JP2008243880A - Porous silicon substrate and its manufacturing method - Google Patents
Porous silicon substrate and its manufacturing method Download PDFInfo
- Publication number
- JP2008243880A JP2008243880A JP2007078287A JP2007078287A JP2008243880A JP 2008243880 A JP2008243880 A JP 2008243880A JP 2007078287 A JP2007078287 A JP 2007078287A JP 2007078287 A JP2007078287 A JP 2007078287A JP 2008243880 A JP2008243880 A JP 2008243880A
- Authority
- JP
- Japan
- Prior art keywords
- single crystal
- silicon single
- crystal substrate
- porous layer
- plane orientation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Landscapes
- Weting (AREA)
Abstract
Description
本発明は、表面に多孔質層を有するシリコン基板およびその製造方法に関する。 The present invention relates to a silicon substrate having a porous layer on its surface and a method for manufacturing the same.
シリコン単結晶における特定の面方位をエッチングすることにより、多孔質形状を制御できることが知られている。該多孔質形状を制御することによって、得られるシリコン基板の諸特性が変化するため、それぞれの用途に適したシリコン半導体基板の多孔質化手法が開発されている。 It is known that the porous shape can be controlled by etching a specific plane orientation in a silicon single crystal. Since various characteristics of the obtained silicon substrate change by controlling the porous shape, a technique for making the silicon semiconductor substrate porous for each application has been developed.
特許文献１にはシリコン基板上面をプラズマエッチングの手法によって円柱状、三角柱状、四角柱状及び六角柱状の島状部からなる多孔質層を形成し、その上部に窒化物半導体層を形成する窒化物系半導体の形成方法が開示されている。該方法によれば該多孔質層上に、平坦性および結晶性が向上された窒化物半導体層を形成できるとされているが、マスキング工程およびプラズマエッチング装置等を必要とし、工程が煩雑、かつ高価な設備を要するため、より簡便な多孔質層形成方法の開発が望まれている。 In Patent Document 1, a nitride layer is formed by forming a porous layer made of cylindrical, triangular, quadrangular, and hexagonal columnar islands on the upper surface of a silicon substrate by plasma etching, and forming a nitride semiconductor layer thereon. A method for forming a semiconductor is disclosed. According to this method, it is said that a nitride semiconductor layer with improved flatness and crystallinity can be formed on the porous layer, but a masking step and a plasma etching apparatus are required, and the steps are complicated. Since expensive equipment is required, development of a simpler porous layer forming method is desired.
シリコン単結晶基板をより簡便な化学的手法によって多孔質化するにあたって、従来、シリコン基板の陽極酸化エッチングによる手法が非特許文献１〜３に知られている。しかし、非特許文献１に記載された方法によれば、（１００）面方位を選択的にエッチングして四角柱状の孔を形成できるが、（１１１）面方位を選択的にエッチングする事が困難である。また、非特許文献２、３に記載されている方法によれば、（１００）面方位あるいは（１１３）面方位が選択的にエッチングされる傾向が強い。このため、（１１１）面方位に限って得られる多孔質表面の平坦化あるいは多孔質層の孔形状制御が困難な状況となっている。 In order to make a silicon single crystal substrate porous by a simpler chemical method, conventionally, a method by anodic oxidation etching of a silicon substrate is known in Non-Patent Documents 1 to 3. However, according to the method described in Non-Patent Document 1, the (100) plane orientation can be selectively etched to form a square columnar hole, but it is difficult to selectively etch the (111) plane orientation. It is. Further, according to the methods described in Non-Patent Documents 2 and 3, the (100) plane orientation or the (113) plane orientation tends to be selectively etched. For this reason, it is difficult to flatten the porous surface obtained only in the (111) plane orientation or to control the pore shape of the porous layer.
シリコン単結晶基板を多孔質化し該多孔質層表面を平坦化するにあたっては、（１１１）面方位のみを表面に残した状態で、かつシリコン単結晶（１１１）面方位を適切な孔密度、孔深度になるよう選択的にエッチングすることが必要であるが、電解酸化法によってそのように（１１１）面方位を多孔質化できる方法は知られていない。 In making a silicon single crystal substrate porous and flattening the surface of the porous layer, only the (111) plane orientation is left on the surface, and the silicon single crystal (111) plane orientation is set to an appropriate pore density and pore size. Although it is necessary to perform selective etching to a depth, there is no known method by which the (111) plane orientation can be made porous by electrolytic oxidation.
本発明は、上記した課題に鑑みなされたもので、シリコン単結晶基板上に電解酸化法によって多孔質層を形成する方法を提供することであり、その目的とするところは、該多孔質層の表面が平坦化するようシリコン単結晶基板の（１１１）面方位のみを表面に残し、かつ、該（１１１）面方位の一部を選択的にエッチングできる方法を提供することである。より詳しくは、シリコン単結晶基板に、電解酸化法によって、適切な孔径及び孔密度の三角柱状孔を生成し、多孔質層を形成する方法を提供することである。 The present invention has been made in view of the above-described problems, and provides a method for forming a porous layer on a silicon single crystal substrate by an electrolytic oxidation method. The object of the present invention is to provide the porous layer. To provide a method in which only the (111) plane orientation of a silicon single crystal substrate is left on the surface so that the surface is planarized, and a part of the (111) plane orientation can be selectively etched. More specifically, the present invention provides a method for forming a porous layer by generating triangular columnar holes having an appropriate hole diameter and hole density on a silicon single crystal substrate by electrolytic oxidation.
本発明者らは、鋭意検討を重ねた結果、特定のシリコン単結晶基板を、所定濃度の水含有フッ酸溶液を電解液として用い、陽極酸化する事により、シリコン基板の（１１１）面方位が選択的にエッチングされてなる三角柱状孔を生成でき、多孔質層を形成できることを見出し、本発明を完成するに至った。 As a result of intensive studies, the present inventors have determined that the (111) plane orientation of a silicon substrate is obtained by anodizing a specific silicon single crystal substrate using a water-containing hydrofluoric acid solution having a predetermined concentration as an electrolytic solution. The inventors have found that a triangular columnar hole formed by selective etching can be generated and a porous layer can be formed, and the present invention has been completed.
すなわち本発明は、 That is, the present invention
（１）シリコン単結晶基板を、電解酸化法によってエッチングし、該シリコン単結晶基板表面に多孔質層を形成するシリコン単結晶基板の製造方法において、
少なくとも５０容量％の水を含むフッ酸溶液からなる電解液中にて電解酸化することを特徴とするシリコン単結晶基板の製造方法。
(1) In a method for manufacturing a silicon single crystal substrate in which a silicon single crystal substrate is etched by electrolytic oxidation to form a porous layer on the surface of the silicon single crystal substrate.
A method for producing a silicon single crystal substrate, comprising performing electrolytic oxidation in an electrolytic solution comprising a hydrofluoric acid solution containing at least 50% by volume of water.
（２）前記シリコン単結晶基板として、１乃至１００Ω・ｃｍの範囲の体積抵抗率を有するＮ型シリコン単結晶基板を用いることを特徴とする前記（１）に記載のシリコン単結晶基板の製造方法。 (2) The method for producing a silicon single crystal substrate according to (1), wherein an N-type silicon single crystal substrate having a volume resistivity in the range of 1 to 100 Ω · cm is used as the silicon single crystal substrate. .
（３）前記電解酸化工程において、電流密度を１乃至２００ｍＡ／ｃｍ２にて電解することを特徴とする前記（１）又は（２）に記載のシリコン単結晶基板の製造方法。 (3) The method for producing a silicon single crystal substrate according to (1) or (2), wherein electrolysis is performed at a current density of 1 to 200 mA / cm 2 in the electrolytic oxidation step.
（４）前記フッ酸溶液からなる電解液が、さらに３０容量％以下のエタノールを含む混合電解液であることを特徴とする前記（１）〜（３）のいずれかに記載のシリコン単結晶基板の製造方法。 (4) The silicon single crystal substrate according to any one of (1) to (3), wherein the electrolytic solution made of the hydrofluoric acid solution is a mixed electrolytic solution further containing 30% by volume or less of ethanol. Manufacturing method.
（５）前記混合電解液が、５０〜７０容量％の水と、２０〜４０容量％のフッ酸と、１０〜３０％のエタノールと、からなる混合電解液であることを特徴とする前記（４）に記載のシリコン単結晶基板の製造方法。 (5) The mixed electrolyte is a mixed electrolyte composed of 50 to 70% by volume of water, 20 to 40% by volume of hydrofluoric acid, and 10 to 30% of ethanol. A method for producing a silicon single crystal substrate according to 4).
（６）前記（１）〜（５）のいずれかに記載されたシリコン単結晶基板の製造方法によって得られるシリコン単結晶基板であって、
該シリコン単結晶基板の（１１１）面方位が基板表面に残り、かつ該（１１１）面方位の少なくとも一部が、選択的に三角柱状にエッチングされてなる多孔質層を有することを特徴とするシリコン単結晶基板。
(6) A silicon single crystal substrate obtained by the method for producing a silicon single crystal substrate according to any one of (1) to (5),
The (111) plane orientation of the silicon single crystal substrate remains on the substrate surface, and at least a part of the (111) plane orientation has a porous layer that is selectively etched into a triangular prism shape. Silicon single crystal substrate.
好ましくは、前記三角柱状のエッチング孔が、１００〜４００個／ｍｍ２の孔密度であり、孔深度が２〜５０μmである。 Preferably, the triangular columnar etching holes have a hole density of 100 to 400 holes / mm 2 and a hole depth of 2 to 50 μm.
本発明によれば、シリコン単結晶基板表面には未エッチング部に相当する（１１１）面方位を残し、かつ、（１１１）面方位を選択的にエッチングする事が可能となり、簡便な方法で該シリコン単結晶基板を多孔質化できる。
また、該多孔質層表面を平坦化でき、かつ、エッチング孔形状が三角柱状構造に制御され、多孔質層を形成することができる。
According to the present invention, the (111) plane orientation corresponding to the unetched portion remains on the surface of the silicon single crystal substrate, and the (111) plane orientation can be selectively etched. The silicon single crystal substrate can be made porous.
Further, the surface of the porous layer can be flattened, and the shape of the etching holes is controlled to a triangular prism structure, so that a porous layer can be formed.
以下、本発明のシリコン単結晶基板の製造方法及びシリコン単結晶基板について詳細に説明する。 Hereinafter, the method for producing a silicon single crystal substrate and the silicon single crystal substrate of the present invention will be described in detail.
本発明は、シリコン単結晶基板を電解液中で電解酸化する事により多孔質層を形成するシリコン単結晶基板の製造方法において、（１１１）面方位のみを表面に残し、かつ該（１１１）面方位の一部を選択的にエッチングし、該シリコン単結晶基板表面に多孔質層を形成するシリコン単結晶基板の製造方法である。 The present invention relates to a method for manufacturing a silicon single crystal substrate in which a porous layer is formed by electrolytic oxidation of a silicon single crystal substrate in an electrolytic solution, leaving only the (111) plane orientation on the surface, and the (111) plane In this method, a part of the orientation is selectively etched to form a porous layer on the surface of the silicon single crystal substrate.
本発明に用いるシリコン単結晶基板は、リン、アンチモン、ヒ素等がドープされたＮ型半導体基板であることが好ましい。また、その体積抵抗率は１Ω・ｃｍ乃至１００Ω・ｃｍの範囲である基板であることが、選択的なエッチングの面から好ましい。 The silicon single crystal substrate used in the present invention is preferably an N-type semiconductor substrate doped with phosphorus, antimony, arsenic or the like. Further, a substrate having a volume resistivity in the range of 1 Ω · cm to 100 Ω · cm is preferable from the viewpoint of selective etching.
電解酸化は、電解液を張った電解槽中にて、シリコン単結晶基板を陽極とし、白金電極等を外部陰極として所定の電解条件にて行う。
この際、電流密度は１乃至２００ｍＡ／ｃｍ２の範囲で電解することが好ましい。１ｍＡ／ｃｍ２未満では、電界強度が足りず、三角柱状の多孔質層が得ることが困難になり、２００ｍＡ／ｃｍ２超では電解電圧が高くなるため、容量の大きな整流器を使用しなければならない上に使用電力量が大きくなって非経済的である。
The electrolytic oxidation is performed in a electrolytic cell filled with an electrolytic solution under a predetermined electrolytic condition using a silicon single crystal substrate as an anode and a platinum electrode or the like as an external cathode.
At this time, electrolysis is preferably performed with a current density in the range of 1 to 200 mA / cm 2 . If it is less than 1 mA / cm 2 , the electric field strength is insufficient and it becomes difficult to obtain a triangular prism-shaped porous layer, and if it exceeds 200 mA / cm 2 , the electrolysis voltage becomes high, so a rectifier having a large capacity must be used. In addition, the amount of power used is large, which is uneconomical.
本発明に用いる電解酸化用の電解液としては、水とフッ酸とを含んだ溶液からなる電解液であることが好ましく、このとき少なくとも５０容量％の水を含んだ電解液とする。水の含有量が５０容量％に満たない場合、（１１１）面方位を選択的にエッチングすることが困難である。例えば、水を５０％未満の２５％にした場合、エッチングされる面方位は、（２０１）面と（１１０）面とが主となる傾向があり、ごく一部の（１１１）面がエッチングされるのみとなりやすい。また、更に水を減量した場合、（１１０）面が主としてエッチングされ、（１１１）面方向は極めてエッチングされにくくなる傾向が見られる。 The electrolytic solution for electrolytic oxidation used in the present invention is preferably an electrolytic solution composed of a solution containing water and hydrofluoric acid. At this time, the electrolytic solution contains at least 50% by volume of water. When the water content is less than 50% by volume, it is difficult to selectively etch the (111) plane orientation. For example, when water is reduced to less than 50% and 25%, the surface orientation to be etched tends to be mainly the (201) plane and the (110) plane, and a very small part of the (111) plane is etched. It is easy to become only. Further, when the amount of water is further reduced, the (110) plane is mainly etched, and the (111) plane direction tends to be extremely difficult to be etched.
電解液として、さらにエタノールを含んだ電解液を用いることが好ましい。
このエタノールの混合比の選択は、基板全面を適切な孔密度および孔深度で（１１１）面方位のみ選択的にエッチングさせるのに重要である。
好ましいエタノール含有量は３０容量％以下であることが好ましく、エタノールの添加効果の面から、より好ましくは１〜３０％、さらに好ましくは１０〜３０容量％である。
従って、好ましい電解液組成は、５０〜７０％の水と、２０〜４０％のフッ酸と、１０〜３０％のエタノールと、からなるものである。
It is preferable to use an electrolytic solution further containing ethanol as the electrolytic solution.
The selection of the mixing ratio of ethanol is important for selectively etching the entire surface of the substrate only with the (111) plane orientation at an appropriate hole density and hole depth.
The preferable ethanol content is preferably 30% by volume or less, more preferably 1 to 30%, and still more preferably 10 to 30% by volume from the viewpoint of the effect of adding ethanol.
Therefore, a preferable electrolytic solution composition is composed of 50 to 70% water, 20 to 40% hydrofluoric acid, and 10 to 30% ethanol.
本発明のシリコン単結晶基板の製造方法によれば、シリコン単結晶基板表面に多数の三角柱状のエッチング孔を形成でき、該基板表面を多孔質化することができる。すなわち、基板表面に対し、垂直方向に三角柱状のエッチング孔を形成することができ、かつ基板表面の一部は（１１１）面方位が残るようにエッチングされるため、表面の平担性が損なわれることもない。該三角柱状エッチング孔の孔径は特に制限がなく、０．１μｍ乃至１．５μｍである。この孔径は電解条件の変更（電流密度、電解時間、浴温度等）によって適宜、制御可能である。 According to the method for producing a silicon single crystal substrate of the present invention, a large number of triangular prism-shaped etching holes can be formed on the surface of the silicon single crystal substrate, and the substrate surface can be made porous. That is, a triangular prism-shaped etching hole can be formed in a direction perpendicular to the substrate surface, and a part of the substrate surface is etched so that the (111) plane orientation remains, so that the flatness of the surface is impaired. It will never happen. The diameter of the triangular columnar etching hole is not particularly limited, and is 0.1 μm to 1.5 μm. This pore diameter can be appropriately controlled by changing electrolysis conditions (current density, electrolysis time, bath temperature, etc.).
以下、添付図面を参照しながら本発明の好適な実施形態を説明する。 Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
水／フッ酸／エタノール混合溶液（容量組成比５０：２５：２５）が準備された電解槽中、リンがドープされ体積抵抗率が２．０〜３．０Ω・ｃｍのＮ型シリコン単結晶（１１１）基板を陽極、白金電極を陰極として、電流密度５０ｍＡ／ｃｍ２にて１２分間通電して陽極酸化する事により、表面に三角形状の孔が形成し、断面には三角柱状孔が観察される多孔質層が形成された基板が得られた。 In an electrolytic cell prepared with a water / hydrofluoric acid / ethanol mixed solution (capacity composition ratio 50:25:25), an N-type silicon single crystal doped with phosphorus and having a volume resistivity of 2.0 to 3.0 Ω · cm ( 111) Using a substrate as an anode and a platinum electrode as a cathode, anodization is performed by energizing for 12 minutes at a current density of 50 mA / cm 2 to form triangular holes on the surface, and triangular columnar holes are observed in the cross section. A substrate having a porous layer formed thereon was obtained.
水／フッ酸／エタノール混合溶液の組成比を変化させ、上記同様の電解条件にて試験し多孔質層の形成状態を観察した。結果を表１に示す。（○：（１１１）面方位が良好にエッチングされたもの、◎：（１１１）面方位がウェーハ全面に良好にエッチングされたもの） The composition ratio of the water / hydrofluoric acid / ethanol mixed solution was changed and tested under the same electrolysis conditions as above to observe the formation state of the porous layer. The results are shown in Table 1. (◯: (111) plane orientation is well etched, ◎: (111) plane orientation is well etched across the wafer)
図１及び図２は実施例９によって得られた三角柱状多孔質層を有するシリコン単結晶（１１１）基板の表面および断面を電子顕微鏡（日立製、Ｓ−２４００）によって観察した像である。 1 and 2 are images obtained by observing the surface and cross section of a silicon single crystal (111) substrate having a triangular columnar porous layer obtained in Example 9 with an electron microscope (Hitachi, S-2400).
表面像からは、三角柱形状の孔が観察され、（１１１）面が選択的にエッチングされている事が示されている。なお、本実施例９によって得られたシリコン単結晶基板表面の三角柱状孔密度は２０５個／ｃｍ２、孔深度は２〜５μｍの範囲であった。 From the surface image, triangular prism-shaped holes are observed, indicating that the (111) plane is selectively etched. Note that the triangular columnar hole density on the surface of the silicon single crystal substrate obtained in Example 9 was 205 holes / cm 2 , and the hole depth was in the range of 2 to 5 μm.
一方、断面像からは、基板表面に対して垂直に、基板厚さ方向に三角柱状の孔が延びて形成されている様子が観察される。以上の事から、（１１１）面が選択的にエッチングされ多孔質層が形成されていることは明確である。 On the other hand, from the cross-sectional image, it is observed that a triangular prism-shaped hole is formed extending in the substrate thickness direction perpendicular to the substrate surface. From the above, it is clear that the (111) plane is selectively etched to form a porous layer.
本発明で得られる三角柱状多孔質層の形成されたシリコン単結晶（１１１）基板は、燃料電池の燃料極、太陽電池の反射防止層、半導体デバイス等に利用する事ができ、中でも六方晶系化合物半導体の成長基板として好適である。 The silicon single crystal (111) substrate on which the triangular columnar porous layer obtained in the present invention is formed can be used for a fuel electrode of a fuel cell, an antireflection layer of a solar cell, a semiconductor device, and the like. It is suitable as a growth substrate for compound semiconductors.
Claims (6)
少なくとも５０容量％の水を含むフッ酸溶液からなる電解液中にて電解酸化することを特徴とするシリコン単結晶基板の製造方法。 In the method for producing a silicon single crystal substrate, the porous layer is formed by electrolytic oxidation of the silicon single crystal substrate.
A method for producing a silicon single crystal substrate, comprising performing electrolytic oxidation in an electrolytic solution comprising a hydrofluoric acid solution containing at least 50% by volume of water.
該シリコン単結晶基板の（１１１）面方位が基板表面に残り、かつ該（１１１）面方位の少なくとも一部が、選択的に三角柱状にエッチングされてなる多孔質層を有することを特徴とするシリコン単結晶基板。 A silicon single crystal substrate obtained by the method for manufacturing a silicon single crystal substrate according to any one of claims 1 to 5,
The (111) plane orientation of the silicon single crystal substrate remains on the substrate surface, and at least a part of the (111) plane orientation has a porous layer that is selectively etched into a triangular prism shape. Silicon single crystal substrate.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2007078287A JP2008243880A (en) | 2007-03-26 | 2007-03-26 | Porous silicon substrate and its manufacturing method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2007078287A JP2008243880A (en) | 2007-03-26 | 2007-03-26 | Porous silicon substrate and its manufacturing method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2008243880A true JP2008243880A (en) | 2008-10-09 |
Family
ID=39914904
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2007078287A Pending JP2008243880A (en) | 2007-03-26 | 2007-03-26 | Porous silicon substrate and its manufacturing method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2008243880A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105755528A (en) * | 2016-04-07 | 2016-07-13 | 厦门大学 | Method for controlling corrosion depth of porous silicon |
-
2007
- 2007-03-26 JP JP2007078287A patent/JP2008243880A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105755528A (en) * | 2016-04-07 | 2016-07-13 | 厦门大学 | Method for controlling corrosion depth of porous silicon |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP2694731B2 (en) | Method of forming holes or trenches in a layer or substrate of n-type doped silicon | |
| US9324534B2 (en) | Cold field electron emitters based on silicon carbide structures | |
| Lee et al. | Strategies for controlling Si nanowire formation during Au-assisted electroless etching | |
| Barillaro et al. | Dimensional constraints on high aspect ratio silicon microstructures fabricated by HF photoelectrochemical etching | |
| US11732377B2 (en) | Methods for fabricating and etching porous silicon carbide structures | |
| Urata et al. | Pore formation in p-type silicon in solutions containing different types of alcohol | |
| Jakubowicz | Nanoporous silicon fabricated at different illumination and electrochemical conditions | |
| Burham et al. | Self-adjusting electrochemical etching technique for producing nanoporous silicon membrane | |
| Gautier et al. | Macroporous silicon hydrogen diffusion layers for micro-fuel cells: from planar to 3D structures | |
| JP2008243880A (en) | Porous silicon substrate and its manufacturing method | |
| JPH06326077A (en) | Formation method for hole structure in silicon substrate | |
| Benor | New insights into the oxidation rate and formation of porous structures on silicon | |
| Zheng et al. | Thick macroporous membranes made of p‐type silicon | |
| JP4637920B2 (en) | Porous silicon and method for producing the same | |
| Guozheng et al. | Influence of etching current density on the morphology of macroporous silicon arrays by photo-electrochemical etching | |
| US5863232A (en) | Fabrication method of micro tip for field emission display device | |
| Zhao et al. | Synthesis of porous silicon through interfacial reactions and measurement of its electrochemical response using cyclic voltammetry | |
| JP2015101536A (en) | Porous silicon self-supporting film having through pore array, and method of manufacturing the same | |
| JP2005264288A (en) | Method for manufacturing etched foil for aluminum electrolytic capacitor, the etched foil, and chemical foil thereof | |
| Cao et al. | Origin of mosaic structure obtained during the production of porous silicon with electrochemical etching | |
| Nadia et al. | Effect of dopant concentration on the pore formation of porous silicon on n-type silicon | |
| Jarimavičiūtė-Žvalionienė et al. | Fabrication of porous silicon microstructures using electrochemical etching | |
| JP2005203529A (en) | Method for manufacturing electrode foil for aluminum electrolytic capacitor | |
| Hubarevich et al. | Thin porous silicon fabricated by electrochemical etching in novel ammonium fluoride solution for optoelectronic applications | |
| Bölen et al. | Crossover of ion through porous silicon based membrane |