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ABSTRACT:
In
conventional IPL systems, high-energy ions (~10KeV) impinge
on a very thin stencil mask, causing heating, scattering,
and sputtering that distort the pattern and eventually ruin
the mask. Berkeley Lab researchers have invented an ion projection
lithography (IPL) system in which low energy ions (< 30eV)
impinge on an electrode that also serves as a mask.
Ka-Ngo Leung and colleagues eliminate the acceleration stage
between the ion source and stencil mask by positioning a thick,
fixed pattern mask that is also used as a beam forming or
extraction electrode directly next to the plasma source. The
plasma contacts the entire electrode or mask and is extracted
through its holes or apertures. The extracted beam then passes
through an accelerator and reduction column to produce a demagnified
pattern on a resist-coated wafer or other targets.
An additional advantage of the Berkeley Lab IPL system design
is that the accelerator and reduction column can be designed
either with beam crossover or without. Beam crossover can
increase the longitudinal energy spread of the beam and produce
image blur. This effect puts an upper limit on the maximum
beam current and therefore on throughput.
This technology also features a mask design for creating a
circular ring pattern, which is typically difficult to achieve
with lithography.
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