Optimization of electron beam lithography and lift-off process for nanofabrication of sub-50 NM gold nanostructures

Official URL: https://risc01.sabanciuniv.edu/record=b2351407 _(Table of contents)

Since the demonstration of the first integrated circuit in the late 1950s, the microelectronics industry has witnessed a vast transformation with transistor densities doubling roughly every two years as a result of continuous scaling down of device dimensions, referred to as miniaturization. The fundamental concept of miniaturization has not only been employed for the realization of ultra large scale integrated (ULSI) circuits with reduced manufacturing costs, lower power consumption, higher speed and computational power; but also, for developing novel transducer elements and energy storage devices by harnessing the unique physical effects that arise at micro/nanoscales such as higher surface-to-volume ratios. One of the most important technologies in micro/nano device fabrication, if not the single most important, is lithography. The broad range of lithographic techniques ranging from conventional optical lithography methods (e.g. ultraviolet-UV, deep ultraviolet-DUV, extreme ultraviolet-EUV) to unconventional ones (e.g. electron beam lithography, x-ray lithography, ion-beam lithography, stereolithography, scanning probe lithography, nanoimprint lithography, directed self-assembly) can be used to create features with microns to tens of nanometer resolution and below. Among these, electron beam lithography (EBL) stands out as a powerful direct-write tool offering nanometer scale patterning capability and is especially useful in low volume R&D prototyping. However, patterning with EBL requires careful balance of process parameters which need to be considered in conjunction with the pattern transfer technology that can be either etching or lift-off specifically for the case metallic layers. Accordingly, this thesis provides a systematic study to address the gap in process optimization of lift-off process based on EBL patterning of sub-50 nm metallic nanostructures using a lower cost PMMA/PMMA positive tone bilayer resist spin approach. The governing parameters in EBL including exposure dose, bake temperature, develop time, developer solution, substrate effect, proximity effect (PE) are experimentally studied and their effects on nanopatterning are characterized by field emission scanning electron microscopy (FE-SEM) of fabricated nanostructures