Strained Si, SiGe, and Ge channels for high-mobility metal-oxide-semiconductor field-effect transistors

Abstract

This article reviews the history and current progress in high-mobility strained Si, SiGe, and Ge channel metal-oxide-semiconductor field-effect transistors (MOSFETs). We start by providing a chronological overview of important milestones and discoveries that have allowed heterostructures grown on Si substrates to transition from purely academic research in the 1980’s and 1990’s to the commercial development that is taking place today. We next provide a topical review of the various types of strain-engineered MOSFETs that can be integrated onto relaxed Si1−xGex, including surface-channel strained Si n- and p-MOSFETs, as well as double-heterostructure MOSFETs which combine a strained Si surface channel with a Ge-rich buried channel. In all cases, we will focus on the connections between layer structure, band structure, and MOS mobility characteristics. Although the surface and starting substrate are composed of pure Si, the use of strained Si still creates new challenges, and we shall also review the literature on short-channel device performance and process integration of strained Si. The review concludes with a global summary of the mobility enhancements available in the SiGe materials system and a discussion of implications for future technology generations.

On the influence of elastic strain on the accommodation of carbon atoms into substitutional sites in strained Si:C layers grown on Si substrates

“…The t crit of a s-Si/ Si 0.8 Ge 0.2 layer is about 14 nm. 18 Using these data, the dependence of t crit of a tensile s-Si 1−y C y / Si layer on the C sub was calculated ͑Fig. 2͒.…”

Evolution of vacancy-related defects upon annealing of ion-implanted germanium

“…Germanium has higher bulk carrier mobilities than Si or SiGe and in consequence holds the possibility of higher channel mobility in metal-oxidesemiconductor field-effect transistor ͑MOSFET͒ devices particularly in the presence of strain. 1 Due to the dominance of silicon in semiconductor industry, very little research has been conducted on the properties of ion-implanted germanium until recently. Some of this work and an extensive comparison of the material properties of silicon and germanium have been compiled by Vanhellemont and Simoen.…”

Electrical compensation via vacancy–donor complexes in arsenic-implanted and laser-annealed germanium

“…Particular efforts have been made to deploy the superior charge carrier mobility of Ge in complementary metal-oxide-semiconductor usage. 1 A few hindrances exist, however, including the poor quality of the native surface oxide GeO 2 2 and the difficulty in obtaining high-enough n-type carrier concentrations for ultra-shallow junctions. 3 While the insulation issue has essentially been resolved by introducing high-j dielectrics as a replacement for SiO 2 a decade ago 4 (directly applicable to Ge), the doping limitations are still to be overcome.…”