The Effect of Doping on the Digital Etching of Silicon-Selective Silicon-Germanium Using Nitric Acids

Yangyang Li; Huilong Zhu; Zhenzhen Kong; Yongkui Zhang; Xuezheng Ai; Guilei Wang; Qi Wang; Ziyi Liu; Shunshun Lu; Lu Xie; Weixing Huang; Yongbo Liu; Chen Li; Junjie Li; Hongxiao Lin; Jiale Su; Chuanbin Zeng; Henry H Radamson

doi:10.3390/nano11051209

The Effect of Doping on the Digital Etching of Silicon-Selective Silicon-Germanium Using Nitric Acids

Nanomaterials (Basel). 2021 May 3;11(5):1209. doi: 10.3390/nano11051209.

Authors

Yangyang Li^{1

2}, Huilong Zhu¹, Zhenzhen Kong¹, Yongkui Zhang¹, Xuezheng Ai¹, Guilei Wang^{1

2

3}, Qi Wang¹, Ziyi Liu^{1

2}, Shunshun Lu¹, Lu Xie^{1

2}, Weixing Huang^{1

2}, Yongbo Liu^{1

2}, Chen Li^{1

2}, Junjie Li¹, Hongxiao Lin^{1

3}, Jiale Su¹, Chuanbin Zeng⁴, 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 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, Guangzhou 510535, China.
⁴ Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China.

Abstract

Gate-all-around (GAA) field-effect transistors have been proposed as one of the most important developments for CMOS logic devices at the 3 nm technology node and beyond. Isotropic etching of silicon-germanium (SiGe) for the definition of nano-scale channels in vertical GAA CMOS and tunneling FETs has attracted more and more attention. In this work, the effect of doping on the digital etching of Si-selective SiGe with alternative nitric acids (HNO₃) and buffered oxide etching (BOE) was investigated in detail. It was found that the HNO₃ digital etching of SiGe was selective to n⁺-Si, p⁺-Si, and intrinsic Si. Extensive studies were performed. It turned out that the selectivity of SiGe/Si was dependent on the doped types of silicon and the HNO₃ concentration. As a result, at 31.5% HNO₃ concentration, the relative etched amount per cycle (REPC) and the etching selectivity of Si_0.72Ge_0.28 for n⁺-Si was identical to that for p⁺-Si. This is particularly important for applications of vertical GAA CMOS and tunneling FETs, which have to expose both the n⁺ and p⁺ sources/drains at the same time. In addition, the values of the REPC and selectivity were obtained. A controllable etching rate and atomically smooth surface could be achieved, which enhanced carrier mobility.

Keywords: HNO3 concentration; digital etch; doping effect; quasi-atomic-layer etching (q-ALE); selective wet etching; vertical gate-all-around (vGAA).

Abstract

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