Patent Publication Number: US-2023135165-A1

Title: Device and method of very high density routing used with embedded multi-die interconnect bridge

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/888,177, filed Aug. 15, 2022, which is a continuation of U.S. patent application Ser. No. 16/322,423, filed on Jan. 31, 2019, now U.S. Pat. No. 11,508,662, issued Nov. 22, 2022, which is a U.S. National Stage Filing under 35 U.S.C. 371 from International Application No. PCT/US2016/054739 filed Sep. 30, 2016 and published in English as WO 2018/063316 on Apr. 5, 2018, the entire contents of which are hereby incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     Embodiments pertain to electronic packages. Some embodiments relate to high density routing used in conjunction with an embedded multi-die interconnect bridge (bridge) in electronic packages. 
     BACKGROUND 
     The electronics industry has continued to face an ever-increasing demand for faster and more powerful processing capacity, as well as increased storage capacity to feed the continuous hunger for faster devices and data rates. Electronic packages contain a wide variety integrated circuits (ICs), dies connected to substrates, and electronic structures of a disparate array of electronic products. Examples of these products include communication devices (e.g., smart phones), computers (e.g., laptops, tablets), vehicular devices, game devices, etc. Increasing miniaturization of ICs, and IC structures to increase the processing power has led to power management and interference issues with the consequent increase in interconnect density within the structures and between dies in an electronics package. 
     One technology to provide dense interconnect routing between dies is an Embedded (Multi-die) Interconnect Bridge. However, due to current fabrication techniques and inherent properties of the dielectric material used to create the bridge, the use of a bridge may result in lossy and capacitive structures. Current bridge-based designs and fabrication techniques may lack flexibility and limit the number of bridge die in a single substrate and use to die having a 55 μm bump pitch of input/output (I/O) bumps on the die. It would be desirable to enable further miniaturization by providing a bridge with enhanced scalability that is capable of connecting to die having smaller bump pitches (e.g., 40 μm) without requiring a costly Si bridge re-design to implement. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       In the figures, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The figures illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document. 
         FIGS.  1 A- 1 H  illustrate cross-sectional views of a fabrication process using a bridge and very high density (VHD) routing using a substrate with a monolithic core in accordance with some embodiments. 
         FIGS.  2 A- 2 L  illustrate cross-sectional views of a fabrication process using a bridge and VHD routing using a coreless substrate in accordance with some embodiments. 
         FIG.  3    illustrates a system level diagram in accordance with some embodiments. 
         FIG.  4    illustrates a method of substrate fabrication in accordance with some embodiments. 
         FIG.  5    illustrates a method of coreless substrate fabrication in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The following description and the drawings sufficiently illustrate specific embodiments to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. Portions and features of some embodiments may be included in, or substituted for, those of other embodiments. Embodiments set forth in the claims encompass all available equivalents of those claims. 
     Microelectronic substrates are generally composed of alternating layers of dielectric material and metal. The metal may be formed from copper, which is patterned to form conductive traces between components on the substrate. The dielectric material may be formed from inorganic materials, such as SiO 2  or SiN, or organic materials. Some microelectronic substrates are formed using semiconductor materials, such as Si, while others may be formed from an organic monolithic core. One or more microelectronic die having integrated circuitry therein, may be physically and electrically attached to the substrate through various bonding techniques, such as ball bonding. The die may be attached to the substrate and connected such that signals are supplied between the die and traces in the substrate. In some embodiments, the signals from one die may be routed to another die through traces in the substrate. 
     As above, bridge technologies may be used to provide interconnections to or between one or more die on a substrate. With the constant demand for increased processing power and device capability, it is desirable to decrease line spacing in devices in which the above technologies are implemented, using very high density (VHD) routing structures within the substrate. In particular, it may be desirable to use ultra-fine lines/spaces (uFLS) for each of the lines and spaces to increase connection interconnectivity as well as permit smaller die packages to be used. The features of uFLS routing typically have a feature size (e.g., width) of about 2 μm. Even though formation of uFLS may be desirable, processing that forms the connections to the bridge unfortunately is currently limited to a relatively wide center-to-center bump pitch. Specifically, current processing technology is limited to a pitch of greater than about 50 μm. Depending on the overall packaging architecture and the corresponding placement of the bumps on the packaged dies, the performance of the overall circuitry may in certain circumstances be limited by the bridge. 
     VHD routing can be used in some situations for die to die interconnection and may be scalable to a variety of bump pitches. Many configurations, such as central processing unit (CPU) to memory, may end up using 4 uFLS layers (layers containing uFLS routing and interconnects). One example of such a structure may include 2 routing layers and 2 ground layers, and may be used regardless of the I/O density available for routing. The use of 4 uFLS layers, however, may have a significant impact on yield and cost of producing the overall structure. 
     It may thus be desirable to augment existing bridges with VHD routing in certain situations, without using multiple uFLS layers. In particular, an alternative to VHD routing is to use the existing bridge for interconnections that would otherwise use the 4 layers and use a single layer VHD for more flexible applications. Examples of these latter applications include CPU to CPU where optimization of the CPU pinouts may be achieved based on the CPU developer, and thus simplifying development. This may enable the bridge to be used with a 40 μm or smaller bump pitch. The use of a single layer VHD with the bridge may also enable a single uFLS layer to be used as a space transformer, which is able to adjust the spacing through the thickness of the layer. The single uFLS layer may be used to reconfigure multiple logic or memory die to work with the same bridge. This may reduce the time between, for example, a system memory down selection and package availability by eliminating the lead time to re-design and build bridge die. 
       FIGS.  1 A- 1 H  illustrate cross-sectional views of a fabrication process using a bridge and VHD routing using a substrate with a monolithic core in accordance with some embodiments. The process shown in  FIGS.  1 A- 1 H  involve patterning uFLS of about 2/2 μm each, which are unable to be formed using conventional processing methods in which bridges are also used. Embedded traces, self-aligned vias and/or zero misalignment vias may be used in the processes shown. In some embodiments, a photo imageable dielectric may be used to form the VHD routing and connect to small vias to the bridges. The processing may be used to fabricate the structure (lines, spaces and vias) through lithographic processes. In some embodiments, the lithographic processes may include laminating the underlying structure (e.g., substrate) with a dry film photoresist. The photoresist may then be patterned by exposure to radiation, such as visible or ultraviolet light. The exposure crosslinks the exposed portion of the dry film photoresist. The unexposed portions of the dry film photoresist may be removed in a developing step, for example, using a developer having about 1% sodium carbonate. The exposed portions of the dry film photoresist can then be electroplated with Cu to form the desired pattern and the exposed portions of the dry film photoresist subsequently removed if desired. In other embodiments, a negative dry film photoresist may be used, in which the exposed portions of the dry film photoresist may be removed in the developing step. In some embodiments, double patterning may be used to form vias. In particular, routing may be provided on a dielectric layer, and the routing followed by re-patterning using lithographic techniques and subsequent plating to form the via. In some embodiments, the use of a masked excimer or CO 2  laser may be avoided when forming the VHD routing. In various embodiments, such a laser may or may not be used to create various vias shown in  FIGS.  1 A- 1 H . 
       FIG.  1 A  shows a substrate  100  formed in accordance with established techniques. The substrate  100  may have a monolithic core  110  formed from an organic material, perhaps containing glass. On one or both sides of the monolthic core  110  alternating layers of dielectric material  112  and metal  114  may be formed and patterned to provide signal routing. The dielectric layer  112  may be formed from an organic insulating material, such as an Ajinomoto build-up film (ABF) layer, and the metal layer  114  may be formed from copper. Each of the dielectric layer  112  and the metal layer  114  may have a thickness of about 10-30 μm, typically ranging from 15-20 μm from an organic material perhaps containing glass. A total of six layers are shown in  FIG.  1 A , although there may be a greater or fewer number of layers on the substrate  100  prior to further processing. 
     As shown in  FIG.  1 A , dielectric layers  112  and metal layers  114  may be formed on opposite sides of the core  110 . The structure may be substantially symmetric around the core  110 ; each dielectric layer  112  and metal layer  114  may have the same layout as a corresponding layer on the side of the core  110 . To provide signal routing from the front side of the substrate  100  to the back side of the substrate  100 , the core  110  may be permeated with one or more vias  122 . On the back side of the substrate  100 , the topmost metal layer  114  may have a solder resist layer  120  patterned such that metal interconnects  116  formed from gold, for example, is plated to exposed portions of the topmost metal layer  114 . A protective film  118  may be formed over the metal interconnects  116  and solder resist layer  120 . The protective film  118  may be separated from the metal interconnects  116  such that no contact exists between the protective film  118  and the metal interconnects  116 . 
     The front side of the core  110  may terminate with a dielectric layer  112 . It is this top side that may further be subjected to processing to provide the bridge. As shown in  FIG.  1 B , copper pillars  124  are plated on the front side to a height just above the thickness of the bridge die. This height may be about 40-60 μm. In particular, an ABF or other organic dielectric layer is provided over the topmost layer shown in  FIG.  1 A . The dielectric layer is then patterned and etched using a lithographic process to form holes in the dielectric layer to the topmost metal layer  114  at predetermined locations. The lithographic process may include deposition and patterning of a photoresist to expose predetermined portions of the underlying structure, deposition of the metal or dielectric layer and stripping of the remaining photoresist thereafter to leave the metal or dielectric layer only on the exposed portions of the structure. Metal is then plated on the structure, in some embodiments using an electroless Cu process, and the dielectric layer stripped away to form the Cu pillars  124 . 
     In  FIG.  1 C , the bridge die  126  containing the uFLS is disposed on the structure shown in  FIG.  1 B , with the uFLS contacts disposed towards the outer portion of the substrate  100 . The Cu pillars  124  extend further upwards than the bridge die  126 . Another dielectric layer is subsequently laminated on the resulting structure. This dielectric layer covers both the bridge die  126  and the Cu pillars  124 . 
     After lamination of the dielectric layer, the surface is planarized as shown in  FIG.  1 D . The planarization may bring the surface down to the level of the bridge die  126 . In fact, the bridge die  126  can be used for endpoint detection for the planarizer. In particular, the outer pads on the existing bridge die  126  may be 6 μm thick, a margin of 1-2 μm thus may exist for grinding into the bridge die  126 . In some embodiments, however, planarizing into the bridge die  126  may be undesirable. In such cases, the planarization endpoint can be set above the bridge die  126  and a thickness target on the Cu pillars  124  may be adjusted. 
     After the substrate  100  has been planarized to the level of the bridge die  126 , a thin dielectric layer  128  may be then laminated on the bridge die  126  and the Cu pillars  124 . Vias  130  through the thin dielectric layer  128  to the bridge die  126  and the Cu pillars  124  may be formed formed with laser drilling (using, as above, an excimer or CO 2  laser, for example). Alternatively, the vias  130  may be formed lithographically using a photo imageable dielectric or through double patterning. Forming the vias using lithographic techniques may be advantageous as alignment may be able to be more closely controlled than when a laser-based process is used. Using lithographic techniques may also improve the Cu plating thickness uniformity as filling of the vias and creation of uFLS traces for routing may be performed in different operations.  FIG.  1 E  shows the substrate  100  after one or more metalizations to fill the vias  130  and create the uFLS traces  132  on the thin dielectric layer  128 . The substrate  100  is now prepared for creation of the uFLS routing, having been planarized to meet the flatness specifications used for lithography. In various embodiments, only one layer containing uFLS (or VHD layer) may be used, as shown, or multiple uFLS layers may be used. 
     In  FIG.  1 F , a solder resist (SR)  134  is deposited on the vias  130  and the uFLS traces  132  on the thin dielectric layer  128 . The solder resist  134  may have a thickness similar to the dielectric layer  112  and metal layer  114 . The solder resist  134  may protect the vias  130  and the uFLS traces  132  prior to attaching die on the surface of the substrate  100 . 
     In  FIG.  1 G , a first level interconnect (FLI) may be formed on the solder resist  134 . As shown, the FLI may be formed after lamination of the solder resist  134  by lithographically opening the solder resist  134 . Cu pillars may then be patterned and plated on the holes opened in the solder resist  134 , resulting in Cu pads  136  used for assembly. The Cu pads  136  can be coated by an organic surface protectant or a similar surface finish to control oxidation. The use of the uFLS traces in  FIG.  1 E  and the FLI and Cu pillars  136  may permit a smaller bump pitch to be achieved. 
     Depending on the assembly requirements, the FLI may also take advantage of formation of the vias through a self-aligned process. Self-aligned FLI formation may begin with lithographic patterning of dry or liquid photoresist to form the uFLS routing layer. A second resist may then be patterned without stripping the first resist. This second layer may define the Cu FLI. After plating using Cu, both layers of photoresist may be stripped away and solder resist laminated on top. The solder resist  134  may then be removed to reveal the via. Self aligned vias may be especially useful for space transforming from a 40 μm bump pitch (or less) to the current bridge having 55 μm contacts as alignment to the bridge may be a limit of bridge scaling. 
     After the organic surface protectant is deposited, as shown in  FIG.  1 H , the die  140  may be attached to the substrate  100 . The die  140  may be CPUs, memory, or any other IC to be connected across the bridge die  126 . The die  140  may be attached to the Cu pads  136  through a Sn or Ag/Sn ball or wedge bond  138 . The use of one or more uFLS layers, rather than a direct connection between the die  140  and the bridge die  126 , as well as use of photo imageable dielectric and lithographic techniques may enable the bump pitch reduction. Although the cross-sectional areas shown in  FIGS.  1 A- 1 H  illustrate only a single bridge die  126  connection between the die  140 , and a single VHD layer, in other embodiments, multiple bridge die may effect connections between the die and/or more than one VHD layer may be used. 
       FIGS.  2 A- 2 L  illustrate cross-sectional views of a fabrication process using a bridge and VHD routing using a coreless substrate in accordance with some embodiments. Coreless creation of the bridge and VHD routing substrate  200  may be initiated essentially in the reverse order of  FIGS.  1 A- 1 H , building the substrate  200  inward (towards where the core is in  FIGS.  1 A- 1 H ) rather than outwards. Warpage of the structure may be controlled by overmold and/or multiple glass cloth layers before being employed in a patch type architecture. Coreless creation of the bridge and VHD routing substrate  200  may be initiated as shown in  FIG.  2 A  by placement of the bridge die  212  on top of a temporary carrier  210 . The temporary carrier  210  may be formed from glass or another insulating structure and may be coated with a release layer  214  to permit the substrate  200  to eventually be removed from the temporary carrier  210 . 
     After the bridge die  212  is placed on top of the temporary carrier  210 , a seed layer  216  may be sputtered on the structure containing the bridge die  212 . The seed layer  216  may cover the entire structure and may be formed from a metal that supports electrolytic plating of the FLI  212  after patterning of the structure, such as Cu. The thickness of the seed layer  216  may range, for example, from about 0.2 μm to about 1 μm. The patterning may be performed using a photolithographic process. Unlike the processing shown in  FIGS.  1 A- 1 H , because the FLI  218  is plated first, before the underlying VHD layers are formed, there may be more flexibility of choice with the metal used for the FLI  218 . For example, rather than being limited to the use of Cu, any combination of Cu, Ni or Sn can be used, depending on product requirements. The bridge die  212  can be used for lithographic alignment of the FLI  218 , although edge detection of the bridge die  212  may be difficult depending on the seed layer thickness. 
     After the FLI  218  is patterned, the seed layer  216  may be removed. The removal may be performed by wet or dry etching. As shown in  FIG.  2 C , a dielectric  220  may subsequently be laminated on the top side of the structure  200 . The dielectric  220  may be laminated over the bridge die  212 , FLI  218  and the exposed portion of the release layer  214  sufficiently to protect the bridge die  212  and the FLI  218 . 
     The carrier  210  can then be put back through the process line and the processes shown in  FIGS.  2 A- 2 C  duplicated to place a bridge die  212  on the opposite side of the carrier  210 . In some embodiments, fabrication may be performed simultaneously on both sides. However, such a process may have an open bridge die on the backside and thereby significantly increase handling risk to the bridge die  212 . In any case, after lamination of the dielectric on the opposite side of the structure  200 , the dielectric  220  is planarized to the bridge die  212  on both sides as shown in  FIG.  2 D . The bridge die  212  can be used for planarization endpoint detection. In some embodiments, the dielectric  220  may be removed to at the bridge die  212 , while in other embodiments the dielectric  220  may be planarized to below the bridge die  212  to thin the bridge die  212 . Thinning may be limited, however, to reduce die cracking risks. Post planarization the dielectric will be flat enough to support uFLS patterning. 
     After planarization, holes  222  may be drilled into the dielectric  220  to expose the FLI  218  as shown in  FIG.  2 E . The holes  222  may be created using lithographic techniques and a wet etching process to create the holes  222 . In some embodiments, the holes  222  may be formed with laser drilling, using a CO 2  or excimer laser. 
     After the holes  222  have been created, a Cu layer may be deposited to create vias and uFLS  224 , as shown in  FIG.  2 F . The combined thickness of the vias  222  and FLI pads  218  may be equal to the post planarization bridge die thickness. The bridge die thickness may be between 40 and 60 μm. In some embodiments, the thickness for the FLI pads  218  is about 20-30 μm leaving an additional 20 μm or so thickness to be spanned by the vias  222 . This may ultimately limit the I/O density on the layer containing the FLI pads  218  due to the relationship between via depth and diameter, which is typically about 1:1. For example, a 20 μm via diameter resulting from a 20 μm via thickness may reduce the I/O density (assuming 2/2 μm line width/space ratio) from 150 I/O/mm to 75 I/O mm compared to a 10 μm thickness via with a corresponding 10 μm width. To overcome this, as above, lithographic techniques and a wet etching process may be used to create the vias  222 . This is done by first patterning the FLI pads  218  then using a second dry film resist to pattern the vias and uFLS  224 , resulting in &gt;2:1 aspect ratio. This may allow the thickness of the vias  222  to be 10 μm or below and at least double the I/O density. 
     After formation of the first uFLS layer  224  additional uFLS layers can be added on top of the first uFLS layer  224 . As shown in  FIG.  2 G , another dielectric layer  226  may be deposited on the first uFLS layer  224 . 
     After the dielectric layer  226  is deposited, a second uFLS layer  228  may be patterned and deposited as shown in  FIG.  2 H . The second uFLS layer  228  may be formed from Cu and deposited using electrolytic plating. The second uFLS layer  228  may be a ground layer. Thus, portions of the first uFLS layer  224  and second uFLS layer  228  may be physically connected through vias while other portions may be isolated. Like the first uFLS layer  224 , the second uFLS layer  228  may be disposed over the bridge die  212 . 
     Additional uFLS layer(s)  230  may be formed using similar processes as above, as shown in  FIG.  2 I . Alternatively, or in addition, as shown in  FIG.  2 J  a further process may be performed if additional VHD routing is not required. The additional layers can be made with glass cloth to increase the rigidity of the substrate  200  and control warpage. The top layers may include a dielectric layer in some portions of the structure  200  and a protective layer  232  in other portions of the structure. 
     Once the final layers are fabricated, the carrier may be removed. As shown in  FIG.  2 K , the structure  200  is depaneled by the carrier  210  being separated from the remaining structure (the substrate). The release layer  214  is then etched away and a thin layer of organic surface protectant  234  applied to protect the substrate. 
     The structure  200  is then assembled by attaching ICs or other modules  236  to the released surface of the substrate. The structure  200  may thus contain active layers on which signals are routed, ground layers, and insulating layers separating the active and ground layers and through which vias connect routing on the active layers, as well as the bridge and die. The structure  200  may use standard bonding processes to attach the modules  236  to the substrate. The resulting substrate may be used as a patch for a PoINT application or used more traditionally as a coreless substrate for high performance mobile applications. 
     An example of an electronic device using the microelectronic structure described above to show an example of a higher level device application for the disclosed subject matter.  FIG.  3    illustrates a system level diagram in accordance with some embodiments. For instance,  FIG.  3    depicts an example of an electronic device (e.g., system) including the structures as described in the present disclosure.  FIG.  3    is included to show an example of a higher level device application for the present invention. In one embodiment, system  300  includes, but is not limited to, a desktop computer, a laptop computer, a netbook, a tablet, a notebook computer, a personal digital assistant (PDA), a server, a workstation, a cellular telephone, a mobile computing device, a smart phone, an Internet appliance or any other type of computing device. In some embodiments, system  300  is a system on a chip (SOC) system. 
     In one embodiment, processor  310  has one or more processing cores  312  and  312 N, where  312 N represents the Nth processor core inside processor  310  where N is a positive integer. In one embodiment, system  300  includes multiple processors including  310  and  305 , where processor  305  has logic similar or identical to the logic of processor  310 . In some embodiments, processing core  312  includes, but is not limited to, pre-fetch logic to fetch instructions, decode logic to decode the instructions, execution logic to execute instructions and the like. In some embodiments, processor  310  has a cache memory  316  to cache instructions and/or data for system  300 . Cache memory  316  may be organized into a hierarchal structure including one or more levels of cache memory. 
     In some embodiments, processor  310  includes a memory controller  314 , which is operable to perform functions that enable the processor  310  to access and communicate with memory  330  that includes a volatile memory  332  and/or a non-volatile memory  334 . In some embodiments, processor  310  is coupled with memory  330  and chipset  320 . Processor  310  may also be coupled to a wireless antenna  378  to communicate with any device configured to transmit and/or receive wireless signals. In one embodiment, the wireless antenna interface  378  operates in accordance with, but is not limited to, the IEEE 802.11 standard and its related family, Home Plug AV (HPAV), Ultra Wide Band (UWB), Bluetooth, WiMax, or any form of wireless communication protocol. 
     In some embodiments, volatile memory  332  includes, but is not limited to, Synchronous Dynamic Random Access Memory (SDRAM), Dynamic Random Access Memory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM), and/or any other type of random access memory device. Non-volatile memory  334  includes, but is not limited to, flash memory, phase change memory (PCM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), or any other type of non-volatile memory device. 
     Memory  330  stores information and instructions to be executed by processor  310 . In one embodiment, memory  330  may also store temporary variables or other intermediate information while processor  310  is executing instructions. In the illustrated embodiment, chipset  320  connects with processor  310  via Point-to-Point (PtP or P-P) interfaces  317  and  322 . Chipset  320  enables processor  310  to connect to other elements in system  300 . In some embodiments of the invention, interfaces  317  and  322  operate in accordance with a PtP communication protocol such as the Intel® QuickPath Interconnect (QPI) or the like. In other embodiments, a different interconnect may be used. 
     In some embodiments, chipset  320  is operable to communicate with processor  310 ,  305 N, display device  340 , and other devices  372 ,  376 ,  374 ,  360 ,  362 ,  364 ,  366 ,  377 , etc. Chipset  320  may also be coupled to a wireless antenna  378  to communicate with any device configured to transmit and/or receive wireless signals. 
     Chipset  320  connects to display device  340  via interface  326 . Display  340  may be, for example, a liquid crystal display (LCD), a plasma display, cathode ray tube (CRT) display, or any other form of visual display device. In some embodiments of the invention, processor  310  and chipset  320  are merged into a single SOC. In addition, chipset  320  connects to one or more buses  350  and  355  that interconnect various elements  374 ,  360 ,  362 ,  364 , and  366 . Buses  350  and  355  may be interconnected together via a bus bridge  372 . In one embodiment, chipset  320  couples with a non-volatile memory  360 , a mass storage device(s)  362 , a keyboard/mouse  364 , and a network interface  366  via interface  324  and/or  304 , smart TV  376 , consumer electronics  377 , etc. 
     In one embodiment, mass storage device  362  includes, but is not limited to, a solid state drive, a hard disk drive, a universal serial bus flash memory drive, or any other form of computer data storage medium. In one embodiment, network interface  366  is implemented by any type of well known network interface standard including, but not limited to, an Ethernet interface, a universal serial bus (USB) interface, a Peripheral Component Interconnect (PCI) Express interface, a wireless interface and/or any other suitable type of interface. In one embodiment, the wireless interface operates in accordance with, but is not limited to, the IEEE 802.11 standard and its related family, Home Plug AV (HPAV), Ultra Wide Band (UWB), Bluetooth, WiMax, or any form of wireless communication protocol. 
     While the modules shown in  FIG.  3    are depicted as separate blocks within the system  300 , the functions performed by some of these blocks may be integrated within a single semiconductor circuit or may be implemented using two or more separate integrated circuits. For example, although cache memory  316  is depicted as a separate block within processor  310 , cache memory  316  (or selected aspects of  316 ) can be incorporated into processor core  312 . 
       FIG.  4    illustrates a method of substrate fabrication in accordance with some embodiments. The method shown in  FIG.  4    may be similar to that show in  FIGS.  1 A- 1 H  and be applied to create the device shown in  FIG.  3   . The method of  FIG.  4    may be applied to a structure formed on a monolithic core. At operation  402 , the substrate is prepared for the addition of the bridge die. The basic substrate may be a POR substrate, having a core and a number of interspaced dielectric and conductive (ground and non ground) layers. The POR substrate may be terminated with a dielectric layer. Vias may be drilled in the dielectric layer to portions of the underlying metal layer, either using a photolithographic or laser drilling process. Once the vias are created, Cu pillars may be formed using a photolithographic process. 
     At operation  404 , the bridge die may be placed on the substrate that contains the pillars. The height of the pillars may be designed to be greater than that of the bridge die so that the pillars extend from the surface of the dielectric farther than the bridge die. The difference in height between the top of the bridge die and the top of the pillars may be about 1-30 μm. 
     At operation  406 , the structure may be prepared for addition of the VHD layer. This may include laminating a dielectric layer (e.g., an ABF layer) over the structure containing the bridge die and pillars. After the lamination, the structure may be planarized to the top of the bridge die or slightly (about 1-2 μm) into the bridge die. 
     At operation  408 , the VHD layer and contact layer may be provided. This may include laminating a dielectric layer on the planarized structure. The a dielectric layer may be drilled into using a lithographic process such that the pillars and contacts on the bridge die are exposed. Subsequently, an electroless process may be used to plate Cu on the structure and the uFLS routing layer formed by liftoff. The use of the lithographic process permits the line/spacing aspect of the uFLS routing layer to be finer than direct contact to the bridge die by the IC. In addition, at least some of the routing may be disposed on portions of the structure that do not overlie the pillars or bridge die. This process may be repeated to provide multiple uFLS routing layers prior to assembly. 
     After all of the uFLS routing layers are fabricated, an organic protective layer may then be deposited on the top uFLS routing layer. Vias may be drilled in the protective layer to expose the uFLS contacts to the pillars and the bridge die and subsequently metallized to form contacts to the underlying structure. ICs or other components may then be assembled in operation  410  by bonding the ICs to the contacts. 
       FIG.  5    illustrates a method of coreless substrate fabrication in accordance with some embodiments. The method shown in  FIG.  5    may be similar to that show in  FIGS.  2 A- 2 L  and be applied to create the device shown in  FIG.  3   . The method of  FIG.  5    may be applied to a coreless structure. At operation  502 , the bridge die may be placed on a carrier impregnated with a liftoff film. The bride die may have contacts that contact the liftoff film and are later used to connect to the ICs. The structure to be formed may be one or two sided, with preparation of the opposing side being performed after protection of the bridge die already provided on the structure. 
     After placement of the bridge, the substrate may be prepared for fabrication of the VHD routing layer at operation  504 . This may include sputtering a thin metal layer over the structure containing the bridge die, patterning a photoresist, plating a FLI and, through liftoff, removing portions of the FLI to provide eventual contacts to the structure to be built. The contacts may be able to be precisely located due to the photoresist process to have a line/spacing of 2 μm. The bridge die and contacts may thus be automatically planarized to the same level. After formation of the FLI, the thin metal layer remaining may be etched away and a dielectric layer laminated on the structure. If desired, now that the bridge and contacts are protected by the ABF, the process up to this point may be applied to the backside of the carrier. 
     After the bridge die has been provided on the backside and protected via another ABF, both surfaces may be planarized to the bridge die level or, in some embodiments, slightly further. Vias may be drilled in the ABF to the contacts, either using a photolithographic or laser drilling process. Once the vias are created, at operation  506  a photolithographic process and subsequent plating may be used to pattern a uFLS layer and fill the vias. 
     At operation  508 , the structure may be completed prior to assembly. The completion may include laminating a dielectric layer on the uFLS layer and bridge die and then patterning a uFLS ground plane layer on the dielectric layer. Subsequently, multiple routing (metal) and dielectric layers may be fabricated on the uFLS ground plane layer, finishing with a surface added protectant. After the addition of the surface added protectant, the structures on both sides of the carrier may be removed, the liftoff film etched away and an OSP used to protect the surface. 
     After all of the uFLS routing layers are fabricated, an organic protective layer may then be deposited on the (now) top layer on which the bridge die and contacts are exposed and/or the bottom layer. ICs or other components may then be assembled in operation  510  by bonding the ICs to the contacts on the surface of the structure and the surface of the bridge die. 
     The structures shown created by the processes in  FIGS.  1 A- 1 H and  2 A- 2 L  and described in  FIGS.  4  and  5    may be used in a variety of manners. For servers, more components may be more tightly integrated, improving performance. Performance may also be improved by using the uFLS layers to do some of the routing as they have superior dielectric properties to the bridge bridge die. High performance mobile devices may also benefit from such structures. In such embodiments, next generation memories may require much higher I/O counts than today. In this segment, the ability to reconfigure and space transform the memory pinout may be quite valuable. 
     EXAMPLES 
     Example 1 is a semiconductor device comprising: a first set of alternating patterned conducting and insulating layers; and an embedded multi-die interconnect bridge disposed on an uppermost layer of the first set of layers, the bridge comprising ultra-fine line-space (uFLS) contacts; and die electrically connected to each other through the bridge, the die comprising contacts having at most about a 40 μm center-to-center pitch. 
     In Example 2, the subject matter of Example 1 optionally includes, further comprising: a monolithic core, the first set of layers disposed on a front side of the core. 
     In Example 3, the subject matter of Example 2 optionally includes, further comprising: a second set of alternating patterned conducting and insulating layers disposed on a back side of the core, a conducting layer of the first and second sets of alternating patterned conducting and insulating layers connected through vias in the core, the first and second set of alternating patterned conducting and insulating layers comprising layers of thicknesses between about 10-30 μm. 
     In Example 4, the subject matter of any one or more of Examples 1-3 optionally include, further comprising: conductive pillars surrounding the bridge, the conductive pillars having a same height as the bridge of about 40-60 μm, and a lateral insulating layer disposed between the bridge and the conductive pillars. 
     In Example 5, the subject matter of Example 4 optionally includes, further comprising: a second set of alternating patterned conducting and insulating layers disposed on the conductive pillars and the bridge, the second set of layers comprising: a first insulating layer adjacent to the bridge and the conductive pillars and having vias disposed therein, and a first conducting layer adjacent to the first insulating layer contacting the contacts on the bridge and the pillars and comprising uFLS traces. 
     In Example 6, the subject matter of Example 5 optionally includes, further comprising: a solder resist of about 10-30 μm disposed on the first conducting layer, and an interconnect layer disposed on the solder resist and connected to the first conductive layer through vias in the solder resist. 
     In Example 7, the subject matter of Example 6 optionally includes that: the die are bonded to and connected to the bridge through the interconnect layer. 
     In Example 8, the subject matter of any one or more of Examples 1-7 optionally include, further comprising: die comprising contacts having at most about a 40 μm center-to-center pitch and connected electrically connected to each other through the bridge and through at least one uFLS layer of the conductive layers on which the bridge is disposed. 
     In Example 9, the subject matter of any one or more of Examples 1-8 optionally include that: the conducting layers comprise copper and the insulating layers comprise an Ajinomoto build-up film (ABF) layer. 
     Example 10 is a method of fabricating a substrate, the method comprising: lithographically fabricating a first set of alternating conducting and insulating layers of thicknesses between about 10-30 μm, the conducting layers comprising ultra-fine line-space (uFLS) routing and connected through vias in the insulating layers; providing an embedded multi-die interconnect bridge comprising ultra-fine line-space (uFLS) contacts; and bonding die to the bridge to electrically connect the die through the bridge and through the uFLS routing, the die comprising contacts having at most about a 40 μm center-to-center pitch through which the die is bonded to the bridge. 
     In Example 11, the subject matter of Example 10 optionally includes that: the first set of layers are fabricated on a front side of a monolithic core comprising glass, and the bridge is deposited on a top layer of the first set of layers. 
     In Example 12, the subject matter of Example 11 optionally includes, further comprising: drilling vias in the core and lithographically patterning and etching a second set of alternating patterned conducting and insulating layers on a back side of the core such that a conducting layer of the first and second sets of layers are electrically connected through the vias. 
     In Example 13, the subject matter of any one or more of Examples 11-12 optionally include that providing the bridge comprises: depositing a photoresist layer on the top layer; lithographically creating vias in the photoresist layer by etching areas of the photoresist layer and depositing a conductor on the photoresist layer containing the etched areas; removing the photoresist layer to provide conductive pillars having a height of about 40-60 μm and expose the top layer; placing the bridge on the top layer, the bridge having a height that is at most the height of the conductive pillars; depositing a bridge insulating layer on the bridge and pillars to cover and separate the bridge and pillars; and planarizing the bridge insulating layer to expose the pillars and the bridge contacts. 
     In Example 14, the subject matter of Example 13 optionally includes that: a thickness of the bridge contacts is 6 μm, and the bridge is used for endpoint detection for planarization such that the planarizing comprises grinding 1-2 μm into the bridge contacts before terminating the planarization. 
     In Example 15, the subject matter of any one or more of Examples 13-14 optionally include that: the height of the pillars and the bridge contacts are about equal, and planarization is set above the bridge such that the planarizing comprises terminating the planarization prior to grinding into the bridge contacts. 
     In Example 16, the subject matter of any one or more of Examples 13-15 optionally include, further comprising: depositing a first insulating layer on the bridge and the conductive pillars; etching vias in the first insulating layer to correspond to the contacts and the pillars; depositing a first conductive layer on the first insulating layer having the vias; planarizing the first conductive layer; lithographically patterning the planarized first conductive layer to form uFLS traces; depositing a solder resist of about 10-30 μm on the patterned first conductive layer; opening holes in the solder resist to correspond to the uFLS traces; and forming a first level interconnect (FLI) on the solder resist by plating a second conductive layer on the solder resist to form pillars in the holes and lithographically patterning the second conductive layer to form uFLS contact pads, wherein the die are bonded to the uFLS contact pads. 
     In Example 17, the subject matter of any one or more of Examples 13-16 optionally include, further comprising: depositing and lithographically patterning a second set of alternating insulating and conducting layers on the bridge and the conductive pillars in which in each insulating layer of the second set of layers: vias are etched, one of the conductive layers is deposited, planarized and lithographically patterned to form uFLS traces; depositing a solder resist of about 10-30 μm on an uppermost conductive layer; opening holes in the solder resist to correspond to the uFLS traces; and forming an interconnect layer on the solder resist by plating another conductive layer on the solder resist to form pillars in the holes and lithographically patterning the other conductive layer to form uFLS contact pads, wherein the die are bonded to the uFLS contact pads. 
     In Example 18, the subject matter of any one or more of Examples 10-17 optionally include that: the bridge is placed on a temporary carrier comprising a liftoff layer such that the bridge contacts contact the liftoff layer, and the first set of layers are fabricated on the bridge, the method further comprising removing the temporary carrier using the liftoff layer prior to bonding the die to the bridge. 
     In Example 19, the subject matter of Example 18 optionally includes that fabricating the first set of layers comprises: sputtering a seed layer on the bridge and liftoff layer, lithographically patterning, on the seed layer, interconnect layer uFLS contacts to which the die is to be bonded and thereafter removing an exposed portion of the seed layer, laminating a bridge insulating layer on the bridge and the interconnect layer uFLS contacts having a height of about 20-30 μm, planarizing the bridge insulating layer to expose the bridge free from exposing the interconnect layer uFLS contacts, drilling holes in the bridge insulating layer to expose the interconnect layer uFLS contacts, and fabricating of the first set of layers by depositing an initial conductive layer and lithographically patterning the initial conductive layer to form vias having a height of at most about 10 μm and the uFLS routing, and subsequently depositing and lithographically patterning the alternating insulating and conducting layers, the insulating layers having vias corresponding with the uFLS routing to permit the conductive layers to electrically connect. 
     In Example 20, the subject matter of Example 19 optionally includes, further comprising: after laminating the bridge insulating layer and prior to planarizing the bridge insulating layer, duplicating operations on an opposite side of the carrier such that a second bridge, a second set of interconnect layer uFLS contacts and a second bridge insulating layer are formed on the opposite side of the carrier and thereafter duplicating processes such that after the removing the temporary carrier a pair of substrates are obtained. 
     Although an embodiment has been described with reference to specific example embodiments, it will be evident that various modifications and changes may be made to these embodiments without departing from the broader scope of the present disclosure. Accordingly, the specification and drawings are to be regarded in an illustrative rather than a restrictive sense. The accompanying drawings that form a part hereof show, by way of illustration, and not of limitation, specific embodiments in which the subject matter may be practiced. The embodiments illustrated are described in sufficient detail to enable those skilled in the art to practice the teachings disclosed herein. Other embodiments may be utilized and derived therefrom, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. This Detailed Description, therefore, is not to be taken in a limiting sense, and the scope of various embodiments is defined only by the appended claims, along with the full range of equivalents to which such claims are entitled. 
     Embodiments of the inventive subject matter may be referred to herein, individually and/or collectively, by the term “embodiment” merely for convenience and without intending to voluntarily limit the scope of this application to any single embodiment or inventive concept if more than one is in fact disclosed. Thus, although specific embodiments have been illustrated and described herein, it should be appreciated that any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the above description. 
     In this document, the terms “a” or “an” are used, as is common in patent documents, to include one or more than one, independent of any other instances or usages of “at least one” or “one or more.” In this document, the term “or” is used to refer to a nonexclusive or, such that “A or B” includes “A but not B,” “B but not A,” and “A and B,” unless otherwise indicated. In this document, the terms “including” and “in which” are used as the plain-English equivalents of the respective terms “comprising” and “wherein.” Also, in the following claims, the terms “including” and “comprising” are open-ended, that is, a system, device, article, composition, formulation, or process that includes elements in addition to those listed after such a term in a claim are still deemed to fall within the scope of that claim. Moreover, in the following claims, the terms “first,” “second,” and “third,” etc. are used merely as labels, and are not intended to impose numerical requirements on their objects. 
     The Abstract of the Disclosure is provided to comply with 37 C.F.R. § 1.72(b), requiring an abstract that will allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment.