Ion beam etching of lead–zirconate–titanate thin films: Correlation between etching parameters and electrical properties evolution

Abstract

Ion beam etching of sputtered Pb(Zrx,Ti1−x)O3 (PZT) with x equal to 0.54 thin films grown on Pt/Ti/SiO2/Si substrates has been performed using pure Ar gas. The etch rate dependence on the process parameters (current density, acceleration voltage, gas pressure) has been investigated. The PZT etch rate can reach 600 Å/min with acceleration voltage of 1000 V and current density of 1 mA/cm2. Selectivity ratios between PZT and masks of various natures (photoresist, Pt, Ti) have been evaluated to determine a pertinent material for etching mask. According to our etching conditions, titanium seems to be the best candidate. We evaluated the PZT surface damage by contact mode atomic force microscopy. It appears that the roughness increases after ion bombardment, and that the grain boundary zone is preferentially etched. For some etching parameters, we also observed electrical damage. Carrying out C(V) and hysteresis loops P(E) measurements before and after etching have provided evidence of degradation. We noted a large decrease in permittivity after the etching process irrespective of the current density and acceleration voltage. Ferroelectric damage was illustrated by a large increase in the average coercive field. For each of the electrical properties under study, the same behavior has been observed after etching: the increase of damage was obtained as a function of the current density and acceleration voltage. The evolution of electrical properties when the PZT layer is protected by a metallic mask has also been studied. We observed very slight variations in the electrical properties.