Thin film thickness measuring method and device based on spectrum confocal

Abstract

The invention relates to the technical field of high-precision measurement, and discloses a thin film thickness measurement method and device based on spectrum confocal. The method comprises the steps that the temperature parameter at the current moment, the focusing wavelength of the upper surface of a measured thin film and the initial focusing position are obtained; calculating the focusing position of the upper surface of the measured film according to the focusing wavelength to obtain the focusing position; calculating a focusing deviation value caused by temperature change according to the focusing wavelength and the temperature parameter; correcting the focusing position according to the focusing deviation value to obtain an actual focusing position at the current moment; the film thickness is calculated according to the actual focusing position and the initial focusing position, the measured film thickness at the current moment is obtained, and the accuracy of film thickness measurement is improved.

Description

Technical Field

[0001] This invention relates to the field of high-precision measurement technology, and more specifically, to a method and device for measuring thin film thickness based on spectral confocalization. Background Technology

[0002] Spectral confocal microscopy, with its advantage of generating continuous focal points along the optical axis using a broadband light source, is widely used in various fields. Based on the principle of chromatic aberration, it achieves precise measurement of film thickness by correlating the position of the surface of the film under test with the peak wavelength of the continuous focal points in the reflection spectrum.

[0003] In actual measurement processes, temperature changes in the environment and the workpiece itself directly affect the final thickness measurement accuracy. To address this issue, existing technologies mainly employ temperature compensation or calibration techniques to reduce the impact of temperature on measurement results. However, these technologies heavily rely on prior modeling and calibration of specific material properties and operating conditions, resulting in a severe lack of universality. This leads to an inability to provide stable and reliable real-time measurement results when facing unknown materials or complex and variable temperature environments, resulting in poor accuracy of film thickness measurements. Summary of the Invention

[0004] In view of this, the present invention provides a method and device for measuring thin film thickness based on spectral confocalization, so as to solve the problem of poor accuracy in thin film thickness measurement.

[0005] In a first aspect, the present invention provides a thin film thickness measurement method based on spectral confocal microscopy, comprising: acquiring the temperature parameters at the current moment, the focusing wavelength of the upper surface of the thin film to be measured, and the initial focusing position; calculating the focusing position of the upper surface of the thin film to be measured based on the focusing wavelength to obtain the focusing position; calculating the focusing deviation caused by temperature change based on the focusing wavelength and the temperature parameters; correcting the focusing position based on the focusing deviation to obtain the actual focusing position at the current moment; and calculating the thin film thickness based on the actual focusing position and the initial focusing position to obtain the thickness of the thin film to be measured at the current moment.

[0006] In one optional embodiment, the temperature parameter includes the ambient temperature, which is the ambient temperature of the spectral confocal film thickness measuring device at the current moment; calculating the focusing deviation caused by temperature change based on the focusing wavelength and the temperature parameter includes: calculating the refractive index change of the lens in the spectral confocal film thickness measuring device due to temperature based on the ambient temperature and the focusing wavelength; calculating the optical power change of a single lens based on the refractive index change; calculating the total optical power change of multiple lenses based on the optical power change of a single lens; and calculating the focusing position change based on the total optical power change to obtain the focusing deviation.

[0007] In one optional embodiment, calculating the temperature-induced refractive index change of the lens in the spectral confocal film thickness measuring device based on the ambient temperature and the focusing wavelength includes: acquiring the initial ambient temperature before measuring the thickness of the film to be measured; calculating the real-time temperature change based on the ambient temperature and the initial ambient temperature; and calculating the temperature-induced refractive index change of the lens in the spectral confocal film thickness measuring device based on the real-time temperature change and the focusing wavelength.

[0008] In one optional implementation, the temperature parameter includes the light source temperature; calculating the focusing deviation caused by temperature change based on the focusing wavelength and the temperature parameter includes: determining the drift rate of the focusing wavelength as the temperature increases based on the light source temperature; calculating the focusing wavelength deviation based on the drift rate and the duration from the start of the measurement to the current moment, thereby obtaining the focusing deviation.

[0009] In one optional implementation, determining the drift rate of the focused wavelength as temperature increases based on the light source temperature includes: obtaining a function of the change in focused wavelength with temperature; and calculating the drift rate of the focused wavelength as temperature increases based on the function of change and the light source temperature.

[0010] In one optional implementation, the focus position is corrected based on the focus deviation to obtain the actual focus position at the current moment, including: calculating the focus wavelength to compensate for the focus wavelength deviation to obtain the actual focus wavelength; calculating the instantaneous slope at the current moment based on the calibration relationship function between the focus wavelength and the pre-constructed focus position; and calculating the focus position based on the actual focus wavelength and the instantaneous slope to obtain the actual focus position at the current moment.

[0011] In one alternative implementation, the focusing wavelength compensation is calculated using the following method: , in, Indicates the actual focusing wavelength. Indicates the focusing wavelength. Indicates the drift rate, This indicates the duration from the start of the measurement to the current moment.

[0012] In one optional implementation, the instantaneous slope at the current moment is calculated based on the focusing wavelength and a pre-constructed calibration relationship function of the focusing position, including: obtaining the pre-constructed calibration relationship function of the focusing position and performing differentiation to obtain the slope function relationship; and using the slope function relationship to calculate the focusing wavelength to obtain the instantaneous slope at the current moment.

[0013] In one alternative implementation, the actual focus position at the current moment is calculated using the following method: , in, Indicates the actual focus position. Indicates the instantaneous slope. It is a constant.

[0014] In a second aspect, the present invention provides a thin film thickness measurement device based on spectral confocal microscopy, comprising: 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 a thin film thickness measurement method based on spectral confocal microscopy.

[0015] The thin film thickness measurement method based on spectral confocalization provided by this invention first acquires temperature parameters, the focusing wavelength of the upper surface, and the initial focusing position. Then, the corresponding focusing position is calculated based on the focusing wavelength to obtain the current focusing position. Subsequently, the focusing deviation caused by temperature is calculated based on the temperature parameters and the focusing wavelength, quantifying the main error and providing core data for accurate compensation. Then, this deviation is used to dynamically correct the focusing position calculated based on the focusing wavelength, directly offsetting the systematic drift introduced by temperature changes and ensuring the accuracy of the measured value. Finally, the thin film thickness is directly obtained by the difference between the actual position of the calibrated upper surface and the initial reference. This embodiment effectively suppresses the interference of temperature on the measurement data through temperature correction, thereby improving the accuracy of thin film thickness measurement. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic flowchart of a thin film thickness measurement method based on spectral confocalization according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the relationship between the focusing wavelength and the focusing position according to an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] According to an embodiment of the present invention, a method for measuring thin film thickness based on spectral confocal microscopy is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than that shown here.

[0020] This embodiment provides a thin film thickness measurement method based on spectral confocal microscopy, which can be used in the aforementioned mobile terminals, such as mobile phones and tablets. Figure 1 This is a flowchart of a thin film thickness measurement method based on spectral confocalization according to an embodiment of the present invention, as shown below. Figure 1 As shown, the process includes the following steps: Step S101: Obtain the current temperature parameters, the focusing wavelength on the upper surface of the film under test, and the initial focusing position.

[0021] This embodiment is applicable to static precision thickness measurement of a thin film using a spectral confocal film thickness measurement device, or dynamic, online thickness monitoring during its continuous processing. The thin film under test can be transparent or semi-transparent. During the spectral confocal film thickness measurement process, the thermal effects of the internal and external environment of the device are the main factors affecting measurement accuracy. The temperature parameter refers to real-time temperature information that reflects the thermal state of the entire measurement device. The spectral confocal film thickness measurement device includes a light source (e.g., a laser, LED, or other light-emitting element), lenses (a single lens or multiple lens groups), a reflector, and a spectrometer. The laser emits a light beam, the lens expands and collimates the beam to convert the point light source into a line light source, the reflector reflects the line light source to illuminate the surface of the thin film under test, and the spectrometer receives the reflected light from the surface of the thin film under test and converts it into a spectral signal. The focusing wavelength (which can also be described as the focusing pixel, i.e., the corresponding pixel position on the spectrometer) refers to the wavelength value (or the pixel index corresponding to the peak intensity of the reflected light from the upper surface of the thin film under test) extracted from the spectral signal at the current moment. Alternatively, the focusing wavelength can also be the focusing wavelength of the lower surface of the thin film under test.

[0022] The initial focusing position is the reference beam focusing position determined by the lower surface of the film under test (i.e., the substrate interface). This position is obtained and locked during the initial calibration of the device (such as when calibrating a standard sample or a bare substrate of known thickness after a cold start). In subsequent measurements, regardless of changes in the upper surface of the film under test, this fixed initial focusing position on the lower surface will be used as the spatial reference zero point for calculating the thickness of the film under test.

[0023] Step S102: Calculate the focusing position on the upper surface of the film under test based on the focusing wavelength to obtain the focusing position.

[0024] This embodiment uses a pre-calibrated model of the focus position with respect to wavelength or pixel to calculate the focus position on the upper surface of the film under test at the current moment. For example, the pre-calibrated model of the focus position with respect to wavelength or pixel is as follows: , in, Indicates the focal point. Indicates the focused wavelength or focused pixel. , , , , , , .

[0025] This embodiment calculates the focusing position affected by temperature at the current moment through a precise calibration model, thereby providing reference geometric position information for subsequent thickness measurement or temperature drift compensation.

[0026] Step S103: Calculate the focusing deviation caused by temperature change based on the focusing wavelength and temperature parameters.

[0027] This embodiment calculates the theoretical offset of the focusing position relative to the standard reference temperature at the current temperature based on the focusing wavelength and temperature parameters, providing core correction data for subsequent compensation.

[0028] Step S104: Correct the focusing position based on the focusing deviation to obtain the actual focusing position at the current moment.

[0029] This embodiment aims to perform temperature compensation on the measurement data to obtain the true focus position. The focus position obtained from the calibration model is corrected according to the focus deviation calculated in step S103, thereby eliminating the error introduced by temperature drift. Finally, the calibrated focus position data representing the true position of the upper surface of the thin film at the current moment is output.

[0030] Step S105: Calculate the film thickness based on the actual focusing position and the initial focusing position to obtain the film thickness at the current moment.

[0031] This embodiment calculates the film thickness based on the calibrated actual focusing position. Specifically, the current actual surface focusing position output in step S104 is compared with the initial focusing position of the lower surface of the film or substrate acquired and stored at the start of the measurement. By calculating the absolute difference between the two, the physical travel distance of the beam scanning between the upper and lower surfaces is directly obtained; this value is the final real-time thickness of the film being measured. Alternatively, the processing thickness (e.g., the thickness obtained by grinding) is calculated based on the actual focusing position obtained at the previous moment and the actual focusing position at the current moment. The thickness of the film being measured at the current moment is then calculated using the original film thickness and the processing thickness.

[0032] The thin film thickness measurement method based on spectral confocal microscopy provided in this embodiment first acquires the temperature parameters, the focusing wavelength of the upper surface, and the initial focusing position. Then, the corresponding focusing position is calculated based on the focusing wavelength to obtain the current focusing position. Subsequently, the focusing deviation caused by temperature is calculated based on the temperature parameters and the focusing wavelength, quantifying the main error and providing core data for accurate compensation. Then, this deviation is used to dynamically correct the focusing position calculated based on the focusing wavelength, directly offsetting the systematic drift introduced by temperature changes and ensuring the accuracy of the measured value. Finally, the thin film thickness is directly obtained by the difference between the actual position of the calibrated upper surface and the initial reference. This embodiment effectively suppresses the interference of temperature on the measurement data through temperature correction, thereby improving the accuracy of thin film thickness measurement.

[0033] In some optional implementations, the temperature parameter includes the ambient temperature, which is the ambient temperature of the spectral confocal film thickness measurement device at the current moment. This ambient temperature typically refers to the value monitored and collected in real time at the measurement moment by a high-precision temperature sensor (such as a platinum resistance thermometer or digital temperature probe) integrated inside or near the spectral confocal film thickness measurement device. Incorporating environmental variables directly into the calculation as the dominant thermal disturbance avoids complex internal heat distribution analysis. Ambient temperature is easy to monitor, data is stable and reliable, and temperature compensation is more convenient.

[0034] Specifically, the process of calculating the focusing deviation caused by temperature change based on the focusing wavelength and temperature parameters in step S103 above mainly includes: Step S1031a: Calculate the change in refractive index of the lens in the spectral confocal film thickness measuring device due to temperature based on the ambient temperature and focusing wavelength.

[0035] Specifically, due to the thermal expansion and contraction effect caused by rising temperature, the size of the lens in the spectral confocal thin film thickness measurement device changes slightly, resulting in a decrease in its refractive index. This change directly affects the focusing characteristics of light, manifesting as a longer focusing distance for the wavelength. In other words, as the temperature rises, the focusing wavelength focused on the surface of the film being measured shifts backward compared to the original shorter wavelength, i.e., the focusing distance increases. Since the focusing position can be calculated using the lens power, which is closely related to its refractive index, the change in focusing position caused by the temperature increase can be estimated and compensated for based on the change in refractive index.

[0036] Step S1032a: Calculate the change in optical power of a single lens based on the change in refractive index.

[0037] For example, the change in optical power of a single lens is calculated using the following method: , in, This represents the change in optical power of a single lens. This represents the change in refractive index of the lens due to temperature variations. and The radius of curvature of a single lens in a spectral confocal thin film thickness measurement device. The thickness of a single lens.

[0038] Step S1033a: Calculate the total change in optical power of multiple lenses based on the change in optical power of a single lens.

[0039] For example, the total change in optical power of multiple lenses is calculated using the following method: , in, This represents the total change in optical power across multiple lenses. This represents the total number of lenses. Let be the change in optical power of the i-th lens. This refers to the spacing between adjacent lenses.

[0040] Step S1034a: Calculate the change in focus position based on the change in total optical power to obtain the focus deviation.

[0041] For example, the focus deviation is obtained by calculating the change in focus position as follows: , in, To focus on the deviation.

[0042] Furthermore, in step S104 above, the focusing position is corrected based on the focusing deviation to obtain the actual focusing position at the current moment: , in, The actual focus position at the current moment. To focus on the location.

[0043] For example: if the initial ambient temperature rises from 20℃ to 30℃, and the focusing wavelength is 500nm, then the actual focusing position at the current moment after compensation is: , This embodiment monitors the ambient temperature in real time and calculates the real-time temperature change. Combined with the actual focusing wavelength, it accurately calculates the change in lens refractive index, thereby dynamically correcting the changes in optical power of individual and multiple lenses. By accumulating the changes in optical power of individual lenses and considering the mutual influence between lenses, the total change in optical power of multiple lenses can be calculated. This step optimizes the optical power of the entire measurement system and improves the overall measurement accuracy. Finally, the change in focusing position is calculated based on the total change in optical power and combined with the initial focusing position to determine the actual focusing position at the current moment. This method, based on the calculation relationship between the refractive index of a single material and the optical power of a thin lens, effectively corrects the influence of temperature on the focusing position, eliminates the influence of temperature changes on spectral confocal thickness measurement, and ensures the accuracy of the measurement results.

[0044] In some optional embodiments, the process of calculating the temperature-induced refractive index change of the lens in the spectral confocal thin film thickness measuring device based on the ambient temperature and focusing wavelength in step S1031a mainly includes: Step S1031a1: Obtain the initial ambient temperature before measuring the thickness of the film under test.

[0045] Before starting the thickness measurement of the film under test, the initial ambient temperature of the environment is acquired and recorded. This temperature will serve as a reference for subsequent temperature change calculations.

[0046] Step S1031a2: Calculate the real-time temperature change based on the ambient temperature and the initial ambient temperature.

[0047] During the measurement process, the ambient temperature is monitored in real time. And calculate the real-time temperature change between it and the initial ambient temperature. This change directly reflects the magnitude of environmental thermal disturbance during the measurement period.

[0048] Step S1031a3: Calculate the change in refractive index of the lens of the spectral confocal film thickness measuring device due to temperature based on the real-time temperature change and the focusing wavelength.

[0049] Specifically, for example, during the operation of a laser's semiconductor device (LED, laser diode), the main wavelength increases by 1 nm for every 10°C increase in internal temperature, which is 0.1 nm / °C. This is a compensation coefficient that can be used to compensate for wavelength drift caused by temperature changes.

[0050] Ideally, the relationship between temperature and refractive index is as follows: , in, Current temperature The refractive index below, Reference temperature Refractive index at (e.g., initial ambient temperature or room temperature) This is the temperature coefficient.

[0051] However, in actual spectral confocal thin film thickness measurement devices, the absolute refractive index of the optical material, i.e., the lens, changes with temperature according to the following relationship: , in, This represents the change in refractive index of the lens due to temperature variations. The relative refractive index, , , , , , All are thermal characteristic constants. for symbols, >0, =1, <0, =-1. Thermal characteristic constants can be provided by optical glass manufacturing companies.

[0052] Therefore, in this invention, the real-time temperature change between the current ambient temperature and the initial ambient temperature can be used as a reference. Actual focusing wavelength Calculate the change in refractive index of the lens in a spectral confocal thin film thickness measurement device due to temperature variations. The formula can be updated to: , in, The relative refractive index of the lens of the spectral confocal thin film thickness measurement device is given at the initial ambient temperature.

[0053] This embodiment introduces a high-order comprehensive model based on the true thermo-optical properties of materials. This model not only includes linear terms related to temperature changes but also incorporates higher-order terms (…). The method accurately characterizes the nonlinear variation of refractive index under actual operating conditions by incorporating wavelength-dependent dispersion terms. This overcomes the limitation of simple linear models, which may produce large errors over a wide temperature range or specific wavelength bands. By directly substituting the real-time focusing wavelength into the model, real-time compensation for wavelength dependence is achieved, making the refractive index calculation more closely match the actual spectral state during measurement. This method significantly improves the accuracy and reliability of refractive index variation calculation, thus providing a solid and accurate data source for the final accurate compensation of focusing deviation. It ensures that the entire temperature compensation maintains high-precision measurement performance in complex practical application environments, thereby improving the accuracy of thin film thickness measurement.

[0054] In some alternative implementations, the temperature parameter includes the temperature of the light source.

[0055] In spectral confocal microscopy measurements, the calculation of thin film thickness depends on the focusing wavelength corresponding to the focusing position on the surface. However, the focusing wavelength is easily affected by temperature and drifts, causing measurement deviations in the focusing position and ultimately leading to distorted thickness results. A key factor causing temperature drift in the focusing wavelength is the heat generated by the light source (e.g., a laser) in the spectral confocal thin film thickness measurement device. During continuous or high-load operation, the light source will continuously heat up due to factors such as internal electro-optical conversion efficiency. This temperature rise directly changes the spectral characteristics of the light source output—the physical mechanism being that the bandgap of the semiconductor material and the optical length of the resonant cavity both change with temperature, causing a thermally induced drift in the center wavelength of the output light, typically manifested as a "redshift" towards longer wavelengths. Taking a laser as an example, its wavelength-temperature coefficient is approximately 0.1 nm / °C. To acquire and correct this temperature drift error in real time, this embodiment utilizes a high-precision temperature sensor to directly monitor the operating temperature of the light source.

[0056] Specifically, the process of calculating the focusing deviation caused by temperature change based on the focusing wavelength and temperature parameters in step S103 above mainly includes: S1031b determines the drift rate of the focusing wavelength as the temperature increases based on the temperature of the light source.

[0057] This embodiment aims to quantify the wavelength drift rate caused by the heating of the light source in real time, which is crucial for achieving high-precision temperature compensation and improving the stability of thickness measurement. This drift rate can be determined through laboratory testing or by using empirical values ​​from crystal diodes.

[0058] S1032b calculates the focusing wavelength deviation based on the drift rate and the time elapsed from the start of the measurement to the current moment, thus obtaining the focusing deviation.

[0059] Drift rate in this embodiment It characterizes the instantaneous rate of change of the focused wavelength with temperature, while the measurement time... This represents the time span from the initial reference point of the measurement (where the temperature effect is considered zero) to the current moment. Multiplying the two together gives... This allows for the direct calculation of the total focusing wavelength deviation caused by the temperature drift effect during that period. This step converts the "rate of change" into the "deviation amount," quantifies the cumulative effect of temperature in the time domain, and provides a clear numerical compensation target for subsequent position correction.

[0060] This embodiment calculates the focusing wavelength deviation based on the drift rate of the focusing wavelength as temperature increases and the measurement duration. It can accurately separate the wavelength drift component caused by temperature fluctuations during long-term operation, effectively overcoming the problem of decreased spectral stability caused by light source heating. This enables the spectral confocal film thickness measurement device to significantly improve the long-term repeatability and absolute accuracy of measurement data in long-term continuous operation and high-precision application scenarios, ensuring the accuracy of film thickness measurement results.

[0061] In some optional embodiments, the process of determining the drift rate of the focusing wavelength with increasing temperature based on the light source temperature in step S1031b mainly includes: Step S1031b1: Obtain the function of the focusing wavelength changing with temperature.

[0062] This embodiment aims to establish a deterministic mathematical model describing the change of the output wavelength of a light source with its own temperature. This change function is usually obtained through precise calibration experiments: under a controllable temperature environment, different steady-state light source temperatures and their corresponding output center wavelengths are recorded, and a magical relationship between the focusing wavelength and temperature is constructed by collecting discrete points and using polynomial or interpolation fitting methods.

[0063] Step S1031b2: Calculate the drift rate of the focusing wavelength as the temperature increases based on the change function and the light source temperature.

[0064] This embodiment dynamically calculates the instantaneous wavelength drift rate at the current moment based on the established change function and real-time monitored light source temperature data, so as to capture and respond in real time to the wavelength drift trend caused by changes in the working state of the light source.

[0065] This embodiment calculates the drift rate of the focused wavelength increase at the current light source temperature based on the function of the focusing wavelength change with temperature, providing accurate and reliable parameters for subsequent real-time error compensation. This not only significantly improves the measurement stability of the spectral confocal system in variable temperature environments, but also enhances its adaptability to continuous operation or high-load conditions, fundamentally improving the long-term repeatability and accuracy of thin film thickness measurement.

[0066] In some optional implementations, the process of correcting the focus position based on the focus deviation to obtain the actual focus position at the current moment in step S104 mainly includes: Step S1041b: The focusing wavelength is compensated based on the focusing wavelength deviation to obtain the actual focusing wavelength.

[0067] Specifically, based on the measurement principle of the spectral confocal thin film thickness measurement device, ideally, the focusing wavelength... With displacement It is a linear relationship, slope It is fixed: , slope Defined as unit focusing wavelength deviation Displacement change caused by change : , For example, a confocal spectral film thickness measurement device is designed with a measurement range of 1 mm, an operating wavelength of 200 nm, and a sensitivity of 5 μm / nm. First, consider static measurement, where the measurement position of the film remains unchanged, and the only factors causing wavelength changes are environmental variations such as temperature. time: , for The focusing wavelength at any given moment; time: , for The focusing wavelength at any given moment; Then displacement bias : , So, wavelength offset : , The displacement deviation can then be calibrated using the following formula. , , The focusing wavelength extracted at the current moment. To extract the focusing wavelength based on the current moment Calculated focal position , It is known that This is the constant representing the focusing wavelength-focusing position relationship, obtained during calibration.

[0068] Because of the focusing wavelength shift caused by temperature increase, it is necessary to obtain the rate of temperature increase of the light source in the spectral confocal thin film thickness measurement device, i.e., the temperature increase per unit time. From this, the drift rate of the focusing wavelength with increasing temperature can be obtained. , which is the wavelength per unit time, measured in nm / ms.

[0069] So, the actual focusing wavelength : , , Right now , Therefore, this embodiment is based on the drift rate Current focusing wavelength And the duration from the start of the measurement to the current moment. Compensation calculations are performed to obtain the actual focusing wavelength. : .

[0070] Step S1042b: Calculate the instantaneous slope at the current moment based on the calibration relationship function between the focusing wavelength and the pre-constructed focusing position.

[0071] The above actual focusing wavelength Although the calculation eliminates thermal drift error, the result is still under ideal conditions. In reality, the relationship between focusing wavelength and focusing position is a non-linear model, meaning the slope changes in real time for different wavelengths. Figure 2 For example, the horizontal axis represents the focusing wavelength, and the vertical axis represents the focusing position, where the relationship curve is non-linear. Therefore, in order to accurately focus the actual wavelength... To convert to an equally precise physical position, the local characteristics at the current working point must be considered, that is, the instantaneous slope at the current moment must be calculated based on the calibration relationship function between the focusing wavelength and the pre-constructed focusing position.

[0072] Step S1043b: Calculate the focusing position based on the actual focusing wavelength and instantaneous slope to obtain the actual focusing position at the current moment.

[0073] For example, the actual focus position at the current moment can be calculated using the following method: , in, Indicates the actual focus position. Indicates the instantaneous slope. It is a constant.

[0074] This embodiment utilizes the product of drift rate and measurement duration to compensate for the measured focusing wavelength in real time, accurately eliminating the wavelength deviation introduced by thermal effects and obtaining the actual focusing wavelength unaffected by temperature. Next, the instantaneous slope at the current actual focusing wavelength is calculated. Finally, the actual focusing wavelength and instantaneous slope are combined, and the actual focusing position at the current moment is obtained through linearization calculation. This process effectively overcomes the errors caused by the sensor's nonlinear response through local linearization, thereby achieving a dual high-precision conversion from wavelength to position at the algorithm level, significantly improving the long-term stability and measurement accuracy of the spectral confocal thin film thickness measurement device under long-term continuous operation.

[0075] In some optional implementations, the process of calculating the instantaneous slope at the current moment based on the focusing wavelength and the pre-constructed calibration relationship function of the focusing position in step S1042b mainly includes: Step S1042b1: Obtain the pre-constructed calibration relationship function of the focus position and perform differentiation to obtain the slope function relationship.

[0076] In practice, the relationship between focusing wavelength and focusing position is a non-linear model, meaning the slope at different wavelengths changes in real time. time: ; time: ; Then displacement bias : ; By taking the derivative of the relational function, we can obtain... , The relationship between the calibrated focus position and the focus wavelength is a function, for example: , in, , , , , , , .

[0077] Step S1042b2: Calculate the focusing wavelength using the slope function relationship to obtain the instantaneous slope at the current moment.

[0078] This embodiment calculates the instantaneous slope at the current moment. This involves differentiating the current relational function and substituting the corresponding focusing wavelength. The instantaneous slope can then be obtained. : .

[0079] This embodiment significantly improves the accuracy of wavelength-position conversion by dynamically solving the instantaneous slope of the nonlinear calibration function at the compensated actual wavelength. Specifically, a nonlinear mapping between wavelength and position is first established based on the calibration relationship function; the slope function as a function of wavelength is obtained by differentiating this function; then, the precise focusing wavelength obtained after temperature compensation is substituted into this derivative function to calculate the instantaneous slope at the current moment. This method can accurately capture the continuous change in sensitivity at different operating wavelengths, thus completely correcting the model error introduced by the nonlinear response characteristics when calculating the actual position. This process not only ensures that temperature drift is eliminated, but also achieves a precise approximation of the local linearization of the nonlinear system at the operating point, thereby enabling the spectral confocal film thickness measurement device to simultaneously possess long-term stability and high precision, improving the accuracy of film thickness measurement.

[0080] A portion of this invention can be applied as a computer program product, such as computer program instructions, which, when executed by a computer, can invoke or provide the methods and / or technical solutions according to the invention through the operation of the computer. Those skilled in the art will understand that the forms in which computer program instructions exist in a computer-readable medium include, but are not limited to, source files, executable files, installation package files, etc. Correspondingly, the ways in which computer program instructions are executed by a computer include, but are not limited to: the computer directly executing the instructions, or the computer compiling the instructions and then executing the corresponding compiled program, or the computer reading and executing the instructions, or the computer reading and installing the instructions and then executing the corresponding installed program. Here, the computer-readable medium can be any available computer-readable storage medium or communication medium accessible to a computer.

[0081] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for measuring thin film thickness based on spectral confocal microscopy, characterized in that, The method includes: Obtain the current temperature parameters, the focusing wavelength on the upper surface of the film under test, and the initial focusing position; The focusing position is calculated based on the focusing wavelength to obtain the focusing position on the upper surface of the film under test; Calculate the focusing deviation caused by temperature change based on the focusing wavelength and the temperature parameter; The focusing position is corrected based on the focusing deviation to obtain the actual focusing position at the current moment; The film thickness is calculated based on the actual focusing position and the initial focusing position to obtain the film thickness at the current moment.

2. The method according to claim 1, characterized in that, The temperature parameter includes the ambient temperature, which is the ambient temperature of the spectral confocal film thickness measurement device at the current moment; The calculation of the focusing deviation caused by temperature change based on the focusing wavelength and the temperature parameter includes: Calculate the change in refractive index of the lens in the spectral confocal thin film thickness measuring device due to temperature based on the ambient temperature and the focusing wavelength; Calculate the change in optical power of a single lens based on the change in refractive index; Calculate the total change in optical power of multiple lenses based on the change in optical power of a single lens; The focus position change is calculated based on the total change in optical power to obtain the focus deviation.

3. The method according to claim 2, characterized in that, The calculation of the temperature-induced refractive index change of the lens in the spectral confocal thin film thickness measuring device based on the ambient temperature and the focusing wavelength includes: Obtain the initial ambient temperature before measuring the thickness of the film under test; Calculate the real-time temperature change based on the ambient temperature and the initial ambient temperature; The change in refractive index of the lens of the spectral confocal thin film thickness measuring device due to temperature is calculated based on the real-time temperature change and the focusing wavelength.

4. The method according to claim 1, characterized in that, The temperature parameter includes the light source temperature; The calculation of the focusing deviation caused by temperature change based on the focusing wavelength and the temperature parameter includes: The drift rate of the focusing wavelength as temperature increases is determined based on the temperature of the light source; The focusing wavelength deviation is calculated based on the drift rate and the time elapsed from the start of the measurement to the current moment, thus obtaining the focusing deviation.

5. The method according to claim 4, characterized in that, Determining the drift rate of the focused wavelength with increasing temperature based on the temperature of the light source includes: Obtain the function of the focusing wavelength changing with temperature; The drift rate of the focusing wavelength as temperature increases is calculated based on the change function and the temperature of the light source.

6. The method according to claim 4, characterized in that, The step of correcting the focusing position based on the focusing deviation to obtain the actual focusing position at the current moment includes: The actual focusing wavelength is obtained by calculating the compensation for the focusing wavelength based on the focusing wavelength deviation. The instantaneous slope at the current moment is calculated based on the calibration relationship function between the focusing wavelength and the pre-constructed focusing position; The focusing position is calculated based on the actual focusing wavelength and the instantaneous slope to obtain the actual focusing position at the current moment.

7. The method according to claim 6, characterized in that, The focusing wavelength compensation is calculated using the following method: ， in, This indicates the actual focusing wavelength. This indicates the focusing wavelength. This represents the drift rate. This indicates the duration from the start of the measurement to the current moment.

8. The method according to claim 6, characterized in that, The calculation of the instantaneous slope at the current moment based on the focusing wavelength and the pre-constructed calibration relationship function of the focusing position includes: Obtain the pre-constructed calibration relationship function of the focal position, and differentiate it to obtain the slope function relationship; The instantaneous slope at the current moment is obtained by calculating the focusing wavelength using the slope function relationship.

9. The method according to claim 6, characterized in that, The actual focus position at the current moment is calculated using the following method: ， in, Indicates the actual focusing position. This represents the instantaneous slope. It is a constant.

10. A thin film thickness measurement device based on spectral confocal microscopy, 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 thin film thickness measurement method based on spectral confocalization as described in any one of claims 1-9.

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