Atomic Layer Deposition of Pb(Zr,Ti)O<inf>x</inf>, Thin Films by a Combination of Binary Atomic Layer Deposition Processes

Abstract

After an evaluation of Zr precursor, quatemary Pb(Zr,Ti)O x [PZT] films were prepared by a combination of binary atomic layer deposition (ALD) processes. ZrO x films were deposited on Pt/TiO x /SiO x /Si substrates using liquid injection ALD. Zr(C 11 H 19 O 2 ) 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 ZrO x films at various deposition temperatures, the Zr precursor appeared to start marked thermal decomposition at a deposition temperature of 360�C. Below this thermal decomposition temperature, a saturated deposition rate of ZrO x films against input of Zr precursor was confirmed. The saturated deposition rate was about 5-6�10-12 mol/cm2 cycle at a deposition temperature of 300�C. Subsequently, binary ALD processes of TiO x and PbO films, whose self-regulated growth mode has been already confirmed, were combined with the ZrO x process into multi-precursor ALD of PZT films. Ti(OC 3 H 7 ) 2 (C 11 H 19 O 2 ) 2 [Ti(Oi-Pr) 2 (DPM) 2 ] and Pb(C 11 H 19 O 2 ) 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 1�(Pb-O) - 2�(Ti-O) - n�(Zr-O) were repeated to deposit PZT films at 240�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 650�C, and the PZT crystal showed a preferred (100)/(001) orientation.