Hacker News Reader

Comment by spark3k | Hacker News Reader

At what point does quantum tunnelling become a problem?

First though, "5nm", "3nm" and so on are just marketing names. There is nothing about "5nm" that makes it "5nm" other than the company in question saying it is. Some things are smaller than 5nm on a given 5nm node, and some are larger. I cannot recall exactly what node this started to be the case (there used to be an actual definition, one for DRAM, one for logic), but it was in the past two decades and got particularly ridiculous beginning around "28nm" up to now. The really concerning physical dimension for quantum tunneling to occur/not occur is "gate length," and that's been basically sitting around ~16nm (actual, real, literal 16nm), plus or minus a few nanometers (depending on the manufacturer and process in question), since about "45nm" (mid-late 2000s). So that one critical dimension isn't getting smaller. And there isn't much they can do about it right now. They are still shrinking other dimensions though, and things don't work like they used to. Powered off transistors aren't really off, and leak power. The workaround for this is that they just use bigger transistors in certain places for what's called "power gating". You get the benefits of having tons of small transistors, with a slight area penalty. In addition to power gating, they have made substantial improvements to the design of the transistors themselves. Gates now wrap around the channel on 3 sides, creating a device known as a Finfet. Silicon dioxide is no longer used as an insulator to the same extent -- hafnium dioxide preforms much better as an insulator. Gates are now metal instead of polysilicon. And there's an assortment of other changes that have occurred or are on the way. So performance has actually managed to improve somewhat, and things have still gotten smaller. The end is near... but not quite yet. Gate length is not going to budge much unless some miracle occurs, though.

The theoretical half pitch size limit for a single exposure EUV is Lambda * 2 or 26nm.

You can get arbitrarily small at the cost of exploding count of masks. I.E. double patterning needs 2X masks, but quad patterning needs 8X. Octuple patterning is completely impractical.

Can't they use a smaller wavelength source? Nothing special about 13nm afaik

13nm * 2 is 26nm.

Using a smaller wavelength is kind of useless for the optical lithography, as below this photons will make too many secondary electrons which will reduce the effective resolution. This is the reason X-ray lithography went nowhere.

This is why the ultimate limit of 157nm lithography was also not so far away from EUV. Also somewhere in between 25nm-30nm

This is also why some people suggest resurrecting 157nm — getting nearly same half pitch without maintenance, and expensive tooling of EUV.

The design of EUV lasers is already completely absurd. It's an awesome piece of engineering, but it's no easier to push the laser wavelength downwards than anything else.

Does the lithography require the tight wavelength or other nice properties of lasers? I had thought they used filtered synchrotron output since a while ago.

Basically everything about the process is absurd, not sure why pushing on the light source is less feasible then any of the other knobs

Diffraction limit becomes a real problem at these feature sizes even with short wavelength light, and the physical properties of short wavelength light start to damage equipment and cause serious other issues even at the current levels.

At some point it’s switching from ‘lots of wiffle balls in a stream’ to ‘high power machine gun fire’, and the physical properties of everything involved become very limiting.

13nm is hard enough. ASML seems to have settled on laser-driven tin plasma light source, which is miserably inefficient: https://en.wikipedia.org/wiki/Extreme_ultraviolet_lithograph

>The required utility resources are significantly larger for EUV compared to 193 nm immersion, even with two exposures using the latter. Hynix reported at the 2009 EUV Symposium that the wall plug efficiency was ~0.02% for EUV, i.e., to get 200-watts at intermediate focus for 100 wafers-per-hour, one would require 1-megawatt of input power

The optical train is also tough. 13nm is getting close to soft x-rays, and photons that hot don't like reflecting, and the optics are rapidly degraded by exposure light:

>EUV collector reflectivity degrades ~0.1-0.3% per billion 50kHz pulses (~10% in ~2 weeks), leading to loss of uptime and throughput [...] Due to the use of EUV mirrors which also absorb EUV light, only a small fraction of the source light is finally available at the wafer. There are 4 mirrors used for the illumination optics, and 6 mirrors for the projection optics. The EUV mask or reticle is itself an additional mirror. With 11 reflections, only ~ 2% of the EUV source light is available at the wafer.

Fixing link https://en.wikipedia.org/wiki/Extreme_ultraviolet_lithograph...

>but it was in the past two decades and got particularly ridiculous beginning around "28nm" up to now.

I wonder if that is some kind of cultural shift that is taking place that started around 2009, or if it's always been like this and I just never noticed.

BMW model numbers used to more or less accurately reflect engine sizes, not anymore, it's just numbers now.

2G, 3G, 4G used to mean something, not anymore.

I could add a remark about the federal reserve, but... I'll just stay away from that. Don't want to be too edgy/turn this into a political discussion (I just think it's interesting from a cultural perspective).

It's like we collectively decided that "it's just numbers, man."

>It's like we collectively decided that "it's just numbers, man."

People with no scruples realized it's easier/cheaper to confuse and persuade people something is better than actually producing something better and that conventional wisdom was wrong.

It's a lot easier to invest in propoganda that convinced improved perceived value than actual value. It's win-win, the consumer thinks they're happy and the producer doesn't have to deal with the mess of hurdles in reality to continue to make money. Conventional wisdom says people are smart and will see through your snake oil, meanwhile, empirical data says people will drink the snake oil if you tell them it's from the fountain of youth.

Advertisers ruin everything.

"our code is fast, flexible, and easily modifiable"

Advertising is cancer on modern society.

http://jacek.zlydach.pl/blog/2019-07-31-ads-as-cancer.html

Waaaaay back in the day, the Electro Motive Division (EMD) of General Motors make railroad locomotive. They had the GP-20 with 2000 horsepower, and the SD-24 with 2400 HP. Then General Electric entered the business with the U-25, having 2500 HP. EMD's next model was the GP-30, with (ahem) 2250 HP. This was in 1961.

So, yeah. This is nothing new. Marketers gonna market.

What’s really disappointing is that we as a society chose to accept commercial prevarication. The fine print exception is sheer bullshit. Dishonest marketing should be treated the same as dishonest weights and measures.

Kind of makes sense. People probably didn't all of a sudden become more dishonest. Thanks.

>2G, 3G, 4G used to mean something, not anymore.

Did they really, though?

2G was accurately labeled (in my experience), sure, but I remember when Verizon started relabeling their HSPA+ (3G) stuff as 4G in my hometown. Not even "4G LTE" (which allowed them to get away with it since it's not actually 4G), they just straight up called it 4G on my Motorola Droid Turbo. When I rooted it, I found out exactly what it was connected with and learned it was all a lie. (When I actually did experience real 4G, the speed difference was shocking.)

AT&T relabeled their 4G network as 5G fairly early on. [0] Then, Verizon decided to copy them. [1] But this wasn't a trend that started with 5G.

[0]: https://www.theverge.com/2020/5/20/21265048/att-5g-e-mislead...

[1] https://telecoms.com/505584/verizon-told-to-stop-lying-about...

> >but it was in the past two decades and got particularly ridiculous beginning around "28nm" up to now.

> I wonder if that is some kind of cultural shift that is taking place that started around 2009, or if it's always been like this and I just never noticed.

> BMW model numbers used to more or less accurately reflect engine sizes, not anymore, it's just numbers now.

When was that and which number? Just looking at the 7 series (surely you didn't mean that number) the E32 build between 86 and 94 had engine sizes between 3 and 5 liters.

> 2G, 3G, 4G used to mean something, not anymore.

So what did the G mean? AFAIK it was generation, but that's a very vague term. Just look at human generations, people are born continously, so you could have two people who are the same age but technically a generation apart because one had very old parents and the other has very young parents/grandparents are they the same generation?

> I could add a remark about the federal reserve, but... I'll just stay away from that. Don't want to be too edgy/turn this into a political discussion (I just think it's interesting from a cultural perspective).

> It's like we collectively decided that "it's just numbers, man."

Quantum tunnelling has already become a problem in most computer components. NAND flash was the first in maybe 2015 to start reporting seeing issues?

Effects are moderately visible and have to be counteracted at 5nm. I heard some rumours about 7nm, but cannot confirm any countermeasures were taken to avoid quantum effects.

It should be noted that "3nm" is now purely for commercial reasons and has no relationship to the size of transistors on board.

It already has been a problem in terms of gate leakage, although largely mitigated by material improvements.

Gate leakage is the phenomenon of quantum tunneling through the gate dielectric barrier and started appearing as gate dielectrics became thinner and thinner. Gate leakage was mitigated by moving to higher k dielectrics (from silicon dioxide, SiO2, to more exotic materials that include other elements such as Hafnium).

Higher k dielectrics allow for the same capacitance per unit area and channel control with a thicker physical gate compared to plain SiO2, reducing gate leakage. This technology change came along with metal gates (which used to be polysilicon) and were a combined advance that Intel incorporated a few years before before TSMC, IIRC circa 2008.

This is a circuit designer's perspective. Someone who actually understands device physics and material properties can chime in to correct me.

Your nickname rings familiar. Ex-Xilinx by any chance?

Do you have any books that you recommend on this topic? would love to get my hands dirty to the degree that i can with this

It's always been a problem to some degree. Keep in mind that 3nm is a misnomer and has no real physical meaning behind it.

From a few years ago until we perfect the QFET and can put it to use.

Reply on news.ycombinator.com