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20nmon
21st April 2009 - 05:12 PM
I am checking out the CD vs dose model for HSQ @ 100 kV:

http://www.nanolithography.gatech.edu/HSQ_dose.html

I don't understand one thing. How come if 60 nm is no resolution problem for the beam, increasing the dose changes the CD?

I don't think it's backscatter because the electrons would have to travel much farther scale to backscatter significant (like tens of microns).
nanomvp
21st April 2009 - 05:28 PM
Maybe the beam spreads by scattering.
guiding_light
21st April 2009 - 05:41 PM
QUOTE
Maybe the beam spreads by scattering.


Yes, but there is more detail to it.

QUOTE (->
QUOTE
Maybe the beam spreads by scattering.


Yes, but there is more detail to it.

I don't understand one thing. How come if 60 nm is no resolution problem for the beam, increasing the dose changes the CD?

I don't think it's backscatter because the electrons would have to travel much farther scale to backscatter significant (like tens of microns).


It's true that 100 keV electrons travel very far, virtually straight through the HSQ at the feature edge. So they are too far away by the time they scatter.

The scattering that is relevant is the low energy electrons released by the incident electrons. These are the secondary electrons. Most of them have very low energies, below 10 eV.

So this CD vs. dose model is a very good proof of how far they can travel and affect the CD. Looks like up to at least 50 nm from each side. If you brought two features this close, you would start seeing this short-range proximity effect.
nanomvp
22nd April 2009 - 04:19 AM
It should depend on how much energy the fast electron lose in the resist. Like some keV.
guiding_light
22nd April 2009 - 08:08 AM
QUOTE (nanomvp+Apr 22 2009, 04:19 AM)
It should depend on how much energy the fast electron lose in the resist. Like some keV.

It's very likely to lose ~ keV, but the energy is lost gradually (eV/angstrom) rather than something choppy like keV/micron. Otherwise thin resists won't even work. The overwhelming majority of secondary electrons are low-energy (nominally 50 eV or less, peaking below 5 eV), though you can certainly pick out a few Auger electrons here and there.
guiding_light
22nd April 2009 - 08:28 AM
Another way to think of it is even keV electrons slow down in the material gradually by the emission of secondary electrons at a rate on the order of 10 eV/nm.
20nmon
22nd April 2009 - 03:35 PM
QUOTE (guiding_light+Apr 22 2009, 08:08 AM)
It's very likely to lose ~ keV, but the energy is lost gradually (eV/angstrom) rather than something choppy like keV/micron. Otherwise thin resists won't even work. The overwhelming majority of secondary electrons are low-energy (nominally 50 eV or less, peaking below 5 eV), though you can certainly pick out a few Auger electrons here and there. Another way to think of it is even keV electrons slow down in the material gradually by the emission of secondary electrons at a rate on the order of 10 eV/nm.

Thanks to nanomvp and guiding light for the discussion. CD vs does is kind of like a clue to the real resolution limit, cool...
nanomvp
23rd April 2009 - 11:50 AM
What do you know my excolleague at HST published a dose model for HSQ very similar to the link above. It is a very dramatic range indeed.

The 100 keV beam spot size was less than 10 nm, so I do think it is the secondary electrons modulating the CD.

It does lead me to wonder, if we can only control our placement of the primary electrons, do we really have any real control over the secondary electrons? I think even the assumption of fixed secondary/primary ratio is extremely questionable.

That the case, these CD vs. dose models can't be set in stone. I am beginning to doubt their inherent utility now.
nanomvp
23rd April 2009 - 01:15 PM
QUOTE
What do you know my excolleague at HST published a dose model for HSQ very similar to the link above. It is a very dramatic range indeed.

The 100 keV beam spot size was less than 10 nm, so I do think it is the secondary electrons modulating the CD.


Microelectronic Engineering
Volumes 73-74, June 2004, Pages 547-552
guiding_light
25th April 2009 - 09:40 AM
QUOTE (nanomvp+Apr 23 2009, 11:50 AM)
What do you know my excolleague at HST published a dose model for HSQ very similar to the link above. It is a very dramatic range indeed.

The 100 keV beam spot size was less than 10 nm, so I do think it is the secondary electrons modulating the CD.

It does lead me to wonder, if we can only control our placement of the primary electrons, do we really have any real control over the secondary electrons? I think even the assumption of fixed secondary/primary ratio is extremely questionable.

That the case, these CD vs. dose models can't be set in stone. I am beginning to doubt their inherent utility now.

Secondary electron yield and rangeare not specified or tabulated as fixed numbers. The random direction and energy following each energy exchange event also fits a distribution. CD vs dose models are frequently updated for this randomness.

nanomvp
1st May 2009 - 04:52 PM
Huh, where is the moderator to remove these Fairys and their useless, uninsightful feedback?
rpenner
1st May 2009 - 07:39 PM
Please see my May Day post.

I am experimenting with non-dictatorial means of moderating.
nanomvp
10th May 2009 - 03:38 AM
QUOTE (rpenner+May 1 2009, 07:39 PM)
Please see my May Day post.

I am experimenting with non-dictatorial means of moderating.

It doesn't seem a very effective way.

Plus New members receive but do not give feedback. Not very appropriate either. New opinions obviously matter more than old ones for supposedly progressive forums like physorg.
Guest_guest
16th May 2009 - 10:58 PM
What is the typical charging during electron beam lithography? I mean, we have backscattered electrons and secondaries leaving the surface, that tends to charge the resist positively, right?
rpenner
17th May 2009 - 12:08 AM
Actually, opinions don't matter to me a whit.

It's the counter-factual trash that gets to me.

Logic that ignores theorems. Math that wants to work with the reals but ignores Cantor and Dedekind. Physics that ignores Galileo, Newton, Fresnel, Fizeau or the evidence summarized by C.M. Will. Cosmology that ignores Hubble, WMAP, stellar evolution and elemental abundances.

And all bold claims without foundation.

Progressive is desirable, but there's a little bit of work to be done on an idea before you start proclaiming that your the next Napoleon or Agatha Heterodyne.
Applied Materials
17th May 2009 - 02:59 AM
QUOTE (Guest_guest+May 16 2009, 10:58 PM)
What is the typical charging during electron beam lithography? I mean, we have backscattered electrons and secondaries leaving the surface, that tends to charge the resist positively, right?


It was recognized early on that the departing secondary electrons lead to positive charging. However, the emphasis was on deflection of the incident electron beam. In actuality, the secondary electrons generated in the resist are much more sensitive and deflected much more strongly by local charging.

There is a paper in the mask products section at the Applied Materials site.

"Reduction of beam-induced pattern placement errors inMEBES®systems"
fog
15th September 2009 - 04:54 PM
So how many nm deflection should beam charging cause? 5nm? 10 nm? Unpredictable?
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