ChemInform Abstract: THE CONTROLLED ETCHING OF SILICON IN CATALYZED ETHYLENEDIAMINE‐PYROCATECHOL‐WATER SOLUTIONS

Reisman, Arnold; Berkenblit, M.; Chan, S. A.; Kaufman, F. B.; Green, D. C.

doi:10.1002/chin.197950002

Cited by 4 publications

(8 citation statements)

References 1 publication

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“…The effects of further additives were studied by Reisman et al (22). They found that when exposing the EDP solution to oxygen, 1,4-benzoquinone and other products are formed, leading to an increase of the etch rate and a darkening of the solution.…”

Section: General Considerationsmentioning

confidence: 99%

“…They found that when exposing the EDP solution to oxygen, 1,4-benzoquinone and other products are formed, leading to an increase of the etch rate and a darkening of the solution. Since commercially available ethylenediamine usually contains an unknown trace amount of pyrazine, Reisman et al (22) proposed to intentionally add enough pyrazine to the solution so that the saturation level is reached. They also found that trace quantities of pyrazine (C4H4N2) lead to an increase of the etch rate.…”

Section: General Considerationsmentioning

confidence: 99%

“…Reisman et al developed two specific solutions optimized for use where either a high etch rate is required ("F"), or where slower etch rates and/or lower temperatures are desired ("S") (22). Reisman et al developed two specific solutions optimized for use where either a high etch rate is required ("F"), or where slower etch rates and/or lower temperatures are desired ("S") (22).…”

Section: General Considerationsmentioning

confidence: 99%

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Anisotropic Etching of Crystalline Silicon in Alkaline Solutions: I . Orientation Dependence and Behavior of Passivation Layers

Seidel

Csepregi

Heuberger

et al. 1990

J. Electrochem. Soc.

1,506

732

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The anisotropic etching behavior of single-crystal silicon and the behavior of SiO2 and Si3N4 in an ethylenediaminebased solution as well as in aqueous KOH, NaOH, and LiOH were studied. The crystal planes bounding the etch front and their etch rates were determined as a function of temperature, crystal orientation, and etchant composition. A correlation was found between the etch rates and their activation energies, with slowly etching crystal surfaces exhibiting higher activation energies and vice versa. For highly concentrated KOH solutions, a decrease of the etch rate with the fourth power of the water concentration was observed. Based on these results, an electrochemical model is proposed, describing the anisotropic etching behavior of silicon in all alkaline solutions. In an oxidation step, four hydroxide ions react with one surface silicon atom, leading to the injection of four electrons into the conduction band. These electrons stay localized near the crystal surface due to the presence of a space charge layer. The reaction is accompanied by the breaking of the backbonds, which requires the thermal excitation of the respective surface state electrons into the conduction band. This step is considered to be rate limiting. In a reduction step, the injected electrons react with water molecules to form new hydroxide ions and hydrogen. It is assumed that these hydroxide ions generated at the silicon surface are consumed in the oxidation reaction rather than those from the bulk electrolyte, since the latter are kept away from the crystal by the repellent force of the negative surface charge. According to this model, monosilicic acid Si(OH)4 is formed as the primary dissolution product in all anisotropic silicon etchants. The anisotropic behavior is due to small differences of the energy levels of the backbond surface states as a function of the crystal orientation.

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Section: General Considerationsmentioning

confidence: 99%

Section: General Considerationsmentioning

confidence: 99%

Section: General Considerationsmentioning

confidence: 99%

See 1 more Smart Citation

Anisotropic Etching of Crystalline Silicon in Alkaline Solutions: I . Orientation Dependence and Behavior of Passivation Layers

Seidel

Csepregi

Heuberger

et al. 1990

J. Electrochem. Soc.

1,506

732

View full text Add to dashboard Cite

show abstract

“…The silicon etchant used in the etching experiments was EDP-S (75 ml ethylenediamine; 12 g pyrocatechol; 0.45 g pyrazine; 1O ml H20) (8). Compared to a conventional EDPmixture, the EDP-S has a lower silicon etch rate, but is instead usable as a residue-and oxidation-resistant etchant for etch temperatures below 100~ and is particularly suitable for etching silicon where a high degree of etch rate control is desired.…”

Section: Methodsmentioning

confidence: 99%

Investigation of Buried Etch Stop Layer in Silicon Made by Nitrogen Implantation

Söderbärg

1992

J. Electrochem. Soc.

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A novel way to fabricate a buried etch stop layer in silicon is presented in this article. The etch stop layer is formed by nitrogen implantation and the investigations show that a dose of 1 9 1017 14N+-ions/cm 2 at 140 keV is enough to effectively stop the silicon etch reaction in an ethylenediamine-pyrocatechol-water solution. The nitrogen concentration where the etch reaction stops was estimated with secondary ion mass spectroscopy measurement to be about 2.5 9 1021 ions/cm 2, which is far below the necessary concentration for nitride formation. As an application example, a 400 nm thin silicon membrane has been fabricated utilizing an etch stop layer formed by nitrogen implantation. By utilizing the anodic bonding and etchback technique, a silicon-on-insulator material with an extremely good surface flatness has also been formed. Finally, the nitrogen implanted silicon etch rate has been investigated with respect to different anneal temperatures. This result shows that the etch stop mechanism formed by the nitrogen implantation disappears when the anneal temperature exceeds 1000~The possibility to fabricate an effective etch stop layer, buried in a silicon wafer, is interesting both for micromechanical applications, e.g., silicon membrane formation, and for microelectronic applications, e.g., silicon-on-insulator (SOI) material by the bonding and etchback technique (1). Today, the most common method is to use a p § layer (usually boron doped) as an etch stop layer. For example, in a mixture of ethylenediamine, pyrocatechol, and water (EDP), a boron concentration above 7.1019 cm -~ is enough to form an effective etch stop layer in silicon (2). This makes it possible to fabricate thin silicon films or membranes with an acceptable surface smoothness. The disadvantage with a p+-layer is that the necessary hole concentration for the etch stop mechanism is unacceptably high for IC applications. Therefore, a much more complicated process, normally including high energy implantation, epitaxial growth, and polishing, must be used if the silicon on top of the p § will be used for semiconductor devices (3).Another method, the so called pn-stop (4), is an electrochemical etch. By applying a specific voltage between the wafer and the etch solution, the p-doped regions of the wafer can be etched, while at the same applied bias, the ndoped regions are passivated and, thus, not etched. This method is powerful when surface smoothness is not a critical parameter. However, there is always a problem when an external voltage is necessary in the etch arrangement, and it is also difficult to get a good etch surface without any "orange-peel pattern" when moderate doping concentrations are used (5).An alternative to these two methods is the formation of an etch stop layer by nitrogen implantation, a method which is investigated in this article. The results show that the implanted nitrogen layer can act as a good etch stop layer, both for electronic and micromechanical applications in silicon. One major advantage in using nitrogen as c...

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“…In that process the front side is protected by a layer of polyimide (16 µm) (PI 2556 HD MicroSystems, Neu-Isenburg, Germany). Then the silicon substrate in the region of the needles is removed by chemical etching with an EDP-S solution (160 g pyrocatechol, 3 g pyrazine and 66 g water per liter ethylenediamine) [18]. In that process the wafer is mounted in a special holder (AMMT GmbH, Frankenthal, Germany) that shields the front side.…”

Section: Fig 1 Electron Micrograph Of a Transistor Needle Chip (Tnc)mentioning

confidence: 99%

Transistor needle chip for recording in brain tissue

Felderer

Fromherz

2011

Appl. Phys. A

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We report on a proof-of-principle experiment for the direct interfacing of transistors with intact brain tissue. A transistor needle chip (TNC) with a TiO 2 surface is fabricated from a silicon-on-insulator wafer and impaled into an acute brain slice cut from hippocampus of the rat. While stimulating the Schaffer collateral, a local field potential is recorded in stratum radiatum of the CA1 region with fieldeffect transistors in the central part of the slice where the tissue is not damaged by the cutting process. After the impalement, the signal amplitude is small. Within an hour, it increases to a stable level around −2 mV as is recorded with a conventional micropipette electrode. The recovery indicates that the tissue is able to adapt to the impaled chip. Upon repeated impalements at the same position, the large signal is observed without delay. A profile of the transistor signal across the slice is due to the boundary conditions of a brain slice with both surfaces held near ground potential. The experiments with the TNC prototype are a basis for the development of silicon needle chips with a large multi-transistor array (MTA) for applications in brain-computer interfacing.

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ChemInform Abstract: THE CONTROLLED ETCHING OF SILICON IN CATALYZED ETHYLENEDIAMINE‐PYROCATECHOL‐WATER SOLUTIONS

Cited by 4 publications

References 1 publication

Anisotropic Etching of Crystalline Silicon in Alkaline Solutions: I . Orientation Dependence and Behavior of Passivation Layers

Anisotropic Etching of Crystalline Silicon in Alkaline Solutions: I . Orientation Dependence and Behavior of Passivation Layers

Investigation of Buried Etch Stop Layer in Silicon Made by Nitrogen Implantation

Transistor needle chip for recording in brain tissue

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