Study of Si(1 0 0) surfaces etched in TMAH solution

Abstract

Si(1 0 0) surfaces treated in a tetramethylammonium hydroxide (TMAH) solution at 70°C have been studied using spectroscopic ellipsometry (SE) and ex situ atomic force microscopy (AFM). The SE data indicate that surface native oxide is etched gradually and then lift-off in places with immersing in the solution. Since the solution attacks bulk silicon more rigorously than the surface native oxide, the Si(1 0 0) surface of partly remained SiO 2 becomes very rough. The AFM image confirms a very roughened sample surface (rms roughness of ∼5.9 nm). Just after the surface native oxide is etched away completely, the SE data yield the spectrum of a nearly flat silicon surface. The AFM rms roughness for this sample is found to be ∼0.7 nm, in excellent agreement with an effective-medium approximation result (∼0.6 nm). A correlation between roughness measured by AFM and SE results has also been discussed.