High Electron and Hole Mobility by Localized Tensile & Compressive Strain Formation Using Ion Implantation and Advanced Annealing of Group IV Materials (Si+C, Si+Ge & Ge+Sn)

Abstract

Since the 90nm node the industry has been using S/D-stressor for strain-channel formation and increased hole & electron mobility.  The S/D-stressor strain-Si method required optimizing the deep S/D junction with the shallow SDE implant junction.  PMOS used recess etch eSiGe for p+ S/D tensile strain with precise lateral gate overlap distance control to induce channel compressive strain for increased hole mobility in Si while NMOS n+ S/D compressive strain is formed by deep amorphous implant with carbon and stacking fault dislocation defects that induces channel tensile strain for increased electron mobility in Si.  With the switch in transistor design from 2-D planar to 3-D FinFET by the industry at the 22nm and 14/16nm nodes, increasing eSiGe Ge content above 55% has reached it’s limit in strain-Si S/D-stressor of -3GPa for hole mobility improvement therefore requiring higher mobility channel material at 10nm and beyond by using: 1) relaxed >70% SiGe to 100% Ge or 2) compressive strain >50% SiGe to 100% Ge for higher hole mobility.  Higher electron mobility requires: 1) relaxed >95% SiGe to 100% Ge, 2) tensile strain-Si on >25% relaxed-SiGe or 3) tensile strain >50% SiGe to 100% Ge.   Using CVD epitaxial growth of SiGe and Ge requires thick SRB (strain relaxed buffer) epilayers by blanket or selective epitaxial growth but this results in threading dislocation in the 106 to 109 /cm2 level results in high n+ and p+ junction leakage.  The reported targets for NMOS is 2% tensile channel strain of >1.5GPa while for PMOS, 2% compressive channel strain of >-1.5GPa at 7nm node [1]. This paper will review strain-Si and strain-Ge formation by ion implantation and advanced annealing to form tensile and compressive strain channel for improved electron and hole mobility in Group IV materials.  Carbon and Si implants was used to form surface tensile strained-channel SiC, GeC and GeSi material while Ge and Sn implants was used to form surface compressive strained-channel SiGe, SiGeSn and GeSn material.  Improved hole mobility (µh) by >4x and electron mobility (ue) by >2x have been reported by use of implantstrain formation [2,3]. References 1] R. Kim et al., IEDM-2015, paper 34.1. 2] J. Borland et al., IWJT-2013, paper S4-4, p.49. 3] J. Borland et al., IWJT-2015, paper S2-1, p.12.