Abstract:
An apparatus and method are provided for picking up an integrated circuit and for facilitating the optical testing thereof. The apparatus comprises a pick-up mechanism that includes a vacuum chamber. The vacuum chamber is defined by an upper portion, an expandable member, and a lower portion. The lower portion defines a suction orifice that is moveable with a movement of the expandable member. An optical pathway is defined by the vacuum chamber, the optical pathway passing through the suction orifice and onto an integrated circuit that is held against the suction orifice via a vacuum pressure applied to the vacuum chamber.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a divisional of copending application Ser. No. 09/428,152 filed on Oct. 27, 1999. 
    
    
     TECHNICAL FIELD 
     The present invention is generally related to the field of integrated circuit fabrication and, more particularly, is related to an apparatus and method for the automated handling and testing of optical integrated circuits. 
     BACKGROUND OF THE INVENTION 
     The electronics industry currently produces thousands of integrated circuits each day. These circuits have come down in cost significantly in more recent years due to the use of effective mass production techniques that facilitate the current high output. The machinery employed in these mass production techniques is quite complex and often performs repetitive tasks. Such machinery is typically engineered for maximum reliability over a large number of operation cycles, whatever the specific operation may entail. 
     In addition to the use of automated machines to produce various integrated circuits, industry also employs automated machines to test the integrated circuits to ensure maximum reliability and quality of the end product. Due to the high volumes created, such testing equipment is designed with the goal in mind to operate with maximum efficiency over numerous cycles without failure. However, some testing systems fall short of this goal. 
     For example, in testing one particular type of integrated circuit, namely, an active pixel sensor, machines are employed to pick up the sensor and place it on a test circuit such that the leads of the sensor come into contact with electrical pads through which the sensor may be tested. Such sensors require that light be applied to their light sensitive surface to determine whether the response of the sensor is within acceptable parameters. 
     However, typical pick-up devices employed to handle such sensors do not provide an ability to both hold the sensor and apply light to the light sensitive surface. In particular, suction cups that are typically used in such handling equipment generally cover the light sensitive surfaces and a proper test may not be performed when such handlers place the sensor against the appropriate test pads. 
     To solve this problem, some have attempted to use suction devices that allow light to illuminate the light sensitive surfaces. However, such machinery has proven unreliable. In particular, such pick-up machines cannot effectively create a reliable vacuum seal with the integrated circuit that allows light to be applied to the light sensitive surfaces over an acceptable number of testing cycles. 
     SUMMARY OF THE INVENTION 
     In light of the foregoing, the present invention provides an apparatus and method for picking up an integrated circuit that facilitates optical testing thereof. Briefly described, the apparatus comprises a pick-up mechanism that includes a vacuum chamber. The vacuum chamber is defined by an upper portion, an expandable member, and a lower portion. The lower portion defines a suction orifice that is moveable with a movement of the expandable member. An optical pathway is defined by the vacuum chamber, the optical pathway passing through the suction orifice and onto an integrated circuit that is held against the suction orifice via a vacuum pressure applied to the vacuum chamber. 
     During operation, the suction orifice is applied to a surface of the integrated circuit and the vacuum is applied to the vacuum chamber, thereby applying a suction hold to the integrated circuit. The expandable member contracts, thereby moving the suction orifice in an axial direction until the integrated circuit comes into contact with a number of contact edges that stop the movement. The expandable member may be, for example, a bellows or other similar device as an integral portion of the vacuum chamber. 
     The present invention can also be viewed as providing a method for picking up and testing an integrated circuit. In this regard, the method can be broadly summarized by the following steps: providing a vacuum chamber having an upper portion, an expandable member, and a lower portion, the lower portion defining a suction orifice, the suction orifice being moveable with a movement of the expandable member; applying the suction orifice to a smooth face of an integrated circuit; evacuating the vacuum chamber to pick up the integrated circuit; and illuminating the smooth face of the integrated circuit with a light that propagates along an optical pathway that passes through the suction orifice. 
     The present invention has numerous advantages, including the movement of the suction orifice that accommodates the use of a more rigid O-ring that provides greater durability and reliability in operation. The movement of the suction orifice also allows the pick-up mechanism to be employed with integrated circuits of varying height with the less durable O-ring. In addition, due to the flexibility of the O-ring and the fact that it is frictionally mounted into the O-ring groove, it is easily replaced by hand when worn, etc. Also, the frictional mounting of the O-ring keeps it in place in the O-ring groove and it does not move into the optical pathway in any way. In addition, the pick-up mechanism allows the automated testing of active pixel sensors, for example, by applying light to the sensor while it is held by the pick-up mechanism which places the sensor over test pads for testing. Also, the over all design of the pick-up mechanism is simple, user friendly, robust and reliable in operation, efficient in operation, and easily implemented for mass commercial production. 
     Other features and advantages of the present invention will become apparent to one with skill in the art upon examination of the following drawings and detailed description. It is intended that all such additional features and advantages be included herein within the scope of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The invention can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
     FIG. 1 is a section view of a pick-up mechanism according to an embodiment of the present invention; 
     FIG. 2 is a section view of the pick-up mechanism of FIG. 1 engaging an integrated circuit; 
     FIG. 3A is a top view of a upper portion employed in the pick-up mechanism of FIG. 1; 
     FIG. 3B is a side view of the upper portion of FIG. 3A; 
     FIG. 4A is a bottom view of a lower portion employed in the pick-up mechanism of FIG. 1; 
     FIG. 4B is a side view of the lower portion of FIG. 4A; 
     FIG. 5A is a top view of an O-ring employed in the pick-up mechanism of FIG. 1; and 
     FIG. 5B is a side view of the O-ring of FIG.  5 A. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     With reference to FIG. 1, shown is a pick-up mechanism  100  according to an embodiment of the present invention. The pick-up mechanism  100  includes a support bracket  103  that provides a support structure for the major components of the pick-up mechanism  100 . The pick-up mechanism  100  also includes a vacuum chamber  105  that is defined by an upper portion  106  top, an expandable member  109 , and a lower portion  113 . The upper portion  106  may comprise, for example, a top flange or other suitable structural member. The expandable portion  109  may comprise, for example, a bellows or other suitable member that expands and contracts accordingly. Also, the lower portion  113  may comprise, for example, a pick-up flange or other suitable structural member. 
     The upper portion  106  is set into the support bracket  103  as shown and is held into place by set screw  116 . The support bracket  103  also includes a vacuum inlet  119  that provides access to a threaded vacuum inlet  123  of the upper portion  106 . An appropriate vacuum fitting  126  is threaded into the threaded vacuum inlet  123  through the vacuum inlet  119  of the support bracket  103  as shown. The expandable member  109  is adhesively attached to the bottom of the upper portion  106  and the top of the lower portion  113  as shown. 
     The pick-up mechanism  100  also includes a mating flange  129  that is removably attached to the bottom of the support bracket  103  via one of a number of means, for example, by bolts, etc. The mating flange  129  restricts the movement of the lower portion  113  in an axial direction  131 . In particular, the lower portion  113  is movable within the mating flange  129  with the movement, i.e., the expansion and/or the contraction, of the expandable member  109 . The mating flange  129  restricts the movement of the lower portion  113  in the axial direction  131 . The mating flange  129  also includes a number of contact edges  133  that together define an integrated circuit stop as will be discussed. 
     The pick-up mechanism  100  further includes a lens/glass diffuser  136  that is seated into the upper portion  106  and adhesively mounted thereto. The expandable member  109  is adhesively mounted to the bottom of the upper portion  106 . Both the lens/glass diffuser  136  and the expandable member  109  are attached to the upper portion  106  using a suitable adhesive to prevent any vacuum leakage as will be discussed. 
     The lower portion  113  is also adhesively attached to the expandable member  109  as shown. The bottom of the lower portion  113  defines a suction orifice  139 . The suction orifice  139  is exposed at its exit face  143 . The lower portion  113  also includes an O-ring groove  146  that is placed around the perimeter of the exit face  143  of the suction orifice  139 . Mounted in the O-ring groove  146  is an O-ring  153 . The O-ring  153  is preferably frictionally mounted into the O-ring groove  146  to provide for easy removal and replacement by hand. The O-ring  153  defines a ceiling junction with an integrated circuit  156  that may include, for example, active pixel sensor circuits. 
     The vacuum chamber  105  generally defines an optical pathway  159  that passes through the lens/glass diffuser  136 , the upper portion  106 , expandable member  109 , and the lower portion  113  and exits out of the suction orifice  139 . The optical pathway  159  advantageously facilitates an optical testing of the integrated circuit  156  while it is held by the pick-up mechanism  100  as will be discussed. 
     With reference to FIG. 2, the operation of the pick-up mechanism  100  is discussed. To begin, the pick-up mechanism  100  is positioned above, for example, an optical integrated circuit  156  or other integrated circuit that is to be tested. The suction orifice  139  is then placed against the upper surface of the integrated circuit  156  such that the O-ring  153  is mated against the upper surface of the integrated circuit  156 . Thereafter, a vacuum pressure is applied to the vacuum inlet  126 , causing the lower portion  113  with the integrated circuit  156  to be pulled upward in an axial motion. 
     The axial movement occurs when the expandable member  109  contracts as shown. The O-ring  153  advantageously creates a vacuum seal with the upper surface of the integrated circuit  156  and therefore the integrated circuit is held against the lower portion  113 . Together the lower portion  113  and the integrated circuit  156  will move upward until the contact edges  133  come into contact with the leads  163  of the integrated circuit  156 . Although two contact edges  133  are shown, it is understood that there may be four contact edges  133  that come into contact with leads  163  that extend from the integrated circuit  156  on all four sides, etc. The integrated circuit  156  is thus seated against the contact edges  133  thereby preventing the further axial movement of the lower portion  113  and the integrated circuit  156 . 
     Thereafter, the pick-up mechanism  100  travels to a new position to place the integrated circuit  156  on contact pads for testing as is known in the art. A light source  166  may then be employed to generate light that propagates along the optical pathway  159  and falls on the sensor  156 . The light source  166  may comprise, for example, a laser, incoherent light, or other suitable light source. Light sensitive components  169  located on the surface of the integrated circuit  156  sense the light and the testing of the integrated circuit  156  is performed. The light sensitive components  169  may be covered by a layer of transparent material, such as glass, etc. Thus, the integrated circuit  156  may comprise, for example, an active pixel sensor or other similar integrated circuit. The integrated circuit  156  is released by relieving the vacuum at the vacuum inlet  126 . 
     The pick-up mechanism  100  provides several benefits including an axial movement of the suction orifice  139  that accommodates the use of a more rigid O-ring  153 . The axial movement allows the pick-up mechanism  100  to be employed with integrated circuits  156  of varying height and at the same time allows the use of the O-ring  153 . In particular, the use of the expandable member  109  allows the suction orifice  139  along with the O-ring  153  to be placed over integrated circuits with greater height as the lower portion  113  will be pushed up into the mating flange  129 , the expandable member  109  contracting accordingly. 
     In addition, due to the material makeup of the O-ring  153 , it can last through thousands of pick-up cycles and is easily replaced by hand. Also, the O-ring  153  stays in place in the O-ring groove  146  and does not block the optical pathway  159  in any way. Thus, the pick-up mechanism  100  facilitates the automated testing of active pixel sensors, for example, by applying light to the sensor while it is held by the pickup mechanism  100  which places the sensor over test pads for testing. 
     The materials that are used to manufacture the support bracket  103 , upper portion  106 , and the lower portion  113  may be, for example, aluminum, steel, or other material. Aluminum or other lightweight materials are preferable as the resulting pick-up mechanism  100  requires less force and energy to manipulate during use, etc. The expandable member  109  may comprise stainless steel or other suitable material that is durable and can withstand repeated use without degradation or developing holes, etc. 
     With reference to FIGS. 3A AND 3B, shown are side and top views of the upper portion  106 . The upper portion  106  facilitates adhesive mounting of the lens/glass diffuser  136  therein. Specifically, a silicon adhesive maybe applied to a contact surface  173  of the upper portion  106  or to the lens/glass diffuser  136 . Thereafter, the lens/glass diffuser  136  is placed into position in the upper portion  106 . The upper portion  106  also includes spill over grooves  176  that accommodate a run over of silicon adhesive. After placing the lens/glass diffuser  136  into the upper portion  106 , it is given a quarter turn, for example, to ensure a proper vacuum seal is formed between the lens/glass diffuser  136  and the upper portion  106 . 
     With reference to FIGS. 4A AND 4B, shown are top and side views of the lower portion  113  according to another embodiment of the present invention. The lower portion  113  includes interior angled surfaces  179 . The interior angled surfaces  179  serve to prevent the light propagating along the optical pathway  159  (FIG. 2) from reflecting off of the interior angled surfaces  179  thereby adversely affecting the uniformity of the light that falls on the light sensitive components  169  (FIG.  2 ). Rather than fall on the light sensitive components  169 , the reflected light propagates toward the opposing interior angled surfaces  179 . The angle of the interior angled surfaces  179  with respect to the optical pathway  159  is, for example, 20 degrees, but other angles may be employed. Also, the interior angled surfaces  179  as well as the entire interior of the lower portion  113  are preferably colored in a non-reflective color such as, for example, flat black to reduce unwanted reflection of the light that propagates along the optical pathway  159 . 
     The O-ring groove  146  located around the suction orifice  139  preferably accommodates the frictional mounting of the O-ring  153  therein. The O-ring groove  146  may appear in many different shapes and sizes, depending upon the particular size and shape of the integrated circuit  156  that one wishes to pick up with the pick-up mechanism  100 . Due to the fact that the O-ring  153  is made of a flexible material, the O-ring can typically be fitted into the O-ring groove  146  even though the O-ring groove  146  is a different shape than the O-ring  153 . 
     The O-ring groove  146  also includes a surface smoothness that is necessary to form a vacuum seal between the O-ring  153  and the lower portion  113 . For best results, the roughness/height index value of the surface of the O-ring groove  146  is generally not greater than 16 microinches, for example, although other smoothness factors may be employed providing that a proper vacuum seal is formed. Alternatively, the O-ring may be mounted into the O-ring groove  146  using an appropriate adhesive, etc., however such a mounting may make the O-ring  153  harder to remove. 
     Finally, with reference to FIGS. 5A AND 5B, shown are side and top views of the O-ring  153 . The O-ring  153  is comprised of a material of sufficient hardness to prevent the integrated circuit  156  (FIG. 1) from sticking to the O-ring  153  itself after the vacuum is relieved in the vacuum chamber  104  (FIG.  1 ). The material of the O-ring  153  is also preferably durability and capable of withstanding harsh atmospheres. For example, the O-ring  153  may be exposed to solvents such as acetone or alcohol in the typical integrated circuit manufacturing environment and should not experience any significant degradation therefrom. One suitable material that may be used for the O-ring  153 , for example, is Viton, manufactured by and commercially available from Pressure Seals, Inc., of South Windsor, Conn. although other suitable materials may be employed as well keeping the above criterion in mind. 
     Many variations and modifications may be made to the above-described embodiment(s) of the invention without departing substantially from the spirit and principles of the invention. All such modifications and variations are intended to be included herein within the scope of the present invention.