To demonstrate the capability of the overall lithography simulator
we present two simulation examples. The first application is the aerial image
simulation of an entire layout of a 4:16 multiplexer realized in
0.25 m technology (cf. Section 8.1). The aerial images
of four mask layers that are critical with respect to lithography
are calculated. Additionally, problematic layout parts are analyzed in
detail. Various illumination apertures as well as phase-shifting masks are
compared whether they can improve the imaging performance.
The second application is a rigorous study of the impact of topography
and defocus effects on the printing of a single contact hole
(cf. Section 8.2). Three differently shaped topographies
are investigated, namely a planar silicon substrate, a dielectric oxide
step, and a reflective a-silicon step, i.e., the step material
is amorphous silicon with optical properties similar to polysilicon.
The nonplanarity
seriously reduces the quality of the printed contact hole, whereby
the impact of the reflective a-silicon is stronger than that of the
dielectric oxide. Off-axis illumination forms are a common approach to achieve
a larger depth of focus. We compare the performance of three different
apertures, namely ideally coherent, partially coherent, and
quadrupole. The tradeoff between high resolution and large depth of focus
is demonstrated.