Method and apparatus for cleaning circuit boards

Abstract

The present invention provides a method and apparatus for cleaning circuit boards that facilitate the identification of the process in which a defect occurred if a defect is found on the circuit board. [Solution] A method for cleaning a substrate comprises at least one cleaning step of cleaning the substrate while supporting it with a support part positioned at a predetermined location, and at least one drying step of drying the substrate while supporting it with a support part positioned at a predetermined location, wherein the cleaning step and the drying step are steps in which at least one of the positions of the support part that supports the substrate and the materials constituting the support part are different from each other.

Description

Technical Field

[0001] The present invention relates to a method for cleaning a substrate and a substrate cleaning apparatus in which at least one of the position of a support portion for supporting the substrate and the material constituting the support portion is different from each other.

Background Art

[0002] In recent years, for further miniaturization of semiconductor devices, EUV (Extreme Ultra Violet) lithography using EUV light having a center wavelength of around 13.5 nm as a light source has been studied. In EUV exposure, due to the characteristics of EUV light, a reflective optical system and a reflective mask are used. The reflective mask has a multilayer reflective film formed on a substrate for reflecting EUV light, and an absorber film for absorbing EUV light is patterned on the multilayer reflective film. EUV light incident on the reflective mask from the illumination optical system of the exposure apparatus is reflected at the portion without the absorber film (opening) and absorbed at the portion with the absorber film (non-opening). As a result, the mask pattern is transferred as a resist pattern onto the resist film on the semiconductor wafer through the reduction projection optical system of the exposure apparatus, and subsequent processing is performed.

[0003] The reflective mask blank used for manufacturing the reflective mask preferably has few surface defects in order to improve the accuracy of the mask pattern. The cause of the generation of surface defects is, for example, particles generated in the manufacturing process of the reflective mask blank. For example, in Patent Document 1, a drying method for a substrate for a mask blank having the following steps has been proposed in order to suppress reattachment of the cleaning liquid due to splashing and improve the yield in spin drying of the substrate for the mask blank after cleaning. (Step 1) A step of supporting the substrate for the mask blank such that one of the two main surfaces of the substrate for the mask blank faces upward and is horizontal (Step 2) A step of rotating the substrate for the mask blank about a rotation axis perpendicular to the main surface and cleaning one of the main surfaces with a cleaning liquid (Step 3) A process for drying a mask blank substrate by performing rotation at a first rotational speed (R1; in rpm) and then rotation at a second rotational speed (R2; in rpm) in that order, so as to satisfy equation (1) or (2) below. 10 ≤ R1 ≤ 150 and 450 ≤ R2 ≤ 750 (1) 150 ≤ R1 ≤ 400 and 450 ≤ R2 ≤ 1500 (2) [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-100702 [Overview of the project] [Problems that the invention aims to solve]

[0005] In Patent Document 1, a mask blank substrate is supported by multiple support pins fixed to a spin table, and the above-mentioned cleaning and drying processes are carried out. Defects may occur in the mask blank substrate after cleaning and drying. In the cleaning and drying processes described above, if the position of the support pins is the same and the material of the support pins is the same, it is difficult to determine whether defects such as particles originating from the support pins occurred in the cleaning or drying process. The present invention aims to provide a method and apparatus for cleaning a substrate that facilitate the identification of the process in which a defect occurred when a defect is found on the substrate. [Means for solving the problem]

[0006] As a result of diligent research, the inventors have found that the above-mentioned problems can be solved by the following configuration. (1) A method for cleaning a substrate, comprising at least one cleaning step of supporting and cleaning the substrate with a support part positioned at a predetermined location, and at least one drying step of supporting and drying the substrate with a support part positioned at a predetermined location, wherein the cleaning step and the drying step are steps in which at least one of the positions of the support part that supports the substrate and the materials constituting the support part are different from each other. (2) A method for cleaning a substrate, comprising at least one cleaning step of cleaning the substrate while supporting it with a support part positioned at a predetermined location, and at least one drying step of drying the substrate while supporting it with a support part positioned at a predetermined location, wherein the cleaning step comprises an acid cleaning step using an acid, and the cleaning step comprises a pre-cleaning step prior to the acid cleaning step using a support part made of a material that dissolves in acid, and in the cleaning step and the drying step, the steps other than the pre-cleaning step are different from each other in terms of the position of the support part that supports the substrate and at least one of the materials that constitute the support part.

[0007] (3) The method for cleaning a substrate according to (1) or (2), wherein the material that dissolves with acid is one of polyvinyl chloride, polycarbonate, polyetheretherketone, polyphenylene sulfide, and polyamide. (4) The method for cleaning a substrate according to any one of (1) to (3), wherein the material of the support used in the drying process is one of polymethyl methacrylate, phenol resin, melamine resin, polyether ether ketone, polyphenylene sulfide, and polyether sulfone. (5) A method for cleaning a substrate according to any one of (1) to (4), wherein the cleaning step is a step that utilizes at least one of UV cleaning, acid cleaning, and alkaline cleaning. (6) A method for cleaning a substrate as described in any one of (1) to (5), wherein the substrate is a substrate for use as a mask blank. (7) A method for cleaning a substrate as described in any one of (1) to (5), wherein the substrate is a glass substrate only, a laminated substrate of a glass substrate and a multilayer reflective film, a laminated substrate of a glass substrate, a multilayer reflective film and an absorbent film, a laminated substrate of a conductive film and a glass substrate, a laminated substrate of a conductive film, a glass substrate and a multilayer reflective film, or a laminated substrate of a conductive film, a glass substrate, a multilayer reflective film and an absorbent film.

[0008] (8) A substrate cleaning apparatus comprising at least one cleaning unit for cleaning a substrate by supporting it with a support part positioned at a predetermined location, and at least one drying unit for drying a substrate by supporting it with a support part positioned at a predetermined location, wherein the cleaning unit and the drying unit differ from each other in the position of the support part that supports the substrate and in at least one of the materials constituting the support part. (9) A substrate cleaning apparatus comprising: a cleaning unit that supports the substrate with support parts positioned in predetermined locations and performs acid cleaning using acid; a pre-cleaning unit that supports the substrate with support parts made of a material that dissolves in acid before the cleaning unit performs acid cleaning and performs pre-cleaning; and a drying unit that supports the substrate with support parts positioned in predetermined locations and dries it, wherein, of the cleaning unit, pre-cleaning unit and drying unit, at least one of the positions of the support parts that support the substrate and the materials constituting the support parts are different from each other, except for the pre-cleaning unit. [Effects of the Invention]

[0009] According to the present invention, if a defect is found in the substrate, a method for cleaning a substrate and a apparatus for cleaning a substrate can be provided that make it easy to identify the process in which the defect occurred. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic diagram showing an example of a substrate cleaning apparatus used in a substrate cleaning method according to an embodiment of the present invention. [Figure 2] This is a schematic plan view showing an example of the arrangement of support parts for supporting a substrate when carrying out the substrate cleaning method according to an embodiment of the present invention. [Figure 3]It is a schematic cross-sectional view showing an example of the arrangement of a support portion that supports a substrate when implementing a method for cleaning a substrate according to an embodiment of the present invention. [Figure 4] It is a schematic cross-sectional view showing an example of a reflective mask blank. [Figure 5] It is a schematic cross-sectional view showing another example of a substrate to be cleaned by the substrate cleaning method according to an embodiment of the present invention. [Figure 6] It is a schematic cross-sectional view showing another example of a substrate to be cleaned by the substrate cleaning method according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the following embodiments are exemplary for explaining the present invention, and the present invention is not limited to the embodiments shown below. Various modifications and substitutions can be made to the following embodiments without departing from the scope of the present invention. Hereinafter, a numerical range represented using "~" means a range including the numerical values described before and after "~" as the lower limit value and the upper limit value.

[0012] As a characteristic point of the first substrate cleaning method of the present invention, it is a substrate cleaning method having at least one cleaning step of supporting and cleaning a substrate by a support portion arranged at a predetermined position, and at least one drying step of supporting and drying a substrate by a support portion arranged at a predetermined position, wherein in the cleaning step and the drying step, at least one of the position of the support portion that supports the substrate and the material constituting the support portion is different from each other. Furthermore, a feature of the second substrate cleaning method of the present invention is that it is a substrate cleaning method comprising at least one cleaning step of cleaning the substrate while supporting it with a support part positioned at a predetermined location, and at least one drying step of drying the substrate while supporting it with a support part positioned at a predetermined location, wherein the cleaning step comprises an acid cleaning step using an acid, and the cleaning step comprises a pre-cleaning step prior to the acid cleaning step using a support part made of a material that dissolves in acid, and of the cleaning step and the drying step, the steps other than the pre-cleaning step are steps in which at least one of the position of the support part that supports the substrate and the material constituting the support part are different from each other. As described above, in the first and second substrate cleaning methods of the present invention, since the position of the support portion that supports the substrate and at least one of the materials constituting the support portion are different from each other, if a defect is found in the substrate, the process in which the defect occurred can be easily identified from the position of the support portion or the material constituting the support portion by identifying the location of the defect or the material of the defect.

[0013] <Example of a circuit board cleaning method and circuit board cleaning apparatus> Figure 1 is a schematic diagram showing an example of a substrate cleaning apparatus used in the substrate cleaning method of the embodiment of the present invention. Figure 2 is a schematic plan view showing an example of the arrangement of support parts that support the substrate when carrying out the substrate cleaning method of the embodiment of the present invention. Figure 3 is a schematic cross-sectional view showing an example of the arrangement of support parts that support the substrate when carrying out the substrate cleaning method of the embodiment of the present invention. The substrate cleaning method of this embodiment comprises at least one cleaning step of supporting the substrate with a support part positioned at a predetermined location and cleaning it, and at least one drying step of supporting the substrate with a support part positioned at a predetermined location and drying it. For example, the substrate cleaning apparatus 10 shown in Figure 1 can be used as a method for cleaning the substrate, but the method is not particularly limited to the substrate cleaning apparatus 10 shown in Figure 1. The substrate cleaning apparatus 10 has a configuration that includes at least one cleaning unit that supports and cleans the substrate using a support part positioned at a predetermined location, and at least one drying unit that supports and dries the substrate using a support part positioned at a predetermined location. More specifically, the substrate cleaning apparatus 10 includes, for example, a first cleaning unit 12, a second cleaning unit 14, a third cleaning unit 16, and a drying unit 18. The first cleaning unit 12, the second cleaning unit 14, the third cleaning unit 16, and the drying unit 18 are arranged in a row within the housing 11. Hereinafter, the substrate cleaning apparatus 10 will simply be referred to as the cleaning apparatus 10.

[0014] The first washing unit 12, the second washing unit 14, the third washing unit 16, and the drying unit 18 are arranged in the direction D. L A straight transport path 20 is provided that extends in a direction parallel to the direction D. L and arrangement direction D L A transport unit 22 that can move in the opposite direction is provided. The transport unit 22 loads and unloads the substrates to be cleaned into the first cleaning unit 12, the second cleaning unit 14, the third cleaning unit 16, and the drying unit 18, respectively. The transport unit 22 also receives the substrates 30 to be cleaned from outside the cleaning apparatus 10 and unloads the cleaned substrates 30 from the cleaning apparatus 10. The transport unit 22 has, for example, an arm for loading and unloading the substrates. The configuration of the transport unit 22 is not particularly limited as long as it performs the functions described above. The first washing unit 12, the second washing unit 14, the third washing unit 16, and the drying unit 18 are, for example, single-wafer type devices, in which substrates are loaded one by one by the transport unit 22 described above, and after washing or drying, the loaded substrates are discharged.

[0015] The first cleaning unit 12 performs UV cleaning using, for example, UV (ultraviolet) light. In UV cleaning, UV light is irradiated onto the surface of the substrate to be cleaned to decompose and remove organic matter present on the surface. The first cleaning unit 12 is a cleaning unit that supports the substrate with support parts positioned in predetermined locations and performs UV cleaning using UV light. The device configuration of the cleaning unit that performs UV cleaning can be, for example, a known configuration that corresponds to a single-wafer type as described above, which can be used as appropriate.

[0016] The second cleaning unit 14 performs, for example, pickling using an acid in the cleaning liquid. In pickling, the cleaning liquid containing an acid is sprayed onto the surface of the substrate to be cleaned to clean the surface to be cleaned. The second cleaning unit 14 is a cleaning unit that supports the substrate by a support portion arranged at a predetermined position and performs pickling using an acid. For the cleaning liquid used in pickling, for example, an acidic solution with a pH (Potential Hydrogen) greater than 1 and less than or equal to 6 (1 < pH ≤ 6) can be used. The acid used in pickling is, for example, hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, or a mixture containing at least one of these. As the mixture, for example, a mixture of sulfuric acid and hydrogen peroxide is used. The device configuration of the cleaning unit that performs pickling can be appropriately utilized, for example, a known one corresponding to the single - sheet type as described above.

[0017] The third cleaning unit 16 performs, for example, alkaline cleaning using an alkali in the cleaning liquid. In alkaline cleaning, the cleaning liquid containing an alkali is sprayed onto the surface of the substrate to be cleaned to clean the surface to be cleaned. The third cleaning unit 16 is a cleaning unit that supports the substrate by a support portion arranged at a predetermined position and performs alkaline cleaning using an alkali. For the cleaning liquid used in alkaline cleaning, for example, an alkaline solution with a pH greater than 9 and less than or equal to 14 (9 < pH ≤ 14) can be used. The alkali used in alkaline cleaning is, for example, ammonia, tetramethylammonium hydroxide, triethanolamine, choline, sodium hydroxide, potassium hydroxide, cesium hydroxide, tetramethylammonium hydroxide, or a mixture containing at least one of these. As the mixture, for example, a mixture of aqueous ammonia and hydrogen peroxide is used. The device configuration of the cleaning unit that performs alkaline cleaning can be appropriately utilized, for example, a known one corresponding to the single - sheet type as described above.

[0018] The drying unit 18 dries the substrate, for example, by spin drying. In spin drying, the substrate is dried by rotating it while it is supported by a support provided on the stage described later. The configuration of the drying unit for spin drying can be, for example, one of the known single-wafer type units as described above.

[0019] The first washing unit 12, the second washing unit 14, the third washing unit 16, and the drying unit 18 are not particularly limited to the configuration described above. Furthermore, the number of washing units and drying units in the washing device 10 is not particularly limited, and the number of washing units and drying units can be appropriately determined depending on the washing method. Furthermore, since the cleaning units are used according to the cleaning method, not all cleaning units may be used depending on the cleaning method. Furthermore, while Figure 1 shows an example where one transport unit 22 is arranged in the transport path 20, the system is not particularly limited to this, and for example, multiple transport units 22 may be arranged.

[0020] The first cleaning unit 12, the second cleaning unit 14, the third cleaning unit 16, and the drying unit 18 each have, for example, a stage 23, as shown in Figure 2. The substrate 30 is supported by eight support parts 24a to 24h provided on this stage 23. As described above, the substrate 30 is placed on eight support parts 24a to 24h on the stage 23 by an arm (not shown) of the transport unit 22, for example, and is also detached from the eight support parts 24a to 24h on the stage 23. The substrate 30 is, for example, a plate-shaped member with a rectangular shape in plan view. Although only support parts 24a and 24c are shown in Figure 3, the shape of support parts 24a to 24h is, for example, a triangular pyramid. As shown in Figure 2, eight support parts 24a to 24h are arranged around the side surface 30c of the substrate 30. As shown in Figure 3, the corners 30d of the substrate 30 are in contact with the inclined surfaces 25 of the support parts 24a to 24h, thereby supporting the substrate 30. When the substrate 30 is chamfered at the corner 30d, the corner 30d is the chamfered portion. Furthermore, the number of support parts for the substrate 30 is not limited to eight; it may be four.

[0021] The positions of the support parts 24a to 24h on the stage 23 are set, for example, with respect to the substrate 30. In this case, for example, as shown in Figure 2, the geometric center of the planar shape of the substrate 30 is taken as the origin O. If the substrate 30 is a square or rectangle in planar view, there are two pairs of opposing sides, and there are two lines passing through the midpoints of the two sides of each pair. The intersection of these two lines is the origin O. Note that the support sections 24a to 24h are not particularly limited to triangular pyramids. With respect to the origin O, two coordinate axes, for example, the x-axis and the y-axis, are set to be orthogonal. This sets the coordinates for the x-axis and y-axis relative to the origin O. The positions of the support parts 24a to 24h can be represented by these coordinates. The positions of the support portions 24a to 24h can also be expressed by the coordinates of the contact points α1 to α8 (see Figure 2) between the corner portion 30d of the substrate 30 and the support portions 24a to 24h. Furthermore, if the support parts 24a to 24h are triangular pyramids, the positions of the support parts 24a to 24h can also be expressed using the coordinates of the vertices P1 to P8 (see Figure 2). The positions of the support parts 24a to 24h can be determined using the coordinates described above. In this case, it is preferable to set one of the x-axis and y-axis coordinate axes parallel to one of the two orthogonal sides 30c, and to set the other of the two orthogonal sides 30c parallel to the other side 30c.

[0022] In the cleaning method, the cleaning step and the drying step are different processes in which at least one of the positions of the support parts 24a to 24h that support the substrate 30 and the materials constituting the support parts 24a to 24h are different from each other. Here, the cleaning process by the first cleaning unit 12 is referred to as the first cleaning process. The cleaning process by the second cleaning unit 14 is referred to as the second cleaning process. The cleaning process by the third cleaning unit 16 is referred to as the third cleaning process. The cleaning apparatus 10 described above can perform three cleaning processes, from the first to the third cleaning process, and one drying process. The order of execution is the first to third cleaning processes, followed by the drying process. Specifically, when changing the position of the support parts 24a to 24h, the position of each support part 24a to 24h shall be different in all processes of the first to third washing processes and the drying process. For example, the positions (x-coordinate, y-coordinate) of the support parts 24a to 24h in the first cleaning unit 12 of the first cleaning process are taken as reference positions. With respect to the reference positions (x-coordinate, y-coordinate) of the support parts 24a to 24h in the first cleaning unit 12, the values ​​of the x-coordinate and y-coordinate are increased or decreased by a predetermined value for each process, for example. Let A be the position (reference position) of the support part in the first cleaning process. Let B be the position of the support parts 24a to 24h in the second cleaning unit 14 of the second cleaning process, let C be the position of the support parts 24a to 24h in the third cleaning unit 16 of the third cleaning process, and let D be the position of the support parts 24a to 24h in the drying unit 18 of the drying process. When the positions of the support parts differ, it means that the positions of the support parts differ by 0.5 mm or more. Due to the ease of identifying the positions of the support parts, it is preferable that the positions of the support parts differ by 1.0 mm or more, more preferably 1.5 mm or more, even more preferably 2.5 mm or more, and even more preferably 3.5 mm or more. There is no particular upper limit to the difference in the positions of the support parts, and the upper limit is appropriately determined depending on the size of the substrate, etc. In all stages of the first to third cleaning and drying processes, the positions of the support parts 24a to 24h are made different. This allows the location of the defect to be identified when the substrate 30 is inspected after the drying process, and the support part closest to the defect to be identified. Since defects originating from the support parts can be identified by the location of the support part, the process at the identified support part location is identified. This makes it possible to identify the process in which the defect occurred. Note that the support part in which the defect occurred is likely to be damaged or worn, such as being scraped, and may be replaced.

[0023] If the positions of the support parts 24a to 24h are different in all of the first to third washing processes and the drying process, the material constituting the support parts is not particularly limited and may be the same in all processes. If the cleaning method includes an acid cleaning step, the support parts in the step preceding the acid cleaning step can be made of materials that are not dissolved by the acid used in the acid cleaning step. This allows for the identification of the step where the defect occurred without being affected by the acid cleaning step.

[0024] In the cleaning method, if the position of the support parts 24a to 24h is changed, the materials constituting the support parts 24a to 24h may be different in all steps of the first cleaning process to the third cleaning process and the drying process. In this case, let a be the material that constitutes the support part for the first washing step, b be the material that constitutes the support part for the second washing step, c be the material that constitutes the support part for the third washing step, and d be the material that constitutes the support part for the drying step. Here, "different constituent materials" means that the constituent elements are different, or, if the constituent elements are the same, that the proportions of the elements are different. In all stages of the first to third cleaning and drying processes, the materials constituting the support parts 24a to 24h are made different. When the substrate 30 is inspected after the drying process, if a defect is found in the substrate, the composition of the defect can be identified, for example, using SEM (Scanning Electron Microscope)-EDX (Energy Dispersive X-ray Spectroscopy), and the support part using the identified material can be identified. By utilizing the fact that defects originating from the support part can be identified by the material constituting the support part, the process of the identified support part can be identified. This makes it possible to identify the process in which the defect occurred. Note that the support part in which the defect occurred is likely to be damaged or worn, such as by abrasion, and may be replaced. If the materials constituting the support parts 24a to 24h are different in all of the first to third washing processes and the drying process, the position of the support parts is not particularly limited and may be the same in all processes.

[0025] Furthermore, the cleaning process may include an acid cleaning process using acid. In this case, the cleaning process may include a pre-cleaning process before the acid cleaning process, using a support made of a material that dissolves in acid. In this case, even if defects occur in the pre-cleaning process, the defects that occurred in the pre-cleaning process will be dissolved by the acid cleaning process. Taking advantage of this, the acid-soluble material used for the support in the pre-cleaning process can be used for the support in the process after the acid cleaning process. In other words, a support made of the same material as the support in the pre-cleaning process can be used in the process after the acid cleaning process. In this case, among the cleaning and drying processes, the processes other than the pre-cleaning process are such that at least one of the positions of the support portion that supports the substrate and the materials constituting the support portion are different from each other. As mentioned above, the position of the support and the materials constituting the support are different, so a detailed explanation is omitted. The pre-cleaning process is a cleaning process performed before the acid cleaning process, and is included in the cleaning process. The cleaning method in the cleaning process (pre-cleaning process) is not particularly limited, but UV cleaning is one example. In this case, the pre-cleaning unit that supports the substrate and performs the pre-cleaning in the cleaning apparatus 10 is the first cleaning unit 12.

[0026] The following describes the support parts used in the substrate cleaning method, the substrate to be cleaned, and the mask blank.

[0027] (Support part) As described above, the support section supports the substrate during the cleaning and drying processes. The support section can be constructed from the same material if its position is changed. On the other hand, if the position of the support part is not changed, the materials used in the washing process and the drying process shall be different, except that the washing process includes an acid washing process. The material used for the support in the drying process is preferably one of the following: PMMA (polymethyl methacrylate), PF (phenol resin), MF (melamine resin), PEEK (polyether ether ketone), PPS (polyphenylene sulfide), and PES (polyether sulfone). The material of the support that dissolves in acid is preferably one of PVC (polyvinyl chloride), PC (polycarbonate), PEEK, PPS, and polyamide. Examples of polyamides include monomer cast nylon, nylon 6, and nylon 66.

[0028] Furthermore, the cleaning method consists of a total of four steps: three cleaning steps and a drying step. The first cleaning step is a UV-based cleaning step, the second cleaning step is an acid cleaning step, the third cleaning step is an alkaline cleaning step, and the drying step is a spin drying step. In this case, it is preferable that the material constituting the support in the first cleaning step (UV cleaning step) is selected from PVC, PE (polyethylene), PP (polypropylene), PC, PTFE (polytetrafluoroethylene), PEEK, PPS, PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), ETFE (tetrafluoroethylene-ethylene copolymer), PVDF (polyvinylidene fluoride), PCTFE (polychlorotrifluoroethylene), and ECTFE (chlorotrifluoroethylene-ethylene copolymer). The material constituting the support in the second cleaning step (acid cleaning step) is preferably selected from PP, PC, epoxy, PFA, FEP, ETFE, PVDF, PCTFE, and ECTFE. The material constituting the support in the third washing step (alkaline washing step) is preferably selected from PVC, ABS (acrylonitrile butadiene styrene resin), PE, PP, PA (polyamide), PMMA, PFA, FEP, ETFE, PVDF, PCTFE, ECTFE, PTFE, PF, MF, PEEK, PPS, and PES. The material constituting the support in the drying process (spin drying process) is preferably selected from PMMA, PF, MF, PEEK, PPS, and PES.

[0029] (substrate) The substrate 30 used in the cleaning method is, for example, a substrate for a mask blank used in the manufacture of reflective masks, etc. The mask blank has a glass substrate. The substrate 30 is, for example, a glass substrate for a mask blank. Here, Figure 4 is a schematic cross-sectional view showing an example of a reflective mask blank. Figure 5 is a schematic cross-sectional view showing another example of a substrate cleaned by the substrate cleaning method of the embodiment of the present invention. Figure 6 is a schematic cross-sectional view showing yet another example of a substrate cleaned by the substrate cleaning method of the embodiment of the present invention. For example, the reflective mask blank 40 shown in Figure 4 has a conductive film 42, a substrate 44, a multilayer reflective film 46, a multilayer reflective protective film 48, and an absorber film 50 stacked in this order. The substrate 44 is, for example, a glass substrate for mask blanks. Note that the reflective mask blank 40 may also have a configuration without the multilayer reflective protective film 48 between the multilayer reflective film 46 and the absorber film 50. Alternatively, the reflective mask blank 40 may have an anti-reflective film on the absorber film 50. The substrates used in the cleaning method are not limited to the glass substrates used for mask blanks as described above; the substrates may also include those in the process of being manufactured as mask blanks. For example, as shown in Figure 5, a laminated substrate 51 in which a substrate 44 and a multilayer reflective film 46 are stacked in that order can be used as a substrate for the cleaning method. The surface 46a of the multilayer reflective film 46 of the laminated substrate 51 corresponds to the surface 30a of the substrate 30. The back surface 44b of the substrate 44 of the laminated substrate 51 corresponds to the back surface 30b of the substrate 30. Furthermore, as shown in Figure 6, for example, a laminated substrate 52 in which a substrate 44, a multilayer reflective film 46, and an absorbent film 50 are stacked in that order can be used as a substrate for the cleaning method. The surface 50a of the absorbent film 50 of the laminated substrate 52 corresponds to the surface 30a of the substrate 30. The back surface 44b of the substrate 44 of the laminated substrate 51 corresponds to the back surface 30b of the substrate 30. Furthermore, the laminated substrates 51 and 52 described above may both have a conductive film 42 on the back surface 44b of the substrate 44, as shown in Figure 4. That is, a laminated substrate in which the conductive film 42, substrate 44, and multilayer reflective film 46 are laminated in that order, or a laminated substrate in which the conductive film 42, substrate 44, multilayer reflective film 46, and absorber film 50 are laminated in that order. Alternatively, a laminated substrate in which the conductive film 42 and substrate 44 are laminated in that order, that is, a configuration in which the conductive film is formed on the entire back surface 30b of the substrate 30 as shown in Figure 3. As will be described later, the conductive film 42 makes it possible to handle the substrate with an electrostatic chuck. The laminated substrate 52 described above may also have a multilayer reflective protective film 48, as shown in Figure 4, between the multilayer reflective film 46 and the absorber film 50.

[0030] (Reflective mask blank) [Substrate for mask blanks] For mask blanks, it is preferable to have a low coefficient of thermal expansion. The thermal expansion coefficient of the substrate for mask blanks is 0 ± 1.0 × 10 at 20°C. -7 A temperature of / ℃ is preferred, and 0±0.3×10 -7 / ℃ is preferable. Materials with a low coefficient of thermal expansion include SiO2-TiO2 glass, but are not limited to these; crystallized glass with precipitated β-quartz solid solution, quartz glass, metallic silicon, and metal substrates can also be used. For SiO2-TiO2 glass, it is preferable to use quartz glass containing 90-95% by mass of SiO2 and 5-10% by mass of TiO2.

[0031] The side of the substrate on which the multilayer reflective film is laminated (hereinafter also referred to as the "first main surface") preferably has high surface smoothness. The surface smoothness of the first main surface can be evaluated by its surface roughness. The surface roughness of the first main surface is preferably 0.15 nm or less in terms of root mean square roughness Rq. Surface roughness can be measured with an atomic force microscope, and the surface roughness will be described as root mean square roughness Rq based on JIS (Japanese Industrial Standards)-B0601. The first main surface is preferably surface-processed to a predetermined flatness in order to improve the pattern transfer accuracy and positional accuracy of the reflective mask obtained using a reflective mask blank. In a predetermined area of ​​the first main surface of the substrate (for example, an area of ​​132 mm × 132 mm), the flatness is preferably 100 nm or less, more preferably 50 nm or less, and even more preferably 30 nm or less. The flatness can be measured using a flatness measuring instrument manufactured by Fujifilm Corporation. The size and thickness of the substrate are determined as appropriate based on the design values ​​of the mask, etc. For example, the outer dimensions may be 6 inches (152 mm) square and the thickness 0.25 inches (6.3 mm). Furthermore, the substrate preferably has high rigidity in order to prevent deformation due to film stress of the film (multilayer reflective film, absorber film, etc.) formed on the substrate. For example, the Young's modulus of the substrate is preferably 65 GPa or higher.

[0032] [Multilayer reflective film] The multilayer reflective film provided on one side of the reflective mask blank is not particularly limited as long as it has the desired properties as a reflective film for the EUV mask blank. The multilayer reflective film preferably has a high reflectivity to EUV light. Specifically, when EUV light is incident on the surface of the multilayer reflective film at an incident angle of 6°, the maximum reflectivity of EUV light around a wavelength of 13.5 nm is preferably 60% or more, and more preferably 65% ​​or more. Similarly, even when a protective film is laminated on the multilayer reflective film, the maximum reflectivity of EUV light around a wavelength of 13.5 nm is preferably 60% or more, and more preferably 65% ​​or more.

[0033] Because multilayer reflective films can achieve high reflectivity of EUV light, they typically use a multilayer reflective film in which a high refractive index layer, which exhibits a high refractive index for EUV light, and a low refractive index layer, which exhibits a low refractive index for EUV light, are alternately stacked multiple times. The multilayer reflective film may be constructed by stacking a high refractive index layer and a low refractive index layer in that order from the substrate side, with each stacking period comprising multiple cycles, or by stacking a low refractive index layer and a high refractive index layer in that order, with each stacking period comprising multiple cycles. A layer containing Si can be used as the high refractive index layer. In addition to pure Si, Si compounds containing one or more elements selected from the group consisting of B, C, N, and O can be used as the Si-containing material. By using a high refractive index layer containing Si, a reflective mask with excellent EUV light reflectivity can be obtained. As the low refractive index layer, a layer containing a metal selected from the group consisting of Mo, Ru, Rh, and Pt, or an alloy thereof, can be used. Si is widely used in the high refractive index layer, and Mo is widely used in the low refractive index layer. In other words, Mo / Si multilayer reflective films are the most common. However, multilayer reflective films are not limited to these, and Ru / Si multilayer reflective films, Mo / Be multilayer reflective films, Mo compound / Si compound multilayer reflective films, Si / Mo / Ru multilayer reflective films, Si / Mo / Ru / Mo multilayer reflective films, and Si / Ru / Mo / Ru multilayer reflective films can also be used.

[0034] The film thickness of each layer constituting the multilayer reflective film and the number of repeating units in each layer can be appropriately selected according to the film material used and the required EUV light reflectance of the reflective layer. Taking a Mo / Si multilayer reflective film as an example, to create a multilayer reflective film with a maximum EUV light reflectance of 60% or more, a Mo film with a film thickness of 2.3±0.1 nm and a Si film with a film thickness of 4.5±0.1 nm should be stacked so that the number of repeating units is between 30 and 60.

[0035] [Protective film] The above-described reflective mask blank may have a protective film on the side opposite to the substrate side of the above-described multilayer reflective film. The protective film is provided to protect the multilayer reflective film from damage during the etching process (usually a dry etching process) when a pattern is formed on the absorber film by the etching process. Materials that can achieve the above objective include materials containing at least one element selected from the group consisting of Ru and Rh. In other words, it is preferable that the protective film contains at least one element selected from the group consisting of Ru and Rh. More specifically, the above materials include elemental Ru metal, Ru alloys containing Ru and one or more metals selected from the group consisting of Si, Ti, Nb, Mo, Rh, and Zr, Rh metal, Rh alloys containing Rh and one or more metals selected from the group consisting of Ru, Ta, Mo, and Zr, Rh-containing nitrides containing the above Rh alloy and nitrogen, and Rh-containing oxynitrides containing the above Rh alloy, nitrogen, and oxygen, as well as other Rh-based materials. Furthermore, examples of materials that can achieve the above objectives include Al, nitrides containing these metals and nitrogen, and Al2O3. Among these, Ru elemental metal, Ru alloy, Rh elemental metal, or Rh alloy are preferred as materials that can achieve the above objectives. As Ru alloys, Ru-Si alloys or Ru-Rh alloys are preferred, and as Rh alloys, Rh-Si alloys or Rh-Ru alloys are preferred.

[0036] The thickness of the protective film is not particularly limited as long as it can perform its function as a protective film. In order to maintain the reflectance of EUV light reflected by the multilayer reflective film, the thickness of the protective film is preferably 1 to 10 nm, more preferably 1.5 to 6 nm, and even more preferably 2 to 5 nm. It is also preferable that the material of the protective film is elemental Ru metal, Ru alloy, elemental Rh metal, or Rh alloy, and that the thickness of the protective film is the preferred thickness described above.

[0037] The protective film may be a single layer or a multilayer film consisting of multiple layers. If the protective film is a multilayer film, it is preferable that each layer constituting the multilayer film is made of the preferred material described above. Furthermore, if the protective film is a multilayer film, it is also preferable that the total thickness of the multilayer film is within the preferred range described above.

[0038] [Absorbing membrane] The absorber film in a reflective mask blank is required to have high contrast between the EUV light reflected by the multilayer reflective film and the EUV light reflected by the absorber film when the absorber film is patterned. A patterned absorber film (absorber film pattern) may function as a binary mask by absorbing EUV light, or it may function as a phase-shift mask that reflects EUV light while interfering with EUV light from a multilayer reflective film to produce contrast.

[0039] When using an absorber film pattern as a binary mask, the absorber film must absorb EUV light and have a low reflectivity of EUV light. Specifically, when EUV light is shone onto the surface of the absorber film, the maximum reflectivity of EUV light around 13.5 nm should ideally be 2% or less. The absorber film may contain one or more metals selected from the group consisting of Ta, Ti, Sn, and Cr, as well as one or more components selected from the group consisting of O, N, B, Hf, and H. Among these, the inclusion of N or B is preferable. The inclusion of N or B allows the crystalline state of the absorber film to be amorphous or microcrystalline. The crystalline state of the absorber membrane is preferably amorphous. This improves the smoothness and flatness of the absorber membrane. Furthermore, when the smoothness and flatness of the absorber membrane are increased, the edge roughness of the absorber membrane pattern is reduced, and the dimensional accuracy of the absorber membrane pattern can be improved. When using an absorber membrane pattern as a binary mask, the thickness of the absorber membrane is preferably 40-70 nm, and more preferably 50-65 nm.

[0040] When using an absorber film pattern as a phase shift mask, the reflectivity of the absorber film to EUV light is preferably 2% or higher. To obtain a sufficient phase shift effect, the reflectivity of the absorber film is preferably 9-15%. Using an absorber film as a phase shift mask improves the contrast of the optical image on the wafer and increases the exposure margin. Examples of materials for forming a phase shift mask include elemental Ru, Ru alloys containing Ru and one or more metals selected from the group consisting of Cr, Au, Pt, Re, Hf, Ta, Ti, and Si, alloys of Ta and Nb, oxides containing Ru alloys or TaNb alloys and oxygen, nitrides containing Ru alloys or TaNb alloys and nitrogen, and oxynitrides containing Ru alloys or TaNb alloys, oxygen, and nitrogen. Examples of materials for forming a phase shift film include elemental Ir, Ir alloys containing Ir and one or more metals selected from the group consisting of Ta, Cr, W, Re, and Si. When an absorber film pattern is used as a phase shift mask, the thickness of the absorber film is preferably 30 to 60 nm, and more preferably 35 to 55 nm.

[0041] The absorber film may be a single layer or a multilayer film consisting of multiple layers. If the absorber film is a single layer, the number of steps in mask blank manufacturing can be reduced, improving production efficiency. If the absorber film is a multilayer film, the layer located on the opposite side of the absorber film from the multilayer reflective protective film side may be an anti-reflective film used when inspecting the absorber film pattern using inspection light (for example, wavelength 193-248 nm).

[0042] [Conductive film] The reflective mask blank may have a conductive film on the side of the substrate opposite to the first main surface (the second main surface). By providing a conductive film, the reflective mask blank can be handled with an electrostatic chuck. The conductive film may include an embodiment that contains one or more first elements selected from the group consisting of Cr and Ta.

[0043] The conductive film contains one or more first elements selected from the group consisting of Cr and Ta. The conductive film may also contain one or more second elements selected from the group consisting of B, C, N, and O. However, the composition of the conductive film is different from the composition of the protective film, which will be described in detail later. Note that different compositions include not only cases where the conductive film and the protective film contain different elements, but also cases where the conductive film and the protective film contain two or more of the same elements, and the elemental content ratios differ between the conductive film and the protective film. The conductive film preferably contains either Cr or Ta as the first element, and more preferably contains Cr. The conductive film preferably contains N as the second element. The conductive film may also preferably contain Cr as the first element and at least N as the second element. Examples of specific materials that constitute the conductive film include elemental Cr, CrN, CrO, CrON, CrB, CrBN, CrC, CrCN, CrOC, elemental Ta, TaN, TaO, TaON, TaB, TaBN, TaC, TaCN, TaOC, CrTaO, and CrTaN, with elemental Cr, CrN, TaN, or TaBN being preferred. Notation such as "CrON" refers to a material containing Cr, O, and N, and the content ratio of these elements is not limited.

[0044] The conductive film preferably has a low sheet resistance. The sheet resistance of the conductive film is preferably 200 Ω / □ or less, and more preferably 100 Ω / □ or less. The thickness of the conductive film is preferably 10 to 1000 nm, and more preferably 100 to 500 nm.

[0045] [Other membranes] The reflective mask blank may have other films. Examples of other films include hard mask films. The hard mask film is preferably positioned on the side opposite to the protective film side of the absorber film. As the hard mask film, it is preferable to use a material that has high resistance to dry etching, such as a Cr-based film or a Si-based film. Examples of Cr-based films include materials containing Cr and one or more elements selected from the group consisting of Cr and O, N, C, and H. Specifically, examples include CrO and CrN. Examples of Si-based films include materials containing Si and one or more elements selected from the group consisting of Si and O, N, C, and H. Specifically, examples include SiO2, SiON, SiN, SiO, Si, SiC, SiCO, SiCN, and SiCON. When a hard mask film is formed on the absorber film, dry etching can be performed even if the minimum line width of the absorber film pattern becomes small. Therefore, it is effective for miniaturizing the absorber film pattern.

[0046] A reflective mask is obtained by patterning the absorber film in a reflective mask blank to form an absorber film pattern. In a reflective mask, the apertures of the absorber film reflect more EUV light, making it suitable for use as a reflective mask for exposure with EUV light. [Examples]

[0047] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. Examples 1 and 2 shown below are embodiments.

[0048] <Example 1> The cleaning apparatus has three cleaning units and one drying unit. In each of the three cleaning units and the drying unit, eight support parts were used to support the substrate described later. The shape of the support parts was a triangular pyramid as shown in Figure 3. In the three cleaning units, the first cleaning unit performs UV cleaning. The support structure of the first cleaning unit is made of PEEK. The second cleaning unit performs acid cleaning. In the second cleaning unit, the support structure is made of PTFE. The third cleaning unit performs alkaline cleaning. In the third cleaning unit, the support structure is made of UHMW-PE (Ultra High Molecular Weight Polyethylene). The drying unit performs spin drying. The support structure of the drying unit is made of PPS.

[0049] In Example 1, a laminated substrate was used, in which a 40nm thick CrN film was formed as a conductive film on the entire back surface of a glass substrate with an outer shape of 152mm x 152mm and a thickness of 6.3mm. The laminated substrate was UV-cleaned using the first cleaning unit under conditions of a substrate rotation speed of 30 rpm. Next, in the second cleaning unit, the laminated substrate was acid-cleaned using SPM (sulfuric acid: 96%, hydrogen peroxide: 4%). Next, the laminated substrate was alkaline-cleaned using ammonia water in the third cleaning unit. Next, the laminated substrates were spin-dried in a drying unit. Defects in the cleaned multilayer substrates were analyzed, and elemental analysis was performed where defects were found, using SEM-EDX. Defects were found in the cleaned multilayer substrates, and sulfur (S) was found to be present in the elements contained within the defects. The support portion containing S is the PPS support portion of the drying unit. From this, it was determined that the defect in the laminated substrate was a defect that occurred during the spin drying process of the drying unit.

[0050] <Example 2> Example 2 used the same cleaning apparatus as Example 1. In Example 2, the cleaning process was the same as in Example 1, except that the position of the support parts was changed in each of the three washing units and one drying unit, and the support parts of each unit were made of PTFE. In Example 2, a laminated substrate was used, in which a 40nm thick CrN film was formed as a conductive film on the entire back surface of a glass substrate with an outer shape of 152mm x 152mm and a thickness of 6.3mm. Also in Example 2, the shape of the support part was a triangular pyramid as shown in Figure 3. The position of the support part of the first cleaning unit (the contact point with the laminated substrate) is represented by a pair of x-coordinate values ​​and y-coordinate values ​​with respect to the origin O of the substrate, as shown in Figure 2. In this case, the positions of the eight support parts of the first cleaning unit are α1(76,40), α2(76,-40), α3(-76,40), α4(-76,-40), α(40,76), α6(40,-76), α7(-40,76), and α8(-40,-76). In the case of α(76,40), 76 represents the x-coordinate value and 40 represents the y-coordinate value. The positions of the eight support parts (contact points with the laminated substrate) of the second cleaning unit were defined as α1 (75.5, 39.5), α2 (75.5, -39.5), α3 (-75.5, 39.5), α4 (-75.5, -39.5), α5 (39.5, 75.5), α6 (39.5, -75.5), α7 (-39.5, 75.5), and α8 (-39.5, -75.5). The positions of the eight support parts (contact points with the laminated substrate) of the third cleaning unit were set as α1(75,39), α2(75,-39), α3(-75,39), α4(-75,-39), α5(39,75), α6(39,-75), α7(-39,75), and α8(-39,-75). The positions of the eight support parts of the drying unit (contact points with the laminated substrate) were defined as α1 (76.5, 40.5), α2 (76.5, -40.5), α3 (-76.5, 40.5), α4 (-76.5, -40.5), α5 (40.5, 76.5), α6 (40.5, -76.5), α7 (-40.5, 76.5), and α8 (-40.5, -76.5). The contact points with the laminated substrate are the contact points α1 and α3 between the corner 30d of the substrate 30 and the support portion 24a, and the support portion 24c, as shown in Figure 3.

[0051] In Example 2, the laminated substrate was cleaned and dried in the same manner as in Example 1. After cleaning, the laminated substrate was inspected for defects using an outer edge inspection machine (BASIC, manufactured by Lasertec Corporation). Defects were found in the cleaned laminated substrate, and their locations were identified. The identified locations were converted to x and y coordinate values ​​relative to the origin of the laminated substrate. As a result, it was found that the location of the defects coincided with the location of the support part of the third cleaning unit. From this, it was determined that the defects in the laminated substrate occurred during the alkaline cleaning of the third cleaning unit. [Explanation of Symbols]

[0052] 10 Washing device 11 cabinets 12. First Washing Unit 14. Second Washing Unit 16. Third Washing Unit 18 Drying Unit 20 Conveyor paths 22 Conveying section 23 stages 24a, 24b, 24c, 24d, 24e, 24f, 24g, 24h Support part 25 Slopes 30 circuit boards 30a, 46a, 50a surface 30b, 44b back side 30c side 30d corner 40 Reflective Mask Blanks 42 Conductive film 44 circuit boards 46 Multilayer reflective film 48 Multilayer reflective protective film 50 Absorbing membrane 51, 52 Multilayer substrate D L Placement direction O Origin P1, P2, P3, P4, P5, P6, P7, P8 vertices α1、α2、α、α4、α5、α6、α7、α8 contact points

Claims

1. A method for cleaning a substrate, comprising at least one cleaning step of supporting and cleaning the substrate with a support part positioned at a predetermined location, and at least one drying step of supporting and drying the substrate with the support part positioned at the predetermined location, A method for cleaning a substrate, wherein the cleaning step and the drying step are steps in which at least one of the positions of the support portion that supports the substrate and the materials constituting the support portion are different from each other.

2. A method for cleaning a substrate, comprising at least one cleaning step of supporting and cleaning the substrate with a support part positioned at a predetermined location, and at least one drying step of supporting and drying the substrate with the support part positioned at the predetermined location, The cleaning process includes an acid cleaning process using an acid, The cleaning process includes a pre-cleaning step prior to the acid cleaning step, in which a support part made of a material that dissolves in the acid is used. A method for cleaning a substrate, wherein, of the cleaning step and the drying step, the steps other than the pre-cleaning step are different steps in which at least one of the position of the support portion that supports the substrate and the material constituting the support portion is different from each other.

3. The method for cleaning a substrate according to claim 2, wherein the material dissolved by the acid is any of polyvinyl chloride, polycarbonate, polyetheretherketone, polyphenylene sulfide, and polyamide.

4. The method for cleaning a substrate according to claim 1 or 2, wherein the material of the support used in the drying step is one of polymethyl methacrylate, phenol resin, melamine resin, polyetheretherketone, polyphenylene sulfide, and polyethersulfone.

5. The method for cleaning a substrate according to claim 1 or 2, wherein the cleaning step is a step utilizing at least one of UV cleaning, acid cleaning, and alkaline cleaning.

6. The method for cleaning a substrate according to claim 1 or 2, wherein the substrate is a substrate for mask blanks.

7. The method for cleaning a substrate according to claim 1 or 2, wherein the substrate is a glass substrate only, a laminated substrate of a glass substrate and a multilayer reflective film, a laminated substrate of a glass substrate, a multilayer reflective film and an absorber film, a laminated substrate of a conductive film and a glass substrate, a laminated substrate of a conductive film, a glass substrate and a multilayer reflective film, or a laminated substrate of a conductive film, a glass substrate, a multilayer reflective film and an absorber film.

8. A substrate cleaning apparatus comprising at least one cleaning unit that supports and cleans the substrate using a support portion positioned at a predetermined location, and at least one drying unit that supports and dries the substrate using a support portion positioned at the predetermined location, A substrate cleaning apparatus wherein the cleaning unit and the drying unit are different from each other in that the position of the support portion that supports the substrate and at least one of the materials constituting the support portion are different from each other.

9. A cleaning unit that supports a substrate with a support part positioned in a predetermined location and performs acid cleaning using acid, The cleaning unit supports the substrate with a support made of a material that dissolves in the acid, and performs a pre-cleaning before the acid cleaning is carried out, and the cleaning unit is a pre-cleaning unit, The drying unit includes a support portion positioned at the predetermined location to support and dry the substrate, A substrate cleaning apparatus in which, among the cleaning unit, the pre-cleaning unit, and the drying unit, all except the pre-cleaning unit, the position of the support portion that supports the substrate and at least one of the materials constituting the support portion are different from each other.

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