Atomic Layer Deposition of Pb(Zr,Ti)Ox, Thin Films by a Combination of Binary Atomic Layer Deposition Processes

After an evaluation of Zr precursor, quatemary Pb(Zr,Ti)Ox [PZT] films were prepared by a combination of binary atomic layer deposition (ALD) processes. ZrOx films were deposited on Pt/TiOx/SiOx/Si substrates using liquid injection ALD. Zr(C11H19O2)4 [Zr(DPM)4] dissolved in ethylcyclohexane (ECH) with a concentration of 0.1 M and water were used as precursor and oxidant, respectively. According to the Arrhenius plot for the deposition rate of ZrOx films at various deposition temperatures, the Zr precursor appeared to start marked thermal decomposition at a deposition temperature of 360ï¿¿C. Below this thermal decomposition temperature, a saturated deposition rate of ZrOx films against input of Zr precursor was confirmed. The saturated deposition rate was about 5-6ï¿¿10^-12 mol/cm²ï¿¿cycle at a deposition temperature of 300ï¿¿C. Subsequently, binary ALD processes of TiOx and PbO films, whose self-regulated growth mode has been already confirmed, were combined with the ZrOx process into multi-precursor ALD of PZT films. Ti(OC3H7)2(C11H19O2)2 [Ti(Oi-Pr)2(DPM)2] and Pb(C11H19O2)2 [Pb(DPM)2] dissolved in ECH with a concentration of 0.1 M were used for PZT film preparation as well as Zr(DPM)4. Unit sequences described as 1ï¿¿(Pb-O) - 2ï¿¿(Ti-O) - nï¿¿(Zr-O) were repeated to deposit PZT films at 240ï¿¿C. In the PZT process, the deposition rates of all cations were higher than those in their binary processes. The Pb/(Zr+Ti) and Zr/(Zr+Ti) ratio was adjusted by repeating the number of Zr-O cycles in a sequence. As-deposited PZT films were amorphous. Crystalline PZT films were obtained after annealing at 650ï¿¿C, and the PZT crystal showed a preferred (- 100)/(001) orientation.