Surface etching, chemical modification and characterization of silicon nitride and silicon oxide—selective functionalization of Si₃N₄and SiO₂

Abstract

The ability to selectively chemically functionalize silicon nitride (Si3N4) or silicon dioxide (SiO2) surfaces after cleaning would open interesting technological applications. In order to achieve this goal, the chemical composition of surfaces needs to be carefully characterized so that target chemical reactions can proceed on only one surface at a time. While wet-chemically cleaned silicon dioxide surfaces have been shown to be terminated with surficial Si-OH sites, chemical composition of the HF-etched silicon nitride surfaces is more controversial. In this work, we removed the native oxide under various aqueous HF-etching conditions and studied the chemical nature of the resulting Si3N4 surfaces using infrared absorption spectroscopy (IRAS), x-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS), and contact angle measurements. We find that HF-etched silicon nitride surfaces are terminated by surficial Si-F and Si-OH bonds, with slightly subsurface Si-OH, Si-O-Si, and Si-NH2 groups. The concentration of surficial Si-F sites is not dependent on HF concentration, but the distribution of oxygen and Si-NH2 displays a weak dependence. The Si-OH groups of the etched nitride surface are shown to react in a similar manner to the Si-OH sites on SiO2, and therefore no selectivity was found. Chemical selectivity was, however, demonstrated by first reacting the -NH2 groups on the etched nitride surface with aldehyde molecules, which do not react with the Si-OH sites on a SiO2 surface, and then using trichloro-organosilanes for selective reaction only on the SiO2 surface (no reactivity on the aldehyde-terminated Si3N4 surface).

A Hydrogen Plasma Treatment for Soft and Selective Silicon Nitride Etching

“…Several reaction mechanisms for the etching of Si 3 N 4 films in HF solution were discussed in the literature, based essentially on the pH and Si x N y stoichiometry . Knotter and Denteneer and Liu et al have proposed an etching mechanism of quasi‐stoichiometric silicon nitride. It consists on the dissolution of one Si atom at the surface by successive breaking of four Si–N bonds .…”

Mg2+/F− Synergy to Enhance the Ionic Conductivity of Na3Zr2Si2PO12 Solid Electrolyte for Solid‐State Sodium Batteries

“…In order to further insight into the existence form of fluorine, F 1s in the surface and interior of NZSP‐0.10MF pellet were detected by high‐resolution XPS (Figure S2). The peak at ∼689 eV corresponds to F−Si/P bond, demonstrating the presence of F − occupying part of the O 2− site in NZSP lattice. Meanwhile, obvious differences in the intensities of F 1s peaks at ∼684 eV, which corresponds to negatively charged F − state, are observed in surface and interior.…”

X-ray microscopic investigation of molecular orientation in a hole carrier thin film for organic solar cells

“…In that case, the silicon nitride has a native oxide layer at the surface. [29] The roughness of the Si3N4 substrate (presented in Supporting information Figure S1) is 0.5 nm (root mean square, RMS). The DIPO-Ph4 coverage is monitored during the evaporation in the evaporation chamber via a quartz balance (QBcoverage).…”

“…The ITO and Si3N4 have a native oxide layer and present a similar roughness (< 1 nm), the surface energy is assumed to equivalent following the literature. [29,31] In addition, the ITO/DIPO-Ph4 interface has already been structurally and electronically described. [32] As interfacial layer, DIPO-Ph4 layer will act as a hole-transport and an electron blocking layer.…”