Nanofabrication and its application in developing high aspect ratio (HAR) and edge Atomic Force Microscopy (AFM) probes

Abstract

This thesis focuses on nanofabrication and its applications which are related to producing atomic force microscope (AFM) probes. This thesis is divided into four chapters. The first chapter brings a preliminary introduction to nanofabrication. The second chapter reviews the history of AFM and fabrication process of AFM probe. Equipping with the basic knowledge, Chapter 3, the main chapter, goes to our work on the batch fabrication of high aspect ratio (HAR) AFM tips. Last but not least, Chapter 4 focuses on another work, batch fabrication of edge probes. In order to obtain a more accurate image of surfaces, high aspect ratio tips are needed to reach the bottom of very deep and narrow trenches. However, currently all commercial HAR tips are produced in a slow, high-cost (~5-20x that of regular AFM tips) way. We have developed a new method to batch fabricate HAR tips. In this fabrication, two kinds of hard masks were deposited at a specific angle followed by two etching processes (dry etching and wet etching respectively). As a result, a small piece of hard mask was formed just on the apex of pyramid tip, which would be the protection layer in the following RIE step. The batch and lithography-free process makes it an efficient and low-cost method. The controllable profile, radius of curvature and aspect ratio of tips can be easily obtained by adjusting gas ratio and etching time in RIE. All the parameters and results were demonstrated clearly assisted by images and schematics. For edge probes, our method to batch fabricate tips on the edge is introduced step by step as well. The objective of every step is presented in detail assisted with schematics and tables.