Local Heating During Electron Beam Patterning of Lithography Masks
Date
1998Author
Vicum, Lars
Publisher
University of Wisconsin-Madison
Metadata
Show full item recordAbstract
The semiconductor industry is constantly seeking to improve the performance of integrated
circuits by drastically increasing the density and reducing the pattern feature size. Accurate
patterning of advanced lithography masks is a key issue in the production of integrated
circuits with sub-0.13 ?m feature size. Predicting and subsequently correcting for the errors
produced in writing the pattern is essential.
One source of pattern error is the heating of the lithography mask during the electron beam
patterning process. Mask heating during writing causes pattern errors through the resist
stress relief, local over- or under-development of the resist due to the temperature dependent
resist sensitivity, and by thermal distortions. These pattern errors depend upon the transient
temperature distribution in the mask during the electron-beam-writing process.
In this thesis local mask temperature profiles are predicted for various writing conditions.
The local mask heating of an optical reticle during writing of a single electron beam flash is
analyzed. The contribution of multiple electron beam flashes on an X-ray mask to global
mask heating during writing is determined by calculating the transient mask temperature
profile during the patterning process using a finite element software package.
Two levels of model are compared. A very detailed small-scale model of pattern writing is
developed with the element size that of a pattern shape. An averaging large-scale model in
which the electron beam energy is distributed over many elements is also developed. The
averaging technique is often used in thermal analyses to reduce computation time. The
average temperature rise and local maximum of the two methods are compared. It is found
that the averaging technique predicts the average temperature rise accurately, but
significantly under-predicts the maximum local temperatures.
A procedure for developing thermal models with high accuracy, minimal number of
elements, and reasonable calculation time is described. Design rules for finite element
models used for the simulation of local mask heating are presented.
Subject
Thesis (M.S.)--University of Wisconsin--Madison, 1998.
Dissertations Academic Mechanical Engineering.
University of Wisconsin--Madison. College of Engineering.
Permanent Link
http://digital.library.wisc.edu/1793/7708Description
Under the supervision of Professors William Beckman and John Mitchell; 135pp.
Citation
Vicum, L. (1998). Local Heating During Electron Beam Patterning of Lithography Masks. Master's Thesis, University of Wisconsin-Madison.