Defect inspection methods

Abstract

Embodiments of the present invention relate to defect inspection methods. According to some embodiments of the present invention, a defect inspection method includes: receiving a substrate having a plurality of patterns; obtaining a grayscale image of the substrate, wherein the grayscale image includes a plurality of regions, and each of the regions has a grayscale value; comparing the grayscale value of each region with a grayscale reference to define a first group, a second group, and an Nth group, wherein each of the first group, the second group, and the Nth group has at least one region; performing a calculation to obtain a score; and determining that the substrate has an ESD defect when the score is greater than a value, and determining that the substrate does not have the ESD defect when the score is less than the value.

Description

Technical Field

[0001] An embodiment of the present invention relates to a defect inspection method. Background Art

[0002] The semiconductor integrated circuit industry has experienced rapid growth over the past few decades. Technological advances in semiconductor materials and design have resulted in ever-smaller and more complex circuits. These material and design advances have been made possible by technological advances in processing and manufacturing techniques. As semiconductors have evolved, the number of interconnected devices per unit area has increased as the size of the smallest component that can be reliably produced has decreased.

[0003] Semiconductor manufacturing relies heavily on photolithography, a process in which light of a given frequency is used to transfer a desired pattern onto a wafer undergoing semiconductor processing. To transfer the pattern onto the wafer, a photomask (also known as a mask or reticle) is typically used. The photomask allows light to be irradiated in the desired pattern onto a layer on the wafer, such as a photoresist (PR) layer. This light reacts chemically to the exposure, removing some portions of the PR and leaving others. The remaining PR is then used to pattern the underlying layer. As component size decreases, the wavelength of light used to pattern the layers in photolithography also decreases, creating additional difficulties and necessitating technological advancements, such as the use of extreme ultraviolet (EUV) light sources and phase-shift masks. Improving photomasks is important for promoting continued progress in the industry, particularly because defects in the patterned layers can worsen during subsequent processing steps in the manufacture of semiconductor devices and integrated circuits. Therefore, improvements in photomasks are needed, including improvements in defect detection. Summary of the Invention

[0004] According to one embodiment of the present invention, a defect inspection method includes: receiving a substrate having a surface and a plurality of patterns placed on the surface; obtaining a grayscale image of the substrate, wherein the grayscale image includes a plurality of regions, and each of the regions has a grayscale value; comparing the grayscale value of each region with a grayscale reference to define a first group, a second group, and an Nth group, wherein each of the first group, the second group, and the Nth group has at least one region, and the regions in the first group have a first difference between their grayscale values ​​and the grayscale reference, the regions in the second group have a second difference between their grayscale values ​​and the grayscale reference, and the regions in the Nth group have an Nth difference between their grayscale values ​​and the grayscale reference; performing a calculation based on the first difference, the second difference, and the Nth difference to obtain a score; and when the score is greater than a value, determining that the substrate has an electrostatic discharge (ESD) defect, and when the score is less than the value, determining that the substrate does not have the ESD defect.

[0005] According to one embodiment of the present invention, a defect inspection method includes: receiving a substrate having a surface and a plurality of patterns placed on the surface; obtaining a grayscale image of the substrate; defining a defect area in the grayscale image, wherein the defect area has a plurality of first areas, and each of the first areas has a grayscale value and a difference between its grayscale value and a grayscale reference; performing a calculation to obtain a score; and when the score is greater than a value, determining that the substrate has a complex defect, and when the score is less than the value, determining that the substrate does not have the complex defect.

[0006] According to one embodiment of the present invention, a defect inspection method includes: receiving a substrate having a surface and a plurality of patterns placed on the surface; obtaining a grayscale image of the substrate; defining a defect area in the grayscale image, wherein the defect area has at least one first area and a plurality of second areas, each of the first and second areas having a grayscale value and a difference between its grayscale value and a grayscale reference; performing a first calculation based on the difference between the grayscale reference and the grayscale value of each of the areas in the defect area to obtain a score; when the score is greater than a value, performing a second calculation to obtain a graph; and when two peaks are shown in the graph, determining that the substrate has a shielding layer extension defect, and when more than two peaks are shown in the graph, determining that the substrate has a hard mask / shielding layer extension defect. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] When read in conjunction with the accompanying drawings, aspects of the present disclosure will be better understood from the following detailed description. It should be noted that, in accordance with standard practice in the industry, the various components are not drawn to scale. In fact, the dimensions of the various components may be arbitrarily increased or decreased for clarity of discussion.

[0008] Figure 1 is a flow chart illustrating a defect inspection method according to aspects of the present disclosure.

[0009] Figure 2 is a cross-sectional view of a photomask according to aspects of the present disclosure.

[0010] Figures 3 to 5 is a schematic diagram of a photomask at various stages according to aspects of the present disclosure in one or more embodiments.

[0011] Figure 6 is a flow chart illustrating a defect inspection method according to aspects of the present disclosure.

[0012] Figures 7 to 14A is a schematic diagram illustrating a photomask at various stages of fabrication according to aspects of the present disclosure in one or more embodiments, and Figure 14B Schematic diagram illustrating a desired photomask.

[0013] Figure 15 and Figure 16A is a schematic diagram illustrating a photomask at various stages of fabrication according to aspects of the present disclosure in one or more embodiments, and Figure 16B Schematic diagram illustrating a desired photomask.

[0014] Figures 17 to 20 is a schematic diagram of a photomask at various stages according to aspects of the present disclosure in one or more embodiments.

[0015] Figure 21A is a portion of the grayscale image of the photomask.

[0016] Figure 21B is a graph showing calculation results according to aspects of the present disclosure in one or more embodiments.

[0017] Figures 22 to 24 is a schematic diagram of a photomask at various stages according to aspects of the present disclosure in one or more embodiments.

[0018] Figure 25A is a portion of the grayscale image of the photomask.

[0019] Figure 25B is a graph showing calculation results according to aspects of the present disclosure in one or more embodiments. DETAILED DESCRIPTION

[0020] The following disclosure provides many different embodiments or examples of the different components for implementing the provided subject matter. Specific examples of components and arrangements are described below to simplify this disclosure. Of course, these are merely examples and are not intended to be restrictive. For example, in the following description, forming a second component above or on a first component may include an embodiment in which the first and second components are formed to be in direct contact, and may also include an embodiment in which an additional component may be formed between the first and second components so that the first and second components may not be in direct contact. In addition, this disclosure may repeat reference numbers and / or letters in various examples. This repetition is for simplicity and clarity purposes and does not itself indicate the relationship between the various embodiments and / or configurations discussed.

[0021] This description of the illustrative embodiments is intended to be read in conjunction with the accompanying drawings, which should be considered part of the entire written description. In the description of the embodiments disclosed herein, any reference to direction or orientation is intended solely for ease of description and is not intended to limit the scope of the present disclosure in any way. Relative terms such as "lower," "upper," "horizontally," "vertically," "above," "below," "upward," "downward," "top," and "bottom," and their derivatives (e.g., "horizontally," "downward," "upward," etc.) should be interpreted as referring to the orientation as described subsequently or as shown in the discussed figures. Such relative terms are for ease of description only, and the device need not be constructed or operated in a specific orientation. Terms such as "attached," "attached," "connected," and "interconnected" refer to relationships in which structures are fixed or attached to each other directly or indirectly through intervening structures, as well as both removable and rigid attachments or relationships, unless expressly stated otherwise. Furthermore, the features and benefits of the present disclosure are illustrated by reference to the embodiments. Therefore, the present disclosure is expressly not limited to such embodiments illustrating some possible non-limiting feature combinations that may exist alone or in other feature combinations, the scope of the present disclosure being defined by the claims appended hereto.

[0022] Although the numerical ranges and parameters setting forth the broad scope of the present disclosure are approximate, the numerical values ​​set forth in the specific examples are reported as precisely as possible. However, any numerical value inherently contains certain errors inevitably caused by the standard deviation found in the corresponding testing measurements. Moreover, as used herein, the terms "substantially," "approximately," or "about" generally mean within a value or range that would be expected by one of ordinary skill in the art. Alternatively, the terms "substantially," "approximately," or "about" mean within an acceptable standard error of the mean when considered by one of ordinary skill in the art. One of ordinary skill in the art will understand that acceptable standard errors can vary from technology to technology. Except in the operating / working examples, or unless otherwise expressly specified, all numerical ranges, amounts, values, and percentages (e.g., for material quantities, durations, temperatures, operating conditions, ratios of amounts, and the like disclosed herein) should be understood as being modified in all instances by the terms "substantially," "approximately," or "about." Therefore, unless otherwise indicated, the numerical parameters set forth in the present disclosure and the appended claims are approximate values ​​that may vary as needed. At the very least, each numerical parameter should be understood in light of the number of reported significant figures and by applying ordinary rounding techniques. Ranges may be expressed herein as from one endpoint to the other or between two endpoints. Unless otherwise specified, all ranges disclosed herein include the endpoints.

[0023] Inspection is an important operation and is used to detect photomask defects after photomask manufacturing is completed or after an exposure operation. Photomask defects can be divided into two categories: hard defects and soft defects. Defects that cannot be removed by a cleaning operation are called hard defects, and defects that can be removed by a cleaning operation are called soft defects. Hard defects include, for example, changes in global uniformity, size errors, or misalignment. When hard defects are found and identified, appropriate operations can be used to repair or reprocess the photomask. In some comparative embodiments, if residual defects (such as Cr residual defects) are detected, post-plasma treatment can be performed. In some comparative embodiments, if localized hard defects are found, ion or electron beams can be used. In some comparative embodiments, if global size error defects are found, chemical solutions can be used. The repaired or reprocessed photomask is then inspected again to ensure mask quality. However, in some comparative embodiments, when using current inspection models, defect types such as electrostatic discharge (ESD) defects and complex defects may not be found.

[0024] ESD defects can occur after the exposure operation. During the exposure operation or during the transfer or storage of the photomask, static electricity can be generated and tends to form an electric field on the photomask. When the electric field attracts charged particles to the photomask, a neutralizing discharge reaction is triggered on the surface of the photomask, thereby burning or melting the mask pattern. ESD defects cannot be easily detected by current inspection methods because ESD defects form an extremely fine layer on the surface. Therefore, a photomask with ESD defects that cannot be detected by inspection tools can be used in subsequent photolithography operations. In some comparative embodiments, the pattern on the photomask with defects cannot be accurately and precisely transferred.

[0025] In addition to ESD defects, there are also complex defects. Complex defects occur when a shielding layer or hard shielding layer that should be removed is still on the photomask. Complex defects include two types. In one type, a shielding layer expansion defect is said to occur when a shielding layer appears at the location where it should be removed. In another type of defect, a hard mask / shielding layer expansion defect is said to occur when a hard masking layer (which should be completely removed from the photomask) appears. The two defect types are called complex defects because both shielding layer expansion defects and hard mask / shielding layer expansion defects show similar results when using current inspection tools, and it is difficult for the inspection tools to determine which type of layer is still on the photomask. It should be noted that the shielding layer and the hard shielding layer are removed by different removal operations. If an unsuitable removal operation is used, the layer planned to be removed will not be removed or other layers may be removed by mistake. Since the inspection tool cannot determine which layer is still on the photomask, further inspection operations are required to avoid unsuitable removal operations. Therefore, existing methods suffer from cycle time waste.

[0026] Therefore, the present disclosure provides a defect inspection method. In some embodiments, the defect inspection method is performed to detect ESD defects. In some embodiments, the defect inspection method provides a first calculation. The first calculation is used to amplify the ESD defect and thus determine the presence of the ESD defect. In some embodiments, the defect inspection method is performed to detect complex defects. In some embodiments, the defect inspection method provides a second calculation. The second calculation helps distinguish between shielding layer extension defects and hard mask / shielding layer extension defects. Therefore, suitable removal operations can be performed. The provided defect inspection method is capable of accurately detecting and identifying defects using current inspection tools. Therefore, inspection reliability can be improved and inspection cycle time can be reduced. In addition, additional costs for tool modifications can be avoided.

[0027] Figure 1 1 is a flow chart illustrating a defect inspection method 100 according to aspects of the present disclosure. Method 100 includes several operations ( 101 , 102 , 103 , 104 , 105 a , and 105 b ). Defect inspection method 100 will be further described according to one or more embodiments. It should be noted that the operations of defect inspection method 100 may be rearranged or otherwise modified within the scope of various aspects. It should be further noted that additional manufacturing processes may be provided before, during, and after method 100 , and that only some of these additional manufacturing processes are briefly described herein. Therefore, other implementations are possible within the scope of the various aspects described herein.

[0028] In some embodiments, the defect inspection method can be used in a lithography system. In some embodiments, the lithography system can be referred to as a scanner operable to perform lithography exposure operations using a corresponding radiation source and exposure mode. In some embodiments, the lithography system can include an optical exposure tool, such as an I-line (365 nm), deep ultraviolet (DUV, having a wavelength less than about 250 nm, but more typically using from about 193 nm to about 230 nm), extreme ultraviolet (EUV), or X-ray exposure tool, or a charged particle tool (e.g., an electron beam writer).

[0029] refer to Figure 2(This is a cross-sectional view of a photomask PM1 according to aspects of the present disclosure.) Photomask PM1 includes a light-transmissive substrate 200 comprising a suitable material, such as a low thermal expansion material (LTEM) or fused silica. In various examples, the LTEM comprises SiO2 doped with TiO2 or another suitable material with low thermal expansion. Photomask PM1 includes a phase-shift layer (PSL) 202 formed above substrate 200. Phase-shift layer 202 is formed to transmit less than approximately 20% of incident light and to produce a phase shift of approximately 180 degrees relative to transmitted light (i.e., light transmitted through the light-transparent substrate). In some embodiments, phase-shift layer 202 comprises molybdenum silicide (MoSi), molybdenum silicide nitride (MoSiN), molybdenum silicide oxynitride (MoSiON), titanium nitride, titanium silicon nitride, or silicon nitride, but the present disclosure is not limited thereto. In some embodiments, photomask PM1 may include a shielding layer 204 above phase-shift layer 202. Shielding layer 204 may include chromium (Cr) and may include other layers, such as chromium oxide, chromium nitride, and chromium oxynitride. While some examples of materials that can be used for each of substrate 200, phase-shift layer 202, and shielding layer 204 are provided, it will be understood that other suitable materials known in the art may also be used without departing from the scope of this disclosure. Additionally, photomask PM1 may include other layers, such as a backside coating and / or an antireflective coating (ARC), though these are not shown. Furthermore, other photomask configurations may also be provided as photomask PM1.

[0030] Still refer to Figure 2 The photomask PM1 may include a pellicle 206 that acts as a protective cover. The pellicle 206 protects the pattern on the substrate 200 from damage and / or contaminating particles. The pellicle 206 may be a thin film on a frame covering the patterned surface of the photomask PM1.

[0031] refer to Figure 2 During the exposure operation, light is directed to the photomask PM1 and reflected by the photomask PM1, and then the light reflected by the photomask PM1 is directed to the wafer. During the exposure operation, the pellicle 206 may absorb light. In some comparative embodiments, thermal effects and static electricity may be generated. Therefore, an undesirable thin film 208 may be formed over the pattern formed by the phase shift layer 202, such as Figure 2 As mentioned above, the thin film 208 is referred to as an ESD defect. In some embodiments, the defect inspection method 100 is performed after the exposure operation.

[0032] refer to Figure 2 In operation 101 , a substrate having a surface and a plurality of patterns disposed on the surface is received.

[0033] In some embodiments, the substrate may be the photomask PM1 mentioned above. In some embodiments, the substrate may be the substrate 200 of the photomask PM1, and the pattern may be formed by the phase-shift layer 202, but the present disclosure is not limited thereto.

[0034] In operation 102 , a grayscale image of a substrate is obtained, wherein the grayscale image includes a plurality of regions, and each of the regions has a grayscale value.

[0035] refer to Figure 3 In some embodiments, the surface of the substrate 200 of the photomask PM1 is scanned by an optical inspection tool to generate an image 210 of the pattern. In some embodiments, the photomask PM1 can be scanned after the pellicle 206 is removed. In some embodiments, the photomask PM1 can be scanned by a reflective optical inspection tool and thus reflective light is generated from the surface of the substrate 200. In the illustrated embodiment, the image is generated by the optical inspection tool and depicts the pattern elements in the pattern of the photomask PM1 as lighter gray on a darker gray background. That is, different parts of the obtained image 210 have different grayscale intensities, and therefore the obtained image 210 is referred to as a grayscale image. In some embodiments, the image 210 can be divided into or defined as a plurality of regions 212. In some embodiments, each of the regions 212 substantially corresponds to a pixel of the reflective optical inspection tool. In some embodiments, the area of ​​each region 212 can be between about 55 nm 2 About 500nm 2 In addition, the image 210 can be converted into a grayscale image by proportionally adjusting the grayscale of the image region by region through light leveling. Therefore, each of the regions 212 obtains a grayscale value.

[0036] In operation 103, the grayscale value of each region 212 is compared with a grayscale reference to define a first group G1, a second group G2, and an Nth group Gn, wherein each of the first group G1, the second group G2, and the Nth group Gn has at least one region 212, and the region 212 in the first group G1 has a first difference between its grayscale value and the grayscale reference, the region 212 in the second group G2 has a second difference between its grayscale value and the grayscale reference, and the region 212 in the Nth group Gn has an Nth difference between its grayscale value and the grayscale reference.

[0037] In some embodiments, a standard or golden image can be provided. The standard or golden image can include a target pattern, to which the pattern of photomask PM1 should be identical. The standard or golden image can be defined or divided into multiple regions. Subsequently, light leveling can be used to scale the standard or golden image to obtain a grayscale reference region by region, thereby converting the golden image. As mentioned above, in some embodiments, each region of the golden image substantially corresponds to a pixel of a reflective optical inspection tool. In some embodiments, the grayscale reference can be obtained from a database of the defect inspection tool. Therefore, the grayscale reference also includes multiple grayscale values.

[0038] In some embodiments, the grayscale value of each of the regions 212 in the image 210 of the photomask PM1 is compared with one of the grayscale values ​​of the grayscale reference. In some embodiments, the grayscale value of the region 212 of the photomask is compared with the grayscale value of the corresponding region of the grayscale reference. Thus, the difference between the grayscale value of each of the regions 212 of the photomask PM1 and the grayscale value of the corresponding region of the grayscale reference is obtained. Reference Figure 4 , each of the regions 212 has differences.

[0039] refer to Figure 5 , the regions 212 are grouped into a first group G1, a second group G2, and an Nth group according to their differences. In some embodiments, the grouping of the regions 212 may be performed according to Table 1:

[0040] Grayscale Difference Weighting Factor Group 1 (G1) -50-0&0-50 0.9 Group 2 (G2) -69--50&50-69 0.925 Group 3 (G3) -89--70&70-89 0.95 Group 4 (G4) -99--90&90-99 0.975 Group 5 (G5) <-100&>100 1

[0041] As shown in Table 1, a range is provided, and regions 212 having differences within the same range are grouped into the same group. In some embodiments, each of the first group G1, the second group G2, and the Nth group Gn has at least one region 212. The regions 212 in the first group G1 have a first difference between their grayscale values ​​and a grayscale reference, the regions 212 in the second group G2 have a second difference between their grayscale values ​​and the grayscale reference, and the regions 212 in the Nth group Gn have an Nth difference between their grayscale values ​​and the grayscale reference. In some embodiments, the first difference is smaller than the second difference, and the (N-1)th difference is smaller than the Nth difference, as shown in Table 1.

[0042] In operation 104, a calculation is performed based on the first difference, the second difference, and the Nth difference to obtain a score. In some embodiments, the calculation is performed according to equation (1):

[0043]

[0044] Where Ws is the score, G is the first zone G1, the second zone G2, the third zone G3 and the Nth zone G N The individual grayscale values ​​in , e1 is the first weighting factor, e2 is the second weighting factor, and e n is the Nth weighting factor.

[0045] In some embodiments, the first weighting factor e1, the second weighting factor e2, and the Nth weighting factor e n The weighting factors may be those provided in Table 1, but the present disclosure is not limited thereto. In such an embodiment, the first weighting factor e1 is smaller than the second weighting factor e2, and the (N-1)th weighting factor e (n-1) Less than the Nth weighting factor e n .

[0046] For example, in some embodiments, the following may be used in the calculation: Figure 5 The differences shown in .

[0047]

[0048] According to equation (1), the score Ws is obtained as shown above.

[0049] In operation 105a, when the score Ws is greater than a value, it is determined that the substrate has an ESD defect. In operation 105b, when the score Ws is less than the value, it is determined that the substrate does not have an ESD defect.

[0050] In some embodiments, the value may be 0.92. In such embodiments, the score Ws (which is 0.921, as mentioned above) is greater than the value, and thus it is determined that the photomask PM1 has an ESD defect.

[0051] It should be noted that the difference between the grayscale values ​​of region 212 of image 210 and the grayscale values ​​of the grayscale reference can reveal variations in the surface condition of the pattern on photomask PM1 after the exposure operation compared to the original surface condition of photomask PM1 or a standard surface condition of photomask PM1. A larger difference, compared to surface conditions found in a similar comparison exhibiting a smaller difference, can indicate that the surface condition of the inspected photomask PM1 differs more significantly from the original surface condition. Furthermore, a larger difference can be amplified by multiplying the grayscale value by a weighting factor. Thus, ESD defects can be easily detected.

[0052] In some embodiments, an aerial image measurement system (AIMS) is used when determining that a substrate has an ESD defect. AIMS is a measurement method that provides the ability to simulate exposure results on a substrate (i.e., a photomask substrate) using information including, but not limited to, optical proximity correction (OPC), mask error enhancement factor (MEEF), and mask 3D effect information. In some embodiments, AIMS can be used to re-inspect ESD defects.

[0053] In some embodiments, determining that photomask PM1 does not have an ESD defect indicates that a thin film has not been formed over the pattern (i.e., phase-shift layer 202); however, such a thin film may have been formed over the pattern but not be thick enough to alter reflection and thus may not be detected. Therefore, photomask PM1 can be used in subsequent exposure operations. In some embodiments, determining that photomask PM1 has an ESD defect indicates that a thin film may have been formed over the pattern (i.e., phase-shift layer 202) and that the thin film is thick enough to alter reflection and thus may adversely affect exposure results. Therefore, photomask PM1 determined to have an ESD defect is removed from subsequent exposure operations, and appropriate operations may be performed to remove the thin film.

[0054] As mentioned above, ESD defects occur when a thin film is formed over the pattern surface of the photomask PM1. ESD defects may be indistinguishable but may still cause serious problems in the exposure operation. By grouping the region 212 into a first group G1, a second group G2, and an Nth group Gn and by providing different weighting factors for different groups, the group with ESD defects can be magnified and therefore more easily identified. In addition, by providing a calculation using equation (1), a score Ws can be easily obtained, which can represent the condition of the entire surface. In addition, when the score Ws is greater than the value, an ESD defect can be detected. In some embodiments, the value is adjustable. In short, the defect inspection method 100 can be performed to detect ESD defects using current inspection tools. Since the defect inspection method 100 provides a weighted model (as shown in equation (1)), ESD defects can be magnified and easily detected.

[0055] Figure 6 is a flow chart showing a defect inspection method 300 according to aspects of the present disclosure, Figures 7 to 14A is a schematic diagram illustrating a photomask at various stages according to aspects of the present disclosure in one or more embodiments, Figure 14B is a schematic diagram illustrating the desired photomask, Figure 15 and Figure 16A is a schematic diagram illustrating a photomask at various stages according to aspects of the present disclosure in one or more embodiments, and Figure 16B is a schematic diagram illustrating a desired photomask. Method 300 includes several operations (301, 302, 303, 304, 305, 306, 307a, and 307b). Defect inspection method 300 will be further described according to one or more embodiments. It should be noted that the operations of defect inspection method 300 may be rearranged or otherwise modified within the scope of various aspects. It should further be noted that additional manufacturing processes may be provided before, during, and after method 300, and that only some of these additional manufacturing processes are briefly described herein. Therefore, other implementations are possible within the scope of the various aspects described herein.

[0056] In some embodiments, the defect inspection method 300 may be performed after a photomask manufacturing operation. In some embodiments, the defect inspection method 300 may be performed after a phase-shift photomask manufacturing operation. In some embodiments, the defect inspection method 300 may be performed after a hard mask attenuated phase-shift mask (HMAPSM) manufacturing operation.

[0057] It should be noted that the same components in method 100 and method 300 may include the same materials, and thus repeated descriptions are omitted for the sake of brevity.

[0058] refer to Figure 7 In some embodiments, the photomask fabrication operation may include the following operations. A substrate 400 is provided. The substrate 400 may be a light-transmissive substrate. A phase-shift layer 402 may be formed on the substrate 400. Deposition of the phase-shift layer 402 may include atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), pulsed laser deposition (PLD), sputtering, spin-on deposition (SOD), or the like, or a combination thereof. In some embodiments, the thickness of the phase-shift layer 402 ranges from approximately 40 nm to approximately 100 nm, depending on the wavelength of the light source. In some embodiments, a greater or lesser thickness increases the deviation from the phase shift by π, thereby reducing pattern resolution. However, those skilled in the art will appreciate that the thickness of the phase-shift layer 402 is determined by the transmittance of the selected material, the wavelength of the light source, and the depth of focus (DOF) during the fabrication process. For example, if the phase-shift layer 402 comprises molybdenum and silicon oxynitride, the thickness of the phase-shift layer 402 may range from approximately 60 nm to approximately 70 nm.

[0059] Still refer to Figure 7 , a shielding layer 404 is formed on the phase-shift layer 402. In some embodiments, the shielding layer 404 may comprise a light-blocking material having a thickness sufficient to block greater than approximately 90% (and more specifically, greater than approximately 99%) of incident light from passing therethrough. In some embodiments, the shielding layer 404 may comprise a stack of layers (e.g., a Cr layer) formed above a glue layer (not shown) as is known in the art. The total thickness of the shielding layer 404 depends on the desired light transmission characteristics and the etch rate in subsequent etching operations. Typically, the thickness of the shielding layer 404 ranges from approximately 500 angstroms to approximately 1500 angstroms and may be formed using conventional CVD, PECVD, or PVD deposition methods.

[0060] A hard mask layer 405 is formed over the mask layer 404. In some embodiments, the hard mask layer 405 comprises silicon nitride, silicon carbide, silicon oxynitride, silicon oxycarbide, or another suitable material. The deposition of the hard mask layer 405 comprises ALD, CVD, PVD, PLD, sputtering, SOD, the like, or a combination thereof. In some embodiments, to help improve the photolithography manufacturing process, the hard mask layer 405 may have anti-reflective properties. In some embodiments, the hard mask layer 405 comprises silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, or other suitable material. In some embodiments, the hard mask layer 405 comprises a single layer. In some embodiments, the hard mask layer 405 comprises multiple layers. In some embodiments, the thickness of the hard mask layer 405 is between approximately 5 nm and approximately 25 nm. In some embodiments, a larger thickness increases manufacturing costs without significantly improving functionality. In some embodiments, a smaller thickness increases the risk of overetching, thereby causing damage to the phase shifter. Subsequently, a patterned photoresist 407 is formed by depositing a layer of photosensitive material and performing a photolithography process (eg, electron beam writing, laser writing, ultraviolet (UV), EUV, or other suitable processes).

[0061] refer to Figure 8 , the pattern of the patterned photoresist layer 407 is transferred to the hard mask layer 405. After the transfer, the patterned photoresist layer 407 is removed. Figure 9 After removing the patterned photoresist layer 407, an etching operation is performed to etch the shielding layer 404 and the phase-shift layer 402 through the patterned hard mask layer 405. Figure 10 and Figure 11 After etching the mask layer 404 and the phase-shift layer 402, the hard mask layer 405 is removed, and another photoresist layer 409 is formed over the substrate 400. Figure 12 , a photolithography operation may be performed to form a patterned photoresist layer 409'. In some embodiments, a portion of the patterned photoresist layer 409' that should be removed by the photolithography operation may remain on the masking layer 404 and may be referred to as a residue 409r, such as Figure 12 Reference Figure 13 In some embodiments, portions of the masking layer 404 are removed by patterning the photoresist layer 409 ′.

[0062] refer to Figure 14A After removing the portion of the phase shift layer 402, the patterned photoresist layer 409' is removed. In some comparative embodiments, the residue 409r may be removed during the removal of the patterned photoresist layer 409', and a photomask PM2 may be obtained. Figure 14A Since the residue 409r may hinder the removal of part of the shielding layer 404, a part of the shielding layer that should be removed may remain on the substrate 400. Figure 14Aand Figure 14B ,in Figure 14B is a schematic diagram illustrating a desired photomask d-PM. In some comparative embodiments, when compared with the desired photomask d-PM, the remaining portion 408a of the shielding layer may be referred to as a shielding layer extension defect. As mentioned above, the shielding layer extension defect 408a is one of the complex defects.

[0063] In addition to masking layer extension defects, complex defects further include hard mask / masking layer extension defects. Figure 15 , in some comparative embodiments, after the pattern of the patterned photoresist layer 407 is transferred and the patterned photoresist layer 407 is removed, a residue 407 ′ of the patterned photoresist layer 407 may remain on the hard mask layer 405 .

[0064] The residue 407' may hinder subsequent etching operations, and thus a portion 405' of the hard mask layer 405 and a portion 404' of the mask layer 404 that should be removed remain over the substrate 400. Figure 16A and Figure 16B ,in Figure 16B is a schematic diagram illustrating the desired photomask d-PM. In some comparative embodiments, when compared with the desired photomask d-PM, the remaining portion 405' of the hard mask layer 405 and the remaining portion 404' of the shielding layer 404 can be collectively referred to as a thin film 408b, and this thin film 408b is referred to as a hard mask / shielding layer extension defect.

[0065] In operation 301 , a substrate having a surface and a plurality of patterns disposed on the surface is received.

[0066] In some embodiments, the substrate may be a photomask PM2 as mentioned above. In some embodiments, the substrate may be a photomask PM2 as mentioned above. Figure 14A or Figure 16A The substrate 400 of the photomask PM2 is shown in FIG. 4 , and the pattern may be formed by the phase-shift layer 402 , but the present disclosure is not limited thereto.

[0067] In operation 302 , a grayscale image of a substrate is obtained, wherein the grayscale image includes a plurality of regions, and each of the regions has a grayscale value.

[0068] refer to Figure 17In some embodiments, the surface of substrate 400 of photomask PM2 is scanned by an optical inspection tool to generate an image 410 of a pattern. In some embodiments, photomask PM2 may be scanned by a reflective optical inspection tool, thereby generating reflected light from the surface of substrate 400. In the illustrated embodiment, the image generated by the optical inspection tool depicts pattern elements in the pattern of photomask PM2 as lighter grays against a darker gray background. That is, different portions of the obtained image 410 have different grayscale intensities, and thus the obtained image 410 is referred to as a grayscale image. In some embodiments, image 410 may be divided or defined into a plurality of regions 412. In some embodiments, each of regions 412 substantially corresponds to a pixel of the reflective optical inspection tool. In some embodiments, regions 412 may be defined along a first direction D1 and a second direction D2 that are perpendicular to each other. In some embodiments, regions 412 may be defined to form an array having columns and rows, but the present disclosure is not limited thereto. Furthermore, image 410 may be converted into a grayscale image by proportionally adjusting the grayscale of the image region by region through optical leveling. Thus, each of regions 412 acquires a grayscale value.

[0069] At operation 303 , a grayscale image of the substrate is compared to a grayscale reference to identify potential defect areas.

[0070] refer to Figure 18 , comparing the grayscale value of each region 412 to a grayscale reference. In some embodiments, a standard or golden image may be provided. The standard or golden image may be an image of the desired photomask d-PM. The standard or golden image may be defined or divided into a plurality of regions. Subsequently, the standard or golden image may be converted by scaling the standard or golden image through light leveling to obtain a grayscale reference region by region. As mentioned above, in some embodiments, each region of the golden image substantially corresponds to a pixel of a reflective optical inspection tool. In some embodiments, the grayscale reference may be obtained from a database of the defect inspection tool. Therefore, the grayscale reference also includes a plurality of grayscale values.

[0071] In some embodiments, the grayscale value of each region 412 in the image 410 of the photomask PM2 is compared with the grayscale value of the grayscale reference. In some embodiments, the grayscale value of each region 412 of the photomask PM2 is compared with the grayscale value of the corresponding region of the grayscale reference. Thus, the difference between the grayscale value of each region 412 of the photomask PM2 and the grayscale value of the corresponding region of the grayscale reference is obtained. Figure 18 , each of the regions 412 has a difference. In addition, when the difference is greater than a value, the region having a difference greater than the value can be identified as a potential defect region 414. In some embodiments, the potential defect region 414 can include one or more regions 412, such as Figure 18 In display.

[0072] In operation 304, the potential defect area is expanded to define a defect area.

[0073] like Figure 19 , the potential defect area 414 is enlarged. In some embodiments, the areas 412 are arranged along the columns and rows as mentioned above, and the potential defect area 414 may include areas 412 having differences greater than the values, wherein such areas are also arranged to form columns and rows. In such embodiments, the potential defect area 414 is enlarged to include at least one column at its right side and one column at its left side. Similarly, the potential defect area 414 is enlarged to include at least one row at its upper side and one row at its lower side. Therefore, the defect area 416 becomes larger than the potential defect area 414. In addition, the defect area 416 has a width along the first direction D1 and a length along the second direction D2. In some embodiments, the width and length are substantially equal. In some embodiments, the area of ​​the defect area 416 is enlarged to be between about 2×2 μm 2 and 0.1×0.1μm 2 It should be noted that if the defect area 416 is smaller than 2×2 μm 2 or larger than 10×10μm 2 , then it can affect defect detection, which is described in the following description.

[0074] In operation 305 , a first group, a second group, and an Nth group are defined, wherein each of the first group, the second group, and the Nth group has at least one first region or at least one second region, regions in the same group have differences within the same range, and regions in different groups have differences within different ranges.

[0075] like Figure 20 , in some embodiments, the regions 412 are grouped into a first group G1 and a second group G2 according to differences. In some embodiments, the grouping of the regions 412 according to differences may be performed according to Table 1 above.

[0076] According to Table 1, a range is provided, and regions 412 having differences within the same range are grouped into the same group. In some embodiments, each of the first group G1 and the second group G2 has at least one region 412. In addition, regions 412 in the same group have differences within the same range, and regions 412 in different groups have differences within different ranges. For example, a region 414 in the first group G1 has a first difference between its grayscale value and the grayscale reference, and a region 412 in the second group G2 has a second difference between its grayscale value and the grayscale reference, as shown in FIG. Figure 20 In some embodiments, the absolute value of the first difference is smaller than the absolute value of the second difference, and the absolute value of the (N-1)th difference is smaller than the absolute value of the Nth difference, as shown in Table 1.

[0077] At operation 306, a first calculation is performed to obtain a score. In some embodiments, the first calculation is performed according to equation (2):

[0078]

[0079] Where Ws is the score, G is the first zone G1, the second zone G2, the third zone G3 and the Nth zone G N The individual grayscale values ​​in , e1 is the first weighting factor, e2 is the second weighting factor, and e n is the Nth weighting factor. In some embodiments, the first weighting factor e1 is smaller than the second weighting factor e2, and the (N-1)th weighting factor e (n-1) Less than the Nth weighting factor e n , as shown in Table 1.

[0080] For example, in some embodiments, the following may be used in the calculation: Figure 20 The differences shown in:

[0081]

[0082] According to equation (2), the score Ws is obtained as mentioned above.

[0083] In operation 307a, when the score Ws is greater than a value, it is determined that the substrate has complex defects. In operation 307b, when the score Ws is less than the value, it is determined that the substrate does not have complex defects.

[0084] In some embodiments, the value may be 0.92. Therefore, when score Ws is 0.949 (which is greater than 0.92), the presence of a complex defect is determined. It should be noted that the difference between the grayscale values ​​of region 412 of image 410 and the grayscale values ​​of the grayscale reference can reveal the variation between the surface condition of the pattern on photomask PM2 after the manufacturing operation and the desired surface condition of the desired photomask d-PM. A larger difference may indicate that the surface condition of the inspected photomask PM2 is more different from the surface condition found in a similar comparison exhibiting a smaller difference. Furthermore, a larger difference can be amplified by multiplying the grayscale value by a weighting factor. Therefore, the presence of a complex defect can be easily determined.

[0085] In some embodiments, an aerial image measurement system (AIMS) is used when determining that a substrate has an ESD defect. AIMS is a measurement method that provides the ability to simulate exposure results on a substrate (i.e., a photomask substrate) using information including, but not limited to, optical proximity correction (OPC), mask error enhancement factor (MEEF), and mask 3D effect information. In some embodiments, AIMS can be used to re-inspect complex defects.

[0086] In some embodiments, the defect inspection method 300 may include further operations (308, 309a, and 309b). Such operations will be further described according to one or more embodiments. It should be noted that the operations of the defect inspection method 300 may be rearranged or otherwise modified within the scope of various aspects. It should be further noted that additional manufacturing processes may be provided before, during, and after the method 300, and that only some of these additional manufacturing processes are briefly described herein. Therefore, other implementations are possible within the scope of the various aspects described herein.

[0087] At operation 308 , a second calculation is performed to obtain a graph.

[0088] In some embodiments, the second calculation is the first derivative of equation (2). In some embodiments, a graph representing the results of the second calculation may be obtained, such as Figure 21B In the Figure 21B , the abscissa indicates the position of the region 412 used in the first calculation and the second calculation, and the ordinate indicates the grayscale value.

[0089] In operation 309a, when two peaks are shown in the graph, it is determined that the substrate has a shielding layer extension defect. In operation 309b, when more than two peaks are shown in the graph, it is determined that the substrate has a hard mask / shielding layer extension defect.

[0090] like Figure 21B As shown in FIG, since two peaks are shown in the graph, it is determined that the photomask PM2 has a shielding layer extension defect. Therefore, not only can the presence of a complex defect be determined but also the type of the complex defect (ie, a shielding layer extension defect) can be identified.

[0091] As mentioned above, after identifying a shielding layer extension defect, the AIMS can be used to recheck for shielding layer extension defects. In some embodiments, further operations can be performed to remove unnecessary shielding layers. For example, a removal operation can be performed. In some embodiments, an etching gas can be used in the removal operation, including Cl2, SnCl4, NOCl, NO2Cl, CCl4, or other suitable gases.

[0092] In addition, the defect inspection method 300 can be used to identify hard mask / shield layer extension defects. For example, in other embodiments, operations 301 to 303 can be performed to identify potential defect areas, such as Figure 22 In display.

[0093] like Figure 23, in operation 304, the potential defect area 414 is enlarged. In some embodiments, the areas 412 are arranged along the columns and rows as mentioned above, and the potential defect area 414 may include areas 412 having differences greater than the values, wherein such areas 412 are also arranged to form columns and rows. In such embodiments, the potential defect area 414 is enlarged to include at least one column at its right side and one column at its left side. Similarly, the potential defect area 414 is enlarged to include at least one row at its upper side and one row at its lower side. Therefore, the defect area 416 is larger than the potential defect area 414. In addition, the defect area 416 has a width along the first direction D1 and a length along the second direction D2. In some embodiments, the width and the length are substantially equal to each other. In some embodiments, the area of ​​the defect area 416 is enlarged to be between about 2×2 μm 2 and 0.1×0.1μm 2 It should be noted that if the defect area 416 is smaller than 2×2 μm 2 or larger than 10×10μm 2 , it can affect defect detection, as described in the following description.

[0094] In operation 305 , a first group, a second group, and an Nth group are defined, wherein each of the first group, the second group, and the Nth group has at least one first region or at least one second region, regions in the same group have differences within the same range, and regions in different groups have differences within different ranges.

[0095] like Figure 24 , in some embodiments, the regions 412 are grouped into a first group G1, a second group G2, and a third group G3 according to differences. In some embodiments, the grouping of the regions 412 according to differences may be performed according to Table 1 above.

[0096] According to Table 1, a range is provided, and regions 412 having differences within the same range are grouped into the same group. In some embodiments, each of the first group G1, the second group G2, and the Nth group Gn has at least one region 412. In addition, regions 412 in the same group have differences within the same range, and regions 412 in different groups have differences within different ranges. For example, a region 414 in the first group G1 has a first difference between its grayscale value and the grayscale reference, a region 412 in the second group G2 has a second difference between its grayscale value and the grayscale reference, and a region 414 in the third group G3 has a third difference between its grayscale value and the grayscale reference, as shown in FIG. Figure 24 In some embodiments, the absolute value of the first difference is smaller than the absolute value of the second difference, and the absolute value of the (N-1)th difference is smaller than the absolute value of the Nth difference, as shown in Table 1.

[0097] At operation 306, a first calculation is performed to obtain a score. In some embodiments, the first calculation is performed according to equation (2).

[0098] For example, in some embodiments, the following may be used in the first calculation: Figure 24 The differences shown in:

[0099]

[0100] According to equation (2), the score Ws is obtained as described above.

[0101] In operation 307a, when the score Ws is greater than a value, it is determined that the substrate has complex defects. In operation 307b, when the score Ws is less than the value, it is determined that the substrate does not have complex defects.

[0102] In some embodiments, the value may be 0.92. Therefore, when score Ws is 0.93 (which is greater than 0.92), the substrate is determined to have a complex defect. It should be noted that the difference between the grayscale values ​​of region 412 of image 410 and the grayscale values ​​of the grayscale reference can reveal the variation between the surface condition of the pattern on photomask PM2 after the manufacturing operation and the desired surface condition of the desired photomask d-PM. A larger difference, compared to the surface condition found in a similar comparison showing a smaller difference, can indicate that the surface condition of the inspected photomask PM2 differs more significantly from the desired surface condition of the desired photomask d-PM. Furthermore, a larger difference can be amplified by multiplying the grayscale value by a weighting factor. Thus, complex defects can be easily identified.

[0103] In some embodiments, AIMS is used when a substrate is determined to have complex defects. AIMS is a measurement method that can simulate exposure results on a substrate (i.e., a photomask substrate) using information including, but not limited to, OPC, MEEF, and mask 3D effects. In some embodiments, AIMS can be used to re-inspect complex defects.

[0104] In some embodiments, operation 308 is performed in which a second calculation is performed to obtain a graph.

[0105] In some embodiments, the second calculation is the first derivative of equation (2). In some embodiments, a graph showing the results of the second calculation may be obtained, such as Figure 25B In the Figure 25B , the abscissa indicates the position of the region 412 used in the first calculation and the second calculation, and the ordinate indicates the grayscale value.

[0106] In operation 309a, when two peaks are shown in the graph, it is determined that the substrate has a shielding layer extension defect. In operation 309b, when more than two peaks are shown in the graph, it is determined that the substrate has a hard mask / shielding layer extension defect.

[0107] like Figure 25B As shown in FIG. 5 , since more than two peaks (ie, four peaks) are shown in the graph, it is determined that the photomask PM2 has a hard mask / shielding layer extension defect.

[0108] As mentioned above, after determining that a hard mask / shielding layer extension defect exists, the AIMS can be used to recheck the hard mask / shielding layer extension defect. In some embodiments, further operations can be performed to remove unnecessary hard mask layers and shielding layers. For example, a first removal operation can be performed to remove unnecessary hard mask layers. In some embodiments, an etching gas can be used in the removal operation, including F2, CF4, SF6, SnF4, XeF2, I2, or other suitable gases. In addition, a second removal operation can be performed to remove the unnecessary shielding layer. The etching gas used in the second removal operation can be similar to the etching gas described above, and therefore, a repeated description is omitted for brevity.

[0109] Furthermore, determining that photomask PM2 does not have complex defects means that thin films 408a and / or 408b have not yet been formed over the pattern (i.e., phase-shift layer 402). However, such thin films 408a and / or 408b may have actually been formed over the pattern, but their thickness may not be sufficient to alter reflection and, therefore, may not be detected. Therefore, photomask PM2 can be used in subsequent exposure operations. In some embodiments, determining that photomask PM2 has complex defects may mean that thin films 408a and / or 408b have already been formed over the pattern (i.e., phase-shift layer 402) and are thick enough to alter reflection, thereby degrading the exposure results. In some embodiments, subsequent operations 308, 309a, and 309b are performed to determine the type of complex defects present. Therefore, appropriate removal operations can be performed.

[0110] As mentioned above, complex defects occur when a thin film is formed over the patterned surface of photomask PM2. Complex defects may be indistinguishable but can cause serious problems during exposure operations. By grouping regions 412 into a first group G1, a second group G2, and an Nth group Gn, and assigning different weighting factors to different groups, the groups likely to contain complex defects can be narrowed down. Furthermore, by performing the first calculation using the equation, a score Ws can be easily obtained, which represents the overall surface condition. Furthermore, when score Ws is greater than a certain value, it is determined that a complex defect is present. In some embodiments, this value is adjustable.

[0111] Defect inspection method 300 can be performed to detect ESD defects. In some embodiments, the defect inspection method provides a weighted model. The weighted model helps amplify ESD defects and, therefore, detect ESD defects. In some embodiments, defect inspection method 300 provides a second calculation that helps distinguish between shielding layer extension defects and hard mask / shielding layer extension defects. Therefore, a suitable removal operation can be performed.

[0112] The present disclosure provides a defect inspection method. In some embodiments, the defect inspection method is performed to detect ESD defects. In some embodiments, the defect inspection method provides a first calculation. The first calculation helps to amplify the ESD defect and thus the ESD defect can be determined. In some embodiments, the defect inspection method is performed to detect complex defects. In some embodiments, the defect inspection method provides two calculations. The first calculation is performed to determine the presence of a complex defect, and the second calculation is performed to distinguish whether the complex defect is a shielding layer extension defect or a hard mask / shielding layer extension defect. Therefore, a suitable removal operation can be performed. The provided defect inspection method is capable of accurately detecting and identifying defects using current inspection tools. Therefore, inspection reliability can be improved and inspection cycle time can be reduced. In addition, additional costs for tool modifications can be saved.

[0113] According to one embodiment of the present disclosure, a defect inspection method is provided. The method includes: receiving a substrate having a surface and a plurality of patterns disposed on the surface; obtaining a grayscale image of the substrate, wherein the grayscale image includes a plurality of regions, each of the regions having a grayscale value; comparing the grayscale value of each region with a grayscale reference to define a first group, a second group, and an Nth group, wherein each of the first group, the second group, and the Nth group has at least one region, and the regions in the first group have a first difference between their grayscale values ​​and the grayscale reference, the regions in the second group have a second difference between their grayscale values ​​and the grayscale reference, and the regions in the Nth group have an Nth difference between their grayscale values ​​and the grayscale reference; performing a calculation based on the first difference, the second difference, and the Nth difference to obtain a score; and determining that the substrate has an electrostatic discharge (ESD) defect when the score is greater than a value, and determining that the substrate does not have the ESD defect when the score is less than the value.

[0114] According to one embodiment of the present disclosure, another defect inspection method is provided. The method includes: receiving a substrate having a surface and a plurality of patterns disposed on the surface; obtaining a grayscale image of the substrate; defining a defect region in the grayscale image, wherein the defect region has a plurality of first regions, each of the first regions having a grayscale value and a difference between its grayscale value and a grayscale reference; performing a calculation to obtain a score; and determining that the substrate has a complex defect when the score is greater than a value, and determining that the substrate does not have the complex defect when the score is less than the value.

[0115] According to one embodiment of the present disclosure, another defect inspection method is provided. The method includes: receiving a substrate having a surface and a plurality of patterns disposed on the surface; obtaining a grayscale image of the substrate; defining a defect region in the grayscale image, wherein the defect region has at least one first region and a plurality of second regions, each of the first and second regions having a grayscale value and a difference between its grayscale value and a grayscale reference; performing a first calculation based on the difference between the grayscale reference and the grayscale value of each of the regions in the defect region to obtain a score; performing a second calculation to obtain a graph when the score is greater than a value; and determining that the substrate has a shielding layer extension defect when two peaks are shown in the graph, and determining that the substrate has a hard mask / shielding layer extension defect when more than two peaks are shown in the graph.

[0116] The foregoing summarizes the features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art will appreciate that they may readily use this disclosure as a basis for designing or modifying other manufacturing processes and structures for carrying out the same purposes and / or achieving the same advantages of the embodiments described herein. Those skilled in the art will also recognize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that various changes, substitutions, and modifications may be made herein without departing from the spirit and scope of the present disclosure.

[0117] Explanation of symbols

[0118] 100: Defect inspection method

[0119] 101: Operation

[0120] 102: Operation

[0121] 103: Operation

[0122] 104: Operation

[0123] 105a: Operation

[0124] 105b: Operation

[0125] 200: Light-transmitting substrate

[0126] 202: Phase shift layer (PSL)

[0127] 204: shielding layer

[0128] 206: Surface membrane

[0129] 208:Thin film

[0130] 210: Image

[0131] 212: District

[0132] 300: Defect Inspection Method

[0133] 301: Operation

[0134] 302: Operation

[0135] 303: Operation

[0136] 304: Operation

[0137] 305: Operation

[0138] 306: Operation

[0139] 307a: Operation

[0140] 307b: Operation

[0141] 308: Operation

[0142] 309a: Operation

[0143] 309b: Operation

[0144] 400: substrate

[0145] 402: Phase shift layer

[0146] 404: Obscured Layer

[0147] 404': Partial

[0148] 405: Hard masking layer

[0149] 405': Partial

[0150] 407: Patterned photoresist

[0151] 407': Residue

[0152] 408a: Remaining part / shielding layer extension defect / film

[0153] 408b: Film

[0154] 409: Photoresist layer

[0155] 409': Patterned photoresist layer

[0156] 409r: Residue

[0157] 410: Image

[0158] 412: District

[0159] 414: Potential defect area

[0160] 416: Defective Area

[0161] d-PM: desired photomask

[0162] PM1: Photomask

[0163] PM2: Photomask

Claims

1. A defect inspection method, comprising: receiving a substrate having a surface and a plurality of patterns disposed on the surface; obtaining a grayscale image of the substrate, wherein the grayscale image comprises a plurality of regions, and each of the regions has a grayscale value; comparing the grayscale value of each region with a grayscale reference to define a first group, a second group, and an Nth group, wherein each of the first group, the second group, and the Nth group has at least one region, and the regions in the first group have a first difference between their grayscale values ​​and the grayscale reference, the regions in the second group have a second difference between their grayscale values ​​and the grayscale reference, and the regions in the Nth group have an Nth difference between their grayscale values ​​and the grayscale reference; performing a calculation based on the first difference, the second difference, and the Nth difference to obtain a score; and When the score is greater than a value, it is determined that the substrate has an electrostatic discharge (ESD) defect, and when the score is less than the value, it is determined that the substrate does not have the ESD defect, wherein The first difference is smaller than the second difference, and the N-1th difference is smaller than the Nth difference, wherein the calculation is performed according to equation (1): Where Ws is the score, G is the first region G1, the second region G2, the third region G3 and the Nth region G N The individual grayscale values ​​in , and e1 is the first weighting factor, e2 is the second weighting factor, e3 is the third weighting factor and e n is the Nth weighting factor.

2. The method of claim 1 , wherein obtaining the grayscale image of the substrate further comprises: scanning the surface of the substrate using an optical inspection tool to produce light reflected from the surface of the substrate; and The grayscale image of the substrate is obtained according to the reflected light. The method according to claim 1 , wherein the substrate is a light-transmitting substrate. The method according to claim 1 , wherein the first weighting factor is smaller than the second weighting factor, and the (N−1)th weighting factor is smaller than the (N)th weighting factor. 5 . The method according to claim 1 , further comprising using an aerial image measurement system (AIMS) when determining that the substrate has the ESD defect.

6. A defect inspection method, comprising: receiving a substrate having a surface and a plurality of patterns disposed on the surface; obtaining a grayscale image of the substrate; defining a defect area in the grayscale image, wherein the defect area has a plurality of first areas, and each of the first areas has a grayscale value and a difference between its grayscale value and a grayscale reference; Perform calculations to obtain points; and When the score is greater than a value, it is determined that the substrate has a complex defect, and when the score is less than the value, it is determined that the substrate does not have the complex defect, wherein the complex defect includes: A masking layer is present at a location where the masking layer should be removed; and A hard mask layer that should be completely removed from the photomask still appears on the photomask, wherein The definition of the defect area in the grayscale image further includes: comparing the grayscale image with the grayscale reference to identify potential defect areas; and The potential defect area is expanded to include a plurality of second areas to define the defect area, wherein the calculation is performed according to equation (2): Wherein Ws is the score, G is the individual grayscale values ​​in the first region G1, the second region G2, and the third region G3, e1 is a first weighting factor, e2 is a second weighting factor, and e3 is a third weighting factor. The method of claim 6 , wherein the substrate comprises a low thermal expansion material. The method of claim 6 , wherein the second region surrounds the first region. 9 . The method of claim 6 , wherein the defect region has a width along a first direction and a length along a second direction, and the width and the length are substantially equal to each other.

10. The method of claim 6, wherein the definition of the defect area in the grayscale image further comprises defining a first group, a second group, and an Nth group, wherein each of the first group, the second group, and the Nth group has at least one first area or at least one second area, the areas in the same group have the difference within the same range, and the areas in different groups have the difference within different ranges. The method of claim 6 , wherein the first weighting factor is smaller than the second weighting factor, and an N−1th weighting factor is smaller than the Nth weighting factor.

12. The method according to claim 6, further comprising: Obtain a first-order derivative of equation (2); and Plot a graph of the first derivative. 13 . The method of claim 12 , wherein when two peaks are shown in the graph, the substrate is determined to have a shielding layer extension defect, and when more than two peaks are shown in the graph, the substrate is determined to have both hard mask and shielding layer extension defects.

14. A defect inspection method, comprising: receiving a substrate having a surface and a plurality of patterns disposed on the surface; obtaining a grayscale image of the substrate; defining a defect area in the grayscale image, wherein the defect area has at least one first area and a plurality of second areas, each of the first and second areas having a grayscale value and a difference between its grayscale value and a grayscale reference; performing a first calculation according to the difference between the grayscale reference and the grayscale value of each of the regions in the defective region to obtain a score; When the score is greater than a value, performing a second calculation to obtain a graph; and When two peaks are shown in the graph, the substrate is determined to have a shielding layer extension defect, and when more than two peaks are shown in the graph, the substrate is determined to have both hard mask and shielding layer extension defects, wherein the first calculation is performed according to equation (3): Wherein Ws is the score, G is the individual grayscale value in the first region G1, the second region G2 and the third region G3, and e1 is the first weighting factor, e2 is the second weighting factor, and e3 is the third weighting factor, wherein the second calculation is a first-order derivative of equation (3).

15. The method of claim 14, wherein the definition of the defect area in the grayscale image further comprises: comparing the grayscale image with the grayscale reference to identify a potential defect region including at least the first region; and The potential defect area is expanded to include the second area to define the defect area.

16. The method of claim 14 , further comprising comparing the grayscale value of each region with the grayscale reference to define a first group, a second group, and an Nth group, wherein each of the first group, the second group, and the Nth group has at least the first region or the second region, each of the regions in the first group has a first difference between its grayscale value and the grayscale reference, each of the regions in the second group has a second difference between its grayscale value and the grayscale reference, and each of the regions in the Nth group has an Nth difference between its grayscale value and the grayscale reference.

Images