ISSUE 5: FEB 2011
Exceptional research highlighted by APS
Feature sizes in lithography
A description of novel techniques in quantum lithography, resulting from QNRF funded research, has been featured on the American Physical Society's 'Physics' website, which highlights exceptional papers published in the Physical Review journal series.
Muhammad Suhail Zubairy of Texas A&M University and his co-authors, Zeyang Liao and Mohammed Al-Amri, had their original paper "Quantum Lithography beyond the Diffraction Limit via Rabi Oscillations" published in Physical Review Letters in October 2010, before the journal's editors selected it for wider promotion to other physicists.
Standard optical lithography is a common tool in creating high-density circuits and micron-scale devices and relies on a thin layer of organic material being patterned with intense light to change its physico-chemical properties. This photo exposure allows the material exposed to light to be dissolved away in a solvent, leaving an often complicated pattern of channels of organic material on a substrate for further processing.
Zubairy and his colleagues propose a two-step process to combat the problem of feature size in standard optical lithography being limited by the wavelength of the light source, typically 100-200nm.
Firstly, a pair of focused laser pulses tuned to the resonant frequency of molecules in the photoresist, create a standing wave pattern to excite a fraction of the molecules. Secondly, a light source pushes the excited molecules into a different state which allows dissolution by a solvent. The first step of the process allows feature sizes which are less than half the wavelength of the source.
The work was partly funded by a NPRP grant from QNRF on "Applications of quantum interferometry and coherence to precision sensing, microscopy and lithography" - NPRP 08-043-1-011.