Etching and Chemical Control of the Silicon Nitride Surface

Abstract

Silicon nitride is used for many technological applications, but a quantitative knowledge of its surface chemistry is still lacking. Native oxynitride at the surface is generally removed using fluorinated etchants, but the chemical composition of surfaces still needs to be determined. In this work, the thinning (etching efficiency) of the layers after treatments in HF and NHF solutions has been followed by using spectroscopic ellipsometry. A quantitative estimation of the chemical bonds found on the surface is obtained by a combination of infrared absorption spectroscopy in ATR mode, X-ray photoelectron spectroscopy, and colorimetry. Si-F bonds are the majority species present at the surface after silicon nitride etching; some Si-OH and a few Si-NH bonds are also present. No Si-H bonds are present, an unfavorable feature for surface functionalization in view of the interest of such mildly reactive groups for achieving stable covalent grafting. Mechanisms are described to support the experimental results, and two methods are proposed for generating surface SiH species: enriching the material in silicon, or submitting the etched surface to a H plasma treatment.

Superconducting Diamond on Silicon Nitride for Device Applications

“…Depth profiling of the partially oxidised silicon nitride surface, that which is comparable to our solvent cleaned surface, carried out by Holloway and Stein, 37 indicate the formation of a graded oxynitride film with a greater proportion of Si-O character at the surface, decreasing into bulk silicon nitride at greater wafer depths. 38 The O 1s peak present in the XPS spectra of silicon nitride following RCA-1 cleaning is greatly decreased in intensity, to that on the order of contaminant carbon. An Si-O peak, corresponding to SiO 2 , could not be fitted to the higher binding energy side of the Si 2p region, confirming a complete dissolution of the surface oxide.…”

“…Etching of the silicon nitride surface oxide has been observed in the literature, under treatment with hydrofluoric acid (HF), and resulted in a similar reduction in the O 1s line in XPS spectra, compared to the non etched surface. 31,38 The oxygen free surface is therefore ascribed to the etching ability of the RCA-1 cleaning solution, and we assign any residual oxygen at the surface to adsorbed oxygen species. Table 1.…”

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. [31][32][33] Knotter and Denteneer [31] and Liu et al [33] have proposed an etching mechanism of quasistoichiometric silicon nitride. It consists on the dissolution of one Si atom at the surface by successive breaking of four Si-N bonds.…”

Quantitative analysis of microplastics coagulation-removal process for clean sea salt production

“…Flocs after coagulation experiments were collected by filtration using a wire mesh with 1-mm pores, and the removal efficiency was calculated by measuring the dry weight of the filter cake.Thus, it may be possible that the removal efficiency was overestimated because the filter cake may contain other ingredients such as coagulants, NaCl, and unknown minerals coexisting in commercial sea salt. To elucidate this point, quantitative analysis of MP flocs was attempted using FTIR spectroscopy in the attenuated total reflectance spectrometer (ATR) mode (Brunet et al 2017;Giacinti Baschetti 2003).…”