PATENT DOCUMENT

Publication Number: US-11395408-B2
Application Number: US-202017005607-A
Country: US
Kind Code: B2

Title: Wafer-level passive array packaging

Abstract:
Wafer level passive array packages and modules are described. In an embodiment, a module includes a circuit board, and a package mounted on the circuit board in which the package includes a plurality of passive components bonded to a bottom side of the die and a plurality of landing pads of the circuit board.

Claims:
What is claimed is: 
     
       1. A module comprising:
 a circuit board including a top side including a first plurality of landing pads; and 
 a package mounted on the circuit board and bonded to the first plurality of landing pads, the package including:
 a die; 
 a plurality of passive components bonded to a bottom side of the die and the first plurality of landing pads of the circuit board; 
 wherein the plurality of passive components is directly underneath the die; and 
 an interposer bonded to the bottom side of the die and bonded to a second plurality of landing pads of the circuit board, wherein the interposer is laterally adjacent to the plurality of passive components; 
 wherein the plurality of passive components is bonded to the die with a first solder material and bonded to the circuit board with a second solder material, wherein the first solder material is characterized by a higher reflow temperature than the second solder material. 
 
 
     
     
       2. The module of  claim 1 , wherein the die includes a redistribution layer (RDL) formed on a back-end-of-the-line (BEOL) build-up structure. 
     
     
       3. The module of  claim 1 , wherein each passive component of the plurality of passive components includes two terminals, each terminal respectively coupled to both the die and the circuit board. 
     
     
       4. The module of  claim 1 :
 wherein the die is encapsulated in a molding compound, and further comprising a redistribution layer (RDL) formed on the molding compound and a back-end-of-the-line (BEOL) build-up structure of the die; and 
 wherein the plurality of passive components is bonded to the RDL. 
 
     
     
       5. The module of  claim 2 , wherein the RDL is formed on and in electrical connection with a plurality of BEOL pads of the BEOL build-up structure, and the plurality of passive components is bonded to a plurality of contact pads of the RDL. 
     
     
       6. The module of  claim 2 , wherein the RDL covers a plurality of test pads of the BEOL build-up structure, wherein the plurality of test pads is electrically open. 
     
     
       7. The module of  claim 3 , further comprising a first circuit connecting the die and the circuit board, wherein a first passive component of the plurality of passive components is connected to the first circuit and configured to provide a vertical shunt interconnect between the die and the circuit board through a first terminal of the first passive component. 
     
     
       8. The module of  claim 3 , further comprising a first circuit connecting the die and the circuit board, wherein a first passive component of the plurality of passive components is connected to the first circuit as a capacitor. 
     
     
       9. The module of  claim 3 , further comprising a first circuit connecting the die and the circuit board, wherein a circuit path of the first circuit passes from the die to a first terminal of a first passive component of the plurality of passive components, through the first passive component to a second terminal of the first passive component, and from the second terminal to the circuit board. 
     
     
       10. The module of  claim 3 , further comprising:
 a first circuit connecting the die and the circuit board, wherein a first passive component of the plurality of passive components is connected to the first circuit and configured to provide a vertical shunt interconnect between the die and the circuit board through a first terminal of the first passive component: and 
 a second circuit comprising:
 a second circuit path that passes from the die to a first terminal of a second passive component of the plurality of passive components, through the second passive component to a second terminal of the second passive component, and from the second terminal to the die; 
 a second circuit path that passes from the die to a first terminal of a second passive component of the plurality of passive components, through the second passive component to a second terminal of the second passive component, and from the second terminal to the circuit board; or 
 a second circuit path that passes from the circuit board to a first terminal of a second passive component of the plurality of passive components, through the second passive component to a second terminal of the second passive component, and from the second terminal to the circuit board. 
 
 
     
     
       11. The module of  claim 4 , wherein a portion of the plurality of passive components extends beyond a perimeter of the die. 
     
     
       12. A module comprising:
 a circuit board including a top side including a first plurality of landing pads; 
 a package mounted on the circuit board and bonded to the first plurality of landing pads, the package including:
 a die; 
 a plurality of passive components bonded to a bottom side of the die and the first plurality of landing pads of the circuit board; 
 wherein the plurality of passive components is directly underneath the die; and 
 an interposer bonded to the bottom side of the die and bonded to a second plurality of landing pads of the circuit board, wherein the interposer is laterally adjacent to the plurality of passive components; 
 wherein each passive component of the plurality of passive components includes two terminals, each terminal respectively coupled to both the die and the circuit board; and 
 
 a first circuit connecting the die and the circuit board, wherein a circuit path of the first circuit passes from the die to a first terminal of a first passive component of the plurality of passive components, through the first passive component to a second terminal of the first passive component, and from the second terminal to the circuit board. 
 
     
     
       13. A module comprising:
 a circuit board including a top side including a first plurality of landing pads; 
 a package mounted on the circuit board and bonded to the first plurality of landing pads, the package including:
 a die; 
 a plurality of passive components bonded to a bottom side of the die and the first plurality of landing pads of the circuit board; 
 wherein the plurality of passive components is directly underneath the die; and 
 an interposer bonded to the bottom side of the die and bonded to a second plurality of landing pads of the circuit board, wherein the interposer is laterally adjacent to the plurality of passive components; 
 wherein each passive component of the plurality of passive components includes two terminals, each terminal respectively coupled to both the die and the circuit board; 
 
 a first circuit connecting the die and the circuit board, wherein a first passive component of the plurality of passive components is connected to the first circuit and configured to provide a vertical shunt interconnect between the die and the circuit board through a first terminal of the first passive component: and 
 a second circuit comprising:
 a second circuit path that passes from the die to a first terminal of a second passive component of the plurality of passive components, through the second passive component to a second terminal of the second passive component, and from the second terminal to the die; 
 a second circuit path that passes from the die to a first terminal of a second passive component of the plurality of passive components, through the second passive component to a second terminal of the second passive component, and from the second terminal to the circuit board; or 
 a second circuit path that passes from the circuit board to a first terminal of a second passive component of the plurality of passive components, through the second passive component to a second terminal of the second passive component, and from the second terminal to the circuit board.

Description:
BACKGROUND 
     Field 
     Embodiments described herein relate to microelectronic packaging, and more particularly wafer-level passive array (WLPA) packaging techniques. 
     Background Information 
     The current market demand for portable and mobile electronic devices such as mobile phones, personal digital assistants (PDAs), digital cameras, portable players, gaming, and other mobile devices requires the integration of more performance and features into increasingly smaller spaces. A traditional microelectronic module may include one or more semiconductor packages and other components mounted onto a circuit board. Packaging solutions such as wafer level chip scale package (WLCSP) technology can allow the semiconductor packages to be no larger than the dice (chips) themselves, further allowing a reduction of footprint. In a traditional module, packages are mounted on a circuit board adjacent to a plurality of passive components that can provide supplemental features such as filtering applications, power supplies, etc. 
     SUMMARY 
     Embodiments describe wafer-level passive array (WLPA) packaging techniques, semiconductor packages and modules thereof. In an embodiment, a module includes a circuit board including a top side including a first plurality of landing pads, and a package mounted on the circuit board and bonded to the first plurality of landing pads. The package may be a WLPA package including a die and a plurality of passive components bonded to both a bottom side of the die and the first plurality of landing pads of the circuit board. Specifically, the plurality of passive components can be bonded to a redistribution layer (RDL) of the die or a fanout RDL on the die. In a particular embodiment, the plurality of passive components is directly underneath the die, within a shadow of the die. 
     In some embodiments, the plurality of passive components is bonded to the die with a first solder material and bonded to the circuit board with a second solder material. The first solder material may be characterized by a higher reflow temperature than the second solder material. For example, this can facilitate the package mounting process and reduce tilting of the passive components. The passive components can have a variety of functions, and functionality can additionally be at least partly determined by connectivity to the die and circuit board using a variety of active, and dummy pads, etc. In some embodiments all passive components may be the same height, while in other embodiments passive components of different heights are accommodated. Exemplary modules may include cavities within the circuit board to accommodate taller passive components. In other embodiments, the plurality of components can be assembled separately as an interposer-type package level. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional side view illustration of a module including a WLPA package in accordance with an embodiment. 
         FIG. 2A  is a schematic cross-sectional side view illustration of a shunt path through a passive component in accordance with an embodiment. 
         FIG. 2B  is a schematic cross-sectional side view illustration of a die only path through a passive component in accordance with an embodiment. 
         FIG. 2C  is a schematic cross-sectional side view illustration of a circuit board only path through a passive component in accordance with an embodiment. 
         FIG. 2D  is a schematic cross-sectional side view illustration of a series path through a passive component in accordance with an embodiment. 
         FIG. 2E  is a schematic cross-sectional side view illustration of a multi-circuit path through a passive component in accordance with an embodiment. 
         FIG. 2F  is a schematic cross-sectional side view illustration of a series path through a passive component in accordance with an embodiment. 
         FIGS. 2G-2H  are schematic cross-sectional side view illustrations of dummy connections without circuit paths in accordance with embodiments. 
         FIG. 3  is a process flow for a method of fabricating a WLPA package in accordance with an embodiment. 
         FIG. 4  is a schematic cross-sectional side view illustration of a WLPA package with an integrated RDL in accordance with an embodiment. 
         FIG. 5  is a schematic cross-sectional side view illustration of a WLPA package with a fanout RDL in accordance with an embodiment. 
         FIG. 6  is a schematic cross-sectional side view illustration for an RDL multi-layer UBM pad in accordance with an embodiment. 
         FIG. 7  is a schematic bottom view illustration of a plurality of passive components bonded to a die within a WLPA package in accordance with an embodiment. 
         FIG. 8  is a schematic cross-sectional side view illustration of a plurality of passive components of a WLPA package mounted on a circuit board in accordance with an embodiment. 
         FIG. 9  is a schematic bottom view illustration of a plurality of passive components and laterally adjacent vertical interconnects bonded to a die within a WLPA package in accordance with an embodiment. 
         FIG. 10A  is a schematic cross-sectional side view illustration of a plurality of passive components and laterally adjacent solder bumps of a WLPA package mounted on a circuit board in accordance with an embodiment. 
         FIG. 10B  is a schematic cross-sectional side view illustration of a plurality of passive components and laterally adjacent conductive pillars of a WLPA package mounted on a circuit board in accordance with an embodiment. 
         FIG. 11  is a schematic bottom view illustration of a plurality of passive components and laterally adjacent interposer bonded to a die within a WLPA package in accordance with an embodiment. 
         FIG. 12  is a schematic cross-sectional side view illustration of a plurality of passive components and laterally adjacent interposer of a WLPA package mounted on a circuit board in accordance with an embodiment. 
         FIGS. 13-15  are schematic cross-sectional side view illustrations of WLPA packages including passive components of different heights mounted on circuit boards in accordance with embodiments. 
         FIGS. 16-17  are schematic cross-sectional side view illustrations of WLPA packages including a package level with embedded passive components in accordance with embodiments. 
         FIG. 18  is a process flow for a method of fabricating a WLPA package with embedded passive components in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments describe wafer-level passive array (WLPA) packaging techniques, semiconductor packages and modules thereof. In an embodiment, a module includes a circuit board including a top side including a first plurality of landing pads, and a package mounted on the circuit board and bonded to the first plurality of landing pads. In accordance with embodiments, the package includes a die and a plurality of passive components (e.g. capacitors, resistors, inductors, combinations thereof, etc.) bonded to both a bottom side of the die and the first plurality of landing pads of the circuit board. Specifically, the plurality of passive components can be bonded to a redistribution layer (RDL) of the die or a fanout RDL on the die. While the following embodiments are described in particular with regard to a plurality of passive components, embodiments may also be applicable to sets of one or more passive components. In an embodiment, a package includes a die and a set of one or more passive components (e.g. capacitors, resistors, inductors, combinations thereof, etc.), with each passive component bonded to both a bottom side of the die and a first set of one or more landing pads of the circuit board. The one or more passive components in accordance with embodiments may be directly underneath the die, and a portion of which may optionally extend beyond a perimeter of the die. 
     In one aspect, the WLPA packaging techniques and packages in accordance with embodiments can reduce area of a module by vertically integrating the passive components underneath a die within the package. Furthermore, such WLPA packaging techniques and packages in accordance with embodiments can more densely occupy available vertical space of modules, particularly when the packages are mounted on a circuit board adjacent to tall components. Thus, the WLPA packages reduce module area and increase vertical packing density of the module. 
     In another aspect, the WLPA packaging techniques in accordance with embodiments are a deviation from WLCSP technology. Similar to WLSCP, a plurality of die areas may be fabricated at the wafer scale, and a back-end-of-the line (BEOL) build-up structure is at least partially formed over the wafer (e.g. silicon) including the plurality of die areas. Rather than completing the BEOL build-up structure, forming a plurality of under bump metallurgy (UBM) pads, and addition of solder bumps, the WLPA packaging techniques in accordance with embodiments may test the partially fabricated BEOL build-up structure, form a redistribution layer (RDL) over the BEOL build-up structure to accommodate pad layout for the plurality of passive components, apply solder material (e.g. bumps, paste) to either the UBM pads or passive components, and attach the plurality of passive components to the RDL, followed by singulation. Solder bumps can then be applied to a circuit board, followed by mounting of the packages onto the circuit board. In this manner, electrical routing between the package die and the circuit board runs through the plurality of passive components, which can also include “dummy” passive components, to complete electrical connectivity. 
     Routing through the plurality of passive components in accordance with embodiments can provide additional functionality, such as enclosing a current loop between the die and a passive component such as a bypass capacitor for performance. This can also allow for reduction of circuit board routing length for sensitive analog signals, and prevent such signals from overlapping other circuit board routing. Furthermore, such a configuration can increase available “on-die” decoupling capacitance or radio frequency (RF) capacitance. For example, this may be facilitated both by location, and providing ceramic dielectrics which would generally be unavailable for capacitors formed within the die. 
     In various embodiments, description is made with reference to figures. However, certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations. In the following description, numerous specific details are set forth, such as specific configurations, dimensions and processes, etc., in order to provide a thorough understanding of the embodiments. In other instances, well-known semiconductor processes and manufacturing techniques have not been described in particular detail in order to not unnecessarily obscure the embodiments. Reference throughout this specification to “one embodiment” means that a particular feature, structure, configuration, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, configurations, or characteristics may be combined in any suitable manner in one or more embodiments. 
     The terms “over”, “to”, “between”, “spanning” and “on” as used herein may refer to a relative position of one layer with respect to other layers. One layer “over”, “spanning” or “on” another layer or bonded “to” or in “contact” with another layer may be directly in contact with the other layer or may have one or more intervening layers. One layer “between” layers may be directly in contact with the layers or may have one or more intervening layers. 
     Referring now to  FIG. 1  a cross-sectional side view illustration is provided of a module  100  including a WLPA package  150  in accordance with an embodiment. As shown, the module  100  includes a circuit board  102  including a top side  104  including a plurality of landing pads  106 . A package  150  is mounted on the circuit board  102  and bonded the plurality of landing pads  106 . The package  150  may include a die  120  and one or more of passive components  130  bonded to both a bottom side  129  of the die  120  and the plurality of landing pads  106  of the circuit board  102 . The one or more passive components  130  may be directly underneath the die  120 , within a shadow of the die  120 . In some embodiments, a portion of the one or more passive components can extend (e.g. laterally) beyond a perimeter of the die  120 . In an embodiment, the bottom side  129  of the die  120  includes a plurality of contact pads  142  to which the passive component(s)  130  are bonded. Each passive component  130  in accordance with embodiments may be bonded to a respective landing pad  106  of the circuit board  102 , or more than one landing pad  106  of the circuit board. Bonding may include physical attachment, electrical connectivity and/or communicative coupling. 
     In a particular configuration, the one or more passive components  130  is bonded to the die  120  with first solder joints  162  and bonded to the circuit board  102  with second solder joints  164 . The first solder material of first solder joints  162  may be characterized by a higher reflow temperature than the second solder material of second solder joints  164  in order to facilitate maintaining alignment (e.g. prevent tilting) of the passive components  130  when mounting the package  150  on the circuit board  102 . 
     One or more additional components  170  or dies may also be bonded to a second plurality of landing pads  110  on the top side  104  of the circuit board  102 , for example with solder joints  166 . The additional components  170  may be taller than the passive components  130 . As shown, locating the passive components  130  underneath the die  120  can save module area, while increasing vertical packing density, particularly when the additional component(s)  170  are taller than the die  120 . In some embodiments the passive components  130  all have the same height, and optionally same size. In other embodiments, groups of passive components  130  of different sizes can be included. 
     The passive components  130  in accordance with embodiments can have a variety of configurations that can provide electrical connection between the die  120  and circuit board  102 . Furthermore, routing to contact pads  142  and landing pads  106  can partially determine functionality of the passive components  130 . For example, dummy contact pads, or dummy landing pads and corresponding routing can be included to determine connectivity and function of the passive components  130 . Furthermore, dummy passive components can be included, where no electrical connection is made between terminals  132 ,  134 . 
     Referring now to  FIGS. 2A-2H  a variety of schematic cross-sectional side view illustrations are provided for electrical connection and circuit paths for a variety of passive component configurations in accordance with embodiments. The various circuit paths can include shunt paths, series paths, die only paths, circuit board only paths, series paths, multi-circuit paths, etc. It is to be appreciated the particular examples provided in  FIGS. 2A-2H  are illustrative, and embodiments are not so limited. Furthermore, modules  100  in accordance with embodiments may include a combination of various electrical connections, such as those illustrated and described with regard to  FIGS. 2A-2H . In some embodiments, a passive component may be oriented laterally with respect to the die and circuit board to facilitate coupling of multiple terminals (e.g. a first and second terminal) on both a top side and bottom side of the passive component. Alternatively, a passive component may be oriented vertically to facilitate coupling of respective terminals to either a top side or bottom side of the passive component. 
       FIG. 2A  is a schematic cross-sectional side view illustration of a shunt path through a passive component in accordance with an embodiment. As shown, a shunt path (or low resistance connection) can flow directly between the contact pads  142  and landing pads  106  through one or more terminals  132 ,  134  of a passive component. In particular, the passive component may be a dummy passive component  130 X without an electrical connection between terminals  132 ,  134  or a high resistance connection therebetween, however this is not required for a shut path. In accordance with embodiments, one or both of the terminals  132 ,  134  can be electrically connected as a shunt path within a circuit connecting the die  120  and circuit board  102 . 
       FIG. 2B  is a schematic cross-sectional side view illustration of a die only path through a passive component in accordance with an embodiment. For clarity, functionality of the passive component within the overlaid circuit path is illustrated as a generic box. In such a configuration, the passive component  130  is only electrically connected to a circuit within the die  120  and can be bonded to dummy landing pads  106 X on the circuit board  102 . For example, the dummy landing pads  106 X may not be electrically connected to routing within the circuit board  102 . In an embodiment, the passive component  130  is connected only to a die circuit only as a passive component, such as capacitor, inductor, resistor, etc. 
     Similar to  FIG. 2B ,  FIG. 2C  is a schematic cross-sectional side view illustration of a circuit board only path through a passive component in accordance with an embodiment. In such a configuration, the passive component  130  is only connected to a circuit within the circuit board  102 , and can be bonded to dummy contact pads  142 X. For example, the dummy contact pads  142 X may not be electrically connected to routing within the redistribution layer  140  (described in more detail with regard to  FIGS. 4-6 ). In an embodiment, the passive component  130  is connected a circuit board circuit only as a passive component, such as capacitor, inductor, resistor, etc. 
     Referring now to  FIG. 2D , a schematic cross-sectional side view illustration is provided of a series path through a passive component  130  in accordance with an embodiment. As shown, the series path may proceed through one of the terminals  132 ,  134  connected to the die  120 , through the passive component  130 , and to the other terminal  132 ,  134  connected to the circuit board  102 . In the illustrated embodiment, terminal  132  electrically connected to the die  120  is bonded to contact pad  142  and dummy landing pad  106 X, while terminal  134  electrically connected to the circuit board  102  is bonded to landing pad  106  and dummy contact pad  142 X. In an embodiment, the passive component  130  is connected a circuit between the die  120  and circuit board  102  as passive component, such as capacitor, inductor, resistor, etc. 
       FIG. 2E  is a schematic cross-sectional side view illustration of a multi-circuit path through a passive component in accordance with an embodiment. As shown, the passive component  130  is connected to circuits in both the die  120  and circuit board  102 . For example, the passive component may be coupled to both the die  120  and circuit board  102  as a passive component, such as capacitor, inductor, resistor, etc. 
     Up until this pint, passive component  130  layouts have been described and illustrated in which the multiple terminals  132 ,  134 , etc. are bonded to both the die  120  and circuit board  102 . However, embodiments are not so limited, and vertical passive components  130  can also be included in which the terminals  132 ,  134  are connected only to the die  120  or circuit board  102  as illustrated in  FIG. 2F . 
     Furthermore, the dummy passive components  130 X can also be included, where the terminals  132 ,  134  are bonded to only dummy landing pads  106 X and dummy contact pads  142  as illustrated in  FIGS. 2G-2H . Such dummy passive components  130 X and connections may be useful for mechanical purposes and stress balancing of the package  150 . 
     Referring now to  FIG. 3  a process flow is provided for a method of fabricating a WLPA package  150  in accordance with an embodiment.  FIG. 4  is a schematic cross-sectional side view illustration of a WLPA package  150  with an integrated RDL  140  in accordance with an embodiment. In interest of clarity and conciseness, the description of the process flow of  FIG. 3  is made with regard to the WLPA package  150  of  FIG. 4 . 
     At operation  3010  a plurality of die areas is patterned in a wafer, such as silicon wafer. Each die area may include a traditional bulk layer  121  (e.g. crystalline silicon) into which devices such as transistors, etc. are formed and a back-end-of-the-line (BEOL) build-up structure  123  which typically includes metallization layers and dielectric layers. For example, build-up structure  123  may be formed using a damascene or dual damascene process to form interconnect layers and vias (e.g. copper, aluminum). For example, such damascene or dual damascene processes may include planarized metallization layers and vias. Dielectric layers, also referred to as interlayer dielectrics, can also be planarized. Suitable materials include oxides (e.g. SiO 2 ), nitrides, low-K dielectrics such as fluorine doped silicon oxide, carbon doped silicon oxide, porous oxides, and spin on dielectrics. The build-up structure  123  may terminate with BEOL pads  124  and test pads  125 . For example, both of which may be copper pads, aluminum pads, etc. Test pads  125  may be designed for automatic test equipment (ATE) probing to verify die area functionality. It is to be appreciated that this processing sequence may stop prematurely compared to conventional BEOL processing which continues all the way to formation of under bump metallurgy (UBM) pads for die mounting. Alternatively, the BEOL build-up structure  123  processing sequence can proceed all the way to formation of UBM pads as contact pads  142 . 
     As shown in  FIG. 4 , at operation  3020  a redistribution layer (RDL) is optionally formed on the partially fabricated and tested BEOL build-up structure  123 . The RDL  140  can include routing layers  144  and dielectric layers  146  similar to the BEOL build-up structure  123 . In some embodiments RDL  140  is formed using the same processing technologies as the BEOL build-up structure  123 , such as damascene or dual damascene and use the same materials as dielectric layers  146 . In such a process the RDL  140  may be indistinguishable from the BEOL build-up structure  123 . The routing layers  144  may be formed on and electrically connected to the BEOL pads  124 , though may cover and insulate the test pads  125 , which can remain electrically open. The RDL  140  may alternatively be formed using different processing technologies as the BEOL build-up structure  123 . For example, the RDL  140  may be formed using thin film techniques, and dielectric layers may be formed of different materials than those of the BEOL build-up structure  123 . In such a process the RDL  140  may be physically distinguishable from the BEOL build-up structure  123  in shape, and composition of the layers. For example, thin film routing layers may include deposited and patterned metal layers without planarization/polishing. Furthermore, a thickness of the metal layer contour may be conformal to the underlying topology. As an example, a thin film metal routing layer may line a via opening (as opposed to a damascene metal which fills the via), however this is not required in all thin film processes. Where the optional RDL is formed, the sequence can include formation of contact pads  142 , such as UBM contact pads at operation  3030 . 
     The optional RDL  140  in accordance with embodiments may be formed for adjustment of the contact pad  142  location in order to accommodate mounting of the plurality of passive components  130 . In this manner, the die wafer can be primarily an off-the-shelf intermediate product where final routing and contact pad  142  location can be adjusted based on passive component  130  size, while underlying device and circuit design of the die is unchanged. 
     At operation  3040  solder material for solder joints  162  can optionally be formed on the RDL  140  contact pads  142  using a suitable technique such as plating, printing, dropping, etc. followed by attaching the plurality of passive components  130  to the contact pads  142  at operation  3050 . Alternatively, the solder material for solder joints  162  can be provided with the passive components  130 . Each passive component  130  in accordance with embodiments may be bonded to a respective contact pad  142  of the RDL  140 , or more than one contact pad  142  of the RDL  140 . Bonding may include physical attachment, electrical connectivity and/or communicative coupling. 
     An underfill material  152 , such as epoxy, etc., may then optionally be applied between the die  120  and components  130 , and laterally surrounding the solder joints  162  at operation  3060 , followed by singulation of individual packages  150  at operation  3070 . Solder material for solder joints  164  may optionally be applied to the exposed terminals  132 ,  134  prior to singulation, or can be applied after singulation. Solder material for solder joints  164  can alternatively, or in addition, be applied to the circuit board (e.g. as paste) for mounting the packages  150 . Solder material for solder joints  164  may be characterized by a lower reflow temperature than the solder material of solder joints  162 . In this manner, solder joints  162  are not reflowed again when mounting the packages onto the circuit board  102 . 
     Referring now to  FIG. 5 , a schematic cross-sectional side view illustration is provided of a WLPA package  150  with a fanout RDL  140  in accordance with an embodiment. The package  150  of  FIG. 5  may be fabricated similarly as that of the package  150  of  FIG. 4 , with the modification of forming the RDL  140  over a reconstituted wafer. In such a process flow, dies  120  are fabricated, singulated, and transferred to a temporary carrier, followed by encapsulation in a molding compound layer  126 . The active side of the dies  120  include BEOL pads  124  and test pads  125  is then exposed, and a fanout RDL  140  can then be formed over the BEOL buildup structure  123  of the dies  120  and molding compound layer  126 . The remainder of the fabrication sequence can then be similar to that described with regard to formation of the package  150  of  FIG. 4 . In such an embodiment, inclusion of a fanout RDL  140  can increase package area available for mounting the passive components  130  such that the number of passive components  130  is not limited by die  120  size, as is the case for the package  150  of  FIG. 4 . Each passive component  130  in accordance with embodiments may be bonded to a respective contact pad  142  of the RDL  140 , or more than one contact pad  142  of the RDL  140 . Bonding may include physical attachment, electrical connectivity and/or communicative coupling. The one or more passive components  130  in accordance with embodiments may be directly underneath the die  120 , and a portion of which may optionally extend beyond a perimeter of the die  120 , which can be facilitated by the fanout RDL  140 . 
     The contact pads  142  in accordance with embodiments described herein can be multi-layer UBM pads, distinguishable from single layer BEOL pads  124  and test pads  125 .  FIG. 6  is a schematic cross-sectional side view illustration for an RDL multi-layer UBM pad in accordance with an embodiment. Such contact pads  142  may include any combination of layers, such as an adhesion layer  202  (e.g. Cr, Ti, Ni, W, TiW) over an RDL routing layer  144 , barrier layer  204  (e.g. Cr, W, Ti, TiW, Ni, Cr), wetting layer  206  (e.g. Cu, Ni, Pd, Pt), and anti-oxidation barrier layer  208  (e.g. Au). Additional dielectric layers may also be included at the exterior surface of the RDL  140 , such as a first passivation layer  147  (e.g. oxide, oxy-nitride, nitride), and second passivation layer  148  (e.g. polyimide). 
       FIG. 7  is a schematic bottom view illustration of a plurality of passive components  130  bonded to a die  120  within a WLPA package  150  in accordance with an embodiment.  FIG. 8  is a schematic cross-sectional side view illustration of a plurality of passive components  130  of a WLPA package  150  mounted on a circuit board  102  in accordance with an embodiment. As shown, the plurality of passive components  130  can substantially populate the bottom side of the package  150  area, with all electrical connections to the circuit board  102  being made through the terminals  132 ,  134  of the passive components  130 . While not separately illustrated, dummy passive components  130 X can also be distributed among the passive components  130 . 
     In some embodiments, additional vertical interconnects can be provided laterally adjacent to the plurality of passive components  130  to provide electrical connection between the circuit board  102  and die  120 .  FIG. 9  is a schematic bottom view illustration of a plurality of passive components  130  and laterally adjacent vertical interconnects bonded to a die within a WLPA package in accordance with an embodiment. For example, in the embodiment illustrated in  FIG. 10A  a plurality of solder bumps  180  (which can be cored, or not cored) are bonded to both the bottom side  129  of the die  120  and a second plurality of landing pads  106  of the circuit board  102 . In the embodiment illustrated in  FIG. 10B  a plurality of conductive pillars  182  (e.g. copper plated) extend from the bottom side  129  of the die  120  and are bonded to a second plurality of landing pads  106  of the circuit board  102 . Such an arrangement may be used to provide a higher density of conductive pillars  182  than density available with the passive component terminals  132 ,  134 . Solder tips  184  may optionally be formed on the bottom sides of conductive pillars  182  to facilitate bonding to the circuit board  102 . Alternative interconnects can also be used, such as printed circuit board (PCB) bars. For example, conductive pillars  182  can be located within PCB bars. 
     In each configuration of  FIGS. 9-10B  the passive components  130  and additional electrical connections are illustrated as being bonded to the bottom side of the die  120 , and directly underneath the die  120 . It is to be appreciated that embodiments are not necessarily so limited, and are also compatible with configuration of  FIG. 5  and fanout RDL  140  where all passive components are not necessarily directly underneath the die  120 . 
       FIG. 11  is a schematic bottom view illustration of a plurality of passive components  130  and laterally adjacent an interposer  192  bonded to a die  120  within a WLPA package  150  in accordance with an embodiment. For example, in the embodiment illustrated in  FIG. 12  a plurality of passive components  130  and laterally adjacent interposer  192  are bonded to both the bottom side  129  of the die  120  and a second plurality of landing pads  106  of the circuit board  102 . The interposer  192  may include a plurality of vertical interconnects  194  (e.g. pillars, vias, etc.) connecting the landing pads  106  of the circuit board  102  and contact pads  142  of the die  120 . The vertical interconnects  194  may be embedded in an insulating material, which may be one or more layers, such as polymer, PCB substrate (e.g. glass-reinforced epoxy laminate), etc. 
     In each configuration of  FIGS. 11-12  the passive components  130  and additional electrical connections are illustrated as being bonded to the bottom side of the die  120 , and directly underneath the die  120 . It is to be appreciated that embodiments are not necessarily so limited, and are also compatible with configuration of  FIG. 5  and fanout RDL  140  where all passive components are not necessarily directly underneath the die  120 . 
     Up until this point embodiments have been described in which the passive components  130  within the package  150  are all the same height, which can facilitate mounting onto the circuit board  102 . In the embodiments illustrated in  FIGS. 13-15  various configurations are described in which the packages  150  include passive components of different heights. In each configuration a first set of one or more passive components  130 A and second set of one or more passive components  130 B are illustrated as being bonded to the bottom side of the die  120 , and directly underneath the die  120 . It is to be appreciated that embodiments are not necessarily so limited, and are also compatible with configuration of  FIG. 5  and fanout RDL  140  where all passive components are not necessarily directly underneath the die  120 . Furthermore, while pluralities of components are described and illustrated, the concepts are also applicable to sets of one or more components of different heights. 
     Referring now to  FIG. 13 , in an embodiment, the first set of one or more passive components  130 A is taller than the second set of one or more passive components  130 B. As illustrated the second set of passive components  130 B may have die only connections. A bottom side of the second set of passive components may optionally be embedded within an adhesive layer  190  (e.g. non-electrically conductive) on a top side  104  of the circuit board  102 . The adhesive layer  190  may provide adhesion of the package  150  to the circuit board  102 , reduce vibration, and mitigate a difference in height between the taller passive components  130 A. In some embodiments, the adhesive layer  190  may include heat channeling functionality. For example, such heat channeling functionality may be used to transfer heat from an interior portion to lateral edges of the package  150  to help dissipate heat. In some embodiments, an addition, distinct layer may be provided laterally above or below adhesive layer  190  to provide heat channeling functionality as described above. In an embodiment, the adhesive layer spans along the top side  104  of the circuit board  102  beyond a lateral edge of the package  150 . 
     The embodiment illustrated in  FIG. 14  includes a similar arrangement of passive components as that provided in  FIG. 13  with different electrical connections. In the illustrated embodiment, the second set of passive components  130 B is now taller than the first set of passive components  130 A, and the second set of passive components  130 B extends into one or more trenches  105  formed in the top side  104  of the circuit board  102 . Similarly, the bottom sides of the second set of passive components  130 B can be embedded in an adhesive layer  190  within the one or more trenches. Adhesive layer  190  may be patterned, and perform the same functions as previously described. Referring to both  FIGS. 13-14 , the circuit board  102  may include electrical routing layers  112  distributed within an electrical routing area  114 . As shown, in  FIG. 13 , the electrical routing area  114  may be across the entire circuit board  102  area. In the embodiment illustrated in  FIG. 14 , the trenches can be formed through one or more layers of circuit board  102  reserved for electrical routing. Thus, one or more electrical routing layers may be excluded from areas directly underneath the one or more trenches  105 . In this manner, partial electrical routing layers  112  may be provided up to a certain metal layer directly under the one or more trenches  105 , or the electrical routing layers  112  may be excluded from areas directly underneath the one or more trenches  105 . 
     The embodiment of  FIG. 15  additionally includes a similar arrangement of passive components as that provided in  FIG. 14 , with the set of passive components  130 A bonded to landing pads  110  on a top side  104  of the circuit board  102 , and the second set of passive components  130 B bonded to landing pads within trenches  105  formed in the top side  104  of the circuit board  102 . The routing area  114  may extend across the entire circuit board  102  area, including underneath the trenches  105 . In some embodiments, the first set of one or more passive components  130 A may all be positioned on one lateral end of package  150 , as viewed from a top-down or cross-sectional perspective. In such embodiments, second set of one or more passive components  130 B may be positioned at an opposing lateral end of package  150 , as similarly viewed from a top-down or cross-sectional perspective. 
     Referring now to  FIGS. 16-17  schematic cross-sectional side view illustrations are provided of WLPA packages  150  including a package level  135  with embedded passive components  130  in accordance with embodiments. In particular, the package level  135  may be similar to an interposer that is separately fabricated and bonded with the die  120 . Thus, the interposer-type package level  135  is not die  120  size limited, can be fabricated separately from the die  120 , and embeds the passive components  130  within an insulating layer  136  (e.g. molding compound) which provides additional mechanical protection. The particular embodiment illustrated in  FIG. 16  is a substrate-less package level  135  in which the terminals  132 ,  134  of the passive components  130  are exposed on both top and bottom sides of the package level  135 . The embodiment illustrated in  FIG. 17  adds a second RDL  138  on a top side  131  of the plurality of passive components  130  and the insulating layer  136 . As shown, the die  120  can be bonded to the second RDL  138  with a plurality of solder joints  162 . Second RDL  138  may include one or more routing layers  137 , dielectric layers  133 , and contact pads  139  similar to those previously described with RDL  140 . 
       FIG. 18  is a process flow for a method of fabricating a WLPA package  150  such as those illustrated in  FIGS. 16-17  in accordance with embodiments. At operation  1810  the plurality of passive components  130  may be attached to a carrier substrate, and then encapsulated with an insulating layer  136  at operation  1820 . To form the interposer-type package level  135  of  FIG. 16  the top surfaces of the passive component  130  terminals  132 ,  134  are exposed and provided with a surface finishing material. To form the interposer-type package level  135  of  FIG. 17  the top surfaces of the passive component  130  terminals  132 ,  134  are exposed, and RDL  138  is formed thereon at operation  1830 . A plurality of dies  120  can then be attached at operation  1840 , for example using flip chip technique, followed by optional underfilling at operation  1850 , and singulation of the packages  150  at operation  1860 . 
     In utilizing the various aspects of the embodiments, it would become apparent to one skilled in the art that combinations or variations of the above embodiments are possible for forming modules and WLPA packages. Although the embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the appended claims are not necessarily limited to the specific features or acts described. The specific features and acts disclosed are instead to be understood as embodiments of the claims useful for illustration.

Metadata:
Filing Date: 20200828
Publication Date: 20220719
Grant Date: 20220719
Priority Date: 20200828
Inventors: MORRISON, SCOTT D.
SHANMUGAM, KARTHIK
CAMENFORTE, RAYMUNDO M.
AGRAWAL, RAKSHIT
CARSON, Flynn P.
DHALIWAL, Kiranjit
Assignee: APPLE INC
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Family ID: 80357524