JP7598532B2 - Coating status detection method and coating status detection device - Google Patents

Description

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

A semiconductor wafer (workpiece) is divided into multiple devices in a lattice pattern by lattice-like streets. Individual devices are manufactured by dividing this semiconductor wafer along the streets. Laser processing machines are well known as machines for dividing semiconductor wafers into multiple devices (chips). Laser processing machines perform laser processing (also called ablation groove processing) in which a laser optical system is moved relative to the semiconductor wafer in the processing feed direction along the streets while irradiating the streets with laser light from the laser optical system, thereby forming processing grooves along the streets.

When performing laser processing of a semiconductor wafer 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. In this case, the protective film is thin, so there is a risk that unevenness or dirt on the surface of the semiconductor wafer may cause areas on the surface of the semiconductor wafer where the protective film is not applied. If laser processing of the semiconductor wafer is performed with such areas remaining, it may cause defects. For this reason, it is necessary to detect the application status of the protective film applied on the surface of the semiconductor wafer before laser processing.

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 unpainted 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 there is a protective film, thereby detecting the presence or absence of unpainted areas on the surface of the semiconductor wafer.

JP 2017-227532 A JP 2017-103281 A JP 2015-065386 A

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, which makes the illumination optical system and detection optical system expensive and complex.

In the protective film detection devices described in Patent Documents 2 and 3, the illumination optical system and detection optical system for using infrared light are also expensive. In addition, the protective film detection devices described in Patent Documents 2 and 3 detect the difference in reflectance of reflected light depending on 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 to the surface of the semiconductor wafer. For this reason, it is not possible to simply determine a reflectance threshold value 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.

The present invention was made in consideration of these circumstances, and aims to provide a coating status detection method and coating status detection device that can easily and inexpensively detect the coating status of a protective film applied to a workpiece.

The 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.

This coating status detection method makes it possible to reduce the reflectance of reflected light in the coated area of the protective film to be lower than the reflectance of reflected light in the uncoated area of the protective film.

In another aspect of the coating status detection method 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 angle of incidence of the illumination light with respect to the surface of the workpiece on which the protective film is coated, and the film thickness of the protective film. This makes it possible to reduce the reflectance of the reflected light in the coated area of the protective film to be lower than the reflectance of the reflected light in the uncoated area of the protective film.

In a coating status detection method according to another aspect 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, and assuming that the refractive index is n, the thickness of the protective film is d, the refraction angle is θ, the short wavelength side limit of the illumination wavelength range of the broadband light source is λ _L , the long wavelength side limit of the illumination wavelength range is λ _H , and the optical path difference between the first reflected light reflected by the front surface of the protective film and the second reflected light reflected by the back surface of the protective film is a = 2nd cos θ, the measurement step

A broadband light source that satisfies formula (1) is used. This makes it possible to take advantage of the phenomenon in which a reduction 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.

In a coating status detection method according to another aspect 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, and assuming that the refractive index is n, the thickness of the protective film is d, the refraction angle is θ, the short wavelength side limit of the illumination wavelength range of the broadband light source is λ _L , the long wavelength side limit of the illumination wavelength range is λ _H , and the optical path difference between the first reflected light reflected by the front surface of the protective film and the second reflected light reflected by the back surface of the protective film is a = 2nd cos θ, the measurement step

A broadband light source that satisfies formula (2) is used. This makes it possible to take advantage of the phenomenon in which a reduction 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.

In another aspect of the coating status detection method of the present invention, the illumination wavelength range of the illumination light is within the range of 400 nm to 1000 nm. This makes it possible to reduce the reflectance of reflected light in the coated area of the protective film to be lower than the reflectance of reflected light in the uncoated area of the protective film.

In the coating status detection method according to another aspect of the present invention, in the coating status detection step, the brightness distribution of the workpiece is detected from the reflected light, and the coating status of the protective film is detected from the brightness distribution of the workpiece. In this way, the coating status of the protective film can be detected from the brightness distribution by utilizing the fact that brightness is reduced due to thin film interference in the coating area where the protective film is applied.

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 obtained based on the 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 the difference or ratio of the 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.

In another aspect of the coating status detection method of the present invention, in the measurement step, illumination light from a broadband light source is incident on the workpiece from an oblique direction. This allows the surface of the workpiece to be illuminated with illumination light over a wide range, making it possible to detect the coating status of the protective film over a wide range.

The 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.

The present invention makes it possible to easily and cheaply detect the coating status of a protective film applied to a workpiece.

1 is a schematic diagram of an application status detection device according to a first embodiment; FIG. 2 is an enlarged cross-sectional view of the semiconductor wafer in FIG. 11 is an explanatory diagram for explaining an example of detection of the coating status of a protective film by a coating status detection unit; FIG. 1 is a graph showing an example of a relationship between the wavelength of reflected light and the reflectance of reflected light for each material of a semiconductor wafer. FIG. 1 is a graph showing an example of a relationship between the wavelength of reflected light and the reflectance of reflected light for each thickness of a protective film. 1 is an explanatory diagram for explaining a change in the reflection angle of reflected light depending on the position on the surface of a semiconductor wafer. 1 is a graph showing an example of a relationship between the wavelength of reflected light and the reflectance of reflected light for each reflection angle of reflected light; FIG. 11 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 a protective film. 11 is a graph showing an example of the relationship between the wavelength of reflected light corresponding to the minimum thickness of a protective film and the reflectance of the reflected light. 5 is a flowchart showing a flow of a process for detecting the coating status of a protective film by the coating status detection device of the first embodiment. 10 is a flowchart showing a procedure for detecting the coating status of a protective film by a coating status detecting device of a second embodiment. FIG. 11 is a schematic diagram of an application status detection device according to a third embodiment. FIG. 13 is a schematic diagram of a coating status detection device according to a fourth embodiment. 11 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. 11 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. 13 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. 13 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. 13 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. 20 is a table showing calculation results of the average reflectance and the 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. 13 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. 22 is a table showing calculation results of the average reflectance and the reduction rate of the 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. 13 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 a protective film formed on the surface of a copper semiconductor wafer. 24 is a table showing calculation results of the average reflectance and the rate of decrease 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. 13 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 a protective film formed on the surface of a copper semiconductor wafer. 26 is a table showing the calculation results of the average reflectance and the reduction rate of the 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. 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 a protective film formed on the surface of a silicon semiconductor wafer. 28 is a table showing the calculation results of the average reflectance and the reduction rate of the 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. 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. 30 is a table showing the calculation results of the average reflectance and the reduction rate of the 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. 11 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. 32 is a table showing the calculation results of the average reflectance and the reduction rate of the reflected light when illumination light in the "illumination wavelength range d" to "illumination wavelength range f" is used for each of the four film thicknesses shown in FIG. 31.

[First embodiment]
FIG. 1 is a schematic diagram of a coating status detection device 10 of the 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 detection device 10 detects the coating status of a protective film 9 that is 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, that is, detects whether or not the protective film 9 is left uncoated 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 the coating 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 the uncoated area WB (see FIG. 3) of the protective film 9.

The application status detection device 10 is broadly composed of an illumination optical system 12 and a detection optical system 16, which constitute the measurement unit of the present invention, and a control device 20.

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

The broadband light source 13 emits broadband light, such as white light, as the 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 range and near ultraviolet range. The illumination wavelength range of this illumination light L1 will be described later.

The diffuser plate 14 diffuses the illumination light L1 emitted from the broadband light source 13 and then makes it incident at an oblique angle on the surface of the semiconductor wafer W. This allows the illumination light L1 to illuminate a wide area 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 placed in place of the diffuser plate 14.

Illumination light L1 incident on the front surface of the semiconductor wafer W at an incident angle θ ₁ is reflected by the front surface of the semiconductor wafer W (including the front surface of the protective film 9). As a result, reflected light L2 is emitted from the front surface of the semiconductor wafer W at a reflection angle θ _3. Here, the reflected light L2 of illumination light L1 incident on the coating area WA of the protective film 9 on the front surface of the semiconductor wafer W at an incident angle θ ₁ includes a first reflected light L2A reflected by the front surface of the protective film 9 and a second reflected light L2B reflected by the rear surface of the protective film 9 (see FIG. 2). Note that the symbol θ ₂ in FIG. 2 indicates the refraction angle of illumination light L1 by the protective film 9.

In the coating 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 θ ₃ (incident angle θ ₁ ), and the film thickness d of the protective film 9. This changes the reflectance of the reflected light L2 reflected in the coating area WA.

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.

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 of the semiconductor wafer W (coated area WA, uncoated area WB, see FIG. 3). This detection optical system 16 includes a lens 17 and a detector 18 that are arranged along the detection optical axis O2.

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.

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

The control device 20 comprehensively controls the operation of the illumination optical system 12 and the detection optical system 16 to detect the coating status of the protective film 9 formed on the surface of the semiconductor wafer W. The control device 20 is configured with a calculation device such as a personal computer, and has a calculation circuit configured with various processors and memories. The various processors include a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), an ASIC (Application Specific Integrated Circuit), and a programmable logic device [e.g., SPLD (Simple Programmable Logic Devices), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Arrays)]. The various functions of the control device 20 may be realized by one processor, or by multiple processors of the same or different types.

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).

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 starting a measurement or the semiconductor wafer W being set at a predetermined inspection position, the measurement control unit 21 causes the broadband light source 13 to emit illumination light L1, and causes the detector 18 to receive reflected light L2 and output a light reception signal. As a result, a light reception signal for reflected light L2 is input from the detector 18 to the application status detection unit 22.

The coating status detection unit 22 detects the coating status of the protective film 9 formed on the surface of the semiconductor wafer W based on the light receiving signal of the reflected light L2 input from the detector 18.

Figure 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 shown by reference characters 3A and 3B in Figure 3, the area on the surface of the semiconductor wafer W where the protective film 9 is coated is the coated area WA, as shown by reference character 3C, and the area where the protective film 9 is left uncoated is the uncoated area WB.

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 is 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 distribution of brightness (light and dark) on the surface of the semiconductor wafer W detected based on the light receiving signal output from the detector 18.

The coating status detection unit 22 detects the coating status of the protective film 9, i.e., detects the presence or absence of uncoated areas WB, by detecting 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.

In this way, 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 receiving signal of the reflected light L2, the brightness of the coating 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 coating area WA must be sufficiently lower than the reflectance of the reflected light L2 in the uncoated area WB.

Here, the reflectance of the reflected light L2 in the coating area WA is affected by thin film interference, and 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 the following Figures 4 to 8.

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

As shown in FIG. 4, the reflectance of the reflected light L2 in 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)].

Figure 5 is an enlarged cross-sectional view of the protective film 9. Figure 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.

As shown in Figure 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. As shown in Figure 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.

Fig. 7 is an explanatory diagram for explaining the change 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.

As shown in Fig. 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 incidence 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.

In this way, the reflectance of the reflected light L2 in the coating 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 θ ₃ , and the film thickness d. For this reason, as shown in Figures 4, 6, and 8, when the illumination wavelength range of the illumination light L1 is a narrow band (including a single wavelength), the reflectance of the reflected light L2 in the coating area WA may not be sufficiently lower than the reflectance of the reflected light L2 in the uncoated area WB depending on the measurement conditions. In this case, the difference between the brightness of the coating area WA and the brightness of the uncoated area WB becomes small, and the detection accuracy of the coating status of the protective film 9 (presence or absence of the uncoated area WB) by the coating status detection unit 22 may decrease.

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 sufficiently reduced below 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 θ ₃ , and the film thickness d).

Figure 9 is an explanatory diagram for explaining the setting of the illumination wavelength range of the illumination light L1 of 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 thickness d of the protective film 9. Note that the thickness d = 0 μm in the figure indicates a semiconductor wafer W on which the protective film 9 is not applied.

As shown in FIG. 9, the waveform (hereinafter referred to as the reflectance waveform) showing the change in reflectance of the reflected light L2 with respect to the wavelength of the illumination light L1 is an approximately trigonometric waveform, and the wavelength of the reflectance waveform changes according to the magnitude of the film thickness d. Therefore, for each film thickness d, the reflectance of the reflected light L2 is high at a certain wavelength of the illumination light L1, and the reflectance of the reflected light L2 is low at another wavelength of the illumination light L1. Therefore, by using broadband light with an illumination wavelength range of, for example, 400 nm to 1000 nm as the illumination light L1, the reflectance of the reflected light L2 is averaged over the illumination wavelength range of the illumination light L1. As a result, the reflectance of the reflected light L2 when "film thickness d>0" can be reliably reduced below the reflectance of the reflected light L2 when "film thickness d=0".

Therefore, in this embodiment, the illumination wavelength range of the illumination light L1 is determined so that the reflectance of the reflected light L2 is averaged over one period 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 period T of the reflectance waveform corresponding to the minimum film thickness d at which the coating status can be detected (film thickness d = 0.5 μm in Figure 9). Specifically, the illumination wavelength range of the illumination light L1 is set to a wavelength bandwidth equivalent to one period T within the wavelength range of 400 nm to 1000 nm (see Figure 10 described below). Below, a method for determining the illumination wavelength range of the illumination light L1 that satisfies such conditions will be specifically described.

The illumination wavelength range of the illumination light L1 is determined based on the refractive index of the protective film 9, the incident angle _θ1 (refractive angle _θ2 ) of the illumination light L1, and the film thickness d of the protective film 9. Here, if the refractive index of the protective film 9 is "n" and the optical path difference between the first reflected light L2A and the second reflected light L2B shown in Fig. 2 is "a", this optical path difference a is expressed as "a = 2nd cos _θ2 ". The refraction angle _θ2 is determined based on the refractive index n and the incident angle _θ1 .

If the short wavelength limit of the illumination wavelength range of illumination light L1 is _λL and the long wavelength limit of illumination light L1 is _λH , then the wavelength _λL is included in the optical path difference a by [(2nd cos _θ2 )/ _λL ] times. If we assume that when the wavelength is increased in this state, it next becomes equal to the optical path difference a at wavelength _λH , then the relationship in the following formula 1 is satisfied.

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

Figure 10 is a graph showing an example of the relationship between the wavelength of reflected light L2 corresponding to the minimum thickness (here, d = 0.5 μm) of the film thickness d of the protective film 9 and the reflectance of reflected light L2. As shown in Figure 10, the above formula [7] (or formula [8], the same applies below) indicates that if the illumination wavelength range of the illumination light L1 is a wavelength bandwidth of one period T or more, the reflectance of reflected light L2 in the coating area WA can be reduced and the coating status of the protective film 9 can be detected by the coating status detection unit 22 even if the film thickness d is the minimum thickness. 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.

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

A similar method can be used to determine the illumination wavelength range of the illumination light L1 such that the reflectance of the reflected light L2 is averaged over one period T or one half period T/2 of the reflectance waveform having the longest wavelength among the reflectance waveforms corresponding to the materials (see FIG. ₄ ) of the multiple semiconductor wafers W. A similar method can also be used to determine the illumination wavelength range of the illumination light L1 such that the reflectance of the reflected light L2 is averaged over one period T or one half period T/2 of the reflectance waveform having the longest wavelength among the reflectance waveforms corresponding to the multiple reflection angles θ 3 (see FIG. 8).

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 _a plurality of measurement conditions (e.g., the material of the semiconductor wafer W, the reflection angle θ 3 , 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 sufficiently reduced below the reflectance of the reflected light L2 in the uncoated area WB.

Figure 11 is a flowchart showing the flow of the process of detecting the application status of the protective film 9 by the application status detection device 10 of the first embodiment, which relates to the application status detection method of the present invention.

As shown in Fig. 11, first, among the reflectance waveforms corresponding to a plurality of measurement conditions (material of semiconductor wafer W, reflection angle θ ₃ , and film thickness d), the 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, the broadband light source 13 capable of emitting illumination light L1 corresponding to the determined illumination wavelength range is used for the coating 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 becomes the illumination wavelength range determined in step S1. This completes preparation for detection of the coating status of the protective film 9 by the coating status detection device 10.

When an operator starts measurement or when a semiconductor wafer W coated with a 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 reflected light L2 is input from the detector 18 to the coating status detection unit 22.

Then, 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 (step S4). At this time, by using the broadband light source 13 of 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 sufficiently reduce the reflectance of the reflected light L2 reflected from the coated area WA below 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.

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 the detection result of the brightness distribution on the surface of the semiconductor wafer W, that is, detects the presence or absence of an uncoated area WB (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 coating area WA and the uncoated area WB, so that the accuracy of detection of the coating status of the protective film 9 by the coating status detection unit 22 can be improved.

As described above, in the coating status detection 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 in the coating area WA can be sufficiently reduced below the reflectance of the reflected light L2 reflected in 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 applied to the surface of the semiconductor wafer W can be detected easily and at low cost.

[Second embodiment]
Next, a coating status detecting device 10 of a second embodiment will be described. 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 front surface of the semiconductor wafer W based on the detection result of the brightness distribution on the front 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 front surface of the semiconductor wafer W based on reflected light L2 from the front surface of the semiconductor wafer W before and after the coating of the protective film 9.

The application status detection device 10 of the second embodiment has basically the same configuration as the application status detection device 10 of the first embodiment, except for some differences in the functions of the measurement control unit 21 and application status detection unit 22 of the control device 20. For this reason, parts that are the same in function or configuration as those of the first embodiment are given the same reference numerals and their description is omitted.

Figure 12 is a flowchart showing the flow of the process of detecting the coating status of the protective film 9 by the coating status detection device 10 of the second embodiment, which relates to the coating status detection 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 that of the first embodiment described in Figure 11 above, so a detailed description will be omitted here.

First, a semiconductor wafer W before being coated with a 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 be used.

Next, the measurement control unit 21 causes the broadband light source 13 to emit illumination light L1 (step S12), and the detector 18 to receive reflected light L2 and output a reception signal (step S13) (corresponding to the measurement step of the present invention). As a result, a 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 based on the detection signal of reflected light L2 (step S14).

Furthermore, 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 θ ₁ (reflection angle θ ₃ )] are the same, the processes from step S11 to step S14 can be omitted when detecting the application status of protective film 9 from the next time onwards.

Once the captured images have been acquired, the semiconductor wafer W coated with the protective film 9 is set in the coating status detection device 10 (step S15).

Then, the measurement control unit 21 repeatedly causes the broadband light source 13 to emit illumination light L1 (step S16), and the detector 18 to receive reflected light L2 and output a reception signal (step S17) (corresponding to the measurement step of the present invention). As a result, a 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).

When the coating status detection unit 22 acquires the captured 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 of the output values (pixel values) in the captured images before and after the application of the protective film 9 (steps S19 and S20). For example, when the captured 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)].

As described above, in the second embodiment, by using a broadband light source 13 with the illumination wavelength range determined in step S10, the reflectance of the reflected light L2 is averaged across this illumination wavelength range, so that the reflectance of the reflected light L2 reflected from the coating area WA can be made sufficiently lower than the reflectance of the 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, so that the accuracy of detection of the coating status of the protective film 9 by the coating status detection unit 22 can be improved. This allows the second embodiment to achieve the same effects as the first embodiment.

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

The coating status detection 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.

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

The broadband light source 13 emits illumination light L1 in the same manner as in each of the above 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 enters the beam splitter 32 through the lens 30.

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 described below. 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 it to the detection optical system 16A.

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 the reflected light L2 incident from the beam splitter 32 through the lens 17, and outputs a received light signal to the control device 20.

The control device 20 of the third embodiment has the same configuration as the control device 20 of each of the above 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 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.

The coaxial epi-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, so 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.

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

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

The ring illumination light source 12B is disposed above the surface of the semiconductor wafer W and emits a 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 a portion 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 is incident on the detection optical system 16B.

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 described above, and includes a lens 17 and a detector 18 arranged along this detection optical axis O2B. The detector 18 receives the reflected light L2 incident through the lens 17 and outputs a light reception signal to the control device 20.

The control device 20 of the fourth embodiment has the same configuration as the control device 20 of each of the above 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 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.

Note that, like the oblique illumination method described in the first and second embodiments, the ring illumination method can illuminate a wide area of the surface of the semiconductor wafer W, but since the illumination light L1 is not specularly reflected in the center of the field of view, the detection accuracy of the coating status of the protective film 9 may be lower than in the first and second embodiments. For this reason, it is preferable to adopt the oblique illumination method described in the first and second embodiments.

[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.

[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 the illumination light L1 reduces the reflectance of the reflected light L2 reflected from the coated area WA below the reflectance of the reflected light L2 reflected from the uncoated area WB, but the present invention is not limited to these Examples.

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 (total of 55 patterns) of a plurality of film thicknesses _d and a plurality of reflection angles θ 3 .

As shown in Fig. 15, a total of 55 patterns (=11 x 5) of combinations of semiconductor wafers _W were assumed, including 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 angles θ 3 (10°, 20°, 30°, 40°, 50°). In each combination, the short-wavelength limit λ _L of the illumination wavelength range of the illumination light L1 was fixed at 500 nm, and the long-wavelength limit λ _H was increased stepwise to calculate the reduction rate of the reflected light L2 at each step. Note that a reduction rate of 0% indicates the reduction rate of the reflected light L2 reflected on the surface of a semiconductor wafer W or the like not coated with a protective film 9 (the same applies below).

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

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 (total of 55 patterns) of a plurality of film thicknesses _d and a plurality of reflection angles θ 3 .

As shown in Fig. 16, a semiconductor wafer W with a total of 55 patterns (=11 x 5) of combinations of 11 types of film thickness d and five types of reflection angles _θ3 was assumed, as in Example 1. Then, for each combination, the long wavelength limit _λH of the illumination wavelength range of the illumination light L1 was fixed at 600 nm, and the short wavelength limit _λL was gradually decreased to calculate the reduction rate of the reflected light L2 at each step. Note that the arrow A1 in Fig. 16 indicates the range that satisfies the above formula [7], and the arrow A2 indicates the range that satisfies the above formula [10] (or formula [11], the same applies below).

It was confirmed that the reflectance of the reflected light L2 in the coating area WA (protective film 9) decreases as the short wavelength limit λ _L is gradually decreased, i.e., 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. In particular, it was confirmed that the reflectance of the reflected light L2 is sufficiently decreased in the illumination wavelength ranges indicated by the arrows A1 and A2. It was also confirmed that the reflectance of the reflected light L2 is lower in the illumination wavelength range indicated by the arrow A1 than in the illumination wavelength range indicated by the arrow A2.

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 (total of 55 patterns) of a plurality of film thicknesses _d and a plurality of reflection angles θ 3 .

As shown in Fig. 17, a semiconductor wafer W with a total of 55 patterns (=11 x 5) of combinations of 11 types of film thickness d and five types of reflection angles _θ3 was assumed, as in Example 1. Then, for each combination, the reduction rate of the reflected light L2 for each of the seven types of illumination light L1 illumination wavelength ranges was calculated. Here, the patterns of the seven types of illumination wavelength ranges were set by changing the long wavelength limit _λH stepwise from 1000 nm to 400 nm in increments of 100 nm, and setting the short wavelength limit _λL that satisfies the following formula [Equation 13] for each long wavelength limit _λH .

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

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 (total of 55 patterns) of a plurality of film thicknesses _d and a plurality of reflection angles θ 3 .

As shown in Fig. 18, a semiconductor wafer W with a total of 55 patterns (=11 x 5) of combinations of 11 types of film thickness d and five types of reflection angles _θ3 was assumed, as in Example 1. Then, for each combination, the reduction rate of the reflected light L2 for each of the seven types of illumination light L1 illumination wavelength ranges was calculated. Here, the patterns of the seven types of illumination wavelength ranges are such that the long wavelength limit _λH is changed in steps of 100 nm from 1000 nm to 400 nm, and a short wavelength limit _λL that satisfies the following formula [14] is set for each long wavelength limit _λH .

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

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 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 thicknesses d (0 μm, 0.5 μm, 1 μm, 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 such as the coating status detection device 10 of the third embodiment.

Note that "illumination wavelength range a" in Fig. 19 is a wavelength range that at least satisfies the above formula (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 formula (7) is determined based on the refractive index n and incident angle _θ1 . Also, "illumination wavelength range b" and "illumination wavelength range c" in Fig. 19 are wavelength ranges that satisfy the above formula (7) with a margin under the above conditions.

Figure 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 Figure 19. As shown in Figure 20, it was confirmed that by determining the illumination wavelength range of illumination light L1 so as to satisfy the above 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.

Example 6
21 is a graph of Example 6 in which the relationship between the wavelength of the illumination light L1 and the reflectance of the reflected light L2 was calculated for each 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 types of thickness d (0 μm, 0.5 μm, 1 μm, 1.5 μm) were assumed as in Example 5. Then, the relationship between the wavelength (350 nm to 1000 nm) of the illumination light L1 and the reflectance of the reflected light L2 was calculated for each of the four types of semiconductor wafers W using an oblique illumination method such as the coating status detection device 10 of the first or second embodiment.

21 is a wavelength range that satisfies the above formula (7) at a minimum under the conditions of refractive index n = 1.5, incident angle θ ₁ = 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.

Figure 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 Figure 21. As shown in Figure 22, it was confirmed that by determining the illumination wavelength range of illumination light L1 so as to satisfy the above 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.

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 is 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 is 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).

Figure 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 Figure 23. As shown in Figure 24, it was confirmed that by determining the illumination wavelength range of illumination light L1 so as to satisfy the above 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.

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 is 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 is 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).

Figure 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 Figure 25. As shown in Figure 26, it was confirmed that by determining the illumination wavelength range of illumination light L1 so as to satisfy the above 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.

<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 is 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 is 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).

Figure 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 Figure 27. As shown in Figure 28, it was confirmed that by determining the illumination wavelength range of illumination light L1 so as to satisfy the above 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.

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 is 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. 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 is 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).

Figure 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 Figure 29. As shown in Figure 30, it was confirmed that by determining the illumination wavelength range of illumination light L1 so as to satisfy the above 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.

Comparative Example
Similar to the above-described Example 5, 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 film thickness d of protective film 9 formed on the surface of an aluminum semiconductor wafer W. Note that "illumination wavelength range d", "illumination wavelength range e", and "illumination wavelength range f" shown in Fig. 31 are wavelength ranges partly not satisfying the above formula (7) or formula (10) under the conditions of refractive index n = 1.5, incident angle θ ₁ = 0°, and film thickness d ≥ 0.5 μm.

Figure 32 is a table showing the calculation results of the average reflectance and the rate of decrease of the reflected light L2 when the illumination light L1 in the "illumination wavelength range d" to "illumination wavelength range f" is used for each of the four film thicknesses d shown in Figure 31. In addition, the frame FR1 in Figure 32 indicates the case where the above formula [7] is satisfied, the frame FR2 indicates the case where the above formula [7] is not satisfied but the above formula [10] is satisfied, and the frame FR3 indicates the case where the above formula [10] is not satisfied. As shown in Figure 32, when the illumination wavelength range of the illumination light L1 is determined so as not to satisfy the above formula [10] (see frame FR3), it was confirmed that the decrease in the average reflectance of the reflected light L2 in the coating area WA (protective film 9) is suppressed, that is, the rate of decrease of the reflected light L2 is reduced, compared to the case where the illumination wavelength range of the illumination light L1 is determined so as to satisfy the above formula [7] or the above formula [10] (see frames FR1 and FR2).

9...protective film 10...coating status detection device 12...illumination optical system 12A...illumination optical system 12B...ring illumination light source 13...broadband light source 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 θ ₁ ...angle of incidence θ ₂ ...angle of refraction θ ₃ ...angle of reflection λ _H ...longer wavelength limit λ _L ...shorter wavelength limit

Claims (8)

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 illumination light emitted from a broadband light source and receiving reflected light from the workpiece;
a coating status detection step of detecting a coating status of the protective film from the reflected light received in the measurement step;
having
determining an illumination wavelength range of the broadband light source based on a refractive index of the protective film, an incident angle of the illumination light with respect to a surface of the workpiece on which the protective film is applied, and a thickness of the protective film;
a refraction angle of the illumination light by the protective film is determined based on the refractive index and the incident angle;
When the refractive index is n, the thickness of the protective film is d, the refraction angle is θ, the short wavelength limit of the illumination wavelength range of the broadband light source is λ _L , the long wavelength limit of the illumination wavelength range is λ _H , and the optical path difference between a first reflected light reflected on the surface of the protective film and a second reflected light reflected on the back surface of the protective film is a = 2nd cos θ, the measurement step uses the broadband light source to satisfy the following formula (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 illumination light emitted from a broadband light source and receiving reflected light from the workpiece;
a coating status detection step of detecting a coating status of the protective film from the reflected light received in the measurement step;
having
determining an illumination wavelength range of the broadband light source based on a refractive index of the protective film, an incident angle of the illumination light with respect to a surface of the workpiece on which the protective film is applied, and a thickness of the protective film;
a refraction angle of the illumination light by the protective film is determined based on the refractive index and the incident angle;
When the refractive index is n, the thickness of the protective film is d, the refraction angle is θ, the short wavelength limit of the illumination wavelength range of the broadband light source is λ _L , the long wavelength limit of the illumination wavelength range is λ _H , and the optical path difference between a first reflected light reflected on the surface of the protective film and a second reflected light reflected on the back surface of the protective film is a = 2nd cos θ, the measurement step uses the broadband light source to satisfy the following formula (2).
3. The coating condition detecting method according to claim 1, wherein the illumination light has an illumination wavelength range of 400 nm to 1000 nm. 3. The coating status detecting method according to claim 1, wherein in the coating status detecting step, a brightness distribution of the workpiece is detected from the reflected light, and the coating status of the protective film is detected from the brightness distribution of the workpiece. The measuring step is performed before and after application of the protective film to the workpiece;
The coating status detection method described in claim 1 or 2, wherein in the coating status detection step, images of the workpiece before and after the application of the protective film are obtained based on the reflected light received in the measurement step before and after the application of the protective film, and the coating status of the protective film is detected from the difference or ratio of output values in the captured images before and after the application of the protective film. 3. The coating condition detecting method according to claim 1, wherein in the measuring step, the illumination light from the broadband light source is incident on the workpiece from an oblique direction. 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 illumination light emitted from a broadband light source and receives reflected light from the workpiece;
a coating status detection unit that detects a coating status of the protective film from the reflected light received by the measurement unit;
Equipped with
determining an illumination wavelength range of the broadband light source based on a refractive index of the protective film, an incident angle of the illumination light with respect to a surface of the workpiece on which the protective film is applied, and a thickness of the protective film;
a refraction angle of the illumination light by the protective film is determined based on the refractive index and the incident angle;
When the refractive index is n, the thickness of the protective film is d, the refraction angle is θ, the short wavelength limit of the illumination wavelength range of the broadband light source is λ _L , the long wavelength limit of the illumination wavelength range is λ _H , and the optical path difference between a first reflected light reflected on the surface of the protective film and a second reflected light reflected on the back surface of the protective film is a = 2nd cos θ, the measurement unit uses the broadband light source to satisfy the following formula (1) .
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 illumination light emitted from a broadband light source and receives reflected light from the workpiece;
a coating status detection unit that detects a coating status of the protective film from the reflected light received by the measurement unit;
Equipped with
determining an illumination wavelength range of the broadband light source based on a refractive index of the protective film, an incident angle of the illumination light with respect to a surface of the workpiece on which the protective film is applied, and a thickness of the protective film;
a refraction angle of the illumination light by the protective film is determined based on the refractive index and the incident angle;
The refractive index is n, the thickness of the protective film is d, the refraction angle is θ, and the short wavelength limit of the illumination wavelength range of the broadband light source is λ _L The long wavelength limit of the illumination wavelength range is λ _H When the optical path difference between the first reflected light reflected from the surface of the protective film and the second reflected light reflected from the back surface of the protective film is a = 2nd cos θ, the measurement unit uses the broadband light source that satisfies the following equation (2).

Images