Study of Si(100) surfaces etched in TMAH solution

Si(1 0 0) surfaces treated in a tetramethylammonium hydroxide (TMAH) solution at 70 degreesC 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 SiO2 becomes very rough. The AFM image confirms a very roughened sample surface (rms roughness of similar to5.9 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 similar to0.7.nm, in excellent agreement with an effective-medium approximation result (similar to0.6 nm). A correlation between roughness measured by AFM and SE results has also been discussed. (C) 2001 Elsevier Science B.V. All rights reserved.