Abstract:
A wafer carrier is described. In one embodiment, the wafer carrier includes a variable aperture shield. The wafer carrier may include an electrically conductive wafer plating jig base having a plurality of concentric overlapping cavities of different depths, each cavity configured to receive a semiconductor wafer of a different size, a plurality of concentric magnetic attractors, at least one positioned within each of the plurality of overlapping cavities, and a cover plate comprising an open center surrounded by a support, the cover plate comprising an attractive material positioned within the support adjacent to the open center and aligned with at least one of the magnetic attractors when the cover plate is positioned over the wafer plating jig base.

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. application Ser. No. 13/250,070, filed Sep. 30, 2011, which claims the benefit of U.S. Provisional Application No. 61/494,339 filed Jun. 7, 2011, and claims the benefit of U.S. Provisional Application No. 61/540,238 filed Sep. 28, 2011. This application is also a continuation-in-part of U.S. application Ser. No. 13/631,204, filed Sep. 28, 2012, which claims the benefit of U.S. Provisional Application No. 61/673,115, filed Jul. 18, 2012, the disclosures of which are hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     This disclosure relates to the field of semiconductor device manufacturing and, in particular, to an adjustable wafer plating shield for wafer plating. 
     BACKGROUND 
     Integrated circuits are formed through a process known as semiconductor device fabrication. The semiconductor device may be formed on a thin slice, or wafer, of semiconductor material, such as silicon crystal. The wafer serves as a substrate for microelectronic devices built on the wafer. During fabrication of these integrated circuits, the silicon wafer is put through a sequence of wet chemical processing steps. One wet chemical processing step in the sequence is electrochemical deposition, commonly known as electroplating. 
     In the electroplating process, electrical current is used to deposit metal ions from a solution onto a wafer, forming a film or patterned structure of metal on the wafer. Certain semiconductor packaging technologies, such as Wafer Level Chip Scale Packaging and Flip Chip, involve multiple electroplating steps. A proper size of a shield between the anode and the wafer is critical to achieve plating uniformity across the wafer surface during the electroplating process. 
     Conventionally, a wafer carrier  100  used for wafer plating is illustrated in  FIG. 1 . The wafer carrier cover  100  typically included in a wafer holder for use in a plating bath and fixed size shield  112  mounted onto the wafer holder. The current method of shielding utilizes multiple fixed-size shields  112 . Each of the fixed size shields  112  vary in size and dictate a fixed expose area that exposes a portion of a wafer. Since different sizes of the exposed area affect the plating uniformity, the fixed-size shields  112  have to be swapped during electroplating depending on the plating parameters. Swapping of the multiple fixed-size shields is commonly a manual operation, which is tedious and lengthy. Also, creating such fixed-sized shields is very expensive. Further, locating the right fixed-size shield that matches the plating parameters is prone to error in wafer plating process. 
     SUMMARY 
     An aspect of the disclosure relates to a wafer carrier comprising an electrically conductive wafer plating jig base having a plurality of concentric overlapping cavities of different depths, each cavity configured to receive a semiconductor wafer of a different size, a plurality of concentric magnetic attractors, at least one positioned within each of the plurality of overlapping cavities, and a cover plate comprising an open center surrounded by a support, the cover plate comprising an attractive material positioned within the support adjacent to the open center and aligned with at least one of the magnetic attractors when the cover plate is positioned over the wafer plating jig base. 
     Particular embodiments may comprise one or more of the following. A variable aperture shield coupled to the cover, the variable aperture shield may comprise a plurality of fins forming a variable aperture, the plurality of fins mounted on the wafer plating jig base, wherein at least one of the plurality of fins is configured to move towards or away from a center of the variable aperture to change a diameter of the variable aperture. Movement of the shield may comprise a rotation of at least one of the plurality of the fins. Rotation of the fins may comprise a simultaneous rotation of the plurality of fins. At least one of the plurality of the fins may overlap a fin adjacent to the at least one of the plurality of the fins upon the rotation. Movement of the plurality of fins may comprise a convergence of the plurality of fins towards the center of the variable aperture. Each of the plurality of fins may comprise a pivot point configured to move the fin with respect to the wafer plating jig base. Each of the plurality of fins may comprise a lever point configured to move the fin towards or away from the center of the variable aperture. The cover plate may be configured to move the lever points of the fin. The cover plate may be clamped onto the wafer plating jig base to align a center of the cover plate with a center of the wafer plating jig base upon movement of the cover plate. The plurality of fins may be positioned between the wafer plating jig base and the cover plate. The cover plate may comprise a handle configured to move the cover plate. 
     According to another aspect, a wafer carrier may comprise a variable aperture shield mounted in a semiconductor plating tank. Particular embodiments may comprise one or more of the following. The variable aperture shield may comprise a fixed base plate, and a plurality of fins forming the variable aperture, the plurality of fins mounted on the fixed base plate, wherein at least one of the plurality of fins is configured to move towards or away from a center of the variable aperture to change a diameter of the variable aperture. The movement may comprise a rotation of at least one of the plurality of the fins. The rotation of the fins may comprise a simultaneous rotation of the plurality of fins. At least one of the plurality of the fins may overlap a fin adjacent to the at least one of the plurality of the fins upon the rotation. The movement of the plurality of fins may comprise a convergence of the plurality of fins towards the center of the variable aperture. Each of the plurality of fins may comprise a pivot point configured to move the fin with respect to the fixed base plate. Each of the plurality of fins may comprise a lever point configured to move the fin towards or away from the center of the variable aperture. The variable aperture shield may further comprise a cover plate mounted onto the fixed base plate. The cover plate may be clamped onto the fixed base plate to align a center of the cover plate with a center of the fixed base plate upon movement of the cover plate. The plurality of fins may be positioned between the fixed base plate and the cover plate. The cover plate may be configured to move the lever points of the fin. The cover plate may comprise a handle configured to move the cover plate. 
     An aspect of the disclosure relates to a method comprising mounting a wafer carrier in a plating bath in a plating tank, the wafer carrier comprising a shield having a variable aperture configured to expose an area of a wafer secured therein, and adjusting the variable aperture of the shield to change a size of the exposed area of the wafer. 
     Particular embodiments may comprise one or more of the following. The shield may comprise a fixed base plate and a plurality of fins forming the variable aperture mounted onto the fixed base plate, wherein at least one of the plurality of fins is configured to move towards or away from a center of the variable aperture. The shield may comprise a cover plate mounted onto the fixed base plate, wherein the adjusting comprising moving the cover plate to provide movement to the plurality of fins. The moving may comprise rotating the cover plate and the movement comprises rotation of the fins. The movement of the fins may comprise overlapping of the fins. Placing a handle of the cover plate above the plating bath, and wherein the moving the cover plate comprising moving the handle of the cover plate via a drive mechanism. 
     An aspect of the disclosure comprises a plating tank; and a wafer carrier comprising a variable aperture shield, wherein the wafer carrier is mounted to a side of the plating tank. 
     Aspects and applications of the disclosure presented here are described below in the drawings and detailed description. Unless specifically noted, it is intended that the words and phrases in the specification and the claims be given their plain, ordinary, and accustomed meaning to those of ordinary skill in the applicable arts. The inventors are fully aware that they can be their own lexicographers if desired. The inventors expressly elect, as their own lexicographers, to use only the plain and ordinary meaning of terms in the specification and claims unless they clearly state otherwise and then further, expressly set forth the “special” definition of that term and explain how it differs from the plain and ordinary meaning. Absent such clear statements of intent to apply a “special” definition, it is the inventors&#39; intent and desire that the simple, plain and ordinary meaning to the terms be applied to the interpretation of the specification and claims. 
     The inventors are also aware of the normal precepts of English grammar. Thus, if a noun, term, or phrase is intended to be further characterized, specified, or narrowed in some way, then such noun, term, or phrase will expressly include additional adjectives, descriptive terms, or other modifiers in accordance with the normal precepts of English grammar. Absent the use of such adjectives, descriptive terms, or modifiers, it is the intent that such nouns, terms, or phrases be given their plain, and ordinary English meaning to those skilled in the applicable arts as set forth above. 
     Further, the inventors are fully informed of the standards and application of the special provisions of 35 U.S.C. §112, ¶ 6. Thus, the use of the words “function,” “means” or “step” in the Description , Drawings, or Claims is not intended to somehow indicate a desire to invoke the special provisions of 35 U.S.C. §112, ¶6, to define the invention. To the contrary, if the provisions of 35 U.S.C. §112, ¶6 are sought to be invoked to define the claimed disclosure, the claims will specifically and expressly state the exact phrases “means for” or “step for, and will also recite the word “function” (i.e., will state “means for performing the function of [insert function]”), without also reciting in such phrases any structure, material or act in support of the function. Thus, even when the claims recite a “means for performing the function of . . . ” or “step for performing the function of . . . ,” if the claims also recite any structure, material or acts in support of that means or step, or that perform the recited function, then it is the clear intention of the inventors not to invoke the provisions of 35 U.S.C. §112, ¶6. Moreover, even if the provisions of 35 U.S.C. §112, ¶6 are invoked to define the claimed disclosure, it is intended that the disclosure not be limited only to the specific structure, material or acts that are described in the preferred embodiments, but in addition, include any and all structures, materials or acts that perform the claimed function as described in alternative embodiments or forms of the invention, or that are well known present or later-developed, equivalent structures, material or acts for performing the claimed function. 
     The foregoing and other aspects, features, and advantages will be apparent to those artisans of ordinary skill in the art from the DETAILED DESCRIPTION and DRAWINGS, and from the CLAIMS. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings. 
         FIG. 1  is a diagram illustrating a conventional wafer carrier fixed size shield. 
         FIG. 2A  is a diagram illustrating an embodiment of a wafer carrier shield. 
         FIG. 2B  is a diagram illustrating a variable aperture field of the wafer carrier cover of  FIG. 2A . 
         FIG. 2C  is a diagram illustrating a variable aperture field of the wafer carrier cover of  FIG. 2A . 
         FIG. 2D  is a diagram illustrating a close-up view of a portion of the wafer carrier cover of  FIG. 2B . 
         FIG. 2E  is a diagram illustrating a close-up view of a fin of the wafer carrier cover of  FIG. 2A . 
         FIGS. 3A-3C  are diagrams illustrating positions of fins of an embodiment of a wafer carrier cover. 
         FIG. 4  is a diagram illustrating a system for wafer plating. 
         FIG. 5  is a flow chart illustrating a method for wafer plating. 
         FIGS. 6A and 6B  are diagrams of a wafer carrier having a variable aperture shield at, respectively, a first open position and a second smaller open position. 
         FIGS. 7A and 7B  are diagrams illustrating a variable aperture shield mounted on a plating tank, the variable aperture shield at, respectively, a first open position and a second smaller open position. 
         FIG. 8  is a diagram illustrating a wafer carrier having a variable aperture shield mounted on a plating tank, the variable aperture shield including a fixed base with multiple overlapping fins. 
         FIG. 9  is a diagram illustrating a stack-up of a variable aperture shield to be mounted on a plating tank. 
         FIG. 10A-10E  illustrates five positions of the variable aperture shield to show the change in aperture of the variable aperture shield by actuating the top lever. 
         FIGS. 11A and 11B  illustrate two exposed area opening sizes for a variable aperture shield placed in a plating tank. 
     
    
    
     DETAILED DESCRIPTION 
     The following description sets forth numerous specific details such as examples of specific systems, components, methods, and so forth, in order to provide a good understanding of several embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that at least some embodiments of the present disclosure may be practiced without these specific details. In other instances, well-known components or methods are not described in detail or are presented in simple block diagram format in order to avoid unnecessarily obscuring the present disclosure. Thus, the specific details set forth are merely exemplary. Particular implementations may vary from these exemplary details and still be contemplated to be within the scope of the present disclosure and claims. 
     Embodiments of an apparatus as described for a wafer carrier that provides the ability to perform wafer plating in an automated, low cost and time efficient manner. The wafer carrier allows for a single adjustable mechanism that changes the size of the exposed area of the wafer. In one embodiment, the wafer carrier includes a variable aperture shield. The variable aperture shield provides for a mechanism to change the size of the exposed area of the wafer as desired for wafer plating. 
       FIGS. 2A-2E  illustrate a particular embodiment of a wafer carrier  200 . The wafer carrier  200  includes a variable aperture shield  201 . The variable aperture shield includes a fixed base plate  210 . In one embodiment, the fixed base plate  210  is formed of plastic or other non-conductive material, although in other embodiments, the fixed base plate  210  is formed from other materials such as ceramic or metal. The wafer carrier  200  also includes a plurality of fins  212  mounted onto the fixed base plate  210  forming a variable aperture  211  as shown in  FIG. 2A . The variable aperture  211  provides for the exposed area for wafer plating. The fin  212  operates to move toward or away from a center of the variable aperture  211 . In one embodiment, the fin  212  rotates in a counterclockwise direction  213  towards the center of the variable aperture  211  as illustrated by the line drawing of the fin  212  in  FIG. 2A . In one embodiment, the fins  212  rotate simultaneously with respect to one another. In one embodiment, the fins  212  move rotationally, although in other embodiments, the fins  212  may have other types of motions such as linear, periodic, or circular motions. In one embodiment, the fin  212  is formed from plastic material or other non-conductive material, although in other embodiments, the fin  212  is formed from other materials such as ceramic or metal. The variable aperture field  201  further includes a cover plate  214  secured to the fixed base plate  210  covering the fins  212  mounted on the fixed base plate  210 . The cover plate  214  includes a rear side  214   a  and a front side  214   b . In the configuration illustrated in  FIG. 2A , the rear side  214   a  is mounted to the fixed base plate  210  such that the fins  212  are placed between the fixed based plate  210  and the rear side  214   a  of the cover plate  214 . In an alternate embodiment, the front side  214   b  is mounted to the fixed base plate  210  such that the fins  212  are mounted on the front side  214   b  of the cover plate  214 . 
     In one embodiment, the cover plate  214  is secured to the fixed base plate  210  via clamps  216  as illustrated in  FIG. 2 , although in other embodiments, the cover plate  214  is pressed or clenched to the fixed base plate  210 . The clamps  216  operate as guide rails such that when the cover plate  214  rotates, the center of the cover plate  214  will always align with the center of the fixed base plate  210  as shown in  FIG. 2 . In one embodiment, the cover plate  214  and the clamps are formed from plastic material or other non-conductive material that is not subject to built upon reduction during processing. Although in other embodiments, the cover plate  214  and the clamps  216  are formed from other materials such as ceramic or metal. As illustrated in  FIG. 2C , the cover plate  214  also includes a handle  215  used to rotate the cover plate  214  as will be described in greater detail below. 
       FIG. 2B  illustrates a particular embodiment of a rear side of the cover plate  214  of  FIG. 2C . The handle  215  is moved away from its original position in  FIG. 2C  in a clockwise direction  217  as illustrated by the line drawing of the handle  215  in  FIG. 2B . This movement of the handle  215  causes the cover plate  214  to also rotate in the clockwise direction  217  as illustrated by the line drawing of the cover plate  214 . This rotation of the cover plate  214  in turn pushes the fin  212  to also rotate in the clockwise direction  217  as illustrated by the line drawing of the fin  212  towards the center of the variable aperture  211  as illustrated by the line drawings of the fin  212  in  FIG. 2B . Although not shown, the movement of the handle  215  in the opposite direction will cause the cover plate  214  to rotate the fin  212  away from the center of the variable aperture  211 . Thus, the cover plate  214  operates to push or pull on the fin  212  toward or away from the center of the variable aperture  211 . The embodiment described above provides for a rotational movement, although in other embodiments, other types of movements such as linear, periodic, or circular may be utilized for motion of the handle  215 , the cover plate  214  and the fin  212 .  FIG. 2D  shows a close-up rear view of the cover plate  214 . In one embodiment, pins  218  are placed on the rear side of the cover plate  214  to rotate the fin  212 , although in other embodiments, a bar, notch or gear may be used in place of the pins. When cover plate  214  moves, the pin  218  moves with the cover plate  214  pushing or pulling on the fin  212  resulting in rotation and overlapping of the fins  212 . 
       FIG. 2E  is a diagram illustrating fin  212   a  and fin  212   b  according to an embodiment of the present disclosure. Each of the fin  212   a  and fin  212   b  are mounted onto the fixed base plate  210  at a pivot point or fulcrum  220 . This pivot point or fulcrum  220  allows the fin  212   a  to rotate in a counterclockwise direction  213  with respect to the fixed base plate  210 . The fin  212   a  also include a lever point  222  located at one end of the fin  212   a  as shown in  FIG. 2B . The rotation of the cover plate  214  pushes the lever points  222  of the fin  212   a  that enables fin  212   a  to rotate at its lever point  222 . The rotation of the fin  212   a  causes the fin  212   a  to overlap with an adjacent fin, i.e. fin  212   b . The fin  212   b  also rotates simultaneously with the fin  212   a  in the counterclockwise direction  213  as illustrated in  FIG. 2B . This rotation and overlapping of the fins  212  result in changing diameter of the variable aperture  211  based on the desired sized required of the exposed area for wafer plating as will be described in greater detail below. 
       FIGS. 3A-3C  illustrates the rotation of the fins  212  of the variable aperture shield  201  of the wafer carrier  200  according to a particular embodiment. As shown in  FIG. 3A , fins  212  are positioned at zero degree rotation providing for the variable aperture  211  having a diameter dl large in size desired for placement of a wafer  230 . In  FIG. 3B , a slight rotation of the cover plate  214  (not shown) in a counterclockwise direction  213  in turn slightly rotates the fins  212  in a counterclockwise direction  213 , which causes the fins  212  to overlap one another. This rotation of the fins  212  pushes the fins  212  towards the center of the variable aperture  211  thus reducing the diameter dl of the variable aperture  211  to diameter d 2  as shown in  FIG. 3B . This reduction in the diameter to d 2  provides for a reduced size desired for placement of the wafer  230 . In  FIG. 3C , the fins  212  are further rotated in the counterclockwise direction  213 , which causes further overlapping of the fins  212  and pushing the fins  212  further towards the center of the variable aperture  211 . This further rotation of the fins  212  results in further reduction in the size of the diameter d 2  of the center of the variable aperture  211  to the diameter d 3 . This further reduction in diameter d 3  provides for a further reduced size desired for plating the wafer  230 . The rotation and the overlapping of the fins  212  cause the convergence of the fins  212  toward the center of the variable aperture  211 . In one embodiment, the overlapping of the fins  212  causes the fins  212  to converge to form a circular shield  219  having a diameter although in other embodiments, the shield may have other shapes and sizes tailored to the particular semiconductor wafer being plated. It should not be assumed that the shape of the wafer will always be circular, though that is currently true in a majority of the cases. The values of the d 1 , d 2  and d 3  vary based on the size of the wafer  230 , the shape of the fin  212  and number of fins  212 . In one non-limiting example, the wafer  230  having an approximate size of 300 mm and depending on the shape and number of the fins, the value of diameter dl may range between 260 mm to 300 mm, the value of diameter d 2  may range between 230 mm to 260 mm, and the value of diameter d 3  may range between 200 mm to 230 mm. In another example, a wafer having an approximate size of 200 mm wafer and depending on the shape and number of the fins, the value of diameter dl may range between 160 nm to 200 mm, the value of diameter d 2  may range between 130 mm to 160 mm, and the value of diameter d 3  may range between 100 mm to 130 mm. 
       FIG. 4  illustrates a particular embodiment of a plating system  400 . The system includes a plating bath  410  having a plating solution  412 . The wafer carrier  200  is placed in the plating bath  410  for wafer plating. The fixed base plate  210  of the wafer carrier  200  is affixed to the plating bath  410  prevent any movement of the fixed base plate  210 . The wafer carrier  200  is placed in the plating bath  410  such that the handle  215  of the cover plate  214  will be positioned above the plating bath  410  as shown in  FIG. 4 . The plating system  400  also includes a drive mechanism  414  coupled to the handle  215  of the wafer carrier  200 . In one embodiment, the drive mechanism  414  is an operator manually moving the handle  215 . In another embodiment, the drive mechanism  414  is a machine that operates to provide for automated movement of the handle  215 . As illustrated in  FIG. 4 , the handle  215  is rotated in either the clockwise direction  217  or the counterclockwise direction  213 . The diameter of the variable aperture  211  is based on a rotation of the cover plate  214 , which in turn will have a corresponding handle position. So, the handle  215  is moved to a specific distance based upon the diameter size desired for the variable aperture  211  for placement of the wafer. 
       FIG. 5  is a flow diagram of one embodiment of a method for wafer plating. Hardware, software or combination of these components may be used to perform method  500 . The method  500  starts from block  502  at which a wafer carrier  200  is placed inside the plating bath  410 . At block  504 , the handle  215  of the cover plate  214  of the wafer carrier is positioned above the plating bath  410 . At block  506 , the handle  215  is rotated via the drive mechanism  414 . This rotation of the handle  215  in turn rotates the cover plate  214 , which causes rotations of the fins  212 . 
       FIGS. 6A and 6B  are diagrams illustrating a wafer carrier  600  having a variable aperture shield  602  that includes a fixed base  604  with multiple overlapping fins  606 . In this particular embodiment, multiple overlapping fins  606  are mounted on a fixed base plate  610 . In use, this wafer carrier, holding a semiconductor wafer, may have its exposed area  614  adjusted between a wide opening A 1  in  FIG. 6A  and a smaller opening A 2  in  FIG. 6B  by adjustment of the handle  620 . In particular embodiments, the variable aperture shield  602  will adjust and operate similar to the variable aperture shields described above. The variable aperture shield  602  can be used to change the size of an exposed area  614  of a semiconductor wafer  616 . In particular use, when a semiconductor wafer of a particular size is placed within the wafer carrier  600 , the handle  620  may be adjusted to adapt the exposed area  614  to the particular size of the semiconductor wafer  616  placed in the wafer carrier  600 . This allows the same shield to be used with a plurality of different wafer carriers and wafers. In particular, in  FIG. 6A , the exposed area  614  (with diameter A 1 ) is when the fins  606  are at a zero degree rotation, creating a large exposed area. In  FIG. 6B , the exposed area  614  (with diameter A 2 ) is when the fins are rotated further, resulting in the exposed area  614  being smaller in  FIG. 6B  than the exposed area  614  in  FIG. 6A . The fins  606  can be configured to rotate simultaneously towards or away from the center to change the size of the exposed area  614 . 
     The following embodiments are directed to a variable-aperture shield separate from the wafer carrier that can be mounted in a plating tank adjacent to where a wafer carrier will be placed.  FIGS. 11A and 11B  illustrate an overall perspective view of a wafer plating system according to a particular embodiment. As described further herein, an annular-shaped shield covers the outer region of the wafer to achieve better plating uniformity across the entire wafer surface including near the edges of the semiconductor wafer. The embodiments described herein are directed to a variable aperture shield mechanism that changes the size of the exposed area of the semiconductor wafer. These embodiments may provide benefits or advantages over conventional solutions in that the embodiments provide a single mechanism to replace multiple fixed-size shields as with the previous embodiments described herein. Additionally, and distinct from conventional shields which are formed as part of the wafer carrier, particular embodiments described hereafter are specifically designed for mounting within the plating tank separate from the wafer carrier so that more generic wafer carriers can be used and shielding can be adjusted and determined through the separate adjustable shield mounted more permanently within the plating tank. In this way, particular embodiments disclosed may adjust the exposed area without swapping in and out the multiple fixed-size shields. In some embodiments, automatic adjustment is possible when integrated into a plating machine and the variable aperture shield&#39;s setting can be configured as a product or process recipe parameter to integrate automatic adjustment into the process flow. 
       FIGS. 7A and 7B  are diagrams illustrating a wafer carrier  618  having a variable aperture shield  622  that includes a fixed base  624  with multiple overlapping fins  626 . In this particular embodiment, multiple overlapping fins  626  are mounted on a fixed base plate  630 . In use, this wafer carrier, holding a semiconductor wafer, may have its exposed area  634  adjusted between a wide opening A 1  in  FIG. 7A  and a smaller opening A 2  in  FIG. 7B  by adjustment of the handle  640 . In particular embodiments, the variable aperture shield  622  will adjust and operate similar to the variable aperture shields described above. The variable aperture shield  622  can be used to change the size of an exposed area  634  of a semiconductor wafer  636 . In particular use, when a semincoductor wafer of a particular size is placed within the wafer carrier  618 , the handle  640  may be adjusted to adapt the exposed area  634  to the particular size of the semiconductor wafer  636  placed in the wafer carrier  618 . This allows the same shield to be used with a plurality of different wafer carriers and wafers. In particular, in  FIG. 7A , the exposed area  634  (with diameter A 1 ) is when the fins  626  are at a zero degree rotation, creating a large exposed area. In  FIG. 7B , the exposed area  634  (with diameter A 2 ) is when the fins are rotated further, resulting in the exposed area  634  being smaller in  FIG. 7B  than the exposed area  634  in  FIG. 7A . The fins  626  can be configured to rotate simultaneously towards or away from the center to change the size of the exposed area  634 . The handle  640  may be moved between positions using a pneumatic actuator. 
     In a particular embodiment with a pneumatic actuator or pneumatic cylinder, the variable shield aperture shield  622  may be made up of CPVC material. The actuation may be performed using a pneumatically actuated cylinder attached to a top handle  640 . The top lever  640  is above a plating solution in the plating tank so that the actuation is done above the plating solution. The position of the top lever  640  determines the size of the cathode shield of the variable shield aperture.  FIG. 7A  illustrates the top handle  640  in a first position and  FIG. 7B  illustrates the top handle  640  in a second position. It should be noted that, by increasing the number of fins of the variable aperture shield  622 , the inside diameter of the shield  634  could be continuously adjustable between an upper and lower limit. Additional fins may help to approximate a circular shape at intermediate values of inside diameters. 
       FIG. 8  is a diagram illustrating a wafer carrier  700  having a variable aperture shield  702  mounted on a plating tank  712 , the variable aperture shield  702  including a fixed base  710  with multiple overlapping fins  706 , according to another embodiment. The variable aperture shield  702  is similar to the variable aperture shield  602  and  622 , but includes a pivot point (also referred to a fulcrum)  720  for each fin  706 . The convergence of the fins  706  forms the exposed area of the shield  702 . Each fin  706  has a pivot point  720  that allows the fin  706  to rotate. In particular, each fin  706  is moved at is lever point  718  to rotate towards or away from the center of the variable aperture shield  702 . 
       FIG. 9  is an exploded view diagram illustrating a stack-up of a variable aperture shield  802  to be mounted on a plating tank according to another embodiment. In this embodiment, the fins  806  are mounted on a fixed base plate  810  at their respective pivot points or fulcrums  820 . A cover plate  822  moves the pivot points  820  of the fins  806  so that when the cover plate  822  rotates (by manually or automatically moving a handle of the cover plate  822 ), the fins  806  simultaneously rotate with the cover plate  822 . The cover plate  822  is clamped to the base plate  810  so that when the cover plate  822  rotates, the cover plate  822  aligns with the center of the base plate  810 . In a further embodiment, spacers  818  may be disposed between the base plate  810  and the cover plate  822  to maintain the cover plate  822  in a designated position. The variable aperture shield  802  can be mounted to a plating tank as described in more detail below with respect to  FIGS. 11A and 11B . 
       FIG. 10A-10E  illustrates five positions of a variable aperture shield  1000  to show the change in aperture of the variable aperture shield  1000  by actuating the top lever  1002  according to one embodiment.  FIG. 10A  illustrates the top lever  1002  in a first position  1004 .  FIG. 10B  illustrates the top lever  1002  in a second position  1006 .  FIG. 10C  illustrates the top lever  1002  in a third position  1008 .  FIG. 10D  illustrates the top lever  1002  in a fourth position  1010 .  FIG. 10E  illustrates the top lever  1002  in a fourth position  1012 . 
       FIGS. 11A and 11B  illustrate a variable aperture shield  1101  placed in a plating tank  1122  according to one embodiment. In this embodiment, the variable aperture shield  1100  is placed in a plating bath comprising plating solution by mounting the variable aperture shield  1100  to structure on or within the plating tank through brackets  1124 . In one embodiment, the variable aperture shield&#39;s  1100  base plate is mounted to the plating tank so that the variable aperture shield  1100  does not move during the plating process. In operation, a wafer  1116  is held by a wafer plating jig  1118 , such as that shown and described in co-pending U.S. patent application Ser. 13/631,204 titled “Magnetically Sealed Wafer Plating Jig System and Method,” filed Sep. 28, 2012, the disclosure of which is incorporated in its entirety herein by this reference. An anode  1104  is placed within the tank on a side of the variable aperture shield  1100  opposite the wafer  1116 . The semiconductor wafer  1116  is held in the wafer plating jig  1118  in front of the plating anode  1104  with one or more plating shields  1100  (variable aperture),  1106  (fixed aperture) between the anode  1104  and the semiconductor wafer  1116 . The handle  1102  of the variable aperture shield  1100  is above the plating solution (not shown). To rotate the fins  1126  to cover a portion of the aperture  120  through the variable aperture shield  1100 , the operator or a machine moves the handle  1102 . The wafer plating jig  1118  is coupled electrically to a control system (not shown) providing the appropriate negative charge to the wafer plating jig  1118  for the plating process through a connector. For this embodiment, the semiconductor wafer  1116  is exposed to an electric current through the plating solution from the anode  1104  through both the variable aperture plating shield  1100  and a fixed aperture plating shield  1106 . The plating process generally is known to those of ordinary skill in the art. 
     During a lot start of the plating process, the desired size of the exposed area is defined as a parameter of the product and process. The desired size corresponds to a rotation of the cover plate, which in turn corresponds to a handle position. When integrated to the machine, the variable aperture shield  1100  makes it possible to automate the process of changing the shield size as triggered by the machine recipe. This will significantly reduce potential plating errors due to wrong shield size. 
     Although the operations of the methods herein are shown and described in a particular order, the order of the operations of each method may be altered so that certain operations may be performed in an inverse order or so that certain operation may be performed, at least in part, concurrently with other operations. In another embodiment, instructions or sub-operations of distinct operations may be in an intermittent and/or alternating manner. 
     The particular features, structures or characteristics described herein may be combined as suitable in one or more embodiments. In addition, while the disclosure has been described in terms of several embodiments, those skilled in the art will recognize that the disclosure is not limited to the embodiments described. The embodiments can be practiced with modification and alteration within the scope of the appended claims. The specification and the drawings are thus to be regarded as illustrative instead of limiting on the disclosure or any particular embodiment.