photoelectric lithography

[Jamie M]

Hi,

I had an idea for a new type of lithography, that uses a photocathode
to convert a 2D light image into a 2D electron beam image which is then
accelerated and focused down smaller with electromagnetic lenses and
projected onto the silicon wafer down to smaller feature sizes than the
light image can make since the electron wavelength is smaller than the
lights wavelength.

cheers,
Jamie

 

[Jamie M]

That's basically how the original electron microscope worked (before the
invention of the SEM), only backwards. There are a lot of difficulties
with it, especially in maintaining decent image correction over a large
field.

Hi,

I guess its like a transmission electron microscope in reverse, I think
there are some modern aberration corrected electron optics that seem
pretty amazing, not sure how they work exactly, but can do spatial
resolution down to 0.05nm apparently.

http://en.wikipedia.org/wiki/Transmission_Electron_Aberration-corrected_Microscope

cheers,
Jamie

 

[Jamie M]

The best lithography is e-beam, and it's used to make masks. But the
beam currents are limited by space-charge distortion, so throughput is
too low for volume production.

The new-new thing is EUV, 13.4 nm light:

http://www.cymer.com/euv_source/

http://www.cymer.com/plasma_chamber_detail/

I saw a presentation on the Zeiss lens that's used on these things. It
looks more like a big diesel engine than any sort of lens. It does
something like 4:1 reduction from the mask to the wafer. There are no
lenses at this wavelength, so it works entirely with grazing-incidence
metal mirrors. I still can't understand how that's possible.

I saw a strange lens recently too, for terahertz light, it is the same
shape as a glass convex lens, but it is made out of teflon, I guess it
works by changing the permeability and permittivity of free space?

cheers,
Jamie

 

[[email protected]]

The best lithography is e-beam, and it's used to make masks. But the
beam currents are limited by space-charge distortion, so throughput is
too low for volume production.

IBM was going to do direct-write E-beam lithography. They even spent $1B on
their own synchrotron (the only privately owned synchrotron) for the source.
....then some wise-ass invented the phase-shift mask.

 

[[email protected]]

I saw a strange lens recently too, for terahertz light, it is the same
shape as a glass convex lens, but it is made out of teflon, I guess it
works by changing the permeability and permittivity of free space?

Of course not. You can't change free space. You can make it not so free,
though. ;-)

 

[[email protected]]

The ASTC (Fishkill Bldg 600) synchrotron was for X-ray litho, not
e-beam. I used to collaborate with some folks up there.

You're right. <slap!>

They were doing direct-write E-Beam before that (for a while, anyway).

 

[Jamie M]

The best lithography is e-beam, and it's used to make masks. But the
beam currents are limited by space-charge distortion, so throughput is
too low for volume production.

Hi,

The throughput for e-beam is limited because it is scanning instead of
projecting a 2D image, but if you project a 2D electron beam image
the throughput could be the same as photo lithography and the beam
current density equal (or less) than scanning e-beam.

cheers,
Jamie