Nanofabrication and Microscopy

This course consists of two parts: 'Nanofabrication' deals with the fabrication of structures that are smaller than 100 nm, while 'Microscopy' concerns the visualisation of such small features. Advanced optical lithography concepts are illustrated by a computer simulation lab with the industry-standard software "GenISys LAB".

We start with a general overview of nanotechnology, explaining why the properties of materials are so different at the nanoscale compared to the microscale. The difference between top-down and bottom-up fabrication is explained and the ultimate industrial nanofabrication process (CMOS) is outlined, including the technological issues related to further scaling according to Moore's Law.

After introducing general microscopy concepts such as magnification, resolution, depth of field and contrast, it is discussed how image formation is achieved in optical microscopy. Many of the principles of optical microscopy also apply to the next topic. Optical lithography is crucial for top-down nanofabrication (and CMOS scaling) because it defines the smallest feature size that can be fabricated. The historical development of optical lithography is presented, up to the present state-of-the-art and looking forward to future developments of this patterning technique.

We then switch back to the microscopies: transmission electron microscopy and scanning electron microscopy enable visualisation of nanoscale structures but image formation, resolution, contrast mechanism and sample preparation are quite different. The images of MOSFET cross-sections will be explained. These particle beam techniques are also used in fabrication: e-beam writing is a serial lithography that enables ~10 nm patterns, while focused ion beam milling has numerous applications in nanofabrication.

We finish the nanofabrication component with a brief description of bottom-up processes such as the chemical synthesis of carbon nanotubes, silicon nanowires and gold nanoparticles. This is put in the context of fabricating nanoelectronic devices by a mix of top-down and bottom-up fabrication processes. For example, carbon nanotubes can be grown in between micro-electrodes by patterning these with a catalyst material. Similar examples from the recent literature will be highlighted.

The computer lab sessions involve simulations of photoresist exposure for different optical lithography techniques and explores various resolution enhancement methods that enable nanometer scale patterning in general and advanced CMOS scaling in particular. As part of the lab you will design your own photomask. The GenISys LAB lithography simulation software is used in commercial nanofabrication facilities and is only available for this module because of a special agreement with the company.

Please note that ELEC6206 Nanofabrication and Microscopy (see the Notes directory for info slides) does not deal with fabrication techniques that are essentially the same as for microfabrication. Etching, deposition and process flow are explained in detail in ELEC6201 Microfabrication, and this module is a prerequisite for ELEC6206 Nanofabrication and Microscopy.

Pre-requisite: ELEC6201