DIRECT NANOMETER SCALE PATTERNING OF SIO2 WITH ELECTRON-BEAM IRRADIATION

Nanometer scale patterns have been fabricated in SiO2 by direct electron-beam exposure. Two techniques have been developed to eliminate the surface contamination and enable the subsequent development of the patterns in HF based wet etches: (1) exposing the oxide through a sacrificial layer (previously reported) and (2) O2 reactive ion etching (RIE). The latter approach eliminates the need for a sacrificial layer and improves resolution by reducing the forward scattering of the beam. To determine the resolution of this process, patterns were fabricated with both 50- and 300-kV electrons in thin SiO2 membrane samples and imaged in transmission. Transmission imaging avoids the resolution limit of secondary electron micrographs set by the lateral range of secondary electrons. At 300 keV with a line dose of 7.5-mu-C/cm, arrays of lines with a period down to 15 nm were achieved as opposed to the 21-nm period previously reported using a sacrificial layer and secondary electron imaging of bulk substrates. A better understanding has also been obtained of the profiles of the patterns in SiO2.