SUBSTRATE TOPOLOGY ORDERS BLOCK COPOLYMER DOMAINS FOR NANOLITHOGRAPHY
In a collaboration with Prof. N.P. Balsara of the University of California at Berkeley, we developed a thermodynamic understanding which governs this phase separation. If such thin films are coated to substrates like Si, and exposed to reactive ion etching conditions, areas covered by the organometallic nanodomains are selectively protected. Thus the negative of the corresponding patterns will be etched into the substrate.
Self-assembly generally produces structures that possess only short-range order. However, long-range order can be imposed if self-assembly takes place on a template. Ordered rows of domains form within the grooves, but, unexpectedly, the domain periodicity is not uniform across the groove. Defects and dislocations in the domain array can be deliberately introduced by variations in groove geometry.
This model system illustrates the power of the templating process in its ability to tailor the spacing of a self-assembled structure and to engineer the location of defects, which enables the design of precisely patterned hierarchical structures for a variety of applications. These results were achieved in a collaborative project with the groups of professor C.A. Ross and E.L. Thomas of MIT.
Figure 7. Nanodots ordered in prefabricated silica grooves after reactive ion etching.
Publication H. B. Eitouni, N. P. Balsara, H. Hanh, J. A. Pople, M. A. Hempenius: Macromolecules 2002, 35, 7765 and J. Y. Cheng, C. A. Ross, E. L. Thomas, H. I. Smith, G. J. Vancso: Appl. Phys. Lett. 2002, 81, 3657.