Washing tank, washing system, and washing method

Abstract

To provide a cleaning tank which can efficiently discharge foreign objects having different physical properties with a structure as simple as possible, and to provide a cleaning system including the cleaning tank and a cleaning method.SOLUTION: A cleaning tank 12 includes: an inner tank 30 having a side part 38 and a bottom part 34; a support 46 disposed within the inner tank 30 and configured to support at least one workpiece 48; a flow nozzle 40 which is provided at the side part 38, arranged below the support 46, and configured to supply a cleaning fluid for cleaning the workpiece 48 to the inner tank 30 to generate swirl flow of the cleaning fluid in the inner tank 30; a discharge port 44 provided in a portion, which is located near the side part 38, of the bottom part 34 or a portion, which is located adjacent to the bottom part 34, of the side part 38 and configured to discharge the cleaning fluid; and an ultrasonic oscillation device 36 provided at the bottom part 34.SELECTED DRAWING: Figure 2

Description

Technical Field

[0004] ,

[0001] The present invention relates to a cleaning tank for cleaning workpieces such as semiconductor wafers and glass substrates, a cleaning system including the cleaning tank, and a cleaning method using the cleaning system.

Background Art

[0002] Generally, in the manufacturing process of semiconductor wafers and glass substrates, cleaning is performed to remove abrasive materials and fragments (hereinafter also referred to as foreign substances) attached to the wafers. This cleaning is often performed by immersing the object to be cleaned in a tank filled with a cleaning liquid. At this time, in order to perform the cleaning efficiently, techniques such as generating a vortex of the cleaning liquid in the tank or using ultrasonic waves are known.

[0003] For example, Patent Document 1 describes a technique of supplying a cleaning liquid including a micro valve from a nozzle disposed in a cleaning tank to generate a swirling flow. Further, Patent Document 2 describes a technique of generating a vortex of a processing liquid by using a storage tank whose wall surface has a spiral shape. Furthermore, Patent Document 3 describes a technique of providing a plurality of nozzles in a processing tank so that the size of the vortex generated in the tank can be adjusted.

[0004] On the other hand, a technique of irradiating ultrasonic waves to a substrate or the like immersed in a cleaning liquid to improve the cleaning efficiency is also known (see, for example, Patent Documents 4-5).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

[0006] It is well known that generating vortices or irradiating ultrasonic waves within a cleaning tank can improve cleaning efficiency. Typically, ultrasonic generators are installed at the bottom of the cleaning tank to eliminate uneven cleaning. However, since the physical properties of foreign matter to be removed from the object being cleaned vary, it is difficult to efficiently remove all of it from the cleaning tank. For example, foreign matter with a relatively high specific gravity tends to move to the outside of the cleaning tank due to the centrifugal force associated with the vortex and then settle, so it tends to adhere to the side walls of the cleaning tank or accumulate near the side walls at the bottom of the cleaning tank. On the other hand, foreign matter with a relatively low specific gravity tends to gather near the center of the vortex and accumulate in the center of the bottom of the cleaning tank. Thus, removing foreign matter that has adhered to or accumulated on the walls or bottom has been a time-consuming, laborious, and costly task.

[0007] In cleaning systems that install ultrasonic generators on the bottom, it is common to install multiple ultrasonic generators across the entire bottom surface or at appropriate intervals to ensure even cleaning in different areas, making it difficult to place the cleaning fluid discharge port in the center of the bottom surface. Because foreign matter accumulates in different parts of the tank depending on its physical properties, the effort and time required for cleaning and maintenance of the cleaning tank increases. It is also possible to consider a configuration with discharge ports both at the bottom and near the side walls of the cleaning tank, but this leads to design constraints and increased costs for the cleaning tank.

[0008] Therefore, the present invention aims to provide a washing tank capable of efficiently discharging foreign substances with different physical properties using the simplest possible configuration, a washing system including the washing tank, and a washing method using the washing system. [Means for solving the problem]

[0009] One aspect of the present disclosure is an inner tank having sides and a bottom, a support disposed within the inner tank for supporting at least one object to be cleaned, and a device provided on the side of the inner tank and positioned below the support, which supplies a cleaning solution for cleaning the object to be cleaned into the inner tank, and inside the inner tank The area in which the object to be cleaned is immersed. to, When the inner tank is viewed from above, the flow in the circumferential direction is within the visible plane. The cleaning tank comprises a flow nozzle configured to generate a swirling flow of cleaning fluid, a discharge port provided near the side of the bottom of the inner tank, or in a portion of the side adjacent to the bottom, configured to discharge the cleaning fluid, and an ultrasonic oscillator provided at the bottom of the inner tank.

[0010] Another aspect of the present disclosure is a method for cleaning at least one object to be cleaned, supported by a support disposed within an inner tank having sides and a bottom, wherein a cleaning solution for cleaning the object to be cleaned is supplied into the inner tank from a flow nozzle provided on the side of the inner tank and positioned below the support, and inside the inner tank The area in which the object to be cleaned is immersed. to, When the inner tank is viewed from above, the flow in the circumferential direction is within the visible plane. The cleaning method includes generating a swirling flow of cleaning fluid, discharging the cleaning fluid from a discharge port provided near the side of the bottom of the inner tank, or in a portion of the side adjacent to the bottom, and emitting ultrasonic waves from an ultrasonic oscillator provided at the bottom of the inner tank at least one of the following times: when the cleaning fluid is being supplied from the flow nozzle and when the cleaning fluid is being discharged from the discharge port.

[0011] Further other embodiments of the present disclosure are cleaning systems comprising a cleaning tank according to one embodiment described above, and a cyclonic filter fluidly connected to the flow nozzle of the inner tank. [Effects of the Invention]

[0012] According to this disclosure, by positioning the flow nozzle that supplies cleaning fluid to the inner tank below the support that supports the object to be cleaned, a swirling flow is generated throughout the tank, thereby increasing cleaning efficiency. In addition, by providing an ultrasonic oscillator at the bottom of the inner tank, foreign matter that has accumulated near the center of the inner tank is moved to the sides of the inner tank, and the foreign matter can be efficiently discharged from a discharge port provided near the sides of the bottom of the inner tank. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram of the cleaning system according to the embodiment. [Figure 2] Figure 1 is a schematic front view of the cleaning tank included in the cleaning system. [Figure 3] Figure 2 is a schematic side view of the washing tank. [Figure 4] Figure 2 is a schematic top view of the washing tank. [Modes for carrying out the invention]

[0014] Figure 1 is a schematic diagram of a cleaning system according to a preferred embodiment. The cleaning system 10 includes a cleaning tank 12, a storage tank 14 for temporarily storing cleaning liquid from the cleaning tank 12, a cyclone filter 16, a pump 18, and a drain tank 20. The storage tank 14 has a filter 22, such as a metal mesh, for filtering the cleaning liquid discharged from the cleaning tank 12. The pump 18 is configured to extract the cleaning liquid from the storage tank 14 and supply it to the cyclone filter 16, and then return the cleaning liquid filtered by the cyclone filter 16 to the cleaning tank 12 and the storage tank 14.

[0015] The storage tank 14 has a roughly cylindrical body 26 and a roughly conical bottom 28, and is configured to form a vortex inside with the cleaning liquid from the cyclone filter 16, so that the cleaning liquid that has passed through the filter 22 is discharged toward the pump 18. The drain tank 20 is configured to collect sludge 24 and the like separated from the cleaning liquid by the cyclone filter 16 and discharge it as drain.

[0016] Figs. 2-4 are respectively a front view, a side view, and a top view showing the schematic configuration of the cleaning tank 12. The cleaning tank 12 has a substantially rectangular parallelepiped-shaped inner tank 30, an outer tank 32 that receives the cleaning liquid overflowing (overflowing) from the inner tank 30, and an ultrasonic oscillator 36 provided at the bottom 34 of the inner tank 30. Note that both the inner tank 30 and the outer tank 32 in the illustrated example are substantially rectangular parallelepiped-shaped, but the present disclosure is not limited to this, and for example, a cylindrical shape may be used. However, due to the configuration of receiving the overflow from the inner tank 30 in the outer tank 32, as shown in FIG. 4, both the inner tank 30 and the outer tank 32 are substantially rectangular in top view, and it is preferable that one side of each is adjacent to each other.

[0017] At least one flow nozzle 40 configured to supply the cleaning liquid from the cyclone filter 16 or the like is provided on the side portion (side wall) 38 of the inner tank 30. Further, a discharge port 44 configured to discharge the cleaning liquid is provided at the bottom 34 of the inner tank 30.

[0018] As shown in FIG. 4, the discharge port 44 is provided near the side portion 38 inside the bottom 34 of the inner tank 30, or at a portion adjacent to the bottom 34 inside the side portion 38. Here, the vicinity of the side portion means, for example, that the distance from the center (or centroid) of the bottom 34 to the discharge port 44 is 1 / 2 or more, 2 / 3 or more, 3 / 4 or more, or 4 / 5 or more of the distance from the center (or centroid) of the bottom 34 passing through the discharge port 44 to the side portion 38.

[0019] A support 46 is arranged in the inner tank 30, and at least one (usually a plurality) of workpieces (works) 48 to be cleaned are supported on the support 46. The workpiece 48 is, for example, a disk-shaped semiconductor wafer with a diameter of 100 mm to 200 mm (4 inches to 8 inches), and is in a state where a lot of dirt adheres, like an as-cut wafer obtained by cutting a single crystal ingot with an inner circumferential cutting machine or a wire saw. In the illustrated example, the workpieces 48 are arranged in alignment on the support 46 in a vertically standing state, but the support 46 may be configured to support the workpieces 48 in different orientations in consideration of cleaning efficiency and the like.

[0020] The flow nozzles 40 are positioned below the support 46. In the example shown in Figure 2-4, the four flow nozzles 40 are positioned at approximately the same height in the height direction of the inner tank 30, which is roughly rectangular (a so-called rectangular tank) when viewed from above. Furthermore, each flow nozzle 40 is positioned at each corner of the inner tank 30 to form a flow parallel to its inner surface, as shown in Figure 4. The reason for this is to form a suitable swirling flow within the rectangular inner tank 30. In other words, in a rectangular tank, the flow along each inner surface may collide with a surface perpendicular to the flow at the corner, becoming turbulent and disappearing. However, by providing flow nozzles at each corner that redirect the flow by a predetermined angle (90 degrees in this case), a swirling flow suitable for cleaning can be formed even if the inner tank 30 is rectangular. Furthermore, if the inner tank 30 is circular when viewed from above (a so-called round tank), a suitable vortex can be formed with just one flow nozzle 40. If the inner tank 30 has a shape other than a round or square tank, the number, orientation, and position of the flow nozzles 40 can be appropriately determined according to its shape in order to form a suitable swirling flow.

[0021] The ultrasonic oscillator 36 is provided at the bottom 34 of the inner tank 30 and is configured to emit ultrasonic waves toward the workpiece 48 supported by the support 46. In the illustrated example, the ultrasonic oscillator 36 is described as a diaphragm type equipped with multiple oscillators 50, but this disclosure is not limited to this, and for example, an immersion ultrasonic type may be used. However, in either case, the ultrasonic oscillator 36 is provided below the flow nozzle 40. Furthermore, in order to further improve cleaning efficiency, the ultrasonic oscillator 36 may be configured to emit ultrasonic waves of different frequencies (for example, two frequencies) simultaneously.

[0022] Next, the cleaning action of the cleaning tank 12 will be explained. Here, it is assumed that the inner tank 30 is filled with cleaning solution (alkaline solution or water, etc.) up to the level indicated by the liquid level 52 (for example, 100 liters), and that the entire workpiece 48 is immersed in the cleaning solution. Furthermore, it is assumed that the flow rate of the cleaning solution (alkaline solution or water, etc.) supplied to the inner tank 30 is slightly greater than the flow rate of the cleaning solution discharged from the discharge port 44, and therefore a portion of the cleaning solution overflows into the outer tank 32.

[0023] By operating the pump 18 (Figure 1) described above, cleaning fluid is supplied from the flow nozzle 40 into the cleaning tank 12. As shown in Figure 4, the flow nozzle 40 is positioned and configured to eject the cleaning fluid at a predetermined flow velocity along the inner surface of the roughly rectangular inner tank 30 when viewed from above. As a result, the cleaning fluid discharged from the nozzle 40 is guided along the inner surface of the side portion 38 of the inner tank 30, forming a swirling flow 56. This swirling flow is also generated above the nozzle 40, thereby effectively cleaning the workpiece 48. At the same time, by emitting ultrasonic waves from the ultrasonic oscillator 36 towards the workpiece 48, foreign matter firmly attached to the workpiece 48 can also be removed.

[0024] More specifically, foreign matter such as wafer fragments, abrasive particles, oil, and residue from the ingot bonding agent attached to the workpiece 48 is separated from the workpiece 48 by swirling flow and ultrasonic waves. Here, the foreign matter contains a mixture of relatively high and low specific gravity particles. The first type of foreign matter, which has a relatively high specific gravity, is moved to the side 38 of the inner tank 30 by the centrifugal force associated with the swirling flow. The first type of foreign matter then gradually sinks due to its own weight while swirling near the side 38 of the inner tank 30, so it does not reattach to the workpiece 48 and can be efficiently discharged from the discharge port 44 located near the side 38 of the bottom 34.

[0025] On the other hand, the second foreign matter, which has a relatively low specific gravity, does not move towards the side portion 38 due to the swirling flow in the inner tank 30, but tends to accumulate in the center of the inner tank 30. In this state, by irradiating ultrasonic waves from the ultrasonic oscillator 36, the second foreign matter can be guided from the center of the inner tank 30 to the side portion 38. Thus, the second foreign matter can also be suitably discharged from the discharge port 44 provided near the side portion of the bottom portion 34.

[0026] To more efficiently remove the second foreign matter, the following process is preferable. First, the supply of cleaning solution is stopped, and the cleaning solution is discharged from the discharge port 44. When the amount of cleaning solution in the inner tank 30 is reduced (for example, when the liquid level is directly below the support 46), ultrasonic waves are emitted (irradiated upwards). This makes it easier to move the second foreign matter, which has accumulated in the center of the inner tank 30, further towards the side 38. Next, the ultrasonic waves are stopped, the cleaning solution is further discharged from the discharge port 44, and ultrasonic waves are irradiated again. By repeating this series of processes of ultrasonic wave emission (irradiation), stopping the ultrasonic waves, and discharging the cleaning solution at least once, it becomes possible to discharge the second foreign matter from the discharge port 44 without leaving any residue on the bottom 34 (especially near the center).

[0027] Furthermore, among the second type of foreign matter, those with particularly low specific gravity float to the liquid surface 52 of the inner tank 30 or its vicinity during cleaning, and are moved to the outer tank 32 by overflow from the inner tank 30, and discharged into the storage tank 14 from the discharge port 54 provided at the bottom of the outer tank 32. Thus, in this embodiment, foreign matter of any specific gravity can be suitably discharged from the inner tank 30, and the frequency and effort of cleaning the inside of the tank can be greatly reduced. In order to facilitate the movement of foreign matter at the bottom 34 to the discharge port 44, the bottom 34 may have an inclined surface with a downward slope toward the discharge port 44, as shown in Figure 3.

[0028] As shown in Figures 2 and 4, this embodiment provides two discharge ports 44, but there may be one or three or more. If there are two or more discharge ports 44, at least one of them can be used as a throttle-controlled drain nozzle. That is, by using the discharge port 44 as a drain nozzle, a downflow is generated in the inner tank 30 in addition to the swirling flow described above, so that the first foreign matter, which has a relatively high specific gravity, is more easily discharged from the discharge port 44.

[0029] Thus, in this embodiment, by using a suitable combination of a flow nozzle and an ultrasonic oscillator, foreign matter of different specific gravities can be allowed to settle and accumulate near the side 38 of the inner tank 30. Therefore, it is not necessary to provide the discharge port 44 near the center of the bottom 34, and the shape of the inner tank 30 is not limited to a cylinder or the like, but can be selected as any shape.

[0030] Referring again to Figure 1, the cleaning system 10 can perform both the extraction of cleaning liquid from the cleaning tank 12 and the supply of the extracted cleaning liquid to the cyclone filter 16 with a single pump 18, and by using such a single-pump system, the overall cost of the system can be reduced. In addition, although cyclone filters are not generally used in semiconductor cleaning processes, in this embodiment, by using the cyclone filter 16, the clean cleaning liquid from which foreign matter and other substances have been removed as sludge 24 can be returned to the cleaning tank 12 using the discharge flow from the cyclone filter 16, so that an efficient cleaning system can be constructed with a small number of parts. However, a filter of the type in which the filter media can be replaced (not shown) may be provided between the outlet of the cyclone filter 16 and the flow nozzle 40 of the cleaning tank 12. In general, with filters of the type in which the filter media can be replaced, the filter media needs to be replaced when clogging occurs, but in this embodiment, relatively large foreign matter can be removed with the cyclone filter 16, so the frequency of filter media replacement can be greatly reduced.

[0031] In the above embodiment, the support 46 is fixed in a suitable position within the inner tank 30, but a means (not shown) for swinging the support 46 up and down may be provided, and swinging the support 46 in the cleaning liquid further enhances the cleaning efficiency. A lift mechanism (not shown) for lifting the support 46 out of the inner tank 30 can also be provided to allow the workpiece to be lifted out of the hot water and dried. Furthermore, this configuration reduces foreign matter that adheres to the side walls, saving time and effort in cleaning the cleaning tank. [Explanation of Symbols]

[0032] 10 Cleaning System 12 Washing tank 14 Storage Tanks 16 Cyclone filter 18 pumps 20 Drain Tank 24 Sludge 30 Inner tank 32 Outer tank 34 Bottom 36. Ultrasonic oscillator 38 Side 40 Flow Nozzles 44 Discharge Ports 46 Support 48 Work 50 Ultrasonic Oscillators

Claims

1. An inner tank having sides and a bottom, A support for at least one object to be cleaned, disposed within the inner tank, A flow nozzle is provided on the side of the inner tank, positioned below the support, and is configured to supply cleaning liquid for cleaning the object to be cleaned into the inner tank, and to generate a swirling flow of cleaning liquid that flows circumferentially in the area inside the inner tank where the object to be cleaned is immersed, within the plane visible when the inner tank is viewed from above. A discharge port is provided in the vicinity of the side portion of the bottom of the inner tank, or in the portion of the side portion adjacent to the bottom, and is configured to discharge the cleaning liquid. An ultrasonic oscillator provided at the bottom of the inner tank, A washing tank having

2. The washing tank according to claim 1, wherein a plurality of the flow nozzles are arranged at the same height with respect to the height of the inner tank.

3. The cleaning tank according to claim 1 or 2, further comprising an outer tank for containing cleaning liquid that overflows from the inner tank.

4. A method for cleaning at least one object to be cleaned, which is supported by a support located in an inner tank having sides and a bottom, From a flow nozzle provided on the side of the inner tank and positioned below the support, a cleaning liquid for cleaning the object to be cleaned is supplied into the inner tank, and a swirling flow of the cleaning liquid is generated in the area inside the inner tank where the object to be cleaned is immersed, flowing circumferentially within the plane visible when the inner tank is viewed from above. The cleaning liquid is discharged from a discharge port provided in the vicinity of the side portion of the bottom of the inner tank, or in the portion of the side portion adjacent to the bottom. At least one of the following states: when the cleaning fluid is being supplied from the flow nozzle and when the cleaning fluid is being discharged from the discharge port, an ultrasonic oscillator provided at the bottom of the inner tank emits ultrasonic waves. A cleaning method that includes [details omitted].

5. The cleaning method according to claim 4, wherein the series of processes of emitting ultrasonic waves from the ultrasonic oscillator, stopping the ultrasonic waves, and discharging the cleaning liquid from the discharge port are repeated at least once.

6. A washing tank according to claim 1 or 2, A cyclone-type filter fluidly connected to the flow nozzle of the inner tank, A cleaning system having the following features.

7. The cleaning system according to claim 6, further comprising a pump configured to extract cleaning liquid from the cleaning tank, pass the extracted cleaning liquid through the cyclone filter, and return it to the inner tank.

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