A Scanning Tunneling Microscope Based Microcolumn System

A novel concept based on scanning tunneling microscope (STM) aligned field emission (SAFE) with microfabricated lenses to form an exceptionally high brightness electron source and miniaturized electron probe forming system has been explored. Electron optical studies have shown that such miniaturized columns can have performance surpassing conventional columns at the same potential. Processes for fabricating microlenses from silicon membrane using electron beam lithography and reactive ion etching (RIE), and a special W field emission tip preparation and annealing procedure have been developed. Prototype 1 kV microcolumns based on this concept measuring 2.5 mm have been successfully fabricated and demonstrated to be fully operational. Scanning electron microscope images in the transmission mode have been achieved. The expected performance of such microcolumns coupled with the very significant reduction in physical column size can open new possibilities in many applications which include microscopy, lithography, metrology, testing, storage, etc. It can be shown that by the use of an array of these miniaturized columns, high throughput sub-100 nm lithography can be achieved.