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

The etching reactions of lead zirconate-titanate (PZT) films with fluorine ions were studied by in situ x-ray photoelectron spectroscopic (XPS) analysis of the ion bombarded films. The bombardment was carried out with a mass separated low energy ion beam in ultrahigh vacuum and at 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 density of 2 X 10(15)/CM2 is assumed) at room temperature led to the removal of about 6 nm of PZT. This etch yield is much higher than the expected sputter yield at 30 eV, a phenomenon which clearly indicates the importance of surface chemistry. The XPS data also show that prior to bombardment, a homogeneous oxide was present but that the bombardment induced a surface enrichment of lead and the formation of metal fluorides. Heating the sample to 300-degrees-C in vacuum desorbed virtually all metal fluorides. The results show that reactive ion etching of PZT films with fluorine chemistry is conceivable. However, the reaction mechanism appeared to be very much dependent on the bombardment energy. For example, an increase of the bombardment energy to 40 eV did not only increase the etch yield but also suppressed the surface enrichment of lead and induced the formation of oxy-fluorides.