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

Contact:

University os texas,
Austin, USA
Website : www.otc.utexas.edu