Adjoint based optimization to enable single mirror optic for extreme ultraviolet lithography

Greggory Scranton

EECS Department
University of California, Berkeley
Technical Report No. UCB/EECS-2017-229
December 15, 2017

http://www2.eecs.berkeley.edu/Pubs/TechRpts/2017/EECS-2017-229.pdf

Traditionally, aberration correction in extreme ultraviolet (EUV) projection optics requires the use of multiple lossy mirrors, which results in prohibitively high source power requirements. We analyze a single spherical mirror projection optical system where aberration correction is built into the mask itself, through Inverse Lithography Technology (ILT). By having fewer mirrors, this would reduce the power requirements for EUV lithography. We model a single spherical mirror system with orders of magnitude more spherical aberration than would ever be tolerated in a traditional multiple mirror system. By using ILT, (implemented by an adjoint-based gradient descent optimization algorithm), we design photomasks that successfully print test patterns, in spite of these enormous aberrations. This mathematical method was tested with a 6 plane wave illumination source. Nonetheless, it would have poor power throughput from a totally incoherent source.

Advisor: Eli Yablonovitch


BibTeX citation:

@mastersthesis{Scranton:EECS-2017-229,
    Author = {Scranton, Greggory},
    Title = {Adjoint based optimization to enable single mirror optic for extreme ultraviolet lithography},
    School = {EECS Department, University of California, Berkeley},
    Year = {2017},
    Month = {Dec},
    URL = {http://www2.eecs.berkeley.edu/Pubs/TechRpts/2017/EECS-2017-229.html},
    Number = {UCB/EECS-2017-229},
    Abstract = {Traditionally, aberration correction in extreme ultraviolet (EUV)
projection optics requires the use of multiple lossy mirrors, which results in
prohibitively high source power requirements. We analyze a single spherical mirror
projection optical system where aberration correction is built into the mask itself,
through Inverse Lithography Technology (ILT). By having fewer mirrors, this
would reduce the power requirements for EUV lithography. We model a single
spherical mirror system with orders of magnitude more spherical aberration than
would ever be tolerated in a traditional multiple mirror system. By using ILT,
(implemented by an adjoint-based gradient descent optimization algorithm), we
design photomasks that successfully print test patterns, in spite of these enormous
aberrations. This mathematical method was tested with a 6 plane wave illumination
source. Nonetheless, it would have poor power throughput from a totally incoherent
source.}
}

EndNote citation:

%0 Thesis
%A Scranton, Greggory
%T Adjoint based optimization to enable single mirror optic for extreme ultraviolet lithography
%I EECS Department, University of California, Berkeley
%D 2017
%8 December 15
%@ UCB/EECS-2017-229
%U http://www2.eecs.berkeley.edu/Pubs/TechRpts/2017/EECS-2017-229.html
%F Scranton:EECS-2017-229