High-resolution electron energy-loss spectroscopy measurements on hydrophilic silicon (100) wafers: Temperature and aging effects

Abstract

The commonly used wet chemical surface treatment of Si wafers before processing generates a hydrophilic surface. This surface is characterized by the presence of singular and associated OH groups and an asymmetric Si–O–Si vibration at 1150 cm−1. It exhibits temperature and aging effects. Freshly prepared surfaces show prevalently singular OH groups. A decline in the OH vibrational signal intensity occurs largely in the first hours of storage. Annealing in UHV showed the OH groups to vanish around 720 K on fresh surfaces and around 570 K on aged surfaces. Hydrocarbons could be detected up to 570 K irrespective of aging. The thin oxide films (about 1 nm) exhibited differences in decomposition behavior depending on storage time. Fresh films disappeared between 1020 and 1070 K and aged films between 1120 and 1170 K. The chemistry of the dissolution process appears to be such that islands of Si emerge in the oxide. This is concluded from dissociative water adsorption from the residual gas on patches of Si in the SiO2 film, leading to Si–H and Si–OH groups on Si.