The hydrogen passivation of (100) silicon surfaces is characterized as a function of the chemical treatment by means of multiple internal reflection infrared (IR) spectroscopy using a novel sample preparation method. The samples are etched in different HF solutions (aqueous HF, HF/HCl/H2O, HF/acetic acid, HF/isopropyl/H2O, and buffered HF) and investigated with and without DI water rinsing. The stability of the surfaces against oxidation and the buildup of a hydrocarbon contamination layer during storage in cleanroom air are examined. The IR peak at 2123 cm-1 is related to a coupling mode between dihydrides and neighboring monohydrides.