Coating status detection method and coating status detection device

Abstract

To provide a coating status detection method and a coating status detection device that can easily detect the coating status of a protective film applied to a workpiece at low cost.SOLUTION: A coating status detection method for detecting the coating status of a protective film 9 applied to a workpiece (semiconductor wafer W) includes a measurement step (steps S2 to S3) of illuminating the workpiece with broadband light (illumination light L1) emitted from a broadband light source 13 and receiving reflected light L2 of the broadband light from the workpiece, and an uncoated area detection step (steps S4 to S5) of detecting an uncoated area where the protective film 9 has not been applied from the reflected light L2 received in the measurement step.SELECTED DRAWING: Figure 11

Description

[Technical Field]

[0001] The present invention relates to a coating status detection method and a coating status detection device for detecting the coating status of a protective film applied to a workpiece. [Background technology]

[0002] A semiconductor wafer (workpiece) is divided into multiple devices in a grid pattern by grid-like streets. Individual devices are manufactured by dividing this semiconductor wafer along the streets. A laser processing machine is well known as a machine for dividing a semiconductor wafer into multiple devices (chips). A laser processing machine performs laser processing (also called ablation groove processing) to form processed grooves along the streets by irradiating laser light from the laser optical system onto the streets while moving the laser optical system relative to the semiconductor wafer in a processing feed direction along the streets.

[0003] When laser processing of semiconductor wafers is performed using a laser processing device, a protective film is applied (formed) on the surface of the semiconductor wafer in advance to prevent debris generated by the laser processing from adhering to the semiconductor wafer. Because the protective film is thin, there is a risk that uncoated areas on the surface of the semiconductor wafer, where the protective film is not applied, may occur due to surface irregularities or contamination on the semiconductor wafer. Performing laser processing of the semiconductor wafer with these uncoated areas can result in defects. Therefore, it is necessary to detect the application status of the protective film applied to the surface of the semiconductor wafer before laser processing.

[0004] Patent Document 1 discloses a fluorescence detection device that irradiates excitation light onto the surface of a semiconductor wafer coated with a protective film containing a fluorescent agent, and detects areas on the surface of the semiconductor wafer where no fluorescence is generated as uncoated areas. Patent Documents 2 and 3 disclose protective film detection devices that irradiate infrared light onto the surface of a semiconductor wafer coated with a protective film, receive reflected light from this surface, and detect the difference in reflectance of the reflected light depending on whether or not the protective film is present, thereby detecting the presence or absence of uncoated areas on the surface of the semiconductor wafer. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2017-227532 [Patent Document 2] Japanese Patent Application Publication No. 2017-103281 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-065386 Summary of the Invention [Problem to be solved by the invention]

[0006] The fluorescence detection device described in Patent Document 1 requires a powerful and uniform excitation light source and a highly sensitive photomultiplier tube to detect weak fluorescence, making the illumination optical system and detection optical system expensive and complex.

[0007] The protective film detection devices described in Patent Documents 2 and 3 also require expensive illumination and detection optics for using infrared light. Furthermore, the protective film detection devices described in Patent Documents 2 and 3 detect differences in reflectance of reflected light due to the presence or absence of a protective film, but this reflectance varies depending on various conditions, such as the material of the semiconductor wafer and the angle of incidence of infrared light with respect to the surface of the semiconductor wafer. For this reason, it is not possible to simply determine a reflectance threshold for determining the presence or absence of a protective film, and it is not possible to easily detect the application status of the protective film applied to the surface of the semiconductor wafer.

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide a coating status detection method and a coating status detection device that can detect the coating status of a protective film applied to a workpiece at low cost and easily. [Means for solving the problem]

[0009] A coating status detection method for achieving the object of the present invention is a coating status detection method for detecting the coating status of a protective film applied to a workpiece, and includes a measurement step of illuminating the workpiece with illumination light emitted from a broadband light source and receiving reflected light from the workpiece, and a coating status detection step of detecting the coating status of the protective film from the reflected light received in the measurement step.

[0010] According to this coating state detection method, the reflectance of light reflected from the coated area of ​​the protective film can be made lower than the reflectance of light reflected from the uncoated area of ​​the protective film.

[0011] In a coating status detection method according to another aspect of the present invention, the illumination wavelength range of the broadband light source is determined based on the refractive index of the protective film, the incident angle of the illumination light with respect to the surface of the workpiece on which the protective film is coated, and the thickness of the protective film, thereby making it possible to reduce the reflectance of reflected light from the coated area of ​​the protective film to be lower than the reflectance of reflected light from the uncoated area of ​​the protective film.

[0012] In another embodiment of the coating status detecting method of the present invention, the refraction angle of illumination light by the protective film is determined based on the refractive index and the incident angle, where n is the refractive index, d is the thickness of the protective film, θ is the refraction angle, and λ is the short wavelength limit of the illumination wavelength range of the broadband light source. L , the long wavelength limit of the illumination wavelength range is λ H In the measurement step, when the optical path difference between the first reflected light reflected on the surface of the protective film and the second reflected light reflected on the back surface of the protective film is a=2ndcosθ,

number

[0013] A broadband light source that satisfies equation (1) is used. This makes it possible to take advantage of the phenomenon that a decrease in reflectance due to thin film interference occurs to a significant extent for various film thicknesses, regardless of the central wavelength of the light source.

[0014] In another embodiment of the coating status detecting method of the present invention, the refraction angle of illumination light by the protective film is determined based on the refractive index and the incident angle, where n is the refractive index, d is the thickness of the protective film, θ is the refraction angle, and λ is the short wavelength limit of the illumination wavelength range of the broadband light source. L , the long wavelength limit of the illumination wavelength range is λ H In the measurement step, when the optical path difference between the first reflected light reflected on the surface of the protective film and the second reflected light reflected on the back surface of the protective film is a=2ndcosθ,

number

[0015] A broadband light source that satisfies equation (2) is used. This makes it possible to take advantage of the phenomenon that a decrease in reflectance due to thin film interference occurs to a considerable extent for various film thicknesses, regardless of the central wavelength of the light source.

[0016] In another aspect of the coating status detection method of the present invention, the illumination light has a wavelength range of 400 nm to 1000 nm, which makes it possible to reduce the reflectance of light reflected from the coated area of ​​the protective film to be lower than the reflectance of light reflected from the uncoated area of ​​the protective film.

[0017] In a coating status detection method according to another aspect of the present invention, the coating status detection step detects a brightness distribution of the workpiece from reflected light, and detects the coating status of the protective film from the brightness distribution of the workpiece. This makes it possible to detect the coating status of the protective film from the brightness distribution by utilizing the phenomenon that brightness is reduced in the coating area where the protective film is applied due to thin film interference.

[0018] In a coating status detection method according to another aspect of the present invention, a measurement step is performed before and after the application of a protective film to a workpiece, and in the coating status detection step, photographed images of the workpiece before and after the application of the protective film are acquired based on reflected light received in the measurement steps before and after the application of the protective film, respectively, and the coating status of the protective film is detected from a difference or ratio of output values ​​in the photographed images before and after the application of the protective film. This makes it possible to detect the coating status of the protective film.

[0019] In a coating status detection method according to another aspect of the present invention, the measurement step includes irradiating the workpiece with illumination light from a broadband light source at an oblique angle, thereby illuminating a wide area of ​​the surface of the workpiece with the illumination light and detecting the coating status of the protective film over a wide area.

[0020] A coating status detection method for achieving the object of the present invention is a coating status detection device that detects the coating status of a protective film applied to a workpiece, and includes a measurement unit that illuminates the workpiece with a broadband light source and receives reflected light from the workpiece, and a coating status detection unit that detects the coating status of the protective film from the reflected light received by the measurement unit. [Effects of the Invention]

[0021] The present invention makes it possible to easily and inexpensively detect the coating condition of a protective film applied to a workpiece. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic view of an application status detecting device according to a first embodiment. [Figure 2] FIG. 2 is an enlarged cross-sectional view of the semiconductor wafer in FIG. [Figure 3] 10 is an explanatory diagram for explaining an example of detection of the application status of a protective film by an application status detection unit. FIG. [Figure 4] 1 is a graph showing an example of the relationship between the wavelength of reflected light and the reflectance of reflected light for each material of a semiconductor wafer. [Figure 5] FIG. 2 is an enlarged cross-sectional view of a protective film. [Figure 6] 10 is a graph showing an example of the relationship between the wavelength of reflected light and the reflectance of reflected light for each thickness of the protective film. [Figure 7] 10 is an explanatory diagram for explaining a change in the reflection angle of reflected light depending on the position on the surface of the semiconductor wafer. FIG. [Figure 8] 10 is a graph showing an example of the relationship between the wavelength of reflected light and the reflectance of reflected light for each reflection angle of reflected light. [Figure 9] 10 is an explanatory diagram for explaining the setting of the illumination wavelength range of illumination light from a broadband light source, and is a graph showing an example of the relationship between the wavelength of illumination light and the reflectance of reflected light for each thickness of the protective film. FIG. [Figure 10] 10 is a graph showing an example of the relationship between the wavelength of reflected light corresponding to the minimum thickness of the protective film and the reflectance of the reflected light. [Figure 11] 5 is a flowchart showing the flow of a process for detecting the coating status of a protective film by the coating status detecting device of the first embodiment. [Figure 12] 10 is a flowchart showing the flow of a process for detecting the coating status of a protective film by the coating status detecting device of the second embodiment. [Figure 13] FIG. 10 is a schematic view of an application status detecting device according to a third embodiment. [Figure 14] FIG. 10 is a schematic view of an application status detecting device according to a fourth embodiment. [Figure 15] 10 is a graph of Example 1 in which the relationship between the illumination wavelength range of illumination light and the reduction rate of reflected light is calculated for each combination of a plurality of film thicknesses and a plurality of reflection angles. [Figure 16] 10 is a graph of Example 2 in which the relationship between the illumination wavelength range of illumination light and the reduction rate of reflected light is calculated for each combination of a plurality of film thicknesses and a plurality of reflection angles. [Figure 17] 10 is a graph of Example 3 in which the relationship between the illumination wavelength range of illumination light and the reduction rate of reflected light is calculated for each combination of a plurality of film thicknesses and a plurality of reflection angles. [Figure 18] 10 is a graph of Example 4 in which the relationship between the illumination wavelength range of illumination light and the reduction rate of reflected light is calculated for each combination of a plurality of film thicknesses and a plurality of reflection angles. [Figure 19]10 is a graph of Example 5 in which the relationship between the wavelength of illumination light and the reflectance of reflected light is calculated for each thickness of a protective film formed on the surface of an aluminum semiconductor wafer. [Figure 20] 20 is a table showing the calculation results of the average reflectance and reduction rate of reflected light when illumination light in "illumination wavelength range a" to "illumination wavelength range c" is used for each of the four film thicknesses shown in FIG. 19. [Figure 21] 10 is a graph of Example 6 in which the relationship between the wavelength of illumination light and the reflectance of reflected light is calculated for each thickness of a protective film formed on the surface of an aluminum semiconductor wafer. [Figure 22] 22 is a table showing the calculation results of the average reflectance and reduction rate of reflected light when illumination light in "illumination wavelength range a" to "illumination wavelength range c" is used for each of the four film thicknesses d shown in FIG. 21. [Figure 23] 10 is a graph of Example 7 in which the relationship between the wavelength of illumination light and the reflectance of reflected light is calculated for each thickness of the protective film formed on the surface of a copper semiconductor wafer. [Figure 24] 24 is a table showing the calculation results of the average reflectance and reduction rate of reflected light when illumination light in "illumination wavelength range a" to "illumination wavelength range c" is used for each of the four film thicknesses shown in FIG. 23. [Figure 25] 10 is a graph of Example 8 in which the relationship between the wavelength of illumination light and the reflectance of reflected light is calculated for each thickness of the protective film formed on the surface of a copper semiconductor wafer. [Figure 26] 26 is a table showing the calculation results of the average reflectance and reduction rate of reflected light when illumination light in "illumination wavelength range a" to "illumination wavelength range c" is used for each of the four film thicknesses shown in FIG. 25. [Figure 27] 13 is a graph of Example 9 in which the relationship between the wavelength of illumination light and the reflectance of reflected light is calculated for each thickness of the protective film formed on the surface of a silicon semiconductor wafer. [Figure 28] 28 is a table showing the calculation results of the average reflectance and reduction rate of reflected light when illumination light in "illumination wavelength range a" to "illumination wavelength range c" is used for each of the four film thicknesses shown in FIG. 27. [Figure 29]13 is a graph of Example 10 in which the relationship between the wavelength of illumination light and the reflectance of reflected light is calculated for each thickness of a protective film formed on the surface of a silicon semiconductor wafer. [Figure 30] 30 is a table showing the calculation results of the average reflectance and reduction rate of reflected light when illumination light in "illumination wavelength range a" to "illumination wavelength range c" is used for each of the four film thicknesses shown in FIG. 29. [Figure 31] 10 is a graph of a comparative example in which the relationship between the wavelength of illumination light and the reflectance of reflected light is calculated for each thickness of a protective film formed on the surface of an aluminum semiconductor wafer. [Figure 32] 32 is a table showing the calculation results of the average reflectance and reduction rate of reflected light when illumination light in "illumination wavelength range d" to "illumination wavelength range f" is used for each of the four film thicknesses shown in FIG. 31. DETAILED DESCRIPTION OF THE INVENTION

[0023] [First embodiment] FIG. 1 is a schematic diagram of a coating status detecting device 10 according to a first embodiment. FIG. 2 is an enlarged cross-sectional view of a semiconductor wafer W in FIG. 1. As shown in FIGS. 1 and 2, the coating status detecting device 10 detects the coating status of a protective film 9 that has been coated (formed) on the surface of a semiconductor wafer W, which is a workpiece, by a known coating method such as spin coating before laser processing of the semiconductor wafer W. In other words, it detects whether or not there is any uncoated portion of the protective film 9 on the surface of the semiconductor wafer W. Hereinafter, the term "surface of the semiconductor wafer W" refers to the surface of the protective film 9 in a coated area WA (see FIG. 3) on the surface of the semiconductor wafer W where the protective film 9 is coated, and refers to the surface of the semiconductor wafer W itself in an uncoated area WB (see FIG. 3) of the protective film 9.

[0024] The application status detecting device 10 is roughly divided into an illumination optical system 12 and a detection optical system 16 which constitute the measuring unit of the present invention, and a control device 20.

[0025] The illumination optical system 12 has an illumination optical axis O1 that is inclined with respect to the normal H to the surface of the semiconductor wafer W, and illuminates the surface of the semiconductor wafer W from an oblique direction. The illumination optical system 12 includes a broadband light source 13 and a diffuser 14 that are arranged along the illumination optical axis O1.

[0026] The broadband light source 13 emits broadband light, such as white light, as illumination light L1. Note that the broadband light is not limited to light in the visible wavelength range, and may also include light in the near-infrared and near-ultraviolet ranges. The illumination wavelength range of this illumination light L1 will be described later.

[0027] The diffuser plate 14 diffuses the illumination light L1 emitted from the broadband light source 13 and then makes the light incident obliquely on the surface of the semiconductor wafer W. This allows the illumination light L1 to illuminate a wide range of the surface of the semiconductor wafer W. Note that if the broadband light source 13 is a surface light source, the diffuser plate 14 may be omitted. Also, a reflector or the like may be disposed instead of the diffuser plate 14.

[0028] Illumination light L1 incident on the surface of the semiconductor wafer W at an incident angle θ1 is reflected by the surface of the semiconductor wafer W (including the surface of the protective film 9). As a result, reflected light L2 is emitted from the surface of the semiconductor wafer W at a reflection angle θ3. Here, the reflected light L2 of illumination light L1 incident on the coating area WA of the protective film 9 on the surface of the semiconductor wafer W at an incident angle θ1 includes a first reflected light L2A reflected by the surface of the protective film 9 and a second reflected light L2B reflected by the back surface of the protective film 9 (see FIG. 2). Note that the symbol θ2 in FIG. 2 indicates the refraction angle of illumination light L1 by the protective film 9.

[0029] In the coated area WA of the protective film 9, thin film interference occurs, in which the first reflected light L2A and the second reflected light L2B reflected by the front and back surfaces of the protective film 9 interfere with each other. Therefore, the first reflected light L2A and the second reflected light L2B strengthen or weaken each other depending on the wavelength of the illumination light L1 (reflected light L2), the material of the semiconductor wafer W, the reflection angle θ3 (incident angle θ1), and the film thickness d of the protective film 9. This changes the reflectance of the reflected light L2 reflected in the coated area WA.

[0030] On the other hand, the reflected light L2 of the illumination light L1 incident at an incident angle θ1 on the uncoated region WB of the protective film 9 on the surface of the semiconductor wafer W (see FIG. 3) contains only light reflected by the surface of the semiconductor wafer W. As a result, in the uncoated region WB, no change in the reflectance of the reflected light L2 due to thin film interference occurs.

[0031] The detection optical system 16 has a detection optical axis O2 that is inclined in the opposite direction to the illumination optical axis O1 with respect to the normal line H, and receives reflected light L2 reflected from the surface (coated area WA, uncoated area WB, see FIG. 3) of the semiconductor wafer W. The detection optical system 16 includes a lens 17 and a detector 18 that are arranged along the detection optical axis O2.

[0032] The lens 17 focuses the reflected light L2 reflected by the surface of the semiconductor wafer W onto the light receiving surface of the detector 18.

[0033] The detector 18 is a two-dimensional light receiving sensor having sensitivity in the wavelength range used for detection, and may be, for example, an image pickup element (camera), a photodetector, etc. The detector 18 outputs a light receiving signal of the reflected light L2 received through the lens 17 to the control device 20.

[0034] The control device 20 comprehensively controls the operations of the illumination optical system 12 and the detection optical system 16 and detects the coating status of the protective film 9 formed on the surface of the semiconductor wafer W. The control device 20 is configured by an arithmetic device such as a personal computer, and includes an arithmetic circuit composed of various processors, memories, etc. The various processors include a central processing unit (CPU), a graphics processing unit (GPU), an application specific integrated circuit (ASIC), and a programmable logic device (e.g., a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA)). The various functions of the control device 20 may be realized by a single processor or by multiple processors of the same or different types.

[0035] The control device 20 functions as a measurement control unit 21 and an application status detection unit 22 by executing a control program (not shown).

[0036] The measurement control unit 21 controls the operation of the broadband light source 13 and the detector 18. For example, in response to an operator's operation to start measurement or when the semiconductor wafer W is set at a predetermined inspection position, the measurement control unit 21 causes the broadband light source 13 to emit illumination light L1 and the detector 18 to receive reflected light L2 and output a light reception signal. As a result, a light reception signal of reflected light L2 is input from the detector 18 to the application status detection unit 22.

[0037] The coating state detection unit 22 detects the coating state of the protective film 9 formed on the surface of the semiconductor wafer W based on the light reception signal of the reflected light L2 input from the detector .

[0038] Fig. 3 is an explanatory diagram for explaining an example of detection of the coating status of the protective film 9 by the coating status detection unit 22. When the protective film 9 is coated on the surface of the semiconductor wafer W as indicated by reference numerals 3A and 3B in Fig. 3, the area on the surface of the semiconductor wafer W where the protective film 9 is coated is the coated area WA, and the area where the protective film 9 remains uncoated is the uncoated area WB, as indicated by reference numeral 3C.

[0039] The reflectance (intensity) of the reflected light L2 reflected from the coated area WA is equal to or less than the reflectance (intensity) of the reflected light L2 reflected from the uncoated area WB due to thin-film interference in the protective film 9. Therefore, when the reflectance of the reflected light L2 from the coated area WA is smaller than the reflectance of the reflected light L2 from the uncoated area WB, the intensity of the reflected light L2 from the coated area WA received by the detector 18 will be smaller than the intensity of the reflected light L2 from the uncoated area WB. In this case, the distribution of the coated area WA and the uncoated area WB on the surface of the semiconductor wafer W can be detected from the brightness distribution (brightness / darkness) on the surface of the semiconductor wafer W detected based on the light reception signal output from the detector 18.

[0040] Therefore, the coating status detection unit 22 detects the brightness distribution on the surface of the semiconductor wafer W based on the light receiving signal of the reflected light L2 input from the detector 18, thereby detecting the coating status of the protective film 9, i.e., detecting whether or not there is an uncoated area WB.

[0041] In order for the coating status detection unit 22 to detect the coating status of the protective film 9 with high accuracy based on the light reception signal of the reflected light L2, the brightness of the coated area WA on the surface of the semiconductor wafer W must be sufficiently lower than the brightness of the uncoated area WB. Therefore, the reflectance of the reflected light L2 in the coated area WA must be sufficiently lower than the reflectance of the reflected light L2 in the uncoated area WB.

[0042] Here, the reflectance of the reflected light L2 in the coating area WA is affected by thin film interference, which varies depending on various measurement conditions, such as the wavelength of the reflected light L2 (illumination light L1), the material of the semiconductor wafer W, the reflection angle θ3, and the film thickness d of the protective film 9, as shown in Figures 4 to 8 below.

[0043] FIG. 4 is a graph showing an example of the relationship between the wavelength of the reflected light L2 and the reflectance of the reflected light L2 for each material of the semiconductor wafer W.

[0044] As shown in FIG. 4, the reflectance of the reflected light L2 at the coating area WA varies depending on the wavelength of the reflected light L2 and the material of the semiconductor wafer W [silicon (Si), copper (Cu), aluminum (Al)].

[0045] Fig. 5 is an enlarged cross-sectional view of the protective film 9. Fig. 6 is a graph showing an example of the relationship between the wavelength of the reflected light L2 and the reflectance of the reflected light L2 for each thickness d of the protective film 9.

[0046] 5, the thickness d of the protective film 9 is not uniform due to the characteristics of the spin coating method used to apply the protective film 9 and the influence of the unevenness of the wiring pattern formed on the surface of the semiconductor wafer W. Furthermore, as shown in FIG. 6, the reflectance of the reflected light L2 in the coating area WA changes depending on the wavelength of the reflected light L2 and the thickness d of the protective film 9.

[0047] Fig. 7 is an explanatory diagram for explaining changes in the reflection angle θ3 of the reflected light L2 depending on the position on the surface (on the coating area WA) of the semiconductor wafer W. Fig. 8 is a graph showing an example of the relationship between the wavelength of the reflected light L2 and the reflectance of the reflected light L2 for each reflection angle θ3 of the reflected light L2.

[0048] 7, the illumination optical system 12 illuminates a wide range of the surface of the semiconductor wafer W with illumination light L1 through the diffuser plate 14, so that the incident angle θ1 of the illumination light L1 changes depending on the position on the surface (on the coating area WA) of the semiconductor wafer W. Therefore, the reflection angle θ3 of the reflected light L2 incident on the detector 18 changes depending on the position on the surface of the semiconductor wafer W. Then, as shown in FIG. 8, the reflectance of the reflected light L2 on the coating area WA changes depending on the wavelength and reflection angle θ3 of the reflected light L2.

[0049] As described above, the reflectance of the reflected light L2 from the coated area WA varies depending on various measurement conditions, such as the wavelength of the reflected light L2 (illumination light L1), the material of the semiconductor wafer W, the reflection angle θ3, and the film thickness d. Therefore, as shown in Figures 4, 6, and 8, when the illumination wavelength range of the illumination light L1 is narrow (including a single wavelength), the reflectance of the reflected light L2 from the coated area WA may not be sufficiently lower than the reflectance of the reflected light L2 from the uncoated area WB, depending on the measurement conditions. In this case, the difference in brightness between the coated area WA and the uncoated area WB becomes smaller, and the accuracy of the detection of the coating status of the protective film 9 (whether or not there is an uncoated area WB) by the coating status detection unit 22 may be reduced.

[0050] Therefore, in this embodiment, by adjusting the wavelength range of the reflected light L2, i.e., the illumination wavelength range of the illumination light L1 emitted from the broadband light source 13, the reflectance of the reflected light L2 in the coated area WA is made sufficiently lower than the reflectance of the reflected light L2 in the uncoated area WB, regardless of measurement conditions other than the illumination wavelength range (such as the material of the semiconductor wafer W, the reflection angle θ3, and the film thickness d).

[0051] 9 is an explanatory diagram for explaining the setting of the illumination wavelength range of the illumination light L1 from the broadband light source 13, and is a graph showing an example of the relationship between the wavelength of the illumination light L1 (reflected light L2) and the reflectance of the reflected light L2 for each film thickness d of the protective film 9. In the figure, film thickness d=0 μm indicates a semiconductor wafer W on which the protective film 9 is not applied.

[0052] As shown in FIG. 9, the waveform showing the change in reflectance of reflected light L2 with respect to the wavelength of illumination light L1 (hereinafter referred to as the reflectance waveform) is a roughly trigonometric waveform, and the wavelength of the reflectance waveform changes depending on the magnitude of film thickness d. Therefore, for each film thickness d, the reflectance of reflected light L2 increases at a certain wavelength of illumination light L1 and decreases at a different wavelength of illumination light L1. Therefore, by using broadband light with an illumination wavelength range of, for example, 400 nm to 1000 nm as illumination light L1, the reflectance of reflected light L2 is averaged across the illumination wavelength range of illumination light L1. As a result, the reflectance of reflected light L2 when "film thickness d > 0" can be reliably reduced compared to the reflectance of reflected light L2 when "film thickness d = 0."

[0053] Therefore, in this embodiment, the illumination wavelength range of illumination light L1 is determined so that the reflectance of reflected light L2 is averaged over one cycle T (one wavelength) of the reflectance waveform with the longest wavelength among the reflectance waveforms corresponding to multiple film thicknesses d, that is, over one cycle T of the reflectance waveform corresponding to the smallest film thickness d at which the coating state can be detected (film thickness d=0.5 μm in FIG. 9). Specifically, the illumination wavelength range of illumination light L1 is set to a wavelength bandwidth equivalent to one cycle T within a wavelength range of 400 nm to 1000 nm (see FIG. 10 described below). A method for determining the illumination wavelength range of illumination light L1 that satisfies these conditions will now be described in detail.

[0054] The illumination wavelength range of illumination light L1 is determined based on the refractive index of protective film 9, the incident angle θ1 (refractive angle θ2) of illumination light L1, and the film thickness d of protective film 9. Here, if the refractive index of protective film 9 is "n" and the optical path difference between the first reflected light L2A and the second reflected light L2B shown in Figure 2 is "a," this optical path difference a is expressed as "a = 2nd cos θ2." Note that the refraction angle θ2 is determined based on the refractive index n and the incident angle θ1.

[0055] The short wavelength limit of the illumination wavelength range of the illumination light L1 is λ L The long wavelength limit of the illumination light L1 is λ H In this case, the wavelength λ L In the optical path difference a, [(2ndcosθ2) / λ LIn this state, when the wavelength is increased, the next wavelength λ H Assuming that the optical path difference is equal to a at , the relationship in the following equation (1) is satisfied.

[0056]

number

[0057] The above formula [1] can be transformed into the following formulas [2] to [6], and is finally transformed into the following formula [7]. Note that instead of formula [7], formula [8] can also be transformed.

[0058]

number

[0059]

number

[0060]

number

[0061]

number

[0062]

number

[0063]

number

[0064]

number

[0065] 10 is a graph showing an example of the relationship between the wavelength of reflected light L2 corresponding to the minimum thickness d of the protective film 9 (here, d = 0.5 μm) and the reflectance of reflected light L2. As shown in FIG. 10, the above formula [7] (or formula [8], which also applies below) indicates that, even if the film thickness d is the minimum thickness, the reflectance of reflected light L2 in the coating area WA can be reduced by the coating status detection unit 22, so long as the illumination wavelength range of the illumination light L1 is a wavelength bandwidth of one period T or more. Therefore, a broadband light source 13 capable of emitting illumination light L1 in an illumination wavelength range that satisfies the above formula [7] is used.

[0066] Note that instead of determining the illumination wavelength range of illumination light L1 so that the reflectance of reflected light L2 is averaged over one period T, the illumination wavelength range of illumination light L1 may be determined so that the reflectance of reflected light L2 is averaged over a half period T / 2 (half the wavelength). In this case, the following [Equation 10] is obtained from the following [Equation 9], which is a modification of the above [Equation 1], and a broadband light source 13 that satisfies this [Equation 10] is used. Note that the following [Equation 11] may be obtained from the following [Equation 9] instead of the [Equation 10], and a broadband light source 13 that can emit illumination light L1 in an illumination wavelength range that satisfies this [Equation 11] may be used.

[0067]

number

[0068]

number

[0069]

number

[0070] A similar method can be used to determine the illumination wavelength range of illumination light L1 such that the reflectance of reflected light L2 is averaged over one cycle T or half cycle T / 2 of the reflectance waveform with the longest wavelength among the reflectance waveforms corresponding to multiple materials of semiconductor wafer W (see FIG. 4).A similar method can also be used to determine the illumination wavelength range of illumination light L1 such that the reflectance of reflected light L2 is averaged over one cycle T or half cycle T / 2 of the reflectance waveform with the longest wavelength among the reflectance waveforms corresponding to multiple reflection angles θ3 (see FIG. 8).

[0071] Furthermore, the illumination wavelength range of the illumination light L1 may be determined so that the reflectance of the reflected light L2 is averaged over one period T or half period T / 2 of the reflectance waveform with the longest wavelength among the reflectance waveforms corresponding to multiple measurement conditions (e.g., the material of the semiconductor wafer W, the reflection angle θ3, and the film thickness d). In this case, regardless of the above-mentioned measurement conditions, the reflectance of the reflected light L2 in the coated area WA can be made sufficiently lower than the reflectance of the reflected light L2 in the uncoated area WB.

[0072] FIG. 11 is a flowchart showing the flow of the process of detecting the application status of the protective film 9 by the application status detecting device 10 of the first embodiment, in accordance with the application status detecting method of the present invention.

[0073] 11, first, among the reflectance waveforms corresponding to a plurality of measurement conditions (material of the semiconductor wafer W, reflection angle θ3, and film thickness d), an illumination wavelength range of illumination light L1 is determined such that the reflectance of reflected light L2 is averaged over one period T or half period T / 2 of the reflectance waveform with the longest wavelength (step S1). Then, a broadband light source 13 capable of emitting illumination light L1 corresponding to the determined illumination wavelength range is used in the application status detection device 10. Note that if the broadband light source 13 is capable of changing the illumination wavelength range of illumination light L1, the control device 20 controls the broadband light source 13 so that the illumination wavelength range is set to the illumination wavelength range determined in step S1. This completes preparations for detection of the application status of the protective film 9 by the application status detection device 10.

[0074] When an operator performs an operation to start measurement or when the semiconductor wafer W coated with the protective film 9 is set at a predetermined inspection position, the measurement control unit 21 causes the broadband light source 13 to emit illumination light L1 (step S2), and the detector 18 to receive reflected light L2 and output a light reception signal (step S3) (corresponding to the measurement step of the present invention). As a result, a light reception signal of the reflected light L2 is input from the detector 18 to the coating status detection unit 22.

[0075] Next, the coating status detection unit 22 detects the brightness distribution on the surface of the semiconductor wafer W based on the light reception signal of the reflected light L2 input from the detector 18 (step S4). At this time, by using the broadband light source 13 with the illumination wavelength range determined in step S1, the reflectance of the reflected light L2 is averaged over this illumination wavelength range. This makes it possible to make the reflectance of the reflected light L2 reflected from the coated area WA sufficiently lower than the reflectance of the reflected light L2 reflected from the uncoated area WB due to thin film interference, and to increase the difference in brightness between the coated area WA and the uncoated area WB on the surface of the semiconductor wafer W.

[0076] Then, the coating status detection unit 22 detects the coating status of the protective film 9 on the surface of the semiconductor wafer W, i.e., detects the presence or absence of an uncoated area WB, based on the detection result of the brightness distribution on the surface of the semiconductor wafer W (step S5, which corresponds to the coating status detection step of the present invention). As described above, the illumination wavelength range of the illumination light L1 is adjusted so as to increase the difference in brightness between the coated area WA and the uncoated area WB, thereby improving the detection accuracy of the coating status of the protective film 9 by the coating status detection unit 22.

[0077] As described above, in the coating status detecting device 10 of the first embodiment, the reflectance of the reflected light L2 is averaged by using broadband light as the illumination light L1, so that the reflectance of the reflected light L2 reflected from the coated area WA can be made sufficiently lower than the reflectance of the reflected light L2 reflected from the uncoated area WB. As a result, there is no need to use an excitation light source and a highly sensitive photomultiplier tube, or an illumination optical system and a detection optical system compatible with infrared light, so that the coating status of the protective film 9 coated on the surface of the semiconductor wafer W can be detected simply and at low cost.

[0078] [Second embodiment] Next, a description will be given of a coating status detecting device 10 of a second embodiment. In the coating status detecting device 10 of the first embodiment, the coating status detecting unit 22 detects the coating status of the protective film 9 on the surface of the semiconductor wafer W based on the detection result of the brightness distribution on the surface of the semiconductor wafer W. In contrast, the coating status detecting device 10 of the second embodiment detects the coating status of the protective film 9 on the surface of the semiconductor wafer W based on reflected light L2 from the surface of the semiconductor wafer W before and after the coating of the protective film 9.

[0079] The application status detecting device 10 of the second embodiment has basically the same configuration as the application status detecting device 10 of the first embodiment, except for some differences in the functions of the measurement control unit 21 and the application status detecting unit 22 of the control device 20. Therefore, parts that are the same in function or configuration as those of the first embodiment are given the same reference numerals, and descriptions thereof will be omitted.

[0080] 12 is a flowchart showing the flow of the process of detecting the coating status of the protective film 9 by the coating status detecting device 10 of the second embodiment, which is related to the coating status detecting method of the present invention. Note that the determination of the illumination wavelength range of the illumination light L1 in step S10 is the same as in the first embodiment described with reference to FIG. 11, and therefore a detailed description thereof will be omitted here.

[0081] First, a semiconductor wafer W before being coated with the protective film 9 is set in the coating status detection device 10 (step S11). This semiconductor wafer W is not limited to a product wafer, and various test wafers may also be used.

[0082] Next, the measurement control unit 21 causes the broadband light source 13 to emit illumination light L1 (step S12), and causes the detector 18 to receive reflected light L2 and output a light reception signal (step S13) (corresponding to the measurement step of the present invention). As a result, a light reception signal of reflected light L2 is input from the detector 18 to the application status detection unit 22, and the application status detection unit 22 acquires a photographed image of the semiconductor wafer W based on the detection signal of reflected light L2 (step S14).

[0083] In addition, by storing the captured image acquired in step S14 in a memory unit (including a database) not shown, if the measurement conditions [wavelength of illumination light L1, material of semiconductor wafer W, incident angle θ1 (reflection angle θ3)] are the same, the processing from step S11 to step S14 can be omitted when detecting the application status of protective film 9 from the next time onwards.

[0084] When the acquisition of the photographed image is completed, the semiconductor wafer W coated with the protective film 9 is set in the coating status detection device 10 (step S15).

[0085] Then, the measurement control unit 21 repeatedly controls the broadband light source 13 to emit illumination light L1 (step S16) and the detector 18 to receive reflected light L2 and output a light reception signal (step S17) (corresponding to the measurement step of the present invention). As a result, a light reception signal of reflected light L2 is input from the detector 18 to the coating status detection unit 22, and the coating status detection unit 22 acquires a photographed image of the semiconductor wafer W (coated area WA, uncoated area WB) based on the detection signal of reflected light L2 (step S18).

[0086] When the coating status detection unit 22 acquires photographed images of the semiconductor wafer W before and after the application of the protective film 9, it detects the coating status of the protective film 9 on the surface of the semiconductor wafer W from the difference or ratio between the output values ​​(pixel values) in the photographed images before and after the application of the protective film 9 (steps S19 and S20). For example, if the photographed image is an 8-bit image, the coating status detection unit 22 calculates the ratio using the following formula [Equation 12]. Then, the coating status detection unit 22 detects the coating status of the protective film 9 on the surface of the semiconductor wafer W based on whether the calculated ratio is equal to or greater than a predetermined threshold value [for example, 248 (97% of 255)].

[0087]

number

[0088] As described above, in the second embodiment, by using the broadband light source 13 with the illumination wavelength range determined in step S10, the reflectance of reflected light L2 is averaged across this illumination wavelength range, making it possible to make the reflectance of reflected light L2 reflected from the coated area WA sufficiently lower than the reflectance of reflected light L2 reflected from the uncoated area WB. As a result, the presence or absence of the uncoated area WB is clearly reflected in the calculation result of the ratio, thereby improving the accuracy with which the coating status of the protective film 9 is detected by the coating status detection unit 22. This provides the same effects as those of the first embodiment in the second embodiment.

[0089] [Third embodiment] Figure 13 is a schematic diagram of an application status detecting device 10 of a third embodiment. In the application status detecting device 10 of each of the above-described embodiments, illumination light L1 illuminates the surface of the semiconductor wafer W from an oblique direction, and reflected light L2 reflected obliquely from the surface of the semiconductor wafer W is received by a detector 18. In contrast, as shown in Figure 13, the application status detecting device 10 of the third embodiment employs a coaxial epi-illumination system. Note that components that are the same in function or configuration as those of the above-described embodiments are designated by the same reference numerals, and their description will be omitted.

[0090] The application status detecting device 10 of the third embodiment includes an illumination optical system 12A, a detection optical system 16A, a beam splitter 32, and a control device 20.

[0091] The illumination optical system 12A has an illumination optical axis O1A perpendicular to the normal line H, and emits illumination light L1 toward a beam splitter 32. The illumination optical system 12A includes a broadband light source 13 and a lens 30 arranged along the illumination optical axis O1A.

[0092] The broadband light source 13 emits illumination light L1 in the same manner as in the above-described embodiments. At this time, the illumination wavelength range of the illumination light L1 is determined in the same manner as in the first embodiment. As a result, the illumination light L1 emitted from the broadband light source 13 passes through a lens 30 and enters a beam splitter 32.

[0093] The beam splitter 32 is disposed at the intersection of the illumination optical axis O1A and the detection optical axis O2A of the detection optical system 16A, which will be described later. The beam splitter 32 reflects a portion of the illumination light L1 incident from the illumination optical system 12A toward the surface of the semiconductor wafer W. This causes the illumination light L1 to be perpendicularly incident on the surface of the semiconductor wafer W. The beam splitter 32 also transmits a portion of the reflected light L2 reflected by the surface of the semiconductor wafer W, and outputs the reflected light to the detection optical system 16A.

[0094] The detection optical system 16A has a detection optical axis O2A parallel to the normal line H, and includes a lens 17 and a detector 18 arranged along this detection optical axis O2A. The detector 18 receives reflected light L2 incident from the beam splitter 32 through the lens 17, and outputs a light reception signal to the control device 20.

[0095] The control device 20 of the third embodiment has the same configuration as the control device 20 of each of the above-described embodiments, and functions as a measurement control unit 21 and an application status detection unit 22. As a result, similar to each of the above-described embodiments, the measurement control unit 21 controls the operation of the broadband light source 13 and the detector 18, and the application status detection unit 22 detects the application status of the protective film 9. As a result, the third embodiment also provides the same effects as the first embodiment.

[0096] The coaxial incident illumination method described in the third embodiment is suitable for magnifying and observing the central portion of the field of view of the detection optical system 16A, and therefore, when detecting the coating condition of the protective film 9 on the surface of a wide area of ​​the semiconductor wafer W, it is preferable to adopt the oblique illumination method described in each of the above embodiments.

[0097] [Fourth embodiment] Fig. 14 is a schematic diagram of an application status detecting device 10 of a fourth embodiment. As shown in Fig. 14, the application status detecting device 10 of the fourth embodiment employs a ring illumination system. Note that components that are the same in function or configuration as those of the above-described embodiments are given the same reference numerals, and descriptions thereof will be omitted.

[0098] The application status detecting device 10 of the fourth embodiment includes a ring illumination light source 12B, a detection optical system 16B, and a control device 20.

[0099] The ring illumination light source 12B is disposed above the surface of the semiconductor wafer W and emits ring-shaped illumination light L1. As a result, the illumination light L1 from the ring illumination light source 12B is incident on the surface of the semiconductor wafer W, and part of the reflected light L2 reflected by the surface of the semiconductor wafer W passes through the central spatial region of the ring illumination light source 12B and enters the detection optical system 16B.

[0100] The detection optical system 16B has a detection optical axis O2B parallel to the normal line H, similar to the detection optical system 16A of the third embodiment, and includes a lens 17 and a detector 18 arranged along this detection optical axis O2B. The detector 18 receives reflected light L2 incident through the lens 17 and outputs a light reception signal to the control device 20.

[0101] The control device 20 of the fourth embodiment has the same configuration as the control device 20 of each of the above-described embodiments, and functions as a measurement control unit 21 and an application status detection unit 22. As a result, similar to each of the above-described embodiments, the measurement control unit 21 controls the operation of the broadband light source 13 and the detector 18, and the application status detection unit 22 detects the application status of the protective film 9. As a result, the fourth embodiment also provides the same effects as the first embodiment.

[0102] Although the ring illumination method can illuminate a wide range of the surface of the semiconductor wafer W, like the oblique illumination method described in the first and second embodiments, the illumination light L1 is not specularly reflected in the central part of the field of view, which may result in a lower detection accuracy for the coating status of the protective film 9 than in the first and second embodiments. For this reason, it is preferable to employ the oblique illumination method described in the first and second embodiments.

[0103] [others] In each of the above embodiments, an application status detection device 10 that detects the application status of a protective film 9 applied to the surface of a semiconductor wafer W has been used as an example, but the present invention can also be applied to an application status detection device that detects the application status of various protective films applied to various workpieces.

[0104] [Examples and Comparative Examples] Below, Examples 1 to 10 of the present invention and a comparative example are shown to explain how using broadband light as illumination light L1 reduces the reflectance of reflected light L2 from the coated area WA compared to the reflectance of reflected light L2 from the uncoated area WB, but the present invention is not limited to these Examples.

[0105] Example 1 FIG. 15 is a graph of Example 1 in which the relationship between the illumination wavelength range of the illumination light L1 and the reduction rate of the reflected light L2 is calculated for each combination (55 patterns in total) of a plurality of film thicknesses d and a plurality of reflection angles θ3.

[0106] As shown in Fig. 15, a total of 55 patterns (=11 x 5) of combinations of semiconductor wafers W were assumed, which consisted of 11 types of film thickness d (900 nm, 920 nm, 940 nm, 960 nm, 980 nm, 1000 nm, 1020 nm, 1040 nm, 1060 nm, 1080 nm, 1010 nm) and five types of reflection angle θ3 (10°, 20°, 30°, 40°, 50°). For each combination, the short wavelength limit λ of the illumination wavelength range of the illumination light L1 was L With the wavelength fixed at 500 nm, the long wavelength limit λ H The reduction rate of the reflected light L2 at each step was calculated while increasing the value in steps. Note that a reduction rate of 0% indicates the reduction rate of the reflected light L2 reflected from the surface of a semiconductor wafer W or the like that is not coated with the protective film 9 (the same applies below).

[0107] Long wavelength limit λ H It was confirmed that the reflectance of the reflected light L2 in the coating area WA (protective film 9) decreases as the illumination wavelength range of the illumination light L1 is gradually increased, that is, as the illumination wavelength range of the illumination light L1 is gradually widened, due to the averaging of the reflectance of the reflected light L2 over this illumination wavelength range.

[0108] <Example 2> FIG. 16 is a graph of Example 2 in which the relationship between the illumination wavelength range of the illumination light L1 and the reduction rate of the reflected light L2 is calculated for each combination (55 patterns in total) of a plurality of film thicknesses d and a plurality of reflection angles θ3.

[0109] 16, similarly to Example 1, a total of 55 patterns (=11×5) of combinations of semiconductor wafers W with 11 types of film thickness d and 5 types of reflection angles θ3 were assumed. In each combination, the long wavelength limit λ of the illumination wavelength range of the illumination light L1 was H With the short wavelength limit λ fixed at 600 nm L The reduction rate of the reflected light L2 was calculated at each step while gradually decreasing the value of [Formula 7]. Note that the arrow A1 in Fig. 16 indicates the range that satisfies the above formula [Formula 10] (or formula [Formula 11]; the same applies below).

[0110] Short wavelength limit λ LIt was confirmed that, as the illumination wavelength range of illumination light L1 is gradually decreased, i.e., as the illumination wavelength range of illumination light L1 is gradually widened, the reflectance of reflected light L2 at the coated area WA (protective film 9) decreases due to the averaging of the reflectance of reflected light L2 over this illumination wavelength range. In particular, it was confirmed that the reflectance of reflected light L2 is sufficiently reduced in the illumination wavelength ranges indicated by arrows A1 and A2. It was also confirmed that the reflectance of reflected light L2 is lower in the illumination wavelength range indicated by arrow A1 than in the illumination wavelength range indicated by arrow A2.

[0111] Example 3 FIG. 17 is a graph of Example 3 in which the relationship between the illumination wavelength range of the illumination light L1 and the reduction rate of the reflected light L2 is calculated for each combination (55 patterns in total) of a plurality of film thicknesses d and a plurality of reflection angles θ3.

[0112] As shown in Fig. 17, similar to Example 1, a total of 55 patterns (=11 x 5) of semiconductor wafers W were assumed, each consisting of 11 types of film thickness d and 5 types of reflection angle θ3. Then, for each combination, the reduction rate of the reflected light L2 for each of the seven types of illumination light L1 in the illumination wavelength range was calculated. Here, the patterns of the seven types of illumination wavelength range were calculated based on the long wavelength limit λ H is changed in steps of 100 nm from 1000 nm to 400 nm, and the individual long wavelength limit λ H The short wavelength limit λ satisfies the following equation

[13] for each L The following is set.

[0113]

number

[0114] It has been confirmed that by setting the illumination wavelength range of the illumination light L1 to a range that satisfies the above equation [Equation 13], i.e., the above equation [Equation 10], the reflectance of the reflected light L2 in the coating area WA (protective film 9) is reduced.

[0115] Example 4 FIG. 18 is a graph of Example 4 in which the relationship between the illumination wavelength range of the illumination light L1 and the reduction rate of the reflected light L2 is calculated for each combination (55 patterns in total) of a plurality of film thicknesses d and a plurality of reflection angles θ3.

[0116] As shown in Fig. 18, similar to Example 1, a total of 55 patterns (=11 x 5) of semiconductor wafers W were assumed, each consisting of 11 types of film thickness d and 5 types of reflection angle θ3. Then, for each combination, the reduction rate of the reflected light L2 for each of the seven types of illumination light L1 in the illumination wavelength range was calculated. Here, the patterns for the seven types of illumination wavelength range are as follows: H is changed in steps of 100 nm from 1000 nm to 400 nm, and the individual long wavelength limit λ H The short wavelength limit λ satisfies the following equation

[14] for each L The following is set.

[0117]

number

[0118] It was confirmed that the reflectance of the reflected light L2 in the coating area WA (protective film 9) was reduced by setting the illumination wavelength range of the illumination light L1 to the range that satisfies the above equation (14), i.e., the above equation (7). Furthermore, it was confirmed that the reflectance of the reflected light L2 in Example 4 was lower than that in Example 3.

[0119] <Example 5> 19 is a graph of Example 5 in which the relationship between the wavelength of illumination light L1 and the reflectance of reflected light L2 was calculated for each film thickness d of the protective film 9 formed on the surface of an aluminum semiconductor wafer W. As shown in FIG. 19, semiconductor wafers W with four different film thicknesses d (0 μm, 0.5 μm, 1 μm, and 1.5 μm) were assumed. Then, the relationship between the wavelength of illumination light L1 (350 nm to 1000 nm) and the reflectance of reflected light L2 was calculated for each of the four types of semiconductor wafers W using a coaxial epi-illumination method like the coating status detecting device 10 of the third embodiment.

[0120] Note that "illumination wavelength range a" in Figure 19 is a wavelength range that at least satisfies the above equation (7) under the conditions of refractive index n = 1.5, incident angle θ1 = 0°, and film thickness d ≧ 0.5 μm. Note that the refraction angle θ2 in the above equation (7) is determined based on the refractive index n and incident angle θ1. Also, "illumination wavelength range b" and "illumination wavelength range c" in Figure 19 are wavelength ranges that satisfy the above equation (7) with a margin under the above conditions.

[0121] Fig. 20 is a table showing the calculation results of the average reflectance and reduction rate of reflected light L2 when using illumination light L1 in "illumination wavelength range a" to "illumination wavelength range c" for each of the four film thicknesses d shown in Fig. 19. As shown in Fig. 20, it was confirmed that by determining the illumination wavelength range of illumination light L1 so as to satisfy the above-mentioned formula [7], the average reflectance of reflected light L2 in the coating area WA (protective film 9) decreases (the reduction rate increases). Furthermore, it was confirmed that the wider the illumination wavelength range of illumination light L1, the more the average reflectance of reflected light L2 decreases (the reduction rate increases) due to the averaging of the reflectance of reflected light L2.

[0122] Example 6 21 is a graph of Example 6 in which the relationship between the wavelength of illumination light L1 and the reflectance of reflected light L2 was calculated for each film thickness d of the protective film 9 formed on the surface of an aluminum semiconductor wafer W. As shown in FIG. 21, semiconductor wafers W with four different film thicknesses d (0 μm, 0.5 μm, 1 μm, and 1.5 μm) were assumed, as in Example 5. Then, the relationship between the wavelength (350 nm to 1000 nm) of illumination light L1 and the reflectance of reflected light L2 was calculated for each of the four types of semiconductor wafers W using an oblique illumination method like the coating status detecting device 10 of the first or second embodiment.

[0123] Note that "illumination wavelength range a" in Fig. 21 is a wavelength range that at least satisfies the above formula (7) under the conditions of refractive index n = 1.5, incident angle θ1 = 45°, and film thickness d ≥ 0.5 μm. Also, "illumination wavelength range b" and "illumination wavelength range c" in Fig. 21 are wavelength ranges that satisfy the above formula (7) with a margin under the above conditions.

[0124] Fig. 22 is a table showing the calculation results of the average reflectance and reduction rate of reflected light L2 when using illumination light L1 in "illumination wavelength range a" to "illumination wavelength range c" for each of the four film thicknesses d shown in Fig. 21. As shown in Fig. 22, it was confirmed that by determining the illumination wavelength range of illumination light L1 so as to satisfy the above-mentioned formula [7], the average reflectance of reflected light L2 in the coating area WA (protective film 9) decreases (the reduction rate increases). Furthermore, it was confirmed that the wider the illumination wavelength range of illumination light L1, the more the average reflectance of reflected light L2 decreases (the reduction rate increases) due to the averaging of the reflectance of reflected light L2.

[0125] Example 7 Fig. 23 is a graph of Example 7, in which the relationship between the wavelength of illumination light L1 and the reflectance of reflected light L2 was calculated for each film thickness d of the protective film 9 formed on the surface of a copper semiconductor wafer W. As shown in Fig. 23, the reflectance of reflected light L2 was calculated in the same manner as in Example 5 (coaxial epi-illumination method) described above, except that the material of the semiconductor wafer W was copper. Note that "illumination wavelength range a" to "illumination wavelength range c" in Fig. 23 are wavelength ranges that satisfy the above formula [7] under the same conditions as in Example 5, except for the refractive index n (copper).

[0126] Fig. 24 is a table showing the calculation results of the average reflectance and reduction rate of reflected light L2 when using illumination light L1 in "illumination wavelength range a" to "illumination wavelength range c" for each of the four film thicknesses d shown in Fig. 23. As shown in Fig. 24, it was confirmed that by determining the illumination wavelength range of illumination light L1 so as to satisfy the above-mentioned formula [7], the average reflectance of reflected light L2 in the coating area WA (protective film 9) decreases (the reduction rate increases). Furthermore, it was confirmed that the wider the illumination wavelength range of illumination light L1, the more the average reflectance of reflected light L2 decreases (the reduction rate increases) due to the averaging of the reflectance of reflected light L2.

[0127] Example 8 Fig. 25 is a graph of Example 8, in which the relationship between the wavelength of illumination light L1 and the reflectance of reflected light L2 was calculated for each film thickness d of the protective film 9 formed on the surface of a copper semiconductor wafer W. As shown in Fig. 25, the reflectance of reflected light L2 was calculated in the same manner as in Example 6 (oblique illumination method) described above, except that the material of the semiconductor wafer W was copper. Note that "illumination wavelength range a" to "illumination wavelength range c" in Fig. 25 are wavelength ranges that satisfy the above formula [7] under the same conditions as in Example 6, except for the refractive index n (copper).

[0128] Fig. 26 is a table showing the calculation results of the average reflectance and reduction rate of reflected light L2 when using illumination light L1 in "illumination wavelength range a" to "illumination wavelength range c" for each of the four film thicknesses d shown in Fig. 25. As shown in Fig. 26, it was confirmed that by determining the illumination wavelength range of illumination light L1 so as to satisfy the above-mentioned formula [7], the average reflectance of reflected light L2 in the coating area WA (protective film 9) decreases (the reduction rate increases). Furthermore, it was confirmed that the wider the illumination wavelength range of illumination light L1, the more the average reflectance of reflected light L2 decreases (the reduction rate increases) due to the averaging of the reflectance of reflected light L2.

[0129] Example 9 Fig. 27 is a graph of Example 9, in which the relationship between the wavelength of illumination light L1 and the reflectance of reflected light L2 was calculated for each film thickness d of the protective film 9 formed on the surface of a silicon semiconductor wafer W. As shown in Fig. 27, the reflectance of reflected light L2 was calculated in the same manner as in Example 5 (coaxial epi-illumination method) described above, except that the material of the semiconductor wafer W was silicon. Note that "illumination wavelength range a" to "illumination wavelength range c" in Fig. 27 are wavelength ranges that satisfy the above formula [7] under the same conditions as in Example 5, except for the refractive index n (silicon).

[0130] Fig. 28 is a table showing the calculation results of the average reflectance and reduction rate of reflected light L2 when using illumination light L1 in "illumination wavelength range a" to "illumination wavelength range c" for each of the four film thicknesses d shown in Fig. 27. As shown in Fig. 28, it was confirmed that by determining the illumination wavelength range of illumination light L1 so as to satisfy the above-mentioned formula [7], the average reflectance of reflected light L2 in the coating area WA (protective film 9) decreases (the reduction rate increases). Furthermore, it was confirmed that the wider the illumination wavelength range of illumination light L1, the more the average reflectance of reflected light L2 decreases (the reduction rate increases) due to the averaging of the reflectance of reflected light L2.

[0131] Example 10 Fig. 29 is a graph of Example 10, in which the relationship between the wavelength of illumination light L1 and the reflectance of reflected light L2 was calculated for each film thickness d of protective film 9 formed on the surface of a silicon semiconductor wafer W. As shown in Fig. 29, the reflectance of reflected light L2 was calculated in the same manner as in Example 6 (oblique illumination method) described above, except that the material of the semiconductor wafer W was silicon. Note that "illumination wavelength range a" to "illumination wavelength range c" in Fig. 29 are wavelength ranges that satisfy the above formula [7] under the same conditions as in Example 6, except for the refractive index n (silicon).

[0132] Fig. 30 is a table showing the calculation results of the average reflectance and reduction rate of reflected light L2 when using illumination light L1 in "illumination wavelength range a" to "illumination wavelength range c" for each of the four film thicknesses d shown in Fig. 29. As shown in Fig. 30, it was confirmed that by determining the illumination wavelength range of illumination light L1 so as to satisfy the above-mentioned formula [7], the average reflectance of reflected light L2 in the coated area WA (protective film 9) decreases (the reduction rate increases). Furthermore, it was confirmed that the wider the illumination wavelength range of illumination light L1, the more the average reflectance of reflected light L2 decreases (the reduction rate increases) due to the averaging of the reflectance of reflected light L2.

[0133] <Comparative Example> Fig. 31 is a graph of a comparative example in which the relationship between the wavelength of illumination light L1 and the reflectance of reflected light L2 is calculated for each thickness d of protective film 9 formed on the surface of an aluminum semiconductor wafer W, as in Example 5. Note that "illumination wavelength range d," "illumination wavelength range e," and "illumination wavelength range f" shown in Fig. 31 are wavelength ranges in which a part of them does not satisfy the above formula (7) or the above formula (10) under the conditions of refractive index n = 1.5, incident angle θ1 = 0°, and film thickness d ≥ 0.5 µm.

[0134] FIG. 32 is a table showing the calculation results of the average reflectance and reduction rate of reflected light L2 when illumination light L1 having illumination wavelength ranges d through f is used for each of the four film thicknesses d shown in FIG. 31. In FIG. 32, the frame FR1 indicates a case where the above formula (7) is satisfied, the frame FR2 indicates a case where the above formula (7) is satisfied but not, and the frame FR3 indicates a case where the above formula (10) is satisfied. As shown in FIG. 32, when the illumination wavelength range of illumination light L1 is determined so as not to satisfy the above formula (10) (see frame FR3), the reduction in the average reflectance of reflected light L2 in the coated area WA (protective film 9) is suppressed, i.e., the reduction rate of reflected light L2 is smaller, compared to when the illumination wavelength range of illumination light L1 is determined so as to satisfy the above formula (7) or the above formula (10) (see frames FR1 and FR2). [Explanation of symbols]

[0135] 9...protective film, 10...coating status detection device, 12...illumination optical system, 12A...illumination optical system, 12B...ring illumination light source, 13...broadband light, 14...diffuser, 16...detection optical system, 16A...detection optical system, 16B...detection optical system, 17...lens, 18...detector, 20...controller, 21...measurement control unit, 22...coating status detection unit, 30...lens, 32...beam splitter, L1...illumination light, L2...reflected light, L2A...first reflected light, L2B...second reflected light, O1...illumination optical axis, O1A...illumination optical axis, O2...detection optical axis, O2A...detection optical axis, O2B...detection optical axis, W...semiconductor wafer, WA...coated area, WB...uncoated area, a...optical path difference, d...film thickness, n...refractive index, θ1...angle of incidence, θ2...angle of refraction, θ3...angle of reflection, λ H ...Long wavelength side limit, λ L...Short wavelength limit

Claims

1. A coating status detection method for detecting a coating status of a protective film applied to a workpiece, comprising: a measuring step of illuminating the workpiece with broadband light emitted from a broadband light source and receiving reflected light of the broadband light from the workpiece; an uncoated area detection step of detecting an uncoated area where the protective film is not coated from the reflected light received in the measurement step; The coating status detection method includes the steps of:

2. A coating status detection device for detecting a coating status of a protective film applied to a workpiece, comprising: a measurement unit that illuminates the workpiece with broadband light emitted from a broadband light source and receives reflected light of the broadband light from the workpiece; an uncoated area detection unit that detects an uncoated area where the protective film is not coated from the reflected light received by the measurement unit; A coating status detection device comprising:

Images