The convergence of top-down and bottom-up nanofabrication: formation of 3D structures

Lithography and the processes associated with it are the backbone of the nanotechnology revolution. Several developments are occurring simultaneously: a drive to reduce minimum feature size leading to advances in microelectronics, the use of lithographically patterned structures to prepare devices for photonics, biotechnology and other forms of nanotechnology and finally the drive to create three-dimensional (3D) structures for device and new materials creation. Thus the controlled formation of nanometer scale structures in two and three dimensions is of increasing interest in many applications. This paper will overview new approaches for the construction of small-scale structures using methods generally considered as next generation lithography. New approaches derived from two photon processes for the formation of complex images and the development of patterned structures will be described. Finally in the production of 3D patterns, the possible role of self-assembly coupled to lithography will be examined. Photodefinable block copolymers with erodable microstructures have been successfully used to form mesoporous materials and will be discussed.