Cleaning apparatus, method for manufacturing a substrate for mask blanks, and cleaning method

Abstract

The present invention provides a cleaning apparatus that suppresses the occurrence of defects on the back surface of a substrate, even if the substrate has a rectangular shape when viewed from above, as well as a method for manufacturing a substrate for mask blanks and a cleaning method. [Solution] This cleaning device has a surface and a back surface opposite to the surface, and has a rectangular shape in plan view. The device cleans the surface of a substrate while rotating the substrate. The cleaning device has a substrate rotating unit for rotating the substrate, a cleaning liquid supply unit for supplying cleaning liquid to the surface of the substrate, and a coating liquid supply unit for supplying coating liquid to the back surface of the substrate. The coating liquid supply unit supplies coating liquid such that the width of the region in the long side direction of the substrate where the coating liquid contacts the back surface of the substrate is greater than the width of the short side of the substrate in that region.

Description

Technical Field

[0001] The present invention relates to a cleaning device used for cleaning a substrate having a rectangular outer shape in a plan view, a method for manufacturing a substrate for a mask blank, and a cleaning method.

Background Art

[0002] In recent years, for further miniaturization of semiconductor devices, EUV (Extreme Ultra Violet) lithography using EUV light with a central 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. The 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, Patent Document 1 proposes a substrate processing method in which a cleaning liquid is discharged onto the surface of the substrate to clean the substrate, and the cleaning liquid is discharged onto the back surface of the substrate from a liquid nozzle.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In this case, if the cleaning solution supplied to the surface of the substrate reaches the back surface of the substrate, it can cause defects, and therefore the back surface of the substrate needs to be cleaned as well. In Patent Document 1, cleaning is performed by discharging a cleaning solution from a liquid nozzle onto the back surface of the substrate. However, in the case of a substrate with a rectangular shape in plan view, the cleaning solution may not spread sufficiently, and defects may occur on the back surface of the substrate, meaning that the prevention of defect occurrence is insufficient. The present invention aims to provide a cleaning apparatus, a method for manufacturing a mask blank substrate, and a cleaning method that suppress the occurrence of defects on the back surface of a substrate, even if the substrate has a rectangular shape in plan view. [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 cleaning apparatus for cleaning the surface of a substrate having a surface and a back surface opposite to the surface, and having a rectangular shape in plan view, while rotating the substrate, comprising a substrate rotating unit for rotating the substrate, a cleaning liquid supply unit for supplying cleaning liquid to the surface of the substrate, and a coating liquid supply unit for supplying coating liquid to the back surface of the substrate, wherein the coating liquid supply unit supplies coating liquid such that the width in the long side direction of the region of the substrate in contact with the back surface of the substrate is greater than the width on the short side of the substrate in that region. (2) The cleaning apparatus according to (1), wherein the coating liquid supply unit supplies the coating liquid such that the width in the long-side direction of the substrate in the area in contact with the back surface of the substrate is greater than the width of the short side of the substrate.

[0007] (3) The cleaning apparatus according to (1) or (2), wherein the coating liquid supply unit has a nozzle for discharging the coating liquid, a supply unit rotating unit for rotating the nozzle, and the nozzle rotates in accordance with the rotation of the substrate rotating unit. (4) The cleaning apparatus according to (1) or (2), wherein the coating liquid supply unit has multiple nozzles for discharging the coating liquid and adjusts the amount of coating liquid from the multiple nozzles in accordance with the rotation of the substrate. (5) The cleaning apparatus according to (3), wherein the coating liquid supply unit has a plurality of nozzles for discharging the coating liquid. (6) The cleaning apparatus according to (3), wherein the coating liquid supply unit has only one nozzle for discharging the coating liquid. (7) A cleaning apparatus according to any one of (3), (5), and (6), wherein, with the substrate stopped, the coating pattern of the coating liquid supplied by the coating liquid supply unit to a virtual surface at a position corresponding to the back surface of the substrate is an elliptical pattern, or a pattern that extends in one direction and the length in another direction perpendicular to the one direction is shorter than the length in the one direction.

[0008] (8) The cleaning apparatus according to any one of (1) to (7), wherein the cleaning solution is ultrapure water, an acid cleaning solution, or an alkaline cleaning solution. (9) The cleaning apparatus according to (8), wherein the acid cleaning solution is sulfuric acid, hydrogen peroxide, or sulfuric acid peroxide. (10) The cleaning apparatus according to (8), wherein the alkaline cleaning solution is ammonia or ammonia hydrogenated water. (11) The cleaning apparatus according to any one of (1) to (10), wherein the substrate is a glass substrate or a glass substrate on which a conductive film is disposed on one side. (12) The cleaning apparatus according to any one of (1) to (10), wherein the substrate is a glass substrate on which a conductive film is disposed on one side and at least one of a multilayer reflective film, an absorbent film, and a protective film is disposed on the other side. (13) The coating solution is pure water, and the cleaning apparatus is as described in any one of (1) to (12). (14) A substrate is a substrate for mask blanks, and the cleaning apparatus is one of the items (1) to (10).

[0009] A method for manufacturing a mask blank substrate, comprising the step of cleaning the substrate using a cleaning apparatus described in any one of (1) to (14). (16) A cleaning method for cleaning the surface of a substrate having a surface and a back surface opposite to the surface, and having a rectangular shape in plan view, while rotating the substrate, wherein a cleaning solution is supplied to the surface of the substrate while the substrate is rotating, and a coating solution is supplied to the back surface of the substrate while the substrate is rotating, and the coating solution is supplied in such a manner that the width of the region in the long side direction of the substrate in contact with the back surface of the substrate is greater than the width of the short side direction of the substrate in that region. (17) The cleaning method according to (16), wherein the coating liquid is supplied such that the width in the long-side direction of the substrate of the area in contact with the back surface of the substrate is greater than the width of the short side of the substrate. (18) The cleaning method according to (16) or (17), wherein the coating liquid is discharged from a nozzle and the nozzle rotates in accordance with the rotation of the substrate rotating part. (19) The cleaning method according to (16) or (17), wherein the coating liquid is dispensed from multiple nozzles and the amount of coating liquid from the multiple nozzles is adjusted in accordance with the rotation of the substrate. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a cleaning apparatus, a method for manufacturing a mask blank substrate, and a cleaning method that suppress the occurrence of defects on the back surface of a substrate, even if the substrate has a rectangular shape in plan view. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic cross-sectional view showing a first example of a cleaning device according to an embodiment of the present invention. [Figure 2] This is a schematic plan view showing the arrangement of substrates in a first example of a cleaning apparatus according to an embodiment of the present invention. [Figure 3] This is a schematic diagram showing an example of a coating liquid discharge port in a first example of a cleaning device according to an embodiment of the present invention. [Figure 4] This is a schematic diagram showing an example of a coating liquid discharge port in a first example of a cleaning device according to an embodiment of the present invention. [Figure 5] This is a schematic cross-sectional view showing a second example of a cleaning device according to an embodiment of the present invention. [Figure 6]It is a schematic plan view showing one step of a cleaning method according to a second example of a cleaning apparatus of an embodiment of the present invention. [Figure 7] It is a schematic plan view showing one step of a cleaning method according to a second example of a cleaning apparatus of an embodiment of the present invention. [Figure 8] It is a schematic plan view showing one step of a cleaning method according to a second example of a cleaning apparatus of an embodiment of the present invention. [Figure 9] It is a schematic cross-sectional view showing an example of a reflective mask blank. [Figure 10] It is a schematic cross-sectional view showing a first example of a substrate to be cleaned by a cleaning apparatus and a cleaning method of an embodiment of the present invention. [Figure 11] It is a schematic cross-sectional view showing a second example of a substrate to be cleaned by a cleaning apparatus and a cleaning method of an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0012] 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. In the following, 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.

[0013] A feature of the cleaning apparatus of the present invention is a cleaning apparatus that rotates a substrate having a front surface and a back surface opposite to the front surface and whose outer shape is rectangular in plan view, and cleans the front surface of the substrate while rotating the substrate, and has a substrate rotation unit that rotates the substrate, a cleaning liquid supply unit that supplies a cleaning liquid to the front surface of the substrate, and a coating liquid supply unit that supplies a coating liquid to the back surface of the substrate, and the coating liquid supply unit supplies the coating liquid so that the width in the long side direction of the substrate in the region where the coating liquid contacts the back surface of the substrate is larger than the width on the short side of the region of the substrate. A distinctive feature of the present invention is a cleaning method for a substrate having a surface and a back surface opposite to the surface, and having a rectangular shape in plan view, which is used to clean the surface of the substrate while rotating it. The method involves supplying a cleaning solution to the surface of the substrate while it is rotating, and supplying a coating solution to the back surface of the substrate while it is rotating, such that the width of the region in the long-side direction of the substrate where the coating solution contacts the back surface of the substrate is greater than the width of the short-side direction of the substrate in that region. In the cleaning apparatus and cleaning method of the present invention, the coating liquid is supplied such that the width of the region in the long-side direction of the substrate in contact with the back surface of the substrate is greater than the width of the short-side direction of the substrate in that region. Therefore, even if the substrate has a rectangular shape in plan view, the coating liquid spreads to the entire back surface of the substrate, and the occurrence of defects on the back surface of the substrate caused by the cleaning liquid supplied to the surface of the substrate seeping into the back surface of the substrate can be suppressed.

[0014] <Example 1 of a cleaning device> Figure 1 is a schematic cross-sectional view showing a first example of a cleaning apparatus according to an embodiment of the present invention. Figure 2 is a schematic plan view showing the arrangement of substrates in the first example of a cleaning apparatus according to an embodiment of the present invention. The cleaning device 10 includes a stage 12, a rotary drive unit 14, a cleaning liquid supply unit 16, a coating liquid supply unit 18, and a control unit 20. The control unit 20 controls the operation of the rotary drive unit 14, the cleaning liquid supply unit 16, and the coating liquid supply unit 18. The stage 12 and the rotating shaft portion 24 of the rotary drive unit 14 are arranged inside a cup 21 having an opening 21a, a bottom portion 21b, and an outer wall 21c. The stage 12 and the rotating shaft portion 24 of the rotary drive unit 14 are surrounded by the outer wall 21c of the cup 21. This prevents the cleaning liquid Lc and coating liquid Ls supplied to the substrate W from splashing outside the cup 21. The configuration of the cup 21 is not particularly limited, but it is preferable that the bottom 21b side is cylindrical and the diameter decreases towards the opening 21a side, forming a frustoconical shape. The frustoconical shape of the opening 21a side further suppresses the scattering of the cleaning liquid Lc and coating liquid Ls supplied to the substrate W to the outside.

[0015] Stage 12 supports the substrate W. Here, the substrate W has a surface W1 and a back surface W2 opposite to surface W1, and as shown in Figure 2, its outer shape is rectangular in plan view. The substrate W has a short side Wa and a long side Wb. Surface W1 and back surface W2 are planar and, for example, parallel to each other. The distance between surface W1 and back surface W2 is the thickness of the substrate W. Multiple support pins 13 are arranged on the surface 12a of the stage 12. The multiple support pins 13 support the back surface W2 of the substrate W with a gap between it and the surface 12a of the stage 12, creating a space between the surface 12a of the stage 12 and the back surface W2 of the substrate W. It is preferable that the substrate W is positioned horizontally on its surface W1 by the support pins 13. For example, as shown in Figure 2, there are 10 support pins 13. Two support pins 13 are positioned at each of the four corners of the substrate W. In addition, one support pin 13 is positioned in the center of the long side Wb of the substrate W.

[0016] As shown in Figure 1, the rotary drive unit 14 has a drive motor 22 and a rotating shaft 24. The drive motor 22 is located below the bottom 21b of the cup 21. The rotating shaft 24 is connected to the drive motor 22, and the rotating shaft 24 is also connected to the stage 12. The stage 12 is rotated by the drive motor 22 and the rotating shaft 24. The drive motor 22 rotates the rotating shaft 24 about the rotation axis C, for example, in the rotation direction R. At this time, the stage 12 also rotates about the rotation axis C, for example, in the rotation direction R. The drive motor 22 of the rotation drive unit 14 rotates the rotating shaft 24 and the stage 12 in a specific rotation direction and at a specific rotation speed. The rotation of the stage 12 causes the substrate W to rotate, and the stage 12 is the substrate rotating part. The drive motor 22 is controlled by the control unit 20.

[0017] The cleaning fluid supply unit 16 includes a cleaning fluid supply source 25, piping 26, and a nozzle 27. The cleaning liquid supply source 25 includes, for example, a tank (not shown) in which the cleaning liquid is stored, and a pump (not shown) that pumps the cleaning liquid from the tank to the nozzle 27. The nozzle 27 discharges the cleaning liquid Lc onto the surface W1 of the substrate W. The nozzle 27 is equipped with a discharge port (not shown), from which the cleaning liquid Lc is discharged. The cleaning fluid supply source 25 is controlled by the control unit 20, which controls the start and stop of the pump operation, as well as the flow rate of the cleaning fluid Lc. The nozzle 27 is connected to the cleaning fluid supply source 25 via piping 26. The piping 26 is equipped with a valve 28 to start or stop the supply of cleaning fluid Lc from the cleaning fluid supply source 25. The control unit 20 controls the opening and closing of the valve 28 to control the discharge of cleaning fluid Lc from the nozzle 27. The nozzle 27 is constructed according to the composition of the cleaning fluid Lc, such as not dissolving in the cleaning fluid Lc.

[0018] The coating liquid supply unit 18 includes a coating liquid supply source 30, piping 32, a rotary joint 33, a nozzle 34, and a supply pipe 36. The coating liquid supply source 30 includes, for example, a tank (not shown) in which the coating liquid Ls is stored, and a pump (not shown) that delivers the coating liquid Ls from the tank to the nozzle 34. The nozzle 34 discharges the coating liquid Ls and is equipped with a discharge port 35 from which the coating liquid Ls is discharged. The coating liquid supply source 30 is controlled by the control unit 20, which controls the start and stop of the pump operation, as well as the flow rate of the coating liquid Ls. The piping 32, the swivel joint 33, the supply pipe 36, and the nozzle 34 are connected. The nozzle 34 is connected to the coating liquid supply source 30 via the piping 32, the swivel joint 33, and the supply pipe 36. The coating liquid Ls from the coating liquid supply source 30 passes through the piping 32, the swivel joint 33, and the supply pipe 36 and reaches the nozzle 34.

[0019] The supply pipe 36 and nozzle 34 are located on the rotating shaft 24. When the rotating shaft 24 rotates around the rotation axis C by the rotary joint 33, the piping 32 does not rotate around the rotation axis C, without following the rotation of the stage 12 (substrate W). The supply pipe 36 and nozzle 34 rotate around the rotation axis C, following the rotation of the stage 12 (substrate W). In this state, the coating liquid Ls from the coating liquid supply source 30 passes through the piping 32, rotary joint 33, and supply pipe 36, and the coating liquid Ls can be discharged from the nozzle 34. Furthermore, the rotary joint 33 is not particularly limited as long as the supply pipe 36 and nozzle 34 can rotate around the rotation axis C in accordance with the rotation of the stage 12 (substrate W), without the piping 32 following the rotation of the stage 12 (substrate W), and the coating liquid Ls can be discharged from the nozzle 34. The drive motor 22 and the rotating shaft portion 24, that is, the rotary drive portion 14, correspond to the rotating portion of the supply unit that rotates the nozzle 34. Since the nozzle 34 rotates in accordance with the rotation of the stage 12 (substrate rotating part), the nozzle 34 rotates in accordance with the rotation of the substrate W on the stage 12. As a result, the relative position of the nozzle 34 and the substrate W on the back surface W2 of the substrate W does not change whether the stage 12 is not rotating (i.e., the substrate W is not rotating) or whether the stage 12 is rotating (i.e., the substrate W is rotating). Therefore, the coating liquid Ls is supplied from the nozzle 34 to the back surface W2 of the substrate W in the same manner.

[0020] The coating liquid supply unit 18 supplies the coating liquid Ls such that, when the substrate W is stationary and not subjected to centrifugal force, the width of the region in the long-side direction of the substrate W in contact with the back surface W2 of the substrate W is greater than the width of the region on the short side of the substrate W. Specifically, when the substrate W is stationary, the coating pattern Ps of the coating liquid Ls supplied by the coating liquid supply unit 18 (nozzle 34) to the virtual surface Pb at a position corresponding to the back surface W2 of the substrate W, as shown in Figure 2, is an elliptical pattern with the short side of the substrate W as the minor axis and the long side as the major axis. As a result, even if the substrate W has a rectangular shape in plan view, centrifugal force is generated as the substrate W rotates, allowing the coating liquid Ls to spread across the entire back surface of the substrate W, i.e., within the back surface. Therefore, even if the cleaning solution Lc is discharged onto the surface W1 of the substrate W and flows around to the back surface W2 of the substrate W, the cleaning solution Lc can be washed away by the coating solution Ls, preventing the cleaning solution Lc from adhering to the back surface W2 of the substrate W, and suppressing the occurrence of defects on the back surface W2 of the substrate W caused by the cleaning solution Lc, etc. The elliptical pattern described above is the coating pattern Ps when the substrate W is stationary and not subjected to centrifugal force. Furthermore, the coating pattern Ps formed by the coating liquid Ls discharged from the nozzle 34 is not limited to the elliptical pattern described above, and may be a pattern that extends in one direction, with the length in the other direction perpendicular to that direction being shorter than the length in the one direction. This pattern is also a coating pattern Ps when the substrate W is stationary and not subjected to centrifugal force. For example, one direction may be the direction of the long side of the substrate W, and the other direction may be the direction of the short side of the substrate W.

[0021] The coating liquid supply unit 18 preferably supplies the coating liquid Ls such that the width of the region in the long-side direction of the substrate W in contact with the back surface W2 of the substrate W is greater than the width of the short side of the substrate W. In this case, for example, by using a spray nozzle in the nozzle 34 and adjusting the discharge pressure of the coating liquid Ls, the coating liquid Ls can be supplied to the back surface W2 of the substrate W as described above. The coating pattern Ps described above can also be obtained, for example, by using a spray nozzle in the nozzle 34 and adjusting the discharge pressure of the coating liquid Ls.

[0022] The cleaning device 10 in Figures 1 and 2 has only one nozzle for discharging the coating liquid Ls and only one outlet for discharging the coating liquid Ls, but it is not limited to this configuration, and there may be multiple nozzles (outlets). Figure 3 is a schematic diagram showing an example of a coating liquid discharge port in a first example of a cleaning device according to an embodiment of the present invention. Figure 4 is a schematic diagram showing an example of a coating liquid discharge port in a first example of a cleaning device according to an embodiment of the present invention. In Figures 3 and 4, the same components as those in the cleaning device 10 shown in Figure 1 are denoted by the same reference numerals, and their detailed descriptions are omitted. For simplification, Figures 3 and 4 show the stage 12, the rotary drive unit 14, and the coating liquid supply unit 18, but the illustration of other components shown in Figure 1 is omitted. The coating liquid supply unit 18a shown in Figure 3 and the coating liquid supply unit 18b shown in Figure 4 are both examples of three nozzles 34a, 34b, and 34c, and have a configuration with three coating liquid Ls discharge ports 35. In addition, in the coating liquid supply unit 18a shown in Figure 3 and the coating liquid supply unit 18b shown in Figure 4, the nozzles 34a, 34b, and 34c rotate around the rotation axis C in accordance with the rotation of the substrate W.

[0023] The coating liquid supply unit 18a shown in Figure 3 has nozzles 34a, 34b, and 34c arranged in a row at predetermined intervals in a direction parallel to the surface 12a of the stage 12. Of the three nozzles 34a to 34c, nozzle 34b is positioned on the rotation axis C of the rotation axis unit 24. The coating liquid supply unit 18a, similar to the coating liquid supply unit 18 shown in Figure 1, has nozzles 34a, 34b, and 34c that rotate together with the stage 12, and the nozzles 34a, 34b, and 34c rotate in accordance with the rotation of the substrate W. Even when the stage 12 rotates, the relative positions of the nozzles 34a, 34b, and 34c and the substrate W remain unchanged. Nozzles 34a, 34b, and 34c are connected to supply pipes 36a, 36b, and 36c, respectively, for supplying coating liquid Ls to the back surface W2 of the substrate W. Each supply pipe 36a, 36b, and 36c is connected to piping 32 via a rotary joint 33. Coating liquid Ls is supplied from the coating liquid supply source 30 through piping 32, rotary joint 33, and supply pipes 36a, 36b, and 36c to the nozzles 34a, 34b, and 34c, and the coating liquid Ls is discharged from the discharge port 35 to supply the coating liquid Ls to the back surface W2 of the substrate W. Nozzles 34a, 34b, and 34c supply the coating liquid Ls to the substrate W in a manner similar to the coating liquid supply unit 18 of the cleaning apparatus 10 shown in Figure 1, such that the width of the region in the long-side direction of the substrate W in contact with the back surface W2 of the substrate W is greater than the width of the region on the short side of the substrate W. Specifically, the coating liquid Ls is supplied to the back surface W2 of the substrate W using the coating pattern Ps shown in Figure 2. Furthermore, as long as the coating liquid Ls can be supplied to the back surface of the substrate W by the nozzles 34a, 34b, and 34c as described above, the coating pattern Ps of the coating liquid Ls discharged from the nozzles 34a, 34b, and 34c is not particularly limited.

[0024] The coating liquid supply unit 18b shown in Figure 4 has, for example, three nozzles 34a, 34b, and 34c, with nozzle 34b being positioned on the rotation axis C. For example, nozzle 34b is positioned so that the discharge direction of the coating liquid Ls is 90° with respect to the surface 12a of the stage 12. Nozzles 34a and 34c are positioned so that the discharge direction of the coating liquid Ls is less than 90° with respect to the surface 12a of the stage 12. The three nozzles 34a, 34b, and 34c are positioned so that the discharge direction of the coating liquid Ls is symmetrical with respect to the rotation axis C of the rotation axis unit 24. The coating liquid supply unit 18b shown in Figure 4, like the coating liquid supply unit 18 shown in Figure 1, has nozzles 34a, 34b, and 34c that rotate together with the stage 12, and the nozzles 34a, 34b, and 34c rotate in accordance with the rotation of the substrate W.

[0025] Nozzles 34a, 34b, and 34c are connected to supply pipes 36a, 36b, and 36c, respectively, for supplying coating liquid Ls to the back surface W2 of the substrate W. Each supply pipe 36a, 36b, and 36c is connected to piping 32 via a rotary joint 33. Coating liquid Ls is supplied from the coating liquid supply source 30 through piping 32, rotary joint 33, and supply pipes 36a, 36b, and 36c to the nozzles 34a, 34b, and 34c, and the coating liquid Ls is discharged from the discharge port 35 to supply the coating liquid Ls to the back surface W2 of the substrate W. Nozzles 34a, 34b, and 34c supply the coating liquid Ls in the same manner as the coating liquid supply unit 18 of the cleaning apparatus 10 shown in Figure 1, such that the width of the region in the long-side direction of the substrate W in contact with the back surface W2 of the substrate W is greater than the width of the region on the short side of the substrate W. Specifically, the coating liquid Ls is supplied in the coating pattern Ps shown in Figure 2. Furthermore, as long as the coating liquid Ls can be supplied to the back surface of the substrate W by the nozzles 34a, 34b, and 34c as described above, the coating pattern Ps of the coating liquid Ls discharged from the nozzles 34a, 34b, and 34c is not particularly limited.

[0026] Although Figures 3 and 4 show coating liquid supply units 18a and 18b with three nozzles 34a, 34b, and 34c and three coating liquid Ls discharge ports 35, the configuration may also consist of two nozzles and two discharge ports, or four or more nozzles and four or more discharge ports. Note that a smaller number of nozzles (discharge ports) simplifies the configuration of the coating liquid supply unit 18.

[0027] <Example 1 of the cleaning method> The method for cleaning the substrate W will be explained using, for example, the cleaning apparatus 10 shown in Figure 1. First, the substrate W is supported on the surface 12a of the stage 12 by the support pins 13 so that the surface W1 of the substrate W is horizontal. Next, the drive motor 22 of the rotary drive unit 14 rotates the stage 12 at a predetermined rotational speed, causing the substrate W to rotate. The method for cleaning the substrate W includes a cleaning step in which, while the substrate W is rotating, a cleaning liquid supply unit 16 supplies cleaning liquid Lc from a nozzle 27 to the surface W1 of the substrate W, and a supply step in which, while the substrate W is rotating, a coating liquid supply unit 18 supplies coating liquid Ls from a nozzle 34 to the back surface W2 of the substrate W. In the supply process, the coating liquid Ls is discharged from the discharge port 35 of the nozzle 34. The nozzle 34 (discharge port 35) rotates in accordance with the rotation of the stage 12 (substrate rotating part). In the supply process, the coating liquid Ls is supplied such that the width of the region in the long-side direction of the substrate W in contact with the back surface W2 of the substrate W is greater than the width of the region on the short-side side of the substrate W. In the cleaning process, a cleaning solution Lc is used as appropriate, depending on the type of substrate W to be cleaned. Similarly, a coating solution Ls is used as appropriate, depending on the type of substrate W, the composition of the cleaning solution Lc, etc. After the cleaning process is completed, the supply of the coating solution Ls is stopped, ending the supply process, and the rotation of the stage 12, i.e., the rotation of the substrate W, is stopped.

[0028] Furthermore, after the cleaning and supply processes are completed, the rotation speed of the stage 12 may be increased to perform so-called spin drying in order to dry the substrate W.

[0029] The timing of starting to supply the cleaning solution Lc and the timing of starting to supply the coating solution Ls may be simultaneous, but from the viewpoint of preventing the cleaning solution Lc from flowing around and adhering to the back surface W2 of the substrate W, it is preferable that the coating solution Ls be supplied first. Furthermore, while the timing of stopping the supply of the cleaning solution Lc and the timing of stopping the supply of the coating solution Ls may be simultaneous, it is preferable that the cleaning solution Lc is stopped first from the viewpoint of preventing the cleaning solution Lc from seeping into and adhering to the back surface W2 of the substrate W. The timing of rotating stage 12 and the timing of starting to supply the cleaning solution Lc and coating solution Ls are not particularly limited; either may come first, or they may occur simultaneously. However, as mentioned above, it is preferable that the supply of the coating solution Ls comes first. The timing of rotation and stopping of stage 12, the timing of starting and stopping the supply of cleaning solution Lc and coating solution Ls are adjusted by the control unit 20. The timing of the start of supply of the cleaning solution Lc and the start of supply of the coating solution Ls being simultaneous means that the timing at which the control unit 20 outputs a control signal to open the valve 28 and the timing at which it outputs a control signal to start operating the pump that delivers the coating solution Ls to the nozzle 34 are the same. The timing of stopping the supply of the cleaning solution Lc and the timing of stopping the supply of the coating solution Ls are considered to be simultaneous when the control unit 20 outputs a control signal to close the valve 28 and outputs a control signal to stop the operation of the pump that delivers the coating solution Ls to the nozzle 34. The timing of rotating the stage 12 and the timing of starting the supply of the cleaning liquid Lc and coating liquid Ls being simultaneous means that the timing at which the control unit 20 outputs a control signal to start driving the drive motor 22 for rotating the stage 12, the timing at which it outputs a control signal to open the valve 28, and the timing at which it outputs a control signal to start operating the pump that delivers the coating liquid Ls to the nozzle 34 are all the same.

[0030] <Second example of a cleaning device> Figure 5 is a schematic cross-sectional view showing a second example of a cleaning apparatus according to an embodiment of the present invention. Figures 6 to 8 are schematic plan views showing one step of a cleaning method according to the second example of a cleaning apparatus according to an embodiment of the present invention. In Figures 5 to 8, the same reference numerals are used for components identical to those in the cleaning apparatus 10 shown in Figure 1, and their detailed descriptions are omitted. The cleaning device 11 shown in Figure 5 has the same configuration as the cleaning device 10 shown in Figure 1, except that it lacks the rotating shaft portion 24 of the rotary drive unit 14, the configuration of the stage 12 is different, and the configuration of the coating liquid supply unit 18c is different. Stage 12 has support pins 13 positioned on its outer edge 12b, for example, two pins 13 at each of the four corners of the substrate W. A total of eight support pins 13 are provided. Note that the support pins 13 are not located in the center of the long side Wb of the substrate W. As will be explained in detail later, the outer edge portion 12b rotates around the rotation axis C, causing the substrate W to rotate.

[0031] In Figure 5, the coating liquid supply unit 18c shows only three nozzles 34a to 34c, but as shown in Figures 6 to 8, it has, for example, nine nozzles 34a to 34i, and the nine nozzles 34a to 34i are configured not to rotate around the rotation axis C in accordance with the rotation of the substrate W. Each of the nine nozzles 34a to 34i has a discharge port 35. The coating liquid supply unit 18c has multiple nozzles that discharge the coating liquid Ls, and each nozzle is equipped with a discharge port from which the coating liquid is discharged. The amount of coating liquid Ls from the multiple nozzles is adjusted in accordance with the rotation of the substrate W. More specifically, as shown in Figures 6 to 8, for example, the amount of coating liquid Ls from each discharge port 35 of the nine nozzles 34a to 34i is adjusted. Adjusting the amount of coating liquid includes setting the amount of coating liquid to zero, that is, not discharging the coating liquid Ls from the nozzles.

[0032] Stage 12 has an outer edge portion 12b and a central portion 12c. Stage 12 is configured such that, for example, the outer edge portion 12b and the central portion 12c can rotate relative to each other by bearings or the like. A drive motor 22 is connected to the outer edge portion 12b. The drive motor 22 rotates the outer edge portion 12b around the rotation axis C, causing the substrate W to rotate around the rotation axis C. The outer edge portion 12b of Stage 12 is the substrate rotating part. As shown in Figure 6, the nine nozzles 34a to 34i are arranged in the central part 12c of the stage 12. Figure 5 shows three of the nine nozzles 34a to 34i, each connected to a supply pipe 36a to 36c. Valves 37a to 37c are provided on the supply pipes 36a to 36c. The valves 37a to 37c are configured to start or stop the supply of coating liquid from the coating liquid supply source 30. The opening and closing of valves 37a to 37c are controlled by the control unit 20. The amount of coating liquid Ls supplied from each discharge port 35 of nozzles 34a to 34c is adjusted by the opening and closing of valves 37a to 37c by the control unit 20. Of the nine nozzles 34a to 34i, nozzles 34d to 34i, excluding the three nozzles 34a to 34c shown in Figure 5, are each connected to a supply pipe (not shown). A valve (not shown) is provided in the supply pipe, and the opening and closing of the valve is controlled by the control unit 20. The opening and closing of the valve by the control unit 20 adjusts the amount of coating liquid Ls dispensed from each discharge port 35 of nozzles 34d to 34i.

[0033] The cleaning device 11 has a configuration with nine nozzles 34a to 34i, but the substrate W rotates over the central part 12c where the nine nozzles 34a to 34i are located, and the substrate W is not always positioned above all of the nozzles 34a to 34i. Therefore, when the substrate W rotates, the coating liquid Ls is supplied to the back surface W2 of the substrate W from the nozzles 34a to 34i that are positioned above the substrate W. In the cleaning device 11, as with the cleaning device 10, when supplying the coating liquid Ls, the coating liquid Ls is supplied in the same way as the coating liquid supply unit 18 of the cleaning device 10 shown in Figure 1, such that the width of the region in the long-side direction of the substrate W in contact with the back surface W2 of the substrate W is greater than the width of the short-side direction of the substrate W in that region. Specifically, the coating liquid Ls is supplied in the coating pattern Ps shown in Figure 2. As a result, the cleaning device 11, as with the cleaning device 10, can suppress the occurrence of defects on the back surface W2 of the substrate W, even if the substrate has a rectangular shape in plan view.

[0034] As shown in Figure 6, the substrate W is placed on the central part 12c which is provided with nine nozzles 34a to 34i. In the state shown in Figure 6, the substrate W is positioned above three nozzles 34a, 34b, and 34c. The coating liquid Ls is discharged from these three nozzles 34a, 34b, and 34c as described above, and no coating liquid is discharged from the remaining nozzles. Next, the substrate W rotates in the rotational direction Rb, and as shown in Figure 7, the substrate W reaches above the three nozzles 34d, 34b, and 34g. In this case, of the nine nozzles 34a to 34i, the coating liquid Ls is discharged from the three nozzles 34d, 34b, and 34g that are below the substrate W, as described above, and no coating liquid is discharged from the remaining nozzles that are not below the substrate W. Next, the substrate W rotates in the rotational direction Rb, and as shown in Figure 8, the substrate W reaches above the nozzles 34e, 34b, and 34h. In this case, of the nine nozzles 34a to 34i, the coating liquid Ls is discharged from the three nozzles 34e, 34b, and 34h that are below the substrate W, as described above, and no coating liquid is discharged from the remaining nozzles that are not below the substrate W. Next, the substrate W rotates in the rotational direction Rb, and although not shown in the diagram, the substrate W reaches above the nozzles 34f, 34b, and 34i. In this case, of the nine nozzles 34a to 34i, the coating liquid Ls is discharged from the three nozzles 34f, 34b, and 34i located below the substrate W, as described above, and no coating liquid is discharged from the remaining nozzles that are not located below the substrate W.

[0035] Next, the substrate W rotates in the rotational direction Rb, returning to the position shown in Figure 6. This causes the substrate W to complete one rotation over the central part 12c of the stage 12 with the nine nozzles 34a to 34i fixed. When the substrate W is rotated in this manner with the nozzles fixed, the coating liquid is discharged from the nozzles located below the substrate W as it rotates. As the substrate W rotates, the coating liquid Ls is supplied to the back surface W2 of the substrate W. Even if the substrate has a rectangular shape in plan view, centrifugal force is generated as the substrate W rotates, causing the coating liquid Ls to spread across the entire back surface W of the substrate W, i.e., within the back surface. Therefore, even if cleaning liquid Lc is discharged onto the surface W1 of the substrate W and flows around to the back surface W2 of the substrate W, the cleaning liquid Lc can be washed away by the coating liquid Ls, preventing the cleaning liquid Lc from adhering to the back surface W2 of the substrate W and suppressing the occurrence of defects on the back surface W2 of the substrate W caused by cleaning liquid Lc, etc. Furthermore, since the nozzle is fixed, the position of the substrate W after a predetermined time has elapsed can be calculated based on the position of the substrate W, the size of the substrate W, and the rotation speed of the substrate W, using the starting position of the substrate W before rotation as a reference. It is preferable to pre-calculate the relationship between the start of rotation of the substrate W and the position of the substrate W after a predetermined time has elapsed for each rotation speed and store it in the control unit 20, for example. This ensures that the coating liquid Ls can be reliably discharged from the nozzle below the substrate W when the substrate W rotates, according to each rotation speed. Furthermore, when dispensing the coating liquid Ls from the nozzle, there is a time lag between opening the valve and the coating liquid Ls reaching the back surface W2 of the substrate W. In other words, there is a time lag. It is even more preferable to adjust the timing of opening the valve, taking into account this time lag between opening the valve and the coating liquid reaching the back surface W2 of the substrate W. In this case, the valve is opened before the substrate W reaches above the nozzle, according to the time lag.

[0036] <Second example of a cleaning method> The method for cleaning the substrate W will be explained using, for example, the cleaning apparatus 11 shown in Figure 5 and Figures 6 to 8. First, the substrate W is supported on the central part 12c of the stage 12 by the support pins 13 on the outer edge 12b so that the surface W1 of the substrate W is horizontal. Next, the drive motor 22 of the rotary drive unit 14 rotates the outer edge 12b (substrate rotating part) of the stage 12 around the rotation axis C at a predetermined rotational speed, causing the substrate W to rotate. The method for cleaning the substrate W includes a cleaning step in which, while the substrate W is rotating, a cleaning liquid supply unit 16 supplies cleaning liquid Lc from a nozzle 27 to the surface W1 of the substrate W, and a supply step in which, while the substrate W is rotating, a coating liquid supply unit 18 supplies coating liquid Ls from a nozzle to the back surface W2 of the substrate W. In the supply process, as described above, the outer edge 12b of the stage 12 is rotated at a predetermined rotational speed, causing the substrate W to rotate. Here, as described above, the relationship between the position of the substrate W after a predetermined time has elapsed from the start of the substrate W's rotation is calculated in advance for each rotational speed. Therefore, when the substrate W rotates at a predetermined rotational speed, it is determined which nozzle the substrate W will be above after a predetermined time has elapsed from the start of the substrate W's rotation, and when the substrate W reaches above the nozzle, the coating liquid Ls is discharged from the nozzle. The discharge of the coating liquid Ls from the nozzle is as shown in Figures 6 to 8 above, so a detailed explanation will be omitted. In the cleaning process, a cleaning solution Lc is used as appropriate, depending on the type of substrate W to be cleaned. Similarly, a coating solution Ls is used as appropriate, depending on the type of substrate W, the composition of the cleaning solution Lc, etc. After the cleaning process is completed, the supply of the coating solution is stopped, ending the supply process, and the rotation of the outer edge 12b of the stage 12, i.e., the rotation of the substrate W, is stopped. Furthermore, after the cleaning and supply processes are completed, the rotation speed of the outer edge portion 12b of the stage 12 may be increased to perform so-called spin drying in order to dry the substrate W.

[0037] The timing of starting to supply the cleaning solution Lc and the timing of starting to supply the coating solution Ls may be simultaneous, but from the viewpoint of preventing the cleaning solution Lc from flowing around and adhering to the back surface W2 of the substrate W, it is preferable that the coating solution Ls be supplied first. Furthermore, while the timing of stopping the supply of the cleaning solution Lc and the timing of stopping the supply of the coating solution Ls may be simultaneous, it is preferable that the cleaning solution Lc is stopped first from the viewpoint of preventing the cleaning solution Lc from seeping into and adhering to the back surface W2 of the substrate W. The timing of rotating the outer edge 12b of the stage 12 and the timing of starting the supply of the cleaning liquid Lc and coating liquid Ls are not particularly limited; either may come first, or they may occur simultaneously. However, as mentioned above, it is preferable that the supply of the coating liquid Ls comes first. The timing of rotation and stopping of the outer edge 12b of the stage 12, the timing of starting and stopping the supply of the cleaning liquid Lc and coating liquid Ls are adjusted by the control unit 20. In addition, while the above-described cleaning apparatus and cleaning method use the surface W1 of the substrate W as the cleaning surface and the back surface W2 of the substrate W as the surface to which the coating liquid is supplied, this is not the only way to do so. The surfaces W1 and W2 of the substrate W may be swapped, with the back surface W2 of the substrate W being the cleaning surface and the surface W1 of the substrate W being the surface to which the coating liquid is supplied. The timing of the start of supply of the cleaning solution Lc and the start of supply of the coating solution Ls being simultaneous means that the timing at which the control unit 20 outputs a control signal to open the valve 28 and the timing at which it outputs a control signal to open the valve of the supply pipe are the same. The fact that the timing of stopping the supply of the cleaning liquid Lc and the timing of stopping the supply of the coating liquid Ls are simultaneous means that the timing at which the control unit 20 outputs a control signal for closing the valve 28 is the same as the timing at which it outputs a control signal for closing the valve of the supply pipe. The fact that the timing of rotating the outer edge portion 12b of the stage 12 described above and the timing of starting the supply of the cleaning liquid Lc and the coating liquid Ls are simultaneous means that the timing at which the control unit 20 outputs a control signal for starting the drive of the drive motor 22 for rotating the outer edge portion 12b of the stage 12 is the same as the timing at which it outputs a control signal for opening the valve 28 and the timing at which it outputs a control signal for opening the valve of the supply pipe.

[0038] <Method for manufacturing a substrate for a mask blank> A step of cleaning a substrate using the cleaning device 10 shown in FIG. 1 and the cleaning device 11 shown in FIG. 5 described above is performed to manufacture a substrate for a mask blank.

[0039] (Cleaning liquid) The cleaning liquid is, for example, ultrapure water, an acid cleaning liquid, or an alkaline cleaning liquid. Note that pure water is water having an electric conductivity of 0.1 or more and less than 15 MΩcm. Ultrapure water is water having an electric conductivity of 15 MΩcm or more. Note that the ultrapure water may contain gas, and the gas contained in the ultrapure water is, for example, carbon dioxide or nitrogen.

[0040] Examples of the acid cleaning liquid include sulfuric acid, hydrogen peroxide, and persulfuric acid. In addition, for the acid cleaning liquid, for example, an acidic solution having a pH (Potential Hydrogen) greater than 1 and equal to or less than 6 (1 < pH ≤ 6) can be used. Examples of the acid used for the acid include hydrochloric acid, nitric acid, phosphoric acid, formic acid, and acetic acid. Examples of the alkaline cleaning liquid include ammonia and ammonia peroxide. In addition, for the alkaline cleaning solution, for example, an alkaline solution with a pH greater than 9 and less than or equal to 14 (9 < pH ≦ 14) can be used. Examples of the alkali used for alkaline cleaning include tetramethylammonium hydroxide, triethanolamine, choline, sodium hydroxide, potassium hydroxide, cesium hydroxide, and tetramethylammonium hydroxide.

[0041] (Coating solution) The coating solution is, for example, pure water. The pure water may contain gas, and the gas contained in the pure water is, for example, carbon dioxide or nitrogen.

[0042] (Support pin) The support pin supports the substrate W on the stage 12 as described above, and preferably arranges the surface of the substrate horizontally. For example, the support pin is made of a material that is not dissolved by the cleaning solution used.

[0043] (Substrate) The substrate W used in the cleaning apparatus and the cleaning method is the object to be cleaned, and has a rectangular outer shape in a plan view as shown in FIG. 2. The ratio b / a of the length b of the long side Wb of the substrate W to the length a of the short side Wa of the substrate W is preferably 1.6 or more. The upper limit of the ratio b / a is often 2.4 or less. For example, the length a of the short side Wa of the substrate W is 5 inches or more. The upper limit of the length a of the short side Wa is often 7 inches or less. In addition, for example, the length b of the long side Wb of the substrate W is 8 inches or more. The upper limit of the length b of the long side Wb is often 16.8 inches or less. The substrate W is, for example, a substrate for a mask blank used in the manufacture of a reflective mask or the like. In addition to this, examples of the substrate W include a glass substrate or a glass substrate with a conductive film disposed on one surface side. In this case, the cleaning surfaces are both surfaces of the glass substrate. In the glass substrate with a conductive film, the surface of the glass substrate on the side where the conductive film is not provided and the surface of the conductive film become the cleaning surfaces. Examples of substrates W include a laminated substrate consisting of a glass substrate and a multilayer reflective film, and a laminated substrate consisting of a glass substrate, a multilayer reflective film, and an absorber film.

[0044] The substrate used for the mask blank mentioned above is, for example, a glass substrate, in which case substrate W is a glass substrate used for the mask blank. Here, Figure 9 is a schematic cross-sectional view showing an example of a reflective mask blank. Figure 10 is a schematic cross-sectional view showing a first example of a substrate cleaned by the cleaning apparatus and cleaning method of an embodiment of the present invention. Figure 11 is a schematic cross-sectional view showing a second example of a substrate cleaned by the cleaning apparatus and cleaning method of an embodiment of the present invention. For example, the reflective mask blank 40 shown in Figure 9 has a conductive film 42, a substrate 44, a multilayer reflective film 46, a protective film 48, and an absorber film 50 stacked in this order. The substrate 44 is a glass substrate. Furthermore, the reflective mask blank 40 may have a configuration without a 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 to be cleaned by the cleaning apparatus and cleaning method are not particularly limited to the glass substrates for mask blanks described above, and the substrates may also include mask blanks in the manufacturing process. The substrate W is, for example, a glass substrate, or a glass substrate with a conductive film arranged on one side.

[0045] Furthermore, for example, the substrate W to be cleaned by the cleaning apparatus and cleaning method is a glass substrate on which a conductive film is arranged on one side and at least one of a multilayer reflective film, an absorbent film, and a protective film is arranged on the other side. Specifically, as shown in Figure 10, the substrate W has a configuration in which a conductive film 42 is arranged on the back surface 44b of the substrate 44 (glass substrate) and a multilayer reflective film 46 is arranged on the front surface 44a of the substrate 44. The conductive film 42, the substrate 44 (glass substrate), and the multilayer reflective film 46 constitute the laminated substrate 51. The back surface 44b of the substrate 44 corresponds to one side, and the front surface 44a corresponds to the other side. The front surface 46a of the multilayer reflective film 46 of the laminated substrate 51 corresponds to the front surface W1 of the substrate W and is the cleaning surface. The front surface 42a of the conductive film 42 of the laminated substrate 51 corresponds to the back surface W2 of the substrate W and is the surface to which the coating liquid is supplied. When cleaning the surface 42a of the conductive film 42, the surface 42a of the conductive film 42 corresponds to the surface W1 of the substrate W and is the cleaning surface, while the surface 46a of the multilayer reflective film 46 of the laminated substrate 51 corresponds to the back surface W2 of the substrate W and is the surface to which the coating liquid is supplied. Furthermore, as shown in Figure 11, the substrate W has a configuration in which a conductive film 42 is placed on the back surface 44b of the substrate 44 (glass substrate), a multilayer reflective film 46 is placed on the front surface 44a of the substrate 44, and an absorber film 50 is placed on the surface of the multilayer reflective film 46 that faces the front surface 44a of the substrate 44. The laminated substrate 52 is composed of the conductive film 42, the substrate 44 (glass substrate), the multilayer reflective film 46, and the absorber film 50. The surface 50a of the absorber film 50 of the laminated substrate 52 corresponds to the front surface W1 of the substrate W and is the cleaning surface. The surface 42a of the conductive film 42 of the laminated substrate 52 corresponds to the back surface W2 of the substrate W and is the surface to which the coating liquid is supplied. When cleaning the surface 42a of the conductive film 42, the surface 42a of the conductive film 42 corresponds to the front surface W1 of the substrate W and is the cleaning surface, and the surface 50a of the absorber film 50 of the laminated substrate 52 corresponds to the back surface W2 of the substrate W and is the surface to which the coating liquid is supplied. Both the laminated substrate 51 and the laminated substrate 52 described above have a conductive film 42 on the back surface 44b of the substrate 44. As will be described later, the conductive film 42 allows for handling with an electrostatic chuck. The laminated substrate 52 described above may also have a protective film 48, as shown in Figure 9, between the multilayer reflective film 46 and the absorber film 50.

[0046] (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.

[0047] 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.

[0048] [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.

[0049] 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.

[0050] 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.

[0051] [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.

[0052] 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.

[0053] 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.

[0054] [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.

[0055] 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.

[0056] 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.

[0057] 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 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).

[0058] [Conductive film] The reflective mask blank may have a conductive film on the side (back side) of the substrate opposite to the first 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.

[0059] 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.

[0060] 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.

[0061] [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.

[0062] 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. [Explanation of symbols]

[0063] 10, 11 Washing equipment 12 stages 12a, 46a, 50a, W1 surface 12b Outer edge 12c central part 13 Support pins 14 Rotary drive unit 16 Cleaning fluid supply unit 18, 18a, 18b, 18c Coating liquid supply section 20 Control Unit 21 cups 21a opening 21b bottom 21c Exterior Wall 22 Drive motor 24 Rotating shaft section 25 Cleaning solution supply source 26, 32 Piping 28, 37a, 37b, 37c valves 30 Coating solution supply source 33. Rotary joint 27, 34, 34a, 34b, 34c, 34d, 34e nozzles 34f, 34g, 34h, 34i nozzle 35 Discharge port 36a, 36b, 36c supply pipe 40 Reflective Mask Blanks 42 Conductive film 44. W substrate 44b, W2 reverse side 46 Multilayer reflective film 48 Protective film 50 Absorbing membrane 51 Multilayer substrate 52 Multilayer substrates C Rotation axis Lc cleaning solution Ls coating solution Pb virtual surface Ps coating pattern R, Rb rotation direction Wa (short side) Wb (long side)

Claims

1. A cleaning apparatus for cleaning the surface of a substrate having a surface and a back surface opposite to the surface, and having a rectangular shape in plan view, while rotating the substrate, A substrate rotating unit that rotates the substrate, A cleaning liquid supply unit that supplies the cleaning liquid to the surface of the substrate, The substrate has a coating liquid supply unit that supplies coating liquid to the back surface of the substrate, The coating liquid supply unit is a cleaning device that supplies the coating liquid such that the width in the long-side direction of the area in contact with the back surface of the substrate is greater than the width on the short-side side of the area.

2. The cleaning apparatus according to claim 1, wherein the coating liquid supply unit supplies the coating liquid such that the width in the long-side direction of the substrate in the area in contact with the back surface of the substrate is greater than the width of the short side of the substrate.

3. The coating liquid supply unit has a nozzle for discharging the coating liquid, The supply unit has a rotating part that rotates the nozzle, The cleaning apparatus according to claim 1, wherein the nozzle rotates in accordance with the rotation of the substrate rotating part.

4. The cleaning apparatus according to claim 1, wherein the coating liquid supply unit has a plurality of nozzles for discharging the coating liquid, and adjusts the amount of coating liquid from the plurality of nozzles in accordance with the rotation of the substrate.

5. The cleaning apparatus according to claim 3, wherein the coating liquid supply unit has a plurality of nozzles for discharging the coating liquid.

6. The cleaning apparatus according to claim 3, wherein the coating liquid supply unit has only one nozzle for discharging the coating liquid.

7. The cleaning apparatus according to claim 3, wherein, with the substrate stopped, the coating pattern of the coating liquid supplied by the coating liquid supply unit to a virtual surface at a position corresponding to the back surface of the substrate is an elliptical pattern, or a pattern that extends in one direction, with the length in another direction perpendicular to the one direction being shorter than the length in the one direction.

8. The cleaning apparatus according to claim 1, wherein the cleaning solution is ultrapure water, an acid cleaning solution, or an alkaline cleaning solution.

9. The cleaning apparatus according to claim 8, wherein the acid cleaning solution is sulfuric acid, hydrogen peroxide, or sulfuric acid peroxide.

10. The cleaning apparatus according to claim 8, wherein the alkaline cleaning solution is ammonia or ammonia hydrochloride.

11. The cleaning apparatus according to claim 1, wherein the substrate is a glass substrate, or a glass substrate on which a conductive film is disposed on one side.

12. The cleaning apparatus according to claim 1, wherein the substrate is a glass substrate on which a conductive film is disposed on one side and at least one of a multilayer reflective film, an absorbent film, and a protective film is disposed on the other side.

13. The cleaning apparatus according to claim 1, wherein the coating liquid is pure water.

14. The cleaning apparatus according to claim 1, wherein the substrate is a substrate for mask blanks.

15. A method for manufacturing a substrate for a mask blank, comprising the step of cleaning the substrate using a cleaning apparatus described in any one of claims 1 to 14.

16. A cleaning method for cleaning the surface of a substrate having a surface and a back surface opposite to the surface, and having a rectangular shape in plan view, while rotating the substrate, While the substrate is rotating, a cleaning solution is supplied to the surface of the substrate. With the substrate in a rotating state, the coating liquid is supplied to the back surface of the substrate. A cleaning method comprising supplying the coating liquid such that the width of the region in the long-side direction of the substrate in contact with the back surface of the substrate is greater than the width of the region on the short side of the substrate.

17. The cleaning method according to claim 16, wherein the coating liquid is supplied such that the width in the long-side direction of the substrate in the area in contact with the back surface of the substrate is greater than the width of the short side of the substrate.

18. The cleaning method according to claim 16 or 17, wherein the coating liquid is discharged from a nozzle, and the nozzle rotates in accordance with the rotation of the substrate.

19. The cleaning method according to claim 16 or 17, wherein the coating liquid is discharged from a plurality of nozzles, and the amount of coating liquid from the plurality of nozzles is adjusted in accordance with the rotation of the substrate.

Images