✧✦Catherine✦✧
today I learned that we (as a civilization) now can put 16 silicon flash dice into a single 700µm microSD card on a commercial scale https://www.ose.com.tw/en/ic-services/memory-product-package/microsdsd
Feb 28 at 5:09pmWeb
Show thread✧✦Catherine✦✧Feb 28

if you think that the precariously balanced tower of flash above is an inaccurate representation of what's going on, i can reassure you that
(a) this is exactly how it looks like, and
(b) SK Hynix is up to 24 layers already (not sure in what application)

https://news.skhynix.com/semiconductor-back-end-process-episode-4-packages-part-2/

Show threadSamantaz FoxFeb 28
@whitequark That's fascinating O.O
Show threadup/downFeb 28
@whitequark I did look into 3D architectures in uni, but still, wtf, especially the left picture, that's so uncanny...
Show threadIgnas KielaFeb 28
@whitequark kioxia does up to 32 high stacks (for larger SSDs but still) https://www.youtube.com/watch?v=ivLvsTnp9fI
A Petabyte in the Palm of My Hand - Kioxia Factory Tour

YouTube
Show threadniconiconiFeb 28
@whitequark
"Mom, can we have vias?"
"No, we have vias at home."
vias at home: jumper-ridden DIY PCBs.

This SD card is the semiconductor version of it, without TSV.
Show threadamyFeb 28
@whitequark the fact i can go to tesco and purchase this marvel of engineering will never not be extremely funny to me
Show threadJernej Simončič �Feb 28
@amy @whitequark At some point I bought a 1TB microSD card and completely forgot about it – until I found it a few days ago under the junk on my desk.
Show thread✧✦Catherine✦✧Feb 28
@jernej__s @amy I had the same experience (I plugged it into my Steam Deck)
Show threadJernej Simončič �Feb 28
@whitequark @amy Hey, I just found another 1TB microSD card I forgot about!
Show threadthe hatterMar 1
@jernej__s @whitequark @amy In this economy, it seems out scatterbrains have left a lot of people with unexpected profit to discover later.
Show threadtwilightFeb 28
@whitequark fascinating to see microscope images of die stacks
Show threadRealGene ☣️Feb 28
@whitequark
When are people going to be buying old cards on eBay to scavenge the gold wire?
Show thread✧✦Catherine✦✧Feb 28
@RealGene they do buy ewaste for this already
Show threadRealGene ☣️Feb 28
@whitequark
Yup. I made a few bucks selling obsolete chips that happened to have gold plated caps…
Show threadAndrew ZonenbergFeb 28
@whitequark @RealGene although almost anything made in the last 10ish years is copper bonded now
Show threadthe hatterMar 1
@RealGene @whitequark it's only got any value in bulk. No doubt some recyclers will offer bundles of 10,000 unsorted SD cards or whatever for the curious consumer to examine, but most of the waste will be consolidated then sent into a few large, experienced enterprises. I've friends who run an assay service with takes ground up chip waste samples direct from manufactuers, giving them a metals breakdown to assess how much to bid for barrels/iso containers which the sample was taken from.
Show threadAndrew ZonenbergFeb 28
@whitequark also each flash die has several hundred layers of stacked bit cells
Show thread✧✦Catherine✦✧Feb 28
@azonenberg yep! Samsung got up to 400 layers last year
Show threadAndrew ZonenbergFeb 28
@whitequark the last one i threw in the fib was "only" 176 iirc
Show thread0xC01DC0FFEEMar 1
@whitequark @azonenberg No fucking way, how are those even economical to manufacture? 
Show threadAndrew ZonenbergMar 1
@0xC01DC0FFEE @whitequark V-NAND is crazy. Basically deposit alternating layers of a couple of materials then drill through the whole stack and you get a vertical abacus-shaped string of hundreds of flash bits
Show thread✧✦Catherine✦✧Mar 1
@azonenberg @0xC01DC0FFEE ohhhhhh.
Show threadAndrew ZonenbergMar 1
@whitequark @0xC01DC0FFEE the transistor channel is vertical polysilicon deposited into a hole that looks kinda like a dram capacitor, except it's ringed by ONO charge trap layers then more poly for the wordlines IIRC
Show threadAndrew ZonenbergMar 1
@whitequark @0xC01DC0FFEE https://www.appliedmaterials.com/us/en/semiconductor/markets-and-inflections/memory/3d-nand.html
3D NAND | Applied Materials

3D NAND, also known as vertical NAND (V-NAND), is a type of non-volatile flash memory, where the cells are stacked vertically to increase storage density.

Applied Materials
Show threadAndrew ZonenbergMar 1
@whitequark @0xC01DC0FFEE also https://thememoryguy.com/3d-nand-making-a-vertical-string/ has some nice drawings
3D NAND: Making a Vertical String - The Memory Guy Blog

(The following is an update of a post that originally ran on 1 November 2013. It was republished in 2024 as a part of a series to honor the 3D NAND inventors who have received the 2024 FMS Lifetime Achievement Award.) Let’s look at how one form of 3D NAND is manufactured. For this post

The Memory Guy Blog - Jim Handy, Objective Analysis, on Semiconductor Memories
Show threadAssimilateborgMar 1
@azonenberg @whitequark @0xC01DC0FFEE
300 layers!!! 😮
Show threadroukemapMar 1
@0xC01DC0FFEE @whitequark @azonenberg The storage layers don't need any individual patterning by photolithography, just careful thickness control in the deposition. There's some other tricky bits, but that's one of the big wins.
Show threadRootWyrm 🇺🇦Mar 1

@whitequark the 24 layer one will truly blow your mind, and then some.

Notice how certain GPUs have weird memory configurations, which are divisible by 12/24/48/96 but not 8/16/32/64?

Those are HBM3/HBM3E. SK Hynix constructs their 24GB and 48GB HBM3E modules by stacking 1GB and 2GB modules 24 high with TSVs.

https://product.skhynix.com/products/dram/hbm/hbm3e.go

Show threadRootWyrm 🇺🇦Mar 1

@whitequark but wait! It gets even fucking *crazier*. Besides the fact that TSV means one bad joint scraps the whole part.

Everyone's heard of the big 3 and ASML.
Nobody's heard of Hanmi, Besi, or Applied Materials. Who are all WAY more important than ASML.

Those are the companies that make the machines that saw wafers, place those layers, and *bond* those layers. Yeah. They're the people responsible for the Jenga.

Show threadEli the BeardedMar 1

@whitequark

So is that how the terabyte-plus microSD cards do it? I have noticed they seem more prone to heat failure than smaller capacity cards

Show thread✧✦Catherine✦✧Mar 1
@elithebearded yeh
Show threadKirtai 🏳️‍⚧️Feb 28
@whitequark
Is this the succulent flesh of which you spoke?
Show threadroukemapFeb 28
@whitequark interesting to think about the order of operations. How many dies do they stack before the first wire bonding pass. 4? 5? Do they trust placing a die right beside the freshly made wire bonds?
Show threadRFeb 28
@whitequark afaik this process also involves very carefully grinding the back side of silicon wafers (the side which doesn't have the transistors) in order to make all the dies as thin as possible
Show thread✧✦Catherine✦✧Feb 28
@r yes
Show threadchristian mockFeb 28
@whitequark and all that just to create a storage format that's too small for human hands to handle.
Show thread✧✦Catherine✦✧Feb 28
@cm shhhhh... if you say that too loudly they'll make a nanoSD card
Show threadchristian mockFeb 28
@whitequark /me deletes previous toot
Show threadRue MohrFeb 28
@whitequark .7mm ea * 16 = 11.6mm thick not inc. substrate........ thats a beefy card.?
Show threadRue MohrFeb 28
@whitequark oh wait, yea, its too early for me to be making social media posts, going to go get coffee. bbl.
Show threadJoe Groff (1M Context)Feb 28
@whitequark is this what the Tower of Babel looked like before it fell
Show threadGreg BellFeb 28
@whitequark @joe foolish rocks, you will do our microscopic bidding!
Show threadAttie GrandeFeb 28
@whitequark Is this "3D NAND" and similar? I always wondered how they achieved the stacking!
Show thread✧✦Catherine✦✧Feb 28
@attie no, 3D NAND is having (up to 400 in recent flash) layers of NAND cells in each die
Show threadAttie GrandeFeb 28
@whitequark Oh, intriguing - thanks!
Show thread🇺🇦 haxadecimal 🚫👑Mar 1
@whitequark @attie
No, Mr. Die, I expect you to bond.
Show threadAndrew ZonenbergFeb 28
@whitequark also looking at that diagram it seems like the 16 die stack is actually two 8 die onfi channels on top of each other mirrored with one coming out the left and one out the right
Show threadRob RicciFeb 28
@whitequark now if we'd only build flash for a purpose other than storing content that's been stolen by our AI overlords
Show threadChris EspinosaMar 1
@whitequark @temptoetiam
16 silicon flash dice? In this economy?
Show threaddojoeMar 1
@whitequark jenga packaging
Show threadmccMar 1
@whitequark Pleasant cognitive dissonance as to whether "Die, Die film, Au Wire" is English, German or French
Show threadDaniel LakelandMar 1
@mcc
Yes
@whitequark
Show threadsegfoxMar 2
@whitequark wow, that sounds like an awesome way to easily expand smartphone storage. I wonder why nobody has though of it yet /s
Show threadchrisgj198Mar 3
@whitequark Once I found out that someone had tried stacking another die on top of a cellphone radio chip I had worked on. They didn't discuss it with us designers beforehand and it didn't work - they had put something conductive over the inductors, which makes a shorted turn and reduces the inductance and Q. I guess a ~200um layer of glass etc. in between would have fixed it.
Show thread✧✦Catherine✦✧Mar 3
@chrisgj198 amazing
Show threadlainz Mar 12
@whitequark even single-molecule transistors are a thing in some labs. Kinda crazy when you think about it
Show threadperrito swagito (maligno) 💯 Mar 12
@lainz @whitequark do you have a source for this it sounds interesting
Show threadlainz Mar 12
@swagpuppy420 @whitequark

en.wikipedia.org/wiki/1_nm_process
Another term used is "two-dimensional semiconductors", referring to the fact the transistor is one molecule or some flat structure anyways.

Fudan University recently built a RV32 processor using such a process
www.nature.com/articles/s41586-025-08759-9
1 nm process - Wikipedia

Show threadperrito swagito (maligno) 💯 Mar 12
@lainz @whitequark >molecular transistors
>look inside
>MOSFET