Defect Detection Method and Defect Detection System for Reflective Mask Body

Abstract

The present invention provides a method and system for defect detection of a reflective mask. This method collects reflected light from the mask to obtain a corresponding light intensity distribution. This light intensity distribution can then be analyzed to reveal defect information within the mask. This method, based on an optical inspection process, enables rapid and non-destructive defect detection of the mask.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a defect detection method and a defect detection system for a reflective mask body. Background Art

[0002] In semiconductor manufacturing, photolithography is a crucial step in achieving pattern transfer. The trend toward more refined patterns is placing higher demands on photolithography, leading to the development of new-generation photolithography technologies such as extreme ultraviolet lithography (EUVL). EUVL uses extreme ultraviolet light with a wavelength of 1 nm to approximately 100 nm (e.g., 13.5 nm) for exposure. Because most materials highly absorb EUV light, a reflective mask is typically used for EUV exposure.

[0003] The reflective mask used for EUV exposure typically has a complex multi-layer structure (specifically, a substrate, multiple reflective layers formed on the substrate, and a mask pattern). During the manufacturing process of this multi-layer structure, defects are inevitable. These defects may originate from pits, bumps, or scratches on the substrate surface, or from the multiple reflective layers above the substrate. Ultimately, these internal defects will propagate from the bottom to the top of the mask along the stacked multiple reflective layers. The size of the defects ultimately mapped to the top surface of the mask may increase, becoming visible, or even shifting laterally. At this point, these propagated and visible defects will seriously affect EUV lithography performance (for example, resolution and contrast).

[0004] Therefore, defect detection of reflective masks for EUV exposure has always been one of the key research issues in this field. Summary of the Invention

[0005] The object of the present invention is to provide a defect detection method for a reflective mask body, so as to realize a fast and non-destructive defect detection process for the mask body.

[0006] To solve the above-mentioned technical problems, the present invention provides a defect detection method for a reflective mask body, comprising: projecting incident light with a wavelength of 2nm-30nm onto at least one detection point on the mask body to be detected, and collecting the corresponding reflected light; and obtaining a corresponding light intensity distribution based on the collected reflected light, and analyzing the light intensity distribution at the detection point to obtain defect information.

[0007] Optionally, the spot size of the incident light is between 1 nm and 100 nm.

[0008] Optionally, the method for obtaining light intensity distribution includes: obtaining light intensity information of main reflected light at the main reflection angle and light intensity information of scattered reflected light deviating from the main reflection angle, so as to obtain a light intensity distribution curve graph distributed at different reflection angles.

[0009] Optionally, the method for obtaining the light intensity information of the scattered reflected light that deviates from the main reflection angle includes: obtaining the light intensity information of the scattered reflected light with a deviation degree between 0° and 10°.

[0010] Optionally, the incident angle of the incident light is the same as the exposure light angle of the reflective mask body.

[0011] Optionally, different detection points are detected while maintaining a fixed incident angle to obtain defect information of a part or the entire surface of the mask body.

[0012] Optionally, the method of analyzing the light intensity distribution of the detection point to obtain defect information includes: judging whether the light intensity distribution of the detection point deviates from a reference light intensity distribution to determine whether there is a defect at the detection point, wherein the reference light intensity distribution is the light intensity distribution of a defect-free area.

[0013] Optionally, the method for determining whether there is a deviation in the light intensity distribution of the detection point includes: determining whether the light intensity distribution curve of the detection point shows at least one of an increased wave width, a decreased wave peak, and multiple peaks relative to the reference light intensity distribution curve; if so, determining that there is a defect in the current detection point.

[0014] Optionally, the specific defect shape of the detection point is inferred based on the graphic shape of the light intensity distribution diagram of the detection point.

[0015] Optionally, the method of inferring the specific defect morphology based on the graphical morphology of the light intensity distribution diagram of the detection point includes: collecting light intensity distribution diagrams corresponding to different defects to form a defect information set; and obtaining a distribution diagram that matches the light intensity distribution diagram of the detection point in the defect information set, and obtaining the corresponding defect information.

[0016] Optionally, the mask body to be inspected is a reflective mask plate having a mask pattern, or a mask blank without a mask pattern.

[0017] Optionally, the detection method includes: projecting incident light with a first spot size onto the mask body to be inspected, and obtaining a corresponding light intensity distribution, so as to obtain the surface uniformity of the layer inside the mask body according to the obtained light intensity distribution; and projecting incident light with a second spot size onto the mask body to be inspected, and obtaining a corresponding light intensity distribution, so as to analyze the defect morphology of the detection point according to the obtained light intensity distribution, wherein the second spot size is smaller than the first spot size.

[0018] Optionally, the size of the first light spot is between 50 nm and 100 nm, and the size of the second light spot is between 1 nm and 50 nm.

[0019] The present invention also provides a defect detection system for a reflective mask body, comprising: a light source for providing detection light with a wavelength of 2nm-30nm and allowing the detection light to be incident on the mask body to be inspected; a supporting platform for supporting the mask body; and a detector for collecting reflected light from the mask body, obtaining a corresponding light intensity distribution based on the collected reflected light, and analyzing the light intensity distribution to obtain defect information of the inspection point.

[0020] Optionally, the detection surface of the detector can move back and forth in at least one direction to collect the main reflected light and the scattered reflected light that deviates from the main reflection angle in the reflected light. Wherein, the detection surface of the detector is, for example, an arc-shaped detection surface.

[0021] Optionally, the defect detection system further includes a focus adjuster, which is arranged on the light-emitting side of the light source and is used to adjust the spot size of the detection light projected onto the mask body.

[0022] In the reflective mask defect detection method provided by the present invention, reflected light from the mask is collected to obtain a corresponding light intensity distribution (further, a light intensity distribution curve can be plotted based on the light intensity distribution). This light intensity distribution is generated based on the morphology of the current detection point. Therefore, the light intensity distribution can be used to analyze and reveal defect information at the current detection point. For example, based on the waveform curve corresponding to the reflected light intensity distribution, if the curve shows an increased width, an asymmetric waveform, or multiple peaks, it can be inferred that the defect information at the detection point is surface roughness, surface contamination, or a surface pit or protrusion. In other words, the defect detection method provided by the present invention, based on an optical detection process, can quickly and non-destructively detect defects in the mask. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a defect detection method for a reflective mask according to an embodiment of the present invention.

[0024] Figure 2 FIG. 4 is a schematic structural diagram of a defect detection process of a reflective mask body according to an embodiment of the present invention.

[0025] Figure 3-Figure 4 Schematic diagrams of two structures of a mask body to be inspected in one embodiment of the present invention.

[0026] Figure 5-Figure 6 FIG. 4 is a light intensity distribution curve obtained during defect detection according to an embodiment of the present invention.

[0027] Figure 7-Figure 8 Schematic diagram of defects in the mask body.

[0028] Figure 9 This is a defect detection system for a reflective mask according to an embodiment of the present invention.

[0029] The accompanying drawings are numerals as follows:

[0030] 110-light source;

[0031] 120-detector;

[0032] 130-carrying platform;

[0033] 140-focuser;

[0034] 150-controller;

[0035] 200-mask body;

[0036] 210-substrate;

[0037] 220-reflective stacking layer;

[0038] 230-covering layer;

[0039] 240-absorption layer;

[0040] 200a-pit defect;

[0041] 200b-raised defect. DETAILED DESCRIPTION

[0042] As described in the background, defects in a mask can affect the accuracy of photolithography processes, leading to the need for effective defect detection. However, for reflective masks, defects are often buried within the multi-layer structure, making them difficult to detect. Accurately determining the defect's location and depth is even more challenging.

[0043] In the existing technology, defect detection is usually performed using methods such as AFM (Atomic Force Microscope), SEM (Scanning Electron Microscope), and TEM (Transmission Electron Microscope). However, these defect detection methods have great limitations and can only detect defect information on the surface of the mask body, or require the mask body to be destroyed to detect and locate defects inside the mask body, and the detection efficiency is low.

[0044] To this end, the present invention provides a defect detection method for a reflective mask body, which can capture defects in the mask body without destroying the mask body. Figure 1 As shown, a defect detection method in an embodiment of the present invention may include the following steps.

[0045] In step S100 , incident light with a wavelength of 2 nm to 30 nm is projected onto at least one detection point on the mask to be detected, and corresponding reflected light is collected.

[0046] In step S200 , a corresponding light intensity distribution is obtained according to the collected reflected light, and the detected light intensity distribution is analyzed to obtain defect information of the detection point.

[0047] That is, in the defect detection method for a reflective mask body provided by the present invention, the defect information (the defect information includes, for example, the defect type, defect depth, and defect size) is characterized by the light intensity distribution of the collected reflected light, thereby realizing an optical detection process of the mask body, and the defect detection of the mask body can be performed quickly and non-destructively.

[0048] The following combination Figure 2-Figure 9 The defect detection method and detection system for the reflective mask body proposed in the present invention are further described in detail with specific embodiments. It should be noted that the drawings are all in a very simplified form and are not in precise proportions, and are only used to facilitate and clearly assist in explaining the purpose of the embodiments of the present invention. It should be recognized that relative terms such as "above", "below", "top", "bottom", "above" and "below" shown in the drawings can be used to describe the relationship between various elements. These relative terms are intended to cover different orientations of elements other than the orientations depicted in the drawings. For example, if the device is inverted relative to the view in the drawing, an element described as being "above" another element would now be below the element.

[0049] In step S100, refer to Figure 2 As shown, incident light with a wavelength of 2nm-30nm is projected onto at least one detection point on the mask body 200 to be detected, and the corresponding reflected light is collected.

[0050] The mask body 200 to be inspected may be a reflective mask having a mask pattern (eg Figure 3 ), or it may be a mask blank without a mask pattern (e.g. Figure 4 shown).

[0051] First reference Figure 3The mask body 200 to be inspected, shown having a mask pattern, specifically includes a substrate 210, a reflective stacked layer 220 formed on the substrate 210, and an absorption layer 240 located on the reflective stacked layer 220. The substrate 210 can be selected from materials with low thermal expansion characteristics and high thermal conductivity. For example, the substrate 210 can be quartz glass, glass-ceramic (Zerodur), ultra-low expansion quartz glass (ULE, also known as zero-expansion glass), etc. The reflective stacked layer 220 is used to reflect incident light and specifically includes alternating stacks of first reflective layers with a low refractive index and second reflective layers with a high refractive index. The material of the first reflective layer with a low refractive index may include molybdenum (Mo), and the material of the second reflective layer with a high refractive index may include silicon (Si). In addition, the absorption layer 240 is used to define the mask pattern of the mask plate. It can be a single-layer film structure or a composite structure formed by stacking multiple films. Its material may include at least one of cobalt (Co), tellurium (Te), hafnium (Hf), nickel (Ni), tantalum (Ta), chromium (Cr), tantalum-based materials, chromium-based materials, etc.

[0052] In a further embodiment, a capping layer 230 may be disposed between the reflective stacked layer 220 and the absorption layer 240. The capping layer 230 may be used to protect the reflective stacked layer 220 from damage and prevent oxidation of the surface of the reflective stacked layer 220. The material of the capping layer 230 may include ruthenium (Ru) or ruthenium oxide, and the thickness of the capping layer 230 may be, for example, 2 nm to 10 nm.

[0053] Next reference Figure 4 The illustrated mask body 200 to be inspected, which lacks a mask pattern, is, for example, a mask blank before a mask pattern is formed. It includes a substrate 210 and a reflective stacked layer 220 formed on the substrate 210. The parameters related to the substrate 210 and the reflective stacked layer 220 can be as described above and will not be further elaborated here. Furthermore, a cover layer 230 may also be formed above the reflective stacked layer 220.

[0054] Continue to refer Figure 2 As shown, during defect detection, the incident light for detection is projected onto the mask 200 to be inspected at an inclined angle. The inclined angle can be adjusted accordingly based on the specific situation. Specifically, the incident angle of the incident light for detection can be the same as the incident angle of the lithography exposure light for the reflective mask. For example, for reflective reticles used for EUV lithography, the exposure light is typically incident on the reflective mask at an angle of 6°. Based on this, when performing defect detection on a mask body for an EUV reticle, the incident angle of the incident light can also be set to 6°.

[0055] It should be noted that in the process of light detection, when the incident light used has a longer wavelength (for example, greater than 100nm), the atomic and molecular roughness of the layer surface in the mask body will be "invisible" and will be considered to be very flat. At this time, symmetrical reflected light will be generated based on mirror reflection, and the light intensity of the reflected light obtained is concentrated, and it is impossible to obtain the light intensity distribution dispersed at different reflection angles.

[0056] Therefore, the detection light (i.e., incident light) used in this embodiment has a short wavelength (e.g., less than 30 nm), so that the wavelength of the incident light is close to the atomic level. At this time, the surface of the layer in the mask body is no longer considered to be a mirror plane, but has a certain degree of roughness that is sufficient to cause scattered reflections in addition to the main reflection. For example Figure 2 As shown, compared with the light of short wavelength, it can detect the roughness on the surface of the layer in the mask body, for example, based on the arrangement of atoms or molecules. At this time, the reflection generated by the light of short wavelength incident on the surface includes the main reflected light ( Figure 2 ) and scattered reflected light ( Figure 2 In this way, reflected light at different reflection angles can be collected to obtain the corresponding light intensity distribution.

[0057] It should be recognized that the "main reflected light" mentioned here refers to the reflected light that is symmetrically reflected based on the incident light, and the incident angle of the incident light and the reflection angle of the main reflected light are equal relative to the normal; the "scattered reflected light" mentioned here refers to other reflected light that deviates from the main reflected light, and the scattered reflected light is reflected from an angular direction that deviates from the main reflection angle.

[0058] In a further embodiment, the wavelength of the incident light is greater than 6 nm. Specifically, when the wavelength of the incident light used is too small (for example, the wavelength of the incident light is no greater than 6 nm), the shorter wavelength incident light has a higher penetrating power and can further detect the atomic structure or lattice structure within the substrate or film layer, which is not conducive to the resolution of defect information. In this embodiment, the wavelength of the light used for detection can be the same as the wavelength of the exposure light required for EUV lithography exposure. For example, the wavelength of the detection light (i.e., incident light) is 13.5 nm, which can detect defect information that can affect EUV lithography.

[0059] In step S200, the light intensity distribution in the corresponding cone space angular direction is obtained according to the collected reflected light, and the detected light intensity distribution is analyzed to obtain defect information of the detection point.

[0060] As described above, in this embodiment, incident light of a shorter wavelength is used as the detection light, and reflected light of different reflection angles can be collected, thereby obtaining the corresponding light intensity distribution. Specifically, the collected reflected light includes the main reflected light corresponding to the main reflection angle (for example, Figure 2 ) and the corresponding scattered reflected light at other reflection angles (e.g., Figure 2 ), and thus obtain the intensity information of the main reflected light and the scattered reflected light. It should be understood that the intensity of the main reflected light and the scattered reflected light in the reflected light from the mask body are both determined by the specific shape of the current inspection point. In other words, different inspection point shapes will result in different reflected light (specifically, differences in the distribution and intensity of the main reflected light and the scattered reflected light). Therefore, the light intensity distribution can be used to analyze and reveal the defect information of the current inspection point.

[0061] Furthermore, the method for obtaining the light intensity distribution of the reflected light includes: obtaining the light intensity information of the main reflected light at the main reflection angle and the light intensity information of the scattered reflected light deviating from the main reflection angle, so as to obtain a light intensity distribution diagram distributed at different reflection angles, that is, a light intensity distribution diagram can be drawn based on the light intensity information of the main reflected light and the scattered reflected light. Figure 5 and Figure 6 As shown, in this embodiment, a light intensity distribution curve at different angles can be plotted based on the obtained reflected light. The X-axis represents the position corresponding to each reflection angle in the reflected light, with 0° on the X-axis representing the reference point that does not deviate from the main reflection angle, and the left and right sides of 0° representing negative and positive deviations from the main reflection angle, respectively. Furthermore, the Y-axis represents light intensity. In one example, light intensity information for scattered reflected light with a deviation between 0° and 10° can be obtained. In actual applications, the degree of deviation corresponding to the receiving range of the detection device can be adjusted. For example, the detection device can receive scattered reflected light with a deviation between 0° and 90°, or even above 90°.

[0062] Key References Figure 5 and Figure 6 The waveform L0 represented by the solid line in the figure is the waveform corresponding to the absence of defects. Specifically, when there is no defect at the detection point, the surface of the layer corresponding to the detection point exhibits uniform roughness. At this time, most of the reflected light is based on specular reflection and corresponds to the main reflection angle, making the main reflected light stronger (i.e., Figure 5 and Figure 6 The light intensity at the 0° position is strong, and most of it is concentrated at the 0° position), while the light intensity of the scattered reflected light is weak (i.e., Figure 5 and Figure 6 The light intensity deviating from the 0° position is greatly reduced).

[0063] Key References Figure 5 and Figure 6 The dotted lines in waveforms L1, L2, and L3 represent waveforms corresponding to the presence of a defect. Specifically, when a defect exists at the inspection point, the reflection conditions in the defective area deviate from those in the non-defective area, resulting in a decrease in the intensity of the main reflected light based on specular reflection in the resulting reflected light (i.e., the light intensity at the 0° position in waveforms L1, L2, and L3 is weaker than the light intensity at the 0° position in waveform L0), and a higher intensity of scattered reflected light is generated (i.e., the light intensity at positions deviating from the 0° position in waveforms L1, L2, and L3 is stronger than the light intensity at positions deviating from the 0° position in waveform L0).

[0064] That is, the light intensity distribution of the reflected light detected in the defective area does not match the light intensity distribution of the reflected light in the non-defective area. For example, relative to the light intensity distribution curve of the non-defective area, the light intensity distribution curve of the defective area has a lower peak, a larger wave width, an asymmetric waveform and / or multiple peaks (for example, Figure 6 The waveform L3 shown in FIG has a double peak, etc. In this embodiment, the light intensity distribution of a defect-free area can be defined as a reference light intensity distribution. Therefore, the method of performing inspection and analysis on a test point to obtain defect information may include determining whether the light intensity distribution of the test point deviates from the reference light intensity distribution, thereby inferring whether a defect exists at the test point. Specifically, the method determines whether the light intensity distribution curve of the test point exhibits at least one of an increased curve width, a decreased peak, and multiple peaks relative to the reference light intensity distribution curve; if so, it is determined that a defect exists at the current test point.

[0065] In an optional solution, after determining that the light intensity distribution at a test point deviates from a reference light intensity distribution, the specific defect morphology at that test point can be further inferred based on the specific distribution of the light intensity at that test point. In this embodiment, the reflected light intensity distribution utilizes a light intensity distribution curve plotted based on the intensity of the reflected light at different reflection angles. Therefore, the specific defect morphology at the test point can be inferred based on the graphical form of the light intensity distribution curve. For example, the defect type, depth, and size at the test point can be inferred based on the deviation of the light intensity distribution curve at the test point from the reference light intensity distribution curve.

[0066] Key References Figure 5 As shown, Figure 5The dotted waveform L1 has a slightly lower peak and a slightly wider width than the solid-line reference waveform L0. Overall, the waveform L1 is still symmetrical relative to 0°. This analysis indicates that the surface roughness of the test point it represents may be high. Figure 5 The waveform L2 represented by the dotted line has a significantly lower peak value and a larger wave width than the reference waveform L0 represented by the solid line. After research and analysis, it can be learned that the waveform L2 reveals that the detection point it represents may have a surface contamination problem.

[0067] As for defects such as large surface roughness and surface contamination in the mask body, they will mainly affect the film thickness uniformity of a few film layers at the bottom of the reflective film stack layer 220, and the probability of inducing them upward to the upper film layers of the reflective film stack layer 220 is low.

[0068] Next reference Figure 6 As shown, Figure 6 The waveform L3 represented by the dotted line has a double peak value relative to the reference waveform L0 represented by the solid line. The double peaks are asymmetrically arranged relative to the 0° position. After research and analysis, it can be learned that the waveform L3 reveals that the detection point it represents may have surface pits or bumps (for example, there are asymmetric pits or bumps on the surface of the substrate in the mask body).

[0069] The pit defect generated in the mask body may be further induced based on the pit on the substrate surface and appear on the top surface of the mask body. Figure 7 As shown, there are already large pits (>10nm in size) on the surface of the substrate 210. These pit defects 200a on the substrate 210 may be formed on the surface of the substrate 210 due to processes such as chemical mechanical polishing (CMP) and cleaning. Based on this, when the reflective stack layer 220 is sequentially formed on the substrate 210, the pit defects 200a on the substrate surface will be replicated straight upward from the substrate and propagated to each film layer of the reflective film stack layer 220, thereby causing corresponding pit defects to appear on the top surface of the mask body.

[0070] Furthermore, the protrusion defects generated in the mask body may be further induced based on the protrusions on the substrate surface and appear on the top surface of the mask body. Figure 8As shown, there are already large (>10nm) bumps on the surface of the substrate 210. These bump defects 200b on the substrate 210 may be formed on the surface of the substrate 210 due to processes such as chemical mechanical polishing (CMP) and cleaning. Based on this, when the reflective film stack layer 220 is sequentially formed on the substrate 210, the bump defects 200 on the substrate surface will be replicated straight upward from the substrate and propagated to the various film layers of the reflective film stack layer 220. In the process of upward propagation, the defect size will also increase, thereby appearing as a larger bump defect on the top surface of the mask body.

[0071] Furthermore, the pit and protrusion defects within the mask body may have been introduced during the fabrication of any of the reflective layers in the reflective stack 220. In this case, the pit and protrusion defects within the mask body are buried within the reflective stack 220. Research and analysis have revealed that defects located at different depths produce different reflection information for the reflected light, and thus, the resulting light intensity distribution also varies. Specifically, deeper defects produce more scattered reflections for the reflected light, resulting in a greater degree of drift in the light intensity distribution.

[0072] In specific applications, the light intensity distribution maps corresponding to different defects can be collected to form a defect information set. Then, when the detection point is detected, the light intensity distribution map of the detection point can be compared with the light intensity distribution map in the defect information set to obtain a distribution map in the defect information set that matches the light intensity distribution map of the detection point, thereby obtaining the corresponding defect information.

[0073] It should be noted that, through steps S100 and S200 described above, defect information can be obtained for any inspection point on the mask body. In a specific example, defect scanning can be performed sequentially at multiple inspection points on the mask body to obtain a local or overall defect distribution on the mask body to be inspected. Furthermore, different inspection points can be inspected at a fixed incident angle to obtain local or overall defect information for the mask body.

[0074] In an optional solution, when executing steps S100 and S200 as described above, the spot size of the detection light (corresponding to the spot size of the incident light) can also be adjusted as needed. Specifically, detection light with a larger spot size can be used to scan the mask body to be inspected, which is mainly used to detect the surface uniformity of the substrate within the mask body, thereby improving detection efficiency. Furthermore, detection light with a smaller spot size can be used to detect key defects at each inspection point in the mask body to be inspected. The key defects include, for example, surface roughness, surface contamination, pit defects, and / or protrusion defects. This can then determine whether a key defect exists at each inspection point, effectively improving the detection sensitivity for key defects.

[0075] For example, in a specific example, the defect detection method for a mask body includes: projecting incident light with a first spot size onto the mask body to be inspected, and obtaining a corresponding light intensity distribution for detecting the surface uniformity of the layer within the mask body; and projecting incident light with a second spot size onto the mask body to be inspected, and obtaining a corresponding light intensity distribution for detecting key defects at inspection points in the mask body to be inspected, wherein the second spot size is smaller than the first spot size. In an optional solution, the incident light with the first spot size can be preferentially used to perform preliminary inspections on multiple inspection points of the mask body to obtain areas within the mask body where surface uniformity anomalies occur; then, the incident light with the second spot size is used to detect key defects in the abnormal areas to infer the specific defect morphology. The size of the first spot size can be between 50nm and 100nm, and the size of the second spot size can be between 1nm and 50nm.

[0076] Based on the same inventive concept, an embodiment of the present invention further provides a defect detection system for a reflective mask body. Figure 2 and Figure 9 As shown, the defect detection system includes: a light source 110, a detector 120, a carrier 130, and a data analysis module (not shown). The light source 110 is used to provide detection light with a wavelength of 2nm-30nm, and the detection light is incident on the mask body on the carrier 130. The detector 120 is used to collect reflected light from the mask body 200, specifically including the main reflected light from the mask body 200 and the scattered reflected light that deviates from the main reflection angle. The detector can further analyze the defect information of the detection point based on the light intensity distribution of the collected reflected light.

[0077] Continue to refer Figure 9 As shown, the defect detection system in this embodiment further includes a focuser 140, which is disposed on the light-emitting side of the light source 110 and is used to adjust the spot size of the detection light projected onto the mask body 200 (for example, the spot size of the detection light can be adjusted to be 1nm-100nm). When it is necessary to perform surface uniformity inspection on the substrate surface within the mask body, the focuser 140 can be used to adjust the detection light to have a larger spot size to improve detection efficiency; and when it is necessary to inspect critical defects within the mask body, the focuser 140 can be used to adjust the detection light to have a smaller spot size to improve detection sensitivity for critical defects.

[0078] Specifically, during the detection of critical defects, the spot size of the detection light used can be adjusted to a minimum, for example, by the focus adjuster 140. For example, the spot size can be controlled to be below 50nm (e.g., a 2nm-10nm spot) to improve the detection sensitivity of defects of 30nm and below. Furthermore, when performing surface uniformity inspection on the surface of a layer within a mask body, the spot size can be controlled to be above 50nm (e.g., a 50nm-100nm spot).

[0079] As described above, the carrier 130 is used to carry the mask body 200. In this embodiment, the carrier 130 can also be used to move the position of the mask body 200, for example, it can be moved on the plane where the mask body is located, so that the detection light emitted by the light source 110 can be irradiated to different positions of the mask body 200, thereby realizing detection of different detection points of the mask body 200. Furthermore, the carrier 130 can also be used to adjust the inclination angle of the mask body 200, and thus adjust the angle between the normal of the mask body 200 and the optical axis of the incident light (i.e., the incident angle). The mask body 200 includes a mask blank without a mask pattern or a mask with a corresponding pattern.

[0080] And, the detector 120 is used to collect the main reflected light located at the main reflection angle and the scattered reflected light deviating from the main reflection angle. The detection surface of the detector 120 (for example, an arc-shaped detection surface) can move back and forth in an arc shape in at least one direction with the main reflection angle position as the center (that is, the main reflection angle position based on the detection point as the center) to collect the main reflected light and the scattered reflected light deviating from the main reflection angle. In a specific example, the detection surface of the detector 120 can move back and forth in two perpendicular directions with the main reflection angle position as the center; or, the detection surface of the detector 120 can move back and forth in multiple directions with the main reflection angle position as the center, so that the detection range of the detector 120 covers a conical area centered on the main reflected light, thereby collecting the reflected light in the spatial angle direction of the cone.

[0081] Furthermore, the detector 120 is also used to obtain a light intensity distribution based on the collected reflected light, and to obtain defect information at the detection point by analyzing the light intensity distribution. Specifically, the light intensity distribution curve of the detection point can be compared with the reference light intensity distribution curve to determine whether the detection point has a defect based on the deviation of the distribution curve. For example, based on whether the light intensity distribution curve of the detection point shows an increased wave width, an asymmetric waveform, or multiple peaks relative to the reference light intensity distribution curve, it can be inferred whether the detection point has defects such as surface roughness, surface contamination, surface pits or protrusions. The defect morphology can be inferred based on the waveform shape of the light intensity distribution curve. For details, please refer to the above embodiment and will not be repeated here.

[0082] Continue to refer Figure 9 As shown, the defect detection system also includes a controller 150, which can be communicatively connected to the light source 110, detector 120 and carrier 130 as described above, so as to control and coordinate the movement and operation of the light source 110, detector 120 and carrier 130.

[0083] The following combination Figure 2 and Figure 9 , a detection process of the defect detection system provided in this embodiment when performing defect detection is described:

[0084] First, the mask body 200 to be inspected (including a mask blank without a mask pattern or a mask with a mask pattern) is placed on the carrier 130. The carrier 130 can fix the position of the mask body 200 to be inspected and adjust the inclination angle of the surface of the mask body 200 to be inspected.

[0085] Next, the controller 150 controls the light source 110 to generate detection light, and projects the detection light onto a detection point on the mask 200 to be inspected. In this embodiment, the light generated by the light source 110 is further adjusted in size by the focus adjuster 140 to further control the spot size of the detection light projected onto the mask 200.

[0086] Next, the detector 120 is used to collect reflected light from the mask body 200. Specifically, the detector 120 is moved back and forth in at least one direction around the main reflection angle to collect the main reflected light and scattered reflected light that deviates from the main reflected light. Furthermore, a light intensity distribution is obtained based on the received reflected light, and then, based on the light intensity distribution, defect information of the inspection point is obtained.

[0087] Next, the mask 200 is moved by the carrier 130 so that the inspection light is projected onto another inspection point of the mask 200, and then defect inspection can be performed on the other inspection point. This cycle is repeated to traverse multiple inspection points of the mask, and the overall defect distribution on the mask can be obtained.

[0088] In summary, the reflective mask defect detection method provided in this embodiment collects reflected light from the mask to obtain a corresponding light intensity distribution. This light intensity distribution can then be used to analyze and reveal defect information within the mask. For example, based on the curve corresponding to the reflected light intensity distribution, if there is an increase in wavelength, waveform asymmetry, or multiple peaks, it can be inferred that the defect information at the detection point is surface roughness, surface contamination, or surface pits or bumps. In other words, the defect detection method provided by the present invention, based on an optical inspection process, can rapidly and non-destructively detect defects in the mask.

[0089] Furthermore, in the defect detection system provided in the above embodiment, the detector is specifically a movable detector, such that the detection surface of the detector can move back and forth in an arc in at least one direction, thereby collecting the main reflected light and the scattered reflected light. In a specific example, the detection range of the detection surface of the detector is, for example, a conical area centered on the main reflected light and having a predetermined radius.

[0090] Furthermore, EUV exposure light can be directly used for defect detection. For example, if the wavelength of EUV exposure light is 13.5nm, detection light with a wavelength of 13.5nm can be used as the incident light for detection. Alternatively, if EUV lithography exposure light is projected onto the reticle at a 6° tilt angle, it can also be incident on the mask to be inspected at a 6° tilt angle for defect detection.

[0091] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. The systems disclosed in the embodiments are described briefly because they correspond to the methods disclosed in the embodiments. For relevant details, refer to the method description.

[0092] Furthermore, although the present invention has been disclosed above with reference to preferred embodiments, the above embodiments are not intended to limit the present invention. Any person skilled in the art can utilize the above disclosed technical content to make many possible changes and modifications to the technical solution of the present invention without departing from the scope of the technical solution of the present invention, or modify the technical solution into equivalent embodiments with equivalent changes. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

[0093] It should also be understood that, unless otherwise specified or indicated, the terms "first", "second", "third", etc. in the specification are merely used to distinguish between the various components, elements, steps, etc. in the specification, and are not used to indicate the logical relationship or sequential relationship between the various components, elements, steps, etc. It should also be recognized that the singular forms "a" and "an" used herein and in the appended claims include plural references unless the context clearly indicates otherwise. For example, a reference to "a step" or "a device" means a reference to one or more steps or devices, and may include secondary steps and secondary devices. All conjunctions used should be understood in the broadest sense. Also, the word "or" should be understood to have the definition of a logical "or", not a logical "exclusive or", unless the context clearly indicates otherwise. In addition, the implementation of the method and / or apparatus in the embodiments of the present invention may include performing the selected tasks manually, automatically, or in combination.

Claims

1. A method for detecting defects in a reflective mask, characterized in that: include: Projecting incident light with a wavelength of 2nm-30nm onto at least one detection point on the mask to be detected, and collecting the corresponding reflected light; as well as, The light intensity distribution of the corresponding cone space angle direction is obtained based on the collected reflected light, and the light intensity distribution of the detection point is analyzed to obtain defect information; in, The method for obtaining the light intensity distribution includes: obtaining light intensity information of the main reflected light at the main reflection angle and light intensity information of the scattered reflected light deviating from the main reflection angle, so as to draw a light intensity distribution curve diagram for different reflection angles; Methods for analyzing the light intensity distribution at the inspection point to obtain defect information include: Projecting incident light with a first spot size onto the mask to be inspected and acquiring a corresponding light intensity distribution to obtain surface uniformity of the layer within the mask according to the acquired light intensity distribution, wherein the size of the first spot is between 50 nm and 100 nm; Incident light with a second spot size is projected onto the mask body to be inspected, and a corresponding light intensity distribution is obtained to analyze the defect morphology of the inspection point according to the obtained light intensity distribution, wherein the second spot size is smaller than the first spot size, and the size of the second spot is between 1nm and 50nm; it is determined whether the light intensity distribution of the inspection point deviates from the reference light intensity distribution, and the reference light intensity distribution is the light intensity distribution of a defect-free area; if the light intensity distribution curve of the inspection point shows at least one of an increased wave width, a decreased wave peak, and multiple peaks relative to the reference light intensity distribution curve, it is determined that there is a defect in the current inspection point; and after determining that the light intensity distribution of the inspection point deviates from the reference light intensity distribution, the defect type, defect depth, and defect size of the inspection point are inferred based on the deviation of the light intensity distribution curve of the inspection point relative to the reference light intensity distribution curve.

2. The defect detection method of a reflective mask body according to claim 1, wherein: The method for obtaining the light intensity information of the scattered reflected light deviating from the main reflection angle includes: Obtain light intensity information of scattered reflected light that deviates from the main reflection angle by degrees between 0° and 10°.

3. The defect detection method of a reflective mask body according to claim 1, wherein: The incident angle of the incident light is the same as the angle of the photolithography exposure light of the reflective mask.

4. The defect detection method of a reflective mask body according to claim 1, wherein: Maintain a fixed incident angle to detect different detection points to obtain local or overall defect information of the mask body.

5. The defect detection method of a reflective mask body according to claim 1, wherein: Methods for inferring defect morphology based on the graphical morphology of the light intensity distribution diagram at the inspection point include: Collecting light intensity distribution maps corresponding to different defects to form a defect information set; and, A distribution diagram that matches the light intensity distribution diagram of the detection point is obtained in the defect information set, and corresponding defect information is acquired.

6. The defect detection method of a reflective mask body according to claim 1, wherein: The mask body to be inspected is a reflective mask plate with a mask pattern, or a mask blank without a mask pattern.

7. A defect detection system for a reflective mask body, characterized in that: Defect detection of a reflective mask body is performed using the defect detection method of a reflective mask body according to any one of claims 1 to 6, wherein the defect detection system of the reflective mask body comprises: A light source is used to provide detection light with a wavelength of 2nm-30nm and make the detection light incident on the mask body to be detected; A carrying platform, used for carrying the mask body; The detector is used to collect reflected light from the mask body, obtain a corresponding light intensity distribution based on the collected reflected light, and analyze the light intensity distribution to obtain defect information of the detection point; specifically, the main reflected light at the main reflection angle and the scattered reflected light deviating from the main reflection angle are collected to draw a light intensity distribution curve for different reflection angles; it is determined whether the light intensity distribution of the detection point deviates from the reference light intensity distribution, and the reference light intensity distribution is the light intensity distribution of the defect-free area; if the light intensity distribution curve of the detection point shows at least one of an increased wave width, a decreased wave peak, and multiple peaks relative to the reference light intensity distribution curve, it is determined that there is a defect in the current detection point; and after determining that the light intensity distribution of the detection point deviates from the reference light intensity distribution, the defect type, defect depth, and defect size at the detection point are inferred based on the deviation of the light intensity distribution curve of the detection point relative to the reference light intensity distribution curve.

8. The defect detection system for a reflective mask body according to claim 7, wherein: The detection surface of the detector can move back and forth in at least one direction to collect the main reflected light and the scattered reflected light that deviates from the angle of the main reflected light.

9. The defect detection system for a reflective mask body according to claim 8, wherein: The detection surface of the detector is an arc-shaped detection surface.

10. The defect detection system for a reflective mask body according to claim 7, wherein: The defect detection system further includes a focus adjuster, which is arranged on the light-emitting side of the light source and is used to adjust the spot size of the detection light projected onto the mask body.

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