Abstract:
An image sensing integrated circuit test device can include a plurality of conductive leads for making electrical contact with at least one integrated circuit device under test. A light directing structure can direct light onto the at least one integrated circuit device under test. The light directing structure includes a top member disposed in a lateral direction and having at least one aperture formed therein. For each aperture, a blocking member can be attached to the top member and disposed in a longitudinal direction around the aperture. The blocking member can prevent light arriving through the aperture from propagating in the lateral direction.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates generally to integrated circuit testing, and more particularly to the testing of image sensing integrated circuit devices. 
       BACKGROUND OF THE INVENTION 
       [0002]    Image sensor integrated circuits typically include a portion for receiving and detecting light, such as an imaging array. Conventionally, image sensor integrated circuits are manufactured in wafer form and then subsequently separated (e.g., sawed) into individual dice. Each die can then be packaged. 
         [0003]    As part of a testing program, most conventional processes can test integrated circuits while in wafer form. A typical test assembly utilized in a wafer test is a probe card. A probe card can include a circuit board, or the like, for both applying and receiving test signals of a tested integrated circuit. Unlike other types of integrated circuits, in order to adequately test an image sensor, it is desirable to apply light to the integrated circuit device being tested. 
         [0004]    To better understand various features of the disclosed embodiments, a conventional image sensor integrated circuit test approach will now be described. 
         [0005]    Referring now to  FIG. 7A , a conventional probe card for testing image sensor integrated circuits is shown in a top plan view and designated by the general reference character  700 . Probe card  700  can include a circuit board portion  702  and a pupil module  704 . A circuit board portion  702  can include electrical interconnections for inputting test signals from a tester to one or more integrated circuits being tested (devices under test, or “DUTs”), as well as outputting test signals from DUTs to the tester. A pupil module  704  can fit into an opening of probe card  702 , and can apply light received on a top surface of the probe card  702  onto one or more DUTs below by focusing such light with lenses. 
         [0006]    Referring now to  FIG. 7B , a conventional pupil module  704  is shown in an exploded side cross sectional view. Pupil module  704  can include a visor  706 , a pupil lens module  708 , a base unit  710 , and a reinforcement board  712 . A visor  706  can allow light to be provided to pupil lens module  708 . Pupil lens module  708  can include a number of pupil lenses positioned adjacent to one another.  FIG. 7B  shows a pupil lens module  708  having eight pupil lenses. Each pupil lens can focus received light onto a different DUT. A base unit  710  can serve to hold lenses of pupil lens module  708  in a fixed position. A reinforcement board  712  can hold base unit, and provide a location for attaching pupil module  704  to probe card  702 . 
         [0007]    Referring now to  FIG. 7C , the optics of a pupil lens  708 - 0 , like one of those included in pupil lens module  708 , are shown in a diagram. Light  720  can be received at an upper end of a pupil lens  708 - 0  and then focused by a lens area  722 . Focused light can be output at a pupil exit position  724  and onto a DUT  726 .  FIG. 7D  shows an outside view of a pupil lens  708 - 0 . 
         [0008]    A conventional focusing test system, like that described above, can be preferred for testing image sensors having shifted color filters and/or microlenses. The difference between illumination resulting from a focusing lens versus that of diffused light is shown in  FIGS. 8A and 8B . Both  FIGS. 8A and 8B  show an integrated circuit substrate  802  that can include photo diodes (one shown as  803 ) for converting incident light into charge. Formed over substrate  802  can be microlenses and color filters  804 . Each microlens and filter can be shifted in a direction parallel to a substrate surface with respect to a photo diode below. 
         [0009]      FIG. 8A  shows illumination  806  resulting from diffused light. An area  808  shows photo diodes that are illuminated in the diffused light case.  FIG. 8B  shows illumination  810  resulting from light applied via a lens. An area  814  shows a photo diode illuminated by such a lens. 
         [0010]    A drawback to a conventional approach like that described above can be the complexity of the assembly required to test image sensors. A conventional pupil lens module has a multiple layer stack of components, including a pupil lens that must be provided for each device tested. As a result, a pupil lens module can be expensive to implement. 
         [0011]    Further, there is very little tolerance in component placements for the module. If any component is not placed correctly, one or more DUTs may not receive the proper illumination for a test. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIGS. 1A and 1B  show top plan and side cross sectional views of a test system according to a first embodiment of the present invention. 
           [0013]      FIGS. 2A to 2D  show top plan, bottom plan, and side cross sectional views of a test system according to a second embodiment of the present invention. 
           [0014]      FIG. 3  is a diagram illustrating one example of a pin hole optic arrangement for providing light to device under test according to one embodiment. 
           [0015]      FIGS. 4A and 4B  show top plan views of a testing arrangement for a test system like that shown in  FIGS. 2A to 2D . 
           [0016]      FIGS. 5A to 5F  show top plan, bottom plan, and side cross sectional views of a test system and arrangement according to another embodiment. 
           [0017]      FIGS. 6A to 6D  show top plan, bottom plan, and side cross sectional views of a test system and arrangement according to another embodiment. 
           [0018]      FIG. 7A to 7D  are various views showing a conventional probe card and associated components for testing an image sensor integrated circuit. 
           [0019]      FIGS. 8A and 8B  are side views showing a portion of an image sensor subjected to diffused light versus light from a lens. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]    Various embodiments of the present invention will now be described in detail with reference to a number of drawings. The embodiments show test devices and methods for testing image sensor integrated circuits (ICs) that can rely on the application of light to a device under test (DUT) by way of a pinhole opening, as opposed to a focusing lens. The embodiments can also allow for fine position adjustment of light transmitting components and can test image sensor ICs in both wafer and packaged form. 
         [0021]    A test device according to a first embodiment is shown in a number of views in  FIGS. 1A and 1B , and designated by the general reference character  100 . A test device  100  can be part of a test system for testing image sensor ICs.  FIG. 1A  is a top plan view of a test device  100 .  FIG. 1B  is a side cross sectional view of test device  100 . 
         [0022]    Referring now to  FIGS. 1A and 1B , a test device  100  can include a card portion  102  and a light providing assembly  104 . A card portion  102  can include a top surface  106 , a bottom surface  108  (not shown in  FIG. 1A ), and an opening  110  (also not shown in  FIG. 1A ). In addition, a card portion  102  can include electrical connections  112  to a DUT  114 . Electrical connections  112  can provide signals to and/or receive signals from a DUT  114 . Electrical connections  112  can take a variety of forms according to the particular form of the DUT  114  (i.e., wafer form, or packaged form). More detailed examples of electrical connections will be shown in other embodiments below. 
         [0023]    A light providing assembly  104  can be positioned within opening  110  of card portion  102 . A light providing assembly  104  can provide a path for light generated from a light source  116  above a top surface  106  to a DUT  114  positioned below a bottom surface  108  of card portion  102 . In the example shown, a light providing assembly  104  can include light direction structure  118  and a base  120 . 
         [0024]    Referring still to  FIGS. 1A and 1B , in the embodiment shown, light providing assembly  118  includes an aperture  122  for directing light onto a DUT  114 . An aperture  122  can be an essentially non-focusing aperture. That is, optics are not utilized to focus light onto a DUT  114 . Preferably, an aperture  122  can provide light via “pin hole” optics. That is, an aperture  122  can be an opening that presents no interfering structure between a light source  116  and a DUT  114 , or that includes a non-focusing transparent element. Even more preferably, apertures  108  can be an opening that is circular in shape. 
         [0025]    Referring to  FIG. 1B , a light providing assembly  118  can include a horizontal portion  118 - 0  and, optionally, a vertical blocking portion  118 - 1 . A horizontal portion  118 - 0  can be essentially parallel to a surface of a DUT  114  that receives light. A light blocking portion  118 - 1  can extend from a horizontal portion  118 - 0  in a direction toward a DUT  114  and can block light from being transmitted in a direction perpendicular to aperture  122 . 
         [0026]    In this way, a test device can include a light directing structure that provides light to a DUT without focusing optics. 
         [0027]    While the first embodiment described above shows one aperture, it is understood that other embodiments can include multiple apertures for testing more than one DUT at a time. In addition, for greater flexibility in a test system, other embodiments can provide some fine position adjustment in any of three dimensions. One very particular example of such an embodiment is shown in  FIGS. 2A to 2D . 
         [0028]    Referring now to  FIG. 2A , a test system is shown in a top plan view and designated by the general reference character  200 . A test system  200  can include some of the same general components as the first embodiment. Thus, like components are referred to by the same reference character but with the first digit being a “2” instead of a “1”. 
         [0029]    In the particular examples of  FIGS. 2A to 2D , a card portion  202  can be a probe card for testing multiple ICs in wafer form. In such an arrangement, DUTs can be integrated circuits formed in the same substrate that have not yet been separated or packaged. A card portion  202  can include conventional circuitry for providing signals from and to a device under test (DUT). In one a particular example, a card portion  202  can include a printed circuit board having interconnection patterns between layers and/or on either or both of the surfaces, as well as electronic components for receiving, transmitting, or conditioning test signals. 
         [0030]    As in the case of  FIGS. 1A and 1B , a light providing assembly  204  can provide a path for light through card portion  202 . However,  FIG. 2A  shows an arrangement in which light can be provided for four different DUTs. In the particular embodiment shown, a light providing assembly  204  includes a light directing structure  218  attached to a base  220 . Light directing structure  218  can include four, non-focusing apertures ( 222 - 0  to  222 - 3 ) aligned with one another along a common axis. In addition, a light directing structure  218  can be adjustable in position with respect to a base  220 . More particularly, a light directing structure  218  can be raised or lowered in position with respect to a base  220 . Such a feature can be accomplished by screws, bolts, spacers, or clamps, as but a few examples. In addition or alternatively, a light directing structure  218  can be moved in a lateral (i.e., X-Y) direction with respect to a base  220 . Such movement can also be accomplished by screws, bolts, spacers, clamps, or even an X-Y translation assembly, such as a rack and pinion assembly, to name but a few possible approaches. 
         [0031]    Referring now to  FIG. 2B , a light directing structure  218  is shown in a bottom plan view. Each aperture ( 222 - 0  to  222 - 3 ) can be surrounded by light blocking portion  218 - 1 . Thus, light received from one aperture for one DUT can be prevented from interfering with an adjacent DUT. 
         [0032]    Referring now to  FIG. 2C , a light providing assembly  204  is shown in a side cross sectional view taken along line X-X of  FIG. 2A . A base  220  can receive light directing structure  218 . In the particular example shown, a light directing structure  218  can be physically held in place with respect to base  220  by clamping members  224 . As but one example, clamping members  224  can be attached to a base by bolts and threaded openings. Preferably, light directing structure  218  can be adjusted in a lateral direction (X and/or Y) prior to being fixed in place. 
         [0033]    Of course, alternate embodiments could include different ways of adjusting position and/or fixing a light directing structure to a base. 
         [0034]    Referring now to  FIG. 2D , a test system  200  is shown in a side cross sectional view taken along line Y-Y of  FIG. 2A . As shown by  FIG. 2D  a light source  216  can be situated above a top surface  206  of card portion  202 , and light can pass through light providing assembly  204  to a DUT  214 . In the example shown, a DUT  214  can be an IC formed in a wafer  226 . 
         [0035]      FIG. 2D  also shows one particular example of electrical connections  212 . In the example shown, electrical connections  212  can be probe card “needle” type connections that extend more in a lateral direction (i.e., parallel to a bottom surface  208 ) than in a longitudinal direction (i.e., perpendicular to a bottom surface  208 ). Probe card needles can contact bond pads on an IC, and provide power and test signals to the DUT(s). 
         [0036]    In this way, a test device can include a light directing structure that provides light without focusing optics to multiple DUTs, and can include fine position adjustments in one, two or three dimensions. 
         [0037]    Referring now to  FIG. 3 , a diagram illustrates one very particular example of the application of light onto a DUT utilizing non-focusing, pin hole optics, like those of the embodiments. Diffuse light can enter a pin hole aperture  312  having a diameter “a”. Alternatively, an aperture  312  can include a light diffusing, transparent structure, such as “milk” glass. However, aperture  312  does not include any focusing effects, such as that provided by a converging lens, or the like. Based on angle “CRA”, a DUT  314  can be positioned a distance “d” below aperture  312  to provide a desired exposure length (½ diagonal) “i”. In one very particular example, an aperture diameter “a” can be 1.79 millimeters (mm) and angle “CRA” can be about 62°. This can result in a length “i” of 2.3 mm at a distance “d” of 5 mm. 
         [0038]    Of course,  FIG. 3  represents but one example, and the dimensions noted should not be construed as limiting to the invention. 
         [0039]    As noted above, a test system like that shown in  FIGS. 2A to 2D  can test multiple DUTs at the same time. One particular arrangement for doing so is shown in  FIGS. 4A and 4B . 
         [0040]      FIG. 4A  is a top plan view of a testing arrangement that can correspond to the test system shown in  FIGS. 2A to 2D .  FIG. 4A  shows a portion of a tested wafer  426 . A wafer  426  can include multiple ICs, one of which is shown as  428 . Of the numerous ICs, four ICs can be DUTs  414 - 0  to  414 - 3  of a same row. A set of electrical connections  412  can make contact with each DUT ( 414 - 0  to  414 - 3 ). The electrical connections  412  of  FIGS. 4A and 4B  can be needle type probes of a probe card.  FIG. 4A  also shows image areas for each DUT, one of which is shown as  430 . An image area  430  can be a resulting area lit according to light passing through a corresponding aperture. 
         [0041]      FIG. 4B  is a magnified view of  FIG. 4A , showing DUTs  414 - 0  and  414 - 1  in more detail. Each DUT ( 414 - 0  and  414 - 1 ) can include test point contacts (in this case bond pads, or the like), situated only on two opposing sides of each die. This can allow testing of a row of ICs, as test connections can be applied only from opposite directions. In the particular example shown in  FIG. 4B , each DUT ( 414 - 0  and  414 - 1 ) has an image sensor array  432 - 0  and  432 - 1 . The image areas  430  of the DUTs ( 414 - 0  and  414 - 1 ) can completely surround the corresponding image sensor array ( 432 - 0  and  432 - 1 ). 
         [0042]    In this way, multiple integrated circuit devices in wafer form can be tested at one time. Of course, fewer or more than four DUTs of a same row could be tested at one time according to available area of a test system (e.g., probe card). Along these same lines, provided sufficient room was available for needle type probes, more than one row could be tested at the same time. 
         [0043]    While the arrangement of  FIGS. 4A and 4B  show the testing of a single row of ICs in a wafer, alternate embodiments can include the testing of multiple rows and utilize different test probe technologies. Further, such alternate embodiments can test dice having probe locations (e.g., bond pads) on three or more sides. One example of such an approach is shown in  FIGS. 5A to 5F . 
         [0044]    Referring now to  FIG. 5A , a test system is shown in a top plan view and designated by the general reference character  500 . A test system  500  can include some of the same general components as the embodiment of  FIG. 2A , thus, like components are referred to by the same reference character but with the first digit being a “5” instead of a “2”. 
         [0045]    Unlike the arrangement of  FIG. 2A , the test system  500  of  FIG. 5A  has a light providing assembly  504  in which light can be provided to multiple rows of DUTs. In the particular embodiment shown, a light providing assembly  504  can include eight, non-focusing apertures (one of which is shown as  522 ) aligned with one another along two parallel axes. As in the case of  FIG. 5A , a light directing structure  518  can be adjustable in position with respect to a base  520 . 
         [0046]      FIG. 5A  also shows a test device  500  that includes “vertical” probes. Vertical probes can extend in a vertical direction downward from test device  500  and onto one or more DUTs. In the particular example illustrated, vertical probes can be incorporated into a light providing assembly  504 . Thus, test device  500  can include an electrical connection  524  between a light providing assembly  504  and a card portion  502 . 
         [0047]    Referring now to  FIG. 5B , a light directing structure  518 , like that shown in  FIG. 5A , is shown in a bottom plan view. Each aperture (one shown as  522 ) can be surrounded by light blocking portion  518 - 1 . Thus, light received from one aperture for one DUT can be prevented from interfering with an adjacent DUT. 
         [0048]    Referring now to  FIG. 5C , a portion of a light directing structure  518  is shown in a magnified bottom plan view. Unlike arrangements incorporating needle type probes, light directing structure  518  can include vertical probes (one shown as  536 ) for providing electrical connection to a DUT. While the arrangement of  FIG. 5C  shows vertical probes that can contact bond pads on all four sides of a DUT, alternate embodiments can include probes on two opposing sides for compatibility with ICs like those shown in  FIG. 4B . 
         [0049]    Referring now to  FIG. 5D , a magnified portion of a light directing structure  518  is shown in a side cross sectional view taken along line D-D of  FIG. 5C . In the very particular arrangement shown, vertical probes (one shown as  536 ) can be situated within light blocking portion  518 - 1 , and include contact points (one shown as  537 ) for contacting a test point (e.g., bond pad) of a DUT. 
         [0050]    Referring now to  FIG. 5E , a top plan view shows a testing arrangement that can correspond to the test system shown in  FIGS. 5A to 5D .  FIG. 5E  shows a portion of a tested wafer  526  having multiple ICs formed therein (one shown as  528 ). Eight of the ICs can be DUTs  514 - 0  to  514 - 7 . Like  FIG. 4A ,  FIG. 5E  also shows image areas for each DUT (one of which is shown as  530 ). 
         [0051]    Referring now to  FIG. 5F , a test system  500  is shown in a side cross sectional view taken along line Y-Y of  FIG. 5A . As noted above,  FIG. 5F  shows one particular example in which electrical connections for DUTs can be vertical type probes that extend in an essentially vertical direction from a bottom surface  508  of card portion  502  only DUT(s) ( 514 - 2 ,  514 - 6 ). 
         [0052]    In this way, multiple rows of IC devices in wafer form can, be tested at one time. In addition, a test system  500  can include vertical type probes for making contact with such IC devices at bond pads on more than two sides of an IC device. It is noted that while  FIGS. 5C and 5D  show vertical type test probes, alternate embodiments can include different probe types formed on a bottom surface of a light blocking portion (e.g.,  518 - 1 ). As but one example, test probes can be micro-electromechanical (MEM) type test probes. 
         [0053]    While embodiments of the present invention can test integrated circuits in wafer form, other embodiments can be used to test ICs in other forms. In particular, embodiments can test image sensor ICs in packaged form. One particular embodiment showing such an arrangement is shown in  FIGS. 6A to 6D . 
         [0054]    Referring now to  FIG. 6A , a test device  600  can include a card portion  602  and a light providing assembly  604 . A card portion  602  can include a top surface  606  having electrical connections (one shown as  612 ) to a DUT  614 . Electrical connections  612  can be compatible with a packaged integrated circuit. In the example of  FIG. 6A , a DUT  614  can have a “ball grid array” type interface, thus electrical connections  612  can be designed to compatible with such a pin arrangement. However, alternate embodiments can have electrical connections compatible with other package types, including but not limited to pin grid arrays, small outline (SOP) type packages, and inline pin type packages (e.g., DIP). 
         [0055]    Referring still to  FIG. 6A , a light providing assembly  604  can include an aperture  622  for directing light onto a DUT  614 . An aperture  622  can be an essentially non-focusing aperture that does not include optics for focusing light onto a DUT  614 . As in the embodiments above, preferably, an aperture  622  can provide light via “pin hole” optics. Light providing assembly  604  can include a horizontal portion  618 - 0  and, optionally, a vertical blocking portion  618 - 1 . A light blocking portion  618 - 1  can extend from a horizontal portion  618 - 0  in a direction toward a DUT  614  and block light from being transmitted in a direction perpendicular to aperture  622 . 
         [0056]    In  FIG. 6A , a DUT  614  can include a transparent cover  638 , a die  640 , and a package  642 . A transparent cover  638  can allow light to be received by IC and converted into electrical data. Preferably, light providing assembly  614  can have dimensions “a” and “d” suitable to generate an image height “i” that covers a desired area of IC (e.g., an image sensor array). It is noted that a DUT  614  can be tested prior placement of transparent cover  638 . 
         [0057]    Referring now to  FIG. 6B , a top plan view shows a testing arrangement that can correspond to the test system shown in  FIG. 6A .  FIG. 6B  shows a tested DUT  614 , which is in packaged form.  FIG. 6B  also show an image area  630  for DUT  614 . Image area  630  can surround an image sensor array  632  of the DUT. 
         [0058]    In this way, a test device can test ICs in packaged form, and not just wafer form. 
         [0059]    Of course, other embodiments can test multiple packaged devices. One arrangement is shown in  FIGS. 6C and 6D . 
         [0060]    Referring now to  FIG. 6C , a light providing assembly  654  is shown in a bottom plan view. Multiple apertures ( 622 - 0  to  222 - 3 ) can be surrounded by light blocking portion  618 - 1 . Thus, light received from one aperture for one DUT can be prevented from interfering with an adjacent DUT. 
         [0061]      FIG. 6D  is a top plan view of a testing arrangement that can correspond to the test system shown in  FIG. 6C .  FIG. 6D  shows a portion of a test device  650  that can hold four DUTs  614 - 0  to  614 - 3 , arranged into a 2×2 array. A set of electrical connections (one shown as  612 ) can make contact with each DUT ( 614 - 0  to  614 - 3 ) to provide test signals to and from the devices.  FIG. 6D  shows image areas for each DUT, one of which is shown as  630 , showing resulting area lit according to light passing through an aperture  612  of a light providing assembly  654 . 
         [0062]    In this way, multiple packaged image sensor devices can be tested with non-focusing light apertures. 
         [0063]    While the above embodiments have been described with directions as “up” and “down”, such directions are not meant to limit the invention to any particular orientation in space. Test systems and/or corresponding DUTs can be oriented at different angles from, or inverted with respect to the various disclosed views. 
         [0064]    Embodiments of the present invention are well suited to performing various other steps or variations of the steps recited herein, and in a sequence other than that depicted and/or described herein. 
         [0065]    For purposes of clarity, many of the details of the various embodiments and the methods of designing and manufacturing the same that are widely known and are not relevant to the present invention have been omitted from the following description. 
         [0066]    It should be appreciated that reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Therefore, it is emphasized and should be appreciated that two or more references to “an embodiment” or “one embodiment” or “an alternative embodiment” in various portions of this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined as suitable in one or more embodiments of the invention. 
         [0067]    Similarly, it should be appreciated that in the foregoing description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention. 
         [0068]    It is also understood that the embodiments of the invention may be practiced in the absence of an element and/or step not specifically disclosed. That is, an inventive feature of the invention can be elimination of an element. 
         [0069]    Accordingly, while the various aspects of the particular embodiments set forth herein have been described in detail, the present invention could be subject to various changes, substitutions, and alterations without departing from the spirit and scope of the invention.