Stoichiometry controlled homogeneous ternary oxide growth in showerhead atomic layer deposition reactor and application for Zr_xHf_1−xO₂

Atomic layer deposition (ALD) processes for binary oxide (AO_y or BO_z) 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 (t_A or t_B and t_O). This approach has been further extended for ternary oxide A_δB_1−δO_λ deposition with (i) super-cycle ALD method (where each super-cycle comprises of m-cycles of AO_y ALD followed by n-cycles of BO_z 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 A^pBO… pulsing sequence for ternary oxide A_δB_1−δO_λ deposition in showerhead ALD reactors. Here, the pulse-A^p 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 –A^che surface coverage [A^che] could be controlled below its saturation limit [A^che]^sat with exposure time t_A and precursor impingement rate k_Aⁱⁿ in the pulse-A^p reaction step. Furthermore, with precursor transport model, we show that k_Aⁱⁿ could be varied with a better control using ampoule temperature T_amp^A and precursor-A carrier gas flow F_i^A together than using T_amp^A alone. As example, we report Zr^pHfO… pulsed deposition of Zr_xHf_1−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 F_Ar^Zr.