Patent Publication Number: US-2023143667-A1

Title: Substrate storage racks for semiconductor processing systems

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application Ser. No. 63/276,918 filed Nov. 8, 2021 titled SUBSTRATE STORAGE RACKS FOR SEMICONDUCTOR PROCESSING SYSTEMS, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF INVENTION 
     The present disclosure generally relates to fabricating semiconductor devices, and more particularly, to storing substrates during the fabrication of semiconductor devices, such as within semiconductor processing systems employed to deposit films onto substrates. 
     BACKGROUND OF THE DISCLOSURE 
     Semiconductor processing systems may include one or more process chambers that are adapted to carry out any number of processes, such as degassing, cleaning or pre-cleaning, deposition such as chemical vapor deposition (CVD), physical vapor deposition (PVD), or atomic layer deposition (ALD), coating, oxidation, nitration, etching (e.g., plasma etch), or the like. One or more load lock chambers may be provided to enable entry and exit of substrates from a factory interface. Each of these process chambers and load lock chambers may be included in a cluster tool, where a plurality of process chambers may be distributed about a transfer chamber, for example. A front-end transfer robot may be housed within the factory interface to transport a substrate (e.g., a silicon wafer, glass plate, or the like) between the factory interface and the load lock, and a back-end transfer robot may be housed within the transfer chamber to transport the substrate between the load lock and one or more of the process modules. Transport of the substrate may be accomplished by one or more end effectors (e.g., clamps or blades) carried by the front-end transfer robot and the back-end transfer robot, and position of the substrate within the process module may be according to a substrate centering sensor within the transfer chamber. 
     During processing, the front-end transfer robot retrieves substrates from a pod and transports the substrates through the factory interface to the load lock. From the load lock, substrates are transported through the transfer module by the back-end transfer robot to the process module, wherein the substrates are and processed according to the requirements of the particular semiconductor device being fabricated. Once processing is complete the substrates are retrieved from the process module by the transfer robot and again transported through the transfer module to the load lock. From the load lock, the processed substrates are transported by the front-end robot through the factory interface to pod, and thereafter removed from the semiconductor processing system to undergo further processing. 
     In some semiconductor processing systems, storage racks may be provided within the one or more of the factory interface, the load lock, and the transfer chamber to store substrates before and/or after processing. The storage racks may facilitate fabrication of semiconductor devices, for example, by providing storage space within the environment of the semiconductor processing system in proximity to resources that could otherwise constrain system throughput. Such storage racks are typically include slotted rails milled from monolithic blocks of substrate-friendly materials, such as quartz or polyether ether ketone (PEEK), and suspended from backing plates for structural support. While generally acceptable for their intended purpose, the tolerances and machining time required to mill slots into such materials adds complexity and cost to the storage rack and the backing plates required to support quartz or PEEK slotted rails can interrupt the otherwise laminar airflow otherwise present within the internal environment of the semiconductor processing system. 
     Such methods and systems have generally been considered suitable for their intended purpose. However, there remains a need in the art for improved substrate storage racks, semiconductor processing systems having storage racks, and methods of making storage racks for semiconductor processing systems. The present disclosure provides a solution to this need. 
     SUMMARY OF THE DISCLOSURE 
     A substrate storage rack is provided. A substrate storage rack for a semiconductor processing system includes a bottom plate, a top plate, and a column assembly. The top plate is spaced apart from the bottom plate, the column assembly connects the top plate to the bottom plate, and a ball member is compressively seated within the column assembly. The ball member protrudes from the column assembly in a direction toward the top plate to support a substrate within the substrate storage rack and on the ball member. 
     In addition to one or more of the features described above, or as an alternative, further examples of the substrate storage rack may include that the ball member is formed from a ceramic material. The ball member may have a diameter that is about 4 millimeters. 
     In addition to one or more of the features described above, or as an alternative, further examples of the substrate storage rack may include that the column assembly is a first column assembly and that the substrate storage rack includes one or more second column assembly. The one or more second column assembly may connect the top plate to the bottom plate. The one or more second column assembly may be spaced apart from the first column assembly by between about 100 millimeters and about 300 millimeters. A shroud member may enclose each of the bottom plate, the top plate, the first column assembly, and the one or more second column assembly. 
     In addition to one or more of the features described above, or as an alternative, further examples of the substrate storage rack may include that the column assembly has a column member and a clamp member. The column member may have a column portion extending longitudinally between the base plate the and top plate and a seating portion extending laterally from the column portion. The clamp member may have a base portion extending longitudinally along the column portion of the column member and a clamping portion extending laterally from the base portion of the clamp member. The clamping portion of the clamp member may compressively fix the ball member against the seating portion and within a pocket defined between the seating portion of the column member and the clamping portion of the clamp member. 
     In addition to one or more of the features described above, or as an alternative, further examples of the substrate storage rack may include at least one of the seating portion of the column member and the clamping portion of the clamp member define a longitudinal slot with a rounded segment and a neck segment extending from the rounded segment. The rounded segment may have a diameter that is smaller than a diameter of the ball member. The ball member may be fixed within the rounded segment of the longitudinal slot. 
     In addition to one or more of the features described above, or as an alternative, further examples of the substrate storage rack may include that the seating portion of column member defines the longitudinal slot. 
     In addition to one or more of the features described above, or as an alternative, further examples of the substrate storage rack may include that the longitudinal slot is a first longitudinal slot defined by the seating portion of the column member, that the clamping portion of the clamp member defines a second longitudinal, and that the ball member is further fixed within the second longitudinal slot. 
     In addition to one or more of the features described above, or as an alternative, further examples of the substrate storage rack may include a spacer member. The spacer member may couple the clamp member to the column member. The spacer member may have a thickness, the ball member may have a diameter, and the thickness of the spacer member may be smaller than the diameter of the ball member. 
     In addition to one or more of the features described above, or as an alternative, further examples of the substrate storage rack may include that the column portion is a first column portion and the that the column member has a second column portion. The second column portion may extend in parallel with the first column portion. The second column portion may be connected to the first column member by the seating portion of the column member. 
     In addition to one or more of the features described above, or as an alternative, further examples of the substrate storage rack may include that the seating portion is a first seating portion and that the column member has one or more second seating portion. The one or more second seating portion may extend laterally from the column portion of the column member. The one or more second seating portion may be longitudinally spaced apart from the first seating portion along a longitudinal length of the column portion of the column member. 
     In addition to one or more of the features described above, or as an alternative, further examples of the substrate storage rack may include that the clamping portion of the clamp member is a first clamping portion and the clamp member has one or more second clamping portion. The one or more second clamping portion may be longitudinally spaced apart from the first clamping portion along a longitudinal length of the column portion of the column member. 
     In addition to one or more of the features described above, or as an alternative, further examples of the substrate storage rack may include that the clamp member is a first clamp member and that the column assembly includes one or more second clamp member. The one or more second clamp member may be connected to the column portion of the column member. The one or more second clamp member may be arranged longitudinally between the first clamp member and the top plate of the substrate storage rack. 
     In addition to one or more of the features described above, or as an alternative, further examples of the substrate storage rack may include that the ball member is a first ball member and that the column assembly includes one or more second ball member. The second ball member may be compressively seated within the column assembly. The one or more second ball member may protrude from the column assembly in a direction toward the top plate of the substrate storage rack. The one or more second ball member may be longitudinally spaced apart from the first ball member along a longitudinal length of the column portion of the column member. 
     In addition to one or more of the features described above, or as an alternative, further examples of the substrate storage rack may include that the column assembly includes a column member sheet body having column member sheet thickness and a clamp member sheet body having a clamp member sheet thickness. The column member sheet thickness of the column member sheet body may be greater than the clamp member sheet thickness of the clamp member sheet body. 
     In addition to one or more of the features described above, or as an alternative, further examples of the substrate storage rack may include that the column member sheet thickness is between about 1 millimeters and about 10 millimeters, and that the clamp member sheet thickness is between about 1 millimeter and about 10 millimeters. 
     A pod, e.g., front opening unified pod (FOUP), is provided. The pod includes an enclosure and a substrate storage rack as described above. The enclosure is arranged to be seated on a load port of a semiconductor processing system. The substrate storage rack is arranged within an interior of the enclosure. 
     A semiconductor processing system is provided. The semiconductor processing system includes a front-end module with a front-end transfer robot, a back-end module with a back-end transfer robot connected to the front-end module, a process module with heater or susceptor connected to the back-end module, and a substrate storage rack as described above. The substrate storage rack is arranged within a movement range of at least one of the front-end transfer robot and the back-end transfer robot. In certain examples, the substrate storage rack may be fixed relative to the front-end module. In accordance with certain examples, the substrate storage rack may be movable relative to the front-end module. It is also contemplated that the substrate storage rack may be movable relative to the semiconductor processing system, such as using an automated material handling system. 
     In addition to one or more of the features described above, or as an alternative, further examples of the semiconductor processing system may include that the front-end module comprises a notch aligner, and that the substrate storage rack is arranged above the notch aligner and within the front-end module. 
     In addition to one or more of the features described above, or as an alternative, further examples of the semiconductor processing system may include that the semiconductor processing system includes a load lock, and that the substrate storage rack is arranged within the load lock. 
     A method of making a substrate storage rack is provided. The method includes forming a column member with a column member and a seating portion using a column member sheet body, the seating member extending laterally from the column portion of the column member. A clamp member with a base portion and a clamping portion extending laterally from the base portion is formed using a clamp member sheet body. A ball member is seated on the seating portion of the column member, the clamp member is registered to the column member using the ball member, and the ball member is compressed between the seating portion of the column member and clamping portion of the clamp member. The ball member is fixed in compression between the seating portion of the column member and the clamping portion of the clamp member by fastening the base portion of the clamp member to the column portion of the column member. 
     This summary is provided to introduce a selection of concepts in a simplified form. These concepts are described in further detail in the detailed description of examples of the disclosure below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       These and other features, aspects, and advantages of the invention disclosed herein are described below with reference to the drawings of certain embodiments, which are intended to illustrate and not to limit the invention. 
         FIG.  1    is a schematic view of a semiconductor processing system with a substrate storage rack in accordance with the present disclosure, showing the substrate storage rack arranged above a notch aligner and within a front-end module chamber of the semiconductor processing system; 
         FIG.  2    is a perspective view of the substrate storage rack of  FIG.  1    according to a first example, showing column assemblies connecting a top plate to a bottom plate within shroud to support substrates within slots defined by the column assemblies on ball members fixed within the column assembly; 
         FIG.  3    is a perspective view of a portion of the substrate storage rack of  FIG.  1    according to the first example, showing ball members fixed between seating portions of a column member and clamping portions of clamp members by radial clamping forces to support substrates on the column assembly; 
         FIG.  4    is an exploded view of a portion of the substrate storage rack of  FIG.  1    according to the first example, showing three clamp members and ball members exploded away from the column member of the column assembly; 
         FIGS.  5 - 9    are plan and perspective views of components the substrate assembly of  FIG.  1    according to the first example, showing the ball member, the column member subsequent to stamping and subsequent to bending during fabrication, and the clamp member subsequent to stamping and subsequent to bending during fabrication; 
         FIG.  10    is a perspective view of the substrate storage rack of  FIG.  1    according to a second example, showing column assemblies connecting a top plate to a bottom plate within shroud to support substrates within slots defined by the column assemblies on ball members fixed within the column assembly; 
         FIG.  11    is a perspective view of a portion of the substrate storage rack of  FIG.  1    according to the second example, showing ball members fixed between seating portions of a column member and clamping portions of a clamp member by tangential clamping forces to support substrates on the column assembly; 
         FIG.  12    is an exploded view of a portion of the substrate storage rack of  FIG.  1    according to the first example, showing the clamp member, ball members, and a spacer member exploded away from the column member of the column assembly; 
         FIGS.  13 - 15    are plan views of components of the substrate storage assembly of  FIG.  1    according to the second example, showing the clamp member, the spacer member, and the column member subsequent to stamping each member; and 
         FIG.  16    is a block diagram of a method making a substrate storage rack in accordance with the present disclosure, showing operations according to an illustrative and non-limiting example of the method. 
     
    
    
     It will be appreciated that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the relative size of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of illustrated embodiments of the present disclosure. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Reference will now be made to the drawings wherein like reference numerals identify similar structural features or aspects of the subject disclosure. For purposes of explanation and illustration, and not limitation, a partial view of an example of a substrate storage rack in accordance with the present disclosure is shown in  FIG.  1    and is designated generally by reference character  100 . Other examples of substrate storage racks, semiconductor processing systems, and methods of making substrate storage racks, or aspects thereof, are provided in  FIGS.  2 - 16   , as will be described. The substrate storage racks of the present disclosure may be used to store substrates during the fabrication of semiconductor devices, such as proximate to notch aligners or load locks in cluster-type semiconductor processing systems employed to deposit films onto substrates, though the present disclosure is not limited to any particular location or to semiconductor processing systems employed to deposit films onto substrates in general. 
     As used herein, a “substrate” refers to any material having a surface onto which material can be deposited. A substrate may include a bulk material such as silicon (e.g., single crystal silicon) or may include one or more layers overlaying the bulk material. Further, a substrate may include various topologies, such as trenches, vias, lines, and the like formed within or on at least a portion of a layer of the substrate. A substrate may include silicon wafer, such as a 200-millimeter silicon wafer, a 300-millimeter silicon wafer, or even a 450-millimeter silicon wafer. 
     Referring to  FIG.  1   , a semiconductor processing system  10  is shown. The semiconductor processing system  10  includes a front-end module  12 , a back-end module  14 , and a process module  16 . The front-end module  12  includes a load port  18 , a front-end enclosure  20 , a front-end gate valve  22 , a load lock  24 , and the substrate storage rack  100 . The load port  18  is configured to seat thereon a pod  26 , e.g., a front-opening unified pod (FOUP) containing a substrate  2 , to move substrates to and from the semiconductor processing system  10 . The front-end enclosure  20  is connected to the load port  18  and houses a front-end transfer robot  28 , a notch aligner  30 , and the substrate storage rack  100 . The front-end transfer robot  28  is supported for movement within the front-end enclosure  20 , has a movement envelope including the substrate storage rack  100 , and is configured to transport substrates, e.g., the substrate  2 , between the load port  18  and the load lock  24  using the substrate storage rack  100 . The notch aligner  30  is supported within the front-end enclosure  20  and is configured to notch-align substrates; e.g., imparting one or more of a predetermined x-shift, y-shift, and rotation in the substrate; within the front-end enclosure  20 . The front-end gate valve  22  is connected to the front-end enclosure  20 , couples the front-end enclosure  20  to the load lock  24 , and is configured to provide selective communication between the front-end enclosure  20  and the load lock  24 . The load lock  24  is connected to the front-end gate valve  22 , and therethrough to the front-end enclosure  20 , and may include a chill plate  32  and/or a park station. Although shown and described herein as having three (3) load ports and two (2) load locks, it is to be understood and appreciated that the semiconductor processing system  10  may have fewer or additional load ports and load locks and remain within the scope of the present disclosure. 
     The back-end module  14  is connected to the front-end module  12  and includes the back-end transfer robot  34 , a back-end gate valve  36 , and a back-end chamber  38 . The back-end gate valve  36  is connected to the load lock  24  and is configured to provide selective communication between the load lock  24  and the back-end chamber  38 . The back-end chamber  38  is connected to the back-end gate valve  36  and houses the back-end transfer robot  34 . The back-end transfer robot  34  is supported within the back-end chamber  38  for movement relative to the load lock  24 , has a movement envelope encompassing both the load lock  24  and the process module  16 , and is configured to transport substrates, e.g., the substrate  2 , between the load lock  24  and the process module  16 . Although shown and described herein as having a singular back-end module, it is to be understood and appreciated that the semiconductor processing system  10  may have more than one back-end module and remain within the scope of the present disclosure. 
     The process module  16  includes a process module gate valve  40 , a reaction chamber  42 , and a susceptor or heater  44 . The process module gate valve  40  is connected to the back-end module  14 , couples the back-end chamber  38  to the reaction chamber  42 , and is configured to provide selective communication between the back-end module  14  and the process module  16 . The reaction chamber  42  is connected to the back-end chamber  38  and houses the susceptor or heater  44 . The susceptor or heater  44  is supported within the reaction chamber  42  and is configured to support substrates, e.g., the substrate  2 , during processing of the substrates. In certain examples the susceptor or heater  44  may be configured to support the substrate  2  during deposition of a film onto the substrate  2 . In accordance with certain examples, the susceptor of heater  44  may be configured to support the substrate  2  during removal of a film from the surface of the substrate  2 . Although shown and described herein in the context of a semiconductor processing system configured for depositing films onto substrates, it is to be understood and appreciated that semiconductor processing systems configured for performing other processing operations may also benefit from the present disclosure. Further, it is to be understood and appreciated that semiconductor processing systems having fewer or additional process modules, as well as process modules including more than one reaction chamber, may also benefit from the present disclosure. 
     In certain examples, the substrate storage rack  100  may be supported within the front-end module  12  and/or within a movement range  50  of the front-end transfer robot  28 . In this respect the substrate storage rack  100  may be supported within the front-end enclosure  20  and above the notch aligner  30 . So positioned, the substrate storage rack  100  enables staging substrates in proximity to the notch aligner  30 , improving throughput in processes where notch alignment could otherwise constrain throughput. Alternatively (or additionally), the substrate storage rack  100  may be supported within the load lock  24 , for example and above the chill plate  32 . Positioning the substrate storage rack  100  within the load lock  24  enables staging substrates in proximity to the chill plate  32 , improving throughput in processes where substrate cooling could otherwise constrain throughput. It is also contemplated that, in accordance with certain examples, the substrate storage rack  100  may be arranged within an interior  46  of an enclosure  48  employed to transfer substrates to and from the semiconductor processing system  10 , e.g., the pod  26 . As will be appreciated by those of skill in the art in view of the present disclosure, this can limit particle generation due to the point support regime employed within the substrate storage rack  100 . 
     With reference to  FIG.  2   , the substrate storage rack  100  is shown. The substrate storage rack  100  includes a base plate  102 , a bottom plate  104 , a top plate  106 , and a shroud  108 . The substrate storage rack  100  also includes a column assembly  110  defining one or more slot  112  configured to seat a substrate, e.g., the substrate  2 , within the one or more slot  112 . In illustrated example the column assembly  110  is first column assembly  110  and the substrate storage rack  100  includes a second column assembly  114  and a third column assembly  116 . The second column assembly  114  is similar to the first column assembly  110 , extends in parallel with the first column assembly  110 , and is offset from the first column assembly  110 . The third column assembly  116  is also similar to the first column assembly  110 , further extends in parallel with the first column assembly  110  and is further offset from both the first column assembly  110  and the second column assembly  114 . In certain examples, the second column assembly  114  may be separated from the first column assembly  110  by less than about 300 millimeters. In accordance with certain examples, one or more of the second column assembly  114  and the third column assembly  116  is offset from the first column assembly  110  by about 90 degrees from a center of the substrate  2 . Although shown and described herein area having three column assemblies, it is to be understood and appreciated that the substrate storage rack  100  may have fewer or additional column assemblies and remain within the scope of the present disclosure. 
     The base plate  102  includes a base plate body  118 . The base plate body  118  may be formed from a metallic material  120 , has a base plate fastener pattern  122 , and defines a base plate aperture  124 . The metallic material  120  may include an aluminum-containing or stainless-steel material, such as 4040 aluminum or 304 stainless steel, which simplifies fabrication of the substrate storage rack  100  by eliminating the need to coat or paint the substrate storage rack  100 . The base plate fastener pattern  122  is configured to both connect the substrate storage rack  100  to the semiconductor processing system  10  (shown in  FIG.  1   ) and the bottom plate  104  to the base plate body  118 . The base plate aperture  124  extends through the base plate body  118 , couples upper surface of the base plate body  118  to the a lower surface of the base plate body  118 , and is configured to provide fluid communication between an interior  126  of the substrate storage rack  100  and interior of the semiconductor processing system  10 . In the illustrated example the base plate  102  is configured to support the substrate storage rack  100  within the front-end enclosure  20  of the front-end module  12  at a location above the notch aligner  30  (shown in  FIG.  1   ). As will be appreciated by those of skill in the art in view of the present disclosure, support of the substrate storage rack  100  in proximity to the notch aligner  30  provides capability to store substrates, e.g., the substrate  2 , in proximity to the notch aligner  30 , limiting the tendency of the notch aligner  30  to constrain throughput in processes that require rotationally aligning substrates prior to transporting substrates to the process module  16 . 
     The bottom plate  104  includes a bottom plate body  128 . The bottom plate body  128  may be formed from a metallic material  130 , has a bottom plate fastener pattern  132 , and defines a bottom plate aperture  134 . The metallic material  130  may include an aluminum-containing or stainless-steel material such as 4040 aluminum or 304 stainless steel. The bottom plate fastener pattern  132  connects each of first column assembly  110 , the second column assembly  114 , and the third column assembly  116  to the bottom plate body  128 . The bottom plate aperture  134  overlaps the base plate aperture  124  and fluidly couples the interior  126  of the substrate storage rack  100  to the base plate aperture  124 . 
     The top plate  106  includes a top plate body  136 . The top plate body  136  may formed from a metallic material  138 , has a top plate fastener pattern  140 , and defines a top plate aperture  142 . The metallic material  138  may include an aluminum-containing or stainless-steel material such as 4040 aluminum or 304 stainless steel. The top plate fastener pattern  140  connects the top plate body  136  to each of the first column assembly  110 , the second column assembly  114 , and the third column assembly  116 , and therethrough to the bottom plate  104 . The top plate aperture  142  is fluidly coupled to the interior  126  of the substrate storage rack  100 , and therethrough to the bottom plate aperture  134 . 
     The shroud  108  includes a shroud body  144 . The shroud body  144  may be formed from a metallic material  146 , bounds the interior  126  of the substrate storage rack  100 , and has an inlet  148  and an outlet  150 . The metallic material  146  may include an aluminum-containing or stainless-steel material such as 4040 aluminum or 304 stainless steel. The inlet  148  is separated from the second column assembly  114  and the third column assembly  116  by the first column assembly  110 . The outlet  150  is separated from the first column assembly  110  by the second column assembly  114  and the third column assembly  116 . It contemplated that the inlet  148  be fluidly coupled to a fan-filter unit supported within an upper recess of the front-end module  12 , that the outlet  150  be fluidly coupled to an interior of the front-end enclosure  20 , and that shroud  108  be configured to flow filtered air from the inlet  148  to the outlet  150  and across a substrate, e.g., the substrate  2  (shown in  FIG.  1   ), seated within the one or more slot  112  while stored within the substrate storage rack  100 . 
     With reference to  FIG.  3   , the first column assembly  110  includes a column member  152 , a clamp member  154 , and a ball member  156 . The column member  152  includes a column member sheet body  158  (shown in  FIG.  5   ) having a column portion  160  and a seating portion  162  (shown in  FIG.  5   ). The column member sheet body  158  may be formed from metallic sheet material  164  (shown in  FIG.  5   ) such as 4040 aluminum or 304 stainless steel and has a thickness  166  (shown in  FIG.  6   ). The thickness  166  may be between about 1 millimeter and about 10 millimeters, or between about 2 millimeters about 8 millimeters, or even between about 3 millimeters and about 6 millimeters. In certain examples, the thickness  166  may be about 2 millimeters. As will be appreciated by those of skill in the art in view of the present disclosure, thicknesses within these ranges allow the column member  152  to be formed from planar sheet stock using a stamping and succeeding bending operation. This simplifies fabrication of the column assembly  110  as it eliminates the need to machine slots into quartz or polyether ether ketone (PEEK) bar stock material, and thereafter support the slotted body on a structural member, simplifying fabrication of the substrate storage rack  100  (shown in  FIG.  1   ). 
     With reference to  FIG.  4   , the column portion  160  of the column member  152  defines a column member axis  168  and has bottom fastener tab  170 , a top fastener tab  172 , and one or more fastener aperture  174 . The bottom fastener tab  170  extends laterally from the column portion  160  and is configured to connect the column member  152  to the bottom plate  104  using the bottom plate fastener pattern  132 . The top fastener tab  172  extends laterally from the column portion  160  at an end opposite the bottom fastener tab  170  and is configured to connect the column member  152  to the top plate  106  using the top plate fastener pattern  140 . The one or more fastener aperture  174  extends through the column portion  160  at a location longitudinally between the bottom fastener tab  170  and the top fastener tab  172  and is configured to couple the clamp member  154  to the column member  152 . 
     In certain examples, the column portion  160  of the column member  152  may define a plurality of fastener apertures  174  extending through the column member sheet body  158 . In such examples, the plurality of fastener apertures  174  may connect a singular clamp member  154  to the column member  152 , increasing stiffness of the column assembly  110 . In accordance with certain examples, the clamp member  154  may be a first clamp member  154  and the plurality of fastener apertures  174  may connect at one second clamp member  176  to the column member  152 , increasing the number of substrates that may be stored in the substrate storage rack  100 . It is contemplated that one or more of the top fastener tab  172  and the bottom fastener tab  170  may be portions of the column member  152 , such as formed using a pressing or bending application, such as with a press brake. It is also contemplated that one or more of the top fastener tab  172  and the bottom fastener tab  170  may be fastened to the column member  152 . As will be appreciated by those of skill in the art in view of the present disclosure, employment of fastened tabs can simplify fabrication of the column assembly  110  by limiting (or eliminating) the tolerance consequences of forming either (or both) the top fastener tab  172  and or the bottom fastener tab  170  using a pressing or bending operation. 
     With reference to  FIGS.  5  and  6   , the column portion  160  may be a first column portion  160  and the column member  152  may have a second column portion  178 . In such examples the second column portion  178  may be similar to the first column portion  160  and is additionally arranged on a side of the column member axis  168  opposite the first column portion  160 . It is contemplated that second column portion  178  be connected to the first column portion  160  by the seating portion  162 . The seating portion  162  may have a first lateral segment  180  extending laterally from the first column portion  160  of the column member  152 , a second lateral segment  182  extending laterally from the second column portion  178  of the column member  152 , and an arcuate segment  184  spanning the column member axis  168  and connecting the first lateral segment  180  to the second lateral segment  182 . 
     It is contemplated that the ball member  156  (shown in  FIG.  3   ) be seated on the seating portion  162  of the column member  152 . In this respect the clamp member  154  and the seating portion  162  of the column member  152  define a pocket  186  between one another, the ball member  156  is at least partially captive within the pocket  186 , and a protruding portion  196  of the ball member  156  protrudes from the pocket  186 . In further respect, the seating portion  162  of the clamp member  154  (shown in  FIG.  3   ) may laterally overlay both the ball member  156  and the arcuate segment  184  of the seating portion  162  to exert a radial clamping force  52  (shown in  FIG.  3   ) on the ball member  156 , i.e., exerted along an axis intersecting the center of a circular substrate positioning within the substrate storage rack  100 , the radial clamping force  52  fixing the ball member  156  within column assembly  110 . 
     With reference to  FIG.  7   , at least one of the arcuate segment  184  and the clamp member  154  may define a longitudinal slot  188  within the pocket  186 . In such examples the ball member  156  (shown in  FIG.  3   ) may be captive within the pocket  186  between the arcuate segment  184  and the clamp member  154  at a position defined by the geometry of the longitudinal slot  188 . For example, the longitudinal slot  188  may include a neck segment  190  and a rounded segment  192 . The neck segment  190  may extend upwards from the rounded segment  192  and have a width that is smaller than a diameter of the rounded segment  192 . The rounded segment  189  may have a diameter that is smaller than a diameter the ball member  156 . As will be appreciated by those of skill in the art in view of the present disclosure, sizing the rounded segment  192  of the longitudinal slot  188  with a diameter that is less than the diameter of the ball member  156  can simplify fabrication of the column assembly  110  (shown in  FIG.  2   ). In this respect the rounded segment  192  of the longitudinal slot  188  may register the ball member  156  relative to the seating portion  162  of the column member  152 . The rounded segment  192  may further retain position of the ball member  156  during assembly of the clamp member  154  onto the column member  152 , limiting (or eliminating) the need for a specialized jig to otherwise support the ball member  156  during the assembly process. The longitudinal slot  188  may be formed using a stamping operation, a punching operation, or a broaching operation. For example, a relatively low-cost push or pull operation may be employed to form the longitudinal slot  188  instead of a more complex and/or costly rotary broaching operation. 
     With continuing reference to  FIGS.  5  and  6   , the seating portion  162  may be a first seating portion  162  and the column member  152  may have one or more second seating portion  194 . In such examples the second seating portion  194  may be similar to the first seating portion  162  and additionally offset longitudinally from the first seating portion  162  along the column member  152  by a height of the one or more slot  112  (shown in  FIG.  3   ). In this respect the height of the one or more slot  112  may be defined between a contact point on a protruding portion  196  (shown in  FIG.  3   ) of the ball member  156  extending upwards from the pocket  186 , the protruding portion  196  above both the seating portion  162  of the column member  152  and a clamping portion  198  of the clamp member  154 . The height of the one or more slot  112  may be between about 1 millimeter and about 10 millimeters, or between 2 millimeters and about 9 millimeters, or between about 4 millimeters and about 8 millimeters. In certain examples, the height of the one or more slot  112  may be about 6 millimeters. As will be appreciated by those of skill in the art in view of the present disclosure, heights within these ranges allow an end effector of the front-end transfer robot  28  (shown in  FIG.  1   ) to move upwards and downwards within the interior  126  of the substrate storage rack  100  to place and retrieve substrates, e.g., the substrate  2  (shown in  FIG.  1   ), in the one or more slot  112 . In the illustrated example the column member  152  has 30 seating portions longitudinally spaced apart from one another along the length of the column member  152 . As will also be appreciated by those of skill in the art in view of the present disclosure, the column member  152  may have fewer or additional seating portions than shown in the illustrated example and remain within the scope of the present disclosure. 
     With reference to  FIGS.  8  and  9   , the clamp member  154  includes a clamp member sheet body  101  with the clamping portion  198  and a base portion  103 . The clamp member sheet body  101  is formed from metallic sheet material  105  and has a thickness  107 . The metallic sheet material  105  may include an aluminum-containing or stainless-steel material, such as 4040 aluminum or 304 stainless steel. In certain examples, the thickness  107  of the clamp member sheet body  101  may be between about 1 millimeter and about 10 millimeters, or between about 1 millimeter about 6 millimeters, or even between about 1 millimeter and about 2 millimeters. In accordance with certain examples, the thickness  107  may be about 1.5 millimeters. As will be appreciated by those of skill in the art in view of the present disclosure, thicknesses within these ranges also allow the clamp member  154  to be formed from planar sheet stock using a stamping and a subsequent bending operation. Forming the clamp member  154  using stamping and bending operations can simplify fabrication of the column assembly  110 , for example, by eliminating machining operations otherwise required to defines slots into bar stock formed from a material suitable for substrate contact, such as quartz or PEEK stock. 
     In certain examples, the base portion  103  of the clamp member  154  may extend in parallel with the first column portion  160  of the column member  152 . In accordance with certain examples, the base portion  103  of the clamp member  154  may be spaced apart from the column member axis  168  (shown in  FIG.  4   ) by the first column portion  160  (shown in  FIG.  5   ) of the column member  152  (shown in  FIG.  3   ). It is also contemplated that the clamp member  154  may have one or more fastener aperture  109  Shown in  FIG.  5   ), and that the base portion  103  of the clamp member  154  may be connected to the first column portion  160  by one or more fastener received in the fastener aperture  109  of the base portion  103  and the one or more fastener aperture  174  of the first column portion  160 . As will be appreciated by those of skill in the art in view of the present disclosure, this provides the column assembly  110  with a composite construction that limits the thickness otherwise required by the column member sheet body  158  and the clamp member sheet body  101 , simplifying the stamping and bending operations used to form the column member  152  and the clamp member  154  from the column member sheet body  158  and the clamp member sheet body  101 , respectively. 
     The clamping portion  198  of the clamp member  154  may extend laterally from the base portion  103  of the clamp member  154 . The clamping portion  198  may further laterally overlay both the ball member  156  (shown in  FIG.  3   ) and the seating portion  162  of the column portion  160 . It is contemplated that the clamping portion  198  urge the ball member  156  toward the seating portion  162  (shown in  FIG.  5   ) of the column member  152  (shown in  FIG.  3   ), compressing the ball member  156  within the pocket  186  (shown in  FIG.  3   ) such that the ball member  156  is captive between the seating portion  162  of the column member  152  and the clamping portion  198  of the clamp member  154  by the radial clamping force  52  (shown in  FIG.  3   ). As will be appreciated by those of skill in the art in view of the present disclosure, clamping the ball member  156  between the clamp member  154  and the column member  152  limits the number or parts otherwise required to fix the ball member  156  within the pocket  186 , simplifying fabrication of the column assembly  110 . 
     In certain examples, the base portion  103  of the clamp member  154  may be a first base portion  103  and that the clamp member  154  may have a second base portion  111 . In such examples the second base portion  111  may extend in parallel with first base portion  103 . The second base portion  111  may be connected to the first base portion  103  of the clamp member  154  by the clamping portion  198  of the clamp member  154 . The second base portion  111  may also be spaced apart from the first base portion  103  by both the first column portion  160  (shown in  FIG.  5   ) and the second column portion  178  (shown in  FIG.  5   ) of the column member  152  (shown in  FIG.  3   ). In this respect the first base portion  103  of the clamp member  154  (shown in  FIG.  3   ) may be fastened to the first column portion  160  and the second base portion  111  may be fastened to second column portion  178  to be fix the clamp member  154  to the column member  152  as well as to clamp the ball member  156  within the column assembly  110  (shown in  FIG.  2   ) between the column member  152  and the clamp member  154 . As will be appreciated by those of skill in the art in view of the present disclosure, fastening the first base portion  103  and the second base portion  111  to the first column portion  160  and the second column portion  178  of the column member  152 , respectively, can increase stiffness of the column assembly  110 . Increasing stiffness of the column assembly  110  in turn allows the column member sheet body  158  and the clamp member sheet body  101  to be relatively thin, simplifying fabrication of the column assembly  110 . 
     In certain examples, the clamping portion  198  may be a first clamping portion  198  and the clamp member  154  may have one or more second clamping portion  113 . In such examples the second clamping portion  113  may be similar to the first clamping portion  198  and may be longitudinally spaced apart from the first clamping portion  198  along the longitudinal length of the first base portion  103  and the second base portion  111  of the clamp member  154 . The second clamping portion  113  may be one of two clamping portions longitudinally spaced along first base portion  103  and the second base portion  111  of the clamp member  154 . The second clamping portion  113  may be one of two or more second clamping portions longitudinally spaced along first base portion  103  and the second base portion  111  of the clamp member  154 . For example, the second clamping portion  113  may be one of ten (10) or eleven (11) clamping portions longitudinally spaced along first base portion  103  and the second base portion  111  of the clamp member  154 , the clamp member  154  having fewer clamping portions than seating portions of the column member  152 . As will be appreciated by those of skill in the art in view of the present disclosure, clamp members having fewer clamping portions than seating portions of the column member can simplify fabrication of the column assembly, for example, by limiting the number of ball members positioned between the clamp member and the column member during assembly of the clamp member to the column member. 
     With continuing reference to  FIG.  4   , the clamp member  154  may be a first clamp member  154  and the column assembly  110  may further include a second clamp member  115  and a third clamp member  117 . In such examples the second clamp member  115  and the third clamp member  117  may be similar to the first clamp member  154 . The second clamp member  115  may be connected to the column member  152  at a location longitudinally between the first clamp member  154  and the top fastener tab  172 , the third clamp member  117  may be connected to the column member  152  at a location longitudinally between the second clamp member  115  and the top fastener tab  172 , and connection may be accomplished by fasteners received within the second clamp member  115  and the third clamp member  117 . Advantageously, column assemblies having more than one clamp member simplify assembly of the column assembly by limiting the number of ball members to a number manageable by a single assembler, e.g., by limiting the number of ball members to ten (10) or eleven (11) ball members. Although shown and described herein as having three (3) clamp members, it is to be understood and appreciated that the column assembly  110  can have fewer or additional clamp members and remain within the scope of the present disclosure. Further, although shown and described herein as having a particular number of clamping portions, the second clamp member  115  having eleven (11) clamping portions while the first clamp member  154  and the third clamp member  117  having ten (10) clamping portions, it is to be understood and appreciated that the column assembly  110  can have one or more clamp member with fewer or additional clamping portions and remain within the scope of the present disclosure. 
     It is contemplated that the ball member  156  be formed from a ball member material  119 . The ball member  156  may also have a diameter that is between about 1 millimeter and 10 millimeters, or between 2 millimeters and about 8 millimeters, or even between about 3 millimeters and about 6 millimeters. The ball member  156  may have a diameter that is about 4 millimeters. As will be appreciated by those of skill in the art, diameters within these ranges allow the ball member  156  to be both captive within the pocket  186  (shown in  FIG.  3   ) and protrude in part above both the seating portion  162  (shown in  FIG.  5   ) of the column member  152  and the clamping portion  198  (shown in  FIG.  4   ) of the clamp member  154 . Protrusion above the seating portion  162  and the clamping portion  198  allows the ball member  156  to space a substrate, the substrate  2  (shown in  FIG.  1   ), with sufficient distance to avoid contact between the underside of the substrate and the seating portion  162  of the column member  152  as well as the clamping portion  198  of the clamp member  154 . As will be appreciated by those of the skill in the art in view of the present disclosure, avoiding contact allows the metallic material  120  and/or the metallic material  130  forming the column member  152  and the clamp member  154  to include alloying elements otherwise prohibited is front-end (copper-free) semiconductor processing systems, such as copper, that can simplify die pressing and/or bending metallic sheet stock. 
     In certain examples, the ball member material  119  may include a ceramic material. For example, the ball member material  119  may include silicon nitride (Si 3 N 4 ), zinc oxide (ZnO 3 ), aluminum oxide (Al 2 O 3 ), or quartz. In accordance with certain examples, the ball member material  119  may consist of or consist essentially of a ceramic material, silicon nitride (Si 3 N 4 ), zinc oxide (ZnO 3 ), aluminum oxide (Al 2 O 3 ), or quartz. As will be appreciated by those of skill in the art in view of the present disclosure, such materials limit size of particulate shed during placement and removal of substrates from within the substrate storage rack  100 , facilitating removal of the particulate with filtered air provided to the substrate storage rack  100 . In certain examples the ball member material  119  may be matched to that forming contact pads carried by the end effector of either (or both) the front-end transfer robot  28  (shown in  FIG.  1   ) and the back-end transfer robot  34  (shown in  FIG.  1   ). As will also be appreciated by those of skill in the art in view of the present disclosure, matching the ball member material  119  to that forming the contact pads carried by the end effector of either (or both) the front-end transfer robot  28  and the back-end transfer robot  34  limits the potential sources of contamination within the semiconductor processing system  10 . Examples of suitable ball members include G5 silicon nitride ceramic ball bearings, available from BC Precision of Chattanooga, Tenn. 
     With reference to  FIGS.  10 - 15   , a substrate storage rack  200  is shown. Referring to  FIG.  10   , the substrate storage rack  200  is similar to the substrate storage rack  100  (shown in  FIG.  1   ) and additionally includes a column assembly  202 . It is contemplated that the column assembly  202  may be a first column assembly  202  and that the substrate storage rack  200  may further include a second column assembly  204  and a third column assembly  206 . The first column assembly  202  connects the top plate  106  to the bottom plate  104  and defines a plurality of slots  208  between the top plate  106  and the bottom plate  104 . The second column assembly  204  and the third column assembly  206  are similar to the first column assembly  202  and are additionally offset from one another about the center of the substrate  2 . In the illustrated example the second column assembly  204  and the third column assembly  116  are offset from the first column assembly  202  by about 90-degrees about the center of the substrate  2 . In the illustrated example the third column assembly  206  is further spaced apart from the second column assembly by a distance that is less that the diameter of the substrate  2 . For example, the third column assembly  206  may be spaced apart from the second column assembly by less than about 300 millimeters, or less than 290 millimeters, or even less than about 280 millimeters. As above, the substrate storage rack  200  may have fewer column assemblies or more column assemblies than shown in the illustrated example and remain within the scope of the present disclosure. 
     Referring to  FIGS.  11  and  12   , the first column assembly  202  includes a column member  210 , a spacer member  212 , a clamp member  214 , and a plurality of ball members  156 . The column member  210  extends longitudinally between the bottom plate  104  (shown in  FIG.  2   ) and the top plate  106  (shown in  FIG.  2   ). The spacer member  212  is arranged along a spacer member axis  216 , is connected to the column member  210 , and is parallel to the column member  210 . The clamp member  214  is separated from the column member  210  by the spacer member  212 , is coupled to the column member  210  by the spacer member  212  and extends in parallel with the column member  210 . It is contemplated that the column member  210  and the clamp member  214  be compressively connected to one another by a plurality of fasteners  218  extending through the spacer member  212  and longitudinally spaced apart from one another along the spacer member axis  216 . It is also contemplated that the plurality of ball members  156  be captive between the column member  210  and the clamp member  214  at locations radially inward of the spacer member  212 . In this respect the plurality of ball members  156  are fixed within the column assembly  202  by tangential clamping forces  220  exerted by the column member  210  and the clamp member  214 . 
     Referring to  FIG.  13   , the column member  210  includes a column member plate body  222  with a thickness  224 , a column portion  226 , and a seating portion  228 . The column member plate body  222  may be formed from a metallic material  230  such as an aluminum-containing alloy or stainless steel. Examples of suitable aluminum-containing alloys and stainless-steel materials include 4040 aluminum and 304 stainless steel. In certain examples, the thickness  224  of the column member plate body  222  may be greater than the thickness  107  (shown in  FIG.  9   ) of the clamp member sheet body  101  (shown in  FIG.  8   ). In accordance with certain examples, the thickness  224  of the column member plate body  222  may be greater than the thickness  166  (shown in  FIG.  6   ) of the column member sheet body  158  (shown in  FIG.  5   ). For example, the thickness  224  of the column member plate body  222  may be between about 2 millimeters and about 20 millimeters, or between about 2 millimeters and about 15 millimeters, or even between about 2 millimeters and about 10 millimeters. The thickness  224  of the column member plate body  222  may be about 3 millimeters. As will be appreciated by those of skill in the art in view of present disclosure, thicknesses within the ranges simplifies fabrication of the column member  210 . 
     The column portion  226  of the column member  210  has a longitudinal length  232  (shown in  FIG.  10   ) spanning the bottom plate  104  (shown in  FIG.  2   ) and the top plate  106  (shown in  FIG.  2   ) of the substrate storage rack  200 . The seating portion  228  of the column member  210  protrudes laterally from the column portion  226  of the column member  210  and radially inward relative to substrates, e.g., the substrate  2  (shown in  FIG.  1   ), supported within the substrate storage rack  200 . In certain examples, the seating portion  228  may be a first seating portion  228  and the column member  210  may have one or more second seating portion  234 . In such examples, the second seating portion  234  may protrude laterally from the column portion  226  of the column member  210 , may be spaced apart from the first seating portion  228  along the longitudinal length of the column member  210 , and may be one of only two (2) seating portions arranged along the longitudinal length  232  of the column member  210 . It is also contemplated that the first seating portion  228  and the second seating portion  234  may be two (2) of twenty-five (25) seating portions, or thirty-one (31) seating portions spaced apart from one another along the longitudinal length  232  of the column member  210 . However, as will be appreciated by those of skill in the art in view of the present disclosure, the column member  210  may have fewer or more seating portions than shown and described herein and remain within the scope of the present disclosure. 
     Referring to  FIG.  14   , the spacer member  212  includes a spacer member plate body  236  with a thickness  238  and a plurality of fastener apertures  240  extending through the spacer member plate body  236 . The plurality of fastener apertures  240  are longitudinally spaced apart from one another along the spacer member axis  216 . In the illustrated example the spacer member  212  has eight (8) fastener apertures  240 . As will be appreciated by those of skill in the art in view of the present disclosure, the spacer member  212  may have fewer or additional fastener apertures  240  and remain within the scope of the present disclosure. 
     The spacer member plate body  236  may be formed from a metallic material  242  such as an aluminum-containing alloy or stainless-steel material, and may be the same as the metallic material  230  forming the column member plate body  222 . In certain examples, the thickness  238  of the spacer member plate body  236  be smaller than the diameter of the ball member  156 . For example, the thickness  238  of the spacer member plate body  236  may be less than 4 millimeters, or less than 3 millimeters, or even less than 2 millimeters. It is also contemplated that, in accordance with certain examples, the thickness  238  of the spacer member plate body  236  may be greater than the thickness  107  (shown in  FIG.  9   ) of the clamp member sheet body  101  (shown in  FIG.  8   ) of the clamp member  154 . In certain examples, the thickness  238  of the spacer member plate body  236  may be greater than the thickness  166  (shown in  FIG.  6   ) of the column member sheet body  158  (shown in  FIG.  5   ). For example, the thickness  238  may be between about 2 millimeters and about 20 millimeters, or between about 2 millimeters and about 15 millimeters, or even between about 2 millimeters and about 10 millimeters. In certain examples, the thickness  238  may be about 3 millimeters. As will be appreciated by those of skill in the art in view of present disclosure, thicknesses within the ranges can simplify assembly of the fabrication of the column assembly  202 , for example, by controlling magnitude of the tangential clamping force  220  (shown in  FIG.  11   ) according selection of thickness  238  of the spacer member plate body  236  and the diameter of the ball member  156 . 
     Referring to  FIG.  15   , the clamp member  214  includes a clamp member plate body  244  with a thickness  246 , a base portion  248 , and a clamping portion  250 . The clamp member plate body  244  may be formed from a metallic material  252 , such as an aluminum-containing alloy or stainless steel like 4040 aluminum or 304 stainless steel, respectively. In certain examples, the metallic material  252  may the same as the metallic material  230  forming the column member plate body  222  and/or the metallic material  230  forming the spacer member plate body  236 . 
     The thickness  246  may be greater than the thickness  107  (shown in  FIG.  9   ) of the clamp member sheet body  101  (shown in  FIG.  8   ), or greater than the thickness  166  (shown in  FIG.  6   ) of the column member sheet body  158  (shown in  FIG.  5   ). For example, the thickness  246  may be between about 2 millimeters and about 20 millimeters, or between about 2 millimeters and about 15 millimeters, or even between about 2 millimeters and about 10 millimeters. The thickness  224  of the clamp member plate body  244  may be about 3 millimeters. In certain examples, the thickness  246  may be or substantially equivalent to the thickness  224  (shown in  FIG.  13   ) of the column member plate body  222  (shown in  FIG.  13   ) and/or the thickness  238  (shown in  FIG.  14   ) of the spacer member plate body  236  (shown in  FIG.  14   ). As will be appreciated by those of skill in the art in view of present disclosure, matching thickness of the clamp member plate body  244  to the column member plate body  222  can limit deformation in one the seating portion  228  and the clamping portion  250  responsive to the tangential clamping force  220  exerted on the ball member  156  during assembly of the column assembly  202  (shown in  FIG.  10   ), simplifying assembly of the column assembly  202 . 
     The base portion  248  of the column member  210  has a longitudinal length  254 . In certain examples the longitudinal length  254  may be substantially equivalent to the longitudinal length  232  of the column portion  226  (shown in  FIG.  13   ) of the column member  210  (shown in  FIG.  11   ). The clamping portion  250  of the clamp member  214  protrudes laterally from the base portion  248  of the column member  210 . It is contemplated that the clamping portion  250  circumferentially overlap the seating portion  228  of the column member  210 , the clamping portion  250  extending radially inward in this respect relative to substrates, e.g., the substrate  2  (shown in  FIG.  1   ), supported within the substrate storage rack  100 . 
     In certain examples, the clamping portion  250  may be a first clamping portion  250  and the clamp member  214  may have one or more second clamping portion  258 . In such examples, the second clamping portion  258  may protrude laterally from the clamping portion  250  of the clamp member  214 , may be spaced apart from the first clamping portion  256  along the longitudinal length  254  of the clamp member  214 , and may be one of only two (2) clamping portions arranged along the longitudinal length  254  of the clamp member  214 . In certain examples, the first clamping portion  256  and the second clamping portion  258  may be two (2) of twenty-five (25) seating portions, or thirty-one (31) seating portions spaced apart from one another along the longitudinal length  254  of the clamp member  214 . It is also contemplated that, in accordance with certain examples, both the clamp member  214  and the column member  210  may have identical numbers of clamping portions and the seating portions. As will be appreciated by those of skill in the art in view of the present disclosure, forming the clamp member  214  and the column member  210  with the same number clamping and seating portions can simplify fabrication of the column assembly  202 , for example, by limiting the number of detail parts included in the assembly and/or error-proofing the assembly. It is further contemplated that the seating portion the seating portion  228  and the clamping portion  250  may a first longitudinal slot  260  (shown in  FIG.  11   ) and a tangentially opposed second longitudinal slot  262  (shown in  FIG.  11   ) seating there is the ball member  156 . As above, this simplifies the assembly of the column assembly  202  as the ball member  156  may be registered and thereafter maintained in one of the first longitudinal slot  260  and the second longitudinal slot  262 , and thereafter clamped therein by force exerted about the other of the first longitudinal slot  260  and the second longitudinal slot  262  as the clamp member  214  is fastened to the column member  210 . 
     With reference to  FIG.  16   , a method  300  of making a substrate storage rack, e.g., the substrate storage rack  100  (shown in  FIG.  1   ), is shown. As shown with box  310 , a column member, e.g., the column member  152  (shown in  FIG.  3   ), is formed having a column portion, e.g., the column portion  160  (shown in  FIG.  3   ), and a seating portion, e.g., the seating portion  162  (shown in  FIG.  3   ), extending laterally from the column portion of the column member. In certain examples, the column member may be formed using a stamping operation, as shown with box  312 . For example, the column member may be stamped from sheet stock, e.g., the column member sheet body  158  (shown in  FIG.  5   ). In accordance with certain examples, the column member may be formed using a bending operation, for example, by bending the column member sheet body that a first column portion, e.g., the first column portion  160  (shown in  FIG.  5   ), and a second column portion, e.g., the second column portion  178  (shown in  FIG.  5   ), extend in parallel with one another on opposite sides of a column member axis, e.g., the column member axis  168  (shown in  FIG.  6   ), as shown with box  314 . 
     As shown with box  320 , a clamp member, e.g., the clamp member  154  (shown in  FIG.  3   ), is formed having a base portion, e.g., the base portion  103  (shown in  FIG.  8   ), and a clamping portion, e.g., the clamping portion  198  (shown in  FIG.  8   ), extending laterally from the base portion of the clamp. In certain examples, the clamp member may also be formed using a stamping operation, as shown with box  322 . In this respect the clamp member may also be stamped from sheet stock, e.g., the clamp member sheet body  101  (shown in  FIG.  8   ). In accordance with certain examples, the clamp member may be formed using a bending operation, for example, by bending the clamp member sheet body such that a first base portion, e.g., the first base portion  103  (shown in  FIG.  8   ), and a second base portion, e.g., the second base portion  111  (shown in FIG. A), extend in parallel with one another. 
     As shown with box  330 , a ball member, e.g., the ball member  156  (shown in  FIG.  3   ), is supported on the seating portion of the column member. In certain examples, the ball member may be supported on a longitudinal slot defined by the seating portion of the column member, e.g., the longitudinal slot  188  (shown in  FIG.  5   ), as shown with box  332 . In accordance with certain example, the ball member may be supported on a longitudinal slot defined by the clamping portion of the clamp member, e.g., the clamping portion longitudinal slot  208  (shown in  FIG.  10   ). It is contemplated that the longitudinal slot maintain position of the ball member relative to at least one of the column member and the clamp member such that the clamp member may be registered to the column member using the ball member, as shown with box  340 . 
     As shown with box  350 , the ball member is thereafter compressed between the clamping portion of the clamp member and the seating portion of the column member. In certain examples, the ball member may be fixed between clamping portion and the seating portion by a radial clamping force exerted on the ball member by the seating portion and the clamping, the radial clamping force intersecting the column member axis, as shown with box  352 . In accordance with certain examples, the ball member may be fixed between the clamping portion and the seating portion by a tangential clamping force exerted by the seating member and the clamp member on the ball member, the tangential clamping force not intersecting a spacer member axis within the column assembly, as shown with box  354 . It is contemplated that the clamp member be fastened to the column member while exerting the clamping force on the ball member, the ball member thereby being compressive fixed within the column assembly between the seating portion of the column member and the clamping portion of the clamp member. 
     Although this disclosure has been provided in the context of certain examples, it will be understood by those skilled in the art that the disclosure extends beyond the specifically described embodiments to other alternative embodiments and/or uses of the examples and obvious modifications and equivalents thereof. In addition, while several variations of the examples of the disclosure have been shown and described in detail, other modifications, which are within the scope of this disclosure, will be readily apparent to those of skill in the art based upon this disclosure. It is also contemplated that various combinations or sub-combinations of the specific features and aspects of the examples may be made and still fall within the scope of the disclosure. It should be understood that various features and aspects of the disclosed examples can be combined with, or substituted for, one another in order to form varying modes of the examples of the disclosure. Thus, it is intended that the scope of the disclosure should not be limited by the particular examples described above. The headings provided herein, if any, are for convenience only and do not necessarily affect the scope or meaning of the devices and methods disclosed herein.