Patent Publication Number: US-2020294924-A1

Title: High density organic bridge device and method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. application Ser. No. 16/135,695, filed Sep. 19, 2018, which is a continuation of U.S. application Ser. No. 15/350,393, filed Nov. 14, 2016, which is a continuation of U.S. patent application Ser. No. 14/992,535, now issued as U.S. Pat. No. 9,548,264, which is a continuation of U.S. patent application Ser. No. 13/722,203, filed Dec. 20, 2012, now issued as U.S. Pat. No. 9,236,366, each of which are incorporated by reference herein in their entirety. 
    
    
     TECHNICAL FIELD 
     Embodiments pertain to integrated circuit (IC) dies, multi-chip packages, and associated methods. More particularly, embodiments pertain to using an organic bridge in an organic package substrate to interconnect dies with a high density interconnect. 
     BACKGROUND 
     In order to enhance performance, processing unit products are increasingly integrating multiple die within the processing unit package in a side-by-side or other multi-chip-module (MCM) format. In traditional MCM format, the chip die are interconnected via connections within the substrate. One way to increase the input-output (IO) capacity is to connect the die through embedded IO bridge die featuring a very high wiring density locally between die. Patterning dense metal features on a silicon substrate is the conventional fabrication approach. This enables very fine feature, size consistent backend metallization, and a great number of IO interconnections. However, there is a significant mismatch between the coefficient of thermal expansion (CTE) of an organic package and a silicon bridge, leading to delamination and cracking between multiple materials. With multiple process steps used in production of the MCM after the silicon bridge has been placed in the substrate, the manufacturing process itself can lead to cracking and delamination. Additionally, embedding an external bridge made out of silicon to increase the local IO makes the silicon bridge ultra-thin and embedding the silicon bridge within the substrate can be challenging. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a general microelectronic process according to some embodiments; 
         FIG. 2  illustrates a plan view of a microelectronic package according to some embodiments; 
         FIG. 3  illustrates a cross sectional view of an organic bridge placed within a substrate according to some embodiments; and 
         FIG. 4  illustrates a process to create an organic bridge according to 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. 
       FIG. 1  illustrates a general microelectronic process according to some embodiments. The process, illustrated generally as  100 , takes assemblies made from a substrate manufacturing process  102 , a bridge manufacturing process  104  and assembles them as shown in  108  to produce a microelectronic package/device such as multichip package  110 . 
     Die manufacturing process  106  is illustrated in dashed form to indicate that the die can be assembled on the substrate and bridge in the same process  108  or in a separate process at a later time. Die manufacturing process  106  can be any process sufficient to produce desired dies that will be incorporated into the final product. No further description of die manufacturing  106  will be given as it is not important to the disclosure herein. 
     Substrate manufacturing process  102  may comprise any process to produce a suitable package substrate that may be used, for example, in multi-chip packaging. Separate substrate manufacturing process  102  allows the process to be tuned effectively for the particular package substrate. In general, this means that the package substrates and process  102  can be tailored to only those aspects driven by the package substrate (and the bridge placement) and not those aspects driven by the bridge itself. In general, this allows using a less expensive process, a process that provides a higher yield, a higher volume, more relaxed geometries on conductors on and within the package substrate, a combination of all of these, or some other particular criteria or combination of criteria. Typically package substrates are made from an organic polymer such as an epoxy. Package substrates may have a variety of materials such as silica, calcium oxide, magnesium oxide, etc., added to the organic polymer to achieve particular properties such as a desired glass transition temperature or other desired properties. 
     Package substrates produced by substrate manufacturing process  102  may include various layers and geometries such as wires and connection points. In one example, substrates can be produced using design rules of about a 40 μm wire width and about a 40 μm wire spacing. Similarly, build-up layers, if any, can be thicker than those used by bridge manufacturing process  104  to produce organic bridges. 
     Bridge manufacturing process  104  may comprise a process to produce a high density interconnect bridge suitable for placement in the package substrate. An example process is discussed in conjunction with  FIG. 4  below. Bridges may be made from an organic polymer such as an epoxy without its own substrate (e.g. with only a few build-up layers or a single build-up layer comprising routing and pad layers). In one embodiment organic bridges produced by bridge manufacturing process  104  are less than about 30 μm thick. In another embodiment, organic bridges produced by bridge manufacturing process  104  are about 15 μm thick. 
     In embodiments of the bridge that have no substrate, when the bridge is placed on the package substrate as part of assembly process  108 , the bridge conforms to the contours of the layer in the package substrate beneath it. This helps minimize inter-material issues such as cracking, chipping or delamination. The thinness of the bridge makes it easier to satisfy any z-height requirements of the process and/or package. For embodiments manufactured without a substrate, bridge manufacturing process  104  can use low cost, reusable glass carriers. 
     The organic polymer used in bridge manufacturing process  104  to produce organic bridges may be the same as, or different from, the organic polymer of the substrate. Since both materials are organic, the organic bridges have better interfacial adhesion (compared, for example, to bridges made out of silicon). Since both materials are organic, cracking, chipping, delamination and other issues associated with use of dissimilar materials can be minimized. 
     Bridge manufacturing process  104  may be designed to produce small, high density geometries in the bridge to carry high density IO interconnects. In one embodiment, organic bridge manufacturing process  104  uses design rules of about 3 μm or less wire width and about 3 μm or less wire spacing. In another embodiment, organic bridge manufacturing process  104  uses design rules of about 3 μm or less in wire width and spacing in some areas or layers and wider wire width and spacing in other areas or layers of the bridge (e.g., about 10 μm wire width and about 10 μm wire spacing). 
       FIG. 2  illustrates a plan view of a microelectronic package according to some embodiments. The package  200  has package substrate  212  and an organic bridge  214  embedded in package substrate  212 . Package substrate  212  may comprise an organic polymer such as an epoxy. Organic bridge  214  may also comprise an organic polymer such as an epoxy. The organic polymer of organic bridge  214  may be the same as, or different from, the organic polymer of package substrate  212 . 
     Organic bridge  214  comprises an interconnect structure  216  located at a location  220  and an interconnect structure  218  located at a location  222 . Interconnect structure  216  and interconnect structure  218  may comprise a plurality of connection points, such as the connection point illustrated as  208 . The various connection points within interconnect structure  216  and  218  are connected by conductive paths. In  FIG. 2 , example conductive paths are illustrated by  210 . Connections between the various connection points are appropriate to the die that will be interconnected by organic bridge  214 . Locations  220  and  221 , shown in dashed lines, indicate the locations where die interconnected by organic bridge  214  will be placed. 
     Interconnect structures  216  &amp;  218  on an organic bridge  214  are typically located toward an end of the organic bridge  214 . Thus, locations  220  and  222  are typically toward the ends of organic bridge  214 . However, the location of interconnect structures  216  &amp;  218  are determined by the die that will be interconnected by the organic bridge  214 . 
     Microelectronic package  200  may comprise multiple organic bridges  214 , each having multiple interconnect structures  216  &amp;  218  in order to interconnect multiple die. In  FIG. 2 , additional organic bridges are illustrated by  202 , interconnect structures are illustrated by  204  and die placement locations are illustrated in dashed lines by  206 . These organic bridges  202  may be similar to organic bridge  214 . Interconnect structures  204  may be similar to interconnect structure  216  and/or interconnect structure  218 . 
       FIG. 3  illustrates a cross sectional view of an organic bridge  202  placed within a substrate according to some embodiments. The assembly, illustrated generally as  300 , may comprise a substrate  302  and an organic bridge  304 . Substrate  302  may be a package substrate  302 , such as that manufactured by substrate manufacturing process  102  of  FIG. 1  and may comprise an organic polymer such as an epoxy. 
     Substrate  302  may comprise connection points  306  to connect a die, such as die  318  and  319  to substrate  302 . Connection points  306  and associated conductive paths (not shown) may adhere to design rules appropriate for substrate  302 . In one embodiment, the design rules of substrate  302  allow larger geometries (for e.g. connection points  306 ) than the design rules of embedded organic bridge  304 . In one example, substrate  302  can be produced using design rules of about a 40 μm wire width and about a 40 μm wire spacing. Similarly, build-up layers, if any, can be thicker than those in organic bridge  304 . 
     Substrate  302  has a recess to receive organic bridge  304 . Depending on the thickness of the dielectric and other layers of substrate  302  and the thickness of organic bridge  304 , the recess may only need to extend into the outermost layer or multiple outermost layers. Such a recess can be formed within substrate  302 , for example, by using laser scribing. 
     Organic bridge  304  may comprise an organic polymer such as an epoxy. The organic polymer of organic bridge  304  may be the same as, or different from, the organic polymer of substrate  302 . For clarity, some of the various layers of organic bridge  304  are illustrated in various patterns so they can be distinguished from the surrounding items. 
     Organic bridge  304  is placed into a recess of substrate  302  using an organic polymer to adhere organic bridge  304  into the recess. The organic polymer can be a dye bonding film, an epoxy, or any other type of organic polymer that sufficiently adheres organic bridge  304  to substrate  302 . In  FIG. 3 , bonding organic bridge  304  to substrate  302  is illustrated by  308 . Since substrate  302  and organic bridge  304  both comprise an organic polymer, layer  308  can adhere organic bridge  304  to substrate  302  in a way that minimizes problems arising from the interface of two dissimilar materials such as chipping, cracking and delamination. 
     Organic bridge  304  is represented in  FIG. 3  by layer  310 ,  312  and  314  and  316 . Layer  310  represents a metal layer within organic bridge  304 , which may be included as part of the bridge  304 . Layer  314  represents a metal routing layer embedded within dielectric layer  312 . Dielectric layer  312  comprises an organic polymer such as an epoxy and represents interleaved dielectric layers  312 . Layer  316  represents a pad layer where, for example, interconnect structures  204  can be formed as part of organic bridge  304 . In one embodiment, the design rules for organic bridge  304  comprise about 3 μm or less wire width and about 3 μm or less wire spacing. In another embodiment, the design rules for organic bridge  304  comprises about 3 μm or less in wire width and spacing in some areas or layers and wider wire width and spacing in other areas or layers of the bridge (e.g., about 10 μm wire width and about 10 μm wire spacing). 
     Some embodiments of organic bridge  304  have no substrate  302 . Such embodiments may comprise routing and pad layers  314  &amp;  316  and, possibly some additional metal layers all with interleaved dielectric layers  312  but without, for example, a substrate  302 . Having no substrate  302  means that those embodiments of organic bridge  304  have no layer that has substantial silicon content. In such embodiments, any “substrate” layer would be made substantially of a metal or an organic polymer such as an epoxy. The organic polymer may include various additives such as silica, calcium oxide, magnesium oxide, or other additive to modify certain desired properties of the organic polymer. 
     In one embodiment organic bridge  304  has no substrate  302  and is about 15 μm thick. In another embodiment organic bridge  304  has no substrate  302  and is less than about 20 μm thick. In yet another embodiment organic bridge  304  has no substrate  302  and is less than about 30 μm thick. Since organic bridge  304  has no substrate  302 . it tends to conform to the contours of the recess into which it is placed. In such embodiments, the lack of a substrate  302  and the thinness of organic bridge  304  allows organic bridge  304  to be incorporated into a solder mask cavity on the surface layer of the of substrate  302  and ultra fine pitch dies can be directly connected by thermo-compression based bonding. 
       FIG. 4  illustrates a process to create an organic bridge  304  according to some embodiments. Such a process can be used, for example, in bridge manufacturing process  104  of  FIG. 1 . In  FIG. 4 , the process illustrated generally as  400  is a spin-on-glass (SoG) technique. SoG has the ability to provide finer trace and spacing than other processes, and thus is illustrated here. However, other processes may also be used. 
     In  402  a carrier wafer of silicon or glass is obtained. Since the incoming carrier wafer will not form part of the final organic bridge  304 , inexpensive, reusable carrier wafers can be used for the process. 
     In  404  a release layer and the lower dielectric (SoG) layer is deposited. As previously described, the dielectric layer  312  comprises an organic polymer such as an epoxy. 
     In  406 , seed layer deposition occurs, for example by sputtering. Dry file resist (DFR) and patterning of the seed layer also occurs. 
     In  408 , plating occurs along with DFR stripping and application of the next dielectric layer  312  using SoG techniques. 
     In  410  via formation occurs along with seed layer deposition using, for example, sputtering. DFR application and patterning also occurs. 
     In  412  continuation of all metal layers occurs along with the final solder resist (SR) layer and patterning. 
     In  414  the resultant assembly is released from the carrier wafer and bridge singulation (e.g. separating the assembly into individual organic bridges  304 ) occurs. 
     In general, organic bridges  304 , such as those described in conjunction with  FIGS. 1-3 , are only a few layers thick, perhaps only the routing layer  314 , pad layer  316 , ground and reference layers for the signal layers, plus interleaved dielectric layers  312 . In such a situation, this two layer organic bridge  304  will be about 15 μm thick. However, if desired, the process illustrated in  408  and/or  410  can be repeated as appropriate to achieve an organic bridge  304  of perhaps three or four layers having a thickness of about 20 μm to about 30 μm. 
     The above detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the disclosure may be practiced. These embodiments are also referred to herein as “examples.” Such examples may include elements in addition to those shown or described. However, the present inventors also contemplate examples in which only those elements shown or described are provided. Moreover, the present inventors also contemplate examples using any combination or permutation of those elements shown or described (or one or more aspects thereof), either with respect to a particular example (or one or more aspects thereof), or with respect to other examples (or one or more aspects thereof) shown or described herein. 
     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 above description is intended to be illustrative, and not restrictive. For example, the above-described examples (or one or more aspects thereof) may be used in combination with each other. Other embodiments may be used, such as by one of ordinary skill in the art upon reviewing the above description. The Abstract is provided to comply with 37 C.F.R. § 1.72(b), to 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. Also, in the above Detailed Description, various features may be grouped together to streamline the disclosure. This should not be interpreted as intending that an unclaimed disclosed feature is essential to any claim. Rather, inventive subject matter may lie in less than all features of a particular disclosed embodiment. Thus, the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments may be combined with each other in various combinations or permutations. The scope of the inventive material should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.