[HN Gopher] Mathematical Compact Models of Advanced Transistors ...
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Mathematical Compact Models of Advanced Transistors [pdf]
Author : nill0
Score : 76 points
Date : 2025-03-29 06:58 UTC (16 hours ago)
(HTM) web link (www2.eecs.berkeley.edu)
(TXT) w3m dump (www2.eecs.berkeley.edu)
| noosphr wrote:
| This is from 2018, anyone in the field know if it's still state
| of the art or a historic curiosity? I know that we've started
| using euv since then which seems like it would change things.
| wtallis wrote:
| > I know that we've started using uev since then which seems
| like it would change things.
|
| Are you asking about EUV lithography? That's a manufacturing
| technique, but this thesis is about modeling the physics of how
| a transistor operates, not the process of building the
| transistor.
| sitkack wrote:
| They are implying that due to smaller features, the
| transistors change and if these models still hold for those
| smaller transistors.
|
| Classic hn well akshully.
| momoschili wrote:
| Well I think both commentators are valid- the effect of
| shrinking a transistor but keeping the same geometry is
| probably well captured by this model. Going from a "10 nm"
| DUV finFET to a "7 nm" EUV finFET, this model probably
| works quite well whether you're manufacturing using EUV or
| DUV.
|
| I think the crux of the matter is the transition from 7 nm
| down to our modern nodes, where the major change was not
| only going from DUV to EUV, but perhaps more importantly
| the change from finFET to multi-gate or gate-all-around FET
| (GAAFET), where this model probably needs significant
| updates to be still valid.
| sitkack wrote:
| The is answer the GP was looking for, thank you.
| wtallis wrote:
| This thesis already covers GAAFETs. What might be
| problematic is that it's modeling cylindrical GAA
| structures, when fabs are trying to implement GAA with
| ribbon/sheet style structures that this model might not
| be able to handle.
| momoschili wrote:
| This might be changing with the slowdown in node advancements,
| but I think it's unlikely you are going to get anything truly
| "state-of-the-art" in publication research. Academia has
| trailed industry in this kind of transistor level semiconductor
| physics for years now. The majority of the state-of-the-art
| models are closely held in your usual suspects (Intel, TSMC,
| etc), and are likely considered significant trade secrets.
| eternauta3k wrote:
| Aren't the fab models usually rough and binned? Which is why
| companies have modeling departments.
| adrian_b wrote:
| The models themselves belong to the companies that make the
| software EDA tools for circuit simulation, i.e. Synopsys,
| Cadence, Siemens (ex Mentor).
|
| While the models used in commercial EDA tools are based on
| those published by academic research, they may have various
| secret tweaks.
|
| What belongs to the foundries, e.g. TSMC, Samsung, Intel,
| UMC, Global Foundries etc., or to the in-house semiconductor
| plants of certain companies, are the values of the model
| parameters, which are determined by fabricating and measuring
| a lot of test devices.
|
| The foundries provide the model parameters to their customers
| included in the so-called Process Design Kits. For each
| semiconductor device fabrication process there is a PDK.
|
| In order to design some custom integrated circuit, you need
| to obtain the PDK and install it in your simulation tools.
|
| Unfortunately, the foundries with up-to-date fabrication
| processes keep secret their PDKs. Otherwise many people could
| attempt to design something like a CPU competitive with
| Intel, because unlike for fabrication, for design all you
| need is a computer and time.
|
| Attempting to design a CPU using one of the obsolete PDKs
| that are available publicly, which are at the level used for
| CPUs like Pentium 4, more than 20 years ago, is futile,
| because the optimal design choices are very different for
| such ancient CMOS fabrication processes, in comparison with
| modern processes, so you would not learn more from that
| experience than when targeting an FPGA.
| RicoElectrico wrote:
| Isn't it that models themselves are public (like BSIM) but
| what you get in a PDK is a macromodel wrapping BSIM with
| another zillion of fudge factors, or at least binned by
| device size? That's what I understood by peeking into
| various PDK models.
| westurner wrote:
| State of the art in transistors?
|
| - "Researchers get spiking neural behavior out of a pair of
| [CMOS] transistors" (2025)
| https://news.ycombinator.com/item?id=43503644
|
| - Memristors
|
| - Graphene-based transistors
|
| EUV and nanolithography?
|
| SOTA alternatives to EUV for nanolithography include NIL
| nanoimprint lithography (at 10-14nm at present fwiu),
| nanoassembly methods like atomic/molecular deposition and
| optical tweezers, and a new DUV _solid-state_ laser light
| source at 193nm.
| ur-whale wrote:
| It's indeed from 2018 and may therefore not be state of the art,
| _but_ , it's really nice to read something like this: it cuts
| through all the marketing hype and pseudo-science-reporting
| articles written on cutting edge semis of the 21st century.
|
| Getting an accurate idea of how things really work down at that
| level is very refreshing.
|
| Also, it scratches an itch I've had for a long time, namely to
| understand how much quantum mechanics is really needed to
| accurately predict/model modern FETs.
| thechao wrote:
| The first chapter reads like the scientific equivalent of "hold
| my beer". I don't pretend to understand it, in the slightest,
| right now, but I love the style!
| eternauta3k wrote:
| If you want to learn and have a physics/EE background, you
| might have better luck with a book like Tsividis (also
| available as a MOOC!)
|
| https://www.amazon.de/-/en/Operation-Modeling-Mos-Transistor...
|
| https://www.coursera.org/learn/mosfet
| quantum_state wrote:
| Wonder if there is an update on the arts ... nice to have
| accurate model of a few transistors ... however, with chips
| operating at GHz, physical layout and the interaction among the
| circuit elements may seem to be more challenging to take care of
| ...
| eternauta3k wrote:
| By the way, fitting compact models is largely done by PhDs
| spending weeks tweaking parameters to get the simulation to match
| measurements. If you can find a method to automate this (which
| _very roughly_ comes down to minimizing a non-convex function of
| ~100 parameters) you can make a lot of money.
| Koncopd wrote:
| Why didn't the PhDs specializing in this area figure this out
| themselves?
| eternauta3k wrote:
| These are physics/EE PhDs. They are not experts in nonlinear
| optimization. Some (those with more programming skills)
| experiment with fancier optimization algorithms (see links),
| but there is a long way to go.
|
| https://ieeexplore.ieee.org/abstract/document/9796144
|
| https://ieeexplore.ieee.org/abstract/document/9665517
|
| https://ieeexplore.ieee.org/abstract/document/10497080
| godelski wrote:
| > These are physics/EE PhDs. > They are not experts
| in nonlinear optimization.
|
| These are not necessarily in disagreement. You can be both!
|
| No one that is an expert in nonlinear optimization has a
| PhD in... nonlinear optimizations. Typically their degree
| is going to be in Mathematics, Computer Science, Electrical
| Engineering, or Physics. The last 2 are commonly found in
| any strongly mathematical subfield.
|
| This is kinda like saying a physicist can't program or is
| terrible. Maybe they can, maybe they can't. My senior
| undergrad CS students are worse programmers than most
| graduate physicists I've seen. One of the best programmers
| I know has a PhD in Mechanical Engineering and works at a
| national lab. I asked him how it ended up like that and he
| said to get his PhD work done he had to do a lot of low
| level stuff, related to what we were doing.
|
| I do agree with your point fwiw, I just thought if we're
| going to nitpick we should nitpick ;)
| almostgotcaught wrote:
| > No one that is an expert in nonlinear optimization has
| a PhD in... nonlinear optimizations. Typically their
| degree is going to be in Mathematics...
|
| Lol wut. On the contrary there are absolutely zero people
| with a "PhD in Mathematics" and definitely very many
| people with PhDs whose dissertations have the words
| "nonlinear optimization" in them.
| godelski wrote:
| > there are absolutely zero people with a "PhD in
| Mathematics"
|
| I'm not sure what this means. You can definitely get a
| degree in mathematics. Your degree is named by the
| department, such as the department of mathematics.[0]
|
| On the contrary, there is absolutely zero departments of
| nonlinear optimization. This is actually a true fact and
| not an alternative one. > whose
| dissertations have the words "nonlinear optimization" in
| them.
|
| And which _departments_ do these people graduate from?
|
| You seem to be missing _critical_ context, which is what
| I was responding to >> These are
| physics/EE PhDs. They are not experts in nonlinear
| optimization.
|
| If you want to say that nobody has a PhD in Mathematics
| you'll need to be consistent with your definition
| (contained in title of dissertation?) and apply this here
| as well. Though I'm not sure what a consistent definition
| could be because there's certainly dissertations
| containing the word Mathematics in both the text and
| title. I'd have to stretch my imagination beyond its
| capacity to properly interpret your intent.
|
| [0] https://mathematics.stanford.edu/academics/graduate-
| students...
| almostgotcaught wrote:
| > I'm not sure what this means. You can definitely get a
| degree in mathematics.
|
| Are you a bot? The text is very clear - I said `PhD` not
| `degree`. You cannot get a `PhD in Mathematics` - the
| title of the PhD is never ever (ever) `PhD in
| Mathematics` (or `Physics` or `Electrical Engineering` or
| `Computer Science`). The department is listed on the
| award as `awarded by X department` but it matters about
| as much as the football team of the school. The only
| thing that matters is the title of the dissertation.
| That's how you get people in physics departments doing
| dissertations that are pure math and vice-versa.
|
| If you still don't understand what I'm saying I'd be
| happy to take a pic of my PhD certificate and send it to
| you.
|
| > You seem to be missing critical context, which is what
| I was responding to
|
| You seem to have selective reading/recall abilities - I
| have directly quoted already what I'm responding to
|
| > No one that is an expert in nonlinear optimization has
| a PhD in... nonlinear optimizations
|
| So I'll repeat - there are many many people that
| literally have PhDs in nonlinear optimization.
| somethingsome wrote:
| Do you have some dataset? And targets? Some starting code for
| the simulation or a software name?
| gautamcgoel wrote:
| Suppose I achieved a breakthrough in nonconvex optimization.
| How would I sell it? Who in the semiconductor industry should I
| approach?
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