Stoichiometry controlled homogeneous ternary oxide growth in showerhead atomic layer deposition reactor and application for ZrxHf1−xO2

Abstract

Atomic layer deposition (ALD) processes for binary oxide (AOy or BOz) growth consist of a sequential introduction of metal precursor (precursor-A or precursor-B) and oxidant-O such that the respective surface reactions are self-limiting with respect to precursor and oxidant exposure times (tA or tB and tO). This approach has been further extended for ternary oxide AδB1−δOλ deposition with (i) super-cycle ALD method (where each super-cycle comprises of m-cycles of AOy ALD followed by n-cycles of BOz ALD), (ii) precursor co-dosing method (where precursor-A and precursor-B are simultaneously pulsed followed by an oxidant-O pulse), and (iii) 3-step ALD (where precursor-A, precursor-B, and oxidant-O are sequentially pulsed). In this Letter, we present a subsaturation pulse initiated 3-step process with ApBO… pulsing sequence for ternary oxide AδB1−δOλ deposition in showerhead ALD reactors. Here, the pulse-Ap reaction step is controlled in the subsaturation regime, while both pulse-B and pulse-O reaction steps are allowed to reach saturation as in a typical ALD. From kinetic simulations, we show that the chemisorbed –Ache surface coverage [Ache] could be controlled below its saturation limit [Ache]sat with exposure time tA and precursor impingement rate kAin in the pulse-Ap reaction step. Furthermore, with precursor transport model, we show that kAin could be varied with a better control using ampoule temperature TampA and precursor-A carrier gas flow FiA together than using TampA alone. As example, we report ZrpHfO… pulsed deposition of ZrxHf1−xO2 ternary oxide samples ZHO1–ZHO4 in a showerhead ALD reactor, and from quantitative XPS analysis, we show that the Zr-fraction (x) could be varied in the range of 0.094 ≤ x ≤ 0.159 with Zr-carrier gas flow FArZr.