Effects of temperature on the etching properties of Bi4-xLaxTi3O12 thin films

The etching properties of Bi4-xLaxTi3O12 (BLT) films etched in an inductively coupled Ar/Cl2 plasma were investigated in terms of the gas mixing ratio, the rf power, and the substrate temperature. We obtained a high etch rate of 433 A/min at 30 .deg. C and 344 A/min at 80 .deg. C in Ar (15 sccm)/Cl2(15 sccm). As the rf power was increased, the ion current density increased, resulting in an increase in the etch rate. To understand the etch mechanism of BLT in a Cl2/Ar plasma, we performed the plasma diagnostics using a Langmuir probe (LP). The LP measurement indicated that the maximum ion density decreased with Cl2 addition, but increased with the rf power. X-ray photoelectron spectroscopy (XPS) narrow scan analysis showed that La-chlorides remained on the etched surface and that the high accumulation of nonvolatile etch byproducts increased at high substrate temperatures. The analysis of surface reactions and the plasma diagnostics in the frameworks of an ion-assisted etching mechanism confirmed the possibility of non-monotonic etch rate behavior due to the concurrence of physical sputtering and chemical etching activated by ion bombardment.