Pseudo Numerical Modeling of Sub-Micron LOCOS Structure
In this work, a simplified numerical approach is taken with the focus
on parameterization of experimental data used in the prediction of
LOCOS shapes. The approach can avoid many difficulties that arise in
both the formulation and general numerical solution of the oxidation
problem. It is labeled a quasi-3D method since it includes solution of
three-dimensional oxidant diffusion and the subsequent parameter
extraction of the three-dimensional effects on the oxidation process.
The method does not specifically calculate the three-dimensional oxide
growth and flow fields but rather it parameterizes a separate
two-dimensional solution and manipulates the results in
three-dimensions based on the oxidant distribution. The result is the
creation of a final three-dimensional LOCOS structure which includes
parameterized results of the fully three-dimensional oxidant
diffusion. While there are limitations to the method in terms of
physical correctness, the results when compared to experiment are
sufficiently encouraging that application for scaling of more complex
isolation structures seems feasible.
The mask structures used for characterization of two- and
three-dimensional oxidation effects are introduced. The surface mesh
generation algorithm for the numerical analysis of three-dimensional
oxidant diffusion is also included. The experimental results are
studied based on a two-dimensional window/mask test structure. Finally
the three-dimensional oxidation effects such as line edge encroachment
phenomena are surveyed based on top view SEM photographs. Comparisons
of two- and three-dimensional pad-oxide punchthrough and field oxide
thinning effects are made using both simulations and experiments.
Hwasik Park
(hspark@gloworm.Stanford.EDU)
AEL 209
Integrated Circuits Laboratory
Stanford University
Stanford, CA 94305-4055