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ABSTRACT:
The universal mask or pattern generator provides an ion projection
lithography (IPL) system that is electronically switchable
to generate a variety of different mask patterns using a single
apparatus. Developed at Berkeley Lab with the support of the
Defense Advanced Research Projects Agency (DARPA), the pattern
generator consists of an array of microapertures on the plasma
electrode and the extraction electrode which are separated
by ~ 5 µm layer of insulating material. Individual beamlets
can be switched on and off to form a lithographic pattern
by biasing the extraction electrode at each microaperture
with respect to the plasma electrode.
Eliminating the stencil mask from the lithographic process
via the Berkeley Lab universal pattern generator would potentially
result in significant cost savings because mask development,
and defect detection and correction would be minimized. The
use of an electronically controlled pattern promises to enable
high throughput and rapid implementation of new designs, since
multiple mask steps are performed by the same machine.
Preliminary calculations indicate that throughput of 30 wafers
(300 mm) per hour or higher could be achieved at current density
of 100 µA/cm2 (at the wafer plane). Currently, 160 nm
features at 566 nm pitch on polymethyl methacrylate (PMMA)
have been achieved with a 10x demagnification column design.
Ka-Ngo Leung and William Barletta have also developed an efficient
multiplex addressing system for producing patterns using the
universal pattern generator. This invention employs an electronic
grid to control the switching of each beamlet so that every
beam hole in the plasma electrode does not have to be individually
wired, greatly reducing the number of wiring connections.
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