Electron beam assisted high aspect ratio, submicrometre etching of passivation SiO2 on large-scale integrated circuits

Abstract

Electron beam assisted high aspect ratio, submicrometre etching of the passivation SiO2 on large-scale integrated circuits (LSIS) with XeF2 as a source gas is described. The end point of the etching process can be determined from either the current absorbed by the specimen or the secondary electron current monitored during the electron beam irradiation. The etched hole diameters at the etching end point are found to be nearly equal to the tail diameters of the electron beam profiles, as reconstructed from the electron beam intensity distributions across a knife edge mounted on a Faraday cup. A groove with a high aspect ratio of ten is formed in 2 mu m thick SiO2 by using the electron beam probe with an energy of 15 keV, a current of 50 pA and a tail diameter of 0.15 mu m.