Ion bombardment energy control for selective fluorocarbon plasma etching of organosilicate glass

Silapunt, Rardchawadee; Wendt, A.; Kirmse, K. H. R.; Losey, Laura

doi:10.1116/1.1676641

Cited by 11 publications

(18 citation statements)

References 19 publications

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“…The difference in etch behavior with tailored and sinusoidal biases is consistent with prior observations 35,36 in fluorocarbon gas mixtures. Si and Si/ SiGe have comparable etch rates under our etching conditions for both bias voltage wave forms.…”

Section: A Optimization Of Etch Selectivitysupporting

confidence: 90%

“…One advantage of helicon plasma etching over RIE is that the plasma source power and self-bias power are decoupled, 33 so that ion bombardment energy can be varied by changing the self-bias voltage. 36 The Si/ SiGe heterostructures used in this experiment were grown by UHV-CVD on a Si substrate and consist of several layers: a thick strain relaxed SiGe virtual substrate with graded composition from 0% to 30% Ge, a strained Si layer, a Si 0.7 Ge 0.3 spacer layer, a Si 0.7 Ge 0.3 dopant layer, and a Si cap layer, as shown in Fig. A dc self-bias voltage develops on the substrate surface relative to the plasma, which governs the average energy of ion bombardment in the absence of ion collisions in the sheath.…”

Section: Methodsmentioning

confidence: 99%

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Anisotropic fluorocarbon plasma etching of Si∕SiGe heterostructures

Ding

Klein

Eriksson

et al. 2007

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

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Fluorocarbon plasma etching of Si∕SiGe heterostructures is demonstrated as a method for fabrication of quantum devices with vertical sidewalls. The heterostructures consist of layers of Si and SiGe, and anisotropic etching of the heterostructures using plasmas to isolate device elements is an attractive approach to fabricating devices. A challenge that has limited the use of fluorocarbon etching is the difference in Si and SiGe etch rates under comparative conditions. Preferential etching of SiGe can lead to undercutting beneath the top Si layer, causing a reduction in critical device dimensions of unknown magnitude. By using fluorocarbon etch gases with high carbon content, fluorocarbon sidewall passivation improves the anisotropy of etched feature profiles by preventing lateral etching of SiGe. Etch results with a C4F8∕Ar∕N2 gas mixture show a straight sidewall profile through the layers of the heterostructure.

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Section: A Optimization Of Etch Selectivitysupporting

confidence: 90%

Section: Methodsmentioning

confidence: 99%

Anisotropic fluorocarbon plasma etching of Si∕SiGe heterostructures

Ding

Klein

Eriksson

et al. 2007

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

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“…3,4 Bombardment by ions of sufficiently high energies can shift a process from one that produces net deposition to one that produces net etching. 4 The more polymerizing the gas mixture, the higher the etch onset ion energy seems to be. 4 The more polymerizing the gas mixture, the higher the etch onset ion energy seems to be.…”

Section: Introductionmentioning

confidence: 99%

“…The ions crossing the sheath during the constant voltage period are expected to all arrive at the substrate with nearly the same energy. 3,4 In fact, the etch rate of the overlying fluorocarbon film itself is strikingly different for sinusoidal and tailored substrate bias voltage wave forms producing the same average ion energy. [11][12][13][14][15] Agarwal and Kushner have recently reported on the effect of nonsinusoidal bias wave forms on simulated profiles of SiO 2 features etched in fluorocarbon plasmas.…”

Section: Introductionmentioning

confidence: 99%

Ion energy control at substrates during plasma etching of patterned structures

Silapunt

Wendt

Kirmse

2007

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

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Influence of ion mixing on the energy dependence of the ion-assisted chemical etch rate in reactive plasmasIn fluorocarbon-based plasma etching of dielectrics, deposition of fluorocarbon on the substrate contributes to a complex surface chemical structure that strongly affects etch rate and etch selectivity. Results reported herein demonstrate that the energy distribution of bombarding ions ͑IED͒ has a significant effect on this polymer layer, subsequently affecting etch rate and selectivity in submicron patterned structures. Specifically, we have narrowed the IED while keeping other process conditions unchanged by tailoring the shape of the rf voltage wave form used for substrate bias. Significant improvements in etch selectivity for organosilicate glass ͑OSG͒ over silicon carbide in a C 4 F 8 /N 2 / Ar plasma have been obtained by using a narrow IED compared to the broad IED resulting from the typical sinusoidal bias wave form. Trenches etched in OSG with the tailored bias voltage wave form show good feature profiles and high selectivity at feature bottoms. Slight differences in feature profiles between tailored and sinusoidal wave forms, as well as variations in etch selectivity with feature depth, are consistent with an enhancement in polymerization at the substrate in the case of the tailored bias voltage wave form.

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“…A substrate bias system equipped with a combination of a programmable voltage wave form generator, a broad-band power amplifier, and a coupling capacitor is used to produce a specially tailored bias voltage wave form, described in more detail in Reference [40]. The tailored wave form was introduced as a method to produce a narrow distribution of ion energies at the substrate, and has shown to be effective in improving etch selectivity of SiO 2 over Si [47] and organosilicate glass (OSG) over Si 3 N 4 and SiC [48].…”

Section: Experiments Setupmentioning

confidence: 99%

Surface Roughening of Polystyrene and Poly(methyl methacrylate) in Ar/O2 Plasma Etching

et al. 2010

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Selectively plasma-etched polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) diblock copolymer masks present a promising alternative for subsequent nanoscale patterning of underlying films. Because mask roughness can be detrimental to pattern transfer, this study examines roughness formation, with a focus on the role of cross-linking, during plasma etching of PS and PMMA. Variables include ion bombardment energy, polymer molecular weight and etch gas mixture. Roughness data support a proposed model in which surface roughness is attributed to polymer aggregation associated with cross-linking induced by energetic ion bombardment. In this model, RMS roughness peaks when cross-linking rates are comparable to chain scissioning rates, and drop to negligible levels for either very low or very high rates of cross-linking. Aggregation is minimal for very low rates of cross-linking, while very high rates produce a continuous cross-linked surface layer with low roughness. Molecular weight shows a negligible effect on roughness, while the introduction of H and F atoms suppresses roughness, apparently by terminating dangling bonds. For PS etched in Ar/O 2 plasmas, roughness decreases with increasing ion energy are tentatively attributed to the formation OPEN ACCESSPolymers 2010, 2 650 of a continuous cross-linked layer, while roughness increases with ion energy for PMMA are attributed to increases in cross-linking from negligible to moderate levels.

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Ion bombardment energy control for selective fluorocarbon plasma etching of organosilicate glass

Cited by 11 publications

References 19 publications

Anisotropic fluorocarbon plasma etching of Si∕SiGe heterostructures

Anisotropic fluorocarbon plasma etching of Si∕SiGe heterostructures

Ion energy control at substrates during plasma etching of patterned structures

Surface Roughening of Polystyrene and Poly(methyl methacrylate) in Ar/O2 Plasma Etching

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