HF Etching of Si-Oxides and Si-Nitrides for Surface Micromachining

Bois, Bert Du; Vereecke, Guy; Witvrouw, Ann; Moor, Piet De; Hoof, Chris Van; Caussemaeker, A. De; Verbist, Agnes

doi:10.1007/978-94-010-0840-2_23

Cited by 18 publications

(16 citation statements)

References 6 publications

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“…Although there are many similarities to etching silicon dioxide films, silicon oxynitride forms a salt in anhydrous fluids that inhibits etching. Similar salts have been reported for Si etching when sources of N and F are readily available, including vapor etching of Si with HNO 3 /HF, NH 4 -buffered HF liquid-phase etching of SiO 2 , , gas-phase HF etching of SiO 2 /Si 3 N 4 stacks, , and plasma etching of silicon nitride with fluorine-based compounds. , In the case of silicon nitride plasma etching, the formation of (NH 4 ) 2 SiF 6 was reported to prevent further removal of the material. , We propose a mechanism for the growth of crystals by the addition of ammonium hexafluorosilicate complexes to the bottom of the salt. Balancing etching and crystal growth is key to etching in a supercritical fluid.…”

Section: Introductionsupporting

confidence: 71%

“…Several experimental observations have shown promise for nonaqueous removal of the salt product layer formed when etching silicon oxynitride in scCO 2 . Ambient heating of the salt layer above 100 °C caused degradation of the solid product, but it has been observed previously that heating of (NH 4 ) 2 SiF 6 under atmospheric conditions may result in a phase change to a liquid melt, which when further evaporated from nanoscale features, could cause damage . Exposure to ultrahigh vacuum during XPS analysis also caused degradation of the salt product layer.…”

Section: Discussionmentioning

confidence: 94%

“…The morphology of (NH 4 ) 2 SiF 6 crystals generated in scCO 2 is notable because this salt is often reported to form as a blue or white porous powder. ,, At processing temperatures below 70 °C, FESEM images depict a surface covered in approximately 100 nm rectangular-shaped crystals after etching in 22.4 mM HF solution. The rectangular shape is a result of the isometric hexoctahedral packing of the salt and has been reported at a much-larger scale (10 μm) for surfaces containing ammonium hexafluorosilicate annealed to 150 °C .…”

Section: Discussionmentioning

confidence: 99%

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Kinetic to Transport-Limited Anhydrous HF Etching of Silicon Oxynitride Films in Supercritical CO₂

2007

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A silicon oxynitride film (SiO0.8N0.2) was etched with anhydrous HF/pyridine mixtures dissolved in supercritical carbon dioxide at 50−75 °C and 160 ± 10 bar to achieve concentrations of 2.8−22.4 mM, spanning the range from kinetically limited to transport-limited etching. The SiF4 and NH3 etching products reacted further, forming an insoluble salt layer chemically identified as (NH4)2SiF6 using FTIR and quantitative XPS and imaged using SEM and AFM. The etching reaction was first-order below 11 mM because the surface was open to the fluid phase between salt crystals, and etching rates were approximately 1 nm/min. In this regime, salt crystals did not hinder etching and formed primarily by the addition of fluorosilicates to the bottom interface with the silicon oxynitride film. The reaction order was less than one above 11 mM HF because lateral growth of salt crystals became significant and hindered transport of the fluid to the film. Between 50 and 70 °C, the salt formed cubic crystals, whereas at 75 °C a powder-like product formed. Partial removal of the (NH4)2SiF6 salt was accomplished by sublimation under ultrahigh vacuum conditions at room temperature.

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Section: Introductionsupporting

confidence: 71%

Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 99%

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Kinetic to Transport-Limited Anhydrous HF Etching of Silicon Oxynitride Films in Supercritical CO₂

2007

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“…Key feature of this layer is that it must stand the whole process, but still be easily removable ultimately. SiO 2 was considered, but standard etching takes place in vapor HF [11], [12], what is not suitable for such application. A thermally releasable sacrificial material was another option.…”

Section: Resultsmentioning

confidence: 99%

Active Electrode Arrays by Chip Embedding in a Flexible Silicone Carrier

Bulcke

Baert

Beyne

et al. 2006

2006 International Conference of the IEEE Engineering in Medicine and Biology Society

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Future cochlear implants demand a higher density of stimulation sites (electrodes) and enhanced functionality (e.g. feedback information). The current generation of implanted cochlear prostheses is making use of a completely "passive scheme" and cannot meet these requirements. An "all-Silicon" concept integrating active components with passive electrodes in Silicon has been proposed but does not offer the flexibility/stretchability of current silicone-based devices. This paper introduces a novel concept based on Silicon chip embedding in a flexible silicone carrier. The process and experimental results will be presented. The concept is also applicable to other types of implanted electrodes, e.g. retinal implants. Driving IC Driving IC Redistributing IC Clock Power Ground Signal Address a.b.c.

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“…The thinning of sample B2 was realized in a SF 6 /O 2 plasma using a RIE-ICP etcher operated at a very low power. The cantilevers were then released by removing the underlying sacrificial thermal SiO 2 using HF (49%) vapour at 35 °C for 120 min [13,14]. The cantilever profile and tip deflection were measured with a laser profilometer and an optical microscope.…”

Section: Methodsmentioning

confidence: 99%

Effect of deposition parameters on the stress gradient of CVD and PECVD poly-SiGe for MEMS applications

Donck

Proost

Rusu

et al. 2004

Micromachining and Microfabrication Process Technology IX

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The effect of the deposition parameters and Ge content on the stress gradient in poly-SiGe films was investigated. The films, ranging in thickness from 1.2 to 2.3 µm, were deposited by chemical vapor deposition (CVD) at 450 ºC and plasma enhanced chemical vapor deposition (PECVD) at 520 ºC. The Ge content was varied between 45 and 64 at%. Xray diffraction revealed that both PECVD and CVD films were polycrystalline. The stress gradient was determined by measuring the deflection of 1 mm long released cantilevers. The stress gradient was found to decrease with increasing Ge content. A CVD film with 55 at% Ge was thinned using a very low power SF 6 /O 2 plasma. The stress gradient was measured as a function of film thickness. The stress profile was calculated by matching the bending moment of the calculated profile to the bending moment obtained from the measured stress gradient. The largest change in stress occurs right at the thin film/substrate interface. PECVD films were found to possess a lower stress gradient compared to CVD films with similar thickness. This was explained by differences in TEM microstructure: CVD films have more Vshaped grains, while PECVD films have more columnar grains.

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HF Etching of Si-Oxides and Si-Nitrides for Surface Micromachining

Cited by 18 publications

References 6 publications

Kinetic to Transport-Limited Anhydrous HF Etching of Silicon Oxynitride Films in Supercritical CO₂

Kinetic to Transport-Limited Anhydrous HF Etching of Silicon Oxynitride Films in Supercritical CO₂

Active Electrode Arrays by Chip Embedding in a Flexible Silicone Carrier

Effect of deposition parameters on the stress gradient of CVD and PECVD poly-SiGe for MEMS applications

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HF Etching of Si-Oxides and Si-Nitrides for Surface Micromachining

Cited by 18 publications

References 6 publications

Kinetic to Transport-Limited Anhydrous HF Etching of Silicon Oxynitride Films in Supercritical CO2

Kinetic to Transport-Limited Anhydrous HF Etching of Silicon Oxynitride Films in Supercritical CO2

Active Electrode Arrays by Chip Embedding in a Flexible Silicone Carrier

Effect of deposition parameters on the stress gradient of CVD and PECVD poly-SiGe for MEMS applications

Contact Info

Product

Resources

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Kinetic to Transport-Limited Anhydrous HF Etching of Silicon Oxynitride Films in Supercritical CO₂

Kinetic to Transport-Limited Anhydrous HF Etching of Silicon Oxynitride Films in Supercritical CO₂