FLUORINE ION ETCHING OF LEAD-ZIRCONATE-TITANATE THIN-FILMS

The etching reactions of lead zirconate-titanate (PZT) films with fluo rine ions were studied by in situ x-ray photoelectron spectroscopic (X PS) analysis of the ion bombarded films. The bombardment was carried o ut with a mass separated low energy ion beam in ultrahigh vacuum and a t 30 and 40 eV. It was found that the bombardment at 30 eV and a dose of 1 X 10(17)/cm2 (equivalent to 50 monolayers if a surface atom densi ty of 2 X 10(15)/CM2 is assumed) at room temperature led to the remova l of about 6 nm of PZT. This etch yield is much higher than the expect ed sputter yield at 30 eV, a phenomenon which clearly indicates the im portance of surface chemistry. The XPS data also show that prior to bo mbardment, a homogeneous oxide was present but that the bombardment in duced a surface enrichment of lead and the formation of metal fluoride s. Heating the sample to 300-degrees-C in vacuum desorbed virtually al l metal fluorides. The results show that reactive ion etching of PZT f ilms with fluorine chemistry is conceivable. However, the reaction mec hanism appeared to be very much dependent on the bombardment energy. F or example, an increase of the bombardment energy to 40 eV did not onl y increase the etch yield but also suppressed the surface enrichment o f lead and induced the formation of oxy-fluorides.