JP2022033601A - Single-wafer cleaning device - Google Patents

Abstract

To provide a single-wafer cleaning device that performs spin-cleaning and spin-drying of a substrate, can suppress mist from reaching the substrate due to bouncing of a cleaning solution, and can prevent occurrences of watermarks and adhesion of a foreign matter and metallic components on the substrate.SOLUTION: A single-wafer cleaning device includes a bottom plate, a rotary table, a cleaning nozzle that supplies a cleaning solution to a substrate, a cylindrical cup that prevents splashing of the cleaning solution, and an exhaust duct that forms a down-flow airflow around the substrate. The single-wafer cleaning device further includes one or both of a cylindrical permeable plate located inside the cup that prevents the cleaning solution that passes to the cup side and bounces back from the cup from reaching the substrate and an exhaust dispersion plate that has a plurality of exhaust ports from the substrate side to the exhaust duct side and through which the downflow airflow around the substrate flows into the exhaust duct through the exhaust ports.SELECTED DRAWING: Figure 1

Description

The present invention relates to a single-wafer cleaning device for cleaning a substrate.

In the conventional single-wafer cleaning device that rotates and cleans the substrate, a cylindrical cup is routinely installed around the substrate in order to shield the cleaning liquid scattered from the substrate during the cleaning and drying processes (for example). , Patent Document 1). In addition, an exhaust duct is installed around the substrate in the cup to form a downflow air flow.

FIG. 8 is a top view and a vertical sectional view showing an example of such a conventional single-wafer cleaning device. The upper side shows a top view, and the lower side shows a vertical cross-sectional view. The single-wafer cleaning device 101 has a table base 103 on a bottom plate 102 of a processing chamber for cleaning, and a rotary table 105 on which a substrate W to be cleaned is held by a substrate holding pin 104 and rotated. is doing. It also has a rotary motor 106 for rotating the rotary table 105.
A back surface cleaning nozzle 107 that supplies cleaning liquid toward the back surface of the substrate W is installed on the rotary table 105, and a surface cleaning nozzle 108 that supplies cleaning liquid toward the surface of the substrate W is installed above the substrate W. Has been done. The surface cleaning nozzle 108 is connected to the arm shaft 110 via the swivel arm 109, and when the arm shaft 110 rotates and the swivel arm 109 swivels, the surface cleaning nozzle 108 swivels and moves in the cup during standby. It can be moved out of the cup.

A cylindrical cup 111 is installed around the substrate W so as to surround the rotary table 105. Further, on the bottom plate 102 inside the cup 111, an exhaust duct 112 that forms a downflow air flow is installed around the substrate W.
When the substrate W is cleaned and dried using such a single-wafer cleaning device 101, the cleaning liquid scattered from the substrate W is shielded by the cup 111, becomes fine mist, and rebounds in the direction of the substrate W. This mist is suppressed by the downflow airflow formed by the exhaust duct 112 to prevent it from reaching the substrate W.

At this time, the exhaust duct 112 is installed around the rotary motor 106, but if a large number of exhaust ducts 112 are installed, the rotary motor 106 cannot be accessed. Therefore, the exhaust duct 112 is installed in the cup 111 in consideration of maintainability. The number of exhaust ducts 112 is two, and they are arranged on opposite sides of the rotary table 105. However, in this case, the downflow is established near the exhaust duct 112 in the cup 111, but at a position 90 ° away from the exhaust duct 112 in the circumferential direction, the exhaust effect tends to be weakened and the downflow tends to be extremely weak. Was there.

JP-A-2007-294490

When the substrate W rotates at a high speed to perform cleaning and drying treatment, droplets of the cleaning liquid are evenly ejected to the cup 111 by 360 °, and there is a symptom that the substrate W becomes a fine mist due to interference with the cup 111 and rebounds in the direction of the substrate W. At a position where the downflow is weak as described above, the bounce mist cannot be controlled and reaches the substrate W, which is detected as a watermark on the substrate, or foreign matter adhering to the cup 111 itself. It caused quality defects such as adhering metal components.

Therefore, an object of the present invention is to provide a single-wafer cleaning device that can prevent mist from rebounding from the cleaning liquid from reaching the substrate in a single-wafer cleaning device that spin-cleans and spin-drys the substrate. ..

In order to achieve the above object, the present invention has a bottom plate and
A rotary table arranged on the bottom plate and rotating to support the substrate to be cleaned, and
A cleaning nozzle that supplies cleaning liquid to the substrate, and
A cylindrical cup arranged on the bottom plate so as to surround the rotary table and preventing the cleaning liquid supplied to the substrate from scattering.
A single-wafer cleaning device disposed at a position inside the cup of the bottom plate and having an exhaust duct for forming a downflow air flow around the substrate.
It is arranged inside the cup and has a through hole from the substrate side to the cup side, and the cleaning liquid scattered from the substrate is passed through the through hole to the cup side and the cup side. A cylindrical permeable plate that prevents the cleaning liquid that has passed through the cup and bounced off the cup from reaching the substrate.
It is a raised bottom arranged above the bottom plate and inside the cup, and has a plurality of exhaust ports from the substrate side to the exhaust duct side, and the airflow of the downflow around the substrate flows. Provided is a single-wafer cleaning apparatus characterized in that the exhaust distribution plate flowing through the exhaust port to the exhaust duct is further provided with any one or both of them.

In such a single-wafer cleaning apparatus of the present invention, by having a transparent plate having a through hole inside the cup, the mist of the cleaning liquid that has passed from the through hole to the cup side and bounced off reaches the substrate. Can be prevented. Further, by having an exhaust dispersion plate having a plurality of exhaust ports above the bottom plate, the downflow airflow around the substrate is made uniform, and even in a position where the downflow is weak in the conventional apparatus, the mist is the substrate in the present invention. Can be prevented from reaching. As a result, it is possible to suppress the generation of watermarks on the substrate and the adhesion of foreign matter to the substrate.

Further, the transparent plate may be arranged at a position where the distance from the cup is 10 mm or less.

With such a thing, it is possible to more reliably prevent the mist of the cleaning liquid bounced off the cup from reaching the substrate.

Further, the permeable plate can be made of any one of PEEK, PPS, PP, PE, PVC, PCTFE, PVDF, and PTFE.

With such a case, corrosion due to the cleaning liquid can be effectively prevented.

Further, the transparent plate can have a width of 100 mm or less in the vertical direction with respect to the position of the substrate supported by the rotary table.

If it is such a thing, it is possible to cope with the case where the cleaning liquid is randomly scattered in the vertical direction.

In addition, two exhaust ducts are arranged.
The two exhaust ducts are located on opposite sides of the rotary table.
The exhaust distribution plate is divided into a plurality of regions in the circumferential direction in a plan view.
As the region is farther from the position of the exhaust duct, the ratio of the area occupied by the plurality of exhaust ports in the region can be increased.

With such a thing, the downflow airflow around the substrate can be more reliably made uniform.

Further, the substrate may be a square substrate or a circular substrate.

The single-wafer cleaning apparatus of the present invention can be suitably used for such a substrate.

Further, the square substrate is a photomask or a flat panel, and the square substrate is a photomask or a flat panel.
The circular substrate can be any one of a glass disk, a Si wafer, a Ge wafer, a GaAs wafer, and a SiC wafer.

The single-wafer cleaning apparatus of the present invention can be particularly preferably used for these substrates.

As described above, the single-wafer cleaning apparatus of the present invention suppresses the mist due to the splashing of the cleaning liquid from reaching the substrate, and prevents the generation of watermarks on the substrate and the adhesion of foreign substances and metal components. be able to.

It is the top view and the vertical sectional view which shows an example of the single-wafer type cleaning apparatus of this invention. It is explanatory drawing which shows the effect of preventing the cleaning liquid from rebounding to a substrate by a permeable plate. It is a graph which shows an example of the aperture ratio of each region in the exhaust distribution plate, and the wind speed of the downflow airflow. It is a distribution map which shows the average mist velocity on the substrate of Example 1 and Comparative Example 1. It is a graph which shows the result of having performed the cross-sectional profile about the flow direction of the substrate of Example 1 and Comparative Example 1. It is the top view and the vertical sectional view which show the measurement position of the mist amount of Example 2 and Comparative Example 2. FIG. It is the top view and the vertical sectional view which shows the measurement position of the mist amount of Example 3. FIG. It is the top view and the vertical sectional view which shows an example of the conventional single-wafer cleaning apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.
(First embodiment)
FIG. 1 is a top view and a vertical sectional view showing an example of the single-wafer cleaning apparatus of the present invention. The upper side shows a top view, and the lower side shows a vertical cross-sectional view. The single-wafer cleaning apparatus 1 of the present invention has a table base 3, a substrate holding pin 4, and a rotary table 5 on the bottom plate 2 of the processing chamber. Further, a rotary motor 6, a back surface cleaning nozzle 7, and a surface cleaning nozzle 8 are installed, and the surface cleaning nozzle 8 can be moved by a swivel arm 9 and an arm shaft 10. In addition, although the cleaning nozzle having two cleaning nozzles for the front surface and the back surface is described here, the present invention is not limited to this, and for example, it includes one cleaning nozzle for the front surface or the back surface. It may be something to do.

A cylindrical cup 11 is installed around the substrate W so as to surround the rotary table 5, and an exhaust duct 12 that forms a downflow air flow around the substrate W is installed on the bottom plate 2 inside the cup 11. Has been done. Here, the two exhaust ducts 12 are arranged on opposite sides of the rotary table 5 with the rotary table 5 interposed therebetween, but the number and positions of the exhaust ducts 12 are not particularly limited.
The above configuration can be, for example, the same as that of the conventional single-wafer cleaning device 101.
In the first embodiment of the single-wafer cleaning device 1 of the present invention, both the permeable plate 13 and the exhaust dispersion plate 14 are further provided. Hereinafter, these two configurations will be described in detail.

First, the transparent plate 13 will be described. FIG. 2 is an explanatory diagram showing the effect of the transparent plate on preventing the cleaning liquid from splashing onto the substrate W. The permeable plate 13 is arranged inside the cup 11, and is composed of a through hole 13a from the substrate side to the cup side and a cleaning liquid shielding portion 13b. That is, the through hole 13a is formed in the plate-shaped main body, and the portion other than the through hole 13a is the cleaning liquid shielding portion 13b. When the cleaning process is performed by the single-wafer cleaning device 1, the droplets of the cleaning liquid scattered from the substrate W due to the rotation of the rotary table 5 reach the cup 11 through the through hole 13a. The arriving droplets bounce toward the substrate side as fine mist due to interference with the cup 11, but are shielded by the cleaning liquid shielding portion 13b due to the presence of the transparent plate 13 to prevent the mist from reaching the substrate W. be able to. As a result, it is possible to suppress the amount of watermarks and the like generated on the substrate.
The diameter size, distribution density, and the like of the through hole 13a are not particularly limited, but for example, the through hole having a diameter of 5 mm can be uniformly distributed over the entire transparent plate.

The position of the transparent plate 13 is not particularly limited, but may be, for example, a position where the distance from the cup 11 is 10 mm or less. With such a case, it is possible to more reliably prevent the mist of the cleaning liquid rebounding from the cup 11 from reaching the substrate W.

The material of the transmissive plate 13 is not particularly limited, but may be made of any one of PEEK, PPS, PP, PE, PVC, PCTFE, PVDF, and PTFE. With such a case, corrosion due to the cleaning liquid can be effectively prevented.

The vertical width of the transparent plate 13 is not particularly limited, but for example, the transparent plate 13 may have a width of 100 mm or less in the vertical direction with respect to the position of the substrate W supported by the rotary table 5.
In a single-wafer cleaning device, for example, when rotating at a high speed of 600 rpm or more, the cleaning liquid tends to scatter at a position almost horizontal to the substrate. Since the cleaning liquid tends to be scattered over a wide range in the vertical direction with respect to the horizontal position of the substrate due to the influence of the outer peripheral portion, it is better to arrange the transmissive plate at a wider angle in the vertical direction than in the horizontal position. A permeable plate having a width of 100 mm or less in the vertical direction can be used even when the cleaning liquid is randomly scattered in the vertical direction in this way.

Next, the exhaust distribution plate 14 will be described. As shown in FIG. 1, the exhaust distribution plate 14 is arranged above the bottom plate 2 and inside the cup 11 as a raised bottom so as to cover the table base 3 in a circumferential shape (ring shape). It has a plurality of exhaust ports 16 for the airflow from the substrate W side to the exhaust duct 12 side, and the downflow airflow around the substrate W is shielded by the airflow shielding portion 15, and the exhaust duct 12 passes through the exhaust port 16. Flow to. In this way, the airflow can be made uniform in the downflow around the substrate by passing the airflow through the plurality of exhaust ports 16, and as a result, the position where the downflow was conventionally weak (away from the exhaust duct 12). Position) can also prevent the cleaning liquid mist from reaching the substrate.

The configuration of the exhaust distribution plate 14 is not particularly limited, but when the two exhaust ducts 12 as shown in FIG. 1 are arranged on opposite sides of the rotary table 5, for example, the exhaust distribution plate 14 Is divided into a plurality of regions 17 in the circumferential direction in a plan view, and the region distant from the position of the exhaust duct 12 has a larger ratio (aperture ratio) of the area occupied by the plurality of exhaust ports 16 in the region 17. Can be. That is, if the regions are divided into four types of regions 17a to 17d as shown in FIG. 1, the region 17a directly above the exhaust duct 12 has the smallest aperture ratio, and the regions 17b, 17c, and 17d have the largest aperture ratios in that order. be able to. In such a case, the downflow airflow around the substrate can be more reliably made uniform, and the mist of the cleaning liquid bounced from the cup 11 or the permeable plate 13 toward the substrate can reach the substrate. It is possible to suppress it more efficiently. The exhaust distribution plate 14 is not limited to a single plate, but may be configured by arranging a plurality of plates (divided plates) having different aperture ratios for each region, for example. The divided plates may be adhered to each other adjacent to each other.
The size of the exhaust port 16 is not particularly limited, but may be, for example, 6 mm or less in diameter.

FIG. 3 is a graph showing an example of the aperture ratio of each region in the exhaust dispersion plate and the wind speed of the downflow airflow. As shown in the figure below in FIG. 3, the areas 17a to 17d are each of four types of areas 1 to 4 in order from the area closest to the exhaust duct 12. The graph on the left side of FIG. 3 shows the opening ratio of each region, and the opening ratio increases as the distance from the position of the exhaust duct 12 increases. It should be noted that the plurality of exhaust ports are formed side by side in a grid pattern, and the aperture ratio can be calculated by the following formula.
Aperture ratio [%] = (D ² / P ² ) x 78.5
(D: Diameter of exhaust port [mm], P: Center distance between adjacent exhaust ports [mm])
That is, it is the area of the exhaust port 16 per unit area of the exhaust distribution plate 14. It is an equation obtained by dividing π · (D / 2) ² , which is the area of the exhaust port 16, by P ² , which is the area surrounded by four adjacent exhaust ports, and multiplying by 100.
In the single-wafer cleaning apparatus 1 of the present invention using such an exhaust dispersion plate 14, the wind speed of the downflow airflow was measured. As a result, as shown in the graph on the right side of FIG. 3, it can be seen that the downflow airflow in each area is uniform.

The substrate W may be, for example, a square substrate or a circular substrate. Further, the square substrate may be a photomask or a flat panel. Further, the circular substrate can be any of a glass disk, a Si wafer, a Ge wafer, a GaAs wafer, and a SiC wafer. Cleaning by the single-wafer cleaning apparatus of the present invention can be particularly preferably used for these substrates, but is not limited thereto.

(Second embodiment)
In the first embodiment of FIG. 1, the one having both the transparent plate 13 and the exhaust dispersion plate 14 has been described as an example, but as another embodiment, only the transparent plate 13 is used. It is possible to have it and not to have the exhaust distribution plate 14. Also in this case, since the effect of shielding the mist of the cleaning liquid rebounding from the cup 11 by the permeable plate 13, it is possible to prevent the mist of the cleaning liquid from reaching the substrate W.

(Third embodiment)
Further, as yet another embodiment, it is possible to have only the exhaust distribution plate 14 and not the transparent plate 13. Also in this case, since the effect of equalizing the downflow airflow around the substrate can be obtained, it is possible to prevent the mist of the cleaning liquid from reaching the substrate W.

As in the second and third embodiments, even if one of the permeable plate 13 and the exhaust dispersion plate 14 is provided, the mist of the cleaning liquid reaches the substrate W significantly more than before. However, in the first embodiment having both of these, it can be prevented more reliably.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited thereto.
(Example 1)
In the third embodiment described above, that is, in the single-wafer cleaning apparatus 1 of the present invention shown in FIG. 1, the one having only the exhaust dispersion plate 14 and not the permeable plate 13 is used as follows. The airflow was measured in steps 1 to 5 shown. The exhaust dispersion plate 14 used was divided into four types of regions having an aperture ratio as shown in FIG.
1. 1. An airflow visualization mist was flowed over the substrate, and the substrate was rotated at 1,500 rpm.
2. 2. A high-speed camera was installed from the outside of the processing room to shoot at 250 fps.
3. 3. Image processing of the captured image was performed, and the mist flow velocity was calculated.
The distribution of the mist flow direction on the substrate was investigated by averaging the data of 4.1 thousand frames.
5. In addition, a cross-sectional profile was made for the flow direction of the substrate, and the fluctuation state of the air flow was measured.

(Comparative Example 1)
The measurement was carried out in the same manner as in Example 1 except that the conventional single-wafer cleaning apparatus 101 shown in FIG. 8 was used.

FIG. 4 is a distribution diagram showing the average mist velocity on the substrate. The upper side shows Example 1 and the lower side shows Comparative Example 1. For the average mist velocity distribution, the displacement vector at each point is obtained by the correlation method in the specified range of the captured image using the fluid analysis software: Flownizer2D2C (DITECT), and the vector within the range at a certain timing (frame). It was obtained by calculating the average value of the group. In the external average mist velocity distribution, in Comparative Example 1, a portion where no flow is generated (the portion indicated by the arrow in the figure below) can be confirmed, and it can be seen that the air flow is in an unstable state. On the other hand, in Example 1, a uniform flow (arrow portion in the above figure) could be observed.

FIG. 5 is a graph showing the result of performing a cross-sectional profile for the flow direction of the substrate. The horizontal axis shows the number of frames, and the vertical axis shows the speed in the tangential direction obtained from the UV coordinate system. This velocity is determined by the elapsed time (frame) at a certain position (the same position in Example 1 and Comparative Example 1 and the position indicated by the arrow in FIG. 4) from the average mist velocity distribution calculated as described above. Obtained by calculating the average speed. Table 1 shows the results of calculating the coefficient of variation (σ / AVE) from FIG.

As shown in Table 1, when the coefficient of variation (σ / AVE) was calculated and compared, it was confirmed that the coefficient of variation was small in Example 1, that is, the airflow fluctuation on the substrate was small.

(Example 2)
In the second embodiment described above, that is, in the single-wafer cleaning apparatus 1 of the present invention shown in FIG. 1, the one having only the permeable plate 13 and not the exhaust dispersion plate 14 is used in the center of the substrate. The amount of mist was measured while rotating the substrate by supplying pure water to the water. The permeable plate 13 had through holes having a diameter of 5 mm uniformly distributed throughout the permeable plate, and was arranged at a position where the distance from the cup 11 was 5 mm. The material was PTFE, and a material having a width of 100 mm in the vertical direction was used. The rotation speed was 1,000 rpm and 1,500 rpm, which are generally used in the drying process. The measurement position of the mist amount was a position where the air flow on the substrate was weak in the conventional single-wafer cleaning device, 50 mm above the substrate, and the measurement time was 3 minutes. FIG. 6 shows the mist amount measurement position 18. The upper side shows a vertical sectional view, and the lower side shows a top view.

(Comparative Example 2)
The amount of mist was measured in the same manner as in Example 2 except that the conventional single-wafer cleaning apparatus 101 shown in FIG. 8 was used.
Table 2 shows the measurement results of the mist amount of Example 2 and Comparative Example 2, and the reduction rate of the mist amount from Comparative Example 2 which is the prior art in Example 2.

As shown in Table 2, in Example 2, the mist suppressing effect of the permeable plate in the vicinity of the cup could be confirmed.

(Example 3)
In the first embodiment described above, that is, a single-wafer cleaning apparatus 1 of the present invention shown in FIG. 1, which has both a permeable plate 13 and an exhaust dispersion plate 14, pure water is used in the center of the substrate. The amount of mist was measured while rotating the substrate. The same exhaust dispersion plate 14 as in Example 1 was used, and the rotation speed was set to 1,500 rpm. The measurement position of the mist amount was performed on the substrate of each of the four types of regions 1 to 4 of the exhaust dispersion plate 14. The measurement time was 3 minutes. FIG. 7 shows the mist amount measurement position 18. The upper side shows a vertical sectional view, and the lower side shows a top view.
Table 3 shows the measurement results of the mist amount of Example 3 and Comparative Example 2, and the reduction rate of the mist amount from Comparative Example 2 which is the prior art in Example 3.

As shown in Table 3, in Example 3, both the effect of suppressing the mist that bounces from the cup toward the substrate by the transparent plate and the effect of suppressing the mist in the processing chamber in which the airflow around the substrate is made uniform by the exhaust dispersion plate are obtained. , A higher inhibitory effect was confirmed. It was also found that the amount of mist in each region was almost the same because the downflow airflow around the substrate was made uniform.

From the above results, in the single-wafer cleaning apparatus of the present invention, it is possible to suppress the mist due to the splashing of the cleaning liquid from reaching the substrate, and as a result, it is possible to prevent the adhesion of foreign substances derived from the mist and the generation of watermarks. It becomes.

The present invention is not limited to the above embodiment. The above embodiment is an example, and any one having substantially the same configuration as the technical idea described in the claims of the present invention and having the same effect and effect is the present invention. It is included in the technical scope of the invention.

1 ... Single-wafer cleaning device of the present invention, 2, 102 ... Bottom plate,
3, 103 ... Table base, 4, 104 ... Board holding pin,
5, 105 ... rotary table, 6, 106 ... rotary motor,
7, 107 ... back surface cleaning nozzle, 8, 108 ... front surface cleaning nozzle,
9, 109 ... swivel arm, 10, 110 ... arm shaft, 11, 111 ... cup,
12, 112 ... Exhaust duct, 13 ... Transparent plate, 13a ... Through hole,
13b ... Cleaning liquid shielding part, 14 ... Exhaust gas dispersion plate, 15 ... Airflow shielding part,
16 ... Exhaust port, 17, 17a, 17b, 17c, 17d ... Region,
18 ... Mist amount measurement position, 101 ... Conventional single-wafer cleaning device, W ... Substrate.

Claims (7)

With the bottom plate
A rotary table arranged on the bottom plate and rotating to support the substrate to be cleaned, and
A cleaning nozzle that supplies cleaning liquid to the substrate, and
A cylindrical cup arranged on the bottom plate so as to surround the rotary table and preventing the cleaning liquid supplied to the substrate from scattering.
A single-wafer cleaning device that is disposed at a position inside the cup of the bottom plate and has an exhaust duct that forms a downflow air flow around the substrate.
It is arranged inside the cup and has a through hole from the substrate side to the cup side, and the cleaning liquid scattered from the substrate is passed through the through hole to the cup side and the cup side. A cylindrical permeable plate that prevents the cleaning liquid that has passed through the cup and bounced off the cup from reaching the substrate.
It is a raised bottom arranged above the bottom plate and inside the cup, and has a plurality of exhaust ports from the substrate side to the exhaust duct side, and the airflow of the downflow around the substrate flows. A single-wafer cleaning device comprising any one or both of the exhaust distribution plates flowing through the exhaust port to the exhaust duct. The single-wafer cleaning device according to claim 1, wherein the transparent plate is arranged at a position where the distance from the cup is 10 mm or less. The single sheet according to claim 1 or 2, wherein the permeable plate is made of any one of PEEK, PPS, PP, PE, PVC, PCTFE, PVDF, and PTFE. Formula cleaning device. The one according to any one of claims 1 to 3, wherein the transparent plate has a width within 100 mm in the vertical direction with respect to the position of the substrate supported by the rotary table. Single-wafer cleaning device. Two of the exhaust ducts are arranged.
The two exhaust ducts are located on opposite sides of the rotary table.
The exhaust distribution plate is divided into a plurality of regions in the circumferential direction in a plan view.
Any of claims 1 to 4, wherein the plurality of regions are located farther from the position of the exhaust duct, and the ratio of the area occupied by the plurality of exhaust ports in the region is larger. The single-wafer cleaning device according to item 1. The single-wafer cleaning apparatus according to any one of claims 1 to 5, wherein the substrate is a square substrate or a circular substrate. The square substrate is a photomask or a flat panel.
The single-wafer cleaning apparatus according to claim 7, wherein the circular substrate is any one of a glass disk, a Si wafer, a Ge wafer, a GaAs wafer, and a SiC wafer.

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