[[extropy-chat] diffraction limit

Dan Clemmensen dgc at cox.net
Sat May 29 14:40:41 UTC 2004


scerir wrote:

>From: "Dan Clemmensen" 
>
>  
>
>>>If lambda is the (de Broglie) wavelenght
>>>of an individual photon, using N entangled
>>>(correlated) photons it could be possible
>>>to imagine to reduce the "diffraction limit" 
>>>and also the minimum feature size of chips, 
>>>since, in this case, the wavelenght might 
>>>be lambda/N.
>>>      
>>>
>
>  
>
>>I don't know if you can do this "in bulk." if you must use a single 
>>beam, you lose the advantage of parallel simultaneous exposure, and the 
>>exposures then take too long for efficient production. This is why 
>>electron-beam lithography is not used for production. The wavelength of 
>>an electron is quite small, so an electron beam can "draw" finer lines 
>>than a light source can. E-beams are used to make the phase-shift masks. 
>>The masks are then used to make (many, many) semiconductor devices.
>>    
>>
>
>I do not know either. Using entangled photons (usual SPDC tech)
>it would be possible to achieve 20nm features (Boto et al.).
>
>But, if the diffraction limit is "violated" by entangled particles, 
>it would be possible, at least in principle, to use entangled 
>electrons (or entangled kaons :-)) to make better phase-shift
>masks. I mean, a beam made of entangled electrons.
>
>  
>
Direct E-beam lithography is used experimentaly, but not for production. 
When using this technology, the beam feature size is not the system 
constraint. The system constraint comes from the materials. This means a 
better beam will not achieve smaller features. I think the E-beam 
diffraction limit is small enough for atomic precision?

The precision of the current phase-shift masks is also not the limiting 
factor. The current limiting factor is the wavelength of the bulk light 
source that can support parallel exposure. The industry tried to go from 
193nm to 153nm, but this required CaF lenses, and these lenses turned 
out to be impossible to build in production quantities. The industry 
then began looking at other tricks. The current new technology is 
"immersion imaging" wherein the air between the lens and the substrate 
is replaced with water. This allows for tighter focusing.

Please note that I am not an expert on this, I just read EETimes a lot.



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