Higher-k Tetragonal Phase Stabilization in Atomic Layer Deposited Hf_1-xZr_xO₂ (0<x<1) Thin Films on Al₂O₃ Passivated Epitaxial-Ge

Abstract

For exploring the prospect of higher-k dielectric phase engineering on a high mobility substrate, films of Hf_1-xZr_xO₂ with varying x-values (0 ≤ x ≤ 1) were deposited on Al₂O₃ passivated Ge substrates using atomic layer deposition (ALD) with a cyclic deposit-anneal-deposit-anneal (DADA) scheme. The evolution of monoclinic to higher-k tetragonal structure with increasing ZrO₂ concentration was probed by grazing incident x-ray diffraction and partial reciprocal space maps using the highly brilliant synchrotron x-ray source at the Cornell High Energy Synchrotron Source (CHESS). A primarily amorphous/nano-crystalline matrix of the as-deposited films changed to randomly aligned grains of nanocry stalline MO₂ (M=Hf, Zr) after post deposition annealing at 800 °C for 200 seconds. In contrast, the DADA films annealed for same thermal budget showed high degree of preferred orientation along certain crystallographic directions. With increasing ZrO₂ content, the structure of the films changed from a monoclinic to a tetragonal phase. A lower amount of ZrO₂ (x = 0.33) was required for stabilizing the tetragonal phase in films grown on Al₂O₃ passivated Ge substrate as compared to similar films grown on a Si substrate via the same DADA process (x ≥ 0.50).