[Libre-silicon-devel] OK. That happened (Funding)
eegerferenc at gmail.com
Fri Dec 18 02:50:06 CET 2020
I recently elaborated further on the optical considerations of the uLED
reticle topic. I put the results into the maskless litho repo as usual:
Please find errors in it...
I plan to prepare a thermomechanical/thermohydraulic FEM simulation
also, to study possible implementations of cooling.
On 12/12/2020 00:29, Staf Verhaegen wrote:
> Éger Ferenc schreef op vr 11-12-2020 om 22:34 [+0100]:
>> To counter this, illumination systems in steppers contain a
>> narrow-band filter (Bragg-filter or similar) to filter out exactly
>> one narrow spectral line (hence I-line and G-line), and additional
>> optics to eliminate off-axis components and increase coherence
>> (therefore, what reaches the reticle is more or less "laser-like",
>> highly coherent and monochromatic radiation with very narrow FWHM).
>> Also, the projection optics in the stepper is usually a "narrow-band"
>> system in terms of wavelength due to dispersion, and fine-tuned to
>> work only at the wavelength of the line it is specified for.
> It is true that old steppers contain spectral line filters; more
> recent steppers use monochromatic lasers.
> But what in lithography is actually done is to use off-axis
> illumination for resolution enhancement. In the extreme one can reach
> double the resolution over coherent illumination (0.25*λ/NA versus
> 0.5*λ/NA). More info on off-axis illumination:
> Off-axis illumination can be implemented by a second lens system
> before the light reaches the reticle where a pupil plane is present
> where one can insert the shape of the off-axis illumination one wants.
> Actual scanners from ASML (which I am familiar with) use more complex
> systems with so-called diffractive optical elements to optimize for
> other effects like lens aberrations, light intensity uniformity,
> minize effect of temperature expansion of materials, etc.
> Libresilicon-developers mailing list
> Libresilicon-developers at list.libresilicon.com
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