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[SOLVED] Probe system for getting transient response of gates?

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lolozzz

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Is there a probe system for getting transient response in deep-submicron (like 20-90 nm) technology node? I have encountered dozens of I/V curve measurement systems. But is it possible to measure gate delay with probe equipment? Have you seen these? What is the precision of these techniques?
 

HF probes tend to be good only for 50-ohm systems. A FET
probe may be better but is not likely good enough.

My test chip strategy tends to be difference based or ring
oscillator based. A good high stage count (prime number)
RO can get you to very good "core gate" delays provided
that you give the RO good local decoupling and make the
output not kick the local rails unduly (like, use a LVDS
output buffer, or resistor-limit a CMOS buffer (maybe even
make the limiter a divider that impedance-matches to
50 ohm cabling, through a bias-T).

Make RO variants that have different wire and fanout loads
(per-stage and identical) and you can readily get to delay
numbers by frequency and N, across supply / temp / load.
Process of course takes more money and/or interaction
with the fab.

Now if you're intent on probing a single naked core-sized
logic gate, I have no encouragement for you there.
 
Many years ago, Frauenhofer Institute Duisburg managed to make on chip transient measurements with electron ray sampling.
 

We used to have a big expensive rig in our Reliability lab
back when I worked for a big semiconductor company,
but it was limited in the frequency it could follow. It
was basically a SEM with the video taken off to a real
time 'scope, and the video bandwidth was not great.

I'm sure things have progressed since, but no idea how
much. Still I think voltage contrast SEM imposes some
limits (need a ton of gain, gain costs BW, etc.).
 

Using equivalent time sampling and periodical signals, the bandwidth is only limited by the gating aperture. But it may be still insufficient for high speed circuits. I must confess I'm not aware of the state-of-the-art.
 

HF probes tend to be good only for 50-ohm systems. A FET

Now if you're intent on probing a single naked core-sized
logic gate, I have no encouragement for you there.

Yeah, I'm definitely interested in it. In my grad work I analyze techniques for gate delay measurement. To elucidate this matter completely I wanted to double check whether oscilloscope approach is possible or not.
By the way, ROs are good enough and I focused on them in my work.
As far as I know, FET probes are only suitable for measuring I/V curves or something static. HF probes seem interesting, but if 50 Ohm load is required on the gate side it won't be a good idea.
 

For super high frequency stuff (which my last
company was into, though I was not) the hot test
ticket seemed to be membrane probes (which could
be designed to maintain 50 ohm impedance all the
way to the DUT pads).

But there you are, back at 50 ohms again.

The problem is that no core gate can drive 50 ohms
meaningfully and would be cooking if it tried.

It might be practical to (say) make a resistor divider
that turns (say) a 0-1.0V swing into a 0-50mV swing
into 50 ohms and loads the gate with 1Kohm. That
might be tolerable power dissipation viz self heating.
Driving the gate with 50 ohms should not be a prob.

But have to consider, and de-embed, the relatively
huge pad capacitance relative to the normal logic
loads.

Maybe membrane probe vendors have good info on
non-RF (non-S-param) test uses.
 
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