Editing chiplet

{{title|Chiplet}}[[File:chiplet design.svg|thumb|class=wikichip_ogimage|right|400px|Chiplet-based design.]]
A '''chiplet''' is an [[integrated circuit]] block that has been specifically designed to work with other similar chiplets to form larger more complex chips. In such chips, a system is subdivided into functional circuit blocks, called "chiplets", that are often made of reusable IP blocks.

== Overview ==
Chiplets refer to the independent constituents which make up a large chip built out of multiple smaller dies. Historically the need to go with multiple chips was driven by the [[reticle limit]] which dictated the maximum size of chip possible to be [[fabricated]]. Designs that exceeded the reticle limit had to be split up into smaller dies in order to be manufacturable. As [[process technologies]] continued to enable higher integration, multiple dies were merged into single, more complex integrated circuits. More recently, economics has resulted in a reversal of that trend. The desire to move to a chiplet-based designed has been driven by the increasing cost of manufacturing devices on leading-edge process nodes. Due to the cost associated with leading-edge nodes, it became advantageous to, once again, de-integrate and break down a large die into smaller 'chiplets' in order to improve [[yield]] and [[binning]].

=== Motivation ===
[[File:amd iedm 2017 dr lisa su keynote 7nm cost.png|thumb|right|At IEDM 2017, AMD CEO Dr. Lisa Su reported cost per yielded mm² for a 250 mm² die.]]
As the industry moves to smaller [[process nodes]], costs for yielding large dies continues to increase. Compared to 250 mm² [[die]] on the [[45 nm process]], the [[16 nm process]] more than doubles the cost/mm² and the [[7 nm process]] nearly double that to 4x the cost per yielded mm². Moving to the [[5 nm]] and even [[3 nm]] nodes, the cost is expected to continue to increase. Fabricating large monolithic dies will becomes increasingly less economical. One solution to easing the economics of manufacturing chips with a large amount of [[transistors]], the industry has started shifting to chiplet-based design whereby a single chip is broken down into multiple smaller chiplets.

==== Example ====
Consider a [[D0]] of 0.1 defects per cm². Now, consider a medium-sized die 18 mm x 20 mm (360 mm²). On a standard 300-millimiter [[wafer size]], up to 150 [[dies]] can be fabricated.

:<math>N_\text{total} = \frac{\pi \times (R - \sqrt{A})^2}{A} = \frac{\pi \times (150 \text{mm} - \sqrt{360 \text{mm²}})^2}{360 \text{mm²}} = 150</math>

Splitting up the same die into four chiplets - 9.5 mm x 10.5 mm (~99 mm²) results in 622 dies instead.

:<math>N_\text{total} = \frac{\pi \times (150 \text{mm} - \sqrt{99 \text{mm²}})^2}{99 \text{mm²}} = 622</math>


:[[File:360mm2 wafer example.svg|600px]]


Below is a plot of percent of [[yield]] per wafer for a die of various sizes versus the same die consisting of two, three, and four chiplets. Note that an additional 10% overhead for the cross-die communication has been added to the chiplet-based design.

:[[File:monolithic design vs chiplet yield.png|800px]]

From the graph above, it can be seen that a 360 mm² monolithic die will have an [[yield]] of 15% while a 4-chiplet design (each 99 mm²) more than doubles the yield to 37%. The total die area of the 4-chiplet design incurs a ~10% area penalty (36 mm² for a combined silicon area of 396 mm²) but the significant improvement in [[yield]] which directly translates to lower cost more than justifies this.

== Challenges ==
{{empty section}}

== Technologies ==
=== Packaging ===
* Intel {{intel|Foveros}}, {{intel|EMIB}}
* TSMC {{tsmc|CoWoS}}, {{tsmc|SoIC}}

=== Interconnect ===
* Intel {{intel|AIB}}, {{intel|UIB}}, {{intel|UPI}}
* AMD {{amd|HyperTransport|HT}}, {{amd|Infinity Fabric|IF}}
* TSMC {{tsmc|LIPINCON}}
* [[CCIX]], [[Gen-Z]], [[OpenCAPI]]
{{expand list}}

== Bibliography ==
* IEDM 2017, Dr. Lisa Su. Keynote presentation.