Electrical Engineering
      and Computer Sciences

Electrical Engineering and Computer Sciences

COLLEGE OF ENGINEERING

UC Berkeley

Simulation of Contrast Enhanced Lithography

R.A. Ferguson

EECS Department
University of California, Berkeley
Technical Report No. UCB/ERL M87/42
1987

http://www.eecs.berkeley.edu/Pubs/TechRpts/1987/ERL-87-42.pdf

The SAMPLE program has been modified to include contrast enhanced lithography. The contrast enhancement material (CEM) and the underlying photoresist are bleached simultaneously to include coupled exposure effects. The CEM is modeled using Dill's model for positive photoresist and a bleachable index of refraction. An energy increment selection routine has been implemented to allow proper convergence for contrast enhanced lithography. An analytical solution to Dill's equations by Babu and Barouch is included for increased speed and reduced storage. The modified program is used to compare several different lithographic techniques to CEM. Simulation shows that the resolution capability and exposure latitude of CEM is superior to single layer photoresists. The CEM and bilayer resist (PCM) processes are equivalent in resolution, linewidth control, and proximity effects both experimentally and in simulation on silicon substrates. Experimentally, however, CEM suffers from a much larger proximity effect than PCM on aluminum substrates which is not seen in simulations. Several factors which are not included in the simulation such as lateral scattering from the substrate and flare may be responsible.


BibTeX citation:

@techreport{Ferguson:M87/42,
    Author = {Ferguson, R.A.},
    Title = {Simulation of Contrast Enhanced Lithography},
    Institution = {EECS Department, University of California, Berkeley},
    Year = {1987},
    URL = {http://www.eecs.berkeley.edu/Pubs/TechRpts/1987/902.html},
    Number = {UCB/ERL M87/42},
    Abstract = {The SAMPLE program has been modified to include contrast enhanced
lithography. The contrast enhancement material (CEM) and the
underlying photoresist are bleached simultaneously to include
coupled exposure effects. The CEM is modeled using Dill's model 
for positive photoresist and a bleachable index of refraction. An
energy increment selection routine has been implemented to allow
proper convergence for contrast enhanced lithography. An analytical
solution to Dill's equations by Babu and Barouch is included for
increased speed and reduced storage. The modified program is used to
compare several different lithographic techniques to CEM. Simulation
shows that the resolution capability and exposure latitude of CEM is
superior to single layer photoresists. The CEM and bilayer resist
(PCM) processes are equivalent in resolution, linewidth control,
and proximity effects both experimentally and in simulation on
silicon substrates. Experimentally, however, CEM suffers from a much
larger proximity effect than PCM on aluminum substrates which is
not seen in simulations.  Several factors which are not included
in the simulation such as lateral scattering from the substrate and
flare may be responsible.}
}

EndNote citation:

%0 Report
%A Ferguson, R.A.
%T Simulation of Contrast Enhanced Lithography
%I EECS Department, University of California, Berkeley
%D 1987
%@ UCB/ERL M87/42
%U http://www.eecs.berkeley.edu/Pubs/TechRpts/1987/902.html
%F Ferguson:M87/42