Method and device for measuring film thickness

Abstract

The present invention discloses a method and device for measuring film thickness. The method for measuring film thickness includes: obtaining optimal probe heights of multiple measuring points of the film to be measured; determining the roughness coefficient of the film to be measured according to each optimal probe height; obtaining the theoretical reflection spectrum of the film to be measured; determining the corrected reflection spectrum according to the roughness coefficient and the theoretical reflection spectrum; and determining the thickness of the film to be measured according to the corrected reflection spectrum. The technical solution of the present invention, by adding the film roughness coefficient to the theoretical reflectivity model, makes the theoretically calculated reflectivity spectrum closer to the actual reflectivity spectrum, thereby improving the accuracy of the measured film thickness.

Description

Technical Field

[0001] The invention relates to the technical field of film thickness measurement, and in particular to a method and device for measuring film thickness. Background Art

[0002] During the manufacturing process, chips will undergo hundreds or thousands of coating processes, and the detection of film thickness is an important step in verifying whether these coating processes are qualified. It also determines whether the final chip yield can meet the design requirements, so accurate measurement of film thickness is crucial.

[0003] When using the traditional spectral reflectance method to measure the thickness of a film, the film to be measured is usually assumed to be a layered structure with a smooth surface. The light beam is incident vertically and then reflected vertically after passing through the film layer. The reflectance spectrum of the film is determined by the ratio of the measured reflected light intensity to the incident light intensity. The theoretically calculated reflectance spectrum is then compared with the measured reflectance spectrum to determine the thickness of the film. However, in the actual production process, due to factors such as deposition flow rate, thermal oxidation temperature or impurities, the actual film is not completely smooth. The surface roughness causes light to scatter when it is reflected on the surface of the material, which weakens the intensity of the directly reflected light, resulting in a decrease in the contrast of the interference fringes or a change in the morphology of the fringes. The light scattering on the rough surface will prevent part of the light from propagating along the expected path, and the incident light beam emitted by the probe is not completely reflected back, causing the actually measured reflectance spectrum to deviate from the theoretical model, resulting in errors in the thickness calculation. Summary of the invention

[0004] The present invention provides a method and device for measuring film thickness to solve the problem of error in film thickness measurement in the prior art. By adding a film roughness coefficient to a theoretical reflectivity model, the theoretically calculated reflectivity spectrum is closer to the actual reflectivity spectrum, thereby improving the accuracy of the measured film thickness.

[0005] In a first aspect, the present invention provides a method for measuring the thickness of a thin film, which is implemented by using a film thickness measurement optical system, wherein the film thickness measurement optical system includes a probe; the method for measuring the thickness of a thin film includes:

[0006] Obtaining optimal probe heights for multiple measurement points of the film to be measured; the optimal probe height is the height of the probe from the surface of the film to be measured when the probe receives the maximum light intensity;

[0007] Determining the roughness coefficient of the film to be tested according to each of the optimal probe heights;

[0008] Obtaining a theoretical reflection spectrum of the film to be tested;

[0009] Determining a corrected reflection spectrum according to the roughness coefficient and the theoretical reflection spectrum;

[0010] The thickness of the film to be measured is determined according to the corrected reflection spectrum.

[0011] Optionally, obtaining optimal probe heights for multiple measuring points of the film to be measured includes:

[0012] A film thickness measurement optical system is used to control the probe of the film thickness measurement optical system to move up and down within a preset height range [h1, h2] above the film to be measured, and at the same time, a spectrometer of the film thickness measurement optical system is controlled to collect light intensity and record the light intensity corresponding to each height position; wherein the focal length hf of the probe is located within the interval [h1, h2];

[0013] According to each height position and its corresponding light intensity, a height-light intensity curve is formed;

[0014] The optimal probe height for each measuring point is determined according to the height-light intensity curve.

[0015] Optionally, determining the optimal probe heights of the multiple measurement points according to the height-light intensity curve includes:

[0016] After the probe is moved to the measuring point, the spectrometer is controlled to read the current light intensity value I0, and the height Hx corresponding to the current light intensity I0 on the height-light intensity curve is determined;

[0017] Determine whether Hx is unique;

[0018] If yes, then Hx is determined to be the optimal probe height for the measurement point.

[0019] Optionally, the film thickness measurement method further includes:

[0020] If the current light intensity I0 corresponds to two heights h_x1 and h_x2 on the height-light intensity curve, the probe is controlled to move upward by a preset height △h, and the spectrometer is controlled to collect the current light intensity value I1; wherein h_x1<h_x2;

[0021] Determine whether I0>I1 is true;

[0022] If yes, the probe is moved downward by (△h+h_x2-hf), and the optimal probe height of the probe after the movement is determined.

[0023] Optionally, the film thickness measurement method further includes:

[0024] If I0<I1, the probe is further moved upward by (hf-h_x1-△h), and the optimal probe height after the movement is determined.

[0025] Optionally, the light source of the probe is laser or broadband light.

[0026] Optionally, when the light source of the probe is broadband light, the light intensity is calculated by a first formula; wherein the first formula is as follows:

[0027] ;

[0028] Among them, I totle is the collected light intensity; [λ min ,λ max ] is the wavelength range; I(λ) is the light intensity corresponding to the wavelength λ.

[0029] Optionally, determining the roughness coefficient of the film to be measured according to the height of each probe includes:

[0030] Calculating the root mean square roughness according to each of the probe heights;

[0031] Based on the Debye-Waller factor model, the roughness coefficient of the film to be tested is determined according to the root mean square roughness.

[0032] Optionally, determining a corrected reflection spectrum according to the roughness coefficient and the theoretical reflection spectrum includes:

[0033] According to the second formula, the corrected reflection spectrum is determined; wherein the second formula is as follows:

[0034] Rcorrected = Rtheoretical * α;

[0035] Wherein, Rcorrected is the corrected reflection spectrum; Rtheoretical is the theoretical reflection spectrum; and α is the roughness coefficient.

[0036] In a second aspect, the present invention provides a device for measuring the thickness of a thin film, characterized in that the device is implemented by using a film thickness measurement optical system, wherein the film thickness measurement optical system includes a probe; and the film thickness measurement method includes:

[0037] An optimal probe height acquisition module is used to acquire the optimal probe heights of multiple measuring points of the film to be measured; the optimal probe height is the height of the probe from the surface of the film to be measured when the probe receives the maximum light intensity;

[0038] A roughness coefficient determination module, used to determine the roughness coefficient of the film to be tested according to each of the optimal probe heights;

[0039] A theoretical reflection spectrum acquisition module, used to acquire the theoretical reflection spectrum of the film to be tested;

[0040] A corrected reflection spectrum determination module, used to determine a corrected reflection spectrum according to the roughness coefficient and the theoretical reflection spectrum;

[0041] The film thickness determination module is used to determine the thickness of the film to be measured according to the corrected reflection spectrum.

[0042] The technical solution of the present invention obtains the optimal probe heights of multiple measuring points of the film to be measured, and determines the roughness coefficient of the film to be measured according to each optimal probe height, so that the roughness coefficient of the film to be measured is obtained by actually measuring the surface morphology of the film to be measured, thereby ensuring the accuracy of the roughness coefficient of the film to be measured. In addition, by obtaining the theoretical reflection spectrum of the film to be measured, the corrected reflection spectrum is determined according to the roughness coefficient and the theoretical reflection spectrum, and then the thickness of the film to be measured is determined according to the corrected reflection spectrum. In this way, the roughness coefficient of the film to be measured can be determined by the optimal probe height of each measuring point, and the film roughness coefficient is added to the theoretical reflectivity model, so that the corrected reflection spectrum obtained by theoretical calculation is closer to the actual reflectivity spectrum, thereby improving the accuracy of the measured film thickness.

[0043] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0045] Figure 1 This is a flow chart of a method for measuring film thickness provided in Example 1 of the present invention.

[0046] Figure 2 An optical system for measuring film thickness provided by an embodiment of the present invention.

[0047] Figure 3 A flow chart of a method for measuring film thickness provided in Embodiment 2 of the present invention.

[0048] Figure 4 This is a flow chart of a method for measuring film thickness provided in Embodiment 3 of the present invention.

[0049] Figure 5 A schematic diagram of the relative position of a probe and a film to be measured during film thickness measurement provided by an embodiment of the present invention.

[0050] Figure 6A schematic diagram of a height-light intensity curve provided by an embodiment of the present invention.

[0051] Figure 7 This is a schematic structural diagram of a device for measuring film thickness provided in Embodiment 4 of the present invention. DETAILED DESCRIPTION

[0052] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0053] It should be noted that the terms "first", "second", "target", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0054] Embodiment 1:

[0055] Figure 1 Flow chart of the method for measuring film thickness provided in Embodiment 1 of the present invention, as shown in FIG. Figure 1 As shown, the measurement method includes:

[0056] S110, obtaining optimal probe heights at multiple measuring points of the film to be measured.

[0057] The film to be tested is a film with a rough surface. In an optional embodiment, the film to be tested may include but is not limited to a silicon dioxide film, a polysilicon film, a silicon nitride film or an aluminum oxide film. The rough surface of the film to be tested causes light to be scattered when reflected on the film surface, resulting in the incident light beam emitted by the probe not being completely reflected back, thereby causing the actual measured reflection spectrum to deviate from the theoretical model, resulting in an error in the determined thickness of the film to be tested.

[0058] The measuring point is the position where the film thickness of the film to be measured is measured. The more measuring points there are and the more evenly they are distributed on the film to be measured, the more the collected roughness information can cover the entire film, so that the roughness coefficient of the film to be measured is determined to be more accurate, but the measurement efficiency will be lower; on the contrary, the fewer measuring points there are, the higher the measurement efficiency is, but it is not conducive to improving the accuracy of the roughness coefficient. In an exemplary embodiment, the film to be measured includes 9 measuring points, and the 9 measuring points are evenly distributed on the surface of the film to be measured.

[0059] Figure 2 The film thickness measurement optical system provided by the embodiment of the present invention is referred to Figure 2 As shown, the film thickness measurement optical system used in this embodiment includes a light source, a spectrometer, a probe, a stage and a motion module, wherein the light source and the spectrometer are coupled to the probe through optical fibers, respectively, the light source is used to emit incident light, the spectrometer is used to receive reflected light and measure the intensity of the reflected light, and the motion module is connected to the probe and the stage, and is used to drive the probe and / or the stage to move so that the probe is located above the measuring point of the film to be measured. When measuring the film to be measured, the film to be measured is placed on the stage, and the incident light is irradiated to the surface of the film to be measured through the probe, and after being reflected by the surface of the film to be measured, it is received by the probe and transmitted to the spectrometer, so as to observe the intensity of the reflected light.

[0060] In an optional embodiment, the light source is a laser or a broadband light. When the light source is a laser, the intensity of the reflected light is the light intensity value at the corresponding wavelength collected by the spectrometer. When the light source is a broadband light, such as a white light source with a wavelength range of 400-1000nm, the light intensity is calculated by the first formula, wherein the first formula is as follows:

[0061] ;

[0062] Among them, I totle is the collected light intensity; [λ min ,λ max ] is the wavelength range; I(λ) is the light intensity corresponding to the wavelength λ.

[0063] The optimal probe height can be understood as the height of the probe from the surface of the film to be tested when the maximum light intensity can be received. In an optional embodiment, when the probe is located above the test point of the film to be tested, the motion module is used to control the probe to move up and down (i.e., away from or close to the film to be tested), and the maximum light intensity of the reflected light collected by the spectrometer is observed. When the probe moves upward, the maximum light intensity decreases, and when the probe moves downward, the maximum light intensity also decreases, and the probe position at this time is determined to be the optimal probe position. In this way, the movement of the stage is controlled by the motion module, so that the probe is successively located above each measurement point of the film to be tested, and when the probe is above each measurement point, the optimal probe position of the measurement point is determined according to the above method, and the optimal probe height for measuring each measurement point of the film to be tested can be determined.

[0064] S120, determining the roughness coefficient of the film to be measured according to each optimal probe height.

[0065] Among them, the roughness coefficient of the film to be tested can be understood as the roughness of the surface of the film to be tested. Since the optimal probe height is the height of the probe from the surface of the film to be tested when the maximum light intensity can be received, that is, the focal length of the probe, the optimal probe height of each measuring point and the distance between the corresponding measuring points are fixed, so that the relationship between the optimal probe heights of each measuring point can represent the surface roughness between each measuring point. Therefore, the roughness coefficient of the film to be tested can be determined according to each optimal probe height.

[0066] In an optional embodiment, the roughness coefficient of the film to be tested is determined according to each optimal probe height, including: calculating the root mean square roughness according to each probe height; and determining the roughness coefficient of the film to be tested according to the root mean square roughness based on the Debye-Waller factor model.

[0067] The root mean square roughness of the film to be tested is determined according to the following formula:

[0068] Roughness= .

[0069] Where Roughness is the root mean square roughness, N is the number of measurement points, and H is the optimal probe height for each measurement point.

[0070] The Debye-Waller factor model is expressed as follows:

[0071] ;

[0072] Among them, α is the roughness coefficient of the film to be tested, and λ is the wavelength of the incident light.

[0073] S130, obtaining a theoretical reflection spectrum of the film to be tested.

[0074] The theoretical reflection spectrum of the film to be tested can be understood as the reflection spectrum of the film to be tested calculated according to the reflection spectrum theory when the film to be tested is equivalent to a film layer structure with a smooth surface.

[0075] In an optional embodiment, the theoretical reflection spectrum of the film to be measured takes into account the influence of the substrate and environmental noise of the film to be measured. Specifically, the reflected light intensity Ssi of the reference film (i.e., the substrate of the film to be measured, such as a bare silicon wafer) is measured by a film thickness measurement optical system, and when the light source is turned off, the environmental noise intensity Sdark is measured, and then the reflected light intensity Ssa of the film to be measured is measured by the film thickness measurement optical system, and then the measured reflection spectrum Rsa=(Ssa-Sdark) / (Ssi-Sdark)*Rsi of the film to be measured is determined; finally, according to the reflection spectrum theory, the theoretical reflection spectrum Rtheoretical (d, n, k, λ) of the film to be measured can be calculated;

[0076] Among them, Rsi is the reflectivity value of Si in the corresponding wavelength range, which can be obtained from the literature; d is the estimated film thickness, n and k are the optical constants of the materials involved in the film structure, and λ is the wavelength of light.

[0077] S140: Determine a corrected reflection spectrum according to the roughness coefficient and the theoretical reflection spectrum.

[0078] The corrected reflection spectrum can be understood as a theoretical reflection spectrum that takes into account the roughness coefficient of the film to be measured. In an optional embodiment, the corrected reflection spectrum is determined according to the roughness coefficient and the theoretical reflection spectrum, including: determining the corrected reflection spectrum according to a second formula. The second formula is as follows:

[0079] Rcorrected = Rtheoretical * α.

[0080] Wherein, Rcorrection is the corrected reflection spectrum; Rtheory is the theoretical reflection spectrum; α is the roughness coefficient.

[0081] S150, determining the thickness of the film to be measured according to the corrected reflection spectrum.

[0082] In an optional embodiment, according to the corrected reflection spectrum Rcorrection, the guessed film thickness in the corrected reflection spectrum is changed, and the thickness of the film to be measured is calculated through a curve fitting process of numerical regression. Exemplarily, the thickness of the film to be measured is calculated through a curve fitting process of numerical regression, including: calculating the goodness of fit value or residual value between the Rcorrection and the measured reflection spectrum of the film to be measured, and determining the guessed film thickness corresponding to the maximum goodness of fit value or the minimum residual as the thickness of the film to be measured.

[0083] In this embodiment, by obtaining the optimal probe heights of multiple measuring points of the film to be measured, the roughness coefficient of the film to be measured is determined according to each optimal probe height, so that the roughness coefficient of the film to be measured is obtained by actually measuring the surface morphology of the film to be measured, thereby ensuring the accuracy of the roughness coefficient of the film to be measured. In addition, by obtaining the theoretical reflection spectrum of the film to be measured, the corrected reflection spectrum is determined according to the roughness coefficient and the theoretical reflection spectrum, and then the thickness of the film to be measured is determined according to the corrected reflection spectrum. In this way, the roughness coefficient of the film to be measured can be determined by the optimal probe height of each measuring point, and the film roughness coefficient is added to the theoretical reflectivity model, so that the corrected reflection spectrum obtained by theoretical calculation is closer to the actual reflectivity spectrum, thereby improving the accuracy of the measured film thickness.

[0084] Embodiment 2:

[0085] Figure 3 This is a flow chart of a method for measuring film thickness provided in the second embodiment of the present invention. Based on the above embodiment, this embodiment further adds a step of how to obtain the optimal probe height of multiple measuring points of the film to be measured. Figure 3 As shown, the method specifically includes:

[0086] S210, using a film thickness measurement optical system, controlling the probe of the film thickness measurement optical system to move up and down within a preset height range [h1, h2] above the film to be measured, and at the same time, controlling the spectrometer of the film thickness measurement optical system to collect light intensity and record the light intensity corresponding to each height position.

[0087] The preset height range [h1, h2] can be determined according to the properties of the probe. The preset height range [h1, h2] is a relatively large height range, and it is necessary to ensure that the focal length hf of the probe is within the interval (h1, h2).

[0088] It should be noted that when the probe of the film thickness measurement optical system is controlled to move up and down within a preset height range [h1, h2] above the film to be measured, the probe can be located above any position of the film to be measured, as long as the light intensity at each height position can be measured. In an exemplary embodiment, the probe of the film thickness measurement optical system is controlled to move up and down within a preset height range [h1, h2] above a measurement point of the film to be measured, so that when the height-light intensity curve is obtained, the optimal probe height of the measurement point can be obtained, so that when the optimal probe height of multiple measurement points is determined according to the height-light intensity curve, the number of operations can be reduced, thereby improving the efficiency of determining the optimal probe height of multiple measurement points and saving time costs.

[0089] S220, forming a height-light intensity curve according to each height position and its corresponding light intensity.

[0090] Specifically, each height position and its corresponding light intensity are marked one by one in the height-light intensity coordinate system and connected into a line, that is, a height-light intensity curve is formed. It can be understood that, since the spectrometer has a collection cycle, when the probe moves up and down above the film to be measured, when the spectrometer collects light intensity, each height of the probe is a discrete value, so that the formed height-light intensity curve is not smooth. In an exemplary embodiment, an initial height-light intensity curve is first formed according to each height position and its corresponding light intensity, and then the initial height-light intensity curve is fitted to obtain a height-light intensity curve, so that a smooth height-light intensity curve can be obtained, so that the optimal probe height of each measuring point determined according to the height-light intensity curve is more accurate, thereby further improving the accuracy of the thickness of the film to be measured.

[0091] S230. Determine the optimal probe height for each measuring point according to the height-light intensity curve.

[0092] Since the optimal probe height is the height of the probe from the surface of the film to be measured when the maximum light intensity can be received, that is, the focal length of the probe, the distance between each measuring point and its optimal probe height is a fixed value, that is, the probe height corresponding to the point with the maximum light intensity in the height-light intensity curve. Therefore, the optimal probe height of each measuring point can be determined based on the height-light intensity curve.

[0093] Specifically, the film to be measured is placed on the stage of the film thickness measurement optical system, and the probe of the film thickness measurement optical system is controlled to move up and down within a preset height range [h1, h2] above the film to be measured. During the up and down movement of the probe, the spectrometer of the film thickness measurement optical system is controlled to collect light intensity and record the light intensity corresponding to each height position, so that a height-light intensity curve can be formed according to each height position and its corresponding light intensity, and then the optimal probe height for each measurement point can be determined according to the height-light intensity curve.

[0094] S240, determining the roughness coefficient of the film to be tested according to each optimal probe height.

[0095] S250, obtaining a theoretical reflection spectrum of the film to be tested.

[0096] S260: Determine a corrected reflection spectrum according to the roughness coefficient and the theoretical reflection spectrum.

[0097] S270, determining the thickness of the film to be measured according to the corrected reflection spectrum.

[0098] In this embodiment, a film thickness measuring optical system is adopted to control the probe of the film thickness measuring optical system to move up and down within a preset height range [h1, h2] above the film to be measured. At the same time, the spectrometer of the film thickness measuring optical system is controlled to collect light intensity and record the light intensity corresponding to each height position, thereby forming a height-light intensity curve. Since the distance between each measuring point and its optimal probe height is a fixed value, that is, the probe height corresponding to the point with the maximum light intensity in the height-light intensity curve, the optimal probe height of each measuring point can be determined according to the height-light intensity curve, thereby improving the accuracy of the nearest probe height of each measuring point.

[0099] Embodiment three:

[0100] Figure 4 This is a flow chart of a method for measuring film thickness provided in the third embodiment of the present invention. Based on the above embodiment, this embodiment further adds a step of determining the optimal probe height of multiple measurement points according to the height-light intensity curve. Figure 4 As shown, the method specifically includes:

[0101] S310, using a film thickness measurement optical system, controlling the probe of the film thickness measurement optical system to move up and down within a preset height range [h1, h2] above the film to be measured, and at the same time, controlling the spectrometer of the film thickness measurement optical system to collect light intensity and record the light intensity corresponding to each height position.

[0102] S320, forming a height-light intensity curve according to each height position and its corresponding light intensity.

[0103] Figure 5 A schematic diagram of the relative position of a probe and a film to be measured during film thickness measurement provided by an embodiment of the present invention, Figure 6 A schematic diagram of a height-light intensity curve provided by an embodiment of the present invention, referring to Figure 5 and Figure 6 As shown, the probe of the film thickness measurement optical system moves up and down within a preset height range [h1, h2] above the film to be measured, and the focal length hf of the probe is located in the interval (h1, h2). While controlling the probe to move up and down within the preset height range [h1, h2] above the film to be measured, the spectrometer is controlled to collect light intensity and record the light intensity corresponding to each height position to form a height-light intensity curve.

[0104] S330, after moving the probe to the measuring point, control the spectrometer to read the current light intensity value I0, and determine the height Hx corresponding to the current light intensity I0 on the height-light intensity curve.

[0105] S340, determine whether Hx is unique; if so, execute S350; if not, execute S360.

[0106] S350, determining Hx as the optimal probe height for the measurement point.

[0107] Among them, when the probe is at the optimal probe position corresponding to the measurement point, the spectrometer collects the maximum intensity of the reflected light. At this time, no matter whether the probe is controlled to move upward or downward, the intensity of the reflected light collected by the spectrometer will decrease. Therefore, it can be seen that the height-intensity curve is a parabola. When Hx is unique, the light intensity corresponding to the height Hx on the height-intensity curve is the maximum light intensity. Therefore, Hx can be determined as the nearest probe position of the measurement point.

[0108] Instead, continue to refer to Figure 6 As shown, when Hx is not unique, it can be seen from the parabolic shape of the height-light intensity curve that the current light intensity I0 corresponds to two heights h_x1 and h_x2 on the height-light intensity curve. At this time, the probe height corresponding to the maximum light intensity is a certain height between h_x1 and h_x2.

[0109] S360, controlling the probe to move upward to a preset height △h, and controlling the spectrometer to collect the current light intensity value I1.

[0110] Among them, h_x1<h_x2.

[0111] S370, determine whether I0>I1 is established; if so, execute S380; if not, execute S390.

[0112] Specifically, when the current light intensity I0 corresponds to two heights h_x1 and h_x2 on the height-light intensity curve, the probe height corresponding to the maximum light intensity is a certain height between h_x1 and h_x2. Therefore, the probe is controlled to move upward to a preset height △h, and the spectrometer is controlled to collect the light intensity I1 after the movement. When I0>I1, that is, as the probe height increases, the light intensity decreases, indicating that the probe height corresponding to the maximum light intensity value is less than the probe height corresponding to the current light intensity I0. Therefore, it can be determined that the optimal probe height of the measurement point is less than the initial probe height, and the initial probe height is h_x2; on the contrary, if I0 is less than I1, that is, as the probe height increases, the light intensity increases, indicating that the probe height corresponding to the maximum light intensity value is greater than the probe height corresponding to the current light intensity I0. Therefore, it can be determined that the nearest probe height of the measurement point is greater than the initial probe height, and the initial probe height is h_x1.

[0113] The initial probe height is the height of the probe at the measuring point when the probe does not move.

[0114] S380, move the probe downward (△h+h_x2-hf), and determine the optimal probe height of the probe after the movement.

[0115] Specifically, when I0>I1, the optimal probe height of the measurement point is less than the initial probe height, and the initial probe height is h_x2. Since the same film thickness measurement optical system is used, the focal length of the probe is the same, and the optimal probe height of each measurement point is the focal length of the probe. Since the probe has moved upward by a preset height △h based on the initial probe height, when the probe is moved downward by △h+h_x2, the probe reaches the surface of the measurement point. At this time, the probe is moved upward by hf to reach the optimal probe height of the measurement point. Therefore, when I0>I1, the probe reaches the optimal probe height of the measurement point after it is moved downward by (△h+h_x2-hf).

[0116] S390, continue to move the probe upward (hf-h_x1-△h), and determine the optimal probe height of the probe after the movement.

[0117] Specifically, when I0<I1, the nearest probe height of the measurement point is greater than the initial probe height, and the initial probe height is h_x1. Since the probe has moved upward by a preset height △h based on the initial probe height, when the probe is moved downward by △h+h_x1, the probe reaches the surface of the measurement point. At this time, the probe is moved upward by hf to reach the optimal probe height of the measurement point. Therefore, when I0<I1, the probe reaches the optimal probe height of the measurement point after it is moved upward by (hf-h_x1-△h).

[0118] It should be noted that after the height-light intensity curve is formed, the probe needs to be moved to each measuring point in turn to determine the optimal probe height for each measuring point.

[0119] S3100, determining the roughness coefficient of the film to be tested according to each optimal probe height.

[0120] S3110. Obtain a theoretical reflection spectrum of the film to be tested.

[0121] S3120. Determine a corrected reflection spectrum based on the roughness coefficient and the theoretical reflection spectrum.

[0122] S3130. Determine the thickness of the film to be measured based on the corrected reflection spectrum.

[0123] In this embodiment, a film thickness measuring optical system is adopted to control the probe of the film thickness measuring optical system to move up and down within a preset height range [h1, h2] above the film to be measured, and at the same time, the spectrometer of the film thickness measuring optical system is controlled to collect light intensity and record the light intensity corresponding to each height position to form a height-light intensity curve, and then the probe is moved to each measuring point in turn, the spectrometer is controlled to read the current light intensity value I0, and the height Hx corresponding to the current light intensity I0 on the height-light intensity curve is determined. When Hx is unique, it indicates that the current probe height is the optimal probe height for the corresponding measuring point, and when the current light intensity I0 corresponds to two heights h_x1 and h_x2 on the height-light intensity curve, by controlling The probe is controlled to move upward to a preset height △h, and the spectrometer is controlled to collect the current light intensity value I1, so that when I0>I1, the probe is moved downward (△h+h_x2-hf), and the optimal probe height of the probe after the movement is determined, and when I0<I1, the probe is continued to move upward (hf-h_x1-△h), and the optimal probe height of the probe after the movement is determined, thereby eliminating the need to continuously move the probe up and down at each measuring point to determine the nearest probe height of the measuring point, which is beneficial to improving the efficiency of thin film thickness measurement. In addition, the number of times the motion module of the film thickness measurement optical system controls the probe to move up and down can be significantly reduced, thereby helping to increase the life of the film thickness measurement optical system.

[0124] Embodiment 4:

[0125] This embodiment provides a device for measuring film thickness. The device can be implemented in the form of hardware and / or software and can be integrated into a controller. Figure 7 The schematic diagram of the structure of the device for measuring the film thickness provided in the fourth embodiment of the present invention is as follows: Figure 7 As shown, the measuring device comprises:

[0126] The optimal probe height acquisition module 410 is used to acquire the optimal probe heights of multiple measurement points of the film to be measured.

[0127] The roughness coefficient determination module 420 is used to determine the roughness coefficient of the film to be measured according to each of the optimal probe heights.

[0128] The theoretical reflection spectrum acquisition module 430 is used to acquire the theoretical reflection spectrum of the film to be tested.

[0129] The corrected reflection spectrum determination module 440 is used to determine the corrected reflection spectrum according to the roughness coefficient and the theoretical reflection spectrum.

[0130] The film thickness determination module 450 is used to determine the thickness of the film to be measured according to the corrected reflection spectrum.

[0131] The device for measuring film thickness provided in the embodiment of the present invention can execute the method for measuring film thickness provided in any embodiment of the present invention, and has the corresponding functional modules and beneficial effects of the execution method. The similarities can be referred to the above description.

[0132] Embodiment five:

[0133] Based on the same concept, an embodiment of the present invention further provides a computer-readable storage medium, which stores computer instructions, and the computer instructions are used to enable a processor to implement the measurement method provided by any of the above embodiments when executed.

[0134] In the context of the present invention, a computer-readable storage medium may be a tangible medium that may contain or store a computer program for use by or in conjunction with an instruction execution system, device, or equipment. A computer-readable storage medium may include, but is not limited to, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, or equipment, or any suitable combination of the foregoing. Alternatively, a computer-readable storage medium may be a machine-readable signal medium. A more specific example of a machine-readable storage medium may include an electrical connection based on one or more lines, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0135] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring film thickness, characterized in that: The film thickness measurement optical system is used for implementation, and the film thickness measurement optical system includes a probe; the film thickness measurement method includes: Obtaining optimal probe heights for multiple measurement points of the film to be measured; the optimal probe height is the height of the probe from the surface of the film to be measured when the probe receives the maximum light intensity; Determining the roughness coefficient of the film to be tested according to each of the optimal probe heights; Obtaining a theoretical reflection spectrum of the film to be tested; Determining a corrected reflection spectrum according to the roughness coefficient and the theoretical reflection spectrum; Determining the thickness of the film to be measured according to the corrected reflection spectrum; Wherein, determining the roughness coefficient of the film to be measured according to each of the optimal probe heights includes: According to each of the optimal probe heights, the root mean square roughness is calculated; wherein the root mean square roughness of the film to be measured is determined according to the following formula: ; Based on the Debye-Waller factor model, the roughness coefficient of the film to be tested is determined according to the root mean square roughness; the Debye-Waller factor model is expressed as follows: ; Wherein, Roughness is the root mean square roughness, N is the number of measurement points, H is the optimal probe height for each measurement point, α is the roughness coefficient of the film to be measured, and λ is the wavelength of the incident light.

2. The method for measuring film thickness according to claim 1, characterized in that: Obtaining optimal probe heights for multiple measuring points of the film to be measured, including: A film thickness measurement optical system is used to control the probe of the film thickness measurement optical system to move up and down within a preset height range [h1, h2] above the film to be measured, and at the same time, a spectrometer of the film thickness measurement optical system is controlled to collect light intensity and record the light intensity corresponding to each height position; wherein the focal length hf of the probe is located within the interval [h1, h2]; According to each height position and its corresponding light intensity, a height-light intensity curve is formed; The optimal probe height for each measuring point is determined according to the height-light intensity curve.

3. The method for measuring film thickness according to claim 2, characterized in that: Determining optimal probe heights of the plurality of measurement points according to the height-light intensity curve includes: After the probe is moved to the measuring point, the spectrometer is controlled to read the current light intensity value I0, and the height Hx corresponding to the current light intensity I0 on the height-light intensity curve is determined; Determine whether Hx is unique; If yes, then Hx is determined to be the optimal probe height for the measurement point.

4. The method for measuring film thickness according to claim 3, characterized in that: Also includes: If the current light intensity I0 corresponds to two heights h_x1 and h_x2 on the height-light intensity curve, the probe is controlled to move upward by a preset height △h, and the spectrometer is controlled to collect the current light intensity value I1; wherein h_x1<h_x2; Determine whether I0>I1 is true; If yes, the probe is moved downward by (△h+h_x2-hf), and the optimal probe height of the probe after the movement is determined.

5. The method for measuring film thickness according to claim 4, characterized in that: Also includes: If I0<I1, the probe is further moved upward by (hf-h_x1-△h), and the optimal probe height after the movement is determined.

6. The method for measuring film thickness according to any one of claims 2 to 5, characterized in that: The light source of the probe is laser or broadband light.

7. The method for measuring film thickness according to claim 6, characterized in that: When the light source of the probe is broadband light, the light intensity is calculated by a first formula; wherein the first formula is as follows: ； Among them, I totle is the collected light intensity; [λ min ,λ max ] is the wavelength range; I(λ) is the light intensity corresponding to the wavelength λ.

8. The method for measuring film thickness according to claim 1, characterized in that: Determining a corrected reflection spectrum according to the roughness coefficient and the theoretical reflection spectrum includes: According to the second formula, the corrected reflection spectrum is determined; wherein the second formula is as follows: Rcorrected = Rtheoretical * α; Wherein, Rcorrected is the corrected reflection spectrum; Rtheoretical is the theoretical reflection spectrum; and α is the roughness coefficient.

9. A device for measuring film thickness, characterized in that: The film thickness measurement is implemented by using a film thickness measurement optical system, the film thickness measurement optical system includes a probe; the film thickness measurement method, the film thickness measurement device, including: An optimal probe height acquisition module is used to acquire the optimal probe heights of multiple measuring points of the film to be measured; the optimal probe height is the height of the probe from the surface of the film to be measured when the probe receives the maximum light intensity; A roughness coefficient determination module, used to determine the roughness coefficient of the film to be tested according to each of the optimal probe heights; A theoretical reflection spectrum acquisition module, used to acquire the theoretical reflection spectrum of the film to be tested; A corrected reflection spectrum determination module, used to determine a corrected reflection spectrum according to the roughness coefficient and the theoretical reflection spectrum; The film thickness determination module is used to determine the thickness of the film to be measured according to the corrected reflection spectrum.

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