3D patterning of silicon by contact etching with anodically biased nanoporous gold electrodes

Abstract

, 3D patterning of silicon by contact etching with anodically biased nanoporous gold electrodes, Electrochemistry Communications (2017Communications ( ), doi:10.1016Communications ( /j.elecom.2017 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. A C C E P T E D M A N U S C R I P T ABSTRACTA novel strategy to achieve 3D pattern transfer into silicon in a single step without using lithography is presented. Etching is performed electrochemically in HF media by contacting silicon with a positively biased, patterned, metal electrode. Dissolution is localized at the Si/metal contacts and patterning is obtained as the electrode digs into the substrate. Previous attempts at imprinting Si using bulk metal electrodes have been limited by electrolyte blockage. Here, the problem is solved by using, for the first time, a nanoporous metal electrode that allows the electrolyte to access the entire Si/metal interface, irrespective of the electrode dimensions. As a proof of concept, imprinting of well-defined arrays of inverted pyramids has been performed with sub-micrometer spatial resolution over 1 mm 2 using a nanoporous gold electrode of the complementary shape. Under a polarization of +0.3 V/SME in 5M HF, the etch rate is ~0.5 µm/min. The pyramidal pattern is imprinted independently of the Si crystallographic orientation. This maskless imprinting technique opens new opportunities in the fabrication of Si microstructures.

3D Patterning of Si by Contact Etching With Nanoporous Metals

“…These directions are those necessarily followed in the case of alkaline etching and lithography (Moreau, 1988). In the same vein, it should be stressed that the facets of the pyramids obtained by contact etching do not correspond to (111) planes as is the case with alkaline etching (Torralba et al, 2017). This independence from the crystallographic orientation is obviously an advantage for creating new or more complex patterns.…”

“…We have recently reported a strategy specially defined to address this problem of large-scale electrolyte diffusion (Torralba et al, 2017). It is based on the use of nanoporous metal electrodes allowing both a “classical” MACE attack, i.e., with an interface consisting of nano-areas of metal and electrolyte in contact with silicon (for which the diffusion length is a few tens of nm) and a possible access of the electrolyte from the bulk of the solution to the interface.…”

“…They were made with nanoporous gold (np-Au) electrodes by electrochemical contact etching. A network of inverted pyramids was partially imprinted in n-type silicon oriented (100) in this way (Torralba et al, 2017).…”

Advances in silicon surface texturization by metal assisted chemical etching for photovoltaic applications

“…The patterned np-Au electrode is positively bias (0.3 V/SME) in HF 5M (2% Ethanol) in the dark and brought into contact with the n-Si under a pressure of 18 g cm -2 . More details about the experimental set-up can be found in reference [6]. Figure 6 gives SEM images of the results after imprinting for 10 min in these conditions.…”

Chemical carving lithography with scanning catalytic probes

“…1). As pressure is applied only in the vertical direction, the etching progresses toward the bottom of the substrate [23][24][25][26][27][28] . Then, when the probe scans sideways, the side of the semiconductor substrate that touches the probe is etched.…”