Ned,

First off, remember that demagnification doesn't reduce fluence
(energy per unit area). For two spot sizes of equal area, the spot
created from the higher demag will have more energy per unit area. If
you neglect losses in the beam path and through different objectives,
the amount of energy present at the image plane is the same as that at
the mask plane. So, if you have a 10 mm square mask, and demagnify it
to a 1 mm square, that will have less energy than a 20 mm mask
demagnified to the same 1 mm square, since the 20 mm mask has more
photons  / energy passing through it, just by virtue of size (assuming
you don't exceed the width of the original beam, etc). The ratio is
p_i = p_m * d^2, where p_i is the image plane fluence (energy
density), p_m is the mask plane fluence, and d is the demagnification.

With that in mind: how deeply do you want to etch, how long is the 1
micron line you want to write, what material do you want to write
into, what wavelength do you want to use (if you know), and what total
amount of time are you willing to spend per pattern? If you want to go
too deep, you're probably going to be limited by aspect ratio related
issues (material removal, etc) before power becomes a real concern. If
you answer those questions, that will be enough info to see if it's
doable.

Kevin P Nichols, Ph.D.

Postdoctoral Scholar
Ismagilov Group
Department of Chemistry
Gordon Center CIS E305
University of Chicago
929 East 57th Street
Chicago, IL 60637

E: kpnichols@uchicago.edu
T: 773-834-8474
F: 773-834-3544

On Mon, Apr 19, 2010 at 9:44 AM, Ned Flanders  wrote:
> Hi all,
>
> I am rather familiar with laser ablation, but my beliefs have been
> somewhat shaken recently, after talking with a laser processing
> company representative: I believed that excimer laser's large-area
> beam profile made them unsuitable for scribing, and that the only way
> to create narrow channels or vias, was by placing a mask to reduce the
> beam profile, and then demagnify what's left - but that would reduce
> the pulse energy drastically. Hence, not the best choice for deep
> scribing of some materials, where a DPSS is much better.
> This guy, however, stated taht an excimer beam can be focused to a
> very tiny spot.
>
> Wht gives? Is my definition of tiny (~1 um) different from his?
> (consider that a DPSS laser has an almost pure TEM00 beam mode, while
> the excimer beam is non-coherent, and much, much wider.
>
> Thanks in advance!
>
> Ned