| AVS 66th International Symposium & Exhibition | |
| Plasma Science and Technology Division | Tuesday Sessions |
| Session PS+EM-TuM |
| Session: | Advanced FEOL |
| Presenter: | Ryoko Sugano, Hitachi, Ltd., Japan |
| Authors: | R. Sugano, Hitachi, Ltd., Japan Y. Ishii, Hitachi High Technologies America Inc. K. Maeda, Hitachi High Technologies America Inc. M. Miura, Hitachi High Technologies, Japan K. Kuwahara, Hitachi High Technologies, Japan |
| Correspondent: | Click to Email |
Simultaneous etching of Si and SiGe is an indispensable process for high throughput in the fabrication of Si/SiGe dual-channel FinFETs. SiGe etch rate is higher than Si etch rate by typical halogen chemistries used for Si etching [1]. Therefore, to control the etch rate between Si and SiGe, it is necessary to develop the chemistry that gives a higher Si etch rate than SiGe etch rate. Recently Ishii et al. have reported that hydrogen plasma selectively etched Si over SiGe, showing the selective Si removal over Ge [2]. In spite of selective Si etching over Ge, the Si-rich surface was observed after the hydrogen plasma exposure. They have attributed the Si-rich surface to hydrogen-induced Si surface segregation [2].
To understand the mechanism of the experimental phenomena on SiGe film described above, we performed ab-initio calculations that combined geometry optimizations and Nudged Elastic Band calculations. In the hydrogen-terminated SiGe surface system, we assumed the reacted states of SiGe were single dimer, in which three hydrogen atoms adsorbed on one of the dimer atoms (SiH3, GeH3) and a single hydrogen atom adsorbed on another of the dimer atoms. We found that the formation with SiH3 was energetically stable and was easy to desorb with a lower activation energy than that with GeH3. We considered that the selective Si removal over Ge was caused by both the selective formation and selective desorption of SiH3. We also calculated the formation energy of the SiGe surface immediately after selective Si removal, which originated from dimer breaking. It was found that the site exchange between the Ge atom in the first layer and the Si atom in the second layer was energetically favorable when another dimer atom left on the surface was terminated with a hydrogen atom. In conclusion, we confirmed experimental results of both selective Si etching over SiGe and Si surface segregation under the condition of hydrogen plasma by performing ab-initio calculations.
[1] G. S. Oehrlein, et al., Appl. Phys. Lett. 58, 2252 (1991).
[2] Y. Ishii et al., Jpn. J. Appl. Phys. 57, 06JC04 (2018).