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

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 Si_1-xGe_x grown on Si substrate. We applied the H⁺ post-implantation which forms defect band at the dislocation clusters above the interface between the Si_1-xGe_x 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 Si_0.8Ge_0.2 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 Si_0.8Ge_0.2 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 Si_0.7Ge_0.3and 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 Si_1-xGe_x/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 Si_1-xGe_x/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)