Etching is the technology at the core of present-day semiconductor manufacturing and is a process of solid material removal from a substrate by means of a chemical (or physical) reaction and is used to transfer a pre-defined pattern into the required substrate. At least one etching step is performed during the manufacture of semiconductor devices. Requirements are:
• Good dimensional transfer
• Minimal mask erosion
• Minimal damage to underlying layers
• Minimal damage to devices
• No contamination
• Good uniformity
• Good reproducibility
• Good control
• Identifiable endpoint
• High throughput
There are, of course, all sorts of problems involved in using the same techniques at the nano level. Photolithography (the use of light to print circuit patterns according to the principles of photography) is particularly problematic for the same reasons that optical microscopes are useless at the nano level: the wave properties of light get in the way. For such reasons, electron or ion beam, nanoimprint, dip pen, X-ray and various other lithographic technologies have been developed.