Though Intel’s annual Innovation occasion doesn’t kick off till tomorrow, the corporate is already publishing some bulletins forward of the present – and it’s not the trivial stuff, both. This morning the corporate is displaying off their preliminary work on growing a glass core substrate and related packaging course of for his or her chips. Because of their progress with analysis and growth on the glass cores, Intel is now planning on introducing glass core substrates to its merchandise within the second half of this decade, permitting them to bundle chips in additional advanced, and in the end higher-performing configurations.
There’s quite a bit to unpack from Intel’s comparatively quick announcement, however at a excessive degree, glass core substrates have been below analysis for over a decade as a substitute for natural substrates, that are extensively utilized in current-generation processors. Basically the medium that typical silicon dies sit on, substrates play an vital half in chip packaging. At first, they supply the structural stability for a chip (silicon dies are fairly fragile and flimsy), and they’re additionally the means by which alerts from silicon dies are carried, both to different on-package dies (i.e. chiplets), or to the massive variety of comparatively sizable pins/pads on the again facet of a chip. And, as chip sizes have elevated over time – and the variety of pins/alerts required by high-end chips has, as properly – so has the necessity for newer and higher supplies to make use of as a substrate, which is what’s been driving Intel’s newest accomplishment.
Finally, what Intel is aiming to do with glass core substrates is to enhance upon what could be finished with current natural substrates, permitting for bigger chips with extra alerts to be routed by the substrate extra cleanly. And whereas it will doubtlessly have advantages for all chips over a protracted sufficient time, the instant focus is on high-end, multi-chiplet processors, the place glass core substrates will provide higher mechanical stability, higher sign integrity, and the power to extra simply route a bigger variety of alerts by a non-silicon medium. Briefly, Intel considers it one of many keys to creating high-performance processors within the subsequent decade.
Substrates: A Fast Recap
The necessity for substrates goes again to among the earliest days for large-scale built-in chips, the place chip designs reached 1000’s and tens of 1000’s of transistors. These small transistors wanted to be wired to a lot bigger pins with a purpose to be put in in methods by comparatively huge human fingers, main as much as the primary chip packages, equivalent to twin in-line packages. These used a body – sometimes a lead body – to carry the precise silicon die, with the body (or alternatively, wire bonds) offering the sign paths between the die and exterior pins.
Intel 4004 Delidded (Picture Courtesy Science Museum Group Assortment On-line – CC BY-SA 4.0)
For the reason that 70s, there have been a number of evolutions in substrate designed. Metallic frames gave strategy to basic ceramic chip within the 90s, after which natural packaging across the flip of the millennium. Every iteration of substrate had higher properties than the final, above all else, making it simpler to route a bigger variety of sign and energy pins to more and more advanced dies.
Whilst you’ll nonetheless discover lead body and ceramic chips right here and there, natural substrates have been the bread and butter of the trade for the final couple of a long time. The natural materials, primarily made from PCB-like materials layered with woven glass laminates, permits for a reasonably large variety of alerts to be routed by a chip, together with fundamental chiplet designs equivalent to Intel’s cellular processors (with PCH separate PCH and CPU dies) in addition to AMD’s chiplet-based Zen processors.
However natural substrates have already been a limiting issue for a while now, particularly in high-end chips. Which is why over the past decade we’ve seen the rise of ultra-high-density interconnect interfaces equivalent to silicon interposers (chip on wafer on substrate), and their derivatives like Intel’s personal EMIB. These have allowed firms to bridge collectively the essential paths of their chips with quick and dense items of silicon, however at pretty excessive prices, and with out solely resolving the drawbacks of natural substrates. In consequence, Intel has additionally been trying to find a real substitute for natural substrates, one that can play properly with massive chips, and whereas not changing the necessity for CoWoS/EMIB on the highest degree, would provide higher sign efficiency and denser routing than natural substrates as we speak.
Glass Core Substrates: Finer, But Stronger
This brings us to the subject of as we speak’s announcement from Intel, glass core substrates. The corporate has been engaged on changing natural substrates with glass for over a decade now, and so they’ve lastly reached the purpose of progress the place they’re prepared to point out it off to the world whereas planning for its use in future merchandise.
At a excessive degree, a glass core substrate is simply that: changing the natural, PCB-like materials of an natural bundle with glass. To make sure, this doesn’t imply changing the total substrate with glass – so Intel shouldn’t be going to be mounting chips on pure items of glass – however moderately, the fabric on the core of the substrate can be made from glass. In the meantime, metallic redistribution layers (RDLs) would nonetheless be current on either side of a chip, offering the precise pathways between numerous pads and solder joints.
Glass Core Substrates In Panel Kind
Whereas tougher to work with than the now well-established natural substrate, Intel considers glass substrates to be superior each in mechanical and electrical properties, which in flip makes them fascinating to make use of in future chips. Or, conversely, much less undesirable than natural substrates when constructing very massive chips.
Ranging from the mechanical facet of matter, Intel studies that cup core substrates provide much better mechanical energy than natural substrates. They’re in a position to face up to increased temperatures higher than natural substrates throughout packaging, leading to much less warping and distortion. Glass can be reportedly simpler to get flatter as properly, which makes packaging and lithography simpler. Lastly, glass has an identical coefficient of thermal growth as silicon (not like natural substrates), that means that what little warping that also happens from warmth is per the dies above, versus having totally different elements of a chip increasing at totally different charges.
Most significantly, maybe, is that every one of these objects taken collectively open the door to producing bigger chips. With a extra secure substrate to mount the dies on, it will likely be potential to have bigger dies and a bigger variety of dies all sharing a single substrate – and thus behaving as a single chip.
Bridging the hole between mechanical and electrical, in response to Intel, they’re additionally in a position to obtain a a lot tighter pitch on the through-glass vias (TGVs) that carry alerts by the substrate itself, permitting for a a lot bigger variety of vias general. Intel is reporting that they’re in a position to house TGVs lower than 100 microns (µm) aside, permitting for a 10-fold enchancment in TGV density. All of which in the end permits for extra flexibility in routing alerts by the substrate core, and to some extent makes it simpler to route alerts with fewer RDL layers.
Assembled Take a look at Chip Substrates
All of this, in flip, permits for not solely bigger chips, however for extra dies to be positioned on a same-sized chip. In keeping with Intel, glass packaging would permit them to position 50% extra dies on a chip – or moderately, the die advanced space inside a chip could possibly be 50% bigger – permitting for extra densely packed chips than what Intel can do as we speak.
Lastly, on {the electrical} facet of issues, glass core substrates, and extra particularly the TGVs, reportedly provide higher electrical efficiency as properly. Owing to the low loss nature of the dielectric utilized in TGVs mixed with the a lot bigger variety of them, Intel says that cup core substrates will permit for cleaner sign routing and energy supply. Within the case of the previous, which means with the ability to do 448G signaling by copper, moderately than having to make use of optical interconnects. In the meantime, lower-loss energy supply would enhance general chip effectivity by that rather more, by lowering the quantity of power that’s misplaced as warmth earlier than it even reaches the processor dies.
Farther down the road nonetheless, glass core substrates must also make co-packaged optics simpler to perform for if you do need to use optical. A glass substrate would permit for optical interconnects to be built-in proper into the chip, moderately than having to tack it on in different manners.
So if glass is so nice, what’s the catch? Whereas Intel is understandably extra excited to speak about what’s good about glass core substrates and what they’ve discovered works properly up to now, one inescapable aspect might be value. Like several new expertise, glass core substrates might be costlier to supply and bundle with than tried and true (and low cost) natural substrates. And whereas Intel isn’t speaking about yields this far out, it will likely be exhausting for glass to compete with natural, a minimum of at first.
Extra broadly talking, glass core substrates additionally implies that Intel must bootstrap a whole ecosystem for the fabric. They aren’t vertically built-in with natural substrates as we speak, and so they gained’t be vertically built-in with glass, both. To that finish, Intel is already working with companions as we speak to develop the required tooling and provide capability, to deliver themselves to preliminary business manufacturing. However over the longer-term, Intel might want to determine how one can make outsourced testing and meeting potential, particularly as Intel plans to supply glass core substrates to IFS prospects sooner or later.
Lastly, it bears noting that whereas glass core substrates permit for a tighter sign pitch than natural substrates, they don’t seem to be a substitute for EMIB, Foveros, or different extra superior packing strategies based mostly round utilizing silicon mediums. A 75µm pitch for a TGV continues to be a far cry from the 45µm pitch of EMIB, by no means thoughts the <10µm pitch deliberate for Foveros Direct. So all of these packaging applied sciences will stay complementary add-ons to glass core substrates, at greatest changing EMIB in fringe circumstances of merchandise that don’t want the total density enhancements of EMIB.
Glass In Motion: Intel’s Absolutely Purposeful Take a look at Chip
The ultimate a part of as we speak’s announcement from Intel relies across the manufacturing facet of issues. As famous earlier, Intel has been engaged on glass core substrates for over 10 years now, and extra lately has been embarking on a three-and-a-half-year pathfinding undertaking to deliver glass core substrates to the subsequent step. Backing these efforts, at this level the corporate has a totally built-in R&D line up and operating in one among their Chandler, Arizona fabs (the identical one which does EMIB). Altogether, Intel has spent over a billion {dollars} on glass core R&D up to now.
The primary fruit of their R&D efforts, Intel has accomplished the meeting of a set of take a look at autos – multi-chip packages constructed over a glass substrate. The chips, which look just like Intel’s ultra-low energy cellular chips (Alder Lake-U 9W?), are reportedly totally purposeful, giving Intel some sensible outcomes to report on. Whereas we don’t have a ton of particulars on the chip, Intel has informed us that it makes use of 3 layers of RDL, and the TGVs have a pitch of 75µm.
Together with proving {the electrical} properties of glass, the small take a look at chip can be meant to show among the bodily properties, as properly. The glass core was made very thick – on the order of 1mm – with a purpose to show that TGVs would work with such a thick core. For the form of huge, high-end chips Intel is planning on utilizing glass core packing for, these chips would require a really thick core with a purpose to hit their measurement objectives, so Intel wanted to show that TGVs would (nonetheless) work at such lengths.
Intel Glass Core Substrates: Coming Later This Decade
Wrapping issues up, as we speak’s announcement serves as a kick-off of kinds for Intel’s glass core substrate period. Following on their decade of R&D work and their pathfinding dash, Intel now believes they’re prepared to start planning for the transition to glass core substrates of their merchandise – albeit a transition that’s nonetheless a number of years out.
If Intel’s product growth goes in response to plan, the corporate intends to start transport glass core merchandise later this decade. The primary merchandise to get the glass core substrate therapy can be their largest and most worthwhile merchandise, equivalent to high-end HPC and AI chips. These are the merchandise most strained by means of natural substrates as we speak as a result of measurement limits these substrates impose, and people are the bounds intel believes would most profit from glass core packaging.
Longer-term, the plan is to waterfall down the expertise from HPC chips into smaller and smaller chips, till the expertise is offered (and viable) for Intel’s rank and file shopper chips. The corporate could be very fast to notice that cup and natural substrates will co-exist for years to return – and, like previous transitions, there’ll possible nonetheless be chips utilizing natural substrates properly after glass is launched – however the firm can be optimistic that they’ll have the ability to deliver the prices of glass core substrates right down to parity with natural substrates, ultimately making it potential to reap the advantages even in lower-priced processors.
And Intel gained’t be holding the expertise to themselves, both. As a part of the corporate’s broader initiative to turn into a world class contract foundry, Intel might be providing glass core substrates to IFS prospects in due time. Whereas it’s far too early to guess when that will be (even Intel merchandise could also be 6 years out), with the ability to provide glass packaging might give Intel a giant leg up over its opponents, particularly for producing high-end, highly-profitable chips.
Above all else, it must be reiterated that there’s quite a lot of work Intel nonetheless must do with a purpose to deliver glass core substrates to the market. But when the corporate is profitable, then the change to glass will usher within the form of main expertise transition that solely occurs each 15 to twenty years.
