# Patent

## Title
High density substrate interconnect formed through inkjet printing

## Abstract

Generally discussed herein are systems and apparatuses that include a dense interconnect bridge and techniques for making the same. According to an example a technique can include creating a multidie substrate, printing an interconnect bridge on the multidie substrate, electrically coupling a first die to a second die by coupling the first and second dies through the interconnect bridge.

## Background
CROSS-REFERENCE TO RELATED APPLICATION
This application is a divisional of and claims the benefit of priority to U.S. patent application Ser. No. 14/036,719, filed on Sep. 25, 2013, which is hereby incorporated by reference herein in its entirety.


TECHNICAL FIELD
Examples generally relate to multichip packages, and more specifically to creating a multichip package with a dense interconnect using inkjet printing technology.
TECHNICAL BACKGROUND
Semiconductor devices, such as electronic devices, can include substrate routing that is of a lower density than some of the routing in a chip that is attached to the substrate. Such devices can include complex routing schemes especially in areas where the attached chip includes higher density routing than the routing in the substrate.



BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings, 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 drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document.
FIGS. 1A-1D illustrate stages of an example of a process of creating a microelectronic die package.
FIGS. 2A-2E illustrate stages of an example of a process for creating an interconnect bridge using inkjet printing technology.
FIG. 3 illustrates an example of a technique for creating an interconnect bridge using printing technology.
FIG. 4 is a schematic of an example of an electronic system.



DESCRIPTION OF EMBODIMENTS
Examples in this disclosure relate to apparatuses and systems that include a printed high density interconnect bridge. Examples also relate to techniques of printing a high density interconnect bridge on a substrate.
The following description includes terms, such as upper, lower, first, second, etc. that are used for descriptive purposes only and are not to be construed as limiting. The examples of an apparatus or article described herein can be manufactured, used, or shipped in a number of positions and orientations. The terms “die” and “chip” generally refer to the physical object that is the basic workpiece that is transformed by various process operations into the desired integrated circuit device. A die is usually singulated from a wafer and wafers may be made of semiconducting, non-semiconducting, or combinations of semiconducting and non-semiconducting materials.
Current board design can be created by incorporating a number of heterogeneous functions, such as Computer Processing Unit (CPU) logic, graphics functions, cache memory, and other functions to create integrated System on Chip (SoC) designs. Such SoC packages can lower the complexity of a product design and can reduce the number of components required by the product. Picking individual packages that implement these functions and designing the board around the packages chosen can be complex. Using individual packages can increase the system board area, power loss, complexity, component count, or costs over an integrated SoC package solution.
The input/output (IO) density in a package substrate can be a function of a substrate's minimum pad size, minimum trace dimensions, minimum space dimensions, or the capability of the manufacturing process. The routing density in a multichip substrate can be several orders of magnitude lower (e.g., about 100 times) than chip level routing density. This routing density can impact cost, size, and performance of a product.
A way to reduce the size of a product can include utilizing a silicon interposer in a package to provide a high density chip to chip interconnection. Such a solution includes a higher cost due to the cost of the silicon interposer, additional assembly and process steps, and compounding yield loss.
A substrate can include a high density interconnect bridge in a BBUL or other substrate with multiple embedded dice (e.g., chips) embedded, at least partially, therein. Such a solution can eliminate a first level interconnect (FLI) die attach and use panel processing to reduce the overall cost. Such a solution can allow a high density interconnect to be situated where it would be advantageous and allow low density interconnect (e.g., routing with a substrate routing technique) where it would be advantageous, such as for routing power or ground lines.
Substrate routing can take up a significant amount of space and can be a factor in the overall size of a die package. By including typical substrate routing techniques, which can result in less dense routing than chip routing techniques, there may not be enough space to route the die without routing through the die. Integrating a high density interconnect bridge in a package or substrate, such as a BBUL package or substrate, can allow for an increase in overall local routing and interconnect density of a package, thus helping to reduce size and cost. One previous solution included embedding a high density, silicon interconnect bridge in a substrate. Assembly of such a package is challenging due to tight tolerance requirements in the x, y, and z directions. The tight tolerance requirements are due, at least in part, to alignment and fitting issues in connecting the chip interconnect bridge to the substrate. In addition, using a chip interconnect bridge (e.g., a silicon interconnect bridge) requires embedding the interconnect bridge during the substrate fabrication process.
By printing, such as by using an inkjet printer, an interconnect bridge on a substrate and then attaching one or more dies to the interconnect bridge, the tight tolerances and difficulty in assembling the package can be avoided. Also, by inkjet printing the interconnect bridge, routing can be changed after the substrate fabrication process, thus allowing for added flexibility in the routing design. Further, inkjet printing allows for more package warpage than the high density chip interconnect bridge approach, since inkjet printing can be applied to uneven or non-flat surfaces. Also, inkjet printing the interconnect bridge can eliminate the wafer thinning process required for the high density chip interconnect bridge approach, and can also eliminate any precautions needed to ensure the chip bridge is not damaged when handling the thin chip interconnect.
Inkjet printing technology can allow for traces as small as a micrometer, or even smaller. The spaces between the traces can be a micrometer or smaller using inkjet printing technology. The same technology can be used to create 3D structures such as micro-bumps, pads, or vias, among others. Inkjet printing technology can also be used to print dielectric material and fill spaces between traces or routing layers, among others. As used herein “print” means to dispense powder or molten material out of a nozzle. Printing is an additive process, as opposed to a subtractive process.
Reference will now be made to the drawings wherein like structures will be provided with like suffix reference designations. In order to show the structures of various examples clearly, the drawings included herein are diagrammatic representations of integrated circuit structures. Thus, the actual appearance of the fabricated structures, for example in a photomicrograph, may appear different while still incorporating subject matter of the illustrated examples. Moreover, the drawings show the structures to aid in understanding the illustrated examples.
FIG. 1A shows an example of a substrate 100A. The substrate 100A can be a Bumpless BuildUp Layer (BBUL) substrate. The substrate 100A can include a plurality of low density interconnect pads 104 (e.g., pads created using substrate routing technology, as opposed to chip routing technology). The substrate 100A can include a plurality of vias 106 that electrically couple low density interconnect pads 104 between buildup layers 108A and 108B. The buildup layers 108A and 108B can include copper (Cu) interconnects (e.g., low density vias 106) and dielectric buildup layers (e.g., Anjinomoto Buildup Film (ABF)). The substrate 100A can include a solder resist 112 situated on a buildup layer 108A and between solder balls 110 or other electrically conductive interconnect elements.
FIG. 1B shows a substrate 100B with a cavity 102 formed in an upper surface 114 of the buildup layer 108B. The cavity 102 can be formed into the substrate 100 during fabrication thereof or can be mechanically machined or laser ablated into the substrate 100 post-fabrication.
FIG. 1C shows the substrate of FIG. 1B after a high density interconnect bridge 118 and high density interconnect pads 116 have been printed on or at least partially in the cavity 102. The high density interconnect pads 116 can be printed to be denser (e.g., more pads per volume) than the low density interconnect pads 104. In one or more examples, the high density interconnect pads 116 can printed up to 100 times denser than the low density interconnect pads 104. The high density interconnect bridge 118 can include one or more printed traces 124, one or more printed vias 120, and dielectric 122 situated over and between the traces 124 and between the vias 120. FIGS. 2A-2E show an example of a process for printing the interconnect bridge 118 in more detail.
FIG. 1D shows the substrate of FIG. 1C with first and second dice 126A and 126B electrically and mechanically coupled to low density interconnect pads 104 and high density interconnect pads 116. The first and second dice 126A and 126B can be encapsulated in molding or a buildup layer 108C. A buildup layer 108 can be used when the die 126 is to be embedded. In one or more embodiments, the dice 126A and 126B may not be completely encapsulated as shown in FIG. 1D. In such embodiments, the dice 126A and 126B can be partially surrounded by a molding or an underfill, so as to protect the electrical connections made to the substrate 100.
FIGS. 2A-2E illustrate an example of a process for inkjet printing a high density interconnect bridge 118. At FIG. 2A one or more traces 124 can be printed on a substrate 200. The material used to print the traces 124 can be gold, silver, copper, or other suitably electrically conductive and printable materials. The printed material can be sintered, such as by microwave sintering or laser sintering, so as to fuse at least some of the printed particles that make up the traces 124 together. The sintering process can help solidify the printed trace 124 and increase the electrical conductivity and mechanical strength of the printed trace 124. At FIG. 2B, one or more vias 120 can be printed on the one or more traces 124. Similar to the traces 124, the vias 120 can be sintered after they are printed.
Dielectric 122 can be printed in between, on, or around the traces 124 and vias 120, such as shown in FIG. 2C. The dielectric 122 can be an organic dielectric, solder resist, ABF film, epoxy, or a combination thereof, among others. The dielectric 122 can be baked after it is printed so as to cure or harden the dielectric 122 and to insulate the traces 124, vias 120, and pads 116 from bridging. One or more pads 116 can be printed so as to form a contact with one or more of the vias 120. The pads 116 can be printed on, over, or around the dielectric 122. The pads 116 can be printed using one of at least two methods. The first method includes printing a thin layer of the pad 116, sintering the thin layer, and repeating until the pad 116 has the specified height. The second method can include using a high-viscosity printing material to print the entire pad 116 and then sintering the high viscosity material. The high viscosity material can help the pad 116 hold shape after printing or before sintering.
Sintering printed metals (e.g., traces, vias, pads, or the like) can produce a metal structure with a sintered grain morphology. The sintered grain morphology is a different morphology than a metal formed in a lithographic process (e.g., a sheet metal). The differences between the two morphologies can be seen using an electron microscope, scanning probe microscope, or other microscope. The sintered grain morphology metals can have different properties (e.g., mechanical strength, conductivity, or the like) than the metals formed using a lithographic process. Sintering includes diffusing atoms of a material at a temperature lower than the melting point of the material being sintered so as to fuse atoms together.
FIG. 2E illustrates a cross-section of the substrate shown in FIG. 2D. As can be seen in FIG. 2E, the dielectric material 122 can be printed on, over, under, or around the traces 124, vias 120, pads 116, and the buildup layer 108B. The via 120 can be printed and sintered so as to be on or in electrical contact with the trace 124. The pad 116 can be printed and sintered so as to be on or in electrical or mechanical contact with the trace 124. The pad 116 can be a Package on Package (PoP) pad, a flip-chip pad, or other type of pad.
FIG. 3 illustrates an example of a technique 300 for inkjet printing an interconnect bridge 118. At 302, a multidie substrate can be created. The multidie substrate can be configured to have at least two dies soldered thereto, such as by including pads that the pads can be electrically and mechanically coupled to. The multidie substrate can be a BBUL substrate or a substrate made from any multidie manufacturing process. At 304, an interconnect bridge 118 can be printed on the multidie substrate. Printing the interconnect bridge 118 on the substrate can include printing one or more traces 124 in the cavity 102. Printing the interconnect bridge 118 in the cavity 102 can include printing a via 120 on a trace 124 of the one or more traces 124. Printing the interconnect bridge 118 in the cavity can include printing a pad 116 on the via 120. Printing the interconnect bridge 118 in the cavity 102 can include printing a dielectric 122 on the via 120 before printing the pad 116 on the via 120. The cavity 102 in the multidie substrate can be formed in the multidie substrate during fabrication of the substrate. The cavity 102 in the substrate can be formed in the substrate after the substrate is fabricated. The interconnect bridge 118 can be printed, such that at least a substantial portion of the interconnect bridge 118 (e.g., the traces 124, at least a portion of the vias 120, and at least a portion of the dielectric and possibly part of the pad 116 is printed in the cavity 102.
The one or more printed traces 124 can be sintered before the via 120 is printed. The via 120 can be sintered before the dielectric 122 is printed. The dielectric 122 can be baked before the pad 116 is printed. The printed pad 116 can be sintered after at least one layer of the pad 116 is printed.
At 306, a first die 126A can be electrically coupled to a second die 126B, such as by coupling the first and the second dies through the interconnect bridge 118. Coupling the first die 126A to the interconnect bridge 118 can include electrically coupling a contact on the first die 126A to the pad 116.
FIG. 4 is a block diagram of a computing device, according to an example embodiment. One or more of the foregoing examples of packages that include a printed interconnect bridge 118, such as those manufactured according to a foregoing process, may be utilized in a computing system, such as computing system 400 of FIG. 4. In one embodiment, multiple such computer systems are utilized in a distributed network to implement multiple components in a transaction based environment. An object-oriented, service-oriented, or other architecture may be used to implement such functions and communicate between the multiple systems and components. One example computing device in the form of a computer 410, may include a processing unit 402, memory 404, removable storage 412, and non-removable storage 414. Memory 404 may include volatile memory 406 and non-volatile memory 408. Computer 410 may include—or have access to a computing environment that includes—a variety of computer-readable media, such as volatile memory 406 and non-volatile memory 408, removable storage 412 and non-removable storage 414. Computer storage includes random access memory (RAM), read only memory (ROM), erasable programmable read-only memory (EPROM) & electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD ROM), Digital Versatile Disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium capable of storing computer-readable instructions. Computer 410 may include or have access to a computing environment that includes input 416, output 418, and a communication connection 420. The computer may operate in a networked environment using a communication connection to connect to one or more remote computers, such as database servers. The remote computer may include a personal computer (PC), server, router, network PC, a peer device or other common network node, or the like. The communication connection may include a Local Area Network (LAN), a Wide Area Network (WAN) or other networks.
Computer-readable instructions stored on a computer-readable medium are executable by the processing unit 402 of the computer 410. A hard drive, CD-ROM, and RAM are some examples of articles including a non-transitory computer-readable medium. For example, a computer program 425 capable of providing a generic technique to perform access control check for data access and/or for doing an operation on one of the servers in a component object model (COM) based system according to the teachings of the present invention may be included on a CD-ROM and loaded from the CD-ROM to a hard drive. The computer-readable instructions allow computer 410 to provide generic access controls in a COM based computer network system having multiple users and servers.
EXAMPLES AND NOTES
The present subject matter may be described by way of several examples.
Example 1 can include subject matter (such as a system, apparatus, method, tangible machine readable medium, etc.) that can include a multi-chip electronic package. The example can include creating a multidie substrate, printing an interconnect bridge on the multidie substrate, and electrically coupling a first die to a second die by coupling the first and second dies through the interconnect bridge.
In Example 2, printing the interconnect bridge of Example 1 can include printing one or more traces on the multidie substrate.
In Example 3, printing the interconnect bridge on the multidie substrate of at least one of Examples 1 and 2 includes printing a via on a trace of the one or more traces.
In Example 4, printing the interconnect bridge on the multidie substrate of at least one of Examples 1-3 includes printing a pad on the via.
In Example 5, coupling the first die to the interconnect bridge of at least one of Examples 1-4 includes electrically coupling a contact on the first die to the pad.
In Example 6, printing the interconnect bridge in the cavity of at least one of Examples 1-5 includes printing a dielectric on the via before printing the pad on the via.
In Example 7, the method of at least one of Examples 1-6 can include sintering the one or more printed traces before printer the via.
In Example 8, the method of at least one of Examples 1-7 can include sintering the printed via before printing the dielectric.
In Example 9, the method of at least one of Examples 1-8 can include baking the printed dielectric before printing the pad.
In Example 10, the method of at least one of Examples 1-9 can include sintering the printed pad.
In Example 11, creating the multidie substrate of at least one of Examples 1-10 can include forming a cavity in the multidie substrate during fabrication of the substrate. wherein printing the interconnect bridge includes printing the interconnect bridge in the cavity.
In Example 12, the method of at least one of Examples 1-11 can include creating a cavity in the substrate after fabricating the substrate.
In Example 13, printing the interconnect bridge of at least one of Examples 1-12 can include printing the interconnect bridge in the cavity.
In Example 14, creating the multidie substrate can include creating a bumpless buildup layer substrate.
In Example 15, the first die can be a memory die and the second die can be a processor die.
In Example 16, the pad can be a flip-chip pad.
In Example 17 an integrated circuit package can include a multidie substrate, an interconnect bridge on the multidie substrate, and a first die electrically coupled to a second die through the interconnect bridge.
In Example 18, the interconnect bridge of at least one of Examples 1-17, can include one or more traces, vias, or pads that exhibit a sintered grain morphology.
In Example 19, the first die of at least one of Examples 1-18 can include a memory die.
In Example 20, the second die of at least one of Examples 1-19 can include a processor die.
In Example 21, the multidie substrate of at least one of Examples 1-20 can include a bumpless buildup layer substrate.
In Example 22, the one or more pads of at least one of Examples 1-21 can include a flip-chip pad.
In Example 23, the multidie substrate of at least one of Examples 1-22 can include a cavity and the interconnect bridge can be situated, at least partially, in the cavity.
In Example 24, the integrated circuit package of at least one of Examples 1-23 can include a molding at least partially surrounding the first and second dies.
Each of these non-limiting examples can stand on its own, or can be combined in various permutations or combinations with one or more of the other examples.
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 methods, apparatuses, and systems discussed herein can be practiced. These embodiments are also referred to herein as “examples.” Such examples can 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 can 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 as examples or embodiments, with each claim standing on its own as a separate embodiment, and it is contemplated that such embodiments can be combined with each other in various combinations or permutations. The scope of the invention should be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled.

## Claims

1. An integrated circuit package comprising:
a multidie substrate including low density routing therein, low density interconnect pads on a surface of the substrate, and a cavity formed therein;
an interconnect bridge inkjet printed and sintered in the cavity of the multidie substrate, wherein the interconnect bridge includes high density routing therein, the high density routing including traces and vias, and the high density routing including pads on a surface of the interconnect bridge, the high density routing exhibits a sintered grain morphology of inkjet printed and sintered metals, the traces including a spacing of a micrometer or less therebetween, wherein the interconnect bridge further includes dielectric material inkjet printed around the traces and the vias; and
a first die and a second die electrically coupled through the traces, vias, and pads of the interconnect bridge, wherein each of the first die and the second die at least partially overlap with the cavity.

2. The integrated circuit package of claim 1, the first die is a memory and the second die is a processor.

3. The integrated circuit package of claim 2, wherein the substrate is a bumpless buildup layer (BBUL) substrate.

4. The integrated circuit package of claim 3, wherein the at least one of the one or more pads is a flip-chip pad.

5. The IC package of claim 3, wherein the BBUL substrate includes:
a first buildup layer with first low density interconnect routing therein, the first low density interconnect routing including one or more traces, vias, and pads;
a second buildup layer on the first buildup layer and with second low density interconnect routing therein, the second low density interconnect routing electrically connected to the first low density interconnect routing.

6. The integrated circuit package of claim 5, wherein the second buildup layer includes the cavity formed therein.

7. The integrated circuit package of claim 6, wherein the first die and the second die are further electrically connected to the second low density interconnect routing.

8. The integrated circuit package of claim 7, wherein the low density interconnect routing includes a routing density that is up to about 100 times less dense than the high density interconnect routing.

9. The integrated circuit package of claim 8, wherein the BBUL substrate includes a third buildup layer, wherein the first and second dies are situated, at least partially, in the third buildup layer, the third buildup layer on the second buildup layer.

10. The integrated circuit package of claim 9, wherein the dielectric is on and between the traces of the interconnect bridge and between the vias of the interconnect bridge, the dielectric between the second and third buildup layers, and the dielectric at least partially in the cavity.

11. The integrated circuit package of claim 8, further comprising a molding material on the second buildup layer and between the first and second dies and the second buildup layer, the molding material at least partially surrounding the first and second dies.

12. The integrated circuit package of claim 11, wherein the dielectric is on and between the traces of the interconnect bridge and between the vias of the interconnect bridge, the dielectric between the second buildup layer and the molding material, and the dielectric at least partially in the cavity.

13. An integrated circuit package comprising:
a multidie bumpless buildup layer (BBUL) substrate including low density interconnect circuitry at least partially therein and thereon, the low density interconnect circuitry including first traces, first vias, and first pads, the multidie substrate including a cavity formed therein;
an interconnect bridge inkjet printed in the cavity of the multidie substrate, wherein the interconnect bridge includes high density interconnect circuitry inkjet printed therein and thereon, the high density interconnect circuitry including second traces, second vias, and second pads that exhibit a sintered grain morphology of a printed and sintered metal, wherein the low density interconnect circuitry is around and under the multidie substrate, the second traces including a spacing of a micrometer or less therebetween, wherein the interconnect bridge further includes dielectric material inkjet printed around the traces and the vias; and
a first die including a third pad electrically connected to a pad of the second pads; and
a second die including a fourth pad electrically connected to another pad of the second pads so as to electrically couple the first die to the second die through the interconnect bridge, wherein each of the first die and the second die overlap with the cavity.

14. The IC package of claim 13, wherein the low density interconnect circuitry includes first low density interconnect routing and second low density interconnect routing, wherein the BBUL substrate includes:
a first buildup layer with first low density interconnect routing therein, the first low density interconnect routing including one or more traces, vias, and pads;
a second buildup layer with second low density interconnect routing therein, the second low density interconnect routing including one or more traces and vias, the second low density interconnect routing electrically connected to the first low density interconnect routing.

15. The integrated circuit package of claim 14, wherein the second buildup layer includes the cavity formed therein.

16. The integrated circuit package of claim 15, wherein the first die and the second die are electrically connected through the second low density interconnect routing.

17. The integrated circuit package of claim 16, wherein the low density interconnect circuitry includes a routing density that is up to about 100 times less dense than the high density interconnect circuitry.

18. The integrated circuit package of claim 17, wherein the first and second dies are situated, at least partially, in a third buildup layer of the BBUL substrate, the third buildup layer on the second buildup layer.

19. The integrated circuit package of claim 18, wherein the dielectric is on and between the traces of the interconnect bridge, the dielectric between the second and third buildup layers; and the dielectric at least partially in the cavity.

20. The integrated circuit package of claim 17, further comprising:
a molding material on the second buildup layer and between the first and second dies and the second buildup layer, the molding material at least partially surrounding the first and second dies; and
wherein the dielectric is on and between the traces of the interconnect bridge, the dielectric between the second buildup layer and the molding material, and the dielectric at least partially in the cavity.