High Resolution Patterning using Electron Beam Lithography and Fabrication of Copper Nanostructure using Atomic Force Microscope Lithography

Abstract

The development of lithography techniques has resulted in considerable progress in the semiconductor industry. In particular, electron beam lithography (EBL) and atomic force microscopy (AFM) lithography are the most promising techniques for fabricating nanostructures on substrates without masks. In this thesis, EBL and AFM lithography were used for high resolution resist patterning and fabricating copper nanostructures, respectively. Newly designed chemically amplified (CA) resists using glycidylmethacrylate (GMA), methylmethacrylate (MMA), and triphenylsulfonium salt methacrylate (TPSMA) as a photo acid generator (PAG) were applied to improve the electron beam lithographic performance such as the sensitivity and resolution. A bounded PAG resist had a higher sensitivity (120 �C/cm2) than a blended PAG resist (300 �C/cm2) and eliminating the post exposure baking (PEB) process could improve resolution and line edge roughness due to the reducing acid diffusion. A high resolution pattern fabricated by EBL at 100 keV acceleration voltages had a line width of 15 nm and the high aspect ratio patterns with 4.6 were used as good mask for transferring Si substrate by reactive ion etching (RIE). Electrochemical reactions based on atomic force microscope (AFM) lithography were used for the fabrication of copper nanostructures, along with the use of n-tridecylamine hydrochloride (TDA∙HCl) as a self assembled monolayer (SAM) for the intermediate layer. The application of a negative sample bias could strongly reduce the copper ions at a point localized by the AFM tip, and the intermediate layer of the TDA�HCl SAM easily removed the residual materials outside the defined patterns after lithography. the fabricated copper nanostructures had a length of 20 �m, height of 45 nm, and width of 160 nm.