EEVblog #866 - Mailbag

Is this wierd thing a slice of Dave's Brain?
Find out in today's Mailbag

SPOILERS:
A silicon wafer bonanza!
KLA Tencor temperature sensing plasma etching wafer video
Bullshit Bingo
Model car controller
A very expensive single photon counter teardown and some experimentation.
Random cheapo Chinese Ebay items! A shocking pen, a wet baby monitor, and the world's worst soldering iron.

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[darraghomeara]

Dave,

I work in the semiconductor ind. Those temperature sensing wafers are used in areas of the process that involve heating up the wafers. This is seen a lot in the lithography steps where the wafers are baked and cooled. Fluctuations in the temp across oven plates causes problems further down the line when the wafers get exposed. These sense wafers are typically used to calibrate the oven plates used to heat the wafers, this ensures that all of the wafer gets heated to the same temperature.

Great show by the way :)

[hgbugalou]

Big Clive got one of those irons and the wire fell out as he was holding it in his hands.

Maybe the next big Chinese special will be some combination of the soldering iron and the wet baby detector!

[ichigo_varactor]

I bought some LED lightbulbs off of China once. They emitted so much interference that it produced a +30 dB noise level on my HF radio. I eventually took one apart and found one of the most scary SMPS circuits ever.

[ElectronicTonic]

Those temp-sensing wafers are so bizarre and beautiful, they should be framed and hung up in the lab.

[Bowowowification]

Dave,
The shock pen was mine, lol. Thanks for the teardown! I wish I could afford to send something more interesting. Still the greatest feeling in the world to have my stuff on your vblog. Been following weekly for years.

[kristinaification]

oh god, I made the mistake of buying one of those sort of soddering irons when I was trying to get into electronics but didn't know what I was doing (and still don't, which is why I gave up for now). Those things are so dangerous and scary to use, mine started smoking through those grates, I used it once and never again.

[voltlog]

The schematic diagram for the "wet babay" alert is hilarious =) They're using "integ-rated" chips none of this "dis-crete" rubish.

[mikeselectricstuff]

Proabbly going negative as scope input unterminated.

[thedvideo]

He seamed to like the £1 soldering iron.

Yes it was me who ordered it for him.

[damonstr]

Still wating for the Altium-I mean the DaveCADHQ building tour!

[johndrachenberg]

"Houy, welcome to everyone's favorite segment mailbag!" Who else at home says the intro every time along with Dave? I can't be the only one...
Edit: Dave, when you start pronouncing Peltier correctly, maybe I'll change my pronunciation of geocaching. :P

[JimGriffOne]

05:51 - It's an 8-bit digital mirror!

[kmaxmax]

The temperature sensing wafer (called on-wafer) is used to measure the different temperature zones in a Dry Etch plasma tool of the Electrostatic Chuck (ESC). For zonal temperature tuning. This is used to control the etch rates on across the inner to outer zones. Critical when you are trying to control etch rates within +-10 Angstroms across the surface of a 300 mm wafer. A couple of tenths of a degree makes all the difference.

[zaprodk]

The blue tape is to hold all the dies together after dicing :D

[KennethScharf]

I used to work at Digital Equipment years ago. The LSI 11-23, was known internally as the "Fonz-11" project, and they had the "two thumbs up" icon from "the Fonz" on the TV show "Happy Days" right there on the Silicon! They also had a support chip known as the "MIC" chip (stood for "multiple level interrupt controller"), and it had 'Mickey Mouse' in the corner of the chip (good thing Disney never found out about that one!). Then there was the 11-73 micro processor chip. It was internally called the "Jaws-11", and had a logo of the 'Great White Shark' from the movie on the chip. I got to look at all of these under a microscope, so I saw the artwork.

[gorak]

Those are single photon avalanche photo diode detectors. My MSc. thesis was based around designing these at the device layout level, and characterizing various designs for integration on the same die with other CMOS circuits for medical applications (and I did it in Canada too, even the silicon wafers were made in Canada!!!). It was quite the happy day when I finally actually saw some of those magical pulses coming out of APDs that I had actually designed! The afterpulsing is generally caused by the detector itself emitting a few photons when the avalanche current starts to flow after a photon is absorbed, and before the quench circuit lowers the reverse bias below the avalanche threshold to stop the current flow. The detectors typically have an array of APDs, so the photons emitted by one APD in avalanche will trigger the breakdown of others in the array. Also slight temperature changes of the junction (just from the larger average current that's flowing while the device is exposed to the more intsense light) shift the avalanche breakdown threshold, which will change the amount of excess bias voltage, which greatly changes the sensitivity of the device. The way to mitigate this is to use an active quench circuit with a gating signal. You want to keep the bias voltage across the device a little below the threshold when you know the device will be exposed to a lot of light (the laser pulse), then you crank the bias voltage up above the threshold when the excitation light is shut off to do the measurements. If I had to guess, the detector is made by Hammamatsu, even the quench circuit and everything else might just be re-badged Hammamatsu kit. If the quench circuit is designed properly, the device will not be damaged by exposure to too much light. There will be a saturation threshold where the device can no longer measure more light and give meaningful results, but as long as the quench circuit keeps the average power flowing to a reasonable level to not cause heat induced damage, there should be no long term effects.

[Ziplock]

At 23:30 it's not photons going through your thumb, it's your thumb emitting IR light due to heat.

[chris]

At 23:10, could the IR from your thumb (body heat) be saturating the camera?

It says detection ranges to 1060nm, and its being cooled with that TEC.

[marcelfilms]

30:22 thats the one i send.
i have a few of those and they run fine after half a year of normal use.

[EnricoConca]

The light saturation of the detector after the LIDAR pulse is due to charge trapping inside the detector. In fact, for atmospheric LIDAR it would be better to employ a gated SPAD detector, which can really be turned off during the laser pulse and pretty much no saturation should occur.