Reactive ion beam etching of ferroelectric materials using an RF inductively coupled ion beam source

Abstract

Reactive Ion Beam Etching (RIBE) has been found to be an extremely useful technique for fabricating highly anisotropic ferroelectric device structures, particularly nonvolatile random access (NVRAM) memory devices, which are difficult to etch by other dry etching methods. The application of ion beam equipment to this field has been limited in the past by the use of standard Kaufman type ion sources, which have very short cathode lifetimes when operated with the reactive gases which are used to attain enhanced selectivity. This problem is solved by using the RF inductively coupled ion source described here. Etch results on ferroelectric PZT and Pt electrodes are presented for the RF source and compared with results for a Kaufman filament ion source. It is shown that RF RIBE with fluorocarbon gases provides higher etch selectivity for the ferroelectric (up to about 4:1 PZT/Pt) combined with relatively high etch rates (650 A/min for PZT at 500 eV). A complete practical ion beam process for patterning ferroelectric device structures is then described, incorporating the ferroelectric RIBE step. Highly anisotropic etched features are shown.