Etching characteristics of SrBi(2)Ya(2)O(9) film with Ar/CHF3 plasma

Among the ferroelectric thin films that have been widely investigated for f erroelectric random access memory (FRAM) applications, the SrBi2Ta2O9 (SBT) thin film is appropriate as a memory capacitor material due to its excelle nt fatigue endurance. However, very few studies on the etch properties of S BT thin films have been reported, even though dry etching is an area that d emands a great deal of attention in the very-large-scale integration of fer roelectric thin-film capacitors for FRAM applications. In this study, SrBi2 Ta2O9 thin films were etched using a magnetically enhanced inductively coup led Ar/CHF3 plasma. Etch properties, such as etch rate, selectivity, and pr ofile, were measured for different gas mixing ratios of CHF3/(Ar+CHF3), whi le the other process conditions were fixed at rf power of 600 W, de-bias vo ltage of -150 V, and chamber pressure of 5 mTorr. The maximum etch rate of SET thin films was 1650 Angstrom/min under CHF3/(Ar+CHF3) of 0.1. Selectivi ties of SBT to Pt and photoresist masks were 1.35 and 0.94, respectively. T he chemical reaction and compositional change of the etched surfaces were i nvestigated by x-ray photoelectron spectroscopy analysis. The Sr and Ta ato ms of SBT films react with fluorine; Sr-F and Ta-F are then removed by phys ical sputtering by Ar ions. The surface of a SBT film etched with CHF3/(ArCHF3)=0.1 was analyzed using secondary ion mass spectrometry. Scanning elec tron microscopy was used to examine etched profiles of SBT thin films. The wall angle of a SBT film etched using CHF3/(Ar+CHF3)=0.1 was approximately 85 degrees. (C) 2000 American Society [S0734-2101(00)04404-3].