Handbook of Cleaning for Semiconductor Manufacturing: Fundamentals and Applications

Chapter 12

Germanium Surface Conditioning and Passivation

Sonja Sioncke1, Yves J. Chabal2, and Martin M. Frank3

1IMEC, Leuven, Belgium

2University of Texas at Dallas, Richardson, Texas, USA

3IBM T.J. Watson Research Center, Yorktown Heights, New York, USA

Abstract

Germanium is a candidate to replace silicon as channel material for the gate electrode. Due to the aqueous solubility and the thermal instability of GeO2, cleaning solutions commonly used for Si are ineffective and must be adapted to this material. Hydrogen passivation of the Ge surface, as compared to Si, is more difficult to achieve and the H-terminated Ge surface is very unstable. Various methods are being used to stabilize the Ge surface; such as, oxidation of the Ge to stoichiometric GeO2, oxynitridation, and even nitridation of the Ge substrate. Oxide-free Ge-surfaces can also be achieved by using HCl or other treatments, but even these are prone to reoxidation. Sulfur-containing passivation is shown to prevent interaction of the Ge channel with the HfO2 gate. Metal and particle removal can be achieved using highly diluted cleaning solutions. This chapter discusses the various methods to passivate the surface and the surface analysis results.

Keywords: germanium, hydrogenation, oxidation, (oxy)nitridation, surface passivation, sulfur passivation, germanium passivation

12.1 Introduction

12.1.1 Germanium Use in Integrated Circuit Transistors

John Bardeen, Walter Brattain, and William Shockley received the Nobel Prize ...