# Patent

## Title
High density organic bridge device and method

## Abstract

Embodiments that allow multi-chip interconnect using organic bridges are described. In some embodiments an organic package substrate has an embedded organic bridge. The organic bridge can have interconnect structures that allow attachment of die to be interconnected by the organic bridge. In some embodiments, the organic bridge comprises a metal routing layer, a metal pad layer and interleaved organic polymer dielectric layers but without a substrate layer. Embodiments having only a few layers may be embedded into the top layer or top few layers of the organic package substrate. Methods of manufacture are also described.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation of U.S. patent application Ser. No. 13/722,203, filed Dec. 20, 2012, which is incorporated by reference herein in its 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 1.5 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 14 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 & 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 & 218 are determined by the die that will be interconnected by the organic bridge 14.
Microelectronic package 200 may comprise multiple organic bridges 214, each having multiple interconnect structures 216 & 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 across 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 & 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 EEGs. 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.

## Claims

1. A microelectronic package comprising:
an organic polymer substrate created using a first set of design rules having a first wire width of about 40 μm and first wire spacing of about 40 μm;
an organic polymer bridge embedded in the substrate, created using a second set of design rules in at least portion of the organic polymer bridge, the second set of design rules having a second wire width of about 3 μm and a second wire spacing of about 3 μm;
a first interconnect structure at a first location of the organic polymer bridge and a second interconnect structure at a second location of the organic polymer bridge; and
an electrically conductive path in the organic polymer bridge connecting the first interconnect structure to the second interconnect structure.

2. The microelectronic package of claim 1 wherein the organic polymer substrate contains a recess and the organic polymer bridge is embedded into the recess using an organic polymer.

3. The microelectronic package of claim 2 wherein the organic polymer substrate and the organic polymer bridge are made from the same organic polymer.

4. The microelectronic package of claim 2 wherein the organic polymer substrate and the organic polymer bridge are made from different organic polymers.

5. The microelectronic package of claim 2 wherein the organic polymer used to bond the organic polymer bridge to the organic polymer substrate is a die bonding film or an epoxy.

6. The microelectronic package of claim 1 wherein the organic polymer bridge comprises a third set of design rules in at least one other portion of the organic bridge, the third set of design rules having third wire width of about 10 μm and a third wire spacing of about 10 μm.

7. The microelectronic package of claim 1 wherein the organic polymer bridge has a total thickness of less than about 20 μm.

8. An organic bridge adapted to interconnect a plurality of die, the organic bridge comprising:
a plurality of metal routing layers;
a metal pad layer;
at least a portion of the plurality of metal routing layers or at least a portion of the metal pad layer or at least a portion of both adhering to a first set of design rules having a first wire width of about 3 μm and first wire spacing of about 3 μm;
interleaved organic polymer dielectric layers between each metal routing layer and the metal pad layer; and
wherein there is no layer made substantially of silicon.

9. The organic bridge of claim 8 wherein at least a second portion of the plurality of metal routing layers or at least a second portion of the metal pad layer or at least a second portion of both adhering to a second set of design rules having a second wire width of about 10 μm and second wire spacing of about 10 μm.

10. The organic bridge of claim 8 wherein all layers have a combined thickness of about 15 μm.

11. The organic bridge of claim 8 wherein the metal pad layer comprises a plurality of interconnect structures.

12. The organic bridge of claim 11 wherein a first of the plurality of interconnect structures is adapted to connect to a first die and wherein a second of the plurality of interconnect structures is adapted to connect to a second die.

13. The organic bridge of claim 8 wherein the organic polymer bridge has a thickness of about 15 μm to about 20 μm.

14. A microelectronic package comprising:
an organic polymer package substrate created using a first set of design rules having a first wire width of about 40 μm and first wire spacing of about 40 μm; and
an organic polymer bridge created using a second set of design rules in at least a portion of the organic bridge having a second wire width of about 3 μm and a second wire spacing of about 3 μm, the organic polymer bridge comprising a metal pad layer, a metal routing layer and interleaved dielectric layers, the organic polymer bridge being embedded in the organic polymer package substrate.

15. The microelectronic package of claim 14 wherein the organic polymer bridge has a thickness of about 15 μm to about 20 μm.

16. The microelectronic package of claim 14 wherein the organic polymer bridge comprises a third set of design rules in at least one other portion of the organic bridge, the third set of design rules having third wire width of about 10 μm and a third wire spacing of about 10 μm.

17. A method comprising:
providing an organic bridge comprising:
a plurality of metal routing layers;
a metal pad layer;
at least a portion of the plurality of metal routing layers or at least a portion of the metal pad layer or at least a portion of both adhering to a first set of design rules having a first wire width of about 3 μm and first wire spacing of about 3 μm;
interleaved organic polymer dielectric layers between each metal routing layer and the metal pad layer, wherein there is no layer made substantially of silicon;

providing an organic package substrate having a recess formed therein; and
bonding the organic bridge into the recess of the organic package using an organic polymer.

18. The method of claim 17, wherein all layers of the organic bridge have a thickness of about 15 gm to about 20 gm.

19. The method of claim 17 wherein the metal pad layer comprises a plurality of interconnects and wherein the method further comprises bonding a first die to one of the plurality of interconnects and bonding a second die to another of the plurality of interconnects, the bonding of the first die and the second die being accomplished using thermo-compression based bonding.

20. The method of claim 17, wherein the organic bridge is bonded into a single buildup layer of the organic package substrate.