Laser fabrication of micron-size apertures for electron beam microcolumns

For electron beam nanolithography and scanning electron microscopy applications, an electrostatic electron lens system called a microcolumn must be assembled. In order to reduce aberrations, laser drilling of the assembled microcolumn system should be highly beneficial. We have drilled micron-size apertures on silicon substrates including molybdenum and tantalum using a 1.064 mu m Nd:YAG laser. In this work, a layer-by-layer evaporation technique using multiple pulse treatment (MPT) is employed in order to minimize melting of the crater wall and maximize the evaporation of the bottom layer of the crater. The machining conditions of an Nd:YAG laser pulsed in the TEM00 mode for ceramic, silicon, and molybdenum diaphragms are optimized. We obtain micron-size apertures for electron beam microcolumn applications such as electron lenses.