The main strengthening mechanism for Inconel 718 (IN718), a Ni-based superalloy, is precipitation hardening by γ′ and γ″ particles. It is thus essential, for good alloy performance, that precipitates with the desired chemical composition have adequate size and dispersion. The distribution of the γ′ and γ″ phases and their chemical composition were investigated in the nickel-based Inconel 718 superalloy by taking advantage of the new capabilities of scanning transmission electron microscopy and energy-dispersive X-ray spectrometry using a windowless multiple detector, a high-brightness Schottky electron gun, and a spherical aberration corrector in the illumination probe optics. A small routine was developed to deconvolute the respective compositions of γ′ and γ″ nanoprecipitates embedded in the γ matrix. Keeping the electron probe current low enough—a few hundred pA—prevented excessive irradiation damage during the acquisition of element maps and brought their spatial resolution down to the atomic column level to track their element compositions. The present results agree with and complement atomic probe tomography observations and Thermo-Calc predictions from the literature. The presence of an Al enrichment at the γ′/γ″ interface—which may control the γ″ phase coarsening—is observed in the last row of Al-Nb-Ti columns along this interface. In addition, a few columns with similar composition changes are found randomly distributed in the γ′ phase.

In this work, hafnium zirconium oxide (HZO)-based 100 × 100 nm2 ferroelectric tunnel junction (FTJ) devices were implemented on a 300 mm wafer platform, using a baseline 65 nm CMOS process technology. FTJs consisting of TiN/HZO/TiN were integrated in between metal 1 (M1) and via 1 (V1) layers. Cross-sectional transmission electron microscopy and energy dispersive x-ray spectroscopy analysis confirmed the targeted thickness and composition of the FTJ film stack, while grazing incidence, in-plane x-ray diffraction analysis demonstrated the presence of orthorhombic phase Pca21 responsible for ferroelectric polarization observed in HZO films. Current measurement, as a function of voltage for both up- and down-polarization states, yielded a tunneling electroresistance (TER) ratio of 2.28. The device TER ratio and endurance behavior were further optimized by insertion of thin Al2O3 tunnel barrier layer between the bottom electrode (TiN) and ferroelectric switching layer (HZO) by tuning the band offset between HZO and TiN, facilitating on-state tunneling conduction and creating an additional barrier layer in off-state current conduction path. Investigation of current transport mechanism showed that the current in these FTJ devices is dominated by direct tunneling at low electric field (E < 0.4 MV/cm) and by Fowler–Nordheim (F–N) tunneling at high electric field (E > 0.4 MV/cm). The modified FTJ device stack (TiN/Al2O3/HZO/TiN) demonstrated an enhanced TER ratio of ∼5 (2.2× improvement) and endurance up to 106 switching cycles. Write voltage and pulse width dependent trade-off characteristics between TER ratio and maximum endurance cycles (Nc) were established that enabled optimal balance of FTJ switching metrics. The FTJ memory cells also showed multi-level-cell characteristics, i.e., 2 bits/cell storage capability. Based on full 300 mm wafer statistics, a switching yield of >80% was achieved for fabricated FTJ devices demonstrating robustness of fabrication and programming approach used for FTJ performance optimization. The realization of CMOS-compatible nanoscale FTJ devices on 300 mm wafer platform demonstrates the promising potential of high-volume large-scale industrial implementation of FTJ devices for various nonvolatile memory applications.

We present a detailed investigation on the nature of the interfacial layer (IL) in ultra-thin TiN/LaLuO₃ (LLO) gate stacks, which is of importance to facilitate CMOS scaling. The molecular beam deposited LaLuO₃ films are found to be amorphous by high-resolution transmission electron microscopy. A ∼9 Å thick LaLuO₃/interlayer transition observed by medium energy ion scattering correlates with the presence of a dual silicate/SiO₂-like interfacial layer derived from the analysis of photoelectron line positions and electron energy loss spectra. A theoretical model is used for the dielectric transition in a bi-layer LaLuO₃/IL structure, linking physical and electrical characterization data. The obtained leakage current of 10⁻³ A/cm² at 1.5 V and equivalent oxide thickness of 0.75 nm for TiN/LaLuO₃ gate stacks are adequate for scaling in the 14-12 nm node.