Role of High-k Interlayer in ZrO₂/High-k/ZrO₂ Insulating Multilayer on Electrical Properties for DRAM Capacitor

Abstract

We studied characteristic of Metal-Insulator-Metal capacitors with ZrO2/high-k/ZrO2 (Z/high-k/Z)-nanolaminate dielectric layers and TiN electrodes. Amorphous Al2O3, (Ta/Nb)Ox (TN) and (Ta/Nb)Ox-Al2O3 (TNA) as high-k interlayer were prepared by atomic layer deposition and post-deposition annealing. The dielectric constant (k) of ZrO2 thin film exhibited about 28 because of tetragonal, orthorhombic and cubic phases. The k value of Z/high-k/Z-nanolaminate dielectric layer is high in order of ZTNZ > ZTNAZ > ZAZ due to the dependence of each k value of Al2O3 (~ 9) and TN (~29). The ZTNAZ layer exhibited lowest leakage current density of 10-8 ~ 10-7 A/cm2 at 0.6 V compared to those of ZAZ and ZTNZ in CET ~ 1.1 nm. We found that the leakage current property of Z/high-k/Z layer is influenced by not only amorphous structure but also band gap width (conduction band offset of ZrO2) of high-k interlayer. We conclude that the TNA material is one of the candidate material as high-k interlayer for future DRAM.

Improvement in ferroelectricity of HfxZr1−xO2thin films using ZrO2seed layer

“…In our previous research on high-k films, ZrO 2 film was determined to be advantageous due to its polycrystalline structure, which consisted mainly of an orthorhombic phase after the ALD process at 300 °C, in contrast to Al 2 O 3 's amorphous structure. 45,46) Therefore, ZrO 2 is expected to play an important role as a nucleation layer for HZO with o-HfO 2 . Materials with different structures were prepared as seed layers: crystallized ZrO 2 (ZrO 2 -seed), amorphous Hf 0.43 Zr 0.57 O 2 (HZO, HZO-seed), and amorphous Al 2 O 3 (Al 2 O 3 -seed).…”

Ferroelectricity of HfxZr1−xO2 Thin Films Fabricated Using TiN Stressor and ZrO2 Nucleation Techniques

“…It is well known that the ferroelectricity of the HZO film is obtained with the emergence of the non-centrosymmetric orthorhombic phase (11,12). The as-grown ALD-ZrO2 film had a polycrystalline structure with the tetragonal or orthorhombic phases, while as-grown ALD-HZO film had an amorphous structure, from XRD data (not shown) (13,14). For the w/o and D-TiN cases, the HZO films have polycrystalline structure by random nucleation and growth.…”

Improvement of Ferroelectricity and Fatigue Property of Thicker HfxZr1−XO2/ZrO2 Bi-layer

“…The stable M phase was generally found to have paraelectric property (1,10). In addition, the k value of M phase is lower than those of O/T/C phases according to the Clausius-Mossotti relation (11)(12)(13)(14). Therefore, the HZO layer crystallized with HfO2, which easily forms stable M phase, had dominantly a polycrystalline structure with M phase, and led to small ferroelectric switching behavior and lower k value, as shown in figures 2 and 3.…”