From Newsgroup: sci.electronics.design
On Sun, 31 May 2026 21:07:59 +1000, Bill Sloman <
bill.sloman@ieee.org>
wrote:
On 31/05/2026 1:26 pm, john larkin wrote:
On Sun, 31 May 2026 12:39:10 +1000, Bill Sloman <bill.sloman@ieee.org>
wrote:
On 31/05/2026 8:19 am, john larkin wrote:
On Sat, 30 May 2026 21:41:47 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@glen--canyon.com> wrote:
On Sat, 30 May 2026 16:19:18 +1000, Bill Sloman <bill.sloman@ieee.org> >>>>>> wrote:
When talking about the ASML EUV light source, John Larkin talked about >>>>>>> envisioning spherical balls of molten tin in a hurricane.
They'd rotate, so they wouldn't be spherical, become oblate spheres at >>>>>>> quite low rotational rates.
https://diposit.ub.edu/server/api/core/bitstreams/78365ce1-8c0c-46af-b48e-0a3432e3da7d/content
talks about rotating droplets of liquid helium as they move from a >>>>>>> oblate to an prolate shape.
The tin droplets are shot out of a tiny nozzle, squeezed out by some >>>>>> sort of piezo vibrator. I don't think they rotate much but they sure >>>>>> wobble.
I wonder if a polarised laser beam could have got the tin spheres to >>>>>>> spin faster and move into helpful shapes.
It's the sort of fundamental question John might have asked.
One big issue for tin droplet detection is that the sphere isn't a >>>>>> nice round sphere, but has multiple vibration modes. There is a mess >>>>>> of higher frequency ripples sloshing all over the liquid surface
scattering light everywhere. The detector output looks like a lot of >>>>>> noise.
If the droplets had been injected into a strong magnetic field, that
would have acted to damp the ripples. Make it a rotating magnetic field
and you'd have spinning droplets with fixed axis of rotation.
There are several drops in mid-air at once and when the giant CO2
laser hits one, the shock wave whacks all the incoming droplets and >>>>>> makes things worse. They call it fratricide.
The detector was all analog and had to be done fast. It couldn't be >>>>>> the classic constant-fraction discriminator that physicists love so >>>>>> much.
Why not? They can be pretty fast, but they do depend on delaying a
portion of the pulse.
Too noisy. A proper droplet detector lowpass filters the worst noise
and then finds the pulse centroid, over a serous range of pulse widths
and amplitudes.
It's really a statistical game.
You really do need to define what you mean by "too noisy".
Seems obvious. Any amount of noise it locating the droplet reduces
wafer fab rate, and costs money. A CFD assumes that every pulse is
identical in shape and is noise-free. Nice theory.
You seem to be claiming that the signal you are looking at has range of >pulse widths, and you have to hit your droplet with your laser shortly
after the signal has peaked, independent of the shape of the rising edge.
We want to hit the droplet dead center, regrdless of the optical
uncertanties.
Presumably you have one or more low powered light source illuminating
the volume where the tin droplet will appear, and several photodetectors >that can detect the light reflected off the droplet.
The droplet passed through a sheet laser and reflected back into a
single photodiode. That's what we had to work with.
If the droplet is vibrating - as you say it is - each detector will see
an occasional photon as the droplet grows, and stop seeing them as the >droplet flies beyond the illuminated space.
Summing the output of several detectors should give you a tolerably >well-behaved signal.
The droplets aren't moving all that fast, so we aren't talking about >nanosecond signal processing here.
One microsecond is a tolerable error.
Of course ASML has moved on in 20+ years. I think (from public
sources) that they are now actively steering the droplets into the
target zone and surely have better optics.
The process is interesting if horrendous. There's stuff online and no
doubt patents. Turns out that wafer throughput is worth a lot.
Many people are spending big bucks to supercede the tin droplet
lithography thing... including just giving up on Moore's Law.
Personally, I don't much need bigger or faster CPUs or DRAM and I
don't need 10 terabytes of solid-state drives in my PCs. Maybe digital semiconductors are like dishtowels and hammers now, good enough.
I would like a sane and stable operating system.
Analog chips and power semiconductors have a way to go still, but they
don't need nanometer features.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
--- Synchronet 3.22a-Linux NewsLink 1.2