Electroplating apparatus and substrate cleaning method

Abstract

The invention provides an electroplating device and a substrate cleaning method, and belongs to the technical field of semiconductor equipment. Comprising a chuck used for keeping a substrate horizontally arranged; the driving device is used for driving the chuck to rotate; a nozzle for discharging a cleaning liquid to clean the substrate held by the chuck; wherein the coverage range of spraying the cleaning liquid to the substrate by the nozzle comprises a forward rotation speed area and a reverse rotation speed area, and the forward rotation speed area is larger than the reverse rotation speed area; the clockwise rotating speed area is an area in which the cleaning liquid sprayed by the nozzle has a speed component along the rotating speed direction of the substrate; the reverse speed region is a region in which the cleaning liquid ejected from the nozzle has a speed component opposite to the rotational speed direction of the substrate. According to the electroplating device and the substrate cleaning method, the position of the nozzle is specifically arranged, so that a large amount of cleaning liquid sprayed by the nozzle falls in the clockwise rotating speed area, the cleaning liquid can be better thrown into the water retaining cover, and the situation that a large amount of cleaning liquid falls into the cathode chamber to dilute cathode electroplating liquid and affect the stability of the electroplating liquid is prevented.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor devices, and particularly relates to an electroplating device and a substrate cleaning method. Background Art

[0002] With the continuous improvement of semiconductor technology, the manufacturing of semiconductor substrates is developing rapidly towards the directions of multi-layer, stacked, functionalized and integrated. The traditional vertical electroplating process can no longer meet the technical requirements of high-quality and high-reliability interconnect holes. Therefore, the horizontal electroplating technology has emerged as the times require. It is a continuation of the development of vertical electroplating technology, that is, a new electroplating technology developed on the basis of vertical electroplating technology. During the horizontal electroplating process, the stability of the electroplating solution has a great impact on the reliability of the electroplated product. Each electroplating process uses a different electroplating solution. In order to prevent the cross-contamination of the electroplating solutions in different electroplating processes and affect the stability of the electroplating solution, the general treatment method in the existing market is: after a substrate undergoes an electroplating process, a cleaning process is performed on the substrate to wash off the electroplating solution carried on the surface of the substrate, and then the substrate is transported to the next electroplating process chamber.

[0003] However, when cleaning the substrate in the existing manner, the water drop volume is large, and a part of the water falls into the cathode chamber of the electroplating device, resulting in the dilution of the electroplating solution in the cathode chamber, which will also affect the stability of the electroplating solution. Therefore, this problem urgently needs to be solved. Summary of the Invention

[0004] In order to avoid the large water drop volume during the substrate cleaning process from affecting the stability of the electroplating solution, the present invention provides an electroplating device, including:

[0005] A chuck for horizontally holding a substrate;

[0006] A driving device for driving the rotation of the chuck;

[0007] A nozzle for spraying a cleaning solution to clean the substrate held by the chuck;

[0008] Wherein, the coverage range of the cleaning solution sprayed by the nozzle onto the substrate includes: a forward rotation speed region and a reverse rotation speed region, and the forward rotation speed region is larger than the reverse rotation speed region; the forward rotation speed region is the region where the cleaning solution sprayed by the nozzle has a speed component in the direction of the substrate rotation speed; the reverse rotation speed region is the region where the cleaning solution sprayed by the nozzle has a speed component opposite to the direction of the substrate rotation speed.

[0009] According to a specific implementation manner of an embodiment of the present application, the nozzle is a fan-shaped nozzle, a circular nozzle, an annular nozzle or a cylindrical nozzle.

[0010] According to a specific implementation manner of an embodiment of the present application, the coverage range of the cleaning liquid sprayed by the nozzle includes the center of the substrate held by the chuck.

[0011] According to a specific implementation manner of an embodiment of the present application, when the cleaning liquid sprayed by the nozzle contacts the substrate, the distance from the boundary of the cleaning liquid in the forward rotation speed region to the center of the substrate is greater than or equal to r / 2, where r is the distance from the center of the substrate to the edge of the substrate.

[0012] According to a specific implementation manner of an embodiment of the present application, the distance from the boundary of the cleaning liquid sprayed by the nozzle in the reverse rotation speed region to the center of the substrate is less than or equal to r / 4.

[0013] According to a specific implementation manner of an embodiment of the present application, the rotation speed of the chuck driven by the driving device is greater than or equal to 50 r / min.

[0014] According to a specific implementation manner of an embodiment of the present application, the flow rate of the cleaning liquid sprayed by the nozzle is 0.5 - 2.5 LPM.

[0015] In a second aspect, the present invention provides a method for cleaning a substrate, including:

[0016] The chuck holds the substrate horizontally;

[0017] The driving device drives the chuck to rotate;

[0018] The nozzle sprays a cleaning liquid onto the substrate to clean the substrate held by the chuck. The coverage range of the cleaning liquid sprayed by the nozzle onto the substrate includes: a forward rotation speed region and a reverse rotation speed region, where the forward rotation speed region is larger than the reverse rotation speed region; the forward rotation speed region is the region where the cleaning liquid sprayed by the nozzle has a velocity component in the direction of the rotation speed of the substrate; the reverse rotation speed region is the region where the cleaning liquid sprayed by the nozzle has a velocity component opposite to the rotation speed direction of the substrate.

[0019] According to a specific implementation manner of an embodiment of the present application, the nozzle is a fan-shaped nozzle, a circular nozzle, an annular nozzle, or a cylindrical nozzle.

[0020] According to a specific implementation manner of an embodiment of the present application, the coverage range of the cleaning liquid sprayed by the nozzle includes the center of the substrate held by the chuck.

[0021] According to a specific implementation manner of an embodiment of the present application, when the cleaning liquid sprayed by the nozzle contacts the substrate, the distance from the boundary of the cleaning liquid in the forward rotation speed region to the center of the substrate is greater than or equal to r / 2, where r is the distance from the center of the substrate to the edge of the substrate.

[0022] In a specific implementation manner according to an embodiment of the present application, the distance from the center of the substrate to the boundary of the reverse rotation speed region where the cleaning liquid ejected from the nozzle is located is less than or equal to r / 4.

[0023] For the electroplating device and the substrate cleaning method of the present invention, by dividing the coverage range of the cleaning liquid ejected from the nozzle into regions according to the rotation direction of the substrate and the flow velocity direction of the cleaning liquid, and setting the position of the nozzle in a targeted manner, when cleaning the substrate, more of the cleaning liquid ejected by the nozzle falls in the forward rotation speed region, so that it can be better thrown into the water baffle and then drained away, thereby effectively reducing the amount of water falling during substrate cleaning, preventing a large amount of cleaning liquid from falling into the cathode chamber and diluting the electroplating solution in the cathode chamber, and affecting the stability of the electroplating solution. Other features and advantages of the present invention will be described in the following specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention. The objectives and other advantages of the present invention can be achieved and obtained by the structures pointed out in the specification, the claims, and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0025] Figure 1 Shows a schematic structural diagram of the electroplating device in an embodiment of the present invention;

[0026] Figure 2 Shows a schematic diagram of the regional division of the water falling area in the cathode chamber during the substrate cleaning process according to an embodiment of the present invention;

[0027] Figure 3 Shows the amount of water falling in each region when the central axis of the cleaning liquid ejected from the nozzle in an embodiment of the present invention passes through the center of the substrate Figure 2 results;

[0028] Figure 4 Shows a schematic structural diagram of the central axis of the cleaning liquid ejected from the nozzle passing through the chuck and the center of the substrate in an embodiment of the present invention;

[0029] Figure 5 Shows a schematic diagram of the flow velocity of the cleaning liquid in an embodiment of the present invention;

[0030] Figure 6 Shows a schematic structural diagram of the central axis of the cleaning liquid ejected from the nozzle not passing through the chuck and the center of the substrate in an embodiment of the present invention;

[0031] Figure 7The schematic flow chart of the substrate cleaning method in the embodiment of the present invention is shown; and

[0032] Figure 8 When the central axis of the cleaning liquid ejected from the nozzle in the embodiment of the present invention does not pass through the center of the substrate Figure 2 The water drop amount results of each region in Detailed implementation manners

[0033] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0034] Please refer to Figure 1 , Figure 1 which shows the schematic structural diagram of the electroplating device in the embodiment of the present invention. As Figure 1 shown, the electroplating device includes an electroplating chamber 100, and the electroplating chamber 100 is separated into two independent chambers by a horizontally arranged ion membrane 200. One side of the ion membrane 200 is an anode chamber 300, and the other side of the ion membrane 200 is a cathode chamber 400. An anode 500 is arranged inside the anode chamber 300; a water baffle 600, a chuck 700 for keeping the substrate horizontally arranged, and a driving device 800 for driving the chuck 700 to rotate are arranged at the top of the cathode chamber 400. It should be understood that the driving device 800 can also be configured to drive the chuck 700 to move in the vertical direction to drive the chuck into or out of the cathode chamber 400 and keep the chuck 700 at a target height. In the actual process, considering that the substrate after each electroplating process needs to be cleaned once to wash off the residual electroplating solution on the substrate, a nozzle 900 for cleaning the substrate is also arranged in the electroplating device. The nozzle 900 includes but is not limited to: a fan-shaped nozzle, a circular nozzle, an annular nozzle or a columnar nozzle. The position of the nozzle 900 can be set according to the actual machine conditions. In this embodiment, the nozzle 900 is fixedly arranged on the water baffle 600. When the electroplating process ends, the driving device 800 drives the chuck 700 to move the substrate 001 upward to move out of the electroplating solution until it moves into the water baffle 600, and then the driving device 800 drives the chuck 700 to rotate to clean the substrate 001. During the cleaning process, part of the cleaning liquid will fall into the cathode chamber 400 along the path of S2, affecting the stability of the electroplating solution. For this reason, the present application proposes a solution. With reference to Figure 5, when the nozzle 900 sprays the cleaning liquid onto the substrate 001, it is required that the coverage range of the cleaning liquid sprayed from the nozzle 900 onto the substrate 001 includes: the forward rotation speed region 901 and the reverse rotation speed region 902, where the forward rotation speed region 901 is larger than the reverse rotation speed region 902. Specifically, when the cleaning liquid lands on the substrate 001, the coverage range of the cleaning liquid can be divided into two regions according to the flow direction of the cleaning liquid. One region is the region where the cleaning liquid sprayed from the nozzle 900 has a velocity component in the direction of the substrate rotation speed, which is called the forward rotation speed region 901; the other region is the region where the cleaning liquid sprayed from the nozzle 900 has a velocity component opposite to the substrate rotation speed direction, which is called the reverse rotation speed region 902. In the actual process, the vicinity of the coverage range of the cleaning liquid in the forward rotation speed region 901 is also considered as the forward rotation speed region; the vicinity of the coverage range of the cleaning liquid in the reverse rotation speed region 902 is also considered as the reverse rotation speed region. In the embodiment of the present invention, when the nozzle 900 sprays the cleaning liquid onto the substrate 001, it is required that the forward rotation speed region 901 is larger than the reverse rotation speed region 902 to reduce the amount of water falling during the cleaning of the substrate 001. It should be understood that in this embodiment, the cleaning liquid can be deionized water.

[0035] In this application, the coverage range of the cleaning liquid sprayed from the nozzle is divided into regions according to the rotation direction of the substrate and the flow direction of the cleaning liquid, and the position of the nozzle is set specifically, so that when cleaning the substrate, most of the cleaning liquid sprayed by the nozzle falls in the forward rotation speed region, which is convenient for being better thrown into the water baffle and then drained away, thereby effectively reducing the amount of water falling during the cleaning of the substrate, preventing a large amount of cleaning liquid from falling into the cathode chamber and diluting the electroplating solution in the cathode chamber, and affecting the stability of the electroplating solution.

[0036] Specific analysis is as follows. During the actual process, it is found that the stability of the electroplating solution is easily affected when cleaning the substrate. To solve this problem, the inventors of this application have analyzed this phenomenon in depth. It is found that when the cleaning liquid sprayed from the nozzle 900 contacts the substrate 001, the driving device 800 drives the chuck 700 and the substrate 001 held by the chuck 700 to rotate, and most of the cleaning liquid is thrown into the water baffle 600 and then drained away through the drain port (not shown) provided on the water baffle 600. However, a small amount of the cleaning liquid will fall into the lower cathode chamber 400 and dilute the cathode electroplating solution, affecting the stability of the cathode electroplating solution. Further, it is found that during the process of cleaning the substrate, the amount of water falling in each region below the substrate is not uniform. Therefore, the inventors of this application have divided the water falling regions below the substrate during the substrate cleaning process. For the specific schematic diagram of the water falling region division, please refer to Figure 2 , Figure 2 , where the arrow on the left indicates the rotation direction of the substrate, and the arrow in the lower right corner indicates the direction of the cleaning liquid sprayed from the nozzle 900. From Figure 2It can be known that A, B, C, and D extend from the center of the substrate 001 to the outside in sequence. The regions A1, B1, C1, D1, A2, B2, C2, and D2 are the forward rotation speed regions, and the regions A5, B5, C5, D5, A6, B6, C6, and D6 are the reverse rotation speed regions. The water drop amounts in each region are measured and statistically analyzed under the following test conditions: the central axis of the cleaning liquid ejected by the nozzle passes through the center of the substrate, the flow rate of the cleaning liquid is 1.5 l / min, the cleaning working time is kept at 60 s, and the chuck rotation speed is 400 rpm. The obtained results are as Figure 3 shown, Figure 3 which shows the water drop amount results in each region when the central axis of the cleaning liquid ejected by the nozzle passes through the center of the substrate Figure 2 ; through Figure 3 it can be known that when cleaning the substrate under the above conditions, after a substrate cleaning process is completed, the average total water drop amount is 120.1 ml. Among them, the water drop amount in the forward rotation speed region is less, while the water drop amount in the reverse rotation speed region is larger. In particular, the difference in the water drop amount between the regions C6 and D6 and the regions C2 and D2 is relatively large. Considering that the reason may be that C2 and D2 are in the coverage range of the cleaning liquid in the forward rotation speed region, while C6 and D6 are in the coverage range of the cleaning liquid in the reverse rotation speed region.

[0037] Furthermore, the reason for the larger water drop amount in C6 / D6 is analyzed as follows: Please refer to Figure 4 , during the process of cleaning the substrate, the central axis of the cleaning liquid ejected by the nozzle 900 passes through the center of the chuck 700, and the center of the chuck 700 overlaps with the center of the substrate 001. Therefore, the central axis of the cleaning liquid ejected by the nozzle 900 will pass through the center of the substrate 001 held by the chuck 700, that is, the cleaning liquid is symmetrically distributed on both sides of the center of the substrate 001. According to the relationship between the flow rate direction of the cleaning liquid ejected by the nozzle 900 and the rotation speed direction of the substrate, the coverage range of the cleaning liquid is divided into a forward rotation speed region 901 and a reverse rotation speed region 902. Among them, the forward rotation speed region 901 refers to the region where the flow rate direction of the cleaning liquid ejected by the nozzle 900 has a component along the rotation speed direction of the substrate; the reverse rotation speed region 902 refers to the region where the flow rate direction of the cleaning liquid ejected by the nozzle 900 has a component against the rotation speed direction of the substrate. In Figure 4 the shown example, the coverage range of the forward rotation speed region 901 is equal to the coverage range of the reverse rotation speed region 902. During the cleaning process, the driving device 800 drives the chuck 700 to drive the substrate 001 held by the chuck 700 to rotate at a high speed. The cleaning liquid ejected by the nozzle 900 onto the substrate 001 gradually flows towards the edge of the substrate 001 due to the centrifugal force, and thus is thrown into the water baffle 600 (as shown by the dashed arrow S1 in Figure 1 ), and there is also part of the cleaning liquid that will fall before completely flowing to the edge (as shown by the dashed arrow S2 in Figure 1 ), please refer to Figure 5, the main reason for the two results is that the cleaning liquid ejected from the nozzle 900 has its own flow rate, and at the same time, the substrate has a relatively high rotational speed. The speeds of the two are superimposed in the forward rotation speed region, and in the reverse rotation speed region, the direction of the flow rate of the cleaning liquid itself is opposite to the rotational speed of the substrate, resulting in a counterflush, causing the cleaning liquid to fail to move to the edge of the substrate 001 and be thrown into the water baffle 600 and then fall into the electroplating chamber.

[0038] In this regard, for the solution to the problem of excessive water drop amount proposed in this application, please refer specifically to Figure 6 , as Figure 6 shown, when setting the nozzle 900, the nozzle 900 is offset relative to the center of the chuck 700, so that the coverage range of the cleaning liquid ejected by the nozzle 900 onto the substrate 001 includes: the forward rotation speed region 901 and the reverse rotation speed region 902, where the forward rotation speed region 901 is larger than the reverse rotation speed region 902. In this way, when the nozzle 900 ejects the cleaning liquid onto the substrate 001 to clean the substrate 001, the area where the flow rate of the cleaning liquid and the centrifugal speed of the substrate are in counterflush will be reduced, thereby achieving the purpose of reducing the water drop amount.

[0039] Furthermore, the coverage range of the cleaning liquid ejected by the nozzle 900 includes the center of the substrate 001 held by the chuck 700. When the cleaning liquid ejected by the nozzle 900 contacts the substrate, the distance from the boundary 9011 of the cleaning liquid in the forward rotation speed region 901 to the center of the substrate 001 is greater than or equal to r / 2, and the distance from the boundary 9021 of the cleaning liquid ejected by the nozzle in the reverse rotation speed region 902 to the center of the substrate 001 is less than or equal to r / 4, where r is the distance from the center of the substrate 001 to the edge of the substrate 001.

[0040] Furthermore, the rotational speed at which the driving device 800 drives the chuck 700 to rotate is greater than or equal to 50 r / min.

[0041] Furthermore, the flow rate of the cleaning liquid ejected by the nozzle is 0.5 - 2.5 LPM.

[0042] At the same time, the applicant of the present invention also proposes a substrate cleaning method, please refer to Figure 7 , and the method includes the following steps:

[0043] Step S100: The chuck holds the substrate horizontally;

[0044] Step S200: The driving device drives the chuck to rotate;

[0045] Step S300: The nozzle sprays a cleaning liquid onto the substrate held by the chuck to clean the substrate. The coverage area where the nozzle sprays the cleaning liquid onto the substrate includes: a forward rotation speed area and a reverse rotation speed area, where the forward rotation speed area is larger than the reverse rotation speed area; the forward rotation speed area is the area where the cleaning liquid ejected from the nozzle has a speed component in the direction of the substrate rotation speed; the reverse rotation speed area is the area where the cleaning liquid ejected from the nozzle has a speed component opposite to the substrate rotation speed direction.

[0046] Furthermore, the nozzle is a fan-shaped nozzle, a circular nozzle, an annular nozzle or a cylindrical nozzle.

[0047] Furthermore, the coverage area where the nozzle sprays the cleaning liquid includes the center of the substrate held by the chuck. When the cleaning liquid ejected from the nozzle contacts the substrate, the distance from the boundary of the cleaning liquid in the forward rotation speed area to the center of the substrate is greater than or equal to r / 2, and the distance from the boundary of the cleaning liquid in the reverse rotation speed area to the center of the substrate is less than or equal to r / 4, where r is the distance from the center of the substrate to the edge of the substrate.

[0048] Exemplarily, please refer to Figure 6 , divide the radius r of the substrate into 6 equal parts. When setting the nozzle 900, the nozzle 900 is offset relative to the centers of the chuck and the substrate, so that the coverage area of the cleaning liquid ejected from the nozzle 900 includes: a forward rotation speed area and a reverse rotation speed area, where the forward rotation speed area accounts for 2 / 3 of the cleaning liquid coverage area. In this embodiment, the distance from the boundary of the cleaning liquid in the forward rotation speed area to the center of the substrate is 2r / 3; the reverse rotation speed area accounts for 1 / 3 of the cleaning liquid coverage area. In this embodiment, the distance from the boundary of the cleaning liquid in the reverse rotation speed area to the center of the substrate is 1r / 3; also under the conditions that the flow rate of the cleaning liquid is 1.5 l / min, the cleaning working time is kept at 60 s, and the chuck rotation speed is 400 rpm, measure and count the water drop amounts in each water falling area in Figure 2 . The obtained results are as shown in Figure 8 . It can be seen from Figure 8 that when cleaning the substrate under the above conditions, after one substrate cleaning process is completed, the average total water drop amount drops to 89.3 ml, and the average water drop amount decreases by 25.6%. Among them, the total water drop amount in the A6 / B6 / C6 / D6 area drops from 11.2 ml to 0.6 ml. The decrease in the water drop amount in the coverage area of the cleaning liquid in the reverse rotation speed area is particularly obvious. Therefore, this solution has a significant effect on optimizing the reduction of the water drop amount.

[0049] Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An electroplating device, characterized in that: Comprising: A chuck for horizontally holding a substrate; A driving device for driving the chuck to rotate; A nozzle for ejecting a cleaning liquid to clean the substrate held by the chuck; Wherein, the coverage range of the cleaning liquid ejected by the nozzle onto the substrate includes: a forward rotation speed region and a reverse rotation speed region, and the forward rotation speed region is larger than the reverse rotation speed region; the forward rotation speed region is the region where the cleaning liquid ejected by the nozzle has a velocity component in the direction of the substrate rotation speed; the reverse rotation speed region is the region where the cleaning liquid ejected by the nozzle has a velocity component opposite to the substrate rotation speed direction.

2. The electroplating device according to claim 1, characterized in that: The nozzle is a sector nozzle, a circular nozzle, an annular nozzle or a cylindrical nozzle.

3. The electroplating device according to claim 1, wherein: The coverage range of the cleaning liquid ejected by the nozzle includes the center of the substrate held by the chuck.

4. The electroplating device according to claim 3, characterized in that: When the cleaning liquid ejected by the nozzle contacts the substrate, the distance from the boundary of the cleaning liquid in the forward rotation speed region to the center of the substrate is greater than or equal to r / 2, where r is the distance from the center of the substrate to the edge of the substrate.

5. The electroplating device according to claim 4, characterized in that: The distance from the boundary of the cleaning liquid in the reverse rotation speed region ejected by the nozzle to the center of the substrate is less than or equal to r / 4.

6. The electroplating device according to claim 1, characterized in that: The rotation speed of the driving device for driving the chuck to rotate is greater than or equal to 50 r / min.

7. The electroplating device according to claim 6, characterized in that: The flow rate of the cleaning liquid ejected by the nozzle is 0.5 - 2.5 LPM.

8. A substrate cleaning method, characterized in that: Comprising: The chuck holds the substrate horizontally; The driving device drives the chuck to rotate; The nozzle ejects a cleaning liquid onto the substrate to clean the substrate held by the chuck, and the coverage range of the cleaning liquid ejected by the nozzle onto the substrate includes: a forward rotation speed region and a reverse rotation speed region, wherein the forward rotation speed region is larger than the reverse rotation speed region; The forward rotation speed region is the region where the cleaning liquid ejected by the nozzle has a velocity component in the direction of the substrate rotation speed; the reverse rotation speed region is the region where the cleaning liquid ejected by the nozzle has a velocity component opposite to the substrate rotation speed direction.

9. The substrate cleaning method according to claim 8, wherein: The nozzle is a sector nozzle, a circular nozzle, an annular nozzle or a cylindrical nozzle.

10. The substrate cleaning method according to claim 8, wherein: The coverage range of the cleaning liquid ejected by the nozzle includes the center of the substrate held by the chuck.

11. The substrate cleaning method according to claim 10, wherein: When the cleaning liquid ejected by the nozzle contacts the substrate, the distance from the boundary of the cleaning liquid in the forward rotation speed region to the center of the substrate is greater than or equal to r / 2, where r is the distance from the center of the substrate to the edge of the substrate.

12. The substrate cleaning method according to claim 11, wherein: The distance from the boundary of the cleaning liquid in the reverse rotation speed region ejected by the nozzle to the center of the substrate is less than or equal to r / 4.

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