4 ms·

Interference of a 193nm wave can only yield a 193nm wave, it being additive. I'm curious what is done to get to 7nm.

anonytrary 9y ago
Could a subtractive mechanism work? For example, if you want to create a 5nm bump, but you only have a 20nm thick tool to draw bumps, you could draw "everything except the 5nm bump". In other words, draw a 20nm thick annulus around a 5nm center, thereby having achieved the desired result: drawing a 5nm object with a 20nm tool. That's a toy example, idk quite how that would translate to photolithography.
- josaka 9y ago
  They do something like this with sidewall patterning: https://en.wikipedia.org/wiki/Spacer_patterning https://en.wikipedia.org/wiki/Spacer_patterning
- dogma1138 9y ago
  It’s not a one off etch it’s a series of etchings and depositions of material over the surface until you get the final product.
baybal2 9y ago
Self aligning quadruple patterning https://blog.lamresearch.com/wp-content/uploads/2015/12/Self-Aligned_Quad_Patterning.jpg https://blog.lamresearch.com/wp-content/uploads/2015/12/Self... Read more here https://en.m.wikipedia.org/wiki/Multiple_patterning https://en.m.wikipedia.org/wiki/Multiple_patterning https://youtu.be/d5uoklMx63I https://youtu.be/d5uoklMx63I
dogma1138 9y ago
As I said nothin actually goes down to 7nm but they use multiple patterning basically the exposure or lack there off can be much finer than the wavelength of the light because they expose it multiple times through slightly different patterning. Also ICs are made hang both subtractive and additive processes basically a series of exposures etches and depositions which at the end create the final product. To put it simply if you have a 5mm mill you can still make a <5 mm feature by milling around say a 1mm square.
- contrarian_ 9y ago
  ELI5 why is the multiple patterning not additive in the same way as interference?
  - QAPereo 9y ago
    You’re not taking the resist mask into account, or multiple passes. https://en.m.wikipedia.org/wiki/Multiple_patterning https://en.m.wikipedia.org/wiki/Multiple_patterning Not sure how to ELI5 it though...
  - posterboy 9y ago
    I have no idea really, but the above explanation implies reminds me on the double slit experiments. Also, inference is additive in the amplitude, but phase shifts much smaller than the wavelengths are used in interferometers to measure layer depths. https://en.wikipedia.org/wiki/Double-slit_experiment https://en.wikipedia.org/wiki/Double-slit_experiment https://en.wikipedia.org/wiki/List_of_types_of_interferometers https://en.wikipedia.org/wiki/List_of_types_of_interferomete...
    - dogma1138 9y ago
      I believe it’s mostly single slit and diffraction, light can pass through holes smaller than its wavelength but even that isn’t needed just yet, nanophotonics will be the next step tho. http://web.eecs.utk.edu/~jaynewu/Teaching/resolution.pdf http://web.eecs.utk.edu/~jaynewu/Teaching/resolution.pdf
  - dogma1138 9y ago
    Forget the patterning and interference for a second. The process isn’t a one off resist mask and etches you have a series of expose, etch and disposition passes over the material. The actual feature size can be made much smaller because it can be the product of multiple exposures, etches and depositions. So let’s say that the smallest feature size you have from a single mask is 200nm by using multiple masks and exposure you basically can build small features which are defined by the overlapping lit or shadow areas of the mask. These features can also be ethched in a controlled manner to create even finer feature size. To simplify it even further take make a shadow of an open palm with fingers fully extended so the gap between the fingers is the largest as you can make it and make an outline of the lit areas, now shift your hand slightly to the left or the right and make an outline of the shadowed area and subtract that from the previous outline it's now smaller without you having to change the size of your pattern or the wavelength of the light.

Could a subtractive mechanism work? For example, if you want to create a 5nm bump, but you only have a 20nm thick tool to draw bumps, you could draw "everything except the 5nm bump". In other words, draw a 20nm thick annulus around a 5nm center, thereby having achieved the desired result: drawing a 5nm object with a 20nm tool. That's a toy example, idk quite how that would translate to photolithography.

josaka 9y ago
They do something like this with sidewall patterning: https://en.wikipedia.org/wiki/Spacer_patterning https://en.wikipedia.org/wiki/Spacer_patterning
dogma1138 9y ago
It’s not a one off etch it’s a series of etchings and depositions of material over the surface until you get the final product.

baybal2 9y ago

Self aligning quadruple patterning https://blog.lamresearch.com/wp-content/uploads/2015/12/Self-Aligned_Quad_Patterning.jpg https://blog.lamresearch.com/wp-content/uploads/2015/12/Self... Read more here https://en.m.wikipedia.org/wiki/Multiple_patterning https://en.m.wikipedia.org/wiki/Multiple_patterning https://youtu.be/d5uoklMx63I https://youtu.be/d5uoklMx63I

dogma1138 9y ago

As I said nothin actually goes down to 7nm but they use multiple patterning basically the exposure or lack there off can be much finer than the wavelength of the light because they expose it multiple times through slightly different patterning. Also ICs are made hang both subtractive and additive processes basically a series of exposures etches and depositions which at the end create the final product. To put it simply if you have a 5mm mill you can still make a <5 mm feature by milling around say a 1mm square.

contrarian_ 9y ago
ELI5 why is the multiple patterning not additive in the same way as interference?
- QAPereo 9y ago
  You’re not taking the resist mask into account, or multiple passes. https://en.m.wikipedia.org/wiki/Multiple_patterning https://en.m.wikipedia.org/wiki/Multiple_patterning Not sure how to ELI5 it though...
- posterboy 9y ago
  I have no idea really, but the above explanation implies reminds me on the double slit experiments. Also, inference is additive in the amplitude, but phase shifts much smaller than the wavelengths are used in interferometers to measure layer depths. https://en.wikipedia.org/wiki/Double-slit_experiment https://en.wikipedia.org/wiki/Double-slit_experiment https://en.wikipedia.org/wiki/List_of_types_of_interferometers https://en.wikipedia.org/wiki/List_of_types_of_interferomete...
  - dogma1138 9y ago
    I believe it’s mostly single slit and diffraction, light can pass through holes smaller than its wavelength but even that isn’t needed just yet, nanophotonics will be the next step tho. http://web.eecs.utk.edu/~jaynewu/Teaching/resolution.pdf http://web.eecs.utk.edu/~jaynewu/Teaching/resolution.pdf
- dogma1138 9y ago
  Forget the patterning and interference for a second. The process isn’t a one off resist mask and etches you have a series of expose, etch and disposition passes over the material. The actual feature size can be made much smaller because it can be the product of multiple exposures, etches and depositions. So let’s say that the smallest feature size you have from a single mask is 200nm by using multiple masks and exposure you basically can build small features which are defined by the overlapping lit or shadow areas of the mask. These features can also be ethched in a controlled manner to create even finer feature size. To simplify it even further take make a shadow of an open palm with fingers fully extended so the gap between the fingers is the largest as you can make it and make an outline of the lit areas, now shift your hand slightly to the left or the right and make an outline of the shadowed area and subtract that from the previous outline it's now smaller without you having to change the size of your pattern or the wavelength of the light.