The Electrical Improvement of PZT Thin Films Etched into CF4/(Cl2+Ar) Plasma

The PZT thin films are one of well-known materials that has been widely studied for ferroelectric random access memory (FRAM). We etched the PZT thin films by $CF_{4}/(Cl_{2}+Ar)$ plasma and investigated improvement in etching damage by $O_{2}$ annealing. The maximum etch rate of the PZT thin films was 157 nrn/min and that the selectivity of the PZT thin films to Pt was 3.1 when $CF_{4}(30{\%})$ was added to a $Cl_{2}(80{\%})/Ar(20{\%})$ gas mixing ratio. To improve the ferroelectric properties of PZT thin films after etching, the samples were annealed for 10 min at various temperatures in $O_{2}$ atmosphere. After $O_{2}$ annealing, the remanent polarization of the asdeposited films was $34.6{\mu}/cm^{2}$ and the sample annealed at 650, 550, and $450^{\circ}C$ was 32.8, 22.3, and $18.6{\mu}/cm^{2}$, respectively. PZT thin films with $O_{2}$ annealing at $450^{\circ}C$ retained $77{\%}$ of their original polarization at 106 cycles. Also as the annealing temperature increased, the fatigue properties improved. And the leakage current was decreased gradually and almost recovered to the as-deposited value after the annealing at $450^{\circ}C$.