Film thickness measurement method and measuring device

Abstract

A film thickness measurement method and device, belonging to the field of optics. The film thickness measurement method comprises the following steps: using light with a wavelength of 300-1000nm to irradiate the film, receiving reflected light from the film and obtaining a corresponding two-dimensional image; using a pre-established mathematical model to calculate and obtain the thickness value of at least part of the pixels constituting the two-dimensional image, and characterizing the film thickness with the average value of the thickness value; the mathematical model includes: the functional relationship between the gray value of the pixel and the thickness value; or, the functional relationship between the RGB, HSV and LAB parameters constituting the pixel and the thickness value. Through the above settings, the operation is convenient and easy to use, the detection speed is fast and the test area is large, the repeatability error is small, and it is not easy to produce large measurement errors.

Description

Technical Field

[0001] The present application relates to the field of optics, and in particular to a film thickness measurement method and a measurement device. Background Art

[0002] In the production of photovoltaic industry, people often need to measure the thickness of the thin film (thin film includes but is not limited to any one of aluminum oxide and silicon nitride film) on the surface of silicon wafer. Specifically, the thickness of the film layer at each point on the silicon wafer needs to be calculated.

[0003] The main technologies currently used to measure film thickness are as follows: 1. Ellipsometer: It uses the polarization effect of light and mathematical model fitting to calculate the film thickness. Its disadvantages are that it has high requirements on the surface of the silicon wafer, the placement of the silicon wafer is more troublesome, the results are seriously inaccurate beyond a certain range, and it can only measure the film thickness of one point. 2. Use microwaves to measure the distance difference. Its disadvantages are that the operation process is cumbersome, the measurement accuracy depends on the accuracy of the object placed by the person, and it can only measure the film thickness of one point. 3. Japanese scholars proposed to use different wavelengths to illuminate multiple different samples, and measure the amount of transmitted light to establish a relationship with the film thickness. This method can only measure thin films on the surface of flat silicon wafers, and it also requires that the refractive index of the film remain unchanged. It is not applicable to aluminum oxide and silicon nitride films. 4. South China University of Technology has also proposed a new elastohydrodynamic lubrication film thickness measurement method based on optical interference, but this method can only be based on an optical elastic fluid dynamic lubrication test bench.

[0004] In view of the above, this application is hereby filed. Summary of the invention

[0005] The present application provides a film thickness measurement method and a measurement device, which can effectively solve at least one of the above-mentioned technical problems.

[0006] The embodiment of the present application is implemented as follows:

[0007] In a first aspect, the present application example provides a film thickness measurement method, which comprises the following steps:

[0008] The film is illuminated by light with a wavelength of 300-1000nm, and the reflected light from the film is received to obtain a corresponding two-dimensional image. The thickness values ​​corresponding to at least part of the pixels constituting the two-dimensional image are calculated and obtained using a pre-established mathematical model, and the average value of the thickness values ​​is used to characterize the film thickness.

[0009] The mathematical model includes: the functional relationship between the grayscale value of the pixel and the thickness value; or the functional relationship between the RGB, HSV and LAB parameters constituting the pixel and the thickness value.

[0010] Through the above-mentioned setting, the operation is convenient and easy to use. The thickness of the film is inferred by the optical path of the light with a wavelength of 300-1000nm in the film, wherein the optical path is equal to the refractive index of the medium multiplied by the distance the light propagates in the film. Therefore, when the refractive index value is considered to change very little, the thickness of the film can be inferred. Therefore, based on the above-mentioned principle, it is only necessary to obtain a two-dimensional image, and by using the functional relationship between the gray value of the pixel and the thickness value or the functional relationship between the RGB, HSV, LAB and the thickness value of the pixel, the thickness value corresponding to the pixel can be calculated to obtain the thickness distribution of the film. Compared with the use of an ellipsometer for detection, the detection speed is fast, the test area is large, and the repeatability error is small, because the present application detects the thickness value of each point on the surface of the film and then takes its average value as the film thickness of the entire film. Compared with the prior art that uses the thickness value of a single point to characterize the film thickness of the entire film, the film thickness of the present application has smaller volatility, higher accuracy, and is not prone to large measurement errors.

[0011] In combination with the first aspect, in some possible examples of the present application, the above-mentioned film includes any one of an aluminum oxide film and a silicon nitride film formed on the surface of the substrate.

[0012] Optionally, the substrate is a silicon wafer with a flat surface or a surface having a velvet structure.

[0013] That is, the reasonable combination of the aluminum oxide film and the silicon nitride film with the light source of a specific wavelength makes the refractive index change very little. The method provided in the present application can not only effectively characterize the film thickness of the aluminum oxide film and the silicon nitride film located on the silicon wafer, but also can effectively characterize the film thickness of the aluminum oxide film and the silicon nitride film formed on the silicon wafer with a velvet structure on the surface.

[0014] In combination with the first aspect, in some possible examples of the present application, the wavelength of the light is 300-500 nm.

[0015] Since the wavelength has a close relationship with the film thickness, using the light of the above wavelengths provides higher sensitivity and higher measurement accuracy.

[0016] Optionally, the light is monochromatic light or white light. Further optionally, the light is monochromatic light, which effectively improves the measurement accuracy.

[0017] In combination with the first aspect, in some possible examples of the present application, the light source that generates light is an LED.

[0018] The light source is LED to ensure long-term light output.

[0019] In combination with the first aspect, in some possible examples of the present application, the two-dimensional image includes any one of a black and white photo and a color photo.

[0020] The reflected light from the film can be accurately and effectively obtained by setting the photo. Meanwhile, those skilled in the art can also choose either black and white photos or color photos according to actual needs.

[0021] In combination with the first aspect, in some possible examples of the present application, the above-mentioned film thickness measurement method also includes: mapping the thickness value corresponding to the pixel to a color value to generate a color image representing the film thickness.

[0022] Color image of film thickness

[0023] Through the above settings, the thickness corresponding to each point of the membrane can be visualized, which makes it easy to observe the thickness changes of the membrane at different locations.

[0024] In a second aspect, the present application example provides a film thickness measuring device for use with the film thickness measuring method provided in the first aspect of the present application, which includes a detection core structure and a control system.

[0025] The detection core structure comprises: a cover body, a light source and a camera. The cover body has a first accommodating cavity. The first accommodating cavity has an accommodating portion for accommodating the film.

[0026] The light source is arranged in the first accommodating cavity, and is used to generate light that is not vertically incident on the accommodating portion. The camera has a rotatable lens, and the lens is located on the optical path of the reflected light from the film to receive the reflected light and obtain a corresponding two-dimensional image.

[0027] The control system is used to calculate and obtain the thickness values ​​and film thickness corresponding to the pixels constituting the two-dimensional image according to the mathematical model.

[0028] Through the above-mentioned setting, the operation is convenient and easy to use. Only the camera is needed to obtain a two-dimensional image, and the control system can calculate the thickness distribution of the entire film through a mathematical model. Compared with the use of an ellipsometer for detection, the detection speed is fast and the test area is large, and the repeatability error is small. Because the present application detects the thickness value of each point on the surface of the film and then takes the average value as the film thickness of the entire film, compared with the prior art that uses a single-point thickness value to characterize the film thickness of the entire film, the film thickness of the present application has smaller volatility, higher accuracy, and is not prone to large measurement errors.

[0029] In combination with the second aspect, in some possible examples of the present application, the light emitting surface of the light source faces the accommodating portion.

[0030] Through the above arrangement, when the film is placed in the accommodating portion, the light emitted by the light source can directly irradiate the film.

[0031] Optionally, the light source is a panel light source having a mounting hole that matches the lens.

[0032] The setting of the panel light source makes the light uniform, soft and bright.

[0033] In combination with the second aspect, in some possible examples of the present application, the detection core structure includes a light diffuser, which is arranged in the cover body and divides the first accommodating cavity into a first cavity and a second cavity, the first cavity is located above the second cavity, and the accommodating part and the lens are respectively located in the second cavity.

[0034] The light source is located in the first cavity and the light emitting surface of the light source faces the side away from the second cavity, so that the light emitted by the light source irradiates the accommodating portion in a diffuse reflection manner.

[0035] Through the above arrangement, by utilizing the coordination of the light homogenizing plate and the orientation of the light emitting surface of the light source, the light emitted by the light source is finally irradiated onto the accommodating portion in a diffuse reflection manner.

[0036] Optionally, the light source is arranged around the lens.

[0037] In combination with the second aspect, in some possible examples of the present application, the light source is an LED light source.

[0038] Through the above settings, the advantages of the LED light source, such as long life, stroboscopic function, easy brightness control and low power consumption, are utilized to effectively increase the life of the film thickness measuring device and reduce energy consumption, while facilitating the adjustment of brightness according to actual needs.

[0039] In combination with the second aspect, in some possible examples of the present application, the light emitted by the light source is monochromatic light or white light, and the wavelength of the light is 300-1000 nm.

[0040] Through the above settings, the accuracy of the final result is guaranteed.

[0041] In combination with the second aspect, in some possible examples of the present application, the distance between the lens and the accommodating portion is adjustable.

[0042] Through the above settings, the distance between the two can be adjusted according to actual needs to obtain better photos.

[0043] Optionally, the camera is a monochrome camera or a color camera.

[0044] That is, the obtained photo is a black and white photo or a color photo.

[0045] In combination with the second aspect, in some possible examples of the present application, the film thickness measuring device includes a tray, the accommodating portion is arranged on the front side of the tray, and the tray and the cover body are slidably matched to place the accommodating portion in or leave the first accommodating cavity.

[0046] By setting the tray, it is convenient to place the membrane in the accommodating part and put it into or leave the first accommodating cavity according to actual needs, which is convenient for sample loading during actual use.

[0047] In combination with the second aspect, in some possible examples of the present application, the cover body has a receiving groove, and the opening of the receiving groove is located at the bottom end of the cover body.

[0048] The film thickness measuring device includes a base, a cover body connected to the base and forming an installation gap therebetween, the base is provided with a guide rail located in the installation gap, the tray is slidably arranged on the guide rail so that the tray can move along the guide rail and the accommodating part selectively closes the opening of the accommodating groove to form a first accommodating cavity.

[0049] Through the above arrangement, the stability of the tray is ensured when it is pulled out, and at the same time, the structure is simple and space is effectively saved. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0051] Figure 1 This is a schematic diagram of the structure of a film thickness measuring device according to an embodiment of the present application;

[0052] Figure 2 An exploded diagram of a film thickness measuring device according to an embodiment of the present application;

[0053] Figure 3 This is a schematic diagram of the structure of the detection core structure 120a according to an embodiment of the present application;

[0054] Figure 4 An exploded view of the detection core structure 120a according to an embodiment of the present application;

[0055] Figure 5 A cross-sectional view of a detection core structure 120a according to an embodiment of the present application;

[0056] Figure 6 This is a schematic structural diagram of a detection core structure 120b of another embodiment of the present application;

[0057] Figure 7 This is a schematic diagram of the structure of the tray of the embodiment of the present application;

[0058] Figure 8 This is a schematic diagram of the structure of the base of an embodiment of the present application;

[0059] Fig. 9 It is a black and white photo obtained under blue light illumination;

[0060] Fig.10 is the mathematical model fitting result of film thickness;

[0061] Fig.11 Schematic diagram of the error results of the film thickness values ​​measured by two methods;

[0062] Fig.12 In the figure, A is a color image of the film thickness, and B is a schematic diagram of the distribution range of the film thickness values ​​of the selected area in A and the visualization output result of the average film thickness value.

[0063] Icons: 10-film thickness measuring device; 101-U-shaped cover; 103-cabinet door; 1031-heat dissipation part; 105-front cover; 110-base; 111-guide rail; 113-limiting piece; 120a-detection core structure; 120b-detection core structure; 121-cover body; 123-first accommodating cavity; 125-light homogenizing plate; 1231-first cavity; 1233-second cavity; 130-light source; 141-camera body; 143-lens; 151-support plate; 153-fixing plate; 155-waist hole; 160-tray; 161-accommodating part; 170-electric control installation plate. DETAILED DESCRIPTION

[0064] The embodiments of the present application will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0065] The following is a detailed description of the film thickness measurement method and the measuring device of the embodiment of the present application:

[0066] The present application provides a film thickness measurement method, the principle of which is: the thickness of the film is inferred by using the optical path of light in the film, where the optical path is equal to the refractive index of the medium multiplied by the distance the light propagates in the film. When the refractive index value can be considered to change very little, the relationship between the optical path and the gray value is used to obtain the thickness value.

[0067] The film thickness measurement method includes the following steps:

[0068] S1. Irradiate the film with light having a wavelength of 300-1000 nm, receive reflected light from the film and obtain a corresponding two-dimensional image.

[0069] Among them, the wavelength of light is 300-500nm.

[0070] The light is monochromatic light or white light.

[0071] Further optionally, the light is monochromatic light, and further optionally, the monochromatic light is blue light.

[0072] Optionally, the light source generating light is an LED.

[0073] Optionally, the two-dimensional image includes any one of a black and white photo and a color photo.

[0074] The film includes any one of an aluminum oxide film and a silicon nitride film formed on the surface of a substrate, wherein the substrate is a silicon wafer with a flat surface or a surface having a velvet structure. Optionally, the substrate includes a silicon wafer with a surface having a velvet structure.

[0075] By defining the above-mentioned specific thin films and selecting the relevant light sources, the refractive index of the medium is kept substantially unchanged, so that the change in the value of the refractive index is very small.

[0076] S2. Use a pre-established mathematical model to calculate and obtain thickness values ​​corresponding to at least part of the pixels constituting the two-dimensional image.

[0077] It should be noted that the thickness value corresponding to each pixel constituting the two-dimensional image can be obtained through mathematical model calculation. However, in the actual process, a more accurate film thickness can also be quickly obtained through the thickness values ​​of some pixels. Therefore, step S2 is to obtain the thickness values ​​corresponding to at least some pixels.

[0078] Optionally, a pre-established mathematical model is used to calculate and obtain a thickness value corresponding to each pixel constituting the two-dimensional image.

[0079] Among them, the mathematical model includes: the functional relationship between the grayscale value of the pixel and the thickness value; or, the functional relationship between the RGB (red R, green G, blue B), HSV (hue H, saturation S, brightness V) and LAB (brightness L, color A, color B) parameters that constitute the pixel and the thickness value.

[0080] It should be noted that the functional relationship between the grayscale value and thickness value of the pixel includes the linear and quadratic functional relationship between the grayscale value and the film thickness of the black and white photo, and the functional relationship between the RGB, HSV, LAB of the pixel and the corresponding thickness value includes but is not limited to multivariate linear and nonlinear functional relationships.

[0081] Generally speaking, if the obtained two-dimensional image is a black and white photo, the thickness value corresponding to the pixel is directly obtained by using the pre-established functional relationship between the gray value and the thickness value of each pixel. If the obtained two-dimensional image is a color photo, the thickness value corresponding to the pixel is calculated and obtained by using the functional relationship between the RGB, HSV, LAB constituting the pixel and the corresponding thickness value.

[0082] In addition, before calculating the thickness value, the obtained two-dimensional image can be converted between black and white photos and color photos according to relevant means, and then the relevant thickness can be calculated based on the pre-established mathematical model of the converted image, which also falls within the scope of protection of this application.

[0083] S3. The film thickness is represented by the average value of the thickness value.

[0084] The average value of the thickness value is used to represent the film thickness, which effectively reduces the deviation.

[0085] Optionally, the film thickness measurement method further includes S4, wherein step S4 can be performed after step S3, or between step S2 and step S3.

[0086] Specifically, step S4 includes: mapping the thickness value corresponding to the pixel to a color value to generate a color image representing the film thickness. The specific operation method of step S4 can refer to the relevant technology and is not limited here. As long as the above settings are implemented, that is, the mapping rule is not limited to the jet, hot and other rules.

[0087] Optionally, step S4 further includes: selecting a partial area of ​​the color image of the film thickness and visually outputting the distribution range of the film thickness values ​​and the average film thickness value in the area, wherein the method of visualizing the distribution range of the film thickness values ​​in the area can be performed in the form of a bar graph or a table.

[0088] The film thickness measurement method and the measuring device of the present application are further described in detail below in conjunction with the embodiments.

[0089] Example

[0090] See also Figure 1 as well as Figure 2 , a film thickness measuring device 10, which includes a shell, a detection core structure 120a and a control system, is suitable for detecting the thickness of a film.

[0091] The thin film is, for example, an aluminum oxide film or a silicon nitride film formed on a silicon wafer, and the surface of the silicon wafer is flat or has a suede structure.

[0092] The shell is made of metal, specifically, iron or aluminum.

[0093] The shell includes a shell wall and a base 110 , wherein the shell wall and the base 110 are connected and jointly define a second accommodating cavity (not shown).

[0094] See also Figure 2 In this embodiment, the base 110 has a first preset direction and a second preset direction that are perpendicular to each other, and the shell wall includes a U-shaped cover 101, a cabinet door 103 and a front cover 105.

[0095] The two side walls of the U-shaped cover 101 are respectively located in the first preset direction, the cabinet door 103 and the front cover 105 are respectively located in the second preset direction and connected with the U-shaped cover 101 to define and form a receiving groove, and the open end of the receiving groove is closed by the base 110 to form a second receiving cavity. In order to facilitate subsequent maintenance, the U-shaped connection end is detachably connected to the cabinet door 103 and the front cover 105, such as screw connection or clamping, etc., which will not be described in detail here.

[0096] The detection core structure 120a is disposed in the second accommodating cavity.

[0097] See also Figure 2 , Figure 3 , Figure 4 as well as Figure 5 The detection core structure 120a includes a cover body 121, a light source 130 and a camera.

[0098] The cover body 121 is used for shading to prevent external light from entering the cover body 121 and also to prevent light from being output from the cover body 121 . Specifically, the cover body 121 can be made of iron or aluminum.

[0099] The cover body 121 has a first accommodating cavity 123 , and the first accommodating cavity 123 has an accommodating portion 161 for accommodating the film; the light source 130 is disposed in the first accommodating cavity 123 , and the light source 130 is used to generate light that can irradiate the accommodating portion 161 .

[0100] The camera includes a camera body 141 and a lens 143, wherein the lens 143 is disposed on the camera body 141 and can rotate relative to the camera body 141, for example, by a threaded connection to achieve rotation, which can be referred to in related technologies and will not be elaborated here; wherein the lens 143 is located on the optical path of the reflected light from the membrane to receive the reflected light from the membrane and obtain a corresponding two-dimensional image.

[0101] like Figure 4 As shown, the light source 130 and the lens 143 are both located above the accommodating portion 161 .

[0102] Specifically, the control system uses a pre-established mathematical model to calculate and obtain the thickness values ​​of at least part of the pixels constituting the two-dimensional image, and characterizes the film thickness with the average value of the thickness values; that is, the control system is used to calculate and obtain the thickness values ​​corresponding to the pixels constituting the two-dimensional image and the film thickness according to the mathematical model.

[0103] The mathematical model includes: the functional relationship between the grayscale value of the pixel and the thickness value; or the functional relationship between the RGB, HSV and LAB parameters constituting the pixel and the thickness value.

[0104] That is, through the above-mentioned setting, the thickness of the film is inferred by the optical path of light in the film, where the optical path is equal to the refractive index of the medium multiplied by the distance the light propagates in the film. When the refractive index value can be considered to change very little, the principle of the thickness of the film can be inferred. Under the condition that the refractive index is basically unchanged, only a two-dimensional image needs to be obtained. By using the functional relationship between the gray value of the pixel and the thickness value or the functional relationship between the RGB, HSV, LAB and the thickness value of the pixel, the thickness value corresponding to the pixel can be calculated to obtain the thickness distribution of the film. Compared with the use of an ellipsometer for detection, the detection speed is fast, the test area is large, and the repeatability error is small. Because the film thickness measuring device 10 of the present application detects the thickness value of each point on the surface of the film and then takes its average value as the film thickness of the entire film, compared with the prior art that uses the thickness value of a single point to characterize the film thickness of the entire film, the film thickness of the present application has smaller volatility, higher accuracy, and is not prone to large measurement errors.

[0105] The light emitted by the light source 130 is monochromatic light or white light. Optionally, the light emitted by the light source 130 is monochromatic light, and the wavelength of the light is 300-1000nm. Optionally, the wavelength of the light is 300-500nm. Optionally, the light source 130 is an LED light source.

[0106] The manner in which the light irradiates the film located in the accommodation portion 161 includes the manner in which the light irradiates the film in a diffuse reflection manner and the manner in which the light irradiates the film directly.

[0107] The first method is a method in which light is irradiated onto the film in a diffusely reflected manner.

[0108] See also Figure 6 , Figure 6 Some other detection core structures 120b provided in this application include Figure 6 The solid arrow in the middle represents the light emitted by the light source 130, and the dotted arrow represents the reflected light received by the lens 143. The detection core structure 120b includes a light diffuser 125, which is disposed in the cover 121 and divides the first accommodating cavity 123 into a first cavity 1231 and a second cavity 1233. The first cavity 1231 is located above the second cavity 1233, and the accommodating portion 161 and the lens 143 are respectively located in the second cavity 1233; the light source 130 is located in the first cavity 1231 and the light emitting surface of the light source 130 faces the side away from the second cavity 1233, so that the light emitted by the light source 130 is irradiated on the accommodating portion 161 in a diffuse reflection manner.

[0109] Specifically, the light homogenizer 125 is horizontally arranged in the cover 121 , the light source 130 is installed on the light homogenizer 125 , the camera body 141 is installed on the light homogenizer 125 and is located in the first cavity 1231 , and in order to ensure the uniformity of light, the light source 130 is arranged around the lens 143 .

[0110] At this time, the light source 130 is, for example, a plurality of strip light sources 130 arranged at intervals in the circumference of the lens 143 , and in this embodiment, a ring-shaped light source is arranged in the circumference of the lens 143 .

[0111] Optionally, the annular light source 130 may be located directly above the film, that is, the axis of the annular light source coincides with the center line of the film.

[0112] Meanwhile, it should be noted that the size of the projection of the light source 130 on the horizontal plane may be equal to the size of the film, or may be smaller or larger than the size of the film, which is not limited here.

[0113] The second method is to irradiate the film with light directly.

[0114] See also Figures 3 to 5 , the light emitting surface of the light source 130 faces the accommodating portion 161. At this time, since there is no light homogenizing plate 125 and the light source 130 is located above the accommodating portion 161, the light generated by the light emitting surface of the light source 130 can directly irradiate the film.

[0115] It should be noted that the light-emitting surface is a plane or a curved surface, and the light-emitting surface refers to the light generated by the light source 130 being transmitted outward from the light-emitting surface.

[0116] Regardless of the first or second configuration, the form of the light source 130 includes but is not limited to a light box, a panel light source, a strip light source or a ring light source, etc., and those skilled in the art can make relevant choices according to actual needs. At the same time, it should be noted that the light source 130 can be detachably arranged in the first accommodating cavity 123, and then the light source 130 of different areas can be configured according to the membranes of different sizes.

[0117] It should be noted that in addition to the above-mentioned setting method, an auxiliary light source (not shown) can also be installed at one end of the panel light source facing the membrane, wherein the auxiliary light source emits light toward one end face of the accommodating portion 161, and the emission direction of the light is the same as the direction of the light emitted by the part of the panel light source blocked by it, that is, when the panel light source is set horizontally, the axis of the auxiliary light source is perpendicular to the panel light source.

[0118] In this embodiment, the light source 130 is a blue LED panel light source that can emit blue light with a wavelength of 465-475nm, wherein the panel light source is arranged in the cover body 121 and serves as the top wall of the first accommodating cavity 123, the light emitting surface of the light source 130 faces the accommodating portion 161, and a mounting hole corresponding to the lens 143 is provided in the middle of the light source 130, and the lens 143 can be arranged in the mounting hole and receive reflected light from the accommodating portion 161.

[0119] Through the light source provided in this embodiment, it is found that the thicker the silicon nitride film is, the lighter its color is. Therefore, the thickness difference between the two films can be simply determined by comparing the colors.

[0120] The camera body 141 can be disposed in the first accommodating cavity 123 , but in order to avoid the shadow caused by the large size of the camera affecting the measurement results, in this embodiment, the camera body 141 is disposed outside the first accommodating cavity 123 , and the lens 143 is extended into the first accommodating cavity 123 .

[0121] The camera can be a color camera or a monochrome camera, and the higher the pixel, the better. In this embodiment, a 25-megapixel monochrome camera is used to obtain a two-dimensional image with one exposure. It is simple to operate and has high spatial resolution. At the same time, it can quantitatively analyze the film thickness distribution with a resolution of less than 1um.

[0122] Optionally, the distance between the lens 143 and the receiving portion 161 is adjustable.

[0123] In this embodiment, in order to achieve the above effect, please refer to Figure 4 The detection core structure 120a includes a mounting frame, and the mounting frame includes a support plate 151 and a fixing plate 153, wherein the end of the support plate 151 is connected to the back of the panel light source 130 by screws, and the middle part of the support plate 151 protrudes to the side away from the panel light source 130, so that the middle part of the support plate 151 does not contact the back of the panel light source 130, so as to prevent the heat dissipation of the panel light source 130 from being affected. The fixing plate 153 is arranged in the middle part of the support plate 151 and extends to the side away from the panel light source 130. The mounting plate has a plurality of waist holes 155 extending vertically, and the camera body 141 cooperates with each waist hole 155 through a plurality of connecting screws (not shown) so that the camera body 141 is installed on the mounting frame and connected and can move vertically along the extension direction of the waist hole 155, so as to drive the lens 143 to move vertically, and the distance between the lens 143 and the accommodating portion 161 is adjusted by adjusting the height of the lens 143.

[0124] See also Figure 2 as well as Figure 7 In order to facilitate the taking and placing of the film from the first accommodating cavity 123 in the subsequent actual measurement process, the film thickness measuring device 10 includes a tray 160, and the accommodating portion 161 is arranged on the front side of the tray 160. The tray 160 and the cover body 121 are slidably matched to make the accommodating portion 161 placed in or out of the first accommodating cavity 123, wherein the accommodating portion 161 is specifically a groove, for example.

[0125] In order to simplify the structure and improve space utilization, optionally, the cover body 121 has a receiving groove, and the opening of the receiving groove is located at the bottom end of the cover body 121.

[0126] See also Figure 2 , Figure 5 as well as Figure 8The film thickness measuring device 10 includes a base 110, a cover body 121 connected to the base 110 and forming an installation gap therebetween, the base 110 is provided with a guide rail 111 located in the installation gap, and the tray 160 is slidably arranged on the guide rail 111 so that the tray 160 can move along the guide rail 111 and the accommodating portion 161 selectively closes the opening of the accommodating groove to form a first accommodating cavity 123.

[0127] That is, during the movement of the tray 160, the receiving portion 161 and the film can be completely located in the receiving groove. Wherein, at least the portion of the tray 160 corresponding to the receiving portion 161 is made of light shielding material.

[0128] Among them, the guide rail 111 extends along the second preset direction. Therefore, the front cover 105 is provided with an opening for the tray 160 to enter and exit the second accommodating cavity. At this time, by pulling out one end of the tray 160 located outside the front cover 105, the tray 160 can be reciprocated along the guide rail 111 to locate the film in the accommodating portion 161 in the first accommodating cavity 123 or take it out from the first accommodating cavity 123.

[0129] A limiting member 113 is disposed at one end of the guide rail 111 away from the front cover 105 , and the limiting member 113 is used to limit the tray from being separated from the guide rail 111 at the end of the guide rail 111 away from the front cover 105 .

[0130] See also Figure 2 The control system includes an electric control installation board 170, a controller (not shown) and a display panel with an input function (not shown), wherein the electric control installation board 170 is located in the second accommodating cavity and is arranged outside the cover body 121, for example, it is arranged on the side of the cover body 121 close to the cabinet door 103, the electric control installation board 170 is electrically connected to the light source 130 and the camera and supplies power to the two, and at this time the cabinet door 103 is provided with a heat dissipation part 1031, and the heat dissipation part 1031 is, for example, a heat dissipation hole and a heat dissipation fan.

[0131] The controller is connected to the electronic control mounting board 170, the light source 130, the camera and the display panel to obtain a two-dimensional image. At the same time, a mathematical model is used to calculate and obtain the thickness value and film thickness corresponding to each pixel constituting the two-dimensional image and output them visually on the display panel. At the same time, the display panel can also input relevant instructions and pass them to the controller. After receiving the signal about the instruction, the controller performs relevant operations. For example, the display panel inputs a photo-taking instruction (the input method includes but is not limited to touch screen clicking), and the controller controls the camera to take a photo after receiving the photo-taking signal. For details, please refer to the relevant technology, which will not be repeated here.

[0132] Furthermore, the film thickness measuring device also includes a photoelectric switch or a contact sensor (not shown) connected to the controller, wherein the photoelectric switch or the contact sensor is used to monitor whether the tray 160 has moved to the target position. When the tray 160 with the film installed moves to the target position, the photoelectric switch or the contact sensor is triggered. At this time, the controller obtains a signal that the photoelectric switch or the contact sensor is triggered. At this time, the controller controls the light source to emit light and controls the camera to take pictures, thereby automatically starting the measurement step.

[0133] The target position can be set according to actual needs. For example, when the accommodating portion 161 closes the opening of the accommodating groove to form the first accommodating cavity 123, the position of the tray 160 is used as the target position. At this time, the photoelectric switch or contact sensor can be set at the end of the tray away from the front cover 105, or it can be set at the end of the cover body away from the front cover 105. As long as the tray 160 reaches the target position, contacts and triggers the contact sensor or non-contact trigger photoelectric switch, and when the tray 160 is pulled outward to move away from the target position, the trigger state of the photoelectric switch or contact sensor is released, the controller can stop detection.

[0134] The controller maps the calculated thickness value corresponding to the pixel to a color value through programming, generates a color image representing the film thickness, and outputs it to the display panel. Optionally, the controller can be programmed to select a partial area of ​​the color image of the film thickness and visualize the distribution range of the film thickness value and the average film thickness value in the output area after obtaining the color image of the film thickness, wherein the method of visualizing the distribution range of the film thickness value in the output area is performed in the form of a bar graph; it should be noted that the above programming setting can be directly realized by purchasing software, or it can be designed by itself according to relevant technologies, and is not limited here.

[0135] The film thickness measuring device 10 obtained in this embodiment is used to perform a film thickness measuring method of a sample, wherein the sample is a single crystal silicon nitride film formed on a silicon wafer having a textured structure.

[0136] The film thickness measurement method includes the following steps:

[0137] After the tray 160 is pulled out, the silicon nitride film is placed in the receiving portion 161 and then the tray 160 is pushed in, wherein the silicon nitride film is located on a side of the silicon wafer facing the light source 130 .

[0138] Turn on the light source 130, which generates light of a fixed wavelength to illuminate the film. The camera receives the reflected light from the film and obtains a corresponding two-dimensional image. The light generated by the light source 130 is blue light with a wavelength of 465-475nm. The obtained black and white photo is as shown in FIG. Fig. 9 shown.

[0139] The control system uses a pre-established mathematical model to calculate and obtain the thickness value of each pixel constituting the two-dimensional image, wherein the mathematical model is a functional relationship between the grayscale value of the pixel and the thickness value.

[0140] Specifically, the mathematical model is y=0.1451x+66.809, where y represents the film thickness value in nm, and x represents the gray value. The average value of the thickness value is used to represent the film thickness (that is, the surface thickness of the film), and the calculated film thickness is 81.80 nm.

[0141] The mathematical model is obtained by using a high-precision imaging ellipsometer to measure the film thickness values ​​at multiple points on the sample. Then, software such as excel, matlab, python, origin, R, SPSS, SAS, etc. are used to perform data fitting (using the least squares method) on the film thickness value and the gray value, such as Fig.10 As shown, the film thickness calculation formula shown above is obtained: y = 0.1451x + 66.809, R 2 It reaches 0.8723, and the fitting effect is good.

[0142] At the same time, the film thickness values ​​measured by high-precision imaging ellipsometer at some points of the above samples were compared with the film thickness values ​​measured in this application, and the error results obtained are as follows: Fig.11 shown.

[0143] At the same time, the thickness value corresponding to the pixel is mapped to a color value, and the two-dimensional image is visualized and rendered based on the color value to generate a color image of the film thickness. The result is as follows Fig.12 As shown in A.

[0144] At the same time, select a part of the color image of the film thickness ( Fig.12 The area selected by the box in A) and visualize the distribution range of the film thickness values ​​and the average film thickness value in the output area. Fig.12 As shown in B.

[0145] Taking a sample of 210*210mm as an example, the time to detect the film thickness using the method shown in this application is less than 0.3s, while it takes about 3h to detect using an ellipsometer. That is, the film thickness detection method provided by this application effectively saves detection time and is more efficient. In addition, the measurement error of the ellipsometer is generally 3nm, while the application can control the error within 1nm.

[0146] In summary, the film thickness measurement method and device provided in the present application only require a camera to take a photo, and the software algorithm can calculate the film thickness of the entire film and the distribution of thickness values ​​at various locations. The operation is simple, and the measurement results have small volatility, high accuracy, and fast detection speed.

[0147] The above are only specific embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A film thickness measurement method, characterized in that: The following steps are involved: irradiating the film with light having a wavelength of 300-1000 nm, receiving reflected light from the film and obtaining a corresponding two-dimensional image; Using a pre-established mathematical model to calculate and obtain thickness values ​​of at least part of the pixels constituting the two-dimensional image, and using an average value of the thickness values ​​to characterize the film thickness; Wherein, the mathematical model includes: a functional relationship between the gray value of the pixel and the thickness value; The film comprises any one of an aluminum oxide film and a silicon nitride film formed on the surface of a substrate, and the substrate is a silicon wafer with a flat surface or a velvet structure on the surface; Among them, the light is blue light with a wavelength of 465-475nm, and the functional relationship between the grayscale value of the pixel and the thickness value is: y = 0.1451x + 66.809, where y represents the film thickness value in nm, x represents the grayscale value, and the average value of the thickness value is used to represent the film thickness.

2. The film thickness measurement method according to claim 1, characterized in that: The light source generating the light is an LED.

3. The film thickness measurement method according to claim 1, characterized in that: The two-dimensional image includes any one of a black-and-white photo and a color photo.

4. The film thickness measurement method according to any one of claims 1 to 3, characterized in that: The method also includes mapping the thickness value corresponding to the pixel into a color value to generate a color image representing the film thickness.

5. A film thickness measuring device for implementing the film thickness measuring method according to claim 1, characterized in that: Including detection core structure and control system; The detection core structure comprises: a cover body, a light source and a camera, the cover body has a first accommodating cavity, and the first accommodating cavity has an accommodating portion for accommodating the film; A light source is disposed in the first accommodating cavity, the light source is used to generate light that can be irradiated to the accommodating portion, the camera has a rotatable lens, the lens is located on the optical path of the reflected light from the film to receive the reflected light and obtain the corresponding two-dimensional image; The control system is used to calculate and obtain the thickness values ​​corresponding to the pixels constituting the two-dimensional image and the film thickness according to the mathematical model.

6. The film thickness measuring device according to claim 5, characterized in that: The light emitting surface of the light source faces the accommodating portion.

7. The film thickness measuring device according to claim 5, characterized in that: The light source is a panel light source, and the panel light source has a mounting hole matched with the lens.

8. The film thickness measuring device according to claim 5, characterized in that: The detection core structure includes a light diffuser, which is disposed in the cover and divides the first accommodating cavity into a first cavity and a second cavity, the first cavity is located above the second cavity, and the accommodating portion and the lens are respectively located in the second cavity; The light source is located in the first cavity and the light emitting surface of the light source faces the side away from the second cavity, so that the light emitted by the light source irradiates the accommodating portion in a diffuse reflection manner.

9. The film thickness measuring device according to claim 8, characterized in that: The light source is arranged around the lens.

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