Abstract:
One or more electronic components can be mounted on the back side of a semiconductor die. The components can be passive components, active components, or combinations thereof. The components can be soldered to signal routes on the back side of the die, the signal routes being attached to the die using a metallization layer or using one or more dielectric layer sections. Placing components on the back side of the die can allow for incorporation of the components without necessarily increasing the form factor of the die&#39;s package.

Description:
FIELD 
     The disclosure relates to semiconductor packaging. 
     BACKGROUND 
     Microchips are often packaged in various containers. It can be desirable to package a microchip with additional components, such as discrete components or other microchips. For example, U.S. Pat. No. 7,005,325 to Chow et al. states: “[P]assive components have been placed on the leadframe [of a semiconductor package] between the leads to eliminate negative electrical effects. These passive devices include capacitors, resistors, and inductors.” See col. 1, lines 33-36. However, including these additional components in a package (e.g., along the periphery of the die) can increase the package form factor. 
     One approach to accommodating two or more microchips inside a single package is described in U.S. Pat. No. 6,768,190 to Yang et al., which discloses “a multi-chip module having a stack type flip-chip design for accommodating two or more chips each having a different function inside a single package, thereby reducing overall production cost.” See col. 2, lines 7-10. 
     SUMMARY 
     A semiconductor assembly can be made up, at least in part, of a semiconductor die having an active side and a back side, with one or more electronic components mounted on the back side of the die. The components can be passive components, active components, or combinations thereof. The components can be attached to the die using a metallization layer or one or more dielectric material sections. Placing components on the back side of the die can allow for incorporation of the components without necessarily increasing the form factor of the die&#39;s package. 
     In one embodiment, a semiconductor assembly comprises a semiconductor die having an active side and a back side, a dielectric material having a first side and a second side, with the first side of the dielectric material attached to the back side of the semiconductor die, a plurality of component pads attached to the second side of the dielectric material section, and one or more electronic components electrically coupled to one or more of the component pads. One or more of the electronic components can be a passive component. A plurality of signal traces can be electrically coupled with the plurality of component pads. A plurality of bond pads can be electrically coupled with the plurality of component pads. In some embodiments, the dielectric material section comprises a first section of dielectric material and a second section of dielectric material. In other embodiments at least one of the one or more electronic components has exactly two terminals. At least one of the electronic components can be in communication with a component pad via a solder connection, wherein the dielectric material provides a solder non-wettable area for the solder connection. In some embodiments the dielectric material section exposes a substantial portion of the back side of the semiconductor die. In other embodiments, the assembly further comprises a metallization layer having a first side and a second side, the first side being attached to the die back side, the metallization layer comprising a plurality of component pads. In yet other embodiments, the assembly is packaged in a flip chip package. The package can further comprise a die paddle and a packaging material, the packaging material at least partially encompassing the semiconductor die. 
     In a further embodiment, a semiconductor assembly comprises a semiconductor die having an active side and a back side, a metallization layer having a first side and a second side, the first side attached to the die back side and the metallization layer comprising a plurality of component pads, and one or more discrete electronic components electrically coupled with at least two of the plurality of component pads. In some embodiments, the one or more discrete electrical components are passive components. In an additional embodiment, the second side of the metallization layer is not in contact with a passivation layer. The assembly can further comprise a plurality of signal traces can be in electrical communication with the plurality of component pads. The assembly can further comprise a plurality of wirebond pads can be in electrical communication with the plurality of component pads. The metallization later can be a selective metallization coating with a mask or a selectively etched metallization coating. In one embodiment, at least one of the electronic components is attached to the component pads via a plurality of solder connects, wherein the die back side provides a solder non-wettable area for at least one of the solder connects. 
     In yet another embodiment, a method of packaging an integrated circuit comprises providing a semiconductor die having an active side and a back side, providing a dielectric material section having an active side and a back side, attaching the first side of the dielectric material section to the back side of the semiconductor die, forming a plurality of component pads on the second side of the dielectric material section, and electrically coupling one or more electronic components with at least two of the plurality of component pads. In some embodiments, at least one of the electronic components can be a passive component. The dielectric material layer can comprise a first section of dielectric material and a second section of dielectric material. Electrically coupling one or more electronic components with at least two of a plurality of component pads can comprise creating one or more solder connections between the electronic components and the component pads, wherein the dielectric material provides a solder non-wettable area for the solder connection. In further embodiments, at least part of the semiconductor die can be encapsulated with one or more packaging materials. 
     In another embodiment a method of making a semiconductor assembly comprises providing a semiconductor die having an active side and a back side, providing a metallization layer having a first side and a second side, the first side being attached to the die back side, wherein the metallization layer comprises a plurality of component pads, and further comprising electrically coupling one or more discrete electronic components with at least two of the plurality of component pads. In a further embodiment, at least one of the discrete electronic components is a passive component. In yet another embodiment, the second side of the metallization layer is not in contact with a passivation layer. 
     The foregoing and other objects, features, and advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view of one embodiment of a semiconductor assembly with a component attached to the back side of a die. 
         FIG. 2  is a cross-sectional view of the embodiment shown in  FIG. 1 . 
         FIG. 3  is a plan view of one embodiment of a semiconductor assembly with a component attached to the back side of a die. 
         FIG. 4  is a plan view of one embodiment of a semiconductor assembly with a component attached to the back side of a die. 
         FIG. 5  is a cross-sectional view of the semiconductor assembly of  FIG. 4 . 
         FIG. 6  is a plan view of one embodiment of a semiconductor assembly with components attached to the back side of a die. 
         FIG. 7  is a cross-sectional view of the semiconductor assembly of  FIG. 6 . 
         FIG. 8  is a plan view of one embodiment of a die in a flip chip package. 
         FIG. 9  is a cross-sectional view of the flip chip package of  FIG. 8 . 
         FIG. 10  is a plan view of one embodiment of a bond-on-lead package. 
         FIG. 11  is a cross-sectional view of the package of  FIG. 10 . 
         FIG. 12  is a flowchart for one embodiment of a method for making a semiconductor assembly. 
         FIG. 13  is a flowchart for one embodiment of a method for making a semiconductor assembly. 
         FIG. 14  is a flowchart for one embodiment of a method for making a semiconductor assembly. 
     
    
    
     DETAILED DESCRIPTION 
     As used in this application and in the claims, the singular forms “a,” “an,” and “the” include the plural forms unless the context clearly dictates otherwise. Additionally, the term “includes” means “comprises.” Further, the term “coupled” means electrically or electromagnetically coupled or linked and does not exclude the presence of intermediate elements between the coupled items. 
     The system, apparatus, and method described herein are provided to exemplify the invention, and the scope of the invention, and the scope of the invention is not limited to such exemplary features. Instead, the present disclosure is directed toward all novel and non-obvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The disclosed embodiments are not limited to any specific aspect or feature or combinations thereof. 
     Although the operations of embodiments of the disclosed method are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language set forth below. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed system, method, and apparatus can be used in conjunction with other systems, methods, and apparatus. Additionally, the description sometimes uses terms like “produce” and “provide” to describe the disclosed method. These terms are high-level abstractions of the actual operations that can be performed. The actual operations that correspond to these terms can vary depending on the particular implementation and are readily discernible by one of ordinary skill in the art. 
       FIG. 1  shows a plan view of one embodiment of a semiconductor assembly  100  comprising an integrated circuit die  110 . The die  110  comprises an active side  130  (shown in  FIG. 2 ) having circuit elements (not shown) and a back side  140 , the back side  140  being substantially opposite to the active side  130 . A section of dielectric material  150  (e.g., circuitry tape or a similar material) can comprise a first surface  152  (shown in  FIG. 2 ) and a second surface  154 . The first surface  152  of the dielectric material section  150  can be attached to the back side  140  by any suitable method. For example, in one embodiment the dielectric material section  150  can be attached by lamination, and in another embodiment, it can be attached by adhesive. Second surface  154  of the dielectric material section  150  includes one or more signal routes such as signal routes  160 ,  162 ,  164 ,  166 . As used in this application and in the claims, “signal route” refers to a section of conductive material for conveying electric signals. The signal route  160  can comprise a component pad  170 , a signal trace  174  and a bond pad  172 . As used in this application and in the claims, “component pad” refers to a region of conductive material for mounting an electronic component, “signal trace” refers to a region of conductive material designed to carry an electric signal, and “bond pad” refers to a region of conductive material for forming a connection with a wire. In some embodiments, the bond pad  172  is positioned adjacent to edge of die  110  to facilitate wire bonding. The signal route  160  can comprise the component pad  170 , the signal trace  174  and the bond pad  172  as separate components, or the signal route  160  can be a continuous piece of conductive material. The signal routes  162 ,  164 ,  166  can comprise components similar to the signal route  160 , although the signal routes  160 ,  162 ,  164 ,  166  can vary with respect to size and shape. An electronic component  180  can be electrically coupled to one or more of the signal routes  160 ,  162 ,  164 ,  166  at, for example, the component pad, using one or more methods known in the art, such as surface-mount technology (SMT). For example,  FIG. 2  illustrates two electronic components  180 ,  184  electrically coupled to the signal routes  166 ,  162 , respectively, via the solder connections  186 ,  188 , respectively. Returning to  FIG. 1 , region  182  exemplifies one position where an electronic component  180  might be configured for positioning relative to the component pads of the signal routes  160 ,  162 . In one embodiment, one or more signal routes such as the signal route  160  can be configured to electrically couple two or more electrical components such as the component  180 . 
       FIG. 2  shows a cross-sectional view of the assembly  100  taken along broken line  2 - 2  indicated in  FIG. 1 . The exemplary embodiment illustrated by  FIG. 2  depicts the signal routes  160 ,  162  as being at least partially embedded in the dielectric material section  150 . A person of ordinary skill in the art will appreciate that, in other embodiments, the signal routes  162 ,  166  can be fabricated on top of the second surface  154  of the dielectric material section  150 . The material of dielectric material section  150  can be selected to provide a solder non-wettable area for the solder connections  186 ,  188 , which can allow for improved solder handling during component mounting. Accordingly, a layer of solder resist on the dielectric material section  150  may be unnecessary. Alternatively, solder resist can be provided as a continuous layer or in selected locations. 
       FIG. 3  shows a plan view of a semiconductor assembly  300 . Back side  340  of die  310  is provided with dielectric material sections  352 ,  354 . In other embodiments, more than two dielectric material sections can be used. The sections can be located as desired, including as required by package requirements, e.g.: component size and functionality, as well as location and availability of lead fingers for wire bonding for components (including die). Although the sections  352 ,  354  are depicted as being generally rectangular, the size and shape of the sections  352 ,  354  can be modified as desired. In some embodiments, dielectric material sections such as the dielectric material sections  150  or  352 ,  354  can be configured to occupy substantially all of a die back side (e.g., die back side  140  as shown in  FIG. 1 ), or they can be configured to leave a substantial area of a die back side unoccupied (e.g., area  356  of  FIG. 3 ). 
     In some embodiments, electronic components such as the component  180  can comprise passive components (e.g., resistors, capacitors, inductors), active components (e.g., transistors, diodes), one or more additional semiconductor die, or combinations thereof. The signal routes can be configured according to a number of terminals of a selected electronic component, e.g., two pads can be fabricated for a two-terminal component such as a resistor, or three pads for a transistor. In further embodiments, more signal routes are fabricated on the dielectric material section  150  than are actually used by electronic components. For example, a generic design of the dielectric material section  150  can be manufactured for use with several embodiments using varying numbers and combinations of electronic components, with some embodiments using more signal routes than other embodiments. 
       FIG. 4  shows a plan view of another representative embodiment of a semiconductor assembly  400  comprising an integrated circuit die  410  having an active side  430  (not shown in this view) and a back side  440 . In this particular embodiment, the back side  440  features a metallization layer  442  comprising two or more signal routes  460 ,  462 ,  464 ,  466 , which can be similar to the signal routes of other embodiments described above. For example, the signal route  460  can comprise a component pad  470 , a signal trace  474  and a bond pad  472 . The signal routes  462 ,  464 ,  466  can comprise components similar to the signal route  460 , although the signal routes  460 ,  462 ,  464 ,  466  can vary in size and shape. The metallization layer  442  can be made of a suitable material, or combinations of suitable materials. In some embodiments, the metallization layer  442  is made of copper or one or more other metals. The metallization layer  442  can be formed by applying a metallization coating to the die back side  440 , followed by selectively etching the back side. In another embodiment, a metallization coating can be selectively applied with a mask during a coating process. One or more electronic components  480  can be electrically coupled to one or more component pads, e.g., the component pad  470  on the signal route  460 . The component can be coupled to the pad using one or more methods known in the art, such as surface-mount technology (SMT). In one embodiment, one or more signal routes  460 ,  462 ,  464 ,  466  can be configured to electrically connect two or more electrical components  480  to each other. Dotted line  482  exemplifies where an electronic component  484  (shown in  FIG. 5 ) might be positioned relative to the signal routes  460 ,  462 . 
       FIG. 5  shows a side cross-sectional view of assembly  400  taken along the broken line  5 - 5  indicated in  FIG. 4 . Relative to  FIG. 4 ,  FIG. 5  depicts an additional electronic component  484 , as well as solder  486 ,  488  used to attach the components  480 ,  484  to their respective signal routes  464 ,  462 . The surface area of die back side  440  that is not covered by the metallization layer  442  (e.g., not covered by signal routes  460 ) can act as a solder non-wettable area. Thus an additional solder resist layer on die back side  440  can be unnecessary. Alternatively, solder resist can be provided as a continuous layer or in selected locations. In one embodiment, no passivation layer is added to the die back side  440  (e.g., on top of the metallization layer  442 ), as the silicon of the die is non-conductive. 
     As was discussed with respect to similar assemblies  100 ,  300 , the electronic components  480 ,  484  can comprise passive components (e.g., resistors, capacitors, inductors), active components (e.g., transistors, diodes), or combinations thereof. In other embodiments, the components  480 ,  484  comprise additional semiconductor die. The component pads can be configured according to a number of terminals of a selected electronic component, e.g., two pads can be fabricated for a two-terminal component such as a resistor, or three pads for a transistor. In some embodiments, more component pads are fabricated in the metallization layer than are actually used by electronic components electrically coupled to the metallization layer. For example, a generic arrangement and number of component pads can be manufactured in the metallization layer for use with multiple embodiments using varying numbers and combinations of electronic components, with some embodiments using more component pads than other embodiments. 
       FIG. 6  shows a plan view of one embodiment of an assembly  600  combining some features of assemblies  100 ,  300  and  400 . For example, a semiconductor die  610  can comprise an active side  630  (shown in  FIG. 7 ) and a back side  640  with a dielectric material section  654  occupying a portion of the backside  640 . The dielectric material section  654  can have one or more signal routes  660 ,  662  to which an electronic component  680  can be attached. The back side of the same die also can feature one or more signal routes  664 ,  666  fabricated in a metallization layer  642 . An electronic component  682  can be attached to the signal routes  664 ,  666 .  FIG. 7  shows a side cross-sectional view of the assembly  600 , taken along the broken line  7 - 7  in  FIG. 6 . As shown in  FIG. 7 , the components  680 ,  682  can be coupled to the signal routes  660 ,  666  with respective solder connections  686 ,  688 . 
       FIG. 8  shows a plan view of one embodiment of a die  810  in a flip chip package  800 . Die  810  is depicted as being similar to the die  310  of assembly  300  of  FIG. 3 , with the dielectric material sections  852 ,  854  attached to the die back side  840 . Additional die embodiments disclosed herein, and embodiments similar thereto also can be packaged in a similar manner. The flip chip package  800  comprises a die paddle  812  and a plurality of leads  814 . One or more electronic components  880  can be electrically coupled to the leads  814  via one or more signal routes  860  and one or more wires  882 . 
       FIG. 9  shows a side cross-sectional view of the chip package  800 , taken along the line  9 - 9  in  FIG. 8 . This view more clearly shows packaging material  884  which can encapsulate some or all of the die  810 , the die paddle  812 , the leads  814  and the electronic components  880 . (Packaging material  884  also appears in  FIG. 8  in spaces around the leads  814  and the die paddle  812 , but the material positioned above the paddle  812  and the die  810  is not shown, to provide a clear view of those components.) A number of materials known in the art can be used for the packaging material  884 . In some embodiments one packaging material  884  is used, and in other embodiments two or more materials  884  are used. The chip package  800  can further comprise bumps  820 , which can provide an electrical coupling between the active side  830  of the die  810  and the one or more leads  814 . The bumps  820  can be arranged in a variety of positions, as is known in the art, and can be coupled to one or more bonding pads (not shown) on the die active side  830 . The leads  814 , bumps  820 , wires  882  and signal routes  860  can provide one or more electrical connections between the active side  830  and the electronic components  880 . 
     Placing the electronic components  880  on the back side  840  of the die  810  can allow for incorporating such components into the chip package  800  without necessarily increasing the area of the package  800 . In some embodiments, a first group of one or more electronic components  880  is placed on the back side  840 , while a second group of the one or more electronic components  880  is placed approximately coplanar to the die  810  (e.g., on the leads  814 ). 
     In some embodiments, the chip package  800  can be incorporated into a chip-scale package (CSP), a ball-grid array (BGA) package, a direct chip array (DCA) package, a multi-chip module (MCM), package-on-package (PoP), package-in-package (PiP), or other packages known in the art. 
       FIG. 10  depicts a plan view of one embodiment of a bond-on-lead (BOL) package  1000 , the exterior of which comprises leads  1014  and at least one packaging material  1084 .  FIG. 11  shows a cross-sectional side view of the BOL package  1000 , taken along the line  11 - 11  in  FIG. 10 . The depicted embodiment is a wirebond design, although in other embodiments a flip chip design can be used with a BOL package. In the depicted embodiment, the semiconductor die  1010  can be configured similarly to the die  110  of the assembly  100 . (Other embodiments described above can also be used with a BOL package.) Dielectric material  1050 , featuring one or more electronic components  1086 , can be attached to the back side  1040  of the die  1010 . Wires  1082  can electrically couple electronic components  1086  with one or more leads  1014 . Wires  1088  can electrically couple the active side  1030  of the die  1010  with leads  1014 . A configuration of the wires  1082 ,  1088  and the leads  1014  can electrically couple the components  1086  with the active side  1030 . 
       FIG. 12  shows a flowchart for one embodiment of a method  1200  for making a semiconductor assembly. A semiconductor die can be provided (step  1210 ) and two or more component pads can be provided (step  1220 ). As is explained below, the component pads can be provided on a dielectric material section or in a metallization layer. One or more electronic components can be electrically coupled with two or more component pads (step  1230 ). In some embodiments, leads and packaging materials can be provided (step  1240 ), which can result in packages similar to packages  800  and  1000  as described above, for example. 
       FIG. 13  shows a flowchart for one embodiment of a method  1300  for making a semiconductor assembly similar to assemblies  100 ,  300 , as described above. In step  1310 , a semiconductor die can be provided. One or more dielectric material sections can be provided (step  1320 ) and attached to the back side of the die (step  1330 ). Component pads can be formed on the one or more dielectric material sections (step  1340 ), and one or more electronic components can be electrically coupled with the component pads (step  1350 ). In some embodiments, leads and packaging materials can be provided (step  1360 ), which can result in packages similar to packages  800  and  1000  as described above, for example. 
       FIG. 14  shows a flowchart for one embodiment of a method  1400  for making a semiconductor assembly similar to assembly  400 , as described above. In step  1410 , a semiconductor die can be provided. A metallization layer can be provided on the back side of the die using, for example, the methods described above with respect to assembly  400  (step  1420 ). The metallization layer can comprise a plurality of component pads, as well as signal traces and wirebond pads. Electronic components can be electrically coupled with at least some of the component pads (step  1430 ). In some embodiments, leads and packaging materials can be provided (step  1440 ), which can result in packages similar to packages  800  and  1000  as described above, for example. 
     Although the steps described above in methods  1200 ,  1300  and  1400  can be executed in the order described, some embodiments can carry out some steps in one or more different orders. For example, in method  1300 , component pads can be formed on the one or more dielectric material sections (step  1340 ) before the sections are attached to the die back side (step  1330 ). Those of ordinary skill in the art will recognize other possible orders for the disclosed methods. 
     In view of the many possible embodiments to which the principles of the disclosed invention may be applied, it should be recognized that the illustrated embodiments are only preferred examples of the invention and should not be taken as limiting the scope of the invention. Rather, the scope of the invention is defined by the following claims. We therefore claim as our invention all that comes within the scope and spirit of these claims.