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Niels Geypen
| Speaker: |
Niels Geypen
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| Date: |
Monday October 11, 2010
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| Title: |
Optimization of
resist profiles using resist modeling techniques
(Master's
thesis presentation)
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Abstract
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Photolithography
is a complex procedure consisting of numerous successive steps. This
thesis focuses on three steps: the exposure, the post exposure bake and
the subsequent development. In order to get a deeper insight in which
physical phenomena are a dominant factor, each step is simulated
separately.
During the exposure a photoactive compound within the resist chemically
reacts to incident light. Hence the model for the exposure contains the
incident light in an optical part and the chemical reaction in a
bleaching part. The optical part mainly consists of solving a system of
Maxwell equations. Initially the optical properties are homogeneous in
layers and in this case an analytical solution is deduced. The
bleaching within the resist will be addressed with Dill's model.
Throughout the post exposure bake the wafer is heated, resulting in
diffusion of the photoactive compound. This diffusion can be
mathematically described by Fick's laws. The resulting boundary value
problem is numerically solved with a finite difference method.
During development a chemical is added and dissolves the exposed areas
within the resist. The rate of the development is determined by Mack's
a-model. The advancement of the developed surface is described using
the level set method. The related advancing front is numerically
tracked by the fast marching method.
The combination of the discretization methods and numerical solvers for
all steps applied to actual test cases matches the related physical
outcome.
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