Cleaning tank, cleaning machine, cleaning method, glass substrate manufacturing method, and EUVL mask blank manufacturing method

Abstract

To provide a technology which improves discharge efficiency of a cleaning fluid accumulated in a cleaning chamber and thereby improves discharge efficiency of particles peeled from an object and fallen into the cleaning fluid.SOLUTION: A cleaning tank 110 has a cleaning chamber 111 for accumulating a cleaning fluid 101, in which an object 190 is immersed, therein. The cleaning fluid 101 supplied from a supply port 112 of a lower surface of the cleaning chamber 111 flows out from a peripheral edge of an upper surface of the cleaning chamber 111. In the cleaning chamber 111, an area of the lower surface is smaller than an area of the upper surface.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a cleaning tank, a cleaning machine, a cleaning method, a method for manufacturing a glass substrate, and a method for manufacturing a mask blank for EUVL. [Background technology]

[0002] In recent years, with the miniaturization of semiconductor devices, EUV lithography (EUVL), an exposure technology using extreme ultraviolet (EUV), has been developed. EUV includes soft X-rays and vacuum ultraviolet light, and specifically refers to light with a wavelength of approximately 0.2 nm to 100 nm. At present, EUV with a wavelength of approximately 13.5 nm is mainly being considered.

[0003] A reflective mask is used in EUVL. A reflective mask has, in that order, a substrate such as a glass substrate, a multilayer reflective film that reflects EUV, and an absorbing film that absorbs EUV. An aperture pattern is formed in the absorbing film. In EUVL, the aperture pattern in the absorbing film is transferred to a target substrate such as a semiconductor substrate. Transferring includes reducing and transferring.

[0004] During the manufacturing process of EUVL mask blanks, the glass substrate or the functional film formed on the glass substrate may need to be cleaned. One of the cleaning methods is ultrasonic cleaning.

[0005] The cleaning method described in Patent Document 1 involves spraying a cleaning solution to which ultrasonic waves have been applied in advance from a nozzle onto the upper surface of a rotating substrate.The cleaning method described in Patent Document 2 involves supplying a cleaning solution between the upper surface of a rotating substrate and the lower surface of an ultrasonic cleaning head, and applying ultrasonic waves to the cleaning solution from the lower surface of the ultrasonic cleaning head, thereby cleaning the upper surface of the substrate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-158664 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-87725 Summary of the Invention [Problem to be solved by the invention]

[0007] An overflow-type cleaning machine may be used to clean objects such as cleaning tools or substrates. The cleaning machine has a cleaning chamber that stores a cleaning solution. The object is immersed in the cleaning solution stored in the cleaning chamber and cleaned by the flow of the cleaning solution. The cleaning solution is supplied from a supply port on the bottom surface of the cleaning chamber and flows out from the top surface of the cleaning chamber.

[0008] One aspect of the present disclosure provides a technology for improving the efficiency of discharging particles that have fallen off an object into the cleaning liquid by improving the efficiency of discharging the cleaning liquid stored in a cleaning chamber. [Means for solving the problem]

[0009] A cleaning tank according to one aspect of the present disclosure includes a cleaning chamber for storing a cleaning liquid in which an object is immersed, and the cleaning liquid is supplied from a supply port on a bottom surface of the cleaning chamber and flows out from a top surface of the cleaning chamber. The area of ​​the bottom surface of the cleaning chamber is smaller than the area of ​​the top surface. [Effects of the Invention]

[0010] According to one aspect of the present disclosure, by making the area of ​​the bottom surface of the cleaning chamber smaller than the area of ​​the top surface, the lower part of the cleaning chamber can be narrowed, and the generation of vortexes in the flow in the lower part of the cleaning chamber can be suppressed. As a result, the efficiency of discharging the cleaning liquid stored in the cleaning chamber can be improved, and the efficiency of discharging particles that have fallen off the object into the cleaning liquid can be improved. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view showing a cleaning machine according to one embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing a cleaning machine according to a first modified example. [Figure 3] FIG. 3 is a cross-sectional view showing a cleaning machine according to a second modified example. [Figure 4] FIG. 4 is a perspective view showing an example of a groove formed on the periphery of the upper surface of the cleaning chamber. [Figure 5] FIG. 5 is a cross-sectional view showing a conventional cleaning machine. [Figure 6] FIG. 6 is a side view showing a substrate cleaning apparatus according to an embodiment. [Figure 7] FIG. 7 is a cross-sectional view showing an example of the internal structure of the cleaning head. [Figure 8] FIG. 8 is a cross-sectional view showing another example of the internal structure of the cleaning head. [Figure 9] FIG. 9 is a plan view showing an example of the movement trajectory of the cleaning head. [Figure 10] FIG. 10 is a flowchart showing a method for manufacturing an EUVL mask blank according to one embodiment. [Figure 11] FIG. 11 is a cross-sectional view showing an example of a substrate. [Figure 12] FIG. 12 is a plan view of the substrate of FIG. [Figure 13] FIG. 13 is a cross-sectional view showing an example of an EUVL mask blank. [Figure 14] FIG. 14 is a cross-sectional view showing an example of an EUVL mask. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In each drawing, the same or corresponding components are denoted by the same reference numerals, and their description may be omitted. In the specification, the symbol "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0013] A cleaning machine 100 according to one embodiment will be described with reference to FIG. 1. The cleaning machine 100 is an overflow type and includes, for example, a cleaning tank 110 and a recovery tank 120. The cleaning tank 110 has a cleaning chamber 111 therein, and a cleaning liquid 101 is stored in the cleaning chamber 111. An object 190 is immersed in the cleaning liquid 101 stored in the cleaning chamber 111 and is cleaned by the flow of the cleaning liquid 101. The cleaning liquid 101 is supplied from a supply port 112 on a lower surface 111D of the cleaning chamber 111 and flows out from the periphery of an upper surface 111U of the cleaning chamber 111. The recovery tank 120 recovers the cleaning liquid 101 that has flowed out of the cleaning tank 110.

[0014] The cleaning solution 101 is not particularly limited, and may be, for example, pure water, an acidic solution, or an alkaline solution. The cleaning solution 101 may be, for example, pure water (e.g., deionized water), a mixture of pure water and X (at least one component selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, and acetic acid), a mixture of pure water and Y (at least one component selected from the group consisting of ammonia, tetramethylammonium hydroxide, triethanolamine, choline, sodium hydroxide, potassium hydroxide, and cesium hydroxide), a mixture of pure water and Z (at least one component selected from the group consisting of hydrogen peroxide, perchlorate ions, and periodate ions), a mixture of pure water, X, and Z, or a mixture of pure water, Y, and Z.

[0015] The cleaning liquid 101 may have at least one gas dissolved therein selected from the group consisting of H gas, CO gas, N gas, O gas, O gas, and Ar gas. Controlling the amount of dissolved gas can improve the cleaning efficiency of the target object 190. The gas dissolved in the cleaning liquid is preferably H gas, CO gas, or N gas, and more preferably CO gas.

[0016] The cleaning machine 100 includes a supply pipe 130 and a discharge pipe 140. The supply pipe 130 is connected to a supply port 112 of the cleaning tank 110 and supplies the cleaning liquid 101 to the supply port 112. On the other hand, the discharge pipe 140 is connected to a discharge port 122 of the recovery tank 120 and discharges the cleaning liquid 101 from the discharge port 122. The discharged cleaning liquid 101 is either discarded or passed through a filter before being returned to the supply pipe 130. The filter purifies the cleaning liquid 101 by collecting particles.

[0017] The object 190 is, for example, a cleaning tool for cleaning a substrate, or the substrate. The cleaning tool is, for example, a cleaning head 30 (see FIGS. 7 and 8). The cleaning head 30, which will be described in detail later, includes a vibration surface 31a that comes into contact with the liquid film F covering the substrate W, and an ultrasonic vibrator 32 that vibrates the vibration surface 31a.

[0018] The vibration surface 31a of the cleaning head 30 is placed facing downward and parallel to the upper surface of the substrate W. The ultrasonic vibrator 32 vibrates the vibration surface 31a to impart ultrasonic vibration to the liquid film F and apply sound pressure to the substrate W. This makes it possible to remove particles adhering to the upper surface Wa of the substrate.

[0019] When the cleaning head 30 cleans the substrate W, the distance between the vibration surface 31a of the cleaning head 30 and the substrate W is short, and particles that have fallen off from the substrate W may adhere to the vibration surface 31a of the cleaning head 30. If particles that have adhered to the vibration surface 31a fall off at an unintended timing, the substrate W may become contaminated.

[0020] Therefore, after cleaning the nth (n is an integer equal to or greater than 1) substrate W, the cleaning head 30 is made to wait inside the cleaning tank 110 before cleaning the n+1th substrate W. Wetting the vibration surface 31a of the cleaning head 30 with the cleaning liquid 101 can prevent the vibration surface 31a from drying out and particles from adhering to the vibration surface 31a.

[0021] The vibration surface 31a of the cleaning head 30 is immersed in the cleaning liquid 101 and is cleaned by the flow of the cleaning liquid 101. The flow of the cleaning liquid 101 applies shear stress to particles adhering to the vibration surface 31a, causing the particles to fall off from the vibration surface 31a. The particles then flow out of the cleaning chamber 111 together with the cleaning liquid 101. This prevents the particles from adhering again to the vibration surface 31a.

[0022] The ultrasonic vibrator 32 may vibrate the vibration surface 31a of the cleaning head 30 while the vibration surface 31a is immersed in the cleaning liquid 101. By utilizing not only the flow of the cleaning liquid 101 but also the vibration of the vibration surface 31a, particles can be peeled off from the vibration surface 31a, thereby improving the particle removal efficiency.

[0023] The cleaning tool serving as the object 190 is not limited to the cleaning head 30. The cleaning tool may be of a contact type or a non-contact type. An example of a contact type cleaning tool is a friction body that rubs the substrate W. The friction body may be a brush or a sponge. An example of a non-contact type cleaning tool is the cleaning head 30, as well as a nozzle that sprays a fluid. The nozzle may be a two-fluid nozzle.

[0024] As described above, the cleaning machine 100 cleans the object 190 by the flow of the cleaning liquid 101. The way the cleaning liquid 101 flows determines the magnitude of shear stress applied to particles and the time it takes for the cleaning liquid 101 to flow from each point in the cleaning chamber 111 to the outside of the cleaning chamber 111. The greater the magnitude of the shear stress, the easier it is for particles to peel off. Furthermore, the shorter the time it takes for the cleaning liquid 101 to flow from each point in the cleaning chamber 111 to the outside of the cleaning chamber 111, the better the efficiency with which the cleaning liquid 101 is discharged. The greater the magnitude of the shear stress and the better the efficiency with which the cleaning liquid 101 is discharged, the better the efficiency with which the particles are discharged. The way the cleaning liquid 101 flows is mainly determined by the shape of the cleaning chamber 111.

[0025] First, the shape of the cleaning chamber 111 of the conventional example will be described with reference to FIG. 5. The cleaning chamber 111 of the conventional example has a rectangular parallelepiped shape. Each of the lower surface 111D and the upper surface 111U of the cleaning chamber 111 is rectangular. The area (S1) of the lower surface 111D is the same as the area (S2) of the upper surface 111U. The cleaning chamber 111 has a constant horizontal cross-sectional area from the lower surface 111D to the upper surface 111U. The lower surface 111D has a supply port 112 at its center. The area (S1A) of the supply port 112 is smaller than the area (S1) of the lower surface 111D (S1A < S1). The ratio (ΔS / S1) of ΔS (ΔS = S1 - S1A) to S1 exceeds 10%. Of the four sides of the upper surface 111U, the cleaning liquid 101 flows out from at least one side (one side in FIG. 5).

[0026] In the cleaning chamber 111 of the conventional example, the area (S1) of the lower surface 111D is the same as the area (S2) of the upper surface 111U. In this case, as shown by the arrow in FIG. 5, a vortex occurs in the flow at the lower part of the cleaning chamber 111, and the cleaning liquid 101 flows back into the supply pipe 130. As a result, the speed of the flow discharged from the supply pipe 130 becomes slow, and the magnitude of the shear stress applied to the particles becomes small. Also, the discharge efficiency of the cleaning liquid 101 deteriorates. Since the magnitude of the shear stress is small and the discharge efficiency of the cleaning liquid 101 is also poor, the discharge efficiency of the particles deteriorates.

[0027] Next, the shape of the cleaning chamber 111 according to the present embodiment will be described with reference to FIG. 1 again. In the cleaning chamber 111 of the present embodiment, the area (S1) of the lower surface 111D is smaller than the area (S2) of the upper surface 111U (S1 < S2). By narrowing the lower part of the cleaning chamber 111, it is possible to suppress the generation of a vortex in the flow at the lower part of the cleaning chamber 111 and suppress the backflow of the cleaning liquid 101 into the supply pipe 130. As a result, the speed of the flow discharged from the supply pipe 130 becomes fast, and the magnitude of the shear stress applied to the particles becomes large. Also, the discharge efficiency of the cleaning liquid 101 is improved. Since the magnitude of the shear stress is large and the discharge efficiency of the cleaning liquid 101 is also good, the discharge efficiency of the particles is improved.

[0028] Preferably, the horizontal cross-sectional area of ​​at least the lower part of the cleaning chamber 111 gradually increases from bottom to top. At least in the lower part of the cleaning chamber 111, a flow that spreads radially from bottom to top can be formed, and the generation of vortices in the flow can be suppressed. The lower part of the cleaning chamber 111 means a region that is a distance of H / 2 or less from the bottom surface 111D of the cleaning chamber 111, where H is the vertical dimension of the cleaning chamber 111.

[0029] The horizontal cross-sectional area may gradually increase from bottom to top throughout the entire cleaning chamber 111. As shown in Figures 2 and 3, the cleaning chamber 111 may have a lower chamber 111-1 whose horizontal cross-sectional area gradually increases from bottom to top, and an upper chamber 111-2 whose horizontal cross-sectional area is constant. The upper chamber 111-2 is disposed above the lower chamber 111-1. In this case, too, it is possible to suppress the generation of vortices in the flow in the lower part of the cleaning chamber 111.

[0030] 1, the cleaning chamber 111 preferably has a ratio (ΔS / S1) of 0% or more and 10% or less. If the ratio (ΔS / S1) is 10% or less, the area (S1) of the lower surface 111D and the area (S1A) of the supply port 112 are approximately the same, so that it is possible to prevent the cleaning liquid 101 from flowing back into the supply pipe 130. The smaller the ratio (ΔS / S1), the more preferable it is, and the ratio (ΔS / S1) may even be 0%.

[0031] Preferably, the cleaning chamber 111 has a circular bottom surface 111D and a circular top surface 111U. When the bottom surface 111D and the top surface 111U are rectangular, as in the conventional example, stagnation of the flow occurs at the four corners of the rectangle. However, if the bottom surface 111D and the top surface 111U are circular, the corners can be eliminated and stagnation of the flow can be suppressed. Therefore, the efficiency of discharging the cleaning liquid 101 can be improved, and the efficiency of discharging particles can also be improved.

[0032] Furthermore, if upper surface 111U is circular, cleaning liquid 101 flows out radially and evenly from the periphery of upper surface 111U. Compared to the conventional example in which upper surface 111U is rectangular and cleaning liquid 101 flows out from one of the four sides of upper surface 111U, it is possible to reduce bias in the flow of cleaning liquid 101 and to reduce variations in the magnitude of shear stress.

[0033] More preferably, the cleaning chamber 111 has a circular horizontal cross section at each point in the vertical direction from the upper surface 111U to the lower surface 111D. In other words, the cleaning chamber 111 has the shape of a rotating body. The rotating body is a solid obtained by rotating a vertical plane figure once around a vertical line passing through the center of the supply port 112. The rotating body is, for example, a truncated cone (see FIG. 1). The rotating body may also be a solid formed by combining a truncated cone and a cylinder (see FIG. 2).

[0034] If the horizontal cross section of the cleaning chamber 111 is circular at each point in the vertical direction from the upper surface 111U to the lower surface 111D, corners can be eliminated at each cross section, and stagnation of the flow can be suppressed. Also, a flow that is symmetrical about the vertical line can be formed at each cross section, and flow bias can be reduced.

[0035] The cleaning chamber 111 has an overall truncated cone shape, as shown in Fig. 1, for example. The angle of inclination θ of the side surface 111S of the cleaning chamber 111 relative to the horizontal plane is, for example, 50° to 80°. If the area (S1) of the lower surface 111D and the area (S2) of the upper surface 111U are kept constant while the angle of inclination θ is reduced, the vertical dimension H of the cleaning chamber 111 becomes smaller, and the volume of the cleaning chamber 111 becomes smaller. The smaller the volume of the cleaning chamber 111, the shorter the time it takes for the cleaning liquid 101 to flow from each point in the cleaning chamber 111 to outside the cleaning chamber 111.

[0036] 1 has only a truncated conical shape as a whole, but as shown in FIG. 2, the cleaning chamber 111 may have a lower chamber 111-1 having a truncated conical shape and an upper chamber 111-2 having a cylindrical shape. The object 190 is placed in the upper chamber 111-2, but not in the lower chamber 111-1. When the object 190 has a cylindrical shape, it is preferable that the upper chamber 111-2 also has a cylindrical shape.

[0037] The lower chamber 111-1 may have the shape of a rotating body in which the inclination angle θ increases from bottom to top, as shown in Fig. 3. As is clear from a comparison of Fig. 3 with Fig. 2, the vertical dimension H1 of the lower chamber 111-1 can be shortened and the volume of the lower chamber 111-1 can be reduced compared to when the inclination angle θ is constant.

[0038] Although not shown, the inclination angle θ may increase from bottom to top not only in the lower chamber 111-1 but also in the entire cleaning chamber 111. This allows the vertical dimension H of the cleaning chamber 111 to be shortened, thereby reducing the volume of the cleaning chamber 111. Note that when the inclination angle θ is constant, the shape is simple and therefore easy to process.

[0039] As shown in Fig. 4, the cleaning tank 110 preferably has a plurality of grooves 114 spaced apart along the periphery of the upper surface 111U of the cleaning chamber 111. The grooves 114 are preferably arranged at equal intervals. Even if the installation precision of the cleaning tank 110 is low and the upper surface 111U of the cleaning chamber 111 is inclined, the presence of a plurality of grooves 114 allows the cleaning liquid 101 to flow out evenly in a radial direction. Therefore, the installation precision of the cleaning tank 110 can be relaxed, and the installation work of the cleaning tank 110 can be simplified.

[0040] The depth and number of grooves 114 are determined so that cleaning liquid 101 flows out evenly from the periphery of upper surface 111U of cleaning chamber 111 even when upper surface 111U is inclined. The depth of groove 114 is not particularly limited, but is, for example, 5 mm to 25 mm. The number of grooves 114 is not particularly limited, but is, for example, 8 to 20. The shape of groove 114 is V-shaped as shown in FIG. 4, but it may also be U-shaped, etc.

[0041] Next, Table 1 shows parameters representing the shape of the cleaning chamber 111 and the results of the fluid simulation. In Table 1, Example 1 is a comparative example, and Examples 2 to 10 are working examples. The cleaning chamber 111 of Example 1 has an overall rectangular parallelepiped shape (see FIG. 5). The cleaning chambers 111 of Examples 2 to 8 have an overall truncated conical shape (see FIG. 1). In the cleaning chamber 111 of Example 9, the lower chamber 111-1 has a truncated conical shape, and the upper chamber 111-2 has a cylindrical shape (see FIG. 2). In the cleaning chamber 111 of Example 10, the lower chamber 111-1 has a rotor shape A described below, and the upper chamber 111-2 has a cylindrical shape (see FIG. 3). The rotor shape A has a shape in which the inclination angle θ increases from bottom to top. In Examples 1 to 10, the conditions for the fluid simulation were the same except for the parameters shown in Table 1.

[0042] [Table 1] In Table 1, "θ" is the inclination angle of the side surface 111S of the cleaning chamber 111 (or lower chamber 111-1), "N" is the number of grooves 114, "S1" is the area of ​​the lower surface 111D of the cleaning chamber 111, "S1A" is the area of ​​the supply port 112, "ΔS / S1" is the ratio of ΔS (ΔS = S1 - S1A) to S1, and "S2" is the area of ​​the upper surface 111U of the cleaning chamber 111.

[0043] Also, in Table 1, "T1" is the maximum time it takes for the cleaning liquid 101 to flow out from each point in the cleaning chamber 111 to the outside of the cleaning chamber 111, and "T2" is the average time it takes for the cleaning liquid 101 to flow out from each point in the cleaning chamber 111 to the outside of the cleaning chamber 111.

[0044] From Table 1, it can be seen that, according to Examples 2 to 10, T1 and T2 can be shortened compared to Example 1, and the efficiency of discharging the cleaning liquid 101 can be improved.

[0045] Next, a substrate cleaning apparatus 1 according to one embodiment will be described with reference to Figures 6 to 9. The substrate cleaning apparatus 1 cleans the substrate W by applying ultrasonic vibrations to a liquid film F formed on the substrate W. Particles adhering to the substrate W can be removed. The substrate cleaning apparatus 1 includes a holder 10, a nozzle 20, a cleaning head 30, a rotation unit 40, a first movement unit 50, a second movement unit 60, and a control unit 90.

[0046] The holder 10 holds the substrate W horizontally. When viewed from above, the substrate W is rectangular (see FIG. 9), but may also be circular. The substrate W includes a glass substrate, a silicon wafer, or a compound semiconductor wafer. The substrate W may also include a functional film formed on a glass substrate or the like. The functional film is, for example, a light-reflecting film, a light-absorbing film, a conductive film, or an insulating film.

[0047] The holder 10 includes a plurality of pins 11 arranged at intervals along the periphery of the substrate W, as shown in FIG. 6, for example. The pins 11 hold the periphery of the substrate W. The substrate W is placed on the pins 11. Because there is space below the substrate W, it is also possible to attach a sensor to the underside of the substrate W. The holder 10 may also hold the substrate W by suction.

[0048] The nozzle 20 supplies the cleaning liquid to the upper surface Wa of the substrate W held by the holder 10, thereby forming a liquid film F. The upper surface Wa of the substrate W is also referred to as the substrate upper surface Wa. The nozzle 20 supplies the cleaning liquid, for example, near the center of the substrate upper surface Wa. The substrate W is rotating, and the cleaning liquid on the substrate W spreads from the center to the periphery of the substrate W due to centrifugal force. As a result, a liquid film F is formed over the entire substrate upper surface Wa. The nozzle 20 may be provided outside the cleaning head 30 as shown in FIG. 6, or may be provided inside the cleaning head 30, although not shown.

[0049] The nozzle 20 is connected to a supply source 22 of the cleaning liquid via a supply line 21. A valve 23 is provided midway along the supply line 21. The valve 23 opens and closes the flow path of the supply line 21. When the valve 23 opens the flow path of the supply line 21, the cleaning liquid is supplied from the supply source 22 to the nozzle 20, and the nozzle 20 ejects the cleaning liquid. When the valve 23 closes the flow path of the supply line 21, the nozzle 20 stops ejecting the cleaning liquid.

[0050] The cleaning liquid is, for example, pure water, a mixture of pure water and X (at least one component selected from the group consisting of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, and acetic acid), a mixture of pure water and Y (at least one component selected from the group consisting of ammonia, tetramethylammonium hydroxide, triethanolamine, choline, sodium hydroxide, potassium hydroxide, and cesium hydroxide), a mixture of pure water and Z (at least one component selected from the group consisting of hydrogen peroxide, perchlorate ions, and periodate ions), a mixture of pure water, X, and Z, or a mixture of pure water, Y, and Z.

[0051] The cleaning liquid may contain at least one gas dissolved therein selected from the group consisting of H2 gas, CO2 gas, N2 gas, O2 gas, O3 gas, and Ar gas. Controlling the amount of dissolved gas can improve the efficiency of cavitation generation and particle removal. The gas dissolved in the cleaning liquid is preferably H2 gas, CO2 gas, or N2 gas, and more preferably CO2 gas.

[0052] 7, the cleaning head 30 includes a vibration surface 31a that contacts the liquid film F and an ultrasonic vibrator 32 that vibrates the vibration surface 31a. The cleaning head 30 includes a vibration plate 31. The vibration plate 31 has a downward vibration surface 31a that contacts the liquid film F and an upward mounting surface 31b to which the ultrasonic vibrator 32 is attached.

[0053] The vibration surface 31a is placed parallel to the substrate upper surface Wa. The size of the vibration surface 31a is, for example, smaller than the size of the substrate upper surface Wa. The shape of the vibration surface 31a is, for example, circular. Note that when the nozzle 20 is provided inside the cleaning head 30, the outlet of the nozzle 20 is formed on the vibration surface 31a.

[0054] Mounting surface 31b may be installed parallel to vibration surface 31a as shown in Fig. 7, or may be installed obliquely to vibration surface 31a as shown in Fig. 8. In Fig. 8, θ is the angle between the normal to vibration surface 31a and the normal to mounting surface 31b. The normal direction to mounting surface 31b is the vibration direction of ultrasonic transducer 32.

[0055] The ultrasonic vibrator 32 vibrates the vibration surface 31a to apply ultrasonic vibrations to the liquid film F and sound pressure to the substrate W. This allows particles adhering to the upper surface Wa of the substrate to be peeled off. The output of the ultrasonic vibrator 32 is controlled by the control unit 90. When the distance D between the cleaning head 30 and the substrate W is constant, the sound pressure acting on the substrate W increases as the output of the ultrasonic vibrator 32 increases.

[0056] As shown in FIG. 6, the rotation unit 40 rotates the substrate W together with the holder 10. The rotation center line 10R of the holder 10 is installed vertically. The holder 10 holds the substrate W so that the rotation center line 10R passes through the center of the substrate W. The rotation unit 40 includes, for example, a servo motor 41. The rotational driving force of the servo motor 41 may be transmitted to the holder 10 via a pulley and belt (not shown), or a gear. The servo motor 41 transmits information regarding the rotational position of the holder 10 to the control unit 90. The rotational position of the holder 10 is expressed as a rotation angle. A stepping motor may be used instead of the servo motor 41.

[0057] The first moving unit 50 moves the cleaning head 30 in a horizontal direction perpendicular to the rotation center line 10R of the holder 10. The cleaning head 30 is moved, for example, between a position directly above the center of the substrate W and a position directly above the periphery of the substrate W. The first moving unit 50 includes, for example, a servo motor 51. The servo motor 51 transmits information regarding the horizontal position of the cleaning head 30 to the control unit 90. A stepping motor may be used instead of the servo motor 51.

[0058] 9, when viewed from above, a cleaning tank 110 is provided on the movement path of the cleaning head 30. After cleaning the nth (n is an integer equal to or greater than 1) substrate W, the cleaning head 30 is made to wait inside the cleaning tank 110 before cleaning the (n+1)th substrate W. Wetting the vibration surface 31a of the cleaning head 30 with the cleaning liquid 101 can prevent the vibration surface 31a from drying out and particles from adhering to the vibration surface 31a. In addition, the vibration surface 31a of the cleaning head 30 can be cleaned by the flow of the cleaning liquid 101.

[0059] 6, the first moving unit 50 moves the cleaning head 30 in a horizontal direction perpendicular to the rotation center line 10R of the holder 10, for example, by rotating a pivot shaft 52. The pivot shaft 52 is fixed to one end of a pivot arm 53, and the cleaning head 30 is fixed to the other end of the pivot arm 53. The pivot center line 30R of the cleaning head 30 is installed vertically.

[0060] Although not shown, the first moving part 50 may move the cleaning head 30 in a horizontal direction perpendicular to the rotation center line 10R of the holder 10 along a horizontal guide rail.

[0061] The second movement unit 60 moves the cleaning head 30 in the vertical direction. For example, the second movement unit 60 moves the cleaning head 30 in the vertical direction by moving the pivot shaft 52 in the vertical direction. The second movement unit 60 includes, for example, a servo motor 61. The second movement unit 60 may include a ball screw that converts the rotational motion of the servo motor 61 into linear motion. The servo motor 61 transmits information regarding the vertical position of the cleaning head 30 to the control unit 90. A stepping motor may be used instead of the servo motor 61. The second movement unit 60 may move the cleaning head 30 in the vertical direction using an air cylinder instead of a motor.

[0062] Although not shown, the second moving part 60 may move the holder 10 in the vertical direction instead of moving the cleaning head 30 in the vertical direction. In either case, the distance D between the substrate W and the cleaning head 30 can be changed.

[0063] The control unit 90 controls the valve 23, the ultrasonic vibrator 32, the rotation unit 40, the first movement unit 50, and the second movement unit 60. The control unit 90 is, for example, a computer, and includes a CPU (Central Processing Unit) 91 and a storage medium 92 such as a memory. The storage medium 92 stores programs that control various processes executed in the substrate cleaning apparatus 1. The control unit 90 controls the operation of the substrate cleaning apparatus 1 by having the CPU 91 execute the programs stored in the storage medium 92.

[0064] Next, the operation of the substrate cleaning apparatus 1, that is, the substrate cleaning method, will be described. First, a transfer robot (not shown) enters the inside of the substrate cleaning apparatus 1 and hands over the substrate W held by the transfer robot to the holder 10. After the holder 10 holds the substrate W horizontally, the transfer robot exits the substrate cleaning apparatus 1. In this manner, the substrate W is loaded.

[0065] Next, the rotating unit 40 rotates the substrate W together with the holder 10, and the nozzle 20 supplies the cleaning liquid near the center of the substrate W. The cleaning liquid on the substrate W spreads from the center to the periphery of the substrate W due to centrifugal force. As a result, a liquid film F is formed over the entire upper surface Wa of the substrate. The supply rate of the cleaning liquid is, for example, 0.1 L / min to 5.0 L / min, and preferably 0.8 L / min to 1.6 L / min.

[0066] Next, the first moving unit 50 adjusts the horizontal position of the cleaning head 30, and the second moving unit 60 adjusts the vertical position of the cleaning head 30, so that the vibration surface 31a of the cleaning head 30 contacts the liquid film F. A desired gap is formed between the cleaning head 30 and the substrate W. The gap is, for example, 0.1 mm to 5.0 mm, and preferably 1.0 mm to 4.0 mm.

[0067] Next, the ultrasonic vibrator 32 vibrates the vibration surface 31a of the cleaning head 30, thereby applying ultrasonic vibration to the liquid film F and applying sound pressure to the upper surface Wa of the substrate.

[0068] Next, the first moving unit 50 moves the cleaning head 30 in a horizontal direction perpendicular to the rotation center line 10R of the holder 10. The cleaning head 30 is moved back and forth between a position directly above the center of the substrate W and a position directly above the periphery of the substrate W. The substrate W is rotating, and the entire upper surface Wa of the substrate is cleaned.

[0069] Next, after the second moving unit 60 raises the cleaning head 30, the first moving unit 50 moves the cleaning head 30 horizontally to a standby position. The standby position is, for example, a position inside the cleaning tank 110. Also, the ultrasonic vibrator 32 stops vibrating the vibration surface 31a, and the nozzle 20 stops supplying the cleaning liquid.

[0070] Next, with the nozzle 20 stopping the supply of the cleaning liquid, the rotation unit 40 rotates the substrate W together with the holder 10, whereby the cleaning liquid on the substrate W is shaken off from the periphery of the substrate W by centrifugal force. The liquid film F is removed from the substrate W, and the substrate W is dried.

[0071] Next, a transfer robot (not shown) enters the inside of the substrate cleaning apparatus 1 and receives the substrate W from the holder 10. After the transfer robot holds the substrate W, the transfer robot exits the substrate cleaning apparatus 1. In this manner, the substrate W is unloaded.

[0072] Next, with reference to Fig. 10, a method for manufacturing the EUVL mask blank 200 shown in Fig. 13 will be described. The method for manufacturing the EUVL mask blank 200 includes steps S101 to S107. For example, a substrate 210 shown in Figs. 11 and 12 is prepared in advance. When the substrate 210 is a glass substrate, steps S101 to S104 are included in the method for manufacturing the glass substrate.

[0073] The substrate 210 includes a first main surface 211 and a second main surface 212 facing opposite to the first main surface 211. The first main surface 211 is rectangular. In this specification, a rectangular shape includes a shape with chamfered corners. A rectangle also includes a square. The second main surface 212 faces opposite to the first main surface 211. Like the first main surface 211, the second main surface 212 is also rectangular.

[0074] The substrate 210 also includes four end surfaces 213, four first chamfered surfaces 214, and four second chamfered surfaces 215. The end surfaces 213 are perpendicular to the first main surface 211 and the second main surface 212. The first chamfered surfaces 214 are formed at the boundaries between the first main surface 211 and the end surfaces 213. The second chamfered surfaces 215 are formed at the boundaries between the second main surface 212 and the end surfaces 213. In this embodiment, the first chamfered surfaces 214 and the second chamfered surfaces 215 are so-called C-chamfered surfaces, but may also be R-chamfered surfaces.

[0075] The substrate 210 is, for example, a glass substrate. The glass of the substrate 210 is preferably quartz glass containing TiO2. Compared to common soda-lime glass, quartz glass has a smaller linear expansion coefficient and undergoes less dimensional change due to temperature changes. The quartz glass may contain 80% to 95% by mass of SiO2 and 4% to 17% by mass of TiO2. When the TiO2 content is 4% to 17% by mass, the linear expansion coefficient is approximately zero near room temperature, and there is almost no dimensional change near room temperature. The quartz glass may contain a third component or impurity other than SiO2 and TiO2.

[0076] The size of the substrate 210 in plan view is, for example, 152 mm in length and 152 mm in width. The length and width may be greater than or equal to 152 mm.

[0077] The substrate 210 has a central region 211A and a peripheral region 211B on its first main surface 211. The central region 211A is a square region excluding a rectangular frame-shaped peripheral region 211B surrounding the central region 211A, and is a region that is processed to a desired flatness in steps S101 to S104 and is a quality assurance region. The quality assurance region has a size of, for example, 142 mm in length and 142 mm in width. The four sides of the central region 211A are parallel to the four end faces 213. The center of the central region 211A coincides with the center of the first main surface 211.

[0078] Although not shown, the second main surface 212 of the substrate 210 also has a central region and a peripheral region, similar to the first main surface 211. The central region of the second main surface 212 is a square region, similar to the central region of the first main surface 211, and is a region that is processed to a desired flatness in steps S101 to S104 of Fig. 10, and is a quality assurance region. The quality assurance region has a size of, for example, 142 mm long and 142 mm wide.

[0079] Step S101 includes polishing the first main surface 211 and the second main surface 212 of the substrate 210. In this embodiment, the first main surface 211 and the second main surface 212 are polished simultaneously using a double-sided polisher (not shown), but they may also be polished sequentially using a single-sided polisher (not shown). In step S101, the substrate 210 is polished while supplying polishing slurry between the polishing pad and the substrate 210.

[0080] Examples of the polishing pad include a urethane-based polishing pad, a nonwoven fabric-based polishing pad, and a suede-based polishing pad. The polishing slurry contains an abrasive and a dispersion medium. The abrasive is, for example, cerium oxide particles. The dispersion medium is, for example, water or an organic solvent. The first main surface 211 and the second main surface 212 may be polished multiple times using abrasives of different materials or particle sizes.

[0081] The abrasive used in step S101 is not limited to cerium oxide particles, and may be, for example, silicon oxide particles, aluminum oxide particles, zirconium oxide particles, titanium oxide particles, diamond particles, or silicon carbide particles.

[0082] Step S102 includes measuring the surface shapes of the first main surface 211 and the second main surface 212 of the substrate 210. To measure the surface shape, for example, a non-contact measuring machine such as a laser interference type is used to prevent the surface from being damaged. The measuring machine measures the surface shape of the central region 211A of the first main surface 211 and the central region of the second main surface 212.

[0083] Step S103 includes locally processing the first main surface 211 and the second main surface 212 of the substrate 210 to improve flatness with reference to the measurement results of step S102. The first main surface 211 and the second main surface 212 are locally processed in that order. The order in which they are processed may be any order, and is not particularly limited.

[0084] For the local processing, for example, at least one method selected from a gas cluster ion beam (GCIB) method, a plasma chemical vaporization machining (PCVM) method, a polishing method using a magnetic fluid, and polishing using a rotary polishing tool is used.

[0085] Step S104 includes performing finish polishing of the first main surface 211 and the second main surface 212 of the substrate 210. In this embodiment, the first main surface 211 and the second main surface 212 are polished simultaneously using a double-sided polisher (not shown), but they may also be polished sequentially using a single-sided polisher (not shown). In step S104, the substrate 210 is polished while a polishing slurry is supplied between the polishing pad and the substrate 210. The polishing slurry contains an abrasive. The abrasive is, for example, colloidal silica particles.

[0086] Step S105 includes forming a conductive film 240 shown in FIG. 13 in a central region of the second main surface 212 of the substrate 210. The conductive film 240 is used to attach the EUVL mask to an electrostatic chuck of an exposure tool. The conductive film 240 is made of, for example, chromium nitride (CrN). The conductive film 240 is formed by, for example, sputtering.

[0087] Step S106 includes forming a multilayer reflective film 220 shown in FIG. 13 in the central region 211A of the first main surface 211 of the substrate 210. The multilayer reflective film 220 reflects EUV. The multilayer reflective film 220 is formed by alternately stacking high-refractive index layers and low-refractive index layers, for example. The high-refractive index layers are made of, for example, silicon (Si), and the low-refractive index layers are made of, for example, molybdenum (Mo). The multilayer reflective film 220 is formed by a sputtering method such as ion beam sputtering or magnetron sputtering.

[0088] Step S107 includes forming an absorbing film 230 shown in FIG. 13 on the multilayer reflective film 220 formed in step S106. The absorbing film 230 absorbs EUV. The absorbing film 230 may be a phase shift film and may shift the phase of EUV. The absorbing film 230 is formed of, for example, a single metal, alloy, nitride, oxide, oxynitride, or the like containing at least one element selected from tantalum (Ta), chromium (Cr), and palladium (Pd). The absorbing film 230 is formed, for example, by sputtering.

[0089] In this embodiment, steps S106 and S107 are performed after step S105, but may be performed before step S105.

[0090] 13 is obtained by the above steps S101 to S107. The EUVL mask blank 200 has, in this order, a conductive film 240, a substrate 210, a multilayer reflective film 220, and an absorbing film 230. Note that the EUVL mask blank 200 may include another film in addition to the conductive film 240, the substrate 210, the multilayer reflective film 220, and the absorbing film 230.

[0091] For example, the EUVL mask blank 200 may further include a low-reflection film. The low-reflection film is formed on the absorbing film 230. Then, an opening pattern 231 is formed in both the low-reflection film and the absorbing film 230. The low-reflection film is used for inspecting the opening pattern 231, and has lower reflectivity to inspection light than the absorbing film 230. The low-reflection film is made of, for example, TaON or TaO. The low-reflection film is formed by, for example, sputtering.

[0092] The EUVL mask blank 200 may further include a protective film. The protective film is formed between the multilayer reflective film 220 and the absorbing film 230. The protective film protects the multilayer reflective film 220 so that the multilayer reflective film 220 is not etched when the absorbing film 230 is etched to form an opening pattern 231 in the absorbing film 230. The protective film is formed of, for example, Ru, Si, or TiO2. The protective film may be formed by, for example, sputtering.

[0093] 14 , the EUVL mask 201 is obtained by forming an opening pattern 231 in an absorbing film 230 of an EUVL mask blank 200. Photolithography and etching are used to form the opening pattern 231. Therefore, the EUVL mask blank 200 may include a resist film used to form the opening pattern 231.

[0094] During the manufacturing process of the EUVL mask blank 200, the substrate 210 or various functional films formed on the substrate 210 may be cleaned. Cleaning using a chemical reaction with acid or alkali, cleaning using a physical action, or a combination of these may be performed. Cleaning using a physical action includes ultrasonic cleaning, scrubbing cleaning, and two-fluid cleaning. Two-fluid cleaning involves spraying a mixture of cleaning liquid and gas.

[0095] Ultrasonic cleaning is performed using, for example, a substrate cleaning apparatus 1 shown in Fig. 6. Ultrasonic cleaning is preferably performed at least one of between steps S104 and S105, between steps S105 and S106, between steps S106 and S107, and after step S107. Although not shown, ultrasonic cleaning may also be performed before or after the application of a low-reflection film, a hard mask film, or a protective film.

[0096] The cleaning tank, cleaning machine, cleaning method, glass substrate manufacturing method, and EUVL mask blank manufacturing method according to the present disclosure have been described above, but the present disclosure is not limited to the above-described embodiments. Various changes, modifications, substitutions, additions, deletions, and combinations are possible within the scope of the claims. These naturally fall within the technical scope of the present disclosure. [Explanation of symbols]

[0097] 101 Cleaning Solution 110 Cleaning tank 111 Cleaning Room 111D Bottom side 111U top 112 Supply port 190 Objects

Claims

1. A cleaning head, the object of which includes a vibration surface that contacts a liquid film covering a substrate and an ultrasonic vibrator that vibrates the vibration surface, A cleaning tank for waiting the object, a cleaning chamber for storing a cleaning liquid in which the object is immersed, the cleaning liquid being supplied from a supply port on the bottom surface of the cleaning chamber and flowing out from the periphery of the top surface of the cleaning chamber; The cleaning chamber has a lower surface area smaller than an upper surface area, The cleaning chamber has a circular lower surface and a circular upper surface, The cleaning tank has a horizontal cross-sectional area that gradually increases from bottom to top in at least the lower part of the cleaning chamber.

2. The cleaning tank of claim 1 , wherein at least a lower portion of the cleaning chamber has a frustoconical shape.

3. 3. The cleaning vessel of claim 1, wherein the cleaning vessel has a plurality of grooves on the periphery of the top surface of the cleaning chamber, the grooves being spaced apart along the periphery.

4. 4. The cleaning tank according to claim 1, wherein the cleaning chamber has a difference between the area of ​​the lower surface and the area of ​​the supply port in proportion to the area of ​​the lower surface of the cleaning chamber, the difference being 10% or less.

5. A cleaning machine comprising: the cleaning tank according to any one of claims 1 to 4; and a recovery tank that recovers the cleaning liquid that has flowed out from the periphery of the upper surface of the cleaning chamber.

6. A cleaning method comprising: immersing the object in the cleaning liquid inside the cleaning tank according to any one of claims 1 to 4; and cleaning the object by a flow of the cleaning liquid.

7. The cleaning method according to claim 6 , further comprising vibrating the vibration surface of the cleaning head with the ultrasonic vibrator while the vibration surface is immersed in the cleaning liquid.

8. 8. The cleaning method according to claim 6, wherein the cleaning liquid is pure water, an acidic solution, an alkaline solution, or pure water, an acidic solution, or an alkaline solution in which a gas is dissolved.

9. forming a liquid film on the glass substrate, and vibrating a vibration surface of a cleaning head with an ultrasonic vibrator while the vibration surface is in contact with the liquid film, thereby cleaning the glass substrate; immersing the vibration surface of the cleaning head in the cleaning liquid inside the cleaning tank according to any one of claims 1 to 4, and cleaning the vibration surface of the cleaning head by a flow of the cleaning liquid; The method for manufacturing a glass substrate includes the steps of:

10. forming a liquid film on the glass substrate or the functional film formed on the glass substrate, and vibrating a vibration surface of a cleaning head with an ultrasonic vibrator while the vibration surface is in contact with the liquid film, thereby cleaning the glass substrate or the functional film; immersing the vibration surface of the cleaning head in the cleaning liquid inside the cleaning tank according to any one of claims 1 to 4, and cleaning the vibration surface of the cleaning head by a flow of the cleaning liquid; A method for manufacturing an EUVL mask blank, comprising:

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