Chemical, energetic, and geometric heterogeneity of device-quality (100) surfaces of single crystalline silicon after HFaq etching

Cerofolini, G. F.; Giussani, A.; Modelli, Alberto; Mascolo, Daniele Di; Ruggiero, Davide; Narducci, Dario; Romano, E.

doi:10.1016/j.apsusc.2008.03.058

Cited by 18 publications

(18 citation statements)

References 43 publications

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“…43 Fitting the Si 2p signal suggests two or three different Si species on the surface: the elemental Si and one or two H-containing Si species Si(SiH)/ Si(SiH 2 ) and/or Si(SiH 2 ) and Si(SiH 3 ). The determined surface species are in good agreement with literature data 40 (see Table 4). The presence of Si(SiH 2 ) groups is most likely a result of the monocrystalline Si(100) wafer.…”

Section: ■ Results and Discussionsupporting

confidence: 90%

“…No signal is observed above 99.5 eV in the Si 2p region (Table 4). Oxidized Si groups show signals between 100.3 and 102.9 eV for Ocontaining surface species 40 and between 100.9 and 106.6 eV for F-containing surface species. 43 Fitting the Si 2p signal suggests two or three different Si species on the surface: the elemental Si and one or two H-containing Si species Si(SiH)/ Si(SiH 2 ) and/or Si(SiH 2 ) and Si(SiH 3 ).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Etching Silicon with HF-H₂O₂-Based Mixtures: Reactivity Studies and Surface Investigations

Gondek

Lippold

Röver³

et al. 2014

J. Phys. Chem. C

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In semiconductor and photovoltaic industries numerous process steps deal with etching and silicon surface modification. The present study focuses on the reactivity of HF-H2O2-based mixtures toward silicon surfaces in a wide range of concentrations. The generally very moderate reactivity is investigated regarding kinetic aspects and the silicon dissolution reactions. The activation energy of silicon dissolution in HF-H2O2 mixtures is determined to be ∼50 kJ/mol, which supports a surface reaction controlled mechanism. This interpretation is checked by oxidation experiments of Si surfaces with HF-free H2O2 solutions. Resulting silicon surfaces were characterized by means of diffuse reflection Fourier transform infrared spectroscopy and photoelectron spectroscopy. Surface properties give hints for an “electrochemical” silicon oxidation. Furthermore, the oxidation behavior of different H2O2 solutions is compared to that of HNO3 solutions. All results suggest kinetically limited silicon dissolution in HF-H2O2 mixtures and hole injection into the silicon surface to be the rate-determining part of the reaction process.

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Section: ■ Results and Discussionsupporting

confidence: 90%

Section: ■ Results and Discussionmentioning

confidence: 99%

Etching Silicon with HF-H₂O₂-Based Mixtures: Reactivity Studies and Surface Investigations

Gondek

Lippold

Röver³

et al. 2014

J. Phys. Chem. C

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“…For curve a, the atmosphere was switched from wet-to dry-air at 12 h, and visa This mechanism is in good agreement with the FT-IR observation that by leaving HF-treated Si surfaces in air, Si-O-Si bonds are formed with Si-H bonds remaining on the surfaces. 5,6 When the atmosphere was switched from dry-air to wet-air, the workfunction increased (E in Figure 4). Replacement of bridgebackbonded O to backbonded OH increases the workfunction, while that of surface O to surface OH decreases it.…”

Section: Resultsmentioning

confidence: 93%

“…HF-etching forms ideal hydrogenterminated Si surfaces (i.e., only mono-hydride, Si-H) in the case of Si(111), 2 while mono-, di-(Si-H 2 ), and tri-(Si-H 3 ) hydride species are produced on technologically more important Si(100) surfaces. [3][4][5] HF-etched Si(100) surfaces with Si-H 2 and Si-H 3 are less stable in air than Si(111). Oxidation of HF-treated Si surfaces is enhanced by the presence of metal contaminants, more active species, defects, fluorineadsorbed sites, etc.…”

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confidence: 97%

Changes in Minority Carrier Lifetime of Hydrogen-Terminated Si Surfaces in Dry- and Wet-Air

Franco

Matsumoto

Kim

et al. 2012

ECS Solid State Letters

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Minority carrier lifetime of HF-treated Si(100) surfaces decreases in wet-air more rapidly than in dry-air. XPS measurements show that OH and O are mainly included in Si by keeping in wet-air and dry-air, respectively. OH cannot form network, and thus backbonded OH generates Si dangling bonds. On the other hand, backbonded O can form Si-O-Si networks, leading to the higher lifetime due to lower defect density. When the atmosphere is switched from dry-air to wet-air, the lifetime greatly decreases, and the workfunction increases. These changes are attributed to dominant formation of backbonded OH.Study on initial oxidation of Si is of importance not only from an academic viewpoint but also for application to semiconductor products such as solar cells and LSI. Semiconductor devices are usually fabricated using Si wafers after cleaning with the RCA method 1 followed by hydrofluoric acid (HF) etching. HF-etching forms ideal hydrogenterminated Si surfaces (i.e., only mono-hydride, Si-H) in the case of Si(111), 2 while mono-, di-(Si-H 2 ), and tri-(Si-H 3 ) hydride species are produced on technologically more important Si(100) surfaces. 3-5 HF-etched Si(100) surfaces with Si-H 2 and Si-H 3 are less stable in air than Si(111). Oxidation of HF-treated Si surfaces is enhanced by the presence of metal contaminants, more active species, defects, fluorineadsorbed sites, etc. 6,7 Initial oxidation of HF-treated Si surfaces were investigated using Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), Ultraviolet photoelectron spectroscopy (UPS), etc. 6-9 Chabal et al., 6 reported that when HFtreated Si(100) surfaces were kept in air, vibrational peaks due to SiH, SiH 2 , SiH(O) 3 , and SiH 2 (O) 2 were observed, indicating that O atoms occupied back-bonds with Si-H bonds remaining on Si surfaces. Hirose et al., 7 also concluded that oxygen attacked Si back-bonds and surface Si-H bonds were still present after the oxygen attack.The minority carrier lifetime strongly affects the electrical characteristics of semiconductor devices. 10 It is greatly decreased by the presence of defect states such as interface states. 11,12 In the case of solar cells, photovoltages are markedly influenced by the minority carrier lifetime. 13 Recombination of electron-hole pairs generated in the surface region proceeds at surface states, resulting in a decrease in the quantum efficiency of short-wavelength light, and thus in a decrease in the photocurrent density. 14 Recombination currents possess a large ideality factor, e.g., 2, 15 and thus, a fill factor is also decreased.In the present study, changes of minority carrier lifetime for HFtreated Si surfaces with time kept in air have been investigated. It is found that the minority carrier lifetime strongly depends on humidity, and concluded that hydroxyl species (OH) under the surfaces decreases the lifetime because the species does not form network, resulting in the production of defect states such as Si dangling bonds. ExperimentalPhosphorus-doped n-type Si(100...

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“…Figure 6. Si 2p XPS spectrum of a (100) Si surface, etched in HF− H 2 O−O 3 mixture (c(HF) = 6.9 mol L −1 ), marked comparing binding energies of Si species with oxidation number in brackets based on Cerofolini et al47 For further information, see Supporting Information.…”

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confidence: 99%

Etching Silicon with Aqueous Acidic Ozone Solutions: Reactivity Studies and Surface Investigations

et al. 2016

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Aqueous acidic ozone (O 3 )-containing solutions are increasingly used for silicon treatment in photovoltaic and semiconductor industries. We studied the behavior of aqueous hydrofluoric acid (HF)-containing solutions (i.e., HF−O 3 , HF−H 2 SO 4 −O 3 , and HF−HCl−O 3 mixtures) toward boron-doped solar-grade (100) silicon wafers. The solubility of O 3 and etching rates at 20 °C were investigated. The mixtures were analyzed for the potential oxidizing species by UV−vis and Raman spectroscopy. Concentrations of O 3 (aq) , O 3 (g) , and Cl 2 (aq) were determined by titrimetric volumetric analysis. F − , Cl − , and SO 4 2− ion contents were determined by ion chromatography. Model experiments were performed to investigate the oxidation of Hterminated silicon surfaces by H 2 O−O 2 , H 2 O−O 3 , H 2 O−H 2 SO 4 −O 3 , and H 2 O−HCl−O 3 mixtures. The oxidation was monitored by diffuse reflection infrared Fourier transformation (DRIFT) spectroscopy. The resulting surfaces were examined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). HF−H 2 O−O 3 mixtures show a polishing etching behavior, whereas HF−HCl−H 2 O−O 3 mixtures exhibit slight anisotropic etching. Formation of pyramidal-like morphologies on (100) silicon surfaces was observed. In all cases, cleaned and H-terminated silicon surfaces are obtained. The results were used to draw conclusions about the dissolution mechanism of silicon in the respective solutions. In HF−H 2 O−O 3 mixtures, silicon is dissolved by an O 3(aq) -diffusion-controlled tetravalent etching mechanism. Interestingly, in H 2 SO 4 -rich aqueous HF−H 2 SO 4 −O 3 solutions, only the native oxide is removed, whereas silicon is not attacked and dissolved. In HCl-containing solutions, Cl 2 or Cl 3− are responsible for silicon oxidation. HCl can be considered as a catalyst resulting in a divalent silicon dissolution mechanism similar to the etching in alkaline solutions.

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Chemical, energetic, and geometric heterogeneity of device-quality (100) surfaces of single crystalline silicon after HFaq etching

Cited by 18 publications

References 43 publications

Etching Silicon with HF-H₂O₂-Based Mixtures: Reactivity Studies and Surface Investigations

Etching Silicon with HF-H₂O₂-Based Mixtures: Reactivity Studies and Surface Investigations

Changes in Minority Carrier Lifetime of Hydrogen-Terminated Si Surfaces in Dry- and Wet-Air

Etching Silicon with Aqueous Acidic Ozone Solutions: Reactivity Studies and Surface Investigations

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Chemical, energetic, and geometric heterogeneity of device-quality (100) surfaces of single crystalline silicon after HFaq etching

Cited by 18 publications

References 43 publications

Etching Silicon with HF-H2O2-Based Mixtures: Reactivity Studies and Surface Investigations

Etching Silicon with HF-H2O2-Based Mixtures: Reactivity Studies and Surface Investigations

Changes in Minority Carrier Lifetime of Hydrogen-Terminated Si Surfaces in Dry- and Wet-Air

Etching Silicon with Aqueous Acidic Ozone Solutions: Reactivity Studies and Surface Investigations

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Etching Silicon with HF-H₂O₂-Based Mixtures: Reactivity Studies and Surface Investigations

Etching Silicon with HF-H₂O₂-Based Mixtures: Reactivity Studies and Surface Investigations