Fundamental research on low energy electron beam assisted selective etching and deposition for submicron LSI fabrication

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1. The specimen chamber in a conventional scanning electron microscope (SEM) was modified to direct gas onto the specimen surface through a gas injection nozzle which had a 0.2 mm diameter. The gas supply system was attached to the SEM specimen chamber.2. Electron beam assisted selective etching of SiO_2 by using XeF_2 gas: (1) Experimental results showed that the etching end point could be determined from either the specimen current or the secondary electron current monitored during the electron beam irradiation. (2) The etch rate were higher at lower primary electron energies, lower specimen temperatures, larger gas flow rates and larger electron beam currents. (3) The etched hole diameters at the etching end point are found to be nearly equal to the tail diameters of the beam profiles. (4) A groove with the high aspect ratio of ten was formed in 2mum thick SiO_2 by using an electron beam probe with an energy of 15 keV, a current of 50 pA and a tail diameter-of 0.15mum.3. Electron beam assisted selective deposition on SiO_2 by using Fe(CO)_5 gas: (1) The deposition rate were higher at lower primary electron energies, lower specimen temperatures, larger gas flow rates and larger electron beam currents. (2) The resistivity was estimated from the measurement of resistance between two Al metal lines which were connected by Fe deposition. The result showed a resistivity of more than six orders of magnitude more than bulk Fe. The cause could be due to the oxide of Al surface.