Silicon etching with oxygen molecular beam assisted by predeposited germanium

• Published in: Applied physics letters 1990-02, Vol.56 (7), p.635-637
• Main Authors: TATSUMI, T, NIINO, T, HIRAYAMA, H
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Mechanical and acoustical properties; adhesion; Physics; Solid surfaces and solid-solid interfaces; Solid-fluid interfaces; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.102721

Si was etched using an O2 molecular beam according to the chemical reaction 2Si+O2→2SiO↑. The minimum etching temperature was decreased by 25 °C when a Ge layer had been deposited on a clean Si surface before etching. At 800 °C, the Ge-coated Si surface was etched while the clean Si surface was not. The O2 partial pressure during etching was 2×10−5 Torr; the etching rate was about 80 Å/min at 800 °C. Auger electron spectroscopy showed that the number of Ge atoms slightly decreased during Si etching. Ge atoms on the surface are thought to weaken Si back bonds by forming a thin Ge-Si alloy layer on the surface. Undercutting at the SiO2 mask edge was suppressed by this Ge predeposition technique at 800 °C because the sidewall without Ge was not etched at this temperature.