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3.1.2 Masks
The next step is applying patterned layers onto the wafer. As already indicated
in the introduction above, this can be done with geometric primitives. For
squares and circles the side length or the diameter has to be specified, for
rectangles and ellipses both length and width or a pair of diameters are
needed. Moreover the primitive can be positioned by shifting the two lateral
coordinates of its center and the thickness of the mask has to be specified. As
an example, Fig. 3.2 shows a circular pattern shifted away from the center
of the simulation domain.
Figure 3.2:
Circular pattern at an arbitrary position on the wafer.
![\begin{figure}\begin{center}
\psfrag{1.2 \247m}[][cb][1.7]{{1.2 \mbox{$\mu\math...
...49\textwidth}{!}{\includegraphics{eps-geo/circle.eps}}}
\end{center}\end{figure}](img128.gif) |
By repeated calls of the masking operation, the primitives can be combined to
form more complex structures. This is very helpful for the generation of simple
masks. If very complex patterns are to be generated, combining the primitives
gets confusing. How layout and lithography tools can then be used as alternative
will be introduced later in Chapter 4. For the moment, however, let's
concentrate on the basics of the solid modeling tool.
Fig. 3.3 shows how four circles -- three thereof are depicted on the
left hand side of the figure -- plus a rectangle form a smoothened H-like
pattern. In the following the pattern will be inverted. Therefor the structure
will be filled with a different material up to a certain level and the first
material will be stripped.
Figure 3.3:
Combined geometric primitives forming simple masks.
![\begin{figure}\begin{center}
\psfrag{1.2 \247m}[][cb][1.7]{{1.2 \mbox{$\mu\math...
...textwidth}{!}{\includegraphics{eps-geo/rectangle.eps}}}
\end{center}\end{figure}](img129.gif) |
Prev: 3.1.1 Defining a Simulation
Up: 3.1 Solid Modeling
Next: 3.1.3 Filling
W. Pyka: Feature Scale Modeling for Etching and
Deposition Processes in Semiconductor Manufacturing