Investigation on Ge0.8Si0.2-Selective Atomic Layer Wet-Etching of Ge for Vertical Gate-All-Around Nanodevice

Lu Xie; Huilong Zhu; Yongkui Zhang; Xuezheng Ai; Junjie Li; Guilei Wang; Anyan Du; Zhenzhen Kong; Qi Wang; Shunshun Lu; Chen Li; Yangyang Li; Weixing Huang; Henry H Radamson

doi:10.3390/nano11061408

Investigation on Ge_0.8Si_0.2-Selective Atomic Layer Wet-Etching of Ge for Vertical Gate-All-Around Nanodevice

Nanomaterials (Basel). 2021 May 26;11(6):1408. doi: 10.3390/nano11061408.

Authors

Lu Xie^{1

2}, Huilong Zhu¹, Yongkui Zhang¹, Xuezheng Ai¹, Junjie Li¹, Guilei Wang^{1

2

3}, Anyan Du¹, Zhenzhen Kong^{1

2

3}, Qi Wang¹, Shunshun Lu¹, Chen Li^{1

2}, Yangyang Li^{1

2}, Weixing Huang^{1

2}, Henry H Radamson^{1

2

3}

Affiliations

¹ Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China.
² Microelectronics Institute, University of Chinese Academy of Sciences, Beijing 100049, China.
³ Research and Development Center of Optoelectronic Hybrid IC, Guangdong Greater Bay Area Institute of Integrated Circuit and System, Guangdong 510535, China.

Abstract

For the formation of nano-scale Ge channels in vertical Gate-all-around field-effect transistors (vGAAFETs), the selective isotropic etching of Ge selective to Ge_0.8Si_0.2 was considered. In this work, a dual-selective atomic layer etching (ALE), including Ge_0.8Si_0.2-selective etching of Ge and crystal-orientation selectivity of Ge oxidation, has been developed to control the etch rate and the size of the Ge nanowires. The ALE of Ge in p⁺-Ge_0.8Si_0.2/Ge stacks with 70% HNO₃ as oxidizer and deionized (DI) water as oxide-removal was investigated in detail. The saturated relative etched amount per cycle (REPC) and selectivity at different HNO₃ temperatures between Ge and p⁺-Ge_0.8Si_0.2 were obtained. In p⁺-Ge_0.8Si_0.2/Ge stacks with (110) sidewalls, the REPC of Ge was 3.1 nm and the saturated etching selectivity was 6.5 at HNO₃ temperature of 20 °C. The etch rate and the selectivity were affected by HNO₃ temperatures. As the HNO₃ temperature decreased to 10 °C, the REPC of Ge was decreased to 2 nm and the selectivity remained at about 7.4. Finally, the application of ALE in the formation of Ge nanowires in vGAAFETs was demonstrated where the preliminary I_d-V_ds output characteristic curves of Ge vGAAFET were provided.

Keywords: atomic layer etching (ALE); dual-selective wet etching; p+-Ge0.8Si0.2/Ge stack; vertical Gate-all-around (vGAA).