MEMs oscillator sensitivity to helium (helium kills iPhones) 

Hi, Nurdrage ! Didn't expect to see you wandering outside your lab. Weird phenomenon, eh?

Why does helium diffuse into silicon while hydrogen does not?

It's not concentraiting the helium; yet it's allowing it to diffuse, like the reactive non-medal is solivating a gas into it? Or is it slipping around imperfections in it's structure

Ozone will also kill all kinds of semiconductors, including LEDs. I was using an ozone generator in a cabinet and it had an LED and microcontroller both die. The concentration probably has to be fairly high and it takes days or weeks to happen.

@@TheLightningStalker Ozone is an oxidizer, so I am sure it will kill sensitive things, but by totally different means.

Dudeeeee this is like a crossover event I never even realized happened! Love both of your guy's content.

thank you for showing conclusions first and I presented the data as if it was a mystery novel.

My question is why? Helium is literally twice the size of hydrogen... how does it diffuse almost 100x faster?

@@tomewyrmdraconus837 A H2 molecule is a lot larger than a He atom.

@@garymarsh23 I doubt hydrogen diffuses through silicon as a dimer. I suppose the potential well of a H interstitial in a silicon lattice is just deeper than for He

@@tomewyrmdraconus837 He_1(atomic) is smaller than H_2 (molecule) - the real question is - why would Sulphur diffuse so rapidly?

need to consider those 'constants' more carefully - keep reading and see Fig. 1.23 - molecular hydrogen diffuses faster than helium in single crystal silicon, search for articles by Douglas Sparks for more insight into this issue

Yes. Power-cycling during the He exposure is a great idea!

Under normal circumstances though, these oscillators are essentially never off in the devices. They might be powered down once you run your battery down to 0 in you iPhone, but that rarely happens.

I had a car like that :)

@@JasperJanssen That's probably true for the 32.768 kHz oscillator on a phone or watch as it is used for the RTC (real time clock). I still think that power cycling it would be informative, though. And on embedded systems which do not need an RTC, one generally only keeps the current oscillator on, so even the 32.768 kHz oscillator will be turned on and off to save power as the device switches to different modes, so again, interesting to test.

Embedded systems can use an small RC resonant oscillator instead of the quarts to save power, but it's much less precise. Modern CPU are too complex and timing is too strict for them to do that, they can't change de PLL that easily while running (they can change the multiplier though, to save power).

Have something you might want to research. Health effects of microwaves at 5 gigahertz. How juxtaposition effects cells and body.

​@@stevepence9869 it's depends on power and distance from the source. Are you interesting wifi or military radars?

@@AxGxP WiFi.

when you see this ratio your have to realize that a good portion of thumbs downs are accidental.

Would be nice to see the dislike counts, but RU-vid just rolled out the removal to all videos...

You can probably check to see what oscillator your phone uses, but unless it's an iPhone 8 (or newer), you're probably safe.

Yes and btw, have to be careful about permeation when doing that since it will pass through o-rings etc. and indicate a false leak!

Except that would only work with iPhone 8 or later... And it'd probably cause more problems than would solve.

Maybe we need to send mass shipments of helium balloons to all the Apple Stores?

@@JlerchTampa Or empty a few bottles of Helium into some Apple warehouses …

They couldn't put in a few drops of epoxy to isolate it?

I wonder if there is any permanent damage even after the He has diffused back out of the device...

arfink Are you sure it’s surface bonding? Sounds like simple diffusion to me, if the oxides would form a diffusion barrier (I don’t know whether they in fact do, though).

Fragilization/embrittlement of metals (or metaloids) by H2 (or He...) induces the structural failure (SF) of the monocrystaline quartz, hence the KIA of the mem. That SF is derived from multiple dislocations (and even early microcrack developments) while in service, wich ultimately act as difussional barries during the postmortem offgassing tests. In fact, offgassing timing is an interesting way of assessing the degree of dislocation networking without resorting to TEM

​@@alterhec if I follow correctly, does this mean it's possible that even the tiniest fissure (crevasse) in a material, especially an alloyed metal; would inhibit diffusion of substancially smaller particles (like elemental He) and possibly even reflect them just like how snow (transparent H2O in solid form but it looks white because of the nucleation of ice secretion) will reflect light since photons are astronomically smaller particles? Probably not the best metaphor but if you disregard the effects of Ionization, Electromagnetism, Radiopacity, etc. maybe it can be a simple model to explain the phenomenon we see with Helium. I am fascinated by this because of the implications it has on superconductivity and everything that was learned in the early days of cryogenic when using Helium to develop what was called a "quantum fluid", just thinking about how electrical conductivity is totally different at incredibly cold temperatures and how wave propagation through a material is seemingly out of this world, nonetheless diffusion of a particle being mind boggling.

100%

this kind of suggest the helium is never bonded, a part of the Si crystal structure. Then the only real force forHe to leave is random motion of the He? What if you shake the device rapidly i wonder if it leave faster?

@@marshalcraft no, Michael Kaliski is spot on with his explaination. Think of the Helium diffusing out of the device the same way you would if you flipped a full water bottle upside down, it would just glug, glug, glug. The difference in this case is that Helium is lighter than air, so it's only going to diffuse (glug) out the top of the device, but unlike the water bottle, there is nothing that can be exchanged in the vacuum. Maybe a better way of explaining this is putting your finger on the end of a straw an pulling it out of the glass. The vacuum will hold the liquid in, but not indefinitely.

Omg Jesus hellos 👋

Achievement unlocked Jesus enlightened

@@deanthemachine96 bruh

That huge ceramic/metal package is actually a mems gyroscope, not an oscillator. I was just using it to show a true hermetic package. The manufacturer could have made it smaller, but it's an older device, and there wasn't as much market pressure on that product to make it tiny.

@@AppliedScience remarkable work. Can you give us a rundown of your workshop / lab setup sometimes? It would be nice to work towards being able to get the kind of insight that you're able to work out in these videos. Having a "shopping list" (or more realistically, a wish list) would be amazing to have as guidance.

This seems plausible, but is it consistent with the 1kPa environment not causing failure of the device? Perhaps it would have failed at 1kPa but it takes longer than the 24 minutes test shown?

Yeah, you don't really gain that much space with that MEMS oscillator.

@@GRBtutorials you should see the difference on an actual phone board. Also strongly affects the thickness of the board. Still agree that a failure mode that easy to encounter (not common, easy. There is a difference :-p) should be avoided for the cost of miniaturizing two components on a board with thousands. Imagine filling helium balloons and having your phone die for 3 days... that's just silly.

But why the failure in the first place? Does the diffused helium reduce the Q-factor of the resonant-H oscillator? (i.e. it contaminates the vacuum inside the MEMS?)

@@ChrisGJohnson It is inconceivable to me that any gas even at 1 atm should kill an oscillation. Perhaps because it is so small that surface to volume ratio so large that any gas will damp it too much. More likely the coupling is so feeble (electric field attraction only) and the desire to save power, they made the drive marginal. (I'll be willing to bet they they used @#$3.3 volts when they should have used 5.) Normally with such close clearance structures, even high gas pressure "looks like a vacuum" because there are so few molecules present in the gap. But this must not be the case. I wonder if MEMS gyros have the same problem?

None of that rubbish PSI...

@@invendelirium I doubt it as he says "strange units".

could have been cm of h2o

kilo pascals

@@gordonwedman3179 imperial>metric

Nope,you have R C timing circuits have been done for almost the dawn of electronics. A crystal oscillator/MEMS is just a better way most of the time. Due to being much more stable.

If you open a small hole in the MEMS, you probably will get Air in it too, which on its own would probably enough to kill the oscillator

With a hole, the air and any HE could be cleared with vacuum. If it recovers immediately after vacuum is applied, then it's presence around the fork is restricting it's motion. If not, then the problem is the HE diffusing into the fork itself, and changing it's characteristics. It would be difficult though. Drill/grind, it stops, and you don't know if it's because you cut into the working bits, or if you let the air in.

@@snaplash If you had access to the right kind of SEM microscope with FIB / GIS attachments it should be possible to do the required machining. Probably not simple, but almost certainly achievable. You can do some crazy things with those technologies! Look at the last "slides" of this PDF for some samples home.iitk.ac.in/~vkjain/L3-IBM-ME698.pdf

I updated the description with a Google Drive link: drive.google.com/drive/folders/1l3mJ4UTs8aY70scH7vDaf0M8pLeP2kqI?usp=sharing

@@AppliedScience thanks!

Thanks for the pictures and your excellent experiments and commentary, Ben! It almost looks like some kind of space ship straight out of a sci-fi novel

@@Micah561 Try shouting "Magnify!" at your screen.

@@spankeyfish *COMPUTER!* (bleep) Magnify image. (bleep) Enhance quality. (bleep)

Correct, MEMS oscillators are usually capped with a silicon wafer; however, interestingly this does not prevent helium permeation, see Output Drifting of Vacuum Packaged MEMS Sensors Due to Room Temperature Helium Exposure, Journal of Sensor Technology Vol.3 No.4(2013) (freely available).

@TheCarmacon not BOE/Liquid HF, Vapor HF a bunch of companies make the tools now for a oxide release layer similar to XeF2 etchers with a poly release. It is typically a Vaporized HF mixed with Ethanol as a carrier allowing ionization to occur and thus etching of the oxide. I think the switch from bulk to surface MEMS processing largely contributed to the development of the vapor HF process. There's a few other inconsistencies(to the paper) in his evaluation of the process flow. They start with a SOI wafer, pattern that then do a oxide fill. They pattern the oxide then do a poly hardmask, the hardmask is then patterned with a series of holes protecting the electrodes and the center of the oscillator giving it a fixed point to hold in place. The HF vapor ignores the thin poly but eats the oxide freeing the proof mass. I would then assume that they do PECVD poly as they're depositing 20um on top, also in the PECVD process the cavity would be pulled to vacuum as well as having the wafer heated to around 400C or so. So if you have a staging step to bring the wafer to temp any condensation should be alleviated and form the seal to the cavity. If the holes are small enough they'll close due to gap-filling besides being hammered with 20um on top of it. This sort of proof-mass release process is not unique with poly-based structures for surface MEMS processes anymore. I certainly see where you're coming from if they started with a bare wafer and not a SOI wafer though it would be obnoxious.

total bullshit

...also twice as bright!

@@realedna Danged millennials, walking around like they rent the place.

And less than half the weight of my 100Mhz analog scope.. (A bit more expensive though.. )

Carful? You mean "as much or as many as a car will hold"?

@@GRBtutorials Good eye! I can't believe that slipped past my spelling detector.

Electric welding would be enough to fry any mobile device. I avoid having any mobile device near anything I am working on, since they can easily break. My grandfather wore his watch on the inside of his wrist to avoid breakage, and I never wore one at all when working, keeping a dollar store watch in my pants pocket.

I was wondering the same thing. Does a MEMs accelerometer under constant force vibrate or is it stationary? If the former, I assume it would suffer the same problem. If the latter, it might be operating at such a low frequency that the helium has no significant effect.

Damn Yankee That’s a different mechanism. Here it has not much to do with substrate interaction, but with partial pressure gradients across the diffusion membrane. It’s easy to produce almost arbitrarily high gradient from outside in, but going inside out, the best you can do is go down to vacuum. If the partial He pressure inside the device is very low to begin with, compared to the partial pressure available when He was forced inside, it’ll take much longer to diffuse it out. That’s the scary thing about diffusing through membranes with very high gradients pointing inside an enclosed system: it’s high impossible to get it out unless you’re willing to wait.

@@absurdengineering It forms a chemical compound called silicon heliide

thumbs up so he will see it

should produce small ics

i second this notion, as basically most important topic

My understanding is all mems devices are susceptible to helium exposure, but exposure to levels of helium that cause problems are not common.

@Ask Questions, Try It - Apart from exposure levels, an important factor to be considered is whether the silicon of MEMS is hermetically sealed or open to gases in the atmosphere. In the case of iPhone 8 and later models, due to space constraint, the MEMS is made extremely small and is not sealed. So, if the MEMS device, - whether it is an oscillator or an accelerometer - is hermetically sealed, it will not be susceptible to helium exposure.

I’d guess its because the penetrating helium is causing strain on the silicon and making its oscillations change?

you mean like, the presence of helium atoms in the crystal lattice changes the hardness/flexibility of the silicon?

KohuGaly or it's just friction between "moving" parts and helium

It may also have something to do with the Reynolds number at that small scale. The effective viscosity would be really high. I saw a RU-vid video where they explained how really small animals actually swim rather than fly through air. To them, air could feel like honey.

Assert.assertTrue(AppliedScience == like) ; //very true!

True

#include "youtube.h" int main(int argc, char* argv[]) { if (argv[1] == "Applied Science") { like(); puts("Liked"); } return 0; }

No way. Helium is smaller than hydrogen because the 2 protons suck the electrons closer to the nucleus than the 1 proton does in hydrogen. But neon has electrons in a whole different orbit than H or He.

nobody cares

Certainly you don't.

I think alpha radiation consists of a helium nucleus. I do not believe alpha radiation creates helium.

@@gordonwedman3179 You're right but it's still Helium, since it's number of protons don't change. Alpha Radiation is just a Helium cation.

Alpha particles don't really penetrate anything, so they'd strike the outside surface, gain 2 electrons, and act like regular helium (unless it reacts with the silicon nucleus). So It would probably act just like regular helium.

I would think you would need to have a very high alpha radiation level to give the same number of nuclei as present in two percent helium gas but I imagine at some point the effect would be the same.

@@gordonwedman3179 Yes it does! As soon as the alpha particle is slowed down, it grabs up 2 electrons to make a complete helium atom. This same effect causes containers with strong alpha emitters to eventually burst because of the accumulated He gas. But alpha particles would mostly be stopped before getting in.

This guys seems to have everything. If he says "So I pulled out my nuclear fusion reactor to test the nuclear energy..." I probably wouldn't be surprised.

He made one.

You don't?

I have an electronic microscope in my garage I need to get working

Uhhhh . . . "strange units, but at least it's KPa . . ." Uhhhh, the Pascal *IS* the metric unit of pressure . . . back up the vidjaoe, and the "strangeness" he's referring to is how the gauge measures not in absolute pressure, or even gauge pressure, as one would usually expect, but in units less than gauge pressure . . . nothing "Imperial" going on here a'tall . . .

@@Roonasaur He meant that even the strange pressure measurement of the gauge is easier to work with than the imperial system

@@MegaFPVFlyer Ok, sure . . . I'm American, so I guess my worldview doesn't revolve around how weird it is.

@@Roonasaur woosh

@@RainBoxRed Yeah yeah yeah, I earned that one I guess. It's YT - I frequently fire off here half-cocked lol

It would be higher frequency than when running in air, but that little cavity is supposed to be a vacuum, so helium should still slow it down.

I'm older than you. I remember when we used tin cans connected by strings for telephones!

TropicalCoder Those phones had a weird dial tone!

I should have mentioned this in the video ;) My guess is that the gas pressure inside the device causes friction between the tuning fork and the stationary electrodes, and this friction causes energy loss. If the energy loss is high enough, the oscillator will not run. It's like slowing down the pendulum of a clock with your hand. It will work with some amount of energy loss (friction), but there is a point at which it will stop due to design limits on how much energy can be put into the oscillator.

Hmm. So friction is not an issue with hydrogen, but a problem with helium? But why it doesn't happen with air? Are the major components (O2, N2, CO2, etc) of air doesn't even get into the device? Could the difference in the electrostatic properties of helium, compared to the gas already inside the MEMs device, be also a problem? Btw, thanks for the answer!

Here’s my guess. Only hydrogen and helium atoms can squeeze through the silicon, so there is never any other gasses inside. And when it’s brought out of a helium environment, the helium will start to leak back out through the silicon, but other gasses in the air cant go in, so it reverts back to a vaccum inside (besides some remaining hydrogen and helium). I guess the hydrogen is small enough or in low enough quantities that it doesn’t affect the mechanism as much as helium

Helium is a smaller molecule than hydrogen, so diffusion is much faster

Hydrogen gas exists mostly as H2 where helium is single He atoms. So even though a hydrogen atom is smaller, in gas form it's not.

It changes the physical parameters of the crystal.not really drag as you aren't moving crystal dislocations around

If the MEMS 'tuning fork' is made to work in a vacuum then the presence of any gas will cause a huge amount of damping. It may even cause current to flow between parts that are supposed to be insulated resulting in no force generation or shorting of the pick-up signal to the common.

@@KallePihlajasaari well, some damping anyways. Most MEMS are small, but not That small. And these devices are designed to run in atmosphere.

@@RobertSzasz MEMS oscillators will always have a vacuum inside, the little "tuning fork" would not be able to oscillate in atmosphere

There are similar sensors,

As a sensor this would be too slow, but I´m sure you could make a sensor in a similar way.

take some Iphones and avarage the times they need to stop working. I am sure you can correlate this value with the amount of he in the air^^