Live data from Hacker News

TSMC Kicks Off Volume Production of 7nm Chips

anandtech.com

61–70 of 111 posts

Re: TSMC Kicks Off Volume Production of 7nm Chips

#61

So one of the most important questions when producing >10nm process is yield . In the article I can't really find yield numbers, and the only thing they mention is the SRAM chips getting "consistent double digits" -- so pessimistically consistently 10% yield. That's not "good" yield. Also, IIRC SRAMs are just about the simplest blocks you can make, which means they're the simplest lithography wise. Simple blocks to m…

> I can't really find yield numbers

This is not surprising - this is trade secret information as it directly translates to profit margin for the process. AFAIK nobody publishes process yield information other than vague handwavy percentages.

You should also expect percent yields of most processes these days to be pretty poor (numerically): each step brings its percent breakage along, so at 100+ steps for these current processes, you're losing a significant fraction of chips. (Even if all of your steps yield 99%, you're down to 36.6% yield after 100 steps, so it's really important to reduce the number of steps as well as their complexity.)

For a process to be profitable it doesn't need to have a perfect, or even "good" yield though (and so-called "perfect wafers" have been vanishingly rare since about the 14nm process step). I've read documentation about very old processes with yields of 60% that were considered "good" at the time, so 10% might not be a terrible overall yield at this process node (e.g. if we take our 36.6% yield example above, 10% total yield would be of 27% of theoretical - certainly room for improvement, but better than many pharmaceutical processes).

This underlines the importance for the switch to EUV - a dozen or more DUV multi-patterning steps can be dropped down to a single EUV step, which eliminates losses along those multi-patterning steps.

Re: TSMC Kicks Off Volume Production of 7nm Chips

#62
post #54
post #18

Earlier quoted context omitted.

Aha I had a question too why wafers are round. The answer is Crystals form in a cylinder then sliced. https://en.wikipedia.org/wiki/Wafer_(electronics)#Formation . Sorry it doesn't answer your question but helped me. :)

You could slice a cylinder the other way. That would give you rectangles, with the short dimension varying. I'm not so sure you'd save any space, but recycling the unused portion might be more reasonable to do.

The problem is that it is a single crystal of silicon. To keep it atomically flat you cannot cut it at any angle. You must cut it across the axis the crystal grows in or the surface will be rough and the wafer will likely crack in half in a stiff breeze.

I suppose you could go for some more on-axis cuts, but the crystal planes are pretty restrictive on what you can do. You'd end up having super long and narrow pieces and such.

http://www.crystal-scientific.com/xtal_orientation.html

Re: TSMC Kicks Off Volume Production of 7nm Chips

#63
post #61

So one of the most important questions when producing >10nm process is yield . In the article I can't really find yield numbers, and the only thing they mention is the SRAM chips getting "consistent double digits" -- so pessimistically consistently 10% yield. That's not "good" yield. Also, IIRC SRAMs are just about the simplest blocks you can make, which means they're the simplest lithography wise. Simple blocks to m…

> I can't really find yield numbers This is not surprising - this is trade secret information as it directly translates to profit margin for the process. AFAIK nobody publishes process yield information other than vague handwavy percentages. You should also expect percent yields of most processes these days to be pretty poor (numerically): each step brings its percent breakage along, so at 100+ steps for these curren…

Agreed. About the only number I'd expect from a foundry is a defect density per unit area, which can be used to derive a yield estimate. It's die-size and design-quality dependent, so the quoted D0 is going to be a best case.

10% most certainly is a terrible yield. If TSMC is kicking off volume production, then they have a mostly-SRAM test vehicle somewhere, probably 288Mb or larger, yielding at 65 pct or better on a consistent basis. A 10% wafer would be a financial disaster.

Re: TSMC Kicks Off Volume Production of 7nm Chips

#64
post #40

I assume the production is already sold out for the next year for Bitcoin/Ethereum miner ASICs... I am wondering for how long will we be stuck with 7mm/10mm (Intel) tech; maybe we will see the last silicon-based improvements in CPUs & GPUs for the next two decades...

ASICs usually trail leading edge nodes by several years.

Re: TSMC Kicks Off Volume Production of 7nm Chips

#65
post #14

Earlier quoted context omitted.

There isn't any feature of the transistors taht are 7nm wide, the smallest feature IIRC is the interconnect, which is about 30n-40nm. "7nm" is marketing wankery. https://en.wikichip.org/wiki/7_nm_lithography_process

I've always assumed that "XX nm" doesn't represent the geometry of any particular feature of the end product, but something related to the wavelength of the radiation used for the imaging process. Maybe it corresponds to the principle emission line of the light source (synchrotron?) In spectral terms, 7 nm is near the border between hard UV radiation and soft X-rays.

This is not correct at all.

Most chips made today are created with multipatterning processes using 193nm lasers and optical masks, known in the field as "Deep Ultraviolet Lithography" (DUV(L)). The industry is pushing towards replacing DUV (which has been pushed to its extremes) with "Extreme Ultraviolet Lithography" (EUV(L)), which uses a 13.5 nm light source (just watch https://www.youtube.com/watch?v=5yTARacBxHI - it's both fascinating and terrifying the trouble that EUV brings) and mirrors since pretty much all matter is opaque to EUV light.

It's a bit maddening to think that features that much smaller than the wavelength of light used can be patterned with that light source, but we've made a science out of it over the past decade with multipatterning and immersion lithography.

Re: TSMC Kicks Off Volume Production of 7nm Chips

#66
post #20

Earlier quoted context omitted.

Well that's annoying. How is anyone supposed to judge anything if they just make numbers up?

Well, after a while or is sort of public knowledge that 10nm Intel is about the same as 12nm AMD, etc. But yes, the industry needs standardized advertising practices badly.

>standardized advertising practices

Oh man, I wish this would happen in any industry...sadly, advertising doesn't seem to see any benefit. Why standardize when you can differentiate?

Re: TSMC Kicks Off Volume Production of 7nm Chips

#67
post #20

Earlier quoted context omitted.

Well that's annoying. How is anyone supposed to judge anything if they just make numbers up?

Well, after a while or is sort of public knowledge that 10nm Intel is about the same as 12nm AMD, etc. But yes, the industry needs standardized advertising practices badly.

Uh, it's the other way around. 10nm Intel is 7nm global foundries. 22nm Intel is superior to 14nm global foundries.

Intel is the one that doesn't fudge their numbers.

Re: TSMC Kicks Off Volume Production of 7nm Chips

#68
post #22

Earlier quoted context omitted.

Yeah, you should take the fact they're not using EUV as the tremendous boulder of salt that it is: these are actually 10nm parts. Node names continue to be washed into Megahertz War-style naming schemes. TSMC's process lines up pretty well with Intel's published numbers for their P1274 10nm process (Contacted Gate Pitch T & I: 54 nm, Minimum Metal Pitch T: 40nm I: 36 nm, High-Density SRAM bitcell size T: 0.027 µm^2 I…

There's a big difference when you compare making 7nm features with about 100 process steps whereas EUV are doing it in like 4 steps.

EUV is still going to be 60+ steps.

Re: TSMC Kicks Off Volume Production of 7nm Chips

#69
post #64
post #40

I assume the production is already sold out for the next year for Bitcoin/Ethereum miner ASICs... I am wondering for how long will we be stuck with 7mm/10mm (Intel) tech; maybe we will see the last silicon-based improvements in CPUs & GPUs for the next two decades...

ASICs usually trail leading edge nodes by several years.

According to what evidence? Due to yeild tolerance, they tend to be among the first made, even getting made during risk production.

Re: TSMC Kicks Off Volume Production of 7nm Chips

#70
post #54

Earlier quoted context omitted.

You could slice a cylinder the other way. That would give you rectangles, with the short dimension varying. I'm not so sure you'd save any space, but recycling the unused portion might be more reasonable to do.

The problem is that it is a single crystal of silicon. To keep it atomically flat you cannot cut it at any angle. You must cut it across the axis the crystal grows in or the surface will be rough and the wafer will likely crack in half in a stiff breeze. I suppose you could go for some more on-axis cuts, but the crystal planes are pretty restrictive on what you can do. You'd end up having super long and narrow pieces…

The orientation is determined by the seed crystal. You can choose whatever you want.

There will of course be long and skinny pieces. These will be much easier to recycle than the unused portions around the edge of a circular wafer; they need not leave the facility that cuts the wafers.

The end result is rectangles of a standard size in one dimension and varying side in the other dimension.

Post reply on HN