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guiding_light
It has been a long time since I posted my thoughts on lithography.

Recently, my group has been investigating thin e-beam resist for better resolution. It turns out the thickness is not independent.

In fact, if you assume the fraction of non-absorbed radiation goes as exp(-az), where a is the absorption coefficient, and z is the depth thickness, you find that your dose must increase for thinner resist, i.e. 1/[1-exp(-az)]. At the same time, thinner resist lets more radiation reach underlying layers and substrate, leading to more damage. The damage increase factor with compensated dose is exp(-az)/[1-exp(-az)].

It works out to roughly inverse proportion to resist thickness, i.e., if you have 70% the resist thickness, you have to add nearly 40% your dose, which increases the damage more than 40%.

The added damage is bad for the product, the extra power consumed for extra dose is bad for the environment.

There should be less green for technology that's becoming less green.
gongii
As much sense as zapping the X-ray patient wearing the thinner shield with higher radiation dose.
rpenner
The Original Poster is talking about fabricating computer chips, not irradiating people.
gongii
QUOTE (rpenner+Apr 7 2009, 08:25 PM)
The Original Poster is talking about fabricating computer chips, not irradiating people.

I screwed up the analogy a little, should be something like someone wearing a thinner radiation suit staying longer near the radiation (like in a nuclear reactor).
guiding_light
QUOTE (gongii+Apr 8 2009, 01:41 PM)
I screwed up the analogy a little, should be something like someone wearing a thinner radiation suit staying longer near the radiation (like in a nuclear reactor).

The negative outcome is analogous, the purpose is not related. In lithography, the thinner film requires the longer exposure, and this is more detrimental to the underlying layers and substrate. The protective radiation shield on the other hand will never be thin.
thickfilm
you'd need at least 400 nm of something to shield from this radiation. That's high material cost just for protection...
lzurha
i wounder if hanging up side down an clearing lymph nodes that way can help heal radition piosioning

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