Synthesis of high-density Hf1-x Lax O2 (HLO) ceramic targets with suppressed secondary phase and growth of thin films by rf magnetron sputtering

초록

Recently, lanthanum (La) has attracted attention as a promising doping element for significantly enhancing the ferroelectric properties of HfO2 thin films. However, comprehensive research on the optimal doping concentration and origin of ferroelectricity in La-doped HfO2 thin films, depending on the fabrication method, is lacking. In this study, Hf1-xLaxO2 [x = 0.05, 0.075, 0.1] (HLO) ceramic targets were synthesized by sintering via the solid-state reaction method at temperatures of 1300-1600 degrees C, and the effect of La doping concentration and sintering temperature on the material properties was analyzed. The properties of the HLO ceramic targets sintered at various temperatures exhibited changes in the lattice structure according to doping concentration. Furthermore, the target density and crystallite size improved, and the La2Hf2O7 impurities decreased with increasing sintering temperatures. Consequently, the sintering condition at 1600 degrees C was identified as the optimal condition for fabricating high-quality targets for thin sputtering deposition. Using these optimized targets, 15 nm-thick Hf0.90La0.10O2 thin films were deposited by RF magnetron sputtering, and metal-ferroelectric-metal (MFM) structured capacitors were fabricated. After 10 3 electric field cycling, the capacitors exhibited a remanent polarization of 2P(r) approximate to 49.9 mu C/cm2, indicating stable ferroelectric switching behavior. These results suggest that target optimization plays an important role in achieving reliable ferroelectric properties in La-doped HfO2 thin films and support their applicability in FeRAM and FeFET devices.

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