Nano technologies -Catalytic Template Method
for Selective Growth of Highly Dense Carbon Nanotubes
Introduction
Carbon nanotubes (CNTs) have been
proposed as building blocks for the future generation
of computer chips, due to their high thermal conductivity,
large current-carrying capacity, and excellent physical
and chemical stabilities. However, to integrate with
conventional chips based on silicon technology, high
dense and ordered aligned CNTs are needed, and a selective
growth of patterned CNT structure is necessary.
Although CNTs have been produced by
many different methods, most of the efforts to control
CNT growth were achieved by adjusting the precursor
gases and their flow rates, synthesis pressure and temperature,
external bias, and catalyst compositions and sizes.
The quality of the CNTs in terms of yield, film coverage,
density, alignment, uniformity, and pattern formation
has not been good enough to meet the requirements of
microelectronics applications. So far, the integration
of CNT structures with devices on silicon chips is very
limited, and significant improvements are required.
Invention Description
Catalyst support layers have often
been used (1) to prevent catalysts from reacting with
the substrates and (2) to strengthen catalyst-substrate
adhesion. We have devised a method for selective growth
of dense and uniform CNT structures using a catalytic
template layer. In our study, we found that a template
formed by depositing a thin Fe catalytic layer on a
thin layer of tantalum, which was originally used as
the barrier layer in copper interconnects, can significantly
enhance the uniform growth of vertically aligned CNT
arrays with density exceeding 10" per cm2.
A series of controlled experiments
has been performed to investigate the effect of the
template materials on CNT growth by thermal chemical
vapor deposition (CVD). Different materials such as
silicon dioxide (SiO2), tantalum (Ta) and chromium (Cr)
thin films with different thicknesses had been used
as the support for the Fe catalyst layer. Only the combination
of FeKa was found to be effective in greatly enhancing
the growth of highly dense CNTs with vertical alignment.
The growth was selective in that it occurred only on
locations covered with the FeITa template.
Benefits
Can improve CNT yield, film coverage
and uniformity
Can produce patterned, highly dense
CNT films with vertical alignment
Simplifies fabrication processes;
easy to scale up
Makes CNTs ready to be integrated
on silicon chips
Market Potential/Applications
The invention may be used to integrate
CNT structures for on-chip interconnect or as thermal
conductors for power distribution or dissipation from
high-performance chips.
IP Status
One U.S. Patent Application Filed.
One PCT Patent Application Filed.
UT Researcher
Paul S. Ho, Ph.D., Department of Mechanical
Engineering, The University of Texas at Austin
Yunyu Wang, Ph.D., Microelectronics Research Center,
The University of Texas at Austin
Li Shi, Ph.D., Department of Mechanical Engineering,
The University of Texas at Austin
Zhen Yao, Ph.D., Department of Physics, The University
of Texas at Austin
