Characterization of silicon surface preparation processes for advanced gate dielectrics

Abstract

This paper gives a short overview of issues associated with the surface preparation of silicon surfaces for advanced gate dielectrics and the appearance and nature of the wafer surface after different chemical treatments. The main portion of the paper demonstrates the use of electrochemical open-circuit potential (OCP) measurements as a simple and powerful technique to investigate and characterize wet silicon surface-preparation processes. This technique provides unique information about the evolution of semiconductor surface reactions in wet- chemical environments and permits the investigation of the kinetics of oxidation and etching processes in situ and in real time. Very good agreement between results obtained by this technique and results from multiple internal reflection-Fourier transform infrared spectroscopy (MIR-FTIR), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry (SE), and contact-angle studies is presented in this paper. A model is also presented which permits the correlation of the measured open circuit potential difference to the thickness of a growing native oxide. The etching behavior of an ultrathin thermally grown silicon oxide layer in hydrofluoric acid (HF) is discussed as a new result obtained using the OCP technique.