The deposition of
thin layers and the etching of trenches are fundamental tasks for the
production of memory cells, power MOSFETs, and backend stacks. The aim
of the current work is to study topography processes, i.e., etching and
deposition processes, on genuinely three-dimensional structures. The
trenches studied are part of the manufacturing process of power
MOSFETs, where voidless filling must be achieved. Another area of
application is the capacitance extraction in interconnect structures,
where the deliberate inclusion of voids serves the purpose of reducing
overall capacitance. Furthermore, these simulations make it possible to
analyze the variations on the feature scale depending on the position
of the single trench on the wafer and in the reactor.
To that goal, the three-dimensional version of our topography simulator
ELSA (Enhanced Level Set
Applications) was completed. It includes narrow banding and a fast
marching algorithm for the suitable extension of the speed function.
The particle trajectories in the simulation domain are tracked via an
iterative radiosity formulation. The ion angular distribution function
entering the simulation domain and the location of the ion sources are
determined by the plasma, and this information enters the feature scale
simulation as a physical boundary condition. Depending on the energy of
the particles, reflection happens either in the specular or luminescent
regime.
Despite the magnitude of computational resources available today, care
had to be taken in the choice of algorithms to achieve reasonable times
for three-dimensional simulations.
Simulation applications are, e.g., the etching of T- and H-shaped
trench junctions and their filling with silicon dioxide. These
geometries require truly three-dimensional simulations which were used
for optimizing the manufacturing steps of power MOSFETs for automotive
applications. The simulator was found to be applicable to a wide range
of both etching and deposition problems and to yield predictive
simulations within a reasonable time frame.
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