Properties of C4F8 inductively coupled plasmas. I. Studies of Ar/c-C4F8 magnetically confined plasmas for etching of SiO2

Li, Xi; Li, Ling; Hua, Xin‐Min; Oehrlein, G. S.; Wang, Yicheng; Vasenkov, Alex V.; Kushner, Mark J.

doi:10.1116/1.1697482

Cited by 28 publications

(24 citation statements)

References 19 publications

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“…6, resemble those of ions measured in low pressure C 4 F 8 rf plasmas by Li et al 4,5 and Goyette et al 24 A primary principle governing our IRIS work is that the apparatus is designed to form molecular beams that contain virtually all of the species present in the plasma. 6, resemble those of ions measured in low pressure C 4 F 8 rf plasmas by Li et al 4,5 and Goyette et al 24 A primary principle governing our IRIS work is that the apparatus is designed to form molecular beams that contain virtually all of the species present in the plasma.…”

Section: Discussionmentioning

confidence: 82%

“…Figures 2 and 3 show the intensities of the six major ions present in C 3 F 8 and C 4 F 8 plasma molecular beams as a function of P, with the source flow set at 10 SCCM ͑gas pressure ϳ45 mTorr͒. 4,5,24 There are two primary ways of analyzing these data: examining the shapes and widths of the distributions, and calculating the mean energy for the individual IEDs. 2.…”

Section: Resultsmentioning

confidence: 99%

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Correlating ion energies and CF2 surface production during fluorocarbon plasma processing of silicon

Martin

Zhou

Fisher

2006

Journal of Applied Physics

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Ion energy distribution ͑IED͒ measurements are reported for ions in the plasma molecular beam source of the imaging of radicals interacting with surfaces ͑IRIS͒ apparatus. The IEDs and relative intensities of nascent ions in C 3 F 8 and C 4 F 8 plasma molecular beams were measured using a Hiden PSM003 mass spectrometer mounted on the IRIS main chamber. The IEDs are complex and multimodal, with mean ion energies ranging from 29 to 92 eV. Integrated IEDs provided relative ion intensities as a function of applied rf power and source pressure. Generally, higher applied rf powers and lower source pressures resulted in increased ion intensities and mean ion energies. Most significantly, a comparison to CF 2 surface interaction measurements previously made in our laboratories reveals that mean ion energies are directly and linearly correlated to CF 2 surface production in these systems.

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Section: Discussionmentioning

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Correlating ion energies and CF2 surface production during fluorocarbon plasma processing of silicon

Martin

Zhou

Fisher

2006

Journal of Applied Physics

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“…This may be attributed to an increase in fluorine availability at the polymer surface since surface analytical studies have shown that the steady state FC film thickness changes little in this regime. 33 Increasing the flow of fluorocarbon growth precursors further leads to strongly increased FC deposition rates on the polymer substrates, which lowers the net etching rate further and ultimately causes a switchover to net FC film deposition at 80% C 4 F 8 . Figure 5͑a͒ also shows data for pure C 4 F 8 .…”

Section: B Effect Of Fluorocarbon Gas Addition To Ar Dischargesmentioning

confidence: 99%

Dependence of photoresist surface modifications during plasma-based pattern transfer on choice of feedgas composition: Comparison of C4F8- and CF4-based discharges

Engelmann¹,

Bruce²,

Weilnboeck³

et al. 2009

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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The authors report a study of the impact of surface chemical factors on etch rates along with surface and line edge roughness introduction for prototypical photoresist (PR) materials and structures during plasma-based pattern transfer employing fluorocarbon (FC) discharges. For selected photoresist materials and model polymers (193nm PR, 248nm, PR, and polymethyladamantyl methacrylate), the influence of bulk polymer properties on plasma durability was clarified by comparing etch rates, surface roughness introduction, and profile evolution of nanostructures. They studied the effects of both fluorocarbon fragment deposition and polymer surface fluorination by gas phase fluorine atoms on plasma etching resistance and surface roughness evolution of the organic materials by comparing discharges fed with C4F8∕Ar or CF4∕Ar∕H2 gas mixtures. The spatial frequency distribution of surface roughness was obtained using fast Fourier transformation of atomic force microscopy data. A graphitic layer was formed for Ar containing discharges on the polymer surfaces. Fluorocarbon deposition on the damaged photoresist affected roughening in two opposing ways: ion-induced mixing with the damaged polymer layer increased surface roughening, whereas for simple FC precursor deposition a reduction in surface roughness was seen. The latter effect was especially important during profile evolution of three-dimensional structures. Fluorination of the photoresist surfaces by fluorine-rich plasma increased polymer etching yields, and for highly fluorinated surfaces inhibited the formation of the graphitic surface layer. The destruction of the adamantyl structure is usually found in fluorocarbon/argon discharges and is a major origin of roughness evolution for 193nm PR materials. Process conditions having high etch yields were found to improve the roughness results of 193nm PR after etch. The fluorination of the photoresist materials prevented the formation of characteristic small scale roughness features at the cost of large scale roughness introduction. Use of low energy density process conditions prevented the introduction of large scale roughness and can be explained by suppression of surface roughness growth by an ion-induced transfer mechanism. Alternatively, CF4∕H2 processing also showed improved roughness results due to a separate layer deposition of the fluorocarbon film on top of the photoresist material. The etch results for all process conditions can be combined in a surface roughening model where the roughening behavior of the film scales linearly with the energy density delivered to the polymer surface during processing. Even for a range of feedgas chemistries, adamantyl-containing polymers show enhanced roughening rates, suggesting that the instability of the adamantyl structure used in 193nm PR polymers is the performance limiting factor for processing these PR materials.

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“…10 The values for EY were obtained from the etch rate and the ion flux as stated in Eq. To see this, we rearranged our results from Sec.…”

Section: A Dependence Of Surface Roughness On Deposited Energy Densitymentioning

confidence: 99%

Plasma-surface interactions of advanced photoresists with C4F8∕Ar discharges: Plasma parameter dependencies

Engelmann¹,

Bruce²,

Sumiya³

et al. 2009

Journal of Vacuum Science &Amp; Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena

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Photoresist modifications by plasma vacuum ultraviolet radiation: The role of polymer structure and plasma chemistry J. Vac. Sci. Technol. B 28, 993 (2010); 10.1116/1.3484249Real-time studies of surface roughness development and reticulation mechanism of advanced photoresist materials during plasma processing One recurring problem in nanoscale processing is roughening of photoresist ͑PR͒ materials during plasma etch. We studied the plasma etch behavior of 248 nm PR, 193 nm PR, and poly methyladamantyl methacrylate while changing the source power level ͑400-1200 W͒, adjusting the bias power to change the self-bias voltage V dc ͑−50 to − 150 V͒, and varying the pressure ͑10-80 mTorr͒ and the amount of fluorocarbon gas additive to the Ar discharge ͑0%-10% c-C 4 F 8 in Ar͒. The authors found that the PR removal is dominated by the ion energy and fluence. Surface fluorination enhanced the removal rates. Two linked mechanisms for the roughening behavior of the films during processing were identified. Changes of PR top surface roughening behavior in response to variations of bias power and pressure could be interpreted by a model of roughness formation which is dominated by a physical pattern transfer mechanism, i.e., roughness amplification through selective ion-induced transfer. When the plasma source power was varied, they observed that roughness formation was linked to the surface energy density deposited during processing. As the energy required to volatilize a volume element from the surface increased, the surface roughening rates grew proportionally. This conversion of excess energy into roughening was found to depend on the molecular structure of the polymer, with adamantyl polymers having a very high roughening constant. Additional effects on the etch behavior arise from fluorination of the samples, as quantified by x-ray photoelectron spectroscopy. High F 2s / F 1s intensity ratios, which indicate deeper fluorination, were measured for rough surface conditions. Smaller F 2s / F 1s ratios indicate near-surface fluorination and correspond to smoother top surfaces and feature sidewalls. Molecular compounds showed roughening behavior relative to the respective cross-linking behavior even when processed in pure Ar discharges, suggesting that the measured surface fluorination mirrors surface morphology. When plasma etching three-dimensional trenches and contact holes patterned in PR, the authors found that the sidewall roughness changed with process parameters in a fashion similar to that seen for blanket surface roughness introduction using the same etch conditions. A close correlation between the surface and sidewall roughness results was obtained, suggesting that their model of polymer surface roughening also applies to resist sidewall evolution during plasma etch.

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Properties of C4F8 inductively coupled plasmas. I. Studies of Ar/c-C4F8 magnetically confined plasmas for etching of SiO2

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Cited by 28 publications

References 19 publications

Correlating ion energies and CF2 surface production during fluorocarbon plasma processing of silicon

Correlating ion energies and CF2 surface production during fluorocarbon plasma processing of silicon

Dependence of photoresist surface modifications during plasma-based pattern transfer on choice of feedgas composition: Comparison of C4F8- and CF4-based discharges

Plasma-surface interactions of advanced photoresists with C4F8∕Ar discharges: Plasma parameter dependencies

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