Method for automatically inspecting, classifying, and removing defect of flat substrate

Abstract

Provided is a method for automatically inspecting, classifying, and removing a defect of a flat substrate, the method comprising: a first step of photographing, using a camera unit, the surface of a flat substrate including a wafer or a mask, and inspecting a defect; a second step of determining, according to preconfigured criteria, whether the defect is removable and one of a plurality of removal methods for the defect, and automatically classifying the defect; a third step of, if the defect is a removable type, moving a defect removal module to a target position where the defect is located; a fourth step of selecting any one unit in the defect removal module according to the removal method for the defect, and removing the defect; and a fifth step of checking whether the defect has been removed.

Description

Method for automatically inspecting, classifying and removing defects on a flat substrate

[0001] The present invention relates, in particular, to a method for automatically performing the entire process of inspecting a flat substrate including a wafer or a mask, determining various defects on the flat substrate, classifying them accordingly, and ultimately removing them.

[0002] Optical inspection equipment is typically used to inspect for defects in substrates such as semiconductor wafers. Conventionally, optical inspection of semiconductor wafers was conducted by comparing black-and-white images captured by a mono camera. However, this method struggled to accurately identify various types of defects, making automatic defect classification difficult and reducing inspection reliability.

[0003] Furthermore, if a defect was discovered on the wafer, it could be removed using a cleaning device. However, this relied on manual labor by the operator, or, if not, resulted in the wafer being discarded altogether, resulting in problems such as reduced product yield and loss of manufacturing costs.

[0004] In addition, there were problems such as the operator's inevitability in the overall process, from inspection of wafers to classification and removal of defects based on the results, and differences in productivity and labor consumption depending on the operator's skill level.

[0005] This is a similar situation in the case of masks including photo masks.

[0006] An embodiment of the present invention has been devised to solve the above problems, and provides a method for automatically inspecting defects on a flat substrate including a wafer or mask, automatically classifying the defects, and automatically removing the defects.

[0007] We aim to improve the reliability of inspection results for flat substrates through an algorithm that minimizes misjudgments during the inspection phase. In the classification phase, we aim to ensure that defects are accurately classified according to pre-established criteria. In the removal phase, we aim to provide a module that allows for selecting different methods depending on the type of defect on the flat substrate.

[0008] The present invention aims to provide a module that prevents floating substances generated during the process of removing defects from remaining on a flat substrate.

[0009] An embodiment of the present invention provides a method for automatically inspecting, classifying, and removing defects in a flat substrate, comprising: a first step of inspecting a defect by capturing an image of the surface of a flat substrate including a wafer or a mask with a camera unit; a second step of automatically classifying the defect by determining whether the defect can be removed and which of a plurality of removal methods for the defect is used according to preset criteria; a third step of moving a defect removal module to a target position where the defect is located if the defect is a type that can be removed; a fourth step of removing the defect by selecting a unit in the defect removal module according to the removal method for the defect; and a fifth step of confirming whether the defect has been removed.

[0010] It is preferable that the above first step inspects for the defect by comparing 1) a reference image obtained by preprocessing an original image of the surface of a flat substrate, and 2) a comparison image obtained by applying a color filter to a color scanned image of the surface of a flat substrate to minimize the difference in brightness.

[0011] In the second step, the removal method is preferably one of a first removal method of spraying gas toward the target location and its surroundings, a second removal method of irradiating a laser beam to the target location, and a third removal method of using the gas and the laser beam simultaneously, depending on the type of the defect.

[0012] In the third step, it is preferable that the defect removal module includes a cleaning unit that detaches the defect in a process of rapidly shrinking and then rapidly expanding the defect (foreign substance) through physical collision of the gas with the defect in response to the first removal method.

[0013] The third removal method preferably removes the defect by spraying the gas to cool the flat substrate and irradiating the laser beam.

[0014] Between the fourth and fifth steps, it is preferable to further include a fourth step for sucking up floating matter generated in the process of removing the defect.

[0015] The above floating material is sucked by a suction unit, and it is preferable that a suction part having a circular cross-section is formed on one side of the suction unit so that the floating material is sucked in a radial direction and is recessed inward.

[0016] According to the problem-solving means of the present invention as discussed above, various effects, including the following, can be expected. However, the present invention is not established only if it exhibits all of the following effects.

[0017] A method according to one embodiment of the present invention enables automatic inspection of defects on a flat substrate including a wafer or mask, automatic classification thereof, and automatic removal thereof.

[0018] Furthermore, the present method can improve the reliability of inspection results for flat substrates containing wafers or masks through an algorithm that minimizes misjudgments during the inspection stage. Furthermore, the present method can accurately classify defects according to preset criteria during the classification stage. Furthermore, the present method can select different methods during the removal stage depending on the type of defect on the flat substrate containing the wafer or mask. Furthermore, the present method can prevent floating particles generated during the defect removal process from remaining on the flat substrate containing the wafer or mask.

[0019] FIG. 1 is a flowchart of a method for automatically inspecting, classifying, and removing defects in a flat substrate according to one embodiment of the present invention.

[0020] Figure 2 is a drawing roughly showing the process of creating a comparison target image with minimized difference in brightness in Figure 1.

[0021] Figure 3 is a schematic diagram of a defect removal module according to one embodiment of the present invention.

[0022] Figure 4 is a schematic diagram showing an enlarged portion of the lower part of Figure 3.

[0023] Figure 5 is a schematic diagram showing the operation method of the laser unit of Figure 3.

[0024] Figure 6 is a schematic diagram showing the operation method of the cleaning unit of Figure 3.

[0025] Figure 7 is a schematic diagram of Figure 4 viewed from above.

[0026] To fully understand the structure and effects of the present disclosure, preferred embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below, and can be implemented in various forms and subject to various modifications. In the following description of the present invention, detailed descriptions of related known functions that are obvious to those skilled in the art and that may unnecessarily obscure the gist of the present invention will be omitted.

[0027] While terms like "first" and "second" may be used to describe various components, these components should not be limited by these terms. These terms may only be used to distinguish one component from another. For example, without departing from the scope of the present disclosure, a first component could be referred to as a "second component," and similarly, a second component could also be referred to as a "first component."

[0028] In this application, terms such as “include” or “have” are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but should be understood not to exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0029] The terminology used in this application is solely for the purpose of describing specific embodiments and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. Unless otherwise defined, terms used in the embodiments of this disclosure are to be interpreted as having the meanings commonly known to those skilled in the art.

[0030] Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

[0031] FIG. 1 is a flowchart illustrating a method for automatically inspecting, classifying, and removing defects in a flat substrate including a wafer or mask according to an embodiment of the present invention. Referring to FIG. 1, the method for automatically inspecting, classifying, and removing defects in a flat substrate (W) including a wafer or mask according to an embodiment of the present invention may include steps 1 (S10) to 5 (S50). Here, steps 1 to 5 may be performed automatically.

[0032] The first step is a step of inspecting for defects by capturing an image of the surface of a flat substrate (W) including a wafer or mask with a camera unit (100). (S10) In one embodiment, the flat substrate (W) including a wafer or mask is only one example of an inspection target, and if the actual use is as an inspection substrate, it is not related to the material such as glass or metal. The mask includes a photo mask, etc. Prior to the first step, the flat substrate (W) including a wafer or mask may be preceded by processes such as loading and alignment.

[0033] Fig. 2 is a drawing roughly showing the process of generating a comparison target image with minimized difference in brightness of Fig. 1. Referring to Fig. 2, more specifically, the first step can inspect for defects by comparing 1) a reference image obtained by preprocessing an original image of a surface of a flat substrate (W) including a wafer or mask, and 2) a comparison target image (CI) with minimized difference in brightness by applying a color filter to a scanned image (SI) obtained by color scanning the surface of a flat substrate (W) including a wafer or mask.

[0034] Here, the original image refers to a color image captured on a flat substrate (W) containing a normal wafer or mask. Furthermore, preprocessing may be performed on a portion or all of at least one original image, selected randomly. Furthermore, image preprocessing may be the same process as converting a scanned image (SI) into a comparison target image (CI).

[0035] And, the scan image (SI) refers to a color image including a defect, that is, an image taken of a flat substrate (W) including a wafer or mask as an inspection target. The color filter may include, for example, an R (red) filter, a G (green) filter, a B (blue) filter, an H (hue) filter, an S (saturation) filter, and a V (value) filter. The scan image (SI) may be first converted into a filter image (FI) by applying the R filter, the G filter, the B filter, the H filter, the S filter, and the V filter, respectively. At this time, the filter image (FI) is a black and white image. Then, the filter image (FI) may be secondarily converted into a smoothed image with visually improved brightness by a preset histogram equalization algorithm. Then, the comparison target image (CI) may be generated by combining any one or at least one of a total of six smoothed images by a preset algorithm.

[0036] That is, the first step is to automatically detect defects on a flat substrate (W) including a wafer or mask, which is an inspection target, by generating a black and white image with no or minimal difference in brightness from a color image generated through a camera unit (100) and then comparing them with each other.

[0037] The second step is to automatically classify defects by determining whether the defect can be removed and which of multiple removal methods can be used for the defect, based on preset criteria. (S20)

[0038] Referring to [Table 1] below, defects can be classified into multiple types. Defects include bumps (B), foreign substances (C), discoloration, etc. on the surface of a flat substrate (W) including a wafer or mask. Foreign substances (C) include metallic, organic, etc. At this time, defects can be automatically classified into one of multiple types according to preset criteria. Then, whether the classified defects can be removed can be automatically determined based on the preset criteria. Then, the removal method for the classified defects can be automatically determined based on the preset criteria.

[0039]

[0040] Defect Type Removal Possible Removal MethodMissing Pattern (Bump) Impossible - Scratch Impossible - Foreign Material Possible Third Removal MethodPR Residue Possible Second Removal MethodUnformed Pattern (Bump) Impossible - Pattern (Bump) dent Impossible - Lump / Nodule Impossible - Bump Discoloration Possible Third Removal MethodRaw Material Possible First Removal MethodMetal Corrosion Possible Second Removal MethodPitting Impossible - Pattern (Bump) Misalign Impossible - Big Pattern (Bump) Impossible - Bridged Pattern (Bump) (Short) Impossible - Missing Pattern (Bump) Impossible - Passivation Damage Possible First Removal MethodUBM Residue Possible First Removal MethodScratch Impossible - Parasitic Bump Possible First Removal MethodForeign Material Possible Third Removal MethodSmall Bump Impossible - Unformed Bump Impossible - Pattern (Ball) Abnormal Impossible - Passivation Discoloration Possible 1st Removal Method RDL Discoloration Possible 1st Removal Method PSV Wrinkle Possible 1st Removal Method RDL Open Impossible - Pattern (Bump) Discoloration Impossible 1st Removal Method

[0041] In one embodiment, whether or not it is removable can be classified into, for example, possible and impossible. In addition, the removal method can be classified into, for example, one of the first removal method to the third removal method depending on the type of defect. First, the first removal method is a method of removing a defect by spraying gas toward a target location and its surrounding area. Then, the second removal method is a method of removing a defect by irradiating a laser beam (L) to the target location. In addition, the third removal method is a method of removing a defect by simultaneously using gas and a laser beam (L). Here, the target location refers to the location of a defect existing on the surface of a flat substrate (W) including a wafer or mask.

[0042] Meanwhile, if it is impossible to remove a defect, the defect may be removed through a manual removal process by an operator, etc., rather than through an automatic removal process by a preset algorithm or without going through a removal step.

[0043] FIG. 3 is a schematic diagram of a defect removal module according to one embodiment of the present invention, FIG. 4 is an enlarged schematic diagram of a lower portion of FIG. 3, FIG. 5 is a schematic diagram showing the operation method of the laser unit of FIG. 3, and FIG. 6 is a schematic diagram showing the operation method of the cleaning unit of FIG. 3.

[0044] The third step is a step of moving the defect removal module to the target position where the defect is located if the defect is of a removable type. (S30) Here, the defect removal module constitutes a part of the cleaner device. The defect removal module can be moved to the target position by, for example, a moving unit (not shown). The moving unit can move the defect removal module to the corresponding coordinates by address data including the coordinates of the target position, etc. In addition, the cleaner device according to one embodiment may include the camera unit (100) described above.

[0045] Meanwhile, the defect removal module may include a cleaning unit (400), a laser unit (200), a suction unit (500), etc. The cleaning unit (400) rapidly shrinks the defect (including foreign substances) through physical collision of gas with the defect (including foreign substances) in response to the first removal method, and then rapidly expands the defect, thereby detaching the defect (including foreign substances).

[0046] The cleaning unit (400) may include a spray nozzle (410) capable of spraying gas. In one embodiment, the cleaning unit may spray gas toward a target location and its surroundings. Here, the gas may be a cooling gas. In one embodiment, the cooling gas is sprayed at high pressure and may include solid CO2 pellets. In addition, the CO2 pellets (P) are preferably solid carbon dioxide (dry ice) formed in a size of several to several tens of micrometers.

[0047] At this time, the process of detaching the defect (foreign substance) will be described in detail. The CO2 pellet (P) having a temperature in the range of -70 to -80 degrees Celsius collides with the defect (foreign substance) and freezes the defect (foreign substance). In the process, the defect (foreign substance) rapidly contracts due to the temperature difference with the surroundings, causing a crack to occur. At this time, the CO2 pellet (P) injected at high speed may partially flow into the gap between the cracks of the defect (foreign substance). Alternatively, the CO2 pellet (P) may partially flow into the gap between the defect (foreign substance) and the flat substrate (W) including the wafer or mask. In addition, the CO2 pellet (P) that has flowed into the defect (foreign substance) may sublimate and, in one embodiment, its volume may expand by more than 800 times.

[0048] Meanwhile, since the CO2 pellets (P) sublimate into gas at room temperature, secondary contamination by the cooling gas itself can be prevented. As the CO2 pellets (P) expand, defects (foreign substances) may be broken by the expansion force or separated from the surface of the flat substrate (W) including the wafer or mask. The cleaning unit (400) can repeat this process to remove defects (foreign substances) attached to the surface of the flat substrate (W) including the wafer or mask. Meanwhile, floating substances may be generated during the defect (foreign substance) removal process by the cleaning unit (400).

[0049] The laser unit (200) irradiates a laser beam (L) to a target position to which a defect (including foreign substances) is attached in response to the second removal method, thereby removing the defect (including foreign substances). The laser unit (200) generates a laser beam (L) having a preset wavelength, pulse width, and output conditions. The laser unit (200) can generate a single pulse or multiple pulse laser beam (L). In addition, the laser beam (L) can be appropriately selected depending on the defect. In addition, the laser scanner unit (210) can adjust the optical axis of the laser beam (L) so that the laser beam (L) is irradiated to a preset position. Meanwhile, floating objects may be generated in the process of removing a defect (foreign substance) using the laser beam (L).

[0050] The third removal method is a method of removing defects by spraying gas to cool a flat substrate (W) including a wafer or mask while irradiating it with a laser beam (L). This method uses a cleaning unit (400) and a laser unit (200) together.

[0051] According to one embodiment of the present invention, in a process of removing a defect (foreign matter) by a laser unit (200), the cleaning unit (400) may be set to spray solid carbon dioxide to prevent thermal damage to a flat substrate (W) including a wafer or mask, thereby cooling the flat substrate (W) including a wafer or mask and simultaneously blowing away floating matter generated in the process of removing a defect (foreign matter).

[0052] That is, the cleaning unit (400) can be operated simultaneously during the defect (foreign substance) removal process by the laser unit (200). In one embodiment, the aforementioned CO2 pellet (P) has been confirmed to be suitable as a cooling gas and a blowing gas through our internal experiments.

[0053] Step 4 is a step of removing a defect by selecting a unit within the defect removal module according to a removal method for the defect. (S40) In one embodiment, any unit may be selected corresponding to the first removal method to the third removal method. In the case of the first removal method, the cleaning unit (400) may be selected, in the case of the second removal method, the laser unit (200) may be selected, and in the case of the third removal method, the cleaning unit (400) and the laser unit (200) may be selected.

[0054] Step 5 is a step for determining whether a defect has been removed (S50). This step may be performed, for example, only on defects determined to be removable. Step 5 may be performed automatically via a camera unit (100).

[0055] Meanwhile, between the fourth and fifth steps, a fourth-first step for sucking floating matter generated during the process of removing defects (foreign substances) may be further included. In one embodiment, the suction unit (500) may suck floating matter generated by the laser unit (200) and / or the cleaning unit (400). At this time, the suction unit (500) operates simultaneously with the laser unit (200) and / or the cleaning unit (400) to prevent floating matter from being reattached to the surface of the flat substrate (W) including the wafer or mask. At this time, the suction unit (500) may be arranged between the objective lens unit (300) and the flat substrate (W) including the wafer or mask. Meanwhile, the suction unit (500) may include a suction unit (510) for sucking air at the target position and its surroundings. In one embodiment, the suction unit (510) may be formed on one side of the suction unit (500).

[0056] Fig. 7 is a schematic diagram of Fig. 4 viewed from above. Referring to Fig. 7, a suction portion (510) is recessed into the inside of the suction unit (500) and may have a circular cross-section so that floating objects are sucked in a radial direction. Such a suction portion (510) can improve suction performance by generating an isotropic flow for floating objects.

[0057] Meanwhile, the inner diameter of the suction part (510) refers to the inner diameter of a circle formed by the cross section of the suction part (510). In one embodiment, the target position may be located at the inner diameter of the suction part (510). That is, the center of the inner diameter of the suction part (510) may be arranged on the optical axis of the objective lens part (300) or may be arranged on the optical path of the objective lens part (300). Alternatively, the center of the inner diameter of the suction part (510) may be arranged on the optical path of the camera unit (100). According to one embodiment, the inner diameter (second diameter) of the suction part (510) is preferably equal to or larger than the outer diameter (first diameter) of the objective lens part (300).

[0058] Referring again to FIG. 7, the cleaning unit (400) may be arranged to face the suction unit (510) and configured to spray carbon dioxide in a dry ice state toward the suction unit (510) during operation of the suction unit (500). For example, the cleaning unit (400) may be arranged on one open side of the suction unit (510). At this time, the cleaning unit (400) may generate anisotropic air flow so that floating objects are guided toward the suction unit (510).

[0059] In addition, as described above, the cleaning unit (400) can cool the surface of the flat substrate (W) including the wafer or mask during the defect (foreign material) removal process by the laser unit (200) by spraying a cooling gas. For example, the cooling gas sprayed by the cleaning unit (400) can be reflected on the surface of the flat substrate (W) including the wafer or mask and guided toward the suction unit (510).

[0060] Although the preferred embodiments of the present invention have been described above by way of example, the scope of the present invention is not limited to these specific embodiments, and may be appropriately modified within the scope described in the claims.

Claims

1. A first step of inspecting for defects by capturing an image of the surface of a flat substrate including a wafer or mask using a camera unit; A second step of automatically classifying the defect by determining whether the defect can be removed and which of a plurality of removal methods for the defect is used based on preset criteria; If the above defect is of a removable type, a third step of moving the defect removal module to the target location where the defect is located; A fourth step of removing the defect by selecting a unit within the defect removal module according to the removal method for the defect; and A method for automatically inspecting, classifying and removing defects on a flat substrate, comprising a fifth step of confirming whether the above defects have been removed.

2. In paragraph 1, The above first step is a method for automatically inspecting, classifying and removing defects in a flat substrate by comparing 1) a reference image obtained by preprocessing an original image of the surface of a flat substrate and 2) a comparison image in which a color filter is applied to a scanned image of the surface of a flat substrate to minimize the difference in brightness and darkness, thereby inspecting the defects.

3. In the first paragraph, in the second step, A method for automatically inspecting, classifying and removing defects on a flat substrate, wherein the above-mentioned removal method is one of a first removal method of spraying gas toward the target position and its surroundings, a second removal method of irradiating a laser beam to the target position, and a third removal method of using the gas and the laser beam simultaneously, depending on the type of the defect.

4. In the third paragraph, in the third step, A method for automatically inspecting, classifying and removing defects on a flat substrate, the defect removal module including a cleaning unit that rapidly shrinks and then rapidly expands the defect (foreign substance) through physical collision of the gas with the defect (foreign substance) in response to the first removal method.

5. In paragraph 3, The third removal method is a method for automatically inspecting, classifying and removing defects on a flat substrate by spraying the gas to cool the flat substrate and irradiating the laser beam to remove the defects.

6. In paragraph 1, Between the above 4th step and the above 5th step, A method for automatically inspecting, classifying and removing defects on a flat substrate, further comprising a step 4-1 of sucking up floating matter generated in the process of removing the above defects.

7. In paragraph 6, The above floating material is sucked by the suction unit, A method for automatically inspecting, classifying and removing defects in a flat substrate, wherein a suction unit having a circular cross-section is formed on one side of the suction unit so that floating matter is sucked in a radial direction.

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