Abstract:
According to various embodiments, systems and methods for packaging a semiconductor device are provided. The disclosure discusses a semiconductor die having a top side and a bottom side that is disposed on a lead frame. An adhesive paste is then applied to attach the semiconductor die to the lead frame such that the adhesive paste fixes the die to a portion of the lead frame. The adhesive paste may be applied directly between die and the lead frame or may be applied in conjunction with a frame tape.

Description:
PRIORITY 
     This application claims the priority and benefit of U.S. Provisional Application No. 62/204,857, filed on Aug. 13, 2015, the entire contents of which is incorporated by reference herein. 
    
    
     BACKGROUND 
     Background 
     In the field of semiconductor packaging, die attach film (DAF) is sometimes used to attach a completed semiconductor die to a substrate or lead frame. While DAFs are easy to use and to apply, they can have certain drawbacks. For instance, DAFs are unable to withstand high wire bond temperatures and are further susceptible to delamination abnormalities between the DAF and lead frame interface layer, which can cause problems in the final product and/or additional production costs. Additionally, DAFs are, themselves, expensive and their use increases the cost of semiconductor production. Accordingly, improvements are needed that do not suffer from the same production quality and abnormalities or cost issues. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are incorporated herein and form a part of the specification of the disclosure. 
         FIG. 1  is an example layout of a semiconductor package according to various embodiments of the disclosure. 
         FIG. 2  is an example cross-sectional view of a semiconductor package according to various embodiments of the disclosure. 
         FIG. 3  is an example layout of a semiconductor package according to various embodiments of the disclosure. 
         FIG. 4  is an example cross-sectional view of a semiconductor package according to various embodiments of the disclosure. 
         FIG. 5  is an example layout of a semiconductor package according to various embodiments of the disclosure. 
         FIG. 6  is a flowchart illustrating a method of producing a semiconductor package according to various embodiments of the disclosure. 
     
    
    
     In the drawings, like reference numbers generally indicate identical or similar elements. Additionally, generally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears. 
     DETAILED DESCRIPTION 
     Provided herein are systems, methods and/or combinations and sub-combinations thereof, for the production of semiconductor packages using adhesive paste to bind a semiconductor die to a lead frame. 
       FIG. 1  is a schematic depicting a semiconductor package  100  according to various embodiments of the disclosure. The semiconductor package  100  includes a semiconductor die  102  that is attached to a lead frame  104  with die attach film (DAF)  106  and a frame tape  108 . The lead frame  104  can be used to connect package leads  110  to the appropriate conductors of the semiconductor die  102 . According to various embodiments, the DAF  106  can be pre-applied during, for instance, an upstream wafer level lamination process.  FIG. 1  depicts the DAF  106  as smaller than the die  102 . This to aid in explanation of the figure. In practice DAF  106  may cover the entire die  102 ; the edges of DAF  106  can be co-extensive with the die  102 . While  FIG. 1  is depicted with a total of 48 lead pins  110 , it should be understood that this is merely for explanation purposes and that any number or pattern, or shape of lead pins could be used and still fall within the scope and spirit of this disclosure. 
     The DAF  106  shown in  FIG. 1  may be comprised of an adhesive layer that is disposed onto the wafer bottom (i.e., backside) during a pre-lamination process. The pre-lamination process, according to some embodiments, could occur before a wafer saw process. The DAF may comprise an adhesive of resin that is disposed on a film such as polyvinyl film, polyolefin film, or polyethylene terephthalate (PET) film. In  FIG. 1 , the DAF is used to attach the die  102  to a pad of a lead frame  104 . In this way, the DAF  106  can be used to form a chip on lead (COL) package  100 . 
       FIG. 2  is a cross sectional view of aspects of a semiconductor package  200 . For instance,  FIG. 2  could depict a cross-sectional view of semiconductor package  100  from  FIG. 1  along the axis of one of the lengths of tape  108  according to various embodiments. As shown in  FIG. 2 , the semiconductor package  200  comprises a die  202  and a lead frame  208 . The die  202  may be a semiconductor die containing a number of logic gates and/or analog semiconductor devices. 
     As shown in  FIG. 2 , the die  202  is attached to the lead frame  208  with a DAF  204  that is attached to bottom side of the die  202  and to a tape layer  206 . According to various embodiments, the tape layer  206  may be similar to the frame tape  108  layer described above with respect to  FIG. 1 . The DAF  204  may comprise an adhesive of resin and disposed on a film such as polyvinyl film, polyolefin film, or polyethylene terephthalate (PET) film. 
     While effective in some respects, the use of die attach films such as DAF  204  can be problematic during semiconductor packaging processes. For instance, in some manufacturing processes, it can be desirable to use a high-temperature wire bond temperature. However, many DAFs have a maximum temperature that is less than the required wire bond temperature. Additionally, DAFs can suffer from delamination during the manufacturing process even when high-temperature methods are not used. Delamination occurs when outgassing occurs during the manufacturing process that causes separation between, for instance, DAF  204  and tape  206 . This is problematic for the integrity of the bond between the die  202  and the lead frame  208 . Additionally, problems can occur during wafer sawing. During wafer sawing, both layers of the laminated die (e.g., die  202 ), which is brittle and hard material such as silicon, and layers of DAF, which is soft elastic, must be sawed through. This can result in DAF (e.g., DAF  204 ) burrs. DAF burrs are remnants or whiskers of DAF adhesive at the bottom and sides of sawn die edges. These adhesive DAF burrs results in various process and multiple quality issues and challenges. For instance, the burrs can cause adjacent dies to “stick” together which can result an adjacent die being picked along with a target die during the production process. This problem can be especially prevalent when dealing with very small die (e.g., less than 2 mm) that have small (e.g., 60 μm and smaller) narrow saw streets between rows and columns of die in sawn wafer. This problem can also result in die cracks, broken die, or chipping die—especially for thin and large (e.g., greater than 8 mm) die. All of these problems result in increased production cost. A better method would be to replace the DAF  204  with a material that is not subject to the same disadvantages from which DAF  204  materials suffer. 
       FIG. 3  is a schematic depicting a semiconductor package  300  according to various embodiments of the disclosure. The semiconductor package  300  includes a semiconductor die  302  that is attached to a lead frame  304  with adhesive paste  306  and a frame tape  308 . The lead frame  304  may comprise any suitable lead frame for the die  302  or a no-lead package such as a dual-flat no-lead (DFN) package or quad-flat no-lead (QFN) package according to various embodiments. 
     In some embodiments, the amount of adhesive paste  306  used to connect the die  302  with the tape  308  is controlled so that it provides maximum coverage of the frame tape  308  without overflowing the edges of the frame tape  308 . In other embodiments the amount of adhesive paste  306  used is simply determined so that it will not overflow the frame tape  308 . The frame tape  308  may also be used to create a die attach paddle for joining the die  302  to the lead frame  304  in some embodiments. 
     While  FIG. 3  depicts a package  300  with three lengths of frame tape  308 , this is simply to illustrate that multiple lengths or shapes of frame tape  308  may be used. According to other embodiments, more or fewer lengths or shapes of frame tape  308  could be used. For instance, in some embodiments, only a single length and shape of frame tape  308  is employed. This is discussed in greater detail, below, with respect to  FIG. 5 . 
     The lead frame  304  can be used to connect package leads  310  to the appropriate conductors of the semiconductor die  302 . While  FIG. 3  is depicted with a total of 48 lead pins  310 , it should be understood that this is merely for explanation purposes and that any number or pattern or shape of lead pins could be used and still fall within the scope and spirit of this disclosure. 
     The adhesive paste  306  shown in  FIG. 3  may comprise any appropriate adhesive paste or liquid adhesive material. For instance, according to some embodiments, the adhesive paste  306  comprises an adhesive of paste that is either electrically insulating or electrically or thermally conducting depending on the specific application. For instance, an entirely polymer-based adhesive paste can be used if an electrically insulating adhesive  306  is desired. Similarly, a thermal or thermally conducting adhesive paste can be used when a thermally or an electrically conducting adhesive paste  306  is desired. In  FIG. 3 , the adhesive paste  306  used to attach the die  302  to a pad of a lead frame  304  In this way, the adhesive paste can be used to form a chip on lead (COL) package  300 . 
       FIG. 4  is a cross sectional view of aspects of a semiconductor package  400 . For instance,  FIG. 4  could depict semiconductor package  300  from  FIG. 3  with the cross section along a length of tape  308 . As shown in  FIG. 4 . the semiconductor package  400  comprises a die  402  and a lead frame  408 . The die  402  may be a semiconductor die containing a number of logic gates and/or analog semiconductor devices. Lead frame  408  may comprise any suitable semiconductor packaging substrate such as a lead frame pad or the like. 
     As shown in  FIG. 4 , the die  402  is attached to the lead frame  408  with an adhesive paste  404  that is attached to one side of the die  402  and to a tape layer  406 . According to various embodiments, the tape layer  406  may be similar to the frame tape  308  layer described above with respect to  FIG. 3 . The adhesive paste  404  may comprise an adhesive of resin and disposed On a film such as polyvinyl film, polyolefin film, or polyethylene terephthalate (PET) film. An encapsulation or seal  410  may be applied to seal the semiconductor package comprising the die  402 , the paste layer  404 , the tape  406 , and the lead frame  408 . 
     While  FIG. 3  describes depicts a package  300  with three lengths of frame tape  308 , this is simply to illustrate that multiple lengths of frame tape  308  may be used. According to other embodiments, more or fewer lengths or shapes of frame tape  308  could be used. Indeed, entirely different lead frame shapes and sizes can be used in conjunction with the disclosed subject matter.  FIG. 5  depicts one such alternative. 
       FIG. 5  is a schematic depicting a semiconductor package  500  according to various embodiments of the disclosure. The semiconductor package  500  includes a semiconductor die  502  that is attached to a lead frame  504  with adhesive paste  506  and a frame tape  508 . In some embodiments, the amount of adhesive paste  506  used to connect the die  502  with the tape  508  is controlled so that it provides maximum coverage of the frame tape  508  without overflowing the edges of the frame tape  508 . In other embodiments the amount of adhesive paste  506  used is simply determined so that it will not overflow the frame tape  308 . 
     In contrast to  FIG. 3 ,  FIG. 5  depicts a package  500  with only a single length of frame tape  508 . The lead frame  504  can be used to connect package leads  510  to the appropriate conductors of the semiconductor die  502 . While  FIG. 5  is depicted with a total of 48 lead pins  510 , it should be understood that this is merely for explanation purposes and that any number or pattern or shape of lead pins could be used and still fall within the scope and spirit of this disclosure. 
     The adhesive paste  506  shown in  FIG. 5  may comprise any appropriate adhesive paste material. For instance, according to some embodiments, the adhesive paste  506  comprises an adhesive of paste that is either electrically insulating or electrically or thermally conducting depending on the specific application. For instance, an entirely polymer-based adhesive paste can be used if an electrically insulating adhesive  506  is desired. Similarly, a thermal or thermally conducting adhesive paste can be used when a thermally or an electrically conducting adhesive paste  506  is desired. In  FIG. 5 , the adhesive paste  506  used to attach the die  502  to a pad of a lead frame  504  In this way, the adhesive paste can be used to form a COL package  500 . 
       FIG. 6  is a flowchart depicting a method  600  of packaging a die (e.g., die  302 ) according to various embodiments of the disclosure. To aid explanation, method  600  will be described with reference to  FIG. 3  as well, but it should be understand that method  600  is not limited to the specific embodiments depicted in  FIG. 3 . According to the method  600  a die  302  is positioned appropriately to enable it to have adhesive paste  306  applied to it at stage  602 . 
     At stage  604 , the appropriate amount of adhesive paste  306  to apply to the die  302  is determined. According to some embodiments, it may be desirable to vary the amount of adhesive paste  306  depending on various factors. For instance, the kind of adhesive paste  306  (e.g., polymer based or silver filled) may affect the amount and pattern (shape) of adhesive paste  306  that needs to be applied to the die  302 . Similarly, the specific geometry of a die  302  could also affect the amount of adhesive paste  306  required. In some embodiments, the amount of adhesive paste  306  to apply to the die  302  may be determined as an amount that will provide maximum coverage without over flowing, for instance, the edges of frame tape  308 . 
     At stage  606 , the determined amount of adhesive paste  306  is applied to the die  302 . According to some embodiments, the adhesive paste  306  could be applied at multiple locations on die  302 . For instance, the adhesive paste  306  may be applied at the points on the die  302  where frame tape  308  is to be disposed. In such embodiments, the adhesive paste  306  may be applied such that it does not overflow the edges of tape  308 . It is also possible, in some embodiments, that the adhesive paste  306  is only applied in a single location. 
     At stage  608 , the die  302  is attached to the lead frame  304  using the adhesive paste  306 . For instance, the die  302  could be attached to a lead frame pad In some embodiments attaching the die  302  to the lead frame  304  may include disposing a frame tape  308  between the adhesive paste  306  and the lead frame  304 . At stage  610  the adhesive paste  306  is cured (by, e.g., applying a particular wavelength of light to the adhesive paste) as appropriate to the particular kind of adhesive paste being employed. At stage  612 , the process of packaging die  302  can be completed according to suitable methods. 
     It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections (if any), is intended to be used to interpret the claims. The Summary and Abstract sections (if any) may set forth one or more but not all exemplary embodiments of the invention as contemplated by the inventor(s), and thus, are not intended to limit the invention or the appended claims in any way. 
     While the invention has been described herein with reference to exemplary embodiments for exemplary fields and applications, it should be understood that the invention is not limited thereto. Other embodiments and modifications thereto are possible, and are within the scope and spirit of the invention. For example, and without limiting the generality of this paragraph, embodiments are not limited to the software, hardware, firmware, and/or entities illustrated in the figures and/or described herein. Further, embodiments (whether or not explicitly described herein) have significant utility to fields and applications beyond the examples described herein. 
     Embodiments have been described herein with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined as long as the specified functions and relationships (or equivalents thereof) are appropriately performed. Also, alternative embodiments may perform functional blocks, steps. operations, methods, etc. using orderings different than those described herein. 
     References herein to “one embodiment,” “an embodiment,” “an example embodiment,” or similar phrases, indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it would be within the knowledge of persons skilled in the relevant art(s) to incorporate such feature, structure, or characteristic into other embodiments whether or not explicitly mentioned or described herein. 
     The breadth and scope of the invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.