Analysis of SiH and SiN vibrational absorption in amorphous SiNx:H films in terms of a charge-transfer model

Tunable Si Dangling Bond Pathway Induced Forming-Free Hydrogenated Silicon Carbide Resistive Switching Memory Device

With the coming of the big data age, the resistive switching memory (RSM) of three-dimensional (3D) high density shows a significant application in information storage and processing due to its simple structure and size-scalable characteristic. However, an electrical initialization process makes the peripheral circuits of 3D integration too complicated to be realized. Here a new forming-free SiC_x:H-based device can be obtained by tuning the Si dangling bond conductive channel. It is discovered that the forming-free behavior can be ascribed to the Si dangling bonds in the as-deposited SiC_x:H films. By tuning the number of Si dangling bonds, the forming-free SiC_x:H RSM exhibits a tunable memory window. The fracture and connection of the Si dangling bond conduction pathway induces the switching from the high-resistance state (HRS) to the low-resistance state (LRS). Our discovery of forming-free SiC_x:H resistive switching memory with tunable pathway opens a way to the realization of 3D high-density memory.

In Situ Monitoring of Surface Reactions during Atomic Layer Etching of Silicon Nitride Using Hydrogen Plasma and Fluorine Radicals

The atomic layer etching (ALE) of silicon nitride (SiN) via a hydrogen plasma followed by exposure to fluorine radicals was investigated by using in situ spectroscopic ellipsometry and attenuated total reflectance Fourier transform infrared (FTIR) spectroscopy to examine the surface reactions and etching mechanism. FTIR spectra of the surface following exposure to the hydrogen plasma showed an increase in the concentration of Si-H and N-H bonds, although the N-H bond concentration plateaued more quickly. In contrast, during fluorine radical exposure, the Si-H bond concentration decreased more rapidly. Secondary ion mass spectrometry demonstrated that the nitrogen atom concentration was decreased to a depth of 4 nm from the surface after the hydrogen plasma treatment and indicated a structure consisting of N-H rich, Si-H rich, and mixed layers. This indicated that Si-H bonds were primarily present near the surface, while N-H bonds were mainly located deeper into the film. The formations of the N-H and Si-H rich layers are important phenomena associated with modification by hydrogen plasma and fluorine radical etching, respectively.

Structural and optical characterization of pure Si-rich nitride thin films

The specific dependence of the Si content on the structural and optical properties of O- and H-free Si-rich nitride (SiNx>1.33) thin films deposited by magnetron sputtering is investigated. A semiempirical relation between the composition and the refractive index was found. In the absence of Si-H, N-H, and Si-O vibration modes in the FTIR spectra, the transverse and longitudinal optical (TO-LO) Si-N stretching pair modes could be unambiguously identified using the Berreman effect. With increasing Si content, the LO and the TO bands shifted to lower wavenumbers, and the LO band intensity dropped suggesting that the films became more disordered. Besides, the LO and the TO bands shifted to higher wavenumbers with increasing annealing temperature which may result from the phase separation between Si nanoparticles (Si-np) and the host medium. Indeed, XRD and Raman measurements showed that crystalline Si-np formed upon 1100°C annealing but only for SiNx<0.8. Besides, quantum confinement effects on the Raman peaks of crystalline Si-np, which were observed by HRTEM, were evidenced for Si-np average sizes between 3 and 6 nm. A contrario, visible photoluminescence (PL) was only observed for SiNx>0.9, demonstrating that this PL is not originating from confined states in crystalline Si-np. As an additional proof, the PL was quenched while crystalline Si-np could be formed by laser annealing. Besides, the PL cannot be explained neither by defect states in the bandgap nor by tail to tail recombination. The PL properties of SiNx>0.9 could be then due to a size effect of Si-np but having an amorphous phase.