Effects of TiN Top Electrode Texturing on Ferroelectricity in Hf_1–xZr_xO₂

Abstract

Ferroelectric memories based on hafnium oxide are an attractive alternative to conventional memory technologies due to their scalability and energy efficiency. However, there are still many open questions regarding the optimal material stack and processing conditions for reliable device performance. Here, we report on the impact of the sputtering process conditions of the commonly used TiN top electrode on the ferroelectric properties of Hf 1– x Zr x O 2 . By manipulating the deposition pressure and chemistry, we control the preferential orientation of the TiN grains between (111) and (002). We observe that (111) textured TiN is superior to (002) texturing for achieving high remanent polarization ( P r ). Furthermore, we find that additional nitrogen supply during TiN deposition leads to >5× greater endurance, possibly by limiting the scavenging of oxygen from the Hf 1– x Zr x O 2 film. These results help explain the large P r variation reported in the literature for Hf 1– x Zr x O 2 /TiN and highlights the necessity of tuning the top electrode of the ferroelectric stack for successful device implementation.

Hafnium Oxide (HfO2) – A Multifunctional Oxide: A Review on the Prospect and Challenges of Hafnium Oxide in Resistive Switching and Ferroelectric Memories

“…[356] In contrast, they assumed oxide electrodes to be transparent to the migration of oxygen vacancies; the fatigue effect in this kind of capacitor is therefore very small. [356] Recently, Athle et al [359] found that the P r of Zr-doped HfO 2 thin films is substantially affected by the texturing of the TiN film as a top electrode, ranging from almost zero for the majority (002) texture up to 30 µC cm -2 for the majority (111) texture.…”

“…Recently, Athle et al [ 359 ] found that the P r of Zr‐doped HfO 2 thin films is substantially affected by the texturing of the TiN film as a top electrode, ranging from almost zero for the majority (002) texture up to 30 µC cm −2 for the majority (111) texture.…”

Improved Endurance of Ferroelectric HfxZr1–xO2 Integrated on InAs Using Millisecond Annealing

“…The simulated peak surface temperatures of 550-710 °C are in the upper range and above the usually reported crystallization temperature of 400-600 °C required to form the ferroelectric orthorhombic phase in HZO. [2,11,[27][28][29] Thus, utilizing pulse energies in the range of 20-30 J cm -2 should yield a sufficiently high peak temperature to achieve ferroelectric properties in the HZO.…”

“…[8] Ferroelectric HfO 2 is typically achieved by crystallization of an amorphous thin film into the non-centrosymmetric orthorhombic phase Pca2 1 , which can be stabilized by doping and appropriate tensile stress from a metal electrode. [9,10] A common practice to achieve the orthorhombic phase is to form an alloy of HfO 2 with Zr, a popular choice due to the stability in the alloy composition. [11] To induce crystallization, a rapid thermal process (RTP) is usually performed in the range of 400-1000 °C for tens of seconds up to minutes.…”

Two-step deposition of TiN capping electrodes to prevent degradation of ferroelectric properties in an in-situ crystallized TiN/Hf0.5Zr0.5O2/TiN device

“…Recently, Athle et al reported that the ferroelectric properties of HZO films could be dependent on the TiN TE texture [40]. Their 111-textured TiN TE sample exhibited a high polarization value.…”