Carbon nanotubes (CNTs) have been researched as a possible important new component in various devices because
they have a promising potential in applications such as microelectronic devices, sensors, actuators and optoelectronic
devices. For the use of CNTs in such applications, especially in mass fabrication, a pattering process for CNT layers that
is compatible with CMOS (Complementary Metal Oxide Semiconductor) processes is necessary. There have been some
reports in the literature on the patterning of CNTs, but either the reported methods were not compatible with CMOS
processes or the capability for precise control of the pattern geometry was not good.
In this paper we describe a new patterning method that can be used in the fabrication of devices and other
applications which use carbon nanotubes as a component material. This method also can be used in the patterning of
other highly porous materials. Further, the process is compatible with conventional microelectronic fabrication
processes and it is high-speed. Single walled carbon nanotube (SWNT) films were patterned by an excimer laser
projection photoablation process at low incident energy conditions. The CNTs were deposited on a quartz substrate, and
then a conventional photoresist was coated on it as a photoablation assistor. The photoresist and the CNTs were
patterned simultaneously by the photoablation process, and then the photoresist was removed. Due to the physical force
of the ablation-dissociated photoresist fragments, the CNTs were patterned cleanly even though the incident fluence on
them was significantly lower than the threshold energy otherwise needed for their direct ablation.
Indium-Tin-Oxide (ITO), which is commonly used in the flat-panel display industry as a transparent conductive
oxide, was patterned cleanly by a non-photolithographic process. For the patterning of ITO on a silicon nitride substrate,
the substrate was coated with photoresist which was patterned by the photoablation process using a KrF (wavelength of
248nm) excimer laser with low fluence conditions. ITO was then deposited on the patterned photoresist by sputtering,
and the final ITO pattern was produced by lift-off. The resulting ITO pattern was clean even though it was patterned
without a conventional photoresist development step and a conventional ITO etching step. This process technology does
not require a developing process and an etching process to make a pattern on the substrate. A reduction of two process
steps will result in substantial cost savings in high-volume production. The production time for the fabrication cycle and
the equipment maintenance will also be decreased. Besides the application of this process to ITO patterning in TFT-LCD
(Thin Film Transistor Liquid Crystal Display) fabrication, it can also be used for patterning other materials and device
structures. It is attractive for a variety of applications in the fabrication of flat-panel displays, other microelectronic
devices and device packaging, because it enables low cost and high throughput.
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