larger thickness can determine the trend information of the reflectivity corresponding to the current thickness.

[0057] S3A, establish a reference database for measuring the thickness of the wafer thin film using a single - wavelength light beam according to different thicknesses, corresponding reflectivities, and trend information. As a first implementation method, each piece of data in the reference database includes the thickness, reflectivity, and trend information of the reflectivity. The trend information is used to indicate the change trend of the reflectivity value in one piece of data compared with the reflectivity in another piece of data with a larger adjacent thickness. For example, the reference database includes the following multiple pieces of data:

[0058] Thickness dn, reflectivity Rn, increasing;

[0059] The thickness dn-1 and the reflectivity Rn-1 increase;

[0060] ……

[0061] The thickness dn-i and the reflectivity Rn-i decrease;

[0062] The thickness d0 and the reflectivity R0 decrease.

[0063] In the reference database, in any thickness period, there are two different thicknesses corresponding to the same reflectivity and different trend information. For example, the reflectivity Rn-1 of the thickness dn-1 is equal to the reflectivity Rn-i of the thickness dn-i, but the trend information of the two data is different. When using this reference database to measure the thickness of a single-wavelength beam, after determining the period in which the current thickness is located and measuring the value of the reflectivity, by combining the change trend information of the reflectivity, a unique piece of data can be matched in the database to obtain the corresponding thickness value.

[0064] As a second implementation manner, reference databases can be established separately according to the trend information. For example, in one reference database, all the reflectivities and thicknesses show an increasing trend, and in another reference database, all the reflectivities and thicknesses show a decreasing trend. The same reference database has a unique trend information, and the trend information is used to indicate the change trend of the reflectivity value in each piece of data in the reference database compared to the reflectivity of another piece of data with a larger adjacent thickness.

[0065] For example, the trend information of the first reference database is increasing, and it includes multiple pieces of data:

[0066] The thickness dn and the reflectivity Rn;

[0067] The thickness dn-1 and the reflectivity Rn-1;

[0068] ……

[0069] The trend information of the second reference database is decreasing, and it includes multiple pieces of data:

[0070] The thickness dn-i and the reflectivity Rn-i;

[0071] ……

[0072] The thickness d0 and the reflectivity R0.

[0073] When there are two reference databases, the two reference databases have different trend information, and there are different thicknesses in the two reference databases corresponding to the same reflectivity. For example, the reflectivity Rn-1 of thickness dn-1 is equal to the reflectivity Rn-i of thickness dn-i, but the two pieces of data belong to different reference databases. When using these two reference databases to measure the thickness of a single-wavelength beam, in the case of determining the period in which the current thickness is located, first determine the corresponding reference database according to the measured trend information of the reflectivity change, and then, according to the value of the reflectivity, a unique piece of data can be matched in the database to obtain the corresponding thickness value.

[0074] In one embodiment, the operation of determining the trend information of the reflectivity changing with the thickness in the above step S2A may specifically include the following operations:

[0075] Starting from the reflectivity corresponding to the maximum thickness within a specific thickness range, compare the reflectivity corresponding to the next smaller thickness with the reflectivity corresponding to the previous larger thickness one by one;

[0076] When the reflectivity corresponding to the smaller thickness is greater than the reflectivity corresponding to the larger thickness, it is determined that the trend of the reflectivity corresponding to the smaller thickness is rising;

[0077] When the reflectivity corresponding to the smaller thickness is less than the reflectivity corresponding to the larger thickness, it is determined that the trend of the reflectivity corresponding to the smaller thickness is falling.

[0078] As an example, assume that the given thickness range is 0 to 200 nm and the resolution is 0.1 nm. For example, for 200 nm, the calculated reflectivity R = 0.6, and for 199.9 nm, the calculated reflectivity R = 0.602. Then, through comparison, it can be determined that the trend of the reflectivity is rising. By calculating the reflectivity at a thickness of 0 in the above manner, the trend information of each reflectivity changing with the thickness can be determined.

[0079] In some embodiments, the established reference database needs to be used to measure the thickness of the wafer thin film during the polishing process. During the polishing process, it is necessary to add polishing liquid to the wafer surface and continuously flush it with water, and there are also other transparent media such as glass and PU between the photodetector and the wafer surface. This complex environment is called a multi-layer film environment in this field, or the wafer thin film is in a multi-layer film state. If the above reference database is established without considering this complex environment, that is, the mathematical model used to calculate the reflectivity is a model applicable to the single-layer film environment, then the obtained reference database is not suitable for measuring the thickness of the wafer thin film in the multi-layer film environment.

[0080] To be able to adapt to the multi-layer film environment, this embodiment further includes the following operations after the above step S3A:

[0081] S4A, convert the reference database into a reference database suitable for the multi-layer film environment using conversion coefficients. Based on the formation of a corresponding relationship curve by the change of reflectance with thickness values, it is found that compared with the corresponding relationship curve between reflectance and thickness in the single-layer film environment, the corresponding relationship curve between reflectance and thickness in the multi-layer film environment is compressed or stretched, and at the same time the whole curve is raised or lowered. Then in this embodiment, the above corresponding relationship is determined as

[0082] ;

[0083] wherein, represents the reflectance in the reference database for the single-layer film environment (the reflectance before conversion), and are conversion coefficients, represents the reflectance in the reference database suitable for the multi-layer film environment (the reflectance after conversion). This step is to process the reflectance in the reference database with the pre-calibrated conversion coefficients and .

[0084] Furthermore, the conversion coefficients and can be calibrated in the following way:

[0085] S01, obtain the reflectances and reflectance of the reflected light of a single-wavelength beam by two wafer films with known different thicknesses in the multi-layer film environment. Two wafer films with known different thicknesses means that the thicknesses of the two wafer films are both known information and they are not equal.

[0086] S02, obtain the reflectances and reflectance of the reflected light of a single-wavelength beam by the two wafer films in the single-layer film environment. It is the same measurement object as in step S01, with the difference being the environment.

[0087] S03, determine the conversion coefficients according to the reflectance , reflectance , reflectance and reflectance . According to the corresponding relationship between the reflectance in the multi-layer film environment and the reflectance in the single-layer film environment, the values of the conversion coefficients can be calculated by solving equations:

[0088] ;

[0089] The above steps S01 and S02 can be executed in an experimental environment, and the calibration of the conversion coefficients is completed through the actually measured reflectances.

[0090] For exampleFigure 3 As shown in the figure, an embodiment of the present invention provides a thickness measurement method for the wafer film polishing process, which can be executed by an electronic device such as a computer or a server, and includes the following operations:

[0091] S1B. During the polishing process of the wafer film, obtain the electrical signal U corresponding to the light intensity of the reflected light of the wafer film for the single-wavelength light beam 1n , and at the same time determine the trend information of the electrical signal U 1n changing with the thickness. Specifically, use a light source emitting single-wavelength light to emit light rays to the surface of the wafer film. The incident light can be perpendicular to the surface of the wafer film or obliquely incident on the surface of the wafer film at a certain angle. Receive the reflected light on the wafer surface through a photoelectric sensor, convert it into an analog electrical signal, and then through optional processing such as analog-to-digital conversion, filtering, and amplification, obtain a digital electrical signal.

[0092] The thickness of the wafer film can affect the intensity of the reflected light, and the magnitude of the light intensity can affect the value of the digital electrical signal. According to the measurement results at different thicknesses, it can be found that the electrical signal shows a periodic change with the change of the thickness.

[0093] In this embodiment, the trend information of the electrical signal changing with the thickness refers to the change trend of the electrical signal as the thickness decreases. During the polishing process, the thickness of the wafer film gradually decreases under the external force polishing. By continuously monitoring the electrical signal, its change trend can be determined, specifically increasing or decreasing.

[0094] S2B. Calculate the reflectivity R of the wafer film for the single-wavelength reflected light according to the electrical signal U 1n and the calibration coefficient k 1n , and the reflectivity also shows a periodic change with the change of the thickness. The relationship between the reflectivity and the electrical signal is a linear correspondence relationship. The specific correspondence formula depends on the type of the electrical signal (such as voltage or current, etc.), generally the voltage value.

[0095] The function of the calibration coefficient k is to establish the relationship between the electrical signal and the reflectivity of the wafer thin film. The calibration coefficient k is at least the value determined before step S2B, and under the condition of not changing the measurement environment and the wafer material, the calibration coefficient remains unchanged at different thicknesses. As an example, assume that at a certain thickness, the measured voltage value is 1.8V, and the reflectivity can be determined to be 0.6 at the same time. Then the calibration coefficient is the ratio of the voltage value to the reflectivity, that is, the calibration coefficient k = 1.8 / 0.6 = 3; under the condition of not changing other conditions and only changing the film thickness, for example, at another thickness, the measured voltage value = 1.5V, and the reflectivity can be determined to be 0.5 at the same time, then the calibration coefficient k = 1.5 / 0.5 = 3.

[0096] Determine the calibration coefficient There are various ways. According to the above example, as long as the reflectivity can be determined, the calibration coefficient can be calculated. If it is necessary to determine the reflectivity, the thickness of the wafer thin film needs to be determined, and there are various ways to measure the thickness. Specifically, for example, before performing the wafer thin film polishing process, a contact or non-contact measurement tool can be used to determine the thickness of the wafer thin film; it can also be an in-situ or off-line measurement during the wafer thin film polishing process.

[0097] S3B. According to the thickness, reflectivity R 1n and trend information at the previous moment, match the thickness d at the current moment in the pre-established reference database 1n , and the reference database includes the reflectivity corresponding to different thicknesses and the trend information of the change of reflectivity with thickness.

[0098] As the first implementation method, each piece of data in the reference database includes the thickness, reflectivity, and the trend information of the reflectivity. The trend information is used to indicate the change trend of the reflectivity value in one piece of data compared with the reflectivity in another piece of data with a larger adjacent thickness. For example, the reference database includes the following multiple pieces of data:

[0099] Thickness , Reflectivity , Increase;

[0100] Thickness , Reflectivity , Increase;

[0101] ……

[0102] Thickness , Reflectivity , Decrease;

[0103] Thickness , Reflectivity , Decrease.

[0104] The reflectance obtained in step S3B and the trend information of the electrical signal are used to match a unique piece of data in the reference database, and the thickness in the matched data is the thickness . When this reference database is used to measure the thickness, after the reflectance value is measured, the unique piece of data can be matched in the database by combining the change trend information to obtain the corresponding thickness value.

[0105] To facilitate matching a unique thickness value in the reference database, it is first necessary to determine the thickness at the previous moment is in a certain thickness cycle in the reference database, and then a unique thickness value is determined in this thickness cycle as the thickness at the current moment, which specifically includes:

[0106] Determine a cycle of data including the thickness in the reference database;

[0107] Match two sets of data according to the reflectance in a cycle of data;

[0108] According to the trend information, determine a set of data from the two sets of data to obtain the thickness .

[0109] For example, starting from the initial polishing, the known initial thickness of 900 nm is used as the thickness at the previous moment. There are thicknesses from 0 to 1000 nm, reflectance, and change trend data in the reference database. To determine the thickness at the current moment, specifically, first determine the data of a thickness cycle where 900 nm is located in the reference database. Then, there are two pieces of data in this thickness cycle that match the reflectance at the current moment, and the trend information of these two sets of data is different. Only the trend information of one set of data is the same as the trend information of the reflectance at the current moment. For example, if the trend of the reflectance at the current moment is rising, and one piece of data is (899.9 nm, reflectance R 899.9 , rising), then the thickness at the current moment is determined to be 899.9 nm. After that, 899.9 nm becomes the thickness at the previous moment, and the absolute thickness value of the wafer film can be determined at any moment during the polishing process by continuously monitoring in the above manner.

[0110] As a second implementation manner, reference databases can be established respectively according to the trend information. For example, all the reflectances and thicknesses with an upward trend are in one reference database, and all the reflectances and thicknesses with a downward trend are in another reference database. The same reference database has a unique trend information, and the trend information is used to indicate the change trend of the reflectance value in each piece of data in the reference database compared with the reflectance of another piece of data with a larger thickness adjacent to it.

[0111] For example, the trend information of the first reference database is increasing, which includes multiple pieces of data:

[0112] Thickness , reflectivity ;

[0113] ……

[0114] Thickness , reflectivity ;

[0115] The trend information of the second reference database is decreasing, which includes multiple pieces of data:

[0116] Thickness , reflectivity , decreasing;

[0117] ……

[0118] Thickness , reflectivity , decreasing.

[0119] When there are two reference databases, the two reference databases have different trend information, and there are different thicknesses in the two reference databases corresponding to the same reflectivity. For example, the reflectivity of thickness is equal to the reflectivity of thickness , but the two pieces of data belong to different reference databases. In step S3B, the trend information of the electrical signal is used to select a reference database, and the thickness at the previous moment and the reflectivity at the current moment are used to match a unique piece of data in the selected database, and the thickness in the matched data is the thickness .

[0120] Regarding the above calibration coefficient k, it can be calculated in the following manner before step S2B:

[0121] Collect the electrical signal corresponding to the light intensity of the reflected light of the single-wavelength beam for the wafer film with a known thickness . For example, before the polishing starts, collect the electrical signal for the wafer film at the initial thickness.

[0122] Calculate the reflectivity of the wafer film for the single-wavelength reflected light according to the thickness . Calculate based on the theoretical model, and a unique reflectivity can be calculated for a given thickness 。

[0123] According to the reflectivity and the electrical signal calculate the calibration coefficient 。The electrical signal is preferably a voltage signal, and the calibration coefficient , in step S2B, 。

[0124] In one embodiment, in step S1B, determine the trend information of the electrical signal changing with the thickness, including:

[0125] S11B, compare the electrical signal collected at the current moment with the electrical signal collected at the previous moment , where the thickness of the wafer thin film at the current moment is less than the thickness of the wafer thin film at the previous moment;

[0126] S12B, obtain the trend information according to the comparison result, where if then the trend information indicates a decrease, and if then the trend information indicates an increase.

[0127] In this solution, the electrical signal is continuously collected during the polishing process, and the electrical signal changes with the decrease of the thickness. The electrical signal collected at the current moment is different from the electrical signal collected at the previous moment. By comparison, the change trend of the electrical signal with the decrease of the thickness can be determined.

[0128] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented 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.

[0129] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, and the combination of processes and / or blocks in the flowcharts and / or block diagrams, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing devices generate for realizing in the process Figure 1 one process or multiple processes and / or blocks Figure 1means for the functions specified in one or more boxes.

[0130] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to operate in a particular manner, such that the instructions stored in the computer-readable memory produce a manufacture including an instruction means that implements the functions specified in one Figure 1 or more processes and / or boxes Figure 1 means for the functions specified in one or more boxes.

[0131] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus, such that a series of operational steps are performed on the computer or other programmable apparatus to produce a computer-implemented process, whereby the instructions executed on the computer or other programmable apparatus provide steps for implementing the functions specified in one Figure 1 or more processes and / or boxes Figure 1 means for the functions specified in one or more boxes.

[0132] Obviously, the above embodiments are only examples for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A method for establishing a reference database for single-wavelength beam thickness measurement, characterized in that, Including: Obtain the reflectivity of the wafer thin film at different thicknesses, where the thickness is a given value, and the corresponding reflectivity is a value calculated by a mathematical model. The reflectivity is the reflectivity of the wafer thin film to light of a specific wavelength, and the reflectivity shows periodic changes with the change of thickness; Determine the trend information of the change of the reflectivity with the thickness, including: starting from the reflectivity corresponding to the maximum thickness within a specific thickness range, one by one compare the reflectivity corresponding to the next smaller thickness with the reflectivity corresponding to the previous larger thickness; when the reflectivity corresponding to the smaller thickness is greater than the reflectivity corresponding to the larger thickness, determine that the trend of the reflectivity corresponding to the smaller thickness is upward; when the reflectivity corresponding to the smaller thickness is less than the reflectivity corresponding to the larger thickness, determine that the trend of the reflectivity corresponding to the smaller thickness is downward; Establish a reference database for measuring the thickness of the wafer thin film with a single-wavelength beam according to the different thicknesses, the corresponding reflectivities and the trend information.

2. The method according to claim 1, wherein Each piece of data in the reference database includes the thickness, the reflectivity and the trend information of the reflectivity. The trend information is used to indicate the change trend of the reflectivity value in one piece of data compared with the reflectivity in another piece of data with a larger adjacent thickness.

3. The method according to claim 2, wherein There are two different thicknesses in the reference database corresponding to the same reflectivity and different trend information.

4. The method according to claim 1, wherein The number of the reference databases is one or two. The same reference database has unique trend information, and the trend information is used to indicate the change trend of the reflectivity value in each piece of data in the reference database compared with the reflectivity in another piece of data with a larger adjacent thickness.

5. The method according to claim 4, wherein When there are two reference databases, the two reference databases have different trend information, and there are different thicknesses in the two reference databases corresponding to the same reflectivity.

6. The method according to claim 1, wherein After obtaining the reference database, it further includes: Use a conversion coefficient to convert the reference database into a reference database applicable to a multi-layer film environment.

7. A thickness measurement method for the wafer film polishing process, characterized in that, Including: During the process of polishing the wafer film, an electrical signal corresponding to the light intensity of the reflected light of the single-wavelength beam by the wafer film is obtained. Meanwhile, the trend information of the electrical signal changing with the thickness is determined, including: comparing the electrical signal collected at the current moment with the electrical signal collected at the previous moment , where the thickness of the wafer film at the current moment is less than the thickness of the wafer film at the previous moment; the trend information is obtained according to the comparison result, where if then the trend information indicates a decrease, and if then the trend information indicates an increase. Based on the said electrical signal and the calibration coefficient calculate the reflectivity of the wafer thin film to a single-wavelength light beam , and the reflectivity shows periodic changes with the change of thickness; According to the thickness at the previous moment , the reflectivity and the trend information, match in a pre-established reference database to obtain the thickness at the current moment , where the reference database includes the reflectivity corresponding to different thicknesses and the trend information of the change of reflectivity with thickness.

8. The method according to claim 7, wherein Before calculating the reflectivity, it further includes: Collect the electrical signal corresponding to the light intensity of the reflected light of a single-wavelength light beam for a wafer thin film with a known thickness ; ; According to the thickness calculate the reflectivity of the wafer thin film to the single-wavelength reflected light ; Calculate the calibration coefficient based on the reflectivity and the electrical signal .

9. The method according to claim 8, wherein The electrical signal is a voltage signal, and the calibration coefficient ; the reflectivity .

10. The method according to claim 7, characterized in that Obtain the thickness at the current moment , including: Determine a period of data including the thickness in the reference database therein; According to the reflectivity Two sets of data are obtained by matching the data in the one cycle; Based on the trend information in the two sets of data to determine a set of data to obtain the thickness .

11. An apparatus for establishing a reference database for single-wavelength beam thickness measurement, characterized in that, Including: 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 execute the method for establishing a single-wavelength beam thickness measurement reference database according to any one of claims 1-6.

12. A thickness measurement device for the wafer thin film polishing process, characterized in that, Including: 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 execute the thickness measurement method for the wafer thin film polishing process according to any one of claims 7-10.

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