Mechanism of Selective Etching of SiGe Layers in SiGe/Si Systems

Kato, Juri; Oka, Hideaki; Kanemoto, Kei; Hisamatsu, H.; Matsuzawa, Yusuke; Kitano, Y.; Hara, Toshiki; Hoshina, Masaki; Ohmi, Shun–ichiro

doi:10.1149/1.2794470

Cited by 11 publications

(5 citation statements)

References 16 publications

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“…10 The differences of the selectivity and etch rate mentioned above within stacked layers and independent samples can be discovered obviously. The differences may be due to changed electrochemical reaction with band offset of SiGe, 41 heterojunction strain, defects and so on which are not be confirmed in our best of knowledge. The oxide growth rate also be affected by the concentration of free carriers especially in early stage of oxidation.…”

Section: Resultsmentioning

confidence: 79%

Study of Isotropic and Si-Selective Quasi Atomic Layer Etching of Si_1−xGe_x

Yin

Zhu

Zhao

et al. 2020

ECS J. Solid State Sci. Technol.

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The lateral and vertical gate-all-around (GAA) field-effect transistors are considered the most promising candidates for next generation logic device at and beyond 3-nm technology node. SiGe plays an important role in these devices as the sacrificial layer or channel material and needs isotropic etching. In this paper, an advanced etching process termed quasi atomic layer etching (qALE) is developed with advantages of controllable etch rate and atomically smooth surfaces. The qALE of SiGe is based on wet chemical etching, in which H2O2 is applied to oxidate the surface with cyclic manner, and diluted buffered oxide etchant (dBOE) is applied to remove the oxide. The profiles of SiGe qALE for quasi-self-limited behavior, etch rate and the effect in concentration and temperature of H2O2 have been studied. The etch per cycle (EPC) of Si0.7Ge0.3 is 0.50 nm and the etching selectivity between Si0.7Ge0.3 and heavily p-type doped silicon is 4.99 in Si/SiGe/Si stacked layers with (110) sidewall. The etch rate and the selectivity are influenced by Ge fraction of SiGe and the boron doping in Si. The root mean square (RMS) roughness after 60 cycles qALE is 0.183 nm indicating atomically smooth surfaces. Finally, the application of qALE for vertical nanowire compared with wet continuous etching is discussed in this work.

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Section: Resultsmentioning

confidence: 79%

Study of Isotropic and Si-Selective Quasi Atomic Layer Etching of Si_1−xGe_x

Yin

Zhu

Zhao

et al. 2020

ECS J. Solid State Sci. Technol.

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“…In addition, when the doping type and concentration are considered, the etching rate relationship with the doping type is p-type < intrinsic < n-type. , In Figure b, the second Si 0.7 Ge 0.3 layer was doped with B at a concentration of 1 × 20 cm –3 . Going through 25% HNO 3 30 s oxidation digital etching, the intrinsic Si 0.7 Ge 0.3 (i-Si 0.7 Ge 0.3 ) tunnel depth was obviously larger than that of the p-type Si 0.7 Ge 0.3 .…”

Section: Results and Discussionmentioning

confidence: 99%

“…According to Turner, HNO 3 was the oxidant. 26 Kato et al 27 analyzed the selective etch of SiGe and Si with the HNA system. They concluded that the selectivity between SiGe and Si was because of the band offset for the valence-band (ΔE v between p + -Si and Si 0.7 Ge 0.3 is ∼0.12 eV).…”

Section: Introductionmentioning

confidence: 99%

Selective Digital Etching of Silicon–Germanium Using Nitric and Hydrofluoric Acids

Zhu

Zhang

et al. 2020

ACS Appl. Mater. Interfaces

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The digital etching characteristics of p+ Si and Si0.7Ge0.3 using the combinations of HNO3 oxidation and BOE oxide removal processes were studied. Experiments showed that oxidation saturates with time due to low activation energy. A physical model was presented to describe the wet oxidation process with nitric acid. The model was calibrated with experimental data and the oxidation saturation time, final oxide thickness, and selectivity between Si0.7Ge0.3 and p+ Si were obtained. The digital etch of laminated Si0.7Ge0.3/p+ Si was also investigated. The depth of the tunnels formed by etching SiGe layers between two Si layers was found in proportion to digital 2 etching cycles. And oxidation would also saturate and the saturated relative etched amount per cycle (REPC) was 0.5 nm (4 monolayers). A corrected selectivity calculation formula was presented. The oxidation model was also calibrated with Si0.7Ge0.3/p+ Si stacks, and selectivity from model was the same with the corrected formula. The model can also be used to analyze process variations and repeatability. And it could act as a guidance for experiment design.Selectivity and repeatability should make a trade-off.

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“…However, SiO x and GeO x are simultaneously formed on the SiGe surface and the GeO x will be dissolved in water, so the oxidation will not stop until sufficient SiO x is formed. [14,15] Therefore, one cycle of self-limited oxidation is completed before this oxidation has been completely removed by the HF solution. This signature is consistent with the phenomenon that oxidation thickness of Si 0.7 Ge 0.3 fin first increases and then turns saturated as HNO 3 solution immersion time going by.…”

Section: Narrowed Si 07 Ge 03 Fin Preparationmentioning

confidence: 99%

Narrowed Si_0.7Ge_0.3 channel FinFET with subthreshold swing of 64 mV/Dec using cyclic self-limited oxidation and removal process

Liu

Wang

2023

Chinese Phys. B

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In this work, a narrowed Si0.7Ge0.3 channel FinFET device using a precise cyclic wet treatment process is demonstrated in detail. Si0.7Ge0.3 fin/per side of 0.63nm can be accurately removed in each cycle by utilizing a self-limited oxidation with 40% HNO3 solution for 40 s and oxidation removal with 1% HF solution for 10 s. As a result, after the dummy gate removal, the fin width of Si0.7Ge0.3 can be narrowed from 20nm to 8nm by utilizing 10 cycles of this wet treatment process. Compared with the conventional Si0.7Ge0.3 FinFET under the similar process, the narrowed Si0.7Ge0.3 channel FinFET using this newly developed wet treatment process can realize a stronger gate control capability because its subthreshold slope can be reduced by 24%, improved from 87 to 64 mV/dec.

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Mechanism of Selective Etching of SiGe Layers in SiGe/Si Systems

Cited by 11 publications

References 16 publications

Study of Isotropic and Si-Selective Quasi Atomic Layer Etching of Si_1−xGe_x

Study of Isotropic and Si-Selective Quasi Atomic Layer Etching of Si_1−xGe_x

Selective Digital Etching of Silicon–Germanium Using Nitric and Hydrofluoric Acids

Narrowed Si_0.7Ge_0.3 channel FinFET with subthreshold swing of 64 mV/Dec using cyclic self-limited oxidation and removal process

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Mechanism of Selective Etching of SiGe Layers in SiGe/Si Systems

Cited by 11 publications

References 16 publications

Study of Isotropic and Si-Selective Quasi Atomic Layer Etching of Si1−xGex

Study of Isotropic and Si-Selective Quasi Atomic Layer Etching of Si1−xGex

Selective Digital Etching of Silicon–Germanium Using Nitric and Hydrofluoric Acids

Narrowed Si0.7Ge0.3 channel FinFET with subthreshold swing of 64 mV/Dec using cyclic self-limited oxidation and removal process

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Study of Isotropic and Si-Selective Quasi Atomic Layer Etching of Si_1−xGe_x

Study of Isotropic and Si-Selective Quasi Atomic Layer Etching of Si_1−xGe_x

Narrowed Si_0.7Ge_0.3 channel FinFET with subthreshold swing of 64 mV/Dec using cyclic self-limited oxidation and removal process