Macroscopic etch anisotropies and microscopic reaction mechanisms: a micromachined structure for the rapid assay of etchant anisotropy

• Published in: Surface science 2000-07, Vol.460 (1), p.21-38
• Main Authors: Wind, Rikard A., Hines, Melissa A.
• Format: Article
• Language: English
• Subjects: Alcohols; Alkali metals; Applied sciences; Computer simulations; Cross-disciplinary physics: materials science; rheology; Design. Technologies. Operation analysis. Testing; Electronics; Etching; Exact sciences and technology; Integrated circuits; Materials science; Microelectronics: LSI, VLSI, ULSI; integrated circuit fabrication technology; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Silicon; Single crystal surfaces; Surface cleaning, etching, patterning; Surface structure, morphology, roughness, and topography; Surface treatments
• ISSN: 0039-6028; 1879-2758
• DOI: 10.1016/S0039-6028(00)00479-9

A new technique for the rapid quantification of orientation-dependent etch rates, which uses micromachined test patterns and optical microscopy, has been developed. The etching of silicon in KOH etchants with and without isopropanol was studied. Etch rates measured with this technique are in good agreement with conventionally measured rates. In most cases, the etch rate anisotropies are well described by a simple model that is based on step-flow etching. Kinetic Monte Carlo simulations of etching were used to test the simple model and to generate approximate morphologies of the etched surfaces. Vicinal Si(110) surfaces display unusual, orientation-dependent etch rates in some etchants; the functional form of the etch rate anisotropy suggests that a morphological transition occurs on these highly reactive faces. In moderately concentrated KOH solutions where isopropanol is readily soluble, the measured etch rate anisotropies suggest that isopropanol stabilizes step-flow etching.