Method and equipment for determining uncertainty of wafer film thickness measurement

Abstract

The invention provides a method and equipment for determining uncertainty of wafer film thickness measurement. The method is applied to the technical field of high-precision measurement. The method comprises the following steps: acquiring an uncertainty component of wafer film thickness measurement by a wafer film thickness measurement device; the uncertainty component comprises a wavelength measurement uncertainty # imgabs0 #, a refractive index measurement uncertainty # imgabs1 #, a refraction angle measurement uncertainty # imgabs2 #, a voltage measurement uncertainty # imgabs3 # and an uncertainty # imgabs4 # caused by calibration coefficient deviation of a standard wafer; and determining the uncertainty of the synthesis standard by using the uncertainty # imgabs5 #, the uncertainty # imgabs6 #, the uncertainty # imgabs7 #, the uncertainty # imgabs8 # and the uncertainty # imgabs9 #. According to the invention, the accuracy of the voltage signal in the wafer film thickness measurement process is improved, and the accurate control of the polishing process end point is further realized.

Description

Technical Field

[0001] The present invention relates to the field of high-precision measurement technology, and in particular to a method and device for determining the uncertainty of wafer film thickness measurement. Background Art

[0002] Wafer polishing is a key step in the semiconductor manufacturing process. Its purpose is to obtain a smooth and clean surface on the wafer surface for subsequent processes. In this process, accurate control of the removal amount is crucial to ensure the quality of the wafer. Traditional polishing endpoint detection methods mainly include infrared method and torque method. These methods can detect the endpoint of polishing, but cannot provide specific removal value, so they cannot meet the needs of online monitoring of removal amount.

[0003] In order to solve this problem, the film thickness detection method based on light intensity has gradually gained attention. This method can obtain the relative removal amount of the wafer during the polishing process in real time and realize online monitoring of the polishing process. The measurement is carried out through an optical wafer film thickness measurement device. The light beam emitted by the light source is expanded and collimated by the lens and then irradiated to the wafer surface. After the incident light is reflected by the thin film, it is received by the photodiode and generates a photocurrent. The photocurrent is linearly related to the incident light intensity and is output in the form of voltage after signal amplification.

[0004] Although the film thickness detection method based on light intensity provides monitoring of the relative removal amount, it still has some shortcomings. In the film thickness measurement system, the film thickness value at the current position is obtained mainly by measuring the voltage value. However, the measured voltage is affected by many factors, resulting in a certain deviation between the actual measured voltage value and the theoretical value, and there is a problem that the deviation cannot be accurately controlled. Therefore, the endpoint detection of the polishing process still faces the problem of insufficient accuracy. Summary of the invention

[0005] In view of this, the present invention provides a method for determining the uncertainty of wafer film thickness measurement, comprising: Obtaining uncertainty components of wafer film thickness measurement by a wafer film thickness measurement device; The wafer film thickness measuring device comprises a light source, a lens, a reflector and a photodiode, wherein the light source is used to emit a light beam, the lens is used to expand and collimate the light beam, and then convert the point light source into a line light source, the reflector is used to reflect the line light source to irradiate the wafer surface, and the photodiode is used to receive the reflected light reflected from the wafer surface and generate an electrical signal; The uncertainty components include the wavelength measurement uncertainty , Refractive index measurement uncertainty , Refraction angle measurement uncertainty , Voltage measurement uncertainty , uncertainty caused by calibration coefficient deviation of standard wafer ; Using uncertainty , , , , Determine the combined standard uncertainty.

[0006] Alternatively, the uncertainty can be calculated using : Get the light source stability error and wavelength calibration error of the wavelength calibration device ; According to the light source stability error and the wavelength calibration error Calculation uncertainty .

[0007] Alternatively, the uncertainty can be calculated using : Obtaining refractive index measurement error using refractive index error measurement equipment ; According to the refractive index measurement error Calculation uncertainty .

[0008] Alternatively, the uncertainty can be calculated using : Obtain the incident angle of the line light source irradiating the wafer surface and incident angle error ; According to the incident angle and the incident angle error Calculation uncertainty .

[0009] Alternatively, the uncertainty can be calculated using : Obtain the true film thickness value of the standard wafer through film thickness measurement equipment And get the corresponding reflectivity ; Obtain known true film thickness values ​​multiple times The voltage value corresponding to the standard wafer is calculated, and the standard deviation s of the voltage value is calculated; According to the number of repeatability measurements And obtain the actual film thickness value of the standard wafer multiple times The corresponding voltage value calculates the voltage average value of the repeatability measurement result ; According to the number of repeatability measurements , standard deviation s and voltage average value Calculation uncertainty .

[0010] Alternatively, the uncertainty can be calculated using : According to the average voltage 1. Uncertainty caused by film thickness-voltage curve fitting error 2. Uncertainty caused by line noise error 3. Uncertainty caused by AD conversion error 4. Calculation uncertainty .

[0011] Alternatively, the uncertainty can be calculated using : ; in, is the uncertainty one, is the second uncertainty, is uncertainty three, is uncertainty four.

[0012] Alternatively, the combined standard uncertainty can be determined using : ; in, Indicates the wafer film thickness, represents the wavelength of the light source, represents the refractive index of the wafer film, is the angle after being refracted to the wafer film surface, Indicates voltage, Indicates the calibration factor.

[0013] A second aspect of the present invention provides a device for determining the uncertainty of wafer film thickness measurement, the 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 so that the processor executes the above-mentioned method for determining the uncertainty of wafer film thickness measurement.

[0014] The present invention obtains in detail various uncertainty components of wafer film thickness measurement by a wafer film thickness measurement device, including wavelength measurement error, refractive index error, refraction angle measurement error, and voltage measurement error, so as to evaluate various error sources that affect the measurement results; and uses these uncertainty components to calculate a synthetic standard uncertainty to comprehensively evaluate the overall accuracy of the measurement results, so as to perform deviation correction, thereby improving the accuracy of the voltage signal during the wafer film thickness measurement process, and ultimately achieving precise control of the polishing process endpoint. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 A diagram of a wafer film thickness measurement device in an embodiment of the present invention; Figure 2 Flow chart of a method for determining uncertainty in wafer film thickness measurement in an embodiment of the present invention. DETAILED DESCRIPTION

[0017] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0019] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0020] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] like Figure 1As shown, an embodiment of the present invention provides a wafer film thickness measuring device, which includes a light source 1, a lens 2, a reflector 3 and a photodiode 4, wherein the light source 1 is used to emit a light beam, the lens 2 is used to expand and collimate the light beam and then convert the point light source into a line light source, the reflector 3 is used to reflect the line light source to irradiate the surface of the wafer 5, and the photodiode 4 is used to receive reflected light reflected from the surface of the wafer and generate an electrical signal.

[0022] The specific working principle of the wafer film thickness measuring device is as follows: the wafer film thickness measuring device is arranged at the bottom of the polishing disk, the wafer to be polished is placed on the polishing pad of the polishing disk, the wafer film thickness measuring device is turned on, and the light source 1 emits a light beam, which is expanded and collimated after passing through the lens 2, and the point light source is converted into a line light source, and is reflected by the reflector 3 to irradiate the surface of the wafer 5. The line light source beam passes through the wafer film and is reflected at the substrate. The reflected light is irradiated to the photodiode 4 of the wafer film thickness measuring device. The photodiode 4 receives the reflected light signal and generates a photocurrent. The size of the photocurrent is linearly related to the size of the light intensity incident on the photodiode 4. After the photocurrent passes through the photoelectric conversion circuit and the signal amplification circuit in the wafer film thickness measuring device, it is output in the form of voltage to obtain an electrical signal.

[0023] Set the relative film thickness value to be removed , record the voltage value of the current electrical signal before polishing After the polishing process begins, the relative change trend of the voltage during the polishing process will be recorded, and the increasing and decreasing states will be recorded. Based on the recorded states and the mathematical model pre-stored in the controller MCU, the voltage value at the polishing end point is determined. And the relative change trend, when the real-time voltage value reaches the polishing end point, , and when it is consistent with the theoretical change trend, it indicates that the polishing process has reached the end point and polishing can be stopped.

[0024] Then, the film thickness information analysis mathematical model is used to analyze and process the electrical signal received by the wafer film thickness measurement device, and the wafer film thickness information is output. Since the measured voltage is affected by many factors, there is a deviation between the actual measured film thickness and the theoretical polishing end point film thickness. Therefore, it is necessary to eliminate the deviation, such as Figure 1 As shown, an embodiment of the present invention provides a method for determining the uncertainty of wafer film thickness measurement, which specifically includes: S1, obtaining the uncertainty component of the wafer film thickness measurement device for the wafer film thickness measurement, wherein the uncertainty component includes the wavelength measurement uncertainty , Refractive index measurement uncertainty , Refraction angle measurement uncertainty , Voltage measurement uncertainty , uncertainty caused by calibration coefficient deviation of standard wafer .

[0025] S2, using uncertainty , , , , Determine the combined standard uncertainty.

[0026] This embodiment obtains in detail the various uncertainty components of the wafer film thickness measurement device, including wavelength measurement error, refractive index error, refraction angle measurement error, and voltage measurement error, to evaluate the various error sources that affect the measurement results; and uses these uncertainty components to calculate the synthetic standard uncertainty to comprehensively evaluate the overall accuracy of the measurement results for deviation correction, thereby improving the accuracy of the voltage signal during the wafer film thickness measurement process and ultimately achieving precise control of the polishing process endpoint.

[0027] It should be noted that this calculation method is only to illustrate how to combine multiple uncertainty components to calculate a total component, and does not mean that all the above components must be introduced in actual application. Those skilled in the art can select the components that affect the measurement results according to actual conditions. Different devices may have different errors, and they should be selected and calculated according to actual conditions.

[0028] Specifically, the error analysis is performed on the mathematical model pre-stored in the MCU. Since there is a specific relationship between the wafer film thickness and the reflectivity, it can be known through experimental verification and data fitting deduction that the relationship between the wafer film thickness and its reflectivity can be approximately expressed by a cosine function. Therefore, assuming that the wafer film thickness is t and the wafer reflectivity is R, taking the incident angle of 15° as an example, the following relationship exists: ; Among them, A and B are constants. is the incident angle The angular velocity value of the cosine model under the condition of 15 degrees, where the angular velocity can be expressed as: ; in, represents the refractive index of the wafer film, is the angle after being refracted to the wafer film surface, is the wavelength of the light source. It can be expressed as: ; in, is the refractive index of air.

[0029] Before the experiment begins, in order to calibrate and correct the mathematical model, the film thickness measurement equipment can be calibrated using a standard wafer with a film thickness of 200nm. The thickness of the standard wafer can be 200nm or other thicknesses. When measuring the reflectivity of the standard wafer under specific conditions, the voltage value of the current standard is obtained. V Reflectivity R is a linear relationship, that is V=kR , the coefficient between voltage and reflectivity can be obtained through the calibration process k , and then substitute the cosine relationship between wafer film thickness and reflectivity R into the linear relationship between voltage and reflectivity, and the relationship between film thickness and voltage can be obtained as follows: ; Therefore, when the polishing end point is reached, the relative film thickness removed at this time is It can be expressed as: ; in, is the wafer film thickness at the polishing end point, is the wafer film thickness measured last time, is the voltage corresponding to the polishing end point, is the voltage corresponding to the previous measurement.

[0030] Uncertainty evaluation is performed for thickness values ​​within a certain range. Based on the above, the thickness t can be expressed by the following relationship.

[0031] ; Therefore, the uncertainty of the film thickness measurement at the wafer polishing endpoint can be expressed as: ; in, ; ; ; ; ; Uncertainty of film thickness measurement at wafer polishing endpoint It is obtained by five uncertainty components, namely wavelength measurement uncertainty , Refractive index measurement uncertainty , Refraction angle measurement uncertainty , Voltage measurement uncertainty , uncertainty caused by calibration coefficient deviation of standard wafer .

[0032] In one embodiment, the uncertainty is calculated as follows : Get the light source stability error and wavelength calibration error of the wavelength calibration device ; According to the light source stability error and the wavelength calibration error Calculation uncertainty .

[0033] Specifically, the wavelength measurement uncertainty comes from the wavelength calibration error and the light source stability error. The wavelength calibration error comes from the higher-precision wavelength calibration device, and the light source stability comes from the temperature drift of the wavelength, the wavelength indication error, and the resolution. Assume that the wavelength stability error is , the wavelength calibration error is , then the measurement uncertainty of the wavelength of the light wave is ; in, is the coverage factor under uniform distribution, which is used to convert the uncertainty range of uniform distribution into standard uncertainty and is used in subsequent calculations. The meanings are the same.

[0034] This embodiment comprehensively considers the main error sources of wavelength measurement, thereby evaluating and optimizing the measurement accuracy of the wafer film thickness measurement device and improving the precise control of the polishing process endpoint.

[0035] In one embodiment, the uncertainty is calculated as follows : Obtaining refractive index measurement error using refractive index error measurement equipment ; According to the refractive index measurement error Calculation uncertainty .

[0036] Specifically, the refractive index is mainly related to the basic properties of the material and can be obtained through equipment such as a spectrometer and an Abbe refractometer. Suppose the error obtained is , then the measurement uncertainty of the refractive index is ; in, is the coverage factor under uniform distribution, which is used to convert the uncertainty range of uniform distribution into standard uncertainty.

[0037] This embodiment uses a spectrometer, Abbe refractometer, etc. to obtain the refractive index measurement error. The measurement uncertainty of the refractive index is calculated based on the refractive index measurement error, which provides a reliable measurement benchmark and accuracy guarantee for the precise control of the subsequent polishing endpoint.

[0038] In one embodiment, the uncertainty is calculated as follows : Obtain the incident angle of the line light source irradiating the wafer surface and incident angle error ; According to the incident angle and the incident angle error Calculation uncertainty .

[0039] Specifically, the refraction angle is mainly related to the following factors: the incident angle, the refractive index of air and the wafer film refractive index . Among them, the influence of air refractive index and film refractive index on refraction angle can be ignored, so the source of its measurement uncertainty is mainly related to the incident angle, which is related to the position of the reflector and the height difference between the measurement system and the wafer. Therefore, the sources of the incident angle error are: optical path installation angle error, measurement system and wafer flatness error, and height error caused by environmental vibration. Assume that the above errors affect the incident angle , then the uncertainty of refractive index measurement can be expressed as: ; This embodiment accurately calculates the uncertainty of refraction angle measurement by quantifying the main sources of refraction angle error, such as optical path installation angle error, measurement system and wafer flatness error, and error caused by environmental vibration. This method not only comprehensively considers the various influencing factors in the measurement process, but also improves the accuracy and reliability of the uncertainty evaluation of the refraction angle measurement and the uncertainty analysis accuracy of the wafer film thickness measurement, thereby ensuring the precise control of the polishing process endpoint.

[0040] in, is the coverage factor under uniform distribution, which is used to convert the uncertainty range of uniform distribution into standard uncertainty.

[0041] In one embodiment, the uncertainty is calculated as follows : Obtain the true film thickness value of the standard wafer through film thickness measurement equipment And get the corresponding reflectivity .

[0042] Obtain known true film thickness values ​​multiple times The voltage value corresponding to the standard wafer, and calculate the standard deviation s of the voltage value; According to the number of repeatability measurements And obtain the actual film thickness value of the standard wafer multiple times The corresponding voltage value calculates the voltage average value of the repeatability measurement result ; According to the number of repeatability measurements , standard deviation s and voltage average value Calculation uncertainty .

[0043] Specifically, the error may also come from the error when calibrating the standard wafer with a nominal film thickness of 200nm, that is, the coefficient between voltage and reflectivity obtained during the calibration process k There is an error in the calibration coefficient of the standard wafer k The specific analysis of the deviation is as follows: First, the film thickness measuring equipment is used to measure the film thickness of a standard wafer with a nominal value of 200nm to obtain its true value. , and calculate the true film thickness value of the standard wafer The corresponding reflectivity is Then, the 200nm standard wafer is placed in the wafer film thickness measurement device of the present invention, and the voltage generated at the photodiode is repeatedly measured. The repeatedly measured voltage value is the true film thickness value. Corresponding voltage value, assuming the number of repeatable measurements is N, the voltage average value is calculated based on the repeatability number N and the voltage value of each measurement, expressed as , the standard deviation is s, then the calibration coefficient k It can be expressed as ; Due to the calibration factor k The uncertainty caused by the deviation is: ; In this embodiment, the standard deviation s and the voltage average value are used. The uncertainty caused by the deviation of the correlation coefficient is calculated by using the number of measurements N. , thereby evaluating and optimizing the measurement accuracy of the wafer film thickness measurement device and improving the precise control of the polishing process endpoint.

[0044] The uncertainty of wafer polishing endpoint film thickness measurement also includes the voltage measurement uncertainty , although the relationship between voltage and film thickness is obtained, in practical applications, due to various experimental conditions and measurement errors, the voltage value calculated directly by the theoretical relationship may be different from the actual measured value. In order to more accurately describe the relationship between voltage and film thickness, the Fourier fitting method is used to fit the film thickness-voltage theoretical curve under a single wavelength. In the fitting process, a point is taken every 5nm as the measurement sample data (taking the number of samples as 200 as an example). Each sample point contains the wafer film thickness and its corresponding voltage value. By calculating these sample points, the fitted film thickness information analysis mathematical model, that is, the film thickness-voltage mathematical model, is obtained. This model can more accurately reflect the actual relationship between voltage and film thickness, but there is still a certain error. This error may come from the limitations of the fitting algorithm itself.

[0045] Therefore, the uncertainty caused by the film thickness-voltage curve fitting error is calculated as follows: A film thickness-voltage mathematical model is established using multiple measurement samples, where the multiple measurement samples are voltage values ​​converted from single-wavelength reflected light collected for wafer films of different thicknesses. The film thickness information analysis mathematical model is specifically a film thickness-voltage mathematical model.

[0046] Calculate the standard deviation of the film thickness-voltage mathematical model.

[0047] The uncertainty is calculated based on the standard deviation of the film thickness-voltage mathematical model and the number of multiple measurement samples.

[0048] Specifically, for the error of the fitting algorithm, the standard deviation of the mathematical model fitting curve was calculated to be 0.0295. The uncertainty caused by the curve fitting error is: ; in, is the uncertainty one.

[0049] This embodiment uses the single-wavelength reflected light voltage values ​​converted by multiple wafer films of different thicknesses to establish a film thickness-voltage mathematical model. Since the error of the mathematical model affects the wafer film thickness measurement, the standard deviation of the mathematical model is calculated to evaluate the fitting error, forming an uncertainty of one, which provides a reliable measurement benchmark and accuracy guarantee for the precise control of the subsequent polishing endpoint.

[0050] In one embodiment, the second uncertainty caused by the film thickness measuring instrument error is calculated in the following manner: According to the number of repeatability measurements And obtain the actual film thickness value of the standard wafer multiple times The corresponding voltage value calculates the voltage average value of the repeatability measurement result ; Obtaining the measurement accuracy of the film thickness measuring device, and calculating the voltage fluctuation value caused by the measurement accuracy deviation when the film thickness measuring device measures the standard wafer; According to the average voltage , the voltage fluctuation value is used to calculate the uncertainty caused by the error of the film thickness measuring instrument.

[0051] The error of the mathematical model for film thickness information analysis may also come from the error of the film thickness measuring device in measuring the film thickness of a standard wafer with a nominal value of 200nm. Since the measurement accuracy of the film thickness measuring device in this embodiment is 0.1nm, the established mathematical model for film thickness information analysis will have errors. According to the measurement, the corresponding voltage fluctuation under a 0.1nm deviation is 0.5mV, that is, when the true value of the wafer film thickness deviates from the nominal value (200nm) by 0.1nm, the voltage output generated by the wafer film thickness measuring device will fluctuate by 0.5mV. Therefore, the uncertainty caused by the error of the film thickness measuring instrument is ; in, is the second uncertainty, is the coverage factor under uniform distribution, which is used to convert the uncertainty range of uniform distribution into standard uncertainty.

[0052] This embodiment evaluates the impact of equipment accuracy on voltage measurement results by quantifying the corresponding relationship between voltage fluctuation and film deviation, improves the accuracy of uncertainty analysis of wafer film thickness measurement, and thus ensures accurate control of the polishing process endpoint.

[0053] In one embodiment, uncertainty three caused by line noise error is calculated in the following manner: According to the average voltage And line noise error value calculation uncertainty 3. Voltage average value That is, the number of times the above-mentioned repeatability measurement results are And obtain the actual film thickness value of the standard wafer multiple times The corresponding voltage values ​​are calculated to obtain the average value.

[0054] Specifically, the line noise error is analyzed: Noise is inevitable in the circuit. When the line generates noise, it will cause voltage fluctuations, which will affect the voltage measurement results. The line noise error is conservatively estimated to be 2mV (which can be set based on previous experience). The resulting uncertainty is: ; in, is uncertainty three, is the coverage factor under uniform distribution, which is used to convert the uncertainty range of uniform distribution into standard uncertainty.

[0055] This embodiment analyzes the line noise error in the wafer film thickness measurement device to obtain the influence of the line noise on the voltage measurement result, thereby accurately calculating the uncertainty three caused by the line noise. This method improves the recognition and control of the noise influence during the voltage measurement process, ensures the accuracy of the measurement result, and thus ensures the precise control of the polishing process endpoint.

[0056] In one embodiment, the uncertainty caused by the AD conversion error is calculated in the following manner: Calculate the resolution of the AD conversion element under the range of the AD conversion element; According to the average voltage And the resolution calculation uncertainty of the AD conversion element IV.

[0057] Specifically, in the photoelectric conversion circuit, the resolution of the AD conversion element used is 12 bits. For a voltage range of 2.5V, the resolution is for: ; The uncertainty caused by AD conversion error is ; in, is uncertainty four, is the coverage factor under uniform distribution, which is used to convert the uncertainty range of uniform distribution into standard uncertainty.

[0058] This embodiment evaluates the uncertainty caused by the AD conversion error through the resolution of the AD conversion element. This method quantitatively evaluates the precision limitation of the AD conversion element in signal processing, which helps to improve the accuracy of the voltage measurement results, and then improves the film thickness measurement results, thereby ensuring accurate control of the polishing process endpoint.

[0059] Therefore, the uncertainty is calculated as follows : According to the average voltage 1. Uncertainty caused by film thickness-voltage curve fitting error 2. Uncertainty caused by line noise error 3. Uncertainty caused by AD conversion error 4. Calculation uncertainty .

[0060] Specifically, the voltage measurement uncertainty can be expressed as: ; This embodiment comprehensively evaluates the uncertainty of voltage measurement by comprehensively considering multiple factors (such as film thickness-voltage curve fitting error, film thickness measuring instrument error, line noise error, AD conversion error, etc.), ensures the comprehensiveness and accuracy of uncertainty evaluation, ensures the accuracy of voltage signal during wafer film thickness measurement, ensures the precision and stability of process control, and thus ensures precise control of the endpoint of the polishing process.

[0061] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may 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.

[0062] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0063] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0064] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0065] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled 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 methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for determining the uncertainty of wafer film thickness measurement, characterized in that: include: Obtaining uncertainty components of wafer film thickness measurement by a wafer film thickness measurement device; The wafer film thickness measuring device comprises a light source, a lens, a reflector and a photodiode, wherein the light source is used to emit a light beam, the lens is used to expand and collimate the light beam, and then convert the point light source into a line light source, the reflector is used to reflect the line light source to irradiate the wafer surface, and the photodiode is used to receive the reflected light reflected from the wafer surface and generate an electrical signal; The uncertainty components include the wavelength measurement uncertainty , Refractive index measurement uncertainty , Refraction angle measurement uncertainty , Voltage measurement uncertainty , Uncertainty caused by deviation of calibration coefficient of standard wafer ; Using uncertainty , , , , Determine the combined standard uncertainty.

2. The method according to claim 1, characterized in that The uncertainty is calculated using the following method: : Get the light source stability error and wavelength calibration error of the wavelength calibration device ; According to the light source stability error and the wavelength calibration error Calculation uncertainty .

3. The method according to claim 1, characterized in that The uncertainty is calculated using the following method: : Obtaining refractive index measurement error using refractive index error measurement equipment ; According to the refractive index measurement error Calculation uncertainty .

4. The method according to claim 1, characterized in that The uncertainty is calculated using the following method: : Obtain the incident angle of the line light source irradiating the wafer surface and incident angle error ; According to the incident angle and the incident angle error Calculation uncertainty .

5. The method according to claim 1, characterized in that The uncertainty is calculated using the following method: : Obtain the true film thickness value of the standard wafer through film thickness measurement equipment And get the corresponding reflectivity ; Obtain known true film thickness values ​​multiple times The voltage value corresponding to the standard wafer is calculated, and the standard deviation s of the voltage value is calculated; According to the number of repeatability measurements And obtain the actual film thickness value of the standard wafer multiple times The corresponding voltage value calculates the voltage average value of the repeatability measurement result ; According to the number of repeatability measurements , standard deviation s and voltage average value Calculation uncertainty .

6. The method according to claim 5, characterized in that The uncertainty is calculated using the following method: : According to the average voltage 1. Uncertainty caused by film thickness-voltage curve fitting error 2. Uncertainty caused by line noise error 3. Uncertainty caused by AD conversion error 4. Calculation uncertainty .

7. The method according to claim 6, characterized in that The uncertainty is calculated using the following method: : ； in, is the uncertainty one, is the second uncertainty, is uncertainty three, is uncertainty four.

8. The method according to claim 1, characterized in that The combined standard uncertainty is determined by : ； in, Indicates the wafer film thickness, represents the wavelength of the light source, represents the refractive index of the wafer film, is the angle after being refracted to the wafer film surface, Indicates voltage, Indicates the calibration factor.

9. A device for determining the uncertainty of wafer film thickness measurement, characterized in that: include: 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 so that the processor executes the method for determining the uncertainty of wafer film thickness measurement as described in any one of claims 1-8.

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