Ion Beam Etching of Silicon Dioxide on Silicon

Abstract

An argon ion beam, 7.5 cm in diameter, with an energy of 0.6 keV and a current density of 0.5 mA/cm−2 is generated in an ion beam etching system using a Kaufman‐type ion source (1), then neutralized by electrons. The principles of ion beam etching are outlined and SEM micrographs of ion etched grooves in thermally grown layers are shown. Grooves 1 μm wide and 0.4 μm deep were obtained using Shipley AZ 1350 H photoresist. The groove profiles are in good agreement with those predicted with the aid of an ion etching model. The slope angle of the sidewalls of the grooves is typically 65°. Redeposition effects reduce the effective ion etch rates for grooves of small linewidths. If the layer is ion etched down to the silicon substrate, a silicon surface layer of about 100Å thickness will be damaged. This damage can be completely removed by wet chemical etching. The enhanced etch rate of ion‐damaged surface layers in buffered hydrofluoric acid is used to taper steps in thermally grown in a controllable process.