Nanofabrication of direct positioning atomic force microscope (AFM) probes and a novel method to attain controllable lift-off

Abstract

This thesis focuses on nanofabrication and its applications in the area related to atomic force microscope (AFM) probes and a novel way of constructing the bi-layer system for liftoff. The contribution of this thesis is therefore the introduction and characterization of nanotechnologies and their applications in fabricating the AFM probes (Part 1). Moreover, an introduction of the liftoff and the exhibition of the experimental results of our technique will be provided (Part 2). The first part of this thesis consists of four chapters. The first chapter brings a brief introduction and an overview of nanotechnologies and nanofabrication to give a big picture of what they are. The second chapter introduces three major nanofabrication techniques that are crucial in manufacturing the AFM tip. Those are evaporation, wet etch and dry etch. The basic concepts, working mechanism and important parameters of these three techniques are discussed. The third chapter presents detail of the AFM probe with its history, principle of operation, fabrication method and carbon nanotube tips. After equipping the knowledge provided in the first three chapters, fabricating a particular direct positioning AFM probe will be discussed next. Therefore, chapter 4 introduces the details of our method to batch fabricate the direct positioning AFM probe step-by-step. Parameters and goals of each step are presented with schematics and SEM images from our results. The second part of this thesis consists of four chapters as well. The first chapter introduces the essentials of a liftoff process and current popular methods to create moderate undercuts. The second chapter describes the experimental process of our technique to acquire controllable undercut by tuning the ratio of ZEP/PMMA mixture. The third part exhibits the results of contrast curves for various mixtures, undercut profiles and Chromium line arrays produced by our liftoff process.