Role of oxygen impurities in etching of silicon by atomic hydrogen

Vepřek, S.; Wang, Chunlin; Vepřek-Heijman, Maritza G. J.

doi:10.1116/1.2884731

Cited by 52 publications

(30 citation statements)

References 80 publications

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“…21,[33][34][35] This oxide layer inhibits the etching of the underlying Si substrate, thus reducing the instantaneous etch rate. 36 The reduction in instantaneous etch rate offsets the longer ion bombardment time, leading to an overall comparable or even slightly decreased removal per cycle. Additionally, the change in instantaneous etch rate within one cycle, i.e., the variation from the initial to the final instantaneous Si etch rate, was increasing with increasing etch step length.…”

Section: Process Parametersmentioning

confidence: 99%

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Characterizing fluorocarbon assisted atomic layer etching of Si using cyclic Ar/C4F8 and Ar/CHF3 plasma

Metzler

Engelmann³

et al. 2016

The Journal of Chemical Physics

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With the increasing interest in establishing directional etching methods capable of atomic scale resolution for fabricating highly scaled electronic devices, the need for development and characterization of atomic layer etching processes, or generally etch processes with atomic layer precision, is growing. In this work, a flux-controlled cyclic plasma process is used for etching of SiO and Si at the Angstrom-level. This is based on steady-state Ar plasma, with periodic, precise injection of a fluorocarbon (FC) precursor (CF and CHF) and synchronized, plasma-based Ar ion bombardment [D. Metzler et al., J. Vac. Sci. Technol., A 32, 020603 (2014) and D. Metzler et al., J. Vac. Sci. Technol., A 34, 01B101 (2016)]. For low energy Ar ion bombardment conditions, physical sputter rates are minimized, whereas material can be etched when FC reactants are present at the surface. This cyclic approach offers a large parameter space for process optimization. Etch depth per cycle, removal rates, and self-limitation of removal, along with material dependence of these aspects, were examined as a function of FC surface coverage, ion energy, and etch step length using in situ real time ellipsometry. The deposited FC thickness per cycle is found to have a strong impact on etch depth per cycle of SiO and Si but is limited with regard to control over material etching selectivity. Ion energy over the 20-30 eV range strongly impacts material selectivity. The choice of precursor can have a significant impact on the surface chemistry and chemically enhanced etching. CHF has a lower FC deposition yield for both SiO and Si and also exhibits a strong substrate dependence of FC deposition yield, in contrast to CF. The thickness of deposited FC layers using CHF is found to be greater for Si than for SiO. X-ray photoelectron spectroscopy was used to study surface chemistry. When thicker FC films of 11 Å are employed, strong changes of FC film chemistry during a cycle are seen whereas the chemical state of the substrate varies much less. On the other hand, for FC film deposition of 5 Å for each cycle, strong substrate surface chemical changes are seen during an etching cycle. The nature of this cyclic etching with periodic deposition of thin FC films differs significantly from conventional etching with steady-state FC layers since surface conditions change strongly throughout each cycle.

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Section: Process Parametersmentioning

confidence: 99%

“…ALE of Si has shown an oxidized layer at the surface which can also inhibit substrate etching, somewhat similar to a thick FC film. 15,36 Additionally, intrinsic etch properties, e.g., bond breaking energies, can lead to differences in etch depth per cycle, enabling material etching selectivity.…”

Section: Materials Etching Selectivitymentioning

confidence: 99%

Characterizing fluorocarbon assisted atomic layer etching of Si using cyclic Ar/C4F8 and Ar/CHF3 plasma

Metzler

Engelmann³

et al. 2016

The Journal of Chemical Physics

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“…17 Briefly, Si etching occurs by means of the successive addition of hydrogen atoms to Si forming Si-H x complexes, where the number of chemisorbed hydrogen atoms (x) grows from x ¼ 1 to 3, i.e., SiH, SiH 2 , and SiH 3 . [51][52][53] The decreasing etch rate as a function of temperature is caused by the increasing heterogeneous recombination of H atoms on the Si surface that release H 2 (g), and this recombination consumes the chemisorbed H atoms needed for the formation of volatile SiH 4 . [51][52][53] The decreasing etch rate as a function of temperature is caused by the increasing heterogeneous recombination of H atoms on the Si surface that release H 2 (g), and this recombination consumes the chemisorbed H atoms needed for the formation of volatile SiH 4 .…”

Section: B Si Removal In Pure-h 2 and H 2 /N 2 Plasmasmentioning

confidence: 99%

“…The addition of an H atom to SiH 3 then generates volatile silane, SiH 4 , which leads to the etching of Si. [51][52][53][54][55][56] As a result, the Si etch rate decreases with increasing temperature in the region of T > 60 C. [51][52][53][54][55][56] As a result, the Si etch rate decreases with increasing temperature in the region of T > 60 C.…”

Section: B Si Removal In Pure-h 2 and H 2 /N 2 Plasmasmentioning

confidence: 99%

Comparison of the effects of downstream H2- and O2-based plasmas on the removal of photoresist, silicon, and silicon nitride

Thedjoisworo

Cheung

Crist³

2013

Journal of Vacuum Science &Amp; Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phen

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For the 45 nm technology node and beyond, there is a need to strip photoresist quickly while suppressing the loss of materials such as polycrystalline silicon (poly-Si) and silicon nitride (Si3N4). To achieve this goal, the authors characterized and compared the effects of downstream pure-H2, H2/N2, and O2/N2 plasmas on the etch behaviors of photoresist, poly-Si, and Si3N4. The addition of N2 to H2 plasma increases the photoresist ash rate to a maximum that is reached at ∼30–40% N2, and the ash rate drops with further addition of N2. At 30% N2 addition, the ash rate increases by a factor of ∼3 when compared to that obtained with pure-H2 plasma. For O2/N2 plasma, the photoresist ash rate also exhibits a maximum, which is attained with 5% N2 addition, and the ash rate drops drastically as more N2 is added. A small addition of N2 increases the H and O radical densities in the H2- and O2-based plasmas, respectively, resulting in the higher ash rates. The ash rate achieved by the O2/N2 chemistry is generally higher than that attained with the H2/N2 chemistry, and the difference becomes more significant at high temperatures. The activation energy for photoresist strip under O2/N2 plasma was measured to be ∼10 kcal/mol, which is higher when compared to the ∼5 kcal/mol measured for both the H2/N2 (30% N2) and the pure-H2 chemistries. At 300 °C, when compared to the O2-based chemistry, the H2-based chemistry was shown to remove Si3N4 with a much lower rate, ∼0.7 Å/min, highlighting the benefit of the latter in conserving material loss. The ability of the H2-based chemistry to suppress material loss and its nonoxidizing property could justify the trade off for its lower ash rates when compared to those obtained using the O2-based chemistry. For the H2-based chemistry, a small N2 addition to the H2 plasma was found to not only increase the ash rate but also suppress the Si etch rate by a factor of 8 to 22, depending on the temperature. Collectively, the H2/N2 chemistry shows a great promise for photoresist-strip applications in the advanced nodes, and it should be run at high temperatures (e.g., T ≥ 300 °C) to maximize the ash rate while still maintaining extremely low Si and Si3N4 losses.

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“…In another case, we were able to operate a glow discharge in the Si(s)/H 2 (g)-system at impurity level of ≤ 3-4 ppm[83].…”

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confidence: 97%

Industrial applications of superhard nanocomposite coatings

Vepřek

Vepřek-Heijman

2008

Surface and Coatings Technology

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152

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Role of oxygen impurities in etching of silicon by atomic hydrogen

Cited by 52 publications

References 80 publications

Characterizing fluorocarbon assisted atomic layer etching of Si using cyclic Ar/C4F8 and Ar/CHF3 plasma

Characterizing fluorocarbon assisted atomic layer etching of Si using cyclic Ar/C4F8 and Ar/CHF3 plasma

Comparison of the effects of downstream H2- and O2-based plasmas on the removal of photoresist, silicon, and silicon nitride

Industrial applications of superhard nanocomposite coatings

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