Silicon Technologies: Ion Implantation and Thermal Treatment

Chapter 4

Epitaxy of Strained Si/Si₁-_x Ge_x Heterostructures ¹

4.1. Introduction

4.1.1. General introduction

This chapter discusses the reduced pressure-chemical vapor deposition (RP-CVD) of Si/SiGe (C) heterostructures for nanoelectronics and opto-electronics. The chapter is structured as follows. Section 4.1 will present: (i) the development since the beginning of the industrial CVD of Si and SiGe; (ii) the epitaxy tool used in CEA-LETI to carry out studies described in this chapter; and (iii) some general concepts of epitaxy which will be useful later on. The epitaxy of strained Si/Si_1-xGe_x and Si/Si_1-yC_y heterostructures as conducting channels of pMOS and nMOS transistors, will be detailed in sections 4.2 and 4.3. The selective epitaxial growth on SOI substrates of Si or SiGe(:B) recessed and raised sources and drains will be described in sections 4.4 and 4.5.

In section 4.6, we will present the structural properties of (i) SiGe virtual substrates and the tensily-strained Si layers grown on top and (ii) the sSOI substrates resulting from them. We will also focus on the electric gains (thanks notably to dual channels) in nMOS and pMOS transistors built on top. The structural, electric and optical devices properties of thick Ge layers and of Ge islands on Si(001) will be described in section 4.7. We will highlight in section 4.8, the exciting possibilities offered from an architectural point of view by the lateral selective etching of SiGe sacrificial layers. Finally, the most ...