| AVS 66th International Symposium & Exhibition | |
| Plasma Science and Technology Division | Tuesday Sessions |
| Session PS+EM-TuM |
| Session: | Advanced FEOL |
| Presenter: | Ryan Sawadichai, University of Houston |
| Authors: | R. Sawadichai, University of Houston Y.-M. Chen, University of Houston P. Basu, University of Houston V.M. Donnelly, University of Houston P. Ruchhoeft, University of Houston D.J. Economou, University of Houston |
| Correspondent: | Click to Email |
Nanopantography is a method for massively parallel writing of nano-sized patterns using an ion beam in combination with a reactive gas. In this process, a broad area, collimated, nearly-monoenergetic ion beam is directed towards an array of micron-scale electrostatic lenses in direct contact with a substrate. By applying an appropriate DC voltage to the lens array with respect to the substrate, the ion beamlet entering each lens converges to a fine spot that can be 100 times smaller than the diameter of each lens. Previously, lenses fabricated directly on the silicon substrate were used to etch 3 nm diameter holes in silicon by exposure to a monoenergetic Ar+ ion beam and chlorine gas. This work reports on the development of removable and reusable free-standing membrane-based electrostatic lens arrays that are designed to pattern any conducting surface. The lens arrays were fabricated on a silicon wafer coated with PMGI, SU-8, gold, copper, and PMMA. Lens openings were lithographically defined, and an acrylic frame was placed over the array. The lens patterns were etched through the SU-8 and the membrane was released by dissolution of the PMGI layer. The applied voltage used to focus the ion beamlets also served to electrostatically clamp the lens array to a conducting substrate, which was observed as a flattening of the membrane against the substrate surface and an increasing capacitance measured between the lens array and the substrate. An array with lens diameters between 0.8 μm and 1.5 μm and dielectric thickness of 1 μm was used to pattern nanoscale features on a silicon substrate using a 70 eV Ar+ ion beam and chlorine gas. Ion trajectory simulations were performed to understand the sensitivity of minimum feature size to the variation of lens potential, lens aspect ratio, and lens size. Simulations agreed with the experimentally observed patterns when chromatic and spherical aberrations were considered. With a thinner dielectric and higher lens voltage, it should be possible to print sub 10-nm features in a step and repeat nanopantography process.