Reflective mask blank and method for manufacturing same

Abstract

Provided is a reflective mask blank having an auxiliary mark in a fiducial mark, the auxiliary mark being capable of being formed by a simple mechanism with a small risk of raising dust. This reflective mask blank is provided with at least a substrate, a multilayer reflective film that is provided on the substrate and reflects exposure light, and an absorber film that is provided on the multilayer reflective film and absorbs the exposure light. And a reference mark formed on the surface of the reflective mask blank on the same side as the multilayer reflective film, the reference mark comprising a main mark as a reference position of a defect position and an auxiliary mark group provided around the main mark, the auxiliary mark group comprising a plurality of auxiliary marks. And a plurality of auxiliary marks which are formed so as to extend in at least one direction at intervals from the main mark as a starting point, and which are all formed in the same shape and in the same direction.

Description

TECHNICAL FIELD

[0001] The present application relates to a reflective mask blank used in semiconductor device manufacturing and the like, and a manufacturing method thereof. BACKGROUND

[0002] In the manufacturing process of semiconductor devices, a photolithography technique is repeatedly used, that is, exposure light is irradiated to a transfer mask, and a circuit pattern formed on the mask is transferred to a semiconductor substrate (semiconductor wafer) through a reduction projection optical system. Conventionally, the wavelength of the exposure light is mainly 193 nm using an argon fluoride (ArF) excimer laser, and by adopting a multi-patterning process, an exposure process and a processing process are combined multiple times to finally form a pattern smaller than the size of the exposure wavelength.

[0003] However, due to the continuous miniaturization of device patterns, more fine patterns need to be formed, and therefore an EUV (Extreme Ultraviolet, hereinafter referred to as "EUV") lithography technique using EUV light having a shorter wavelength than the ArF excimer laser as exposure light has started to emerge. EUV light is light having a wavelength of about 0.2 to 100 nm, more specifically, light having a wavelength of about 13.5 nm. Since this EUV light has extremely low transmittance to matter, a conventional transmission-type projection optical system or mask cannot be used, and therefore a reflective optical element is used. In addition, with respect to a mask used for pattern transfer, a reflective mask has been proposed.

[0004] The reflective mask is a mask in which a multilayer reflective film that reflects EUV light is formed on a substrate, and a pattern-shaped absorber film that absorbs EUV light is formed on the multilayer reflective film (hereinafter referred to as an EUV reflective mask). On the other hand, a state before the absorber film of the reflective mask is patterned (including a state in which a resist film is formed) is referred to as a reflective mask blank, and is used as a material for the reflective mask (hereinafter, referred to as an EUV reflective mask blank).

[0005] In the EUV reflective mask, when a defect in the form of a recess or a protrusion exists in the surface layer or the film, the reflectivity of the EUV light in the defect portion decreases, and thus the desired transfer pattern cannot be obtained at the time of wafer exposure. In particular, when the defect exists in the multilayer reflective film or between the multilayer reflective film and the substrate, even if the height of the defect is only a few nm, a phase shift deviation of the reflected light of the EUV light occurs around it due to the destruction of the periodic structure of the multilayer reflective film, and thus a local decrease in reflectivity occurs, which has a particularly large impact on the pattern shape transferred to the wafer. Such a defect is referred to as a phase defect. Since the phase defect exists in or under the film, it is difficult to correct. On the other hand, when a defect exists on the multilayer reflective film or on the absorber film, the intensity of the reflected light of the EUV light attenuates, and thus this defect is referred to as an amplitude defect with respect to the phase defect.

[0006] In order to avoid the influence of phase defects and amplitude defects on the transferred pattern, Defect Mitigation (hereinafter referred to as DM technology) is proposed, which masks the phase defects by the absorber pattern. In the DM technology, the position of a defect in a coordinate system defined by a reference mark generated on an EUV reflective mask blank is determined by defect detection, the position of the reference mark is determined by the mask factory, and appropriate coordinate conversion is performed to obtain the position information of the defect on the EUV reflective mask blank in the coordinate system inside the mask factory.

[0007] Prior art documents Patent documents

[0008] Patent document 1: Japanese Patent No. 6713251 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] In patent document 1, it is described that by dividing the reference mark into a main mark and an auxiliary mark, the main mark is formed by FIB (Focused Ion Beam), and the auxiliary mark is formed by a micro-indenter-based indentation method, thereby forming the reference mark at low cost and high precision. In addition, by setting the length of the long side of the auxiliary mark in the plan view to 200 μm or more and 600 μm or less, and setting the depth to be below the film thickness of the multilayer reflective film, an auxiliary mark can be formed which does not cause damage to the substrate and is easy to regenerate the substrate. In order to form the above-mentioned auxiliary mark in the up-down and left-right directions of the main mark, the example of patent document 1 presents a method of rotating the micro-indenter around the main mark, but in this case, the rotation axis of the micro-indenter and the pressing axis of the micro-indenter need to be set apart, thereby complicating the mechanism. In addition, since the rotation mechanism is provided on the substrate, the risk of dust generation increases.

[0011] The present invention is proposed to solve the above problems, and aims to provide a reflective mask blank having an auxiliary mark in a reference mark, which can be formed by a simple mechanism and with a small risk of dust generation, and a manufacturing method thereof.

[0012] MEANS FOR SOLVING THE PROBLEMS

[0013] In order to achieve the above-mentioned object, the present invention provides a reflective mask blank, which is at least provided with a substrate, a multilayer reflective film provided on the substrate and reflecting exposure light, and an absorber film provided on the multilayer reflective film and absorbing the exposure light, and is provided with a reference mark formed on the same side of the reflective mask blank as the multilayer reflective film, The reference mark is composed of a main mark that is a reference position of a defect position and a group of auxiliary marks arranged around the main mark, The group of auxiliary marks is composed of a plurality of auxiliary marks formed so as to extend in at least one direction with a space between them from the main mark as a starting point, and the plurality of auxiliary marks are all formed in the same shape and in the same direction.

[0014] According to the reflective mask blank of the present application, the auxiliary marks in the reference mark can be formed by a simple mechanism and with less risk of dust generation. Since the auxiliary marks do not need to be formed by a conventional complex mechanism with a high risk of dust generation, the present application can provide a low-cost and low-defect reference-mark-equipped reflective mask blank (particularly, an EUV-use reflective mask blank).

[0015] At this time, the auxiliary mark can be a recess in the shape of an inverted cone with an apex angle of 55 degrees or more, or a recess in the shape of an inverted gable roof with a ridge length of 50 μm or less, or a recess in the shape of an inverted quadrangular prism with a long side of the upper surface of 50 μm or less.

[0016] For example, when the auxiliary mark is formed by an indentation method using a micro indenter, the depth of the auxiliary mark is suppressed to be below the thickness of the multilayer reflective film, in which case the depth of the auxiliary mark is very shallow with respect to its length (size) in plan view, and in order to obtain the desired shape with good reproducibility, it can be necessary to press the micro indenter on the substrate with a high degree of parallelism. In this case, in order to reproduce the desired shape, the installation of the micro indenter and the setting of the substrate require a high degree of precision. However, if the auxiliary mark (in this case, in other words, the micro indenter) has the specific shape described above, a high degree of precision is not required in the installation of the micro indenter and the setting of the substrate, and the shape is easily reproduced.

[0017] In addition, the auxiliary mark can be formed in the same layer as the main mark, or on a side further from the substrate than the layer in which the main mark is formed.

[0018] In this way, when the auxiliary mark is formed, the main mark can be formed as a mark, and thus the auxiliary mark can be formed more simply.

[0019] In addition, the present application provides a method of manufacturing a reflective mask blank, which is a method of manufacturing a reflective mask blank having at least a step of forming a multilayer reflective film that reflects exposure light on a substrate, a step of forming an absorber film that absorbs the exposure light on the multilayer reflective film, and a step of forming a reference mark on a surface of the reflective mask blank on the same side as the multilayer reflective film, the reference mark being composed of a main mark that is a reference position of a defect position and a group of auxiliary marks arranged around the main mark; When the group of the auxiliary marks in the reference mark is formed, a plurality of auxiliary marks are formed by a micro-press head-based indentation method, starting from the main mark, extending in at least one direction with a space between the auxiliary marks, and forming the plurality of auxiliary marks in the same shape and in the same direction, thereby forming the group of the auxiliary marks composed of the plurality of auxiliary marks.

[0020] According to the manufacturing method of the reflective mask blank according to the present application, the auxiliary marks in the reference mark can be formed by a simple mechanism and with a small risk of dust generation. Therefore, the present application can provide a low-cost and low-defect reflective mask blank with a reference mark (particularly, a reflective mask blank for EUV) compared to conventional techniques.

[0021] At this time, as the micro-press head, a micro-press head having an inverted cone shape with an apex angle of 55 degrees or more, an inverted gable roof shape with a ridge length of 50 μm or less, or an inverted quadrangular prism shape with a long side of the upper surface of 50 μm or less can be used.

[0022] By using the micro-press head having the specific shape as described above, high precision is not required in mounting the micro-press head and setting the substrate, and the shape of the auxiliary mark can be formed with high reproducibility.

[0023] In addition, when the main mark is formed, the main mark can be formed by FIB processing.

[0024] In this way, the main mark can be formed with high precision.

[0025] In addition, when the auxiliary mark is formed, a defect inspection machine equipped with the micro-press head can be used.

[0026] Some defect inspection machines also have an indentation function equipped with a micro-press head. In this case, a new device does not need to be introduced for forming the auxiliary mark, and thus the cost can be reduced.

[0027] In addition, the auxiliary mark can be formed after the main mark is formed.

[0028] In this way, the auxiliary mark can be formed using the main mark as a mark, and thus the device for forming the auxiliary mark does not need to have high processing position precision, and is simpler.

[0029] Effects of the Invention

[0030] According to the reflective mask blank and the manufacturing method thereof according to the present application, the auxiliary mark can be formed without using a conventional complex mechanism with a high risk of dust generation. Therefore, the present application can provide a low-cost and low-defect reflective mask blank with a reference mark. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1is an example of a cross-sectional view of a reflective mask blank of the present application.

[0032] Figure 2 is a top view showing an example of the arrangement of the reference marks in the present application.

[0033] Figure 3 is a view showing an example of the shape and arrangement of the main marks and the auxiliary mark group that constitute the reference marks in the present application.

[0034] Figure 4 is an example of a top view of the main marks in the present application.

[0035] Figure 5 is an example of a view showing the three-dimensional shape and top view shape of the auxiliary marks in the present application (three-dimensional shape and top view shape of the micro-pressure head).

[0036] Figure 6 is a view showing the cross-sectional shape of the auxiliary marks when the micro-pressure head is in the shape of a cone and the surface of the substrate when the substrate is tilted.

[0037] Figure 7 is a view showing the cross-sectional shape of the auxiliary marks when the micro-pressure head is in the shape of a pent roof and the surface of the substrate when the substrate is tilted. DETAILED DESCRIPTION

[0038] As described above, with respect to the auxiliary marks in the reference marks of the reflective mask blank, there is a need for a product that can be formed with a simple mechanism and with a small risk of dust raising.

[0039] Accordingly, the present inventors and others have conducted intensive research on reflective mask blanks and have found that a reflective mask blank (a substrate having at least a multilayer reflective film and an absorber film) that has reference marks (a main mark and an auxiliary mark group) formed on the same side as the multilayer reflective film and that has the auxiliary mark group composed of a plurality of auxiliary marks that extend in at least one direction with a spacing between them from the main mark and that are all formed in the same shape and in the same direction can form the auxiliary marks with a simple mechanism and with a small risk of dust raising, thereby making it possible to achieve a low-cost and low-defect reflective mask blank with reference marks, thereby completing the present application.

[0040] Furthermore, it was discovered that by including a step in the manufacturing method of forming reference marks (main marks and a group of auxiliary marks) on the surface of the reflective mask blank on the same side as the multilayer reflective film, and by using a micro-indentation method to form multiple auxiliary marks that start from the main mark, are spaced apart from each other, extend in at least one direction, and are all formed in the same shape and direction, a group of auxiliary marks is formed. In this way, the auxiliary marks in the reference marks can be formed with a simple mechanism and a low risk of dust generation, thereby enabling the manufacture of low-cost, low-defect reflective mask blanks with reference marks, thus completing the present invention.

[0041] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited thereto.

[0042] First, the reflective mask blank of the present invention will be described. Figure 1 An example schematic diagram of the reflective mask blank according to the present invention is shown. Although an EUV reflective mask blank has been described as an example, the present invention is not limited thereto. Figure 1 In the process, the reflective mask blank 1 firstly includes: a substrate 10, a multilayer reflective film 20 formed on the surface of the substrate 10 for reflecting exposure light, an absorber film 30 formed on the multilayer reflective film 20 for absorbing exposure light, and a reference mark 40 formed on the surface of the reflective mask blank. Although Figure 1 While not explicitly described, a protective film can be formed between the multilayer reflective film 20 and the absorber film 30 to prevent damage to the multilayer reflective film 20 when patterns are formed on the absorber film 30. Additionally, a hard mask film can be disposed on the absorber film 30, serving as an etching mask during dry etching of the absorber film 30. Furthermore, a conductive film can be disposed on the inner side of the substrate 10, serving as an antistatic layer when used in electrostatic chuck operation. Other functional layers may also be disposed.

[0043] As a substrate for EUV light exposure, substrate 10 preferably has low thermal expansion characteristics, for example, a coefficient of thermal expansion of ±2×10⁻⁶. -8 Within the range of / ℃, ±5×10 is preferred. -9 The substrate is formed from a material within the range of / ℃. Furthermore, the substrate 10 preferably has a sufficiently flat surface, and the RMS value of the surface roughness of the main surface of the substrate 10 is 0.5 nm or less, particularly preferably 0.2 nm or less. Such surface roughness can be obtained by grinding the substrate 10, etc.

[0044] The multilayer reflective film 20 is typically a multilayer film formed by alternately stacking low-refractive-index and high-refractive-index materials; in this case, it is a film that reflects EUV light as the exposure light. Figure 1In one embodiment, the multilayer reflective film 20 has a laminated portion 25 composed of a multilayer in which layers 21 having a relatively high refractive index for EUV light and layers 22 having a relatively low refractive index for EUV light are alternately laminated. In the laminated portion 25, it is preferable that Si (silicon) is periodically laminated in the layers 21 having a relatively high refractive index for EUV light, and Mo (molybdenum) is periodically laminated in the layers 22 having a relatively low refractive index for EUV light (in this case, the laminated portion 25 is a Si / Mo laminated portion). Here, each of the Si layers 21 and the Mo layers 22 can be a layer formed of silicon single substance and molybdenum single substance, or can contain other components. Further, a diffusion preventing layer can be provided between the Si layers 21 and the Mo layers 22. The diffusion preventing layer can be provided between all of the Si layers 21 and the Mo layers 22, or can be provided between a part of the Si layers 21 and the Mo layers 22.

[0045] The number of laminated layers of the Si layers 21 and the Mo layers 22 is preferably, for example, 40 or more (40 or more layers respectively), and is preferably 60 or less (60 or less layers respectively).

[0046] The thickness of the Si layers 21 and the Mo layers 22 of the Si / Mo laminated portion 25 can be appropriately set according to the exposure wavelength, and the thickness of the Si layers 21 is preferably 5 nm or less, and the thickness of the Mo layers 22 is preferably 4 nm or less. The lower limit of the thickness of the Si layers 21 is not particularly limited, but is generally 1 nm or more. The lower limit of the thickness of the Mo layers 22 is not particularly limited, but is generally 1 nm or more. The thickness of the Si layers 21 and the Mo layers 22 can be set as long as high reflectivity for EUV light can be achieved. In addition, the thickness of each of the Si layers 21 and the Mo layers 22 can be constant, or can be different for each layer. The total thickness of the Si / Mo laminated portion 25 is generally about 250 to 450 nm.

[0047] In addition, the multilayer reflective film 20 can have a structure of a Si / Ru laminated portion 25 composed of a multilayer in which Si layers 21 and Ru (ruthenium) layers 22 are alternately laminated.

[0048] There is no limitation on the material of the absorber film 30, and any material that can absorb exposure light and be subjected to patterning processing can be used. As the material of the absorber film 30, for example, a tantalum (Ta)-containing or chromium (Cr)-containing material is preferably used. In addition, the Ta-containing or Cr-containing material can contain oxygen (O), nitrogen (N), carbon (C), boron (B), or the like. As the Ta-containing material, there are listed Ta monomer, and tantalum compounds such as TaO, TaN, TaON, TaC, TaCN, TaCO, TaCON, TaB, TaOB, TaNB, TaONB, TaCB, TaCNB, TaCOB, and TaCONB. As the Cr-containing material, there are specifically listed Cr monomer, and chromium compounds such as CrO, CrN, CrON, CrC, CrCN, CrCO, CrCON, CrB, CrOB, CrNB, CrNB, CrONB, CrCB, CrCNB, CrCOB, and CrCONB. In addition, the absorber film 30 can be a multilayer structure made of these materials. In addition, the absorber film 30 can be used as a phase shift mask.

[0049] In addition, as described above, a protective film can be formed between the multilayer reflective film 20 and the absorber film 30. As the protective film, it is necessary to have a function of protecting the multilayer reflective film 20 from the effects of various dry etching and washing in the manufacturing process of the reflective mask, the exposure environment at the time of using the reflective mask, and washing processing in the regeneration process after using the reflective mask, and therefore a protective film that is resistant to various processes is preferably used, which contains an additive element such as niobium (Nb), zirconium (Zr), titanium (Ti), and rhodium (Rh). In addition, the protective film can be a multilayer structure made of these materials.

[0050] On the side of the absorber film 30 away from the substrate 10, a hard mask film (etching mask film of the absorber film 30) can be provided, which is preferably in contact with the absorber film 30 and has different etching characteristics from the absorber film 30. This hard mask film functions as a film that functions as an etching mask when dry etching the absorber film 30. After forming the absorber pattern, this hard mask film can be left as a part of the absorber film 30, for example, and used as a reflectance reducing layer for reducing the reflectance of the wavelength of light used in detection such as pattern detection; or it can be removed so as not to remain on the EUV reflective mask.

[0051] As the material of the hard mask film, for example, a Cr-containing material is preferably used, and it can be a multilayer structure. The hard mask film formed of a Cr-containing material is particularly suitable for the case where the absorber film 30 is formed of a Ta-containing material but not a Cr-containing material.

[0052] The hard mask film can be formed by a magnetron sputtering method, for example.

[0053] The film thickness of the hard mask film is not particularly limited, but is typically about 5 to 20 nm.

[0054] A conductive film can be provided on the inner side of the substrate 10 as an antistatic layer when used as an electrostatic chuck. The sheet resistance of the conductive film is preferably 100 Ω / D or less, and the material thereof is not particularly limited. As the material of the conductive film, for example, a material containing tantalum (Ta) or a material containing chromium (Cr) is preferably used. In addition, the material containing Ta or the material containing Cr can contain oxygen (O), nitrogen (N), carbon (C), boron (B), or the like. As the material containing Ta, there are listed Ta monomer, and tantalum compounds such as TaO, TaN, TaON, TaC, TaCN, TaCO, TaCON, TaB, TaOB, TaNB, TaONB, TaCB, TaCNB, TaCOB, and TaCONB. As the material containing Cr, there are specifically listed Cr monomer, and chromium compounds such as CrO, CrN, CrON, CrC, CrCN, CrCO, CrCON, CrB, CrOB, CrNB, CrNB, CrONB, CrCB, CrCNB, CrCOB, and CrCONB. In addition, the conductive film can be a multilayer structure made of these materials.

[0055] The film thickness of the conductive film is not particularly limited, but is typically about 5 to 100 nm. The film thickness of the conductive film is preferably formed so that the film stress of the conductive film can be balanced with the multilayer reflective film 20 and the absorber pattern after the absorber pattern is formed.

[0056] The conductive film can be formed before the multilayer reflective film 20 is formed, or can be formed after all the films on the multilayer reflective film 20 side of the substrate 10 are formed. In addition, the conductive film can be formed after some of the films on the multilayer reflective film 20 side of the substrate 10 are formed, and then the remaining films on the multilayer reflective film 20 side of the substrate 10 are formed.

[0057] The conductive film can be formed by, for example, a magnetron sputtering method.

[0058] Further, a resist film can be formed on the side of the reflective mask blank for EUV that is farthest from the substrate 10. The resist film is preferably an electron beam (EB) resist.

[0059] Figure 2 An example of the arrangement of the reference mark is shown. Although the reference mark 40 is arranged so as to be provided in each of the four corners on the same side of the reflective mask blank 1 as the multilayer reflective film 20 in Figure 1 Figure 2 The reference mark 40 is arranged so as to be provided in each of the four corners on the same side of the reflective mask blank 1 as the multilayer reflective film 20 in the above-described embodiment, but the formation position and the number thereof are not particularly limited, and three or more are preferably formed so as not to be on the same straight line. However, in order to prevent the reference mark 40 from overlapping the main pattern in the reflective mask for EUV, it is preferable to form the reference mark 40 on the outer side of the main pattern formation region.​

[0060] Figure 3 Examples of the shape and arrangement of the main mark and the auxiliary mark group constituting the reference mark in the present application are shown. As shown in Figure 3 , the reference mark 40 includes the main mark 41 as a reference of the defect position and the auxiliary mark group 42 arranged around the main mark 41, and the auxiliary mark group 42 is composed of a plurality of auxiliary marks 43. Although the auxiliary mark group 42 (42a, 42b, 42c, 42d) is arranged in four directions of up, down, left and right of the main mark 41 in Figure 3 , the arrangement direction of the auxiliary mark group 42 is not particularly limited. As long as the plurality of auxiliary marks 43 constituting the auxiliary mark group 42 are spaced apart from each other and extend in at least one direction from the main mark 41 as described later, the arrangement direction of the auxiliary mark group 42 is not particularly limited. For example, the auxiliary mark group 42 can extend in only one of the up, down, left and right directions of the main mark 41, or can extend in two or three directions. By limiting the extension direction of the auxiliary mark group 42, the number of auxiliary marks 43 constituting the auxiliary mark group 42 can be reduced, and thus the processing speed can be improved.

[0061] Since the main mark 41 is used as a reference of the defect position, it is preferable to be formed by FIB processing (hereinafter, also referred to as FIB) or photolithography which can be processed with high accuracy. Although the main mark 41 is formed by removing a part of the multilayer reflective film 20 in Figure 1 , the main mark 41 can be formed by removing the entire multilayer reflective film 20, can be removed up to the substrate under the multilayer reflective film 20, or can be formed on other layers such as the substrate 10 or the absorber film 30. In addition, the main mark 41 can be formed to span a plurality of layers. However, in order to be used as a reference position of the phase defect, the main mark 41 is preferably used as a reference position for defect detection of the multilayer reflective film 20, and thus is preferably formed on the substrate 10, the multilayer reflective film 20 or the protective film.

[0062] In addition, although an example of the shape of the main mark 41 is shown in Figure 4 , the shape of the main mark in the present application is not limited thereto. As shown in Figure 4As shown, in a plan view, it can be conceived as a cross, a circle, a rectangle, etc., and the longitudinal and lateral lengths (dimensions) LI, L2 thereof are preferably 0.1 μm or more, because if they are too small, visibility can be poor. In addition, in the case where the main marks 41 are formed using FIB, the size of the main marks 41 is preferably 500 μm or less, and more preferably 100 μm or less, because if it is too large, time is required for processing. In addition, the depth of the main marks 41 is preferably 40 nm or more, and 500 nm or less, because if it is too shallow, contrast can be poor, and in order to suppress damage to the substrate and facilitate reproduction. Further, in the case where the main marks 41 are formed using FIB, the depth of the main marks is more preferably 150 nm or less, because if it is too deep, time is required for processing. In the case where the main marks 41 are formed using FIB, the current value thereof is preferably 100 pA or less, because if the side wall angle of the mark in the cross-sectional shape is made vertical, contrast at the time of detection is improved.

[0063] The auxiliary mark group 42 is composed of a plurality of auxiliary marks 43. Since it functions as a sign for finding the main mark 41, its size is not particularly limited as long as it is a size that can be detected by the detector or plotter, and specifically, the size L3 of the auxiliary mark group 42 is preferably larger than the main mark, and is 50 μm or more, and preferably 1 mm or less (refer to FIG. 6). Figure 3 ].

[0064] The auxiliary marks 43 that constitute the auxiliary mark group 42 are only required to be a plurality, and the number thereof is not particularly limited, but in order to prevent loss of the sign function, it is preferably a certain number or more, and in addition, in order to prevent a decrease in processing speed due to too many numbers, it is preferably a certain number or less. Therefore, the number of the auxiliary marks 43 that constitute each auxiliary mark group 42 is preferably, for example, 3 or more and 20 or less.

[0065] In addition, although the interval PI between adjacent auxiliary marks 43 is not limited, if the interval PI is too wide, it is difficult to determine from observation of a certain auxiliary mark 43 which direction the main mark 41 exists in, in the field of view of the detector or plotter, and thus it is difficult to achieve the function as a sign for finding the main mark 41, and therefore the interval PI between adjacent auxiliary marks 43 is preferably 30 μm or less. For the same reason, the interval P2 between the main mark 41 and the auxiliary mark 43 adjacent to the main mark 41 is also preferably 30 μm or less.

[0066] On the other hand, if the interval P1 between the adjacent auxiliary marks 43 is too narrow, the number of the auxiliary marks 43 required increases, which lowers the processing speed, and in order to form the auxiliary marks 43, intensive punching or the like is performed, which increases the risk of damage to the substrate, and therefore the interval P1 between the adjacent auxiliary marks 43 is preferably 3 μm or more. As for the interval P2 between the main marks 41 and the auxiliary marks 43 adjacent to the main marks 41, when it is too narrow, there is a risk of damage to the main marks 41 due to positional deviation at the time of punching, and therefore the interval P2 is preferably 3 μm or more.

[0067] The auxiliary marks 43 are elements of the auxiliary mark group 42 that are marks of the main marks 41, and are, for example, recesses that can be formed by using an indentation method of a micro press head.

[0068] Although in the Figure 1 above the auxiliary marks 43 are formed so as to pass through the absorber film 30 and a portion of the multilayer reflective film 20, the layer in which the auxiliary marks 43 are formed is not particularly limited. The auxiliary marks 43 can be formed on the same layer as the main marks 41, or can be formed on a different layer. In addition, the auxiliary marks 43 can be formed so as to span a plurality of layers. However, when the auxiliary marks 43 are formed on the substrate 10 or the multilayer reflective film 20 or the protective film, since film formation is required after the auxiliary marks 43 are formed, if a defect is generated in the process of forming the auxiliary marks 43, it becomes a defect in the film, and there is a risk that it cannot be removed by washing, and therefore it is preferable to form the auxiliary marks 43 after the absorber film is formed.

[0069] In addition, it is preferable to form the auxiliary marks 43 after the main marks 41 are formed. In this way, the auxiliary marks 43 can be formed using the main marks 41 as marks, and therefore the device that forms the auxiliary marks 43 does not need to have a high machining position accuracy.

[0070] In addition, as Figure 3 shown in the drawing, the plurality of auxiliary marks 43 that constitute the auxiliary mark group 42 are all formed in the same shape and in the same direction. With such auxiliary marks 43, for example, when the auxiliary marks 43 are formed by using an indentation method of a micro press head, the auxiliary marks 43 can be formed by only parallel movement of the substrate or the micro press head without rotating the micro press head, and therefore a complicated mechanism is not required, and since an additional drive section does not need to be provided on the substrate, the risk of dust generation is small. Therefore, a low-cost and low-defect reflective mask blank that does not adhere to dust or the like can be obtained.

[0071] In addition, although an example of the shape of the auxiliary marks 43 is shown in the Figure 5 above, the shape of the auxiliary marks 43 in the present application is not limited thereto. Figure 5Four patterns are shown, the upper side is a perspective view of each pattern, and the lower side is a plan view of each pattern. Note that these patterns are examples of the shape of the micro press head (particularly the tip portion thereof) used when forming the auxiliary mark 43.

[0072] The left two are recesses in the shape of an inverted cone (circular cone on the left, square pyramid on the right). In addition, the third from the left is a recess in the shape of an inverted gable roof. The last one is a recess in the shape of an inverted square frustum. The auxiliary mark 43 is preferably a recess having such a shape.

[0073] Then, a more preferable form of the auxiliary mark 43 is a recess in the shape of an inverted cone with a vertex angle of 55 degrees or more, or a recess in the shape of an inverted gable roof with a ridge length of 50 μm or less, or a recess in the shape of an inverted square frustum with a long side of the upper surface of 50 μm or less.

[0074] These shapes are selected because they can be formed with relatively high reproducibility. Details will be described later in this regard.

[0075] Next, the manufacturing method of the reflective mask blank according to the present application will be described.

[0076] First, as the main process, at least a process of forming the multilayer reflective film 20 on the substrate 10 and a process of forming the absorber film 30 on the multilayer reflective film 20 are included. Other functional layers, such as the protective film, the hard mask film, the conductive film, the resist film, etc. described above can also be formed as needed. The method of forming these films is not particularly limited, and for example, the above-described materials can be used to form films in the same manner as conventional methods (sputtering, etc.).

[0077] Then, the manufacturing method of the reflective mask blank according to the present application further includes a process of forming the reference mark 40 (the main mark 41 and the auxiliary mark group 42) on the same side surface as the multilayer reflective film 20.

[0078] Note that, as described above, the main mark 41 is preferably formed on the substrate 10, the multilayer reflective film 20, or the protective film. After the substrate is prepared or after these films are formed, the main mark 41 can be formed with high precision by, for example, FIB processing or photolithography.

[0079] In addition, as described above, the auxiliary mark group 42 (the plurality of auxiliary marks 43) is preferably formed after the absorber film 30 is formed, and is formed by the indentation method using a micro press head in the manufacturing method according to the present application. At this time, the plurality of auxiliary marks 43 are formed with a spacing from each other, extending in at least one direction from the main mark 41, and are all formed in the same shape and in the same direction. The auxiliary mark group 42 is formed by forming a plurality of such auxiliary marks 43.

[0080] Since the auxiliary mark group 42 is formed by indentation using a micro-indenter, it can be performed at a low cost. Furthermore, when forming the auxiliary marks 43, it is not necessary to rotate the micro-indenter as in conventional methods; therefore, it can be easily implemented using a relatively simple mechanism, for example, that allows parallel movement of the micro-indenter or the substrate. Additionally, the risk of dust generation due to rotating the micro-indenter via a drive mechanism or similar device can be prevented, and a low-defect reflective mask blank can be manufactured.

[0081] While there are no particular limitations on the material constituting the tip of the micro-indenter used to form the auxiliary mark 43, a durable hard material, such as diamond or sapphire, is preferred.

[0082] Although the shape of the tip of the micro-indenter used to form the auxiliary mark 43 is not particularly limited, in order to stabilize the stamping shape, such as Figure 5 As shown, the preferred structure is an inverted cone shape (cone, square pyramid, etc.), or an inverted hip roof shape, or an inverted truncated square shape, with its apex, edge, or face pressing against the substrate.

[0083] More preferably, the tip of the micro-pressure head is shaped as an inverted cone with an angle of 55 degrees or more, or as an inverted hip roof with a ridge length of 50 μm or less, or as an inverted frustum with a long side of the upper surface of 50 μm or less. This will be explained in detail below.

[0084] Figure 6 It is an illustrative representation of the use of Figure 5 The diagram shows the cross-sectional shape of section A-A', marked with auxiliary symbols, and the substrate surface when the substrate is tilted, in the case of a cone-shaped micro-indenter. When the tip of the micro-indenter is cone-shaped, as shown... Figure 6 As shown, consider the change in the shape of the auxiliary mark caused by improper installation of the micro-pressure head or improper setting of the substrate when the substrate is tilted relative to the stamping direction.

[0085] θ: Angle of the tip (apex angle) of the micro-indenter h1: Depth of auxiliary markings when the substrate is not tilted. h2: Depth of auxiliary markings when the substrate is tilted. L5: Length of auxiliary markers in the top view r: The ratio of h1 to L5 (L5 / h1) α: Inclination of the substrate surface h2 / h1: The rate of change of auxiliary marker depth due to variations in θ, r, and α. Here, h2 / h1 is represented by Equation 1, and its calculation results are shown in Table 1.

[0086] h2 / h1=cos(θ / 2+α) / cos(θ / 2)···(Formula 1)

[0087] [Table 1]

[0088] As can be seen, the rate of change of the depth of the auxiliary mark (h2 / h1) is relatively gentle with respect to the change in α. That is, as can be seen, by making the tip shape of the micro presser a cone, the shape of the auxiliary mark is stable.

[0089] Here, the length L5 of the auxiliary mark in plan view is preferably 500 nm or more because if it is too small, visibility is poor. On the other hand, in consideration of the regeneration of the substrate, the depth of the auxiliary mark is preferably comparable to the film thickness to suppress damage to the substrate, and is preferably 500 nm or less. In order to satisfy h1≤ 500 nm and L5≥ 500 nm, it is necessary to make r≥ 1, and therefore, according to Table 1, θ is preferably 55 degrees or more. In addition, by making θ this angle, it is possible to prevent deterioration of durability due to the tip shape of the micro presser becoming too thin, and it is possible to reduce the risk of dust generation due to damage to the micro presser at the time of pressing.

[0090] On the other hand, Figure 7 is a cross-sectional view schematically showing the case where a micro presser of a Figure 5 pent roof shape as shown in FIG. 1 is used. In the case where the tip of the micro presser is a pent roof or a shape in which its edges or faces press against the substrate like a quadrangular pyramid, as shown in FIG. 2, the change in the shape of the auxiliary mark when the substrate is inclined with respect to the pressing direction is considered. Figure 7

[0091] h1: depth of the auxiliary mark in the state where the substrate is not inclined h2: depth of the shallower side of the auxiliary mark in the state where the substrate is inclined L5: length of the bottom of the auxiliary mark (length of the ridge) r: ratio of h1 to L5 (L5 / h1) α: inclination of the substrate surface h2 / h1: rate of change in the depth of both ends of the auxiliary mark due to changes in r and α Here, h2 / h1 is represented by the following formula 2, and the calculation result is shown in Table 2.

[0092] h2 / h1 = 1 - r tan α ··· (Formula 2)

[0093] [Table 2]

[0094] ​As can be seen, in the case of the gabled roof shape, compared to the case of the cone shape shown in Table 1, as r increases, the change in the depth ratio of the ends of the punch shape increases as α increases, and when the length L5 is longer than the depth hi of the auxiliary mark, a slight inclination of the substrate surface causes a change in the shape of the auxiliary mark.

[0095] In consideration of the reproduction of the substrate, the depth of the auxiliary mark is preferably, for example, equivalent to the film thickness, to suppress damage to the substrate, and is preferably 500 nm or less. In addition, in order to allow the inclination α of the substrate surface to be 1 mrad, the depth change rate h2 / h1 of the ends of the auxiliary mark needs to be controlled to be within 10%, according to Table 2, and in the case of hi ≤ 500 nm, the length of the face or edge of the substrate against which the micro press head is pressed (the length of the ridge) is preferably 50 μm or less.

[0096] Note that, in the case of using a micro press head in the shape of a truncated pyramid, the length of the face or edge of the substrate against which the micro press head is pressed (the long side of the upper surface) is preferably 50 μm or less in the case of hi ≤ 500 nm, in substantially the same manner as in the case of the gabled roof shape.

[0097] In addition, as can be seen from Tables 1 and 2, in the case of using a micro press head in the shape of a cone, the change in the depth of the auxiliary mark (h2 / h1) with respect to α is more gradual than in the case of using a micro press head in the shape of a gabled roof or a truncated pyramid, and thus it is more preferable to use a micro press head in the shape of a cone from the viewpoint of the stability of the reproduction of the auxiliary mark (shape stability).

[0098] Regarding the setting of the substrate and the excessive installation of the micro press head of the mechanism when using the indentation method, since high precision is not required, the shape of the micro press head is preferably the above-described shape (particularly, the shape of a cone).

[0099] Here, the significance of forming the auxiliary mark group 42 will be described again. The position of the reference mark 40 can be determined by a defect inspection machine (for example, the MAGICS series manufactured by Lasertec Corporation), a coordinate measuring device (for example, the LMSIPRO series manufactured by KLA-Tencor Corporation), an electron beam plotter (for example, the MBM series manufactured by Nuflare Corporation), or the like, but as long as the deviation of the coordinate system of the device for generating the main mark 41 and the above-described detector can be grasped in advance, the reference mark 40 can be detected relatively easily by detecting the position after shifting the coordinate system from the designed position of the main mark 41 by the deviation amount. In this case, the auxiliary mark group 42 is not necessarily required, and the reference mark 40 can be detected even by only the main mark 41.

[0100] However, the mask factory cannot necessarily easily and accurately grasp the amount of deviation between the coordinate system of the device for forming the main mark 41 manufactured by the blank manufacturer and the coordinate system of the inspection machine or the plotting machine owned by the mask factory itself, in which case the mask factory uses the auxiliary mark group 42 as a clue to find the main mark 41.

[0101] Note that, when forming the auxiliary mark 43, the dent function using a micro indenter mounted on the defect inspection machine can also be used. In this case, there is no need to introduce a new device for forming the auxiliary mark 43, so that the cost can be reduced.

[0102] [Embodiment]

[0103] Hereinafter, the present application will be described more specifically by way of examples and comparative examples, but the present application is not limited to these examples.

[0104] (Embodiment 1) On a substrate 10 made of quartz glass of 152 mm square and 6.35 mm thick, a multilayer reflective film 20 was formed by DC pulse magnetron sputtering using a molybdenum (Mo) target and a silicon (Si) target, with the two targets opposed to the main surface of the substrate 10 and the substrate 10 being self-rotated. The sputtering device on which the targets were mounted and the substrate 10 were set can mount two targets and the two targets can be discharged successively or simultaneously. First, while argon (Ar) gas was flowing through the chamber, electric power was applied to the silicon (Si) target to form a silicon (Si) layer of 4 nm in thickness, and then the application of electric power to the silicon (Si) target was stopped. Next, while argon (Ar) gas was flowing through the chamber, electric power was applied to the molybdenum (Mo) target to form a molybdenum (Mo) layer of 3 nm in thickness, and then the application of electric power to the molybdenum (Mo) target was stopped. The operation of forming these silicon (Si) layer and molybdenum (Mo) layer was taken as one cycle, and 40 cycles were repeated to form the multilayer reflective film 20.

[0105] Next, a protective film in contact with the multilayer reflective film 20 was formed by DC pulse magnetron sputtering using a Ru target, with the Ru target opposed to the main surface of the substrate 10 and the substrate 10 being self-rotated.

[0106] Next, by irradiating a prescribed position of the protective film with a FIB, the entire protective film of the irradiated portion and a part of the multilayer reflective film 20 were removed, and a main mark 41 in the shape of a cross of 1 μm in width and 5 μm in length in plan view was formed. At this time, the current value of the FIB was about 50 pA. The depth of the main mark 41 was 100 nm as observed by an atomic force microscope (AFM).

[0107] Next, the surface of the protective film was detected by a defect inspection machine. By this defect inspection, information including the position of the main mark 41 and the position of defects on the surface of the protective film was obtained. Figure 1Since the deviation between the coordinate system of the FIB that formed the main mark 41 and the coordinate system of the defect inspection machine has been grasped in advance, the main mark 41 can be easily detected by detecting the mark at a position that is shifted from the design position by the amount of deviation of the coordinate system as a target. On the other hand, when the deviation between the coordinate system of the FIB and the coordinate system of the defect inspection machine is not considered and an attempt is made to directly detect the mark with the processing coordinates in the FIB coordinate system as a target, the main mark 41 cannot be detected in the field of view of the defect inspection machine and is detected by spirally searching the periphery, so it takes a longer time to detect the main mark 41 than when the deviation of the coordinate system is corrected.

[0108] Next, the Ta target is used so as to face the Ta target to the main surface of the substrate 10, and the substrate 10 is self-rotated while DC pulse magnetron sputtering is performed, thereby forming the absorber film 30 in contact with the protective film.

[0109] Next, the surface of the absorber film 30 is detected by the defect inspection machine. By this defect inspection, information including the position of the main mark 41 and the position of defects on the surface of the absorber film 30 is obtained. Figure 2 Since the deviation between the coordinate system of the FIB that formed the main mark 41 and the coordinate system of the defect inspection machine has been grasped in advance, the main mark 41 can be easily detected by detecting the mark at a position that is shifted from the design position by the amount of deviation of the coordinate system as a target. On the other hand, when the deviation between the coordinate system of the FIB and the coordinate system of the defect inspection machine is not considered and an attempt is made to directly detect the mark with the processing coordinates in the FIB coordinate system as a target, the main mark 41 cannot be detected in the field of view of the defect inspection machine and is detected by spirally searching the periphery, so it takes a longer time to detect the main mark 41 than when the deviation of the coordinate system is corrected.

[0110] Next, the Cr target is used so as to face the Cr target to the main surface of the substrate 10, and the substrate 10 is self-rotated while DC pulse magnetron sputtering is performed, thereby forming the hard mask film in contact with the absorber film 30, and an EUV reflective mask blank is produced.

[0111] Next, a plurality of auxiliary marks 43 are formed around the main mark 41 transferred to the hard mask film by an indentation method using a micro indenter having a tip shape of a tetragonal pyramid with a 136-degree tetragonal pyramid tip, thereby forming an auxiliary mark group 42. At this time, by repeating the punching and moving the base of the substrate that carries the substrate, 10 auxiliary marks 43 in the up, down, left, and right directions of the main mark in a plan view (in the plan view, each auxiliary mark 43 has a size of a square of about 5 μm) are formed. The distance P1 between the adjacent auxiliary marks 43 is designed in advance to be 10 μm, and the size L3 of the auxiliary mark group 42 is designed in advance to be about 140 μm.

[0112] Next, the surface of the hard mask film is detected by a defect detector. By this defect detection, information including the position of the main mark 41 and the position of defects on the surface of the hard mask film is obtained Figure 3 Since the deviation between the coordinate system of the FIB in which the main mark 41 is formed and the coordinate system of the defect detector is grasped in advance, the main mark 41 can be easily detected by shifting the search position of the mark with respect to the design position by the amount of the deviation between the coordinate systems and then detecting it. On the other hand, when the deviation between the coordinate system of the FIB and the coordinate system of the defect detector is not taken into account and an attempt is made to directly detect the mark with the processing coordinates in the FIB coordinate system as the target, the main mark 41 cannot be detected in the field of view of the defect detector, but the auxiliary mark group 42 can be detected. By using the auxiliary mark group 42 as a clue, the main mark 41 can be relatively easily detected.

[0113] The generated reference mark 40 is observed by SEM. When an attempt is made to directly detect the mark with the processing coordinates in the FIB coordinate system as the target without taking into account the deviation between the FIB coordinate system and the SEM coordinate system, the auxiliary mark group 42 is confirmed in the field of view of the SEM.

[0114] Further, the center portion of the reference mark 40 is observed with the auxiliary mark group 42 as a clue and with a magnification, and the presence of the main mark 41 is confirmed. The 10 auxiliary marks 43 are confirmed in the up-and-down and left-and-right directions of the main mark 41, and it is confirmed that each of the auxiliary marks 43 is formed in a square shape of about 5 μm in size in a plan view with good shape reproducibility. In addition, it is confirmed that the size of the auxiliary mark group 42 is about 140 μm and that the shape thereof is the same as the designed shape.

[0115] Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiments having substantially the same structure as that recited in the technical idea of the claims of the present application, achieving the same effects, are included in the technical scope of the present application.

[0116] Explanation of Reference Numerals 1: reflective mask blank of the present application; 10: substrate; 20: multilayer reflective film; 21: layer having a relatively high refractive index for EUV light (Si layer); 22: layer having a relatively low refractive index for EUV light (Mo layer or Ru layer); 25: layer stack (Si / Mo layer stack or Si / Ru layer stack); 30: absorber film; 40: reference mark; 41: main mark; 42, 42a, 42b, 42c, 42d: auxiliary mark group; 43: auxiliary mark.

Claims

1. A reflective mask blank, the reflective mask blank comprising at least a substrate, a multilayer reflective film disposed on the substrate and reflecting exposure light, and an absorber film disposed on the multilayer reflective film and absorbing the exposure light, characterized in that, The reflective mask blank has a reference mark formed on the surface of the reflective mask blank on the same side as the multilayer reflective film. The reference marker consists of a main marker serving as the reference position for the defect location and a group of auxiliary markers arranged around the main marker. The auxiliary marker group consists of multiple auxiliary markers, which are arranged such that they extend in at least one direction from the main marker, with gaps between them. All of the auxiliary marks are formed in the same shape and in the same direction.

2. The reflective mask blank according to claim 1, characterized in that, The auxiliary markings are inverted cone-shaped recesses with a vertex angle of 55 degrees or more, or inverted hip-shaped recesses with a ridge length of 50 μm or less, or inverted frustum-shaped recesses with a long side of the upper surface of 50 μm or less.

3. The reflective mask blank according to claim 1 or 2, characterized in that, The auxiliary mark is formed on the same layer as the main mark, or on a layer above the layer on which the main mark is formed.

4. A method for manufacturing a reflective mask blank, characterized in that, The manufacturing method has at least the following characteristics: The process of forming a multilayer reflective film on a substrate to reflect exposure light; and The process of forming an absorber film on the multilayer reflective film to absorb the exposed light; The manufacturing method further includes a step of forming a reference mark on the surface of the reflective mask blank on the same side as the multilayer reflective film, wherein the reference mark consists of a main mark serving as a reference position for a defect location and a group of auxiliary marks arranged around the main mark; When the auxiliary mark group in the reference mark is formed, multiple auxiliary marks are formed by indentation based on the micro-indenter, starting from the main mark and extending in at least one direction with intervals between them, so that all the multiple auxiliary marks are formed in the same shape and in the same direction, thereby forming the auxiliary mark group composed of the multiple auxiliary marks.

5. The method for manufacturing a reflective mask blank according to claim 4, characterized in that, As the micro-pressure head, an inverted cone shape with a apex angle of 55 degrees or more, an inverted hip shape with a ridge length of 50 μm or less, or an inverted frustum shape with a long side of the upper surface of 50 μm or less are used.

6. The method for manufacturing a reflective mask blank according to claim 4, characterized in that, When the auxiliary mark is formed, the main mark is formed through FIB processing.

7. The method for manufacturing a reflective mask blank according to claim 5, characterized in that, When the auxiliary mark is formed, the main mark is formed through FIB processing.

8. A method for manufacturing a reflective mask blank according to any one of claims 4 to 7, characterized in that, When the auxiliary mark is formed, a defect inspection machine equipped with the micro-indenter is used.

9. A method for manufacturing a reflective mask blank according to any one of claims 4 to 7, characterized in that, The auxiliary marker is formed after the main marker is formed.

10. The method for manufacturing a reflective mask blank according to claim 8, characterized in that, The auxiliary marker is formed after the main marker is formed.

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