Patent Publication Number: US-2023146080-A1

Title: Electroplating system including an improved base structure

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     The present application claims priority to U.S. Provisional Patent Application No. 63/278,108, filed on Nov. 11, 2021, the entire disclosure of which is incorporated herein by reference. 
    
    
     FIELD 
     Embodiments of the present disclosure relate generally to semiconductor electroplating systems, and more particularly to mechanisms of reducing crystallization residual in semiconductor electroplating systems. 
     BACKGROUND 
     Semiconductor devices are used in a variety of electronic applications, such as personal computers, cell phones, digital cameras, and other electronic equipment. The semiconductor industry continues to improve the integration density of various electronic components (e.g., transistors, diodes, resistors, capacitors, etc.) by continual reductions in minimum feature size, which allows more components to be integrated into a given chip area. 
     During the manufacturing of the semiconductor devices, various processing steps are used to fabricate integrated circuits on a semiconductor wafer. Examples of processing steps include surface passivation, photolithography, ion implantation, etching, plasma ashing, thermal treatments, chemical vapor deposition (CVD), atomic layer deposition (ALD), physical vapor deposition (PVD), molecular beam epitaxy (MBE), electroplating, chemical-mechanical polishing (CMP), and the like. Various semiconductor processing equipment and tools (e.g., extreme ultraviolet (EUV) lithography systems) have been developed for those processing steps. There is a need to improve the performance and reduce maintenance cost of those semiconductor processing equipment and tools. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG.  1    is a diagram illustrating an example electroplating system in accordance with some embodiments. 
         FIG.  2    is a diagram illustrating the example electroplating system shown in  FIG.  1    in a cleaning procedure in accordance with some embodiments. 
         FIG.  3    is a diagram illustrating a schematic top view of the base structure shown in  FIG.  1    in accordance with some embodiments. 
         FIG.  4 A  is a side view of an example shield structure in accordance with some embodiments. 
         FIG.  4 B  is a top view of the example shield structure shown in  FIG.  4 A  in accordance with some embodiments. 
         FIG.  5    is a top view of an example shield structure in accordance with some embodiments. 
         FIG.  6    is an example method of manufacturing a base structure in an electroplating system in accordance with some embodiments. 
         FIG.  7    is an example method of cleaning the electroplating system shown in  FIG.  2    in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following disclosure provides many different embodiments, or examples, for implementing different features of the subject matter provided. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. 
     Some embodiments of the disclosure are described. Additional operations can be provided before, during, and/or after the stages described in these embodiments. Some of the stages that are described can be replaced or eliminated for different embodiments. Some of the features described below can be replaced or eliminated and additional features can be added for different embodiments. Although some embodiments are discussed with operations performed in a particular order, these operations may be performed in another logical order. 
     The electroplating processes are used for deposition of conductive layers over the semiconductor wafer. Generally, an electroplating process includes depositing or plating positively charged ions (e.g., metal ions) onto a negatively charged substrate (e.g., a semiconductor wafer), which is used as a source of electrons. In one implementation, a seed layer (or a metal layer) is first deposited over the semiconductor wafer to provide an electrical path across the surfaces. An electrical current is then supplied to the seed layer or the metal layer, thereby electroplating the semiconductor wafer surface with an appropriate metal (e.g., copper, aluminum, or any suitable metallic material). 
     One typical example of electroplating processes is copper electroplating, which may be used to create copper interconnects and vertical interconnect accesses (vias) that link components together in an integrated circuit (IC). In the example of copper electroplating, a silicon wafer and a copper source are placed in a plating solution (sometimes also referred to as a “plating bath”), which typically contains copper sulfate (CuSO 4 ) and sulfuric acid. When a current is applied, copper ions deposit on the wafer over time. The amount of copper deposited on the wafer is directly controlled by the current flow, which supplies electrons needed for the cupric ion reduction reaction (i.e., Cu 2+ +2e − →Cu). Additionally, parameters such as the temperature of the plating solution, the rate of the plating solution flow, and the chemical composition of the plating solution can be adjusted to control the properties of the copper layer that is deposited over the wafer. It should be understood that although the disclosure uses copper electroplating as an example, the inventive concepts in the disclosure are generally applicable to the electroplating of other materials as needed. 
     Electroplating process is typically conducted using an electroplating system. The electroplating system generally includes, among other things, a container which accommodates the plating solution, an anode immersed in the plating solution, a wafer holder assembly which holds the wafer from the above, and a base structure (also referred to as a “cup”) which supports the wafer from the bottom and provides the electrical connection between the wafer and a low (electric) potential (i.e., causing the wafer to act as a cathode which attracts positive ions). In other words, the wafer that is going to be electroplated is located between the base structure and the wafer holder assembly. During the electroplating process, the wafer holder assembly, the base structure, and the wafer therebetween rotate together at the same speed. Plating solution residual (e.g., CuSO 4  crystal in the example of copper electroplating) may accumulate over the base structure and/or the wafer holder assembly over time. Thus, periodic or occasional cleaning procedures are necessary to remove the accumulated plating solution residual. The cleaning procedure reduces the usage and increases the maintenance time of the electroplating system in a foundry, consumes a significant amount of water and energy, and requires the involvement of applied engineers, which may be a critical human resource in a foundry. 
     More importantly, the base structure typically has some shield structures extending in the vertical direction and configured to protect the wafer, the wafer holder assembly, and the base structure. As a result, some right-angle corners exist in the base structures. Plating solution residual may accumulate at those right-angle corners easily and may be very challenging to clean using conventional cleaning procedures. Automatic cleaning procedures sometimes are not good enough to clean the plating solution residual accumulated at those right-angle corners. Therefore, manual cleaning, which is inefficient and labor-intensive, might be inevitable. 
     On the other hand, uncleaned plating solution residual may result in high impedance between the wafer and the base structure, which in turn increases power consumption of the electroplating system during the electroplating process. In some cases, the high impedance may even cause the electroplating process to be interrupted. Accordingly, maintaining a relatively low impedance between the wafer and the base structure by reducing the plating solution residual, is very meaningful. 
     In accordance with some aspects of the disclosure, improved electroplating systems having an improved base structure and corresponding methods are provided for addressing the aforementioned plating solution residual problem. In some embodiments, the base structure in accordance with the disclosure includes a pair of shield structures. Each of the shield structures, in those embodiments, includes three features: (1) discharging openings; (2) bevels; and (3) baffles. In one embodiment, a shield structure includes discharging openings. In one embodiment, a shield structure includes discharging openings and bevels. In another embodiment, a shield structure includes discharging openings and baffles. In yet another embodiment, a shield structure includes discharging openings, bevels, and baffles. In that embodiment, the bevels are configured to guide plating solution residual toward the corresponding discharging openings in a cleaning procedure. In various embodiments, the plating solution residual is discharged through the discharging openings in a cleaning procedure. In those embodiments, the baffles prevent the plating solution residual from reentering the base structure through the discharging openings. Details of these features will be described below with reference to  FIGS.  1 - 7   . As a result, these techniques enable, among other benefits, the following benefits: increasing discharging efficiency of the plating solution residual; consuming less water and energy during the cleaning procedure; increasing usage and reducing the maintenance time of the electroplating system; and reducing the necessary human involvement and saving critical human resource in a foundry. Moreover, adding the shield structure having one or more of these aspects is cost-effective. 
       FIG.  1    is a diagram illustrating an example electroplating system  100  in accordance with some embodiments. In the example of  FIG.  1   , the electroplating system  100  includes, among other things, a container  102 , a wafer holder assembly  108 , a base structure (also referred to as a “cup”)  118 , an anode  106 , and a cleaning nozzle. The container  102  accommodates plating solution  104 . The anode  106  is immersed in the plating solution  104 . 
     The wafer holder assembly  108  is configured to hold a wafer  132  to be electroplated. In the example of  FIG.  1   , the wafer holder assembly  108  includes a rotatable spindle  110  that can rotate around a vertical axis, as denoted as rotational movement  196  in  FIG.  1   . The rotation of the rotatable spindle  110  causes the wafer holder assembly  108  and the wafer  132  to rotate at the same speed. The wafer holder assembly  108  further includes a wafer holder body  112  and a wafer attachment member  114 . In some implementations, the wafer holder body  112  is a flat cylinder. The wafer attachment member  114  is attached to the bottom surface of the wafer holder body  112 . The wafer  132  is beneath and attached to the wafer attachment member  114 . In the example of  FIG.  1   , the wafer attachment member  114  has a size comparable to but slightly larger than that of the wafer  132 . 
     In the example shown in  FIG.  1   , the base structure  118  includes, among other things, an annular member  120 , a contact ring  122 , and a pair of shield structures  124 . The base structure  118  is configured to support the wafer  132  and protect the wafer  132  and the wafer holder assembly  108 . The annular member  120  is an annular structure concentrically around the wafer attachment member  114  and the wafer  132 . The contact ring  122  is attached to the inner surface of the annular member  120 . The contact ring  122  is in contact with the edge of the wafer  132 , therefore, providing the electrical connection between the wafer  132  and a low potential (i.e., causing the wafer to act as a cathode that attracts positive ions) provided by a power supply. In some implementations, the height of the contact ring  122  in the vertical direction is lower than that of the annular member  120 . In some implementations, the height of the contact ring  122  in the vertical direction is comparable to but slightly lower than that of the annular member  120 . In other words, there may be right-angle corners at the intersection area between the annular member  120  and the contact ring  122 . As explained above, plating solution residual  130  may accumulate at those right-angle corners over time and may be hard to clean using conventional approaches. In some embodiments, the base structure may further include an annular plate  126 , and both the annular member  120  and the contact ring  122  are attached to the upper surface of the annular plate  126 . As a result, the stability of the base structure  118  may be increased. 
     In the example shown in  FIG.  1   , the pair of shield structures  124  include a first shield structure  124   a  and a second shield structure  124   b  arranged in an opposite manner. The pair of shield structures  124  are attached to the upper surface of the annular member  120  and extend in the vertical direction. The shield structures  124  are configured to protect the wafer holder assembly  108  and the wafer  132 . Details of the pair of shield structures  124  in accordance with some embodiments will be described below with reference to  FIGS.  3 - 6   . 
     The base structure  118 , the wafer holder assembly  108 , and the wafer  132  there-between can move together in the vertical direction, as denoted as the vertical movement  192  in  FIG.  1   . For instance, during the electroplating process, the base structure  118  and the wafer  132  are immersed in the plating solution  104 . Additionally, the wafer holder assembly  108  can move, relative to the base structure  118 , in the vertical direction, as denoted as the vertical movement  194  in  FIG.  1   . As such, the wafer holder assembly  108  can be separated from the base structure  118  a bit when needed, which is helpful in situations like maintenance. On the other hand, the wafer holder assembly  108 , the wafer  132 , and the base structure  118  can rotate at the same speed, as denoted as the rotational movement  196  in  FIG.  1   . 
       FIG.  2    is a diagram illustrating the example electroplating system  100  shown in  FIG.  1    in a cleaning procedure in accordance with some embodiments. In the example of  FIG.  2   , the wafer  132  of  FIG.  1    has been removed after the electroplating process, and the base structure  118  and the wafer holder assembly  108  have been pulled out of the plating solution  104 , using the vertical movement  192 , for cleaning. During the cleaning procedure, the cleaning nozzle  128  ejects cleaning liquid (e.g., water) toward the base structure  118 , and the wafer holder assembly  108  and the base structure  118  are rotating in the meantime. The combination of the cleaning liquid flow and the centrifugal force resulted from the rotation drives the plating solution residual  130  out of the base structure  118  and the wafer holder assembly  108 . Details of how the pair of shield structures  124  improve the cleaning performance in accordance with some embodiments will be described below with reference to  FIGS.  3 - 6   . 
       FIG.  3    is a diagram illustrating a schematic top view of the base structure  118  of  FIG.  1    in accordance with some embodiments. As shown in  FIG.  3   , the contact ring  122  is attached to the inner surface of the annular member  120 , whereas the first shield structure  124   a  and the second shield structure  124   b  are attached to the upper surface of the annular member  120 . In the example of  FIG.  3   , the first shield structure  124   a  and the second shield structure  124   b  are situated, opposite to each other, at the circumference of the outer surface of the annular member  120 . The openings  134  are designed to make it easier to operate the wafer holder assembly  108  and the wafer  132  without blocking them. It should be noted that the position of the pair of shield structures  124  may be adjusted along the radial direction (i.e., closer to the center of the annular member  120  or farther from the center of the annular member  120 ) in other implementations. Likewise, it should be noted that the size of the openings  134 , relative to the pair of shield structures  124 , may be adjusted in other implementations. It should be noted that, although the example in  FIGS.  1 - 3    is directed to the case of two shield structures  124 , other numbers of shield structures are within the scope of the disclosure. 
     In the example shown in  FIG.  3   , the first shield structure  124   a  and the second shield structure  124   b  have the same structure. The second shield structure  124   b  can be regarded as the first shield structure  124   a  with a 180-degree rotation in the clockwise direction. As such, the description below is directed to one of the first shield structure  124   a  and the second shield structure  124   b  for simplicity. 
     In the example shown in  FIG.  3   , the second shield structure  124   b  includes a curved plate  310   b . The curved plate  310   b  extends in the vertical direction. In some implementations, the curved plate  310   b  is aligned with the outer surface of the annular member  120 , in the top view. In other words, the curved plate  310   b  is a portion of the cylindrical surface of a right circular cylinder. It should be noted that, in other implementations, the curved plate  310   b  may have other geometries as needed, which are also within the scope of the disclosure. 
     The curved plate  310   b  has multiple discharging openings  304 . The discharging openings  304  are configured to discharge the plating solution residual  130  in the cleaning procedure. In the example of  FIG.  3   , there are two discharging openings  304 . In some embodiments, the number of discharging openings  304  is one. In other embodiments, the number of discharging openings  304  is three. In yet other embodiments, the number of discharging openings  304  is between four and six. In still some other examples, the number of discharging openings  304  is more or fewer than the numbers mentioned above. Thus, it will be understood by one skilled in the art that, the number of discharging opening  304  is not specifically limited in the present disclosure. 
     As shown in the enlarged portion of the second shield structure  124   b  in  FIG.  3   , for each discharging opening  304 , there is a corresponding bevel (also referred to as a “slope”)  306 . The bevel  306  begins at an inner surface of the curved plate  310   b  and ends at the corresponding discharging opening  304 . In one implementation, the bevel  306  is a slope, and the bevel  306  is cut in the curved plate  310   b  at an angle θ, in the top view. The angle θ is an angle between the bevel  306  and the tangential surface (denoted in the dashed line in  FIG.  3   ) of the curved plate  310   b . The bevels  306  can guide the plating solution residual  130  toward corresponding discharging openings  304 , therefore, increasing the discharging efficiency of the plating solution residual  130 . It should be noted that the bevel  306  may be a curved surface in other implementations. 
     During a cleaning procedure, the cleaning nozzle  128  ejects cleaning liquid toward the base structure  118 . The liquid flow  302  is schematically illustrated as arrows in  FIG.  3   . The liquid flow  302  may hit the outer surface  116  (as denoted as the dashed circle in  FIG.  3   ) of the wafer holder body  112  (as shown in  FIG.  1   ) and bound back toward the curved plate  310   a  of the first shield structure  124   a . As a result, the liquid flow  302  collectively advances through the gap between the outer surface  116  of the wafer holder body  112  and the first shield structure  124   a.    
     The liquid flow  302  flushes the plating solution residual  130  accumulated in the base structure  118 . The bevels  306  guide the liquid flow  302  toward corresponding discharging openings  130 . As such, the plating solution residual  130  is driven out of the base structure  118  through the bevels  306  and corresponding discharging openings  304 . Without the bevels  306  and the discharging openings  304 , the plating solution residual  130  would have to advance through a long path before it can exit the base structure  118  at the distal end  312   a  of the first shield structure  124   a . As such, the existence of the bevels  306  and corresponding discharging openings  304  significantly increases the discharging efficiency of the plating solution residual  130 . 
     On the other hand, in addition to the liquid flow  302 , the centrifugal force due to the rotation of the base structure  118  also drives the plating solution residual  130  towards the bevels  306  and corresponding discharging openings  304 . The faster the base structure  118  rotates, the larger the centrifugal force is. 
     It should be noted that the number of discharging openings  304  on the shield structure  124   a  may be selected based on the following considerations. If the number of discharging openings  304  is relatively large, it is easier to drive the plating solution residual  130  out of the base structure  118 , but it may consume more cleaning liquid to have enough cleaning liquid that can arrive at the distal end  312   a . If the number of discharging openings  304  is relatively small, it is harder to drive the plating solution residual  130  out of the base structure  118 , but it may consume less cleaning liquid to have enough cleaning liquid that can arrive at the distal end  312   a . Accordingly, the number of discharging openings  304  may be a result of a tradeoff between discharging efficiency and cleaning liquid consumption. Again, in the example of  FIG.  3   , the optimal number of discharging openings  304  is two, though other optimal numbers may be employed in accordance with different parameters of the electroplating system  100  such as the rotation speed, the flow rate coming out of the cleaning nozzle  128 . A method can be employed to determine the optimal number of discharging openings  304  using a trial-and-error approach. An alternative method can be employed to determine the optimal number of discharging openings  304  using simulation tools. 
     Similar considerations mentioned in the previous paragraph can be applied to the choice of the size of the discharging openings  304 , which will not be described in detail again. Generally speaking, the larger the discharging openings  304  are, the higher the discharging efficiency is, at the expense of larger cleaning liquid consumption. 
       FIG.  4 A  is a side view of an example shield structure  124   c  in accordance with some embodiments.  FIG.  4 B  is a top view of the example shield structure  124   c  of  FIG.  4 A  in accordance with some embodiments. It should be noted that the curved place  310  is illustrated as flat for simplicity. As shown in  FIGS.  4 A and  4 B , the discharging openings  304   a  and  304   b  are located in the curved plate  310   c . In the example in  FIGS.  4 A and  4 B , the discharging openings  304   a  and  304   b  are situated at the same height h 2  in the vertical direction. The discharging openings  304   a  and  304   b  have the same width a 1  and the same height h 1 . The bevels  306   a  and  306   b  correspond to the discharging openings  304   a  and  304   b , respectively. The bevels  306   a  and  306   b  have the same height h 1  as those of the discharging openings  304   a  and  304   b . The bevels  305   a  and  306   b  have the same width a 2 . In the example in  FIGS.  4 A and  4 B , a 2  is larger than a 1 . In other examples, a 2  may be smaller than a 1 . In yet other examples, a 2  may be equal to a 1 . 
     In the top view shown in  FIG.  4 B , the angle θ is determined by the width a 2  and the thickness (l 1 −l 2 ), in accordance with the equation tan θ=(l 1 −l 2 )/a 2 . In other words, the angle θ may be adjusted as needed by adjusting one or more of the dimensional parameters a 2 , l 1 , and l 2 . Likewise, the optimal value of the angle θ may be determined using a trial-and-error approach or simulation tools, in view of the tradeoff between discharging efficiency and cleaning liquid consumption. 
     In a non-limiting example, the following set of dimensional parameters of the shield structure  124   c  are determined: a 1  is equal to 7 cm; a 2  ranges from 5 cm to 30 cm; h 2  is equal to 15 cm; h 1  ranges from 5 cm to 20 cm; l 2  is equal to 8 cm; the angle θ ranges from 20 degrees to 50 degrees. 
       FIG.  5    is a top view of an example shield structure  124   d  in accordance with some embodiments. The example shield structure  124   d  is identical to the example shield structure  124   c  except that the shield structure  124   d  includes multiple baffles  330   d  and  330   e  (collectively,  330 ). The baffles  330   d  and  330   e  correspond to discharging openings  304   d  and  304   e , respectively. Each of the baffles  330  has one end attached to the curved plate  310   d  and another end extending outward radially. The angle between the baffle  330   d  and the tangential surface of the curved plate  310   d  is β. The baffle  330   d  may protect the corresponding discharging opening  304   d  by preventing rebounding liquid flow  303  from reentering the discharging opening  304   d . As shown in  FIG.  5   , the liquid flow  302  may rebound at the inner surface  103  of the container  102  and move toward the shield structure  124   d . For instance, the rebounding liquid flow  303  coming out of the discharging opening  304   e  may reenter the shield structure  124   d  through the neighboring discharging opening  304   d  if there is no baffle  330   d . As such, the baffles  330  can prevent cleaning liquid and plating solution residual  130  from reentering the shield structure  124   d  through the discharging openings  304   d  and  304   e , thus increasing discharging efficiency and securing cleaning performance. 
     Likewise, the optimal value of the angle β may be determined using a trial-and-error approach or simulation tools. In one non-limiting example, the angle β ranges from 5 degrees to 45 degrees. 
     According to some experimental data, the usage (e.g., available time) of the electroplating system is increased by 1.1%; applied engineer loading is reduced by 36 hours per month; scrap reduction operations are reduced by two times per year. 
       FIG.  6    is an example method  600  of manufacturing a base structure in an electroplating system in accordance with some embodiments. The method  600  includes operations  602 ,  604 ,  606 ,  608 ,  610 , and  612 . 
     At operation  602 , an annular member (e.g., the annular member  120  in  FIG.  3   ) is provided. At operation  604 , a contact ring (e.g., the contact ring  122  in  FIG.  3   ) is attached to the inner surface of the annular member. The contact ring is capable of being electrically connected to a wafer in a cleaning procedure. At operation  606 , a pair of shield structures (e.g., the shield structures  124   a  and  124   b  in  FIG.  3   ) are attached to an upper surface of the annular member. The pair of shield structures extend in a vertical direction. For each shield structure, at operation  608 , a plurality of discharging openings (e.g., the discharging openings  304  in  FIG.  3   ) is formed in a curved plate (e.g., the curved planes  310   a  and  310   b  in  FIG.  3   ) of each of the shield structures. For each shield structure, at operation  610 , a plurality of bevels (e.g., the bevels  306  in  FIG.  3   ), corresponding to the plurality of discharging openings, respectively, are formed in the curved plate of each of the shield structures. In some embodiments, for each shield structure, at operation  612 , a plurality of baffles (e.g., the baffles  330   d  and  330   e  in  FIG.  5   ), corresponding to the plurality of discharging openings, respectively, to the curved plate of each of the shield structures. 
     It should be noted that the order of the operations in the method  600  is not constrained to that shown in  FIG.  6    or described herein. Several of the operations could occur in a different order without affecting the final result. 
       FIG.  7    is an example method  700  of cleaning the electroplating system of  FIG.  2    in accordance with some embodiments. The method  700  includes operations  702 ,  704 , and  706 . At operation  702 , the wafer (e.g., the wafer  132  in  FIG.  2   ) is removed. At operation  704 , the base structure (e.g., the base structure  118  in  FIG.  2   ) and the wafer holder assembly (e.g., the wafer holder assembly  108  in  FIG.  2   ) are rotated. At operation  706 , cleaning liquid is ejected toward the based structure. In one implementation, the cleaning liquid is ejected by a cleaning nozzle (e.g., the cleaning nozzle  128  in  FIG.  2   ). It should be noted that the order of the operations in the method  600  is not constrained to that shown in  FIG.  6    or described herein. Several of the operations could occur in a different order without affecting the final result. 
     In accordance with some aspects of the disclosure, a base structure in an electroplating system is provided. The base structure includes: an annular member; a contact ring attached to an inner surface of the annular member and configured to be electrically connected to a wafer in an electroplating process; and a pair of shield structures attached to an upper surface of the annular member and extending in an vertical direction. Each of the pair of shield structures includes: a curved plate comprising a plurality of discharging openings, wherein plating solution residual is discharged through the plurality of discharging openings in a cleaning procedure; and a plurality of bevels, each of the plurality of bevels corresponding to each of the plurality of discharging openings and configured to guide the plating solution residual toward the corresponding discharging opening in the cleaning procedure. 
     In accordance with some aspects of the disclosure, a method of manufacturing a base structure in an electroplating system is provided. The method includes the following operations: providing an annular member; attaching a contact ring capable of being electrically connected to a wafer in An electroplating process to an inner surface of the annular member; attaching a pair of shield structures, extending in an vertical direction, to an upper surface of the annular member; forming a plurality of discharging openings in a curved plate of each of the shield structures; and forming a plurality of bevels, corresponding to the plurality of discharging openings, respectively, in the curved plate of each of the shield structures. 
     In accordance with some aspects of the disclosure, an electroplating system is provided. The electroplating system includes: a container; a plating solution in the container; an anode connected to a first electric potential; a wafer holder assembly, capable of rotating and configured to hold a wafer during an electroplating process; and a base structure. The base structure includes: an annular member; a contact ring attached to an inner surface of the annular member and configured to be electrically connected between the wafer and a second electric potential lower than the first electric potential during the electroplating process; and a pair of shield structures attached to an upper surface of the annular member and extending in an vertical direction. Each of the pair of shield structures includes: a curved plate comprising a plurality of discharging openings, wherein plating solution residual is discharged through the plurality of discharging openings in a cleaning procedure; and a plurality of bevels, each of the plurality of bevels corresponding to each of the plurality of discharging openings and configured to guide the plating solution residual toward the corresponding discharging opening in the cleaning procedure. 
     The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure.