Abstract:
A method of forming molding standoff structures on integrated circuit devices is disclosed which includes forming a plurality of standoff structures on a substantially rectangular sheet of transparent material and, after forming the standoff structures, singulating the substantially rectangular sheet of transparent material into a plurality of individual transparent members, each of which comprise at least one of the plurality of standoff structures.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to the field of manufacturing and package of microelectronic devices, and, more particularly, to a method of forming molded standoff structures on integrated circuit devices. 
     2. Description of the Related Art 
     Microelectronic devices generally have a die (i.e., a chip) that includes integrated circuitry having a high density of very small components. In a typical process, a large number of die are manufactured on a single wafer using many different processes that may be repeated at various stages (e.g., implanting, doping, photolithography, chemical vapor deposition, plasma vapor deposition, plating, planarizing, etching, etc.). Each of the die typically include an array of very small bond pads electrically coupled to the integrated circuitry. The bond pads are the external electrical contacts on the die through which the supply voltage, signals, etc. are transmitted to and from the integrated circuitry. The die are then separated from one another (i.e., singulated) by backgrinding and cutting the wafer. After the wafer has been singulated, the individual die are typically “packaged” to couple the bond pads to a larger array of electrical terminals that can be more easily coupled to the various power supply lines, signal lines and ground lines. 
     An individual die can be packaged by electrically coupling the bond pads on the die to arrays of pins, ball pads or other types of electrical terminals, and then encapsulating the die to protect it from environmental factors (e.g., moisture, particulates, static electricity and physical impact). For example, in one application, the bond pads can be electrically connected to contacts on an interposer substrate that has an array of ball pads. The die and a portion of the interposer substrate are then encapsulated with molding compound. 
     Electronic products require packaged microelectronic devices to have an extremely high density of components in a very limited space. For example, the space available for memory devices, processors, displays and other microelectronic components is quite limited in cell phones, PDAs, portable computers and many other products. As such, there is a strong drive to reduce the height of the packaged microelectronic device and the surface area or “footprint” of the microelectronic device on a printed circuit board. Reducing the size of the microelectronic device is difficult because high performance microelectronic devices generally have more bond pads, which result in larger ball grid arrays and thus larger footprints. 
     Image sensor die present additional packaging problems. Image sensor die include an active area that is responsive to electromagnetic radiation, e.g., light emitted from a light source. In packaging, it is important to cover and protect the active area without obstructing or distorting the passage of light or other electromagnetic radiation. Typically, an image sensor die is packaged by placing the die in a recess of a ceramic substrate and attaching a glass window to the die over the active area to hermetically seal the package. 
       FIG. 1  is a schematic, partial cross-sectional view of an illustrative example of a prior art image sensor die  10  formed in a semiconducting substrate  12 . The image sensor die  10  comprises a window or glass  14  that is positioned above an active area  18  formed in the substrate  12 . The active area  18  typically contains a plurality of sensor cells (not shown) that are responsive to electromagnetic radiation that passes through the window  14 . The image sensor die  10  further includes a plurality of bond pads  22  and a schematically depicted integrated circuitry  20  that is electrically coupled to the bond pads  22  and the active area  18 . An adhesive or epoxy  16  is used to attach the window  14  to the substrate  12 . 
     Also depicted in  FIG. 1  are a plurality of standoff structures  24  that may be formed on the substrate  12 . Among other things, the standoff structures  24  are provided to maintain at least a set distance (corresponding to the height of the standoff structures  24 ) between the glass  14 . Such standoff structures  24  may not be present in all applications 
     One illustrative technique for manufacturing the standoff structures  24  involves the use of traditional equipment used in manufacturing integrated circuit devices. For example, a sheet of glass, typically supplied as a square or rectangular piece of material, is initially cut into so-called “glass rounds.” These glass rounds have substantially the same round configuration as that of the semiconducting substrates, e.g., eight to twelve inches in diameter, that are used in manufacturing integrated circuit devices. After the glass rounds are formed, the standoff structures  24  are formed using traditional processing tools commonly found in semiconductor manufacturing operations. For example, the glass rounds may be positioned in a photolithography tool and the standoff structures  24  may be formed by performing traditional photolithography processes, e.g., spin-coat, soft-bake, expose, develop, hard-bake. Of course, using this technique, the standoff structures  24  may have any desired shape or configuration. Another technique might involve deposition of a layer of material on the glass round, followed by the formation of a masking layer, e.g., a patterned layer of photoresist material. Third, a traditional etching process may be performed to define the standoff structures  24  from the layer of material. 
     After the standoff structures  24  are formed, the glass round is then cut into a plurality of individual glass pieces or windows  14  that will be positioned over individual die, as depicted in  FIG. 1 . The aforementioned process of forming the standoff structures  24  is relatively expensive and time-consuming. Moreover, employing such manufacturing techniques may occupy very valuable semiconductor manufacturing equipment and therefore prevent the use of such equipment for manufacturing integrated circuit die. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which: 
         FIG. 1  is an example of an illustrative prior art image sensor die; 
         FIGS. 2A-2C  are examples of illustrative standoff structures that may be formed on a window for an integrated circuit device; 
         FIG. 3  depicts a plurality of standoff structures having varied end configurations; 
         FIG. 4  is a schematic cross-sectional side view of one illustrative technique for forming the standoff structures described herein; and 
         FIG. 5  is a schematic cross-sectional view of an illustrative transparent member having a plurality of standoff structures formed thereabove. 
     
    
    
     While the subject matter disclosed herein is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
     Although various regions and structures shown in the drawings are depicted as having very precise, sharp configurations and profiles, those skilled in the art recognize that, in reality, these regions and structures are not as precise as indicated in the drawings. Additionally, the relative sizes of the various features and doped regions depicted in the drawings may be exaggerated or reduced as compared to the size of those features or regions on fabricated devices. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the subject matter disclosed herein. 
     In general, the present subject matter is directed to using transfer molding techniques to form standoff structures on a transparent cover or glass of an integrated circuit device. As shown in  FIG. 2A , a plurality of standoff structures  32  are formed on a surface  31  of a transparent member  30 . Ultimately, the transparent member  30  may be cut or singulated into the final desired size, as reflected by the dashed line  34 . Thereafter, the singulated portions of the transparent member  30  will ultimately be positioned above an area of a die having light sensing circuitry formed therein. In the illustrative example depicted in  FIG. 2A , the dashed line  34  depicts the final outline of portions of the transparent member  30  that will be cut and placed over an individual die. 
     The transparent member  30  may be comprised of any of a number of materials that are suitable for the intended purpose of the transparent member  30 . In one illustrative example, the transparent member  30  is comprised of glass. The transparent member  30  is normally supplied in square or rectangular sheets. According to one aspect of the present disclosure, standoff structures  32  may be formed on the transparent member  30  in its as-supplied configuration, e.g., square or rectangular. This avoids the time and cost associated with forming glass rounds from a rectangular piece of material as was done using prior art techniques described above. 
     As illustrated in  FIGS. 2A-2C , the standoff structures  32  described herein may be formed to any desired shape or configuration, e.g., rectangular or round posts, lines, etc. As shown in  FIG. 2A , the standoff structures  32  are rectangular post structures. After all of the standoff structures  32  are formed, the transparent member  30  may be cut into the desired shape or configuration, as indicated by the dashed line  34 , using known techniques. For example, as depicted in  FIG. 2A , the four standoff structures  32  may be employed in positioning a singulated portion of the transparent member  30  above an integrated circuit die. In  FIG. 2B , the illustrative standoff structures  32  are essentially line-type members that may be positioned on opposite sides of the active area of the integrated circuit die. In  FIG. 2C , the standoff structure  32  is essentially one continuous structure that extends around the outer perimeter of the interior portion of the transparent member  30 . 
     As indicated previously, the size, shape and configuration of the standoff structures  32  described herein may vary. For example,  FIG. 3  depicts a plurality of standoff structures  32  formed on the surface  31  of the transparent member  30 . The contact end  33  of the standoff structure  32 , the end that will contact the substrate, may be formed so as to have any desired configuration. For example, as shown in  FIG. 3 , the contact end  33  of the illustrative standoff structures  32 A,  32 B,  32 C and  32 D, respectively, is planar, concave, convex and grooved or castled. Thus, the configuration of the contact end  33  may be varied to facilitate attachment of the glass member  30  to an individual die. 
     As mentioned previously, the standoff structures  32  described herein may be formed using known transfer molding techniques. Transfer molding is a widely adopted method for plastic encapsulation of semiconductor devices. In transfer molding, the mold generally includes a lower half and an upper half. The lower half of the mold will typically include multiple cavities and a concave portion, called a pot, which communicates with the multiple cavities through runners. A thermosetting resin is heated in the pot and fed therefrom by a plunger. The resin reaches the cavities through the runners. The resin is typically then heated to cure the resin. 
       FIG. 4  schematically depicts an illustrative transfer molding apparatus  40  that may be employed to form the standoff structures described herein. Of course, not all details of an actual molding apparatus are depicted in  FIG. 4  so as not to obscure the present invention. As shown therein, the transfer molding apparatus  40  comprises an upper half  42 A and a lower half  42 B. The transparent member  30  is positioned in a cavity  46  formed in the lower half  42 B of the mold  40 . A plurality of mold cavities  44  are formed in the upper half  42 A of the mold  40 . The cavities  44  generally correspond to the desired configuration of the standoff structures  32  to be formed on the transparent member  30 . For example,  FIG. 4  is a cross-sectional view taken at the location depicted in  FIG. 2A . The cavities  44  in  FIG. 4  generally correspond to the illustrative rectangular post standoff structures  32  depicted in  FIG. 2A . The desired molding material, e.g., an epoxy or traditional mold compound, is introduced into the mold, as indicated by the arrow  50 . The mold material exits the pot  48  and flows to the desired cavities  44  via the schematically depicted runners  52 . 
     After the transfer molding process is complete, and the standoff structures  32  are formed on the surface  31  of the transparent member  30 , the mold  40  is separated and the transparent member  30 , with the standoff structures  32  formed thereon, is removed from the mold  40  and trimmed as necessary. A schematic cross-sectional view of the transparent member  30  at this point in the process is depicted in  FIG. 5 . A dicing or cutting process is then performed to singulate the transparent member  30  into the desired individual members, as reflected by the dashed line  34  depicted in  FIGS. 2A-2C . An adhesive material may then be applied to the contact surface  33  of the standoff structures  32  so that the singulated transparent members or window may be attached to the die. The physical size of the standoff structures  32  may also vary, e.g., they may have a height of approximately 70-120 μm. The thickness of the transparent member  30  may also vary, e.g., it may have a thickness of approximately 400-550 μm.