Cryogenic reactive ion etching of silicon in SF6

Bestwick, Tim D.; Oehrlein, G. S.; Angell, David

doi:10.1063/1.104240

Cited by 33 publications

(17 citation statements)

References 9 publications

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“…Furthermore, there has recently been an increasing interest in low temperature plasma etching as a high anisotropy, low damage technique. [15][16][17][18][19][20] This motivated the detailed study on the temperature dependence of both the product distribution and the reaction layer dynamics which is described in this article. In the next section a brief description of the experimental setup will be given.…”

Section: 910mentioning

confidence: 99%

“…3,4 Initially there was some disagreement on the thickness of this layer. From high resolution XPS-experiments it was estimated to be 4 monolayers of fluorine atoms, 5 in which the unit monolayer ͑ML͒ is defined as the surface density of the sample studied ͓Si͑100͒: 1 MLϭ6.86ϫ10 18 m Ϫ2 ]. Other groups, however, reported layers as thick as 13 ML ͑Refs.…”

Section: Introductionmentioning

confidence: 99%

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Si/XeF2 etching: Temperature dependence

Vugts

Verschueren

Eurlings

et al. 1996

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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The temperature dependence of the Si͑100͒/XeF 2 etch reaction is studied quantitatively in a molecular beam setup. At a sample temperature of 150 K the reaction probability reaches unity initially, after which the XeF 2 condenses on the surface and blocks the etching process. For increasing temperatures the XeF 2 reaction probability initially decreases from 100% at 150 K down to 20% around 400 K, but for temperatures above 600 K it increases again up to 45% at 900 K. In a simple reaction scheme the high etch rate at low temperatures is explained by a XeF 2 -precursor, with an activation energy for desorption of 32Ϯ4 meV. Furthermore the increased etch rate at high temperatures is explained by the desorption of SiF 2 with an activation energy of 260Ϯ30 meV. The steady-state fluorine content of the SiF x reaction layer, measured using thermal desorption spectroscopy, reaches a maximum of 5.5 monolayers at 300 K. For increasing temperatures it decreases to a submonolayer coverage above 700 K. The temperature dependence of the formation of the reaction layer is described well by including the XeF 2 -precursor in a previously developed adsorption model.

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Section: 910mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Si/XeF2 etching: Temperature dependence

Vugts

Verschueren

Eurlings

et al. 1996

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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“…[17][18][19][20][21] These studies have explored the Si etching mechanisms, electrical characteristics of SF 6 discharges during Si etching, and the impact of different diluents on etching properties. Experiments and theoretical analysis have highlighted the important role that F atoms, ions, and wafer temperature play in Si etching.…”

Section: Introductionmentioning

confidence: 99%

Model for a multiple-step deep Si etch process

Rauf

Dauksher

Clemens

et al. 2002

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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A multiple-step deep Si etch process involving separate etching and polymerization steps is often employed for fabrication of microelectromechanical systems, microfluidics devices, and other assorted deep structures in Si. An integrated plasma equipment-feature evolution model for this multiple-step deep Si etch process is described in this article. In the two-dimensional plasma equipment model, the etching (SF6/O2) and polymerization [octafluorocyclobutane(c-C4F8)] chemistries are separately simulated assuming steady-state conditions. The outputs of the equipment simulations are combined in a string-based feature profile evolution model to simulate the multiple-step deep Si etch process. In the plasma equipment models, detailed gas phase plasma chemistries including electron impact processes, ion–molecule reactions, and neutral chemistry have been considered for both the etching and polymerization gas mixtures. The plasma–surface interaction mechanisms in the feature profile evolution model are based on qualitative information available in literature and the correlation of modeling results with experimental data. Under the relevant operating conditions, F is assumed to be the primary Si etchant, film deposition in c-C4F8 is due to sticking of C, CF2, and C2F4 under ion bombardment, and the polymer is etched by energetic ions through physical sputtering. It is demonstrated that predictions of the resulting model are in close agreement with experiments. The validated model is used to understand the dynamics of the multiple-step deep Si etch process and how etching characteristics can be controlled using a variety of process parameters. Etching characteristics have been found to be quite sensitive to gas pressure, coil power, bias power, and relative step time during both etching and polymerization processes. The Si etch rate and feature sidewall angle are coupled to each other over a wide range of operating conditions.

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“…These effects are probably the explanation for the high anisotropy obtained in cryogenic etching. 7,10,11 …”

Section: ͑3͒mentioning

confidence: 99%

“…Recently there has been increasing interest in low temperature plasma etching. [7][8][9][10][11] It was found that lower substrate temperatures can lead to an increase in anisotropy and a decrease in substrate damage. This motivated a beam study on the influence of sample temperature in ion-assisted processes.…”

Section: Introductionmentioning

confidence: 99%

Ion-assisted Si/XeF2 etching: Temperature dependence in the range 100–1000 K

Vugts¹,

Hermans²,

Beijerinck³

1996

Journal of Vacuum Science &Amp; Technology A: Vacuum, Surfaces, and Films

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The Ar+-ion enhanced Si(100)/XeF2 reaction is studied in a multiple beam setup for silicon temperatures from 100 K up to 1000 K. The XeF2 flux is 2.7 monolayers/s and the Ar+ flux 0.033 monolayers/s at an energy of 1000 eV. Both the XeF2 consumption and the SiFx production are measured by mass spectrometry. The enhancement of the etch rate peaks around 250 K as is observed in both the XeF2 and SiFx signals. The gradual decline above 250 K is attributed to a diminished surface fluorination and XeF2 precursor concentration. The dropoff below 250 K is presumably caused by sputtering of the XeF2 precursor, as is concluded from the temperature dependence of the XeF+/XeF2+ signal ratio. Around 175 K this decrease is so strong that the ions seem to no longer enhance, but rather reduce, the etch rate. Below 150 K the ions are driving the etch process. In this range the spontaneous process is blocked by XeF2 condensation, but the ion-assisted process continues due to sputtering or dissociation of the condensate.

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Cryogenic reactive ion etching of silicon in SF6

Cited by 33 publications

References 9 publications

Si/XeF2 etching: Temperature dependence

Si/XeF2 etching: Temperature dependence

Model for a multiple-step deep Si etch process

Ion-assisted Si/XeF2 etching: Temperature dependence in the range 100–1000 K

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