Abstract

With the extreme miniaturization of parts, components, devices and systems in various fields such as electronics and medicine; machining and fabrication of nano-scale features have gained tremendous attention. The development of cost-effective methods that are capable of writing or replicating nano-structures in a wide range of materials represents one of the greatest technical challenges now facing nano-fabrication. There has been a growing interest in using scanning probe microscopes (SPMs) as tools for nanofabrication. This dissertation's research is an attempt to utilize the principles of electric discharge machining (EDM) and electro chemical machining (ECM) to machine at nanoscale using the atomic force microscope (AFM). The experiments included machining an array of cavities using a single tip, machining of grooves, 2D machining, micro machining, and studying the effect of electrostatic forces on machining.

The experiments setup included: A Multimode AFM as the machining platform, deionized water as the machining medium, samples made of copper and gold films, and conductive AFM probes used as the machining tools. All the experiments were conducted at room temperature and pressure. Each machining experiment was done by first scanning the sample in deionized water. One of four proposed methods was then chosen to set the desired gap distance prior machining. The voltage was then applied between the tip and the workpiece for the specified time. Finally, another scan was taken to the sample to reveal the topographical effects induced by the tip-to-substrate bias.

Machining a series of cavities using a single tip was achieved and the depths of the machined cavities ranged between 17 nm and 53 nm. A study was conducted to investigate the stability of the machined nano cavities. It was found that these features were stable within the 48 hours time frame of the experiment and scanning itself played a major role in features destruction. Nano-grooves as deep as 54 nm, as wide as 300 nm, and as long as 13 μm were successfully machined. The length of the groove was limited by the maximum scan size of the AFM scanner. There was a high consistency in the groove's width and depth across the groove. Mechanical scratching was found to be not involved in grooves machining.

Machining in deionized water led to uncertainty about the mechanism of the machining process. The most two probable mechanisms involved in the machining process were EDM and mechanical hammering due to the electrostatic forces. It is expected that the electro-machining process using the AFM can be extended to other conducting tool materials such as copper, cobalt and nickel, and to be capable of machining any electrically conductive material including hard and difficult-to-cut materials.