FOCUSED ION-BEAM DIRECT DEPOSITION OF METAL THIN-FILM

Focused ion-beam direct deposition has been developed as a new method for fabricating patterned metal films directly on substrates. The prin ciple of this method is to perform ion-beam deposition by low-energy f ocused ion beams. We designed and constructed a low-energy focused ion -beam apparatus for direct deposition. Metal ions are extracted from l iquid metal ion source, accelerated to 20 keV for single charged ions, focused, mass separated, deflected, and finally, decelerated to 30-10 00 eV in this system. The beam diameter estimated by the deposited lin ewidth can be tuned between 0.5 and 8 mu m and the beam current varies from 40 pA to 10 nA corresponding to the beam diameter for the Au+ io n in the energy range from 30 to 200 eV. The sticking probabilities of ion-beam deposition were measured and the critical energies for Au+, Cu+, Al+, and Nb2+ were about 210, 230, 800, and 1300 eV, respectively . The purity of gold film was measured by Auger electron spectroscopy and secondary-ion-mass spectroscopy. The concentration of carbon and o xygen was estimated below 100 ppm and was consistent with theoreticall y expected amounts. Resistivities of deposited gold, copper, and alumi num line were measured 1.5-1.6 times larger than that of bulk gold, 1. 2-1.5 times larger than that of bulk copper, and 2.2-2.7 times larger than that of bulk aluminum. The critical temperature of deposited niob ium line was also measured and a clear relationship was obtained betwe en the critical temperature and the concentration of contaminations. ( C) 1996 American Institute of Physics.