Etch characteristics of SrBi₂Ta₂O₉ (SBT) thin films using magnetized inductively coupled plasmas

In this study, SrBi₂Ta₂O₉ (SBT) thin films were etched using a magnetized inductively coupled plasma (MICP) and their etch characteristics were investigated as a function of Cl₂/Ar gas mixing ratio, inductive power and bias voltage. The SBT etch rate appeared to show the highest value when Cl₂ concentration in the Cl₂/Ar mixture was 30%, even though the SBT etch rate remained nearly constant when the Cl₂ concentration in the mixture was higher than 10%. SBT etch rates were also strongly influenced by both inductive power and bias voltage. This result implies that the etching of SBT is dependent upon both ion bombardment and chemical reaction. An etch rate of 150 nm/min could be obtained using 30% Cl₂/70% Ar, 6.7 Pa of operation pressure, 600 W of inductive power, and -300 V of bias voltage. The etch selectivity of SBT over Pt, and photoresist were less than 0.5 and 1.0 ∼ 1.2, respectively, when the Cl₂ was more than 10% in Cl₂/Ar mixtures. An SBT (200 nm)/Pt (100 nm)/Ti (100 nm) heterostructure was etched using the MICP with 30% Cl₂/70% Ar mixture, which resulted in an anisotropic etch profile without the formation of sidewall residue.