# Patent

## Title
High density interconnect device and method

## Abstract

Embodiments that allow both high density and low density interconnection between microelectronic die and motherboard via Direct Chip Attach (DCA) are described. In some embodiments, microelectronic die have a high density interconnect with a small bump pitch located along one edge and a lower density connection region with a larger bump pitch located in other regions of the die. The high density interconnect regions between die are interconnected using an interconnecting bridge made out of a material that can support high density interconnect manufactured into it, such as silicon. The lower density connection regions are used to attach interconnected die directly to a board using DCA. The high density interconnect can utilize current Controlled Collapsed Chip Connection (C4) spacing when interconnecting die with an interconnecting bridge, while allowing much larger spacing on circuit boards.

## Background
TECHNICAL FIELD
Embodiments pertain to integrated circuit (IC) dies, die packages, and associated methods. More particularly, embodiments pertain to using an interconnecting bridge such as a silicon bridge to interconnect dies with a high density interconnect.
BACKGROUND
Direct Chip Attach (DCA) on board is a concept that may allow significant cost savings by eliminating the package. However, board design rules have not scaled at the same rate as Controlled Collapsed Chip Connection (C4) bump pitch. Thus, in order to use DCA, the bump pitch of the chip die needs to be large enough to accommodate the board design rules, and that size bump pitch would be much larger than current technology allows for dies. This limits the number of interconnects that may be made using DCA.
As long as the bump pitch of the die is large enough to accommodate the board pad size and the line/space rules, DCA remains an attractive solution. However, in the System On Chip (SOC) area and in other high density interconnect applications, DCA is yet to be considered due to the mismatch between the C4 bump pitch scaling of current generation SOC die and the board pad size and line/space rules.



BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates microelectronic dies, according to some embodiments;
FIG. 2 illustrates a process to interconnect microelectronic dies and to mount interconnected microelectronic dies, according to some embodiments; and
FIG. 3 illustrates a process to create a recess in a circuit board to receive a 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 microelectronic dies, according to some embodiments. The illustrated embodiments allow dense interconnects between dies in DCA type situations while still accommodating board pad size and line/space rules. FIG. 1 illustrates two dies 100 and 102, and an interconnecting bridge 104 suitable for interconnecting the two dies. Such a bridge may be, for example, a silicon bridge. In some embodiments one die, such as die 100, may be a processor die such as SOC, Central Processing Unit (CPU), Digital Signal Processor (DSP), Graphics Processing Unit (GPU), Advanced Processing Unit (APU), or other type of processor.
Die 100 has a high density interconnect 106. High density interconnect 106 has a low bump pitch to allow a high number of connections in a small area. In one example, the bump pitch is from about 30 μm to about 90 μm. A high density interconnect may be used to connect die 100 to another die where a high number of connections would be advantageous. An example would be where die 100 is a SOC and is connected through high density interconnect 106 to a memory die.
Die 100 may contain other connection regions spread around different parts of the die. In the illustrated embodiment, die 100 has connection region 108 around the remaining sides of the die and connection region 110 located more centrally. The bump pitch of connection region 108 and the bump pitch of connection region 110 allow DCA of die 100 to a circuit board. As such, the bump pitch of connection region 108 and the bump pitch of connection region 110 are sized to accommodate the pad size and line/space rules of the board. The bump pitch of connection region 108 may be the same as or different than the bump pitch of connection region 110, depending on the embodiment. This will result in a bump pitch for connection region 108 and connection region 110 that is greater than the bump pitch of high density interconnect 106. Current design rules allow a spacing for a High Density Interconnect (HDI) type board that is no tighter than about 60 μm to about 75 μm.
When die 100 is a processor die, such as a SOC die, high density interconnect 106, which is located adjacent to one side, may house the memory connections. Other input/output connections may be contained in connection region 108, which is adjacent to the remaining three sides. Finally, power connections may be very sparsely populated (relatively) without affecting performance. Therefore, power connections may be more centrally located as in connection region 110. Additionally, or alternatively, some power connections may be interleaved in other regions as desired. In this example, the bump pitch of connection region 108 may be the same as, or different than, the bump pitch of connection region 110.
Die 102, which may be a memory die or some other type of die, also has a high density interconnect 112. High density interconnect 112 has a low bump pitch to allow a high number of connections in a small area. In one example, the bump pitch is from about 30 μm to about 90 μm. The bump pitch of high density interconnect 112 may match that of high density interconnect 106.
Die 102 may also have connection region 114. In one example, die 102 is a memory die and connection region 114 contains power connections for the die. The bump pitch in connection region 114 may be sized to accommodate DCA of die 102 to a circuit board, such as a HDI type board. As such, the bump pitch of connection region 114 will be no tighter than about 60 μm to about 75 μm using current pad and line/space rules.
Interconnecting bridge 104 is a die designed to interconnect die 100 and die 102. To accomplish this, interconnecting bridge 104 has two high density interconnects, 116 and 118. The bump pitch of high density interconnect 116 is sized to match the bump pitch of high density interconnect 106, and the bump pitch of high density interconnect 118 is sized to match the bump pitch of high density interconnect 112. Typically the bump pitch of high density interconnect 116 will match that of high density interconnect 118, but different bump pitches may be used.
FIG. 2 illustrates a process to interconnect microelectronic dies and to mount interconnected microelectronic dies, according to some embodiments. In FIG. 2, the process begins with the manufacture of an interconnect bridge (e.g., a silicon bridge) 200. The bridge, such as bridge 104 of FIG. 1, has high density interconnects at its ends to interconnect dies, and appropriate interconnections between the two high density interconnects are made in order for the dies to be connected. The high density interconnects have connection pads (or bumps) 204, which have a bump pitch 206. As previously mentioned, the bump pitch for the high density interconnects may be the same or may be different, depending on the particular embodiment. As illustrated in FIG. 2, the connection mechanism such as solder on pads may be provided with higher temperature solder 202 (higher in comparison to 224) during the manufacturing process.
Once the interconnecting bridge 200 is manufactured, it may be used to interconnect other die. In FIG. 2, this transition is illustrated by arrow 208. In the particular example of FIG. 2, interconnecting bridge 200 will be used to interconnect die 214 and die 216. Die 214 and die 216 have high density interconnects located so that the distance between the high density interconnects may be bridged by interconnecting bridge 200 when they are correctly oriented. Specifically, in FIG. 2, the high density interconnects are located adjacent to an edge of the die, as illustrated by 224 and 226. The bump pitch of the high density interconnects is sized to match the corresponding high density interconnect of interconnecting bridge 200. Since interconnecting bridge 200 has previously been manufactured with high temperature solder 202 covering the connection pads of its high density interconnects, it is generally not necessary to provide the die's high density interconnects with high temperature solder, although this is simply an example.
Die 214 and die 216 also have a connection area with connection pads 222 with bump pitch 212. Connection pads 222 may also be provided with solder 220 during manufacture of die 214 and die 216 (or as part of a separate process). The bump pitch 212 is sized appropriately for attachment to a circuit board, as explained below. Although FIG. 2 illustrates all connection areas of both die 214 and die 216 having the same bump pitch, that is simply an example, and different connection areas within a die or different connection areas between dies may have different bump pitch.
Die 214 and die 216 may be placed in a carrier 218 and oriented so that their high density interconnects are located toward one another. Interconnecting bridge 200 is flipped and attached to die 214 and 216 through a bonding process, such as thermal compression bonding, solder reflow, and the like. This is illustrated by arrow 210.
After die 214 and die 216 are interconnected by interconnecting bridge 200, they may be mounted on a circuit board, such as a HDI type board. In FIG. 2, this transition is illustrated by arrow 228.
In FIG. 2, an appropriate board is illustrated by board 230. Board 230 is typically a HDI type board with multiple layers and microvias on the top one to three layers. In preparing the board, the high density interconnect may be called out specifically along with the connection points 234 (and their associated bump pitch) in the die (such as die 214 and die 216) that will directly attach to the board.
The circuit board may be prepared by creating a hole or recess where interconnecting bridge 200 will reside when the assembly is attached to the board. In FIG. 2 that hole is illustrated by 232. Although a hole between all layers of board 230 is illustrated, this is an example only. A recess sufficient to accommodate the interconnecting bridge may also be used.
The assembly of die 214, die 216, and interconnecting bridge 200 is flipped and attached to board 230 using a DCT technology, as illustrated in FIG. 2. In attaching the assembly to board 230, a solder melting temperature hierarchy may be maintained so that the solder joints of already bonded interfaces do not melt when later solder joints are made. If desired, a material, such as an epoxy or some other material, may be placed in hole 232 in order to provide mechanical support for interconnecting bridge 200, depending on the embodiment. Such mechanical support is, however, optional.
Using an interconnecting bridge 200 to interconnect die 214 and 216 can allow a very high density interconnection to be made between, for example, a SOC die and a memory die, while allowing greatly relaxed tolerances on circuit board production and assembly. Thus, the entire assembly can be mounted to the board 230 using Surface Mount Technology (SMT) because the board pitch can be, for example, from about 250 μm to about 400 μm while still maintaining tight bump pitch on the high density interconnects (for example, from about 30 μm to about 90 μm).
FIG. 3 illustrates a process to create a recess in a circuit board to receive a bridge, according to some embodiments. The process begins as illustrated in 300 when planar copper is patterned with subtractive or semi-subtractive on the layer to be connected to the component along with other patterning. This can result in multiple layers 302 (typical) and various features, such as 304. In the figure, the bridge attachment side is shown at the top of the board 303.
In 306, a releasable layer 308 is applied through squeeze. The thickness of the layer 308 is approximately the same thickness as the copper of that layer.
In 310, subsequent layers are added to create various desired features, such as microvia 314, until solder resist layer 312 is applied, and all layers of the board are complete.
In 316, recess 318 is created by removing the buildup layers where the bridge is to reside. This can be accomplished through laser scribing or by using a photo sensitive material in the area, which is later to be removed, and then using light to remove the photo sensitive material. After the buildup layers are removed, the releasable layer is removed, and a de-smear process is used to clean out the remnants from the releasable layer.
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,” “third,” and so forth 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 system comprising;
a System on Chip (SOC) die having a first die edge and first die surface, the SOC die comprising:
a first die high density interconnect located adjacent to the first die edge on the first die surface, the first die high density interconnect having a first bump pitch; and
a first die connection region located on the first die surface, the first die connection region having a second bump pitch; and
a memory die having a second die edge and a second die surface, the memory die comprising:
a second die high density interconnect located adjacent to the second die edge on the second die surface, the second die high density interconnect having the first bump pitch; and
a second die connection region located on the second die surface, the second die connection region having a third bump pitch; and
a bridge having a plurality of high density interconnects having the first bump pitch, one of the plurality of high density interconnects connected to the first die high density interconnect and another of the plurality of high density interconnects connected to the second die high density interconnect.

2. The system of claim 1, wherein the first die connection region comprises input/output connections.

3. The system of claim 2, wherein the first die connection region is located on the first die surface adjacent to a second edge of the first die.

4. The system of claim 3, wherein the first die further comprises a power connection region located centrally on the first die surface.

5. The system of claim 1, wherein the second die connection region comprises power connections.

6. The system of claim 1, wherein the first bump pitch is smaller than the second bump pitch, and the first bump pitch is smaller than the third bump pitch.

7. The system of claim 1, wherein the second bump pitch is about equal to the third bump pitch.

8. A microelectronic die comprising;
a high density interconnect located adjacent to a first edge on a first surface, the high density interconnect having a first bump pitch from about 30 μm to about 90 μm, the high density interconnect bump pitch sized to connect to an interconnecting bridge; and
a connection region located adjacent to a second edge on the first surface, the connection region having a second bump pitch sized to accommodate Direct Chip Attach (DCA) of the die to a circuit board.

9. The die of claim 8, further comprising a power connection region located on the first surface interior to the high density interconnect and the connection region.

10. The die of claim 8, wherein the connection region comprises power connections.

11. The die of claim 8, wherein the connection region comprises input/output connections.

12. The die of claim 9, wherein the die is a System On Chip (SOC) die.

13. The die of claim 10, wherein the die is a memory die.

14. The die of claim 8, wherein the first bump pitch is less than the second bump pitch.

15. A method, comprising:
providing an interconnecting bridge having a plurality of high density interconnects with a first bump pitch;
providing a first die having a first die high density interconnect with the first hump pitch located adjacent to a first die edge and having a first die connection region with a second hump pitch greater than the first hump pitch;
providing a second die having a second die high density interconnect with the first hump pitch located adjacent to a second die edge and having a second die connection region with a third bump pitch greater than the first bump pitch;
interconnecting the first die and the second die by connecting one of the high density interconnects of the interconnecting bridge to the first die high density interconnect and connecting the another of the high density interconnects of the interconnecting bridge to the second die high density interconnect;
connecting the interconnected first die and second die to a circuit board by connecting the first die connection region to the circuit board and connecting the second die connecting region to the circuit board; and
wherein a solder temperature hierarchy is maintained such that solder joints of already bonded interfaces do not melt when later solder joints are made.

16. The method of claim 15, wherein the first die is a System On Chip (SOC) die, and the second die is a memory die.

17. The method of claim 15, wherein a first set of bumps is attached by other than solder connection mechanism and a second set of bumps is attached by a solder mechanism, and wherein a temperature hierarchy is maintained so that already bonded interfaces do not melt when later solder joints are made.

18. The method of claim 15, wherein the circuit board has a recess to receive the interconnecting bridge when the interconnected first die and second die are connected to the circuit board.

19. The method of claim 15, wherein the circuit board has a hole to receive the interconnecting bridge when the interconnected first die and second die are connected to the circuit board.