Effect of methane-hydrogen gas admixture on the selectivity toward platinum in dry etching of lead zirconate titanate (PZT) thin films by inductively coupled plasma reactive ion etching

This work illustrates the effectiveness of introducing CH₄/H₂ to the etch chemistry on boosting the selectivity toward Pt in dry patterning of Pb(Zr_xTi_1−x)O₃ (PZT) thin films via inductively coupled plasma reactive ion etching. A significant increase in etch selectivity from 6.3 to 21 with respect to Pt is observed upon the addition of 20 vol. % CH₄/H₂ to a CHF₃/Cl₂/BCl₃ gas mixture, while the etch rate remains constant at 50 nm min⁻¹. It is believed that the simultaneous presence of BCl₃ and CH₄/H₂ enhances the chemical aspect of the etch mechanism by reduction of Pb through BCl₃ and subsequent reaction with CH₄/H₂. Using this approach in a soft-landing step is expected to simplify the process flow and increase the throughput in industrial PZT patterning by allowing a precise etch stop while maintaining high etch rates and aspect ratios in a single process.