Study of macroporous silicon electrochemical etching in 3D structured N type silicon substrates

Abstract

In this paper, the electrochemical etching of 3D n‐type substrates is investigated. These types of 3D structures are of interest to increase the active surface of some systems. Our aim is to improve a MEMS (Micro‐Electro Mechanical System) micro fuel cell power through total surface enhancement without any modification of the cell footprint. To reach this objective, we perform a gas diffusion layer using localized macro‐porous silicon. The porous area total surface is improved through trench formation (before porous silicon etching). This is supposed to allow a better power to surface ratio for manufactured fuel cell. The Figure on the right hand side introduces the aimed MEMS based micro fuel cell. The geometrical parameters of the designed structures and the manufacturing process influence are presented. To perform 3D structures, two types of anisotropic etching techniques have been used, alkaline etching of silicon and deep reactive ion etching (DRIE). Additional steps such as a doping layer have been used to improve the results obtained with the initial micro‐fabrication process. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

A Silicon-Embedded Inductor Surrounded by Porous Silicon for Improved Quality Factor

“…It was demonstrated in previous work that it is possible to perform conformal PS layers even on textured surfaces. 22 In fact, in the case of highly doped silicon, the holes that are required for the electrochemical reaction (see PS formation Equation 1 from Ref. 24) equation are provided near the silicon surface by means of tunneling effects.…”

“…Previous study has shown that a high silicon surface doping level is essential for achieving conformal PS formation. 22 Therefore, low-resistivity (1 m .cm) silicon wafers were used in this work for simple experimental demonstration. For normal-resistivity (10-30 .cm) substrates, a step of diffusion doping and drive-in should be added before the anodization.…”

Integration of porous silicon in microfuel cells: a review

“…Afterwards, subsequent PS etching in a 30% HF mixture with acetic acid as wetting agent (in potentiostatic conditions at 3.1 V) was performed to produce macro‐PS. It permits to perform porous 3D structures that are presented in Figure . This picture shows a structure partially porous with 30% of the total surface presenting pores going through the silicon substrate to perform the flow channel function.…”

“…Structure observed after single‐side alkaline etching and an anodization under potentiostatic conditions at 3.1 V during 4 h in a HF 30%–acetic acid–water electrolyte, after .…”

“…Scanning electron microscopy image of the improved 3D structure of macroporous silicon for miniaturized fuel cell support application obtained after a potentiostatic etching (3.1 V) in HF–acetic acid solution during 4 h, after .…”