Influence of Hydrogen Post-Implantation on Threading Dislocation Density in Strain-Relaxed Sige Layer

Abstract

According to International Technology Roadmap for Semiconductor (ITRS), the development of MOSFETs based on SiGe or Ge is necessary for the next generation technology beyond 10-nm C-MOSFETs, because electron and hole mobility of Ge substrate is three and four times higher than those of a conventional Si MOSFETs, respectively. However, due to the lattice mismatch of 4.2 % between Si and Ge, many threading dislocations are generated, resulted in increasing the leakage current of the C-MOSFETs. The threading dislocation density of graded SiGe layer utilized currently is higher than 105 cm-2, which is too high to be applied in mass production because of degrading productivity and performance of the C-MOSFETs. To overcome this drawback in realizing sub 10-nm C-MOSFETs, a novel process technology should be developed to reduce the threading dislocation density. In this study, we designed a novel technology to reduce the threading dislocations in strain-relaxed Si1-xGex grown on Si substrate. We applied the H+ post-implantation which forms defect band at the dislocation clusters above the interface between the Si1-xGex layer and the Si substrate, acting as a dislocation sink. We investigated how the hydrogen-ion implantation followed by annealing affected the surface characteristics, such as dislocation pit and cross-hatch pattern density related the threading dislocation. In particular, the cross-hatch pattern density of the Si0.8Ge0.2 layer on the Si substrate was about 4x104 cm-1, as shown in Fig. 1(a). On the other hand, when hydrogen ions were implanted into the relaxed Si0.8Ge0.2 layer with an dose of 5x1015 cm-2, the cross-hatch pattern density was reduced to about 1.18x104 cm-1, as shown in Fig. 1(b). Also, there was a high threading dislocation density in the case of 30-at% Ge concentration, as shown in Fig. 2(a). However, for the case of hydrogen ion implantation, a dose of 5x1015 cm-2, both threading and misfit dislocations near the interface between Si0.7Ge0.3and Si substrate were significantly reduced, as shown in Fig. 2(b). Therefore, we present the mechanism of the strain relaxation resulted in the formation of the threading dislocation in Si1-xGex/Si (100) substrate. In addition, we explain how H+ implantation affects the cross-hatch pattern density related the threading dislocation. Furthermore, we report the process technology and optimized the implanted energy, dose, and the position of dislocation sink in Si1-xGex/Si structure via ion implantation. * This work was financially supported by the Brain Korea 21 Plus Program in 2015 and SiWEDS (Silicon Wafer Engineering and Defect Science). Reference [1] J. G. Park et al., Mat. Sci. Eng. B 134142-153 (2006) [2] S. Takagi, Strained-Si CMOS Technology in Advanced Gate Stacks for High-Mobility Semiconductors, Springer Berlin Heidelberg 1 (2007) Figure 1