Film thickness measurement method

Abstract

To measure the film thickness without assuming film thickness fluctuation.SOLUTION: A film thickness measurement method for measuring metal film thickness includes the first, second, and third steps. In the first step, the surface color of the metal film is measured. In the second step, the color distance is calculated using the surface color. In the third step, the film thickness is calculated by applying the color distance calculated in the second step to the relationship between the metal film thickness and color distance, which is set for each type of metal film.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a method for measuring film thickness. [Background technology]

[0002] Removal of a metal film on a substrate is required in various situations, for example, etching a metal film on a silicon wafer to avoid arcing during processing of the silicon wafer.

[0003] The etching technique itself is well known. After the etching, it is desirable to remove the metal film sufficiently, for example, to the extent that arcing does not occur. For example, if the thickness of the metal film remaining after etching is greater than a given threshold, further etching is performed. On the other hand, if the etching is excessive, the substrate will be damaged.

[0004] Such damage thins the substrate. The thinner the substrate, the more likely it is that such damage will cause cracks. For example, a silicon wafer has a circular portion near its periphery, commonly known as a bevel. The thickness of the bevel becomes thinner as it approaches the periphery. Excessive etching of the bevel is likely to cause the above-mentioned cracks.

[0005] Although not limited to bevels, in order to perform etching that removes a metal film on a substrate but does not damage the substrate, it is desirable to measure the thickness of the metal film that remains after etching.

[0006] There are well-known methods for optically determining the thickness of non-metallic films, for example, by spectral interference using multiple reflections in oxide films (see, for example, Patent Document 1 and Non-Patent Documents 1, 2, and 3). However, in the case of metal films, most of the irradiated light is reflected by the surface layer of the metal film, making it difficult to obtain a specific spectral waveform that depends on the film thickness. Therefore, it is difficult to determine the thickness of metal films by spectral interference.

[0007] Patent Document 2 discloses a technique for calculating film thickness using light reflected from the surface of a metal film. In the technique exemplified in Patent Document 2, pixels in a color image of a substrate are converted into coordinates of two color channels, and the metal film is polished to a target film thickness using a path of the coordinates that moves as the metal film is polished.

[0008] Non-Patent Document 4 discloses the color of metals, but does not mention the relationship with the metal film thickness. An example of film thickness measurement using interference is disclosed in Patent Document 3.

[0009] Patent Document 4 discloses an etching process on the bevel (bevel etching). [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-279297 [Patent Document 2] Patent No. 7088910 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-29455 [Patent Document 4] Japanese Patent Application Publication No. 2023-153470 [Non-patent literature]

[0011] [Non-Patent Document 1] Hasegawa, "Examination of the method for determining the oxide film thickness on iron surface by interference color," Journal of the Japan Institute of Metals, Vol. 25, No. 12, pp. 773-776, 1961 [Non-patent document 2] Uchida, Kado, Yamada, and Kato, "Measurement of the Thickness of Chromium Hydrous Oxide Film on Tin-Free Steel by Ellipsometry," Journal of the Japan Institute of Metals, Vol. 33, No. 11, pp. 1286-1290, 1969 [Non-patent document 3] Matsuda, Sugimoto, and Sawada, "Measurement of the Thickness and Optical Constants of Passive Films on 18-8 Stainless Steel by Ellipsometry," Journal of the Japan Institute of Metals, Vol. 39, No. 8, pp. 848-856, 1975 [Non-patent document 4] Yamaguchi, "Color of Metals," Journal of the Japan Institute of Metals, Vol. 8, No. 11, pp. 758-763, 1969 Summary of the Invention [Problem to be solved by the invention]

[0012] In Patent Document 2, film thickness variations are reflected in the paths of coordinates of two color channels. However, in both of these paths, the paths may intersect, and multiple different film thicknesses may correspond to the same coordinate. Therefore, when one of the coordinates is obtained, it is not necessarily possible to uniquely obtain the corresponding film thickness. In other words, the technology in Patent Document 2 is considered to have a problem in that it is not possible to estimate film thickness from a color image without tracking the coordinates that move with film thickness variations. This problem leads to the problem that film thickness cannot be measured without tracking film thickness variations.

[0013] The present disclosure has been made in view of the above-mentioned problems, and aims to provide a technique for measuring film thickness without relying on tracking film thickness fluctuations. [Means for solving the problem]

[0014] The film thickness measurement method according to the present disclosure is a method for measuring the film thickness of a metal film, and a first aspect thereof comprises a first step of measuring a surface color, which is the color exhibited by the surface of the metal film; a second step of calculating a color distance using the surface color; and a third step of calculating the film thickness by applying the color distance obtained in the second step to a relationship between the film thickness of the metal film and the color distance, which is set for each type of metal film.

[0015] A second aspect of the film thickness measurement method according to the present disclosure is the first aspect, wherein the surface color is a color exhibited by the surface exposed by etching the metal film.

[0016] A third aspect of the film thickness measurement method according to the present disclosure is the second aspect thereof, further comprising a fourth step of specifying the metal species, which is performed before the third step, and which determines the film thickness by applying the color distance obtained in the second step to the relationship for the metal species specified in the fourth step.

[0017] A fourth aspect of the film thickness measurement method according to the present disclosure is the third aspect, wherein the relationship is determined for each of the metal species before the fourth step.

[0018] A fifth aspect of the film thickness measurement method according to the present disclosure is the fourth aspect, wherein the metal species is one or more selected from ruthenium, molybdenum, and tungsten.

[0019] A sixth aspect of the film thickness measurement method according to the present disclosure is the fifth aspect, wherein when the metal species is ruthenium, the film thickness is determined in the range of 30 nm or more and 50 nm or less.

[0020] A seventh aspect of the film thickness measurement method according to the present disclosure is the fifth aspect, wherein when the metal species is molybdenum, the film thickness is determined in the range of 30 nm or more and 50 nm or less.

[0021] An eighth aspect of the film thickness measurement method according to the present disclosure is the fifth aspect thereof, wherein when the metal species is tungsten, the film thickness is determined in the range of 50 nm or more and 350 nm or less.

[0022] A ninth aspect of the film thickness measurement method according to the present disclosure is any one of the first to eighth aspects, wherein in the second step, the color distance in the CIE1976 (L*a*b*) color space is determined.

[0023] A tenth aspect of the film thickness measurement method according to the present disclosure is the ninth aspect, wherein in the relationship, the film thickness monotonically decreases with respect to the color distance.

[0024] An eleventh aspect of the film thickness measurement method according to the present disclosure is any one of the first to tenth aspects, wherein in the first step, 50% or more of the light irradiating the surface of the metal film is reflected from the surface and received by a color sensor, and the surface color is measured. [Effects of the Invention]

[0025] According to the film thickness measurement method of the first aspect, the film thickness can be determined using color information obtained from the metal surface without the need to track the film thickness fluctuations.

[0026] According to the film thickness measuring method of the second aspect, the surface color can be measured with high accuracy.

[0027] The film thickness measurement method according to any of the third to eighth aspects improves the accuracy of film thickness measurement.

[0028] Both the film thickness measurement methods according to the ninth and tenth aspects provide a highly valid calibration curve.

[0029] According to the film thickness measuring method of the eleventh aspect, the surface color can be measured with high accuracy. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 10 is a graph illustrating the relationship between color distance and film thickness. [Figure 2] FIG. 10 is a graph illustrating the relationship between color distance and film thickness. [Figure 3] FIG. 10 is a graph illustrating the relationship between color distance and film thickness. [Figure 4] 1 is a flowchart showing a process for determining a metal film thickness in the present disclosure. [Figure 5] 10 is a flowchart illustrating the details of step S1 for one metal type. [Figure 6] FIG. 1 is a diagram illustrating an example of a schematic configuration of a substrate processing apparatus. [Figure 7] FIG. 2 is a block diagram illustrating a schematic configuration of a control unit. [Figure 8] FIG. 1 is a perspective view illustrating a configuration for measuring a surface color. [Figure 9] FIG. 10 is a side view showing a state in which the head unit has advanced to an imaging position. DETAILED DESCRIPTION OF THE INVENTION

[0031] Hereinafter, each embodiment of the present disclosure will be described with reference to the accompanying drawings. The components described in each embodiment are merely examples, and the scope of the present disclosure is not intended to be limited to these examples. The drawings are merely schematic illustrations. In the drawings, the dimensions and number of each part may be exaggerated or simplified as necessary to facilitate understanding. In the drawings, parts having similar configurations and functions are assigned the same reference numerals, and duplicate explanations are appropriately omitted.

[0032] In this specification, unless otherwise specified, expressions indicating relative or absolute positional relationships (e.g., "parallel," "orthogonal," "center") not only indicate the exact positional relationship, but also indicate a state including tolerances and a state in which the same level of functionality is obtained. Expressions indicating that two or more things are equal not only indicate a state in which they are strictly equal quantitatively, but also indicate a state in which there is a tolerance or a difference that allows the same level of functionality to be obtained.

[0033] Unless otherwise specified, expressions indicating shapes not only represent geometrically strict shapes, but also represent shapes having irregularities or chamfers, for example, within the scope of obtaining the same degree of effect.

[0034] The expressions "comprise," "include," or "have" an element are not exclusive expressions that exclude the presence of other elements.

[0035] Unless otherwise specified, the expression "connected" includes a state in which two elements are in contact with each other, as well as a state in which two elements are separated by another element.

[0036] <1. Adoption of color distance> In this embodiment, a color distance is used to obtain the thickness of the metal film, and the color distance may be, for example, the Euclidean distance ΔE defined by equation (1).

[0037]

number

[0038] In formula (1), the values ​​Ls, As, and Bs (hereinafter also referred to as the L value Ls, the a* value As, and the b* value Bs, respectively) are introduced as the L value, the a* value, and the b* value in the CIE1976 (L*a*b) color space (hereinafter tentatively referred to as the "CIELAB color space"). In the color distance exemplified later, the L value Ls, the a* value As, and the b* value Bs are respectively adopted as the L value Ls, the a* value As, and the b* value Bs, respectively, of the L value, a* value, and b* value in the CIELAB color space of the color exhibited by the surface of a mirror-finished silicon substrate (hereinafter tentatively referred to as the "reference color").

[0039] In equation (1), the values ​​Lm, Am, and Bm (hereinafter also referred to as the L value Lm, the a* value Am, and the b* value Bm, respectively) are introduced as the L value, a* value, and b* value in the CIELAB color space of the color exhibited by the surface of the metal film whose thickness is to be measured (hereinafter tentatively referred to as the "surface color").

[0040] In this embodiment, the thickness of the metal film is obtained from information on the surface color, so as long as the L value Ls, the a* value As, and the b* value Bs are fixed, it is not a prerequisite that the metal film be formed on a substrate exhibiting a reference color (a silicon substrate in the above example). In other words, it is not necessary to adopt the color exhibited by the surface of the substrate on which the metal film, the thickness of which is to be measured, is formed as the reference color.

[0041] The L value Lm, a* value Am, and b* value Bm are obtained by a so-called color sensor that measures the surface color. The L value Ls, a* value As, and b* value Bs are also obtained by a color sensor that measures the reference color. For example, the color sensor CFO100 from Micro-Epsilon Corporation can be used as the color sensor. For example, white light is used as the light that illuminates the surface of the metal film when measuring the reference color (hereinafter tentatively referred to as "measurement light").

[0042] <2. Relationship between color distance and film thickness> Figures 1, 2, and 3 are graphs illustrating the relationship between color distance and metal film thickness. Figure 1 illustrates a case where ruthenium is used as the metal film material. Figure 2 illustrates a case where molybdenum is used as the metal film material. Figure 3 illustrates a case where tungsten is used as the metal film material.

[0043] In these graphs, the horizontal axis represents the color distance calculated from the surface color and the reference color, and the vertical axis represents the film thickness calculated from the sheet resistance.

[0044] In Figures 1, 2, and 3, measurement points are plotted as black circles, and regression lines G1, G2, and G3 based on these measurement points are shown as dashed lines. In each of Figures 1, 2, and 3, the equations of the regression lines G1, G2, and G3 are also shown, with the color distance as the variable x and the film thickness [nm] as the variable y. The coefficients of determination R for the regression lines G1, G2, and G3 are also shown. 2 The slope of each of the regression lines G1, G2, and G3 is negative, and it can be said that the film thickness decreases monotonically with increasing color distance.

[0045] Figures 1, 2, and 3 all show examples of metal films formed on mirror-polished silicon substrates with notches. In all of these cases, data from the position directly opposite the notch when viewing the silicon substrate from the normal direction is used, as this position is thought to be the least affected by the mechanical stress of the notch.

[0046] 1, 2, and 3, it can be seen that there is an approximately linear relationship between the film thickness calculated from the sheet resistance and the color distance for each type of metal. If the relationship between the color distance obtained by measuring the surface color and the film thickness calculated from the sheet resistance is calculated in advance as a calibration curve for each type of metal, the film thickness calculated from the sheet resistance can be accurately estimated from the color distance obtained from the surface color measurement and the calibration curve. Moreover, this estimation does not require tracking of film thickness fluctuations.

[0047] In the present disclosure, the thickness of a metal film exhibiting a surface color can be estimated from a color distance that depends on the surface color, or the thickness can be measured. For example, the thickness calculated from the sheet resistance can be used as the actual thickness, or the actual thickness can be further estimated based on the thickness calculated from the sheet resistance.

[0048] As can be seen from FIGS. 1 and 2, in the range of metal film thicknesses of several tens of nanometers, the relationship between color distance and film thickness is obtained as regression lines G1 and G2, which can be used as calibration curves.

[0049] As can be seen from FIG. 3, even when the thickness of the metal film is in the range from several tens of nm to several hundreds of nm, the relationship between the color distance and the film thickness can be obtained as a regression line G3, which can be used as a calibration curve.

[0050] For at least ruthenium and molybdenum, film thickness can be determined using a monotonically decreasing line with respect to color distance in the range of 30 nm to 50 nm. For at least tungsten, film thickness can be determined using a monotonically decreasing line with respect to color distance in the range of 50 nm to 350 nm. Measuring film thickness using surface color in the range where the calibration curve is valid, for example, in the range where the coefficient of determination is equal to or greater than a threshold, contributes to improving the accuracy of film thickness measurement.

[0051] The color distances used in Figures 1, 2, and 3 use the reference color of a mirror-finished silicon substrate. If a substrate other than silicon is used to present the reference color, the L value (Ls), a* value (As), and b* value (Bs) will also differ. Therefore, it is desirable to specify the reference color and the type of metal (tentatively referred to as "metal type" below) for which the film thickness is to be determined in the calibration curve. Considering the possibility that the calibration curves may differ for each metal type, obtaining a calibration curve for each metal type contributes to improving the accuracy of film thickness measurements.

[0052] 4 is a flowchart showing the steps of determining the thickness of a metal film in the present disclosure. The flowchart also includes a pre-process step of determining a calibration curve. The flowchart includes steps S1, S21, S22, S23, and S24.

[0053] This pre-processing is illustrated by step S1 in Fig. 4. In step S1, a calibration curve is created and saved. The calibration curve is created for each metal type with a fixed reference color, and saved.

[0054] Step S21 is a step of specifying the metal type. In reference to Figures 1, 2, and 3, one of ruthenium, molybdenum, and tungsten is specified in step S21.

[0055] Step S22 is a process of measuring the surface color. A specific example of measuring the surface color will be described in detail later.

[0056] Step S23 is a step of obtaining the color distance, which is calculated using the surface color measured in step S22 and, for example, equation (1).

[0057] Step S24 is a process for determining the film thickness. In step S24, the color distance determined in step S23 is applied to the calibration curve for the metal type specified in step S21 from the calibration curves saved in step S1, to determine the film thickness of the metal.

[0058] The order of steps S21 and S22 may be reversed as long as they are executed before step S24, because the execution result of step S23 is not affected even if the order of steps S21 and S22 is reversed.

[0059] 5 is a flowchart illustrating the details of step S1 for one metal type. When multiple metal types are expected, step S1 is executed for each different metal type, and then step S21 is executed.

[0060] Step S1 includes steps S10, S11, S12, S13, S14, S15, and S16.

[0061] Step S10 is a step of specifying the metal type. In reference to Figures 1, 2, and 3, one of ruthenium, molybdenum, and tungsten is specified in step S10.

[0062] After step S10 is executed, step S11 is executed. Step S11 is a process of acquiring color distances. A plurality of color distances are acquired for each film thickness of the metal type specified in step S10.

[0063] In terms of Figure 1: The surface color of ruthenium having a film thickness of 67.7 nm estimated from the sheet resistance is measured, and a color distance of 99.45 is obtained between the surface color and the reference color; The surface color of ruthenium having a film thickness of 50.3 nm estimated from the sheet resistance is measured, and a color distance of 100.09 is obtained between the surface color and the reference color; The surface color of ruthenium having a film thickness of 33.2 nm estimated from the sheet resistance is measured, and a color distance of 100.32 is obtained from the surface color and the reference color.

[0064] In terms of Figure 2: The surface color of molybdenum with a film thickness of 71.6 nm estimated from the sheet resistance is measured, and a color distance of 98.64 is obtained between the surface color and the reference color; The surface color of molybdenum with a film thickness of 42.7 nm estimated from the sheet resistance is measured, and a color distance of 99.22 is obtained between the surface color and the reference color; The surface color of molybdenum having a film thickness of 27.6 nm estimated from the sheet resistance is measured, and a color distance of 99.73 is obtained from the surface color and the reference color.

[0065] In terms of Figure 3: The surface color of tungsten with a film thickness of 373.3 nm estimated from the sheet resistance is measured, and a color distance of 94.97 is obtained between the surface color and the reference color; The surface color of tungsten with a film thickness of 320.8 nm estimated from the sheet resistance is measured, and a color distance of 99.28 is obtained between the surface color and the reference color; The surface color of tungsten with a film thickness of 203.4 nm estimated from the sheet resistance is measured, and a color distance of 105.09 is obtained between the surface color and the reference color; The surface color of tungsten with a film thickness of 110.1 nm estimated from the sheet resistance is measured, and a color distance of 107.87 is obtained between the surface color and the reference color; The surface color of tungsten with a film thickness of 54.3 nm estimated from the sheet resistance is measured, and a color distance of 112.28 is obtained from the surface color and the reference color.

[0066] Step S12 is a step of creating a regression line, in which the regression line is created using the color distance for each film thickness obtained in step S11.

[0067] In accordance with FIG. 1, for ruthenium, regression equation (2) is created as an equation showing a regression line G1 that indicates the relationship between the color distance value x and the film thickness y.

[0068]

number

[0069] In accordance with FIG. 2, for molybdenum, regression equation (3) is created as an equation showing a regression line G2 that indicates the relationship between the color distance value x and the film thickness y.

[0070]

number

[0071] In accordance with FIG. 3, for tungsten, regression equation (4) is created as an equation showing a regression line G3 that indicates the relationship between the color distance value x and the film thickness y.

[0072]

number

[0073] Step S13 is a step for determining whether the regression line created in step S12 can be used as a calibration curve. In the example of FIG. 5, it is determined whether the coefficient of determination exceeds a threshold value. For example, the threshold value is 0.9. To avoid a situation in which the coefficient of determination becomes 1, making step S13 essentially meaningless, it is desirable to obtain color distances for three or more film thicknesses in step S11.

[0074] If the result of the determination in step S13 is positive, for example, if the coefficient of determination exceeds 0.9, step S14 is executed. Step S14 is a process of saving the regression line obtained in step S12 as a calibration curve. This is because the relationship between color distance and film thickness obtained by a regression line with a coefficient of determination exceeding a threshold value is considered to be suitable for determining film thickness from color distance. The coefficient of determination R shown in Figures 1, 2, and 3 is 2 are all greater than 0.9, and all three regression equations (2), (3), and (4) described above result in a positive judgment in step S13, and all of the regression lines G1, G2, and G3 are saved as calibration curves in step S14. By executing step S14, step S1 for one metal species is completed.

[0075] For example, when ruthenium is designated in step S10, regression equation (2) is saved as calibration curve data. For example, when molybdenum is designated in step S10, regression equation (3) is saved as calibration curve data. For example, when tungsten is designated in step S10, regression equation (4) is saved as calibration curve data.

[0076] If the determination result in step S13 is negative, for example, if the coefficient of determination is 0.9 or less, step S15 is executed.

[0077] Step S15 is a step for determining whether to acquire more color distances. This is because it is expected that an increase in the number of samples will cause the coefficient of determination of the newly created regression line to exceed a threshold. For example, if an upper limit is set on the number of samples for measuring color distances, it is determined whether the number of samples exceeds the upper limit.

[0078] For example, even if the number of samples reaches the upper limit, if the coefficient of determination does not exceed the threshold, the judgment result in step S15 is negative. In this case, the obtained regression line is assumed to have low reliability as a calibration curve. If the judgment result in step S15 is negative, the calibration curve is not saved in step S16, and step S1 for one metal species is completed.

[0079] If the determination result of step S15 is positive, step S11 is executed, and a new regression line is created in step S12. The regression line may be created using not only the color distance obtained by the newly executed step S11, but also the color distance obtained by the previously executed step S11.

[0080] From the above flowchart, it can be said that the relationship between the thickness of the metal film and the color distance is found for each metal type in step S1. For example, the metal type is selected from one or more of ruthenium, molybdenum, and tungsten.

[0081] <3. Example of substrate processing> FIG. 6 is a diagram illustrating an example of the schematic configuration of a substrate processing apparatus 1. The substrate processing apparatus 1 includes a processing chamber 100, a rotation mechanism 2, a splash prevention mechanism 3, a processing mechanism 4, a heating mechanism 5, and an imaging mechanism 6. In FIG. 6, a so-called right-handed Cartesian coordinate system is used. Specifically, the Z direction is defined as the vertically upward direction. A head unit 6G, which will be described later, moves along the Y direction and the opposite direction. FIG. 6 is a view taken in the opposite direction to the X direction.

[0082] The rotation mechanism 2 , the anti-scattering mechanism 3 , the processing mechanism 4 , the heating mechanism 5 and the imaging mechanism 6 are all housed within the processing chamber 100 .

[0083] The rotation mechanism 2, the anti-scattering mechanism 3, the processing mechanism 4, the heating mechanism 5 and the imaging mechanism 6 are all communicatively connected to the control unit 8, for example electrically, and operate according to instructions from the control unit 8.

[0084] A general computer, for example, is employed as the control unit 8. The control unit 8 controls each part of the substrate processing apparatus 1 by having a CPU serving as a main control unit perform arithmetic processing in accordance with procedures written in a program. As a result, the substrate processing apparatus 1 supplies a processing liquid to the peripheral portion of the upper surface of a substrate 9 in the processing chamber, thereby performing substrate processing, for example, bevel etching. A plurality of substrate processing apparatuses 1 may be connected to the control unit 8, and a single control unit 8 may control the plurality of substrate processing apparatuses 1.

[0085] The rotation mechanism 2 holds the substrate 9 in a substantially horizontal position and rotates it around a vertical rotation axis 20 that passes through the center of the main surface of the substrate 9. For example, the rotation axis 20 is parallel to the Z direction.

[0086] The rotation mechanism 2 includes a spin chuck 21. The spin chuck 21 is a disk-shaped member smaller than the substrate 9, and its upper surface is substantially horizontal (its normal direction is substantially vertical). The central axis of the spin chuck 21 coincides with the rotation axis 20, for example.

[0087] A rotating shaft portion 22 is connected to the lower surface of the spin chuck 21. The rotating shaft portion 22 extends in the vertical direction, and the axis of the rotating shaft portion 22 coincides with the rotation axis 20.

[0088] A rotation drive unit 23, exemplified by a motor, is connected to the rotation shaft unit 22. The rotation drive unit 23 drives the rotation shaft unit 22 to rotate around its axis in response to a rotation command from the control unit 8. This allows the spin chuck 21 to rotate around the rotation axis 20 together with the rotation shaft unit 22. The rotation drive unit 23 and the rotation shaft unit 22 function to rotate the spin chuck 21 around the rotation axis 20.

[0089] A through-hole (not shown) is provided in the center of the spin chuck 21, and the through-hole communicates with the internal space of the rotating shaft portion 22. A pump (not shown) is connected to the internal space via a pipe in which a valve (not shown) is installed.

[0090] The pump and valve operate in response to commands from the control unit 8, thereby selectively applying negative pressure to the spin chuck 21. For example, when negative pressure is applied to the spin chuck 21 with the substrate 9 placed on the upper surface of the spin chuck 21 in a substantially horizontal position, the spin chuck 21 suction-holds the substrate 9 from below. When the negative pressure on the spin chuck 21 is released or positive pressure is applied, the substrate 9 can be removed from the upper surface of the spin chuck 21.

[0091] The anti-scattering mechanism 3 has a guard 31 and a liquid receiving portion 32. The guard 31 is cylindrical and is provided so as to surround the outer periphery of the substrate 9 held by the spin chuck 21. In Figure 6, the cross section of the guard 31 is drawn on a plane that includes the rotation axis 20 and is parallel to the Y direction.

[0092] The guard 31 is raised in the Z direction by a well-known lifting mechanism (not shown) and lowered to the opposite side of the Z direction. Figure 6 shows the guard 31 in its fully lowered state (hereinafter tentatively referred to as the "lowered state"). In the lowered state, the upper end of the guard 31 is positioned below the substrate 9 held by the spin chuck 21. When the guard 31 is in the lowered state (see Figure 6), the guard 31 is less likely to interfere with the placement and removal of the substrate 9 onto the spin chuck 21.

[0093] When the guard 31 is fully raised in the X direction (hereinafter tentatively referred to as the "upper state"), the upper end of the guard 31 is positioned higher than the substrate 9 (not shown) held by the spin chuck 21. When the guard 31 is in the upper state, the guard 31 surrounds the outer periphery of the substrate 9 held by the spin chuck 21.

[0094] During bevel etching, the processing liquid used for the bevel etching is scattered from the substrate 9 due to the rotation of the substrate 9. The inner peripheral surface of the guard 31 in the upper position prevents the processing liquid from scattering onto the processing mechanism 4 or the imaging mechanism 6. The processing liquid scattered onto the inner peripheral surface of the guard 31 in the upper position is guided to the liquid receiving portion 32. The liquid receiving portion 32 contributes to the recovery of the processing liquid used in the processing.

[0095] The processing mechanism 4 has a base 41 , a rotation support shaft 42 , an arm 43 , and a nozzle 44 .

[0096] The base 41 is fixed to the processing chamber 100. A rotation support shaft 42 is provided so as to be freely rotatable relative to the base 41. An arm 43 extends horizontally from the rotation support shaft 42. A nozzle 44 is attached to the tip of the arm 43.

[0097] The arm 43 swings as the pivot shaft 42 rotates in response to a control command from the control unit 8. The swinging of the arm 43 causes a nozzle 44 attached to the tip of the arm 43 to move between a retracted position where it is retracted from above the substrate 9 to the side (in FIG. 6, the nozzle 44 in the retracted position is shown by a solid line) and a discharge position above the peripheral edge of the substrate 9 (in FIG. 6, the nozzle 44 in the discharge position is drawn by a chain line together with the arm 43). The discharge position is, for example, directly above the substrate 9, and more specifically, above the peripheral edge of the substrate 9.

[0098] The nozzle 44 discharges a processing liquid (not shown) at the discharge position in response to a supply command from the control unit 8. The processing liquid is supplied from outside the processing chamber 100.

[0099] As the nozzle 44 discharges the processing liquid while the spin chuck 21 rotates, the processing liquid is supplied to the peripheral edge of the substrate 9. For example, the processing liquid is an etchant that etches a metal film, and bevel etching of the substrate 9 is performed by the etchant.

[0100] The heating mechanism 5 is composed of an annular heater 51. The heater 51 has a built-in heating element that extends in the circumferential direction of the substrate 9 along the peripheral edge of the lower surface of the substrate 9. The heater 51 generates heat in accordance with commands from the control unit 8, and the peripheral edge of the substrate 9 is heated by this heat. This heating increases the temperature of the peripheral edge of the substrate 9 to a value suitable for bevel etching.

[0101] The imaging mechanism 6 has a base 6A, a rotational support shaft 6B, an arm 6C, a head driving section 6D, a light source 6E, and a head section 6G.

[0102] A base 6A is fixed to the processing chamber 100. A rotation support shaft 6B is provided rotatably on the base 6A. An arm 6C extends horizontally from the rotation support shaft 6B. A head part 6G is attached to the tip of the arm 6C.

[0103] The arm 6C moves as the pivotal shaft 6B rotates in response to a control command from the control unit 8. As the arm 6C moves, the head unit 6G attached to the tip of the arm 6C moves back and forth, for example, along the Y direction, between a retracted position where it is retracted from above the substrate 9 to the side (in FIG. 6, the head unit 6G in the retracted position is shown by a solid line) and an imaging position where it images the peripheral portion of the substrate 9 (in FIG. 6, the head unit 6G in the imaging position is shown by a chain line).

[0104] The control unit 8 comprehensively controls the operation of the substrate processing apparatus 1. FIG.

[0105] The control unit 8 has, for example, a calculation unit 801, a memory 802, a storage unit 803, and an input / output interface 804. The calculation unit 801 is configured, for example, by one or more central processing units (CPUs). The memory 802 is configured, for example, by a volatile storage medium such as a RAM (Random Access Memory). The storage unit 803 is configured, for example, by a non-volatile storage medium such as a hard disk drive (HDD) or a solid state drive (SSD).

[0106] The storage unit 803 can store, for example, programs and various information. The calculation unit 801 can implement various functions by, for example, reading and executing programs stored in the storage unit 803. At this time, the memory 802 is used, for example, as a workspace, and stores information that is temporarily generated or acquired.

[0107] The input / output interface 804 has a function of inputting and outputting data between the control unit 8 and the outside.

[0108] At least a part of the functional configuration realized by the control unit 8 may be realized by hardware such as a dedicated electronic circuit, for example.

[0109] <4. Surface color measurement> Fig. 8 is a perspective view illustrating a configuration for measuring surface color. For ease of explanation, Fig. 8 shows the substrate 9, guard 31, head unit 6G, and a portion of arm 6C on the substrate 9 side, and does not depict other components.

[0110] 9 is a side view showing the state in which the head unit 6G has advanced to the imaging position. This side view is obtained by viewing in the direction opposite to the X direction. For ease of explanation, FIG. 9 shows a part of the substrate 9 and a part of the head unit 6G on the substrate 9 side, and other components are omitted.

[0111] The head unit 6G has an imaging head 62 and a dark box 63. The imaging head 62 images the bevel 91 (see FIG. 9). The dark box 63 houses a color sensor 631 (see FIG. 9) that measures the surface color. The arm 6C is connected to the head unit 6G and moves the imaging head 62 and the dark box 63 forward in the direction opposite to the Y direction or backward in the Y direction.

[0112] 8 depicts the guard 31 in a lower state, and the guard 31 in a higher state is also depicted in dashed lines.

[0113] 8 shows the head unit 6G in the retracted position. The path along which the head unit 6G moves to the imaging position is also shown by a chain line.

[0114] When the substrate 9 is processed, the guard 31 is raised to the upper position in the Z direction to prevent the processing liquid from splashing onto the processing mechanism 4 or the imaging mechanism 6. The head unit 6G moves toward the substrate 9 to measure the surface color of the metal 92 formed on the Z direction side of the substrate 9 (hereinafter, tentatively referred to as "metal on the substrate"). In order not to impede this movement, the guard 31 is lowered as illustrated in FIG. 8 prior to measuring the surface color.

[0115] The head unit 6G moves from the retracted position in the opposite direction to the Y direction to the imaging position. At the imaging position, the color sensor 631 measures the surface color of the metal 92 on the board.

[0116] After the surface color of the metal 92 on the substrate is measured, the head unit 6G retreats in the Y direction to the retreat position, and the state shown in FIG. 8 is obtained.

[0117] The imaging head 62 is provided with a hole 621 that penetrates in the X direction. The side of the hole 621 opposite to the Y direction is open, allowing the substrate 9 to be inserted into the hole 621. The imaging head 62 is provided with a plurality of mirrors 622 in the hole 621 that are used to observe the bevel 91. The mirrors 622 are arranged in the hole 621. The imaging head 62 uses the mirrors 622 to capture an image of the bevel 91. Such imaging is known from, for example, Patent Document 4, and the details thereof will not be described in this disclosure.

[0118] Color sensor 631 measures the surface color of metal 92 on the substrate from the direction opposite to the Z direction. Such measurements are performed in step S22 (see FIG. 4) and step S11 (see FIG. 5).

[0119] Such surface color measurement can be performed in situ, without removing the bevel-etched substrate 9 from the processing chamber 100. Therefore, if it is determined that the etching of the metal 92 on the substrate is insufficient, further bevel etching can be performed without removing the substrate 9, thereby simplifying the processing and shortening the processing time.

[0120] The surface color is measured by the color sensor 631 under the control of the control unit 8. For example, the memory unit 803 stores reference color data (for example, L value Ls, a* value As, b* value Bs) and a calibration curve for each metal type.

[0121] The calculation unit 801: Obtain surface color data (e.g., L value Lm, a* value Am, b* value Bm) from the color sensor 631 via the input / output interface 804 (see step S22 in FIG. 4); Using the surface color data and the reference color data (e.g., L value Ls, a* value As, b* value Bs) obtained from the storage unit 803, a calculation is performed according to formula (1) to determine the color distance (see step S23 in FIG. 4); Apply the color distance to a calibration curve (e.g., equations (2), (3), and (4)) to determine the film thickness (see step S24 in FIG. 4); The film thickness is output to the outside via the input / output interface 804.

[0122] For example, an output device, such as the display device 7, is connected to the control unit 8 via the input / output interface 804. The film thickness is output from the output device, for example, displayed.

[0123] <5. Transformation> In the above embodiment, the measurement of the surface color is not limited to the measurement of the surface color at the bevel 91. For example, the area of ​​the on-substrate metal 92 closer to the center of the substrate 9 than the bevel 91 may be the target of the surface color measurement.

[0124] The surface color of a metal film is preferably measured after etching, as exemplified by the bevel etching described above. This is because it can be performed in situ. Furthermore, the surface roughness of the metal film after etching is smaller than that of the metal film after, for example, chemical mechanical polishing, and the surface color can be obtained with high accuracy. In this case, the surface color can be said to be the color exhibited by the surface exposed by etching of the metal film.

[0125] From the viewpoint of high accuracy of the measured surface color, it is preferable that 50% or more of the measurement light is reflected from the metal film and received by the color sensor 631 to measure the surface color. This percentage includes not only the reflectance on the surface of the metal film but also the reduction due to loss of received light caused by scattering of the measurement light on the metal film.

[0126] The measurement light is not limited to white light, but it is preferable that the measurement light has the same wavelength distribution as the light irradiated when obtaining the reference color, from the viewpoint of calculating the color distance with high accuracy.

[0127] The value indicating the surface color is not limited to a value expressed in the CIELAB color space. Values ​​expressed in other color spaces may also be used as the value indicating the surface color. From the viewpoint of calculating the color distance with high accuracy, it is desirable that the value indicating the surface color and the value indicating the reference color are values ​​in the same color space. As illustrated in Figures 1, 2, and 3, calculating the color distance in the CIELAB color space contributes to obtaining a highly valid calibration curve. In this calibration curve, the color distance corresponds one-to-one with the film thickness, and different film thicknesses do not correspond to the same color information as in Patent Document 2. Instead, the film thickness is uniquely determined for each metal type with respect to the color distance.

[0128] It goes without saying that all or part of the components constituting each of the above-described embodiments and various modified examples can be combined as appropriate within a range that does not cause contradictions. [Explanation of symbols]

[0129] 631 Color Sensor G1, G2, G3 regression lines S1 Step S21 Step (4th process) S22 Step (1st process) S23 Step (2nd Process) S24 Step (3rd process)

Claims

1. A method for measuring the thickness of a metal film, comprising: a first step of measuring a surface color, which is a color exhibited by the surface of the metal film; a second step of determining a color distance using the surface color; a third step of calculating the film thickness by applying the color distance obtained in the second step to a relationship between the film thickness of the metal film and the color distance, which is set for each metal type that is the type of the metal film; A film thickness measurement method comprising:

2. 2. The film thickness measurement method according to claim 1, wherein the surface color is a color exhibited by the surface exposed by etching the metal film.

3. a fourth step, which is executed before the third step and specifies the metal type; Further provided with 3. The film thickness measurement method according to claim 2, wherein the third step calculates the film thickness by applying the color distance obtained in the second step to the relationship for the metal species specified in the fourth step.

4. The film thickness measurement method according to claim 3 , wherein the relationship is determined for each of the metal species before the fourth step.

5. 5. The film thickness measuring method according to claim 4, wherein the metal species is one or more selected from the group consisting of ruthenium, molybdenum, and tungsten.

6. 6. The film thickness measuring method according to claim 5, wherein when the metal species is ruthenium, the film thickness is determined in the range of 30 nm or more and 50 nm or less.

7. 6. The film thickness measuring method according to claim 5, wherein when the metal species is molybdenum, the film thickness is determined in the range of 30 nm to 50 nm.

8. 6. The film thickness measuring method according to claim 5, wherein when the metal species is tungsten, the film thickness is determined in the range of 50 nm or more and 350 nm or less.

9. 9. The film thickness measuring method according to claim 1, wherein in the second step, the color distance is determined in a CIE 1976 (L*a*b*) color space.

10. 10. The film thickness measurement method according to claim 9, wherein in the relationship, the film thickness monotonically decreases with respect to the color distance.

11. 9. The film thickness measurement method according to claim 1, wherein in the first step, 50% or more of the light irradiating the surface of the metal film is reflected from the surface and received by a color sensor, thereby measuring the surface color.

Images