Property study of phase change materials for nanopatterning

• Main Author: Khoo, Chee Ying.
• Other Authors: Gan Chee Lip
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/15327
• Institution: Nanyang Technological University

A lithography technique called “laser thermal lithography” was proposed for fabricating nanometer-sized structure beyond the optical diffraction limit. It has great potential as an optical disk mastering process for ultra-high density optical Read Only Memory (ROM) technology. By utilizing the idea of Super Resolution Near Field (Super-RENS) structure, the introduction of a mask layer is able to further reduce the dimensions formed on the laser thermal lithography (LTL) structure. Sn7.0Ge20.6Sb20.7Te51.7 was used as the mask layer in the structure. Its properties were investigated to determine the suitability of such material as a mask layer. The thermal analysis showed approximately identical crystallization temperature but lower melting temperature than Ge2Sb2Te5 phase change material. It has a higher activation energy than that of Ge2Sb2Te5, which indicates that it has a better thermal stability. The response speed of the material to laser is more than sufficient for its application as a mask layer. A focused laser spot with wavelength of 650 nm and numerical aperture of 0.65 was used to generate a spatially confined hot area in the top most dielectric layer. The structure was then etched using hydrogen fluoride. Nanodots of 400-nm dimensions were successfully fabricated by this technique, beyond the theoretical diffraction limit of the optical system. This can be further developed as a simple, fast and low-cost lithography technique for application in optical mastering.