Abstract:
The invention provides a method of testing a circuit on a substrate. Generally speaking, a substrate is located in a transfer chuck, a surface of a test chuck is moved into contact with a substrate, the substrate is secured to the test chuck, the test chuck is moved relative to the transfer chuck so that the substrate moves off the transfer chuck, terminals on the substrate are moved into contact with contacts to electrically connect the circuit through the terminals and the contacts to an electric tester, signals are relayed through the terminal and the contacts between the electric tester and the circuit, the terminals are disengaged from the contacts, and the substrate is removed from the test chuck.

Description:
RELATED APPLICATIONS 
   This is a continuation of application Ser. No. 10/035,508, now U.S. Pat. No. 6,861,859, filed on Oct. 22, 2001. 

   BACKGROUND OF THE INVENTION 
   1). Field of the Invention 
   This invention relates to a method and apparatus for testing circuits on substrates. 
   2). Discussion of Related Art 
   Electronic circuits are often manufactured on semiconductor wafers. A saw is then used to cut the wafer into individual dies, each carrying a respective circuit. The dies are then mounted to other substrates which provide both structural support and electric communication to other devices. 
   It is often required to test such circuits at various stages during manufacture and before they are sold. An apparatus used for testing such a circuit usually includes a plurality of spring contacts which are brought into contact with terminals connected to the circuit. Electronic signals are then relayed through the contacts and terminals between an electric tester and the circuit so as to test functional integrity of the circuit. 
   SUMMARY OF THE INVENTION 
   The invention provides a method of testing a circuit on a substrate. For example, a substrate is located in a transfer chuck, a surface of a test chuck is moved into contact with a substrate, the substrate is secured to the test chuck, the test chuck is moved relative to the transfer chuck so that the substrate moves off the transfer chuck, terminals on the substrate are moved into contact with contacts to electrically connect the circuit through the terminals and the contacts to an electric tester, signals are relayed through the terminals and the contacts between the electric tester and the circuit, the terminals are disengaged from the contacts, and the substrate is removed from the test chuck. 
   According to one aspect of the invention an image is recorded of a surface of the substrate while still on the transfer chuck, for example while moving off the transfer chuck. 
   According to another aspect of the invention, an image is recorded of a surface of the substrate in a single pass. 
   According to a further aspect of the invention, a plurality of substrates are simultaneously held by the test chuck and may be simultaneously scanned and may be simultaneously heated or cooled. 
   The invention also provides a corresponding apparatus. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention is further described by way of example with reference to the accompanying drawings wherein: 
       FIG. 1  is a perspective view of an apparatus used for testing circuits on substrates according to an embodiment of the invention; 
       FIG. 2  is a view similar to  FIG. 1  where a top plate is removed; 
       FIG. 3  is an end view of a portion of a transfer chuck of the apparatus; 
       FIG. 4  is a plan view of the transfer chuck illustrating loading of a first substrate; 
       FIG. 5  is a view similar to  FIG. 4  after the transfer chuck is moved and more substrates are loaded in the transfer chuck; 
       FIG. 6  is an end view of the transfer chuck with the substrates thereon, further illustrating an thermal conditioning chuck; 
       FIG. 7  is a view similar to  FIG. 6  after the thermal conditioning chuck is moved so as to elevate the substrates, and air is provided through the thermal conditioning chuck to heat the substrates; 
       FIG. 7A  is an enlarged view of a portion of  FIG. 7 ; 
       FIG. 8  is a perspective view similar to the perspective view of  FIG. 2  after the transfer chuck is moved off the thermal conditioning chuck and the substrates are aligned with a test chuck; 
       FIG. 9  is an end view illustrating the transfer chuck and the test chuck; 
       FIG. 10  is a view similar to  FIG. 9  after the test chuck is elevated so as to elevate the substrates, and a vacuum is applied to secure the substrates to the test chuck; 
       FIG. 11  is a perspective view illustrating how the test chuck removes the substrates from the transfer chuck; 
       FIG. 12  is a side view illustrating components of the apparatus used to capture a two-dimensional image of an upper surface of each substrate; 
       FIG. 13  is a view similar to  FIG. 12  illustrating the location of the test chuck after the images are captured and the substrates are aligned with contacts; 
       FIG. 14  is a plan view illustrating an example of a substrate which is tested utilizing the apparatus; 
       FIG. 15  is an enlarged view of a die and terminals on the substrate; 
       FIG. 16  is a perspective view illustrating movement of the test chuck to again insert the substrates into the transfer chuck; 
       FIG. 17  is a perspective view illustrating the substrates after they are located in the transfer chuck but before they are removed therefrom utilizing substrate removal apparatus; and 
       FIG. 18  is a view similar to  FIG. 17  after one of the substrates is removed from the transfer chuck and a further substrate is located on the transfer chuck. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIGS. 1 and 2  illustrate apparatus  20  used for testing circuits on substrates, according an embodiment of the invention. The apparatus  20  includes a support frame  22 , and, either directly or indirectly mounted to the support frame  22 , substrate feeding apparatus  24 , a transfer chuck  26 , thermal conditioning apparatus  28 , a platen  30 , a test chuck  32 , a top plate  34 , a probe substrate  36 , contacts  38  (shown in exaggerated detail), an electric tester  40 , and substrate removal apparatus  42 . 
   The substrate feeding apparatus  24  includes a feed cartridge  46  and a conveyor system  48  located next to the feed cartridge  46 . A plurality of substrates are located in the feed cartridge  46 . The substrates are then fed one after another onto the conveyor system  48 . The conveyor system  48  transfers the substrates from the feed cartridge  46  to the transfer chuck  26 . 
     FIGS. 3 and 4  illustrate the transfer chuck  26  in more detail. The transfer chuck  26  has six slots  50 A–F formed therein. Each slot, for example, the slot  50 B, has two opposing supports  52 A and  52 B with a respective gap  54  between the supports  52 A and  52 B. 
   A substrate  56 A is fed from the conveyor system  48  into the slot  50 A. The substrate  56 A is dropped onto the supports  52 A and  52 B of the slot  50 A. A lower surface of the substrate  56 A is then exposed to the gap  54 . 
   As shown on  FIG. 5 , the transfer chuck  26  is movable in a direction  58  relative to the support frame. The transfer chuck  26  is first moved so that the conveyor system  48  is aligned with the slot  50 B. Another substrate  56 B is then loaded into the slot  50 B. The transfer chuck  26  is then moved so that the slot  50 C is aligned with the conveyor system  48 . Another substrate  56 C is then located in the slot  50 C. The conveyor  48  does not fill the slots  50 D–F with substrates. 
   The transfer chuck  26  is then moved back into its position as shown in  FIG. 4 . As shown in  FIG. 6 , the substrates  56 A–C are thereby located over an thermal conditioning chuck  60  of the thermal conditioning apparatus  28 . The thermal conditioning chuck  60  has an upper side having three high surfaces  62  alternated by two low surfaces  64 . Each high surface  62  is located below a respective one of the substrates  56 A–C. An air outlet opening  66  is formed into a lower surface of the thermal conditioning chuck  60 . Air suction openings  68  lead off the air outlet opening  66  and have air entry points in the surfaces  62 . Although not shown in  FIG. 6 , it should be understood that each surface  62  has a plurality of air suction openings  68  spaced from one another into the paper. 
   The thermal conditioning apparatus also includes resistive elements  69 A and cooling passages  69 B, which are located within the thermal conditioning chuck  60 . 
   Air is then pumped in a direction  74  out of the air suction opening  66  so that vacuums are created in the air suction openings  68  and on the lower surfaces of the substrates  56 A–C. The vacuums secure the substrates  56 A–C to the surfaces  62 . 
   The thermal conditioning chuck  60  is movable relative to the support frame  22  in a vertical direction  70 . As shown in  FIG. 7 , such movement of the thermal conditioning chuck  60  moves the surfaces  62  in between the gaps  54  so that each surface  62  contacts a respective lower surface of a respective one of the substrates  56 A–C. Further movement of the thermal conditioning chuck  60  in the direction  70  elevates the substrates  56 A–C from the supports  52 A and  52 B. The substrates  56 A–C are still laterally supported by sidewalls  72  extending upwardly from the supports  52 A and  52 B. 
   As shown in  FIG. 7A , each substrate  56  has one or more dies  108  on its lower surface. The surface  62  has a recess  78  between two ledges  80 . The dies  108  fit into the recess  78  when the surface  62  moves up. The ledges  80  make contact with the substrate  56  next to the dies  108  and between the supports  52 A and B. 
   The substrates  56 A–C are then either heated or cooled. The substrates may be heated by applying a voltage so that current conducts through the resistive elements  69 A. The resistive elements heat the thermal conditioning chuck  60 , which in turn heats the substrates  56 A–C. Alternatively, a cold fluid flowing through the passages  69 B may cool the thermal conditioning chuck  60  and the substrates  56 A–C. As such, the substrates  56 A–C can be heated or cooled to any selected temperature between −55° and 150° C. Because the dies  108  ( FIG. 7A ) are in the recess  78 , the material around the recess  78  assists in maintaining the temperature of the dies  108  at a desired level, especially near edges of the substrate  56 . 
   It takes approximately one minute to heat or cool the substrates  56 A–C, whereafter the air flow is turned off. The thermal conditioning chuck  60  is then moved in a direction opposite to the direction  70  so that the substrates  56 A–C drop onto the supports  52 A and  52 B. The thermal conditioning chuck  60  is moved further down so that the surfaces  62  are located below the gaps  54 . 
   As shown in  FIG. 8 , the transfer chuck  56  is moved in a direction  78  so that the substrates  56 A–C are moved off the thermal conditioning chuck  60 . The test chuck is movable on the platen  30  in horizontal x and y-directions and in a vertical z-direction. The test chuck  32  is first aligned with the substrates  56 A–C and then moved in a direction  30  and underneath the transfer chuck  26 . The test chuck  32  typically includes a forcer which rides on the platen  30 , and is known in the art. 
     FIG. 9  illustrates the test chuck  32  located below the transfer chuck  26 . The test chuck  32  has an upper side having three higher surfaces  84  with two lower surfaces  86  between them. Each higher surface  84  is located directly below a respective one of the gaps  54 . An air outlet opening  88  is formed out of the test chuck  32 . Air outlet passages  90  are formed into the surfaces  84  and are connected to the air outlet opening  88 . 
   The test chuck  32  is movable in a vertically upward z-direction  92 . As shown in  FIG. 10 , such movement of the test chuck  32  moves the surfaces  84  through the gaps  54  so that the surfaces  84  contact the lower surfaces of the substrates  56 A–C. Further movement of the test chuck  32  in the z-direction  92  elevates the substrates  56 A–C off the supports  52 A and  52 B. 
   A vacuum is then created within the air outlet opening  88  which creates a vacuum in each one of the air outlet openings  90 . The vacuums created in the air outlet openings  90  suck the substrates  56 A–C down onto the surfaces  84 . The substrates  56 A–C are so secured to the test chuck  32 . 
   The test chuck  32  includes a lower portion  32 A and an upper portion  32 B. The lower portion  32 A is movable relative to the support frame. The upper portion  32 B is disengageably secured to the lower portion  32 A, and is thus “carried” by the lower portion. The upper portion  32 B has the raised and recessed formations  84  and  86 . The upper portion  32 B is disengageable from the lower portion  32 A to allow for interchangeability with another upper portion  32 B with raised and recess formations sized for accommodating other substrates having larger or smaller widths than the substrates  56 A–C. The gaps  54  are also adjustable to match widths on raised formations on a selected upper portion  32 B. 
   As shown in  FIG. 11 , the test chuck  32  is then moved in a horizontal y-direction  96 . Such movement moves the substrates  56 A–C out of the slots  50 A–C. 
   As shown in  FIG. 12 , the apparatus also includes an image recordation device in the form of a line scanner  98  which is mounted in a stationary position to the support frame  22 . The line scanner  98  has a lens  100 . The lens  100  focuses on a line represented by a point  102  in  FIG. 12  and extending into the paper. The line represented by the point  102  is located approximately 2 cm to the left of a location  104  where the substrates  56  leave the transfer chuck  26 , as measured in the direction  96 . One of the substrates  56  is approximately 20 cm long as measured in the direction  96 . An entire lower surface of the substrates  56  is located on a respective upper surface of the test chuck  32 . 
   Because of the relative lengths and distances, and in particular because the substrate  56  is longer than the distance between the locations  102  and  104 , the lens  100  begins to focus on an upper surface of the substrates  56  while it is still located over the transfer chuck  26  and as it moves off the transfer chuck  26 . The lens  100  simultaneously focuses on a line across upper surfaces of the substrates  56 A–C in a similar manner. A one-dimensional image of the upper surface of each substrate  100  is taken along the line represented by the location  102 , and provided by the line scanner  98  to an image capture device such as memory of a digital camera. Movement of the substrates  56  in the direction  96  moves the line represented by the location  102  across upper surfaces of the substrates  56  so that two-dimensional areas of the upper surfaces of the substrates  56  are scanned. A computer knows the speed at which the test chuck  32  moves in a direction  96  so that a two-dimensional image of the upper surfaces of each of the substrates  56  is rendered by logic of the computer. 
   The test chuck  32  is then further moved in the direction  96  until one of the substrates  56  is located below the contacts  38 . It should be noted that the substrates  56  are moved in unison and pass by lens  100  only once. The test chuck  32  is thus not, for example, moved back and forth in the direction  96  and in a direction opposing the direction  96  past the lens  100 . Because of a single pass past the lens  100 , a very rough, although sufficient single image of upper surfaces of the substrates  56  is created but no time is lost by again scanning upper surfaces of the substrates  56 . The image is still accurate to approximately 12 microns, which is at least an order of magnitude more accurate than what conventional handlers used for positioning of components or motherboards and other purposes are designed to be capable of. (Multiple passes may be required for other applications. For example, contacts on a wafer may be too small to accurately scan in a single pass. Multiple scans may be carried out, with each subsequent scan being used to more accurately locate the contacts on the wafer.) 
   The test chuck  32  can then be moved in x-, y-, and z-directions so that each one of the contacts  38  is brought into contact with a respective set of terminals on one of the substrates  56 , followed by x-, y-, and z-movement of the test chuck  32  so that each one of the contacts  38  contacts a respective terminal on the other substrate, followed then by the third substrate. The contacts  38  are all electronically connected to the tester  40  so that test signals can be provided between the tester  40  and the terminals. 
     FIGS. 14 and 15  illustrate one of the substrates, for example the substrate  56 A, in more detail. The substrate  56 A includes a flexible sheet  104 , a plurality of rigid substrates  106 , and a plurality of electronic dies  108 . The rigid substrates  106  are mounted to the flexible sheet  104 . A plurality of the dies  108  are mounted on and protrude from a rear surface of a respective one of the rigid substrates  106 . An electronic circuit is formed on a frontal surface of each one of the dies  108 . A plurality of terminals  110  are located on each die  108  and are connected to the circuit formed in the respective die  108 . 
   The contacts  38  shown in  FIG. 13  make contact with the terminals  110 . Electronic signals are transmitted between the electric tester  40  shown in  FIG. 1  through the contacts  38  and the terminals  110  to and from the circuit formed in the die  108 . By relaying signals back and forth, the circuit within the die  108  can be tested with the electric tester  40 . Once the circuit is tested, the test chuck  32  is moved vertically downward so as to disengage the terminal  110  from the contacts  36 . The test chuck  2  is then moved in x- and y-directions to align terminals of another one of the dies  108  with the contacts  36 , whereafter the test chuck  32  is moved vertically upward so as to engage the terminals of the other die  108  with the contacts  38 . It may also be possible to test more of the dies  108  at once. 
   Once the circuits in all the dies  108  are tested, the test chuck  32  is moved in an x-direction so that each one of the substrates  56 A–C is aligned with a respective one of the slots  50 D–F. As shown in  FIG. 16 , the test chuck  32  is then moved in a direction  108  so that the substrates  56 A–C are located in the slots  50 D–F respectively. The vacuum on the test chuck is then released so that the substrates  56 A–C are released from the test chuck  32 . The test chuck  32  is then dropped so that the substrates  56 A–C drop into supports of the slots  50 D–F. 
   As shown in  FIGS. 17 and 18 , the substrate removal apparatus  42  includes a retracting tool  110 , a conveyor system  112 , and a removal cassette  114 . The retracting tool  110  is first used to move the substrate  56 A onto the conveyor system  112 . The conveyor system then moves the substrate  56 A into the removal cassette  114 . While the substrate  56 A is moved into the removal cassette  114 , another substrate  56 D is moved into the slot  50 A. 
   The transfer chuck  26  is then moved in a direction illustrated by the direction  58  in  FIG. 5  so that the substrates  56 B and  56 C are removed while additional substrates are located in the slots  50 B and  50 C. 
   While certain exemplary embodiments have been described and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative and not restrictive of the current invention, and that this invention is not restricted to the specific constructions and arrangements shown and described since modifications may occur to those ordinarily skilled in the art.