A nanopillar can be considered as semi conducting material patterned, by using electron beam lithography and dry etching, into a three-dimensional cylinder with diameter less than 100 nm. In general, epitaxially grown super lattice or multiple quantum well structures are used as the ‘substrate’ material for these nanopillars. Using electron beam lithography and reactive ion etching techniques, low dimensional nanopillar structures can be formed.
Nanoscale transistor, optical chips, biosensors, micro fluidics and micro mirror chips are limited by photolithography, specifically, light wavelengths and electron beam lithography (e-beam litho) cannot expose an entire chip at once.
Nanopillar collapse
When lithography processes was done it was necessary to prevent nanopillar collapse at the 10nm level, but the collapse phenomenon has helped researchers to find a new application. Researchers from MIT's Research Laboratory of Electronics and Singapore's Engineering Agency for Science, Technology and Research have developed a new technique that could produce 10nm chip features using plastic pillar deposition and predetermined pillar collapses.
Process
Etching a pillar into the resist by focusing an e-beam on a single spot, scattering sparse pillars across the chip and allowing them to collapse into more complex patterns could increase e-beam lithography efficiency.
The layer of resist deposited in e-beam lithography is so thin that, after the unexposed resist has been washed away, the fluid that naturally remains behind is enough to submerge the pillars. As the fluid evaporates and the pillars emerge, the surface tension of the fluid remaining between the pillars causes them to collapse.
Collapse control
Researchers from Lanzhou University in China showed how two pillars will collapse toward each other if they are very close. Also by controlling the shape of isolated pillars, they can be made to collapse in whatever direction they are chosen.
Slightly flattening one side of the pillar will cause it to collapse in the opposite direction and partially flattened pillars collapse in the intended direction with about 98% reliability, which is a good "starting point" to build toward industrial yields. The controlled collapse of structures on the micrometer scale has been in use to produce materials with novel optical properties for several years.