Annihilation of Threading Dislocations in Strain-Relaxed Si1-XGex Layer By Hydrogen Ion Implantation

Abstract

According to the international technology roadmap for semiconductor (ITRS), the development of MOSFETs based on the strain technology is necessary for the next generation technology beyond 10-nm C-MOSFETs. By being applied the strain in the channel of MOSFET, the electron mobility can be enhanced results in the higher current in MOS channel at the fixed gate voltage and oxide thickness. However, due to the lattice mismatch of 4.2 % between Si and Ge, many threading dislocations are generated during the epitaxial growth, resulted in increasing the leakage current of the C-MOSFETs. Currently, the threading dislocation density of 3-µm-thick X-at% (>30-at%) graded Si1-xGex layer is higher than 105 cm-2, which is too high level to be applied in mass production because of degrading the productivity and the performance of the C-MOSFETs. In this study, for that reason, to reduce threading dislocations in the strain-relaxed Si1-xGex layer, we investigated how the hydrogen ion implantation annihilated the threading dislocations in strain-relaxed Si1-xGex layer/Si (100) substrate. First, a relaxed Si1-xGex layer was grown on a Si (100) substrate by epitaxial growth. Second, hydrogen ions were implanted onto the interface between the strain-relaxed Si1-xGex layer and the Si substrate. After ion implantation, the sample was annealed at 800oC for 30 min in a nitrogen ambient. For the case of hydrogen ion implantation with a dose of 5ⅹ1015 cm-2, it was confirmed that the cross-hatch pattern density and the surface roughness was decreased and threading dislocations near the interface were not observed in hydrogen ion-implanted Si1-xGex/Si wafer as shown in Fig. 1. In addition, as shown in Fig. 2, by using in-situ real-time high-resolution TEM, it was confirmed that a threading dislocation in hydrogen ion-implanted Si0.7Ge0.3 layer/Si substrate was annihilated with hydrogen-related defect while the TEM specimen was being annealed at 600oC for 30 min in the heating holder. Therefore, we present the formation mechanism of threading dislocations in a strain-relaxed Si1-xGex layer/Si (100) substrate and the annihilation mechanism of how the threading dislocations are annihilated by hydrogen ion implantation.* This work was financially supported by the Brain Korea 21 Plus Program in 2016 and SiWEDS (Silicon Wafer Engineering and Defect Science). Reference [1] J. G. Park et al., Mat. Sci. Eng. B 134 142-153 (2006) [2] S. Takagi, Strained-Si CMOS Technology in Advanced Gate Stacks for High-Mobility Semiconductors, Springer Berlin Heidelberg 1 (2007) Figure 1