Morphology and chemical termination of HF-etched Si3N4 surfaces

• Published in: Applied physics letters Vol. 105; no. 26
• Main Authors: Liu, Li-Hong, Debenedetti, William J. I., Peixoto, Tatiana, Gokalp, Sumeyra, Shafiq, Natis, Veyan, Jean-François, Michalak, David J., Hourani, Rami, Chabal, Yves J.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 29-12-2014
• Subjects: Applied physics; Atomic force microscopy; Deionization; Etching; Fluorine; Microcrystals; Morphology; Organic chemistry; Scanning electron microscopy; Silicon nitride; X ray spectra
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4905282

Several reports on the chemical termination of silicon nitride films after HF etching, an important process in the microelectronics industry, are inconsistent claiming N-Hx, Si-H, or fluorine termination. An investigation combining infrared and x-ray photoelectron spectroscopies with atomic force and scanning electron microscopy imaging reveals that under some processing conditions, salt microcrystals are formed and stabilized on the surface, resulting from products of Si3N4 etching. Rinsing in deionized water immediately after HF etching for at least 30 s avoids such deposition and yields a smooth surface without evidence of Si-H termination. Instead, fluorine and oxygen are found to terminate a sizeable fraction of the surface in the form of Si-F and possibly Si-OH bonds. The relatively unique fluorine termination is remarkably stable in both air and water and could lead to further chemical functionalization pathways.