Understanding the pH dependence of silicon etching: the importance of dissolved oxygen in buffered HF etchants

✍ Scribed by Simon P. Garcia; Hailing Bao; Melissa A. Hines

• Book ID: 104201977
• Publisher: Elsevier Science
• Year: 2003
• Tongue: English
• Weight: 265 KB
• Volume: 541
• Category: Article
• ISSN: 0039-6028
• DOI: 10.1016/s0039-6028(03)00952-x

✦ Synopsis

Dissolved O 2 is found to have a profound effect on the morphology of Si(1 1 1) surfaces etched in buffered hydrofluoric acid (BHF). Atomically smooth surfaces were exposed to BHF containing varying amounts of dissolved O 2 and the resulting changes in etch morphology were measured with scanning tunneling microscopy. These morphological changes were correlated with spectral changes in the infrared absorption spectrum. Surfaces etched in BHF containing dissolved O 2 are much rougher than those etched in O 2 -free BHF. This effect is explained by kinetic competition between O 2 -induced and etchant-induced oxidation reactions which are followed by rapid etching of the oxidized species. Dissolved O 2 alters the net site-specific reactivity of low pH BHF and leads to the production of rougher surfaces. The previously observed pH dependence of Si(1 1 1) etch morphology is also explained by this kinetic competition.