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For Ayar Labs, the corporate finest identified for optical chip-to-chip interconnects, the industry-wide adoption of chiplets couldn’t have come at a greater time. These silicon and packaging applied sciences allow Ayar’s silicon photonics chiplets, which convert from {the electrical} area into the optical area for chip-to-chip communication, to get round copper hyperlinks’ bandwidth bottlenecks, cut back energy and latency, and lengthen attain.
“It’s good to be fortunate,” Ayar Labs CEO Charlie Wuischpard mentioned with amusing throughout an unique interview with EE Occasions at Ayar’s Santa Clara, California-based headquarters.
“I wouldn’t say we foresaw [chiplets], however actually it offers a touchdown zone for the expertise,” he mentioned. “If not for the chiplet, we’d be making the argument to try to embed this set of IP both into the silicon or perhaps as a standalone module exterior, which in both case would have had its further challenges.”
Chiplets supply the chance to develop specialised features on completely different course of applied sciences, then package deal them collectively on a silicon interposer in a tightly built-in method. This implies Ayar’s TeraPHY silicon photonics die, which makes use of a 45-nm GlobalFoundries course of, may be co-packaged with a buyer’s giant processor die, which is perhaps on a cutting-edge 7-nm course of (or beneath).
Quite than integrating Ayar’s total TeraPHY chiplet onto the processor die, sooner or later, Ayar might license its electrical blocks or sub-blocks to prospects to place onto processor chiplets as a substitute for creating customized options, Wuischpard mentioned. A extra possible situation could be to additional separate the optical and electrical components of Ayar’s design into two chiplets for sure functions.
Each choices keep on the desk, “and we’re getting extra of these sorts of requests coming in,” he mentioned, suggesting {that a} buyer won’t want the two Tbps bandwidth Ayar’s present chiplet presents. For instance, a sensor software may want to maneuver to optical hyperlinks for ultra-low energy information motion, maybe preferring a drop to a couple hundred Gbps to allow ultra-low energy in a tiny footprint.
Subsequent-gen chiplets
Ayar continues to be deciding what’s subsequent on the product roadmap, but it surely may embrace adjusting levers, such because the variety of wavelengths used (at the moment eight), the bandwidth enabled by every wavelength (at the moment 32 Gbps), and the variety of macros (transmit-receive pairs, at the moment eight per eraPHY chiplet).
On the laser facet, Ayar has plans underway to assist a number of TeraPHY chiplets with a single laser supply. This is smart because the laser is an costly a part of the system. However there are trade-offs, Wuischpard mentioned, together with having to counting on only one supply with out redundancy.
“It’s a multivariate downside, there’s rather a lot happening,” he mentioned. “We now have to attempt to choose one of the best route ahead among the many decisions, and a part of that’s getting the precise buyer suggestions.”
Far-future prospects for Ayar’s expertise roadmap embrace the potential to be used in quantum computer systems the place the warmth misplaced from copper wires could cause issues. One other chance is perhaps embedding quantum safety capabilities into optical hyperlinks.
“We’ve acquired photons… there are issues we are able to do with these photons, after we’ve acquired them below our management,” he mentioned.
Whereas Wuischpard didn’t go too far into the small print, one chance is perhaps implementing quantum key distribution (QKD) in brief haul optical hyperlinks. With QKD, the quantum state of successive photons traversing the hyperlink acts as a quantum-proof encryption key.
Ecosystem constructing
Once we discuss concerning the inevitable change from copper to optical chip-to-chip interconnect, the expertise, whereas tough, is just a chunk of the puzzle. Commercializing that expertise and constructing an ecosystem that permits it to thrive is essential. This ecosystem is a key strategic precedence for Ayar. The corporate should be certain that its chiplets can match into all the suitable packaging flows, whereas concurrently lining up its buyer base.
Ayar counts the enterprise capital arms of key suppliers (Utilized Supplies and GlobalFoundries) and key prospects (Nvidia, Intel, Hewlett Packard Enterprise, and Lockheed Martin) in its group of strategic traders.
Does this symbolize a essential mass, or are extra potential prospects essential at this stage to make an ecosystem?
“Any a kind of firms has the amount to allow an organization like us to thrive,” Wuischpard mentioned. “However our aspirations are greater than that.”
Ayar desires to make a pervasive commonplace for everybody to make use of to assist speed up the widespread adoption of optical chip-to-chip hyperlinks.
“I don’t assume there’s anyone near us as an impartial who may present this, however [we’re] making an attempt to determine how a small firm establishes an ordinary that can be utilized by all,” he mentioned.
A normal would imply lowered want for proprietary options, which Wuischpard considers might be Ayar’s primary opponents right this moment.
“One of many large firms may say, ‘That is too vital, I’m simply going to throw lots of engineers at it, and do it myself’,” he mentioned. “However then you must ask: Would that simply be for his or her profit, or will it have interoperability with the remainder of the {industry}? It leads again to an {industry} want to be extra broadly adopted, in order that it’s actually an {industry} resolution, reasonably than a selected one-customer resolution.”
Carry on the competitors
Trade-wide adoption would imply extra than simply Ayar making the I/O chiplets.
Wuischpard attracts a parallel with Intel licensing x86 to AMD, noting that there could also be a time limit when the corporate ought to facilitate creation of some opponents.
“In the long term, having one other chiplet provider that’s related or equal would in all probability not be the worst factor, if we are able to monetize it in some trend,” he mentioned. “These conversations are nonetheless underway.”
Wuischpard famous that Ayar has already created a multi-source settlement on the laser sources required to energy its optical hyperlinks. Laser producer Sivers Photonics is already producing the Ayar Labs SuperNova 8-wavelength distributed suggestions laser array as a part of this settlement.
Welcoming the UCIe commonplace
Ayar is eagerly trying ahead to the adoption of the unified chiplet interconnect categorical (UCIe) commonplace, which is designed to allow a chiplet ecosystem the place heterogeneous chiplets may be mixed-and-matched. (UCIe contains the memory-to-processor chiplet commonplace compute categorical hyperlink (CXL)).
In the present day, Ayar makes use of a proprietary electrical interface between processor and optical chiplet, however the firm plans to be UCIe-compatible going ahead.
“Our world seemed very difficult—at the same time as a chiplet, there are many completely different interfaces for various requirements,” he mentioned. “With UCIe and CXL, it’s actually boiled issues down. There’s proprietary stuff on the market… however individuals are collapsing round these requirements rather more than among the different ones that existed.”
It’s completely attainable to create a customized model of the TeraPHY chiplet for buyer’s protocols, equivalent to NVLink or Infinity Cloth, Wuischpard mentioned, however that will require a brand new tapeout.
Manufacturing course of
Ayar is delivery TeraPHY chiplets right this moment and is aspiring to ship “hundreds of models” in 2023, ramping to larger volumes over the subsequent couple of years.
“We’ve acquired a number of alternatives with particular person volumes within the roughly million-unit vary, which might be unbelievable, and there’s a push to do these sooner reasonably than later,” Wuischpard mentioned. “The query is, can we get the whole lot in place quick sufficient to do this roll out sooner, simply given the cycle time in semiconductors.”
Because the demand for semiconductors has bounced again following the pandemic, Ayar, like many fabless firms, has seen schedules delayed because of foundry capability. This delayed the qualification of Ayar’s manufacturing course of a number of quarters, lastly attaining qualification in June. The following step is to work on yields and prices, Wuischpard mentioned.
“There’s been lots of work on securing all of the contracts for volumes, establishing all of the protocols for high quality and acceptance ranges, simulating what the yields needs to be,” he mentioned. “Additionally, and this isn’t apparent however applies to all chiplet makers: you must have a very good take a look at setting.”
Ayar has invested considerably in optical and electrical wafer testers to execute this testing at excessive velocity. This a part of the method will in the end be moved to an outsourced semiconductor meeting and take a look at home (OSAT), but it surely’s as much as Ayar to determine the take a look at patterns earlier than this could occur. Ayar offers prospects with identified good die (KGD), which is very vital contemplating there may be a number of Ayar dies co-packaged with a buyer’s processor.
“By the identical token, we wish to be certain that our foundry is offering us wafers which are excessive yielding,” Wuischpard mentioned. “All people goes via this to a level, however as a small provider, I feel you’ve actually acquired to show your self, and also you do this partly via the rigor that you’ve in your testing.”
How will all of it prove?
What’s Wuischpard’s endgame? An acquisition by an organization like Intel or Nvidia could be an apparent potential final result, however Wuischpard mentioned this kind of exit will not be an express a part of the plan.
“If you happen to’re constructing an organization to get purchased, you’re not going to construct the proper of firm,” he mentioned. “Somebody may come alongside; I simply wish to guarantee that we’re not angling for that as a aim on the outset.”
Wuischpard’s perception is that the place there are large expertise transitions, just like the shift from copper wires to optical fibers, new impartial firms may be created.
“If we’re even moderately near our objectives, I feel there’s a possibility to be a standalone, impartial supplier,” he mentioned. “That may attraction to our founders specifically, as a result of it might imply the widest attainable adoption of the expertise they’ve poured their life’s blood into.”
