The discovery of ferroelectricity in HfO2-based materials in 2011 provided new research directions and opportunities. In particular, for atomic layer deposited Hf0.5Zr0.5O2 (HZO) films, it is possible to obtain homogenous thin films with satisfactory ferroelectric properties at a low thermal budget process. Based on experiment demonstrations over the past 10 years, it is well known that HZO films show excellent ferroelectricity when sandwiched between TiN top and bottom electrodes. This work reports a comprehensive study on the effect of TiN top and bottom electrodes on the ferroelectric properties of HZO thin films (10 nm). Investigations showed that during HZO crystallization, the TiN bottom electrode promoted ferroelectric phase formation (by oxygen scavenging) and the TiN top electrode inhibited non-ferroelectric phase formation (by stress-induced crystallization). In addition, it was confirmed that the TiN top and bottom electrodes acted as a barrier layer to hydrogen diffusion into the HZO thin film during annealing in a hydrogen-containing atmosphere. These features make the TiN electrodes a useful strategy for improving and preserving the ferroelectric properties of HZO thin films for next-generation memory applications.

In this Letter, the robust ferroelectric properties of low-temperature (350 °C) Hf0.5Zr0.5O2 (HZO) films are investigated. We demonstrate that the lower crystallization temperature of HZO films originates from a densified film deposition with an anhydrous H2O2 oxidant in the atomic layer deposition process. As a consequence of this densification, H2O2-based HZO films showed completely crystallinity with fewer defects at a lower annealing temperature of 350 °C. This reduction in the crystallization temperature additionally suppresses the oxidation of TiN electrodes, thereby improving device reliability. The low-temperature crystallization process produces an H2O2-based HZO capacitor with a high remanent polarization ( Pr), reduced leakage current, high breakdown voltage, and better endurance. Furthermore, while an O3-based HZO capacitor requires wake-up cycling to achieve stable Pr, the H2O2-based HZO capacitor demonstrates a significantly reduced wake-up nature. Anhydrous H2O2 oxidant enables the fabrication of a more reliable ferroelectric HZO device using a low process thermal budget (350 °C).

Leakage current, that causes interferences in the read/write operation, arising from neighboring unselected or half-selected memory cells is considered as one of the main hurdles to be overcome to increase density of cross-point memory arrays. In this work, the common drawbacks for a Ag-based steep-slope threshold switching selector, threshold voltage variability, and poor cycling endurance have been mended. This is achieved by lightly doping the switching layer with Ag instead of implementing the Ag active electrode that acts as a reservoir, which provides unlimited access of Ag to the selector medium. Here, we doped polycrystalline ZnO with Ag, fabricated by facile electrochemical deposition, making a prototypical candidate for the crystalline switching layer. When the amount of Ag is limited by doping, switching characteristics, that is, threshold voltage variability and cycling endurance, are improved. Lastly, different mechanisms causing a threshold switching device to fail are also discussed for the two different test vehicles. It has been found that an unlimited Ag source causes the devices to fail in a short-circuited manner, and a limited Ag source results in devices to fail in an open-circuited manner, after repeated measurements.

In recent times, the requirements have become extremely stringent for employing silicon nitride (SiN x ) films in various types of applications. For instance, high etch resistance coating is required for a film to act as an etch stop layer and gate spacer for nanoscale patterning for next-generation semiconductor devices. In this study, a chlorodisilane precursor, 1,1,1-trichlorodisilane (3CDS, Si 2 H 3 Cl 3 ), was used to deposit SiN x films using a hollow cathode plasma-enhanced atomic layer deposition system and compared with the SiN x films deposited using hexachlorodisilane (HCDS, Si 2 Cl 6 ) as well as pentachlorodisilane (PCDS, Si 2 HCl 5 ). In the process temperature range of 310−435 °C, a self-limiting surface reaction behavior with 4 × 10 3 L of 3CDS exposure and 2 × 10 6 L of NH 3 plasma exposure was observed. 3CDS particularly gives ∼45 and ∼20% higher growth per cycle than HCDS and PCDS, respectively. In addition, the SiN x films deposited using 3CDS at 480 °C have improved the wet etch rate (0.4 nm/min in 200:1 HF) and density (2.88 g/cm 3 ). Analyzed with time-of-flight secondary ion mass spectrometry, the 3CDS-derived SiN x films contain less hydrogen than the SiN x films formed using HCDS under identical process conditions. These superior film properties can be attributed to the unique structural characteristics of 3CDS, where the three chlorine and three hydrogen atoms are localized on each of the two silicon atoms. The SiN x films deposited on nanotrenches with a high aspect ratio (6:1) at 390 and 480 °C showed >85% and >65% conformality, respectively, and high etch resistance (1.9 and 0.8 nm/min, respectively, in 200:1 HF), suggesting that high-quality SiN x films can be formed from 3CDS on both planar and patterned surfaces.

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