Wafer surface inspection method, wafer surface inspection apparatus, and electronic component manufacturing method

Abstract

The present invention relates to a method for inspecting a wafer surface, a wafer surface inspection apparatus, and a method for manufacturing an electronic component. The method for inspecting the surface of a wafer includes the following steps: irradiating the surface of the wafer with a laser beam having three or more different wavelengths; detecting reflected light from the surface of the wafer when the surface of the wafer is irradiated with the laser beam; and determining whether there is a foreign object on the surface of the wafer based on the reflectance of the surface of the wafer with respect to the laser beam having three or more different wavelengths, wherein the step of determining whether there is a foreign object includes a step of determining whether the foreign object is a metal or a non-metal.

Description

Technical Field

[0001] The present invention relates to a method for inspecting the surface of a wafer, an apparatus for inspecting the surface of a wafer, and a method for manufacturing an electronic component. Background Art

[0002] The surface of a wafer is inspected by irradiating the surface of the wafer with light. For example, Japanese Patent Application Laid-Open No. H7-134103 discloses a technique for detecting surface defects. Japanese Patent Application Laid-Open Nos. 2005-147874 and 2018-517902 disclose techniques for detecting foreign matter adhering to the surface. Summary of the Invention

[0003] Metal foreign matter may adhere to a wafer, or non-metal foreign matter such as a resist may adhere to the wafer. Preferably, when the foreign matter is metal, the wafer is determined to be a good product, and when the foreign matter is non-metal, the wafer is determined to be a defective product. Therefore, it is important to determine whether the foreign matter is metal or non-metal. However, it may take a long time to determine the foreign matter. Accordingly, an object of the present invention is to provide a method for inspecting the surface of a wafer that can quickly determine whether the foreign matter is metal or non-metal.

[0004] According to a first aspect of the present invention, there is provided a method for inspecting the surface of a wafer, the method including the steps of: irradiating the surface of the wafer with a laser beam having three or more different wavelengths; detecting reflected light from the surface of the wafer when the surface of the wafer is irradiated with the laser beam; and determining whether there is foreign matter on the surface of the wafer based on the reflectance of the surface of the wafer with respect to the laser beam having three or more different wavelengths, wherein the step of determining whether there is foreign matter includes a step of determining whether the foreign matter is metal or non-metal.

[0005] According to a second aspect of the present invention, there is provided an apparatus for inspecting the surface of a wafer, the apparatus including: a laser source that irradiates the surface of the wafer with a laser beam having three or more different wavelengths; a detector that detects reflected light from the wafer when the surface of the wafer is irradiated with the laser beam; and a controller that determines whether there is foreign matter and whether the foreign matter is metal or non-metal based on the reflectance with respect to the laser beam having three or more different wavelengths.

[0006] According to a third aspect of the present invention, there is provided a method for manufacturing an electronic component, including the following steps: forming a metal layer on the surface of a wafer; forming a resist pattern on the surface of the metal layer; after the step of forming the resist pattern, irradiating the surface of the wafer with a laser beam having three or more different wavelengths to determine whether there is a foreign object on the surface of the wafer based on the reflectance regarding the three or more laser beams; when there is a foreign object, determining whether the foreign object is a metal or a non-metal; when there is no foreign object or the foreign object is a metal, forming a plating layer on the metal layer. Description of the Drawings

[0007] Figure 1 is a schematic diagram showing a surface inspection device according to a first embodiment;

[0008] Figures 2A to 2D is a cross-sectional view showing a method for manufacturing a capacitor;

[0009] Figures 3A to 3C is a cross-sectional view showing a method for manufacturing a capacitor;

[0010] Figure 4A and Figure 4B is a cross-sectional view showing a method for manufacturing a capacitor;

[0011] Figure 5 is a flowchart of a surface inspection method;

[0012] Figures 6A to 6C shows the reflectance;

[0013] Figures 7A to 7C shows the reflectance;

[0014] Figure 8A and Figure 8B shows the relationship between the difference in the thickness of the resist and the reflectance;

[0015] Figures 9A to 9C shows the reflectance; and

[0016] Figure 10 shows the relationship between the difference in the thickness of the resist and the reflectance. Detailed Description of the Invention

[0017] Description of Embodiments of the Present Invention

[0018] First, the details of embodiments of the present invention will be described as listed below. An embodiment of the present invention is (1) a method for inspecting the surface of a wafer, the method comprising the steps of: irradiating the surface of the wafer with a laser beam having three or more different wavelengths; detecting the reflected light from the surface of the wafer when the surface of the wafer is irradiated with the laser beam; and determining whether there is a foreign object on the surface of the wafer based on the reflectivity of the surface of the wafer with respect to the laser beam having three or more different wavelengths, wherein the step of determining whether there is a foreign object includes the step of determining whether the foreign object is a metal or a non-metal. The reflectivity of a metal does not vary much with wavelength, while the reflectivity of a non-metal such as a resist varies periodically with wavelength. Therefore, it is possible to quickly determine whether there is a foreign object and whether the foreign object is a metal or a non-metal.

[0019] (2) The step of determining whether the foreign object is a metal or a non-metal may include the steps of: obtaining each reflectivity at different wavelengths; and determining whether the foreign object is a metal or a non-metal based on the difference between two reflectivities of each reflectivity at different wavelengths. Compared with a metal foreign object, the difference in reflectivities of a non-metal foreign object such as a resist at different wavelengths is larger. Therefore, it is possible to accurately determine whether there is a foreign object and whether the foreign object is a metal or a non-metal.

[0020] (3) The step of determining whether the foreign object is a metal or a non-metal may include the steps of: obtaining the maximum reflectivity and the minimum reflectivity among each reflectivity at different wavelengths, obtaining the difference between the maximum reflectivity and the minimum reflectivity and the sum of the maximum reflectivity and the minimum reflectivity, and determining that the foreign object is a metal when the ratio of the difference to the sum is less than 0.15, and determining that the foreign object is a non-metal when the ratio is 0.15 or greater. Compared with a metal foreign object, the difference in reflectivities of a non-metal foreign object such as a resist at different wavelengths is larger. Therefore, the ratio obtained from the sum and the difference between the reflectivities is also large. Therefore, it is possible to accurately determine whether there is a foreign object and whether the foreign object is a metal or a non-metal.

[0021] (4) Each of the three or more different wavelengths of the laser beam may be 600 nm or greater. The reflectivity of a metal does not vary much with a laser beam having a wavelength of 600 nm or greater. On the other hand, the reflectivity of a non-metal such as a resist varies periodically. Therefore, it is possible to accurately determine whether there is a foreign object and whether the foreign object is a metal or a non-metal.

[0022] (5) The method may further include the step of: irradiating the surface of the wafer with a laser beam having five or more different wavelengths. It is possible to accurately determine whether there is a foreign object and whether the foreign object is a metal or a non-metal.

[0023] (6) An apparatus for inspecting the surface of a wafer, comprising: a laser source that irradiates the surface of the wafer with a laser beam having three or more different wavelengths; a detector that detects reflected light from the wafer when the surface of the wafer is irradiated with the laser beam; and a controller that determines whether there is a foreign object and whether the foreign object is metal or non-metal based on the reflectance of the laser beam having three or more different wavelengths. The reflectance of a non-metal such as a resist varies periodically with respect to the wavelength. Therefore, it is possible to accurately determine whether there is a foreign object and whether the foreign object is metal or non-metal.

[0024] (7) A method for manufacturing an electronic component, comprising the steps of: forming a metal layer on the surface of a wafer; forming a resist pattern on the surface of the metal layer; after the step of forming the resist pattern, irradiating the surface of the wafer with a laser beam having three or more different wavelengths to determine whether there is a foreign object on the surface of the wafer based on the reflectance of the three or more laser beams; when there is a foreign object, determining whether the foreign object is metal or non-metal; and when there is no foreign object or the foreign object is metal, forming a plating layer on the metal layer. The reflectance of a non-metal such as a resist varies periodically with respect to the wavelength. Therefore, it is possible to accurately determine whether there is a foreign object and whether the foreign object is metal or non-metal.

[0025] (8) The electronic component may be a capacitor, the plating layer may be included in the lower electrode of the capacitor, and the manufacturing method may further comprise the steps of: forming a dielectric film on the plating layer; and forming an upper electrode on the dielectric film. Non-metal foreign objects may cause defects in the dielectric film, resulting in a short circuit between the electrodes. By determining whether the foreign object is metal or non-metal, the manufacturing of capacitors that may cause a short circuit is prevented.

[0026] Details of embodiments of the present invention

[0027] Specific examples of a method for inspecting the surface of a wafer, a surface inspection apparatus, and a method for manufacturing an electronic component according to an embodiment of the present invention will be described below with reference to the accompanying drawings. It should be noted that the present invention is not limited to these examples, but is shown by the claims, and it is intended that all modifications be included in the equivalent forms of the claims and the scope of the claims.

[0028] First Embodiment

[0029] Surface Inspection Apparatus

[0030] Figure 1 Schematically shows a surface inspection apparatus 100 according to the first embodiment. As Figure 1 shown, the surface inspection apparatus 100 includes a controller 10, a laser source 12, and a detector 14. The object to be inspected is a wafer 20, and a foreign object 22 may adhere to the surface of the wafer 20.

[0031] The laser source 12 is a semiconductor laser including, for example, gallium indium phosphide (GaInP) and aluminum gallium indium phosphide (AlGaInP). The oscillation wavelength of the laser source 12 can be adjusted by the composition of the semiconductor, and the laser source 12 emits laser beams having three or more different wavelengths. The three wavelengths are, for example, more than 600 nm and less than 1000 nm. The detector 14 includes a light receiving element such as, but not limited to, a photodiode.

[0032] The controller 10 includes arithmetic means such as, but not limited to: a central processing unit (CPU) and a storage device such as a hard disk drive (HDD). The controller 10 is coupled to the laser source 12 and the detector 14 to control them. The controller 10 calculates the light reflectivity of the foreign matter 22 based on the intensity of the light emitted from the laser source 12 and the intensity of the reflected light received by the detector 14.

[0033] When the foreign matter 22 is a metal, the laser beam is reflected by the surface of the foreign matter 22. On the other hand, when the foreign matter 22 is an organic substance such as a resist, the foreign matter 22 is transparent. Therefore, a part of the laser beam is reflected by the surface of the foreign matter 22, and another part of the laser beam is reflected by the interface between the foreign matter 22 and the wafer 20. Since the two reflected lights interfere with each other, as described later, the intensity of the reflected light varies periodically with respect to the wavelength.

[0034] Wafer 20

[0035] Electronic components such as, but not limited to, metal-insulator-metal (MIM) capacitors are formed on the wafer 20. The manufacturing method of the capacitor includes surface inspection. Figures 2A to 2D [[ID=##]]And Figures 3A to 4B is a cross-sectional view showing the manufacturing method of the capacitor. Figure 2A Figures A to D show examples without foreign matter attachment.

[0036] As Figure 2A shown, a dielectric film 30 and a polyimide film 32 are formed on the surface of the wafer 20, and then a seed metal 40 (metal layer) is formed by sputtering or the like. The seed metal 40 includes a titanium (Ti) layer 34, a gold (Au) layer 36, and a Ti layer 38 stacked in sequence from the wafer 20 side. As Figure 2B shown, a resist 42 is formed on the Ti layer 38. The resist 42 is a positive resist based on phenolic resin, which has, for example, a refractive index of 1.6 and a thickness of 1.5 ± 0.1 μm. A resist pattern is formed by exposure and development with ultraviolet light. The exposed area of the resist 42 is removed, and an opening 43 is formed in this area.

[0037] As Figure 2CAs shown, the Ti layer 38 included in the seed metal 40 and exposed from the opening 43 is removed by reactive ion etching (RIE) using, for example, a fluorine-based gas. The Au plating layer 44 is formed by electroplating using the seed metal 40. The plating layer 44 is filled into the opening 43. The Au layer 36 of the seed metal 40 is the same Au as the plating layer 44, and thus its illustration is omitted.

[0038] As Figure 2D shown, the resist 42 is removed, and then the Ti layer 38, the Au layer 36, and the Ti layer 34 are removed by etching. After that, a dielectric film 46 is formed on the plating layer 44. A seed metal 48 is formed on the surface of the dielectric film 46. The seed metal 48 includes, for example, a Ti layer and an Au layer. Titanium tungsten (TiW) can be used for the seed metals 40 and 48. The Au plating layer 50 is formed by electroplating. The seed metal 40 and the plating layer 44 are used as the lower electrode of the capacitor, and the seed metal 48 and the plating layer 50 are used as the upper electrode.

[0039] Figures 3A to 4B An example of foreign matter attachment is shown. As Figure 3A shown, the foreign matter 22 remains in the opening 43. When the foreign matter 22 is metal, the foreign matter 22 is included in the Figure 2C shown plating layer 44. On the other hand, when the foreign matter 22 is a resist, a defect is formed in the plating layer 44.

[0040] For example, foreign matter may attach to the resist 42, and the area under the foreign matter may not be exposed. The unexposed area is not removed by development but remains as the foreign matter 22. As Figure 3B shown, while the foreign matter 22 of the resist remains, the plating layer 44 is formed between the resist 42 and the foreign matter 22 by electroplating. The plating layer 44 is not formed in the area where the foreign matter 22 exists. As Figure 3C shown, when the resist 42 and the foreign matter 22 are removed, a void 47 is formed in the area where the foreign matter 22 exists.

[0041] As Figure 4A shown, the dielectric film 46 is formed. The dielectric film 46 is formed along the surface of the plating layer 44 and thins from the upper surface to the side surface of the plating layer 44. Therefore, a void 49 is formed in the dielectric film 46. As Figure 4B shown, the seed metal 48 is formed by sputtering, and the plating layer 50 is further formed by electroplating. The seed metal 48 is formed along the surface of the dielectric film 46, but thins and disappears at a distance closer to the other end of the void 49. The plating layer 50 is not formed in the part where the seed metal 48 does not exist, and a void 51 is formed at the position surrounded by the plating layer 50, the dielectric film 46, and the plating layer 4,4.

[0042] The dielectric film 46 is thin in the void 49 and may form defects. Accordingly, a leakage path is formed along the void 49, and a short circuit occurs between the plating layer 44 and the plating layer 50. In addition, water such as plating solution may remain in the void 51.

[0043] When there is no foreign matter on the wafer 20, a capacitor is manufactured by the Figures 2A to 2D steps shown. In addition, even when a metal foreign matter adheres to the surface of the wafer 20, the metal foreign matter is included in the plating layer 44. Accordingly, voids and leakage paths are not easily formed. On the other hand, as Figures 3A to 4B shown, when a foreign matter 22 which is a residue of the resist 42 adheres to the surface of the wafer 20, voids and leakage paths are formed and a short circuit occurs. Accordingly, instead of determining all wafers 20 having the foreign matter 22 as defective products, when the foreign matter 22 is non-metal, the wafer 20 is determined as a defective product. When the foreign matter 22 is metal, the wafer 20 is determined as a non-defective product, and the plating layer 44 is formed as Figure 2C shown. Accordingly, it is determined whether the foreign matter 22 on the wafer 20 is metal or non-metal such as resist by using the light reflectance.

[0044] Figure 5 is a flowchart of a surface inspection method. For example, the surface inspection is performed after forming the resist pattern and before forming the plating layer 44. As Figure 5 shown, a laser source 12 irradiates the foreign matter 22 with a laser beam (step S10), and a detector 14 detects reflected light from the foreign matter 22 (step S12). The laser beam includes light of, for example, three or more wavelengths, and all wavelengths are 650 nm or more.

[0045] A controller 10 obtains respective reflectivities at wavelengths based on the intensity of the laser beam and the intensity of the reflected light (step S14). The reflectivity is a ratio of the intensity of the emitted laser beam to the intensity of the reflected light. The controller 10 calculates a difference between a maximum reflectivity R1 and a minimum reflectivity R2 among the respective reflectivities at wavelengths and a sum of the maximum reflectivity R1 and the minimum reflectivity R2 (step S16), and calculates a ratio R of the difference to the sum (step S18). That is, the ratio R is calculated by the following expression.

[0046] R = (R1 - R2) / (R1 + R2)

[0047] The controller 10 determines whether the ratio R is equal to or greater than a threshold Rth (step S20). The threshold Rth is, for example, 0.15. When it is determined as "No" in step S20, the controller 10 determines that there is no foreign matter 22 on the wafer 20 or the foreign matter 22 is metal (step S22). When there is no foreign matter 22, the emitted light is reflected by the Ti layer 38 of the seed metal. In this case, compared with the case of a metal foreign matter, for a laser beam having a wavelength of 600 nm or more, the reflectance does not change significantly. Therefore, the ratio R does not become equal to or greater than the threshold Rth. Therefore, the threshold Rth can be used to determine whether there is foreign matter 22. On the other hand, when it is determined as "Yes", the controller 10 determines that there is foreign matter 22 on the wafer 20 and the foreign matter 22 is a non-metal such as an organic substance (step S24). The control ends as described above. As described above, when there is no foreign matter 22 or when the foreign matter 22 is metal, the plating layer 44 is formed. On the other hand, when the foreign matter 22 is a non-metal, the plating layer 44 is not formed, and the wafer 20 is determined to be defective.

[0048] Figures 6A to 7C The reflectance is shown. The horizontal axis represents the wavelength of the laser beam, and the laser source 12 emits laser beams having three wavelengths of 635 nm, 670 nm, and 690 nm represented by the dotted line. The vertical axis represents the reflectance. The dotted line represents an example in which the foreign matter 22 is gold (Au), the dashed line represents an example in which the foreign matter 22 is copper (Cu), and the dash-dotted line represents an example in which the foreign matter 22 is silver (Ag). The solid line represents an example in which the foreign matter 22 is a resist.

[0049] Figures 6A to 6C Examples in which the thickness of the resist is 1.48 μm, an example in which the thickness of the resist is 1.50 μm, and an example in which the thickness of the resist is 1.52 μm are shown, respectively. Figures 7A to 7C Examples in which the thickness of the resist is 1.43 μm, an example in which the thickness of the resist is 1.50 μm, and an example in which the thickness of the resist is 1.57 μm are shown, respectively.

[0050] As Figures 6A to 7C shown, when the foreign matter 22 is metal, the reflectance is low at short wavelengths and high at long wavelengths. For example, the difference between the reflectance at a wavelength of 635 nm and the reflectance at a wavelength of 670 nm is less than 0.2. On the other hand, the reflectance of the resist changes periodically with respect to the wavelength. For example, as Figures 6A to 6C shown, the difference between the reflectance at a wavelength of 635 nm and the reflectance at a wavelength of 670 nm is greater than the difference in the example of metal, and is 0.2 or more. Therefore, it is possible to determine whether the foreign matter 22 is metal or resist by using the difference between the reflectances.

[0051] More specifically, the controller 10 calculates the difference between the maximum reflectance and the minimum reflectance among the respective reflectances at three wavelengths and the sum of the maximum reflectance and the minimum reflectance, and then calculates the ratio R of the difference to the sum. For example, assume that among the respective reflectances at the three wavelengths of 635 nm, 670 nm, and 690 nm, the reflectance at the 635 nm wavelength is the maximum, while the reflectance at the 670 nm wavelength is the minimum. The controller 10 calculates the difference between the reflectance at 635 nm and the reflectance at 670 nm and the sum of the reflectance at 635 nm and the reflectance at 670 nm ( Figure 5 in step S16). The controller 10 calculates their ratio R, i.e., difference / sum, and compares the ratio R with the threshold Rth (steps S18 and S20).

[0052] Compared with the reflectance of the metal, the reflectance of the resist varies greatly between the wavelengths of 635 nm and 670 nm. Therefore, the ratio R in the resist is greater than the ratio R in the metal. For example, when the ratio R is less than the threshold Rth of 0.15, it is determined that there is no foreign matter 22 on the wafer 20 or the foreign matter 22 is metal (step S22). On the other hand, when the ratio R is equal to or greater than the threshold Rth, it is determined that the foreign matter 22 is non-metal (step S24). In Figure 6A , Figure 6B and Figure 6C in the example, by using the reflectance at 635 nm and the reflectance at 670 nm, it is possible to detect that the foreign matter 22 is resist.

[0053] In Figure 7A the example where the resist shown has a thickness of 1.43 μm, among the respective reflectances at the three wavelengths, the reflectance at the 635 nm wavelength is the maximum, while the reflectance at the 690 nm wavelength is the minimum. In the example where the resist has Figure 7B the thickness of 1.50 μm shown, the reflectance of the resist is the maximum at the 635 nm wavelength and the minimum at the 670 nm wavelength. Therefore, it is possible to determine whether the foreign matter 22 is metal or non-metal based on the difference and the sum between the reflectances at these wavelengths.

[0054] On the other hand, in Figure 7C the example where the thickness of the resist shown is 1.57 μm, the reflectance at 635 nm and the reflectance at 670 nm are almost equal. Therefore, it is difficult to determine whether the foreign matter 22 is metal or non-metal by using these reflectances. In this case, since the difference between them is large, the reflectance at the 670 nm wavelength and the reflectance at the 690 nm wavelength are used.

[0055] As described above, the reflectance varies according to the thickness of the resist. Figure 8A andFigure 8B The relationship between the difference in the thickness of the resist and the reflectance is shown. The horizontal axis represents the thickness of the resist, and the vertical axis represents the difference in reflectance. Figure 8A The difference in reflectance in [reference] is the difference between the reflectance of the resist with respect to a laser beam having a wavelength λ of 635 nm and the reflectance of the resist with respect to a laser beam having a wavelength λ of 670 nm. As Figure 8A shown, at thicknesses of 1.43 μm, 1.47 μm, 1.50 μm, and 1.53 μm, the reflectance difference is -0.2 or less. That is, at thicknesses of 1.43 μm, 1.47 μm, 1.50 μm, and 1.53 μm, the absolute value of the reflectance difference is 0.2 or greater. On the other hand, at a thickness of 1.57 μm, the reflectance difference is greater than -0.1, and its absolute value is less than 0.1. The reflectance difference of the resist is approximately equal to the reflectance difference of the metal, and the ratio R also becomes smaller. Therefore, it is difficult to determine using laser beams having wavelengths of 635 nm and 670 nm. Therefore, irradiation with a laser beam having three or more wavelengths is effective.

[0056] Figure 8B The difference in reflectance in [reference] is the difference between the minimum reflectance and the maximum reflectance among the reflectance with respect to a laser beam having a wavelength of 635 nm, the reflectance with respect to a laser beam having a wavelength of 670 nm, and the reflectance with respect to a laser beam having a wavelength of 690 nm. As Figure 8B shown, the reflectance difference is -0.1 or less at any thickness. The reflectance difference is approximately -0.3 at thicknesses of 1.43 μm and 1.50 μm, and approximately -0.2 at a thickness of 1.57 μm. As described above, at these thicknesses, irradiation with a laser beam having three wavelengths makes the absolute value of the reflectance difference larger and the ratio R also larger. Therefore, whether the foreign matter 22 is metal or non-metal can be accurately determined by irradiating with a laser beam having three or more wavelengths.

[0057] In the first embodiment, the laser source 12 irradiates the surface of the wafer 20 with a laser beam having three or more wavelengths, and the detector 14 detects the reflected light. The controller 10 determines whether there is a foreign matter 22 and whether the foreign matter 22 is metal or non-metal based on the reflectance of the surface with respect to the laser beam. When the foreign matter 22 is a non-metal such as a resist, the reflected lights interfere with each other, and thus, the reflectance varies periodically with respect to the wavelength. When there is no foreign matter 22 or when the foreign matter 22 is metal, the reflectance does not vary periodically with respect to the wavelength. Therefore, the determination can be made based on the difference in the behavior of the above-mentioned reflectance with respect to the wavelength. For example, a method such as energy dispersive X-ray spectroscopy (EDX) takes several minutes to analyze one foreign matter 22, and the determination takes a long time. In contrast, in the first embodiment, it is possible to quickly determine whether there is a foreign matter 22 and whether the foreign matter 22 is metal or non-metal based on the reflectance with respect to the laser beam.

[0058] The controller 10 obtains respective reflectivities at different wavelengths and performs determination based on the difference between two reflectivities. The reflectivity of the resist varies periodically with respect to the wavelength, and the difference between the reflectivities of the resist is greater than the difference between the reflectivities of the metal. Therefore, high-precision determination can be performed. For example, when the difference between the reflectivities is a predetermined value or greater, it can be determined that the foreign matter 22 is a resist, and when the difference is less than the predetermined value, it can be determined that there is no foreign matter 22 or the foreign matter 22 is a metal. However, since the absolute value of the reflectivity varies according to the surface roughness of the foreign matter 22, the accuracy of the determination may decrease when only the difference between the reflectivities is used.

[0059] In view of this, the controller 10 calculates the difference and the sum between the maximum reflectivity and the minimum reflectivity among the respective reflectivities at the wavelength, and also calculates the ratio R of the difference to the sum. For example, when the ratio R is less than 0.15, the controller 10 determines that there is no foreign matter 22 or the foreign matter 22 is a metal. For example, when the ratio R is 0.15 or greater, the controller 10 determines that the foreign matter 22 is a non-metal. Therefore, high-precision determination can be performed.

[0060] Three or more different wavelengths of the laser beam are preferably 600 nm or greater. For example, as Figure 6A shown, the reflectivity of the metal is low at short wavelengths and high at long wavelengths. The reflectivity of copper is about 0.7 at a wavelength of 500 nm, and is 0.9 nm or greater and almost constant at wavelengths of 600 nm or greater. On the other hand, the reflectivity of the resist varies periodically with respect to the wavelength. By using a laser beam with a wavelength of 600 nm or greater, the ratio R obtained from the metal foreign matter becomes smaller and the ratio R obtained from the resist foreign matter becomes larger. Therefore, accurate determination can be performed. When there is no foreign matter 22, the ratio R is small because the light is reflected by the metal on the surface of the wafer 20.

[0061] A seed metal 40 is formed on the surface of the wafer 20, and a resist 42 is formed on the seed metal 40. After forming the pattern of the resist 42, residues of the resist will form the foreign matter 22. In the first embodiment, it is possible to determine that the foreign matter 22 is a resist. For example, the inside of the opening 43 of the resist 42 can be scanned by the laser beam. When the ratio R is less than 0.15, the controller 10 estimates that the metal foreign matter or the seed metal 40 is irradiated by the laser beam, and when the ratio R is 0.15 or greater, the controller 10 estimates that the resist foreign matter is irradiated by the laser beam. Therefore, it can be determined whether the foreign matter 22 is a metal or a non-metal.

[0062] A plating layer 44 is formed on a seed metal 40, and the plating layer 44 serves as a lower electrode of a capacitor. Metallic foreign matter is included in the plating layer 44. On the other hand, resist foreign matter causes defects in the plating layer 44 and the dielectric film 46, and forms a leakage path in the capacitor. When a voltage is applied to the capacitor, a short circuit through the leakage path is likely to occur. Passive elements and active elements other than the capacitor can be formed on the wafer 20. When forming pads, residues of the resist may form foreign matter. In the first embodiment, it is determined whether the foreign matter 22 is metal or resist. The wafers 20 adhered with resist foreign matter are screened out as defective, thereby preventing the manufacture of defective capacitors.

[0063] Second Embodiment

[0064] Also in the second embodiment, as in the first embodiment, the processing shown in Figure 1 is performed using the surface inspection device 100 shown in Figure 5 . The second embodiment uses laser beams of five wavelengths.

[0065] Figures 9A to 9C The reflectance is shown, and examples in which the resist has a thickness of 1.40 μm, an example in which the resist has a thickness of 1.50 μm, and an example in which the resist has a thickness of 1.60 μm are shown respectively. The laser source 12 emits laser beams of five wavelengths of 658 nm, 690 nm, 705 nm, 730 nm, and 780 nm represented by dotted lines. When the foreign matter 22 is metal, the reflectance is low at short wavelengths and high at long wavelengths. On the other hand, when the foreign matter 22 is resist, the reflectance changes periodically with respect to the wavelength.

[0066] As Figure 5 shown, the controller 10 calculates the difference between them, their sum, and the ratio R of the difference to the sum using the maximum reflectance and the minimum reflectance among the reflectances of the resist. In the example shown in Figure 9A , among the respective reflectances at the five wavelengths, the reflectance of the resist is the maximum at 690 nm and the minimum at 730 nm. In the example shown in Figure 9B , among the respective reflectances at the five wavelengths, the reflectance of the resist is the maximum at 730 nm and the minimum at 780 nm. In the example shown in Figure 9C , among the respective reflectances at the five wavelengths, the reflectance of the resist is the maximum at 780 nm and the minimum at 705 nm. The difference between these reflectances is greater than that of metal. Therefore, the controller 10 can determine whether there is foreign matter 22 and whether the foreign matter 22 is metal or non-metal by calculating the ratio R from these reflectances.

[0067] Figure 10Shows the relationship between the difference in the thickness of the resist and the reflectivity. The horizontal axis represents the thickness of the resist, and the vertical axis represents the difference in reflectivity. The difference in reflectivity is the difference between the maximum reflectivity and the minimum reflectivity among the laser beams with wavelengths of 658 nm, 690 nm, 705 nm, 730 nm, and 780 nm. As Figure 10 shown, the maximum reflectivity difference is approximately -0.2, and the reflectivity difference is approximately -0.3 at a thickness of 1.45 to 1.6. Therefore, the ratio R is large. Accordingly, it is possible to accurately determine whether there is a foreign object 22 or whether the foreign object 22 is metal or non-metal by irradiating with laser beams of five wavelengths. Laser beams of five or more wavelengths such as six wavelengths or eight wavelengths can be used.

[0068] In the second embodiment, the laser source 12 emits laser beams of five or more wavelengths, and the controller 10 determines whether there is a foreign object 22 and whether the foreign object 22 is metal or non-metal based on the reflectivity of the foreign object 22 with respect to the laser beams. Therefore, it is possible to quickly determine whether the foreign object 22 is metal or non-metal. In particular, using laser beams of five or more wavelengths makes the ratio R in the resist larger. On the other hand, the reflectivity of the metal does not change significantly with respect to five or more wavelengths, and thus the ratio R is small. Therefore, high-precision determination can be performed.

[0069] Although the embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and alterations can be made without departing from the spirit and scope of the present invention.

Claims

1. A method for inspecting the surface of a wafer, the method comprising the steps of: irradiating the surface of the wafer with a laser beam having three or more different wavelengths; detecting reflected light from the surface of the wafer when irradiating the surface of the wafer with the laser beam; determining whether there is a foreign object on the surface of the wafer based on the reflectivity of the surface of the wafer with respect to the laser beam having the three or more different wavelengths; and when there is a foreign object, determining whether the foreign object is a metal or a non-metal, wherein determining whether the foreign object is a metal or a non-metal includes the following steps: obtaining a maximum reflectivity and a minimum reflectivity among the reflectivities at the different wavelengths, obtaining a difference between the maximum reflectivity and the minimum reflectivity and a sum of the maximum reflectivity and the minimum reflectivity, and when the ratio of the difference to the sum is less than 0.15, determining that the foreign object is a metal, and when the ratio is 0.15 or greater, determining that the foreign object is a non-metal.

2. The method according to claim 1, wherein each of the three or more different wavelengths of the laser beam is 600 nm or greater.

3. The method according to claim 1, further comprising the step of: irradiating the surface of the wafer with a laser beam having five or more different wavelengths.

4. An apparatus for inspecting the surface of a wafer, the apparatus comprising: a laser source that irradiates the surface of the wafer with a laser beam having three or more different wavelengths; a detector that detects reflected light from the wafer when irradiating the surface of the wafer with the laser beam; and a controller that determines whether there is a foreign object and whether the foreign object is a metal or a non-metal based on the reflectivity with respect to the laser beam having the three or more different wavelengths, wherein the controller determines whether the foreign object is a metal or a non-metal by the following operations: obtaining a maximum reflectivity and a minimum reflectivity among the reflectivities at the different wavelengths, obtaining a difference between the maximum reflectivity and the minimum reflectivity and a sum of the maximum reflectivity and the minimum reflectivity, and when the ratio of the difference to the sum is less than 0.15, determining that the foreign object is a metal, and when the ratio is 0.15 or greater, determining that the foreign object is a non-metal.

5. A method for manufacturing an electronic component, comprising the steps of: forming a metal layer on the surface of a wafer; forming a resist pattern on the surface of the metal layer; after the step of forming the resist pattern, irradiating the surface of the wafer with a laser beam having three or more different wavelengths to determine whether there is a foreign object on the surface of the wafer based on the reflectivity with respect to the three or more laser beams; when there is the foreign object, determining whether the foreign object is a metal or a non-metal; and when there is no foreign object or when the foreign object is a metal, forming a plating layer on the metal layer, wherein the step of determining whether the foreign object is a metal or a non-metal includes the following operations: Obtain the maximum reflectance and the minimum reflectance among the reflectances at the different wavelengths, Obtain the difference between the maximum reflectance and the minimum reflectance and the sum of the maximum reflectance and the minimum reflectance, and When the ratio of the difference to the sum is less than 0.15, determine that the foreign object is a metal, and when the ratio is 0.15 or greater, determine that the foreign object is a non-metal.

6. The manufacturing method according to claim 5, wherein, The electronic component is a capacitor, The coating layer is included in the lower electrode of the capacitor, and The manufacturing method further includes the following steps: Form a dielectric film on the coating layer; and Form an upper electrode on the dielectric film.

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