Patent Publication Number: US-11639957-B2

Title: Planar ring radiation barrier for cryogenic wafer test system

Description:
TECHNICAL FIELD 
     This disclosure relates generally to classical and superconducting computing systems, and more specifically to a radiation barrier for a cryogenic wafer test system. 
     BACKGROUND 
     Fabrication of integrated circuits (ICs) fundamentally requires testing to determine if the electronic circuits operate as intended. Testing is typically performed at the die level on a given wafer device-under-test (DUT), prior to the many die on the wafer being cut and mounted in respective packages to form the associated “chips”. Test systems are typically operated at an environment that simulates typical operation of the circuit to be tested on the respective wafer DUT. Thus, typical semiconductor-based ICs are tested at a non-cryogenic temperature (e.g., “room-temperature”) to determine efficacy of the circuit. Similarly, typical superconducting circuits are tested at cryogenic temperatures. Such testing of superconducting circuits at cryogenic temperatures can be both expensive and labor-intensive. For example, for a typical superconducting die test, the wafer DUT is diced into individual chips, placed into special fixtures, and dipped into a liquid helium Dewar, which can be time consuming and helium intensive, and thus not scalable for high volume throughput. 
     SUMMARY 
     One example includes a cryogenic wafer test system. The system includes a first chamber that is cooled to a cryogenic temperature and a wafer chuck confined within the first chamber. The wafer chuck can be configured to accommodate a wafer device-under-test (DUT) comprising a plurality of superconducting die. The system also includes a second chamber that is held at a non-cryogenic temperature and which comprises a wafer chuck actuator system configured to provide at least one of translational and rotational motion of the wafer chuck via mechanical linkage interconnecting the wafer chuck and the wafer chuck actuator system. The system further includes a radiation barrier arranged between the first chamber and the second chamber and through which the mechanical linkage extends, the radiation barrier being configured to provide a thermal gradient between the cryogenic temperature of the first chamber and the non-cryogenic temperature of the second chamber. 
     Another example includes a cryogenic wafer test system. The system includes a first chamber that is cooled to a cryogenic temperature and a second chamber that is held at a non-cryogenic temperature. The system also includes a radiation barrier arranged between the first chamber and the second chamber and comprising a plurality of overlapping planar rings of incrementally increasing size between a first ring and a last ring of the overlapping planar rings. The radiation barrier can be configured to provide a thermal gradient between the cryogenic temperature of the first chamber and the non-cryogenic temperature of the second chamber. The system further includes a mechanical linkage extending through the radiation barrier, such that at least one of the overlapping planar rings of the radiation barrier is configured to slide along a next contiguous one of the overlapping planar rings in response to lateral motion of the mechanical linkage along a plane that is parallel with each of the overlapping planar rings of the radiation barrier. 
     Another example includes a cryogenic wafer test system. The system includes a first chamber that is cooled to a cryogenic temperature and a wafer chuck confined within the first chamber. The wafer chuck can be configured to accommodate a wafer device-under-test (DUT) comprising a plurality of superconducting die. The system also includes a second chamber that is held at a non-cryogenic temperature and which comprises a wafer chuck actuator system configured to provide at least one of translational and rotational motion of the wafer chuck via mechanical linkage interconnecting the wafer chuck and the wafer chuck actuator system. The system further includes a radiation barrier arranged between the first chamber and the second chamber and through which the mechanical linkage extends and being configured to provide a thermal gradient between the cryogenic temperature of the first chamber and the non-cryogenic temperature of the second chamber. The radiation barrier includes a plurality of overlapping planar rings from a thermally conductive material, and arranged in an incrementally increasing size between a first ring and a last ring of the overlapping planar rings, such that at least one of the overlapping planar rings of the radiation barrier is configured to slide along a next contiguous one of the overlapping planar rings in response to lateral motion of the mechanical linkage along a plane that is parallel with each of the overlapping planar rings of the radiation barrier. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates an example of a cryogenic wafer test system. 
         FIG.  2    illustrates an example diagram of a cryogenic wafer test system. 
         FIG.  3    illustrates another example diagram of a cryogenic wafer test system. 
         FIG.  4    illustrates an example diagram of motion of the wafer chuck. 
         FIG.  5    illustrates an example diagram of a radiation barrier. 
         FIG.  6    illustrates another example diagram of a radiation barrier. 
     
    
    
     DETAILED DESCRIPTION 
     This disclosure relates generally to classical and superconducting computing systems, and more specifically to a radiation barrier break for a cryogenic wafer test system. The cryogenic wafer test system includes a first chamber that is cooled to a cryogenic temperature in a vacuum. The first chamber includes a wafer chuck configured to accommodate a wafer device-under-test (DUT) comprising a plurality of superconducting die that can undergo testing via at least one wafer prober arranged in the first chamber. The cryogenic wafer test system also includes a second chamber, such as separated from the first chamber by a radiation barrier. The second chamber can likewise be evacuated, and can be held at a non-cryogenic temperature. The second chamber includes a wafer chuck actuator system configured to provide at least one of translational and rotational motion of the wafer chuck to facilitate alignment and contact of a plurality of electrical contacts of the superconducting die to the respective plurality of electrical probe contacts of the at least one wafer prober. 
     As described herein, the terms “first chamber” and “second chamber” can refer to two separate portions of a same chamber (e.g., “upper chamber portion” and “lower chamber portion”, respectively) that are separated by the radiation barrier, as described in greater detail herein. As also described herein, the term “cryogenic” describes a temperature that is equal to or less than approximately 10 Kelvin, and the term “non-cryogenic” describes a temperature that is greater than the cryogenic temperature. For example, the ambient temperature of the first chamber can be equal to or less than approximately 10 Kelvin, while components within the first chamber (e.g., the wafer chuck) can have a temperature of equal to or less than approximately 5 Kelvin. 
     The radiation barrier can be arranged as a plurality of overlapping planar rings. For example, the overlapping planar rings can each be formed from and/or coated with a thermally conductive material (e.g., copper and/or gold), and can be arranged in an incrementally increasing size between a first ring and a last ring of the overlapping planar rings. For example, the first ring can be the smallest ring and can be coupled to the mechanical linkage, such that each next contiguous ring has a larger inner diameter (ID) and a larger outer diameter (OD), with the last ring having the largest ID and the largest OD. Therefore, in response to lateral motion of the mechanical linkage along a plane that is parallel with each of the overlapping planar rings, the overlapping planar rings can slide along a next contiguous one of the overlapping planar rings. Therefore, given the incrementally increasing ID and OD of the overlapping planar rings, at an extreme lateral position of the mechanical linkage, the overlapping planar rings provide no gaps through which radiation can pass in a direct line from the second chamber to the first chamber, and therefore occludes radiation from being able to pass through the radiation barrier from the second chamber to the first chamber. Likewise, upon returning to a neutral position (e.g., from an extreme lateral position), the overlapping planar rings provide no gaps through the radiation barrier between the first and second chambers. Accordingly, the radiation barrier can maintain a sufficient thermal gradient to maintain the cryogenic temperature of the first chamber despite the non-cryogenic temperature of the second chamber, and can facilitate the translational motion of the mechanical linkage through the radiation barrier. 
       FIG.  1    illustrates an example of a cryogenic wafer test system  10 . The cryogenic wafer test system  10  can be configured substantially the same as the cryogenic wafer test system described in, which is incorporated in its entirety herein by reference. The cryogenic wafer test system  10  can be configured to perform testing of each of a plurality of superconducting die on a wafer DUT. For example, the wafer DUT can have a minimum diameter of approximately fifteen centimeters, and can include several hundred separate die (e.g., with each die being sized at approximately five mm 2 ) to be tested. In the example of  FIG.  1   , the cryogenic wafer test system  10  includes a first chamber  12  and a second chamber  14 , with the second chamber  14  being located beneath the first chamber  12 . For example, the first and second chambers  12  and  14  can be separated by a radiation barrier that is configured to provide a thermal gradient between the first and second chambers  12  and  14 . Therefore, the first chamber  12  can be held to a cryogenic temperature to test the superconducting die and the second chamber  14  can be held to a non-cryogenic temperature. For example, the first chamber  12  can be coupled to liquid (e.g., helium) coolant lines  16  to bring the temperature of the first chamber  12  down to the cryogenic temperature (e.g., approximately 5 K or lower). For example, the liquid coolant lines  16  can be coupled to a plurality of heat exchangers in the first chamber  12 , such as statically coupled to a surface (e.g., bottom surface) of the first chamber  12  and flexibly coupled to a wafer chuck on which the superconducting die is tested. As an example, the first and second chambers  12  and  14  can both be at a same pressure (e.g., evacuated), and the radiation barrier can facilitate mechanical interface between the first and second chambers  12  and  14 , as described in greater detail herein. 
       FIG.  2    illustrates an example diagram of a cryogenic wafer test system  50 . The cryogenic wafer test system  50  can correspond to the cryogenic wafer test system  10  in the example of  FIG.  1   . Therefore, reference is to be made to the example of  FIG.  1    in the following description of the example of  FIG.  2   . 
     The cryogenic wafer test system  50  includes a first chamber  52  and a second chamber  54  that can correspond, respectively, to the first and second chambers  12  and  14  in the example of  FIG.  1   . As an example, the first and second chambers  52  and  54  can both be at a same pressure (e.g., evacuated), and the first chamber  52  is cooled to a cryogenic temperature. The first chamber  52  includes a wafer chuck  56  configured to accommodate a wafer DUT comprising a plurality of superconducting die to be tested. The cryogenic wafer test system  50  also includes at least one wafer prober  58  arranged in the first chamber  52 . The wafer prober(s)  58  includes electrical probe contacts that are implemented to provide physical contact to electrical contacts of a superconducting die of the plurality of superconducting die to implement a test of the superconducting die. 
     The second chamber  54  includes a wafer chuck actuator system  60  configured to provide at least one of translational and rotational motion of the wafer chuck  56 . Therefore, the wafer chuck  56  can be manipulated to facilitate alignment and contact of the plurality of electrical contacts of the superconducting die to the respective plurality of electrical probe contacts of the wafer prober(s)  58 . The translational motion can include motion of the wafer chuck  56  along three orthogonal axes, and the rotational motion can provide rotation of the wafer chuck  56  about an axis perpendicular to a planar surface of the wafer DUT. Therefore, the wafer chuck actuator system  60  is configured to facilitate motion of the wafer DUT to align the electrical contacts of a given one of the superconducting die to the electrical probe contacts of the wafer prober(s)  58 . Thus, the wafer chuck actuator system  60  can provide precision contact of the electrical contacts of the respective one of the superconducting die to the electrical probe contacts of the wafer prober(s)  58  to facilitate the test of the respective one of the superconducting die. 
     Referring back to the example of  FIG.  1   , the first chamber  12  can include a substantially transparent viewing window  18  that can provide an overhead view to the inside the first chamber  12 . Therefore, the viewing window  18  can provide a view of the planar surface of the wafer DUT to facilitate the alignment of the wafer DUT to the wafer prober(s)  58 , and thus the electrical contacts of the wafer DUT to the respective electrical prober contacts of the wafer prober(s)  58 , via the wafer chuck actuator system  60 . As an example, the viewing window can be formed of any of a variety of substantially transparent crystalline materials that can facilitate operation in the first chamber  12  at the cryogenic temperature. As another example, the cryogenic wafer test system  10  can include an electronic vision system (not shown) that can provide approximately real-time imaging of the first chamber  12  through the viewing window  18 . Accordingly, the vision system can further facilitate alignment of the electrical contacts on the surface of the superconducting die to the respective electrical probe contacts on the wafer prober(s)  58  to allow for real-time adjustments of the position of the wafer DUT via the wafer chuck actuator system  60  for aligning the electrical contacts to the electrical probe contacts. 
     Referring back to the example of  FIG.  2   , the second chamber  54  is demonstrated as separated from the first chamber  52  by a radiation barrier  62 . As described herein, the radiation barrier  62  is configured to provide a thermal gradient between the first and second chambers  52  and  54  by occluding direct line radiation from propagating from the second chamber  54  to the first chamber  52 . For example, because both the first and second chambers  52  and  54  can be evacuated, there is substantially no convection heat transfer that can occur from the second chamber  54  to the first chamber  52 . Thus, only radiation can provide heat transfer from the second chamber  54  to the first chamber  52 . As a result, by occluding direct line radiation from propagating from the second chamber  54  to the first chamber  52 , the radiation barrier  62  can substantially mitigate heat transfer from the second chamber  54  to the first chamber  52 . Therefore, the first chamber  52  can be held to a cryogenic temperature (e.g., approximately 5 K or lower) to test the superconducting die and the second chamber  54  can be held to a non-cryogenic temperature. As described in greater detail herein, the radiation barrier  62  can facilitate mechanical interface between the first and second chambers  52  and  54 . Therefore, the wafer chuck actuator system  60  can be mechanically coupled to the wafer chuck  56  through the radiation barrier  62  to facilitate the translational and/or rotational motion of the wafer chuck  56  via the wafer chuck actuator system  60  through the radiation barrier  62 . 
     The arrangement of the cryogenic wafer test system  50  can thus facilitate a more efficient testing environment of superconducting die than typical superconducting test fixtures. For example, by facilitating motion of the wafer chuck  56 , and thus the wafer DUT, via the wafer chuck actuator system  60 , the cryogenic wafer test system  50  can test multiple superconducting die sequentially in an indexed manner on the wafer DUT, as opposed to testing individually cut superconducting die that have been individually cooled via dipping into a liquid Dewar. As a result, by performing tests iteratively on each of the superconducting die on the wafer DUT, the process of testing each of the superconducting die in an indexed manner can be significantly more efficient by saving time between testing of each individual superconducting die, as well as by saving energy and cooling material (e.g., liquid helium) by operating the first chamber  52  that encapsulates the wafer DUT at the cryogenic temperature. Accordingly, the cryogenic wafer test system  50  provides for much more efficient testing than typical systems that implement die testing, and can provide for testing a large number of die in a superconducting environment in an indexed manner. 
       FIG.  3    illustrates another example diagram of a cryogenic wafer test system  100 . The cryogenic wafer test system  100  can correspond to the cryogenic wafer test system  10  in the example of  FIG.  1   . Therefore, reference is to be made to the example of  FIG.  1    in the following description of the example of  FIG.  3   . 
     The cryogenic wafer test system  100  includes a first chamber  102  and a second chamber  104  that can correspond, respectively, to the first and second chambers  12  and  14  in the example of  FIG.  1   . The first and second chambers  102  and  104  are demonstrated in the example of  FIG.  3    in a cross-sectional view. The first and second chambers  102  and  104  each include a perimeter wall  106  that substantially surround and enclose the respective first and second chambers. In the example of  FIG.  3   , the first chamber  102  includes heat exchangers  108  that are arranged on a thermally conductive (e.g., aluminum) bottom surface  110  of the first chamber  102 . The bottom surface  110  has an aperture  112  that provides an opening between the first and second chambers  102  and  104 . The heat exchangers  108  can be configured to receive a cooling fluid (e.g., liquid helium) to cool the first chamber  102  to a cryogenic temperature (e.g., in a vacuum). Additionally, the first chamber includes a wafer chuck  114  configured to accommodate a wafer DUT comprising a plurality of superconducting die to be tested. In the example of  FIG.  3   , the wafer chuck  114  can include a thermally conductive surface on which another heat exchanger  108  is arranged. Therefore, the heat exchanger  108  can likewise be provided a cooling liquid (e.g., helium), such as via a flexible hose to allow for the cooling liquid to be provided to the heat exchanger  108  as it moves with the wafer chuck  114 , to cool the first chamber  102  to the cryogenic temperature. The cryogenic wafer test system  100  also includes at least one wafer prober  116  arranged in the first chamber  102 . 
     In the example of  FIG.  3   , the first chamber  102  also includes a radiation shield  118  and a magnetic shield  120  that are arranged interior with respect to the perimeter wall  106 . The radiation shield  118  can, for example, provide thermal insulation of the first chamber  102  to assist in maintaining the first chamber at the cryogenic temperature. The magnetic shield  120  can provide protection for the wafer DUT on the wafer chuck  114  from external magnetic fields, such as to provide more accurate testing. The first chamber  102  also includes a substantially transparent viewing window  122  that can provide an overhead view to the inside the first chamber  102 . Therefore, the viewing window  122  can provide a view of the planar surface of the wafer DUT to facilitate the alignment of the wafer DUT to the wafer prober(s)  116  (e.g., via a vision system), and thus the electrical contacts of the wafer DUT to the respective electrical prober contacts of the wafer prober(s)  116 . For example, the viewing window  122  can be formed from a thermally insulating transparent or translucent material, such as a crystalline material (e.g., sapphire), to mitigate ambient heating of the first chamber  102 . As another example, a thermal shutter (not shown) can cover the viewing window  122  to help stabilize the cryogenic temperature of the first chamber  102  when the viewing window  122  is not needed for alignment. 
     The second chamber  104  includes a wafer chuck actuator system  124  configured to provide at least one of translational and rotational motion of the wafer chuck  114  via a mechanical linkage  126 . As an example, the mechanical linkage  126  can be configured as a shaft that can extend along an axis and/or rotate about the axis. Therefore, the wafer chuck  114  can be manipulated to facilitate alignment and contact of the plurality of electrical contacts of the superconducting die to the respective plurality of electrical probe contacts of the wafer prober(s)  116 . The translational motion can include motion of the wafer chuck  114  along three orthogonal axes, and the rotational motion can provide rotation of the wafer chuck  114  about an axis perpendicular to a planar surface of the wafer DUT. Therefore, the wafer chuck actuator system  124  is configured to facilitate motion of the wafer DUT to align the electrical contacts of a given one of the superconducting die to the electrical probe contacts of the wafer prober(s)  116 . Thus, the wafer chuck actuator system  124  can provide precision contact of the electrical contacts of the respective one of the superconducting die to the electrical probe contacts of the wafer prober(s)  116  to facilitate the test of the respective one of the superconducting die. 
     In the example of  FIG.  3   , the cryogenic wafer test system  100  also includes a radiation barrier  128 . The radiation barrier  128  is coupled to the mechanical linkage  126  and is arranged to obstruct radiation that could propagate in a straight line from the second chamber  104 , through the aperture  112 , and into the first chamber  102 . Therefore, the radiation barrier  128  is configured to provide a thermal gradient between the first and second chambers  102  and  104 . Therefore, the first chamber  102  can be held to a cryogenic temperature (e.g., approximately 5 K or lower) to test the superconducting die and the second chamber  104  can be held to a non-cryogenic temperature. As described herein, the radiation barrier  128  can facilitate mechanical interface between the first and second chambers  102  and  104  while maintaining the thermal gradient between the first and second chambers  102  and  104 . Therefore, the wafer chuck actuator system  124  can be mechanically coupled to the wafer chuck  114  through the radiation barrier  128  to facilitate the translational and/or rotational motion of the wafer chuck  114  via the wafer chuck actuator system  124  through the radiation barrier  128 . 
     In the example of  FIG.  3   , the radiation barrier  128  is demonstrated as a plurality of overlapping planar rings  130  through which the mechanical linkage  126  extends from the wafer chuck actuator system  124  to the wafer chuck  114 . For example, the overlapping planar rings  130  can each be formed from and/or coated with a thermally conductive material (e.g., copper and/or gold), and can be arranged in an incrementally increasing size between a first ring (e.g., on the bottom) and a last ring (e.g., on the top) of the overlapping planar rings  130 . As an example, the overlapping planar rings  130  can be formed from copper and coated with gold. As another example, the overlapping planar rings  130  can be formed from a thermally conductive metal. As an example, the first ring (e.g., on the bottom) can have a thermally conductive and flexible coupling (e.g., a metallic braid or thermal strap) to the wafer chuck  114 , such that the heat exchanger  108  on the wafer chuck  114  can provide thermal cooling of the first ring, and thus the radiation barrier  128 . Similarly, the last ring (e.g., on the top) can have a thermally conductive and flexible coupling (e.g., a metallic braid or thermal strap) to the bottom surface  110  of the first chamber  102 , such that the heat exchanger  108  on the bottom surface  110  can provide thermal cooling of the last ring, and thus the radiation barrier  128 . 
     For example, the first ring can be the smallest ring and can be coupled to the mechanical linkage  126 , such that each next contiguous ring has a larger inner diameter (ID) and a larger outer diameter (OD), with the last ring having the largest ID and the largest OD. As an example, the mechanical linkage  126  can include a flange upon which the first ring can rest via gravity, and therefore without mechanical coupling. Thus, the remaining overlapping planar rings  130  can each rest upon the respective ring below by gravity. The last ring, and thus the largest ring, can have a range of motion that is limited by fixed mechanical limits in the first chamber  102 , such as posts that extend from the bottom surface  110  or the inner surface of the perimeter wall  106  (e.g., the magnetic barrier  120 ). Therefore, in response to lateral motion of the mechanical linkage  126  along a plane that is parallel with each of the overlapping planar rings  130 , one or more of the overlapping planar rings  130  can slide along a next contiguous one of the overlapping planar rings  130 . Additionally, the radiation barrier  128  can move up and down as the wafer chuck  114  moves up and down via the mechanical linkage  126 . 
     Therefore, given the incrementally increasing ID and OD of the overlapping planar rings, at an extreme lateral position of the mechanical linkage  126 , the overlapping planar rings  130  provide no gaps through the radiation barrier  128  between the first and second chambers  102  and  104  through which radiation can propagate in a straight line from the second chamber  104  to the first chamber  102 . In other words, the radiation barrier  128  provides a mechanical range of lateral motion of the mechanical linkage  126  while preventing any gaps between the first and second chambers  102  and  104  through which radiation can pass through the radiation barrier  128  in a straight line. Likewise, when returning to a neutral position (e.g., from the extreme lateral position), the overlapping planar rings  130  provide no gaps through the radiation barrier  128  between the first and second chambers  102  and  104 . Accordingly, the radiation barrier  128  can maintain a sufficient thermal gradient to maintain the cryogenic temperature of the first chamber  102  despite the non-cryogenic temperature of the second chamber  104 , and can facilitate the translational motion of the mechanical linkage  126  through the radiation barrier  128 . Additionally, the interior of the first chamber  102  can be coated with a radiation damping material to absorb radiation that may bounce from the radiation barrier  128  to within the first chamber  102 . 
       FIG.  4    illustrates an example diagram  150  of motion of a wafer chuck. The diagram  150  can correspond to demonstration of motion of a wafer chuck  152  via a wafer chuck actuator system  154 . As an example, the wafer chuck  152  can correspond to the wafer chuck  56  and the wafer chuck  114  in the respective examples of  FIGS.  2  and  3   , and the wafer chuck actuator system  154  can correspond to the wafer chuck actuator system  60  or the wafer chuck actuator system  124  in the respective examples of  FIGS.  2  and  3   . Therefore, reference is to be made to the example of  FIGS.  2  and  3    in the following description of the example of  FIG.  4   . 
     In the example of  FIG.  4   , the wafer chuck  152  and the wafer chuck actuator system  154  are demonstrated as coupled via a mechanical linkage  156  that extends from the wafer chuck actuator system  154  through a radiation barrier  158  to the wafer chuck  152 . As an example, the mechanical linkage  156  can correspond to any of a variety of mechanical and physical connections between the wafer chuck  152  and the wafer actuator system  154 . For example, the mechanical linkage  156  can be configured as a cylindrical or prismatic shaft arranged within a sleeve portion that is coupled to the radiation barrier  158 , with the shaft extending between the wafer chuck actuator system  154  and the wafer chuck  152  to provide motion of the wafer chuck  152  in response to motion of or electrical commands from the wafer chuck actuator system  154 . As another example, the mechanical linkage  156  can include other or additional mechanical components, such as including gears, motors, servos, or a variety of other mechanical connection means. 
     In the example of  FIG.  4   , the wafer chuck actuator system  154  can perform translational motion or provide control commands to the wafer chuck  152  for translational motion, demonstrated at  160  as motion along three orthogonal axes (e.g., X, Y, and Z-axes). In response to the translational motion of or the control commands provided from the wafer chuck actuator system  154 , the wafer chuck  152  can perform corresponding translational motion along the respective three orthogonal axes (e.g., the corresponding X, Y, and Z-axes), demonstrated at  162 , via the mechanical linkage  156 . Similarly, the wafer chuck actuator system  154  can perform rotational motion or provide control commands to the wafer chuck  152  for rotational motion, demonstrated as the circular arrow at  164  (e.g., about an angle θ). In response to the rotational motion of or the control commands provided from the wafer chuck actuator system  154 , the wafer chuck  152  can perform corresponding rotational motion about an axis perpendicular to a surface of the wafer chuck  152  (e.g., about an axis of the mechanical linkage  156 ), demonstrated at  166  (e.g., about the corresponding angle θ), via the mechanical linkage  156 . 
     As a result, the wafer chuck actuator system  154  can be implemented by a user of the cryogenic wafer test system  50  to provide translational and/or rotational motion of the wafer chuck  152 , and thus the wafer DUT that is affixed to the wafer chuck  152  during testing of the superconducting die on the wafer DUT. Furthermore, based on the overlapping ring arrangement of the radiation barrier  158 , the wafer chuck actuator system  154  can move the wafer chuck  152  in a lateral motion (e.g., planar motion in the XZ-plane) without opening a gap between the first and second chambers  102  and  104  through which radiation can pass in a straight line. Therefore, the radiation barrier  158  can maintain the thermal gradient between the first and second chambers  102  and  104 , such as to maintain a cryogenic temperature in the first chamber  102  while facilitating the motion of the wafer chuck  152  in the first chamber  102  based on the controls provided by the wafer chuck actuator system  154  in the second chamber  104 . In other words, the radiation barrier  158  can allow mechanical communication between the cryogenic first chamber  102  and the non-cryogenic second chamber  104  via the mechanical linkage  156  that extends from the first chamber  102  to the second chamber  104 . As a result, the radiation barrier  158  can facilitate the efficient wafer testing of the cryogenic wafer test system  50  to allow for testing of a large number of die on a wafer in an indexed manner, as described above. 
       FIG.  5    illustrates an example diagram  200  of a radiation barrier. The diagram  200  demonstrates a first view  202  and a second view  204  of the radiation barrier  206 . The radiation barrier  206  can correspond to the radiation barrier  62 ,  128 , or  158  in the respective example of  FIGS.  2 - 4   . Therefore, reference is to be made to the examples of  FIGS.  2 - 4    in the following description of the examples of  FIG.  5   . 
     The first view  202  is demonstrated as a cross-sectional view of a portion of the mechanical linkage and the radiation barrier  206 , taken along “A” in the second view  204  that is demonstrated as an underneath view of the radiation barrier  206 . The first and second view  202  and  204  also each include the mechanical linkage  208 , demonstrated as including a shaft  210  that extends between the wafer chuck (e.g., the wafer chuck  56 ,  108 ,  152 ) and the wafer actuator system (e.g., the wafer actuator system  60 ,  124 ,  154 ), and is therefore configured to slide along and rotate about the Y-axis. The mechanical linkage  208  can also move in a planar motion along the XZ-plane. In the example of  FIG.  5   , the mechanical linkage  208  includes a flange  212 , such as integrally formed with the shaft portion of the mechanical linkage  208 . 
     The radiation barrier  206  is demonstrated as a plurality of overlapping planar rings, such that the overlapping planar rings are not mechanically coupled to each other in any way other than through contact and gravity. The rings are demonstrated with a darker shading to correspond to the cross-section of the material and a lighter shading to correspond to the hollow interior of the ring (inside the ID of the respective rings). The overlapping planar rings can each be formed from and/or coated with a thermally conductive material (e.g., copper and/or gold), and are arranged in an incrementally increasing size between a first ring  214  and a last ring  216  of the overlapping planar rings. In the example of  FIG.  5   , the first ring  214  is the smallest ring and rests upon the flange  212 , such that each next contiguous ring has a larger ID and a larger OD, with the last ring  216  having the largest ID and the largest OD. Each of the rings also includes a lip  218  arranged at approximately the OD and which extends in the −Y direction. As described in greater detail herein, the lip  218  is arranged such that the ring below the respective one of the rings contacts the lip  218  to facilitate motion in the XZ-plane of the respective one of the rings. The second view  204  thus demonstrates the concentricity of the rings of the radiation barrier  206  in a neutral position, and thus with the mechanical linkage  208  and each of the rings of the radiation barrier  206  being axially aligned. 
       FIG.  6    illustrates another example diagram  250  of a radiation barrier. The diagram  200  demonstrates a first view  252  and a second view  254  of the radiation barrier  206 . The diagram  250  demonstrates the result of lateral motion of the mechanical linkage  208  to an extreme position in the XZ-plane (along the X-axis in the example of  FIG.  6   ). Therefore, reference is to be made to the examples of  FIG.  5    in the following description of the example of  FIG.  5   . 
     In the example of  FIG.  6   , in response to lateral motion of the mechanical linkage  208  along the X-axis, the OD of the flange  212  can contact the lip  218  of the first ring  214 , which causes the first ring  214  to being moving along the X-axis. The OD of the first ring  214  can then contact the lip  218  of the next contiguous ring (e.g., above the first ring  214 ), which can cause the next contiguous ring to begin moving along the X-axis. Such a sequence can continue until the OD of the ring below the last ring  216  contacts the lip  218  of the last ring  216 , which thus corresponds to a bound of the motion along the X-axis. Based on the relative diameter of the ID and OD of the contiguous rings relative to each other, the ID of a given ring overlaps the OD of the next contiguous ring (e.g., below) along the axis opposite the direction of the motion. As described above, the last ring  216  can have a motion limit that is based on a fixed mechanical obstacle, such that the other rings can slide beneath the last ring  216  as the mechanical linkage  208  moves after the last ring  216  contacts the fixed mechanical obstacle. As a result, there is no gap between the overlapping planar rings through the radiation barrier  206 , and therefore no gap between the first and second chambers through which radiation can pass from the second chamber to the first chamber in a straight line. Accordingly, the overlapping planar rings can slide along each other as the mechanical linkage  208  moves along the XZ-plane to maintain no gaps in the radiation barrier  206  between the first and second chambers to maintain the thermal gradient between the first and second chambers. 
     The sequence of motion of the rings is not limited to as described herein. For example, some of the rings can move along with the rings below them, without contact of the OD with the lip  218  of the next contiguous ring, based on friction. Thus, the lips  218  can merely provide a boundary of motion while maintaining no gaps between two contiguous rings. As another example, the arrangement of the rings is not limited to as demonstrated in the example of  FIGS.  5  and  6   . For example, the rings can be inverted relative to that demonstrated in the examples of  FIGS.  5  and  6   , such that the smallest first ring  214  can be on the top of the radiation barrier  206  and the largest last ring  216  can be on the bottom of the radiation barrier  206 , with all of the rings being below the flange  212 . As another example, the rings can be flexibly coupled to the mechanical linkage  208  or to a fixed portion of the first or second chamber to provide elasticity of the motion of the rings of the radiation barrier  206 . Thus, the rings of the radiation barrier  206  can flexibly move back to the neutral position demonstrated in the second view  204  of the example of  FIG.  5    in response to the motion of the mechanical linkage  208  back to the neutral position to maintain the coaxial concentricity of the rings in the neutral position. Accordingly, the radiation barrier  206  can be arranged in a variety of ways. 
     What have been described above are examples of the present invention. It is, of course, not possible to describe every conceivable combination of components or methodologies for purposes of describing the present invention, but one of ordinary skill in the art will recognize that many further combinations and permutations of the present invention are possible. Accordingly, the present invention is intended to embrace all such alterations, modifications and variations that fall within the spirit and scope of the appended claims. Additionally, where the disclosure or claims recite “a,” “an,” “a first,” or “another” element, or the equivalent thereof, it should be interpreted to include one or more than one such element, neither requiring nor excluding two or more such elements. As used herein, the term “includes” means includes but not limited to, and the term “including” means including but not limited to. The term “based on” means based at least in part on.