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Comment by comboy | Hacker News Reader

Can somebody explain a NAND shortage to me? Because without understanding it, it sounds like "we are out of bits".

Feast/famine cycle--it goes all the way back to DRAM in semiconductors (it's why Intel got out of DRAM).

Demand for memory spikes (new application, got cheap enough, etc.)

All the companies begin constructing new fab lines simultaneously (because, if you are more than a few months late when a new technology comes online, your competitors get all the nice, fat initial profit margins while you get the nasty bulk profit margins).

Fab lines take a while to build, but demand is still increasing. Prices spike.

Fab lines come online. Supply skyrockets. Prices crash.

Now that capacity has increased dramatically and prices are low, people start finding new uses for the cheap memory.

Demand slowly builds. Prices recover slowly.

Suddenly, somebody finds a new application for memory. Demand spikes.

Lather, rinse, repeat.

Out of serious curiosity, what are these new apps that are using more and more RAM, at least for the last few cycles?

It seems like 8 GB has been the default amount for most consumer PCs for years now. This is in contrast to 15-20 years ago where PC manufacturers would really double ram every 2 years.

Moore's law broke for DRAM a while ago. RAM now gets more expensive when you shrink.

For the time being, Moore's Law still seems to be operating for flash. But I doubt it's got many more iterations left.

Factories are not able to produce enough physical goods to keep up with demand.

It sounds like the demand sharply increased recently due to smartphones and other advancements while production stayed steady.

But back when we had shortage in HDD production a few years ago, it was because many companies used factory based near some catastrophe. Here it's "just" silicon, are there only so few fabs all over the world that are able to manufacture these?

Right, it was the flooding in Thailand that knocked Western Digital offline etc....

Basically, yes. Fabs are hugely expensive and they can only pump out so many wafers. The article is saying that it looks like demand is outstripping the capacity of the fabs to increase supply.

Last one - so if a fab can produce wafers at say 14nm - is there something else that can be stopping it from producing 14nm NAND flash? I mean apart from the quality.

I imagined fabs like 3d printers. I thought the toughest part is the design, and once you have it, there's now plenty of places where you can print it.

> is there something else that can be stopping it from producing 14nm NAND flash? I mean apart from the quality.

Well, you'd need the machines for that – there’s only a handful of companies able to build the EUV lithographic machines for that, most of them small German companies with a few dozen to hundred employees.

And they can’t just increase production.

Or rather, it takes years. Of course they can increase production eventually...

But the silicon factories cost billions each, so no-one is going to scale up because of a temporary shortage. The same, even more so, for the factory-factories.

The fabs don't want to increase production of current 'old' technologies and are transitioning to smaller die processes and ramping up 3D production so there's a perfect storm of increasing demand and fab refurbishments reducing availability.

In logic, smaller is faster: less capacitance, shorter channels, and thinner oxides means faster switching.

In memory, smaller means less space to store your bits. I remember a quote from somewhere that with TLC at 20nm, you could lose only 1 ELECTRON PER YEAR from the floating gate to meet the memory retention spec.

Also, NAND had smaller feature sizes than logic for some time, before they really hit the wall. They innovated a lot of advanced techniques like quad patterning for memory cells. It helps in memory that you are optimizing for one and only one cell.

Thanks!

Flash fabs are different than logic fabs (that's about the extent of my understanding so I won't try to explain why). Also, logic fabs may not have much idle capacity either.

Design for stuff like nand includes a bunch of process steps that have a huge impact on the devices. NAND might require different equipment from what is already being used. It all requires intense calibration and many engineers with quite a lot of experience.

Intel planned (don't know if they ended up doing it) to convert a plant built in 2010 to memory fabrication and it was going to cost 3.5 billion dollars and take years.

It's not plug and play.

High density chip fabrication processes are not commodiy services. Each foundry's process has its own design rules that your chip needs to take into account. And that's for logic. 3D NAND fabrication requires different materials and methods than logic fabrication, and each of the four manufacturers has their own design with its own manufacturing challenges. At least one or two of them have had to make significant adjustments in their fundamental memory cell design between their first announced prototypes and the shipping products that have layer counts high enough to offer competitive cost/GB.

Step #1, observe generation migration from disk to flash, especially in the under $100 where minimum disk prices give a huge advantage to flash Step #2 invest in production facilities that take 2 years to build Step #3 watch the price/bit curve carefully to optimize your return on investment Step #4 Have note7 ship by a million (with 32-128GB each) Step #5 recall them all and throw them away Step #6 recall the replacements Step #7 have apple (finally) double the size (16-32GB) of the minimum size iphone 7 Step #8 have 1TB SSDs finally hit price points that enthusiasts and professionals would consider

So basically those investing 2 years ago... invested wisely. After all it's not like demand driving prices higher is bad for those who produce flash.

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