Analysis of surface-reaction layers formed by etching Si3N4 with pulsed-microwave plasma. (12th May 2015)

• Record Type: Journal Article
• Authors: Matsui, Miyako; Morimoto, Michikazu; Ikeda, Norihiko
• Is Part Of: Japanese journal of applied physics. Volume 54:Number 6(2015:Jun.)Supplement 2
• Publication Date: 2015-05-12
• Subjects: Physics -- Periodicals; 621.05
• DOI: 10.7567/JJAP.54.06GB02
• Languages: English
• ISSNs: 0021-4922

Abstract

Abstract: The mechanism of highly selective etching of Si3 N4 by a pulsed-microwave electron-cyclotron-resonance plasma was investigated by analyzing surface-reaction layers formed by etching using a CH3 F/O2 /Ar gas chemistry. A hydrofluorocarbon (HFC) layer formed not only on nonpatterned materials (Si3 N4 and others) but also at the bottoms of line-and-space patterns were analyzed by X-ray photoelectron spectroscopy. Thermal reactivity between the HFC layer and the Si3 N4 layer was also investigated by thermal-desorption spectroscopy. The investigation results show that nitrogen contained in the Si3 N4 layer thermally reacted with the HFC layer to form NH3 or HCN, and silicon contained in Si3 N4 had high reactivity with fluorine contained in the HFC layer. Owing to the high reactivity between the fluorine-rich HFC layer and the Si3 N4 layer in the pulsed-microwave plasma, the HFC layer became thin, even at a low wafer bias, and thus promoted ion-assisted etching. A wide process window was provided by the formation of the fluorine-rich thin HFC layer using the pulsed-microwave plasma.