Apparatus and method for cleaning wafers

Abstract

Embodiments of the present application disclose an apparatus and method for cleaning a wafer, the apparatus which may include a cleaning tank, a first pump for pumping the etching solution at the bottom of the cleaning tank to the surface of the etching solution contained in the cleaning tank via the outside of the cleaning tank during the process of immersing the wafer in the etching solution contained in the cleaning tank, so that the etching solution contained in the cleaning tank as a whole is moved downward until it is held stationary relative to the wafer, and a second pump for pumping the etching solution at the surface to the bottom of the cleaning tank via the outside of the cleaning tank during the process of removing the wafer from the etching solution contained in the cleaning tank, so that the etching solution contained in the cleaning tank as a whole is moved upward until it is held stationary relative to the wafer.

Description

Technical Field

[0001] Cross-reference to Related Applications This application claims the priority of Chinese Patent Application No. 202311075026.8, filed in China on August 24, 2023, the entire content of which is incorporated herein by reference. This application relates to the field of semiconductor wafer production, and particularly to an apparatus and method for cleaning wafers.

Background Art

[0002] Among the currently used wafer cleaning methods, one method is to immerse the wafer in a cleaning liquid. The chemical components contained in the cleaning liquid cause an etching effect on the wafer, and the contaminants on the surface of the wafer will detach from the wafer together with the etched wafer material.

[0003] The wafer is usually clamped to facilitate transfer between various processing apparatuses including the cleaning apparatus before cleaning. On the other hand, since the clamping of the wafer is usually realized by contacting the clamping mechanism with the periphery of the wafer, a large amount of contaminants such as contamination particles and metals will adhere to the periphery of the wafer.

[0004] In conventional cleaning methods, wafers must be immersed in a cleaning solution contained in a cleaning tank of a cleaning device in order to achieve cleaning. In this process, a large amount of contaminants attached to the periphery of the wafer are moved upward relative to the wafer by the impact action of the cleaning solution. Since wafers are usually immersed in the cleaning solution in a way that holds them vertically, the contaminants attached to the periphery are transferred to the main surface of the wafer. As a result, the cleaning effect on the main surface is reduced, and a large amount of locally scattered light scatter (LLS) particles that were originally present at the periphery cannot be removed from the main surface by cleaning. On the other hand, after the wafer cleaning is complete, it is necessary to remove the wafer from the cleaning solution contained in the cleaning tank. In this process, a large amount of contaminants that have detached from the wafer's periphery and remain in the cleaning solution, but are still concentrated near the wafer's periphery, move downward relative to the wafer. Since wafers are usually held vertically and removed by moving them upward along the vertical direction, these contaminants are still transferred to the main surface of the wafer, negatively affecting the cleaning effect of the main surface, and a large amount of LLS particles remain on the main surface of the wafer. In the wafer's usage process, the wafer's periphery may be removed in some processing step, but the part of the wafer other than the periphery is actually used. Therefore, if the cleanliness of the main surface is not high enough, in other words, if contaminants remain, it will negatively affect the performance of products such as electronic components obtained afterward. [Overview of the project] [Problems that the invention aims to solve]

[0005] To solve the above problems, the embodiment of the present invention aims to provide an apparatus and method for cleaning wafers that can prevent a large amount of contaminants attached to the periphery of the wafer from being transferred to the main surface of the wafer during the process of immersing the wafer in the cleaning solution to achieve cleaning, and during the process of removing the wafer from the cleaning solution after cleaning is complete, thereby achieving a better cleaning effect and improving the performance of products manufactured from the wafers.

[0006] The technical aspects of this application are realized as follows:

[0007] In the first aspect, an embodiment of the present application is an apparatus for cleaning wafers, the apparatus is Washing tank body, During the process of immersing the wafer in the etching solution contained in the cleaning tank, a first pump is provided to pump the etching solution at the bottom of the cleaning tank to the surface of the etching solution contained in the cleaning tank via the outside of the cleaning tank, so that the etching solution contained in the cleaning tank as a whole moves downward until it is held stationary relative to the wafer. The present invention provides a wafer cleaning apparatus that includes a second pump for pumping the etching solution at the liquid surface to the bottom of the cleaning tank via the outside of the cleaning tank during the process of removing the wafer from the etching solution contained in the cleaning tank, so that the etching solution contained in the cleaning tank as a whole moves upward until it is held stationary relative to the wafer.

[0008] During the process of immersing the wafer in the etching solution, the etching solution as a whole moves downward until it is held stationary relative to the wafer. In other words, there is no relative motion between the etching solution and the wafer, and no impact effect is generated on the wafer by the etching solution. Therefore, even if a large amount of contaminants are attached to the periphery of the wafer, these contaminants are not transferred to the main surface of the wafer, ensuring the cleaning effect of the main surface and avoiding the situation where a large amount of LLS particles originally present at the periphery cannot be removed from the main surface by cleaning. Furthermore, during the process of removing the wafer from the etching solution, the etching solution as a whole moves upward until it is held stationary relative to the wafer. In other words, there is no relative motion between the etching solution and the wafer. Therefore, a large amount of contaminants that have detached from the periphery of the wafer and are present in the etching solution are held stationary relative to the wafer, just like the etching solution, and are not transferred to the main surface of the wafer. As a result, the cleaning effect of the main surface is maintained, and the situation where a large amount of LLS particles are present on the main surface of the wafer is avoided. In this way, after cleaning is complete, the main surface of the wafer, in other words, the part that is actually used, can be made highly clean, and the performance of products manufactured from the cleaned wafer is guaranteed.

[0009] In an optional embodiment of the present invention, the apparatus further includes a first conduit, the first pump being provided in the first conduit, the first opening of the first conduit leading to the interior of the cleaning tank at the bottom of the cleaning tank, and the second opening of the first conduit being provided at the top of the cleaning tank.

[0010] Thus, when the first pump pumps the etching solution, the first opening of the first pipeline is connected to the inside of the cleaning tank at the bottom of the cleaning tank, so the etching solution at the bottom of the cleaning tank leaves the cleaning tank. On the other hand, since the second opening of the first pipeline is located at the top of the cleaning tank, the etching solution leaves the first pipeline at the top of the cleaning tank and then reaches the liquid surface of the etching solution EL contained in the cleaning tank.

[0011] In an optional embodiment of the present invention, the apparatus further includes a second conduit, the second pump being provided in the second conduit, the first opening of the second conduit being connected to the interior of the cleaning tank at the bottom of the cleaning tank, and the second opening of the second conduit being provided below the liquid surface of the etching solution contained in the cleaning tank, and adjacent to the liquid surface.

[0012] Thus, when the second pump pumps the etching solution, the second opening of the second pipeline is located below the liquid surface of the etching solution contained in the cleaning tank, adjacent to the liquid surface, so the etching solution at the liquid surface leaves the cleaning tank. On the other hand, since the first opening of the second pipeline leads to the inside of the cleaning tank at the bottom of the cleaning tank, the etching solution leaves the second pipeline at the bottom of the cleaning tank and then reaches the bottom of the cleaning tank.

[0013] In an optional embodiment of the present invention, the apparatus further includes an overflow tank, and when excess etching solution is injected into the cleaning tank, the etching solution at the liquid level overflows from the cleaning tank into the overflow tank, and the etching solution in the overflow tank is pumped by the second pump.

[0014] The presence of an overflow tank makes pumping the etching solution at the liquid surface easier and simpler. This is because it eliminates the need to consider whether the solution being pumped is the etching solution at the liquid surface.

[0015] In an optional embodiment of the present invention, the apparatus further includes an overflow pipeline, the second pump being provided in the overflow pipeline, the first opening of the overflow pipeline being connected to the interior of the overflow tank, and the second opening of the overflow pipeline being connected to the interior of the washing tank at the bottom of the washing tank.

[0016] Thus, when the second pump pumps the etching solution, the first opening of the overflow pipe leads to the inside of the overflow tank, allowing the second pump to pump the etching solution inside the overflow tank. On the other hand, since the second opening of the overflow pipe leads to the inside of the cleaning tank at the bottom of the cleaning tank, the etching solution leaves the overflow pipe at the bottom of the cleaning tank and then reaches the bottom of the cleaning tank.

[0017] In an optional embodiment of the present invention, the apparatus further includes a first filter for filtering an etching solution flowing through the pumping path of the first pump.

[0018] In this way, if, for example, impurities or contaminants from the wafer enter the pumping path of the first pump, filtration can prevent such impurities or contaminants from returning to the washing tank.

[0019] In an optional embodiment of the present invention, the apparatus further includes a second filter for filtering an etching solution flowing through the pumping path of the second pump.

[0020] In this way, if, for example, impurities or contaminants from the wafer enter the pumping path of the second pump, filtration can prevent such impurities or contaminants from returning to the washing tank.

[0021] In a selective embodiment of the present invention, the etching solution is for removing the oxide film on the surface of the wafer.

[0022] In a selective embodiment of the present invention, the etching solution is hydrofluoric acid.

[0023] In the second aspect, an embodiment of the present application is a method for cleaning a wafer, the method being: During the process of immersing the wafer in the etching solution contained in the cleaning tank body, by pumping the etching solution at the bottom of the cleaning tank body via the outside of the cleaning tank body to the liquid surface of the etching solution contained in the cleaning tank body, the etching solution contained in the cleaning tank body as a whole is moved downward until it is held stationary with respect to the wafer. During the process of removing the wafer from the etching solution contained in the cleaning tank body, by pumping the etching solution at the liquid surface via the outside of the cleaning tank body to the bottom of the cleaning tank body, the etching solution contained in the cleaning tank body as a whole is moved upward until it is held stationary with respect to the wafer. The method further provides a method for cleaning a wafer including this.

Brief Description of the Drawings

[0024] [Figure 1] Figure 1 is a schematic diagram of an apparatus for cleaning a wafer according to an embodiment of the present application. [Figure 2] Figure 2 is a schematic diagram of an apparatus for cleaning a wafer according to another embodiment of the present application. [Figure 3] Figure 3 is a schematic diagram of an apparatus for cleaning a wafer according to another embodiment of the present application. [Figure 4] Figure 4 is a schematic diagram of an apparatus for cleaning a wafer according to another embodiment of the present application. [Figure 5] Figure 5 is a schematic diagram of an apparatus for cleaning a wafer according to another embodiment of the present application. [Figure 6] Figure 6 is a schematic diagram of a method for cleaning a wafer according to an embodiment of the present application.

Modes for Carrying Out the Invention

[0025] Hereinafter, referring to the accompanying drawings in the embodiments of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described.

[0026] Referring to Figure 1, an embodiment of the present application provides an apparatus 1 for cleaning a wafer W, which may include a cleaning tank 10, a first pump 11, and a second pump 12. The first pump 11 is used to pump the etching solution EL at the bottom 10B of the cleaning tank 10 to the liquid level LS of the etching solution EL contained in the cleaning tank 10, via the outside of the cleaning tank 10, during the process of immersing the wafer W in the etching solution EL contained in the cleaning tank 10, such that the wafer W shown in Figure 1 moves from the position shown by the dashed line to the position shown by the solid line along the direction of the white arrow A1. Here, "etching solution EL at the bottom 10B" may refer to the etching solution EL in the region demarcated by the dashed line BL1 and the bottom 10B shown in Figure 1, and "liquid level LS of the etching solution EL" may refer to the region demarcated by the dashed line BL2 and the liquid level LS shown in Figure 1. In Figure 1, the flow path of the etching solution EL pumped by the first pump 11 is schematically shown by a solid line with a double white arrow, and the flow direction of the etching solution EL is schematically shown by the arrow attached to the solid line. As can be easily understood from Figure 1, when the etching solution EL contained in the cleaning tank 10 leaves the cleaning tank 10 and is replenished to the liquid level LS, the etching solution EL contained in the cleaning tank 10 moves downward as a whole. How to ensure that the etching solution EL is held stationary relative to the immersed wafer W, or in other words, how to ensure that the movement speed of the etching solution EL is equal to the immersion speed of the wafer W, is determined by the cross-sectional area of ​​the cleaning tank 10 and the pumping flow rate of the first pump 11. Therefore, the pumping flow rate of the first pump 11 can be calculated according to the immersion speed of the wafer W and the cross-sectional area of ​​the cleaning tank 10. If the first pump 11 pumps the etching solution EL at that pumping flow rate, the movement speed of the etching solution EL and the immersion speed of the wafer W will be equal. The second pump 12 is used to pump the etching solution EL at the liquid level LS to the bottom 10B of the cleaning tank 10 via the outside of the cleaning tank 10, during the process of removing the wafer W from the cleaning tank 10 so that, for example, the wafer W shown in Figure 1 moves from the position shown by the solid line to the position shown by the dashed line along the direction of the white arrow A2. Here, "etching solution EL at the liquid level LS" may be, for example, the etching solution EL in the area demarcated by the dashed line BL2 and the liquid level LS shown in Figure 1, and "bottom 10B of the cleaning tank 10" may be, for example, the area demarcated by the dashed line BL1 and the bottom 10B shown in Figure 1. In Figure 1, the flow path of the etching solution EL pumped by the second pump 12 is schematically shown by a solid line with a double black arrow, and the flow direction of the etching solution EL is schematically shown by the arrow attached to the solid line. As can be easily understood from Figure 1, when the etching solution EL at the liquid surface LS leaves the cleaning tank 10 and is replenished at the bottom 10B, the etching solution EL contained in the cleaning tank 10 moves upward as a whole. As for how to ensure that the etching solution EL is held stationary relative to the wafer W being removed, or in other words, how to ensure that the movement speed of the etching solution EL and the removal speed of the wafer W are equal, the movement speed of the etching solution EL is determined by the cross-sectional area of ​​the cleaning tank 10 and the pumping flow rate of the second pump 12. Therefore, the pumping flow rate of the second pump 12 can be calculated according to the removal speed of the wafer W and the cross-sectional area of ​​the cleaning tank 10. If the second pump 12 pumps the etching solution EL at that pumping flow rate, the movement speed of the etching solution EL and the removal speed of the wafer W will be equal.

[0027] In the apparatus 1 according to the above embodiment of the present application, during the process of immersing the wafer W in the etching solution EL, the etching solution EL as a whole is moved downward until it is held stationary relative to the wafer W. In other words, there is no relative motion between the etching solution EL and the wafer W, and no impact effect is generated on the wafer W by the etching solution EL. Therefore, even if a large amount of contaminants are attached to the periphery of the wafer W, these contaminants are not transferred to the main surface of the wafer W, the cleaning effect of the main surface is guaranteed, and the situation in which a large amount of LLS particles that were originally present at the periphery cannot be removed from the main surface by cleaning is avoided. Furthermore, during the process of removing the wafer W from the etching solution EL, the etching solution EL as a whole moves upward until it is held stationary relative to the wafer W. In other words, there is no relative motion between the etching solution EL and the wafer W. Therefore, the large amount of contaminants that detach from the periphery of the wafer W and are present in the etching solution EL are held stationary relative to the wafer W, just like the etching solution EL, and are not transferred to the main surface of the wafer W. As a result, the cleaning effect on the main surface is maintained, and the situation in which a large amount of LLS particles are present on the main surface of the wafer W is avoided. Thus, after the cleaning is complete, the main surface of the wafer W, in other words, the part that is actually used, can be given a high degree of cleanliness, and the performance of the product manufactured from the cleaned wafer W is guaranteed.

[0028] Regarding the specific implementation method by which the first pump 11 pumps the etching solution EL as described above, in an optional embodiment of the present invention, referring to Figure 2, the apparatus 1 may further include a first conduit 13, the first pump 11 may be provided in the first conduit 13, the first opening 131 of the first conduit 13 may be connected to the inside of the cleaning tank 10 at the bottom 10B of the cleaning tank 10, and the second opening 132 of the first conduit 13 may be provided at the top 10T of the cleaning tank 10. In this way, when the first pump 11 pumps the etching solution EL, since the first opening 131 of the first conduit 13 is connected to the inside of the cleaning tank 10 at the bottom 10B of the cleaning tank 10, the etching solution EL at the bottom 10B of the cleaning tank 10 will leave the cleaning tank 10. On the other hand, since the second opening 132 of the first conduit 13 is located at the top 10T of the cleaning tank body 10, the etching solution EL leaves the first conduit 13 at the top 10T of the cleaning tank body 10 and then reaches the liquid level LS of the etching solution EL contained in the cleaning tank body 10.

[0029] Regarding the specific implementation method by which the second pump 12 pumps the etching solution EL as described above, in a selective embodiment of the present invention, referring to Figure 3, the apparatus 1 may further include a second pipeline 14, the second pump 12 may be provided in the second pipeline 14, the first opening 141 of the second pipeline 14 may be connected to the inside of the cleaning tank 10 at the bottom 10B of the cleaning tank 10, and the second opening 142 of the second pipeline 14 may be provided below the liquid level LS of the etching solution EL contained in the cleaning tank 10, and adjacent to the liquid level LS. In this way, when the second pump 12 pumps the etching solution EL, since the second opening 142 of the second pipeline 14 is provided below the liquid level LS of the etching solution EL contained in the cleaning tank 10, and adjacent to the liquid level LS, the etching solution EL at the liquid level LS will leave the cleaning tank 10. On the other hand, since the first opening 141 of the second conduit 14 is connected to the inside of the cleaning tank body 10 at the bottom 10B of the cleaning tank body 10, the etching solution EL leaves the second conduit 14 at the bottom 10B of the cleaning tank body 10 and then reaches the bottom 10B of the cleaning tank body 10.

[0030] In an optional embodiment of the present invention, referring to Figure 4, the apparatus 1 may further include an overflow tank 15, and when excess etching solution EL is injected into the cleaning tank 10, the etching solution EL at the liquid level LS may overflow from the cleaning tank 10 into the overflow tank 15, and the etching solution EL in the overflow tank 15 may be pumped by the second pump 12. First, when the etching solution EL overflows from the cleaning tank 10, the etching solution EL leaving the cleaning tank 10 is always the etching solution EL at the liquid level LS, and then, since the overflowed etching solution EL flows into the overflow tank 15, when the etching solution EL in the overflow tank 15 is pumped by the second pump 12, it is equivalent to pumping the etching solution EL at the liquid level LS. In this embodiment, the presence of the overflow tank 15 makes pumping the etching solution EL at the liquid level LS simpler and easier. This is because it is not necessary to consider whether it is the etching solution EL at the liquid level LS that is being pumped.

[0031] For a specific implementation method of the second pump 12 pumping the etching solution EL as described above, refer to Figure 5. The apparatus 1 may further include an overflow pipeline 16, the second pump 12 may be provided in the overflow pipeline 16, the first opening 161 of the overflow pipeline 16 may be connected to the inside of the overflow tank 15, and the second opening 162 of the overflow pipeline 16 may be connected to the inside of the cleaning tank 10 at the bottom 10B of the cleaning tank 10. In this way, when the second pump 12 pumps the etching solution EL, the first opening 161 of the overflow pipeline 16 is connected to the inside of the overflow tank 15, so it is possible to pump the etching solution EL in the overflow tank 15. On the other hand, since the second opening 162 of the overflow pipe 16 is connected to the inside of the cleaning tank 10 at the bottom 10B of the cleaning tank 10, the etching solution EL leaves the overflow pipe 16 at the bottom 10B of the cleaning tank 10 and then reaches the bottom 10B of the cleaning tank 10.

[0032] In an optional embodiment of the present invention, with reference to Figure 1, the apparatus 1 may further include a first filter 17 for filtering the etching solution EL flowing through the pumping path of the first pump 11, and as specifically shown in Figure 1, the first filter 17 may be located downstream of the first pump 11 in the flow direction of the etching solution EL. In this way, if, for example, impurities or contaminants from the wafer W enter the pumping path of the first pump 11, filtration can prevent such impurities or contaminants from returning to the washing tank 10.

[0033] In an optional embodiment of the present invention, with reference to Figure 1, the apparatus 1 may further include a second filter 18 for filtering the etching solution EL flowing through the pumping path of the second pump 12, and as specifically shown in Figure 1, the second filter 18 may be located downstream of the second pump 12 in the flow direction of the etching solution EL. In this way, if, for example, impurities or contaminants from the wafer W enter the pumping path of the second pump 12, filtration can prevent such impurities or contaminants from returning to the washing tank 10.

[0034] Selectively, the etching solution EL may be used to remove the oxide film on the surface of the wafer W, thereby removing any contaminating particles or other impurities contained in the oxide film. Furthermore, selectively, such an etching solution may be hydrofluoric acid.

[0035] Referring together to Figures 6 and 1, the embodiments of the present application further provide a method for cleaning a wafer W, the method being: Step S601 involves immersing the wafer W in the etching solution EL contained in the cleaning tank 10, and pumping the etching solution EL at the bottom 10B of the cleaning tank 10 to the liquid level LS of the etching solution EL contained in the cleaning tank 10 via the outside of the cleaning tank 10, so that the etching solution EL contained in the cleaning tank 10 as a whole is moved downward until it is held stationary relative to the wafer W. The process of removing the wafer W from the etching solution EL contained in the cleaning tank 10 may include step S602, in which the etching solution EL at the liquid level LS is pumped to the bottom 10B of the cleaning tank 10 via the outside of the cleaning tank 10, so that the etching solution EL contained in the cleaning tank 10 as a whole is moved upward until it is held stationary relative to the wafer W.

[0036] Unless otherwise defined, technical or scientific terms used in this application have the ordinary meanings that a person skilled in the art can understand. The terms “first,” “second,” and similar terms used in this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similar terms such as “includes” or “incorporates” mean that the element or component listed before the term includes, but does not exclude, the element or component and its equivalents listed after the term. Similar terms such as “connected” or “linked” may include electrical connections, whether directly or indirectly, and are not limited to physical or mechanical connections. “Up,” “down,” “left,” “right,” etc., merely indicate relative positions, and if the absolute position of the object being described changes, the relative position may change accordingly.

[0037] It should be explained that the technical embodiments described in the present invention can be combined in any way, as long as they do not contradict each other.

[0038] The above describes only specific embodiments of the present application, and the scope of protection is not limited thereto. A person skilled in the art can easily conceive of modifications and substitutions within the technical scope described in the present application, and all such modifications and substitutions should be considered within the scope of protection of the present application. Therefore, the scope of protection of the present application should be in accordance with the attached claims.

Claims

1. An apparatus for cleaning wafers, wherein the apparatus is Washing tank body, During the process of immersing the wafer in the etching solution contained in the cleaning tank, a first pump is provided to pump the etching solution at the bottom of the cleaning tank to the surface of the etching solution contained in the cleaning tank via the outside of the cleaning tank, so that the etching solution contained in the cleaning tank as a whole moves downward until it is held stationary relative to the wafer. An apparatus for cleaning a wafer, comprising: a second pump for pumping the etching solution at the liquid surface to the bottom of the cleaning tank via the outside of the cleaning tank during the process of removing the wafer from the etching solution contained in the cleaning tank, so that the etching solution contained in the cleaning tank as a whole moves upward until it is held stationary relative to the wafer.

2. The apparatus according to claim 1, further comprising a first conduit, wherein the first pump is provided in the first conduit, the first opening of the first conduit leads to the inside of the cleaning tank at the bottom of the cleaning tank, and the second opening of the first conduit is provided at the top of the cleaning tank.

3. The apparatus according to claim 1, further comprising a second pipeline, wherein the second pump is provided in the second pipeline, the first opening of the second pipeline is connected to the inside of the cleaning tank at the bottom of the cleaning tank, and the second opening of the second pipeline is provided below the liquid surface of the etching solution contained in the cleaning tank, adjacent to the liquid surface.

4. The apparatus according to claim 1, further comprising an overflow tank, wherein when excess etching solution is injected into the cleaning tank, the etching solution at the liquid surface overflows from the cleaning tank into the overflow tank, and the etching solution in the overflow tank is pumped by the second pump.

5. The apparatus according to claim 4, further comprising an overflow pipeline, wherein the second pump is provided in the overflow pipeline, the first opening of the overflow pipeline leads to the interior of the overflow tank, and the second opening of the overflow pipeline leads to the interior of the washing tank at the bottom of the washing tank.

6. The apparatus according to claim 1, further comprising a first filter, the first filter for filtering an etching solution flowing through the pumping path of the first pump.

7. The apparatus according to claim 1, further comprising a second filter, the second filter for filtering an etching solution flowing through the pumping path of the second pump.

8. The apparatus according to any one of claims 1 to 7, wherein the etching solution is for removing an oxide film from the surface of the wafer.

9. The apparatus according to claim 8, wherein the etching solution is hydrofluoric acid.

10. A method for cleaning a wafer, wherein the method is During the process of immersing the wafer in the etching solution contained in the cleaning tank, the etching solution at the bottom of the cleaning tank is pumped to the surface of the etching solution contained in the cleaning tank via the outside of the cleaning tank, so that the etching solution contained in the cleaning tank as a whole moves downward until it is held stationary relative to the wafer. A method for cleaning a wafer, comprising the process of removing the wafer from the etching solution contained in the cleaning tank, by pumping the etching solution at the liquid surface to the bottom of the cleaning tank via the outside of the cleaning tank, so that the etching solution contained in the cleaning tank as a whole moves upward until it is held stationary relative to the wafer.

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